Science.gov

Sample records for acoustic time scale

  1. Full-Field Imaging of Acoustic Motion at Nanosecond Time and Micron Length Scales

    SciTech Connect

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

    2002-10-01

    A full-field view laser ultrasonic imaging method has been developed that measures acoustic motion at a surface without scanning. Images are recorded at normal video frame rates by employing dynamic holography using photorefractive interferometric detection. By extending the approach to ultra high frequencies, an acoustic microscope has been developed capable of operation on the nanosecond time and micron length scales. Both acoustic amplitude and phase are recorded allowing full calibration and determination of phases to within a single arbitrary constant. Results are presented of measurements at frequencies at 800-900 MHz illustrating a multitude of normal mode behavior in electrically driven thin film acoustic resonators. Coupled with microwave electrical impedance measurements, this imaging mode provides an exceptionally fast method for evaluation of electric to acoustic coupling and performance of these devices. Images of 256x240 pixels are recorded at 18Hz rates synchronized to obtain both in-phase and quadrature detection of the acoustic motion. Simple averaging provides sensitivity to the subnanometer level calibrated over the image using interferometry. Identification of specific acoustic modes and their relationship to electrical impedance characteristics show the advantages and overall high speed of the technique.

  2. Computational Fluid Dynamics Study on the Effects of RATO Timing on the Scale Model Acoustic Test

    NASA Technical Reports Server (NTRS)

    Nielsen, Tanner; Williams, B.; West, Jeff

    2015-01-01

    The Scale Model Acoustic Test (SMAT) is a 5% scale test of the Space Launch System (SLS), which is currently being designed at Marshall Space Flight Center (MSFC). The purpose of this test is to characterize and understand a variety of acoustic phenomena that occur during the early portions of lift off, one being the overpressure environment that develops shortly after booster ignition. The SLS lift off configuration consists of four RS-25 liquid thrusters on the core stage, with two solid boosters connected to each side. Past experience with scale model testing at MSFC (in ER42), has shown that there is a delay in the ignition of the Rocket Assisted Take Off (RATO) motor, which is used as the 5% scale analog of the solid boosters, after the signal to ignite is given. This delay can range from 0 to 16.5ms. While this small of a delay maybe insignificant in the case of the full scale SLS, it can significantly alter the data obtained during the SMAT due to the much smaller geometry. The speed of sound of the air and combustion gas constituents is not scaled, and therefore the SMAT pressure waves propagate at approximately the same speed as occurs during full scale. However, the SMAT geometry is much smaller allowing the pressure waves to move down the exhaust duct, through the trench, and impact the vehicle model much faster than occurs at full scale. To better understand the effect of the RATO timing simultaneity on the SMAT IOP test data, a computational fluid dynamics (CFD) analysis was performed using the Loci/CHEM CFD software program. Five different timing offsets, based on RATO ignition delay statistics, were simulated. A variety of results and comparisons will be given, assessing the overall effect of RATO timing simultaneity on the SMAT overpressure environment.

  3. A mixed time integration method for large scale acoustic fluid-structure interaction

    SciTech Connect

    Christon, M.A.; Wineman, S.J.; Goudreau, G.L.; Foch, J.D.

    1994-07-18

    The transient, coupled, interaction of sound with structures is a process in which an acoustic fluid surrounding an elastic body contributes to the effective inertia and elasticity of the body. Conversely, the presence of an elastic body in an acoustic medium influences the behavior of propagating disturbances. This paper details the application of a mixed explicit-implicit time integration algorithm to the fully coupled acoustic fluidstructure interaction problem. Based upon a dispersion analysis of the semi-discrete wave equation a second-order, explicit scheme for solving the wave equation is developed. The combination of a highly vectorized, explicit, acoustic fluid solver with an implicit structural code for linear elastodynamics has resulted in a simulation tool, PING, for acoustic fluid-structure interaction. PING`s execution rates range from 1{mu}s/Element/{delta}t for rigid scattering to 10{mu}s/Element/{delta}t for fully coupled problems. Several examples of PING`s application to 3-D problems serve in part to validate the code, and also to demonstrate the capability to treat complex geometry, acoustic fluid-structure problems which require high resolution meshes.

  4. Scale Model Thruster Acoustic Measurement Results

    NASA Technical Reports Server (NTRS)

    Kenny, R. Jeremy; Vargas, Magda B.

    2013-01-01

    Subscale rocket acoustic data is used to predict acoustic environments for full scale rockets. Over the last several years acoustic data has been collected during horizontal tests of solid rocket motors. Space Launch System (SLS) Scale Model Acoustic Test (SMAT) was designed to evaluate the acoustics of the SLS vehicle including the liquid engines and solid rocket boosters. SMAT is comprised of liquid thrusters scalable to the Space Shuttle Main engines (SSME) and Rocket Assisted Take Off (RATO) motors scalable to the 5-segment Reusable Solid Rocket Motor (RSTMV). Horizontal testing of the liquid thrusters provided an opportunity to collect acoustic data from liquid thrusters to characterize the acoustic environments. Acoustic data was collected during the horizontal firings of a single thruster and a 4-thruster (Quad) configuration. Presentation scope. Discuss the results of the single and 4-thruster acoustic measurements. Compare the measured acoustic levels of the liquid thrusters to the Solid Rocket Test Motor V - Nozzle 2 (SRTMV-N2).

  5. Acoustic characteristics of 1/20-scale model helicopter rotors

    NASA Technical Reports Server (NTRS)

    Shenoy, Rajarama K.; Kohlhepp, Fred W.; Leighton, Kenneth P.

    1986-01-01

    A wind tunnel test to study the effects of geometric scale on acoustics and to investigate the applicability of very small scale models for the study of acoustic characteristics of helicopter rotors was conducted in the United Technologies Research Center Acoustic Research Tunnel. The results show that the Reynolds number effects significantly alter the Blade-Vortex-Interaction (BVI) Noise characteristics by enhancing the lower frequency content and suppressing the higher frequency content. In the time domain this is observed as an inverted thickness noise impulse rather than the typical positive-negative impulse of BVI noise. At higher advance ratio conditions, in the absence of BVI, the 1/20 scale model acoustic trends with Mach number follow those of larger scale models. However, the 1/20 scale model acoustic trends appear to indicate stall at higher thrust and advance ratio conditions.

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

    PubMed

    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.

  7. Acoustic Source Localization via Time Difference of Arrival Estimation for Distributed Sensor Networks Using Tera-Scale Optical Core Devices

    DOE PAGES

    Imam, Neena; Barhen, Jacob

    2009-01-01

    For real-time acoustic source localization applications, one of the primary challenges is the considerable growth in computational complexity associated with the emergence of ever larger, active or passive, distributed sensor networks. These sensors rely heavily on battery-operated system components to achieve highly functional automation in signal and information processing. In order to keep communication requirements minimal, it is desirable to perform as much processing on the receiver platforms as possible. However, the complexity of the calculations needed to achieve accurate source localization increases dramatically with the size of sensor arrays, resulting in substantial growth of computational requirements that cannot bemore » readily met with standard hardware. One option to meet this challenge builds upon the emergence of digital optical-core devices. The objective of this work was to explore the implementation of key building block algorithms used in underwater source localization on the optical-core digital processing platform recently introduced by Lenslet Inc. This demonstration of considerably faster signal processing capability should be of substantial significance to the design and innovation of future generations of distributed sensor networks.« less

  8. Scaling and dimensional analysis of acoustic streaming jets

    NASA Astrophysics Data System (ADS)

    Moudjed, B.; Botton, V.; Henry, D.; Ben Hadid, H.; Garandet, J.-P.

    2014-09-01

    This paper focuses on acoustic streaming free jets. This is to say that progressive acoustic waves are used to generate a steady flow far from any wall. The derivation of the governing equations under the form of a nonlinear hydrodynamics problem coupled with an acoustic propagation problem is made on the basis of a time scale discrimination approach. This approach is preferred to the usually invoked amplitude perturbations expansion since it is consistent with experimental observations of acoustic streaming flows featuring hydrodynamic nonlinearities and turbulence. Experimental results obtained with a plane transducer in water are also presented together with a review of the former experimental investigations using similar configurations. A comparison of the shape of the acoustic field with the shape of the velocity field shows that diffraction is a key ingredient in the problem though it is rarely accounted for in the literature. A scaling analysis is made and leads to two scaling laws for the typical velocity level in acoustic streaming free jets; these are both observed in our setup and in former studies by other teams. We also perform a dimensional analysis of this problem: a set of seven dimensionless groups is required to describe a typical acoustic experiment. We find that a full similarity is usually not possible between two acoustic streaming experiments featuring different fluids. We then choose to relax the similarity with respect to sound attenuation and to focus on the case of a scaled water experiment representing an acoustic streaming application in liquid metals, in particular, in liquid silicon and in liquid sodium. We show that small acoustic powers can yield relatively high Reynolds numbers and velocity levels; this could be a virtue for heat and mass transfer applications, but a drawback for ultrasonic velocimetry.

  9. Scaling and dimensional analysis of acoustic streaming jets

    SciTech Connect

    Moudjed, B.; Botton, V.; Henry, D.; Ben Hadid, H.

    2014-09-15

    This paper focuses on acoustic streaming free jets. This is to say that progressive acoustic waves are used to generate a steady flow far from any wall. The derivation of the governing equations under the form of a nonlinear hydrodynamics problem coupled with an acoustic propagation problem is made on the basis of a time scale discrimination approach. This approach is preferred to the usually invoked amplitude perturbations expansion since it is consistent with experimental observations of acoustic streaming flows featuring hydrodynamic nonlinearities and turbulence. Experimental results obtained with a plane transducer in water are also presented together with a review of the former experimental investigations using similar configurations. A comparison of the shape of the acoustic field with the shape of the velocity field shows that diffraction is a key ingredient in the problem though it is rarely accounted for in the literature. A scaling analysis is made and leads to two scaling laws for the typical velocity level in acoustic streaming free jets; these are both observed in our setup and in former studies by other teams. We also perform a dimensional analysis of this problem: a set of seven dimensionless groups is required to describe a typical acoustic experiment. We find that a full similarity is usually not possible between two acoustic streaming experiments featuring different fluids. We then choose to relax the similarity with respect to sound attenuation and to focus on the case of a scaled water experiment representing an acoustic streaming application in liquid metals, in particular, in liquid silicon and in liquid sodium. We show that small acoustic powers can yield relatively high Reynolds numbers and velocity levels; this could be a virtue for heat and mass transfer applications, but a drawback for ultrasonic velocimetry.

  10. Nonlinear ultrafast acoustics at the nano scale.

    PubMed

    van Capel, P J S; Péronne, E; Dijkhuis, J I

    2015-02-01

    Pulsed femtosecond lasers can generate acoustic pulses propagating in solids while displaying either diffraction, attenuation, nonlinearity and/or dispersion. When acoustic attenuation and diffraction are negligible, shock waves or solitons can form during propagation. Both wave types are phonon wavepackets with characteristic length scales as short as a few nanometer. Hence, they are well suited for acoustic characterization and manipulation of materials on both ultrafast and ultrashort scales. This work presents an overview of nonlinear ultrasonics since its first experimental demonstration at the beginning of this century to the more recent developments. We start by reviewing the main properties of nonlinear ultrafast acoustic propagation based on the underlying equations. Then we show various results obtained by different groups around the world with an emphasis on recent work. Current issues and directions of future research are discussed.

  11. Acoustic Treatment Design Scaling Methods. Phase 2

    NASA Technical Reports Server (NTRS)

    Clark, L. (Technical Monitor); Parrott, T. (Technical Monitor); Jones, M. (Technical Monitor); Kraft, R. E.; Yu, J.; Kwan, H. W.; Beer, B.; Seybert, A. F.; Tathavadekar, P.

    2003-01-01

    The ability to design, build and test miniaturized acoustic treatment panels on scale model fan rigs representative of full scale engines provides not only cost-savings, but also an opportunity to optimize the treatment by allowing multiple tests. To use scale model treatment as a design tool, the impedance of the sub-scale liner must be known with confidence. This study was aimed at developing impedance measurement methods for high frequencies. A normal incidence impedance tube method that extends the upper frequency range to 25,000 Hz. without grazing flow effects was evaluated. The free field method was investigated as a potential high frequency technique. The potential of the two-microphone in-situ impedance measurement method was evaluated in the presence of grazing flow. Difficulties in achieving the high frequency goals were encountered in all methods. Results of developing a time-domain finite difference resonator impedance model indicated that a re-interpretation of the empirical fluid mechanical models used in the frequency domain model for nonlinear resistance and mass reactance may be required. A scale model treatment design that could be tested on the Universal Propulsion Simulator vehicle was proposed.

  12. Scale Model Thruster Acoustic Measurement Results

    NASA Technical Reports Server (NTRS)

    Vargas, Magda; Kenny, R. Jeremy

    2013-01-01

    The Space Launch System (SLS) Scale Model Acoustic Test (SMAT) is a 5% scale representation of the SLS vehicle, mobile launcher, tower, and launch pad trench. The SLS launch propulsion system will be comprised of the Rocket Assisted Take-Off (RATO) motors representing the solid boosters and 4 Gas Hydrogen (GH2) thrusters representing the core engines. The GH2 thrusters were tested in a horizontal configuration in order to characterize their performance. In Phase 1, a single thruster was fired to determine the engine performance parameters necessary for scaling a single engine. A cluster configuration, consisting of the 4 thrusters, was tested in Phase 2 to integrate the system and determine their combined performance. Acoustic and overpressure data was collected during both test phases in order to characterize the system's acoustic performance. The results from the single thruster and 4- thuster system are discussed and compared.

  13. Acoustic Studies of the Large Scale Ocean Circulation

    NASA Technical Reports Server (NTRS)

    Menemenlis, Dimitris

    1999-01-01

    Detailed knowledge of ocean circulation and its transport properties is prerequisite to an understanding of the earth's climate and of important biological and chemical cycles. Results from two recent experiments, THETIS-2 in the Western Mediterranean and ATOC in the North Pacific, illustrate the use of ocean acoustic tomography for studies of the large scale circulation. The attraction of acoustic tomography is its ability to sample and average the large-scale oceanic thermal structure, synoptically, along several sections, and at regular intervals. In both studies, the acoustic data are compared to, and then combined with, general circulation models, meteorological analyses, satellite altimetry, and direct measurements from ships. Both studies provide complete regional descriptions of the time-evolving, three-dimensional, large scale circulation, albeit with large uncertainties. The studies raise serious issues about existing ocean observing capability and provide guidelines for future efforts.

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

    PubMed Central

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

    2016-01-01

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

  15. Verification of Ares I Liftoff Acoustic Environments via the Ares I Scale Model Acoustic Test

    NASA Technical Reports Server (NTRS)

    Counter, Douglas; Houston, Janice

    2012-01-01

    The Ares I Scale Model Acoustic Test (ASMAT) program was implemented to verify the predicted Ares I liftoff acoustic environments and to determine the acoustic reduction gained by using an above deck water sound suppression system. The test article included a 5% scale Ares I vehicle model and Mobile Launcher with tower. Acoustic and pressure data were measured by over 200 instruments. The ASMAT results are compared to Ares I-X flight data.

  16. SLS Scale Model Acoustic Test Liftoff Results and Comparisons

    NASA Technical Reports Server (NTRS)

    Houston, Janice; Counter, Douglas; Giacomoni, Clothilde

    2015-01-01

    The liftoff phase induces acoustic loading over a broad frequency range for a launch vehicle. These external acoustic environments are then used in the prediction of internal vibration responses of the vehicle and components which result in the qualification levels. Thus, predicting these liftoff acoustic (LOA) environments is critical to the design requirements of any launch vehicle. If there is a significant amount of uncertainty in the predictions or if acoustic mitigation options must be implemented, a subscale acoustic test is a feasible design phase test option to verify the LOA environments. The NASA Space Launch System (SLS) program initiated the Scale Model Acoustic Test (SMAT) to verify the predicted SLS LOA environments.

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

    NASA Astrophysics Data System (ADS)

    Cuntz, Manfred

    1990-01-01

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

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

    SciTech Connect

    Cuntz, M. Heidelberg Universitaet )

    1990-01-01

    Theoretical models for chromospheric structures of late-type giant stars are computed, including the time-dependent propagation of acoustic waves. Models with short-period monochromatic shock waves as well as a spectrum of acoustic waves are discussed, and the method is applied to the stars Arcturus, Aldebaran, and Betelgeuse. Chromospheric extent, defined as the monotonic decrease with height of the time-averaged electron densities, are found to be 1.12, 1.13, and 1.22 stellar radii for the three stars, respectively; this corresponds to a time-averaged electron density of 10 to the 7th/cu cm. Predictions of the extended chromospheric obtained using a simple scaling law agree well with those obtained by the time-dependent wave models; thus, the chromospheres of all stars for which the scaling law is valid consist of the same number of pressure scale heights. 74 refs.

  19. Ares I Scale Model Acoustic Test Instrumentation for Acoustic and Pressure Measurements

    NASA Technical Reports Server (NTRS)

    Vargas, Magda B.; Counter, Douglas

    2011-01-01

    Ares I Scale Model Acoustic Test (ASMAT) is a 5% scale model test of the Ares I vehicle, launch pad and support structures conducted at MSFC to verify acoustic and ignition environments and evaluate water suppression systems Test design considerations 5% measurements must be scaled to full scale requiring high frequency measurements Users had different frequencies of interest Acoustics: 200 - 2,000 Hz full scale equals 4,000 - 40,000 Hz model scale Ignition Transient: 0 - 100 Hz full scale equals 0 - 2,000 Hz model scale Environment exposure Weather exposure: heat, humidity, thunderstorms, rain, cold and snow Test environments: Plume impingement heat and pressure, and water deluge impingement Several types of sensors were used to measure the environments Different instrument mounts were used according to the location and exposure to the environment This presentation addresses the observed effects of the selected sensors and mount design on the acoustic and pressure measurements

  20. Time and timing in the acoustic recognition system of crickets

    PubMed Central

    Hennig, R. Matthias; Heller, Klaus-Gerhard; Clemens, Jan

    2014-01-01

    The songs of many insects exhibit precise timing as the result of repetitive and stereotyped subunits on several time scales. As these signals encode the identity of a species, time and timing are important for the recognition system that analyzes these signals. Crickets are a prominent example as their songs are built from sound pulses that are broadcast in a long trill or as a chirped song. This pattern appears to be analyzed on two timescales, short and long. Recent evidence suggests that song recognition in crickets relies on two computations with respect to time; a short linear-nonlinear (LN) model that operates as a filter for pulse rate and a longer integration time window for monitoring song energy over time. Therefore, there is a twofold role for timing. A filter for pulse rate shows differentiating properties for which the specific timing of excitation and inhibition is important. For an integrator, however, the duration of the time window is more important than the precise timing of events. Here, we first review evidence for the role of LN-models and integration time windows for song recognition in crickets. We then parameterize the filter part by Gabor functions and explore the effects of duration, frequency, phase, and offset as these will correspond to differently timed patterns of excitation and inhibition. These filter properties were compared with known preference functions of crickets and katydids. In a comparative approach, the power for song discrimination by LN-models was tested with the songs of over 100 cricket species. It is demonstrated how the acoustic signals of crickets occupy a simple 2-dimensional space for song recognition that arises from timing, described by a Gabor function, and time, the integration window. Finally, we discuss the evolution of recognition systems in insects based on simple sensory computations. PMID:25161622

  1. Acoustic Treatment Design Scaling Methods. Volume 4; Numerical Simulation of the Nonlinear Acoustic Impedance of a Perforated Plate Single-Degree-of-Freedom Resonator Using a Time-Domain Finite Difference Method

    NASA Technical Reports Server (NTRS)

    Kraft, R. E.

    1999-01-01

    Single-degree-of-freedom resonators consisting of honeycomb cells covered by perforated facesheets are widely used as acoustic noise suppression liners in aircraft engine ducts. The acoustic resistance and mass reactance of such liners are known to vary with the intensity of the sound incident upon the panel. Since the pressure drop across a perforated liner facesheet increases quadratically with the flow velocity through the facesheet, this is known as the nonlinear resistance effect. In the past, two different empirical frequency domain models have been used to predict the Sound Pressure Level effect of the incident wave on the perforated liner impedance, one that uses the incident particle velocity in isolated narrowbands, and one that models the particle velocity as the overall velocity. In the absence of grazing flow, neither frequency domain model is entirely accurate in predicting the nonlinear effect that is measured for typical perforated sheets. The time domain model is developed in an attempt to understand and improve the model for the effect of spectral shape and amplitude of multi-frequency incident sound pressure on the liner impedance. A computer code for the time-domain finite difference model is developed and predictions using the models are compared to current frequency-domain models.

  2. Acoustic asymmetric transmission based on time-dependent dynamical scattering

    NASA Astrophysics Data System (ADS)

    Wang, Qing; Yang, Yang; Ni, Xu; Xu, Ye-Long; Sun, Xiao-Chen; Chen, Ze-Guo; Feng, Liang; Liu, Xiao-Ping; Lu, Ming-Hui; Chen, Yan-Feng

    2015-06-01

    An acoustic asymmetric transmission device exhibiting unidirectional transmission property for acoustic waves is extremely desirable in many practical scenarios. Such a unique property may be realized in various configurations utilizing acoustic Zeeman effects in moving media as well as frequency-conversion in passive nonlinear acoustic systems and in active acoustic systems. Here we demonstrate a new acoustic frequency conversion process in a time-varying system, consisting of a rotating blade and the surrounding air. The scattered acoustic waves from this time-varying system experience frequency shifts, which are linearly dependent on the blade’s rotating frequency. Such scattering mechanism can be well described theoretically by an acoustic linear time-varying perturbation theory. Combining such time-varying scattering effects with highly efficient acoustic filtering, we successfully develop a tunable acoustic unidirectional device with 20 dB power transmission contrast ratio between two counter propagation directions at audible frequencies.

  3. Acoustic asymmetric transmission based on time-dependent dynamical scattering

    PubMed Central

    Wang, Qing; Yang, Yang; Ni, Xu; Xu, Ye-Long; Sun, Xiao-Chen; Chen, Ze-Guo; Feng, Liang; Liu, Xiao-ping; Lu, Ming-Hui; Chen, Yan-Feng

    2015-01-01

    An acoustic asymmetric transmission device exhibiting unidirectional transmission property for acoustic waves is extremely desirable in many practical scenarios. Such a unique property may be realized in various configurations utilizing acoustic Zeeman effects in moving media as well as frequency-conversion in passive nonlinear acoustic systems and in active acoustic systems. Here we demonstrate a new acoustic frequency conversion process in a time-varying system, consisting of a rotating blade and the surrounding air. The scattered acoustic waves from this time-varying system experience frequency shifts, which are linearly dependent on the blade’s rotating frequency. Such scattering mechanism can be well described theoretically by an acoustic linear time-varying perturbation theory. Combining such time-varying scattering effects with highly efficient acoustic filtering, we successfully develop a tunable acoustic unidirectional device with 20 dB power transmission contrast ratio between two counter propagation directions at audible frequencies. PMID:26038886

  4. Ensemble Pulsar Time Scale

    NASA Astrophysics Data System (ADS)

    Yin, D. S.; Gao, Y. P.; Zhao, S. H.

    2016-05-01

    Millisecond pulsars can generate another type of time scale that is totally independent of the atomic time scale, because the physical mechanisms of the pulsar time scale and the atomic time scale are quite different from each other. Usually the pulsar timing observational data are not evenly sampled, and the internals between data points range from several hours to more than half a month. What's more, these data sets are sparse. And all these make it difficult to generate an ensemble pulsar time scale. Hence, a new algorithm to calculate the ensemble pulsar time scale is proposed. Firstly, we use cubic spline interpolation to densify the data set, and make the intervals between data points even. Then, we employ the Vondrak filter to smooth the data set, and get rid of high-frequency noise, finally adopt the weighted average method to generate the ensemble pulsar time scale. The pulsar timing residuals represent clock difference between the pulsar time and atomic time, and the high precision pulsar timing data mean the clock difference measurement between the pulsar time and atomic time with a high signal to noise ratio, which is fundamental to generate pulsar time. We use the latest released NANOGRAV (North American Nanohertz Observatory for Gravitational Waves) 9-year data set to generate the ensemble pulsar time scale. This data set is from the newest NANOGRAV data release, which includes 9-year observational data of 37 millisecond pulsars using the 100-meter Green Bank telescope and 305-meter Arecibo telescope. We find that the algorithm used in this paper can lower the influence caused by noises in timing residuals, and improve long-term stability of pulsar time. Results show that the long-term (> 1 yr) frequency stability of the pulsar time is better than 3.4×10-15.

  5. Travel-time sensitivity kernels in ocean acoustic tomography

    NASA Astrophysics Data System (ADS)

    Skarsoulis, E. K.; Cornuelle, B. D.

    2004-07-01

    Wave-theoretic ocean acoustic propagation modeling is combined with the peak arrival approach for tomographic travel-time observables to derive the sensitivity kernel of travel times with respect to sound-speed variations. This is the Born-Fréchet kernel relating the three-dimensional spatial distribution of sound-speed variations with the induced travel-time variations. The derivation is based on the first Born approximation of the Green's function. The application of the travel-time sensitivity kernel to an ocean acoustic waveguide gives a picture close to the ray-theoretic one in the case of high frequencies. However, in the low-frequency case, of interest in ocean acoustic tomography, for example, there are significant deviations. Low-frequency travel times are sensitive to sound-speed changes in Fresnel-zone-scale areas surrounding the eigenrays, but not on the eigenrays themselves, where the sensitivity is zero. Further, there are areas of positive sensitivity, where, e.g., a sound-speed increase results in an increase of arrival times, i.e., a further delay of arrivals, in contrast with the common expectation. These findings are confirmed by forward acoustic predictions from a coupled-mode code.

  6. Pulsar time scale

    SciTech Connect

    Il'in, V.G.; Llyasov, Yu.P.; Kuz'min, A.D.; Pushkin, S.B.; Palii, G.N.; Shabanova, T.V.; Shchitov, Yu.P.

    1984-05-01

    In this article a new time scale is proposed, that of pulsar time PT which is based on the regular sequence of time intervals between pulses of a pulsar's radio emissions. In discussing variations in the arrival times of pulsar radio emissions, three kinds of variations in the radiation periods are described. PSR 0834 + 06 is used as the basic reference pulsar. Time scales are also determined for reference pulsars PSR 0905 + 08 and 1919 + 21. The initial parameters for the three reference pulsars needed for managing a PT scale are presented. The basic PT scale is defined as the continuous sequence of time intervals between radio-emission pulses of the basic reference pulsar.

  7. Space Time Processing, Environmental-Acoustic Effects

    DTIC Science & Technology

    1987-08-15

    5) In the cases of a harmonic field which is steady or for a random field which is spatially homogeneous and temporally stationary, one can infer...relationships define the acoustic-space-time field for the class of harmonic and random functions which are spatially homogeneous and temporally stationary...When the field is homogeneous and sta- tionary, then (in large average limits) spatial and temporal average values approach the statistically

  8. Acoustic thermometry time series in the North Pacific

    NASA Astrophysics Data System (ADS)

    Dushaw, B. D.; Howe, B. M.; Mercer, J. A.; Worcester; Npal Group*, P. F.

    2002-12-01

    Acoustic measurements of large-scale, depth-averaged temperatures are continuing in the North Pacific as a follow on to the Acoustic Thermometry of Ocean Climate (ATOC) project. An acoustic source is located just north of Kauai. It transmits to six receivers to the east at 1-4-Mm ranges and one receiver to the northwest at about 4-Mm range. The transmission schedule is six times per day at four-day intervals. The time series were obtained from 1998 through 1999 and, after a two-year interruption because of permitting issues, began again in January 2002 to continue for at least another five years. The intense mesoscale thermal variability around Hawaii is evident in all time series; this variability is much greater than that observed near the California coast. The paths to the east, particularly those paths to the California coast, show cooling this year relative to the earlier data. The path to the northwest shows a modest warming. The acoustic rays sample depths below the mixed layer near Hawaii and to the surface as they near the California coast or extend north of the sub-arctic front. The temperatures measured acoustically are compared with those inferred from TOPEX altimetry, ARGO float data, and with ECCO (Estimating the Circulation and Climate of the Ocean) model output. This on-going data collection effort, to be augmented over the next years with a more complete observing array, can be used for, e.g., separating whole-basin climate change from low-mode spatial variability such as the Pacific Decadal Oscillation (PDO). [*NPAL (North Pacific Acoustic Laboratory) Group: J. A. Colosi, B. D. Cornuelle, B. D. Dushaw, M. A. Dzieciuch, B. M. Howe, J. A. Mercer, R. C. Spindel, and P. F. Worcester. Work supported by the Office of Naval Research.

  9. Ocean acoustic tomography - Travel time biases

    NASA Technical Reports Server (NTRS)

    Spiesberger, J. L.

    1985-01-01

    The travel times of acoustic rays traced through a climatological sound-speed profile are compared with travel times computed through the same profile containing an eddy field. The accuracy of linearizing the relations between the travel time difference and the sound-speed deviation at long ranges is assessed using calculations made for two different eddy fields measured in the eastern Atlantic. Significant nonlinearities are found in some cases, and the relationships of the values of these nonlinearities to the range between source and receiver, to the anomaly size associated with the eddies, and to the positions of the eddies are studied. An analytical model of the nonlinearities is discussed.

  10. Acoustic Source Localization via Time Difference of Arrival Estimation for Distributed Sensor Networks using Tera-scale Optical-Core Devices

    SciTech Connect

    Imam, Neena; Barhen, Jacob

    2009-01-01

    For real-time acoustic source localization applications, one of the primary challenges is the considerable growth in computational complexity associated with the emergence of ever larger, active or passive, distributed sensor networks. These sensors rely heavily on battery-operated system components to achieve highly functional automation in signal and information processing. In order to keep communication requirements minimal, it is desirable to perform as much processing on the receiver platforms as possible. However, the complexity of the calculations needed to achieve accurate source localization increases dramatically with the size of sensor arrays, resulting in substantial growth of computational requirements that cannot be readily met with standard hardware. One option to meet this challenge builds upon the emergence of digital optical-core devices. The objective of this work was to explore the implementation of key building block algorithms used in underwater source localization on the optical-core digital processing platform recently introduced by Lenslet Inc. This demonstration of considerably faster signal processing capability should be of substantial significance to the design and innovation of future generations of distributed sensor networks.

  11. Ares I Scale Model Acoustic Tests Instrumentation for Acoustic and Pressure Measurements

    NASA Technical Reports Server (NTRS)

    Vargas, Magda B.; Counter, Douglas D.

    2011-01-01

    The Ares I Scale Model Acoustic Test (ASMAT) was a development test performed at the Marshall Space Flight Center (MSFC) East Test Area (ETA) Test Stand 116. The test article included a 5% scale Ares I vehicle model and tower mounted on the Mobile Launcher. Acoustic and pressure data were measured by approximately 200 instruments located throughout the test article. There were four primary ASMAT instrument suites: ignition overpressure (IOP), lift-off acoustics (LOA), ground acoustics (GA), and spatial correlation (SC). Each instrumentation suite incorporated different sensor models which were selected based upon measurement requirements. These requirements included the type of measurement, exposure to the environment, instrumentation check-outs and data acquisition. The sensors were attached to the test article using different mounts and brackets dependent upon the location of the sensor. This presentation addresses the observed effect of the sensors and mounts on the acoustic and pressure measurements.

  12. Irreversibility time scale.

    PubMed

    Gallavotti, G

    2006-06-01

    Entropy creation rate is introduced for a system interacting with thermostats (i.e., for a system subject to internal conservative forces interacting with "external" thermostats via conservative forces) and a fluctuation theorem for it is proved. As an application, a time scale is introduced, to be interpreted as the time over which irreversibility becomes manifest in a process leading from an initial to a final stationary state of a mechanical system in a general nonequilibrium context. The time scale is evaluated in a few examples, including the classical Joule-Thompson process (gas expansion in a vacuum).

  13. Perception of acoustic scale and size in musical instrument sounds

    PubMed Central

    van Dinther, Ralph; Patterson, Roy D.

    2010-01-01

    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. PMID:17069313

  14. Frequency effects on the scale and behavior of acoustic streaming.

    PubMed

    Dentry, Michael B; Yeo, Leslie Y; Friend, James R

    2014-01-01

    Acoustic streaming underpins an exciting range of fluid manipulation phenomena of rapidly growing significance in microfluidics, where the streaming often assumes the form of a steady, laminar jet emanating from the device surface, driven by the attenuation of acoustic energy within the beam of sound propagating through the liquid. The frequencies used to drive such phenomena are often chosen ad hoc to accommodate fabrication and material issues. In this work, we seek a better understanding of the effects of sound frequency and power on acoustic streaming. We present and, using surface acoustic waves, experimentally verify a laminar jet model that is based on the turbulent jet model of Lighthill, which is appropriate for acoustic streaming seen at micro- to nanoscales, between 20 and 936 MHz and over a broad range of input power. Our model eliminates the critically problematic acoustic source singularity present in Lighthill's model, replacing it with a finite emission area and enabling determination of the streaming velocity close to the source. At high acoustic power P (and hence high jet Reynolds numbers ReJ associated with fast streaming), the laminar jet model predicts a one-half power dependence (U∼P1/2∼ ReJ) similar to the turbulent jet model. However, the laminar model may also be applied to jets produced at low powers-and hence low jet Reynolds numbers ReJ-where a linear relationship between the beam power and streaming velocity exists: U∼P∼ReJ2. The ability of the laminar jet model to predict the acoustic streaming behavior across a broad range of frequencies and power provides a useful tool in the analysis of microfluidics devices, explaining peculiar observations made by several researchers in the literature. In particular, by elucidating the effects of frequency on the scale of acoustically driven flows, we show that the choice of frequency is a vitally important consideration in the design of small-scale devices employing acoustic streaming

  15. Frequency effects on the scale and behavior of acoustic streaming

    NASA Astrophysics Data System (ADS)

    Dentry, Michael B.; Yeo, Leslie Y.; Friend, James R.

    2014-01-01

    Acoustic streaming underpins an exciting range of fluid manipulation phenomena of rapidly growing significance in microfluidics, where the streaming often assumes the form of a steady, laminar jet emanating from the device surface, driven by the attenuation of acoustic energy within the beam of sound propagating through the liquid. The frequencies used to drive such phenomena are often chosen ad hoc to accommodate fabrication and material issues. In this work, we seek a better understanding of the effects of sound frequency and power on acoustic streaming. We present and, using surface acoustic waves, experimentally verify a laminar jet model that is based on the turbulent jet model of Lighthill, which is appropriate for acoustic streaming seen at micro- to nanoscales, between 20 and 936 MHz and over a broad range of input power. Our model eliminates the critically problematic acoustic source singularity present in Lighthill's model, replacing it with a finite emission area and enabling determination of the streaming velocity close to the source. At high acoustic power P (and hence high jet Reynolds numbers ReJ associated with fast streaming), the laminar jet model predicts a one-half power dependence (U ˜P1/2˜ ReJ) similar to the turbulent jet model. However, the laminar model may also be applied to jets produced at low powers—and hence low jet Reynolds numbers ReJ—where a linear relationship between the beam power and streaming velocity exists: U ˜P˜ReJ2. The ability of the laminar jet model to predict the acoustic streaming behavior across a broad range of frequencies and power provides a useful tool in the analysis of microfluidics devices, explaining peculiar observations made by several researchers in the literature. In particular, by elucidating the effects of frequency on the scale of acoustically driven flows, we show that the choice of frequency is a vitally important consideration in the design of small-scale devices employing acoustic streaming

  16. Opportunities for shear energy scaling in bulk acoustic wave resonators.

    PubMed

    Jose, Sumy; Hueting, Raymond J E

    2014-10-01

    An important energy loss contribution in bulk acoustic wave resonators is formed by so-called shear waves, which are transversal waves that propagate vertically through the devices with a horizontal motion. In this work, we report for the first time scaling of the shear-confined spots, i.e., spots containing a high concentration of shear wave displacement, controlled by the frame region width at the edge of the resonator. We also demonstrate a novel methodology to arrive at an optimum frame region width for spurious mode suppression and shear wave confinement. This methodology makes use of dispersion curves obtained from finite-element method (FEM) eigenfrequency simulations for arriving at an optimum frame region width. The frame region optimization is demonstrated for solidly mounted resonators employing several shear wave optimized reflector stacks. Finally, the FEM simulation results are compared with measurements for resonators with Ta2O5/ SiO2 stacks showing suppression of the spurious modes.

  17. Streaming Velocities and the Baryon Acoustic Oscillation Scale.

    PubMed

    Blazek, Jonathan A; McEwen, Joseph E; Hirata, Christopher M

    2016-03-25

    At the epoch of decoupling, cosmic baryons had supersonic velocities relative to the dark matter that were coherent on large scales. These velocities subsequently slow the growth of small-scale structure and, via feedback processes, can influence the formation of larger galaxies. We examine the effect of streaming velocities on the galaxy correlation function, including all leading-order contributions for the first time. We find that the impact on the baryon acoustic oscillation (BAO) peak is dramatically enhanced (by a factor of ∼5) over the results of previous investigations, with the primary new effect due to advection: if a galaxy retains memory of the primordial streaming velocity, it does so at its Lagrangian, rather than Eulerian, position. Since correlations in the streaming velocity change rapidly at the BAO scale, this advection term can cause a significant shift in the observed BAO position. If streaming velocities impact tracer density at the 1% level, compared to the linear bias, the recovered BAO scale is shifted by approximately 0.5%. This new effect, which is required to preserve Galilean invariance, greatly increases the importance of including streaming velocities in the analysis of upcoming BAO measurements and opens a new window to the astrophysics of galaxy formation.

  18. Pressure Sensitivity Kernels Applied to Time-reversal Acoustics

    DTIC Science & Technology

    2009-06-29

    diversity in passive time reversal com- munications,” Journal of the Acoustical Society of America, October 2006, Vol. 120, Issue 4, pp. 2067-2076. xvi 5...communications. J. Acoustic Soc. Am., 115:2468–2468, 2004. [3] P. Gerstoft. Inversion of seismo-acoustic data using genetic algorithms and a posteriori...average of focal spots tends to have high stability.[6] The presence of spatial diversity (large arrays) has the same effect as an ensemble average and

  19. An optoacoustic point source for acoustic scale model measurements.

    PubMed

    Bolaños, Javier Gómez; Pulkki, Ville; Karppinen, Pasi; Hæggström, Edward

    2013-04-01

    A massless acoustic source is proposed for scale model work. This source is generated by focusing a pulsed laser beam to rapidly heat the air at the focal point. This produces an expanding small plasma ball which generates a sonic impulse that may be used as an acoustic point source. Repeatability, frequency response, and directivity of the source were measured to show that it can serve as a massless point source. The impulse response of a rectangular space was determined using this type of source. A good match was found between the predicted and the measured impulse responses of the space.

  20. Location and acoustic scale cues in concurrent speech recognition1

    PubMed Central

    Ives, D. Timothy; Vestergaard, Martin D.; Kistler, Doris J.; Patterson, Roy D.

    2010-01-01

    Location and acoustic scale cues have both been shown to have an effect on the recognition of speech in multi-speaker environments. This study examines the interaction of these variables. Subjects were presented with concurrent triplets of syllables from a target voice and a distracting voice, and asked to recognize a specific target syllable. The task was made more or less difficult by changing (a) the location of the distracting speaker, (b) the scale difference between the two speakers, and∕or (c) the relative level of the two speakers. Scale differences were produced by changing the vocal tract length and glottal pulse rate during syllable synthesis: 32 acoustic scale differences were used. Location cues were produced by convolving head-related transfer functions with the stimulus. The angle between the target speaker and the distracter was 0°, 4°, 8°, 16°, or 32° on the 0° horizontal plane. The relative level of the target to the distracter was 0 or −6 dB. The results show that location and scale difference interact, and the interaction is greatest when one of these cues is small. Increasing either the acoustic scale or the angle between target and distracter speakers quickly elevates performance to ceiling levels. PMID:20550271

  1. Scaling of membrane-type locally resonant acoustic metamaterial arrays.

    PubMed

    Naify, Christina J; Chang, Chia-Ming; McKnight, Geoffrey; Nutt, Steven R

    2012-10-01

    Metamaterials have emerged as promising solutions for manipulation of sound waves in a variety of applications. Locally resonant acoustic materials (LRAM) decrease sound transmission by 500% over acoustic mass law predictions at peak transmission loss (TL) frequencies with minimal added mass, making them appealing for weight-critical applications such as aerospace structures. In this study, potential issues associated with scale-up of the structure are addressed. TL of single-celled and multi-celled LRAM was measured using an impedance tube setup with systematic variation in geometric parameters to understand the effects of each parameter on acoustic response. Finite element analysis was performed to predict TL as a function of frequency for structures with varying complexity, including stacked structures and multi-celled arrays. Dynamic response of the array structures under discrete frequency excitation was investigated using laser vibrometry to verify negative dynamic mass behavior.

  2. Overview of the Ares I Scale Model Acoustic Test Program

    NASA Technical Reports Server (NTRS)

    Counter, Douglas D.; Houston, Janice D.

    2011-01-01

    Launch environments, such as lift-off acoustic (LOA) and ignition overpressure (IOP), are important design factors for any vehicle and are dependent upon the design of both the vehicle and the ground systems. LOA environments are used directly in the development of vehicle vibro-acoustic environments and IOP is used in the loads assessment. The NASA Constellation Program had several risks to the development of the Ares I vehicle linked to LOA. The risks included cost, schedule and technical impacts for component qualification due to high predicted vibro-acoustic environments. One solution is to mitigate the environment at the component level. However, where the environment is too severe for component survivability, reduction of the environment itself is required. The Ares I Scale Model Acoustic Test (ASMAT) program was implemented to verify the Ares I LOA and IOP environments for the vehicle and ground systems including the Mobile Launcher (ML) and tower. An additional objective was to determine the acoustic reduction for the LOA environment with an above deck water sound suppression system. ASMAT was a development test performed at the Marshall Space Flight Center (MSFC) East Test Area (ETA) Test Stand 116 (TS 116). The ASMAT program is described in this presentation.

  3. Acoustic resonance in MEMS scale cylindrical tubes with side branches

    NASA Astrophysics Data System (ADS)

    Schill, John F.; Holthoff, Ellen L.; Pellegrino, Paul M.; Marcus, Logan S.

    2014-05-01

    Photoacoustic spectroscopy (PAS) is a useful monitoring technique that is well suited for trace gas detection. This method routinely exhibits detection limits at the parts-per-million (ppm) or parts-per-billion (ppb) level for gaseous samples. PAS also possesses favorable detection characteristics when the system dimensions are scaled to a microelectromechanical system (MEMS) design. One of the central issues related to sensor miniaturization is optimization of the photoacoustic cell geometry, especially in relationship to high acoustical amplification and reduced system noise. Previous work relied on a multiphysics approach to analyze the resonance structures of the MEMS scale photo acoustic cell. This technique was unable to provide an accurate model of the acoustic structure. In this paper we describe a method that relies on techniques developed from musical instrument theory and electronic transmission line matrix methods to describe cylindrical acoustic resonant cells with side branches of various configurations. Experimental results are presented that demonstrate the ease and accuracy of this method. All experimental results were within 2% of those predicted by this theory.

  4. Nanolitre-scale crystallization using acoustic liquid-transfer technology

    SciTech Connect

    Villaseñor, Armando G.; Wong, April; Shao, Ada; Garg, Ankur; Donohue, Timothy J.; Kuglstatter, Andreas; Harris, Seth F.

    2012-08-01

    Acoustic droplet ejection achieves precise, tipless, non-invasive transfer of diverse aqueous solutions, enabling nanolitre-scale crystallization trials. The rapid and scalable technique demonstrated successful crystal growth with diverse targets in drop volumes as small as 20 nl. Focused acoustic energy allows accurate and precise liquid transfer on scales from picolitre to microlitre volumes. This technology was applied in protein crystallization, successfully transferring a diverse set of proteins as well as hundreds of precipitant solutions from custom and commercial crystallization screens and achieving crystallization in drop volumes as small as 20 nl. Only higher concentrations (>50%) of 2-methyl-2, 4-pentanediol (MPD) appeared to be systematically problematic in delivery. The acoustic technology was implemented in a workflow, successfully reproducing active crystallization systems and leading to the discovery of crystallization conditions for previously uncharacterized proteins. The technology offers compelling advantages in low-nanolitre crystallization trials by providing significant reagent savings and presenting seamless scalability for those crystals that require larger volume optimization experiments using the same vapor-diffusion format.

  5. Ares I Scale Model Acoustic Test Overpressure Results

    NASA Technical Reports Server (NTRS)

    Casiano, M. J.; Alvord, D. A.; McDaniels, D. M.

    2011-01-01

    A summary of the overpressure environment from the 5% Ares I Scale Model Acoustic Test (ASMAT) and the implications to the full-scale Ares I are presented in this Technical Memorandum. These include the scaled environment that would be used for assessing the full-scale Ares I configuration, observations, and team recommendations. The ignition transient is first characterized and described, the overpressure suppression system configuration is then examined, and the final environment characteristics are detailed. The recommendation for Ares I is to keep the space shuttle heritage ignition overpressure (IOP) suppression system (below-deck IOP water in the launch mount and mobile launcher and also the crest water on the main flame deflector) and the water bags.

  6. Ares I Scale Model Acoustic Test Above Deck Water Sound Suppression Results

    NASA Technical Reports Server (NTRS)

    Counter, Douglas D.; Houston, Janice D.

    2011-01-01

    The Ares I Scale Model Acoustic Test (ASMAT) program test matrix was designed to determine the acoustic reduction for the Liftoff acoustics (LOA) environment with an above deck water sound suppression system. The scale model test can be used to quantify the effectiveness of the water suppression system as well as optimize the systems necessary for the LOA noise reduction. Several water flow rates were tested to determine which rate provides the greatest acoustic reductions. Preliminary results are presented.

  7. Time Scales: Terrestrial

    NASA Astrophysics Data System (ADS)

    Petit, G.; Murdin, P.

    2000-11-01

    Terrestrial time is at present derived from atomic clocks. The SI second, the unit of time of the international system of units, has been defined since 1967 in terms of a hyperfine transition of the cesium atom and the best primary frequency standards now realize it with a relative uncertainty of a few parts in 1015, which makes it the most accurately measurable physical quantity. INTERNATIONAL A...

  8. Phase Time and Envelope Time in Time-Distance Analysis and Acoustic Imaging

    NASA Technical Reports Server (NTRS)

    Chou, Dean-Yi; Duvall, Thomas L.; Sun, Ming-Tsung; Chang, Hsiang-Kuang; Jimenez, Antonio; Rabello-Soares, Maria Cristina; Ai, Guoxiang; Wang, Gwo-Ping; Goode Philip; Marquette, William; Ehgamberdiev, Shuhrat; Landenkov, Oleg

    1999-01-01

    Time-distance analysis and acoustic imaging are two related techniques to probe the local properties of solar interior. In this study, we discuss the relation of phase time and envelope time between the two techniques. The location of the envelope peak of the cross correlation function in time-distance analysis is identified as the travel time of the wave packet formed by modes with the same w/l. The phase time of the cross correlation function provides information of the phase change accumulated along the wave path, including the phase change at the boundaries of the mode cavity. The acoustic signals constructed with the technique of acoustic imaging contain both phase and intensity information. The phase of constructed signals can be studied by computing the cross correlation function between time series constructed with ingoing and outgoing waves. In this study, we use the data taken with the Taiwan Oscillation Network (TON) instrument and the Michelson Doppler Imager (MDI) instrument. The analysis is carried out for the quiet Sun. We use the relation of envelope time versus distance measured in time-distance analyses to construct the acoustic signals in acoustic imaging analyses. The phase time of the cross correlation function of constructed ingoing and outgoing time series is twice the difference between the phase time and envelope time in time-distance analyses as predicted. The envelope peak of the cross correlation function between constructed ingoing and outgoing time series is located at zero time as predicted for results of one-bounce at 3 mHz for all four data sets and two-bounce at 3 mHz for two TON data sets. But it is different from zero for other cases. The cause of the deviation of the envelope peak from zero is not known.

  9. Time scale independent signal transmission

    NASA Astrophysics Data System (ADS)

    Faltin, L.

    1980-05-01

    The paper presents a method which permits the conversion of time scale variations occurring during signal transmission into time shifts proportionally related to these variations. It is demonstrated that the method can be used to reject the adverse effects of the time scale variations (such as wow and flutter in magnetic tape recordings) and/or to determine the scale change exactly (such as would be required in Doppler signal processing). Finally, it is noted that since the system performance degrades with rising frequency of the time scale distortions, an upper bound for this frequency is derived.

  10. Micro/meso scale fatigue damage accumulation monitoring using nonlinear acoustic vibro-modulation measurements

    NASA Astrophysics Data System (ADS)

    Zagrai, Andrei; Donskoy, Dimitri; Chudnovsky, Alexander; Golovin, Edward; Agarwala, Vinod S.

    2006-03-01

    Monitoring the incipient damage at the earliest possible stage is essential for predicting structural performance and remaining life of structural components. Existing prognostic methodologies incorporate conventional SHM and NDE techniques responsive to cracks and delaminations resulted from the irreversible material fracture and disintegration at the macro-scale. There is an increasing need for technologies that could allow for monitoring material degradation at the micro/meso scale before the onset of the macro-scale fracture. In this contribution, we report results of the real-time monitoring of the material micro/meso scale degradation using the nonlinear acoustic vibro-modulation technique. The technique explores nonlinear acoustic interaction of high frequency ultrasound and low frequency structural vibration at the site of the incipient damage. The indicator of the damage severity, nonlinear acoustic damage index (DI), was measured in real time during the strain-controlled three-point bending fatigue test of aluminum and steel specimens. Nondestructively, degradation of the specimen was revealed through the increase in the DI, which correlated well with the respective decrease in the specimen's stiffness. Destructive SEM examination confirmed sensitivity of the DI to the incipient micro/meso scale damage and advocated for utilizing the vibro-modulation approach for assessment of material degradation before fracture.

  11. Evolution of Time Scales

    DTIC Science & Technology

    2006-12-01

    estimates of ET, and it did not include relativistic effects. 5. ATOMIC TIME Following the appearance of the first operational Caesium beam frequency...with Wm Markowitz and R. G. Hall at the USNO, determined the frequency of the NPL Caesium standard with respect to the second of ET. Photographs of the...known UT2 determined from optical observations made at the USNO. This information was used to calibrate the Caesium beam atomic clock at NPL. The

  12. Compact Star Time Scales

    NASA Astrophysics Data System (ADS)

    Swank, J. H.

    1996-12-01

    A major goal of RXTE is to investigate the fastest timing signals from compact stars, especially neutron stars and black holes. Signals have now been found from many (at least nine) low mass X-ray binaries containing neutron stars in the frequency range (100-1200 Hz) expected for the rotation period of the neutron star after being spun up by accretion over a long period. The kilohertz frequency domain for these sources is simpler than the domain of oscillations below about 50 Hz in that a few isolated features can dominate over white noise. However there are three main features to consider (not all present at the same time) and at least two are quasiperiodic with varying widths and frequencies. Several models are pitting their predictions against the behavior of these features, but the bursters, especially, appear to be revealing the neutron stars's spin. It is consistent with our beliefs that no black hole candidate has shown the same complex of signals, although at least one QPO frequency of a few hundred Hz could be expected in black hole candidates by analogy to the 67 Hz observed from GRS 1915+105. The observations also provide critical tests of the interpretions of the lower frequency (5-50 Hz) QPO and the variable noise seen in both low magnetic field neutron stars and black hole candidates. The kilohertz features have not been seen from the accreting pulsars with relatively high magnetic fields, but high luminosity pulsars (such as last year's transient, GRO J1744-28) reveal signatures of the dynamic interaction between the accretion flow, the magnetic field, and perhaps the neutron star surface in addition to their coherent pulsations.

  13. Validation of High-Fidelity CFD/CAA Framework for Launch Vehicle Acoustic Environment Simulation against Scale Model Test Data

    NASA Technical Reports Server (NTRS)

    Liever, Peter A.; West, Jeffrey S.

    2016-01-01

    A hybrid Computational Fluid Dynamics and Computational Aero-Acoustics (CFD/CAA) modeling framework has been developed for launch vehicle liftoff acoustic environment predictions. The framework couples the existing highly-scalable NASA production CFD code, Loci/CHEM, with a high-order accurate discontinuous Galerkin solver developed in the same production framework, Loci/THRUST, to accurately resolve and propagate acoustic physics across the entire launch environment. Time-accurate, Hybrid RANS/LES CFD modeling is applied for predicting the acoustic generation physics at the plume source, and a high-order accurate unstructured discontinuous Galerkin (DG) method is employed to propagate acoustic waves away from the source across large distances using high-order accurate schemes. The DG solver is capable of solving 2nd, 3rd, and 4th order Euler solutions for non-linear, conservative acoustic field propagation. Initial application testing and validation has been carried out against high resolution acoustic data from the Ares Scale Model Acoustic Test (ASMAT) series to evaluate the capabilities and production readiness of the CFD/CAA system to resolve the observed spectrum of acoustic frequency content. This paper presents results from this validation and outlines efforts to mature and improve the computational simulation framework.

  14. Validation of High-Fidelity CFD/CAA Framework for Launch Vehicle Acoustic Environment Simulation against Scale Model Test Data

    NASA Technical Reports Server (NTRS)

    Liever, Peter A.; West, Jeffrey S.; Harris, Robert E.

    2016-01-01

    A hybrid Computational Fluid Dynamics and Computational Aero-Acoustics (CFD/CAA) modeling framework has been developed for launch vehicle liftoff acoustic environment predictions. The framework couples the existing highly-scalable NASA production CFD code, Loci/CHEM, with a high-order accurate Discontinuous Galerkin solver developed in the same production framework, Loci/THRUST, to accurately resolve and propagate acoustic physics across the entire launch environment. Time-accurate, Hybrid RANS/LES CFD modeling is applied for predicting the acoustic generation physics at the plume source, and a high-order accurate unstructured mesh Discontinuous Galerkin (DG) method is employed to propagate acoustic waves away from the source across large distances using high-order accurate schemes. The DG solver is capable of solving 2nd, 3rd, and 4th order Euler solutions for non-linear, conservative acoustic field propagation. Initial application testing and validation has been carried out against high resolution acoustic data from the Ares Scale Model Acoustic Test (ASMAT) series to evaluate the capabilities and production readiness of the CFD/CAA system to resolve the observed spectrum of acoustic frequency content. This paper presents results from this validation and outlines efforts to mature and improve the computational simulation framework.

  15. Acoustic Telemetry Reveals Large-Scale Migration Patterns of Walleye in Lake Huron

    PubMed Central

    Hayden, Todd A.; Holbrook, Christopher M.; Fielder, David G.; Vandergoot, Christopher S.; Bergstedt, Roger A.; Dettmers, John M.; Krueger, Charles C.; Cooke, Steven J.

    2014-01-01

    Fish migration in large freshwater lacustrine systems such as the Laurentian Great Lakes is not well understood. The walleye (Sander vitreus) is an economically and ecologically important native fish species throughout the Great Lakes. In Lake Huron walleye has recently undergone a population expansion as a result of recovery of the primary stock, stemming from changing food web dynamics. During 2011 and 2012, we used acoustic telemetry to document the timing and spatial scale of walleye migration in Lake Huron and Saginaw Bay. Spawning walleye (n = 199) collected from a tributary of Saginaw Bay were implanted with acoustic tags and their migrations were documented using acoustic receivers (n = 140) deployed throughout U.S. nearshore waters of Lake Huron. Three migration pathways were described using multistate mark-recapture models. Models were evaluated using the Akaike Information Criterion. Fish sex did not influence migratory behavior but did affect migration rate and walleye were detected on all acoustic receiver lines. Most (95%) tagged fish migrated downstream from the riverine tagging and release location to Saginaw Bay, and 37% of these fish emigrated from Saginaw Bay into Lake Huron. Remarkably, 8% of walleye that emigrated from Saginaw Bay were detected at the acoustic receiver line located farthest from the release location more than 350 km away. Most (64%) walleye returned to the Saginaw River in 2012, presumably for spawning. Our findings reveal that fish from this stock use virtually the entirety of U.S. nearshore waters of Lake Huron. PMID:25506913

  16. Acoustic telemetry reveals large-scale migration patterns of walleye in Lake Huron

    USGS Publications Warehouse

    Hayden, Todd A.; Holbrook, Christopher; Fielder, David G.; Vandergoot, Christopher S.; Bergstedt, Roger A.; Dettmers, John M.; Krueger, Charles C.; Cooke, Steven J.

    2014-01-01

    Fish migration in large freshwater lacustrine systems such as the Laurentian Great Lakes is not well understood. The walleye (Sander vitreus) is an economically and ecologically important native fish species throughout the Great Lakes. In Lake Huron walleye has recently undergone a population expansion as a result of recovery of the primary stock, stemming from changing food web dynamics. During 2011 and 2012, we used acoustic telemetry to document the timing and spatial scale of walleye migration in Lake Huron and Saginaw Bay. Spawning walleye (n = 199) collected from a tributary of Saginaw Bay were implanted with acoustic tags and their migrations were documented using acoustic receivers (n = 140) deployed throughout U.S. nearshore waters of Lake Huron. Three migration pathways were described using multistate mark-recapture models. Models were evaluated using the Akaike Information Criterion. Fish sex did not influence migratory behavior but did affect migration rate and walleye were detected on all acoustic receiver lines. Most (95%) tagged fish migrated downstream from the riverine tagging and release location to Saginaw Bay, and 37% of these fish emigrated from Saginaw Bay into Lake Huron. Remarkably, 8% of walleye that emigrated from Saginaw Bay were detected at the acoustic receiver line located farthest from the release location more than 350 km away. Most (64%) walleye returned to the Saginaw River in 2012, presumably for spawning. Our findings reveal that fish from this stock use virtually the entirety of U.S. nearshore waters of Lake Huron.

  17. Theoretical study of time-dependent, ultrasound-induced acoustic streaming in microchannels.

    PubMed

    Muller, Peter Barkholt; Bruus, Henrik

    2015-12-01

    Based on first- and second-order perturbation theory, we present a numerical study of the temporal buildup and decay of unsteady acoustic fields and acoustic streaming flows actuated by vibrating walls in the transverse cross-sectional plane of a long straight microchannel under adiabatic conditions and assuming temperature-independent material parameters. The unsteady streaming flow is obtained by averaging the time-dependent velocity field over one oscillation period, and as time increases, it is shown to converge towards the well-known steady time-averaged solution calculated in the frequency domain. Scaling analysis reveals that the acoustic resonance builds up much faster than the acoustic streaming, implying that the radiation force may dominate over the drag force from streaming even for small particles. However, our numerical time-dependent analysis indicates that pulsed actuation does not reduce streaming significantly due to its slow decay. Our analysis also shows that for an acoustic resonance with a quality factor Q, the amplitude of the oscillating second-order velocity component is Q times larger than the usual second-order steady time-averaged velocity component. Consequently, the well-known criterion v(1)≪c(s) for the validity of the perturbation expansion is replaced by the more restrictive criterion v(1)≪c(s)/Q. Our numerical model is available as supplemental material in the form of comsol model files and matlab scripts.

  18. Nonlinear effects of dark energy clustering beyond the acoustic scales

    SciTech Connect

    Anselmi, Stefano; Sefusatti, Emiliano E-mail: dlopez_n@ictp.it

    2014-07-01

    We extend the resummation method of Anselmi and Pietroni (2012) to compute the total density power spectrum in models of quintessence characterized by a vanishing speed of sound. For standard ΛCDM cosmologies, this resummation scheme allows predictions with an accuracy at the few percent level beyond the range of scales where acoustic oscillations are present, therefore comparable to other, common numerical tools. In addition, our theoretical approach indicates an approximate but valuable and simple relation between the power spectra for standard quintessence models and models where scalar field perturbations appear at all scales. This, in turn, provides an educated guess for the prediction of nonlinear growth in models with generic speed of sound, particularly valuable since no numerical results are yet available.

  19. An invisible acoustic sensor based on parity-time symmetry

    NASA Astrophysics Data System (ADS)

    Fleury, Romain; Sounas, Dimitrios; Alù, Andrea

    2015-01-01

    Sensing an incoming signal is typically associated with absorbing a portion of its energy, inherently perturbing the measurement and creating reflections and shadows. Here, in contrast, we demonstrate a non-invasive, shadow-free, invisible sensor for airborne sound waves at audible frequencies, which fully absorbs the impinging signal, without at the same time perturbing its own measurement or creating a shadow. This unique sensing device is based on the unusual scattering properties of a parity-time (PT) symmetric metamaterial device formed by a pair of electro-acoustic resonators loaded with suitably tailored non-Foster electrical circuits, constituting the acoustic equivalent of a coherent perfect absorber coupled to a coherent laser. Beyond the specific application to non-invasive sensing, our work broadly demonstrates the unique relevance of PT-symmetric metamaterials for acoustics, loss compensation and extraordinary wave manipulation.

  20. An invisible acoustic sensor based on parity-time symmetry.

    PubMed

    Fleury, Romain; Sounas, Dimitrios; Alù, Andrea

    2015-01-06

    Sensing an incoming signal is typically associated with absorbing a portion of its energy, inherently perturbing the measurement and creating reflections and shadows. Here, in contrast, we demonstrate a non-invasive, shadow-free, invisible sensor for airborne sound waves at audible frequencies, which fully absorbs the impinging signal, without at the same time perturbing its own measurement or creating a shadow. This unique sensing device is based on the unusual scattering properties of a parity-time (PT) symmetric metamaterial device formed by a pair of electro-acoustic resonators loaded with suitably tailored non-Foster electrical circuits, constituting the acoustic equivalent of a coherent perfect absorber coupled to a coherent laser. Beyond the specific application to non-invasive sensing, our work broadly demonstrates the unique relevance of PT-symmetric metamaterials for acoustics, loss compensation and extraordinary wave manipulation.

  1. Linear and Nonlinear Time Reverse Acoustics in Geomaterials

    NASA Astrophysics Data System (ADS)

    Sutin, A.; Johnson, P. A.; Tencate, J.

    2004-12-01

    Linear and Nonlinear Time Reverse Acoustics in Geomaterials P. A. Johnson, A.Sutin and J. TenCate Time Reversal Acoustics (TRA) is one of the most interesting topics to have emerged in modern acoustics in the last 40 years. Much of the seminal research in this area has been carried out by the group at the Laboratoire Ondes et Acoustique at the University of Paris 7, who have demonstrated the ability and robustness of TRA (using Time Reversal Mirrors) to provide spatial control and focusing of an ultrasonic beam (e.g. Fink, 1999). The ability to obtain highly focused signals with TRA has numerous applications, including lithotripsy, ultrasonic brain surgery, nondestructive evaluation and underwater acoustic communication. Notably, the study of time reversal in solids and in the earth is still relatively new. The problem is fundamentally different from the purely acoustic one due to the excitation and propagation of both compressional (bulk) and shear waves as well as the scattering and potentially high dissipation of the medium. We conducted series of TRA experiments in different solids using direct-coupled transducers on solids in tandem with a large bandwidth laser vibrometer detector. A typical time reversal experiment was carried out using the following steps (Sutin et al. 2004a). Laboratory experiments were conducted in different geomaterials of different shapes and sizes, including Carrera marble, granite and Berea sandstone. We observed that, in spite of potentially huge numbers of wave conversions (e.g., compressional to shear, shear to compressional, compressional/shear to surface waves, etc.) for each reflection at each free surface, time reversal still provides significant spatial and temporal focusing in these different geophysical materials. The typical size of the focal area is approximately equivalent to the shear wavelength and the focal area, but becomes larger with increasing wave attenuation (Sutin et al. 2004a; Delsanto et al., 2003)). The TR

  2. Acoustically trapped colloidal crystals that are reconfigurable in real time.

    PubMed

    Caleap, Mihai; Drinkwater, Bruce W

    2014-04-29

    Photonic and phononic crystals are metamaterials with repeating unit cells that result in internal resonances leading to a range of wave guiding and filtering properties and are opening up new applications such as hyperlenses and superabsorbers. Here we show the first, to our knowledge, 3D colloidal phononic crystal that is reconfigurable in real time and demonstrate its ability to rapidly alter its frequency filtering characteristics. Our reconfigurable material is assembled from microspheres in aqueous solution, trapped with acoustic radiation forces. The acoustic radiation force is governed by an energy landscape, determined by an applied high-amplitude acoustic standing wave field, in which particles move swiftly to energy minima. This creates a colloidal crystal of several milliliters in volume with spheres arranged in an orthorhombic lattice in which the acoustic wavelength is used to control the lattice spacing. Transmission acoustic spectroscopy shows that the new colloidal crystal behaves as a phononic metamaterial and exhibits clear band-pass and band-stop frequencies which are adjusted in real time.

  3. Classical chaos and the sensitivity of the acoustic field to small-scale ocean structure

    NASA Astrophysics Data System (ADS)

    Palmer, D. R.; Georges, T. M.; Jones, R. M.

    1991-04-01

    Ray theory is usually the basis of data inversion schemes for acoustic remote sensing of the ocean. Chaotic ray paths are expected to be present whenever the ocean environment possesses small-scale, range-dependent structure. We are studying the implications of their presence for data inversion schemes. Using numerical simulations we consider ray-path characteristics for acoustic remote sensing of the Florida Current. We find small-scale bathymetric structure results in chaotic ray paths and an exponential proliferation of eigenrays. As a result, for each feature in the time-of-arrival pattern, there is associated not a single eigenray but a group, thereby limiting the spatial resolution of a remote sensing system.

  4. Shaping and timing gradient pulses to reduce MRI acoustic noise.

    PubMed

    Segbers, Marcel; Rizzo Sierra, Carlos V; Duifhuis, Hendrikus; Hoogduin, Johannes M

    2010-08-01

    A method to reduce the acoustic noise generated by gradient systems in MRI has been recently proposed; such a method is based on the linear response theory. Since the physical cause of MRI acoustic noise is the time derivative of the gradient current, a common trapezoid current shape produces an acoustic gradient coil response mainly during the rising and falling edge. In the falling edge, the coil acoustic response presents a 180 degrees phase difference compared to the rising edge. Therefore, by varying the width of the trapezoid and keeping the ramps constant, it is possible to suppress one selected frequency and its higher harmonics. This value is matched to one of the prominent resonance frequencies of the gradient coil system. The idea of cancelling a single frequency is extended to a second frequency, using two successive trapezoid-shaped pulses presented at a selected interval. Overall sound pressure level reduction of 6 and 10 dB is found for the two trapezoid shapes and a single pulse shape, respectively. The acoustically optimized pulse shape proposed is additionally tested in a simulated echo planar imaging readout train, obtaining a sound pressure level reduction of 12 dB for the best case.

