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Sample records for acoustic oscillations baos

  1. DETECTING BARYON ACOUSTIC OSCILLATIONS

    SciTech Connect

    Labatie, A.; Starck, J. L.

    2012-02-20

    Baryon acoustic oscillations (BAOs) are a feature imprinted in the galaxy distribution by acoustic waves traveling in the plasma of the early universe. Their detection at the expected scale in large-scale structures strongly supports current cosmological models with a nearly linear evolution from redshift z Almost-Equal-To 1000 and the existence of dark energy. In addition, BAOs provide a standard ruler for studying cosmic expansion. In this paper, we focus on methods for BAO detection using the correlation function measurement {xi}-hat. For each method, we want to understand the tested hypothesis (the hypothesis H{sub 0} to be rejected) and the underlying assumptions. We first present wavelet methods which are mildly model-dependent and mostly sensitive to the BAO feature. Then we turn to fully model-dependent methods. We present the method used most often based on the {chi}{sup 2} statistic, but we find that it has limitations. In general the assumptions of the {chi}{sup 2} method are not verified, and it only gives a rough estimate of the significance. The estimate can become very wrong when considering more realistic hypotheses, where the covariance matrix of {xi}-hat depends on cosmological parameters. Instead, we propose to use the {Delta}l method based on two modifications: we modify the procedure for computing the significance and make it rigorous, and we modify the statistic to obtain better results in the case of varying covariance matrix. We verify with simulations that correct significances are different from the ones obtained using the classical {chi}{sup 2} procedure. We also test a simple example of varying covariance matrix. In this case we find that our modified statistic outperforms the classical {chi}{sup 2} statistic when both significances are correctly computed. Finally, we find that taking into account variations of the covariance matrix can change both BAO detection levels and cosmological parameter constraints.

  2. BAO Cosmography

    SciTech Connect

    Lazkoz, Ruth; Escamilla-Rivera, Celia; Salzano, Vincenzo; Sendra, Irene; Alcaniz, Jailson E-mail: alcaniz@on.br E-mail: vincenzo.salzano@ehu.es

    2013-12-01

    Cosmography provides a model-independent way to map the expansion history of the Universe. In this paper we simulate a Euclid-like survey and explore cosmographic constraints from future Baryonic Acoustic Oscillations (BAO) observations. We derive general expressions for the BAO transverse and radial modes and discuss the optimal order of the cosmographic expansion that provides reliable cosmological constraints. Through constraints on the deceleration and jerk parameters, we show that future BAO data have the potential to provide a model-independent check of the cosmic acceleration as well as a discrimination between the standard ΛCDM model and alternative mechanisms of cosmic acceleration.

  3. Cosmological implications of baryon acoustic oscillation measurements

    NASA Astrophysics Data System (ADS)

    Aubourg, Éric; Bailey, Stephen; Bautista, Julian E.; Beutler, Florian; Bhardwaj, Vaishali; Bizyaev, Dmitry; Blanton, Michael; Blomqvist, Michael; Bolton, Adam S.; Bovy, Jo; Brewington, Howard; Brinkmann, J.; Brownstein, Joel R.; Burden, Angela; Busca, Nicolás G.; Carithers, William; Chuang, Chia-Hsun; Comparat, Johan; Croft, Rupert A. C.; Cuesta, Antonio J.; Dawson, Kyle S.; Delubac, Timothée; Eisenstein, Daniel J.; Font-Ribera, Andreu; Ge, Jian; Le Goff, J.-M.; Gontcho, Satya Gontcho A.; Gott, J. Richard; Gunn, James E.; Guo, Hong; Guy, Julien; Hamilton, Jean-Christophe; Ho, Shirley; Honscheid, Klaus; Howlett, Cullan; Kirkby, David; Kitaura, Francisco S.; Kneib, Jean-Paul; Lee, Khee-Gan; Long, Dan; Lupton, Robert H.; Magaña, Mariana Vargas; Malanushenko, Viktor; Malanushenko, Elena; Manera, Marc; Maraston, Claudia; Margala, Daniel; McBride, Cameron K.; Miralda-Escudé, Jordi; Myers, Adam D.; Nichol, Robert C.; Noterdaeme, Pasquier; Nuza, Sebastián E.; Olmstead, Matthew D.; Oravetz, Daniel; Pâris, Isabelle; Padmanabhan, Nikhil; Palanque-Delabrouille, Nathalie; Pan, Kaike; Pellejero-Ibanez, Marcos; Percival, Will J.; Petitjean, Patrick; Pieri, Matthew M.; Prada, Francisco; Reid, Beth; Rich, James; Roe, Natalie A.; Ross, Ashley J.; Ross, Nicholas P.; Rossi, Graziano; Rubiño-Martín, Jose Alberto; Sánchez, Ariel G.; Samushia, Lado; Santos, Ricardo Tanausú Génova; Scóccola, Claudia G.; Schlegel, David J.; Schneider, Donald P.; Seo, Hee-Jong; Sheldon, Erin; Simmons, Audrey; Skibba, Ramin A.; Slosar, Anže; Strauss, Michael A.; Thomas, Daniel; Tinker, Jeremy L.; Tojeiro, Rita; Vazquez, Jose Alberto; Viel, Matteo; Wake, David A.; Weaver, Benjamin A.; Weinberg, David H.; Wood-Vasey, W. M.; Yèche, Christophe; Zehavi, Idit; Zhao, Gong-Bo; BOSS Collaboration

    2015-12-01

    We derive constraints on cosmological parameters and tests of dark energy models from the combination of baryon acoustic oscillation (BAO) measurements with cosmic microwave background (CMB) data and a recent reanalysis of Type Ia supernova (SN) data. In particular, we take advantage of high-precision BAO measurements from galaxy clustering and the Lyman-α forest (LyaF) in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). Treating the BAO scale as an uncalibrated standard ruler, BAO data alone yield a high confidence detection of dark energy; in combination with the CMB angular acoustic scale they further imply a nearly flat universe. Adding the CMB-calibrated physical scale of the sound horizon, the combination of BAO and SN data into an "inverse distance ladder" yields a measurement of H0=67.3 ±1.1 km s-1 Mpc-1 , with 1.7% precision. This measurement assumes standard prerecombination physics but is insensitive to assumptions about dark energy or space curvature, so agreement with CMB-based estimates that assume a flat Λ CDM cosmology is an important corroboration of this minimal cosmological model. For constant dark energy (Λ ), our BAO +SN +CMB combination yields matter density Ωm=0.301 ±0.008 and curvature Ωk=-0.003 ±0.003 . When we allow more general forms of evolving dark energy, the BAO +SN +CMB parameter constraints are always consistent with flat Λ CDM values at ≈1 σ . While the overall χ2 of model fits is satisfactory, the LyaF BAO measurements are in moderate (2 - 2.5 σ ) tension with model predictions. Models with early dark energy that tracks the dominant energy component at high redshift remain consistent with our expansion history constraints, and they yield a higher H0 and lower matter clustering amplitude, improving agreement with some low redshift observations. Expansion history alone yields an upper limit on the summed mass of neutrino species, ∑mν<0.56 eV (95% confidence), improving to ∑mν<0.25 eV if we include the

  4. Application of Wavelet Packet Analysis to the Measurement of the Baryon Acoustic Oscillation

    NASA Astrophysics Data System (ADS)

    Kadowaki, Kevin; Garcia, Noel; Ford, Taurean; Pando, Jesus; SDSS-FAST Collaboration

    2016-03-01

    We develop a method of wavelet packet analysis to measure the Baryon Acoustic Oscillation (BAO) peak and apply this method to the CMASS galaxy catalog from the SDSS Baryon Oscillation Spectroscopic Survey (BOSS) collaboration. We compare our results to a fiducial ?CDM flat cosmological model and detect a BAO signature in the power spectrum comparable to the previous consensus results of the BOSS collaboration. We find DA = 1365rd /rd , fid at z = . 54 . Member ID Forthcoming.

  5. Isocurvature modes and Baryon Acoustic Oscillations

    SciTech Connect

    Mangilli, Anna; Verde, Licia; Beltran, Maria E-mail: licia.verde@icc.ub.edu

    2010-10-01

    The measurement of Baryonic Acoustic Oscillations from galaxy surveys is well known to be a robust and powerful tool to constrain dark energy. This method relies on the knowledge of the size of the acoustic horizon at radiation drag derived from Cosmic Microwave Background Anisotropy measurements. In this paper we quantify the effect of non-standard initial conditions in the form of an isocurvature component on the determination of dark energy parameters from future BAO surveys. In particular, if there is an isocurvature component (at a level still allowed by present data) but it is ignored in the CMB analysis, the sound horizon and cosmological parameters determination is biased, and, as a consequence, future surveys may incorrectly suggest deviations from a cosmological constant. In order to recover an unbiased determination of the sound horizon and dark energy parameters, a component of isocurvature perturbations must be included in the model when analyzing CMB data. Fortunately, doing so does not increase parameter errors significantly.