  5. Time-Reversal Acoustics and Maximum-Entropy Imaging

    SciTech Connect

    Berryman, J G

    2001-08-22

    Target location is a common problem in acoustical imaging using either passive or active data inversion. Time-reversal methods in acoustics have the important characteristic that they provide a means of determining the eigenfunctions and eigenvalues of the scattering operator for either of these problems. Each eigenfunction may often be approximately associated with an individual scatterer. The resulting decoupling of the scattered field from a collection of targets is a very useful aid to localizing the targets, and suggests a number of imaging and localization algorithms. Two of these are linear subspace methods and maximum-entropy imaging.

  6. Acoustic measurements of a full-scale coaxial helicopter

    NASA Technical Reports Server (NTRS)

    Mosher, M.; Peterson, R. L.

    1983-01-01

    Acoustic data were obtained during a full-scale test of the XH-59A Advancing Blade Concept (ABC) Technology Demonstrator in the NASA Ames 40- by 80-Foot Wind Tunnel. The XH-59A is a research helicopter with two coaxial rotors and hingeless blades. Performance, vibration, noise at various forward speeds, rotor lift coefficients, and rotor shaft angles of attack were investigated. In general, the noise level is shown to increase with rotor lift coefficient except under certain operating conditions where it is increased by significant impulsive blade/vortex interactions. The impulsivity appears to depend upon how the lift is distributed between the two rotors. The noise levels measured are shown to be slightly higher than on a modern conventional rotor tested in the same facility.

  7. Space Launch System Scale Model Acoustic Test Ignition Overpressure Testing

    NASA Technical Reports Server (NTRS)

    Nance, Donald K.; Liever, Peter A.

    2015-01-01

    The overpressure phenomenon is a transient fluid dynamic event occurring during rocket propulsion system ignition. This phenomenon results from fluid compression of the accelerating plume gas, subsequent rarefaction, and subsequent propagation from the exhaust trench and duct holes. The high-amplitude unsteady fluid-dynamic perturbations can adversely affect the vehicle and surrounding structure. Commonly known as ignition overpressure (IOP), this is an important design-to environment for the Space Launch System (SLS) that NASA is currently developing. Subscale testing is useful in validating and verifying the IOP environment. This was one of the objectives of the Scale Model Acoustic Test (SMAT), conducted at Marshall Space Flight Center (MSFC). The test data quantifies the effectiveness of the SLS IOP suppression system and improves the analytical models used to predict the SLS IOP environments. The reduction and analysis of the data gathered during the SMAT IOP test series requires identification and characterization of multiple dynamic events and scaling of the event waveforms to provide the most accurate comparisons to determine the effectiveness of the IOP suppression systems. The identification and characterization of the overpressure events, the waveform scaling, the computation of the IOP suppression system knockdown factors, and preliminary comparisons to the analytical models are discussed.

  8. Space Launch System Scale Model Acoustic Test Ignition Overpressure Testing

    NASA Technical Reports Server (NTRS)

    Nance, Donald; Liever, Peter; Nielsen, Tanner

    2015-01-01

    The overpressure phenomenon is a transient fluid dynamic event occurring during rocket propulsion system ignition. This phenomenon results from fluid compression of the accelerating plume gas, subsequent rarefaction, and subsequent propagation from the exhaust trench and duct holes. The high-amplitude unsteady fluid-dynamic perturbations can adversely affect the vehicle and surrounding structure. Commonly known as ignition overpressure (IOP), this is an important design-to environment for the Space Launch System (SLS) that NASA is currently developing. Subscale testing is useful in validating and verifying the IOP environment. This was one of the objectives of the Scale Model Acoustic Test, conducted at Marshall Space Flight Center. The test data quantifies the effectiveness of the SLS IOP suppression system and improves the analytical models used to predict the SLS IOP environments. The reduction and analysis of the data gathered during the SMAT IOP test series requires identification and characterization of multiple dynamic events and scaling of the event waveforms to provide the most accurate comparisons to determine the effectiveness of the IOP suppression systems. The identification and characterization of the overpressure events, the waveform scaling, the computation of the IOP suppression system knockdown factors, and preliminary comparisons to the analytical models are discussed.

  9. Acoustic streaming jets: A scaling and dimensional analysis

    SciTech Connect

    Botton, V. Henry, D.; Millet, S.; Ben-Hadid, H.; Garandet, J. P.

    2015-10-28

    We present our work on acoustic streaming free jets driven by ultrasonic beams in liquids. These jets are steady flows generated far from walls by progressive acoustic waves. As can be seen on figure 1, our set-up, denominated AStrID for Acoustic Streaming Investigation Device, is made of a water tank in which a 29 mm plane source emits continuous ultrasonic waves at typically 2 MHz. Our approach combines an experimental characterization of both the acoustic pressure field (hydrophone) and the obtained acoustic streaming velocity field (PIV visualization) on one hand, with CFD using an incompressible Navier-Stokes solver on the other hand.

  10. Acoustic streaming jets: A scaling and dimensional analysis

    NASA Astrophysics Data System (ADS)

    Botton, V.; Moudjed, B.; Henry, D.; Millet, S.; Ben-Hadid, H.; Garandet, J. P.

    2015-10-01

    We present our work on acoustic streaming free jets driven by ultrasonic beams in liquids. These jets are steady flows generated far from walls by progressive acoustic waves. As can be seen on figure 1, our set-up, denominated AStrID for Acoustic Streaming Investigation Device, is made of a water tank in which a 29 mm plane source emits continuous ultrasonic waves at typically 2 MHz. Our approach combines an experimental characterization of both the acoustic pressure field (hydrophone) and the obtained acoustic streaming velocity field (PIV visualization) on one hand, with CFD using an incompressible Navier-Stokes solver on the other hand.

  11. Multi-carrier Communications over Time-varying Acoustic Channels

    NASA Astrophysics Data System (ADS)

    Aval, Yashar M.

    Acoustic communication is an enabling technology for many autonomous undersea systems, such as those used for ocean monitoring, offshore oil and gas industry, aquaculture, or port security. There are three main challenges in achieving reliable high-rate underwater communication: the bandwidth of acoustic channels is extremely limited, the propagation delays are long, and the Doppler distortions are more pronounced than those found in wireless radio channels. In this dissertation we focus on assessing the fundamental limitations of acoustic communication, and designing efficient signal processing methods that cam overcome these limitations. We address the fundamental question of acoustic channel capacity (achievable rate) for single-input-multi-output (SIMO) acoustic channels using a per-path Rician fading model, and focusing on two scenarios: narrowband channels where the channel statistics can be approximated as frequency- independent, and wideband channels where the nominal path loss is frequency-dependent. In each scenario, we compare several candidate power allocation techniques, and show that assigning uniform power across all frequencies for the first scenario, and assigning uniform power across a selected frequency-band for the second scenario, are the best practical choices in most cases, because the long propagation delay renders the feedback information outdated for power allocation based on the estimated channel response. We quantify our results using the channel information extracted form the 2010 Mobile Acoustic Communications Experiment (MACE'10). Next, we focus on achieving reliable high-rate communication over underwater acoustic channels. Specifically, we investigate orthogonal frequency division multiplexing (OFDM) as the state-of-the-art technique for dealing with frequency-selective multipath channels, and propose a class of methods that compensate for the time-variation of the underwater acoustic channel. These methods are based on multiple

  12. Method for distinguishing multiple targets using time-reversal acoustics

    DOEpatents

    Berryman, James G.

    2004-06-29

    A method for distinguishing multiple targets using time-reversal acoustics. Time-reversal acoustics uses an iterative process to determine the optimum signal for locating a strongly reflecting target in a cluttered environment. An acoustic array sends a signal into a medium, and then receives the returned/reflected signal. This returned/reflected signal is then time-reversed and sent back into the medium again, and again, until the signal being sent and received is no longer changing. At that point, the array has isolated the largest eigenvalue/eigenvector combination and has effectively determined the location of a single target in the medium (the one that is most strongly reflecting). After the largest eigenvalue/eigenvector combination has been determined, to determine the location of other targets, instead of sending back the same signals, the method sends back these time reversed signals, but half of them will also be reversed in sign. There are various possibilities for choosing which half to do sign reversal. The most obvious choice is to reverse every other one in a linear array, or as in a checkerboard pattern in 2D. Then, a new send/receive, send-time reversed/receive iteration can proceed. Often, the first iteration in this sequence will be close to the desired signal from a second target. In some cases, orthogonalization procedures must be implemented to assure the returned signals are in fact orthogonal to the first eigenvector found.

  13. Time Reversal Acoustic Communication Using Filtered Multitone Modulation

    PubMed Central

    Sun, Lin; Chen, Baowei; Li, Haisen; Zhou, Tian; Li, Ruo

    2015-01-01

    The multipath spread in underwater acoustic channels is severe and, therefore, when the symbol rate of the time reversal (TR) acoustic communication using single-carrier (SC) modulation is high, the large intersymbol interference (ISI) span caused by multipath reduces the performance of the TR process and needs to be removed using the long adaptive equalizer as the post-processor. In this paper, a TR acoustic communication method using filtered multitone (FMT) modulation is proposed in order to reduce the residual ISI in the processed signal using TR. In the proposed method, FMT modulation is exploited to modulate information symbols onto separate subcarriers with high spectral containment and TR technique, as well as adaptive equalization is adopted at the receiver to suppress ISI and noise. The performance of the proposed method is assessed through simulation and real data from a trial in an experimental pool. The proposed method was compared with the TR acoustic communication using SC modulation with the same spectral efficiency. Results demonstrate that the proposed method can improve the performance of the TR process and reduce the computational complexity of adaptive equalization for post-process. PMID:26393586

  14. Acoustic FMRI noise: linear time-invariant system model.

    PubMed

    Rizzo Sierra, Carlos V; Versluis, Maarten J; Hoogduin, Johannes M; Duifhuis, Hendrikus Diek

    2008-09-01

    Functional magnetic resonance imaging (fMRI) enables sites of brain activation to be localized in human subjects. For auditory system studies, however, the acoustic noise generated by the scanner tends to interfere with the assessments of this activation. Understanding and modeling fMRI acoustic noise is a useful step to its reduction. To study acoustic noise, the MR scanner is modeled as a linear electroacoustical system generating sound pressure signals proportional to the time derivative of the input gradient currents. The transfer function of one MR scanner is determined for two different input specifications: 1) by using the gradient waveform calculated by the scanner software and 2) by using a recording of the gradient current. Up to 4 kHz, the first method is shown as reliable as the second one, and its use is encouraged when direct measurements of gradient currents are not possible. Additionally, the linear order and average damping properties of the gradient coil system are determined by impulse response analysis. Since fMRI is often based on echo planar imaging (EPI) sequences, a useful validation of the transfer function prediction ability can be obtained by calculating the acoustic output for the EPI sequence. We found a predicted sound pressure level (SPL) for the EPI sequence of 104 dB SPL compared to a measured value of 102 dB SPL. As yet, the predicted EPI pressure waveform shows similarity as well as some differences with the directly measured EPI pressure waveform.

  15. Cylindrical acoustical holography applied to full-scale jet noise.

    PubMed

    Wall, Alan T; Gee, Kent L; Neilsen, Tracianne B; Krueger, David W; James, Michael M

    2014-09-01

    Near-field acoustical holography methods are used to predict sound radiation from an engine installed on a high-performance military fighter aircraft. Cylindrical holography techniques are an efficient approach to measure the large and complex sound fields produced by full-scale jets. It is shown that a ground-based, one-dimensional array of microphones can be used in conjunction with a cylindrical wave function field representation to provide a holographic reconstruction of the radiated sound field at low frequencies. In the current work, partial field decomposition methods and numerical extrapolation of data beyond the boundaries of the hologram aperture are required prior to holographic projection. Predicted jet noise source distributions and directionality are shown for four frequencies between 63 and 250 Hz. It is shown that the source distribution narrows and moves upstream, and that radiation directionality shifts toward the forward direction, with increasing frequency. A double-lobe feature of full-scale jet radiation is also demonstrated.

  16. Convergence methods on time scales

    NASA Astrophysics Data System (ADS)

    Turan, Ceylan; Duman, Oktay

    2013-10-01

    In this paper, we introduce the concepts of lacunary statistical convergence and strongly lacunary Cesàro summability of delta measurable functions on time scales and obtain some inclusion results between them. We also display some examples containing discrete and continuous cases.

  17. Measured acoustic characteristics of ducted supersonic jets at different model scales

    NASA Technical Reports Server (NTRS)

    Jones, R. R., III; Ahuja, K. K.; Tam, Christopher K. W.; Abdelwahab, M.

    1993-01-01

    A large-scale (about a 25x enlargement) model of the Georgia Tech Research Institute (GTRI) hardware was installed and tested in the Propulsion Systems Laboratory of the NASA Lewis Research Center. Acoustic measurements made in these two facilities are compared and the similarity in acoustic behavior over the scale range under consideration is highlighted. The study provide the acoustic data over a relatively large-scale range which may be used to demonstrate the validity of scaling methods employed in the investigation of this phenomena.

  18. Atomic time scales and pulsars

    NASA Astrophysics Data System (ADS)

    Petit, G.

    2014-12-01

    I review the atomic time scales generated by the BIPM, International Atomic Time TAI and the realization of Terrestrial Time TT(BIPM). TT(BIPM) is shown to be now accurate to within a few 10..16 in relative frequency and the performances of TAI and TT(BIPM) are compared. Millisecond pulsars have a very regular period of rotation and data from several pulsars may be used to realize an ensemble pulsar timescale. It is shown that a pulsar timescale may detect past instabilities in TAI. However TT(BIPM) is much more stable than TAI and should be used as a reference in pulsar analysis. Since the beginning of regular millisecond pulsar observations in the 1980s, primary standards and atomic time have gained one order of magnitude in accuracy every ~ 12 years, and this trend should continue for some time.

  19. Characterization of the Scale Model Acoustic Test Overpressure Environment using Computational Fluid Dynamics

    NASA Technical Reports Server (NTRS)

    Nielsen, Tanner; West, Jeff

    2015-01-01

    The Scale Model Acoustic Test (SMAT) is a 5% scale test of the Space Launch System (SLS), which is currently being designed at Marshall Space Flight Center (MSFC). The purpose of this test is to characterize and understand a variety of acoustic phenomena that occur during the early portions of lift off, one being the overpressure environment that develops shortly after booster ignition. The pressure waves that propagate from the mobile launcher (ML) exhaust hole are defined as the ignition overpressure (IOP), while the portion of the pressure waves that exit the duct or trench are the duct overpressure (DOP). Distinguishing the IOP and DOP in scale model test data has been difficult in past experiences and in early SMAT results, due to the effects of scaling the geometry. The speed of sound of the air and combustion gas constituents is not scaled, and therefore the SMAT pressure waves propagate at approximately the same speed as occurs in full scale. However, the SMAT geometry is twenty times smaller, allowing the pressure waves to move down the exhaust hole, through the trench and duct, and impact the vehicle model much faster than occurs at full scale. The DOP waves impact portions of the vehicle at the same time as the IOP waves, making it difficult to distinguish the different waves and fully understand the data. To better understand the SMAT data, a computational fluid dynamics (CFD) analysis was performed with a fictitious geometry that isolates the IOP and DOP. The upper and lower portions of the domain were segregated to accomplish the isolation in such a way that the flow physics were not significantly altered. The Loci/CHEM CFD software program was used to perform this analysis.

  20. Accessing the exceptional points of parity-time symmetric acoustics

    PubMed Central

    Shi, Chengzhi; Dubois, Marc; Chen, Yun; Cheng, Lei; Ramezani, Hamidreza; Wang, Yuan; Zhang, Xiang

    2016-01-01

    Parity-time (PT) symmetric systems experience phase transition between PT exact and broken phases at exceptional point. These PT phase transitions contribute significantly to the design of single mode lasers, coherent perfect absorbers, isolators, and diodes. However, such exceptional points are extremely difficult to access in practice because of the dispersive behaviour of most loss and gain materials required in PT symmetric systems. Here we introduce a method to systematically tame these exceptional points and control PT phases. Our experimental demonstration hinges on an active acoustic element that realizes a complex-valued potential and simultaneously controls the multiple interference in the structure. The manipulation of exceptional points offers new routes to broaden applications for PT symmetric physics in acoustics, optics, microwaves and electronics, which are essential for sensing, communication and imaging. PMID:27025443

  1. Acoustic modal analysis of a full-scale annular combustor

    NASA Technical Reports Server (NTRS)

    Karchmer, A. M.

    1982-01-01

    An acoustic modal decomposition of the measured pressure field in a full scale annular combustor installed in a ducted test rig is described. The modal analysis, utilizing a least squares optimization routine, is facilitated by the assumption of randomly occurring pressure disturbances which generate equal amplitude clockwise and counter-clockwise pressure waves, and the assumption of statistical independence between modes. These assumptions are fully justified by the measured cross spectral phases between the various measurement points. The resultant modal decomposition indicates that higher order modes compose the dominant portion of the combustor pressure spectrum in the range of frequencies of interest in core noise studies. A second major finding is that, over the frequency range of interest, each individual mode which is present exists in virtual isolation over significant portions of the spectrum. Finally, a comparison between the present results and a limited amount of data obtained in an operating turbofan engine with the same combustor is made. The comparison is sufficiently favorable to warrant the conclusion that the structure of the combustor pressure field is preserved between the component facility and the engine.

  2. Time-instant sampling based encoding of time-varying acoustic spectrum

    NASA Astrophysics Data System (ADS)

    Sharma, Neeraj Kumar

    2015-12-01

    The inner ear has been shown to characterize an acoustic stimuli by transducing fluid motion in the inner ear to mechanical bending of stereocilia on the inner hair cells (IHCs). The excitation motion/energy transferred to an IHC is dependent on the frequency spectrum of the acoustic stimuli, and the spatial location of the IHC along the length of the basilar membrane (BM). Subsequently, the afferent auditory nerve fiber (ANF) bundle samples the encoded waveform in the IHCs by synapsing with them. In this work we focus on sampling of information by afferent ANFs from the IHCs, and show computationally that sampling at specific time instants is sufficient for decoding of time-varying acoustic spectrum embedded in the acoustic stimuli. The approach is based on sampling the signal at its zero-crossings and higher-order derivative zero-crossings. We show results of the approach on time-varying acoustic spectrum estimation from cricket call signal recording. The framework gives a time-domain and non-spatial processing perspective to auditory signal processing. The approach works on the full band signal, and is devoid of modeling any bandpass filtering mimicking the BM action. Instead, we motivate the approach from the perspective of event-triggered sampling by afferent ANFs on the stimuli encoded in the IHCs. Though the approach gives acoustic spectrum estimation but it is shallow on its complete understanding for plausible bio-mechanical replication with current mammalian auditory mechanics insights.

  3. Full-circular surface acoustic wave excitation for high resolution acoustic microscopy using spherical lens and time gate technology.

    PubMed

    Ishikawa, I; Katakura, K; Ogura, Y

    1999-01-01

    With a fixed gate width under the condition where the focus of an acoustic lens was set inside the sample, we varied signal taking-in time. Discrimination was made between differences in time required for an ultrasonic signal reflected from the sample to reach the acoustic lens. This process also enabled three types of images to be obtained separately: the surface reflection wave image, a combination of images based on the interference of the surface reflection wave with surface acoustic waves, and the surface acoustic wave image. Thus it was presumed that this process also would reveal the causes of image contrast and allow an easy interpretation of images. Furthermore, the image resolution was improved, because the surface acoustic wave image was drawn by an ultrasonic beam produced by full-circular surface acoustic wave excitation propagating toward the center converging concentrically; the theoretical resolution was 0.4 times the value of the surface acoustic wave wavelength lambda(R) and independent of the defocus value of the acoustic lens. Several kinds of samples were observed with this method. The results showed that the new method permitted observation of the internal structures of samples while offering new knowledge through the data reflecting the ultrasonic wave damping and scatter drawn on the display.

  4. Time Scales in Particulate Systems

    NASA Astrophysics Data System (ADS)

    Zhang, Duan

    2013-06-01

    While there are many interests of studying interactions of individual particles, macroscopic collective behavior of particles are our main interest in many practical applications. In this talk, I will give a brief overview of the multiscale methods connecting the physics at individual particles to macroscopic quantities and averaged equations. The emphasis will be on dense dissipative particulate systems, such as powders. Unlike conservative particle systems, such as molecular systems, in a dissipative particle system the concept of thermodynamic equilibrium is not very useful unless in very special cases, because the only true thermodynamically equilibrium state in these systems is the state in which nothing moves. Other than idealized simple systems, mesoscale structures are common and important in many practical systems, especially in dissipative systems. Spatial correlations of these mesoscale structures, such as force chains in dense granular system, particle clusters and streamers in fluidized beds have received some recent attentions, partly because they can be visualized. This talk will emphasize the effects of time correlations related to the mesoscale structures. To consider time correlations and history information of the system, I will introduce the mathematical foundation of the Liouville equation, its applicability and limitations. I will derive the generalized Liouville equations for particulate systems with and without interstitial fluids, and then use them to study averaged transport equations and related closures. Interactions among the time scale of particle interactions, the time scale of the mesocale structures, and the time scale of the physical problem as represented by strain rate will be discussed. The effect of these interactions on the closure relations will be illustrated. I will also discuss possible numerical methods of solving the averaged equations, and multiscale numerical algorithms bridging the particle level calculations to

  5. Symmetry analysis for nonlinear time reversal methods applied to nonlinear acoustic imaging

    NASA Astrophysics Data System (ADS)

    Dos Santos, Serge; Chaline, Jennifer

    2015-10-01

    Using symmetry invariance, nonlinear Time Reversal (TR) and reciprocity properties, the classical NEWS methods are supplemented and improved by new excitations having the intrinsic property of enlarging frequency analysis bandwidth and time domain scales, with now both medical acoustics and electromagnetic applications. The analysis of invariant quantities is a well-known tool which is often used in nonlinear acoustics in order to simplify complex equations. Based on a fundamental physical principle known as symmetry analysis, this approach consists in finding judicious variables, intrinsically scale dependant, and able to describe all stages of behaviour on the same theoretical foundation. Based on previously published results within the nonlinear acoustic areas, some practical implementation will be proposed as a new way to define TR-NEWS based methods applied to NDT and medical bubble based non-destructive imaging. This paper tends to show how symmetry analysis can help us to define new methodologies and new experimental set-up involving modern signal processing tools. Some example of practical realizations will be proposed in the context of biomedical non-destructive imaging using Ultrasound Contrast Agents (ACUs) where symmetry and invariance properties allow us to define a microscopic scale-invariant experimental set-up describing intrinsic symmetries of the microscopic complex system.

  6. Development of an Acoustic Signal Analysis Tool “Auto-F” Based on the Temperament Scale

    NASA Astrophysics Data System (ADS)

    Modegi, Toshio

    The MIDI interface is originally designed for electronic musical instruments but we consider this music-note based coding concept can be extended for general acoustic signal description. We proposed applying the MIDI technology to coding of bio-medical auscultation sound signals such as heart sounds for retrieving medical records and performing telemedicine. Then we have tried to extend our encoding targets including vocal sounds, natural sounds and electronic bio-signals such as ECG, using Generalized Harmonic Analysis method. Currently, we are trying to separate vocal sounds included in popular songs and encode both vocal sounds and background instrumental sounds into separate MIDI channels. And also, we are trying to extract articulation parameters such as MIDI pitch-bend parameters in order to reproduce natural acoustic sounds using a GM-standard MIDI tone generator. In this paper, we present an overall algorithm of our developed acoustic signal analysis tool, based on those research works, which can analyze given time-based signals on the musical temperament scale. The prominent feature of this tool is producing high-precision MIDI codes, which reproduce the similar signals as the given source signal using a GM-standard MIDI tone generator, and also providing analyzed texts in the XML format.

  7. Shelf-Scale Mapping of Fish Distribution Using Active and Passive Acoustics

    NASA Astrophysics Data System (ADS)

    Wall, Carrie C.

    Fish sound production has been associated with courtship and spawning behavior. Acoustic recordings of fish sounds can be used to identify distribution and behavior. Passive acoustic monitoring (PAM) can record large amounts of acoustic data in a specific area for days to years. These data can be collected in remote locations under potentially unsafe seas throughout a 24-hour period providing datasets unattainable using observer-based methods. However, the instruments must withstand the caustic ocean environment and be retrieved to obtain the recorded data. This can prove difficult due to the risk of PAMs being lost, stolen or damaged, especially in highly active areas. In addition, point-source sound recordings are only one aspect of fish biogeography. Passive acoustic platforms that produce low self-generated noise, have high retrieval rates, and are equipped with a suite of environmental sensors are needed to relate patterns in fish sound production to concurrently collected oceanographic conditions on large, synoptic scales. The association of sound with reproduction further invokes the need for such non-invasive, near-real time datasets that can be used to enhance current management methods limited by survey bias, inaccurate fisher reports, and extensive delays between fisheries data collection and population assessment. Red grouper (Epinephelus morio) exhibit the distinctive behavior of digging holes and producing a unique sound during courtship. These behaviors can be used to identify red grouper distribution and potential spawning habitat over large spatial scales. The goal of this research was to provide a greater understanding of the temporal and spatial distribution of red grouper sound production and holes on the central West Florida Shelf (WFS) using active sonar and passive acoustic recorders. The technology demonstrated here establishes the necessary methods to map shelf-scale fish sound production. The results of this work could aid resource

  8. Drive Rig Mufflers for Model Scale Engine Acoustic Testing

    NASA Technical Reports Server (NTRS)

    Stephens, David

    2010-01-01

    Testing of air breathing propulsion systems in the 9x15 foot wind tunnel at NASA Glenn Research Center depends on compressed air turbines for power. The drive rig turbines exhaust directly to the wind tunnel test section, and have been found to produce significant unwanted noise that reduces the quality of the acoustic measurements of the model being tested. In order to mitigate this acoustic contamination, a muffler can be attached downstream of the drive rig turbine. The modern engine designs currently being tested produce much less noise than traditional engines, and consequently a lower noise floor is required of the facility. An acoustic test of a muffler designed to mitigate this extraneous noise is presented, and a noise reduction of 8 dB between 700 Hz and 20 kHz was documented, significantly improving the quality of acoustic measurements in the facility.

  9. On measuring the absolute scale of baryon acoustic oscillations

    NASA Astrophysics Data System (ADS)

    Sutherland, Will

    2012-10-01

    The baryon acoustic oscillation (BAO) feature in the distribution of galaxies provides a fundamental standard ruler which is widely used to constrain cosmological parameters. In most analyses, the comoving length of the ruler is inferred from a combination of cosmic microwave background (CMB) observations and theory. However, this inferred length may be biased by various non-standard effects in early universe physics; this can lead to biased inferences of cosmological parameters such as H0, Ωm and w, so it would be valuable to measure the absolute BAO length by combining a galaxy redshift survey and a suitable direct low-z distance measurement. One obstacle is that low-redshift BAO surveys mainly constrain the ratio rS/DV(z), where DV is a dilation scale which is not directly observable by standard candles. Here, we find a new approximation DV(z)≃34DL(43z)(1+43z)-1(1-0.02455 z3+0.0105 z4) which connects DV to the standard luminosity distance DL at a somewhat higher redshift; this is shown to be very accurate (relative error <0.2 per cent) for all Wilkinson Microwave Anisotropy Probe compatible Friedmann models at z < 0.4, with very weak dependence on cosmological parameters H0, Ωm, Ωk, w. This provides a route to measure the absolute BAO length using only observations at z ≲ 0.3, including Type Ia supernovae, and potentially future H0-free physical distance indicators such as gravitational lenses or gravitational wave standard sirens. This would provide a zero-parameter check of the standard cosmology at 103 ≲ z ≲ 105, and can constrain the number of relativistic species Neff with fewer degeneracies than the CMB.

  10. Aerodynamic and acoustic test of a United Technologies model scale rotor at DNW

    NASA Technical Reports Server (NTRS)

    Yu, Yung H.; Liu, Sandy R.; Jordan, Dave E.; Landgrebe, Anton J.; Lorber, Peter F.; Pollack, Michael J.; Martin, Ruth M.

    1990-01-01

    The UTC model scale rotors, the DNW wind tunnel, the AFDD rotary wing test stand, the UTRC and AFDD aerodynamic and acoustic data acquisition systems, and the scope of test matrices are discussed and an introduction to the test results is provided. It is pointed out that a comprehensive aero/acoustic database of several configurations of the UTC scaled model rotor has been created. The data is expected to improve understanding of rotor aerodynamics, acoustics, and dynamics, and lead to enhanced analytical methodology and design capabilities for the next generation of rotorcraft.

  11. High-throughput screening and scale-up of cocrystals using resonant acoustic mixing.

    PubMed

    Nagapudi, Karthik; Umanzor, Evelyn Yanez; Masui, Colin

    2017-02-14

    This paper explores the effectiveness of resonant acoustic mixing RAM for screening and scale up of cocrystals. 16 cocrystal systems were selected as test cases based on previous literature precedent. A 96 well plate set up in conjunction with zirconia beads was used for cocrystal screening using RAM. A success rate of 80% was obtained in the screen for plates containing solvent or solvent plus Zirconia beads. A proof of concept production of hydrated and anhydrous cocrystals of 1:1 Theophylline Citric acid system at a 400mg scale was demonstrated using solvent and bead assisted RAM. Finally the parameters affecting the scale up of 2:1 Theophylline Oxalic acid cocrystals was explored in a systematic fashion using a Design of Experiments DOE approach. The RAM parameters of acceleration and mixing time were optimized using the DOE approach. A quantitative XRPD method was developed to determine the extent of conversion to the cocrystal when using RAM Mixing time of 2h and an acceleration of 60G were determined to be optimal. The optimized parameters were used to demonstrate scale up of 2:1 Theophylline Oxalic acid cocrystals at an 80 gram scale with a net yield of 94%. RAM is thus established as an environmentally friendly mechanochemical technique for both high throughput screening and scaled up production of cocrystals.

  12. Acoustic characteristics of large-scale STOL models at forward speed

    NASA Technical Reports Server (NTRS)

    Falarski, M. D.; Aoyagi, K.; Koenig, D. G.

    1972-01-01

    Wind-tunnel investigations of the acoustic characteristics of the externally blown jet flap (EBF) and augmentor wing STOL concepts are discussed. The large-scale EBF model was equipped with a triple-slotted flap blown by four JT15D turbofan engines with circular, coannular exhaust nozzles. The large-scale augmentor wing model was equipped with an unlined augmentor blown by a slot primary nozzle. The effects of airspeed and angle of attack on the acoustics of the EBF were small. Flap deflection had a greater effect on the acoustics of the augmentor wing than did airspeed. The total sound power was also significantly higher for landing indicating that turning in the augmentor generated acoustic energy. Airspeed produced a small aft shift in acoustic directivity with no significant change in the peak perceived noise levels or sound power levels. Small-scale research of the acoustics for the augmentor wing has shown that by blowing an acoustically treated augmentor with a lobed primary nozzle, the 95-PNdb noise level goal can be achieved or surpassed.

  13. Validation and Simulation of ARES I Scale Model Acoustic Test -1- Pathfinder Development

    NASA Technical Reports Server (NTRS)

    Putnam, G. C.

    2011-01-01

    The Ares I Scale Model Acoustics Test (ASMAT) is a series of live-fire tests of scaled rocket motors meant to simulate the conditions of the Ares I launch configuration. These tests have provided a well documented set of high fidelity measurements useful for validation including data taken over a range of test conditions and containing phenomena like Ignition Over-Pressure and water suppression of acoustics. To take advantage of this data, a digital representation of the ASMAT test setup has been constructed and test firings of the motor have been simulated using the Loci/CHEM computational fluid dynamics software. Within this first of a series of papers, results from ASMAT simulations with the rocket in a held down configuration and without water suppression have then been compared to acoustic data collected from similar live-fire tests to assess the accuracy of the simulations. Detailed evaluations of the mesh features, mesh length scales relative to acoustic signals, Courant-Friedrichs-Lewy numbers, and spatial residual sources have been performed to support this assessment. Results of acoustic comparisons have shown good correlation with the amplitude and temporal shape of pressure features and reasonable spectral accuracy up to approximately 1000 Hz. Major plume and acoustic features have been well captured including the plume shock structure, the igniter pulse transient, and the ignition overpressure. Finally, acoustic propagation patterns illustrated a previously unconsidered issue of tower placement inline with the high intensity overpressure propagation path.

  14. Uncertainty estimation in seismo-acoustic reflection travel time inversion.

    PubMed

    Dettmer, Jan; Dosso, Stan E; Holland, Charles W

    2007-07-01

    This paper develops a nonlinear Bayesian inversion for high-resolution seabed reflection travel time data including rigorous uncertainty estimation and examination of statistical assumptions. Travel time data are picked on seismo-acoustic traces and inverted for a layered sediment sound-velocity model. Particular attention is paid to picking errors which are often biased, correlated, and nonstationary. Non-Toeplitz data covariance matrices are estimated and included in the inversion along with unknown travel time offset (bias) parameters to account for these errors. Simulated experiments show that neglecting error covariances and biases can cause misleading inversion results with unrealistically high confidence. The inversion samples the posterior probability density and provides a solution in terms of one- and two-dimensional marginal probability densities, correlations, and credibility intervals. Statistical assumptions are examined through the data residuals with rigorous statistical tests. The method is applied to shallow-water data collected on the Malta Plateau during the SCARAB98 experiment.

  15. Acoustic fluidization and the scale dependence of impact crater morphology

    NASA Technical Reports Server (NTRS)

    Melosh, H. J.; Gaffney, E. S.

    1983-01-01

    A phenomenological Bingham plastic model has previously been shown to provide an adequate description of the collapse of impact craters. This paper demonstrates that the Bingham parameters may be derived from a model in which acoustic energy generated during excavation fluidizes the rock debris surrounding the crater. Experimental support for the theoretical flow law is presented. Although the Bingham yield stress cannot be computed without detailed knowledge of the initial acoustic field, the Bingham viscosity is derived from a simple argument which shows that it increases as the 3/2 power of crater diameter, consistent with observation. Crater collapse may occur in material with internal dissipation Q as low as 100, comparable to laboratory observations of dissipation in granular materials. Crater collapse thus does not require that the acoustic field be regenerated during flow.

  16. Acoustic fluidization and the scale dependence of impact crater morphology

    NASA Astrophysics Data System (ADS)

    Melosh, H. J.; Gaffney, E. S.

    1983-11-01

    A phenomenological Bingham plastic model has previously been shown to provide an adequate description of the collapse of impact craters. This paper demonstrates that the Bingham parameters may be derived from a model in which acoustic energy generated during excavation fluidizes the rock debris surrounding the crater. Experimental support for the theoretical flow law is presented. Although the Bingham yield stress cannot be computed without detailed knowledge of the initial acoustic field, the Bingham viscosity is derived from a simple argument which shows that it increases as the 3/2 power of crater diameter, consistent with observation. Crater collapse may occur in material with internal dissipation Q as low as 100, comparable to laboratory observations of dissipation in granular materials. Crater collapse thus does not require that the acoustic field be regenerated during flow.

  17. (A new time of flight) Acoustic flow meter using wide band signals and adaptive beamforming techniques

    NASA Astrophysics Data System (ADS)

    Murgan, I.; Ioana, C.; Candel, I.; Anghel, A.; Ballester, J. L.; Reeb, B.; Combes, G.

    2016-11-01

    In this paper we present the result of our research concerning the improvement of acoustic time of flight flow metering for water pipes. Current flow meters are based on the estimation of direct time of flight by matched filtering of the received and emitted signals by acoustic transducers. Currently, narrow band signals are used, as well as a single emitter/receptor transducer configuration. Although simple, this configuration presents a series of limitations such as energy losses due to pipe wall/water interface, pressure/flow transients, sensitivity to flow induced vibrations, acoustic beam deformations and shift due to changes in flow velocity and embedded turbulence in the flow. The errors associated with these limitations reduce the overall robustness of existing flow meters, as well as the measured flow rate range and lower accuracy. In order to overcome these limitations, two major innovations were implemented at the signal processing level. The first one concerns the use of wide band signals that optimise the power transfer throughout the acoustic path and also increase the number of velocity/flow readings per second. Using wide band signals having a high duration-bandwidth product increases the precision in terms of time of flight measurements and, in the same time, improves the system robustness. The second contribution consists in the use of a multiple emitter - multiple receivers configuration (for one path) in order to compensate the emitted acoustic beam shift, compensate the time of flight estimation errors and thus increase the flow meter's robustness in case of undesired effects such as the “flow blow” and transient/rapid flow rate/velocity changes. Using a new signal processing algorithm that take advantage of the controlled wide band content coming from multiple receivers, the new flow meters achieves a higher accuracy in terms of flow velocity over a wider velocity range than existing systems. Tests carried out on real scale experimental

  18. Acoustic Performance of Drive Rig Mufflers for Model Scale Engine Testing

    NASA Technical Reports Server (NTRS)

    Stephens, David, B.

    2013-01-01

    Aircraft engine component testing at the NASA Glenn Research Center (GRC) includes acoustic testing of scale model fans and propellers in the 9- by15-Foot Low Speed Wind Tunnel (LSWT). This testing utilizes air driven turbines to deliver power to the article being studied. These air turbines exhaust directly downstream of the model in the wind tunnel test section and have been found to produce significant unwanted noise that reduces the quality of the acoustic measurements of the engine model being tested. This report describes an acoustic test of a muffler designed to mitigate the extraneous turbine noise. The muffler was found to provide acoustic attenuation of at least 8 dB between 700 Hz and 20 kHz which significantly improves the quality of acoustic measurements in the facility.

  19. Time-Accurate Simulations and Acoustic Analysis of Slat Free-Shear-Layer. Part 2

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R.; Singer, Bart A.; Lockard, David P.

    2002-01-01

    Unsteady computational simulations of a multi-element, high-lift configuration are performed. Emphasis is placed on accurate spatiotemporal resolution of the free shear layer in the slat-cove region. The excessive dissipative effects of the turbulence model, so prevalent in previous simulations, are circumvented by switching off the turbulence-production term in the slat cove region. The justifications and physical arguments for taking such a step are explained in detail. The removal of this excess damping allows the shear layer to amplify large-scale structures, to achieve a proper non-linear saturation state, and to permit vortex merging. The large-scale disturbances are self-excited, and unlike our prior fully turbulent simulations, no external forcing of the shear layer is required. To obtain the farfield acoustics, the Ffowcs Williams and Hawkings equation is evaluated numerically using the simulated time-accurate flow data. The present comparison between the computed and measured farfield acoustic spectra shows much better agreement for the amplitude and frequency content than past calculations. The effect of the angle-of-attack on the slat's flow features radiated acoustic field are also simulated presented.

  20. Acoustic Treatment Design Scaling Methods. Volume 3; Test Plans, Hardware, Results, and Evaluation

    NASA Technical Reports Server (NTRS)

    Yu, J.; Kwan, H. W.; Echternach, D. K.; Kraft, R. E.; Syed, A. A.

    1999-01-01

    The ability to design, build, and test miniaturized acoustic treatment panels on scale-model fan rigs representative of the full-scale engine provides not only a cost-savings, but an opportunity to optimize the treatment by allowing tests of different designs. To be able to use scale model treatment as a full-scale design tool, it is necessary that the designer be able to reliably translate the scale model design and performance to an equivalent full-scale design. The primary objective of the study presented in this volume of the final report was to conduct laboratory tests to evaluate liner acoustic properties and validate advanced treatment impedance models. These laboratory tests include DC flow resistance measurements, normal incidence impedance measurements, DC flow and impedance measurements in the presence of grazing flow, and in-duct liner attenuation as well as modal measurements. Test panels were fabricated at three different scale factors (i.e., full-scale, half-scale, and one-fifth scale) to support laboratory acoustic testing. The panel configurations include single-degree-of-freedom (SDOF) perforated sandwich panels, SDOF linear (wire mesh) liners, and double-degree-of-freedom (DDOF) linear acoustic panels.

  1. A Stochastic Semiclassical Time Front Prediction for Ocean Acoustics

    NASA Astrophysics Data System (ADS)

    Hegewisch, Katherine; Tomsovic, Steven

    2008-05-01

    Low frequency sound propagates in the ocean within a wave guide formed by the confining effects of temperature, salinity and pressure on the sound speed. This wave guide enables long range propagation upwards of 3000 km. Within the wave guide, sound scatters due to range dependent sound speed oscillations from internal waves and gives rise to wave chaos, where most of the classical rays are chaotic. This chaos poses challenges to ray predictions of the range and frequency dependence of properties of the 'time fronts', the acoustic arrivals in depth and time. Though semiclassical theory works well for strongly chaotic systemss, finding the necessary eigenrays for long ranges is unrealistic here. Instead, we utilize semiclassical and perturbation theories ONLY for short ranges and extend these results to long ranges using a previously introduced diffusive theory. We verify the diffusive assumptions and demonstrate the analytic results for these theories for short ranges before arriving at a stochastic prediction.

  2. Target detection and localization in shallow water: an experimental demonstration of the acoustic barrier problem at the laboratory scale.

    PubMed

    Marandet, Christian; Roux, Philippe; Nicolas, Barbara; Mars, Jérôme

    2011-01-01

    This study demonstrates experimentally at the laboratory scale the detection and localization of a wavelength-sized target in a shallow ultrasonic waveguide between two source-receiver arrays at 3 MHz. In the framework of the acoustic barrier problem, at the 1/1000 scale, the waveguide represents a 1.1-km-long, 52-m-deep ocean acoustic channel in the kilohertz frequency range. The two coplanar arrays record in the time-domain the transfer matrix of the waveguide between each pair of source-receiver transducers. Invoking the reciprocity principle, a time-domain double-beamforming algorithm is simultaneously performed on the source and receiver arrays. This array processing projects the multireverberated acoustic echoes into an equivalent set of eigenrays, which are defined by their launch and arrival angles. Comparison is made between the intensity of each eigenray without and with a target for detection in the waveguide. Localization is performed through tomography inversion of the acoustic impedance of the target, using all of the eigenrays extracted from double beamforming. The use of the diffraction-based sensitivity kernel for each eigenray provides both the localization and the signature of the target. Experimental results are shown in the presence of surface waves, and methodological issues are discussed for detection and localization.

  3. Acoustic Survey of a 3/8-Scale Automotive Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Booth, Earl R., Jr.; Romberg, Gary; Hansen, Larry; Lutz, Ron

    1996-01-01

    An acoustic survey that consists of insertion loss and flow noise measurements was conducted at key locations around the circuit of a 3/8-scale automotive acoustic wind tunnel. Descriptions of the test, the instrumentation, and the wind tunnel facility are included in the current report, along with data obtained in the test in the form of 1/3-octave-band insertion loss and narrowband flow noise spectral data.

  4. A Study of Acoustic Reflections in Full-Scale Rotor Low Frequency Noise Measurements Acquired in Wind Tunnels

    NASA Technical Reports Server (NTRS)

    Barbely, Natasha L.; Sim, Ben W.; Kitaplioglu, Cahit; Goulding, Pat, II

    2010-01-01

    Difficulties in obtaining full-scale rotor low frequency noise measurements in wind tunnels are addressed via residual sound reflections due to non-ideal anechoic wall treatments. Examples illustrated with the Boeing-SMART rotor test in the National Full-Scale Aerodynamics Complex (NFAC) 40- by 80-Foot Wind Tunnel facility demonstrated that these reflections introduced distortions in the measured acoustic time histories that are not representative of free-field rotor noise radiation. A simplified reflection analysis, based on the method of images, is used to examine the sound measurement quality in such "less-than-anechoic" environment. Predictions of reflection-adjusted acoustic time histories are qualitatively shown to account for some of the spurious fluctuations observed in wind tunnel noise measurements

  5. Time-distance domain transformation for Acoustic Emission source localization in thin metallic plates.

    PubMed

    Grabowski, Krzysztof; Gawronski, Mateusz; Baran, Ireneusz; Spychalski, Wojciech; Staszewski, Wieslaw J; Uhl, Tadeusz; Kundu, Tribikram; Packo, Pawel

    2016-05-01

    Acoustic Emission used in Non-Destructive Testing is focused on analysis of elastic waves propagating in mechanical structures. Then any information carried by generated acoustic waves, further recorded by a set of transducers, allow to determine integrity of these structures. It is clear that material properties and geometry strongly impacts the result. In this paper a method for Acoustic Emission source localization in thin plates is presented. The approach is based on the Time-Distance Domain Transform, that is a wavenumber-frequency mapping technique for precise event localization. The major advantage of the technique is dispersion compensation through a phase-shifting of investigated waveforms in order to acquire the most accurate output, allowing for source-sensor distance estimation using a single transducer. The accuracy and robustness of the above process are also investigated. This includes the study of Young's modulus value and numerical parameters influence on damage detection. By merging the Time-Distance Domain Transform with an optimal distance selection technique, an identification-localization algorithm is achieved. The method is investigated analytically, numerically and experimentally. The latter involves both laboratory and large scale industrial tests.

  6. Deconvolution of acoustic emissions for source localization using time reverse modeling

    NASA Astrophysics Data System (ADS)

    Kocur, Georg Karl

    2017-01-01

    Impact experiments on small-scale slabs made of concrete and aluminum were carried out. Wave motion radiated from the epicenter of the impact was recorded as voltage signals by resonant piezoelectric transducers. Numerical simulations of the elastic wave propagation are performed to simulate the physical experiments. The Hertz theory of contact is applied to estimate the force impulse, which is subsequently used for the numerical simulation. Displacements at the transducer positions are calculated numerically. A deconvolution function is obtained by comparing the physical (voltage signal) and the numerical (calculated displacement) experiments. Acoustic emission signals due to pencil-lead breaks are recorded, deconvolved and applied for localization using time reverse modeling.

  7. Taming the Exceptional Points of Parity-Time Symmetric Acoustics

    NASA Astrophysics Data System (ADS)

    Dubois, Marc; Shi, Chengzhi; Chen, Yun; Cheng, Lei; Ramezani, Hamidreza; Wang, Yuan; Zhang, Xiang

    Parity-time (PT) symmetric concept and development lead to a wide range of applications including coherent perfect absorbers, single mode lasers, unidirectional cloaking and sensing, and optical isolators. These new applications and devices emerge from the existence of a phase transition in PT symmetric complex-valued potential obtained by balancing gain and loss materials. However, the systematic extension of such devices is adjourned by the key challenge in the management of the complex scattering process within the structure in order to engineer PT phase and exceptional points. Here, based on active acoustic elements, we experimentally demonstrate the simultaneous control of complex-valued potentials and multiple interference inside the structure at any given frequency. This method broadens the scope of applications for PT symmetric devices in many fields including optics, microwaves, electronics, which are crucial for sensing, imaging, cloaking, lasing, absorbing, etc.

  8. Dynamic acoustics for the STAR-100. [computer algorithms for time dependent sound waves in jet

    NASA Technical Reports Server (NTRS)

    Bayliss, A.; Turkel, E.

    1979-01-01

    An algorithm is described to compute time dependent acoustic waves in a jet. The method differs from previous methods in that no harmonic time dependence is assumed, thus permitting the study of nonharmonic acoustical behavior. Large grids are required to resolve the acoustic waves. Since the problem is nonstiff, explicit high order schemes can be used. These have been adapted to the STAR-100 with great efficiencies and permitted the efficient solution of problems which would not be feasible on a scalar machine.

  9. Statistical Modeling of Large-Scale Signal Path Loss in Underwater Acoustic Networks

    PubMed Central

    Llor, Jesús; Malumbres, Manuel Perez

    2013-01-01

    In an underwater acoustic channel, the propagation conditions are known to vary in time, causing the deviation of the received signal strength from the nominal value predicted by a deterministic propagation model. To facilitate a large-scale system design in such conditions (e.g., power allocation), we have developed a statistical propagation model in which the transmission loss is treated as a random variable. By applying repetitive computation to the acoustic field, using ray tracing for a set of varying environmental conditions (surface height, wave activity, small node displacements around nominal locations, etc.), an ensemble of transmission losses is compiled and later used to infer the statistical model parameters. A reasonable agreement is found with log-normal distribution, whose mean obeys a log-distance increases, and whose variance appears to be constant for a certain range of inter-node distances in a given deployment location. The statistical model is deemed useful for higher-level system planning, where simulation is needed to assess the performance of candidate network protocols under various resource allocation policies, i.e., to determine the transmit power and bandwidth allocation necessary to achieve a desired level of performance (connectivity, throughput, reliability, etc.). PMID:23396190

  10. Passive acoustic methods for fine-scale tracking of harbour porpoises in tidal rapids.

    PubMed

    Macaulay, Jamie; Gordon, Jonathan; Gillespie, Douglas; Malinka, Chloë; Northridge, Simon

    2017-02-01

    The growing interest in generating electrical power from tidal currents using tidal turbine generators raises a number of environmental concerns, including the risk that marine mammals might be injured or killed through collision with rotating turbine blades. To understand this risk, information on how marine mammals use tidal rapid habitats and in particular, their underwater movements and dive behaviour is required. Porpoises, which are the most abundant small cetacean at most European tidal sites, are difficult animals to tag, and the limited size of tidal habitats means that any telemetered animal would be likely to spend only a small proportion of time within them. Here, an alternative approach is explored, whereby passive acoustic monitoring (PAM) is used to obtain fine scale geo-referenced tracks of harbour porpoises in tidal rapid areas. Large aperture hydrophone arrays are required to obtain accurate locations of animals from PAM data and automated algorithms are necessary to process the large quantities of acoustic data collected on such systems during a typical survey. Methods to automate localisation, including a method to match porpoise detections on different hydrophones and separate different vocalising animals, and an assessment of the localisation accuracy of the large aperture hydrophone array are presented.

  11. Acoustic emissions (AE) monitoring of large-scale composite bridge components

    NASA Astrophysics Data System (ADS)

    Velazquez, E.; Klein, D. J.; Robinson, M. J.; Kosmatka, J. B.

    2008-03-01

    Acoustic Emissions (AE) has been successfully used with composite structures to both locate and give a measure of damage accumulation. The current experimental study uses AE to monitor large-scale composite modular bridge components. The components consist of a carbon/epoxy beam structure as well as a composite to metallic bonded/bolted joint. The bonded joints consist of double lap aluminum splice plates bonded and bolted to carbon/epoxy laminates representing the tension rail of a beam. The AE system is used to monitor the bridge component during failure loading to assess the failure progression and using time of arrival to give insight into the origins of the failures. Also, a feature in the AE data called Cumulative Acoustic Emission counts (CAE) is used to give an estimate of the severity and rate of damage accumulation. For the bolted/bonded joints, the AE data is used to interpret the source and location of damage that induced failure in the joint. These results are used to investigate the use of bolts in conjunction with the bonded joint. A description of each of the components (beam and joint) is given with AE results. A summary of lessons learned for AE testing of large composite structures as well as insight into failure progression and location is presented.

  12. Imaging of Acoustically Coupled Oscillations Due to Flow Past a Shallow Cavity: Effect of Cavity Length Scale

    SciTech Connect

    P. Oshkai; M. Geveci; D. Rockwell; M. Pollack

    2002-12-12

    Flow-acoustic interactions due to fully turbulent inflow past a shallow axisymmetric cavity mounted in a pipe are investigated using a technique of high-image-density particle image velocimetry in conjunction with unsteady pressure measurements. This imaging leads to patterns of velocity, vorticity, streamline topology, and hydrodynamic contributions to the acoustic power integral. Global instantaneous images, as well as time-averaged images, are evaluated to provide insight into the flow physics during tone generation. Emphasis is on the manner in which the streamwise length scale of the cavity alters the major features of the flow structure. These image-based approaches allow identification of regions of the unsteady shear layer that contribute to the instantaneous hydrodynamic component of the acoustic power, which is necessary to maintain a flow tone. In addition, combined image analysis and pressure measurements allow categorization of the instantaneous flow patterns that are associated with types of time traces and spectra of the fluctuating pressure. In contrast to consideration based solely on pressure spectra, it is demonstrated that locked-on tones may actually exhibit intermittent, non-phase-locked images, apparently due to low damping of the acoustic resonator. Locked-on flow tones (without modulation or intermittency), locked-on flow tones with modulation, and non-locked-on oscillations with short-term, highly coherent fluctuations are defined and represented by selected cases. Depending on which of,these regimes occur, the time-averaged Q (quality)-factor and the dimensionless peak pressure are substantially altered.

  13. Application of acoustic feedback to target detection in a waveguide: experimental demonstration at the ultrasonic scale.

    PubMed

    Roux, Philippe; Marandet, Christian; La Rizza, Patrick; Kuperman, W A

    2011-07-01

    People are familiar with the acoustic feedback phenomenon, which results in a loud sound that is heard when a musician plays an electric instrument directly into a speaker. Acoustic feedback occurs when a source and a receiver are connected both acoustically through the propagation medium and electrically through an amplifier, such that the amplified received signal is continuously re-emitted by the source. The acoustic feedback can be initiated from a continuous sine wave. When the emitter and the receiver are in phase, resonance is obtained, which appears to be highly sensitive to any fluctuation of the propagation medium. Another procedure consists in initiating the acoustic feedback from a continuous loop of ambient noise. It then generates an unstable self-sustained feedback oscillator (SFO) that is tested here as a method for monitoring temperature fluctuations of a shallow-water oceanic environment. The goal of the present study is to reproduce and study the SFO at the laboratory scale in an ultrasonic waveguide. The experimental results demonstrate the potential applications of the SFO for the detection of a target in the framework of the acoustic-barrier problem in shallow-water acoustics.

  14. Control of Thermo-Acoustics Instabilities: The Multi-Scale Extended Kalman Approach

    NASA Technical Reports Server (NTRS)

    Le, Dzu K.; DeLaat, John C.; Chang, Clarence T.

    2003-01-01

    "Multi-Scale Extended Kalman" (MSEK) is a novel model-based control approach recently found to be effective for suppressing combustion instabilities in gas turbines. A control law formulated in this approach for fuel modulation demonstrated steady suppression of a high-frequency combustion instability (less than 500Hz) in a liquid-fuel combustion test rig under engine-realistic conditions. To make-up for severe transport-delays on control effect, the MSEK controller combines a wavelet -like Multi-Scale analysis and an Extended Kalman Observer to predict the thermo-acoustic states of combustion pressure perturbations. The commanded fuel modulation is composed of a damper action based on the predicted states, and a tones suppression action based on the Multi-Scale estimation of thermal excitations and other transient disturbances. The controller performs automatic adjustments of the gain and phase of these actions to minimize the Time-Scale Averaged Variances of the pressures inside the combustion zone and upstream of the injector. The successful demonstration of Active Combustion Control with this MSEK controller completed an important NASA milestone for the current research in advanced combustion technologies.

  15. Acoustic fluidization and the scale dependence of impact crater morphology.

    NASA Astrophysics Data System (ADS)

    Melosh, H. J.; Gaffney, E. S.

    1983-02-01

    A phenomenological Bingham plastic model has previously been shown to provide an adequate description of the collapse of impact craters. This paper demonstrates that the Bingham parameters may be derived from a model in which acoustic energy generated during excavation fluidizes the rock debris surrounding the crater. Experimental support for the theoretical flow law is presented. The Bingham viscosity is derived from a simple argument which shows that it increases as the 3/2 power of crater diameter, consistent with observation. Crater collapse may occur in material with internal dissipation Q as low as 100, comparable to laboratory observations of dissipation in granular materials.

  16. Stability of Rasch Scales over Time

    ERIC Educational Resources Information Center

    Taylor, Catherine S.; Lee, Yoonsun

    2010-01-01

    Item response theory (IRT) methods are generally used to create score scales for large-scale tests. Research has shown that IRT scales are stable across groups and over time. Most studies have focused on items that are dichotomously scored. Now Rasch and other IRT models are used to create scales for tests that include polytomously scored items.…

  17. Acoustical Direction Finding with Time-Modulated Arrays.

    PubMed

    Clark, Ben; Flint, James A

    2016-12-11

    Time-Modulated Linear Arrays (TMLAs) offer useful efficiency savings over conventional phased arrays when applied in parameter estimation applications. The present paper considers the application of TMLAs to acoustic systems and proposes an algorithm for efficiently deriving the arrival angle of a signal. The proposed technique is applied in the frequency domain, where the signal and harmonic content is captured. Using a weighted average method on harmonic amplitudes and their respective main beam angles, it is possible to determine an estimate for the signal's direction of arrival. The method is demonstrated and evaluated using results from both numerical and practical implementations and performance data is provided. The use of Micro-Electromechanical Systems (MEMS) sensors allows time-modulation techniques to be applied at ultrasonic frequencies. Theoretical predictions for an array of five isotropic elements with half-wavelength spacing and 1000 data samples suggest an accuracy of ± 1 ∘ within an angular range of approximately ± 50 ∘ . In experiments of a 40 kHz five-element microphone array, a Direction of Arrival (DoA) estimation within ± 2 . 5 ∘ of the target signal is readily achieved inside a ± 45 ∘ range using a single switched input stage and a simple hardware setup.

  18. Acoustical Direction Finding with Time-Modulated Arrays

    PubMed Central

    Clark, Ben; Flint, James A.

    2016-01-01

    Time-Modulated Linear Arrays (TMLAs) offer useful efficiency savings over conventional phased arrays when applied in parameter estimation applications. The present paper considers the application of TMLAs to acoustic systems and proposes an algorithm for efficiently deriving the arrival angle of a signal. The proposed technique is applied in the frequency domain, where the signal and harmonic content is captured. Using a weighted average method on harmonic amplitudes and their respective main beam angles, it is possible to determine an estimate for the signal’s direction of arrival. The method is demonstrated and evaluated using results from both numerical and practical implementations and performance data is provided. The use of Micro-Electromechanical Systems (MEMS) sensors allows time-modulation techniques to be applied at ultrasonic frequencies. Theoretical predictions for an array of five isotropic elements with half-wavelength spacing and 1000 data samples suggest an accuracy of ±1∘ within an angular range of approximately ±50∘. In experiments of a 40 kHz five-element microphone array, a Direction of Arrival (DoA) estimation within ±2.5∘ of the target signal is readily achieved inside a ±45∘ range using a single switched input stage and a simple hardware setup. PMID:27973432

  19. Real-time vehicle noise cancellation techniques for gunshot acoustics

    NASA Astrophysics Data System (ADS)

    Ramos, Antonio L. L.; Holm, Sverre; Gudvangen, Sigmund; Otterlei, Ragnvald

    2012-06-01

    Acoustical sniper positioning systems rely on the detection and direction-of-arrival (DOA) estimation of the shockwave and the muzzle blast in order to provide an estimate of a potential snipers location. Field tests have shown that detecting and estimating the DOA of the muzzle blast is a rather difficult task in the presence of background noise sources, e.g., vehicle noise, especially in long range detection and absorbing terrains. In our previous work presented in the 2011 edition of this conference we highlight the importance of improving the SNR of the gunshot signals prior to the detection and recognition stages, aiming at lowering the false alarm and miss-detection rates and, thereby, increasing the reliability of the system. This paper reports on real-time noise cancellation techniques, like Spectral Subtraction and Adaptive Filtering, applied to gunshot signals. Our model assumes the background noise as being short-time stationary and uncorrelated to the impulsive gunshot signals. In practice, relatively long periods without signal occur and can be used to estimate the noise spectrum and its first and second order statistics as required in the spectral subtraction and adaptive filtering techniques, respectively. The results presented in this work are supported with extensive simulations based on real data.

  20. Use of large-scale acoustic monitoring to assess anthropogenic pressures on Orthoptera communities.

    PubMed

    Penone, Caterina; Le Viol, Isabelle; Pellissier, Vincent; Julien, Jean-François; Bas, Yves; Kerbiriou, Christian

    2013-10-01

    Biodiversity monitoring at large spatial and temporal scales is greatly needed in the context of global changes. Although insects are a species-rich group and are important for ecosystem functioning, they have been largely neglected in conservation studies and policies, mainly due to technical and methodological constraints. Sound detection, a nondestructive method, is easily applied within a citizen-science framework and could be an interesting solution for insect monitoring. However, it has not yet been tested at a large scale. We assessed the value of a citizen-science program in which Orthoptera species (Tettigoniidae) were monitored acoustically along roads. We used Bayesian model-averaging analyses to test whether we could detect widely known patterns of anthropogenic effects on insects, such as the negative effects of urbanization or intensive agriculture on Orthoptera populations and communities. We also examined site-abundance correlations between years and estimated the biases in species detection to evaluate and improve the protocol. Urbanization and intensive agricultural landscapes negatively affected Orthoptera species richness, diversity, and abundance. This finding is consistent with results of previous studies of Orthoptera, vertebrates, carabids, and butterflies. The average mass of communities decreased as urbanization increased. The dispersal ability of communities increased as the percentage of agricultural land and, to a lesser extent, urban area increased. Despite changes in abundances over time, we found significant correlations between yearly abundances. We identified biases linked to the protocol (e.g., car speed or temperature) that can be accounted for ease in analyses. We argue that acoustic monitoring of Orthoptera along roads offers several advantages for assessing Orthoptera biodiversity at large spatial and temporal extents, particularly in a citizen science framework.

  1. Acoustics

    NASA Technical Reports Server (NTRS)

    Goodman, Jerry R.; Grosveld, Ferdinand

    2007-01-01

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

  2. Extending acoustic data measured with small-scale supersonic model jets to practical aircraft exhaust jets

    NASA Astrophysics Data System (ADS)

    Kuo, Ching-Wen

    2010-06-01

    Modern military aircraft jet engines are designed with variable geometry nozzles to provide optimum thrust in different operating conditions within the flight envelope. However, the acoustic measurements for such nozzles are scarce, due to the cost involved in making full-scale measurements and the lack of details about the exact geometry of these nozzles. Thus the present effort at The Pennsylvania State University and the NASA Glenn Research Center, in partnership with GE Aviation, is aiming to study and characterize the acoustic field produced by supersonic jets issuing from converging-diverging military style nozzles. An equally important objective is to develop a scaling methodology for using data obtained from small- and moderate-scale experiments which exhibits the independence of the jet sizes to the measured noise levels. The experimental results presented in this thesis have shown reasonable agreement between small-scale and moderate-scale jet acoustic data, as well as between heated jets and heat-simulated ones. As the scaling methodology is validated, it will be extended to using acoustic data measured with small-scale supersonic model jets to the prediction of the most important components of full-scale engine noise. When comparing the measured acoustic spectra with a microphone array set at different radial locations, the characteristics of the jet noise source distribution may induce subtle inaccuracies, depending on the conditions of jet operation. A close look is taken at the details of the noise generation region in order to better understand the mismatch between spectra measured at various acoustic field radial locations. A processing methodology was developed to correct the effect of the noise source distribution and efficiently compare near-field and far-field spectra with unprecedented accuracy. This technique then demonstrates that the measured noise levels in the physically restricted space of an anechoic chamber can be appropriately

  3. Staggered-grid finite-difference acoustic modeling with the Time-Domain Atmospheric Acoustic Propagation Suite (TDAAPS).

    SciTech Connect

    Aldridge, David Franklin; Collier, Sandra L.; Marlin, David H.; Ostashev, Vladimir E.; Symons, Neill Phillip; Wilson, D. Keith

    2005-05-01

    This document is intended to serve as a users guide for the time-domain atmospheric acoustic propagation suite (TDAAPS) program developed as part of the Department of Defense High-Performance Modernization Office (HPCMP) Common High-Performance Computing Scalable Software Initiative (CHSSI). TDAAPS performs staggered-grid finite-difference modeling of the acoustic velocity-pressure system with the incorporation of spatially inhomogeneous winds. Wherever practical the control structure of the codes are written in C++ using an object oriented design. Sections of code where a large number of calculations are required are written in C or F77 in order to enable better compiler optimization of these sections. The TDAAPS program conforms to a UNIX style calling interface. Most of the actions of the codes are controlled by adding flags to the invoking command line. This document presents a large number of examples and provides new users with the necessary background to perform acoustic modeling with TDAAPS.

  4. Coded acoustic wave sensors and system using time diversity

    NASA Technical Reports Server (NTRS)

    Solie, Leland P. (Inventor); Hines, Jacqueline H. (Inventor)

    2012-01-01

    An apparatus and method for distinguishing between sensors that are to be wirelessly detected is provided. An interrogator device uses different, distinct time delays in the sensing signals when interrogating the sensors. The sensors are provided with different distinct pedestal delays. Sensors that have the same pedestal delay as the delay selected by the interrogator are detected by the interrogator whereas other sensors with different pedestal delays are not sensed. Multiple sensors with a given pedestal delay are provided with different codes so as to be distinguished from one another by the interrogator. The interrogator uses a signal that is transmitted to the sensor and returned by the sensor for combination and integration with the reference signal that has been processed by a function. The sensor may be a surface acoustic wave device having a differential impulse response with a power spectral density consisting of lobes. The power spectral density of the differential response is used to determine the value of the sensed parameter or parameters.

  5. Acoustic characteristics of large-scale STOL model at forward speed

    NASA Technical Reports Server (NTRS)

    Falarski, M. D.; Aoyagi, K.; Koenig, D. G.

    1972-01-01

    Wind-tunnel investigations of the acoustic characteristics of the externally blown jet flap (EBF) and augmentor wing STOL concepts are dicussed. The large-scale EBF model was equipped with a triple-slotted blown by four JT15D turbofan engines with circular, coannular exhaust nozzles. The large-scale augmentor wing model was equipped with an unlined augmentor blown by a slot primary nozzle. The effects of airspeed and angle of attack on the acoustics of the EBF were small. At a forward speed of 60 knots, the impingement noise of the landing flap was approximately 2 db lower than in the static tests. Angle of attack increased the impingement noise approximately 0.1 decibels per degree. Flap deflection had a greater effect on the acoustics of the augmentor wing than did airspeed. For a nozzle pressure ratio of 1.9, the peak perceived noise level of the landing flap was 3 to 5 PNdb higher than that of the takeoff flap. The total sound power was also significantly higher for landing indicating that turning in the augmentor generated acoustic energy. Airspeed produced a small aft shift in acoustic directivity with no significant change in the peak perceived noise levels or sound power levels.

  6. Improved jet noise modeling using a new time-scale.

    PubMed

    Azarpeyvand, M; Self, R H

    2009-09-01

    To calculate the noise emanating from a turbulent flow using an acoustic analogy knowledge concerning the unsteady characteristics of the turbulence is required. Specifically, the form of the turbulent correlation tensor together with various time and length-scales are needed. However, if a Reynolds Averaged Navier-Stores calculation is used as the starting point then one can only obtain steady characteristics of the flow and it is necessary to model the unsteady behavior in some way. While there has been considerable attention given to the correct way to model the form of the correlation tensor less attention has been given to the underlying physics that dictate the proper choice of time-scale. In this paper the authors recognize that there are several time dependent processes occurring within a turbulent flow and propose a new way of obtaining the time-scale. Isothermal single-stream flow jets with Mach numbers 0.75 and 0.90 have been chosen for the present study. The Mani-Gliebe-Balsa-Khavaran method has been used for prediction of noise at different angles, and there is good agreement between the noise predictions and observations. Furthermore, the new time-scale has an inherent frequency dependency that arises naturally from the underlying physics, thus avoiding supplementary mathematical enhancements needed in previous modeling.

  7. Improved Forecasts for the Baryon Acoustic Oscillations and Cosmological Distance Scale

    NASA Astrophysics Data System (ADS)

    Seo, Hee-Jong; Eisenstein, Daniel J.

    2007-08-01

    We present the cosmological distance errors achievable using the baryonic acoustic oscillations as a standard ruler. We begin from a Fisher matrix formalism that is upgraded from earlier Seo and Eisenstein work. We isolate the information from the baryonic peaks by excluding distance information from other less robust sources. Meanwhile, we accommodate the Lagrangian displacement distribution into the Fisher matrix calculation to reflect the gradual loss of information in scale and in time due to nonlinear growth, nonlinear bias, and nonlinear redshift distortions. We then show that we can contract the multidimensional Fisher matrix calculations into a two-dimensional or even one-dimensional formalism with physically motivated approximations. We present the resulting fitting formula for the cosmological distance errors from galaxy redshift surveys as a function of survey parameters and nonlinearity, which saves us going through the 12 dimensional Fisher matrix calculations. Finally, we show excellent agreement between the distance error estimates from the revised Fisher matrix and the precision on the distance scale recovered from N-body simulations.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  9. Review of time scales. [Universal Time-Ephemeris Time-International Atomic Time

    NASA Technical Reports Server (NTRS)

    Guinot, B.

    1974-01-01

    The basic time scales are presented: International Atomic Time, Universal Time, and Universal Time (Coordinated). These scales must be maintained in order to satisfy specific requirements. It is shown how they are obtained and made available at a very high level of precision.

  10. Acoustic Resonators for Far-Field Control of Sound on a Subwavelength Scale

    NASA Astrophysics Data System (ADS)

    Lemoult, Fabrice; Fink, Mathias; Lerosey, Geoffroy

    2011-08-01

    We prove experimentally that broadband sounds can be controlled and focused at will on a subwavelength scale by using acoustic resonators. We demonstrate our approach in the audible range with soda cans, that is, Helmholtz resonators, and commercial computer speakers. We show that diffraction-limited sound fields convert efficiently into subdiffraction modes in the collection of cans that can be controlled coherently in order to obtain focal spots as thin as 1/25 of a wavelength in air. We establish that subwavelength acoustic pressure spots are responsible for a strong enhancement of the acoustic displacement at focus, which permits us to conclude with a visual experiment exemplifying the interest of our concept for subwavelength sensors and actuators.

  11. Time scale in quasifission reactions

    SciTech Connect

    Back, B.B.; Paul, P.; Nestler, J.

    1995-08-01

    The quasifission process arises from the hindrance of the complete fusion process when heavy-ion beams are used. The strong dissipation in the system tends to prevent fusion and lead the system towards reseparation into two final products of similar mass reminiscent of a fission process. This dissipation slows down the mass transfer and shape transformation and allows for the emission of high energy {gamma}-rays during the process, albeit with a low probability. Giant Dipole {gamma} rays emitted during this time have a characteristic spectral shape and may thus be discerned in the presence of a background of {gamma} rays emitted from the final fission-like fragments. Since the rate of GDR {gamma} emission is very well established, the strength of this component may therefore be used to measure the timescale of the quasifission process. In this experiment we studied the reaction between 368-MeV {sup 58}Ni and a {sup 165}Ho target, where deep inelastic scattering and quasifission processes are dominant. Coincidences between fission fragments (detected in four position-sensitive avalanche detectors) and high energy {gamma} rays (measured in a 10{close_quotes} x 10{close_quotes} actively shielded NaI detector) were registered. Beams were provided by the Stony Brook Superconducting Linac. The {gamma}-ray spectrum associated with deep inelastic scattering events is well reproduced by statistical cooling of projectile and target-like fragments with close to equal initial excitation energy sharing. The y spectrum associated with quasifission events is well described by statistical emission from the fission fragments alone, with only weak evidence for GDR emission from the mono-nucleus. A 1{sigma} limit of t{sub ss} < 11 x 10{sup -21} s is obtained for the mono-nucleus lifetime, which is consistent with the lifetime obtained from quasifission fragment angular distributions. A manuscript was accepted for publication.

  12. Time reversal acoustics for small targets using decomposition of the time reversal operator

    NASA Astrophysics Data System (ADS)

    Simko, Peter C.

    The method of time reversal acoustics has been the focus of considerable interest over the last twenty years. Time reversal imaging methods have made consistent progress as effective methods for signal processing since the initial demonstration that physical time reversal methods can be used to form convergent wave fields on a localized target, even under conditions of severe multipathing. Computational time reversal methods rely on the properties of the so-called 'time reversal operator' in order to extract information about the target medium. Applications for which time reversal imaging have previously been explored include medical imaging, non-destructive evaluation, and mine detection. Emphasis in this paper will fall on two topics within the general field of computational time reversal imaging. First, we will examine previous work on developing a time reversal imaging algorithm based on the MUltiple SIgnal Classification (MUSIC) algorithm. MUSIC, though computationally very intensive, has demonstrated early promise in simulations using array-based methods applicable to true volumetric (three-dimensional) imaging. We will provide a simple algorithm through which the rank of the time reversal operator subspaces can be properly quantified so that the rank of the associated null subspace can be accurately estimated near the central pulse wavelength in broadband imaging. Second, we will focus on the scattering from small acoustically rigid two dimensional cylindrical targets of elliptical cross section. Analysis of the time reversal operator eigenmodes has been well-studied for symmetric response matrices associated with symmetric systems of scattering targets. We will expand these previous results to include more general scattering systems leading to asymmetric response matrices, for which the analytical complexity increases but the physical interpretation of the time reversal operator remains unchanged. For asymmetric responses, the qualitative properties of the

  13. Acoustic Treatment Design Scaling Methods. Volume 1; Overview, Results, and Recommendations

    NASA Technical Reports Server (NTRS)

    Kraft, R. E.; Yu, J.

    1999-01-01

    Scale model fan rigs that simulate new generation ultra-high-bypass engines at about 1/5-scale are achieving increased importance as development vehicles for the design of low-noise aircraft engines. Testing at small scale allows the tests to be performed in existing anechoic wind tunnels, which provides an accurate simulation of the important effects of aircraft forward motion on the noise generation. The ability to design, build, and test miniaturized acoustic treatment panels on scale model fan rigs representative of the fullscale engine provides not only a cost-savings, but an opportunity to optimize the treatment by allowing tests of different designs. The primary objective of this study was to develop methods that will allow scale model fan rigs to be successfully used as acoustic treatment design tools. The study focuses on finding methods to extend the upper limit of the frequency range of impedance prediction models and acoustic impedance measurement methods for subscale treatment liner designs, and confirm the predictions by correlation with measured data. This phase of the program had as a goal doubling the upper limit of impedance measurement from 6 kHz to 12 kHz. The program utilizes combined analytical and experimental methods to achieve the objectives.

  14. Long term stability of atomic time scales

    NASA Astrophysics Data System (ADS)

    Petit, G.; Arias, F.

    2015-03-01

    We review the stability and accuracy achieved by the reference atomic time scales TAI and TT(BIPM). We show that they presently are in the low 10-16 in relative value, based on the performance of primary standards, of the ensemble time scale and of the time transfer techniques. We consider how the 1 × 10-16 value could be reached or superseded and which are the present limitations to attain this goal.

  15. The effect of time-variant acoustical properties on orchestral instrument timbres

    NASA Astrophysics Data System (ADS)

    Hajda, John Michael

    1999-06-01

    The goal of this study was to investigate the timbre of orchestral instrument tones. Kendall (1986) showed that time-variant features are important to instrument categorization. But the relative salience of specific time-variant features to each other and to other acoustical parameters is not known. As part of a convergence strategy, a battery of experiments was conducted to assess the importance of global amplitude envelope, spectral frequencies, and spectral amplitudes. An omnibus identification experiment investigated the salience of global envelope partitions (attack, steady state, and decay). Valid partitioning models should identify important boundary conditions in the evolution of a signal; therefore, these models should be based on signal characteristics. With the use of such a model for sustained continuant tones, the steady-state segment was more salient than the attack. These findings contradicted previous research, which used questionable operational definitions for signal partitioning. For the next set of experiments, instrument tones were analyzed by phase vocoder, and stimuli were created by additive synthesis. Edits and combinations of edits controlled global amplitude envelope, spectral frequencies, and relative spectral amplitudes. Perceptual measurements were made with distance estimation, Verbal Attribute Magnitude Estimation, and similarity scaling. Results indicated that the primary acoustical attribute was the long-time-average spectral centroid. Spectral centroid is a measure of the center of energy distribution for spectral frequency components. Instruments with high values of spectral centroid (bowed strings) sound nasal while instruments with low spectral centroid (flute, clarinet) sound not nasal. The secondary acoustical attribute was spectral amplitude time variance. Predictably, time variance correlated highly with subject ratings of vibrato. The control of relative spectral amplitudes was more salient than the control of global

  16. Imaging of Acoustically Coupled Oscillations Due to Flow Past a Shallow Cavity: Effect of Cavity Length Scale

    SciTech Connect

    P Oshkai; M Geveci; D Rockwell; M Pollack

    2004-05-24

    Flow-acoustic interactions due to fully turbulent inflow past a shallow axisymmetric cavity mounted in a pipe, which give rise to flow tones, are investigated using a technique of high-image-density particle image velocimetry in conjunction with unsteady pressure measurements. This imaging leads to patterns of velocity, vorticity, streamline topology, and hydrodynamic contributions to the acoustic power integral. Global instantaneous images, as well as time-averaged images, are evaluated to provide insight into the flow physics during tone generation. Emphasis is on the manner in which the streamwise length scale of the cavity alters the major features of the flow structure. These image-based approaches allow identification of regions of the unsteady shear layer that contribute to the instantaneous hydrodynamic component of the acoustic power, which is necessary to maintain a flow tone. In addition, combined image analysis and pressure measurements allow categorization of the instantaneous flow patterns that are associated with types of time traces and spectra of the fluctuating pressure. In contrast to consideration based solely on pressure spectra, it is demonstrated that locked-on tones may actually exhibit intermittent, non-phase-locked images, apparently due to low damping of the acoustic resonator. Locked-on flow tones (without modulation or intermittency), locked-on flow tones with modulation, and non-locked-on oscillations with short-term, highly coherent fluctuations are defined and represented by selected cases. Depending on which of these regimes occur, the time-averaged Q (quality)-factor and the dimensionless peak pressure are substantially altered.

  17. Real-time observation of coherent acoustic phonons generated by an acoustically mismatched optoacoustic transducer using x-ray diffraction

    SciTech Connect

    Persson, A. I. H.; Andreasson, B. P.; Enquist, H.; Jurgilaitis, A.; Larsson, J.

    2015-11-14

    The spectrum of laser-generated acoustic phonons in indium antimonide coated with a thin nickel film has been studied using time-resolved x-ray diffraction. Strain pulses that can be considered to be built up from coherent phonons were generated in the nickel film by absorption of short laser pulses. Acoustic reflections at the Ni–InSb interface leads to interference that strongly modifies the resulting phonon spectrum. The study was performed with high momentum transfer resolution together with high time resolution. This was achieved by using a third-generation synchrotron radiation source that provided a high-brightness beam and an ultrafast x-ray streak camera to obtain a temporal resolution of 10 ps. We also carried out simulations, using commercial finite element software packages and on-line dynamic diffraction tools. Using these tools, it is possible to calculate the time-resolved x-ray reflectivity from these complicated strain shapes. The acoustic pulses have a peak strain amplitude close to 1%, and we investigated the possibility to use this device as an x-ray switch. At a bright source optimized for hard x-ray generation, the low reflectivity may be an acceptable trade-off to obtain a pulse duration that is more than an order of magnitude shorter.

  18. Time evolution of ion-acoustic double layers in an unmagnetized plasma

    SciTech Connect

    Bharuthram, R.; Momoniat, E.; Mahomed, F.; Singh, S. V.; Islam, M. K.

    2008-08-15

    Ion-acoustic double layers are examined in an unmagnetized, three-component plasma consisting of cold ions and two temperature electrons. Both of the electrons are considered to be Boltzmann distributed and the ions follow the usual fluid dynamical equations. Using the method of characteristics, a time-dependent solution for ion-acoustic double layers is obtained. Results of the findings may have important consequences for the real time satellite observations in the space environment.

  19. Adolescent Time Attitude Scale: Adaptation into Turkish

    ERIC Educational Resources Information Center

    Çelik, Eyüp; Sahranç, Ümit; Kaya, Mehmet; Turan, Mehmet Emin

    2017-01-01

    This research is aimed at examining the validity and reliability of the Turkish version of the Time Attitude Scale. Data was collected from 433 adolescents; 206 males and 227 females participated in the study. Confirmatory factor analysis performed to discover the structural validity of the scale. The internal consistency method was used for…

  20. Time Scales in Turbulence and Sediment Concentration Over Mobile Sand Dunes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The relationship between turbulent fluid motions and sediment particles over mobile sand dunes may be better understood by examining the time scales over which the quantities fluctuate. In laboratory experiments performed at the USDA-ARS-National Sedimentation Laboratory, profiles of acoustic backs...

  1. Characteristic Time Scales of Characteristic Magmatic Processes and Systems

    NASA Astrophysics Data System (ADS)

    Marsh, B. D.

    2004-05-01

    times comes from the observed durations and rates of volcanism. There can be little doubt that the temporal styles of volcanism are the same as those of magmatism in general. Volcano repose times, periodicity, eruptive fluxes, acoustic emission structures, lava volumes, longevity, etc. must also be characteristic of pluton-dominated systems. We must therefore give up some classical concepts (e.g., instantaneous injection of crystal-free magma as an initial condition) for any plutonic/chambered system and move towards an integrated concept of magmatism. Among the host of process-related time scales, probably the three most fundamental of any magmatic system are (1) the time scale associated with crystal nucleation (J) and growth (G) (tx}=C{1(G3 J)-{1}/4; Zieg & Marsh, J. Pet. 02') along with the associated scales for mean crystal size (L) and population (N), (2) the time scale associated with conductive cooling controlled by a local length scale (d) (tc}=C{2 d2/K; K is thermal diffusivity), and (3) the time scale associated with intra-crystal diffusion (td}=C{3 L2/D; D is chemical diffusivity). It is the subtle, clever, and insightful application of time scales, dovetailed with realistic system geometry and attention paid to the analogous time scales of volcanism, that promises to reveal the true dynamic integration of magmatic systems.

  2. Assessment at full scale of exhaust nozzle to wing size on STOL-OTW acoustic characteristics

    NASA Technical Reports Server (NTRS)

    Vonglahn, U.; Grosbeck, D.

    1979-01-01

    On the basis of static aero/acoustic data obtained at model scale, the effect of exhaust nozzle size on flyover noise is evaluated at full scale for different STOL-OTW nozzle configurations. Three types of nozzles are evaluated: a circular/deflector nozzle mounted above the wing; a slot/deflector nozzle mounted on the wing; and a slot nozzle mounted on the wing. The nozzle exhaust plane location, measured from the wing leading edge, was varied from 10 to 46 percent of the wing chord (flaps retracted). Flap angles of 20 deg (takeoff) and 60 deg (approach) are included in the study. Initially, perceived noise levels (PNL) are calculated as a function flyover distance at 152m altitude. From these plots, static EPNL values (defined as flyover relative noise levels), are obtained as functions of nozzle size for equal aerodynamic performance (lift and thrust). The acoustic benefits attributable to nozzle size relative to a given wing chord size are assessed.

  3. Mouse Activity across Time Scales: Fractal Scenarios

    PubMed Central

    Lima, G. Z. dos Santos; Lobão-Soares, B.; do Nascimento, G. C.; França, Arthur S. C.; Muratori, L.; Ribeiro, S.; Corso, G.

    2014-01-01

    In this work we devise a classification of mouse activity patterns based on accelerometer data using Detrended Fluctuation Analysis. We use two characteristic mouse behavioural states as benchmarks in this study: waking in free activity and slow-wave sleep (SWS). In both situations we find roughly the same pattern: for short time intervals we observe high correlation in activity - a typical 1/f complex pattern - while for large time intervals there is anti-correlation. High correlation of short intervals ( to : waking state and to : SWS) is related to highly coordinated muscle activity. In the waking state we associate high correlation both to muscle activity and to mouse stereotyped movements (grooming, waking, etc.). On the other side, the observed anti-correlation over large time scales ( to : waking state and to : SWS) during SWS appears related to a feedback autonomic response. The transition from correlated regime at short scales to an anti-correlated regime at large scales during SWS is given by the respiratory cycle interval, while during the waking state this transition occurs at the time scale corresponding to the duration of the stereotyped mouse movements. Furthermore, we find that the waking state is characterized by longer time scales than SWS and by a softer transition from correlation to anti-correlation. Moreover, this soft transition in the waking state encompass a behavioural time scale window that gives rise to a multifractal pattern. We believe that the observed multifractality in mouse activity is formed by the integration of several stereotyped movements each one with a characteristic time correlation. Finally, we compare scaling properties of body acceleration fluctuation time series during sleep and wake periods for healthy mice. Interestingly, differences between sleep and wake in the scaling exponents are comparable to previous works regarding human heartbeat. Complementarily, the nature of these sleep-wake dynamics could lead to a better

  4. Acoustics Reflections of Full-Scale Rotor Noise Measurements in NFAC 40- by 80-Foot Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Barbely, Natasha Lydia; Kitaplioglu, Cahit; Sim, Ben W.

    2012-01-01

    The objective of current research is to identify the extent of acoustic time history distortions due to wind tunnel wall reflections. Acoustic measurements from the recent full-scale Boeing-SMART rotor test (Fig. 2) will be used to illustrate the quality of noise measurement in the NFAC 40- by 80-Foot Wind Tunnel test section. Results will be compared to PSU-WOPWOP predictions obtained with and without adjustments due to sound reflections off wind tunnel walls. Present research assumes a rectangular enclosure as shown in Fig. 3a. The Method of Mirror Images7 is used to account for reflection sources and their acoustic paths by introducing mirror images of the rotor (i.e. acoustic source), at each and every wall surface, to enforce a no-flow boundary condition at the position of the physical walls (Fig. 3b). While conventional approach evaluates the "combined" noise from both the source and image rotor at a single microphone position, an alternative approach is used to simplify implementation of PSU-WOPWOP for this reflection analysis. Here, an "equivalent" microphone position is defined with respect to the source rotor for each mirror image that effectively renders the reflection analysis to be a one rotor, multiple microphones problem. This alternative approach has the advantage of allowing each individual "equivalent" microphone, representing the reflection pulse from the associated wall surface, to be adjusted by the panel absorption coefficient illustrated in Fig. 1a. Note that the presence of parallel wall surfaces requires an infinite number of mirror images (Fig. 3c) to satisfy the no-flow boundary conditions. In the present analysis, up to four mirror images (per wall surface) are accounted to achieve convergence in the predicted time histories

  5. Hydrodynamics, Acoustics and Scaling of Traveling Bubble Cavitation

    DTIC Science & Technology

    1993-09-24

    distribution around the Schiebe headform 4 Figure B. I Rayleigh - Plesset bubble radius as a function of time 7 Figure B.2 Initial streamtube radius versus...the first two processes. These processes tend to produce small transverse vortices with vapor/gas filled cores. It was noted that the collapse phase ...and the important bubble-to-bubble interactions seen (particularly over the larger headforms) it becomes clear that the spherical Rayleigh - Plesset

  6. Anomalous properties of the acoustic excitations in glasses on the mesoscopic length scale

    PubMed Central

    Monaco, Giulio; Mossa, Stefano

    2009-01-01

    The low-temperature thermal properties of dielectric crystals are governed by acoustic excitations with large wavelengths that are well described by plane waves. This is the Debye model, which rests on the assumption that the medium is an elastic continuum, holds true for acoustic wavelengths large on the microscopic scale fixed by the interatomic spacing, and gradually breaks down on approaching it. Glasses are characterized as well by universal low-temperature thermal properties that are, however, anomalous with respect to those of the corresponding crystalline phases. Related universal anomalies also appear in the low-frequency vibrational density of states and, despite a longstanding debate, remain poorly understood. By using molecular dynamics simulations of a model monatomic glass of extremely large size, we show that in glasses the structural disorder undermines the Debye model in a subtle way: The elastic continuum approximation for the acoustic excitations breaks down abruptly on the mesoscopic, medium-range-order length scale of ≈10 interatomic spacings, where it still works well for the corresponding crystalline systems. On this scale, the sound velocity shows a marked reduction with respect to the macroscopic value. This reduction turns out to be closely related to the universal excess over the Debye model prediction found in glasses at frequencies of ≈1 THz in the vibrational density of states or at temperatures of ≈10 K in the specific heat. PMID:19805115

  7. Feature extraction from time domain acoustic signatures of weapons systems fire

    NASA Astrophysics Data System (ADS)

    Yang, Christine; Goldman, Geoffrey H.

    2014-06-01

    The U.S. Army is interested in developing algorithms to classify weapons systems fire based on their acoustic signatures. To support this effort, an algorithm was developed to extract features from acoustic signatures of weapons systems fire and applied to over 1300 signatures. The algorithm filtered the data using standard techniques then estimated the amplitude and time of the first five peaks and troughs and the location of the zero crossing in the waveform. The results were stored in Excel spreadsheets. The results are being used to develop and test acoustic classifier algorithms.

  8. Real-time monitoring of acoustic linear and nonlinear behavior of titanium alloys during cyclic loading

    SciTech Connect

    Frouin, J.; Maurer, J.; Sathish, S.; Eylon, D.; Na, J.K.; Matikas, T.E.

    2000-07-01

    Variation in acoustic nonlinearity has been monitored in real time during fatigue, on four dog-bone specimens of Ti-6Al-4V, under low cycle fatigue conditions, from the virgin state all the way to fracture. The results of these experiments show that the acoustic nonlinearity undergoes large changes during the fatigue and follows a similar trend for the material under given fatigue test conditions. Transmission electron microscopic (TEM) examination of the samples with similar composition fatigues to different stages indicates a gradual change in the microstructure and dislocation density, which correlates with the changes in acoustic nonlinearity.

  9. Time domain characteristics of wave motion in dispersive and anisotropic continuum acoustic metamaterials.

    PubMed

    Wang, Zhaojun; Zhou, Xiaoming

    2016-12-01

    The authors study the wave propagation in continuum acoustic metamaterials whose all or not all of the principal elements of the mass tensor or the scalar compressibility can be negative due to wave dispersion. Their time-domain wave characteristics are particularly investigated by the finite-difference time-domain (FDTD) method, in which algorithms for the Drude and Lorentz dispersion pertinent to acoustic metamaterials are provided necessarily. Wave propagation nature of anisotropic acoustic metamaterials with all admissible material parameters are analyzed in a general manner. It is found that anomalous negative refraction phenomena can appear in several dispersion regimes, and their unique time-domain signatures have been discovered by the FDTD modeling. It is further proposed that two different metamaterial layers with specially assigned dispersions could comprise a conjugate pair that permits wave propagation only at specific points in the wave vector space. The time-domain pulse simulation verifies that acoustic directive radiation capable of modulating radiation angle with the wave frequency can be realized with this conjugate pair. The study provides the detailed analysis of wave propagation in anisotropic and dispersive acoustic mediums, which makes a further step toward dispersion engineering and transient wave control through acoustic metamaterials.

  10. Acoustic Travel-Time Tomography of the Atmosphere at the Boulder Atmospheric Observatory

    DTIC Science & Technology

    2012-06-12

    REPORT Acoustic travel-time tomography of the atmosphere at the Boulder Atmospheric Observatory 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: see...Triangle Park, NC 27709-2211 15. SUBJECT TERMS acoustic tomography, temperature and velocity fields Vladimir Ostashev, Sergey Vecherin, Keith Wilson ...atmosphere at the Boulder Atmospheric Observatory Report Title ABSTRACT see Abstract in the paper Conference Name: 16th International Symposium for the

  11. Nonlinear response - A time domain approach. [with applications to acoustic fatigue, spacecraft and composite materials

    NASA Technical Reports Server (NTRS)

    Vaicaitis, R.

    1986-01-01

    The present paper reviews the basic concepts of nonlinear response of panels to surface flow and acoustic pressures, simulation of random processes, time domain solutions and the Monte Carlo Method. Applications of this procedure to the orbit-on-demand space vehicles, acoustic fatigue and composite materials are discussed. Numerical examples are included for a variety of nonlinear problems to illustrate the applicability of this method.

  12. Observing Reality on Different Time Scales

    NASA Astrophysics Data System (ADS)

    Alyushin, Alexey

    2005-10-01

    In the first part of the paper, I examine cases of acceleration of perception and cognition and provide my explanation of the mechanism of the effect. The explanation rests on the conception of neuronal temporal frames, or windows of simultaneity. Frames have different standard durations and yield to stretching and compressing. I suggest it to be the cause of the effect, as well as the ground for differences in perceptive time scales of living beings. In the second part, I apply the conception of temporal frames to model observation in the extended time scales that reach far beyond the temporal perceptive niche of individual living beings. Duration of a frame is taken as the basic parameter setting a particular time scale. By substituting a different frame duration, we set a hypothetical time scale and emulate observing reality in a wider or a narrower angle of embracing events in time. I discuss the status of observer in its relation to objective reality, and examine how reality does change its appearance when observed in different time scales.

  13. Detection of nonlinear picosecond acoustic pulses by time-resolved Brillouin scattering

    SciTech Connect

    Gusev, Vitalyi E.

    2014-08-14

    In time-resolved Brillouin scattering (also called picosecond ultrasonic interferometry), the time evolution of the spatial Fourier component of an optically excited acoustic strain distribution is monitored. The wave number is determined by the momentum conservation in photon-phonon interaction. For linear acoustic waves propagating in a homogeneous medium, the detected time-domain signal of the optical probe transient reflectivity shows a sinusoidal oscillation at a constant frequency known as the Brillouin frequency. This oscillation is a result of heterodyning the constant reflection from the sample surface with the Brillouin-scattered field. Here, we present an analytical theory for the nonlinear reshaping of a propagating, finite amplitude picosecond acoustic pulse, which results in a time-dependence of the observed frequency. In particular, we examine the conditions under which this information can be used to study the time-evolution of the weak-shock front speed. Depending on the initial strain pulse parameters and the time interval of its nonlinear transformation, our theory predicts the detected frequency to either be monotonically decreasing or oscillating in time. We support these theoretical predictions by comparison with available experimental data. In general, we find that picosecond ultrasonic interferometry of nonlinear acoustic pulses provides access to the nonlinear acoustic properties of a medium spanning most of the GHz frequency range.

  14. Time scales involved in emergent market coherence

    NASA Astrophysics Data System (ADS)

    Kwapień, J.; Drożdż, S.; Speth, J.

    2004-06-01

    In addressing the question of the time scales characteristic for the market formation, we analyze high-frequency tick-by-tick data from the NYSE and from the German market. By using returns on various time scales ranging from seconds or minutes up to 2 days, we compare magnitude of the largest eigenvalue of the correlation matrix for the same set of securities but for different time scales. For various sets of stocks of different capitalization (and the average trading frequency), we observe a significant elevation of the largest eigenvalue with increasing time scale. Our results from the correlation matrix study can be considered as a manifestation of the so-called Epps effect. There is no unique explanation of this effect and it seems that many different factors play a role here. One of such factors is randomness in transaction moments for different stocks. Another interesting conclusion to be drawn from our results is that in the contemporary markets the emergence of significant correlations occurs on time scales much smaller than in the more distant history.

  15. Delayed Alumina Scale Spallation on Rene'n5+y: Moisture Effects and Acoustic Emission

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Morscher, Gregory N.

    2001-01-01

    The single crystal superalloy Rene'N5 (with or without Y-doping and hydrogen annealing) was cyclically oxidized at 1150 C for 1000 hours. After considerable scale growth (>= 500 hours), even the adherent alumina scales formed on Y-doped samples exhibited delayed interfacial spallation during subsequent water immersion tests, performed up to one year after oxidation. Spallation was characterized by weight loss, the amount of spalled area, and acoustic emission response. Hydrogen annealing (prior to oxidation) reduced spallation both before and after immersion, but without measurably reducing the bulk sulfur content of the Y-doped alloys. The duration and frequency of sequential, co-located acoustic emission events implied an interfacial crack growth rate at least 10(exp -3) m/s, but possibly higher than 10(exp 2) m/s. This is much greater than classic moisture-assisted slow crack growth rates in bulk alumina (10(exp -6) to 10(exp -3) m/s), which may still have occurred undetected by acoustic emission. An alternative failure sequence is proposed: an incubation process for preferential moisture ingress leads to a local decrease in interfacial toughness, thus allowing fast fracture driven by stored strain energy.

  16. Testing and verification of a scale-model acoustic propagation system.

    PubMed

    Sagers, Jason D; Ballard, Megan S

    2015-12-01

    This paper discusses the design and operation of a measurement apparatus used to conduct scale-model underwater acoustic propagation experiments, presents experimental results for an idealized waveguide, and compares the measured results to data generated by two-dimensional (2D) and three-dimensional (3D) numerical models. The main objective of this paper is to demonstrate the capability of the apparatus for a simple waveguide that primarily exhibits 2D acoustic propagation. The apparatus contains a computer-controlled positioning system that accurately moves a receiving transducer in the water layer above a scale-model bathymetry while a stationary source transducer emits broadband pulsed waveforms. Experimental results are shown for a 2.133 m × 1.219 m bathymetric part possessing a flat-bottom bathymetry with a translationally invariant wedge of 10° slope along one edge. Beamformed results from a synthetic horizontal line array indicate the presence of strong in-plane arrivals along with weaker diffracted and horizontally refracted arrivals. A simulated annealing inversion method is applied to infer values for five waveguide parameters with the largest measurement uncertainty. The inferred values are then used in a 2D method of images model and a 3D adiabatic normal-mode model to simulate the measured acoustic data.

  17. Time-Scale Modification of Complex Acoustic Signals in Noise

    DTIC Science & Technology

    1994-02-04

    of 8), the object suffers from what is referred to here as the "bean bag effect," e.g., a hammer slamming against a metal plate is perceived as a...parameters are then interpolated from one frame to the next at the matched frequencies so that they may be upsampled to the original sampling rate. The...against a metal plate is perceived as a bean bag falling on a wooden floor. Two alternative methods that result in the proper temporal correlation

  18. Scaling and Multiscaling in Financial Time Series

    DTIC Science & Technology

    2007-11-02

    Prescribed by ANSI Std Z39-18 Outline 1/ A brief overview of financial markets • Basic definitions and problems related to finance • Scaling in finance 2...quantitative finance • Rational investment and risk management - Price dynamics - Risk quantification and control - Financial instruments: derivatives... finance • Supported by empirical observations • Practical interests. - Stability over time scales (by aggregation) - The same model is valid over a wide

  19. An eighth-scale speech source for subjective assessments in acoustic models

    NASA Astrophysics Data System (ADS)

    Orlowski, R. J.

    1981-08-01

    The design of a source is described which is suitable for making speech recordings in eighth-scale acoustic models of auditoria. An attempt was made to match the directionality of the source with the directionality of the human voice using data reported in the literature. A narrow aperture was required for the design which was provided by mounting an inverted conical horn over the diaphragm of a high frequency loudspeaker. Resonance problems were encountered with the use of a horn and a description is given of the electronic techniques adopted to minimize the effect of these resonances. Subjective and objective assessments on the completed speech source have proved satisfactory. It has been used in a modelling exercise concerned with the acoustic design of a theatre with a thrust-type stage.

  20. Multi-scale morphology analysis of acoustic emission signal and quantitative diagnosis for bearing fault

    NASA Astrophysics Data System (ADS)

    Wang, Wen-Jing; Cui, Ling-Li; Chen, Dao-Yun

    2016-04-01

    Monitoring of potential bearing faults in operation is of critical importance to safe operation of high speed trains. One of the major challenges is how to differentiate relevant signals to operational conditions of bearings from noises emitted from the surrounding environment. In this work, we report a procedure for analyzing acoustic emission signals collected from rolling bearings for diagnosis of bearing health conditions by examining their morphological pattern spectrum (MPS) through a multi-scale morphology analysis procedure. The results show that acoustic emission signals resulted from a given type of bearing faults share rather similar MPS curves. Further examinations in terms of sample entropy and Lempel-Ziv complexity of MPS curves suggest that these two parameters can be utilized to determine damage modes.

  1. Quantifying the Effect of Compression Hearing Aid Release Time on Speech Acoustics and Intelligibility

    ERIC Educational Resources Information Center

    Jenstad, Lorienne M.; Souza, Pamela E.

    2005-01-01

    Compression hearing aids have the inherent, and often adjustable, feature of release time from compression. Research to date does not provide a consensus on how to choose or set release time. The current study had 2 purposes: (a) a comprehensive evaluation of the acoustic effects of release time for a single-channel compression system in quiet and…

  2. Global scale precipitation from monthly to centennial scales: empirical space-time scaling analysis, anthropogenic effects

    NASA Astrophysics Data System (ADS)

    de Lima, Isabel; Lovejoy, Shaun

    2016-04-01

    The characterization of precipitation scaling regimes represents a key contribution to the improved understanding of space-time precipitation variability, which is the focus here. We conduct space-time scaling analyses of spectra and Haar fluctuations in precipitation, using three global scale precipitation products (one instrument based, one reanalysis based, one satellite and gauge based), from monthly to centennial scales and planetary down to several hundred kilometers in spatial scale. Results show the presence - similarly to other atmospheric fields - of an intermediate "macroweather" regime between the familiar weather and climate regimes: we characterize systematically the macroweather precipitation temporal and spatial, and joint space-time statistics and variability, and the outer scale limit of temporal scaling. These regimes qualitatively and quantitatively alternate in the way fluctuations vary with scale. In the macroweather regime, the fluctuations diminish with time scale (this is important for seasonal, annual, and decadal forecasts) while anthropogenic effects increase with time scale. Our approach determines the time scale at which the anthropogenic signal can be detected above the natural variability noise: the critical scale is about 20 - 40 yrs (depending on the product, on the spatial scale). This explains for example why studies that use data covering only a few decades do not easily give evidence of anthropogenic changes in precipitation, as a consequence of warming: the period is too short. Overall, while showing that precipitation can be modeled with space-time scaling processes, our results clarify the different precipitation scaling regimes and further allow us to quantify the agreement (and lack of agreement) of the precipitation products as a function of space and time scales. Moreover, this work contributes to clarify a basic problem in hydro-climatology, which is to measure precipitation trends at decadal and longer scales and to

  3. Transient nearfield acoustic holography based on an interpolated time-domain equivalent source method.

    PubMed

    Zhang, Xiao-Zheng; Bi, Chuan-Xing; Zhang, Yong-Bin; Xu, Liang

    2011-09-01

    Transient nearfield acoustic holography based on an interpolated time-domain equivalent source method (ESM) is proposed to reconstruct transient acoustic fields directly in the time domain. Since the equivalent source strengths solved by the traditional time-domain ESM formulation cannot be used to reconstruct the pressure on the source surface directly, an interpolation function is introduced to develop an interpolated time-domain ESM formulation which permits one to deduce an iterative reconstruction process. As the reconstruction process is ill-conditioned and especially there exists a cumulative effect of errors, the Tikhonov regularization is used to stabilize the process. Numerical examples of reconstructing transient acoustic fields from a baffled planar piston, an impulsively accelerating sphere and a cube box, respectively, demonstrate that the proposed method not only can effectively reconstruct transient acoustic fields in the time domain, but also can visualize acoustic fields in the space domain. And, in the first numerical example, the cumulative effect of errors and the validity of using the Tikhonov regularization to suppress the errors are described.

  4. Acoustic Performance Of New Designs Of Traffic Noise Barriers: Full Scale Tests

    NASA Astrophysics Data System (ADS)

    Watts, G. R.; Crombie, D. H.; Hothersall, D. C.

    1994-10-01

    Full scale tests of acoustical performance are reported on a range of promising traffic noise barrier shapes which had previously been identified by mathematical and scale modelling work. The designs chosen for testing were T-shaped, multiple edge barriers and double barriers. A test facility was established at the Transport Research Laboratory (TRL) in order to examine effectiveness under full scale conditions. This consisted of a 20 m length of noise barrier with interchangeable barrier panels, a large flat asphalt surface and a transportable speaker system capable of sufficient output to represent typical traffic noise. Screening performance was measured up to 80 m behind the barriers over a flat grassland area and at heights above the ground of 1·5 and 4·5 m. It was concluded that the average increase in acoustic screening of 2 m high T-shaped, multiple edge and double barriers compared with a simple plane reflecting barrier of identical overall height ranged from 1·4 to 3·6dB(A) depending on detailed design. It was suggested that a full scale test of a promising design should be carried out at a suitable highway location in order to validate fully these test results.

  5. Travel-time tomography in shallow water: experimental demonstration at an ultrasonic scale.

    PubMed

    Roux, Philippe; Iturbe, Ion; Nicolas, Barbara; Virieux, Jean; Mars, Jérôme I

    2011-09-01

    Acoustic tomography in a shallow ultrasonic waveguide is demonstrated at the laboratory scale between two source-receiver arrays. At a 1/1,000 scale, the waveguide represents a 1.1-km-long, 52-m-deep ocean acoustic channel in the kilohertz frequency range. Two coplanar arrays record the transfer matrix in the time domain of the waveguide between each pair of source-receiver transducers. A time-domain, double-beamforming algorithm is simultaneously performed on the source and receiver arrays that projects the multi-reflected acoustic echoes into an equivalent set of eigenrays, which are characterized by their travel times and their launch and arrival angles. Travel-time differences are measured for each eigenray every 0.1 s when a thermal plume is generated at a given location in the waveguide. Travel-time tomography inversion is then performed using two forward models based either on ray theory or on the diffraction-based sensitivity kernel. The spatially resolved range and depth inversion data confirm the feasibility of acoustic tomography in shallow water. Comparisons are made between inversion results at 1 and 3 MHz with the inversion procedure using ray theory or the finite-frequency approach. The influence of surface fluctuations at the air-water interface is shown and discussed in the framework of shallow-water ocean tomography.

  6. Pseudo-time-reversal symmetry and topological edge states in two-dimensional acoustic crystals

    NASA Astrophysics Data System (ADS)

    Mei, Jun; Chen, Zeguo; Wu, Ying

    2016-09-01

    We propose a simple two-dimensional acoustic crystal to realize topologically protected edge states for acoustic waves. The acoustic crystal is composed of a triangular array of core-shell cylinders embedded in a water host. By utilizing the point group symmetry of two doubly degenerate eigenstates at the Γ point, we can construct pseudo-time-reversal symmetry as well as pseudo-spin states in this classical system. We develop an effective Hamiltonian for the associated dispersion bands around the Brillouin zone center, and find the inherent link between the band inversion and the topological phase transition. With numerical simulations, we unambiguously demonstrate the unidirectional propagation of acoustic edge states along the interface between a topologically nontrivial acoustic crystal and a trivial one, and the robustness of the edge states against defects with sharp bends. Our work provides a new design paradigm for manipulating and transporting acoustic waves in a topologically protected manner. Technological applications and devices based on our design are expected in various frequency ranges of interest, spanning from infrasound to ultrasound.

  7. Pseudo-time-reversal symmetry and topological edge states in two-dimensional acoustic crystals

    PubMed Central

    Mei, Jun; Chen, Zeguo; Wu, Ying

    2016-01-01

    We propose a simple two-dimensional acoustic crystal to realize topologically protected edge states for acoustic waves. The acoustic crystal is composed of a triangular array of core-shell cylinders embedded in a water host. By utilizing the point group symmetry of two doubly degenerate eigenstates at the Γ point, we can construct pseudo-time-reversal symmetry as well as pseudo-spin states in this classical system. We develop an effective Hamiltonian for the associated dispersion bands around the Brillouin zone center, and find the inherent link between the band inversion and the topological phase transition. With numerical simulations, we unambiguously demonstrate the unidirectional propagation of acoustic edge states along the interface between a topologically nontrivial acoustic crystal and a trivial one, and the robustness of the edge states against defects with sharp bends. Our work provides a new design paradigm for manipulating and transporting acoustic waves in a topologically protected manner. Technological applications and devices based on our design are expected in various frequency ranges of interest, spanning from infrasound to ultrasound. PMID:27587311

  8. New developments in real-time processing of full waveform acoustic televiewer data

    NASA Astrophysics Data System (ADS)

    Deltombe, Jean-Luc; Schepers, Reinhard

    2004-01-01

    The new full wave Acoustic Borehole Imager tool (ABI) is a multi-echo (amplitude and traveltime) system that gives optimum performance under a wide range of borehole conditions and is an improvement over existing single echo acoustic televiewer tools. The principle of the multi-echo system is the digital recording of each reflected acoustic wave train. Then, real-time processing of the acoustic data is made by a downhole Digital Signal Processor (DSP) to extract all valuable information, which is further compressed before transmission to the surface such that no special requirements are imposed on data transmission rates or on logging speed. Also, recording of the full acoustic waveform enables major improvements to the dynamic range of the system. Information about echoes from the tool's acoustic window provides the possibility to predict tool generated coherent noise and allows detection of echoes from the borehole wall, which are much smaller than coherent noise signals. When used in a PVC cased borehole, the system can be automatically adapted to record both the reflection at the casing and at the borehole wall. When used inside steel casing, the tool can detect echoes from the inner wall and the outer wall of the steel casing and the resulting data can used to calculate amount inner corrosion, outer corrosion, and remaining casing thickness. If the borehole casing was grouted with cement, information can be gathered about the presence and absence of cement and the quality of cement bonding.

  9. Structure of Student Time Management Scale (STMS)

    ERIC Educational Resources Information Center

    Balamurugan, M.

    2013-01-01

    With the aim of constructing a Student Time Management Scale (STMS), the initial version was administered and data were collected from 523 standard eleventh students. (Mean age = 15.64). The data obtained were subjected to Reliability and Factor analysis using PASW Statistical software version 18. From 42 items 14 were dropped, resulting in the…

  10. Acoustic characteristics of a large-scale augmentor wing model at forward speed

    NASA Technical Reports Server (NTRS)

    Falarski, M. D.; Koenig, D. G.

    1973-01-01

    The augmentor wing concept is being studied as one means of attaining short takeoff and landing (STOL) performance in turbofan powered aircraft. Because of the stringent noise requirements for STOL operation, the acoustics of the augmentor wing are undergoing extensive research. The results of a wind tunnel investigation of a large-scale swept augmentor model at forward speed are presented. The augmentor was not acoustically treated, although the compressor supplying the high pressure primary air was treated to allow the measurement of only the augmentor noise. Installing the augmentor flap and shroud on the slot primary nozzle caused the acoustic dependence on jet velocity to change from eighth power to sixth power. Deflecting the augmentor at constant power increased the perceived noise level in the forward quadrant. The effect of airspeed was small. A small aft shift in perceived noise directivity was experienced with no significant change in sound power. Sealing the lower augmentor slot at a flap deflection of 70 deg reduced the perceived noise level in the aft quadrant. The seal prevented noise from propagating through the slot.

  11. Acoustic measurements of a full-scale coaxial hingeless rotor helicopter

    NASA Technical Reports Server (NTRS)

    Peterson, R. L.; Mosher, M.

    1983-01-01

    Acoustic data were obtained during a full-scale test of the XH-59A Advancing Blade Concept Technology Demonstrator in the 40- by 80-Foot Wind Tunnel. The XH-59A is a research helicopter with two coaxial rotors and hingeless blades. Performance, vibration, and noise at various forward speeds, rotor lift coefficients and rotor shaft angles of attack were investigated. The noise data were acquired over an isolated rotor lift coefficient range of 0.024 to 0.162, an advance ratio range of 0.23 to 0.45 corresponding to tunnel wind speeds of 89 to 160 knots, and angles of attack from 0 deg to 10 deg. Acoustic data are presented for seven microphone locations for all run conditions where the model noise is above the background noise. Model test configuration and performance information are also listed. Acoustic waveforms, dBA, and 1/3-octave spectra as functions of operating condition for selected data points and microphones are presented. In general, the noise level is shown to increase with rotor lift coefficient except under certain operating conditions where significant impulsive blade/vortex interactions increase noise levels.

  12. Comparison of the acoustic characteristics of large-scale models of several propulsive-lift concepts

    NASA Technical Reports Server (NTRS)

    Falarski, M. D.; Aiken, T. N.; Aoyagi, K.; Koenig, D. G.

    1974-01-01

    Wind-tunnel acoustic investigations were performed to determine the acoustic characteristics and the effect of forward speed on the over-the-wing externally blown jet flap (OTW), the under-the-wing externally blown jet flap (UTW), the internally blown jet flap (IBF), and the augmentor wing (AW). The data presented represent the basic noise generated by the powered-lift system without acoustic treatment, assuming all other noise sources, such as the turbofan compressor noise, have been suppressed. Under these conditions, when scaled to a 100,000-lb aircraft, the OTW concept exhibited the lowest perceived noise levels, because of dominant low-frequency noise and wing shielding of the high-frequency noise. The AW was the loudest configuration, because of dominant high-frequency noise created by the high jet velocities and small nozzle dimensions. All four configurations emitted noise 10 to 15 PNdB higher than the noise goal of 95 PNdB at 500 ft.

  13. Shallow-water acoustic tomography from angle measurements instead of travel-time measurements.

    PubMed

    Aulanier, Florian; Nicolas, Barbara; Mars, Jérôme I; Roux, Philippe; Brossier, Romain

    2013-10-01

    For shallow-water waveguides and mid-frequency broadband acoustic signals, ocean acoustic tomography (OAT) is based on the multi-path aspect of wave propagation. Using arrays in emission and reception and advanced array processing, every acoustic arrival can be isolated and matched to an eigenray that is defined not only by its travel time but also by its launch and reception angles. Classically, OAT uses travel-time variations to retrieve sound-speed perturbations; this assumes very accurate source-to-receiver clock synchronization. This letter uses numerical simulations to demonstrate that launch-and-reception-angle tomography gives similar results to travel-time tomography without the same requirement for high-precision synchronization.

  14. Time-reversal acoustics and ultrasound-assisted convection-enhanced drug delivery to the brain.

    PubMed

    Olbricht, William; Sistla, Manjari; Ghandi, Gaurav; Lewis, George; Sarvazyan, Armen

    2013-08-01

    Time-reversal acoustics is an effective way of focusing ultrasound deep inside heterogeneous media such as biological tissues. Convection-enhanced delivery is a method of delivering drugs into the brain by infusing them directly into the brain interstitium. These two technologies are combined in a focusing system that uses a "smart needle" to simultaneously infuse fluid into the brain and provide the necessary feedback for focusing ultrasound using time-reversal acoustics. The effects of time-reversal acoustics-focused ultrasound on the spatial distribution of infused low- and high-molecular weight tracer molecules are examined in live, anesthetized rats. Results show that exposing the rat brain to focused ultrasound significantly increases the penetration of infused compounds into the brain. The addition of stabilized microbubbles enhances the effect of ultrasound exposure.

  15. Changes in Wisconsin English over 110 Years: A Real-Time Acoustic Account

    ERIC Educational Resources Information Center

    Delahanty, Jennifer

    2011-01-01

    The growing set of studies on American regional dialects have to date focused heavily on vowels while few examine consonant features and none provide acoustic analysis of both vowel and consonant features. This dissertation uses real-time data on both vowels and consonants to show how Wisconsin English has changed over time. Together, the…

  16. A case-study comparison of computer modeling and scale modeling in acoustics consulting

    NASA Astrophysics Data System (ADS)

    Calamia, Paul T.

    2002-05-01

    As an alternate or compliment to computer models, acoustics consultants often make use of scale models to evaluate the efficacy of architectural designs. The intention of this paper is to compare the two modeling approaches, using one or more case studies, to explore the pros and cons of each. Topics of comparison will include cost, geometric representations, effective bandwidths, propagation phenomena (e.g., diffraction), simulation of material properties, and auralization. Where possible, measured data from existing spaces will be presented to provide a reference for the modeled data.

  17. Time-resolved coherent X-ray diffraction imaging of surface acoustic waves.

    PubMed

    Nicolas, Jan-David; Reusch, Tobias; Osterhoff, Markus; Sprung, Michael; Schülein, Florian J R; Krenner, Hubert J; Wixforth, Achim; Salditt, Tim

    2014-10-01

    Time-resolved coherent X-ray diffraction experiments of standing surface acoustic waves, illuminated under grazing incidence by a nanofocused synchrotron beam, are reported. The data have been recorded in stroboscopic mode at controlled and varied phase between the acoustic frequency generator and the synchrotron bunch train. At each time delay (phase angle), the coherent far-field diffraction pattern in the small-angle regime is inverted by an iterative algorithm to yield the local instantaneous surface height profile along the optical axis. The results show that periodic nanoscale dynamics can be imaged at high temporal resolution in the range of 50 ps (pulse length).

  18. Distributed acoustic mapping based on interferometry of phase optical time-domain reflectometry

    NASA Astrophysics Data System (ADS)

    Wang, Chang; Wang, Chen; Shang, Ying; Liu, Xiaohui; Peng, Gangding

    2015-07-01

    We demonstrate the design and characterization of a distributed optical fiber sensing system based on Michelson interferometer of the phase sensitive optical time domain reflectometer (φ-OTDR) for acoustic measurement. Phase, amplitude, frequency response and location information can be directly obtained at the same time by using the passive 3×3 coupler demodulation. In order to simulate sound profiles of seismic or hydroacoustic imaging, experiments on detection of multiple piezoelectric transducers (PZT) are carried out. The result shows that our system can well demodulate different acoustic sources with different intensities.

  19. Time-resolved coherent X-ray diffraction imaging of surface acoustic waves

    PubMed Central

    Nicolas, Jan-David; Reusch, Tobias; Osterhoff, Markus; Sprung, Michael; Schülein, Florian J. R.; Krenner, Hubert J.; Wixforth, Achim; Salditt, Tim

    2014-01-01

    Time-resolved coherent X-ray diffraction experiments of standing surface acoustic waves, illuminated under grazing incidence by a nanofocused synchrotron beam, are reported. The data have been recorded in stroboscopic mode at controlled and varied phase between the acoustic frequency generator and the synchrotron bunch train. At each time delay (phase angle), the coherent far-field diffraction pattern in the small-angle regime is inverted by an iterative algorithm to yield the local instantaneous surface height profile along the optical axis. The results show that periodic nanoscale dynamics can be imaged at high temporal resolution in the range of 50 ps (pulse length). PMID:25294979

  20. Tempo and scale of biogenic effects on high-frequency acoustic propagation near the marine sediment-water interface in shallow water

    NASA Astrophysics Data System (ADS)

    Jumars, Peter

    2003-04-01

    Organisms have natural scales, such as lifetimes, body sizes, frequencies of movement to new locations, and residence times of material in digestive systems, and each scale has potential implications for acoustic effects. The effects of groups of organisms, like organisms themselves, aggregate in space and time. This review, including an assortment of unpublished information, examines examples of such aggregations, many of them documented acoustically. Light synchronizes many activities. Macroscopic animals forage primarily under cover of darkness. This phasing applies both to animals that extend appendages above the sediment-water interface and to animals that leave the seabed at night. Whereas their bottom-modifying activities are concentrated in nocturnal or crepuscular fashion, the bottom-modifying activities of the visual feeders follow a different phasing and often dominate the rate of change in acoustic backscatter from the interface. Light also acts through its effects on primary production, often concentrated in a very thin surficial layer atop the seabed. The supersaturation of oxygen does, and microbubble nucleation may, result. Where tidal velocities are large, light-set patterns are often tidally modulated. Activities of animals living below the seabed, however, remain a mystery, whose primary hope for solution is acoustic. [Work supported by ONR and DEPSCoR.

  1. Scaling the Martian Walls of Time

    NASA Astrophysics Data System (ADS)

    Thornton, Nikki; Yagloski, Joseph; Fledderman, Joe; OMarr, Gregg; Weber, Ben; Carlins, Chris; Krishna, Shubh; Sloan, Kevin; Merriman, Taite; Borowski, David

    2000-01-01

    On Earth, when scientists want to investigate planetary history they take a core sample, with deeper fragments corresponding to older materials. In essence, descending through sedimentary layers is like going back in time. But creating a robot capable of taking samples more than a few meters below the planetary surface is still beyond the current available technology. The cliffhanger idea takes advantage of the natural surface features of Mars to explore the history of the planet without digging. So interesting and difficult questions can be answered not with the brute force of a drill, but with creative mission design. Penn State University HEDS-UP team has designed a novel Mars mission approach. A main Lander with a Rover and a Cliffhanger will land near cliffs of Valles Mariners. Especially design cannon (gas, guided munitions or rocket) will deploy a long rope into the canyon. The rover will carry the cliffhanger to the edge of Valles Marineris following the rope, attach the cliffhanger to the rope. The Cliffhanger will then climb a 2 km down the rope and will allow the team to study sedimentary layers of rock on the side of the cliff. Samples and high-resolution images will be taken and delivered to the Lander for further investigation (optical multispectral imaging microscope, spectrometry) and sending the results to Earth. The robot has been designed to have the capability for locomotion at any angle (including somewhat uphill slopes) but maximum effective After the mission of rope-climbing is completed, the Rover am Lander will embark on another long-term mission to provide meteorological and geological data over a long period of time (long-term Mars Observatory), and perform acoustic and seismic experiments on the surface of Mars in preparation for human arrival.

  2. Accuracy metrics for judging time scale algorithms

    NASA Technical Reports Server (NTRS)

    Douglas, R. J.; Boulanger, J.-S.; Jacques, C.

    1994-01-01

    Time scales have been constructed in different ways to meet the many demands placed upon them for time accuracy, frequency accuracy, long-term stability, and robustness. Usually, no single time scale is optimum for all purposes. In the context of the impending availability of high-accuracy intermittently-operated cesium fountains, we reconsider the question of evaluating the accuracy of time scales which use an algorithm to span interruptions of the primary standard. We consider a broad class of calibration algorithms that can be evaluated and compared quantitatively for their accuracy in the presence of frequency drift and a full noise model (a mixture of white PM, flicker PM, white FM, flicker FM, and random walk FM noise). We present the analytic techniques for computing the standard uncertainty for the full noise model and this class of calibration algorithms. The simplest algorithm is evaluated to find the average-frequency uncertainty arising from the noise of the cesium fountain's local oscillator and from the noise of a hydrogen maser transfer-standard. This algorithm and known noise sources are shown to permit interlaboratory frequency transfer with a standard uncertainty of less than 10(exp -15) for periods of 30-100 days.

  3. An acoustic travel time method for continuous velocity monitoring in shallow tidal streams

    NASA Astrophysics Data System (ADS)

    Razaz, Mahdi; Kawanisi, Kiyosi; Nistor, Ioan; Sharifi, Soroosh

    2013-08-01

    Long-term variations of streamflow in a tidal channel were measured using a Fluvial Acoustic Tomography (FAT) system through one transmission path. FAT is an innovative acoustic technology that utilizes the time-of-travel method to determine velocity between two points from multiple ray paths that traverse the entire cross-section of stream. Due to high spatial variability of flow distribution stationary ADCP measurements were not likely to yield true section-averaged flow velocity and moving-boat ADCP method was therefore used to provide reference data. As such, two short-term moving boat ADCP campaigns were carried out by the authors. In the first campaign, a couple of acoustic stations were added to the FAT system in order to resolve flow angularity in addition to the mean velocity. Comparing the FAT results with corresponding ADCP section-averaged flow direction and velocity indicated remarkable consistency. Second campaign was designed to capture the influence of salt wedge intrusion on the sound propagation pattern. It was found that FAT velocity measurements bias high if acoustic stations lay inside the cooler freshwater layer. Ray-tracing hindcasts suggest that installing acoustic stations inside the salt wedge may significantly improve function of output of the system. Comparing salinities evaluated from long-term FAT travel time records with nodal salinity measurements provided by conductivity-temperature sensors reveals the potential ability of FAT in measuring salt flux.

  4. HIGH-PRECISION PREDICTIONS FOR THE ACOUSTIC SCALE IN THE NONLINEAR REGIME

    SciTech Connect

    Seo, Hee-Jong; Eckel, Jonathan; Eisenstein, Daniel J.; Mehta, Kushal; Metchnik, Marc; Padmanabhan, Nikhil; Pinto, Phillip; Takahashi, Ryuichi; White, Martin; Xu, Xiaoying

    2010-09-10

    We measure shifts of the acoustic scale due to nonlinear growth and redshift distortions to a high precision using a very large volume of high-force-resolution simulations. We compare results from various sets of simulations that differ in their force, volume, and mass resolution. We find a consistency within 1.5-sigma for shift values from different simulations and derive shift alpha(z) -1 = (0.300\\pm 0.015)% [D(z)/D(0)]^{2} using our fiducial set. We find a strong correlation with a non-unity slope between shifts in real space and in redshift space and a weak correlation between the initial redshift and low redshift. Density-field reconstruction not only removes the mean shifts and reduces errors on the mean, but also tightens the correlations: after reconstruction, we recover a slope of near unity for the correlation between the real and redshift space and restore a strong correlation between the low and the initial redshifts. We derive propagators and mode-coupling terms from our N-body simulations and compared with Zeldovich approximation and the shifts measured from the chi^2 fitting, respectively. We interpret the propagator and the mode-coupling term of a nonlinear density field in the context of an average and a dispersion of its complex Fourier coefficients relative to those of the linear density field; from these two terms, we derive a signal-to-noise ratio of the acoustic peak measurement. We attempt to improve our reconstruction method by implementing 2LPT and iterative operations: we obtain little improvement. The Fisher matrix estimates of uncertainty in the acoustic scale is tested using 5000 (Gpc/h)^3 of cosmological PM simulations from Takahashi et al. (2009). (abridged)

  5. Hemispheric Asymmetries in Substorm Recovery Time Scales

    NASA Technical Reports Server (NTRS)

    Fillingim, M. O.; Chua, D H.; Germany, G. A.; Spann, James F.

    2009-01-01

    Previous statistical observations have shown that the recovery time scales of substorms occurring in the winter and near equinox (when the nighttime auroral zone was in darkness) are roughly twice as long as the recovery time scales for substorms occurring in the summer (when the nighttime auroral region was sunlit). This suggests that auroral substorms in the northern and southern hemispheres develop asymmetrically during solstice conditions with substorms lasting longer in the winter (dark) hemisphere than in the summer (sunlit) hemisphere. Additionally, this implies that more energy is deposited by electron precipitation in the winter hemisphere than in the summer one during substorms. This result, coupled with previous observations that have shown that auroral activity is more common when the ionosphere is in darkness and is suppressed when the ionosphere is in daylight, strongly suggests that the ionospheric conductivity plays an important role governing how magnetospheric energy is transferred to the ionosphere during substorms. Therefore, the ionosphere itself may dictate how much energy it will accept from the magnetosphere during substorms rather than this being an externally imposed quantity. Here, we extend our earlier work by statistically analyzing the recovery time scales for a large number of substorms observed in the conjugate hemispheres simultaneously by two orbiting global auroral imagers: Polar UVI and IMAGE FUV. Our current results are consistent with previous observations. The recovery time scales are observed to be longer in the winter (dark) hemisphere while the auroral activity has a shorter duration in the summer (sunlit) hemisphere. This leads to an asymmetric energy input from the magnetosphere to the ionosphere with more energy being deposited in the winter hemisphere than in the summer hemisphere.

  6. Special Issue on Time Scale Algorithms

    DTIC Science & Technology

    2008-01-01

    unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 IOP PUBLISHING METROLOGIA Metrologia 45 (2008) doi:10.1088/0026-1394/45/6/E01...special issue of Metrologia presents selected papers from the Fifth International Time Scale Algorithm Symposium (VITSAS), including some of the...Paris at the BIPM in 2002 (see Metrologia 40 (3), 2003) • 5th Symposium: in San Fernando, Spain at the ROA in 2008. The early symposia were concerned

  7. Time Scales, Coherency, and Weak Coupling.

    DTIC Science & Technology

    1980-10-01

    U. S. Department of Energy, Electric Energy Systems Division, under Contract EX-76-C-01-2088; in part by the National Science Foundation under Grant...for the degree of Doctor of Philosophy in Electrical Engineering in the Graduate College of the University of Illinois at Urbana-Champaign, 1980... Electrical Engineering University of Illinois at Urbana-Champaign, 1980 In this thesis we study a relation between time scales and structural properties of

  8. Time scales of the stick–slip dynamics of the peeling of an adhesive tape

    PubMed Central

    Mishra, Nachiketa; Parida, Nigam Chandra; Raha, Soumyendu

    2015-01-01

    The stick–slip dynamics of the peeling of an adhesive tape is characterized by bifurcations that have been experimentally well studied. In this work, we investigate the time scale in which the the stick–slips happen leading to the bifurcations. This is fundamental to understanding the triboluminescence and acoustic emissions associated with the bifurcations. We establish a relationship between the time scale of the bifurcations and the inherent mathematical structure of the peeling dynamics by studying a characteristic time quantity associated with the dynamics. PMID:25663802

  9. A comment on the use of flushing time, residence time, and age as transport time scales

    USGS Publications Warehouse

    Monsen, N.E.; Cloern, J.E.; Lucas, L.V.; Monismith, Stephen G.

    2002-01-01

    Applications of transport time scales are pervasive in biological, hydrologic, and geochemical studies yet these times scales are not consistently defined and applied with rigor in the literature. We compare three transport time scales (flushing time, age, and residence time) commonly used to measure the retention of water or scalar quantities transported with water. We identify the underlying assumptions associated with each time scale, describe procedures for computing these time scales in idealized cases, and identify pitfalls when real-world systems deviate from these idealizations. We then apply the time scale definitions to a shallow 378 ha tidal lake to illustrate how deviations between real water bodies and the idealized examples can result from: (1) non-steady flow; (2) spatial variability in bathymetry, circulation, and transport time scales; and (3) tides that introduce complexities not accounted for in the idealized cases. These examples illustrate that no single transport time scale is valid for all time periods, locations, and constituents, and no one time scale describes all transport processes. We encourage aquatic scientists to rigorously define the transport time scale when it is applied, identify the underlying assumptions in the application of that concept, and ask if those assumptions are valid in the application of that approach for computing transport time scales in real systems.

  10. Liquidity crises on different time scales.

    PubMed

    Corradi, Francesco; Zaccaria, Andrea; Pietronero, Luciano

    2015-12-01

    We present an empirical analysis of the microstructure of financial markets and, in particular, of the static and dynamic properties of liquidity. We find that on relatively large time scales (15 min) large price fluctuations are connected to the failure of the subtle mechanism of compensation between the flows of market and limit orders: in other words, the missed revelation of the latent order book breaks the dynamical equilibrium between the flows, triggering the large price jumps. On smaller time scales (30 s), instead, the static depletion of the limit order book is an indicator of an intrinsic fragility of the system, which is related to a strongly nonlinear enhancement of the response. In order to quantify this phenomenon we introduce a measure of the liquidity imbalance present in the book and we show that it is correlated to both the sign and the magnitude of the next price movement. These findings provide a quantitative definition of the effective liquidity, which proves to be strongly dependent on the considered time scales.

  11. Liquidity crises on different time scales

    NASA Astrophysics Data System (ADS)

    Corradi, Francesco; Zaccaria, Andrea; Pietronero, Luciano

    2015-12-01

    We present an empirical analysis of the microstructure of financial markets and, in particular, of the static and dynamic properties of liquidity. We find that on relatively large time scales (15 min) large price fluctuations are connected to the failure of the subtle mechanism of compensation between the flows of market and limit orders: in other words, the missed revelation of the latent order book breaks the dynamical equilibrium between the flows, triggering the large price jumps. On smaller time scales (30 s), instead, the static depletion of the limit order book is an indicator of an intrinsic fragility of the system, which is related to a strongly nonlinear enhancement of the response. In order to quantify this phenomenon we introduce a measure of the liquidity imbalance present in the book and we show that it is correlated to both the sign and the magnitude of the next price movement. These findings provide a quantitative definition of the effective liquidity, which proves to be strongly dependent on the considered time scales.

  12. Multidimensional scaling of musical time estimations.

    PubMed

    Cocenas-Silva, Raquel; Bueno, José Lino Oliveira; Molin, Paul; Bigand, Emmanuel

    2011-06-01

    The aim of this study was to identify the psycho-musical factors that govern time evaluation in Western music from baroque, classic, romantic, and modern repertoires. The excerpts were previously found to represent variability in musical properties and to induce four main categories of emotions. 48 participants (musicians and nonmusicians) freely listened to 16 musical excerpts (lasting 20 sec. each) and grouped those that seemed to have the same duration. Then, participants associated each group of excerpts to one of a set of sine wave tones varying in duration from 16 to 24 sec. Multidimensional scaling analysis generated a two-dimensional solution for these time judgments. Musical excerpts with high arousal produced an overestimation of time, and affective valence had little influence on time perception. The duration was also overestimated when tempo and loudness were higher, and to a lesser extent, timbre density. In contrast, musical tension had little influence.

  13. Quantifying the effect of compression hearing aid release time on speech acoustics and intelligibility.

    PubMed

    Jenstad, Lorienne M; Souza, Pamela E

    2005-06-01

    Compression hearing aids have the inherent, and often adjustable, feature of release time from compression. Research to date does not provide a consensus on how to choose or set release time. The current study had 2 purposes: (a) a comprehensive evaluation of the acoustic effects of release time for a single-channel compression system in quiet and (b) an evaluation of the relation between the acoustic changes and speech recognition. The release times under study were 12, 100, and 800 ms. All of the stimuli were VC syllables from the Nonsense Syllable Task spoken by a female talker. The stimuli were processed through a hearing aid simulator at 3 input levels. Two acoustic measures were made on individual syllables: the envelope-difference index and CV ratio. These measurements allowed for quantification of the short-term amplitude characteristics of the speech signal and the changes to these amplitude characteristics caused by compression. The acoustic analyses revealed statistically significant effects among the 3 release times. The size of the effect was dependent on characteristics of the phoneme. Twelve listeners with moderate sensorineural hearing loss were tested for their speech recognition for the same stimuli. Although release time for this single-channel, 3:1 compression ratio system did not directly predict overall intelligibility for these nonsense syllables in quiet, the acoustic measurements reflecting the changes due to release time were significant predictors of phoneme recognition. Increased temporal-envelope distortion was predictive of reduced recognition for some individual phonemes, which is consistent with previous research on the importance of relative amplitude as a cue to syllable recognition for some phonemes.

  14. Time dependent inflow-outflow boundary conditions for 2D acoustic systems

    NASA Technical Reports Server (NTRS)

    Watson, Willie R.; Myers, Michael K.

    1989-01-01

    An analysis of the number and form of the required inflow-outflow boundary conditions for the full two-dimensional time-dependent nonlinear acoustic system in subsonic mean flow is performed. The explicit predictor-corrector method of MacCormack (1969) is used. The methodology is tested on both uniform and sheared mean flows with plane and nonplanar sources. Results show that the acoustic system requires three physical boundary conditions on the inflow and one on the outflow boundary. The most natural choice for the inflow boundary conditions is judged to be a specification of the vorticity, the normal acoustic impedance, and a pressure gradient-density gradient relationship normal to the boundary. Specification of the acoustic pressure at the outflow boundary along with these inflow boundary conditions is found to give consistent reliable results. A set of boundary conditions developed earlier, which were intended to be nonreflecting is tested using the current method and is shown to yield unstable results for nonplanar acoustic waves.