  6. Baryon Acoustic Oscillation Intensity Mapping of Dark Energy

    NASA Astrophysics Data System (ADS)

    Chang, Tzu-Ching; Pen, Ue-Li; Peterson, Jeffrey B.; McDonald, Patrick

    2008-03-01

    The expansion of the Universe appears to be accelerating, and the mysterious antigravity agent of this acceleration has been called “dark energy.” To measure the dynamics of dark energy, baryon acoustic oscillations (BAO) can be used. Previous discussions of the BAO dark energy test have focused on direct measurements of redshifts of as many as 109 individual galaxies, by observing the 21 cm line or by detecting optical emission. Here we show how the study of acoustic oscillation in the 21 cm brightness can be accomplished by economical three-dimensional intensity mapping. If our estimates gain acceptance they may be the starting point for a new class of dark energy experiments dedicated to large angular scale mapping of the radio sky, shedding light on dark energy.

  7. Efficient reconstruction of linear baryon acoustic oscillations in galaxy surveys

    NASA Astrophysics Data System (ADS)

    Burden, A.; Percival, W. J.; Manera, M.; Cuesta, Antonio J.; Vargas Magana, Mariana; Ho, Shirley

    2014-12-01

    Reconstructing an estimate of linear baryon acoustic oscillations (BAO) from an evolved galaxy field has become a standard technique in recent analyses. By partially removing non-linear damping caused by bulk motions, the real-space BAO peak in the correlation function is sharpened, and oscillations in the power spectrum are visible to smaller scales. In turn these lead to stronger measurements of the BAO scale. Future surveys are being designed assuming that this improvement has been applied, and this technique is therefore of critical importance for future BAO measurements. A number of reconstruction techniques are available, but the most widely used is a simple algorithm that decorrelates large-scale and small-scale modes approximately removing the bulk-flow displacements by moving the overdensity field. We consider the practical implementation of this algorithm, looking at the efficiency of reconstruction as a function of the assumptions made for the bulk-flow scale, the shot-noise level in a random catalogue used to quantify the mask and the method used to estimate the bulk-flow shifts. We also examine the efficiency of reconstruction against external factors including galaxy density, volume and edge effects, and consider their impact for future surveys. Throughout we make use of the mocks catalogues created for the Baryon Oscillation Spectroscopic Survey (BOSS) Date Release 11 samples covering 0.43 < z < 0.7 (CMASS) and 0.15 < z < 0.43 (LOWZ), to empirically test these changes.

  8. 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. PMID:27058069

  9. 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.

  10. Measuring baryon acoustic oscillations from the clustering of voids

    NASA Astrophysics Data System (ADS)

    Liang, Yu; Zhao, Cheng; Chuang, Chia-Hsun; Kitaura, Francisco-Shu; Tao, Charling

    2016-07-01

    We investigate the necessary methodology to optimally measure the baryon acoustic oscillation (BAO) signal from voids, based on galaxy redshift catalogues. To this end, we study the dependence of the BAO signal on the population of voids classified by their sizes. We find for the first time the characteristic features of the correlation function of voids including the first robust detection of BAOs in mock galaxy catalogues. These show an anti-correlation around the scale corresponding to the smallest size of voids in the sample (the void exclusion effect), and dips at both sides of the BAO peak, which can be used to determine the significance of the BAO signal without any priori model. Furthermore, our analysis demonstrates that there is a scale-dependent bias for different populations of voids depending on the radius, with the peculiar property that the void population with the largest BAO significance corresponds to tracers with approximately zero bias on the largest scales. We further investigate the methodology on an additional set of 1000 realistic mock galaxy catalogues reproducing the SDSS-III/BOSS CMASS DR11 data, to control the impact of sky mask and radial selection function. Our solution is based on generating voids from randoms including the same survey geometry and completeness, and a post-processing cleaning procedure in the holes and at the boundaries of the survey. The methodology and optimal selection of void populations validated in this work have been used to perform the first BAO detection from voids in observations, presented in a companion paper.

  11. Stable And Oscillating Acoustic Levitation

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B.; Garrett, Steven L.

    1988-01-01

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

  12. Have baryonic acoustic oscillations in the galaxy distribution really been measured?

    NASA Astrophysics Data System (ADS)

    Cabré, Anna; Gaztañaga, Enrique

    2011-03-01

    Recent publications claim that there is no convincing evidence for measurements of the baryonic acoustic oscillation (BAO) feature in galaxy samples using either monopole or radial information. Different claims seem contradictory: data are either not consistent with the BAO model or data are consistent with both the BAO model and featureless models without BAO. We investigate this point with a set of 216 realistic mock galaxy catalogues extracted from MICE 7680, one of the largest volume dark matter simulation run to date, with a volume of 1300 cubical gigaparsecs. Our mocks cover similar volume, densities and bias as the real galaxies and provide 216 realizations of the lambda or ω=-1 cold dark matter (ωCDM) BAO model. We find that only 20 per cent of the mocks show a statistically significant (3σ) preference for the true (input) ωCDM BAO model as compared to a featureless (non-physical) model without BAO. Thus the volume of current galaxy samples is not yet large enough to claim that the BAO feature has been detected. Does this mean that we cannot locate the BAO position? Using a simple (non-optimal) algorithm we show that in 50 per cent (100 per cent) of the mocks, we can find the BAO position within 5 per cent (20 per cent) of the true value. These two findings are not in contradiction: the former is about model selection and the later is about parameter fitting within a model. We conclude that current monopole and radial BAO measurements can be used as standard rulers if we assume ωCDM type of models.

  13. Measuring the speed of light with baryon acoustic oscillations.

    PubMed

    Salzano, Vincenzo; Dąbrowski, Mariusz P; Lazkoz, Ruth

    2015-03-13

    In this Letter, we describe a new method to use baryon acoustic oscillations (BAO) to derive a constraint on the possible variation of the speed of light. The method relies on the fact that there is a simple relation between the angular diameter distance (D(A)) maximum and the Hubble function (H) evaluated at the same maximum-condition redshift, which includes speed of light c. We note the close analogy of the BAO probe with a laboratory experiment: here we have D(A) which plays the role of a standard (cosmological) ruler, and H^{-1}, with the dimension of time, as a (cosmological) clock. We evaluate if current or future missions such as Euclid can be sensitive enough to detect any variation of c.

  14. Measuring the speed of light with baryon acoustic oscillations.

    PubMed

    Salzano, Vincenzo; Dąbrowski, Mariusz P; Lazkoz, Ruth

    2015-03-13

    In this Letter, we describe a new method to use baryon acoustic oscillations (BAO) to derive a constraint on the possible variation of the speed of light. The method relies on the fact that there is a simple relation between the angular diameter distance (D(A)) maximum and the Hubble function (H) evaluated at the same maximum-condition redshift, which includes speed of light c. We note the close analogy of the BAO probe with a laboratory experiment: here we have D(A) which plays the role of a standard (cosmological) ruler, and H^{-1}, with the dimension of time, as a (cosmological) clock. We evaluate if current or future missions such as Euclid can be sensitive enough to detect any variation of c. PMID:25815922

  15. The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: BAO measurement from the LOS-dependent power spectrum of DR12 BOSS galaxies

    NASA Astrophysics Data System (ADS)

    Gil-Marín, Héctor; Percival, Will J.; Cuesta, Antonio J.; Brownstein, Joel R.; Chuang, Chia-Hsun; Ho, Shirley; Kitaura, Francisco-Shu; Maraston, Claudia; Prada, Francisco; Rodríguez-Torres, Sergio; Ross, Ashley J.; Schlegel, David J.; Schneider, Donald P.; Thomas, Daniel; Tinker, Jeremy L.; Tojeiro, Rita; Vargas Magaña, Mariana; Zhao, Gong-Bo

    2016-08-01

    We present an anisotropic analysis of the baryon acoustic oscillation (BAO) scale in the twelfth and final data release of the Baryon Oscillation Spectroscopic Survey (BOSS). We independently analyse the LOWZ and CMASS galaxy samples: the LOWZ sample contains 361 762 galaxies with an effective redshift of zLOWZ = 0.32; the CMASS sample consists of 777 202 galaxies with an effective redshift of zCMASS = 0.57. We extract the BAO peak position from the monopole power-spectrum moment, α0, and from the μ2 moment, α2, where μ is the cosine of the angle to the line of sight. The μ2-moment provides equivalent information to that available in the quadrupole but is simpler to analyse. After applying a reconstruction algorithm to reduce the BAO suppression by bulk motions, we measure the BAO peak position in the monopole and μ2-moment, which are related to radial and angular shifts in scale. We report H(zLOWZ)rs(zd) = (11.60 ± 0.60) × 103 km s-1 and DA(zLOWZ)/rs(zd) = 6.66 ± 0.16 with a cross-correlation coefficient of r_{HD_A}=0.41, for the LOWZ sample; and H(zCMASS)rs(zd) = (14.56 ± 0.37) × 103 km s-1 and DA(zCMASS)/rs(zd) = 9.42 ± 0.13 with a cross-correlation coefficient of r_{HD_A}=0.47, for the CMASS sample. We demonstrate that our results are not affected by the fiducial cosmology assumed for the analysis. We combine these results with the measurements of the BAO peak position in the monopole and quadrupole correlation function of the same data set (Cuesta et al. 2016, companion paper) and report the consensus values: H(zLOWZ)rs(zd) = (11.63 ± 0.69) × 103 km s-1 and DA(zLOWZ)/rs(zd) = 6.67 ± 0.15 with r_{HD_A}=0.35 for the LOWZ sample; H(zCMASS)rs(zd) = (14.67 ± 0.42) × 103 km s-1 and DA(zCMASS)/rs(zd) = 9.47 ± 0.12 with r_{HD_A}=0.52 for the CMASS sample.