  15. Acousto-Optic Interaction in Surface Acoustic Waves and Its Application to Real Time Signal Processing.

    DTIC Science & Technology

    1977-12-30

    ACOUSTO - OPTIC INTERACTION IN SURFACE ACOUSTIC WAVES AND ITS APP--ETC(U) DEC 77 0 SCHUMER, P DAS NOOOIJ -75-C-0772 NCLASSIFIED MA-ONR-30 Nt.EE E’h...CHART NAT*NAL BUREAU OF STANDARDS 1-63- ACOUSTO - OPTIC INTERACTION IN SURFACE ACOUSTIC WAVES AND ITS APPLICATION TO REAL TIME SIGNAL PROCESSING By 00 D... Acousto - optics , Integrated optics, Optical Signal Processing. 20. AbSKTRACT (Continue an reverse side it neceary and idewnt& by block mum ber) The

  16. Acoustic sensor for real-time control for the inductive heating process

    DOEpatents

    Kelley, John Bruce; Lu, Wei-Yang; Zutavern, Fred J.

    2003-09-30

    Disclosed is a system and method for providing closed-loop control of the heating of a workpiece by an induction heating machine, including generating an acoustic wave in the workpiece with a pulsed laser; optically measuring displacements of the surface of the workpiece in response to the acoustic wave; calculating a sub-surface material property by analyzing the measured surface displacements; creating an error signal by comparing an attribute of the calculated sub-surface material properties with a desired attribute; and reducing the error signal below an acceptable limit by adjusting, in real-time, as often as necessary, the operation of the inductive heating machine.

  17. Vector Brillouin optical time-domain analyzer for high-order acoustic modes.

    PubMed

    Dossou, Michel; Bacquet, Denis; Szriftgiser, Pascal

    2010-11-15

    Thanks to a double-frequency phase modulation scheme, we report a vector Brillouin optical time-domain analyzer (BOTDA). This BOTDA has a high immunity level to noise, and it features a phase spectrogram capability. It is well suited for complex situations involving several acoustic resonances, such as high-order longitudinal modes. It has notably been used to characterize a dispersion-shifted fiber, allowing us to report spectrograms with multiple acoustic resonances. A very high 57 dB dynamic range is also reported for 100-ns-long pulses simultaneously with a 16 cm numerical resolution.

  18. Clock Synchronization Through Time-Variant Underwater Acoustic Channels

    DTIC Science & Technology

    2012-09-01

    stage, we analyze a series of chirp responses to identify the least time -varying multipath present in the channel between the two nodes. Based on the... based on the detected arrivals and determines the most stable one based on the correlation coefficient of a model fit to the time -of-arrival estimates...short periods of time . Nevertheless, signal fluctuations can occur due to transceiver motion or inherent changes within the propagation medium

  19. Xylem cavitation resistance can be estimated based on time-dependent rate of acoustic emissions.

    PubMed

    Nolf, Markus; Beikircher, Barbara; Rosner, Sabine; Nolf, Anton; Mayr, Stefan

    2015-10-01

    Acoustic emission (AE) analysis allows nondestructive monitoring of embolism formation in plant xylem, but signal interpretation and agreement of acoustically measured hydraulic vulnerability with reference hydraulic techniques remain under debate. We compared the hydraulic vulnerability of 16 species and three crop tree cultivars using hydraulic flow measurements and acoustic emission monitoring, proposing the use of time-dependent AE rates as a novel parameter for AE analysis. There was a linear correlation between the water potential (Ψ) at 50% loss of hydraulic conductivity (P50 ) and the Ψ at maximum AE activity (Pmaxrate ), where species with lower P50 also had lower Pmaxrate (P < 0.001, R(2)  = 0.76). Using AE rates instead of cumulative counts for AE analysis allows more efficient estimation of P50 , while excluding problematic AE at late stages of dehydration.

  20. Acoustic signal characteristics of laser induced cavitation in DDFP droplet: Spectrum and time-frequency analysis.

    PubMed

    Feng, Yi; Qin, Dui; Zhang, Jun; Ma, Chenxiang; Wan, Mingxi

    2015-01-01

    Cavitation has great application potential in microvessel damage and targeted drug delivery. Concerning cavitation, droplet vaporization has been widely investigated in vitro and in vivo with plasmonic nanoparticles. Droplets with a liquid dodecafluoropentane (DDFP) core enclosed in an albumin shell have a stable and simple structure with good characteristics of laser absorbing; thus, DDFP droplets could be an effective aim for laser-induced cavitation. The DDPF droplet was prepared and perfused in a mimic microvessel in the optical microscopic system with a passive acoustic detection module. Three patterns of laser-induced cavitation in the droplets were observed. The emitted acoustic signals showed specific spectrum components at specific time points. It was suggested that a nanosecond laser pulse could induce cavitation in DDPF droplets, and specific acoustic signals would be emitted. Analyzing its characteristics could aid in monitoring the laser-induced cavitation process in droplets, which is meaningful to theranostic application.

  1. Brain Blood Flow Related to Acoustic Laryngeal Reaction Time in Adult Developmental Stutterers.

    ERIC Educational Resources Information Center

    Watson, Ben C.; And Others

    1992-01-01

    This study sought to identify patterns of impaired acoustic laryngeal reaction time as a function of response complexity parallel to metabolic measures of brain function. Findings indicated that the disruption in speech motor control for 16 adult male developmental stutterers was systematically related to metabolic asymmetry in left superior and…

  2. Time-domain characterization of the acoustic damping of a perforated liner with bias flow.

    PubMed

    Zhong, Zhiyuan; Zhao, Dan

    2012-07-01

    Combustion instabilities are caused by the interaction of unsteady heat releases and acoustic waves. To mitigate combustion instabilities, perforated liners, typically subjected to a low Mach number bias flow (a cooling flow through perforated holes), are fitted along the bounding walls of a combustor. They dissipate the acoustic waves by generating vorticity at the rims of perforated apertures. To investigate the absorption of plane waves by a perforated liner with bias flow, a time-domain numerical model of a cylindrical lined duct is developed. The liners' damping mechanism is characterized by using a time-domain "compliance." The development of such time-domain compliance is based on simplified or unsimplified Rayleigh conductivity. Numerical simulations of two different configurations of lined duct systems are performed by combining a 1D acoustic wave model with the compliance model. Comparison is then made between the results from the present models, and those from the experiment and the frequency-domain model of previous investigation [Eldredge and Dowling, J. Fluid Mech. 485, 307-335(2003)]. Good agreement is observed. This confirms that the present model can be used to simulate the propagation and dissipation of acoustic plane waves in a lined duct in real-time.

  3. Effect of Foreshortening on Center-to-Limb Variations of Measured Acoustic Travel Times

    NASA Astrophysics Data System (ADS)

    Zhao, Junwei; Stejko, Andrey; Chen, Ruizhu

    2016-03-01

    We use data observed near the solar disk center by the Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI) to mimic observations at high-latitude areas after applying geometric transform and projection. These data are then used to study how foreshortening affects the time-distance measurements of acoustic travel times. We find that foreshortening reduces the measured mean travel-times through altering the acoustic-power weighting in different harmonic degrees, but the level of reduction and the latitude dependence are not as strong as those measured from the observation data at the same latitude. Foreshortening is not found to be accountable for the systematic center-to-limb effect in the measured acoustic travel-time differences, which is an essential factor for a reliable inference of the Sun's meridional-circulation profile. The differences in the acoustic power spectrum between the mimicked data and the observation data in high-latitude areas suggest that the optical spectrum-line formation height or convection cells in these areas may be the primary cause of the center-to-limb effect in helioseismic analyses.

  4. Reaction time to changes in the tempo of acoustic pulse trains.

    NASA Technical Reports Server (NTRS)

    Smith, R. P.; Warm, J. S.; Westendorf, D. H.

    1973-01-01

    Investigation of the ability of human observers to detect accelerations and decelerations in the rate of presentation of pulsed stimuli, i.e., changes in the tempo of acoustic pulse trains. Response times to accelerations in tempo were faster than to decelerations. Overall speed of response was inversely related to the pulse repetition rate.

  5. Time Ephemeris and General Relativistic Scale Factor

    NASA Astrophysics Data System (ADS)

    Fukushima, Toshio

    2010-11-01

    Time ephemeris is the location-independent part of the transformation formula relating two time coordinates such as TCB and TCG (Fukushima 2009). It is computed from the corresponding (space) ephemerides providing the relative motion of two spatial coordinate origins such as the motion of geocenter relative to the solar system barycenter. The time ephemerides are inevitably needed in conducting precise four dimensional coordinate transformations among various spacetime coordinate systems such as the GCRS and BCRS (Soffel et al. 2003). Also, by means of the time average operation, they are used in determining the information on scale conversion between the pair of coordinate systems, especially the difference of the general relativistic scale factor from unity such as LC. In 1995, we presented the first numerically-integrated time ephemeris, TE245, from JPL's planetary ephemeris DE245 (Fukushima 1995). It gave an estimate of LC as 1.4808268457(10) × 10-8, which was incorrect by around 2 × 10-16. This was caused by taking the wrong sign of the post-Newtonian contribution in the final summation. Four years later, we updated TE245 to TE405 associated with DE405 (Irwin and Fukushima 1999). This time the renewed vale of LC is 1.48082686741(200) × 10-8 Another four years later, by using a precise technique of time average, we improved the estimate of Newtonian part of LC for TE405 as 1.4808268559(6) × 10-8 (Harada and Fukushima 2003). This leads to the value of LC as LC = 1.48082686732(110) × 10-8. If we combine this with the constant defining the mean rate of TCG-TT, LG = 6.969290134 × 10-10 (IAU 2001), we estimate the numerical value of another general relativistic scale factor LB = 1.55051976763(110) × 10-8, which has the meaning of the mean rate of TCB-TT. The main reasons of the uncertainties are the truncation effect in time average and the uncertainty of asteroids' perturbation. As a compact realization of the time ephemeris, we prepared HF2002, a Fortran

  6. Time ephemeris and general relativistic scale factor

    NASA Astrophysics Data System (ADS)

    Fukushima, Toshio

    2010-01-01

    Time ephemeris is the location-independent part of the transformation formula relating two time coordinates such as TCB and TCG (Fukushima 1995). It is computed from the corresponding (space) ephemerides providing the relative motion of two spatial coordinate origins such as the motion of geocenter relative to the solar system barycenter. The time ephemerides are inevitably needed in conducting precise four dimensional coordinate transformations among various spacetime coordinate systems such as the GCRS and BCRS (Soffel et al. 2003). Also, by means of the time average operation, they are used in determining the information on scale conversion between the pair of coordinate systems, especially the difference of the general relativistic scale factor from unity such as LC. In 1995, we presented the first numerically-integrated time ephemeris, TE245, from JPL's planetary ephemeris DE245 (Fukushima 1995). It gave an estimate of LC as 1.4808268457(10) × 10-8, which was incorrect by around 2 × 10-16. This was caused by taking the wrong sign of the post-Newtonian contribution in the final summation. Four years later, we updated TE245 to TE405 associated with DE405 (Irwin and Fukushima 1999). This time the renewed vale of LC is 1.48082686741(200) × 10-8 Another four years later, by using a precise technique of time average, we improved the estimate of Newtonian part of LC for TE405 as 1.4808268559(6) × 10-8 (Harada and Fukushima 2003). This leads to the value of LC as LC = 1.48082686732(110) × 10-8. If we combine this with the constant defining the mean rate of TCG-TT, LG = 6.969290134 × 10-10 (IAU 2001), we estimate the numerical value of another general relativistic scale factor LB = 1.55051976763(110) × 10-8, which has the meaning of the mean rate of TCB-TT. The main reasons of the uncertainties are the truncation effect in time average and the uncertainty of asteroids' perturbation. The former is a natural limitation caused by the finite length of numerical

  7. Time Ephemeris and Relativistic Scaling of Ephemerides

    NASA Astrophysics Data System (ADS)

    Fukushima, Toshio

    2009-05-01

    Time ephemeris is the location-independent part of the transformation formula relating two time coordinates such as TCB and TCG. It is computed from the corresponding (space) ephemerides providing the relative motion of two spatial coordinate origins associated such as the motion of geocenter relative to the solar system barycenter. The time ephemerides are inevitablly needed in conducting a precise four-dimensional coordinate transformation among various spacetime coodrinate systems such as the GCRS and BCRS. Also, by means of the time average operation, it is useful in determining the information on scale conversion between the pair of coordinate systems, especially scale conversion factors such as LC. In 1995, we presented the first numerically-integrated time ephemeris, TE245, from JPL's planetary ephemeris DE245 (Fukushima 1995, A&Ap, 294, 895-906). Four years later, we updated it to TE405 associated with DE405 (Irwin and Fukushima 1999, A&Ap, 348, 642-652). The former gave an estimate of LC, the scale conversion factor between TCB and TCG, as 1.4808268457(10) x 10-8. Meanwhile the latter renewed it as 1.48082686741(200) x 10-8. Another four years later, by using a precise technique of time avarage, we improved the estimate as 1.4808268559(6) x 10-8 (Harada and Fukushima 2003, AJ, 126, 2557-2561). The main reasons of these uncertainties are the truncation effect in time average and the uncertainty of asteroids' perturbation. The former is a natural limitation caused by the finite length of numerical planetary ephemerides and the latter is due to the uncertainty of masses of some heavy asteroids. In the talk, we review the post-Newtonian formulas to integrate time ephemerides as well as some practical details on their numerical integration. Also, we explain two kinds of techniques of time average. One is a semi-numerical approach as explained in 1991 A&Ap article and the other is purely numerical as given in 2003 AJ paper.

  8. Acoustic Emission Patterns and the Transition to Ductility in Sub-Micron Scale Laboratory Earthquakes

    NASA Astrophysics Data System (ADS)

    Ghaffari, H.; Xia, K.; Young, R.

    2013-12-01

    We report observation of a transition from the brittle to ductile regime in precursor events from different rock materials (Granite, Sandstone, Basalt, and Gypsum) and Polymers (PMMA, PTFE and CR-39). Acoustic emission patterns associated with sub-micron scale laboratory earthquakes are mapped into network parameter spaces (functional damage networks). The sub-classes hold nearly constant timescales, indicating dependency of the sub-phases on the mechanism governing the previous evolutionary phase, i.e., deformation and failure of asperities. Based on our findings, we propose that the signature of the non-linear elastic zone around a crack tip is mapped into the details of the evolutionary phases, supporting the formation of a strongly weak zone in the vicinity of crack tips. Moreover, we recognize sub-micron to micron ruptures with signatures of 'stiffening' in the deformation phase of acoustic-waveforms. We propose that the latter rupture fronts carry critical rupture extensions, including possible dislocations faster than the shear wave speed. Using 'template super-shear waveforms' and their network characteristics, we show that the acoustic emission signals are possible super-shear or intersonic events. Ref. [1] Ghaffari, H. O., and R. P. Young. "Acoustic-Friction Networks and the Evolution of Precursor Rupture Fronts in Laboratory Earthquakes." Nature Scientific reports 3 (2013). [2] Xia, Kaiwen, Ares J. Rosakis, and Hiroo Kanamori. "Laboratory earthquakes: The sub-Rayleigh-to-supershear rupture transition." Science 303.5665 (2004): 1859-1861. [3] Mello, M., et al. "Identifying the unique ground motion signatures of supershear earthquakes: Theory and experiments." Tectonophysics 493.3 (2010): 297-326. [4] Gumbsch, Peter, and Huajian Gao. "Dislocations faster than the speed of sound." Science 283.5404 (1999): 965-968. [5] Livne, Ariel, et al. "The near-tip fields of fast cracks." Science 327.5971 (2010): 1359-1363. [6] Rycroft, Chris H., and Eran Bouchbinder

  9. Deciphering Time Scale Hierarchy in Reaction Networks.

    PubMed

    Nagahata, Yutaka; Maeda, Satoshi; Teramoto, Hiroshi; Horiyama, Takashi; Taketsugu, Tetsuya; Komatsuzaki, Tamiki

    2016-03-03

    Markovian dynamics on complex reaction networks are one of the most intriguing subjects in a wide range of research fields including chemical reactions, biological physics, and ecology. To represent the global kinetics from one node (corresponding to a basin on an energy landscape) to another requires information on multiple pathways that directly or indirectly connect these two nodes through the entire network. In this paper we present a scheme to extract a hierarchical set of global transition states (TSs) over a discrete-time Markov chain derived from first-order rate equations. The TSs can naturally take into account the multiple pathways connecting any pair of nodes. We also propose a new type of disconnectivity graph (DG) to capture the hierarchical organization of different time scales of reactions that can capture changes in the network due to changes in the time scale of observation. The crux is the introduction of the minimum conductance cut (MCC) in graph clustering, corresponding to the dividing surface across the network having the "smallest" transition probability between two disjoint subnetworks (superbasins on the energy landscape) in the network. We present a new combinatorial search algorithm for finding this MCC. We apply our method to a reaction network of Claisen rearrangement of allyl vinyl ether that consists of 23 nodes and 66 links (saddles on the energy landscape) connecting them. We compare the kinetic properties of our DG to those of the transition matrix of the rate equations and show that our graph can properly reveal the hierarchical organization of time scales in a network.

  10. Scaling laws from geomagnetic time series

    USGS Publications Warehouse

    Voros, Z.; Kovacs, P.; Juhasz, A.; Kormendi, A.; Green, A.W.

    1998-01-01

    The notion of extended self-similarity (ESS) is applied here for the X - component time series of geomagnetic field fluctuations. Plotting nth order structure functions against the fourth order structure function we show that low-frequency geomagnetic fluctuations up to the order n = 10 follow the same scaling laws as MHD fluctuations in solar wind, however, for higher frequencies (f > l/5[h]) a clear departure from the expected universality is observed for n > 6. ESS does not allow to make an unambiguous statement about the non triviality of scaling laws in "geomagnetic" turbulence. However, we suggest to use higher order moments as promising diagnostic tools for mapping the contributions of various remote magnetospheric sources to local observatory data. Copyright 1998 by the American Geophysical Union.

  11. Comparison between psycho-acoustics and physio-acoustic measurement to determine optimum reverberation time of pentatonic angklung music concert hall

    NASA Astrophysics Data System (ADS)

    Sudarsono, Anugrah S.; Merthayasa, I. G. N.; Suprijanto

    2015-09-01

    This research tried to compare psycho-acoustics and Physio-acoustic measurement to find the optimum reverberation time of soundfield from angklung music. Psycho-acoustic measurement was conducted using a paired comparison method and Physio-acoustic measurement was conducted with EEG Measurement on T3, T4, FP1, and FP2 measurement points. EEG measurement was conducted with 5 persons. Pentatonic angklung music was used as a stimulus with reverberation time variation. The variation was between 0.8 s - 1.6 s with 0.2 s step. EEG signal was analysed using a Power Spectral Density method on Alpha Wave, High Alpha Wave, and Theta Wave. Psycho-acoustic measurement on 50 persons showed that reverberation time preference of pentatonic angklung music was 1.2 second. The result was similar to Theta Wave measurement on FP2 measurement point. High Alpha wave on T4 measurement gave different results, but had similar patterns with psycho-acoustic measurement

  12. Periodic Time-Domain Nonlocal Nonreflecting Boundary Conditions for Duct Acoustics

    NASA Technical Reports Server (NTRS)

    Watson, Willie R.; Zorumski, William E.

    1996-01-01

    Periodic time-domain boundary conditions are formulated for direct numerical simulation of acoustic waves in ducts without flow. Well-developed frequency-domain boundary conditions are transformed into the time domain. The formulation is presented here in one space dimension and time; however, this formulation has an advantage in that its extension to variable-area, higher dimensional, and acoustically treated ducts is rigorous and straightforward. The boundary condition simulates a nonreflecting wave field in an infinite uniform duct and is implemented by impulse-response operators that are applied at the boundary of the computational domain. These operators are generated by convolution integrals of the corresponding frequency-domain operators. The acoustic solution is obtained by advancing the Euler equations to a periodic state with the MacCormack scheme. The MacCormack scheme utilizes the boundary condition to limit the computational space and preserve the radiation boundary condition. The success of the boundary condition is attributed to the fact that it is nonreflecting to periodic acoustic waves. In addition, transient waves can pass rapidly out of the solution domain. The boundary condition is tested for a pure tone and a multitone source in a linear setting. The effects of various initial conditions are assessed. Computational solutions with the boundary condition are consistent with the known solutions for nonreflecting wave fields in an infinite uniform duct.

  13. Wireless acoustic modules for real-time data fusion using asynchronous sniper localization algorithms

    NASA Astrophysics Data System (ADS)

    Hengy, S.; De Mezzo, S.; Duffner, P.; Naz, P.

    2012-11-01

    The presence of snipers in modern conflicts leads to high insecurity for the soldiers. In order to improve the soldier's protection against this threat, the French German Research Institute of Saint-Louis (ISL) has been conducting studies in the domain of acoustic localization of shots. Mobile antennas mounted on the soldier's helmet were initially used for real-time detection, classification and localization of sniper shots. It showed good performances in land scenarios, but also in urban scenarios if the array was in the shot corridor, meaning that the microphones first detect the direct wave and then the reflections of the Mach and muzzle waves (15% distance estimation error compared to the actual shooter array distance). Fusing data sent by multiple sensor nodes distributed on the field showed some of the limitations of the technologies that have been implemented in ISL's demonstrators. Among others, the determination of the arrays' orientation was not accurate enough, thereby degrading the performance of data fusion. Some new solutions have been developed in the past year in order to obtain better performance for data fusion. Asynchronous localization algorithms have been developed and post-processed on data measured in both free-field and urban environments with acoustic modules on the line of sight of the shooter. These results are presented in the first part of the paper. The impact of GPS position estimation error is also discussed in the article in order to evaluate the possible use of those algorithms for real-time processing using mobile acoustic nodes. In the frame of ISL's transverse project IMOTEP (IMprovement Of optical and acoustical TEchnologies for the Protection), some demonstrators are developed that will allow real-time asynchronous localization of sniper shots. An embedded detection and classification algorithm is implemented on wireless acoustic modules that send the relevant information to a central PC. Data fusion is then processed and the

  14. Selective attention to temporal features on nested time scales.

    PubMed

    Henry, Molly J; Herrmann, Björn; Obleser, Jonas

    2015-02-01

    Meaningful auditory stimuli such as speech and music often vary simultaneously along multiple time scales. Thus, listeners must selectively attend to, and selectively ignore, separate but intertwined temporal features. The current study aimed to identify and characterize the neural network specifically involved in this feature-selective attention to time. We used a novel paradigm where listeners judged either the duration or modulation rate of auditory stimuli, and in which the stimulation, working memory demands, response requirements, and task difficulty were held constant. A first analysis identified all brain regions where individual brain activation patterns were correlated with individual behavioral performance patterns, which thus supported temporal judgments generically. A second analysis then isolated those brain regions that specifically regulated selective attention to temporal features: Neural responses in a bilateral fronto-parietal network including insular cortex and basal ganglia decreased with degree of change of the attended temporal feature. Critically, response patterns in these regions were inverted when the task required selectively ignoring this feature. The results demonstrate how the neural analysis of complex acoustic stimuli with multiple temporal features depends on a fronto-parietal network that simultaneously regulates the selective gain for attended and ignored temporal features.

  15. Acoustic sensor for monitoring adhesion of Neuro-2A cells in real-time.

    PubMed

    Khraiche, Massoud Louis; Zhou, Anhong; Muthuswamy, Jit

    2005-05-15

    Neuronal adhesion plays a fundamental role in growth, migration, regeneration and plasticity of neurons. However, current methods for studying neuronal adhesion cannot monitor this phenomenon quantitatively in real-time. In this work, we demonstrate the use of an acoustic sensor to measure adhesion of neuro-blastoma cells (Neuro-2A) in real-time. An acoustic sensor consisting of a quartz crystal sandwiched between gold electrodes was placed in a flow cell and filled with 600 microl of phosphate buffered saline (PBS). Two sets of in vitro experiments were performed using sensors that had uncoated gold electrodes and sensors that were coated with a known neuronal adhesion promoter (poly-l-lysine or PLL). The instantaneous resonant frequency and the equivalent motional resistance of the acoustic sensor were monitored every second. Cell Tracker was used to confirm neuronal adhesion to the surface. Addition of 10 microl of media and Neuro-2A cells into the above set-up elicited exponential changes in the resonant frequency and motional resistance of the quartz crystal with time to reach steady state in the range of 2-11 h. The steady-state change in resonant frequency in response to addition of neurons was linearly related to the number of Neuro-2A cells added (R2=0.94). Acoustic sensors coated with the adhesion promoter, PLL showed a much higher change in resonant frequency for approximately the same number of neurons. We conclude that the acoustic sensor has sufficient sensitivity to monitor neuronal adhesion in real-time. This has potential applications in the study of mechanisms of neuron-substrate interactions and the effect of molecular modulators in the extra cellular matrix.

  16. Acoustic imaging with time reversal methods: From medicine to NDT

    NASA Astrophysics Data System (ADS)

    Fink, Mathias

    2015-03-01

    This talk will present an overview of the research conducted on ultrasonic time-reversal methods applied to biomedical imaging and to non-destructive testing. We will first describe iterative time-reversal techniques that allow both focusing ultrasonic waves on reflectors in tissues (kidney stones, micro-calcifications, contrast agents) or on flaws in solid materials. We will also show that time-reversal focusing does not need the presence of bright reflectors but it can be achieved only from the speckle noise generated by random distributions of non-resolved scatterers. We will describe the applications of this concept to correct distortions and aberrations in ultrasonic imaging and in NDT. In the second part of the talk we will describe the concept of time-reversal processors to get ultrafast ultrasonic images with typical frame rates of order of 10.000 F/s. It is the field of ultrafast ultrasonic imaging that has plenty medical applications and can be of great interest in NDT. We will describe some applications in the biomedical domain: Quantitative Elasticity imaging of tissues by following shear wave propagation to improve cancer detection and Ultrafast Doppler imaging that allows ultrasonic functional imaging.

  17. Acoustic characteristics of a large scale wind-tunnel model of a jet flap aircraft

    NASA Technical Reports Server (NTRS)

    Falarski, M. D.; Aiken, T. N.; Aoyagi, K.

    1975-01-01

    The expanding-duct jet flap (EJF) concept is studied to determine STOL performance in turbofan-powered aircraft. The EJF is used to solve the problem of ducting the required volume of air into the wing by providing an expanding cavity between the upper and lower surfaces of the flap. The results are presented of an investigation of the acoustic characteristics of the EJF concept on a large-scale aircraft model powered by JT15D engines. The noise of the EJF is generated by acoustic dipoles as shown by the sixth power dependence of the noise on jet velocity. These sources result from the interaction of the flow turbulence with flap of internal and external surfaces and the trailing edges. Increasing the trailing edge jet from 70 percent span to 100 percent span increased the noise 2 db for the equivalent nozzle area. Blowing at the knee of the flap rather than the trailing edge reduced the noise 5 to 10 db by displacing the jet from the trailing edge and providing shielding from high-frequency noise. Deflecting the flap and varying the angle of attack modified the directivity of the underwing noise but did not affect the peak noise. A forward speed of 33.5 m/sec (110 ft/sec) reduced the dipole noise less than 1 db.

  18. Subjective scaling of spatial room acoustic parameters influenced by visual environmental cues

    PubMed Central

    Valente, Daniel L.; Braasch, Jonas

    2010-01-01

    Although there have been numerous studies investigating subjective spatial impression in rooms, only a few of those studies have addressed the influence of visual cues on the judgment of auditory measures. In the psychophysical study presented here, video footage of five solo music∕speech performers was shown for four different listening positions within a general-purpose space. The videos were presented in addition to the acoustic signals, which were auralized using binaural room impulse responses (BRIR) that were recorded in the same general-purpose space. The participants were asked to adjust the direct-to-reverberant energy ratio (D∕R ratio) of the BRIR according to their expectation considering the visual cues. They were also directed to rate the apparent source width (ASW) and listener envelopment (LEV) for each condition. Visual cues generated by changing the sound-source position in the multi-purpose space, as well as the makeup of the sound stimuli affected the judgment of spatial impression. Participants also scaled the direct-to-reverberant energy ratio with greater direct sound energy than was measured in the acoustical environment. PMID:20968367

  19. [Research on Time-frequency Characteristics of Magneto-acoustic Signal of Different Thickness Medium Based on Wave Summing Method].

    PubMed

    Zhang, Shunqi; Yin, Tao; Ma, Ren; Liu, Zhipeng

    2015-08-01

    Functional imaging method of biological electrical characteristics based on magneto-acoustic effect gives valuable information of tissue in early tumor diagnosis, therein time and frequency characteristics analysis of magneto-acoustic signal is important in image reconstruction. This paper proposes wave summing method based on Green function solution for acoustic source of magneto-acoustic effect. Simulations and analysis under quasi 1D transmission condition are carried out to time and frequency characteristics of magneto-acoustic signal of models with different thickness. Simulation results of magneto-acoustic signal were verified through experiments. Results of the simulation with different thickness showed that time-frequency characteristics of magneto-acoustic signal reflected thickness of sample. Thin sample, which is less than one wavelength of pulse, and thick sample, which is larger than one wavelength, showed different summed waveform and frequency characteristics, due to difference of summing thickness. Experimental results verified theoretical analysis and simulation results. This research has laid a foundation for acoustic source and conductivity reconstruction to the medium with different thickness in magneto-acoustic imaging.

  20. Cratering time scales for the Galilean satellites

    NASA Technical Reports Server (NTRS)

    Shoemaker, E. M.; Wolfe, R. F.

    1982-01-01

    An attempt is made to estimate the present cratering rate for each Galilean satellite within the correct order of magnitude and to extend the cratering rates back into the geologic past on the basis of evidence from the earth-moon system. For collisions with long and short period comets, the magnitudes and size distributions of the comet nuclei, the distribution of their perihelion distances, and the completeness of discovery are addressed. The diameters and masses of cometary nuclei are assessed, as are crater diameters and cratering rates. The dynamical relations between long period and short period comets are discussed, and the population of Jupiter-crossing asteroids is assessed. Estimated present cratering rates on the Galilean satellites are compared and variations of cratering rate with time are considered. Finally, the consistency of derived cratering time scales with the cratering record of the icy Galilean satellites is discussed.

  1. Acoustic and optical methods to infer water transparency at Time Series Station Spiekeroog, Wadden Sea

    NASA Astrophysics Data System (ADS)

    Schulz, Anne-Christin; Badewien, Thomas H.; Garaba, Shungudzemwoyo P.; Zielinski, Oliver

    2016-11-01

    Water transparency is a primary indicator of optical water quality that is driven by suspended particulate and dissolved material. A data set from the operational Time Series Station Spiekeroog located at a tidal inlet of the Wadden Sea was used to perform (i) an inter-comparison of observations related to water transparency, (ii) correlation tests among these measured parameters, and (iii) to explore the utility of both acoustic and optical tools in monitoring water transparency. An Acoustic Doppler Current Profiler was used to derive the backscatter signal in the water column. Optical observations were collected using above-water hyperspectral radiometers and a submerged turbidity metre. Bio-fouling on the turbidity sensors optical windows resulted in measurement drift and abnormal values during quality control steps. We observed significant correlations between turbidity collected by the submerged metre and that derived from above-water radiometer observations. Turbidity from these sensors was also associated with the backscatter signal derived from the acoustic measurements. These findings suggest that both optical and acoustic measurements can be reasonable proxies of water transparency with the potential to mitigate gaps and increase data quality in long-time observation of marine environments.

  2. Acoustic Treatment Design Scaling Methods. Volume 2; Advanced Treatment Impedance Models for High Frequency Ranges

    NASA Technical Reports Server (NTRS)

    Kraft, R. E.; Yu, J.; Kwan, H. W.

    1999-01-01

    The primary purpose of this study is to develop improved models for the acoustic impedance of treatment panels at high frequencies, for application to subscale treatment designs. Effects that cause significant deviation of the impedance from simple geometric scaling are examined in detail, an improved high-frequency impedance model is developed, and the improved model is correlated with high-frequency impedance measurements. Only single-degree-of-freedom honeycomb sandwich resonator panels with either perforated sheet or "linear" wiremesh faceplates are considered. The objective is to understand those effects that cause the simple single-degree-of- freedom resonator panels to deviate at the higher-scaled frequency from the impedance that would be obtained at the corresponding full-scale frequency. This will allow the subscale panel to be designed to achieve a specified impedance spectrum over at least a limited range of frequencies. An advanced impedance prediction model has been developed that accounts for some of the known effects at high frequency that have previously been ignored as a small source of error for full-scale frequency ranges.

  3. Small scale aspects of warm dark matter: Power spectra and acoustic oscillations

    SciTech Connect

    Boyanovsky, Daniel; Wu Jun

    2011-02-15

    We provide a semianalytic derivation of approximate evolution equations for density perturbations of warm dark matter candidates that decoupled while relativistic with arbitrary distribution functions, their solutions at small scales, and a simple numerical implementation that yields their transfer functions and power spectra. Density perturbations evolve through three stages: radiation domination when the particle is relativistic and nonrelativistic and matter domination. An early integrated Sachs-Wolfe effect during the first stage leads to an enhancement of density perturbations and a plateau in the transfer function for k < or approx. k{sub fs}, the free-streaming wave vector. An effective fluid description emerges at small scales which includes the effects of free streaming in initial conditions and inhomogeneities. The transfer function features warm dark matter acoustic oscillations at scales k > or approx. 2k{sub fs}. A simple analytic interpolation of the power spectra between large and small scales and a numerical implementation valid for arbitrary distribution functions is provided. As an application we study the power spectra for two models of sterile neutrinos with m{approx}keV produced nonresonantly and compare our results to those obtained from Boltzmann codes.

  4. Parametric instabilities in picosecond time scales

    SciTech Connect

    Baldis, H.A.; Rozmus, W.; Labaune, C.; Mounaix, Ph.; Pesme, D.; Baton, S.; Tikhonchuk, V.T.

    1993-03-01

    The coupling of intense laser light with plasmas is a rich field of plasma physics, with many applications. Among these are inertial confinement fusion (ICF), x-ray lasers, particle acceleration, and x-ray sources. Parametric instabilities have been studied for many years because of their importance to ICF; with laser pulses with duration of approximately a nanosecond, and laser intensities in the range 10{sup 14}--10{sup 15}W/cm{sup 2} these instabilities are of crucial concern because of a number of detrimental effects. Although the laser pulse duration of interest for these studies are relatively long, it has been evident in the past years that to reach an understanding of these instabilities requires their characterization and analysis in picosecond time scales. At the laser intensities of interest, the growth rate for stimulated Brillouin scattering (SBS) is of the order of picoseconds, and of an order of magnitude shorter for stimulated Raman scattering (SRS). In this paper the authors discuss SBS and SRS in the context of their evolution in picosecond time scales. They describe the fundamental concepts associated with their growth and saturation, and recent work on the nonlinear treatment required for the modeling of these instabilities at high laser intensities.

  5. Small scale model static acoustic investigation of hybrid high lift systems combining upper surface blowing with the internally blown flap

    NASA Technical Reports Server (NTRS)

    Cole, T. W.; Rathburn, E. A.

    1974-01-01

    A static acoustic and propulsion test of a small radius Jacobs-Hurkamp and a large radius Flex Flap combined with four upper surface blowing (USB) nozzles was performed. Nozzle force and flow data, flap trailing edge total pressure survey data, and acoustic data were obtained. Jacobs-Hurkamp flap surface pressure data, flow visualization photographs, and spoiler acoustic data from the limited mid-year tests are reported. A pressure ratio range of 1.2 to 1.5 was investigated for the USB nozzles and for the auxiliary blowing slots. The acoustic data were scaled to a four-engine STOL airplane of roughly 110,000 kilograms or 50,000 pounds gross weight, corresponding to a model scale of approximately 0.2 for the nozzles without deflector. The model nozzle scale is actually reduced to about .17 with deflector although all results in this report assume 0.2 scale factor. Trailing edge pressure surveys indicated that poor flow attachment was obtained even at large flow impingement angles unless a nozzle deflector plate was used. Good attachment was obtained with the aspect ratio four nozzle with deflector, confirming the small scale wind tunnel tests.

  6. Chronic stroke and aging: the impact of acoustic stimulus intensity on fractionated reaction time.

    PubMed

    Coombes, Stephen A; Janelle, Christopher M; Cauraugh, James H

    2009-03-13

    In control samples, intense acoustic "go" stimuli accelerate the central and peripheral motor processes that compose simple reaction time movements. The goal of the current study was to determine whether movements that are initiated to intense acoustic cues facilitate simple reaction times in (1) adults with chronic stroke as compared to age matched controls and (2) in older as compared to younger adults. EMG and force data were collected from three groups (stroke, older adults, and younger adults) during a ballistic wrist and finger extension task. Movements were made to the onset of 80 dB and 107 dB acoustic cues and simple reaction times were fractionated into premotor and motor components. The present findings offer two important contributions to the literature. First, increases in stimulus intensity led to faster motor times in the impaired limb of stroke subjects. Second, increased stimulus intensity led to faster premotor reaction times across all groups, although an age rather than a stroke-specific motor deficit was evidenced, with the younger control group displaying significantly faster premotor times. Findings are integrated with previous evidence concerning post stroke corticospinal tract integrity and are interpreted via mechanisms which address stroke and age-related changes in motoneurons and activity in motor units.

  7. ACOUSTIC SCALE FROM THE ANGULAR POWER SPECTRA OF SDSS-III DR8 PHOTOMETRIC LUMINOUS GALAXIES

    SciTech Connect

    Seo, Hee-Jong; Ho, Shirley; White, Martin; Reid, Beth; Schlegel, David J.; Cuesta, Antonio J.; Padmanabhan, Nikhil; Ross, Ashley J.; Percival, Will J.; Nichol, Robert C.; Saito, Shun; De Putter, Roland; Eisenstein, Daniel J.; Xu Xiaoying; Skibba, Ramin; Schneider, Donald P.; Verde, Licia; Bizyaev, Dmitry; Brewington, Howard; Brinkmann, J.; and others

    2012-12-10

    We measure the acoustic scale from the angular power spectra of the Sloan Digital Sky Survey III (SDSS-III) Data Release 8 imaging catalog that includes 872, 921 galaxies over {approx}10,000 deg{sup 2} between 0.45 < z < 0.65. The extensive spectroscopic training set of the Baryon Oscillation Spectroscopic Survey luminous galaxies allows precise estimates of the true redshift distributions of galaxies in our imaging catalog. Utilizing the redshift distribution information, we build templates and fit to the power spectra of the data, which are measured in our companion paper, to derive the location of Baryon acoustic oscillations (BAOs) while marginalizing over many free parameters to exclude nearly all of the non-BAO signal. We derive the ratio of the angular diameter distance to the sound horizon scale D{sub A} (z)/r{sub s} = 9.212{sup +0.416}{sub -{sub 0.404}} at z = 0.54, and therefore D{sub A} (z) = 1411 {+-} 65 Mpc at z = 0.54; the result is fairly independent of assumptions on the underlying cosmology. Our measurement of angular diameter distance D{sub A} (z) is 1.4{sigma} higher than what is expected for the concordance {Lambda}CDM, in accordance to the trend of other spectroscopic BAO measurements for z {approx}> 0.35. We report constraints on cosmological parameters from our measurement in combination with the WMAP7 data and the previous spectroscopic BAO measurements of SDSS and WiggleZ. We refer to our companion papers (Ho et al.; de Putter et al.) for investigations on information of the full power spectrum.

  8. Non-intrusive, high-resolution, real-time, two-dimensional imaging of multiphase materials using acoustic array sensors

    SciTech Connect

    Cassiède, M.; Shaw, J. M.

    2015-04-15

    Two parallel multi-element ultrasonic acoustic arrays combined with sets of focal laws for acoustic signal generation and a classical tomographic inversion algorithm are used to generate real-time two-dimensional micro seismic acoustic images of multiphase materials. Proof of concept and calibration measurements were performed for single phase and two phase liquids, uniform polyvinyl chloride (PVC) plates, and aluminum cylinders imbedded in PVC plates. Measurement artefacts, arising from the limited range of viewing angles, and the compromise between data acquisition rate and image quality are discussed. The angle range of scanning and the image resolution were varied, and the effects on the quality of the reproduction of the speed of sound profiles of model solids and liquids with known geometries and compositions were analysed in detail. The best image quality results were obtained for a scanning angle range of [−35°, 35°] at a step size of 2.5° post processed to generate images on a 40 μm square grid. The data acquisition time for high quality images with a 30 mm × 40 mm view field is 10 min. Representation of two-phase solids with large differences in speed of sound between phases and where one phase is dispersed in the form of macroscopic objects (greater than 1 mm in diameter) proved to be the most difficult to image accurately. Liquid-liquid and liquid-vapor phase boundaries, in micro porous solids by contrast, were more readily defined. Displacement of air by water and water by heptane in natural porous limestone provides illustrative kinetic examples. Measurement results with these realistic cases demonstrate the feasibility of the technique to monitor in real time and on the micrometer length scale local composition and flow of organic liquids in inorganic porous media, one of many envisioned engineering applications. Improvement of data acquisition rate is an area for future collaborative study.

  9. Non-intrusive, high-resolution, real-time, two-dimensional imaging of multiphase materials using acoustic array sensors

    NASA Astrophysics Data System (ADS)

    Cassiède, M.; Shaw, J. M.

    2015-04-01

    Two parallel multi-element ultrasonic acoustic arrays combined with sets of focal laws for acoustic signal generation and a classical tomographic inversion algorithm are used to generate real-time two-dimensional micro seismic acoustic images of multiphase materials. Proof of concept and calibration measurements were performed for single phase and two phase liquids, uniform polyvinyl chloride (PVC) plates, and aluminum cylinders imbedded in PVC plates. Measurement artefacts, arising from the limited range of viewing angles, and the compromise between data acquisition rate and image quality are discussed. The angle range of scanning and the image resolution were varied, and the effects on the quality of the reproduction of the speed of sound profiles of model solids and liquids with known geometries and compositions were analysed in detail. The best image quality results were obtained for a scanning angle range of [-35°, 35°] at a step size of 2.5° post processed to generate images on a 40 μm square grid. The data acquisition time for high quality images with a 30 mm × 40 mm view field is 10 min. Representation of two-phase solids with large differences in speed of sound between phases and where one phase is dispersed in the form of macroscopic objects (greater than 1 mm in diameter) proved to be the most difficult to image accurately. Liquid-liquid and liquid-vapor phase boundaries, in micro porous solids by contrast, were more readily defined. Displacement of air by water and water by heptane in natural porous limestone provides illustrative kinetic examples. Measurement results with these realistic cases demonstrate the feasibility of the technique to monitor in real time and on the micrometer length scale local composition and flow of organic liquids in inorganic porous media, one of many envisioned engineering applications. Improvement of data acquisition rate is an area for future collaborative study.

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

    NASA Astrophysics Data System (ADS)

    Karlsen, Jonas T.; Augustsson, Per; Bruus, Henrik

    2016-09-01

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

  11. Time-frequency Analysis for Acoustic Emission Signals of Hypervelocity Impact

    NASA Astrophysics Data System (ADS)

    Liu, W. G.; Pang, B. J.; Zhang, W.; Sun, F.; Guan, G. S.

    The risk of collision of man-made orbital debris with spacecraft in near Earth orbits continues to increase A major of the space debris between 1mm and 10mm can t be well tracked in Earth orbits Damage from these un-tracked debris impacts is a serious hazard to aircraft and spacecraft These on-orbit collisions occur at velocities exceeding 10km s and at these velocities even very small particles can create significant damage The development of in-situ impact detecting system is indispensable for protecting the spacecraft from tragedy malfunction by the debris Acoustic Emission AE detecting technique has been recognized as an important technology for non-destructive detecting due to the AE signals offering a potentially useful additional means of non-invasively gathering concerning the state of spacecrafts Also Acoustic emission health monitoring is able to detect locate and assess impact damage when the spacecrafts is impacted by hypervelocity space debris and micrometeoroids This information can help operators and designers at the ground station take effective measures to maintain the function of spacecraft In this article Acoustic emission AE is used for characterization and location for hypervelocity Impacts Two different Acoustic Emission AE sensors were used to detect the arrival time and signals of the hits Hypervelocity Impacts were generated with a two-stage light-gas gun firing small Aluminum ball projectiles 4mm 6 4mm In the impact studies the signals were recorded with Disp AEwin PAC instruments by the conventional crossing

  12. A micromachined silicon parallel acoustic delay line (PADL) array for real-time photoacoustic tomography (PAT)

    NASA Astrophysics Data System (ADS)

    Cho, Young Y.; Chang, Cheng-Chung; Wang, Lihong V.; Zou, Jun

    2015-03-01

    To achieve real-time photoacoustic tomography (PAT), massive transducer arrays and data acquisition (DAQ) electronics are needed to receive the PA signals simultaneously, which results in complex and high-cost ultrasound receiver systems. To address this issue, we have developed a new PA data acquisition approach using acoustic time delay. Optical fibers were used as parallel acoustic delay lines (PADLs) to create different time delays in multiple channels of PA signals. This makes the PA signals reach a single-element transducer at different times. As a result, they can be properly received by single-channel DAQ electronics. However, due to their small diameter and fragility, using optical fiber as acoustic delay lines poses a number of challenges in the design, construction and packaging of the PADLs, thereby limiting their performances and use in real imaging applications. In this paper, we report the development of new silicon PADLs, which are directly made from silicon wafers using advanced micromachining technologies. The silicon PADLs have very low acoustic attenuation and distortion. A linear array of 16 silicon PADLs were assembled into a handheld package with one common input port and one common output port. To demonstrate its real-time PAT capability, the silicon PADL array (with its output port interfaced with a single-element transducer) was used to receive 16 channels of PA signals simultaneously from a tissue-mimicking optical phantom sample. The reconstructed PA image matches well with the imaging target. Therefore, the silicon PADL array can provide a 16× reduction in the ultrasound DAQ channels for real-time PAT.

  13. Identification of Damaged Wheat Kernels and Cracked-Shell Hazelnuts with Impact Acoustics Time-Frequency Patterns

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A new adaptive time-frequency (t-f) analysis and classification procedure is applied to impact acoustic signals for detecting hazelnuts with cracked shells and three types of damaged wheat kernels. Kernels were dropped onto a steel plate, and the resulting impact acoustic signals were recorded with ...

  14. EDITORIAL: Special issue on time scale algorithms

    NASA Astrophysics Data System (ADS)

    Matsakis, Demetrios; Tavella, Patrizia

    2008-12-01

    This special issue of Metrologia presents selected papers from the Fifth International Time Scale Algorithm Symposium (VITSAS), including some of the tutorials presented on the first day. The symposium was attended by 76 persons, from every continent except Antarctica, by students as well as senior scientists, and hosted by the Real Instituto y Observatorio de la Armada (ROA) in San Fernando, Spain, whose staff further enhanced their nation's high reputation for hospitality. Although a timescale can be simply defined as a weighted average of clocks, whose purpose is to measure time better than any individual clock, timescale theory has long been and continues to be a vibrant field of research that has both followed and helped to create advances in the art of timekeeping. There is no perfect timescale algorithm, because every one embodies a compromise involving user needs. Some users wish to generate a constant frequency, perhaps not necessarily one that is well-defined with respect to the definition of a second. Other users might want a clock which is as close to UTC or a particular reference clock as possible, or perhaps wish to minimize the maximum variation from that standard. In contrast to the steered timescales that would be required by those users, other users may need free-running timescales, which are independent of external information. While no algorithm can meet all these needs, every algorithm can benefit from some form of tuning. The optimal tuning, and even the optimal algorithm, can depend on the noise characteristics of the frequency standards, or of their comparison systems, the most precise and accurate of which are currently Two Way Satellite Time and Frequency Transfer (TWSTFT) and GPS carrier phase time transfer. The interest in time scale algorithms and its associated statistical methodology began around 40 years ago when the Allan variance appeared and when the metrological institutions started realizing ensemble atomic time using more than

  15. 5 Percent Ares I Scale Model Acoustic Test: Overpressure Characterization and Analysis

    NASA Technical Reports Server (NTRS)

    Alvord, David; Casiano, Matthew; McDaniels, Dave

    2011-01-01

    During the ignition of a ducted solid rocket motor (SRM), rapid expansion of injected hot gases from the motor into a confined volume causes the development of a steep fronted wave. This low frequency transient wave propagates outward from the exhaust duct, impinging the vehicle and ground structures. An unsuppressed overpressure wave can potentially cause modal excitation in the structures and vehicle, subsequently leading to damage. This presentation details the ignition transient f indings from the 5% Ares I Scale Model Acoustic Test (ASMAT). The primary events of the ignition transient environment induced by the SRM are the ignition overpressure (IOP), duct overpressure (DOP), and source overpressure (SOP). The resulting observations include successful knockdown of the IOP environment through use of a Space Shuttle derived IOP suppression system, a potential load applied to the vehicle stemming from instantaneous asymmetrical IOP and DOP wave impingement, and launch complex geometric influences on the environment. The results are scaled to a full-scale Ares I equivalent and compared with heritage data including Ares I-X and both suppressed and unsuppressed Space Shuttle IOP environments.

  16. Near-Real-Time Acoustic Monitoring of Beaked Whales and Other Cetaceans Using a Seaglider™

    PubMed Central

    Klinck, Holger; Mellinger, David K.; Klinck, Karolin; Bogue, Neil M.; Luby, James C.; Jump, William A.; Shilling, Geoffrey B.; Litchendorf, Trina; Wood, Angela S.; Schorr, Gregory S.; Baird, Robin W.

    2012-01-01

    In most areas, estimating the presence and distribution of cryptic marine mammal species, such as beaked whales, is extremely difficult using traditional observational techniques such as ship-based visual line transect surveys. Because acoustic methods permit detection of animals underwater, at night, and in poor weather conditions, passive acoustic observation has been used increasingly often over the last decade to study marine mammal distribution, abundance, and movements, as well as for mitigation of potentially harmful anthropogenic effects. However, there is demand for new, cost-effective tools that allow scientists to monitor areas of interest autonomously with high temporal and spatial resolution in near-real time. Here we describe an autonomous underwater vehicle – a glider – equipped with an acoustic sensor and onboard data processing capabilities to passively scan an area for marine mammals in near-real time. The glider was tested extensively off the west coast of the Island of Hawai'i, USA. The instrument covered approximately 390 km during three weeks at sea and collected a total of 194 h of acoustic data. Detections of beaked whales were successfully reported to shore in near-real time. Manual analysis of the recorded data revealed a high number of vocalizations of delphinids and sperm whales. Furthermore, the glider collected vocalizations of unknown origin very similar to those made by known species of beaked whales. The instrument developed here can be used to cost-effectively screen areas of interest for marine mammals for several months at a time. The near-real-time detection and reporting capabilities of the glider can help to protect marine mammals during potentially harmful anthropogenic activities such as seismic exploration for sub-sea fossil fuels or naval sonar exercises. Furthermore, the glider is capable of under-ice operation, allowing investigation of otherwise inaccessible polar environments that are critical habitats for many

  17. Near-real-time acoustic monitoring of beaked whales and other cetaceans using a Seaglider™.

    PubMed

    Klinck, Holger; Mellinger, David K; Klinck, Karolin; Bogue, Neil M; Luby, James C; Jump, William A; Shilling, Geoffrey B; Litchendorf, Trina; Wood, Angela S; Schorr, Gregory S; Baird, Robin W

    2012-01-01

    In most areas, estimating the presence and distribution of cryptic marine mammal species, such as beaked whales, is extremely difficult using traditional observational techniques such as ship-based visual line transect surveys. Because acoustic methods permit detection of animals underwater, at night, and in poor weather conditions, passive acoustic observation has been used increasingly often over the last decade to study marine mammal distribution, abundance, and movements, as well as for mitigation of potentially harmful anthropogenic effects. However, there is demand for new, cost-effective tools that allow scientists to monitor areas of interest autonomously with high temporal and spatial resolution in near-real time. Here we describe an autonomous underwater vehicle--a glider--equipped with an acoustic sensor and onboard data processing capabilities to passively scan an area for marine mammals in near-real time. The glider was tested extensively off the west coast of the Island of Hawai'i, USA. The instrument covered approximately 390 km during three weeks at sea and collected a total of 194 h of acoustic data. Detections of beaked whales were successfully reported to shore in near-real time. Manual analysis of the recorded data revealed a high number of vocalizations of delphinids and sperm whales. Furthermore, the glider collected vocalizations of unknown origin very similar to those made by known species of beaked whales. The instrument developed here can be used to cost-effectively screen areas of interest for marine mammals for several months at a time. The near-real-time detection and reporting capabilities of the glider can help to protect marine mammals during potentially harmful anthropogenic activities such as seismic exploration for sub-sea fossil fuels or naval sonar exercises. Furthermore, the glider is capable of under-ice operation, allowing investigation of otherwise inaccessible polar environments that are critical habitats for many

  18. Time Horizon and Social Scale in Communication

    NASA Astrophysics Data System (ADS)

    Krantz, D. H.

    2010-12-01

    In 2009 our center (CRED) published a first version of The Psychology of Climate Change Communication. In it, we attempted to summarize facts and concepts from psychological research that could help guide communication. While this work focused on climate change, most of the ideas are at least partly applicable for communication about a variety of natural hazards. Of the many examples in this guide, I mention three. Single-action bias is the human tendency to stop considering further actions that might be needed to deal with a given hazard, once a single action has been taken. Another example is the importance of group affiliation in motivating voluntary contributions to joint action. A third concerns the finding that group participation enhances understanding of probabilistic concepts and promotes action in the face of uncertainty. One current research direction, which goes beyond those included in the above publication, focuses on how time horizons arise in the thinking of individuals and groups, and how these time horizons might influence hazard preparedness. On the one hand, individuals sometimes appear impatient, organizations look for immediate results, and officials fail to look beyond the next election cycle. Yet under some laboratory conditions and in some subcultures, a longer time horizon is adopted. We are interested in how time horizon is influenced by group identity and by the very architecture of planning and decision making. Institutional changes, involving long-term contractual relationships among communities, developers, insurers, and governments, could greatly increase resilience in the face of natural hazards. Communication about hazards, in the context of such long-term contractual relationships might look very different from communication that is first initiated by immediate threat. Another new direction concerns the social scale of institutions and of communication about hazards. Traditionally, insurance contracts share risk among a large

  19. Real-time reporting of baleen whale passive acoustic detections from ocean gliders.

    PubMed

    Baumgartner, Mark F; Fratantoni, David M; Hurst, Thomas P; Brown, Moira W; Cole, Tim V N; Van Parijs, Sofie M; Johnson, Mark

    2013-09-01

    In the past decade, much progress has been made in real-time passive acoustic monitoring of marine mammal occurrence and distribution from autonomous platforms (e.g., gliders, floats, buoys), but current systems focus primarily on a single call type produced by a single species, often from a single location. A hardware and software system was developed to detect, classify, and report 14 call types produced by 4 species of baleen whales in real time from ocean gliders. During a 3-week deployment in the central Gulf of Maine in late November and early December 2012, two gliders reported over 25,000 acoustic detections attributed to fin, humpback, sei, and right whales. The overall false detection rate for individual calls was 14%, and for right, humpback, and fin whales, false predictions of occurrence during 15-min reporting periods were 5% or less. Transmitted pitch tracks--compact representations of sounds--allowed unambiguous identification of both humpback and fin whale song. Of the ten cases when whales were sighted during aerial or shipboard surveys and a glider was within 20 km of the sighting location, nine were accompanied by real-time acoustic detections of the same species by the glider within ±12 h of the sighting time.

  20. A particle filtering approach for spatial arrival time tracking in ocean acoustics.

    PubMed

    Jain, Rashi; Michalopoulou, Zoi-Heleni

    2011-06-01

    The focus of this work is on arrival time and amplitude estimation from acoustic signals recorded at spatially separated hydrophones in the ocean. A particle filtering approach is developed that treats arrival times as "targets" and tracks their "location" across receivers, also modeling arrival time gradient. The method is evaluated via Monte Carlo simulations and is compared to a maximum likelihood estimator, which does not relate arrivals at neighboring receivers. The comparison demonstrates a significant advantage in using the particle filter. It is also shown that posterior probability density functions of times and amplitudes become readily available with particle filtering.

  1. Acoustic time delay estimation and sensor network self-localization: Experimental results

    NASA Astrophysics Data System (ADS)

    Ash, Joshua N.; Moses, Randolph L.

    2005-08-01

    Experimental results are presented on propagation, coherence, and time-delay estimation (TDE) from a microphone array in an outdoor aeroacoustic environment. The primary goal is to understand the achievable accuracy of acoustic TDE using low-cost, commercial off-the-shelf (COTS) speakers and microphones. In addition, through the use of modulated pseudo-noise sequences, the experiment seeks to provide an empirical understanding of the effects of center frequency, bandwidth, and signal duration on TDE effectiveness and compares this to the theoretical expectations established by the Weiss-Weinstein lower bound. Finally, sensor network self-localization is performed using a maximum likelihood estimator and the time-delay estimates. Experimental network localization error is presented as a function of the acoustic calibration signal parameters.

  2. Gust Acoustics Computation with a Space-Time CE/SE Parallel 3D Solver

    NASA Technical Reports Server (NTRS)

    Wang, X. Y.; Himansu, A.; Chang, S. C.; Jorgenson, P. C. E.; Reddy, D. R. (Technical Monitor)

    2002-01-01

    The benchmark Problem 2 in Category 3 of the Third Computational Aero-Acoustics (CAA) Workshop is solved using the space-time conservation element and solution element (CE/SE) method. This problem concerns the unsteady response of an isolated finite-span swept flat-plate airfoil bounded by two parallel walls to an incident gust. The acoustic field generated by the interaction of the gust with the flat-plate airfoil is computed by solving the 3D (three-dimensional) Euler equations in the time domain using a parallel version of a 3D CE/SE solver. The effect of the gust orientation on the far-field directivity is studied. Numerical solutions are presented and compared with analytical solutions, showing a reasonable agreement.

  3. Time reversal invariance for a one-dimensional model of contact acoustic nonlinearity

    NASA Astrophysics Data System (ADS)

    Blanloeuil, Philippe; Francis Rose, L. R.; Veidt, Martin; Wang, Chun H.

    2017-04-01

    The interaction of a one-dimensional (1D) wave packet with a contact interface characterized by a unilateral contact law is investigated analytically and through a finite difference model. It is shown that this interaction leads to the generation of higher harmonic, sub-harmonic and zero-frequency components in the reflected wave, resulting in a pulse distortion that is attributable to contact acoustic nonlinearity. However, the results also show that the re-emission of a time reversed version of this distorted first reflection results in a healing of the distortions and a perfect recovery of the original pulse shape, thereby demonstrating time reversal invariance for this type of contact acoustic nonlinearity. A step-by-step analysis of the contact interaction provides insights into both the distortion arising from the first interaction and the subsequent healing during the second interaction. These findings suggest that time reversal invariance should also apply more generally for scatterers exhibiting non-dissipative contact acoustic nonlinearity.

  4. Analysis of concert hall acoustics via visualizations of time-frequency and spatiotemporal responses.

    PubMed

    Pätynen, Jukka; Tervo, Sakari; Lokki, Tapio

    2013-02-01

    Acousticians and other practitioners alike often describe acoustic conditions in performance spaces with standard objective parameters. Apart from a few exceptions, the parameters are calculated by integrating the sound energy of the impulse responses over time; this makes them inadequate for researching the acoustics in detail, especially in the early part of the room impulse response. This paper proposes a method based on time-frequency and spatiotemporal presentations to overcome the lack of detail in the standard analysis. In brief, the proposed methods visualize the cumulative development of the sound field as a function of frequency or direction by forward-integrating the energy in the impulse response in short time frames. Analysis on the measurements from six concert halls concentrates particularly on interpreting the results in light of the seat dip effect. Earlier research has concluded that the seat dip effect is reduced by reflection from low overhead surfaces. In contrast, the current results indicate that the seat dip attenuation in the frequency response is corrected the best when the hall provides most lateral reflections. These findings suggest that the proposed analysis is suitable for explaining concert hall acoustics in detail.

  5. Acoustic Surveys of a Scaled-Model CESTOL Transport Aircraft in Static and Forward Speed Conditions

    NASA Technical Reports Server (NTRS)

    Burnside, Nathan; Horne, Clifton

    2012-01-01

    An 11% scale-model of a Cruise-Efficient Short Take-off and Landing (CESTOL) scalemodel test was recently completed. The test was conducted in the AEDC National Full-Scale Aerodynamic Complex (NFAC) 40- by 80-Foot Wind Tunnel at NASA Ames Research Center. The model included two over-wing pod-mounted turbine propulsion simulators (TPS). The hybrid blended wing-body used a circulation control wing (CCW) with leadingand trailing-edge blowing. The bulk of the test matrix included three forward velocities (40 kts, 60 kts, and 100kts), angle-of-attack variation between -5 and 25 , and CCW mass flow variation. Seven strut-mounted microphones outboard of the left wing provided source directivity. A phased microphone array was mounted outboard of the right wing for source location. The goal of this paper is to provide a preliminary look at the acoustic data acquired during the Advanced Model for Extreme Lift and Improved Aeroacoustics (AMELIA) test for 0 angle-of-attack and 0 sideslip conditions. Data presented provides a good overview of the test conditions and the signal-to-noise quality of the data. TPS height variation showed a difference of 2 dB to 3 dB due to wing shielding. Variation of slot mass flow showed increases of 12 dB to 26 dB above the airframe noise and the TPS increased the overall levels an additional 5 dB to 10 dB.

  6. Tunneling times of acoustic phonon packets through a distributed Bragg reflector

    PubMed Central

    2014-01-01

    The longwave phenomenological model is used to make simple and precise calculations of various physical quantities such as the vibrational energy density, the vibrational energy, the relative mechanical displacement, and the one-dimensional stress tensor of a porous silicon distributed Bragg reflector. From general principles such as invariance under time reversal, invariance under space reflection, and conservation of energy density flux, the equivalence of the tunneling times for both transmission and reflection is demonstrated. Here, we study the tunneling times of acoustic phonon packets through a distributed Bragg reflector in porous silicon multilayer structures, and we report the possibility that a phenomenon called Hartman effect appears in these structures. PMID:25237288

  7. An efficient stabilized boundary element formulation for 2D time-domain acoustics and elastodynamics

    NASA Astrophysics Data System (ADS)

    Soares, D.; Mansur, W. J.

    2007-07-01

    The present paper describes a procedure that improves efficiency, stability and reduces artificial energy dissipation of the standard time-domain direct boundary element method (BEM) for acoustics and elastodynamics. Basically, the developed procedure modifies the boundary element convolution-related vector, being very easy to implement into existing codes. A stabilization parameter is introduced into the recent-in-time convolution operations and the operations related to the distant-in-time convolution contributions are approximated by matrix interpolations. As it is shown in the numerical examples presented at the end of the text, the proposed formulation substantially reduces the BEM computational cost, as well as its numerical instabilities.

  8. Outcrop-scale acoustic facies analysis and latest Quaternary development of Hueneme and Dume submarine fans, offshore California

    USGS Publications Warehouse

    Piper, D.J.W.; Hiscott, R.N.; Normark, W.R.

    1999-01-01

    The uppermost Quaternary deposits of the Hueneme and Dume submarine fans in the Santa Monica Basin have been investigated using a closed-spaced grid of boomer seismic-reflection profiles, which give vertical resolution of a few tens of centimetres with acoustic penetration to 50 m. Acoustic facies integrated with geometry define six architectural elements, some with discrete subelements that are of a scale that can be recognized in outcrops of ancient turbidite systems. In the Santa Monica Basin, the relationship of these elements to fan morphology, stratigraphy and sediment source is precisely known. The width of upper Hueneme fan valley has been reduced from 5 km since the last glacial maximum to 1 km at present by construction of laterally confined sandy levees within the main valley. The middle fan comprises three main subelements: thick sand deposits at the termination of the fan valley, low-gradient sandy lobes typically 5 km long and < 10 m thick, and scoured lobes formed of alternating sand and mud beds with many erosional depressions. The site of thickest lobe sediment accumulation shifts through time, with each sand bed deposited in a previous bathymetric low (i.e. compensation cycles). The lower fan and basin plain consists of sheet-like alternations of sand and mud with shallow channels and lenses. Variations in the rate of late Quaternary sea level rise initiated changes in sediment facies distribution. At lowstand, and during the approximately 11 ka stillstand in sea level, the Hueneme Fan was fed largely by hyperpycnal flow from the Santa Clara River delta, depositing high sediment waves on the right hand levee and thick sandy lobes on the middle fan. At highstand of sea level, most turbidity currents were generated by failure of silty prodelta muds. In contrast, the smaller Dume Fan was apparently always fed from littoral drift of sand through a single-canyon point source.

  9. Time Scales, Bedforms and Bedload Transport

    NASA Astrophysics Data System (ADS)

    Dhont, B.

    2015-12-01

    Bedload transport rates in mountain streams may exhibit wide fluctuations even under constant flow conditions. A better understanding of bedload pulses is key to predict natural hazards induced by torrential activity and sediment issues in mountainous areas. Several processes such as bedforms migration, grain sorting and random particles' trajectories are evoked as the driving agents of pulse formation and development. Quantifying the effects of these processes is a difficult task. This work aims to investigate the interactions between bedload transport and bedform dynamics in steep gravel-bed rivers. Experiments are carried out in a 17-m long 60-cm wide flume inclined at an angle of 2.7%. The bed is initially flat and made of homogenous natural gravel with a mean diameter of 6 mm. We imposed 200 identical hydrographs (of 1 hr duration) at the flume inlet (the bed surface was not flattened out during these cycling floods). The input hydrograph and the input sediment discharge are nearly triangular. Bed topography is measured after each flood using ultrasound sensors while the bedload transport rate is steadily monitored at the outlet using accelerometers (accelerometers fixed on metallic plates record the impacts of the grains flowing out of the flume). For the sake of comparison, a similar experiment consisting of 19 floods of 10 hours is carried out under constant supply conditions. We show that accelerometers are a cost effective technique to obtain high-frequency bedload discharge data. Spectral analysis of the bedload timeseries is used to highlight the different time scales corresponding to different bedload transport processes. We show that long timeseries are necessary to capture the different processes that drive bedload transport, including the resilience time after a perturbation of the bed. The alternate bars that develop and migrate along the flume are found to significantly influence bedload transport rate fluctuations.

  10. Iterative Receiver in Time-Frequency Domain for Shallow Water Acoustic Channel

    NASA Astrophysics Data System (ADS)

    Zhao, Liang; Ge, Jianhua

    2012-03-01

    Inter-symbol interference (ISI) caused by multi-path propagation, especially in shallow water channel, degrades the performance of underwater acoustic (UWA) communication systems. In this paper, we combine soft minimum mean squared error (MMSE) equalization and the serially concatenated trellis coded modulation (SCTCM) decoding to develop an iterative receiver in time-frequency domain (TFD) for underwater acoustic point to point communications. Based on sound speed profile (SSP) measured in the lake and finite-element ray (FER) tracing method (Bellhop), the shallow water channel is constructed to evaluate the performance of the proposed iterative receiver. The results suggest that the proposed iterative receiver can reduce the calculation complexity of the equalizer and obtain better performance using less receiving elements.