  16. Surface acoustic wave stabilized oscillators

    NASA Technical Reports Server (NTRS)

    Parker, T. E.; Lee, D. L.; Leja, I.

    1979-01-01

    Four areas of surface acoustic wave (SAW) controlled oscillators were investigated and a number of 401.2 MHz oscillators were constructed that showed improved performance. Aging studies on SAW devices packaged in HC36/U cold weld enclosures produced frequency drifts as low as 0.4 ppm in 35 weeks and drift rates well under 0.5 ppm/year. Temperature compensation circuits have substantially improved oscillator temperature stability, with a deviation of + or - 4 ppm observed over the range -45 C to + 40 C. High efficiency amplifiers were constructed for SAW oscillators and a dc to RF efficiency of 44 percent was obtained for an RF output of 25 mW. Shock and vibration tests were made on four oscillators and all survived 500 G shock pulses unchanged. Only when white noise vibration (20 Hz to 2000 Hz) levels of 20 G's rms were applied did some of the devices fail.

  17. Surface acoustic wave stabilized oscillators

    NASA Technical Reports Server (NTRS)

    Parker, T. E.

    1978-01-01

    A number of 401.2 MHz surface acoustic wave (SAW) controlled oscillators were built and tested. The performance of these oscillators was evaluated for possible use as stable oscillators in communication systems. A short term frequency stability of better than 1 x 10 to the minus 9th power for one second was measured for the SAW oscillators. Long term frequency drift was measured and was found to be dependent on SAW design and packaging. Drift rates ranging from 15 ppm in twenty weeks to 2.5 ppm in twenty weeks were observed. Some further improvement was required. The temperature dependence of the saw oscillators was evaluated and it was concluded that some form of temperature compensation will be necessary to meet the requirements of some communication systems.

  18. Model-independent dark energy equation of state from unanchored baryon acoustic oscillations

    NASA Astrophysics Data System (ADS)

    Evslin, Jarah

    2016-09-01

    Ratios of line of sight baryon acoustic oscillation (BAO) peaks at two redshifts only depend upon the average dark energy equation of states between those redshifts, as the dependence on anchors such as the BAO scale or the Hubble constant is canceled in a ratio. As a result, BAO ratios provide a probe of dark energy which is independent of both the cosmic distance ladder and the early evolution of universe. In this note, we use ratios to demonstrate that the known tension between the Lyman alpha forest BAO measurement and other probes arises entirely from recent (0.57 < z < 2.34) cosmological expansion. Using ratios of the line of sight Lyman alpha forest and BOSS CMASS BAO scales, we show that there is already more than 3 σ tension with the standard ΛCDM cosmological model which implies that either (i) The BOSS Lyman alpha forest measurement of the Hubble parameter was too low as a result of a statistical fluctuation or systematic error or else (ii) the dark energy equation of state falls steeply at high redshift.

  19. Modeling the reconstructed BAO in Fourier space

    NASA Astrophysics Data System (ADS)

    Seo, Hee-Jong; Beutler, Florian; Ross, Ashley J.; Saito, Shun

    2016-08-01

    The density field reconstruction technique, which partially reverses the non-linear degradation of the Baryon acoustic oscillation (BAO) feature in the galaxy redshift surveys, has been successful in substantially improving the cosmology constraints from recent surveys such as Baryon Oscillation Spectroscopic Survey (BOSS). We estimate the efficiency of the method as a function of various reconstruction details. To directly quantify the BAO information in non-linear density fields before and after reconstruction, we calculate the cross-correlations (i.e. propagators) of the pre(post)-reconstructed density field with the initial linear field using a mock sample that mimics the clustering of the BOSS galaxies. The results directly provide the BAO damping as a function of wavenumber that can be implemented into the Fisher matrix analysis. We focus on investigating the dependence of the propagator on a choice of smoothing filters and on two major different conventions of the redshift-space density field reconstruction that have been used in literature. By estimating the BAO signal to noise for each case, we predict constraints on the angular diameter distance and Hubble parameter using the Fisher matrix analysis. We thus determine an optimal Gaussian smoothing filter scale for the signal-to-noise level of the BOSS CMASS. We also present appropriate BAO fitting models for different reconstruction methods based on the first- and second-order Lagrangian perturbation theory in Fourier space. Using the mock data, we show that the modified BAO fitting model can substantially improve the accuracy of the BAO position in the best fits as well as the goodness of the fits.

  20. NONLINEAR BEHAVIOR OF BARYON ACOUSTIC OSCILLATIONS IN REDSHIFT SPACE FROM THE ZEL'DOVICH APPROXIMATION

    SciTech Connect

    McCullagh, Nuala; Szalay, Alexander S.

    2015-01-10

    Baryon acoustic oscillations (BAO) are a powerful probe of the expansion history of the universe, which can tell us about the nature of dark energy. In order to accurately characterize the dark energy equation of state using BAO, we must understand the effects of both nonlinearities and redshift space distortions on the location and shape of the acoustic peak. In a previous paper, we introduced a novel approach to second order perturbation theory in configuration space using the Zel'dovich approximation, and presented a simple result for the first nonlinear term of the correlation function. In this paper, we extend this approach to redshift space. We show how to perform the computation and present the analytic result for the first nonlinear term in the correlation function. Finally, we validate our result through comparison with numerical simulations.

  1. Time-sliced perturbation theory II: baryon acoustic oscillations and infrared resummation

    NASA Astrophysics Data System (ADS)

    Blas, Diego; Garny, Mathias; Ivanov, Mikhail M.; Sibiryakov, Sergey

    2016-07-01

    We use time-sliced perturbation theory (TSPT) to give an accurate description of the infrared non-linear effects affecting the baryonic acoustic oscillations (BAO) present in the distribution of matter at very large scales. In TSPT this can be done via a systematic resummation that has a simple diagrammatic representation and does not involve uncontrollable approximations. We discuss the power counting rules and derive explicit expressions for the resummed matter power spectrum up to next-to leading order and the bispectrum at the leading order. The two-point correlation function agrees well with N-body data at BAO scales. The systematic approach also allows to reliably assess the shift of the baryon acoustic peak due to non-linear effects.

  2. Signatures of the Primordial Universe from Its Emptiness: Measurement of Baryon Acoustic Oscillations from Minima of the Density Field.

    PubMed

    Kitaura, Francisco-Shu; Chuang, Chia-Hsun; Liang, Yu; Zhao, Cheng; Tao, Charling; Rodríguez-Torres, Sergio; Eisenstein, Daniel J; Gil-Marín, Héctor; Kneib, Jean-Paul; McBride, Cameron; Percival, Will J; Ross, Ashley J; Sánchez, Ariel G; Tinker, Jeremy; Tojeiro, Rita; Vargas-Magana, Mariana; Zhao, Gong-Bo

    2016-04-29

    Sound waves from the primordial fluctuations of the Universe imprinted in the large-scale structure, called baryon acoustic oscillations (BAOs), can be used as standard rulers to measure the scale of the Universe. These oscillations have already been detected in the distribution of galaxies. Here we propose to measure BAOs from the troughs (minima) of the density field. Based on two sets of accurate mock halo catalogues with and without BAOs in the seed initial conditions, we demonstrate that the BAO signal cannot be obtained from the clustering of classical disjoint voids, but it is clearly detected from overlapping voids. The latter represent an estimate of all troughs of the density field. We compute them from the empty circumsphere centers constrained by tetrahedra of galaxies using Delaunay triangulation. Our theoretical models based on an unprecedented large set of detailed simulated void catalogues are remarkably well confirmed by observational data. We use the largest recently publicly available sample of luminous red galaxies from SDSS-III BOSS DR11 to unveil for the first time a >3σ BAO detection from voids in observations. Since voids are nearly isotropically expanding regions, their centers represent the most quiet places in the Universe, keeping in mind the cosmos origin and providing a new promising window in the analysis of the cosmological large-scale structure from galaxy surveys. PMID:27176512

  3. Signatures of the Primordial Universe from Its Emptiness: Measurement of Baryon Acoustic Oscillations from Minima of the Density Field

    NASA Astrophysics Data System (ADS)

    Kitaura, Francisco-Shu; Chuang, Chia-Hsun; Liang, Yu; Zhao, Cheng; Tao, Charling; Rodríguez-Torres, Sergio; Eisenstein, Daniel J.; Gil-Marín, Héctor; Kneib, Jean-Paul; McBride, Cameron; Percival, Will J.; Ross, Ashley J.; Sánchez, Ariel G.; Tinker, Jeremy; Tojeiro, Rita; Vargas-Magana, Mariana; Zhao, Gong-Bo

    2016-04-01

    Sound waves from the primordial fluctuations of the Universe imprinted in the large-scale structure, called baryon acoustic oscillations (BAOs), can be used as standard rulers to measure the scale of the Universe. These oscillations have already been detected in the distribution of galaxies. Here we propose to measure BAOs from the troughs (minima) of the density field. Based on two sets of accurate mock halo catalogues with and without BAOs in the seed initial conditions, we demonstrate that the BAO signal cannot be obtained from the clustering of classical disjoint voids, but it is clearly detected from overlapping voids. The latter represent an estimate of all troughs of the density field. We compute them from the empty circumsphere centers constrained by tetrahedra of galaxies using Delaunay triangulation. Our theoretical models based on an unprecedented large set of detailed simulated void catalogues are remarkably well confirmed by observational data. We use the largest recently publicly available sample of luminous red galaxies from SDSS-III BOSS DR11 to unveil for the first time a >3 σ BAO detection from voids in observations. Since voids are nearly isotropically expanding regions, their centers represent the most quiet places in the Universe, keeping in mind the cosmos origin and providing a new promising window in the analysis of the cosmological large-scale structure from galaxy surveys.

  4. Signatures of the Primordial Universe from Its Emptiness: Measurement of Baryon Acoustic Oscillations from Minima of the Density Field.

    PubMed

    Kitaura, Francisco-Shu; Chuang, Chia-Hsun; Liang, Yu; Zhao, Cheng; Tao, Charling; Rodríguez-Torres, Sergio; Eisenstein, Daniel J; Gil-Marín, Héctor; Kneib, Jean-Paul; McBride, Cameron; Percival, Will J; Ross, Ashley J; Sánchez, Ariel G; Tinker, Jeremy; Tojeiro, Rita; Vargas-Magana, Mariana; Zhao, Gong-Bo

    2016-04-29

    Sound waves from the primordial fluctuations of the Universe imprinted in the large-scale structure, called baryon acoustic oscillations (BAOs), can be used as standard rulers to measure the scale of the Universe. These oscillations have already been detected in the distribution of galaxies. Here we propose to measure BAOs from the troughs (minima) of the density field. Based on two sets of accurate mock halo catalogues with and without BAOs in the seed initial conditions, we demonstrate that the BAO signal cannot be obtained from the clustering of classical disjoint voids, but it is clearly detected from overlapping voids. The latter represent an estimate of all troughs of the density field. We compute them from the empty circumsphere centers constrained by tetrahedra of galaxies using Delaunay triangulation. Our theoretical models based on an unprecedented large set of detailed simulated void catalogues are remarkably well confirmed by observational data. We use the largest recently publicly available sample of luminous red galaxies from SDSS-III BOSS DR11 to unveil for the first time a >3σ BAO detection from voids in observations. Since voids are nearly isotropically expanding regions, their centers represent the most quiet places in the Universe, keeping in mind the cosmos origin and providing a new promising window in the analysis of the cosmological large-scale structure from galaxy surveys.

  5. A cross-check for H0 from Lyman-α Forest and Baryon Acoustic Oscillations

    NASA Astrophysics Data System (ADS)

    Busti, V. C.; Guimarães, R. N.; Lima, J. A. S.

    2016-04-01

    A new method is proposed to infer the Hubble constant H0 through the observed mean transmitted flux from high-redshift quasars and the baryon acoustic oscillations (BAOs). A semi-analytical model for the cosmological-independent volume density distribution function was adopted; it allowed us to obtain constraints on the cosmological parameters once a moderate knowledge of the Inter Galactic Medium (IGM) parameters is assumed. Our analysis, based on two different samples of Lyman-α forest and the BAO measurement, restricts (h, Ωm) to the intervals 0.19 ≤ Ωm ≤ 0.23 and 0.53 ≤ h ≤ 0.82 (1σ). Although the constraints are weaker compared with other estimates, we point out that, with a bigger sample and a better knowledge of the IGM, this method could provide complementary results to measure the Hubble constant independently of the cosmic distance ladder.

  6. Quasar-Lyman α forest cross-correlation from BOSS DR11: Baryon Acoustic Oscillations

    SciTech Connect

    Font-Ribera, Andreu; Kirkby, David; Blomqvist, Michael; Busca, Nicolas; Aubourg, Éric; Bautista, Julian; Ross, Nicholas P.; Bailey, Stephen; Beutler, Florian; Carithers, Bill; Slosar, Anže; Rich, James; Delubac, Timothée; Bhardwaj, Vaishali; Bizyaev, Dmitry; Brewington, Howard; Brinkmann, Jon; Brownstein, Joel R.; Dawson, Kyle S.; and others

    2014-05-01

    We measure the large-scale cross-correlation of quasars with the Lyα forest absorption, using over 164,000 quasars from Data Release 11 of the SDSS-III Baryon Oscillation Spectroscopic Survey. We extend the previous study of roughly 60,000 quasars from Data Release 9 to larger separations, allowing a measurement of the Baryonic Acoustic Oscillation (BAO) scale along the line of sight c/(H(z = 2.36)r{sub s}) = 9.0±0.3 and across the line of sight D{sub A}(z = 2.36)/r{sub s} = 10.8±0.4, consistent with CMB and other BAO data. Using the best fit value of the sound horizon from Planck data (r{sub s} = 147.49 Mpc), we can translate these results to a measurement of the Hubble parameter of H(z = 2.36) = 226±8 km s{sup −1} Mpc{sup −1} and of the angular diameter distance of D{sub A}(z = 2.36) = 1590±60 Mpc. The measured cross-correlation function and an update of the code to fit the BAO scale (baofit) are made publicly available.

  7. Quasar-Lyman α forest cross-correlation from BOSS DR11: Baryon Acoustic Oscillations

    NASA Astrophysics Data System (ADS)

    Font-Ribera, Andreu; Kirkby, David; Busca, Nicolas; Miralda-Escudé, Jordi; Ross, Nicholas P.; Slosar, Anže; Rich, James; Aubourg, Éric; Bailey, Stephen; Bhardwaj, Vaishali; Bautista, Julian; Beutler, Florian; Bizyaev, Dmitry; Blomqvist, Michael; Brewington, Howard; Brinkmann, Jon; Brownstein, Joel R.; Carithers, Bill; Dawson, Kyle S.; Delubac, Timothée; Ebelke, Garrett; Eisenstein, Daniel J.; Ge, Jian; Kinemuchi, Karen; Lee, Khee-Gan; Malanushenko, Viktor; Malanushenko, Elena; Marchante, Moses; Margala, Daniel; Muna, Demitri; Myers, Adam D.; Noterdaeme, Pasquier; Oravetz, Daniel; Palanque-Delabrouille, Nathalie; Pâris, Isabelle; Petitjean, Patrick; Pieri, Matthew M.; Rossi, Graziano; Schneider, Donald P.; Simmons, Audrey; Viel, Matteo; Yeche, Christophe; York, Donald G.

    2014-05-01

    We measure the large-scale cross-correlation of quasars with the Lyα forest absorption, using over 164,000 quasars from Data Release 11 of the SDSS-III Baryon Oscillation Spectroscopic Survey. We extend the previous study of roughly 60,000 quasars from Data Release 9 to larger separations, allowing a measurement of the Baryonic Acoustic Oscillation (BAO) scale along the line of sight c/(H(z = 2.36)rs) = 9.0±0.3 and across the line of sight DA(z = 2.36)/rs = 10.8±0.4, consistent with CMB and other BAO data. Using the best fit value of the sound horizon from Planck data (rs = 147.49 Mpc), we can translate these results to a measurement of the Hubble parameter of H(z = 2.36) = 226±8 km s-1 Mpc-1 and of the angular diameter distance of DA(z = 2.36) = 1590±60 Mpc. The measured cross-correlation function and an update of the code to fit the BAO scale (baofit) are made publicly available.

  8. Baryon acoustic oscillations in 2D: Modeling redshift-space power spectrum from perturbation theory

    NASA Astrophysics Data System (ADS)

    Taruya, Atsushi; Nishimichi, Takahiro; Saito, Shun

    2010-09-01

    We present an improved prescription for the matter power spectrum in redshift space taking proper account of both nonlinear gravitational clustering and redshift distortion, which are of particular importance for accurately modeling baryon acoustic oscillations (BAOs). Contrary to the models of redshift distortion phenomenologically introduced but frequently used in the literature, the new model includes the corrections arising from the nonlinear coupling between the density and velocity fields associated with two competitive effects of redshift distortion, i.e., Kaiser and Finger-of-God effects. Based on the improved treatment of perturbation theory for gravitational clustering, we compare our model predictions with the monopole and quadrupole power spectra of N-body simulations, and an excellent agreement is achieved over the scales of BAOs. Potential impacts on constraining dark energy and modified gravity from the redshift-space power spectrum are also investigated based on the Fisher-matrix formalism, particularly focusing on the measurements of the Hubble parameter, angular diameter distance, and growth rate for structure formation. We find that the existing phenomenological models of redshift distortion produce a systematic error on measurements of the angular diameter distance and Hubble parameter by 1%-2% , and the growth-rate parameter by ˜5%, which would become non-negligible for future galaxy surveys. Correctly modeling redshift distortion is thus essential, and the new prescription for the redshift-space power spectrum including the nonlinear corrections can be used as an accurate theoretical template for anisotropic BAOs.