  11. An optimal modification of a Kalman filter for time scales

    NASA Technical Reports Server (NTRS)

    Greenhall, C. A.

    2003-01-01

    The Kalman filter in question, which was implemented in the time scale algorithm TA(NIST), produces time scales with poor short-term stability. A simple modification of the error covariance matrix allows the filter to produce time scales with good stability at all averaging times, as verified by simulations of clock ensembles.

  12. An optimization approach to multi-dimensional time domain acoustic inverse problems.

    PubMed

    Gustafsson, M; He, S

    2000-10-01

    An optimization approach to a multi-dimensional acoustic inverse problem in the time domain is considered. The density and/or the sound speed are reconstructed by minimizing an objective functional. By introducing dual functions and using the Gauss divergence theorem, the gradient of the objective functional is found as an explicit expression. The parameters are then reconstructed by an iterative algorithm (the conjugate gradient method). The reconstruction algorithm is tested with noisy data, and these tests indicate that the algorithm is stable and robust. The computation time for the reconstruction is greatly improved when the analytic gradient is used.

  13. Acoustic Pulse Echoes Probed with Time-Resolved X-Ray Triple-Crystal Diffractometry

    SciTech Connect

    Hayashi, Yujiro; Tanaka, Yoshihito; Kirimura, Tomoyuki; Ishikawa, Tetsuya; Tsukuda, Noboru; Kuramoto, Eiichi

    2006-03-24

    Acoustic pulse echoes generated by femtosecond laser irradiation were detected using time-resolved x-ray triple-crystal diffractometry. The determined time-dependent longitudinal strain component for pulse echoes in silicon and gallium arsenide plates showed that the polarity of the strain pulse was dependent on the optically induced initial stress, and that the bipolar pulse waveform was gradually deformed and broadened in the course of propagation. The three-dimensional wave front distortion of pulse echoes was shown simply as the pulse duration broadening, which was consistent with a boundary roughness for an unpolished plate.

  14. Study of the transit time of pressure propagation in an acoustic delay line

    NASA Astrophysics Data System (ADS)

    Song, Yunn-Fang; Chen, Ching-Iue; Chang, Chu-Nan; You, Jean-Luh; Hwang, Fu-Kwun; Hsu, Chih-Ying

    1986-12-01

    A fast sensor was used as a vacuum gauge to measure the transit time of a gas pressure through an acoustic delay line (ADL). The results were compared with the predictions of two theoretical models. We found that in the rupture pressure range of 101 to 104 Pa, the predictions of Jean and Rauss' model, based on the assumption that the flow of gas be a gas fluid, set lower boundaries for the observed transit times; while the predictions of our model, based on the molecular motion, set the upper ones.

  15. Finite-difference time-domain approach to acoustic radiation force problems

    NASA Astrophysics Data System (ADS)

    Silva, Glauber T.

    2005-09-01

    Acoustic radiation force plays a major role in elastography methods such as vibro-acoustography, acoustic radiation force, shear wave elasticity, and supersonic shear wave imaging. The radiation force (dynamic or static) exerted on an object by an incident wave can be obtained by solving the acoustic scattering problem for the object. However, only in rather simple cases the scattering of waves can be described by exact analytical expressions. In this work, we developed an algorithm based on the finite-difference time-domain (FDTD) method to compute the radiation force exerted on arbitrary shaped objects. The algorithm simulates the wave propagation in a finite extended medium with an embedded object. The radiation force is obtained by numerically calculating a surface integral of the momentum flux, which depends on the incident and scattered fields. Absorbing boundary conditions are used to truncate the medium. We compute the radiation force exerted on a rigid and soft cylinder by a plane wave. Results are in agreement with the theoretical predictions. Discrepancies due to numerical dispersion in the algorithm are under investigation. The presented method might be used to calculate the radiation force on complex objects present in elastography techniques. [Work supported by FAPEAL/CNPq, Brazil.

  16. Finite Difference Time Marching in the Frequency Domain: A Parabolic Formulation for Aircraft Acoustic Nacelle Design

    NASA Technical Reports Server (NTRS)

    Baumeister, Kenneth J.; Kreider, Kevin L.

    1996-01-01

    An explicit finite difference iteration scheme is developed to study harmonic sound propagation in aircraft engine nacelles. To reduce storage requirements for large 3D problems, the time dependent potential form of the acoustic wave equation is used. To insure that the finite difference scheme is both explicit and stable, time is introduced into the Fourier transformed (steady-state) acoustic potential field as a parameter. Under a suitable transformation, the time dependent governing equation in frequency space is simplified to yield a parabolic partial differential equation, which is then marched through time to attain the steady-state solution. The input to the system is the amplitude of an incident harmonic sound source entering a quiescent duct at the input boundary, with standard impedance boundary conditions on the duct walls and duct exit. The introduction of the time parameter eliminates the large matrix storage requirements normally associated with frequency domain solutions, and time marching attains the steady-state quickly enough to make the method favorable when compared to frequency domain methods. For validation, this transient-frequency domain method is applied to sound propagation in a 2D hard wall duct with plug flow.

  17. Detection of crossover time scales in multifractal detrended fluctuation analysis

    NASA Astrophysics Data System (ADS)

    Ge, Erjia; Leung, Yee

    2013-04-01

    Fractal is employed in this paper as a scale-based method for the identification of the scaling behavior of time series. Many spatial and temporal processes exhibiting complex multi(mono)-scaling behaviors are fractals. One of the important concepts in fractals is crossover time scale(s) that separates distinct regimes having different fractal scaling behaviors. A common method is multifractal detrended fluctuation analysis (MF-DFA). The detection of crossover time scale(s) is, however, relatively subjective since it has been made without rigorous statistical procedures and has generally been determined by eye balling or subjective observation. Crossover time scales such determined may be spurious and problematic. It may not reflect the genuine underlying scaling behavior of a time series. The purpose of this paper is to propose a statistical procedure to model complex fractal scaling behaviors and reliably identify the crossover time scales under MF-DFA. The scaling-identification regression model, grounded on a solid statistical foundation, is first proposed to describe multi-scaling behaviors of fractals. Through the regression analysis and statistical inference, we can (1) identify the crossover time scales that cannot be detected by eye-balling observation, (2) determine the number and locations of the genuine crossover time scales, (3) give confidence intervals for the crossover time scales, and (4) establish the statistically significant regression model depicting the underlying scaling behavior of a time series. To substantive our argument, the regression model is applied to analyze the multi-scaling behaviors of avian-influenza outbreaks, water consumption, daily mean temperature, and rainfall of Hong Kong. Through the proposed model, we can have a deeper understanding of fractals in general and a statistical approach to identify multi-scaling behavior under MF-DFA in particular.

  18. Time-domain delay-and-sum beamforming for time-reversal detection of intermittent acoustic sources in flows.

    PubMed

    Rakotoarisoa, Ifanila; Fischer, Jeoffrey; Valeau, Vincent; Marx, David; Prax, Christian; Brizzi, Laurent-Emmanuel

    2014-11-01

    This study focuses on the identification of intermittent aeroacoustic sources in flows by using the time-domain beamforming technique. It is first shown that this technique can be seen as a time-reversal (TR) technique, working with approximate Green functions in the case of a shear flow. Some numerical experiments investigate the case of an array measurement of a generic acoustic pulse emitted in a wind-tunnel flow, with a realistic multi-arm spiral array. The results of the time-domain beamforming successfully match those given by a numerical TR technique over a wide range of flow speeds (reaching the transonic regime). It is shown how the results should be analyzed in a focusing plane parallel to the microphone array in order to estimate the location and emission time of the pulse source. An experimental application dealing with the aeroacoustic radiation of a bluff body in a wind-tunnel flow is also considered, and shows that some intermittent events can be clearly identified in the noise radiation. Time-domain beamforming is then an efficient tool for analyzing intermittent acoustic sources in flows, and is a computationally cheaper alternative to the numerical TR technique, which should be used for complex configurations where the Green function is not available.

  19. Noether theorem for Birkhoffian systems on time scales

    NASA Astrophysics Data System (ADS)

    Song, Chuan-Jing; Zhang, Yi

    2015-10-01

    Birkhoff equations on time scales and Noether theorem for Birkhoffian system on time scales are studied. First, some necessary knowledge of calculus on time scales are reviewed. Second, Birkhoff equations on time scales are obtained. Third, the conditions for invariance of Pfaff action and conserved quantities are presented under the special infinitesimal transformations and general infinitesimal transformations, respectively. Fourth, some special cases are given. And finally, an example is given to illustrate the method and results.

  20. Investigation of an acoustical holography system for real-time imaging

    NASA Astrophysics Data System (ADS)

    Fecht, Barbara A.; Andre, Michael P.; Garlick, George F.; Shelby, Ronald L.; Shelby, Jerod O.; Lehman, Constance D.

    1998-07-01

    A new prototype imaging system based on ultrasound transmission through the object of interest -- acoustical holography -- was developed which incorporates significant improvements in acoustical and optical design. This system is being evaluated for potential clinical application in the musculoskeletal system, interventional radiology, pediatrics, monitoring of tumor ablation, vascular imaging and breast imaging. System limiting resolution was estimated using a line-pair target with decreasing line thickness and equal separation. For a swept frequency beam from 2.6 - 3.0 MHz, the minimum resolution was 0.5 lp/mm. Apatite crystals were suspended in castor oil to approximate breast microcalcifications. Crystals from 0.425 - 1.18 mm in diameter were well resolved in the acoustic zoom mode. Needle visibility was examined with both a 14-gauge biopsy needle and a 0.6 mm needle. The needle tip was clearly visible throughout the dynamic imaging sequence as it was slowly inserted into a RMI tissue-equivalent breast biopsy phantom. A selection of human images was acquired in several volunteers: a 25 year-old female volunteer with normal breast tissue, a lateral view of the elbow joint showing muscle fascia and tendon insertions, and the superficial vessels in the forearm. Real-time video images of these studies will be presented. In all of these studies, conventional sonography was used for comparison. These preliminary investigations with the new prototype acoustical holography system showed favorable results in comparison to state-of-the-art pulse-echo ultrasound and demonstrate it to be suitable for further clinical study. The new patient interfaces will facilitate orthopedic soft tissue evaluation, study of superficial vascular structures and potentially breast imaging.

  1. Real-time RNN-based acoustic thermometry with feedback control

    NASA Astrophysics Data System (ADS)

    Hsu, Stephen J.; Nam, Joana H.; Fan, Liexiang; Brunke, Shelby S.; Sekins, K. Michael

    2017-03-01

    A major obstacle to the widespread adoption of HIFU therapy is the development of a suitable method of monitoring the a blation therapy in real-time. While MR-thermometry has emerged as a promising method for HIFU therapy monitoring, acoustic guidance has continuously been sought for reasons of cost and practicality. We have previously demonstrated the potential of acoustic thermometry, by using a recurrent neural network (RNN) to estimate changes in tissue temperature during HIFU ablation therapies. A limitation of this method is that an excessive therapeutic dose can cause multiple, non-linear changes within the ultrasound data, resulting in unreliable temperature estimates from the RNN. Accordingly, we propose a revised method of dosing wherein closed loop feedback is used to provide a controlled and specific dose; not only to ensure an efficacious lesion, but also to preserve the integrity of the ultrasound image, thereby producing accurate temperature estimates from the RNN. This investigation of controlling the thermal dose using feedback was performed on ex vivo bovine liver. The acoustic parameters used as inputs to the RNN were: changes in integrated backscatter intensity, thermal strain, and decorrelation. The therapeutic dose was delivered using a 1.1 MHz, 2D-array HIFU transducer transmitting at regular intervals during a 40-second dose. Interleaved between these regular HIFU dose intervals, volumetric ultrasound images were acquired on a Siemens ACUSON SC2000, with a 4Zlc probe. Feedback was introduced to the system by varying the HIFU duty cycle, in order to minimize the difference between a desired temperature curve (assigned a priori) and the estimated focal temperature values. Two methods were used for obtaining the focal temperature: the first was direct measurement using a 75-micron copper-constantan thermocouple embedded within the liver sample, and the second was temperature estimation as calculated from the RNN-based output temperatures

  2. Acoustic and aerodynamic testing of a scale model variable pitch fan

    NASA Technical Reports Server (NTRS)

    Jutras, R. R.; Kazin, S. B.

    1974-01-01

    A fully reversible pitch scale model fan with variable pitch rotor blades was tested to determine its aerodynamic and acoustic characteristics. The single-stage fan has a design tip speed of 1160 ft/sec (353.568 m/sec) at a bypass pressure ratio of 1.5. Three operating lines were investigated. Test results show that the blade pitch for minimum noise also resulted in the highest efficiency for all three operating lines at all thrust levels. The minimum perceived noise on a 200-ft (60.96 m) sideline was obtained with the nominal nozzle. At 44% of takeoff thrust, the PNL reduction between blade pitch and minimum noise blade pitch is 1.8 PNdB for the nominal nozzle and decreases with increasing thrust. The small nozzle (6% undersized) has the highest efficiency at all part thrust conditions for the minimum noise blade pitch setting; although, the noise is about 1.0 PNdB higher for the small nozzle at the minimum noise blade pitch position.

  3. Time scales in Galveston Bay: An unsteady estuary

    NASA Astrophysics Data System (ADS)

    Rayson, Matthew D.; Gross, Edward S.; Hetland, Robert D.; Fringer, Oliver B.

    2016-04-01

    Estuarine time scales including the turnover, particle e-folding time, the age (calculated with a passive tracer), and residence time (calculated with Lagrangian particles) were computed using a three-dimensional hydrodynamic model of Galveston Bay, a low-flow, partially stratified estuary. Time scales were computed during a time period when river flow varied by several orders of magnitude and all time scales therefore exhibited significant temporal variability because of the unsteadiness of the system. The spatial distributions of age and residence time were qualitatively similar and increased from 15 days in a shipping channel to >45 days in the upper estuary. Volume-averaged age and residence time decreased during high-flow conditions. Bulk time scales, including the freshwater and salinity turnover times, were far more variable due to the changing river discharge and salt flux through the estuary mouth. A criterion for calculating a suitable averaging time is discussed to satisfy a steady state assumption and to estimate a more representative bulk time scale. When scaled with a freshwater advective time, all time scales were approximately equal to the advective time scale during high-flow conditions and many times higher during low-flow conditions. The mean age, Lagrangian residence, and flushing times exhibited a relationship that was weakly dependent on the freshwater advective time scale demonstrating predictability even in an unsteady, realistic estuary.

  4. A real-time method for autonomous passive acoustic detection-classification of humpback whales.

    PubMed

    Abbot, Ted A; Premus, Vincent E; Abbot, Philip A

    2010-05-01

    This paper describes a method for real-time, autonomous, joint detection-classification of humpback whale vocalizations. The approach adapts the spectrogram correlation method used by Mellinger and Clark [J. Acoust. Soc. Am. 107, 3518-3529 (2000)] for bowhead whale endnote detection to the humpback whale problem. The objective is the implementation of a system to determine the presence or absence of humpback whales with passive acoustic methods and to perform this classification with low false alarm rate in real time. Multiple correlation kernels are used due to the diversity of humpback song. The approach also takes advantage of the fact that humpbacks tend to vocalize repeatedly for extended periods of time, and identification is declared only when multiple song units are detected within a fixed time interval. Humpback whale vocalizations from Alaska, Hawaii, and Stellwagen Bank were used to train the algorithm. It was then tested on independent data obtained off Kaena Point, Hawaii in February and March of 2009. Results show that the algorithm successfully classified humpback whales autonomously in real time, with a measured probability of correct classification in excess of 74% and a measured probability of false alarm below 1%.

  5. Performance assessment and calibration of a profiling lab-scale acoustic Doppler velocimeter for application over mixed sand-gravel beds

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Acoustic Doppler velocimetry has made high-resolution turbulence measurements in sediment-laden flows possible. Recent developments have resulted in a commercially available lab-scale acoustic Doppler profiling device, a Nortek Vectrino II, that allows for three-dimensional velocity data to be colle...

  6. Multi-stage pulse tube cryocooler with acoustic impedance constructed to reduce transient cool down time and thermal loss

    NASA Technical Reports Server (NTRS)

    Gedeon, David R. (Inventor); Wilson, Kyle B. (Inventor)

    2008-01-01

    The cool down time for a multi-stage, pulse tube cryocooler is reduced by configuring at least a portion of the acoustic impedance of a selected stage, higher than the first stage, so that it surrounds the cold head of the selected stage. The surrounding acoustic impedance of the selected stage is mounted in thermally conductive connection to the warm region of the selected stage for cooling the acoustic impedance and is fabricated of a high thermal diffusivity, low thermal radiation emissivity material, preferably aluminum.

  7. A Quaternary Geomagnetic Instability Time Scale

    NASA Astrophysics Data System (ADS)

    Singer, B. S.

    2013-12-01

    Reversals and excursions of Earth's geomagnetic field create marker horizons that are readily detected in sedimentary and volcanic rocks worldwide. An accurate and precise chronology of these geomagnetic field instabilities is fundamental to understanding several aspects of Quaternary climate, dynamo processes, and surface processes. For example, stratigraphic correlation between marine sediment and polar ice records of climate change across the cryospheres benefits from a highly resolved record of reversals and excursions. The temporal patterns of dynamo behavior may reflect physical interactions between the molten outer core and the solid inner core or lowermost mantle. These interactions may control reversal frequency and shape the weak magnetic fields that arise during successive dynamo instabilities. Moreover, weakening of the axial dipole during reversals and excursions enhances the production of cosmogenic isotopes that are used in sediment and ice core stratigraphy and surface exposure dating. The Geomagnetic Instability Time Scale (GITS) is based on the direct dating of transitional polarity states recorded by lava flows using the 40Ar/39Ar method, in parallel with astrochronologic age models of marine sediments in which O isotope and magnetic records have been obtained. A review of data from Quaternary lava flows and sediments yields a GITS comprising 10 polarity reversals and 27 excursions during the past 2.6 million years. Nine of the ten reversals bounding chrons and subchrons are associated with 40Ar/39Ar ages of transitionally-magnetized lava flows. The tenth, the Guass-Matuyama chron boundary, is tightly bracketed by 40Ar/39Ar dated ash deposits. Of the 27 well-documented excursions, 14 occurred during the Matuyama chron and 13 during the Brunhes chron; 19 have been dated directly using the 40Ar/39Ar method on transitionally-magnetized volcanic rocks and form the backbone of the GITS. Excursions are clearly not the rare phenomena once thought

  8. A Study of Mexican Free-Tailed Bat Chirp Syllables: Bayesian Functional Mixed Models for Nonstationary Acoustic Time Series

    PubMed Central

    MARTINEZ, Josue G.; BOHN, Kirsten M.; CARROLL, Raymond J.

    2013-01-01

    We describe a new approach to analyze chirp syllables of free-tailed bats from two regions of Texas in which they are predominant: Austin and College Station. Our goal is to characterize any systematic regional differences in the mating chirps and assess whether individual bats have signature chirps. The data are analyzed by modeling spectrograms of the chirps as responses in a Bayesian functional mixed model. Given the variable chirp lengths, we compute the spectrograms on a relative time scale interpretable as the relative chirp position, using a variable window overlap based on chirp length. We use 2D wavelet transforms to capture correlation within the spectrogram in our modeling and obtain adaptive regularization of the estimates and inference for the regions-specific spectrograms. Our model includes random effect spectrograms at the bat level to account for correlation among chirps from the same bat, and to assess relative variability in chirp spectrograms within and between bats. The modeling of spectrograms using functional mixed models is a general approach for the analysis of replicated nonstationary time series, such as our acoustical signals, to relate aspects of the signals to various predictors, while accounting for between-signal structure. This can be done on raw spectrograms when all signals are of the same length, and can be done using spectrograms defined on a relative time scale for signals of variable length in settings where the idea of defining correspondence across signals based on relative position is sensible. PMID:23997376

  9. A Study of Mexican Free-Tailed Bat Chirp Syllables: Bayesian Functional Mixed Models for Nonstationary Acoustic Time Series.

    PubMed

    Martinez, Josue G; Bohn, Kirsten M; Carroll, Raymond J; Morris, Jeffrey S

    2013-06-01

    We describe a new approach to analyze chirp syllables of free-tailed bats from two regions of Texas in which they are predominant: Austin and College Station. Our goal is to characterize any systematic regional differences in the mating chirps and assess whether individual bats have signature chirps. The data are analyzed by modeling spectrograms of the chirps as responses in a Bayesian functional mixed model. Given the variable chirp lengths, we compute the spectrograms on a relative time scale interpretable as the relative chirp position, using a variable window overlap based on chirp length. We use 2D wavelet transforms to capture correlation within the spectrogram in our modeling and obtain adaptive regularization of the estimates and inference for the regions-specific spectrograms. Our model includes random effect spectrograms at the bat level to account for correlation among chirps from the same bat, and to assess relative variability in chirp spectrograms within and between bats. The modeling of spectrograms using functional mixed models is a general approach for the analysis of replicated nonstationary time series, such as our acoustical signals, to relate aspects of the signals to various predictors, while accounting for between-signal structure. This can be done on raw spectrograms when all signals are of the same length, and can be done using spectrograms defined on a relative time scale for signals of variable length in settings where the idea of defining correspondence across signals based on relative position is sensible.

  10. Wideband Multichannel Time-Reversal Processing for Acoustic Communications in a Tunnel-like Structure

    SciTech Connect

    Candy, J V; Chambers, D H; Robbins, C L; Guidry, B L; Poggio, A J; Dowla, F; Hertzog, C A

    2006-01-12

    The development of multichannel time-reversal (T/R) processing techniques continues to progress rapidly especially when the need to communicate in a highly reverberative environment becomes critical. The underlying T/R concept is based on time-reversing the Green's function characterizing the uncertain communications channel investigating the deleterious dispersion and multipath effects. In this paper, attention is focused on two major objectives: (1) wideband communications leading to a time reference modulation technique; and (2) multichannel acoustic communications in a tunnel (or cave or pipe) with many obstructions, multipath returns, severe background noise, disturbances, long propagation paths ({approx}180) with disruptions (bends). For this extremely hostile environment, it is shown that multichannel T/R receivers can easily be extended to the wideband designs while demonstrating their performance in both the ''canonical'' stairwell of our previous work as well as a tunnel-like structure. Acoustic information signals are transmitted with an 8-element host or base station array to two client receivers with a significant loss in signal levels due to the propagation environment. In this paper, the results of the new wideband T/R processor and modulation scheme are discussed to demonstrate the overall performance for both high (24-bit) and low (1-bit) bit level analog-to-digital (A/D) converter designs. These results are validated by performing proof-of-principle acoustic communications experiments in air. It is shown that the resulting T/R receivers are capable of extracting the transmitted coded sequence from noisy microphone array measurements with zero-bit error.

  11. Assessment of Systematic Measurement Errors for Acoustic Travel-Time Tomography of the Atmosphere

    DTIC Science & Technology

    2013-01-01

    times obtained with Algorithm 3, the reconstructions become relatively accurate, see Figs. 6(g), 6( h ), and 6(i). The magnitudes of all fields are...Temperature. (e) u0 þ u. (f) v0 þ v. Reconstruction with the estimated systematic errors by Algorithm 3: (g) Temperature. ( h ) u0 þ u. (i) v0 þ v. TABLE V...tomographic monitoring of the atmospheric surface layer,” J. Atmos. Ocean. Technol. 11, 751–769 (1994). 2A. Ziemann, K. Arnold, and A. Raabe , “Acoustic

  12. Acoustic emission monitoring from a lab scale high shear granulator--a novel approach.

    PubMed

    Watson, N J; Povey, M J W; Reynolds, G K; Xu, B H; Ding, Y

    2014-04-25

    A new approach to the monitoring of granulation processes using passive acoustics together with precise control over the granulation process has highlighted the importance of particle-particle and particle-bowl collisions in acoustic emission. The results have shown that repeatable acoustic results could be obtained but only when a spray nozzle water addition system was used. Acoustic emissions were recorded from a transducer attached to the bowl and an airborne transducer. It was found that the airborne transducer detected very little from the granulation and only experienced small changes throughout the process. The results from the bowl transducer showed that during granulation the frequency content of the acoustic emission shifted towards the lower frequencies. Results from the discrete element model indicate that when larger particles are used the number of collisions the particles experience reduces. This is a result of the volume conservation methodology used in this study, therefore larger particles results in less particles. These simulation results coupled with previous theoretical work on the frequency content of an impacting sphere explain why the frequency content of the acoustic emissions reduces during granule growth. The acoustic system used was also clearly able to identify when large over-wetted granules were present in the system, highlighting its benefit for detecting undesirable operational conditions. High-speed photography was used to study if visual changes in the granule properties could be linked with the changing acoustic emissions. The high speed photography was only possible towards the latter stages of the granulation process and it was found that larger granules produced a higher magnitude of acoustic emission across a broader frequency range.

  13. Ocean acoustic reverberation tomography.

    PubMed

    Dunn, Robert A

    2015-12-01

    Seismic wide-angle imaging using ship-towed acoustic sources and networks of ocean bottom seismographs is a common technique for exploring earth structure beneath the oceans. In these studies, the recorded data are dominated by acoustic waves propagating as reverberations in the water column. For surveys with a small receiver spacing (e.g., <10 km), the acoustic wave field densely samples properties of the water column over the width of the receiver array. A method, referred to as ocean acoustic reverberation tomography, is developed that uses the travel times of direct and reflected waves to image ocean acoustic structure. Reverberation tomography offers an alternative approach for determining the structure of the oceans and advancing the understanding of ocean heat content and mixing processes. The technique has the potential for revealing small-scale ocean thermal structure over the entire vertical height of the water column and along long survey profiles or across three-dimensional volumes of the ocean. For realistic experimental geometries and data noise levels, the method can produce images of ocean sound speed on a smaller scale than traditional acoustic tomography.

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

    SciTech Connect

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

    2015-08-14

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

  15. Acoustic Performance of a Real-Time Three-Dimensional Sound-Reproduction System

    NASA Technical Reports Server (NTRS)

    Faller, Kenneth J., II; Rizzi, Stephen A.; Aumann, Aric R.

    2013-01-01

    The Exterior Effects Room (EER) is a 39-seat auditorium at the NASA Langley Research Center and was built to support psychoacoustic studies of aircraft community noise. The EER has a real-time simulation environment which includes a three-dimensional sound-reproduction system. This system requires real-time application of equalization filters to compensate for spectral coloration of the sound reproduction due to installation and room effects. This paper describes the efforts taken to develop the equalization filters for use in the real-time sound-reproduction system and the subsequent analysis of the system s acoustic performance. The acoustic performance of the compensated and uncompensated sound-reproduction system is assessed for its crossover performance, its performance under stationary and dynamic conditions, the maximum spatialized sound pressure level it can produce from a single virtual source, and for the spatial uniformity of a generated sound field. Additionally, application examples are given to illustrate the compensated sound-reproduction system performance using recorded aircraft flyovers

  16. Computational Analyses in Support of Sub-scale Diffuser Testing for the A-3 Facility. Part 3; Aero-Acoustic Analyses and Experimental Validation

    NASA Technical Reports Server (NTRS)

    Allgood, Daniel C.; Graham, Jason S.; McVay, Greg P.; Langford, Lester L.

    2008-01-01

    A unique assessment of acoustic similarity scaling laws and acoustic analogy methodologies in predicting the far-field acoustic signature from a sub-scale altitude rocket test facility at the NASA Stennis Space Center was performed. A directional, point-source similarity analysis was implemented for predicting the acoustic far-field. In this approach, experimental acoustic data obtained from "similar" rocket engine tests were appropriately scaled using key geometric and dynamic parameters. The accuracy of this engineering-level method is discussed by comparing the predictions with acoustic far-field measurements obtained. In addition, a CFD solver was coupled with a Lilley's acoustic analogy formulation to determine the improvement of using a physics-based methodology over an experimental correlation approach. In the current work, steady-state Reynolds-averaged Navier-Stokes calculations were used to model the internal flow of the rocket engine and altitude diffuser. These internal flow simulations provided the necessary realistic input conditions for external plume simulations. The CFD plume simulations were then used to provide the spatial turbulent noise source distributions in the acoustic analogy calculations. Preliminary findings of these studies will be discussed.

  17. Tone and Broadband Noise Separation from Acoustic Data of a Scale-Model Counter-Rotating Open Rotor

    NASA Technical Reports Server (NTRS)

    Sree, David; Stephens, David B.

    2014-01-01

    Renewed interest in contra-rotating open rotor technology for aircraft propulsion application has prompted the development of advanced diagnostic tools for better design and improved acoustical performance. In particular, the determination of tonal and broadband components of open rotor acoustic spectra is essential for properly assessing the noise control parameters and also for validating the open rotor noise simulation codes. The technique of phase averaging has been employed to separate the tone and broadband components from a single rotor, but this method does not work for the two-shaft contra-rotating open rotor. A new signal processing technique was recently developed to process the contra-rotating open rotor acoustic data. The technique was first tested using acoustic data taken of a hobby aircraft open rotor propeller, and reported previously. The intent of the present work is to verify and validate the applicability of the new technique to a realistic one-fifth scale open rotor model which has 12 forward and 10 aft contra-rotating blades operating at realistic forward flight Mach numbers and tip speeds. The results and discussions of that study are presented in this paper.

  18. Tone and Broadband Noise Separation from Acoustic Data of a Scale-Model Contra-Rotating Open Rotor

    NASA Technical Reports Server (NTRS)

    Sree, Dave; Stephens, David B.

    2014-01-01

    Renewed interest in contra-rotating open rotor technology for aircraft propulsion application has prompted the development of advanced diagnostic tools for better design and improved acoustical performance. In particular, the determination of tonal and broadband components of open rotor acoustic spectra is essential for properly assessing the noise control parameters and also for validating the open rotor noise simulation codes. The technique of phase averaging has been employed to separate the tone and broadband components from a single rotor, but this method does not work for the two-shaft contra-rotating open rotor. A new signal processing technique was recently developed to process the contra-rotating open rotor acoustic data. The technique was first tested using acoustic data taken of a hobby aircraft open rotor propeller, and reported previously. The intent of the present work is to verify and validate the applicability of the new technique to a realistic one-fifth scale open rotor model which has 12 forward and 10 aft contra-rotating blades operating at realistic forward flight Mach numbers and tip speeds. The results and discussions of that study are presented in this paper.

  19. Linking Response-Time Parameters onto a Common Scale

    ERIC Educational Resources Information Center

    van der Linden, Wim J.

    2010-01-01

    Although response times on test items are recorded on a natural scale, the scale for some of the parameters in the lognormal response-time model (van der Linden, 2006) is not fixed. As a result, when the model is used to periodically calibrate new items in a testing program, the parameter are not automatically mapped onto a common scale. Several…

  20. On time scales and time synchronization using LORAN-C as a time reference signal

    NASA Technical Reports Server (NTRS)

    Chi, A. R.

    1974-01-01

    The long term performance of the eight LORAN-C chains is presented in terms of the Coordinated Universal Time (UTC) of the U.S. Naval Observatory (USNO); and the use of the LORAN-C navigation system for maintaining the user's clock to a UTC scale is described. The atomic time scale and the UTC of several national laboratories and observatories relative to the international atomic time are reported. Typical performance of several NASA tracking station clocks, relative to the USNO master clock, is also presented.

  1. Outer scales of temperature turbulence and dynamic turbulence from the data of acoustic sounding of the atmosphere

    NASA Astrophysics Data System (ADS)

    Shamanaeva, L. G.; Krasnenko, N. P.; Kapegesheva, O. F.

    2014-11-01

    The outer scale of turbulence plays an important role in the theory of atmospheric turbulence. It specifies the lowfrequency boundary of the inertial subrange of fluctuation spectra of the atmospheric meteorological parameters, is used to construct models of the atmospheric turbulence and to estimate the excess turbulent attenuation of waves in the atmosphere. Outer scales of the wind velocity, temperature, humidity, and ozone concentration were previously determined, in particular, from direct airborne measurements of the spectral power density of these parameters, and their dependences on the altitude above the underlying surface, its properties, and type of the atmospheric stratification were demonstrated. For optical radiation propagating in the surface layer, the outer scale of temperature turbulence was determined from measurements of the variance of phase fluctuations of optical waves propagating along the near-ground paths. Unlike the optical waves, the acoustic wave propagation in the atmospheric boundary layer is influenced simultaneously by the temperature fluctuations caused by thermal convection and by the velocity fluctuations (dynamic turbulence caused by the wind shear). Their relative contributions depend on the ratio of the outer scales of the dynamic turbulence and temperature turbulence. In the present work, a method of simultaneous acoustic sounding of the outer scales of dynamic turbulence and temperature turbulence is suggested, and combined influence of these parameters on the acoustic wave propagation is estimated. Temporal dynamics of vertical profiles of the outer scales of dynamic turbulence and temperature turbulence is analyzed. The efficiency of the suggested method is confirmed by the results of comparison with the data of laser sensing of these parameters and their theoretical estimates, which demonstrate their good agreement.

  2. Automatic fault diagnosis of rotating machines by time-scale manifold ridge analysis

    NASA Astrophysics Data System (ADS)

    Wang, Jun; He, Qingbo; Kong, Fanrang

    2013-10-01

    This paper explores the improved time-scale representation by considering the non-linear property for effectively identifying rotating machine faults in the time-scale domain. A new time-scale signature, called time-scale manifold (TSM), is proposed in this study through combining phase space reconstruction (PSR), continuous wavelet transform (CWT), and manifold learning. For the TSM generation, an optimal scale band is selected to eliminate the influence of unconcerned scale components, and the noise in the selected band is suppressed by manifold learning to highlight the inherent non-linear structure of faulty impacts. The TSM reserves the non-stationary information and reveals the non-linear structure of the fault pattern, with the merits of noise suppression and resolution improvement. The TSM ridge is further extracted by seeking the ridge with energy concentration lying on the TSM signature. It inherits the advantages of both the TSM and ridge analysis, and hence is beneficial to demodulation of the fault information. Through analyzing the instantaneous amplitude (IA) of the TSM ridge, in which the noise is nearly not contained, the fault characteristic frequency can be exactly identified. The whole process of the proposed fault diagnosis scheme is automatic, and its effectiveness has been verified by means of typical faulty vibration/acoustic signals from a gearbox and bearings. A reliable performance of the new method is validated in comparison with traditional enveloping methods for rotating machine fault diagnosis.

  3. The Space-Time Conservative Schemes for Large-Scale, Time-Accurate Flow Simulations with Tetrahedral Meshes

    NASA Technical Reports Server (NTRS)

    Venkatachari, Balaji Shankar; Streett, Craig L.; Chang, Chau-Lyan; Friedlander, David J.; Wang, Xiao-Yen; Chang, Sin-Chung

    2016-01-01

    Despite decades of development of unstructured mesh methods, high-fidelity time-accurate simulations are still predominantly carried out on structured, or unstructured hexahedral meshes by using high-order finite-difference, weighted essentially non-oscillatory (WENO), or hybrid schemes formed by their combinations. In this work, the space-time conservation element solution element (CESE) method is used to simulate several flow problems including supersonic jet/shock interaction and its impact on launch vehicle acoustics, and direct numerical simulations of turbulent flows using tetrahedral meshes. This paper provides a status report for the continuing development of the space-time conservation element solution element (CESE) numerical and software framework under the Revolutionary Computational Aerosciences (RCA) project. Solution accuracy and large-scale parallel performance of the numerical framework is assessed with the goal of providing a viable paradigm for future high-fidelity flow physics simulations.

  4. Real-time decomposition and recognition of acoustical patterns with an analog neural computer

    NASA Astrophysics Data System (ADS)

    Mueller, Paul; Van der Spiegel, Jan; Blackman, David; Donham, Christopher; Cummings, Ralph

    1992-09-01

    A prototype programmable analog neural computer has been assembled from over 100 custom VLSI modules containing neurons, synapses, routing switches, and programmable synaptic time constants. The modules are directly interconnected and arbitrary network configurations can be programmed. Connection symmetry and modular construction allow expansion of the network to any size. The network runs in real time analog mode, but connection architecture as well as neuron and synapse parameters are controlled by a digital host. Network performance is monitored by the host through an A/D interface and used in the implementation of learning algorithms. The machine is intended for real time, real world computations. In its current configuration maximal speed is equivalent to that of a digital machine capable of 1011 FLOPS. The programmable synaptic time constants permit the real time computation of temporal patterns as they occur in speech and other acoustic signals. Several applications involving the dynamic decomposition and recognition of acoustical patterns including speech signals (phonemes) are described. The decomposition network is loosely based on the primary auditory system of higher vertebrates. It extracts and represents by the activity in different neuron arrays the following pattern primitives: frequency, bandwidth, amplitude, amplitude modulation, amplitude modulation frequency, frequency modulation, frequency modulation frequency, duration, sequence. The frequency tuned units are the first stage and form the input space for subsequent stages that extract the other primitives, e.g., bandwidth, amplitude modulation, etc., for different frequency bands. Acoustic input generates highly specific, relatively sparse distributed activity in this feature space, which is decoded and recognized by units trained by specific input patterns such as phonemes or diphones or active sonar patterns. Through simple feedback connections in conjunction with synaptic time constants the

  5. Speech timing and linguistic rhythm: on the acoustic bases of rhythm typologies.

    PubMed

    Rathcke, Tamara V; Smith, Rachel H

    2015-05-01

    Research into linguistic rhythm has been dominated by the idea that languages can be classified according to rhythmic templates, amenable to assessment by acoustic measures of vowel and consonant durations. This study tested predictions of two proposals explaining the bases of rhythmic typologies: the Rhythm Class Hypothesis which assumes that the templates arise from an extensive vs a limited use of durational contrasts, and the Control and Compensation Hypothesis which proposes that the templates are rooted in more vs less flexible speech production strategies. Temporal properties of segments, syllables and rhythmic feet were examined in two accents of British English, a "stress-timed" variety from Leeds, and a "syllable-timed" variety spoken by Panjabi-English bilinguals from Bradford. Rhythm metrics were calculated. A perception study confirmed that the speakers of the two varieties differed in their perceived rhythm. The results revealed that both typologies were informative in that to a certain degree, they predicted temporal patterns of the two varieties. None of the metrics tested was capable of adequately reflecting the temporal complexity found in the durational data. These findings contribute to the critical evaluation of the explanatory adequacy of rhythm metrics. Acoustic bases and limitations of the traditional rhythmic typologies are discussed.

  6. Transcranial ultrasonic therapy based on time reversal of acoustically induced cavitation bubble signature

    PubMed Central

    Gâteau, Jérôme; Marsac, Laurent; Pernot, Mathieu; Aubry, Jean-Francois; Tanter, Mickaël; Fink, Mathias

    2010-01-01

    Brain treatment through the skull with High Intensity Focused Ultrasound (HIFU) can be achieved with multichannel arrays and adaptive focusing techniques such as time-reversal. This method requires a reference signal to be either emitted by a real source embedded in brain tissues or computed from a virtual source, using the acoustic properties of the skull derived from CT images. This non-invasive computational method focuses with precision, but suffers from modeling and repositioning errors that reduce the accessible acoustic pressure at the focus in comparison with fully experimental time-reversal using an implanted hydrophone. In this paper, this simulation-based targeting has been used experimentally as a first step for focusing through an ex vivo human skull at a single location. It has enabled the creation of a cavitation bubble at focus that spontaneously emitted an ultrasonic wave received by the array. This active source signal has allowed 97%±1.1% of the reference pressure (hydrophone-based) to be restored at the geometrical focus. To target points around the focus with an optimal pressure level, conventional electronic steering from the initial focus has been combined with bubble generation. Thanks to step by step bubble generation, the electronic steering capabilities of the array through the skull were improved. PMID:19770084

  7. Gauge-invariant coupled gravitational, acoustical, and electromagnetic modes on most general spherical space-times

    NASA Astrophysics Data System (ADS)

    Gerlach, Ulrich H.; Sengupta, Uday K.

    1980-09-01

    The coupled Einstein-Maxwell system linearized away from an arbitrarily given spherically symmetric background space-time is reduced from its four-dimensional to a two-dimensional form expressed solely in terms of gauge-invariant geometrical perturbation objects. These objects, which besides the gravitational and electromagnetic, also include mass-energy degrees of freedom, are defined on the two-manifold spanned by the radial and time coordinates. For charged or uncharged arbitrary matter background the odd-parity perturbation equations for example, reduce to three second-order linear scalar equations driven by matter and charge inhomogeneities. These three equations describe the intercoupled gravitational, electromagnetic, and acoustic perturbational degrees of freedom. For a charged black hole in an asymptotically de Sitter space-time the gravitational and electromagnetic equations decouple into two inhomogeneous scalar wave equations.

  8. Improved tests for global warming trend extraction in ocean acoustic travel-time data. Final technical report

    SciTech Connect

    Bottone, S.; Gray, H.L.; Woodward, W.A.

    1996-04-01

    A possible indication of the existence of global climate warming is the presence of a trend in the travel time of an acoustic signal along several ocean paths over a period of many years. This report describes new, improved tests for testing for linear trend in time series data with correlated residuals. We introduce a bootstrap based procedure to test for trend in this setting which is better adapted to controlling the significance levels. The procedure is applied to acoustic travel time data generated by the MASIG ocean model. It is shown how to generalize the improved method to multivariate, or vector, time series, which, in the ocean acoustics setting, corresponds to travel time data on many ocean paths. An appendix describes the TRENDS software, which enables the user to perform these calculations using a graphical user interface (GUI).

  9. Acoustic Target Classification Using Multiscale Methods

    DTIC Science & Technology

    1998-01-01

    other vehicular activities well; because it represents dominant spectral peaks better than a short time Fourier transform. In the wavelet transform based...approach; multiscale features are obtained with a wavelet transform . Multiscale classification methods were applied to acoustic data collected at...This study considers the classification of acoustic signatures using features extracted at multiple scales from hierarchical models and a wavelet

  10. Frequency Scaling for Evaluation of Shale and Mudstone Properties from Acoustic Velocities

    NASA Astrophysics Data System (ADS)

    Suarez-Rivera, R.; Willson, S. M.; Nakagawa, S.; Magnar-Ness, O.

    2001-12-01

    In subsurface oil and gas exploration, seismic wave (stress wave) measurement is one of the most important tools for determining the properties of overburden and predicting reservoir conditions such as pore pressure, fracture gradient, and stress distribution. To achieve detailed and reliable knowledge of the reservoir, an integrated analysis can be performed on the seismic properties of rocks measured at different scales ranging from laboratory core, boreholes (well logging) and reservoir itself (surface seismic). However, particularly for sedimentary rocks containing a large amount of clay minerals, such integration is not a straightforward task because of velocity dispersion that makes waves of different frequencies travel at different velocities. The ultimate goal of this study is to devise a methodology for frequency scaling based on laboratory measurements of wave propagation at different frequency ranges. To this end, we have examined the mechanical and acoustic (seismic) properties of strongly dispersive sedimentary rocks. Shales were selected as principal rocks of interest for their predominance in the overburden and the direct impact on the well construction cost. Two types of shales were cored from outcrops(Pierre I and Mancos) and tested under varying conditions of loading (hydrostatic versus uniaxial-strain), orientation to bedding (parallel, perpendicular and oblique). Wave measurements were conducted under four ranges of frequency: Static and quasi-static (seismic frequency, approximately 7 Hz) data was obtained from high-accuracy, low-speed stress-strain measurements, and sonic data (0.4 kHz-9 kHz) was obtained from gas-confined resonant bar tests. For ultrasonic data (150 kHz-1 MHz), a frequency-domain phase analysis was applied to compute frequency-dependent phase and group velocities. Over these ranges, both Pierre and Mancos shales showed a smooth and monotonic increase in compressional and shear wave velocities with frequency. Strong velocity

  11. Clinical Studies of Real-Time Monitoring of Lithotripter Performance Using Passive Acoustic Sensors

    NASA Astrophysics Data System (ADS)

    Leighton, T. G.; Fedele, F.; Coleman, A. J.; McCarthy, C.; Ryves, S.; Hurrell, A. M.; De Stefano, A.; White, P. R.

    2008-09-01

    This paper describes the development and clinical testing of a passive device which monitors the passive acoustic emissions generated within the patient's body during Extracorporeal Shock Wave Lithotripsy (ESWL). Designed and clinically tested so that it can be operated by a nurse, the device analyses the echoes generated in the body in response to each ESWL shock, and so gives real time shock-by-shock feedback on whether the stone was at the focus of the lithotripter, and if so whether the previous shock contributed to stone fragmentation when that shock reached the focus. A shock is defined as being `effective' if these two conditions are satisfied. Not only can the device provide real-time feedback to the operator, but the trends in shock `effectiveness' can inform treatment. In particular, at any time during the treatment (once a statistically significant number of shocks have been delivered), the percentage of shocks which were `effective' provides a treatment score TS(t) which reflects the effectiveness of the treatment up to that point. The TS(t) figure is automatically delivered by the device without user intervention. Two clinical studies of the device were conducted, the ethics guidelines permitting only use of the value of TS(t) obtained at the end of treatment (this value is termed the treatment score TS0). The acoustically-derived treatment score was compared with the treatment score CTS2 given by the consultant urologist at the three-week patient's follow-up appointment. In the first clinical study (phase 1), records could be compared for 30 out of the 118 patients originally recruited, and the results of phase 1 were used to refine the parameter values (the `rules') with which the acoustic device provides its treatment score. These rules were tested in phase 2, for which records were compared for 49 of the 85 patients recruited. Considering just the phase 2 results (since the phase 1 data were used to draw up the `rules' under which phase 2 operated

  12. North Pacific Acoustic Laboratory and Deep Water Acoustics

    DTIC Science & Technology

    2015-09-30

    of basin-wide sound speed ( temperature ) fields obtained by the combination of acoustic, altimetry, and other data types with ocean general...GOALS The ultimate limitations to the performance of long-range sonar are due to ocean sound speed perturbations and the characteristics of the...receptions. 5. To improve basin-scale ocean sound -speed predictions via assimilation of acoustic travel-time and other data into numerical ocean

  13. Scale-dependent intrinsic entropies of complex time series.

    PubMed

    Yeh, Jia-Rong; Peng, Chung-Kang; Huang, Norden E

    2016-04-13

    Multi-scale entropy (MSE) was developed as a measure of complexity for complex time series, and it has been applied widely in recent years. The MSE algorithm is based on the assumption that biological systems possess the ability to adapt and function in an ever-changing environment, and these systems need to operate across multiple temporal and spatial scales, such that their complexity is also multi-scale and hierarchical. Here, we present a systematic approach to apply the empirical mode decomposition algorithm, which can detrend time series on various time scales, prior to analysing a signal's complexity by measuring the irregularity of its dynamics on multiple time scales. Simulated time series of fractal Gaussian noise and human heartbeat time series were used to study the performance of this new approach. We show that our method can successfully quantify the fractal properties of the simulated time series and can accurately distinguish modulations in human heartbeat time series in health and disease.

  14. Time-domain analysis of resonant acoustic nonlinearity arising from cracks in multilayer ceramic capacitors

    NASA Astrophysics Data System (ADS)

    Johnson, Ward L.; Kim, Sudook A.; White, Grady S.; Herzberger, Jaemi; Peterson, Kirsten L.; Heyliger, Paul R.

    2016-02-01

    Acoustic nonlinearity of cracked and uncracked multilayer ceramic capacitors (MLCCs) was characterized through time-domain analysis of resonant waveforms following tone-burst excitation. A phase-sensitive receiver was employed to measure the phase, relative to a reference sinusoid, of decaying oscillations of a resonant mode near 1 MHz that was excited through ferroelectric coupling within the barium-titanate-based ceramic of the MLCC. Amplitude dependence of the resonant frequency during decay of the oscillations was characterized through measurements of changes in the resonant phase versus time. Waveforms were analyzed by fitting the recorded RF amplitude versus time to a decaying exponential and inserting the parameters of this fit into a second function to fit the time-dependent phase, with amplitude dependence of the resonant frequency incorporated in the second function. The measurements and analyses were performed on unmounted type-1210 MLCCs before and after quenching in ice water from elevated temperatures. This thermal treatment generated surface-breaking cracks in a fraction of the specimens. Measurements of a nonlinear parameter B of the capacitors before quenching were used to set a range corresponding to plus and minus three standard deviations (±3σ) relative to the mean of a Gaussian fit to the distribution of this parameter. 93 % of the values of B determined for heat-treated MLCCs with cracks were outside of this ±3σ range of the as-received MLCCs, while only 10 % of the values of B for heat-treated MLCCs without visible cracks were outside this range. These results indicate that time-domain nonlinear measurements with tone-burst excitation are a promising approach for rapid nondestructive detection of cracks that have no significant initial effect on the electrical characteristics of an MLCC but can evolve into conductive pathways during service and lead to electrical-device failure. They also illustrate the potential of this approach for

  15. Timing signatures of large scale solar eruptions

    NASA Astrophysics Data System (ADS)

    Balasubramaniam, K. S.; Hock-Mysliwiec, Rachel; Henry, Timothy; Kirk, Michael S.

    2016-05-01

    We examine the timing signatures of large solar eruptions resulting in flares, CMEs and Solar Energetic Particle events. We probe solar active regions from the chromosphere through the corona, using data from space and ground-based observations, including ISOON, SDO, GONG, and GOES. Our studies include a number of flares and CMEs of mostly the M- and X-strengths as categorized by GOES. We find that the chromospheric signatures of these large eruptions occur 5-30 minutes in advance of coronal high temperature signatures. These timing measurements are then used as inputs to models and reconstruct the eruptive nature of these systems, and explore their utility in forecasts.

  16. Sensitivity kernels of finite-frequency travel times in ocean acoustic tomography

    NASA Astrophysics Data System (ADS)

    Skarsoulis, Emmanuel K.; Cornuelle, Bruce D.

    2004-05-01

    Wave theoretic modeling is applied to obtain travel-time sensitivity kernels representing the amount by which travel times are affected by localized sound-speed variations anywhere in the medium. In the ray approximation travel times are sensitive to medium changes only along the corresponding eigenrays. In the wave-theoretic approach the perturbations of peak arrival times are expressed in terms of pressure perturbations, which are further related with the underlying sound-speed perturbations using the first Born approximation. In this way, an integral representation of travel-time perturbations is obtained in terms of sound-speed perturbations; the associated kernel represents the spatial sensitivity of travel times to sound-speed perturbations. The application of the travel-time sensitivity kernel to an ocean acoustic waveguide gives a picture close to the ray-theoretic one in the high-frequency case but significantly differs at lower frequencies. Low-frequency travel times are sensitive to sound-speed changes in areas surrounding the eigenrays, but not on the eigenrays themselves, where the sensitivity is zero. Further, there are areas of positive sensitivity, where, e.g., a sound-speed increase results in a counter-intuitive increase of arrival times. These findings are confirmed by independent forward calculations.

  17. Time-Efficient High-Rate Data Flooding in One-Dimensional Acoustic Underwater Sensor Networks

    PubMed Central

    Kwon, Jae Kyun; Seo, Bo-Min; Yun, Kyungsu; Cho, Ho-Shin

    2015-01-01

    Because underwater communication environments have poor characteristics, such as severe attenuation, large propagation delays and narrow bandwidths, data is normally transmitted at low rates through acoustic waves. On the other hand, as high traffic has recently been required in diverse areas, high rate transmission has become necessary. In this paper, transmission/reception timing schemes that maximize the time axis use efficiency to improve the resource efficiency for high rate transmission are proposed. The excellence of the proposed scheme is identified by examining the power distributions by node, rate bounds, power levels depending on the rates and number of nodes, and network split gains through mathematical analysis and numerical results. In addition, the simulation results show that the proposed scheme outperforms the existing packet train method. PMID:26528983

  18. Acoustic source localization using time-difference of arrival and neural-network analysis

    NASA Astrophysics Data System (ADS)

    Jiang, Nan; Dong, Jiancheng; Ying, Ren D.

    2013-03-01

    The developing embedded technology requires revolutions in human-machine interaction. In this paper, we propose a novel method using localization of the taping sound on the table to replace the keyboard as manual input device. The method is applicable with a quad-channel-array collection of acoustic signals, from which the time-of-arrival differences and the position information could be estimated. In practice, as our table is in a limited size and the material properties are complex, the traditional localization algorithm based on time-of-arrival differences contains a sizable margin for error. Furthermore, we use neural-network analysis to improve recognition accuracy. Then experiments and simulations are carried out to verify this signal processing algorithm.

  19. Crack identification by 3D time-domain elastic or acoustic topological sensitivity

    NASA Astrophysics Data System (ADS)

    Bellis, Cédric; Bonnet, Marc

    2009-03-01

    The topological sensitivity analysis, based on the asymptotic behavior of a cost functional associated with the creation of a small trial flaw in a defect-free solid, provides a computationally-fast, non-iterative approach for identifying flaws embedded in solids. This concept is here considered for crack identification using time-dependent measurements on the external boundary. The topological derivative of a cost function under the nucleation of a crack of infinitesimal size is established, in the framework of time-domain elasticity or acoustics. The simplicity and efficiency of the proposed formulation is enhanced by the recourse to an adjoint solution. Numerical results obtained on a 3-D elastodynamic example using the conventional FEM demonstrate the usefulness of the topological derivative as a crack indicator function. To cite this article: C. Bellis, M. Bonnet, C. R. Mecanique 337 (2009).

  20. Facial reanimation after acoustic neuroma resection: options and timing of intervention.

    PubMed

    Boahene, Kofi

    2015-04-01

    Facial paralysis following acoustic neuroma (AN) resection can be devastating, but timely and strategic intervention can minimize the resulting facial morbidity. A central strategy in reanimating the paralyzed face after AN resection is to restore function of the native facial muscles using available facial nerves or repurposed cranial nerves, mainly the hypoglossal or masseter nerves. The timing of reinnervation is the single most influential factor that determines outcomes in facial reanimation surgery. The rate of recovery of facial function in the first 6 months following AN resection may be used to predict ultimate facial function. Patients who show no signs of recovery in the first 6 months, even when their facial nerves are intact, recover poorly and are candidates for early facial reinnervation. With delay, facial muscles become irreversibly paralyzed. Reanimation in irreversible paralysis requires the transfer of functional muscle units such as the gracilis or the temporalis muscle tendon unit.

  1. Real-time measurement of electron beam weld penetration in uranium by acoustic emission monitoring

    SciTech Connect

    Whittaker, J.W.; Murphy, J.L.

    1991-07-01

    High quality electron beam (EB) welds are required in uranium test articles. Acoustic emission (AE) techniques are under development with the goal of measuring weld penetration in real-time. One technique, based on Average Signal Level (ASL) measurement was used to record weld AE signatures. Characteristic AE signatures were recorded for bead-on-plate (BOP) and butt joint (BJ) welds made under varied welding conditions. AE waveforms were sampled to determine what microscopic AE behavior led to the observed macroscopic signature features. Deformation twinning and weld expulsion are two of the main sources of emission. AE behavior was correlated with weld penetration as measured by standard metallographic techniques. The ASL value was found to increase approximately linearly with weld penetration in BJ welds. These results form the basis for a real-time monitoring technique for weld penetration. 5 refs.

  2. Assessment of systematic measurement errors for acoustic travel-time tomography of the atmosphere.

    PubMed

    Vecherin, Sergey N; Ostashev, Vladimir E; Wilson, D Keith

    2013-09-01

    Two algorithms are described for assessing systematic errors in acoustic travel-time tomography of the atmosphere, the goal of which is to reconstruct the temperature and wind velocity fields given the transducers' locations and the measured travel times of sound propagating between each speaker-microphone pair. The first algorithm aims at assessing the errors simultaneously with the mean field reconstruction. The second algorithm uses the results of the first algorithm to identify the ray paths corrupted by the systematic errors and then estimates these errors more accurately. Numerical simulations show that the first algorithm can improve the reconstruction when relatively small systematic errors are present in all paths. The second algorithm significantly improves the reconstruction when systematic errors are present in a few, but not all, ray paths. The developed algorithms were applied to experimental data obtained at the Boulder Atmospheric Observatory.

  3. Signal Restoration of Non-stationary Acoustic Signals in the Time Domain

    NASA Technical Reports Server (NTRS)

    Babkin, Alexander S.

    1988-01-01

    Signal restoration is a method of transforming a nonstationary signal acquired by a ground based microphone to an equivalent stationary signal. The benefit of the signal restoration is a simplification of the flight test requirements because it could dispense with the need to acquire acoustic data with another aircraft flying in concert with the rotorcraft. The data quality is also generally improved because the contamination of the signal by the propeller and wind noise is not present. The restoration methodology can also be combined with other data acquisition methods, such as a multiple linear microphone array for further improvement of the test results. The methodology and software are presented for performing the signal restoration in the time domain. The method has no restrictions on flight path geometry or flight regimes. Only requirement is that the aircraft spatial position be known relative to the microphone location and synchronized with the acoustic data. The restoration process assumes that the moving source radiates a stationary signal, which is then transformed into a nonstationary signal by various modulation processes. The restoration contains only the modulation due to the source motion.

  4. Time-dependent seafloor acoustic backscatter (10-100 kHz).

    PubMed

    Sternlicht, Daniel D; de Moustier, Christian P

    2003-11-01

    A time-dependent model of the acoustic intensity backscattered by the seafloor is described and compared with data from a calibrated, vertically oriented, echo-sounder operating at 33 and 93 kHz. The model incorporates the characteristics of the echo-sounder and transmitted pulse, and the water column spreading and absorption losses. Scattering from the water-sediment interface is predicted using Helmholtz-Kirchhoff theory, parametrized by the mean grain size, the coherent reflection coefficient, and the strength and exponent of a power-law roughness spectrum. The composite roughness approach of Jackson et al. [J. Acoust. Soc. Am. 79, 1410-1422 (1986)], modified for the finite duration of the transmitted signal, is used to predict backscatter from subbottom inhomogeneities. It depends on the sediment's volume scattering and attenuation coefficients, as well as the interface characteristics governing sound transmission into the sediment. Estimation of model parameters (mean grain size, roughness spectrum strength and exponent, volume scattering coefficient) reveals ambiguous ranges for the two spectral components. Analyses of model outputs and of physical measurements reported in the literature yield practical constraints on roughness spectrum parameter settings appropriate for echo-envelope-based sediment classification procedures.

  5. Acoustic masking disrupts time-dependent mechanisms of memory encoding in word-list recall.

    PubMed

    Cousins, Katheryn A Q; Dar, Hayim; Wingfield, Arthur; Miller, Paul

    2014-05-01

    Recall of recently heard words is affected by the clarity of presentation: Even if all words are presented with sufficient clarity for successful recognition, those that are more difficult to hear are less likely to be recalled. Such a result demonstrates that memory processing depends on more than whether a word is simply "recognized" versus "not recognized." More surprising is that, when a single item in a list of spoken words is acoustically masked, prior words that were heard with full clarity are also less likely to be recalled. To account for such a phenomenon, we developed the linking-by-active-maintenance model (LAMM). This computational model of perception and encoding predicts that these effects will be time dependent. Here we challenged our model by investigating whether and how the impact of acoustic masking on memory depends on presentation rate. We found that a slower presentation rate causes a more disruptive impact of stimulus degradation on prior, clearly heard words than does a fast rate. These results are unexpected according to prior theories of effortful listening, but we demonstrated that they can be accounted for by LAMM.

  6. A methodology to condition distorted acoustic emission signals to identify fracture timing from human cadaver spine impact tests.

    PubMed

    Arun, Mike W J; Yoganandan, Narayan; Stemper, Brian D; Pintar, Frank A

    2014-12-01

    While studies have used acoustic sensors to determine fracture initiation time in biomechanical studies, a systematic procedure is not established to process acoustic signals. The objective of the study was to develop a methodology to condition distorted acoustic emission data using signal processing techniques to identify fracture initiation time. The methodology was developed from testing a human cadaver lumbar spine column. Acoustic sensors were glued to all vertebrae, high-rate impact loading was applied, load-time histories were recorded (load cell), and fracture was documented using CT. Compression fracture occurred to L1 while other vertebrae were intact. FFT of raw voltage-time traces were used to determine an optimum frequency range associated with high decibel levels. Signals were bandpass filtered in this range. Bursting pattern was found in the fractured vertebra while signals from other vertebrae were silent. Bursting time was associated with time of fracture initiation. Force at fracture was determined using this time and force-time data. The methodology is independent of selecting parameters a priori such as fixing a voltage level(s), bandpass frequency and/or using force-time signal, and allows determination of force based on time identified during signal processing. The methodology can be used for different body regions in cadaver experiments.

  7. Modeling orbital changes on tectonic time scales

    NASA Technical Reports Server (NTRS)

    Crowley, Thomas J.

    1992-01-01

    Geologic time series indicate significant 100 ka and 400 ka pre-Pleistocene climate fluctuations, prior to the time of such fluctuations in Pleistocene ice sheets. The origin of these fluctuations must therefore depend on phenomena other than the ice sheets. In a previous set of experiments, we tested the sensitivity of an energy balance model to orbital insolation forcing, specifically focusing on the filtering effect of the Earth's geography. We found that in equatorial areas, the twice-yearly passage of the sun across the equator interacts with the precession index to generate 100 ka and 400 ka power in our modeled time series. The effect is proportional to the magnitude of land in equatorial regions. We suggest that such changes may reflect monsoonal variations in the real climate system, and the subsequent wind and weathering changes may transfer some of this signal to the marine record. A comparison with observed fluctuations of Triassic lake levels is quite favorable. A number of problems remain to be studied or clarified: (1) the EBM experiments need to be followed up by a limited number of GCM experiments; (2) the sensitivity to secular changes in orbital forcing needs to be examined; (3) the possible modifying role of sedimentary processes on geologic time series warrants considerably more study; (4) the effect of tectonic changes on Earth's rotation rate needs to be studied; and (5) astronomers need to make explicit which of their predictions are robust and geologists and astronomers have to agree on which of the predictions are most testable in the geologic record.

  8. Scaling of coupled dilatancy-diffusion processes in space and time

    NASA Astrophysics Data System (ADS)

    Main, I. G.; Bell, A. F.; Meredith, P. G.; Brantut, N.; Heap, M.

    2012-04-01

    Coupled dilatancy-diffusion processes resulting from microscopically brittle damage due to precursory cracking have been observed in the laboratory and suggested as a mechanism for earthquake precursors. One reason precursors have proven elusive may be the scaling in space: recent geodetic and seismic data placing strong limits on the spatial extent of the nucleation zone for recent earthquakes. Another may be the scaling in time: recent laboratory results on axi-symmetric samples show both a systematic decrease in circumferential extensional strain at failure and a delayed and a sharper acceleration of acoustic emission event rate as strain rate is decreased. Here we examine the scaling of such processes in time from laboratory to field conditions using brittle creep (constant stress loading) to failure tests, in an attempt to bridge part of the strain rate gap to natural conditions, and discuss the implications for forecasting the failure time. Dilatancy rate is strongly correlated to strain rate, and decreases to zero in the steady-rate creep phase at strain rates around 10-9 s-1 for a basalt from Mount Etna. The data are well described by a creep model based on the linear superposition of transient (decelerating) and accelerating micro-crack growth due to stress corrosion. The model produces good fits to the failure time in retrospect using the accelerating acoustic emission event rate, but in prospective tests on synthetic data with the same properties we find failure-time forecasting is subject to systematic epistemic and aleatory uncertainties that degrade predictability. The next stage is to use the technology developed to attempt failure forecasting in real time, using live streamed data and a public web-based portal to quantify the prospective forecast quality under such controlled laboratory conditions.

  9. Time reversal transfer: Exploring the robustness of time reversed acoustics in media with geometry perturbations.

    PubMed

    Kober, Jan; Dvorakova, Zuzana; Prevorovsky, Zdenek; Krofta, Josef

    2015-07-01

    In this letter, fundamentals of transferring a time reversal experiment between similar objects are discussed. The time reversal experiment consists of two steps: forward propagation, when a source excites the medium and a complex wave field is created, and back propagation, resulting in time reversal focusing. Here the procedure of performing the first step on one specimen and the second step on another is investigated. The theory of time reversal transfer is explained on an example of object shape variations. However, conclusions of the theoretical analysis are applicable universally. The feasibility of the proposed procedure is validated in experiments modeling conditions in practice.

  10. Developments and field tests of low-frequency portable acoustic transducers for a mobile exploration and time lapse experiment of a sea-bottom reservoir

    NASA Astrophysics Data System (ADS)

    Tsuruga, K.; Kasahara, J.; Hasada, Y.; Kondo, H.

    2013-12-01

    Depth, scale and resolutions of geophysical explorations for mineral resources are controlled by transmitted seismic energy and wavelength (frequency range). Most explorations in marine have been conducted by survey ship system with arrayed acoustic sources whose dominant frequency range is about 10 to 500 Hz. On the other hand, for shallow parts of sea bottom structure survey, some sub-bottom profilers with frequency range around 3.5kHz are used. To monitor a time lapse of a sea bottom reservoir such as an oil, gas, or methane hydrate reservoir as well as to exploit a mobile survey near a sea bottom by AUVs, it is necessary to use a broadband portable acoustic transducer with a dominant frequency range of 500 Hz to 5 kHz. We have been developing several types of portable acoustic transducers and a transmitting and recording system which is accurately controlled by a GPS clock (Tsuruga et al., 2012). In this pater, we report the new broadband acoustic portable transducers which have larger power than the original cylindrical acoustic transducers in a low frequency range (<5 kHz), partly funded by JOGMEC, and show the preliminary results of field tests at the shallow sea bottom around 32 m deep by means of the transducers and hydrophone receivers array. Each transducer repeatedly transmitted Chirp signals with a unit period of 500 msec in two frequency ranges of 0.5k-4.5kHz and 4k-16kHz . We stacked 500-ms data by 28 times to obtain a transfer function of each source-receiver pair in the time and frequency domains. The preliminary results suggest as the follows: (i) it is successful to broaden the frequency bandwidth (i.e., 2k-10kHz) by extending a geometrical resonance length of a cylindrical acoustic transducers, and (ii) the observation at the sea bottom with accurately controlled timing systems of transmitter and data-logger is very useful to identify the stable and/or unstable seismic phases, that is, waves propagating in a underground and/or in a sea water as

  11. Generation of Acoustic-Gravity Waves in Ionospheric HF Heating Experiments: Simulating Large-Scale Natural Heat Sources

    NASA Astrophysics Data System (ADS)

    Pradipta, Rezy

    In this thesis, we investigate the potential role played by large-scale anomalous heat sources (e.g. prolonged heat wave events) in generating acoustic-gravity waves (AGWs) that might trigger widespread plasma turbulence in the ionospheric layer. The main hypothesis is that, the thermal gradients associated with the heat wave fronts could act as a source of powerful AGW capable of triggering ionospheric plasma turbulence over extensive areas. In our investigations, first we are going to examine a case study of the summer 2006 North American heat wave event. Our examination of GPS-derived total electron content (TEC) data over the North American sector reveals a quite noticeable increase in the level of daily plasma density fluctuations during the summer 2006 heat wave period. Comparison with the summer 2005 and summer 2007 data further confirms that the observed increase of traveling ionospheric disturbances (TIDs) during the summer 2006 heat wave period was not simply a regular seasonal phenomenon. Furthermore, a series of field experiments had been carried out at the High-frequency Active Auroral Research Program (HAARP) facility in order to physically simulate the process of AGW/TID generation by large-scale thermal gradients in the ionosphere. In these ionospheric HF heating experiments, we create some time-varying artificial thermal gradients at an altitude of 200--300 km above the Earth's surface using vertically-transmitted amplitude-modulated 0-mode HF heater waves. For our experiments, a number of radio diagnostic instruments had been utilized to detect the characteristic signatures of heater-generated AGW/TID. So far, we have been able to obtain several affirmative indications that some artificial AGW/TID are indeed being radiated out from the heated plasma volume during the HAARP-AGW experiments. Based on the experimental evidence, we may conclude that it is certainly quite plausible for large-scale thermal gradients associated with severe heat wave

  12. On stabilisability of nonlinear systems on time scales

    NASA Astrophysics Data System (ADS)

    Bartosiewicz, Zbigniew; Piotrowska, Ewa

    2013-01-01

    In this article, stabilisability of nonlinear finite-dimensional control systems on arbitrary time scales is studied. The classical results on stabilisation of nonlinear continuous-time and discrete-time systems are extended to systems on arbitrary time scales with bounded graininess function. It is shown that uniform exponential stability of the linear approximation of a nonlinear system implies uniform exponential stability of the nonlinear system. Then this result is used to show a similar implication for uniform exponential stabilisability.

  13. Time-Accurate Simulations and Acoustic Analysis of Slat Free-Shear Layer

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R.; Singer, Bart A.; Berkman, Mert E.

    2001-01-01

    A detailed computational aeroacoustic analysis of a high-lift flow field is performed. Time-accurate Reynolds Averaged Navier-Stokes (RANS) computations simulate the free shear layer that originates from the slat cusp. Both unforced and forced cases are studied. Preliminary results show that the shear layer is a good amplifier of disturbances in the low to mid-frequency range. The Ffowcs-Williams and Hawkings equation is solved to determine the acoustic field using the unsteady flow data from the RANS calculations. The noise radiated from the excited shear layer has a spectral shape qualitatively similar to that obtained from measurements in a corresponding experimental study of the high-lift system.

  14. Excised acoustic black holes: The scattering problem in the time domain

    SciTech Connect

    Cherubini, C.; Federici, F.; Tosi, M.P.; Succi, S.

    2005-10-15

    The scattering process of a dynamic perturbation impinging on a draining-tub model of an acoustic black hole is numerically solved in the time domain. Analogies with real black holes of general relativity are explored by using recently developed mathematical tools involving finite elements methods, excision techniques, and constrained evolution schemes for strongly hyperbolic systems. In particular it is shown that superradiant scattering of a quasimonochromatic wave packet can produce strong amplification of the signal, offering the possibility of a significant extraction of rotational energy at suitable values of the angular frequency of the vortex and of the central frequency of the wave packet. The results show that theoretical tools recently developed for gravitational waves can be brought to fruition in the study of other problems in which strong anisotropies are present.

  15. Comparative study of acoustic relaxation time of cholesteric liquid crystal and mixtures

    NASA Astrophysics Data System (ADS)

    Bhave, Manisha G.; Gharde, Rita; Radha, S.

    2016-09-01

    The present study focuses on the relaxation processes in Cholesteric Liquid Crystal and mixtures. We have dispersed two different monomers in CLC to form Polymer dispersed liquid crystals (PDCLCs). PDLC films have a remarkable electro-optical behavior since they can be switched from highly light scattering state (OFF) to transparent state (ON) simply by application of an electric field. We have also doped ferroelectric nano - powder (NP) in CLC. The phase transitions occurred at temperatures lower than those exhibited by the mesogenic component before doping. The viscosity, ultrasonic velocity and density show variation with change in the material as well as temperature. The acoustic relaxation time and ultrasonic attenuation decrease with increase in temperature for CLC and CLC+NP. The parameters of PDCLC2 in comparison with PDCLC1 are more linear in isotropic and anisotropic regions. For PDCLC2 the values reach maximum value at the Cholesteric-isotropic transition.

  16. Acoustic resolution photoacoustic Doppler velocity measurements in fluids using time-domain cross-correlation

    NASA Astrophysics Data System (ADS)

    Brunker, J.; Beard, P.

    2013-03-01

    Blood flow measurements have been demonstrated using the acoustic resolution mode of photoacoustic sensing. This is unlike previous flowmetry methods using the optical resolution mode, which limits the maximum penetration depth to approximately 1mm. Here we describe a pulsed time correlation photoacoustic Doppler technique that is inherently flexible, lending itself to both resolution modes. Doppler time shifts are quantified via cross-correlation of pairs of photoacoustic waveforms generated in moving absorbers using pairs of laser light pulses, and the photoacoustic waves detected using an ultrasound transducer. The acoustic resolution mode is employed by using the transducer focal width, rather than the large illuminated volume, to define the lateral spatial resolution. The use of short laser pulses allows depth-resolved measurements to be obtained with high spatial resolution, offering the prospect of mapping flow within microcirculation. Whilst our previous work has been limited to a non-fluid phantom, we now demonstrate measurements in more realistic blood-mimicking phantoms incorporating fluid suspensions of microspheres flowing along an optically transparent tube. Velocities up to 110 mm/s were measured with accuracies approaching 1% of the known velocities, and resolutions of a few mm/s. The velocity range and resolution are scalable with excitation pulse separation, but the maximum measurable velocity was considerably smaller than the value expected from the detector focal beam width. Measurements were also made for blood flowing at velocities up to 13.5 mm/s. This was for a sample reduced to 5% of the normal haematocrit; increasing the red blood cell concentration limited the maximum measurable velocity so that no results were obtained for concentrations greater than 20% of a physiologically realistic haematocrit. There are several possible causes for this limitation; these include the detector bandwidth and irregularities in the flow pattern. Better

  17. Time scales of tunneling decay of a localized state

    SciTech Connect

    Ban, Yue; Muga, J. G.; Sherman, E. Ya.; Buettiker, M.

    2010-12-15

    Motivated by recent time-domain experiments on ultrafast atom ionization, we analyze the transients and time scales that characterize, aside from the relatively long lifetime, the decay of a localized state by tunneling. While the tunneling starts immediately, some time is required for the outgoing flux to develop. This short-term behavior depends strongly on the initial state. For the initial state, tightly localized so that the initial transients are dominated by over-the-barrier motion, the time scale for flux propagation through the barrier is close to the Buettiker-Landauer traversal time. Then a quasistationary, slow-decay process follows, which sets ideal conditions for observing diffraction in time at longer times and distances. To define operationally a tunneling time at the barrier edge, we extrapolate backward the propagation of the wave packet that escaped from the potential. This extrapolated time is considerably longer than the time scale of the flux and density buildup at the barrier edge.

  18. Scale Model Acoustic Test Validation of IOP-SS Water Prediction using Loci-STREAM-VoF

    NASA Technical Reports Server (NTRS)

    Nielsen, Tanner; West, Jeff

    2015-01-01

    The Scale Model Acoustic Test (SMAT) is a 5% scale test of the Space Launch System (SLS), which is currently being designed at Marshall Space Flight Center (MSFC). SMAT consists of a 5% scale representation of the ignition overpressure sound-suppression system (IOP-SS) that is being tested to quantify the water flow and induced air entrainment in and around the mobile launcher exhaust hole. This data will be compared with computational fluid dynamics (CFD) simulations using the newly developed Loci-STREAM Volume of Fluid (VoF) methods. Compressible and incompressible VoF methods have been formulated, and are currently being used to simulate the water flow of SMAT IOP-SS. The test data will be used to qualitatively and quantitatively assess and validate the VoF methods.

  19. Assessment at full scale of nozzle/wing geometry effects on OTW aero-acoustic characteristics. [short takeoff aircraft noise

    NASA Technical Reports Server (NTRS)

    Groesbeck, D.; Vonglahn, U.

    1979-01-01

    The effects on acoustic characteristics of nozzle type and location on a wing for STOL engine over-the-wing configurations are assessed at full scale on the basis of model-scale data. Three types of nozzle configurations are evaluated: a circular nozzle with external deflector mounted above the wing, a slot nozzle with external deflector mounted on the wing and a slot nozzle mounted on the wing. Nozzle exhaust plane locations with respect to the wing leading edge are varied from 10 to 46 percent chord (flaps retracted) with flap angles of 20 (takeoff altitude) and 60 (approach attitude). Perceived noise levels (PNL) are calculated as a function of flyover distance at 152 m altitude. From these plots, static EPNL values, defined as flyover relative noise levels, are calculated and plotted as a function of lift and thrust ratios. From such plots the acoustic benefits attributable to variations in nozzle/deflector/wing geometry at full scale are assessed for equal aerodynamic performance.

  20. Use of acoustic wave travel-time measurements to probe the near-surface layers of the Sun

    NASA Technical Reports Server (NTRS)

    Jefferies, S. M.; Osaki, Y.; Shibahashi, H.; Duvall, T. L., Jr.; Harvey, J. W.; Pomerantz, M. A.

    1994-01-01

    The variation of solar p-mode travel times with cyclic frequency nu is shown to provide information on both the radial variation of the acoustic potential and the depth of the effective source of the oscillations. Observed travel-time data for waves with frequency lower than the acoustic cutoff frequency for the solar atmosphere (approximately equals 5.5 mHz) are inverted to yield the local acoustic cutoff frequency nu(sub c) as a function of depth in the outer convection zone and lower atmosphere of the Sun. The data for waves with nu greater than 5.5 mHz are used to show that the source of the p-mode oscillations lies approximately 100 km beneath the base of the photosphere. This depth is deeper than that determined using a standard mixing-length calculation.

  1. Shaping volumetric light distribution through turbid media using real-time three-dimensional opto-acoustic feedback.

    PubMed

    Deán-Ben, X Luís; Estrada, Héctor; Razansky, Daniel

    2015-02-15

    Focusing light through turbid media represents a highly fascinating challenge in modern biophotonics. The unique capability of opto-acoustics for high-resolution imaging of light absorption contrast in deep tissues can provide a natural and efficient feedback to control light delivery in a scattering medium. While the basic feasibility of using opto-acoustic readings as a feedback mechanism for wavefront shaping has been recently reported, the suggested approaches may require long acquisition times, making them challenging to be translated into realistic tissue environments. In an attempt to significantly accelerate dynamic wavefront shaping capabilities, we present here a feedback-based approach using real-time three-dimensional opto-acoustic imaging assisted with genetic-algorithm-based optimization. The new technique offers robust performance in the presence of noisy measurements and can simultaneously control the scattered wave field in an entire volumetric region.

  2. Time series of temperature in Fram Strait determined from the 2008-2009 DAMOCLES acoustic tomography measurements and an ocean model

    NASA Astrophysics Data System (ADS)

    Sagen, Hanne; Dushaw, Brian D.; Skarsoulis, Emmanuel K.; Dumont, Dany; Dzieciuch, Matthew A.; Beszczynska-Möller, Agnieszka

    2016-07-01

    A pilot acoustic tomography program in Fram Strait during 2008-2009 measured a year-long record of acoustic travel times along a 130 km range acoustic path crossing the West Spitsbergen Current. Individual ray arrivals were not observed. Rather, the arrival patterns consisted of a single, stable, broad arrival pulse of about 100 ms duration. Travel time variations of ±0.15 s recorded the vigorous mesoscale environment of the region and the seasonal cycle. To estimate ocean temperature from the tomography data an inverse scheme employed a high-resolution ocean model for Fram Strait as the reference ocean. The information from the tomographic measurements is primarily average temperature. Estimated temperatures, averaged over 0-1000 m depth and over range, had a mean of 1.11°C and variations of ±0.33°C; the uncertainty of the tomography estimates was about 60m°C. Agreement with an alternate inverse approach based on EOFs and a Markov Chain Monte Carlo inversion scheme relying on a matched-peak approach was excellent, indicating a robust estimate for ocean temperature. The inverse estimates for average temperature agreed with the equivalent estimates from hydrographic sections obtained along the acoustic path at the start and end of the program. Among other deficiencies, the ocean model greatly underestimated the intensity of the mesoscale fluctuations and exhibited a warm bias of about 0.38°C in section-averaged temperature. Tomographic measurements in Fram Strait offer unique large-scale temperature constraints for ocean models through data assimilation. It is anticipated that these constraints will lead to more accurate estimates of the circulation and transports in Fram Strait.

  3. On the Assessment of Acoustic Scattering and Shielding by Time Domain Boundary Integral Equation Solutions

    NASA Technical Reports Server (NTRS)

    Hu, Fang Q.; Pizzo, Michelle E.; Nark, Douglas M.

    2016-01-01

    Based on the time domain boundary integral equation formulation of the linear convective wave equation, a computational tool dubbed Time Domain Fast Acoustic Scattering Toolkit (TD-FAST) has recently been under development. The time domain approach has a distinct advantage that the solutions at all frequencies are obtained in a single computation. In this paper, the formulation of the integral equation, as well as its stabilization by the Burton-Miller type reformulation, is extended to cases of a constant mean flow in an arbitrary direction. In addition, a "Source Surface" is also introduced in the formulation that can be employed to encapsulate regions of noise sources and to facilitate coupling with CFD simulations. This is particularly useful for applications where the noise sources are not easily described by analytical source terms. Numerical examples are presented to assess the accuracy of the formulation, including a computation of noise shielding by a thin barrier motivated by recent Historical Baseline F31A31 open rotor noise shielding experiments. Furthermore, spatial resolution requirements of the time domain boundary element method are also assessed using point per wavelength metrics. It is found that, using only constant basis functions and high-order quadrature for surface integration, relative errors of less than 2% may be obtained when the surface spatial resolution is 5 points-per-wavelength (PPW) or 25 points-per-wavelength squared (PPW2).

  4. Classification of Hazelnut Kernels by Using Impact Acoustic Time-Frequency Patterns

    NASA Astrophysics Data System (ADS)

    Kalkan, Habil; Ince, Nuri Firat; Tewfik, Ahmed H.; Yardimci, Yasemin; Pearson, Tom

    2007-12-01

    Hazelnuts with damaged or cracked shells are more prone to infection with aflatoxin producing molds ( Aspergillus flavus). These molds can cause cancer. In this study, we introduce a new approach that separates damaged/cracked hazelnut kernels from good ones by using time-frequency features obtained from impact acoustic signals. The proposed technique requires no prior knowledge of the relevant time and frequency locations. In an offline step, the algorithm adaptively segments impact signals from a training data set in time using local cosine packet analysis and a Kullback-Leibler criterion to assess the discrimination power of different segmentations. In each resulting time segment, the signal is further decomposed into subbands using an undecimated wavelet transform. The most discriminative subbands are selected according to the Euclidean distance between the cumulative probability distributions of the corresponding subband coefficients. The most discriminative subbands are fed into a linear discriminant analysis classifier. In the online classification step, the algorithm simply computes the learned features from the observed signal and feeds them to the linear discriminant analysis (LDA) classifier. The algorithm achieved a throughput rate of 45 nuts/s and a classification accuracy of 96% with the 30 most discriminative features, a higher rate than those provided with prior methods.

  5. Controlling sound with acoustic metamaterials

    NASA Astrophysics Data System (ADS)

    Cummer, Steven A.; Christensen, Johan; Alù, Andrea

    2016-03-01

    Acoustic metamaterials can manipulate and control sound waves in ways that are not possible in conventional materials. Metamaterials with zero, or even negative, refractive index for sound offer new possibilities for acoustic imaging and for the control of sound at subwavelength scales. The combination of transformation acoustics theory and highly anisotropic acoustic metamaterials enables precise control over the deformation of sound fields, which can be used, for example, to hide or cloak objects from incident acoustic energy. Active acoustic metamaterials use external control to create effective material properties that are not possible with passive structures and have led to the development of dynamically reconfigurable, loss-compensating and parity-time-symmetric materials for sound manipulation. Challenges remain, including the development of efficient techniques for fabricating large-scale metamaterial structures and converting laboratory experiments into useful devices. In this Review, we outline the designs and properties of materials with unusual acoustic parameters (for example, negative refractive index), discuss examples of extreme manipulation of sound and, finally, provide an overview of future directions in the field.

  6. Electrochemical-acoustic time of flight: in operando correlation of physical dynamics with battery charge and health

    SciTech Connect

    Hsieh, AG; Bhadra, S; Hertzberg, BJ; Gjeltema, PJ; Goy, A; Fleischer, JW; Steingart, DA

    2015-01-01

    We demonstrate that a simple acoustic time-of-flight experiment can measure the state of charge and state of health of almost any closed battery. An acoustic conservation law model describing the state of charge of a standard battery is proposed, and experimental acoustic results verify the simulated trends; furthermore, a framework relating changes in sound speed, via density and modulus changes, to state of charge and state of health within a battery is discussed. Regardless of the chemistry, the distribution of density within a battery must change as a function of state of charge and, along with density, the bulk moduli of the anode and cathode changes as well. The shifts in density and modulus also change the acoustic attenuation in a battery. Experimental results indicating both state-of-charge determination and irreversible physical changes are presented for two of the most ubiquitous batteries in the world, the lithium-ion 18650 and the alkaline LR6 (AA). Overall, a one-or two-point acoustic measurement can be related to the interaction of a pressure wave at multiple discrete interfaces within a battery, which in turn provides insights into state of charge, state of health, and mechanical evolution/degradation.

  7. Calibrating passive acoustic monitoring: correcting humpback whale call detections for site-specific and time-dependent environmental characteristics.

    PubMed

    Helble, Tyler A; D'Spain, Gerald L; Campbell, Greg S; Hildebrand, John A

    2013-11-01

    This paper demonstrates the importance of accounting for environmental effects on passive underwater acoustic monitoring results. The situation considered is the reduction in shipping off the California coast between 2008-2010 due to the recession and environmental legislation. The resulting variations in ocean noise change the probability of detecting marine mammal vocalizations. An acoustic model was used to calculate the time-varying probability of detecting humpback whale vocalizations under best-guess environmental conditions and varying noise. The uncorrected call counts suggest a diel pattern and an increase in calling over a two-year period; the corrected call counts show minimal evidence of these features.

  8. Imaging of human tooth using ultrasound based chirp-coded nonlinear time reversal acoustics.

    PubMed

    Dos Santos, Serge; Prevorovsky, Zdenek

    2011-08-01

    Human tooth imaging sonography is investigated experimentally with an acousto-optic noncoupling set-up based on the chirp-coded nonlinear time reversal acoustic concept. The complexity of the tooth internal structure (enamel-dentine interface, cracks between internal tubules) is analyzed by adapting the nonlinear elastic wave spectroscopy (NEWS) with the objective of the tomography of damage. Optimization of excitations using intrinsic symmetries, such as time reversal (TR) invariance, reciprocity, correlation properties are then proposed and implemented experimentally. The proposed medical application of this TR-NEWS approach is implemented on a third molar human tooth and constitutes an alternative of noncoupling echodentography techniques. A 10 MHz bandwidth ultrasonic instrumentation has been developed including a laser vibrometer and a 20 MHz contact piezoelectric transducer. The calibrated chirp-coded TR-NEWS imaging of the tooth is obtained using symmetrized excitations, pre- and post-signal processing, and the highly sensitive 14 bit resolution TR-NEWS instrumentation previously calibrated. Nonlinear signature coming from the symmetry properties is observed experimentally in the tooth using this bi-modal TR-NEWS imaging after and before the focusing induced by the time-compression process. The TR-NEWS polar B-scan of the tooth is described and suggested as a potential application for modern echodentography. It constitutes the basis of the self-consistent harmonic imaging sonography for monitoring cracks propagation in the dentine, responsible of human tooth structural health.

  9. Real-time monitoring of human blood clotting using a lateral excited film bulk acoustic resonator

    NASA Astrophysics Data System (ADS)

    Chen, Da; Wang, Jingjng; Wang, Peng; Guo, Qiuquan; Zhang, Zhen; Ma, Jilong

    2017-04-01

    Frequent assay of hemostatic status is an essential issue for the millions of patients using anticoagulant drugs. In this paper, we presented a micro-fabricated film bulk acoustic sensor for the real-time monitoring of blood clotting and the measurement of hemostatic parameters. The device was made of an Au/ZnO/Si3N4 film stack and excited by a lateral electric field. It operated under a shear mode resonance with the frequency of 1.42 GHz and had a quality factor of 342 in human blood. During the clotting process of blood, the resonant frequency decreased along with the change of blood viscosity and showed an apparent step-ladder curve, revealing the sequential clotting stages. An important hemostatic parameter, prothrombin time, was quantitatively determined from the frequency response for different dilutions of the blood samples. The effect of a typical anticoagulant drug (heparin) on the prothrombin time was exemplarily shown. The proposed sensor displayed a good consistency and clinical comparability with the standard coagulometric methods. Thanks to the availability of direct digital signals, excellent potentials of miniaturization and integration, the proposed sensor has promising application for point-of-care coagulation technologies.

  10. Time reversal multiple-input/multiple-output acoustic communication enhanced by parallel interference cancellation.

    PubMed

    Song, Aijun; Badiey, Mohsen

    2012-01-01

    Multiple-input/multiple-output (MIMO) techniques can lead to significant improvements of underwater acoustic communication capabilities. In this paper, receivers based on time reversal processing are developed for high frequency underwater MIMO channels. Time reversal followed by a single channel decision feedback equalizer, aided by frequent channel updates, is used to compensate for the time-varying inter-symbol interference. A parallel interference cancellation method is incorporated to suppress the co-channel interference in the MIMO system. The receiver performance is demonstrated by a 2008 shallow water experiment in Kauai, Hawaii. In the experiment, high frequency MIMO signals centered at 16 kHz were transmitted every hour during a 35 h period from an 8-element source array to a wide aperture 16-element vertical receiving array at 4 km range. The interference cancellation method is shown to generate significant performance enhancement, on average 2-4 dB in the output signal-to-noise ratio per data stream, throughout the 35 h MIMO transmissions. Further, communication performance and achieved data rates exhibit significant changes over the 35 h period as a result of stratification of the water column.

  11. Liquidity spillover in international stock markets through distinct time scales.

    PubMed

    Righi, Marcelo Brutti; Vieira, Kelmara Mendes

    2014-01-01

    This paper identifies liquidity spillovers through different time scales based on a wavelet multiscaling method. We decompose daily data from U.S., British, Brazilian and Hong Kong stock markets indices in order to calculate the scale correlation between their illiquidities. The sample is divided in order to consider non-crisis, sub-prime crisis and Eurozone crisis. We find that there are changes in correlations of distinct scales and different periods. Association in finest scales is smaller than in coarse scales. There is a rise on associations in periods of crisis. In frequencies, there is predominance for significant distinctions involving the coarsest scale, while for crises periods there is predominance for distinctions on the finest scale.

  12. Liquidity Spillover in International Stock Markets through Distinct Time Scales

    PubMed Central

    Righi, Marcelo Brutti; Vieira, Kelmara Mendes

    2014-01-01

    This paper identifies liquidity spillovers through different time scales based on a wavelet multiscaling method. We decompose daily data from U.S., British, Brazilian and Hong Kong stock markets indices in order to calculate the scale correlation between their illiquidities. The sample is divided in order to consider non-crisis, sub-prime crisis and Eurozone crisis. We find that there are changes in correlations of distinct scales and different periods. Association in finest scales is smaller than in coarse scales. There is a rise on associations in periods of crisis. In frequencies, there is predominance for significant distinctions involving the coarsest scale, while for crises periods there is predominance for distinctions on the finest scale. PMID:24465918

  13. Multiple time scale complexity analysis of resting state FMRI.

    PubMed

    Smith, Robert X; Yan, Lirong; Wang, Danny J J

    2014-06-01

    The present study explored multi-scale entropy (MSE) analysis to investigate the entropy of resting state fMRI signals across multiple time scales. MSE analysis was developed to distinguish random noise from complex signals since the entropy of the former decreases with longer time scales while the latter signal maintains its entropy due to a "self-resemblance" across time scales. A long resting state BOLD fMRI (rs-fMRI) scan with 1000 data points was performed on five healthy young volunteers to investigate the spatial and temporal characteristics of entropy across multiple time scales. A shorter rs-fMRI scan with 240 data points was performed on a cohort of subjects consisting of healthy young (age 23 ± 2 years, n = 8) and aged volunteers (age 66 ± 3 years, n = 8) to investigate the effect of healthy aging on the entropy of rs-fMRI. The results showed that MSE of gray matter, rather than white matter, resembles closely that of f (-1) noise over multiple time scales. By filtering out high frequency random fluctuations, MSE analysis is able to reveal enhanced contrast in entropy between gray and white matter, as well as between age groups at longer time scales. Our data support the use of MSE analysis as a validation metric for quantifying the complexity of rs-fMRI signals.

  14. Assessment at full scale of exhaust nozzle-to-wing size on STOL-OTW acoustic characteristics

    NASA Technical Reports Server (NTRS)

    Von Glahn, U.; Groesbeck, D.

    1979-01-01

    On the basis of static zero/acoustic data obtained at model scale, the effect of exhaust nozzle size on flyover noise is evaluated at full scale for different STOL-OTW nozzle configurations. Three types of nozzles are evaluated: a circular/deflector nozzle mounted above the wing, a slot/deflector nozzle mounted on the wing, and a slot nozzle mounted on the wing. The nozzle exhaust plane location, measured from the wing leading edge was varied from 10 to 46 percent of the wing chord (flaps retracted). Flap angles of 20 deg (takeoff) and 60 deg (approach) are included in the study. Initially, perceived noise levels (PNL) are calculated as a function of flyover distance at 152 m altitude. From these plots static EPNL values, defined as flyover relative noise levels, then are obtained as functions of nozzle size for equal aerodynamic performance (lift and thrust). On the basis of these calculations, the acoustic benefits attributable to nozzle size relative to a given wing chord size are assessed.

  15. Validation of the facial dysfunction domain of the Penn Acoustic Neuroma Quality-of-Life (PANQOL) Scale.

    PubMed

    Lodder, Wouter L; Adan, Guleed H; Chean, Chung S; Lesser, Tristram H; Leong, Samuel C

    2017-04-08

    The objective of this study is to evaluate the strength of content validity within the facial dysfunction domain of the Penn Acoustic Neuroma Quality-of-Life (PANQOL) Scale and to compare how it correlates with a facial dysfunction-specific QOL instrument (Facial Clinimetric Evaluation, FaCE). The study design is online questionnaire survey. Members of the British Acoustic Neuroma Association received both PANQOL questionnaires and the FaCE scale. 158 respondents with self-identified facial paralysis or dysfunction had completed PANQOL and FaCE data sets for analysis. The mean composite PANQOL score was 53.5 (range 19.2-93.5), whilst the mean total FaCE score was 50.9 (range 10-95). The total scores of the PANQOL and FaCE correlated moderate (r = 0.48). Strong correlation (r = 0.63) was observed between the PANQOL's facial dysfunction domain and the FaCE total score. Of all the FaCE domains, social function was strongly correlated with the PANQOL facial dysfunction domain (r = 0.66), whilst there was very weak-to-moderate correlation (range 0.01-0.43) to the other FaCE domains. The current study has demonstrated a strong correlation between the facial dysfunction domains of PANQOL with a facial paralysis-specific QOL instrument.

  16. Extreme reaction times determine fluctuation scaling in human color vision

    NASA Astrophysics Data System (ADS)

    Medina, José M.; Díaz, José A.

    2016-11-01

    In modern mental chronometry, human reaction time defines the time elapsed from stimulus presentation until a response occurs and represents a reference paradigm for investigating stochastic latency mechanisms in color vision. Here we examine the statistical properties of extreme reaction times and whether they support fluctuation scaling in the skewness-kurtosis plane. Reaction times were measured for visual stimuli across the cardinal directions of the color space. For all subjects, the results show that very large reaction times deviate from the right tail of reaction time distributions suggesting the existence of dragon-kings events. The results also indicate that extreme reaction times are correlated and shape fluctuation scaling over a wide range of stimulus conditions. The scaling exponent was higher for achromatic than isoluminant stimuli, suggesting distinct generative mechanisms. Our findings open a new perspective for studying failure modes in sensory-motor communications and in complex networks.

  17. Acoustic levitation of a large solid sphere

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  18. Modes and emergent time scales of embayed beach dynamics

    NASA Astrophysics Data System (ADS)

    Ratliff, Katherine M.; Murray, A. Brad

    2014-10-01

    In this study, we use a simple numerical model (the Coastline Evolution Model) to explore alongshore transport-driven shoreline dynamics within generalized embayed beaches (neglecting cross-shore effects). Using principal component analysis (PCA), we identify two primary orthogonal modes of shoreline behavior that describe shoreline variation about its unchanging mean position: the rotation mode, which has been previously identified and describes changes in the mean shoreline orientation, and a newly identified breathing mode, which represents changes in shoreline curvature. Wavelet analysis of the PCA mode time series reveals characteristic time scales of these modes (typically years to decades) that emerge within even a statistically constant white-noise wave climate (without changes in external forcing), suggesting that these time scales can arise from internal system dynamics. The time scales of both modes increase linearly with shoreface depth, suggesting that the embayed beach sediment transport dynamics exhibit a diffusive scaling.

  19. The limit order book on different time scales

    NASA Astrophysics Data System (ADS)

    Eisler, Zoltán; Kertész, János; Lillo, Fabrizio

    2007-06-01

    Financial markets can be described on several time scales. We use data from the limit order book of the London Stock Exchange (LSE) to compare how the fluctuation dominated microstructure crosses over to a more systematic global behavior.

  20. NEA Scout Solar Sail: Half-scale Fold Time Lapse

    NASA Video Gallery

    In this time lapse, the Near-Earth Asteroid Scout (NEA Scout) CubeSat team rolls a half-scale prototype of the small satellite's solar sail in preparation for a deployment test. During its mission,...

  1. Diffusion Time-Scale of Porous Pressure-Sensitive Paint

    NASA Technical Reports Server (NTRS)

    Liu, Tianshu; Teduka, Norikazu; Kameda, Masaharu; Asai, Keisuke

    2001-01-01

    Pressure-sensitive paint (PSP) is an optical pressure sensor that utilizes the oxygen quenching of luminescence. PSP measurements in unsteady aerodynamic flows require fast time response of the paint. There are two characteristic time-scales that are related to the time response of PSP. One is the luminescent lifetime representing an intrinsic physical limit for the achievable temporal resolution of PSP. Another is the time-scale of oxygen diffusion across the PSP layer. When the time-scale of oxygen diffusion is much larger than the luminescent lifetime, the time response of PSP is controlled by oxygen diffusion. In a thin homogenous polymer layer where diffusion is Fickian, the oxygen concentration 1021 can be described by the diffusion equation in one-dimension.

  2. Multichannel time-reversal processing for acoustic communications in a highly reverberant environment

    NASA Astrophysics Data System (ADS)

    Candy, James V.; Poggio, Andrew J.; Chambers, David H.; Guidry, Brian L.; Robbins, Christopher L.; Kent, Claudia A.

    2005-10-01

    The development of time-reversal (T/R) communication systems is a recent signal processing research area dominated by applying T/R techniques to communicate in hostile environments. The fundamental concept is based on time-reversing the impulse response or Green's function characterizing the uncertain communications channel to mitigate deleterious dispersion and multipath effects. In this paper, we extend point-to-point to array-to-point communications by first establishing the basic theory to define and solve the underlying multichannel communications problem and then developing various realizations of the resulting T/R receivers. We show that not only do these receivers perform well in a hostile environment, but they also can be implemented with a ``1 bit'' analog-to-digital converter design structure. We validate these results by performing proof-of-principle acoustic communications experiments in air. It is shown that the resulting T/R receivers are capable of extracting the transmitted coded sequence from noisy microphone array measurements with zero-bit error.

  3. Gust Acoustic Response of a Single Airfoil Using the Space-Time CE/SE Method

    NASA Technical Reports Server (NTRS)

    Scott, James (Technical Monitor); Wang, X. Y.; Chang, S. C.; Himansu, A.; Jorgenson, P. C. E.

    2003-01-01

    A 2D parallel Euler code based on the space-time conservation element and solution element (CE/SE) method is validated by solving the benchmark problem I in Category 3 of the Third CAA Workshop. This problem concerns the acoustic field generated by the interaction of a convected harmonic vortical gust with a single airfoil. Three gust frequencies, two gust configurations, and three airfoil geometries are considered. Numerical results at both near and far fields are presented and compared with the analytical solutions, a frequency-domain solver GUST3D solutions, and a time-domain high-order Discontinuous Spectral Element Method (DSEM) solutions. It is shown that the CE/SE solutions agree well with the GUST3D solution for the lowest frequency, while there are discrepancies between CE/SE and GUST3D solutions for higher frequencies. However, the CE/SE solution is in good agreement with the DSEM solution for these higher frequencies. It demonstrates that the CE/SE method can produce accurate results of CAA problems involving complex geometries by using unstructured meshes.

  4. Quadratic Time-Frequency Analysis of Hydroacoustic Signals as Applied to Acoustic Emissions of Large Whales

    NASA Astrophysics Data System (ADS)

    Le Bras, Ronan; Victor, Sucic; Damir, Malnar; Götz, Bokelmann

    2014-05-01

    In order to enrich the set of attributes in setting up a large database of whale signals, as envisioned in the Baleakanta project, we investigate methods of time-frequency analysis. The purpose of establishing the database is to increase and refine knowledge of the emitted signal and of its propagation characteristics, leading to a better understanding of the animal migrations in a non-invasive manner and to characterize acoustic propagation in oceanic media. The higher resolution for signal extraction and a better separation from other signals and noise will be used for various purposes, including improved signal detection and individual animal identification. The quadratic class of time-frequency distributions (TFDs) is the most popular set of time-frequency tools for analysis and processing of non-stationary signals. Two best known and most studied members of this class are the spectrogram and the Wigner-Ville distribution. However, to be used efficiently, i.e. to have highly concentrated signal components while significantly suppressing interference and noise simultaneously, TFDs need to be optimized first. The optimization method used in this paper is based on the Cross-Wigner-Ville distribution, and unlike similar approaches it does not require prior information on the analysed signal. The method is applied to whale signals, which, just like the majority of other real-life signals, can generally be classified as multicomponent non-stationary signals, and hence time-frequency techniques are a natural choice for their representation, analysis, and processing. We present processed data from a set containing hundreds of individual calls. The TFD optimization method results into a high resolution time-frequency representation of the signals. It allows for a simple extraction of signal components from the TFD's dominant ridges. The local peaks of those ridges can then be used for the signal components instantaneous frequency estimation, which in turn can be used as

  5. Performance study of Lagrangian methods: reconstruction of large scale peculiar velocities and baryonic acoustic oscillations

    NASA Astrophysics Data System (ADS)

    Keselman, J. A.; Nusser, A.

    2017-01-01

    NoAM for "No Action Method" is a framework for reconstructing the past orbits of observed tracers of the large scale mass density field. It seeks exact solutions of the equations of motion (EoM), satisfying initial homogeneity and the final observed particle (tracer) positions. The solutions are found iteratively reaching a specified tolerance defined as the RMS of the distance between reconstructed and observed positions. Starting from a guess for the initial conditions, NoAM advances particles using standard N-body techniques for solving the EoM. Alternatively, the EoM can be replaced by any approximation such as Zel'dovich and second order perturbation theory (2LPT). NoAM is suitable for billions of particles and can easily handle non-regular volumes, redshift space, and other constraints. We implement NoAM to systematically compare Zel'dovich, 2LPT, and N-body dynamics over diverse configurations ranging from idealized high-res periodic simulation box to realistic galaxy mocks. Our findings are (i) Non-linear reconstructions with Zel'dovich, 2LPT, and full dynamics perform better than linear theory only for idealized catalogs in real space. For realistic catalogs, linear theory is the optimal choice for reconstructing velocity fields smoothed on scales {buildrel > over {˜}} 5 h^{-1}{Mpc}.(ii) all non-linear back-in-time reconstructions tested here, produce comparable enhancement of the baryonic oscillation signal in the correlation function.

  6. Validation and Simulation of Ares I Scale Model Acoustic Test - 2 - Simulations at 5 Foot Elevation for Evaluation of Launch Mount Effects

    NASA Technical Reports Server (NTRS)

    Strutzenberg, Louise L.; Putman, Gabriel C.

    2011-01-01

    The Ares I Scale Model Acoustics Test (ASMAT) is a series of live-fire tests of scaled rocket motors meant to simulate the conditions of the Ares I launch configuration. These tests have provided a well documented set of high fidelity measurements useful for validation including data taken over a range of test conditions and containing phenomena like Ignition Over-Pressure and water suppression of acoustics. Expanding from initial simulations of the ASMAT setup in a held down configuration, simulations have been performed using the Loci/CHEM computational fluid dynamics software for ASMAT tests of the vehicle at 5 ft. elevation (100 ft. real vehicle elevation) with worst case drift in the direction of the launch tower. These tests have been performed without water suppression and have compared the acoustic emissions for launch structures with and without launch mounts. In addition, simulation results have also been compared to acoustic and imagery data collected from similar live-fire tests to assess the accuracy of the simulations. Simulations have shown a marked change in the pattern of emissions after removal of the launch mount with a reduction in the overall acoustic environment experienced by the vehicle and the formation of highly directed acoustic waves moving across the platform deck. Comparisons of simulation results to live-fire test data showed good amplitude and temporal correlation and imagery comparisons over the visible and infrared wavelengths showed qualitative capture of all plume and pressure wave evolution features.

  7. Galaxy merger time-scales in the Illustris Simulation

    NASA Astrophysics Data System (ADS)

    Rojas, Areli; Rodriguez-Gomez, Vicente; Hernquist, Lars E.; Wellons, Sarah; Moreno, Jorge

    2017-01-01

    In this project we are investigate merger time-scales, define as the time delays from dark matter halo viral crossing to galaxy-galaxy coalescence. Our project uses merger history trees drawn from the Illustris Simulation, a cosmological hydrodynamic run that follows the formation and evolution of galaxies across cosmic time. Preliminary results indicate that merger time-scales are not sensitive to stellar mass or mass ratio, in stark contrast to what has been found earlier with cosmological dark-matter-only simulations. Work towards understanding the source of this disagreement is currently in progress.

  8. Vorticity statistics and the time scales of turbulent strain.

    PubMed

    Moriconi, L; Pereira, R M

    2013-07-01

    Time scales of turbulent strain activity, denoted as the strain persistence times of first and second order, are obtained from time-dependent expectation values and correlation functions of Lagrangian rate-of-strain eigenvalues taken in particularly defined statistical ensembles. Taking into account direct numerical simulation data, our approach relies on heuristic closure hypotheses which allow us to establish a connection between the statistics of vorticity and strain. It turns out that softly divergent prefactors correct the usual "1/s" strain time-scale estimate of standard turbulence phenomenology, in a way which is consistent with the phenomenon of vorticity intermittency.

  9. Very short NMR relaxation times of anions in ionic liquids: new pulse sequence to eliminate the acoustic ringing.

    PubMed

    Klimavicius, Vytautas; Gdaniec, Zofia; Balevicius, Vytautas

    2014-11-11

    NMR relaxation processes of anions were studied in two neat imidazolium-based room temperature ionic liquids (RTILs) 1-decyl-3-methyl-imidazolium bromide- and chloride. The spin-lattice and spin-spin relaxations of 81Br and 35Cl nuclei were found to be extremely fast due to very strong quadrupolar interactions. The determined relaxation rates are comparable with those observed in the solids or in some critical organic solute/water/salt systems. In order to eliminate the acoustic ringing of the probe-head during relaxation times measurements the novel pulse sequence has been devised. It is based on the conventional inversion recovery pulse sequence, however, instead of the last 90° pulse the subsequence of three 90° pulses applied along axes to fulfill the phase cycling condition is used. Using this pulse sequence it was possible to measure T1 for both studied nuclei. The viscosity measurements have been carried out and the rotational correlation times were calculated. The effective 35Cl quadrupolar coupling constant was found to be almost one order lower than that for 81Br, i.e. 1.8 MHz and 16.0 MHz, respectively. Taking into account the facts that the ratio of (Q(35Cl)/Q(81Br))2≈0.1 and EFG tensors on the anions are quite similar, analogous structural organizations are expected for both RTILs. The observed T1/T2 (1.27-1.44) ratios were found to be not sufficiently high to confirm the presence of long-living (on the time scale of ≥10(-8) s) mesoscopic structures or heterogeneities in the studied neat ionic liquids.

  10. Russian national time scale long-term stability

    NASA Technical Reports Server (NTRS)

    Alshina, A. P.; Gaigerov, B. A.; Koshelyaevsky, N. B.; Pushkin, S. B.

    1994-01-01

    The Institute of Metrology for Time and Space NPO 'VNIIFTRI' generates the National Time Scale (NTS) of Russia -- one of the most stable time scales in the world. Its striking feature is that it is based on a free ensemble of H-masers only. During last two years the estimations of NTS longterm stability based only on H-maser intercomparison data gives a flicker floor of about (2 to 3) x 10(exp -15) for averaging times from 1 day to 1 month. Perhaps the most significant feature for a time laboratory is an extremely low possible frequency drift -- it is too difficult to estimate it reliably. The other estimations, free from possible inside the ensemble correlation phenomena, are available based on the time comparison of NTS relative to the stable enough time scale of outer laboratories. The data on NTS comparison relative to the time scale of secondary time and frequency standards at Golitzino and Irkutsk in Russia and relative to NIST, PTB and USNO using GLONASS and GPS time transfer links gives stability estimations which are close to that based on H-maser intercomparisons.

  11. Exponentials and Laplace transforms on nonuniform time scales

    NASA Astrophysics Data System (ADS)

    Ortigueira, Manuel D.; Torres, Delfim F. M.; Trujillo, Juan J.

    2016-10-01

    We formulate a coherent approach to signals and systems theory on time scales. The two derivatives from the time-scale calculus are used, i.e., nabla (forward) and delta (backward), and the corresponding eigenfunctions, the so-called nabla and delta exponentials, computed. With these exponentials, two generalised discrete-time Laplace transforms are deduced and their properties studied. These transforms are compatible with the standard Laplace and Z transforms. They are used to study discrete-time linear systems defined by difference equations. These equations mimic the usual continuous-time equations that are uniformly approximated when the sampling interval becomes small. Impulse response and transfer function notions are introduced. This implies a unified mathematical framework that allows us to approximate the classic continuous-time case when the sampling rate is high or to obtain the standard discrete-time case, based on difference equations, when the time grid becomes uniform.

  12. The scaling of time series size towards detrended fluctuation analysis

    NASA Astrophysics Data System (ADS)

    Gao, Xiaolei; Ren, Liwei; Shang, Pengjian; Feng, Guochen

    2016-06-01

    In this paper, we introduce a modification of detrended fluctuation analysis (DFA), called multivariate DFA (MNDFA) method, based on the scaling of time series size N. In traditional DFA method, we obtained the influence of the sequence segmentation interval s, and it inspires us to propose a new model MNDFA to discuss the scaling of time series size towards DFA. The effectiveness of the procedure is verified by numerical experiments with both artificial and stock returns series. Results show that the proposed MNDFA method contains more significant information of series compared to traditional DFA method. The scaling of time series size has an influence on the auto-correlation (AC) in time series. For certain series, we obtain an exponential relationship, and also calculate the slope through the fitting function. Our analysis and finite-size effect test demonstrate that an appropriate choice of the time series size can avoid unnecessary influences, and also make the testing results more accurate.

  13. Resistivity scaling and electron relaxation times in metallic nanowires

    SciTech Connect

    Moors, Kristof; Sorée, Bart; Magnus, Wim; Tőkei, Zsolt

    2014-08-14

    We study the resistivity scaling in nanometer-sized metallic wires due to surface roughness and grain-boundaries, currently the main cause of electron scattering in nanoscaled interconnects. The resistivity has been obtained with the Boltzmann transport equation, adopting the relaxation time approximation of the distribution function and the effective mass approximation for the conducting electrons. The relaxation times are calculated exactly, using Fermi's golden rule, resulting in a correct relaxation time for every sub-band state contributing to the transport. In general, the relaxation time strongly depends on the sub-band state, something that remained unclear with the methods of previous work. The resistivity scaling is obtained for different roughness and grain-boundary properties, showing large differences in scaling behavior and relaxation times. Our model clearly indicates that the resistivity is dominated by grain-boundary scattering, easily surpassing the surface roughness contribution by a factor of 10.

  14. Universal scaling function in discrete time asymmetric exclusion processes

    NASA Astrophysics Data System (ADS)

    Chia, Nicholas; Bundschuh, Ralf

    2005-03-01

    In the universality class of the one dimensional Kardar-Parisi-Zhang surface growth, Derrida and Lebowitz conjectured the universality of not only the scaling exponents, but of an entire scaling function. Since Derrida and Lebowitz' original publication this universality has been verified for a variety of continuous time systems in the KPZ universality class. We study the Derrida-Lebowitz scaling function for multi-particle versions of the discrete time Asymmetric Exclusion Process. We find that in this discrete time system the Derrida-Lebowitz scaling function not only properly characterizes the large system size limit, but even accurately describes surprisingly small systems. These results have immediate applications in searching biological sequence databases.

  15. Trends in Surface Radiation Budgets at Climatic Time Scales

    NASA Astrophysics Data System (ADS)

    Pinker, R. T.; Zhang, B.; Ma, Y.

    2015-12-01

    For assessment of variability and trends in the Earth Radiation Balance, information is needed at climatic time scales. Satellite observations have been instrumental for advancing the understanding of radiative balance at global scale, however, the length of available satellite records is limited due to the frequent changes in the observing systems. In this paper we report on an effort to synthesize satellite observations from independent sources to estimates shortwave and longwave surface radiative fluxes at climatic time scales and use them to learn about their variability and trends at global scale with a focus on the tropics. An attempt will be made to learn from the comparison about possible causes of observed trends. The radiative fluxes were derived in the framework of the MEaSURES and NEWS programs; they are evaluated against ground observations and compared to independent satellite and model estimates. Attention is given to updated knowledge on radiative balance as compared to what is known from shorter time records.

  16. [Physiological-occupational assessment of acoustic load with equal energy but different time and informational characteristics].

    PubMed

    Suvorov, G A; Shkarinov, L N; Kravchenko, O K; Kur'erov, N N

    1999-01-01

    The article deals with results of experimental study comparing effects of 4 types of acoustic load--noise (constant and impulse) and music (electronic symphonic one and rap)--on hearing sensitivity, processes in nervous system and subjective evaluation. All types of acoustic load were equal in energy (on evaluation according to equivalent level during the experiment). The study included 2 levels of load--90 and 95 dB. The differences revealed demonstrate importance of impulse parameters of noise and musical load for reactions of acoustic analyzer and central nervous system. The experiments show that evaluation of harm caused by temporary and impulse noises should be based not only on assessment of specific (hearing) function, but also on parameters of central nervous system state. The authors found that music of certain acoustic and informational parameters may harm hearing function.

  17. Controllability of multiplex, multi-time-scale networks

    NASA Astrophysics Data System (ADS)

    Pósfai, Márton; Gao, Jianxi; Cornelius, Sean P.; Barabási, Albert-László; D'Souza, Raissa M.

    2016-09-01

    The paradigm of layered networks is used to describe many real-world systems, from biological networks to social organizations and transportation systems. While recently there has been much progress in understanding the general properties of multilayer networks, our understanding of how to control such systems remains limited. One fundamental aspect that makes this endeavor challenging is that each layer can operate at a different time scale; thus, we cannot directly apply standard ideas from structural control theory of individual networks. Here we address the problem of controlling multilayer and multi-time-scale networks focusing on two-layer multiplex networks with one-to-one interlayer coupling. We investigate the practically relevant case when the control signal is applied to the nodes of one layer. We develop a theory based on disjoint path covers to determine the minimum number of inputs (Ni) necessary for full control. We show that if both layers operate on the same time scale, then the network structure of both layers equally affect controllability. In the presence of time-scale separation, controllability is enhanced if the controller interacts with the faster layer: Ni decreases as the time-scale difference increases up to a critical time-scale difference, above which Ni remains constant and is completely determined by the faster layer. We show that the critical time-scale difference is large if layer I is easy and layer II is hard to control in isolation. In contrast, control becomes increasingly difficult if the controller interacts with the layer operating on the slower time scale and increasing time-scale separation leads to increased Ni, again up to a critical value, above which Ni still depends on the structure of both layers. This critical value is largely determined by the longest path in the faster layer that does not involve cycles. By identifying the underlying mechanisms that connect time-scale difference and controllability for a simplified

  18. Inferring Patterns in Network Traffic: Time Scales and Variations

    DTIC Science & Technology

    2014-10-21

    2014 Carnegie Mellon University Inferring Patterns in Network Traffic : Time Scales and Variation Soumyo Moitra smoitra@sei.cmu.edu...number. 1. REPORT DATE 21 OCT 2014 2. REPORT TYPE N/A 3. DATES COVERED 4. TITLE AND SUBTITLE Inferring Patterns in Network Traffic : Time...method and metrics for Situational Awareness • SA  Monitoring trends and changes in traffic • Analysis over timeTime series data analysis • Metrics

  19. Non-invasive and real-time passive acoustic mapping of ultrasound-mediated drug delivery

    NASA Astrophysics Data System (ADS)

    Choi, James J.; Carlisle, Robert C.; Coviello, Christian; Seymour, Len; Coussios, Constantin-C.

    2014-09-01

    New classes of biologically active materials, such as viruses, siRNA, antibodies and a wide range of engineered nanoparticles have emerged as potent agents for diagnosing and treating diseases, yet many of these agents fail because there is no effective route of delivery to their intended targets. Focused ultrasound and its ability to drive microbubble-seeded cavitation have been shown to facilitate drug delivery. However, cavitation is difficult to control temporally and spatially, making prediction of therapeutic outcomes deep in the body difficult. Here, we utilized passive acoustic mapping in vivo to understand how ultrasound parameters influence cavitation dynamics and to correlate spatial maps of cavitation to drug delivery. Focused ultrasound (center frequency: 0.5 MHz, peak-rarefactional pressure: 1.2 MPa, pulse length: 25 cycles or 50,000 cycles, pulse repetition interval: 0.02, 0.2, 1 or 3 s, number of pulses: 80 pulses) was applied to murine xenograft-model tumors in vivo during systemic injection of microbubbles with and without cavitation-sensitive liposomes or type 5 adenoviruses. Analysis of in vivo cavitation dynamics through several pulses revealed that cavitation was more efficiently produced at a lower pulse repetition frequency of 1 Hz than at 50 Hz. Within a pulse, inertial cavitation activity was shown to persist but reduced to 50% and 25% of its initial magnitude in 4.3 and 29.3 ms, respectively. Both through several pulses and within a pulse, the spatial distribution of cavitation was shown to change in time due to variations in microbubble distribution present in tumors. Finally, we demonstrated that the centroid of the mapped cavitation activity was within 1.33  ±  0.6 mm and 0.36 mm from the centroid location of drug release from liposomes and expression of the reporter gene encoded by the adenovirus, respectively. Thus passive acoustic mapping not only unraveled key mechanisms whereby a successful outcome is achieved

  20. Time-reversal acoustic focusing system as a virtual random phased array.

    PubMed

    Sarvazyan, Armen; Fillinger, Laurent; Gavrilov, Leonid

    2010-04-01

    This paper compares the performance of two different systems for dynamic focusing of ultrasonic waves: conventional 2-D phased arrays (PA) and a focusing system based on the principles of time-reversed acoustics (TRA). Focused ultrasound fields obtained in the experiments with the TRA focusing system (TRA FS), which employs a liquid-filled reverberator with 4 piezotransducers attached to its wall, are compared with the focused fields obtained by mathematical simulation of PAs comprised from several tens to several hundreds of elements distributed randomly on the array surface. The experimental and simulated focusing systems had the same aperture and operated at a frequency centered about 600 kHz. Experimental results demonstrated that the TRA FS with a small number of channels can produce complex focused patterns and can steer them with efficiency comparable to that of a PA with hundreds of elements. It is shown that the TRA FS can be realized using an extremely simple means, such as a reverberator made of a water-filled plastic bottle with just a few piezotransducers attached to its walls.

  1. Real-Time Debonding Monitoring of Composite Repaired Materials via Electrical, Acoustic, and Thermographic Methods

    NASA Astrophysics Data System (ADS)

    Grammatikos, S. A.; Kordatos, E. Z.; Matikas, T. E.; Paipetis, A. S.

    2014-01-01

    The electrical properties of composite materials have been thoroughly investigated recently for the detection and monitoring of damage in carbon fiber-reinforced polymers (CFRPs) under mechanical loading. Carbon nanotubes are incorporated in the polymer matrix of CFRPs for the enhancement of their electrical properties. The electrical properties have shown to be sensitive to the damage state of the material and hence their monitoring provides the profile of their structural deterioration. The aim of the paper is the cross-validation and benchmarking of an electrical potential change monitoring (EPCM) technique against acoustic emission (AE) and lock-in thermography (LT). All techniques successfully identified damage and its propagation. Thermography was more efficient in quantifying damage and describing dynamically the debond topology, as it provided full 2D imaging of the debond in real time. EPCM was successful in providing quantitative information on debond propagation and its directionality. AE provided consistent information on damage propagation. All techniques identified three stages in the fatigue life of the interrogated coupons. The representation of the fatigue behavior as a function of life fraction, the correlation of AE data with EPCM and LT data, and most importantly the consistent behavior of all tested coupons allowed for both the direct and indirect cross-correlation of all employed methodologies, which consistently identified all aforementioned fatigue life stages.

  2. Subpilot-scale testing of acoustically enhanced cyclone collectors. Final report, September 1988--September 1994

    SciTech Connect

    Galica, M.A.; Campbell, A.H.; Rawlins, D.C.

    1994-08-01

    Gas turbines are used to recover energy from high temperature exhaust gases in coal-fired pressurized-fluidized bed, combined-cycle power generation systems. However, prior to entering the turbine hot-section, the majority of the fly ash must be removed in order to protect the turbine components from erosion, corrosion, and deposition of the ash. The U.S. Department of Energy under the direction of the Morgantown Energy Technology Center (METC) sponsored the development of an acoustically enhanced cyclone collector which offers the potential of achieving environmental control standards under Pressurized Fluid Bed Combustors (PFBC) conditions without the need for post-turbine particulate control. Pulse combustors developed by Manufacturing and Technology Conversation International, Inc. (MTCI) produced the acoustic power necessary to agglomerate ash particles into sizes large enough to be collected in a conventional cyclone system. A hot gas cleanup system that meets both turbine protection and emissions requirements without post-turbine particulate controls would also have improved overall system economics.

  3. Multiple-time scales analysis of physiological time series under neural control.

    PubMed

    Peng, C K; Hausdorff, J M; Havlin, S; Mietus, J E; Stanley, H E; Goldberger, A L

    1998-01-01

    We discuss multiple-time scale properties of neurophysiological control mechanisms, using heart rate and gait regulation as model systems. We find that scaling exponents can be used as prognostic indicators. Furthermore, detection of more subtle degradation of scaling properties may provide a novel early warning system in subjects with a variety of pathologies including those at high risk of sudden death.

  4. Multiple-time scales analysis of physiological time series under neural control

    NASA Technical Reports Server (NTRS)

    Peng, C. K.; Hausdorff, J. M.; Havlin, S.; Mietus, J. E.; Stanley, H. E.; Goldberger, A. L.

    1998-01-01

    We discuss multiple-time scale properties of neurophysiological control mechanisms, using heart rate and gait regulation as model systems. We find that scaling exponents can be used as prognostic indicators. Furthermore, detection of more subtle degradation of scaling properties may provide a novel early warning system in subjects with a variety of pathologies including those at high risk of sudden death.

  5. Broken scale invariance in time-dependent trapping potentials

    NASA Astrophysics Data System (ADS)

    Gharashi, Seyed Ebrahim; Blume, D.

    2016-12-01

    The response of a cold atom gas with contact interactions to a smoothly varying external harmonic confinement in the nonadiabatic regime is studied. The time variation of the angular frequency is varied such that the system is, for vanishing or infinitely strong contact interactions, scale invariant. The time evolution of the system with broken scale invariance (i.e., the time evolution of the system with finite interaction strength) is contrasted with that for a scale invariant system, which exhibits Efimovian-like expansion dynamics that is characterized by log-periodic oscillations with unique period and amplitude. It is found that the breaking of the scale invariance by the finiteness of the interactions leads to a time dependence of the oscillation period and amplitude. It is argued, based on analytical considerations for atomic gases of arbitrary size and numerical results for two one-dimensional particles, that the oscillation period approaches that of the scale-invariant system at large times. The role of the time-dependent contact in the expansion dynamics is analyzed.

  6. Non-conforming curved finite element schemes for time-dependent elastic-acoustic coupled problems

    NASA Astrophysics Data System (ADS)

    Rodríguez-Rozas, Ángel; Diaz, Julien

    2016-01-01

    High-order numerical methods for solving time-dependent acoustic-elastic coupled problems are introduced. These methods, based on Finite Element techniques, allow for a flexible coupling between the fluid and the solid domain by using non-conforming meshes and curved elements. Since characteristic waves travel at different speeds through different media, specific levels of granularity for the mesh discretization are required on each domain, making impractical a possible conforming coupling in between. Advantageously, physical domains may be independently discretized in our framework due to the non-conforming feature. Consequently, an important increase in computational efficiency may be achieved compared to other implementations based on conforming techniques, namely by reducing the total number of degrees of freedom. Differently from other non-conforming approaches proposed so far, our technique is relatively simpler and requires only a geometrical adjustment at the coupling interface at a preprocessing stage, so that no extra computations are necessary during the time evolution of the simulation. On the other hand, as an advantage of using curvilinear elements, the geometry of the coupling interface between the two media of interest is faithfully represented up to the order of the scheme used. In other words, higher order schemes are in consonance with higher order approximations of the geometry. Concerning the time discretization, we analyze both explicit and implicit schemes. These schemes are energy conserving and, for the explicit case, the stability is guaranteed by a CFL condition. In order to illustrate the accuracy and convergence of these methods, a set of representative numerical tests are presented.

  7. Time scale bias in erosion rates of glaciated landscapes.

    PubMed

    Ganti, Vamsi; von Hagke, Christoph; Scherler, Dirk; Lamb, Michael P; Fischer, Woodward W; Avouac, Jean-Philippe

    2016-10-01

    Deciphering erosion rates over geologic time is fundamental for understanding the interplay between climate, tectonic, and erosional processes. Existing techniques integrate erosion over different time scales, and direct comparison of such rates is routinely done in earth science. On the basis of a global compilation, we show that erosion rate estimates in glaciated landscapes may be affected by a systematic averaging bias that produces higher estimated erosion rates toward the present, which do not reflect straightforward changes in erosion rates through time. This trend can result from a heavy-tailed distribution of erosional hiatuses (that is, time periods where no or relatively slow erosion occurs). We argue that such a distribution can result from the intermittency of erosional processes in glaciated landscapes that are tightly coupled to climate variability from decadal to millennial time scales. In contrast, we find no evidence for a time scale bias in spatially averaged erosion rates of landscapes dominated by river incision. We discuss the implications of our findings in the context of the proposed coupling between climate and tectonics, and interpreting erosion rate estimates with different averaging time scales through geologic time.

  8. Time scale bias in erosion rates of glaciated landscapes

    PubMed Central

    Ganti, Vamsi; von Hagke, Christoph; Scherler, Dirk; Lamb, Michael P.; Fischer, Woodward W.; Avouac, Jean-Philippe

    2016-01-01

    Deciphering erosion rates over geologic time is fundamental for understanding the interplay between climate, tectonic, and erosional processes. Existing techniques integrate erosion over different time scales, and direct comparison of such rates is routinely done in earth science. On the basis of a global compilation, we show that erosion rate estimates in glaciated landscapes may be affected by a systematic averaging bias that produces higher estimated erosion rates toward the present, which do not reflect straightforward changes in erosion rates through time. This trend can result from a heavy-tailed distribution of erosional hiatuses (that is, time periods where no or relatively slow erosion occurs). We argue that such a distribution can result from the intermittency of erosional processes in glaciated landscapes that are tightly coupled to climate variability from decadal to millennial time scales. In contrast, we find no evidence for a time scale bias in spatially averaged erosion rates of landscapes dominated by river incision. We discuss the implications of our findings in the context of the proposed coupling between climate and tectonics, and interpreting erosion rate estimates with different averaging time scales through geologic time. PMID:27713925

  9. Auroral Substorm Time Scales: Seasonal and IMF Variations

    NASA Technical Reports Server (NTRS)

    Chua, D.; Parks, G. K.; Brittnacher, M.; Germany, G. A.; Spann, J. F.; Six, N. Frank (Technical Monitor)

    2002-01-01

    The time scales and phases of auroral substorm, activity are quantied in this study using the hemispheric power computed from Polar Ultraviolet Imager (UVI) images. We have applied this technique to several hundred substorm events and we are able to quantify how the characterist act, of substorms vary with season and IMF Bz orientation. We show that substorm time scales vary more strongly with season than with IMF Bz orientation. The recovery time for substorm. activity is well ordered by whether or not the nightside oral zone is sunlit. The recovery time scales for substorms occurring in the winter and equinox periods are similar and are both roughly a factor of two longer than in summer when the auroral oval is sunlit. Our results support the hypothesis that the ionosphere plays an active role in governing the dynamics of the aurora.

  10. Acoustic emission analysis on tensile failure of steam-side oxide scales formed on T22 alloy superheater tubes

    SciTech Connect

    Huang, Jun-Lin; Zhou, Ke-Yi Xu, Jian-Qun; Wang, Xin-Meng; Tu, Yi-You

    2014-07-28

    Failure of steam-side oxide scales on boiler tubes can seriously influence the safety of coal-fired power plants. Uniaxial tensile tests employing acoustic emission (AE) monitoring were performed, in this work, to investigate the failure behavior of steam-side oxide scales on T22 alloy boiler superheater tubes. The characteristic frequency spectra of the captured AE signals were obtained by performing fast Fourier transform. Three distinct peak frequency bands, 100-170, 175-250, and 280-390 kHz, encountered in different testing stages were identified in the frequency spectra, which were confirmed to, respectively, correspond to substrate plastic deformation, oxide vertical cracking, and oxide spalling with the aid of scanning electronic microscopy observations, and can thus be used for distinguishing different oxide failure mechanisms. Finally, the critical cracking strain of the oxide scale and the interfacial shear strength of the oxide/substrate interface were estimated, which are the critical parameters urgently desired for modeling the failure behavior of steam-side oxide scales on boiler tubes of coal-fired power plants.

  11. Acoustic emission analysis on tensile failure of steam-side oxide scales formed on T22 alloy superheater tubes

    NASA Astrophysics Data System (ADS)

    Huang, Jun-Lin; Zhou, Ke-Yi; Wang, Xin-Meng; Tu, Yi-You; Xu, Jian-Qun

    2014-07-01

    Failure of steam-side oxide scales on boiler tubes can seriously influence the safety of coal-fired power plants. Uniaxial tensile tests employing acoustic emission (AE) monitoring were performed, in this work, to investigate the failure behavior of steam-side oxide scales on T22 alloy boiler superheater tubes. The characteristic frequency spectra of the captured AE signals were obtained by performing fast Fourier transform. Three distinct peak frequency bands, 100-170, 175-250, and 280-390 kHz, encountered in different testing stages were identified in the frequency spectra, which were confirmed to, respectively, correspond to substrate plastic deformation, oxide vertical cracking, and oxide spalling with the aid of scanning electronic microscopy observations, and can thus be used for distinguishing different oxide failure mechanisms. Finally, the critical cracking strain of the oxide scale and the interfacial shear strength of the oxide/substrate interface were estimated, which are the critical parameters urgently desired for modeling the failure behavior of steam-side oxide scales on boiler tubes of coal-fired power plants.

  12. Deviations from uniform power law scaling in nonstationary time series

    NASA Technical Reports Server (NTRS)

    Viswanathan, G. M.; Peng, C. K.; Stanley, H. E.; Goldberger, A. L.

    1997-01-01

    A classic problem in physics is the analysis of highly nonstationary time series that typically exhibit long-range correlations. Here we test the hypothesis that the scaling properties of the dynamics of healthy physiological systems are more stable than those of pathological systems by studying beat-to-beat fluctuations in the human heart rate. We develop techniques based on the Fano factor and Allan factor functions, as well as on detrended fluctuation analysis, for quantifying deviations from uniform power-law scaling in nonstationary time series. By analyzing extremely long data sets of up to N = 10(5) beats for 11 healthy subjects, we find that the fluctuations in the heart rate scale approximately uniformly over several temporal orders of magnitude. By contrast, we find that in data sets of comparable length for 14 subjects with heart disease, the fluctuations grow erratically, indicating a loss of scaling stability.

  13. Thermodynamics constrains allometric scaling of optimal development time in insects.

    PubMed

    Dillon, Michael E; Frazier, Melanie R

    2013-01-01

    Development time is a critical life-history trait that has profound effects on organism fitness and on population growth rates. For ectotherms, development time is strongly influenced by temperature and is predicted to scale with body mass to the quarter power based on 1) the ontogenetic growth model of the metabolic theory of ecology which describes a bioenergetic balance between tissue maintenance and growth given the scaling relationship between metabolism and body size, and 2) numerous studies, primarily of vertebrate endotherms, that largely support this prediction. However, few studies have investigated the allometry of development time among invertebrates, including insects. Abundant data on development of diverse insects provides an ideal opportunity to better understand the scaling of development time in this ecologically and economically important group. Insects develop more quickly at warmer temperatures until reaching a minimum development time at some optimal temperature, after which development slows. We evaluated the allometry of insect development time by compiling estimates of minimum development time and optimal developmental temperature for 361 insect species from 16 orders with body mass varying over nearly 6 orders of magnitude. Allometric scaling exponents varied with the statistical approach: standardized major axis regression supported the predicted quarter-power scaling relationship, but ordinary and phylogenetic generalized least squares did not. Regardless of the statistical approach, body size alone explained less than 28% of the variation in development time. Models that also included optimal temperature explained over 50% of the variation in development time. Warm-adapted insects developed more quickly, regardless of body size, supporting the "hotter is better" hypothesis that posits that ectotherms have a limited ability to evolutionarily compensate for the depressing effects of low temperatures on rates of biological processes. The

  14. Thermodynamics Constrains Allometric Scaling of Optimal Development Time in Insects

    PubMed Central

    Dillon, Michael E.; Frazier, Melanie R.