  9. Supernova and baryon acoustic oscillation constraints on (new) polynomial dark energy parametrizations: current results and forecasts

    NASA Astrophysics Data System (ADS)

    Sendra, Irene; Lazkoz, Ruth

    2012-05-01

    In this work we introduce two new polynomial parametrizations of dark energy and explore their correlation properties. The parameters to fit are the equation-of-state values at z= 0 and z= 0.5, which have naturally low correlation and have already been shown to improve the popular Chevallier-Polarski-Linder (CPL) parametrization. We test our models with low-redshift astronomical probes: type Ia supernovae and baryon acoustic oscillations (BAO), in the form of both current and synthetic data. Specifically, we present simulations of measurements of the radial and transversal BAO scales similar to those expected in a BAO high-precision spectroscopic redshift survey such as EUCLID. According to the Bayesian deviance information criterion (DIC), which penalizes large errors and correlations, we show that our models perform better than the CPL reparametrization proposed by Wang (in terms of z= 0 and z= 0.5). This is due to the combination of lower correlation and smaller relative errors. The same holds for a frequentist perspective: the figure-of-merit is larger for our parametrizations.

  10. Baryon acoustic oscillations in 2D: Modeling redshift-space power spectrum from perturbation theory

    SciTech Connect

    Taruya, Atsushi; Nishimichi, Takahiro; Saito, Shun

    2010-09-15

    We present an improved prescription for the matter power spectrum in redshift space taking proper account of both nonlinear gravitational clustering and redshift distortion, which are of particular importance for accurately modeling baryon acoustic oscillations (BAOs). Contrary to the models of redshift distortion phenomenologically introduced but frequently used in the literature, the new model includes the corrections arising from the nonlinear coupling between the density and velocity fields associated with two competitive effects of redshift distortion, i.e., Kaiser and Finger-of-God effects. Based on the improved treatment of perturbation theory for gravitational clustering, we compare our model predictions with the monopole and quadrupole power spectra of N-body simulations, and an excellent agreement is achieved over the scales of BAOs. Potential impacts on constraining dark energy and modified gravity from the redshift-space power spectrum are also investigated based on the Fisher-matrix formalism, particularly focusing on the measurements of the Hubble parameter, angular diameter distance, and growth rate for structure formation. We find that the existing phenomenological models of redshift distortion produce a systematic error on measurements of the angular diameter distance and Hubble parameter by 1%-2%, and the growth-rate parameter by {approx}5%, which would become non-negligible for future galaxy surveys. Correctly modeling redshift distortion is thus essential, and the new prescription for the redshift-space power spectrum including the nonlinear corrections can be used as an accurate theoretical template for anisotropic BAOs.

  11. PRSA hydrogen tank thermal acoustic oscillation study

    NASA Technical Reports Server (NTRS)

    Riemer, D. H.

    1979-01-01

    The power reactant storage assembly (PRSA) hydrogen tank test data were reviewed. Two hundred and nineteen data points illustrating the effect of flow rate, temperature ratio and configuration were identified. The test data were reduced to produce the thermal acoustic oscillation parameters. Frequency and amplitude were determined for model correlation. A comparison of PRSA hydrogen tank test data with the analytical models indicated satisfactory agreement for the supply and poor agreement for the full line.

  12. Galaxy bias and its effects on the Baryon acoustic oscillations measurements

    SciTech Connect

    Mehta, Kushal T.; Seo, Hee -Jong; Eckel, Jonathan; Eisenstein, Daniel J.; Metchnik, Marc; Pinto, Philip; Xu, Xiaoying

    2011-05-31

    The baryon acoustic oscillation (BAO) feature in the clustering of matter in the universe serves as a robust standard ruler and hence can be used to map the expansion history of the universe. We use high force resolution simulations to analyze the effects of galaxy bias on the measurements of the BAO signal. We apply a variety of Halo Occupation Distributions (HODs) and produce biased mass tracers to mimic different galaxy populations. We investigate whether galaxy bias changes the non-linear shifts on the acoustic scale relative to the underlying dark matter distribution presented by Seo et al. (2009). For the less biased HOD models (b < 3), we do not detect any shift in the acoustic scale relative to the no-bias case, typically 0.10% ± 0.10%. However, the most biased HOD models (b > 3) show a shift at moderate significance (0.79% ± 0.31% for the most extreme case). We test the one-step reconstruction technique introduced by Eisenstein et al. (2007) in the case of realistic galaxy bias and shot noise. The reconstruction scheme increases the correlation between the initial and final (z = 1) density fields achieving an equivalent level of correlation at nearly twice the wavenumber after reconstruction. Reconstruction reduces the shifts and errors on the shifts. We find that after reconstruction the shifts from the galaxy cases and the dark matter case are consistent with each other and with no shift. The 1σ systematic errors on the distance measurements inferred from our BAO measurements with various HODs after reconstruction are about 0.07%-0.15%.

  13. Damping of thermal acoustic oscillations in hydrogen systems

    NASA Technical Reports Server (NTRS)

    Gu, Youfan; Timmerhaus, Klaus D.

    1991-01-01

    Acoustic waves initiated by a large temperature gradient along a tube are defined as thermal acoustic oscillations (TAOs). These oscillations have been damped by introducing such sound absorbing techniques as acoustic filters, resonators, etc.. These devices serve as an acoustic sink that is used to absorb or dissipate the acoustic energy thereby eliminating or damping such oscillations. Several empirical damping techniques, such as attaching a resonator as a side branch or inserting a wire in the tube, have been developed in the past and have provided reasonable success. However, the effect of connecting tube radius, length, and resonator volume on the damping of thermal acoustic oscillations has not been evaluated quantitatively. Further, these methods have not been effective when the oscillating tube radius was relatively large. Detailed theoretical analyses of these techniques including a newly developed method for damping oscillations in a tube of relatively large radius are provided in this presentation.

  14. Damping of thermal acoustic oscillations in hydrogen systems

    NASA Astrophysics Data System (ADS)

    Gu, Youfan; Timmerhaus, Klaus D.

    Acoustic waves initiated by a large temperature gradient along a tube are defined as thermal acoustic oscillations (TAOs). These oscillations have been damped by introducing such sound absorbing techniques as acoustic filters, resonators, etc.. These devices serve as an acoustic sink that is used to absorb or dissipate the acoustic energy thereby eliminating or damping such oscillations. Several empirical damping techniques, such as attaching a resonator as a side branch or inserting a wire in the tube, have been developed in the past and have provided reasonable success. However, the effect of connecting tube radius, length, and resonator volume on the damping of thermal acoustic oscillations has not been evaluated quantitatively. Further, these methods have not been effective when the oscillating tube radius was relatively large. Detailed theoretical analyses of these techniques including a newly developed method for damping oscillations in a tube of relatively large radius are provided in this presentation.

  15. Fitting methods for baryon acoustic oscillations in the Lyman-α forest fluctuations in BOSS data release 9

    SciTech Connect

    Kirkby, David; Margala, Daniel; Blomqvist, Michael; Slosar, Anže; Bailey, Stephen; Carithers, Bill; Busca, Nicolás G.; Bautista, Julian E.; Brownstein, Joel R.; Dawson, Kyle S.; Croft, Rupert A.C.; Font-Ribera, Andreu; Miralda-Escudé, Jordi; Myers, Adam D.; Nichol, Robert C.; Pâris, Isabelle; Petitjean, Patrick; and others

    2013-03-01

    We describe fitting methods developed to analyze fluctuations in the Lyman-α forest and measure the parameters of baryon acoustic oscillations (BAO). We apply our methods to BOSS Data Release 9. Our method is based on models of the three-dimensional correlation function in physical coordinate space, and includes the effects of redshift-space distortions, anisotropic non-linear broadening, and broadband distortions. We allow for independent scale factors along and perpendicular to the line of sight to minimize the dependence on our assumed fiducial cosmology and to obtain separate measurements of the BAO angular and relative velocity scales. Our fitting software and the input files needed to reproduce our main BOSS Data Release 9 results are publicly available.

  16. Quasinormal acoustic oscillations in the Michel flow

    NASA Astrophysics Data System (ADS)

    Chaverra, Eliana; Morales, Manuel D.; Sarbach, Olivier

    2015-05-01

    We study spherical and nonspherical linear acoustic perturbations of the Michel flow, which describes the steady radial accretion of a perfect fluid into a nonrotating black hole. The dynamics of such perturbations are governed by a scalar wave equation on an effective curved background geometry determined by the acoustic metric, which is constructed from the spacetime metric and the particle density and four-velocity of the fluid. For the problem under consideration in this paper the acoustic metric has the same qualitative features as an asymptotically flat, static and spherically symmetric black hole, and thus it represents a natural astrophysical analogue black hole. As for the case of a scalar field propagating on a Schwarzschild background, we show that acoustic perturbations of the Michel flow exhibit quasinormal oscillations. Based on a new numerical method for determining the solutions of the radial mode equation, we compute the associated frequencies and analyze their dependency on the mass of the black hole, the radius of the sonic horizon and the angular momentum number. Our results for the fundamental frequencies are compared to those obtained from an independent numerical Cauchy evolution, finding good agreement between the two approaches. When the radius of the sonic horizon is large compared to the event horizon radius, we find that the quasinormal frequencies scale approximately like the surface gravity associated with the sonic horizon.

  17. The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Observational systematics and baryon acoustic oscillations in the correlation function

    NASA Astrophysics Data System (ADS)

    Ross, Ashley J.; Beutler, Florian; Chuang, Chia-Hsun; Pellejero-Ibanez, Marcos; Seo, Hee-Jong; Vargas-Magaña, Mariana; Cuesta, Antonio J.; Percival, Will J.; Burden, Angela; Sánchez, Ariel G.; Grieb, Jan Niklas; Reid, Beth; Brownstein, Joel R.; Dawson, Kyle S.; Eisenstein, Daniel J.; Ho, Shirley; Kitaura, Francisco-Shu; Nichol, Robert C.; Olmstead, Matthew D.; Prada, Francisco; Rodríguez-Torres, Sergio A.; Saito, Shun; Salazar-Albornoz, Salvador; Schneider, Donald P.; Thomas, Daniel; Tinker, Jeremy; Tojeiro, Rita; Wang, Yuting; White, Martin; Zhao, Gong-bo

    2016-09-01

    We present baryon acoustic oscillation (BAO) scale measurements determined from the clustering of 1.2 million massive galaxies with redshifts 0.2 < z < 0.75 distributed over 9300 square degrees, as quantified by their redshift-space correlation function. In order to facilitate these measurements, we define, describe, and motivate the selection function for galaxies in the final data release (DR12) of the SDSS III Baryon Oscillation Spectroscopic Survey (BOSS). This includes the observational footprint, masks for image quality and Galactic extinction, and weights to account for density relationships intrinsic to the imaging and spectroscopic portions of the survey. We simulate the observed systematic trends in mock galaxy samples and demonstrate that they impart no bias on baryon acoustic oscillation (BAO) scale measurements and have a minor impact on the recovered statistical uncertainty. We measure transverse and radial BAO distance measurements in 0.2 < z < 0.5, 0.5 < z < 0.75, and (overlapping) 0.4 < z < 0.6 redshift bins. In each redshift bin, we obtain a precision that is 2.7 per cent or better on the radial distance and 1.6 per cent or better on the transverse distance. The combination of the redshift bins represents 1.8 per cent precision on the radial distance and 1.1 per cent precision on the transverse distance. This paper is part of a set that analyses the final galaxy clustering dataset from BOSS. The measurements and likelihoods presented here are combined with others in Alam et al. (2016) to produce the final cosmological constraints from BOSS.

  18. Errores sistemáticos en la escala de las BAO

    NASA Astrophysics Data System (ADS)

    Scóccola, C. G.

    2016-08-01

    The large current and future galaxy surveys require very precise theoretical predictions of the baryon acoustic oscillations (BAO). In this contribution article I briefly comment on the physical processes that lead to these oscillations, and review a work where we use large -body cosmological simulations to study any systematic shift and damping of the BAO due to non-linear effects in the growth of structure. The precision of the simulations used for this work allows to resolve the dark matter subhalos, which enable to study with great accuracy (better than 0.02 for dark matter and 0.07 for low bias halos) small shifts toward larger wavenumbers (), and a non-linear damping of the BAO in the power spectrum.

  19. EFFECT OF MODEL-DEPENDENT COVARIANCE MATRIX FOR STUDYING BARYON ACOUSTIC OSCILLATIONS

    SciTech Connect

    Labatie, A.; Starck, J. L.

    2012-12-01

    Large-scale structures in the universe are a powerful tool to test cosmological models and constrain cosmological parameters. A particular feature of interest comes from baryon acoustic oscillations (BAOs), which are sound waves traveling in the hot plasma of the early universe that stopped at the recombination time. This feature can be observed as a localized bump in the correlation function at the scale of the sound horizon r{sub s} . As such, it provides a standard ruler and a lot of constraining power in the correlation function analysis of galaxy surveys. Moreover, the detection of BAOs at the expected scale gives strong support to cosmological models. Both of these studies (BAO detection and parameter constraints) rely on a statistical modeling of the measured correlation function {xi}-circumflex. Usually {xi}-circumflex is assumed to be Gaussian, with a mean {xi}{sub {theta}} depending on the cosmological model and a covariance matrix C generally approximated as a constant (i.e., independent of the model). In this article, we study whether a realistic model-dependent C {sub {theta}} changes the results of cosmological parameter constraints compared to the approximation of a constant covariance matrix C. For this purpose, we use a new procedure to generate lognormal realizations of the luminous red galaxy sample of the Sloan Digital Sky Survey Data Release 7 to obtain a model-dependent C {sub {theta}} in a reasonable time. The approximation of C {sub {theta}} as a constant creates small changes in the cosmological parameter constraints on our sample. We quantify this modeling error using a lot of simulations and find that it only has a marginal influence on cosmological parameter constraints for current and next-generation galaxy surveys. It can be approximately taken into account by extending the 1{sigma} intervals by a factor Almost-Equal-To 1.3.

  20. The Correlation Function of Galaxy Clusters and Detection of Baryon Acoustic Oscillations

    NASA Astrophysics Data System (ADS)

    Hong, T.; Han, J. L.; Wen, Z. L.; Sun, L.; Zhan, H.

    2012-04-01

    We calculate the correlation function of 13,904 galaxy clusters of z <= 0.4 selected from the cluster catalog of Wen et al. The correlation function can be fitted with a power-law model ξ(r) = (r/R 0)-γ on the scales of 10 h -1 Mpc <= r <= 50 h -1 Mpc, with a larger correlation length of R 0 = 18.84 ± 0.27 h -1 Mpc for clusters with a richness of R >= 15 and a smaller length of R 0 = 16.15 ± 0.13 h -1 Mpc for clusters with a richness of R >= 5. The power-law index of γ = 2.1 is found to be almost the same for all cluster subsamples. A pronounced baryon acoustic oscillations (BAO) peak is detected at r ~ 110 h -1 Mpc with a significance of ~1.9σ. By analyzing the correlation function in the range of 20 h -1 Mpc <= r <= 200 h -1 Mpc, we find that the constraints on distance parameters are Dv (zm = 0.276) = 1077 ± 55(1σ) Mpc and h = 0.73 ± 0.039(1σ), which are consistent with the cosmology derived from Wilkinson Microwave Anisotropy Probe (WMAP) seven-year data. However, the BAO signal from the cluster sample is stronger than expected and leads to a rather low matter density Ω m h 2 = 0.093 ± 0.0077(1σ), which deviates from the WMAP7 result by more than 3σ. The correlation function of the GMBCG cluster sample is also calculated and our detection of the BAO feature is confirmed.

  1. THE CORRELATION FUNCTION OF GALAXY CLUSTERS AND DETECTION OF BARYON ACOUSTIC OSCILLATIONS

    SciTech Connect

    Hong, T.; Han, J. L.; Wen, Z. L.; Sun, L.; Zhan, H.

    2012-04-10

    We calculate the correlation function of 13,904 galaxy clusters of z {<=} 0.4 selected from the cluster catalog of Wen et al. The correlation function can be fitted with a power-law model {xi}(r) = (r/R{sub 0}){sup -{gamma}} on the scales of 10 h{sup -1} Mpc {<=} r {<=} 50 h{sup -1} Mpc, with a larger correlation length of R{sub 0} = 18.84 {+-} 0.27 h{sup -1} Mpc for clusters with a richness of R {>=} 15 and a smaller length of R{sub 0} = 16.15 {+-} 0.13 h{sup -1} Mpc for clusters with a richness of R {>=} 5. The power-law index of {gamma} = 2.1 is found to be almost the same for all cluster subsamples. A pronounced baryon acoustic oscillations (BAO) peak is detected at r {approx} 110 h{sup -1} Mpc with a significance of {approx}1.9{sigma}. By analyzing the correlation function in the range of 20 h{sup -1} Mpc {<=} r {<=} 200 h{sup -1} Mpc, we find that the constraints on distance parameters are D{sub v} (z{sub m} = 0.276) = 1077 {+-} 55(1{sigma}) Mpc and h = 0.73 {+-} 0.039(1{sigma}), which are consistent with the cosmology derived from Wilkinson Microwave Anisotropy Probe (WMAP) seven-year data. However, the BAO signal from the cluster sample is stronger than expected and leads to a rather low matter density {Omega}{sub m} h{sup 2} = 0.093 {+-} 0.0077(1{sigma}), which deviates from the WMAP7 result by more than 3{sigma}. The correlation function of the GMBCG cluster sample is also calculated and our detection of the BAO feature is confirmed.