    2013-01-01

    Development time is a critical life-history trait that has profound effects on organism fitness and on population growth rates. For ectotherms, development time is strongly influenced by temperature and is predicted to scale with body mass to the quarter power based on 1) the ontogenetic growth model of the metabolic theory of ecology which describes a bioenergetic balance between tissue maintenance and growth given the scaling relationship between metabolism and body size, and 2) numerous studies, primarily of vertebrate endotherms, that largely support this prediction. However, few studies have investigated the allometry of development time among invertebrates, including insects. Abundant data on development of diverse insects provides an ideal opportunity to better understand the scaling of development time in this ecologically and economically important group. Insects develop more quickly at warmer temperatures until reaching a minimum development time at some optimal temperature, after which development slows. We evaluated the allometry of insect development time by compiling estimates of minimum development time and optimal developmental temperature for 361 insect species from 16 orders with body mass varying over nearly 6 orders of magnitude. Allometric scaling exponents varied with the statistical approach: standardized major axis regression supported the predicted quarter-power scaling relationship, but ordinary and phylogenetic generalized least squares did not. Regardless of the statistical approach, body size alone explained less than 28% of the variation in development time. Models that also included optimal temperature explained over 50% of the variation in development time. Warm-adapted insects developed more quickly, regardless of body size, supporting the “hotter is better” hypothesis that posits that ectotherms have a limited ability to evolutionarily compensate for the depressing effects of low temperatures on rates of biological processes

  15. Mathematical Modeling of Space-time Variations in Acoustic Transmission and Scattering from Schools of Swim Bladder Fish (FY14 Annual Report)

    DTIC Science & Technology

    2014-09-30

    Mathematical modeling of space-time variations in acoustic transmission and scattering from schools of swim bladder fish (FY14 Annual Report...domain theory of acoustic scattering from, and propagation through, schools of swim bladder fish at and near the swim bladder resonance frequency...coupled differential equations. It incorporates a verified swim bladder scattering kernel for the individual fish, includes multiple scattering

  16. Multi scale analysis by acoustic emission of damage mechanisms in natural fibre woven fabrics/epoxy composites.

    NASA Astrophysics Data System (ADS)

    Bonnafous, C.; Touchard, F.; Chocinski-Arnault, L.

    2010-06-01

    This paper proposes to develop an experimental program to characterize the type and the development of damage in composite with complex microstructure. A multi-scale analysis by acoustic emission has been developed and applied to hemp fibre woven fabrics/epoxy composite. The experimental program consists of tensile tests performed on single yarn, neat epoxy resin and composite materials to identify their AE amplitude signatures. A statistical analysis of AE amplitude signals has been realised and correlated with microscopic observations. Results have enabled to identify three types of damage in composites and their associated AE amplitudes: matrix cracking, interfacial debonding and reinforcement damage and fracture. Tracking of these damage mechanisms in hemp/epoxy composites has been performed to show the process of damage development in natural fibre reinforced composites.

  17. Ocean Basin Impact of Ambient Noise on Marine Mammal Detectability, Distribution, and Acoustic Communication

    DTIC Science & Technology

    2015-07-06

    Technical Report 4. TITLE AND SUBTITLE Ocean Basin Impact of Ambient Noise on Marine Mammal Distribution, and Acoustic Communication 3. DATES...ultimate goal of this research is to enhance the understanding of global ocean noise and how variability in sound level impacts marine mammal acoustic...it relates to marine mammal active acoustic space and acoustic communication. This work increases the spatial range and time scale of prior

  18. A methane-based time scale for Vostok ice

    NASA Astrophysics Data System (ADS)

    Ruddiman, William F.; Raymo, Maureen E.

    2003-02-01

    Tuning the Vostok methane signal to mid-July 30°N insolation yields a new ice-core gas time scale. This exercise has two rationales: (1) evidence supporting Kutzbach's theory that low-latitude summer insolation in the northern hemisphere controls the strength of tropical monsoons, and (2) interhemispheric CH 4 gradients showing that the main control of orbital-scale CH 4 variations is tropical (monsoonal) sources. The immediate basis for tuning CH 4 to mid-July insolation is the coincident timing of the most recent (pre-anthropogenic) CH 4 maximum at 11,000-10,500 calendar years ago and the most recent July 30°N insolation maximum (all ages in this paper are in calendar years unless specified as 14C years). The resulting CH 4 gas time scale diverges by as much as 15,000 years from the GT4 gas time scale (Petit et al., Nature 399 (1999) 429) prior to 250,000 years ago, but it matches fairly closely a time scale derived by tuning ice-core δ18O atm to a lagged insolation signal (Shackleton, Science 289 (2000) 1897). Most offsets between the CH 4 and δ18O atm time scales can be explained by assuming that tropical monsoons and ice sheets alternate in controlling the phase of the δ18O atm signal. The CH 4 time scale provides an estimate of the timing of the Vostok CO 2 signal against SPECMAP marine δ18O, often used as an index of global ice volume. On the CH 4 time scale, all CO 2 responses are highly coherent with SPECMAP δ18O at the orbital periods. CO 2 leads δ18O by 5000 years at 100,000 years (eccentricity), but the two signals are nearly in-phase at 41,000 years (obliquity) and 23,000 years (precession). The actual phasing between CO 2 and ice volume is difficult to infer because of likely SST overprints on the SPECMAP δ18O signal. CO 2 could lead, or be in phase with, ice volume, but is unlikely to lag behind the ice response.

  19. Segregation time-scales in model granular flows

    NASA Astrophysics Data System (ADS)

    Staron, Lydie; Phillips, Jeremy C.

    2016-04-01

    Segregation patterns in natural granular systems offer a singular picture of the systems evolution. In many cases, understanding segregation dynamics may help understanding the system's history as well as its future evolution. Among the key questions, one concerns the typical time-scales at which segregation occurs. In this contribution, we present model granular flows simulated by means of the discrete Contact Dynamics method. The granular flows are bi-disperse, namely exhibiting two grain sizes. The flow composition and its dynamics are systematically varied, and the segregation dynamics carefully analyzed. We propose a physical model for the segregation that gives account of the observed dependence of segregation time scales on composition and dynamics. References L. Staron and J. C. Phillips, Stress partition and micro-structure in size-segregating granular flows, Phys. Rev. E 92 022210 (2015) L. Staron and J. C. Phillips, Segregation time-scales in bi-disperse granular flows, Phys. Fluids 26 (3), 033302 (2014)

  20. Time Scales for Energy Release in Hall Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Huba, J. D.; Rudakov, L. I.

    2004-05-01

    We present a study of the time scales for energy release in 2D Hall magnetic reconnection. We use the NRL Hall MHD code VooDoo for this study. We consider a 2D reversed field current layer with a magnetic perturbation that initiates the reconnection process. We use boundary conditions that allow inflow and outflow (i.e., not periodic) and let the system reach a steady state. We find that the system goes through three stages: a relatively long current layer thinning process, a fast reconnection phase, and a final steady state phase. We define the time scale for energy release as the fast reconnection period: from onset to steady state. Preliminary results indicate that the time for energy release scales as the initial thickness of the current layer. We apply these results to the magnetotail and magnetopause. Research supported by NASA and ONR.

  1. Time-dependent scaling patterns in high frequency financial data

    NASA Astrophysics Data System (ADS)

    Nava, Noemi; Di Matteo, Tiziana; Aste, Tomaso

    2016-10-01

    We measure the influence of different time-scales on the intraday dynamics of financial markets. This is obtained by decomposing financial time series into simple oscillations associated with distinct time-scales. We propose two new time-varying measures of complexity: 1) an amplitude scaling exponent and 2) an entropy-like measure. We apply these measures to intraday, 30-second sampled prices of various stock market indices. Our results reveal intraday trends where different time-horizons contribute with variable relative amplitudes over the course of the trading day. Our findings indicate that the time series we analysed have a non-stationary multifractal nature with predominantly persistent behaviour at the middle of the trading session and anti-persistent behaviour at the opening and at the closing of the session. We demonstrate that these patterns are statistically significant, robust, reproducible and characteristic of each stock market. We argue that any modelling, analytics or trading strategy must take into account these non-stationary intraday scaling patterns.

  2. Real time and non-destructive analysis of tablet coating thickness using acoustic microscopy and infrared diffuse reflectance spectroscopy.

    PubMed

    Bikiaris, D; Koutri, I; Alexiadis, D; Damtsios, A; Karagiannis, G

    2012-11-15

    Tablet coating thicknesses were estimated using several techniques such as weight gain and scanning electron microscopy (SEM), in comparison with acoustic microscopy and diffuse reflectance spectroscopy. Acoustic microscopy, used for the first time in such an application, is based on the physical phenomenon of ultrasound propagation through the materials and the echoes generated by their interfaces. Based on the time of flights (TOFs) of the echoes from the coating surface and the tablet, it is possible to calculate the coating thickness. In order to evaluate the accuracy and robustness of these methods, drug tablets were coated with Kollicoat SR polymer for several times, so that to prepare tablets with different coating thicknesses. Tablets with 3, 6 and 9 wt% coating material have been prepared and based on SEM micrographs it was found that the tablet coating thickness is 71.99 ± 1.2 μm, 92.5 ± 1.7 μm and 132.3 ± 2.1 μm, respectively (SEM analysis). The tablet coating thicknesses measured with acoustic microscopy and infrared diffuse reflectance spectroscopy, were in agreement with those obtained using SEM. This verifies that both techniques can be successfully applied for real time and non-destructive thickness measurements of tablet coating. Furthermore, both techniques, compared with SEM and weight gained measurements, are fast and fully automated.

  3. Improving the Geologic Time Scale (Jean Baptiste Lamarck Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Gradstein, Felix M.

    2010-05-01

    The Geologic Time Scale (GTS) provides the framework for the physical, chemical and biological processes on Earth. The time scale is the tool "par excellence" of the geological trade, and insight in its construction, strength, and limitations enhances its function and its utility. Earth scientists should understand how time scales are constructed and its myriad of physical and abstract data are calibrated, rather than merely using ages plucked from a convenient chart or card. Calibration to linear time of the succession of events recorded in the rocks on Earth has three components: (1) the standard stratigraphic divisions and their correlation in the global rock record, (2) the means of measuring linear time or elapsed durations from the rock record, and (3) the methods of effectively joining the two scales, the stratigraphic one and the linear one. Under the auspices of the International Commission on Stratigraphy (ICS), the international stratigraphic divisions and their correlative events are now largely standardized, especially using the GSSP (Global Stratigraphic Section and Point) concept. The means of measuring linear time or elapsed durations from the rock record are objectives in the EARTH TIME and GTS NEXT projects, that also are educating a new generation of GTS dedicated scientists. The U/Pb, Ar/Ar and orbital tuning methods are intercalibrated, and external error analysis improved. Existing Ar/Ar ages become almost 0.5% older, and U/Pb ages stratigraphically more realistic. The new Os/Re method has potential for directly dating more GSSP's and its correlative events. Such may reduce scaling uncertainty between the sedimentary levels of an age date and that of a stage boundary. Since 1981, six successive Phanerozoic GTS have been published, each new one achieving higher resolution and more users. The next GTS is scheduled for 2011/2012, with over 50 specialists taking part. New chapters include an expanded planetary time scale, sequence stratigraphy

  4. Acoustic neuroma

    MedlinePlus

    Vestibular schwannoma; Tumor - acoustic; Cerebellopontine angle tumor; Angle tumor; Hearing loss - acoustic; Tinnitus - acoustic ... Acoustic neuromas have been linked with the genetic disorder neurofibromatosis type 2 (NF2). Acoustic neuromas are uncommon.

  5. Evaluation of Scaling Invariance Embedded in Short Time Series

    PubMed Central

    Pan, Xue; Hou, Lei; Stephen, Mutua; Yang, Huijie; Zhu, Chenping

    2014-01-01

    Scaling invariance of time series has been making great contributions in diverse research fields. But how to evaluate scaling exponent from a real-world series is still an open problem. Finite length of time series may induce unacceptable fluctuation and bias to statistical quantities and consequent invalidation of currently used standard methods. In this paper a new concept called correlation-dependent balanced estimation of diffusion entropy is developed to evaluate scale-invariance in very short time series with length . Calculations with specified Hurst exponent values of show that by using the standard central moving average de-trending procedure this method can evaluate the scaling exponents for short time series with ignorable bias () and sharp confidential interval (standard deviation ). Considering the stride series from ten volunteers along an approximate oval path of a specified length, we observe that though the averages and deviations of scaling exponents are close, their evolutionary behaviors display rich patterns. It has potential use in analyzing physiological signals, detecting early warning signals, and so on. As an emphasis, the our core contribution is that by means of the proposed method one can estimate precisely shannon entropy from limited records. PMID:25549356

  6. Evaluation of scaling invariance embedded in short time series.

    PubMed

    Pan, Xue; Hou, Lei; Stephen, Mutua; Yang, Huijie; Zhu, Chenping

    2014-01-01

    Scaling invariance of time series has been making great contributions in diverse research fields. But how to evaluate scaling exponent from a real-world series is still an open problem. Finite length of time series may induce unacceptable fluctuation and bias to statistical quantities and consequent invalidation of currently used standard methods. In this paper a new concept called correlation-dependent balanced estimation of diffusion entropy is developed to evaluate scale-invariance in very short time series with length ~10(2). Calculations with specified Hurst exponent values of 0.2,0.3,...,0.9 show that by using the standard central moving average de-trending procedure this method can evaluate the scaling exponents for short time series with ignorable bias (≤0.03) and sharp confidential interval (standard deviation ≤0.05). Considering the stride series from ten volunteers along an approximate oval path of a specified length, we observe that though the averages and deviations of scaling exponents are close, their evolutionary behaviors display rich patterns. It has potential use in analyzing physiological signals, detecting early warning signals, and so on. As an emphasis, the our core contribution is that by means of the proposed method one can estimate precisely shannon entropy from limited records.

  7. Going up in time and length scales in modeling polymers

    NASA Astrophysics Data System (ADS)

    Grest, Gary S.

    Polymer properties depend on a wide range of coupled length and time scales, with unique macroscopic viscoelastic behavior stemming from interactions at the atomistic level. The need to probe polymers across time and length scales and particularly computational modeling is inherently challenging. Here new paths to probing long time and length scales including introducing interactions into traditional bead-spring models and coarse graining of atomistic simulations will be compared and discussed. Using linear polyethylene as a model system, the degree of coarse graining with two to six methylene groups per coarse-grained bead derived from a fully atomistic melt simulation were probed. We show that the degree of coarse graining affects the measured dynamic. Using these models we were successful in probing highly entangled melts and were able reach the long-time diffusive regime which is computationally inaccessible using atomistic simulations. We simulated the relaxation modulus and shear viscosity of well-entangled polyethylene melts for scaled times of 500 µs. Results for plateau modulus are in good agreement with experiment. The long time and length scale is coupled to the macroscopic viscoelasticity where the degree of coarse graining sets the minimum length scale instrumental in defining polymer properties and dynamics. Results will be compared to those obtained from simple bead-spring models to demonstrate the additional insight that can be gained from atomistically inspired coarse grained models. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  8. Time scales of crystal mixing in magma mushes

    NASA Astrophysics Data System (ADS)

    Schleicher, Jillian M.; Bergantz, George W.; Breidenthal, Robert E.; Burgisser, Alain

    2016-02-01

    Magma mixing is widely recognized as a means of producing compositional diversity and preconditioning magmas for eruption. However, the processes and associated time scales that produce the commonly observed expressions of magma mixing are poorly understood, especially under crystal-rich conditions. Here we introduce and exemplify a parameterized method to predict the characteristic mixing time of crystals in a crystal-rich magma mush that is subject to open-system reintrusion events. Our approach includes novel numerical simulations that resolve multiphase particle-fluid interactions. It also quantifies the crystal mixing by calculating both the local and system-wide progressive loss of the spatial correlation of individual crystals throughout the mixing region. Both inertial and viscous time scales for bulk mixing are introduced. Estimated mixing times are compared to natural examples and the time for basaltic mush systems to become well mixed can be on the order of 10 days.

  9. Time scales for molecule formation by ion-molecule reactions

    NASA Technical Reports Server (NTRS)

    Langer, W. D.; Glassgold, A. E.

    1976-01-01

    Analytical solutions are obtained for nonlinear differential equations governing the time-dependence of molecular abundances in interstellar clouds. Three gas-phase reaction schemes are considered separately for the regions where each dominates. The particular case of CO, and closely related members of the Oh and CH families of molecules, is studied for given values of temperature, density, and the radiation field. Nonlinear effects and couplings with particular ions are found to be important. The time scales for CO formation range from 100,000 to a few million years, depending on the chemistry and regime. The time required for essentially complete conversion of C(+) to CO in the region where the H3(+) chemistry dominates is several million years. Because this time is longer than or comparable to dynamical time scales for dense interstellar clouds, steady-state abundances may not be observed in such clouds.

  10. Dynamics symmetries of Hamiltonian system on time scales

    SciTech Connect

    Peng, Keke Luo, Yiping

    2014-04-15

    In this paper, the dynamics symmetries of Hamiltonian system on time scales are studied. We study the symmetries and quantities based on the calculation of variation and Lie transformation group. Particular focus lies in: the Noether symmetry leads to the Noether conserved quantity and the Lie symmetry leads to the Noether conserved quantity if the infinitesimal transformations satisfy the structure equation. As the new application of result, at end of the article, we give a simple example of Noether symmetry and Lie symmetry on time scales.

  11. Dynamics symmetries of Hamiltonian system on time scales

    NASA Astrophysics Data System (ADS)

    Peng, Keke; Luo, Yiping

    2014-04-01

    In this paper, the dynamics symmetries of Hamiltonian system on time scales are studied. We study the symmetries and quantities based on the calculation of variation and Lie transformation group. Particular focus lies in: the Noether symmetry leads to the Noether conserved quantity and the Lie symmetry leads to the Noether conserved quantity if the infinitesimal transformations satisfy the structure equation. As the new application of result, at end of the article, we give a simple example of Noether symmetry and Lie symmetry on time scales.

  12. The Effect of Nasal Obstruction after Different Nasal Surgeries Using Acoustic Rhinometry and Nasal Obstruction Symptom Evaluation Scale

    PubMed Central

    Kahraman, Erkan; Cil, Yakup; Incesulu, Armagan

    2016-01-01

    BACKGROUND The efficiency of nasal surgeries can be determined by objective or subjective methods. We have assessed the effect of nasal obstruction after different nasal surgeries using Acoustic Rhinometry (AR) and Nasal Obstruction Symptom Evaluation (NOSE) Scale. METHODS Between May 2011 and May 2012, 40 young adult patients and 10 healthy volunteers as control group who referred to Otorhinolaryngology Clinic in Eskisehir Military Hospital due to nasal obstruction were enrolled. Depending on operation, patients were divided into four equal groups. Group 1: Septoplasty, Group 2: Septoplasty with sprader graft, Group 3: Septorinoplasty and Group 4: Septorhinoplasty with spreader graft. The patients completed NOSE scale, 1 week before and 1 month after the surgery and AR measurements. RESULTS There were a significant improvement in mean NOSE scores of patients and statistical difference was found between pre and post-operational values for each group. There was a statistically significant change of the mean minimal cross section areas (MCA) of the deviated side of nasal passages measured by AR between pre and postoperative period. CONCLUSION In patients with nasal obstruction, functional nasal surgeries which were performed after appropriate medical examination and with right operation methods had a positive impact on quality of life and patient satisfaction. We observed that nasal findings were correlated with NOSE scores and MCA values. So, we suggest that NOSE scale and AR to be used for evaluation of the efficiency of functional nasal surgeries. PMID:27853686

  13. Active Travel-Time Tomography using a Distributed Acoustic Sensing Array

    NASA Astrophysics Data System (ADS)

    Lancelle, C.; Fratta, D.; Lord, N. E.; Wang, H. F.; Chalari, A.

    2015-12-01

    Distributed acoustic sensing (DAS) is a sensor array used for monitoring ground motion by utilizing the interaction of light pulses with sections of a fiber-optic cable. In September 2013 a field test was conducted at the NEES@UCSB Garner Valley field site in Southern California incorporating DAS technology. A 762-meter-long fiber-optic cable was trenched to a depth of about 0.3 m in a rectangular design with two interior diagonal segments. The fiber was excited by a number of sources, including a 45 kN shear shaker and a smaller 450 N portable mass shaker, both of which were available through NEES@UCLA. In addition to these sources, signals were recorded from a minivib source and hammer blows on a steel plate, as well as 8 hours of overnight ambient noise recording. One goal of the field test was to evaluate the use of DAS for tomographic studies. The large number of measurement points inherent to DAS lends itself well to this type of study. Tomograms were constructed using two of the active-sources at multiple locations. There were 8 minivib locations within the array and 13 hammer locations along the boundary of the array. Travel-time data were collected with the DAS array. Two-dimensional velocity tomograms were constructed for different resolutions from the two active sources and compared. In all the images, the lowest velocities lie near the center of the array with higher velocities surrounding this area. The impact results, however, may contain an artifact due to multiple propagation modes. This research is part of the DOE's PoroTomo project.

  14. Real-time detection of undersea mines: a complete screening and acoustic fusion processing system

    NASA Astrophysics Data System (ADS)

    Sacramone, Anthony; Desai, Mukund N.

    1999-08-01

    A complete mine detection/classification (D/C) system has been specified and implemented, which runs in real-time, and has been exercised on the latest available dual-frequency side-scan sonar acoustic image sets. The compete DC system is comprised of a collection of algorithms that has been developed and evolved at Draper Laboratory over the past decade. The detection process consists of image normalization, enhancement, segmentation, and feature extraction algorithms. The enhancement algorithm is a variant of a Markov Random Field based anomaly screener developed in FY-94. The feature that were extracted were those derived in FY-93. A distance constrained matching algorithm, which was developed in FY-95, is used to generate a list of high and low frequency fused tokens. The classification process involves the evaluation of a hierarchy of three multi-layer perceptron neural networks: HF, LF, and HF/LF fused. Research performed in FY-95 also concentrated on the development of several variants of information fusion with hierarchical neural networks. The 'discriminant-combining' variant of fusion was selected as part of this DC system. In addition, a classification post- processing and decision node statistic modification step, which was developed in FY-96, was included. This paper will describe the algorithm that were implemented. However, the emphasis will be on the performance results of processing the latest available side-scan imagery, comparison of single sensor vs dual-frequency sensor results, and the issues that were encountered while exercising the DC system on the new data set.

  15. A Permanent Automated Real-Time Passive Acoustic Monitoring System for Bottlenose Dolphin Conservation in the Mediterranean Sea

    PubMed Central

    Brunoldi, Marco; Bozzini, Giorgio; Casale, Alessandra; Corvisiero, Pietro; Grosso, Daniele; Magnoli, Nicodemo; Alessi, Jessica; Bianchi, Carlo Nike; Mandich, Alberta; Morri, Carla; Povero, Paolo; Wurtz, Maurizio; Melchiorre, Christian; Viano, Gianni; Cappanera, Valentina; Fanciulli, Giorgio; Bei, Massimiliano; Stasi, Nicola; Taiuti, Mauro

    2016-01-01

    Within the framework of the EU Life+ project named LIFE09 NAT/IT/000190 ARION, a permanent automated real-time passive acoustic monitoring system for the improvement of the conservation status of the transient and resident population of bottlenose dolphin (Tursiops truncatus) has been implemented and installed in the Portofino Marine Protected Area (MPA), Ligurian Sea. The system is able to detect the simultaneous presence of dolphins and boats in the area and to give their position in real time. This information is used to prevent collisions by diffusing warning messages to all the categories involved (tourists, professional fishermen and so on). The system consists of two gps-synchronized acoustic units, based on a particular type of marine buoy (elastic beacon), deployed about 1 km off the Portofino headland. Each one is equipped with a four-hydrophone array and an onboard acquisition system which can record the typical social communication whistles emitted by the dolphins and the sound emitted by boat engines. Signals are pre-filtered, digitized and then broadcast to the ground station via wi-fi. The raw data are elaborated to get the direction of the acoustic target to each unit, and hence the position of dolphins and boats in real time by triangulation. PMID:26789265

  16. Using a numerical model to understand the connection between the ocean and acoustic travel-time measurements.

    PubMed

    Powell, Brian S; Kerry, Colette G; Cornuelle, Bruce D

    2013-10-01

    Measurements of acoustic ray travel-times in the ocean provide synoptic integrals of the ocean state between source and receiver. It is known that the ray travel-time is sensitive to variations in the ocean at the transmission time, but the sensitivity of the travel-time to spatial variations in the ocean prior to the acoustic transmission have not been quantified. This study examines the sensitivity of ray travel-time to the temporally and spatially evolving ocean state in the Philippine Sea using the adjoint of a numerical model. A one year series of five day backward integrations of the adjoint model quantify the sensitivity of travel-times to varying dynamics that can alter the travel-time of a 611 km ray by 200 ms. The early evolution of the sensitivities reveals high-mode internal waves that dissipate quickly, leaving the lowest three modes, providing a connection to variations in the internal tide generation prior to the sample time. They are also strongly sensitive to advective effects that alter density along the ray path. These sensitivities reveal how travel-time measurements are affected by both nearby and distant waters. Temporal nonlinearity of the sensitivities suggests that prior knowledge of the ocean state is necessary to exploit the travel-time observations.

  17. Acoustic testing of a supersonic tip speed fan with acoustic treatment and rotor casting slots. Quiet engine program scale model fan C

    NASA Technical Reports Server (NTRS)

    Kazin, S. B.

    1973-01-01

    Acoustic tests were conducted on a high tip speed (1550 ft/sec, 472.44 m/sec) single stage fan with varying amounts of wall acoustic treatment and with circumferential slots over the rotor blade tips. The slots were also tested with acoustic treatment placed behind the slots. The wall treatment results show that the inlet treatment is more effective at high fan speeds and aft duct treatment is more effective at low fan speeds. Maximum PNL's on a 200-foot (60.96 m) sideline show the untreated slots to have increased the rear radiated noise at approach. However, when the treatment was added to the slots inlet radiated noise was decreased, resulting in little change relative to the solid casing on an EPNL basis.

  18. Separation of Time Scales in a Quantum Newton's Cradle.

    PubMed

    van den Berg, R; Wouters, B; Eliëns, S; De Nardis, J; Konik, R M; Caux, J-S

    2016-06-03

    We provide detailed modeling of the Bragg pulse used in quantum Newton's-cradle-like settings or in Bragg spectroscopy experiments for strongly repulsive bosons in one dimension. We reconstruct the postpulse time evolution and study the time-dependent local density profile and momentum distribution by a combination of exact techniques. We further provide a variety of results for finite interaction strengths using a time-dependent Hartree-Fock analysis and bosonization-refermionization techniques. Our results display a clear separation of time scales between rapid and trap-insensitive relaxation immediately after the pulse, followed by slow in-trap periodic behavior.

  19. Satellite attitude prediction by multiple time scales method

    NASA Technical Reports Server (NTRS)

    Tao, Y. C.; Ramnath, R.

    1975-01-01

    An investigation is made of the problem of predicting the attitude of satellites under the influence of external disturbing torques. The attitude dynamics are first expressed in a perturbation formulation which is then solved by the multiple scales approach. The independent variable, time, is extended into new scales, fast, slow, etc., and the integration is carried out separately in the new variables. The theory is applied to two different satellite configurations, rigid body and dual spin, each of which may have an asymmetric mass distribution. The disturbing torques considered are gravity gradient and geomagnetic. Finally, as multiple time scales approach separates slow and fast behaviors of satellite attitude motion, this property is used for the design of an attitude control device. A nutation damping control loop, using the geomagnetic torque for an earth pointing dual spin satellite, is designed in terms of the slow equation.

  20. Speech Compensation for Time-Scale-Modified Auditory Feedback

    ERIC Educational Resources Information Center

    Ogane, Rintaro; Honda, Masaaki

    2014-01-01

    Purpose: The purpose of this study was to examine speech compensation in response to time-scale-modified auditory feedback during the transition of the semivowel for a target utterance of /ija/. Method: Each utterance session consisted of 10 control trials in the normal feedback condition followed by 20 perturbed trials in the modified auditory…

  1. Gott time machines, BTZ black hole formation, and choptuik scaling

    PubMed

    Birmingham; Sen

    2000-02-07

    We study the formation of Banados-Teitelboim-Zanelli black holes by the collision of point particles. It is shown that the Gott time machine, originally constructed for the case of vanishing cosmological constant, provides a precise mechanism for black hole formation. As a result, one obtains an exact analytic understanding of the Choptuik scaling.

  2. Stellar differential rotation and coronal time-scales

    NASA Astrophysics Data System (ADS)

    Gibb, G. P. S.; Jardine, M. M.; Mackay, D. H.

    2014-10-01

    We investigate the time-scales of evolution of stellar coronae in response to surface differential rotation and diffusion. To quantify this, we study both the formation time and lifetime of a magnetic flux rope in a decaying bipolar active region. We apply a magnetic flux transport model to prescribe the evolution of the stellar photospheric field, and use this to drive the evolution of the coronal magnetic field via a magnetofrictional technique. Increasing the differential rotation (i.e. decreasing the equator-pole lap time) decreases the flux rope formation time. We find that the formation time is dependent upon the lap time and the surface diffusion time-scale through the relation τ_Form ∝ √{τ_Lapτ_Diff}. In contrast, the lifetimes of flux ropes are proportional to the lap time (τLife∝τLap). With this, flux ropes on stars with a differential rotation of more than eight times the solar value have a lifetime of less than 2 d. As a consequence, we propose that features such as solar-like quiescent prominences may not be easily observable on such stars, as the lifetimes of the flux ropes which host the cool plasma are very short. We conclude that such high differential rotation stars may have very dynamical coronae.

  3. An evaluation of acoustic seabed classification techniques for marine biotope monitoring over broad-scales (>1 km 2) and meso-scales (10 m 2-1 km 2)

    NASA Astrophysics Data System (ADS)

    van Rein, H.; Brown, C. J.; Quinn, R.; Breen, J.; Schoeman, D.

    2011-07-01

    Acoustic seabed classification is a useful tool for monitoring marine benthic habitats over broad-scales (>1 km 2) and meso-scales (10 m 2-1 km 2). Its utility in this context was evaluated using two approaches: by describing natural changes in the temporal distribution of marine biotopes across the broad-scale (4 km 2), and by attempting to detect specific experimentally-induced changes to kelp-dominated biotopes across the meso-scale (100 m 2). For the first approach, acoustic backscatter mosaics were constructed using sidescan sonar and multibeam echosounder data collected from Church Bay (Rathlin Island, Northern Ireland) in 1999, 2008 and 2009. The mosaics were manually segmented into acoustic facies, which were ground-truthed using a drop-video camera. Biotopes were classified from the video by multivariate exploratory analysis and cross-tabulated with the acoustic facies, showing a positive correlation. These results were integrated with bathymetric data to map the distribution of seven unique biotopes in Church Bay. Kappa analysis showed the biotope distribution was highly similar between the biotope maps, possibly due to the stability of bedforms shaped by the tidal regime around Rathlin Island. The greatest biotope change in this approach was represented by seasonal and annual changes in the growth of the seagrass, Zostera marina. In the second approach, sidescan sonar data were collected before and after the removal of 100 m 2 of kelp from three sites. Comparison of the data revealed no differences between the high-resolution backscatter imagery. It is concluded that acoustic seabed classification can be used to monitor change over broad- and meso-scales but not necessarily for all biotopes; its success depends on the type of acoustic system employed and the biological characteristics of the target biotope.

  4. Doppler effect reduction based on time-domain interpolation resampling for wayside acoustic defective bearing detector system

    NASA Astrophysics Data System (ADS)

    Liu, Fang; He, Qingbo; Kong, Fanrang; Liu, Yongbin

    2014-06-01

    In the wayside Acoustic Defective Bearing Detector (ADBD) system, the recorded acoustic signal will be severely distorted by the Doppler effect because of the high moving speed of the railway vehicle, which is a barrier that would badly reduce the effectiveness of online defect detection. This paper proposes a simple and effective method, called time-domain interpolation resampling (TIR), to remove the Doppler effect embedded in the acoustic signal. The TIR is conducted in three steps. First, the time vector for resampling is calculated according to the kinematic analysis. Second, the amplitude of the distorted signal is demodulated. Third, the distorted signal is re-sampled using spline interpolation. In this method, both the spectrum structure and the amplitudes of the distorted signal can be restored. The effectiveness of TIR is verified by means of simulation studies and train roller bearing experiments with various types of defects. It is also compared to an existing Doppler effect reduction method that is based on the instantaneous frequency estimation using Hilbert transform. Results indicate that the proposed TIR method has the superior performance in removing the Doppler effect, and can be well implemented to Doppler effect reduction for the ADBD system.

  5. 'Megapclicks': acoustic click trains and buzzes produced during night-time foraging of humpback whales (Megaptera novaeangliae).

    PubMed

    Stimpert, Alison K; Wiley, David N; Au, Whitlow W L; Johnson, Mark P; Arsenault, Roland

    2007-10-22

    Humpback whales (Megaptera novaeangliae) exhibit a variety of foraging behaviours, but neither they nor any baleen whale are known to produce broadband clicks in association with feeding, as do many odontocetes. We recorded underwater behaviour of humpback whales in a northwest Atlantic feeding area using suction-cup attached, multi-sensor, acoustic tags (DTAGs). Here we describe the first recordings of click production associated with underwater lunges from baleen whales. Recordings of over 34000 'megapclicks' from two whales indicated relatively low received levels at the tag (between 143 and 154dB re 1 microPa pp), most energy below 2kHz, and interclick intervals often decreasing towards the end of click trains to form a buzz. All clicks were recorded during night-time hours. Sharp body rolls also occurred at the end of click bouts containing buzzes, suggesting feeding events. This acoustic behaviour seems to form part of a night-time feeding tactic for humpbacks and also expands the known acoustic repertoire of baleen whales in general.

  6. A multi-band spectral subtraction-based algorithm for real-time noise cancellation applied to gunshot acoustics

    NASA Astrophysics Data System (ADS)

    Ramos, António L. L.; Holm, Sverre; Gudvangen, Sigmund; Otterlei, Ragnvald

    2013-06-01

    Acoustical sniper positioning is based on the detection and direction-of-arrival estimation of the shockwave and the muzzle blast acoustical signals. In real-life situations, the detection and direction-of-arrival estimation processes is usually performed under the influence of background noise sources, e.g., vehicles noise, and might result in non-negligible inaccuracies than can affect the system performance and reliability negatively, specially when detecting the muzzle sound under long range distance and absorbing terrains. This paper introduces a multi-band spectral subtraction based algorithm for real-time noise reduction, applied to gunshot acoustical signals. The ballistic shockwave and the muzzle blast signals exhibit distinct frequency contents that are affected differently by additive noise. In most real situations, the noise component is colored and a multi-band spectral subtraction approach for noise reduction contributes to reducing the presence of artifacts in denoised signals. The proposed algorithm is tested using a dataset generated by combining signals from real gunshots and real vehicle noise. The noise component was generated using a steel tracked military tank running on asphalt and includes, therefore, the sound from the vehicle engine, which varies slightly in frequency over time according to the engine's rpm, and the sound from the steel tracks as the vehicle moves.

  7. Generation and Propagation of a Picosecond Acoustic Pulse at a Buried Interface: Time-Resolved X-Ray Diffraction Measurements

    SciTech Connect

    Lee, S.H.; Cavalieri, A.L.; Fritz, D.M.; Swan, M.C.; Reis, D.A.; Hegde, R.S.; Reason, M.; Goldman, R.S.

    2005-12-09

    We report on the propagation of coherent acoustic wave packets in (001) surface oriented Al{sub 0.3}Ga{sub 0.7}As/GaAs heterostructure, generated through localized femtosecond photoexcitation of the GaAs. Transient structural changes in both the substrate and film are measured with picosecond time-resolved x-ray diffraction. The data indicate an elastic response consisting of unipolar compression pulses of a few hundred picosecond duration traveling along [001] and [001] directions that are produced by predominately impulsive stress. The transmission and reflection of the strain pulses are in agreement with an acoustic mismatch model of the heterostructure and free-space interfaces.

  8. 4-D imaging of seepage in earthen embankments with time-lapse inversion of self-potential data constrained by acoustic emissions localization

    NASA Astrophysics Data System (ADS)

    Rittgers, J. B.; Revil, A.; Planes, T.; Mooney, M. A.; Koelewijn, A. R.

    2015-02-01

    New methods are required to combine the information contained in the passive electrical and seismic signals to detect, localize and monitor hydromechanical disturbances in porous media. We propose a field experiment showing how passive seismic and electrical data can be combined together to detect a preferential flow path associated with internal erosion in a Earth dam. Continuous passive seismic and electrical (self-potential) monitoring data were recorded during a 7-d full-scale levee (earthen embankment) failure test, conducted in Booneschans, Netherlands in 2012. Spatially coherent acoustic emissions events and the development of a self-potential anomaly, associated with induced concentrated seepage and internal erosion phenomena, were identified and imaged near the downstream toe of the embankment, in an area that subsequently developed a series of concentrated water flows and sand boils, and where liquefaction of the embankment toe eventually developed. We present a new 4-D grid-search algorithm for acoustic emissions localization in both time and space, and the application of the localization results to add spatially varying constraints to time-lapse 3-D modelling of self-potential data in the terms of source current localization. Seismic signal localization results are utilized to build a set of time-invariant yet spatially varying model weights used for the inversion of the self-potential data. Results from the combination of these two passive techniques show results that are more consistent in terms of focused ground water flow with respect to visual observation on the embankment. This approach to geophysical monitoring of earthen embankments provides an improved approach for early detection and imaging of the development of embankment defects associated with concentrated seepage and internal erosion phenomena. The same approach can be used to detect various types of hydromechanical disturbances at larger scales.

  9. Ion Acoustic Wave Frequencies and Onset Times During Type 3 Solar Radio Bursts

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.; Robinson, P. A.

    1995-01-01

    Conflicting interpretations exist for the low-frequency ion acoustic (S) waves often observed by ISEE 3 in association with intense Langmuir (L) waves in the source regions of type III solar radio bursts near 1 AU. Two indirect lines of observational evidence, as well as plasma theory, suggest they are produced by the electrostatic (ES) decay L yields L(PRIME) + S. However, contrary to theoretical predictions, an existing analysis of the wave frequencies instead favors the electromagnetic (EM) decays L yields T + S, where T denotes an EM wave near the plasma frequency. This conflict is addressed here by comparing the observed wave frequencies and onset times with theoretical predictions for the ES and EM decays, calculated using the time-variable electron beam and magnetic field orientation data, rather than the nominal values used previously. Field orientation effects and beam speed variations are shown analytically to produce factor-of-three effects, greater than the difference in wave frequencies predicted for the ES and EM decays; effects of similar magnitude occur in the events analyzed here. The S-wave signals are extracted by hand from a sawtooth noise background, greatly improving the association between S waves and intense L waves. Very good agreement exists between the time-varying predictions for the ES decay and the frequencies of most (but not all) wave bursts. The waves occur only after the ES decay becomes kinematically allowed, which is consistent with the ES decay proceeding and producing most of the observed signals. Good agreement exists between the EM decay's predictions and a significant fraction of the S-wave observations while the EM decay is kinematically allowed. The wave data are not consistent, however, with the EM decay being the dominant nonlinear process. Often the observed waves are sufficiently broadband to overlap simultaneously the frequency ranges predicted for the ES and EM decays. Coupling the dominance of the ES decay with this

  10. Characterizing Complex Time Series from the Scaling of Prediction Error.

    NASA Astrophysics Data System (ADS)

    Hinrichs, Brant Eric

    This thesis concerns characterizing complex time series from the scaling of prediction error. We use the global modeling technique of radial basis function approximation to build models from a state-space reconstruction of a time series that otherwise appears complicated or random (i.e. aperiodic, irregular). Prediction error as a function of prediction horizon is obtained from the model using the direct method. The relationship between the underlying dynamics of the time series and the logarithmic scaling of prediction error as a function of prediction horizon is investigated. We use this relationship to characterize the dynamics of both a model chaotic system and physical data from the optic tectum of an attentive pigeon exhibiting the important phenomena of nonstationary neuronal oscillations in response to visual stimuli.

  11. Energy and time determine scaling in biological and computer designs.

    PubMed

    Moses, Melanie; Bezerra, George; Edwards, Benjamin; Brown, James; Forrest, Stephanie

    2016-08-19

    Metabolic rate in animals and power consumption in computers are analogous quantities that scale similarly with size. We analyse vascular systems of mammals and on-chip networks of microprocessors, where natural selection and human engineering, respectively, have produced systems that minimize both energy dissipation and delivery times. Using a simple network model that simultaneously minimizes energy and time, our analysis explains empirically observed trends in the scaling of metabolic rate in mammals and power consumption and performance in microprocessors across several orders of magnitude in size. Just as the evolutionary transitions from unicellular to multicellular animals in biology are associated with shifts in metabolic scaling, our model suggests that the scaling of power and performance will change as computer designs transition to decentralized multi-core and distributed cyber-physical systems. More generally, a single energy-time minimization principle may govern the design of many complex systems that process energy, materials and information.This article is part of the themed issue 'The major synthetic evolutionary transitions'.

  12. Acoustic Treatment Design Scaling Methods. Volume 5; Analytical and Experimental Data Correlation

    NASA Technical Reports Server (NTRS)

    Chien, W. E.; Kraft, R. E.; Syed, A. A.

    1999-01-01

    The primary purpose of the study presented in this volume is to present the results and data analysis of in-duct transmission loss measurements. Transmission loss testing was performed on full-scale, 1/2-scale, and 115-scale treatment panel samples. The objective of the study was to compare predicted and measured transmission loss for full-scale and subscale panels in an attempt to evaluate the variations in suppression between full- and subscale panels which were ostensibly of equivalent design. Generally, the results indicated an unsatisfactory agreement between measurement and prediction, even for full-scale. This was attributable to difficulties encountered in obtaining sufficiently accurate test results, even with extraordinary care in calibrating the instrumentation and performing the test. Test difficulties precluded the ability to make measurements at frequencies high enough to be representative of subscale liners. It is concluded that transmission loss measurements without ducts and data acquisition facilities specifically designed to operate with the precision and complexity required for high subscale frequency ranges are inadequate for evaluation of subscale treatment effects.

  13. Validation of the Penn Acoustic Neuroma Quality-of-Life Scale (PANQOL) for Spanish-Speaking Patients.

    PubMed

    Medina, Maria Del Mar; Carrillo, Alvaro; Polo, Ruben; Fernandez, Borja; Alonso, Daniel; Vaca, Miguel; Cordero, Adela; Perez, Cecilia; Muriel, Alfonso; Cobeta, Ignacio

    2017-04-01

    Objective To perform translation, cross-cultural adaptation, and validation of the Penn Acoustic Neuroma Quality-of-Life Scale (PANQOL) to the Spanish language. Study Design Prospective study. Setting Tertiary neurotologic referral center. Subjects and Methods PANQOL was translated and translated back, and a pretest trial was performed. The study included 27 individuals diagnosed with vestibular schwannoma. Inclusion criteria were adults with untreated vestibular schwannoma, diagnosed in the past 12 months. Feasibility, internal consistency, test-retest reliability, construct validity, and ceiling and floor effects were assessed for the present study. Results The mean overall score of the PANQOL was 69.21 (0-100 scale, lowest to highest quality of life). Cronbach's α was 0.87. Intraclass correlation coefficient was performed for each item, with an overall score of 0.92. The κ coefficient scores were between moderate and almost perfect in more than 92% of patients. Anxiety and energy domains of the PANQOL were correlated with both physical and mental components of the SF-12. Hearing, balance, and pain domains were correlated with the SF-12 physical component. Facial and general domains were not significantly correlated with any component of the SF-12. Furthermore, the overall score of the PANQOL was correlated with the physical component of the SF-12. Conclusion Feasibility, internal consistency, reliability, and construct validity outcomes in the current study support the validity of the Spanish version of the PANQOL.

  14. Acoustic biosensors

    PubMed Central

    Fogel, Ronen; Seshia, Ashwin A.

    2016-01-01

    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. PMID:27365040

  15. Acoustic biosensors.

    PubMed

    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.

  16. Wavelet analysis and scaling properties of time series

    NASA Astrophysics Data System (ADS)

    Manimaran, P.; Panigrahi, Prasanta K.; Parikh, Jitendra C.

    2005-10-01

    We propose a wavelet based method for the characterization of the scaling behavior of nonstationary time series. It makes use of the built-in ability of the wavelets for capturing the trends in a data set, in variable window sizes. Discrete wavelets from the Daubechies family are used to illustrate the efficacy of this procedure. After studying binomial multifractal time series with the present and earlier approaches of detrending for comparison, we analyze the time series of averaged spin density in the 2D Ising model at the critical temperature, along with several experimental data sets possessing multifractal behavior.

  17. Anomalous multiphoton photoelectric effect in ultrashort time scales.

    PubMed

    Kupersztych, J; Raynaud, M

    2005-09-30

    In a multiphoton photoelectric process, an electron needs to absorb a given number of photons to escape the surface of a metal. It is shown for the first time that this number is not a constant depending only on the characteristics of the metal and light, but varies with the interaction duration in ultrashort time scales. The phenomenon occurs when electromagnetic energy is transferred, via ultrafast excitation of electron collective modes, to conduction electrons in a duration less than the electron energy damping time. It manifests itself through a dramatic increase of electron production.

  18. Precise stellar surface gravities from the time scales of convectively driven brightness variations

    PubMed Central

    Kallinger, Thomas; Hekker, Saskia; García, Rafael A.; Huber, Daniel; Matthews, Jaymie M.

    2016-01-01

    A significant part of the intrinsic brightness variations in cool stars of low and intermediate mass arises from surface convection (seen as granulation) and acoustic oscillations (p-mode pulsations). The characteristics of these phenomena are largely determined by the stars’ surface gravity (g). Detailed photometric measurements of either signal can yield an accurate value of g. However, even with ultraprecise photometry from NASA’s Kepler mission, many stars are too faint for current methods or only moderate accuracy can be achieved in a limited range of stellar evolutionary stages. This means that many of the stars in the Kepler sample, including exoplanet hosts, are not sufficiently characterized to fully describe the sample and exoplanet properties. We present a novel way to measure surface gravities with accuracies of about 4%. Our technique exploits the tight relation between g and the characteristic time scale of the combined granulation and p-mode oscillation signal. It is applicable to all stars with a convective envelope, including active stars. It can measure g in stars for which no other analysis is now possible. Because it depends on the time scale (and no other properties) of the signal, our technique is largely independent of the type of measurement (for example, photometry or radial velocity measurements) and the calibration of the instrumentation used. However, the oscillation signal must be temporally resolved; thus, it cannot be applied to dwarf stars observed by Kepler in its long-cadence mode. PMID:26767193

  19. Precise stellar surface gravities from the time scales of convectively driven brightness variations.

    PubMed

    Kallinger, Thomas; Hekker, Saskia; García, Rafael A; Huber, Daniel; Matthews, Jaymie M

    2016-01-01

    A significant part of the intrinsic brightness variations in cool stars of low and intermediate mass arises from surface convection (seen as granulation) and acoustic oscillations (p-mode pulsations). The characteristics of these phenomena are largely determined by the stars' surface gravity (g). Detailed photometric measurements of either signal can yield an accurate value of g. However, even with ultraprecise photometry from NASA's Kepler mission, many stars are too faint for current methods or only moderate accuracy can be achieved in a limited range of stellar evolutionary stages. This means that many of the stars in the Kepler sample, including exoplanet hosts, are not sufficiently characterized to fully describe the sample and exoplanet properties. We present a novel way to measure surface gravities with accuracies of about 4%. Our technique exploits the tight relation between g and the characteristic time scale of the combined granulation and p-mode oscillation signal. It is applicable to all stars with a convective envelope, including active stars. It can measure g in stars for which no other analysis is now possible. Because it depends on the time scale (and no other properties) of the signal, our technique is largely independent of the type of measurement (for example, photometry or radial velocity measurements) and the calibration of the instrumentation used. However, the oscillation signal must be temporally resolved; thus, it cannot be applied to dwarf stars observed by Kepler in its long-cadence mode.

  20. Powered-Lift Aerodynamics and Acoustics. [conferences

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Powered lift technology is reviewed. Topics covered include: (1) high lift aerodynamics; (2) high speed and cruise aerodynamics; (3) acoustics; (4) propulsion aerodynamics and acoustics; (5) aerodynamic and acoustic loads; and (6) full-scale and flight research.

  1. Classifying acoustic signals into phoneme categories: average and dyslexic readers make use of complex dynamical patterns and multifractal scaling properties of the speech signal

    PubMed Central

    2015-01-01

    Several competing aetiologies of developmental dyslexia suggest that the problems with acquiring literacy skills are causally entailed by low-level auditory and/or speech perception processes. The purpose of this study is to evaluate the diverging claims about the specific deficient peceptual processes under conditions of strong inference. Theoretically relevant acoustic features were extracted from a set of artificial speech stimuli that lie on a /bAk/-/dAk/ continuum. The features were tested on their ability to enable a simple classifier (Quadratic Discriminant Analysis) to reproduce the observed classification performance of average and dyslexic readers in a speech perception experiment. The ‘classical’ features examined were based on component process accounts of developmental dyslexia such as the supposed deficit in Envelope Rise Time detection and the deficit in the detection of rapid changes in the distribution of energy in the frequency spectrum (formant transitions). Studies examining these temporal processing deficit hypotheses do not employ measures that quantify the temporal dynamics of stimuli. It is shown that measures based on quantification of the dynamics of complex, interaction-dominant systems (Recurrence Quantification Analysis and the multifractal spectrum) enable QDA to classify the stimuli almost identically as observed in dyslexic and average reading participants. It seems unlikely that participants used any of the features that are traditionally associated with accounts of (impaired) speech perception. The nature of the variables quantifying the temporal dynamics of the speech stimuli imply that the classification of speech stimuli cannot be regarded as a linear aggregate of component processes that each parse the acoustic signal independent of one another, as is assumed by the ‘classical’ aetiologies of developmental dyslexia. It is suggested that the results imply that the differences in speech perception performance between

  2. Using novel acoustic and visual mapping tools to predict the small-scale spatial distribution of live biogenic reef framework in cold-water coral habitats

    NASA Astrophysics Data System (ADS)

    De Clippele, L. H.; Gafeira, J.; Robert, K.; Hennige, S.; Lavaleye, M. S.; Duineveld, G. C. A.; Huvenne, V. A. I.; Roberts, J. M.

    2017-03-01

    Cold-water corals form substantial biogenic habitats on continental shelves and in deep-sea areas with topographic highs, such as banks and seamounts. In the Atlantic, many reef and mound complexes are engineered by Lophelia pertusa, the dominant framework-forming coral. In this study, a variety of mapping approaches were used at a range of scales to map the distribution of both cold-water coral habitats and individual coral colonies at the Mingulay Reef Complex (west Scotland). The new ArcGIS-based British Geological Survey (BGS) seabed mapping toolbox semi-automatically delineated over 500 Lophelia reef `mini-mounds' from bathymetry data with 2-m resolution. The morphometric and acoustic characteristics of the mini-mounds were also automatically quantified and captured using this toolbox. Coral presence data were derived from high-definition remotely operated vehicle (ROV) records and high-resolution microbathymetry collected by a ROV-mounted multibeam echosounder. With a resolution of 0.35 × 0.35 m, the microbathymetry covers 0.6 km2 in the centre of the study area and allowed identification of individual live coral colonies in acoustic data for the first time. Maximum water depth, maximum rugosity, mean rugosity, bathymetric positioning index and maximum current speed were identified as the environmental variables that contributed most to the prediction of live coral presence. These variables were used to create a predictive map of the likelihood of presence of live cold-water coral colonies in the area of the Mingulay Reef Complex covered by the 2-m resolution data set. Predictive maps of live corals across the reef will be especially valuable for future long-term monitoring surveys, including those needed to understand the impacts of global climate change. This is the first study using the newly developed BGS seabed mapping toolbox and an ROV-based microbathymetric grid to explore the environmental variables that control coral growth on cold-water coral

  3. The Importance of Rotational Time-scales in Accretion Variability

    NASA Astrophysics Data System (ADS)

    Costigan, Gráinne; Vink, Joirck; Scholz, Aleks; Testi, Leonardo; Ray, Tom

    2013-07-01

    For the first few million years, one of the dominant sources of emission from a low mass young stellar object is from accretion. This process regulates the flow of material and angular moments from the surroundings to the central object, and is thought to play an important role in the definition of the long term stellar properties. Variability is a well documented attribute of accretion, and has been observed on time-scales of from days to years. However, where these variations come from is not clear. Th current model for accretion is magnetospheric accretion, where the stellar magnetic field truncates the disc, allowing the matter to flow from the disc onto the surface of the star. This model allows for variations in the accretion rate to come from many different sources, such as the magnetic field, the circumstellar disc and the interaction of the different parts of the system. We have been studying unbiased samples of accretors in order to identify the dominant time-scales and typical magnitudes of variations. In this way different sources of variations can be excluded and any missing physics in these systems identified. Through our previous work with the Long-term Accretion Monitoring Program (LAMP), we found 10 accretors in the ChaI region, whose variability is dominated by short term variations of 2 weeks. This was the shortest time period between spectroscopic observations which spanned 15 months, and rules out large scale processes in the disk as origins of this variability. On the basis of this study we have gone further to study the accretion signature H-alpha, over the time-scales of minutes and days in a set of Herbig Ae and T Tauri stars. Using the same methods as we used in LAMP we found the dominant time-scales of variations to be days. These samples both point towards rotation period of these objects as being an important time-scale for accretion variations. This allows us to indicate which are the most likely sources of these variations.

  4. Design of broadband time-domain impedance boundary conditions using the oscillatory-diffusive representation of acoustical models.

    PubMed

    Monteghetti, Florian; Matignon, Denis; Piot, Estelle; Pascal, Lucas

    2016-09-01

    A methodology to design broadband time-domain impedance boundary conditions (TDIBCs) from the analysis of acoustical models is presented. The derived TDIBCs are recast exclusively as first-order differential equations, well-suited for high-order numerical simulations. Broadband approximations are yielded from an elementary linear least squares optimization that is, for most models, independent of the absorbing material geometry. This methodology relies on a mathematical technique referred to as the oscillatory-diffusive (or poles and cuts) representation, and is applied to a wide range of acoustical models, drawn from duct acoustics and outdoor sound propagation, which covers perforates, semi-infinite ground layers, as well as cavities filled with a porous medium. It is shown that each of these impedance models leads to a different TDIBC. Comparison with existing numerical models, such as multi-pole or extended Helmholtz resonator, provides insights into their suitability. Additionally, the broadly-applicable fractional polynomial impedance models are analyzed using fractional calculus.

  5. Real-time temperature estimation and monitoring of HIFU ablation through a combined modeling and passive acoustic mapping approach.

    PubMed

    Jensen, C R; Cleveland, R O; Coussios, C C

    2013-09-07

    Passive acoustic mapping (PAM) has been recently demonstrated as a method of monitoring focused ultrasound therapy by reconstructing the emissions created by inertially cavitating bubbles (Jensen et al 2012 Radiology 262 252-61). The published method sums energy emitted by cavitation from the focal region within the tissue and uses a threshold to determine when sufficient energy has been delivered for ablation. The present work builds on this approach to provide a high-intensity focused ultrasound (HIFU) treatment monitoring software that displays both real-time temperature maps and a prediction of the ablated tissue region. This is achieved by determining heat deposition from two sources: (i) acoustic absorption of the primary HIFU beam which is calculated via a nonlinear model, and (ii) absorption of energy from bubble acoustic emissions which is estimated from measurements. The two sources of heat are used as inputs to the bioheat equation that gives an estimate of the temperature of the tissue as well as estimates of tissue ablation. The method has been applied to ex vivo ox liver samples and the estimated temperature is compared to the measured temperature and shows good agreement, capturing the effect of cavitation-enhanced heating on temperature evolution. In conclusion, it is demonstrated that by using PAM and predictions of heating it is possible to produce an evolving estimate of cell death during exposure in order to guide treatment for monitoring ablative HIFU therapy.

  6. SIMULTANEOUS BILATERAL REAL-TIME 3-D TRANSCRANIAL ULTRASOUND IMAGING AT 1 MHZ THROUGH POOR ACOUSTIC WINDOWS

    PubMed Central

    Lindsey, Brooks D.; Nicoletto, Heather A.; Bennett, Ellen R.; Laskowitz, Daniel T.; Smith, Stephen W.

    2013-01-01

    Ultrasound imaging has been proposed as a rapid, portable alternative imaging modality to examine stroke patients in pre-hospital or emergency room settings. However, in performing transcranial ultrasound examinations, 8%–29% of patients in a general population may present with window failure, in which case it is not possible to acquire clinically useful sonographic information through the temporal bone acoustic window. In this work, we describe the technical considerations, design and fabrication of low-frequency (1.2 MHz), large aperture (25.3 mm) sparse matrix array transducers for 3-D imaging in the event of window failure. These transducers are integrated into a system for real-time 3-D bilateral transcranial imaging—the ultrasound brain helmet—and color flow imaging capabilities at 1.2 MHz are directly compared with arrays operating at 1.8 MHz in a flow phantom with attenuation comparable to the in vivo case. Contrast-enhanced imaging allowed visualization of arteries of the Circle of Willis in 5 of 5 subjects and 8 of 10 sides of the head despite probe placement outside of the acoustic window. Results suggest that this type of transducer may allow acquisition of useful images either in individuals with poor windows or outside of the temporal acoustic window in the field. PMID:23415287

  7. Simultaneous bilateral real-time 3-d transcranial ultrasound imaging at 1 MHz through poor acoustic windows.

    PubMed

    Lindsey, Brooks D; Nicoletto, Heather A; Bennett, Ellen R; Laskowitz, Daniel T; Smith, Stephen W

    2013-04-01

    Ultrasound imaging has been proposed as a rapid, portable alternative imaging modality to examine stroke patients in pre-hospital or emergency room settings. However, in performing transcranial ultrasound examinations, 8%-29% of patients in a general population may present with window failure, in which case it is not possible to acquire clinically useful sonographic information through the temporal bone acoustic window. In this work, we describe the technical considerations, design and fabrication of low-frequency (1.2 MHz), large aperture (25.3 mm) sparse matrix array transducers for 3-D imaging in the event of window failure. These transducers are integrated into a system for real-time 3-D bilateral transcranial imaging-the ultrasound brain helmet-and color flow imaging capabilities at 1.2 MHz are directly compared with arrays operating at 1.8 MHz in a flow phantom with attenuation comparable to the in vivo case. Contrast-enhanced imaging allowed visualization of arteries of the Circle of Willis in 5 of 5 subjects and 8 of 10 sides of the head despite probe placement outside of the acoustic window. Results suggest that this type of transducer may allow acquisition of useful images either in individuals with poor windows or outside of the temporal acoustic window in the field.

  8. Time scale of diffusion in molecular and cellular biology

    NASA Astrophysics Data System (ADS)

    Holcman, D.; Schuss, Z.

    2014-05-01

    Diffusion is the driver of critical biological processes in cellular and molecular biology. The diverse temporal scales of cellular function are determined by vastly diverse spatial scales in most biophysical processes. The latter are due, among others, to small binding sites inside or on the cell membrane or to narrow passages between large cellular compartments. The great disparity in scales is at the root of the difficulty in quantifying cell function from molecular dynamics and from simulations. The coarse-grained time scale of cellular function is determined from molecular diffusion by the mean first passage time of molecular Brownian motion to a small targets or through narrow passages. The narrow escape theory (NET) concerns this issue. The NET is ubiquitous in molecular and cellular biology and is manifested, among others, in chemical reactions, in the calculation of the effective diffusion coefficient of receptors diffusing on a neuronal cell membrane strewn with obstacles, in the quantification of the early steps of viral trafficking, in the regulation of diffusion between the mother and daughter cells during cell division, and many other cases. Brownian trajectories can represent the motion of a molecule, a protein, an ion in solution, a receptor in a cell or on its membrane, and many other biochemical processes. The small target can represent a binding site or an ionic channel, a hidden active site embedded in a complex protein structure, a receptor for a neurotransmitter on the membrane of a neuron, and so on. The mean time to attach to a receptor or activator determines diffusion fluxes that are key regulators of cell function. This review describes physical models of various subcellular microdomains, in which the NET coarse-grains the molecular scale to a higher cellular-level, thus clarifying the role of cell geometry in determining subcellular function.

  9. Stability of the high-order finite elements for acoustic or elastic wave propagation with high-order time stepping

    NASA Astrophysics Data System (ADS)

    De Basabe, Jonás D.; Sen, Mrinal K.

    2010-04-01

    We investigate the stability of some high-order finite element methods, namely the spectral element method and the interior-penalty discontinuous Galerkin method (IP-DGM), for acoustic or elastic wave propagation that have become increasingly popular in the recent past. We consider the Lax-Wendroff method (LWM) for time stepping and show that it allows for a larger time step than the classical leap-frog finite difference method, with higher-order accuracy. In particular the fourth-order LWM allows for a time step 73 per cent larger than that of the leap-frog method; the computational cost is approximately double per time step, but the larger time step partially compensates for this additional cost. Necessary, but not sufficient, stability conditions are given for the mentioned methods for orders up to 10 in space and time. The stability conditions for IP-DGM are approximately 20 and 60 per cent more restrictive than those for SEM in the acoustic and elastic cases, respectively.

  10. Tailored real-time scaling of heteronuclear couplings.

    PubMed

    Schilling, Franz; Glaser, Steffen J

    2012-10-01

    Heteronuclear couplings are a valuable source of molecular information, which is measured from the multiplet splittings of an NMR spectrum. Radiofrequency irradiation on one coupled nuclear spin allows to modify the effective coupling constant, scaling down the multiplet splittings in the spectrum observed at the resonance frequency of the other nuclear spin. Such decoupling sequences are often used to collapse a multiplet into a singlet and can therefore simplify NMR spectra significantly. Continuous-wave (cw) decoupling has an intrinsic non-linear offset dependence of the scaling of the effective J-coupling constant. Using optimal control pulse optimization, we show that virtually arbitrary off-resonance scaling of the J-coupling constant can be achieved. The new class of tailored decoupling pulses is named SHOT (Scaling of Heteronuclear couplings by Optimal Tracking). Complementing cw irradiation, SHOT pulses offer an alternative approach of encoding chemical shift information indirectly through off-resonance decoupling, which however makes it possible for the first time to achieve linear J scaling as a function of offset frequency. For a simple mixture of eight aromatic compounds, it is demonstrated experimentally that a 1D-SHOT {(1)H}-(13)C experiment yields comparable information to a 2D-HSQC and can give full assignment of all coupled spins.

  11. Space and time scales in human-landscape systems.

    PubMed

    Kondolf, G Mathias; Podolak, Kristen

    2014-01-01

    Exploring spatial and temporal scales provides a way to understand human alteration of landscape processes and human responses to these processes. We address three topics relevant to human-landscape systems: (1) scales of human impacts on geomorphic processes, (2) spatial and temporal scales in river restoration, and (3) time scales of natural disasters and behavioral and institutional responses. Studies showing dramatic recent change in sediment yields from uplands to the ocean via rivers illustrate the increasingly vast spatial extent and quick rate of human landscape change in the last two millennia, but especially in the second half of the twentieth century. Recent river restoration efforts are typically small in spatial and temporal scale compared to the historical human changes to ecosystem processes, but the cumulative effectiveness of multiple small restoration projects in achieving large ecosystem goals has yet to be demonstrated. The mismatch between infrequent natural disasters and individual risk perception, media coverage, and institutional response to natural disasters results in un-preparedness and unsustainable land use and building practices.

  12. Time-average based on scaling law in anomalous diffusions

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Joo

    2015-05-01

    To solve the obscureness in measurement brought about from the weak ergodicity breaking appeared in anomalous diffusions, we have suggested the time-averaged mean squared displacement (MSD) /line{δ 2 (τ )}τ with an integral interval depending linearly on the lag time τ. For the continuous time random walk describing a subdiffusive behavior, we have found that /line{δ 2 (τ )}τ ˜ τ γ like that of the ensemble-averaged MSD, which makes it be possible to measure the proper exponent values through time-average in experiments like a single molecule tracking. Also, we have found that it has originated from the scaling nature of the MSD at an aging time in anomalous diffusion and confirmed them through numerical results of the other microscopic non-Markovian model showing subdiffusions and superdiffusions with the origin of memory enhancement.

  13. Sublinear scaling for time-dependent stochastic density functional theory

    SciTech Connect

    Gao, Yi; Neuhauser, Daniel; Baer, Roi; Rabani, Eran

    2015-01-21

    A stochastic approach to time-dependent density functional theory is developed for computing the absorption cross section and the random phase approximation (RPA) correlation energy. The core idea of the approach involves time-propagation of a small set of stochastic orbitals which are first projected on the occupied space and then propagated in time according to the time-dependent Kohn-Sham equations. The evolving electron density is exactly represented when the number of random orbitals is infinite, but even a small number (≈16) of such orbitals is enough to obtain meaningful results for absorption spectrum and the RPA correlation energy per electron. We implement the approach for silicon nanocrystals using real-space grids and find that the overall scaling of the algorithm is sublinear with computational time and memory.

  14. Implementation of a Distributed Time Based Simulation of Underwater Acoustic Networking Using Java

    DTIC Science & Technology

    2006-09-01

    submarine. The first submarine was a mere toy compared to the machines of today. Although William Bourne first drew plans for one in 1578, it was...dynamic environment. Currently, shortcuts are being taken, by both sides , which make the validity of their results questionable. For underwater...offered by the computer scientist. However, several validation attempts have been made at the edges. 11 Two examples on the acoustic side are the Navy

  15. Time-Resolved Studies of the Acoustic Vibrational Modes of Metal and Semiconductor Nano-objects.

    PubMed

    Major, Todd A; Lo, Shun Shang; Yu, Kuai; Hartland, Gregory V

    2014-03-06

    Over the past decade, there have been a number of transient absorption studies of the acoustic vibrational modes of metal and semiconductor nanoparticles. This Perspective provides an overview of this work. The way that the frequencies of the observed modes depend on the size and shape of the particles is described, along with their damping. Future research directions are also discussed, especially how these measurements provide information about the way nano-objects interact with their environment.

  16. The Acoustic Signature of Woodford Shale and Upscale Relationship from Nano-Scale Mechanical Properties and Mineralogy

    NASA Astrophysics Data System (ADS)

    Tran, M. H.; Abousleiman, Y. N.; Hoang, S. K.; Ortega, A. J.; Bobko, C.; Ulm, F.