  2. REMOVING BARYON-ACOUSTIC-OSCILLATION PEAK SHIFTS WITH LOCAL DENSITY TRANSFORMS

    SciTech Connect

    McCullagh, Nuala; Neyrinck, Mark C.; Szalay, Alexander S.; Szapudi, Istvan

    2013-01-20

    Large-scale bulk flows in the universe distort the initial density field, broadening the baryon-acoustic-oscillation (BAO) feature that was imprinted when baryons were strongly coupled to photons. Additionally, there is a small shift inward in the peak of the conventional overdensity correlation function, a mass-weighted statistic. This shift occurs when high-density peaks move toward each other. We explore whether this shift can be removed by applying to the density field a transform (such as a logarithm) that gives fairer statistical weight to fluctuations in underdense regions. Using configuration-space perturbation theory in the Zel'dovich approximation, we find that the log-density correlation function shows a much smaller inward shift in the position of the BAO peak at low redshift than is seen in the overdensity correlation function. We also show that if the initial, Lagrangian density of matter parcels could be estimated at their Eulerian positions, giving a displaced-initial-density field, its peak shift would be even smaller. In fact, a transformed field that accentuates underdensities, such as the reciprocal of the density, pushes the peak the other way, outward. In our model, these shifts in the peak position can be attributed to shift terms, involving the derivative of the linear correlation function, that entirely vanish in this displaced-initial-density field.

  3. A Detection of Baryon Acoustic Oscillations from the Distribution of Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Hong, Tao; Han, J. L.; Wen, Z. L.

    2016-08-01

    We calculate the correlation function of 79,091 galaxy clusters in the redshift region of z≤slant 0.5, selected from the WH15 cluster catalog. With a weight of cluster mass, a significant baryon acoustic oscillation (BAO) peak is detected on the correlation function with a significance of 3.7σ . By fitting the correlation function with a ΛCDM model curve, we find {D}v(z=0.331){r}d{fid}/{r}d=1261.5+/- 48 Mpc, which is consistent with the Planck 2015 cosmology. We find that the correlation function of the higher mass sub-sample shows a higher amplitude at small scales of r\\lt 80 {h}-1 {{Mpc}}, which is consistent with our previous result. The two-dimensional correlation function of this large sample of galaxy clusters shows a faint BAO ring with a significance of 1.8σ , from which we find that the distance scale parameters on directions across and along the line of sight are {α }σ =1.02+/- 0.06 and {α }π =0.94+/- 0.10, respectively.

  4. Plasma Shape Effects on Geodesic Acoustic Oscillations

    SciTech Connect

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

    2006-11-30

    Geodesic acoustic mode (GAM) oscillations in tokamak plasmas are known to be sensitive to the value of the safety factor q. Through its linear and nonlinear interactions with ITG turbulence it has recently been shown in direct numerical global simulations that the turbulence driven heat transport is larger when GAM oscilations of large amplitude are present, resulting in an anomalous transport scaling with the inverse plasma current. GAM dispersion relations have been derived for circular, large aspect ratio configurations, and, recently, for helical configurations. Linear simulation results are presented using the global, PIC, finite element codes GYGLES and ORB5 for the GAM frequency, damping rate and Rosenbluth-Hinton residual zonal flow for a scan in plasma elongation. It is found that CAM frequency slightly decreases, while GAM damping rate and residual zonal flows increase with elongation. Nonlinear ITG simulations using the ORB5 code show that elongation reduces heat transport and that this is related to the plasma current and not q alone.

  5. Investigation of acoustic streaming patterns around oscillating sharp edges

    PubMed Central

    Nama, Nitesh; Huang, Po-Hsun; Huang, Tony Jun; Costanzo, Francesco

    2014-01-01

    Oscillating sharp edges have been employed to achieve rapid and homogeneous mixing in microchannels using acoustic streaming. Here we use a perturbation approach to study the flow around oscillating sharp edges in a microchannel. This work extends prior experimental studies to numerically characterize the effect of various parameters on the acoustically induced flow. Our numerical results match well with the experimental results. We investigated multiple device parameters such as the tip angle, oscillation amplitude, and channel dimensions. Our results indicate that, due to the inherent nonlinearity of acoustic streaming, the channel dimensions could significantly impact the flow patterns and device performance. PMID:24903475

  6. Behaviour of a Premixed Flame Subjected to Acoustic Oscillations

    PubMed Central

    Qureshi, Shafiq R.; Khan, Waqar A.; Prosser, Robert

    2013-01-01

    In this paper, a one dimensional premixed laminar methane flame is subjected to acoustic oscillations and studied. The purpose of this analysis is to investigate the effects of acoustic perturbations on the reaction rates of different species, with a view to their respective contribution to thermoacoustic instabilities. Acoustically transparent non reflecting boundary conditions are employed. The flame response has been studied with acoustic waves of different frequencies and amplitudes. The integral values of the reaction rates, the burning velocities and the heat release of the acoustically perturbed flame are compared with the unperturbed case. We found that the flame's sensitivity to acoustic perturbations is greatest when the wavelength is comparable to the flame thickness. Even in this case, the perturbations are stable with time. We conclude that acoustic fields acting on the chemistry do not contribute significantly to the emergence of large amplitude pressure oscillations. PMID:24376501

  7. Thermal acoustic oscillations, volume 2. [cryogenic fluid storage

    NASA Technical Reports Server (NTRS)

    Spradley, L. W.; Sims, W. H.; Fan, C.

    1975-01-01

    A number of thermal acoustic oscillation phenomena and their effects on cryogenic systems were studied. The conditions which cause or suppress oscillations, the frequency, amplitude and intensity of oscillations when they exist, and the heat loss they induce are discussed. Methods of numerical analysis utilizing the digital computer were developed for use in cryogenic systems design. In addition, an experimental verification program was conducted to study oscillation wave characteristics and boiloff rate. The data were then reduced and compared with the analytical predictions.

  8. Tension between SNeIa and BAO: current status and future forecasts

    SciTech Connect

    Escamilla-Rivera, Celia; Lazkoz, Ruth; Salzano, Vincenzo; Sendra, Irene E-mail: ruth.lazkoz@ehu.es E-mail: irene.sendra@ehu.es

    2011-09-01

    Using real and synthetic Type Ia SNe (SNeIa) and baryon acoustic oscillations (BAO) data representing current observations forecasts, this paper investigates the tension between those probes in the dark energy equation of state (EoS) reconstruction considering the well known CPL model and Wang's low correlation reformulation. In particular, here we present simulations of BAO data from both the the radial and transverse directions. We also explore the influence of priors on Ω{sub m} and Ω{sub b} on the tension issue, by considering 1σ deviations in either one or both of them. Our results indicate that for some priors there is no tension between a single dataset (either SNeIa or BAO) and their combination (SNeIa+BAO). Our criterion to discern the existence of tension (σ-distance) is also useful to establish which is the dataset with most constraining power; in this respect SNeIa and BAO data switch roles when current and future data are considered, as forecasts predict and spectacular quality improvement on BAO data. We also find that the results on the tension are blind to the way the CPL model is addressed: there is a perfect match between the original formulation and that by the correlation optimized proposed in Wang (2008), but the errors on the parameters are much narrower in all cases of our exhaustive exploration, thus serving the purpose of stressing the convenience of this reparametrization.

  9. Thermal Acoustic Oscillation: Causes, Detection, Analysis and Prevention

    NASA Technical Reports Server (NTRS)

    Christie, Robert J.; Hartwig, Jason W.

    2014-01-01

    The presentation discusses the causes of Thermal Acoustic Oscillations, how it can be detected, analyzed and prevented. It also discusses where it can occur, where it doesn't occur and practical mitigation techniques.

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

    NASA Astrophysics Data System (ADS)

    Rajabi, Majid; Mojahed, Alireza

    2016-11-01

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

  11. Redshift weights for baryon acoustic oscillations: application to mock galaxy catalogues

    NASA Astrophysics Data System (ADS)

    Zhu, Fangzhou; Padmanabhan, Nikhil; White, Martin; Ross, Ashley J.; Zhao, Gongbo

    2016-09-01

    Large redshift surveys capable of measuring the baryon acoustic oscillation (BAO) signal have proven to be an effective way of measuring the distance-redshift relation in cosmology. Building off the work in Zhu et al., we develop a technique to directly constrain the distance-redshift relation from BAO measurements without splitting the sample into redshift bins. We apply the redshift weighting technique in Zhu et al. to the clustering of galaxies from 1000 Quick particle mesh (QPM) mock simulations after reconstruction and achieve a 0.75 per cent measurement of the angular diameter distance DA at z = 0.64 and the same precision for Hubble parameter H at z = 0.29. These QPM mock catalogues mimic the clustering and noise level of the Baryon Oscillation Spectroscopic Survey Data Release 12 (DR12). We compress the correlation functions in the redshift direction on to a set of weighted correlation functions. These estimators give unbiased DA and H measurements across the entire redshift range of the combined sample. We demonstrate the effectiveness of redshift weighting in improving the distance and Hubble parameter estimates. Instead of measuring at a single `effective' redshift as in traditional analyses, we report our DA and H measurements at all redshifts. The measured fractional error of DA ranges from 1.53 per cent at z = 0.2 to 0.75 per cent at z = 0.64. The fractional error of H ranges from 0.75 per cent at z = 0.29 to 2.45 per cent at z = 0.7. Our measurements are consistent with a Fisher forecast to within 10-20 per cent depending on the pivot redshift. We further show the results are robust against the choice of fiducial cosmologies, galaxy bias models, and redshift-space distortions streaming parameters.