    2007-12-01

    The complex composition of shale, the most encountered and problematic lithology in the Earth's crust, has puzzled many researchers attempting to find the key for understanding their micro- and macro-scale acoustic and mechanical signatures. Recent advances in nano-technology, in particular the progress of the Atomic Force Microscope (AFM) base indentation technique, have made it possible to mechanically study porous material at a nano scale (10-9 m) and consequently have allowed linking shale mechanical properties to intrinsic micro- and macro-properties such as porosity, packing density, and mineralogy. Based on more than 20,000 nano- indentation tests conducted on a number of shales with varying physical properties, a GeoGenomeTM model was developed to upscale macroscopic shale mechanical parameters from mineralogy composition, porosity, and packing density. In this work, the mechanical properties such as the elastic stiffness coefficients, Cij, and the anisotropic Biot's Pore Pressure Coefficients, αij, of the Woodford shale, were acquired using sonic log data and Ultra-Sonic Pulse Velocity (UPV) measurements conducted on preserved retrieved shale core samples from a 200-ft well drilled in the Woodford formation, in Oklahoma. Furthermore, the dependency of the Cij and αij, on applied stresses and the relationship between the dynamic moduli and the quasi-static moduli were also investigated using an array of piezoelectric crystals mounted around the samples while subjecting the samples to different applied stress states using a series of tri-axial tests. X-Ray Diffraction (XRD) and mercury injection tests were also performed on the retrieved core samples to obtain mineralogy composition and porosity of the shale at different depths. Comparison of the simulated mechanical and poromechanical properties and stiffness coefficients using the Quantitative GeoGenomeTM Mineralogy Simulator (QGGMSTM) with field and acoustic lab measurements showed excellent agreement

  17. Snoddy (1926) revisited: time scales of motor learning.

    PubMed

    Stratton, Shannon M; Liu, Yeou-Teh; Hong, Siang Lee; Mayer-Kress, Gottfried; Newell, Karl M

    2007-11-01

    The authors investigated the time scales of the learning of a mirror-tracing task to reexamine G. S. Snoddy's (1926) original claim and the received theoretical view (A. Newell & P. S. Rosenbloom, 1981) that motor learning follows a power law. Adult participants (N = 16) learned the tracing task in either a normal or a reversed visual-image condition over 5 consecutive days of practice and then performed 1 day of practice 1 week later and again 1 month later. The reversed-image group's performance was poorer than that of the normal-image group throughout the practice. An exponential was the best fitting function on individual data, but the power-law function was the best fit on the group-averaged data. The findings provided preliminary evidence that 2 characteristic time scales, (a) fast, dominated by warm-up, and (b) slow, dominated by persistent change, capture individuals' performance in the learning of the mirror-tracing task.

  18. A study of Venus rotation at short time scale

    NASA Astrophysics Data System (ADS)

    Cottereau, L.; Souchay, J.

    2009-12-01

    Venus which can be considered as the twin sister of the Earth in view of its global characteristics (size, density) has been the subject of many investigations to understand its slow retrograde rotation (243d) and its rather small obliquity (2°.63). Many of these studies concern the evolution of Venus rotation at very long time scales. Here we present a complete model of Venus precession and nutation based on Hamiltonian formalism for short times scales. We apply a theoretical framework already used by Kinoshita (1977) for the rigid Earth. After calculating the effects due to the gravitational tide exerted by the Sun, we also evaluate the indirect planetary effects due to the perturbation of the planets. We compare our results with those obtained by Souchay et al. (1999) on the Earth. At last we present the prospect for future studies among which are the polhody, the effects of the atmosphere and of the core-mantle interaction.

  19. HMC algorithm with multiple time scale integration and mass preconditioning

    NASA Astrophysics Data System (ADS)

    Urbach, C.; Jansen, K.; Shindler, A.; Wenger, U.

    2006-01-01

    We present a variant of the HMC algorithm with mass preconditioning (Hasenbusch acceleration) and multiple time scale integration. We have tested this variant for standard Wilson fermions at β=5.6 and at pion masses ranging from 380 to 680 MeV. We show that in this situation its performance is comparable to the recently proposed HMC variant with domain decomposition as preconditioner. We give an update of the "Berlin Wall" figure, comparing the performance of our variant of the HMC algorithm to other published performance data. Advantages of the HMC algorithm with mass preconditioning and multiple time scale integration are that it is straightforward to implement and can be used in combination with a wide variety of lattice Dirac operators.

  20. Assestment of correlations and crossover scale in electroseismic time series

    NASA Astrophysics Data System (ADS)

    Guzman-Vargas, L.; Ramírez-Rojas, A.; Angulo-Brown, F.

    2009-04-01

    Evaluating complex fluctuations in electroseismic time series is an important task not only for earthquake prediction but also for understanding complex processes related to earthquake preparation. Previous studies have reported alterations, as the emergence of correlated dynamics in geoelectric potentials prior to an important earthquake (EQ). In this work, we apply the detrended fluctuation analysis and introduce a statistical procedure to characterize the presence of crossovers in scaling exponents, to analyze the fluctuations of geoelectric time series monitored in two sites located in Mexico. We find a complex behavior characterized by the presence of a crossover in the correlation exponents in the vicinity of a M=7.4 EQ occurred on Sept. 14, 1995. Finally, we apply the t-student test to evaluate the level of significance between short and large scaling exponents.

  1. Statistical Analysis of Sensor Network Time Series at Multiple Time Scales

    NASA Astrophysics Data System (ADS)

    Granat, R. A.; Donnellan, A.

    2013-12-01

    Modern sensor networks often collect data at multiple time scales in order to observe physical phenomena that occur at different scales. Whether collected by heterogeneous or homogenous sensor networks, measurements at different time scales are usually subject to different dynamics, noise characteristics, and error sources. We explore the impact of these effects on the results of statistical time series analysis methods applied to multi-scale time series data. As a case study, we analyze results from GPS time series position data collected in Japan and the Western United States, which produce raw observations at 1Hz and orbit corrected observations at time resolutions of 5 minutes, 30 minutes, and 24 hours. We utilize the GPS analysis package (GAP) software to perform three types of statistical analysis on these observations: hidden Markov modeling, probabilistic principle components analysis, and covariance distance analysis. We compare the results of these methods at the different time scales and discuss the impact on science understanding of earthquake fault systems generally and recent large seismic events specifically, including the Tohoku-Oki earthquake in Japan and El Mayor-Cucupah earthquake in Mexico.

  2. Apparatus for real-time acoustic imaging of Rayleigh-Bénard convection

    SciTech Connect

    Kuehn, Kerry, K.

    2008-10-28

    We have successfully designed, built and tested an experimental apparatus which is capable of providing the first real-time ultrasound images of Rayleigh-B\\'{e}nard convection in optically opaque fluids confined to large aspect ratio experimental cells. The apparatus employs a modified version of a commercially available ultrasound camera to capture images (30 frames per second) of flow patterns in a fluid undergoing Rayleigh Bénard convection. The apparatus was validated by observing convection rolls in 5cSt polydimethylsiloxane (PDMS) polymer fluid. Our first objective, after having built the apparatus, was to use it to study the sequence of transitions from diffusive to time--dependent heat transport in liquid mercury. The aim was to provide important information on pattern formation in the largely unexplored regime of very low Prandtl number fluids. Based on the theoretical stability diagram for liquid mercury, we anticipated that straight rolls should be stable over a range of Rayleigh numbers, between 1708 and approximately 1900. Though some of our power spectral densities were suggestive of the existence of weak convection, we have been unable to unambiguously visualize stable convection rolls above the theoretical onset of convection in liquid mercury. Currently, we are seeking ways to increase the sensitivity of our apparatus, such as (i) improving the acoustic impedance matching between our materials in the ultrasound path and (ii) reducing the noise level in our acoustic images due to turbulence and cavitation in the cooling fluids circulating above and below our experimental cell. If we are able to convincingly improve the sensitivity of our apparatus, and we still do not observe stable convection rolls in liquid mercury, then it may be the case that the theoretical stability diagram requires revision. In that case, either (i) straight rolls are not stable in a large aspect ratio cell at the Prandtl numbers associated with liquid mercury, or (ii) they

  3. Studies of Ion Acoustic Decay

    SciTech Connect

    Drake, R.P.; Bauer, B.S.; Baker, K.L. |

    1994-03-07

    In this project, we advanced knowledge of Ion Acoustic Decay on several fronts. In this project, we have developed and demonstrated the capability to perform experimental and theoretical studies of the Ion Acoustic Decay Instability. We have at the same time demonstrated an improved capability to do multichannel spectroscopy and Thomson scattering. We made the first observations of the time-resolved second harmonic emission at several angles simultaneously, and the first observations of the emission both parallel and perpendicular to the electric field of the laser light. We used Thomson scattering to make the first observations of the plasma waves driven by acoustic decay in a warm plasma with long density scale lengths. We also advanced both the linear and the nonlinear theory of this instability. We are thus prepared to perform experiments to address this mechanism as needed for applications.

  4. Adaptive Haar transforms with arbitrary time and scale splitting

    NASA Astrophysics Data System (ADS)

    Egiazarian, Karen O.; Astola, Jaakko T.

    2001-05-01

    The Haar transform is generalized to the case of an arbitrary time and scale splitting. To any binary tree we associate an orthogonal system of Haar-type functions - tree-structured Haar (TSH) functions. Unified fast algorithm for computation of the introduced tree-structured Haar transforms is presented. It requires 2(N - 1) additions and 3N - 2 multiplications, where N is transform order or, equivalently, the number of leaves of the binary tree.

  5. Solar Irradiance Variations on Active Region Time Scales

    NASA Technical Reports Server (NTRS)

    Labonte, B. J. (Editor); Chapman, G. A. (Editor); Hudson, H. S. (Editor); Willson, R. C. (Editor)

    1984-01-01

    The variations of the total solar irradiance is an important tool for studying the Sun, thanks to the development of very precise sensors such as the ACRIM instrument on board the Solar Maximum Mission. The largest variations of the total irradiance occur on time scales of a few days are caused by solar active regions, especially sunspots. Efforts were made to describe the active region effects on total and spectral irradiance.

  6. Time-scale and branching ratios in sequential multifragmentation

    SciTech Connect

    Moretto, L.G.; Phair, L.; Tso, K.; Jing, K.; Wozniak, G.J.

    1994-04-01

    Experimental intermediate-mass-fragment multiplicity distributions are shown to be binomial at all excitation energies. From these distributions a single binary event probability can be extracted that has the thermal dependence p= exp[{minus}B/T]. Thus, it is inferred that multi fragmentation is a sequence of thermal binary events. The increase of p with excitation energy implies a corresponding contraction of the time-scale and explains recently observed fragment-fragment and fragment-spectator Coulomb correlations.

  7. TASEP on a Ring in Sub-relaxation Time Scale

    NASA Astrophysics Data System (ADS)

    Baik, Jinho; Liu, Zhipeng

    2016-12-01

    Interacting particle systems in the KPZ universality class on a ring of size L with O( L) number of particles are expected to change from KPZ dynamics to equilibrium dynamics at the so-called relaxation time scale t=O(L^{3/2}). In particular the system size is expected to have little effect to the particle fluctuations in the sub-relaxation time scale 1≪ t≪ L^{3/2}. We prove that this is indeed the case for the totally asymmetric simple exclusion process (TASEP) with two types of initial conditions. For flat initial condition, we show that the particle fluctuations are given by the Airy_1 process as in the infinite TASEP with flat initial condition. On the other hand, the TASEP on a ring with step initial condition is equivalent to the periodic TASEP with a certain shock initial condition. We compute the fluctuations explicitly both away from and near the shocks for the infinite TASEP with same initial condition, and then show that the periodic TASEP has same fluctuations in the sub-relaxation time scale.

  8. Time scale interactions and the coevolution of humans and water

    NASA Astrophysics Data System (ADS)

    Sivapalan, Murugesu; Blöschl, Günter

    2015-09-01

    We present a coevolutionary view of hydrologic systems, revolving around feedbacks between environmental and social processes operating across different time scales. This brings to the fore an emphasis on emergent phenomena in changing water systems, such as the levee effect, adaptation to change, system lock-in, and system collapse due to resource depletion. Changing human values play a key role in the emergence of these phenomena and should therefore be considered as internal to the system. Guidance is provided for the framing and modeling of these phenomena to test alternative hypotheses about how they arose. A plurality of coevolutionary models, from stylized to comprehensive system-of-system models, may assist strategic water management for long time scales through facilitating stakeholder participation, exploring the possibility space of alternative futures, and helping to synthesize the observed dynamics in a wide range of case studies. Future research opportunities lie in exploring emergent phenomena arising from time scale interactions through historical, comparative, and process studies of human-water feedbacks.

  9. Scaling brain size, keeping timing: evolutionary preservation of brain rhythms.

    PubMed

    Buzsáki, György; Logothetis, Nikos; Singer, Wolf

    2013-10-30

    Despite the several-thousand-fold increase of brain volume during the course of mammalian evolution, the hierarchy of brain oscillations remains remarkably preserved, allowing for multiple-time-scale communication within and across neuronal networks at approximately the same speed, irrespective of brain size. Deployment of large-diameter axons of long-range neurons could be a key factor in the preserved time management in growing brains. We discuss the consequences of such preserved network constellation in mental disease, drug discovery, and interventional therapies.

  10. Scaling Brain Size, Keeping Timing: Evolutionary Preservation of Brain Rhythms

    PubMed Central

    Buzsáki, György; Logothetis, Nikos; Singer, Wolf

    2014-01-01

    Despite the several-thousand-fold increase of brain volume during the course of mammalian evolution, the hierarchy of brain oscillations remains remarkably preserved, allowing for multiple-time-scale communication within and across neuronal networks at approximately the same speed, irrespective of brain size. Deployment of large-diameter axons of long-range neurons could be a key factor in the preserved time management in growing brains. We discuss the consequences of such preserved network constellation in mental disease, drug discovery, and interventional therapies. PMID:24183025

  11. Fine Scale Baleen Whale Behavior Observed Via Tagging Over Daily Time Scales

    DTIC Science & Technology

    2014-09-30

    find areas where copepods are exhibiting weak diel vertical migration behavior. APPROACH Most tracking studies rely on radio or acoustic ...carrying a radio transmitter are limited to very short periods when the animal is at the surface and the tag is exposed to air. Acoustic transmitters...Wildlife Computers MK10-PATF tag. An AOR AR8200 wideband radio receiver, ublox GPS, and a BlackBox KVM extender were housed inside a weather -proof box

  12. AST Launch Vehicle Acoustics

    NASA Technical Reports Server (NTRS)

    Houston, Janice; Counter, D.; Giacomoni, D.

    2015-01-01

    The liftoff phase induces acoustic loading over a broad frequency range for a launch vehicle. These external acoustic environments are then used in the prediction of internal vibration responses of the vehicle and components which result in the qualification levels. Thus, predicting these liftoff acoustic (LOA) environments is critical to the design requirements of any launch vehicle. If there is a significant amount of uncertainty in the predictions or if acoustic mitigation options must be implemented, a subscale acoustic test is a feasible pre-launch test option to verify the LOA environments. The NASA Space Launch System (SLS) program initiated the Scale Model Acoustic Test (SMAT) to verify the predicted SLS LOA environments and to determine the acoustic reduction with an above deck water sound suppression system. The SMAT was conducted at Marshall Space Flight Center and the test article included a 5% scale SLS vehicle model, tower and Mobile Launcher. Acoustic and pressure data were measured by approximately 250 instruments. The SMAT liftoff acoustic results are presented, findings are discussed and a comparison is shown to the Ares I Scale Model Acoustic Test (ASMAT) results.

  13. Challenges of Integrated Modeling Across Space and Time Scales

    NASA Astrophysics Data System (ADS)

    Jagers, B.; Donchyts, G.; Baart, F.; Schellekens, J.; Winsemius, H.

    2015-12-01

    New data collection methods combined with rapid advances in processing technologies enabled by increases in data processing and storage capabilities are causing an significant shift in our modeling capabilities. Freely available global data sets allow us to build more quickly models for bigger areas. By linking the right data, models, and tools we gain significant insight at scales that hadn't considered possible a few decades ago. However, by increasing the spatial extent of our models, we risk missing regionally important critical elements by limitations of model resolution, processes selected, or blind spots in our big data world. At the same time we are pushing the time scales of our models from events and seasonal scale out to decades, centuries, or millennia to simulate the dynamics of the earth surface under varying external conditions. Also here we simplify and ignore to gain performance to resolve bigger time and space domains; are we including all the relevant elements in our models? These elements are often easy to spot from the right perspective. However, what is that perspective when you try to comprehend the results of baffling integrated global models and the amount of data is overwhelming? At the same time we want to know results with an ever increasing accuracy and detail: Will my house flood? Can we reduce flood risk, increase shipping capacity here, and at the same time reduce the maintenance costs by optimizing our dredging strategy? Can we build a number of interoperable cyberinfrastructures that when combined address all these questions? This presentation gives an overview of our work in this field at Deltares, and the main challenges that we foresee.

  14. Multiple time scale behaviors and network dynamics in liquid methanol.

    PubMed

    Sharma, Ruchi; Chakravarty, Charusita; Milotti, Edoardo

    2008-07-31

    Canonical ensemble molecular dynamics simulations of liquid methanol, modeled using a rigid-body, pair-additive potential, are used to compute static distributions and temporal correlations of tagged molecule potential energies as a means of characterizing the liquid state dynamics. The static distribution of tagged molecule potential energies shows a clear multimodal structure with three distinct peaks, similar to those observed previously in water and liquid silica. The multimodality is shown to originate from electrostatic effects, but not from local, hydrogen bond interactions. An interesting outcome of this study is the remarkable similarity in the tagged potential energy power spectra of methanol, water, and silica, despite the differences in the underlying interactions and the dimensionality of the network. All three liquids show a distinct multiple time scale (MTS) regime with a 1/ f (alpha) dependence with a clear positive correlation between the scaling exponent alpha and the diffusivity. The low-frequency limit of the MTS regime is determined by the frequency of crossover to white noise behavior which occurs at approximately 0.1 cm (-1) in the case of methanol under standard temperature and pressure conditions. The power spectral regime above 200 cm (-1) in all three systems is dominated by resonances due to localized vibrations, such as librations. The correlation between alpha and the diffusivity in all three liquids appears to be related to the strength of the coupling between the localized motions and the larger length/time scale network reorganizations. Thus, the time scales associated with network reorganization dynamics appear to be qualitatively similar in these systems, despite the fact that water and silica both display diffusional anomalies but methanol does not.

  15. Large-scale Advanced Propfan (LAP) performance, acoustic and weight estimation, January, 1984

    NASA Technical Reports Server (NTRS)

    Parzych, D.; Shenkman, A.; Cohen, S.

    1985-01-01

    In comparison to turbo-prop applications, the Prop-Fan is designed to operate in a significantly higher range of aircraft flight speeds. Two concerns arise regarding operation at very high speeds: aerodynamic performance and noise generation. This data package covers both topics over a broad range of operating conditions for the eight (8) bladed SR-7L Prop-Fan. Operating conditions covered are: Flight Mach Number 0 - 0.85; blade tip speed 600-800 ft/sec; and cruise power loading 20-40 SHP/D2. Prop-Fan weight and weight scaling estimates are also included.

  16. Evaluation of a scale-model experiment to investigate long-range acoustic propagation

    NASA Technical Reports Server (NTRS)

    Parrott, Tony L.; Mcaninch, Gerry L.; Carlberg, Ingrid A.

    1987-01-01

    Tests were conducted to evaluate the feasibility of using a scale-model experiment situated in an anechoic facility to investigate long-range sound propagation over ground terrain. For a nominal scale factor of 100:1, attenuations along a linear array of six microphones colinear with a continuous-wave type of sound source were measured over a wavelength range from 10 to 160 for a nominal test frequency of 10 kHz. Most tests were made for a hard model surface (plywood), but limited tests were also made for a soft model surface (plywood with felt). For grazing-incidence propagation over the hard surface, measured and predicted attenuation trends were consistent for microphone locations out to between 40 and 80 wavelengths. Beyond 80 wavelengths, significant variability was observed that was caused by disturbances in the propagation medium. Also, there was evidence of extraneous propagation-path contributions to data irregularities at more remote microphones. Sensitivity studies for the hard-surface and microphone indicated a 2.5 dB change in the relative excess attenuation for a systematic error in source and microphone elevations on the order of 1 mm. For the soft-surface model, no comparable sensitivity was found.

  17. Time scaling of tree rings cell production in Siberia

    NASA Astrophysics Data System (ADS)

    Popkova, Margarita; Babushkina, Elena; Tychkov, Ivan; Shishov, Vladimir; Vaganov, Eugene

    2016-04-01

    It is assumed that an annual tree-ring growth is adequately determined by a linear function of local or regional precipitation and temperature with a set of coefficients that are temporally invariant. But often that relations are non-linear. The process-based tree-ring VS-model can be used to resolve the critical processes linking climate variables to tree-ring formation. This work describes a new block of VS-model which allows to estimate a cell production in tree rings and transfer it into time scale based on the simulated integral growth rates of the model. In the algorithm of time identification for cell production we used a integral growth rates simulated by the VS-model for each growing season. The obtained detailed approach with a calculation of the time of each cell formation improves significantly the date accuracy of new cell formation in growing season. As a result for each cell in the tree-ring we estimate the temporal moment of the cell production corresponded to the seasonal growth rate in the same time scale. The approach was applied and tested for the cell measurements obtained for Scots pine (Pinus sylvestris) for the period 1964-2013 in Malaya Minusa river (Khakassia, South Siberia). The work was supported by the Russian Science Foundation (RSF # 14-14-00219)

  18. Flow excursion time scales in the advanced neutron source reactor

    SciTech Connect

    Sulfredge, C.D.

    1995-04-01

    Flow excursion transients give rise to a key thermal limit for the proposed Advanced Neutron Source (ANS) reactor because its core involves many parallel flow channels with a common pressure drop. Since one can envision certain accident scenarios in which the thermal limits set by flow excursion correlations might be exceeded for brief intervals, a key objective is to determine how long a flow excursion would take to bring about a system failure that could lead to fuel damage. The anticipated time scale for flow excursions has been examined by subdividing the process into its component phenomena: bubble nucleation and growth, deceleration of the resulting two-phase flow, and finally overcoming thermal inertia to heat up the reactor fuel plates. Models were developed to estimate the time required for each individual stage. Accident scenarios involving sudden reduction in core flow or core exit pressure have been examined, and the models compared with RELAP5 output for the ANS geometry. For a high-performance reactor like the ANS, flow excursion time scales were predicted to be in the millisecond range, so that even very brief transients might lead to fuel damage. These results should prove useful whenever one must determine the time involved in any portion of a flow excursion transient.

  19. Near-field acoustic streaming jet

    NASA Astrophysics Data System (ADS)

    Moudjed, B.; Botton, V.; Henry, D.; Millet, S.; Garandet, J. P.; Ben Hadid, H.

    2015-03-01

    A numerical and experimental investigation of the acoustic streaming flow in the near field of a circular plane ultrasonic transducer in water is performed. The experimental domain is a parallelepipedic cavity delimited by absorbing walls to avoid acoustic reflection, with a top free surface. The flow velocities are measured by particle image velocimetry, leading to well-resolved velocity profiles. The theoretical model is based on a linear acoustic propagation model, which correctly reproduces the acoustic field mapped experimentally using a hydrophone, and an acoustic force term introduced in the Navier-Stokes equations under the plane-wave assumption. Despite the complexity of the acoustic field in the near field, in particular in the vicinity of the acoustic source, a good agreement between the experimental measurements and the numerical results for the velocity field is obtained, validating our numerical approach and justifying the planar wave assumption in conditions where it is a priori far from obvious. The flow structure is found to be correlated with the acoustic field shape. Indeed, the longitudinal profiles of the velocity present a wavering linked to the variations in acoustic intensity along the beam axis and transverse profiles exhibit a complex shape strongly influenced by the transverse variations of the acoustic intensity in the beam. Finally, the velocity in the jet is found to increase as the square root of the acoustic force times the distance from the origin of the jet over a major part of the cavity, after a strong short initial increase, where the velocity scales with the square of the distance from the upstream wall.

  20. The Role of Time-Scales in Socio-hydrology

    NASA Astrophysics Data System (ADS)

    Blöschl, Günter; Sivapalan, Murugesu

    2016-04-01

    Much of the interest in hydrological modeling in the past decades revolved around resolving spatial variability. With the rapid changes brought about by human impacts on the hydrologic cycle, there is now an increasing need to refocus on time dependency. We present a co-evolutionary view of hydrologic systems, in which every part of the system including human systems, co-evolve, albeit at different rates. The resulting coupled human-nature system is framed as a dynamical system, characterized by interactions of fast and slow time scales and feedbacks between environmental and social processes. This gives rise to emergent phenomena such as the levee effect, adaptation to change and system collapse due to resource depletion. Changing human values play a key role in the emergence of these phenomena and should therefore be considered as internal to the system in a dynamic way. The co-evolutionary approach differs from the traditional view of water resource systems analysis as it allows for path dependence, multiple equilibria, lock-in situations and emergent phenomena. The approach may assist strategic water management for long time scales through facilitating stakeholder participation, exploring the possibility space of alternative futures, and helping to synthesise the observed dynamics of different case studies. Future research opportunities include the study of how changes in human values are connected to human-water interactions, historical analyses of trajectories of system co-evolution in individual places and comparative analyses of contrasting human-water systems in different climate and socio-economic settings. Reference Sivapalan, M. and G. Blöschl (2015) Time scale interactions and the coevolution of humans and water. Water Resour. Res., 51, 6988-7022, doi:10.1002/2015WR017896.

  1. Terrestrial Waters and Sea Level Variations on Interannual Time Scale

    NASA Technical Reports Server (NTRS)

    Llovel, W.; Becker, M.; Cazenave, A.; Jevrejeva, S.; Alkama, R.; Decharme, B.; Douville, H.; Ablain, M.; Beckley, B.

    2011-01-01

    On decadal to multi-decadal time scales, thermal expansion of sea waters and land ice loss are the main contributors to sea level variations. However, modification of the terrestrial water cycle due to climate variability and direct anthropogenic forcing may also affect sea level. For the past decades, variations in land water storage and corresponding effects on sea level cannot be directly estimated from observations because these are almost non-existent at global continental scale. However, global hydrological models developed for atmospheric and climatic studies can be used for estimating total water storage. For the recent years (since mid-2002), terrestrial water storage change can be directly estimated from observations of the GRACE space gravimetry mission. In this study, we analyse the interannual variability of total land water storage, and investigate its contribution to mean sea level variability at interannual time scale. We consider three different periods that, each, depend on data availability: (1) GRACE era (2003-2009), (2) 1993-2003 and (3) 1955-1995. For the GRACE era (period 1), change in land water storage is estimated using different GRACE products over the 33 largest river basins worldwide. For periods 2 and 3, we use outputs from the ISBA-TRIP (Interactions between Soil, Biosphere, and Atmosphere-Total Runoff Integrating Pathways) global hydrological model. For each time span, we compare change in land water storage (expressed in sea level equivalent) to observed mean sea level, either from satellite altimetry (periods 1 and 2) or tide gauge records (period 3). For each data set and each time span, a trend has been removed as we focus on the interannual variability. We show that whatever the period considered, interannual variability of the mean sea level is essentially explained by interannual fluctuations in land water storage, with the largest contributions arising from tropical river basins.

  2. Ocean acoustic tomography

    NASA Astrophysics Data System (ADS)

    Cornuelle, Bruce D.; Worcester, Peter F.; Dzieciuch, Matthew A.

    2008-10-01

    Ocean acoustic tomography (OAT) was proposed in 1979 by Walter Munk and Carl Wunsch as an analogue to x-ray computed axial tomography for the oceans. The oceans are opaque to most electromagnetic radiation, but there is a strong acoustic waveguide, and sound can propagate for 10 Mm and more with distinct multiply-refracted ray paths. Transmitting broadband pulses in the ocean leads to a set of impulsive arrivals at the receiver which characterize the impulse response of the sound channel. The peaks observed at the receiver are assumed to represent the arrival of energy traveling along geometric ray paths. These paths can be distinguished by arrival time, and by arrival angle when a vertical array of receivers is available. Changes in ray arrival time can be used to infer changes in ocean structure. Ray travel time measurements have been a mainstay of long-range acoustic measurements, but the strong sensitivity of ray paths to range-dependent sound speed perturbations makes the ray sampling functions uncertain in real cases. In the ray approximation travel times are sensitive to medium changes only along the corresponding eigenrays. Ray theory is an infinite-frequency approximation, and its eikonal equation has nonlinearities not found in the acoustic wave equation. We build on recent seismology results (kernels for body wave arrivals in the earth) to characterize the kernel for converting sound speed change in the ocean to travel time changes using more complete propagation physics. Wave-theoretic finite frequency kernels may show less sensitivity to small-scale sound speed structure.

  3. On the resolution of phonological constraints in spoken production: Acoustic and response time evidence.

    PubMed

    Bürki, Audrey; Frauenfelder, Ulrich H; Alario, F-Xavier

    2015-10-01

    This study examines the production of words the pronunciation of which depends on the phonological context. Participants produced adjective-noun phrases starting with the French determiner un. The pronunciation of this determiner requires a liaison consonant before vowels. Naming latencies and determiner acoustic durations were shorter when the adjective and the noun both started with vowels or both with consonants, than when they had different onsets. These results suggest that the liaison process is not governed by the application of a local contextual phonological rule; they rather favor the hypothesis that pronunciation variants with and without the liaison consonant are stored in memory.

  4. Statistical Space-Time-Frequency Characterization of MIMO Shallow Water Acoustic Channels

    DTIC Science & Technology

    2010-06-01

    top and bottom. The surface and bottom boundaries reflect an acoustic signal, which results in multiple eigenrays travelling between the Tx and Rx, as...Rx receives 2S downward arriving eigenrays , each one having different number of s surface and b bottom reflections, where 1 ≤ s ≤ S, and s−1 ≤ b ≤ s...Similarly, there are 2B upward arriving eigenrays with b bottom and s surface reflections, where 1 ≤ b ≤ B and b−1 ≤ s ≤ b. Note that exact positions

  5. Decay of surface nanostructures via long-time-scale dynamics

    SciTech Connect

    Voter, A.F.; Stanciu, N.

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The authors have developed a new approach for extending the time scale of molecular dynamics simulations. For infrequent-event systems, the category that includes most diffusive events in the solid phase, this hyperdynamics method can extend the simulation time by a few orders of magnitude compared to direct molecular dynamics. The trajectory is run on a potential surface that has been biased to raise the energy in the potential basins without affecting the transition state region. The method is described and applied to surface and bulk diffusion processes, achieving microsecond and millisecond simulation times. The authors have also developed a new parallel computing method that is efficient for small system sizes. The combination of the hyperdynamics with this parallel replica dynamics looks promising as a general materials simulation tool.

  6. Optimal Control Modification for Time-Scale Separated Systems

    NASA Technical Reports Server (NTRS)

    Nguyen, Nhan T.

    2012-01-01

    Recently a new optimal control modification has been introduced that can achieve robust adaptation with a large adaptive gain without incurring high-frequency oscillations as with the standard model-reference adaptive control. This modification is based on an optimal control formulation to minimize the L2 norm of the tracking error. The optimal control modification adaptive law results in a stable adaptation in the presence of a large adaptive gain. This study examines the optimal control modification adaptive law in the context of a system with a time scale separation resulting from a fast plant with a slow actuator. A singular perturbation analysis is performed to derive a modification to the adaptive law by transforming the original system into a reduced-order system in slow time. A model matching conditions in the transformed time coordinate results in an increase in the actuator command that effectively compensate for the slow actuator dynamics. Simulations demonstrate effectiveness of the method.

  7. Absolute calibration of the Greenland time scale: implications for Antarctic time scales and for Δ 14C

    NASA Astrophysics Data System (ADS)

    Shackleton, N. J.; Fairbanks, R. G.; Chiu, Tzu-chien; Parrenin, F.

    2004-07-01

    We propose a new age scale for the two ice cores (GRIP and GISP2) that were drilled at Greenland summit, based on accelerator mass spectrometry 14C dating of foraminifera in core MD95-2042 (Paleoceanography 15 (2000) 565), calibrated by means of recently obtained paired 14C and 230Th measurements on pristine corals (Marine radiocarbon calibration curve spanning 10,500 to 50,000 years BP (thousand years before present) Based on paired 230Th/ 234U/ 238U and 14C dates on Pristine Corals Geological Society of America Bulletin, 2003, submitted for publication). The record of core MD95-2042 can be correlated very precisely to the Greenland ice cores. Between 30 and 40 ka BP our scale is 1.4 ka older than the GRIP SS09sea time scale (Journal of Quaternary Science 16 (2001) 299). At the older end of Marine Isotope Stage 3 we use published 230Th dates from speleothems to calibrate the record. Using this scale we show a Δ 14C record that is broadly consistent with the modelled record (Earth Planet. Sci. Lett. 200 (2002) 177) and with the data of Hughen et al. (Science 303 (2004) 202), but not consistent with the high values obtained by Beck et al. (Science 292 (2001) 2453) or by Voelker et al. (Radiocarbon 40 (1998) 517). We show how a set of age scales for the Antarctic ice cores can be derived that are both fully consistent with the Greenland scale, and glaciologically reasonable.

  8. Online Doppler Effect Elimination Based on Unequal Time Interval Sampling for Wayside Acoustic Bearing Fault Detecting System.

    PubMed

    Ouyang, Kesai; Lu, Siliang; Zhang, Shangbin; Zhang, Haibin; He, Qingbo; Kong, Fanrang

    2015-08-27

    The railway occupies a fairly important position in transportation due to its high speed and strong transportation capability. As a consequence, it is a key issue to guarantee continuous running and transportation safety of trains. Meanwhile, time consumption of the diagnosis procedure is of extreme importance for the detecting system. However, most of the current adopted techniques in the wayside acoustic defective bearing detector system (ADBD) are offline strategies, which means that the signal is analyzed after the sampling process. This would result in unavoidable time latency. Besides, the acquired acoustic signal would be corrupted by the Doppler effect because of high relative speed between the train and the data acquisition system (DAS). Thus, it is difficult to effectively diagnose the bearing defects immediately. In this paper, a new strategy called online Doppler effect elimination (ODEE) is proposed to remove the Doppler distortion online by the introduced unequal interval sampling scheme. The steps of proposed strategy are as follows: The essential parameters are acquired in advance. Then, the introduced unequal time interval sampling strategy is used to restore the Doppler distortion signal, and the amplitude of the signal is demodulated as well. Thus, the restored Doppler-free signal is obtained online. The proposed ODEE method has been employed in simulation analysis. Ultimately, the ODEE method is implemented in the embedded system for fault diagnosis of the train bearing. The results are in good accordance with the bearing defects, which verifies the good performance of the proposed strategy.

  9. Stability analysis and design of time-domain acoustic impedance boundary conditions for lined duct with mean flow.

    PubMed

    Liu, Xin; Huang, Xun; Zhang, Xin

    2014-11-01

    This work develops the so-called compensated impedance boundary conditions that enable stable time domain simulations of sound propagation in a lined duct with uniform mean flow, which has important practical interest for noise emission by aero-engines. The proposed method is developed analytically from an unusual perspective of control that shows impedance boundary conditions act as closed-loop feedbacks to an overall duct acoustic system. It turns out that those numerical instabilities of time domain simulations are caused by deficient phase margins of the corresponding control-oriented model. A particular instability of very low frequencies in the presence of steady uniform background mean flow, in addition to the well known high frequency numerical instabilities at the grid size, can be identified using this analysis approach. Stable time domain impedance boundary conditions can be formulated by including appropriate phaselead compensators to achieve desired phase margins. The compensated impedance boundary conditions can be simply designed with no empirical parameter, straightforwardly integrated with ordinary linear acoustic models, and efficiently calculated with no need of resolving sheared boundary layers. The proposed boundary conditions are validated by comparing against asymptotic solutions of spinning modal sound propagation in a duct with a hard-soft interface and reasonable agreement is achieved.

  10. Online Doppler Effect Elimination Based on Unequal Time Interval Sampling for Wayside Acoustic Bearing Fault Detecting System

    PubMed Central

    Ouyang, Kesai; Lu, Siliang; Zhang, Shangbin; Zhang, Haibin; He, Qingbo; Kong, Fanrang

    2015-01-01

    The railway occupies a fairly important position in transportation due to its high speed and strong transportation capability. As a consequence, it is a key issue to guarantee continuous running and transportation safety of trains. Meanwhile, time consumption of the diagnosis procedure is of extreme importance for the detecting system. However, most of the current adopted techniques in the wayside acoustic defective bearing detector system (ADBD) are offline strategies, which means that the signal is analyzed after the sampling process. This would result in unavoidable time latency. Besides, the acquired acoustic signal would be corrupted by the Doppler effect because of high relative speed between the train and the data acquisition system (DAS). Thus, it is difficult to effectively diagnose the bearing defects immediately. In this paper, a new strategy called online Doppler effect elimination (ODEE) is proposed to remove the Doppler distortion online by the introduced unequal interval sampling scheme. The steps of proposed strategy are as follows: The essential parameters are acquired in advance. Then, the introduced unequal time interval sampling strategy is used to restore the Doppler distortion signal, and the amplitude of the signal is demodulated as well. Thus, the restored Doppler-free signal is obtained online. The proposed ODEE method has been employed in simulation analysis. Ultimately, the ODEE method is implemented in the embedded system for fault diagnosis of the train bearing. The results are in good accordance with the bearing defects, which verifies the good performance of the proposed strategy. PMID:26343657

  11. Multiple-time scaling and universal behavior of the earthquake interevent time distribution.

    PubMed

    Bottiglieri, M; de Arcangelis, L; Godano, C; Lippiello, E

    2010-04-16

    The interevent time distribution characterizes the temporal occurrence in seismic catalogs. Universal scaling properties of this distribution have been evidenced for entire catalogs and seismic sequences. Recently, these universal features have been questioned and some criticisms have been raised. We investigate the existence of universal scaling properties by analyzing a Californian catalog and by means of numerical simulations of an epidemic-type model. We show that the interevent time distribution exhibits a universal behavior over the entire temporal range if four characteristic times are taken into account. The above analysis allows us to identify the scaling form leading to universal behavior and explains the observed deviations. Furthermore, it provides a tool to identify the dependence on the mainshock magnitude of the c parameter that fixes the onset of the power law decay in the Omori law.

  12. Multiple-Time Scaling and Universal Behavior of the Earthquake Interevent Time Distribution

    SciTech Connect

    Bottiglieri, M.; Godano, C.; Lippiello, E.; Arcangelis, L. de

    2010-04-16

    The interevent time distribution characterizes the temporal occurrence in seismic catalogs. Universal scaling properties of this distribution have been evidenced for entire catalogs and seismic sequences. Recently, these universal features have been questioned and some criticisms have been raised. We investigate the existence of universal scaling properties by analyzing a Californian catalog and by means of numerical simulations of an epidemic-type model. We show that the interevent time distribution exhibits a universal behavior over the entire temporal range if four characteristic times are taken into account. The above analysis allows us to identify the scaling form leading to universal behavior and explains the observed deviations. Furthermore, it provides a tool to identify the dependence on the mainshock magnitude of the c parameter that fixes the onset of the power law decay in the Omori law.

  13. Defining a trend for time series using the intrinsic time-scale decomposition

    NASA Astrophysics Data System (ADS)

    Restrepo, Juan M.; Venkataramani, Shankar; Comeau, Darin; Flaschka, Hermann

    2014-08-01

    We propose criteria that define a trend for time series with inherent multi-scale features. We call this trend the tendency of a time series. The tendency is defined empirically by a set of criteria and captures the large-scale temporal variability of the original signal as well as the most frequent events in its histogram. Among other properties, the tendency has a variance no larger than that of the original signal; the histogram of the difference between the original signal and the tendency is as symmetric as possible; and with reduced complexity, the tendency captures essential features of the signal. To find the tendency we first use the intrinsic time-scale decomposition (ITD) of the signal, introduced in 2007 by Frei and Osorio, to produce a set of candidate tendencies. We then apply the criteria to each of the candidates to single out the one that best agrees with them. While the criteria for the tendency are independent of the signal decomposition scheme, it is found that the ITD is a simple and stable methodology, well suited for multi-scale signals. The ITD is a relatively new decomposition and little is known about its outcomes. In this study we take the first steps towards a probabilistic model of the ITD analysis of random time series. This analysis yields details concerning the universality and scaling properties of the components of the decomposition.

  14. Time scale algorithms for an inhomogeneous group of atomic clocks

    NASA Technical Reports Server (NTRS)

    Jacques, C.; Boulanger, J.-S.; Douglas, R. J.; Morris, D.; Cundy, S.; Lam, H. F.

    1993-01-01

    Through the past 17 years, the time scale requirements at the National Research Council (NRC) have been met by the unsteered output of its primary laboratory cesium clocks, supplemented by hydrogen masers when short-term stability better than 2 x 10(exp -12)tau(sup -1/2) has been required. NRC now operates three primary laboratory cesium clocks, three hydrogen masers, and two commercial cesium clocks. NRC has been using ensemble averages for internal purposes for the past several years, and has a realtime algorithm operating on the outputs of its high-resolution (2 x 10(exp -13) s at 1 s) phase comparators. The slow frequency drift of the hydrogen masers has presented difficulties in incorporating their short-term stability into the ensemble average, while retaining the long-term stability of the laboratory cesium frequency standards. We report on this work on algorithms for an inhomogeneous ensemble of atomic clocks, and on our initial work on time scale algorithms that could incorporate frequency calibrations at NRC from the next generation of Zacharias fountain cesium frequency standards having frequency accuracies that might surpass 10(exp -15), or from single-trapped-ion frequency standards (Ba+, Sr+,...) with even higher potential accuracies. The requirements for redundancy in all the elements (including the algorithms) of an inhomogeneous ensemble that would give a robust real-time output of the algorithms are presented and discussed.

  15. The role of time scales in extrinsic noise propagation

    NASA Astrophysics Data System (ADS)

    Iyer-Biswas, Srividya; Pedraza, Juan Manuel; Jayaprakash, C.

    2009-03-01

    Cell-to cell variability in the number of proteins has been studied extensively experimentally. There are many sources of this stochastic variability or noise that can be classified as intrinsic, due to the stochasticity of chemical reactions and extrinsic, due to environmental differences. The different stages in the production of proteins in response to a stimulus, the signaling cascade before transcription, transcription, and translation are characterized by different time scales. We analyze how these time scales determine the effect of the reactions at each stage on different sources of noise. For example, even if intrinsic noise dominates the fluctuations in mRNA number, for typical degradation rates, extrinsic noise can dominate corresponding protein number fluctuations. Such results are important in determining the importance of intrinsic noise at earlier stages of a genetic network on the products of subsequent stages. We examine cases in which the dynamics of the extrinsic noise can lead to differences from cases in which extrinsic noise arises from static (in time) cell-to-cell variations. We will interpret the experiments of Pedraza et al*. in the light of these results. *J. M. Pedraza et al, Science 25 March 2005:Vol. 307. no. 5717, pp. 1965 - 1969.

  16. Time Scale Optimization and the Hunt for Astronomical Cycles in Deep Time Strata

    NASA Astrophysics Data System (ADS)

    Meyers, Stephen R.

    2016-04-01

    A valuable attribute of astrochronology is the direct link between chronometer and climate change, providing a remarkable opportunity to constrain the evolution of the surficial Earth System. Consequently, the hunt for astronomical cycles in strata has spurred the development of a rich conceptual framework for climatic/oceanographic change, and has allowed exploration of the geologic record with unprecedented temporal resolution. Accompanying these successes, however, has been a persistent skepticism about appropriate astrochronologic testing and circular reasoning: how does one reliably test for astronomical cycles in stratigraphic data, especially when time is poorly constrained? From this perspective, it would seem that the merits and promise of astrochronology (e.g., a geologic time scale measured in ≤400 kyr increments) also serves as its Achilles heel, if the confirmation of such short rhythms defies rigorous statistical testing. To address these statistical challenges in astrochronologic testing, a new approach has been developed that (1) explicitly evaluates time scale uncertainty, (2) is resilient to common problems associated with spectrum confidence level assessment and 'multiple testing', and (3) achieves high statistical power under a wide range of conditions (it can identify astronomical cycles when present in data). Designated TimeOpt (for "time scale optimization"; Meyers 2015), the method employs a probabilistic linear regression model framework to investigate amplitude modulation and frequency ratios (bundling) in stratigraphic data, while simultaneously determining the optimal time scale. This presentation will review the TimeOpt method, and demonstrate how the flexible statistical framework can be further extended to evaluate (and optimize upon) complex sedimentation rate models, enhancing the statistical power of the approach, and addressing the challenge of unsteady sedimentation. Meyers, S. R. (2015), The evaluation of eccentricity

  17. Time scales in the context of general relativity.

    PubMed

    Guinot, Bernard

    2011-10-28

    Towards 1967, the accuracy of caesium frequency standards reached such a level that the relativistic effect could not be ignored anymore. Corrections began to be applied for the gravitational frequency shift and for distant time comparisons. However, these corrections were not applied to an explicit theoretical framework. Only in 1991 did the International Astronomical Union provide metrics (then improved in 2000) for a definition of space-time coordinates in reference systems centred at the barycentre of the Solar System and at the centre of mass of the Earth. In these systems, the temporal coordinates (coordinate times) can be realized on the basis of one of them, the International Atomic Time (TAI), which is itself a realized time scale. The definition and the role of TAI in this context will be recalled. There remain controversies regarding the name to be given to the unit of coordinate times and to other quantities appearing in the theory. However, the idea that astrometry and celestial mechanics should adopt the usual metrological rules is progressing, together with the use of the International System of Units, among astronomers.

  18. Analysis of a micro-scale pump which uses controlled acoustic streaming for fluid locomotion

    SciTech Connect

    Dohner, J.L.

    1998-01-01

    In this report the analysis of a micro-scale pump is described. This micro-pump uses active control to produce a distributed body force in a fluid micro-channel. The desired effect of this body force is to drive fluid through the channel. Limitations, assumptions, and design parameters are discussed. The mathematical analysis of pump dynamics is explained in detail. A perturbation analysis is used on the equations of mass, momentum and state to produce equations of motion for first and second order effects. The first order effects are described by linear wave motion in the fluid and are found by using integral equation methods. The second order effects are driven by body forces resulting from first order effects. Thus, by controlling the production of wave motion in the channel, second order excitation can also be controlled. This report is all theory and therefore needs experimental validation. Although many of the assumptions used in this report have been used elsewhere in the literature and have been found to be sufficient, there are many aspects of the problem which have been left unresolved. In particular, flow separation in the fluid channel is a critical problem. If the fluid does not separate, pumping will occur through the channel, however, if internal or external forces are not sufficient to stop separation, this type of pump will not function.

  19. Simultaneous acoustic and dielectric real time curing monitoring of epoxy systems

    NASA Astrophysics Data System (ADS)

    Gkikas, G.; Saganas, Ch.; Grammatikos, S. A.; Aggelis, D. G.; Paipetis, A. S.

    2012-04-01

    The attainment of structural integrity of the reinforcing matrix in composite materials is of primary importance for the final properties of the composite structure. The detailed monitoring of the curing process on the other hand is paramount (i) in defining the optimal conditions for the impregnation of the reinforcement by the matrix (ii) in limiting the effects of the exotherm produced by the polymerization reaction which create unwanted thermal stresses and (iii) in securing optimal behavior in matrix controlled properties, such as off axis or shear properties and in general the durability of the composite. Dielectric curing monitoring is a well known technique for distinguishing between the different stages of the polymerization of a typical epoxy system. The technique successfully predicts the gelation and the vitrification of the epoxy and has been extended for the monitoring of prepregs. Recent work has shown that distinct changes in the properties of the propagated sound in the epoxy which undergoes polymerization is as well directly related to the gelation and vitrification of the resin, as well as to the attainment of the final properties of the resin system. In this work, a typical epoxy is simultaneously monitored using acoustic and dielectric methods. The system is isothermally cured in an oven to avoid effects from the polymerization exotherm. Typical broadband sensors are employed for the acoustic monitoring, while flat interdigital sensors are employed for the dielectric scans. All stages of the polymerization process were successfully monitored and the validity of both methods was cross checked and verified.

  20. Numerical time domain modeling of the ultrasonic NDT with electromagnetic acoustic and piezoelectric transducers

    NASA Astrophysics Data System (ADS)

    Marklein, R.; Langenberg, K.-J.; Hübschen, G.; Willems, H.

    2000-05-01

    In principle, apart from laser generated ultrasound, two types of transducers, electromagnetic acoustic transducers (EMAT) and piezoelectric transducers, are applied in ultrasonic NDT. Piezoelectric transducers are primarily used to generate pressure, shear vertical, and Rayleigh waves; whereas electromagnetic acoustic transducers are primarily used to generate shear horizontal as well as Rayleigh waves. This paper presents numerical results for both transducer types in 2-D applying the EFIT code (EFIT: Elastodynamic Finite Integration Technique), which has been developed to simulate in 2-D the SH case and P-SV case separately. Three different cases will be studied in detail: (1.) detection of a backwall breaking notch in an isotropic test block, (2.) crack detection in an isotropic pipeline, and (3.) detection of a cracking an austenitic weld. In case (1.) and (3.) different wave modes (P-, SV-, and R-wave) as well as different inclination angles are used, whereas in case (2.), different wave modes are generated (guided SH-waves and R-waves). The numerical results will be validated against measurements if available.

  1. Scaling in a Continuous Time Model for Biological Aging

    NASA Astrophysics Data System (ADS)

    de Almeida, R. M. C.; Thomas, G. L.

    In this paper, we consider a generalization to the asexual version of Penna model for biological aging, where we take a continuous time limit. The genotype associated to each individual is an interval of real numbers over which Dirac δ-functions are defined, representing genetically programmed diseases to be switched on at defined ages of the individual life. We discuss two different continuous limits for the evolution equation and two different mutation protocols, to be implemented during reproduction. Exact stationary solutions are obtained and scaling properties are discussed.

  2. Plant succession as an integrator of contrasting ecological time scales.

    PubMed

    Walker, Lawrence R; Wardle, David A

    2014-09-01

    Ecologists have studied plant succession for over a hundred years, yet our understanding of the nature of this process is incomplete, particularly in relation to its response to new human perturbations and the need to manipulate it during ecological restoration. We demonstrate how plant succession can be understood better when it is placed in the broadest possible temporal context. We further show how plant succession can be central to the development of a framework that integrates a spectrum of ecological processes, which occur over time scales ranging from seconds to millions of years. This novel framework helps us understand the impacts of human perturbations on successional trajectories, ecosystem recovery, and global environmental change.

  3. Time scales and relaxation dynamics in quantum-dot lasers

    SciTech Connect

    Erneux, Thomas; Viktorov, Evgeny A.; Mandel, Paul

    2007-08-15

    We analyze a three-variable rate equation model that takes into account carrier capture and Pauli blocking in quantum dot semiconductor lasers. The exponential decay of the relaxation oscillations is analyzed from the linearized equations in terms of three key parameters that control the time scales of the laser. Depending on their relative values, we determine two distinct two-variable reductions of the rate equations in the limit of large capture rates. The first case leads to the rate equations for quantum well lasers, exhibiting relaxation oscillations dynamics. The second case corresponds to dots nearly saturated by the carriers and is characterized by the absence of relaxation oscillations.

  4. Formation processes and time scales for meteorite parent bodies

    NASA Technical Reports Server (NTRS)

    Weidenschilling, S. J.

    1988-01-01

    The transition from small particles suspended in the solar nebula to the planetesimals (asteroids) that became the parent bodies of meteorites is examined. Planetesimals probably grew by coagulation of grain aggregates that collided due to different rates of settling and drag-induced orbital decay. Their growth was accompanied by radial transport of solids, possibly sufficient to deplete the primordial mass in the asteroid zone, but with relatively little mixing. The formation of asteroid-sized planetesimals was probably rapid, on a time scale less than 1 Myr.

  5. Time-Dependent Earthquake Forecasts on a Global Scale

    NASA Astrophysics Data System (ADS)

    Rundle, J. B.; Holliday, J. R.; Turcotte, D. L.; Graves, W. R.

    2014-12-01

    We develop and implement a new type of global earthquake forecast. Our forecast is a perturbation on a smoothed seismicity (Relative Intensity) spatial forecast combined with a temporal time-averaged ("Poisson") forecast. A variety of statistical and fault-system models have been discussed for use in computing forecast probabilities. An example is the Working Group on California Earthquake Probabilities, which has been using fault-based models to compute conditional probabilities in California since 1988. An example of a forecast is the Epidemic-Type Aftershock Sequence (ETAS), which is based on the Gutenberg-Richter (GR) magnitude-frequency law, the Omori aftershock law, and Poisson statistics. The method discussed in this talk is based on the observation that GR statistics characterize seismicity for all space and time. Small magnitude event counts (quake counts) are used as "markers" for the approach of large events. More specifically, if the GR b-value = 1, then for every 1000 M>3 earthquakes, one expects 1 M>6 earthquake. So if ~1000 M>3 events have occurred in a spatial region since the last M>6 earthquake, another M>6 earthquake should be expected soon. In physics, event count models have been called natural time models, since counts of small events represent a physical or natural time scale characterizing the system dynamics. In a previous research, we used conditional Weibull statistics to convert event counts into a temporal probability for a given fixed region. In the present paper, we move belyond a fixed region, and develop a method to compute these Natural Time Weibull (NTW) forecasts on a global scale, using an internally consistent method, in regions of arbitrary shape and size. We develop and implement these methods on a modern web-service computing platform, which can be found at www.openhazards.com and www.quakesim.org. We also discuss constraints on the User Interface (UI) that follow from practical considerations of site usability.

  6. Mathematical Modeling of Space-Time Variations in Acoustic Transmission and Scattering from Schools of Swim Bladder Fish

    DTIC Science & Technology

    2015-09-30

    1996 (Ref. 1), based upon the harmonic solution of sets of coupled differential equations, each describing scattering from one fish. The Love swim...side of the empty core, thus reducing the acoustic interactions between them. REFERENCES (1) C. Feuillade, R. W. Nero and R. H. Love , "A low...frequency acoustic scattering model for small schools offish," J. Acoust. Soc. Am., 99, 196-208 (1996). (2) R. H. Love , "Resonant acoustic scattering by

  7. Deep Water Ocean Acoustics

    DTIC Science & Technology

    2016-04-30

    OASIS, INC. 1 Report No. QSR-14C0172-Ocean Acoustics-043016 Quarterly Progress Report Technical and Financial Deep Water Ocean Acoustics...understanding of the impact of the ocean and seafloor environmental variability on deep- water (long-range) ocean acoustic propagation and to...improve our understanding. During the past few years, the physics effects studied have been three-dimensional propagation on global scales, deep water

  8. First-Order Acoustic Wave Equation Reverse Time Migration Based on the Dual-Sensor Seismic Acquisition System

    NASA Astrophysics Data System (ADS)

    You, Jiachun; Liu, Xuewei; Wu, Ru-Shan

    2017-03-01

    We analyze the mathematical requirements for conventional reverse time migration (RTM) and summarize their rationale. The known information provided by current acquisition system is inadequate for the second-order acoustic wave equations. Therefore, we introduce a dual-sensor seismic acquisition system into the coupled first-order acoustic wave equations. We propose a new dual-sensor reverse time migration called dual-sensor RTM, which includes two input variables, the pressure and vertical particle velocity data. We focus on the performance of dual-sensor RTM in estimating reflection coefficients compared with conventional RTM. Synthetic examples are used for the study of estimating coefficients of reflectors with both dual-sensor RTM and conventional RTM. The results indicate that dual-sensor RTM with two inputs calculates amplitude information more accurately and images structural positions of complex substructures, such as the Marmousi model, more clearly than that of conventional RTM. This shows that the dual-sensor RTM has better accuracy in backpropagation and carries more information in the directivity because of particle velocity injection. Through a simple point-shape model, we demonstrate that dual-sensor RTM decreases the effect of multi-pathing of propagating waves, which is helpful for focusing the energy. In addition, compared to conventional RTM, dual-sensor RTM does not cause extra memory costs. Dual-sensor RTM is, therefore, promising for the computation of multi-component seismic data.

  9. Generalized dynamic scaling for quantum critical relaxation in imaginary time.

    PubMed

    Zhang, Shuyi; Yin, Shuai; Zhong, Fan

    2014-10-01

    We study the imaginary-time relaxation critical dynamics of a quantum system with a vanishing initial correlation length and an arbitrary initial order parameter M0. We find that in quantum critical dynamics, the behavior of M0 under scale transformations deviates from a simple power law, which was proposed for very small M0 previously. A universal characteristic function is then suggested to describe the rescaled initial magnetization, similar to classical critical dynamics. This characteristic function is shown to be able to describe the quantum critical dynamics in both short- and long-time stages of the evolution. The one-dimensional transverse-field Ising model is employed to numerically determine the specific form of the characteristic function. We demonstrate that it is applicable as long as the system is in the vicinity of the quantum critical point. The universality of the characteristic function is confirmed by numerical simulations of models belonging to the same universality class.

  10. Nonlinear Dynamics of Extended Hydrologic Systems over long time scales

    NASA Astrophysics Data System (ADS)

    Lall, Upmanu

    2014-05-01

    We often view our knowledge of hydrology and hence of nature as intransient, at least over the time scales over which we study processes we wish to predict and understand. Over the last few decades, this assumption has come under question, largely because of the vocal expression of a changing climate, but also the recurrent demonstration of significant land use change, both of which significantly affect the boundary conditions for terrestrial hydrology that is our forte. Most recently, the concepts of hydromorphology and social hydrology have entered the discussion, and the notion that climate and hydrology influence human action, which in turn shapes hydrology, is being recognized. Finally, as a field, we seem to be coming to the conclusion that the hydrologic system is an open system, whose boundaries evolve in time, and that the hydrologic system, at many scales, has a profound effect on the systems that drive it -- whether they be the ecological and climatic systems, or the social system. What a mess! Complexity! Unpredictability! At a certain level of abstraction, one can consider the evolution of these coupled systems with nonlinear feedbacks and ask what types of questions are relevant in terms of such a coupled evolution? What are their implications at the planetary scale? What are their implications for a subsistence farmer in an arid landscape who may under external influence achieve a new transient hydro-ecological equilibrium? What are the implications for the economy and power of nations? In this talk, I will try to raise some of these questions and also provide some examples with very simple dynamical systems that suggest ways of thinking about some practical issues of feedback across climate, hydrology and human behavior.

  11. Complex Processes from Dynamical Architectures with Time-Scale Hierarchy

    PubMed Central

    Perdikis, Dionysios; Huys, Raoul; Jirsa, Viktor

    2011-01-01

    The idea that complex motor, perceptual, and cognitive behaviors are composed of smaller units, which are somehow brought into a meaningful relation, permeates the biological and life sciences. However, no principled framework defining the constituent elementary processes has been developed to this date. Consequently, functional configurations (or architectures) relating elementary processes and external influences are mostly piecemeal formulations suitable to particular instances only. Here, we develop a general dynamical framework for distinct functional architectures characterized by the time-scale separation of their constituents and evaluate their efficiency. Thereto, we build on the (phase) flow of a system, which prescribes the temporal evolution of its state variables. The phase flow topology allows for the unambiguous classification of qualitatively distinct processes, which we consider to represent the functional units or modes within the dynamical architecture. Using the example of a composite movement we illustrate how different architectures can be characterized by their degree of time scale separation between the internal elements of the architecture (i.e. the functional modes) and external interventions. We reveal a tradeoff of the interactions between internal and external influences, which offers a theoretical justification for the efficient composition of complex processes out of non-trivial elementary processes or functional modes. PMID:21347363

  12. Surface Radiation Budget Variability at Climatic Time Scales

    NASA Astrophysics Data System (ADS)

    Pinker, R. T.; Ma, Y.; Nussbaumer, E.

    2014-12-01

    Information on Earth Radiation Balance is needed at climatic time scales for enabling assessment of variability and trends in the forcing functions of the climate system. Satellite observations have been instrumental for advancing the understanding of such balance at global scale; yet, the length of available records does not meet climatic needs. Major issues hindering such efforts are related to the frequent changes in satellite observing systems, including the specification of the satellite instruments, and changes in the quality of atmospheric inputs that drive the inference schemes. In this paper we report on an effort to synthesize estimates of shortwave, longwave and spectral surface radiative fluxes by fusing observations from numerous satellite platforms that include MODIS observations. This information was obtained in the framework of the MEaSURES and NEWS programs; it will be evaluated against ground observations and compared to independent satellite and model estimates. Attention will be given to updates on our knowledge on the radiative balance as compared to what is known from shorter time records.

  13. Multiple-time-scale motion in molecularly linked nanoparticle arrays.

    PubMed

    George, Christopher; Szleifer, Igal; Ratner, Mark

    2013-01-22

    We explore the transport of electrons between electrodes that encase a two-dimensional array of metallic quantum dots linked by molecular bridges (such as α,ω alkaline dithiols). Because the molecules can move at finite temperatures, the entire transport structure comprising the quantum dots and the molecules is in dynamical motion while the charge is being transported. There are then several physical processes (physical excursions of molecules and quantum dots, electronic migration, ordinary vibrations), all of which influence electronic transport. Each can occur on a different time scale. It is therefore not appropriate to use standard approaches to this sort of electron transfer problem. Instead, we present a treatment in which three different theoretical approaches-kinetic Monte Carlo, classical molecular dynamics, and quantum transport-are all employed. In certain limits, some of the dynamical effects are unimportant. But in general, the transport seems to follow a sort of dynamic bond percolation picture, an approach originally introduced as formal models and later applied to polymer electrolytes. Different rate-determining steps occur in different limits. This approach offers a powerful scheme for dealing with multiple time scale transport problems, as will exist in many situations with several pathways through molecular arrays or even individual molecules that are dynamically disordered.

  14. Complex processes from dynamical architectures with time-scale hierarchy.

    PubMed

    Perdikis, Dionysios; Huys, Raoul; Jirsa, Viktor

    2011-02-10

    The idea that complex motor, perceptual, and cognitive behaviors are composed of smaller units, which are somehow brought into a meaningful relation, permeates the biological and life sciences. However, no principled framework defining the constituent elementary processes has been developed to this date. Consequently, functional configurations (or architectures) relating elementary processes and external influences are mostly piecemeal formulations suitable to particular instances only. Here, we develop a general dynamical framework for distinct functional architectures characterized by the time-scale separation of their constituents and evaluate their efficiency. Thereto, we build on the (phase) flow of a system, which prescribes the temporal evolution of its state variables. The phase flow topology allows for the unambiguous classification of qualitatively distinct processes, which we consider to represent the functional units or modes within the dynamical architecture. Using the example of a composite movement we illustrate how different architectures can be characterized by their degree of time scale separation between the internal elements of the architecture (i.e. the functional modes) and external interventions. We reveal a tradeoff of the interactions between internal and external influences, which offers a theoretical justification for the efficient composition of complex processes out of non-trivial elementary processes or functional modes.

  15. Reusable Launch Vehicle Control In Multiple Time Scale Sliding Modes

    NASA Technical Reports Server (NTRS)

    Shtessel, Yuri; Hall, Charles; Jackson, Mark

    2000-01-01

    A reusable launch vehicle control problem during ascent is addressed via multiple-time scaled continuous sliding mode control. The proposed sliding mode controller utilizes a two-loop structure and provides robust, de-coupled tracking of both orientation angle command profiles and angular rate command profiles in the presence of bounded external disturbances and plant uncertainties. Sliding mode control causes the angular rate and orientation angle tracking error dynamics to be constrained to linear, de-coupled, homogeneous, and vector valued differential equations with desired eigenvalues placement. Overall stability of a two-loop control system is addressed. An optimal control allocation algorithm is designed that allocates torque commands into end-effector deflection commands, which are executed by the actuators. The dual-time scale sliding mode controller was designed for the X-33 technology demonstration sub-orbital launch vehicle in the launch mode. Simulation results show that the designed controller provides robust, accurate, de-coupled tracking of the orientation angle command profiles in presence of external disturbances and vehicle inertia uncertainties. This is a significant advancement in performance over that achieved with linear, gain scheduled control systems currently being used for launch vehicles.

  16. Cell assemblies at multiple time scales with arbitrary lag constellations

    PubMed Central

    Russo, Eleonora; Durstewitz, Daniel

    2017-01-01

    Hebb's idea of a cell assembly as the fundamental unit of neural information processing has dominated neuroscience like no other theoretical concept within the past 60 years. A range of different physiological phenomena, from precisely synchronized spiking to broadly simultaneous rate increases, has been subsumed under this term. Yet progress in this area is hampered by the lack of statistical tools that would enable to extract assemblies with arbitrary constellations of time lags, and at multiple temporal scales, partly due to the severe computational burden. Here we present such a unifying methodological and conceptual framework which detects assembly structure at many different time scales, levels of precision, and with arbitrary internal organization. Applying this methodology to multiple single unit recordings from various cortical areas, we find that there is no universal cortical coding scheme, but that assembly structure and precision significantly depends on the brain area recorded and ongoing task demands. DOI: http://dx.doi.org/10.7554/eLife.19428.001 PMID:28074777

  17. Designing for development: Across the scales of time.

    PubMed

    Cole, Michael

    2016-11-01

    This essay traces the history of an activity designed to promote the intellectual and social development of elementary-age schoolchildren during the afterschool hours. Following in the footsteps of Urie Bronfenbrenner, I highlight his argument that just as all human development occurs in contexts of varying levels of inclusiveness and mutual interchange, human development occurs at intersecting scales of time that themselves vary in character and duration. The task of exploring Bronfenbrenner's idea confronts scholars interested in person-context coconstitutive processes with a difficult methodological requirement; they must study simultaneously the history of persons (at the microgenetic and ontogenetic time scales) as well the history of "the contexts of development" in which the persons participate. A project implementing such a study focused on the life course of the system of activity is described, followed by a discussion of the lessons to be learned from a temporally extensive study of persons developing in contexts that are themselves changing. (PsycINFO Database Record

  18. A comparison of linear acoustic theory with experimental noise data for a small-scale hovering rotor

    NASA Technical Reports Server (NTRS)

    Farassat, F.; Morris, C. E. K., Jr.; Nystrom, P. A.

    1979-01-01

    Linear acoustic calculations based on full aerodynamic data as input are presented and compared with measured cases reported by Boxwell et al. (1978). The full aerodynamic data are obtained using three programs giving radial loading, chordwise loading, and chordwise position of transition. It is shown that in the theoretical results the most significant noise source mechanism is due to blade thickness. Thus the conclusions of Boxwell et al. as to the importance of nonlinearities around the blades are upheld. These conclusions concern the width, shape and the level of the acoustic pressure calculated from linear acoustic theory. Some of the approximations involved in the application of acoustic analogy using quadrupole sources are discussed. It is necessary that the near- and far-field problems of rotating blades be treated together as shown for the case of an oscillating sphere.

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

    NASA Astrophysics Data System (ADS)

    Panek, Petr; Prochazka, Ivan

    2007-09-01

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

  20. Two-Dimensional Beam Tracing from Visibility Diagrams for Real-Time Acoustic Rendering

    NASA Astrophysics Data System (ADS)

    Antonacci (Eurasip Member), F.; Sarti (Eurasip Member), A.; Tubaro (Eurasip Member), S.

    2010-12-01

    We present an extension of the fast beam-tracing method presented in the work of Antonacci et al. (2008) for the simulation of acoustic propagation in reverberant environments that accounts for diffraction and diffusion. More specifically, we show how visibility maps are suitable for modeling propagation phenomena more complex than specular reflections. We also show how the beam-tree lookup for path tracing can be entirely performed on visibility maps as well. We then contextualize such method to the two different cases of channel (point-to-point) rendering using a headset, and the rendering of a wave field based on arrays of speakers. Finally, we provide some experimental results and comparisons with real data to show the effectiveness and the accuracy of the approach in simulating the soundfield in an environment.