  12. Optimizing baryon acoustic oscillation surveys - II. Curvature, redshifts and external data sets

    NASA Astrophysics Data System (ADS)

    Parkinson, David; Kunz, Martin; Liddle, Andrew R.; Bassett, Bruce A.; Nichol, Robert C.; Vardanyan, Mihran

    2010-02-01

    We extend our study of the optimization of large baryon acoustic oscillation (BAO) surveys to return the best constraints on the dark energy, building on Paper I of this series by Parkinson et al. The survey galaxies are assumed to be pre-selected active, star-forming galaxies observed by their line emission with a constant number density across the redshift bin. Star-forming galaxies have a redshift desert in the region 1.6 < z < 2, and so this redshift range was excluded from the analysis. We use the Seo & Eisenstein fitting formula for the accuracies of the BAO measurements, using only the information for the oscillatory part of the power spectrum as distance and expansion rate rulers. We go beyond our earlier analysis by examining the effect of including curvature on the optimal survey configuration and updating the expected `prior' constraints from Planck and the Sloan Digital Sky Survey. We once again find that the optimal survey strategy involves minimizing the exposure time and maximizing the survey area (within the instrumental constraints), and that all time should be spent observing in the low-redshift range (z < 1.6) rather than beyond the redshift desert, z > 2. We find that, when assuming a flat universe, the optimal survey makes measurements in the redshift range 0.1 < z < 0.7, but that including curvature as a nuisance parameter requires us to push the maximum redshift to 1.35, to remove the degeneracy between curvature and evolving dark energy. The inclusion of expected other data sets (such as WiggleZ, the Baryon Oscillation Spectroscopic Survey and a stage III Type Ia supernova survey) removes the necessity of measurements below redshift 0.9, and pushes the maximum redshift up to 1.5. We discuss considerations in determining the best survey strategy in light of uncertainty in the true underlying cosmological model.

  13. The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations in Fourier-space

    DOE PAGES

    Beutler, Florian; Seo, Hee -Jong; Ross, Ashley J.; McDonald, Patrick; Saito, Shun; Bolton, Adam S.; Joel R. Brownstein; Chuang, Chia -Hsun; Cuesta, Antonio J.; Eisenstein, Daniel J.; et al

    2016-07-13

    Here, we analyse the Baryon Acoustic Oscillation (BAO) signal of the final Baryon Oscillation Spectroscopic Survey (BOSS) data release (DR12). Our analysis is performed in Fourier-space, using the power spectrum monopole and quadrupole. The dataset includes 1 198 006 galaxies over the redshift range 0.2 < z < 0.75. We divide this dataset into three (overlapping) redshift bins with the effective redshifts zeff = 0.38, 0.51 and 0.61. We demonstrate the reliability of our analysis pipeline using N-body simulations as well as 1000 MultiDark-Patchy mock catalogues, which mimic the BOSS-DR12 target selection. We apply density eld reconstruction to enhance themore » BAO signal-to-noise ratio. By including the power spectrum quadrupole we can sep-arate the line-of-sight and angular modes, which allows us to constrain the angular diameter distance DA(z) and the Hubble parameter H ( z ) separately. We obtain two independent 1 : 6% and 1 : 5% constraints on DA(z) and 2.9% and 2.3% constraints on H(z) for the low (zeff = 0.38) and high (zeff = 0.61) redshift bin, respectively. We obtain two independent 1% and 0.9% constraints on the angular averaged distance DV(z), when ignoring the Alcock-Paczynski e ect. The detection significance of the BAO signal is of the order of 8σ (post-reconstruction) for each of the three redshift bins. Our results are in good agreement with the Planck prediction within CDM. This paper is part of a set that analyses the final galaxy clustering dataset from BOSS. The measurements and likelihoods presented here are combined with others in Alam et al. (2016) to produce the final cosmological constraints from BOSS.« less

  14. The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations in Fourier-space

    NASA Astrophysics Data System (ADS)

    Beutler, Florian; Seo, Hee-Jong; Ross, Ashley J.; McDonald, Patrick; Saito, Shun; Bolton, Adam S.; Brownstein, Joel R.; Chuang, Chia-Hsun; Cuesta, Antonio J.; Eisenstein, Daniel J.; Font-Ribera, Andreu; Grieb, Jan Niklas; Hand, Nick; Kitaura, Francisco-Shu; Modi, Chirag; Nichol, Robert C.; Percival, Will J.; Prada, Francisco; Rodriguez-Torres, Sergio; Roe, Natalie A.; Ross, Nicholas P.; Salazar-Albornoz, Salvador; Sánchez, Ariel G.; Schneider, Donald P.; Slosar, Anže; Tinker, Jeremy; Tojeiro, Rita; Vargas-Magaña, Mariana; Vazquez, Jose A.

    2016-09-01

    We analyse the Baryon Acoustic Oscillation (BAO) signal of the final Baryon Oscillation Spectroscopic Survey (BOSS) data release (DR12). Our analysis is performed in Fourier-space, using the power spectrum monopole and quadrupole. The dataset includes 1 198 006 galaxies over the redshift range 0.2 < z < 0.75. We divide this dataset into three (overlapping) redshift bins with the effective redshifts zeff = 0.38, 0.51 and 0.61. We demonstrate the reliability of our analysis pipeline using N-body simulations as well as ˜1000 MultiDark-Patchy mock catalogues, which mimic the BOSS-DR12 target selection. We apply density field reconstruction to enhance the BAO signal-to-noise ratio. By including the power spectrum quadrupole we can separate the line-of-sight and angular modes, which allows us to constrain the angular diameter distance DA(z) and the Hubble parameter H(z) separately. We obtain two independent 1.6% and 1.5% constraints on DA(z) and 2.9% and 2.3% constraints on H(z) for the low (zeff = 0.38) and high (zeff = 0.61) redshift bin, respectively. We obtain two independent 1% and 0.9% constraints on the angular averaged distance DV(z), when ignoring the Alcock-Paczynski effect. The detection significance of the BAO signal is of the order of 8σ (post-reconstruction) for each of the three redshift bins. Our results are in good agreement with the Planck prediction within ΛCDM. This paper is part of a set that analyses the final galaxy clustering dataset from BOSS. The measurements and likelihoods presented here are combined with others in Alam et al. (2016) to produce the final cosmological constraints from BOSS.

  15. BigBOSS: The Ground-Based Stage IV BAO Experiment

    SciTech Connect

    Schlegel, David; Bebek, Chris; Heetderks, Henry; Ho, Shirley; Lampton, Michael; Levi, Michael; Mostek, Nick; Padmanabhan, Nikhil; Perlmutter, Saul; Roe, Natalie; Sholl, Michael; Smoot, George; White, Martin; Dey, Arjun; Abraham, Tony; Jannuzi, Buell; Joyce, Dick; Liang, Ming; Merrill, Mike; Olsen, Knut; Salim, Samir

    2009-04-01

    The BigBOSS experiment is a proposed DOE-NSF Stage IV ground-based dark energy experiment to study baryon acoustic oscillations (BAO) and the growth of structure with an all-sky galaxy redshift survey. The project is designed to unlock the mystery of dark energy using existing ground-based facilities operated by NOAO. A new 4000-fiber R=5000 spectrograph covering a 3-degree diameter field will measure BAO and redshift space distortions in the distribution of galaxies and hydrogen gas spanning redshifts from 0.2< z< 3.5. The Dark Energy Task Force figure of merit (DETF FoM) for this experiment is expected to be equal to that of a JDEM mission for BAO with the lower risk and cost typical of a ground-based experiment.

  16. Sectorial oscillation of acoustically levitated nanoparticle-coated droplet

    NASA Astrophysics Data System (ADS)

    Zang, Duyang; Chen, Zhen; Geng, Xingguo

    2016-01-01

    We have investigated the dynamics of a third mode sectorial oscillation of nanoparticle-coated droplets using acoustic levitation in combination with active modulation. The presence of nanoparticles at the droplet surface changes its oscillation amplitude and frequency. A model linking the interfacial rheology and oscillation dynamics has been proposed in which the compression modulus ɛ of the particle layer is introduced into the analysis. The ɛ obtained with the model is in good agreement with that obtained by the Wilhelmy plate approach, highlighting the important role of interfacial rheological properties in the sectorial oscillation of droplets.

  17. MODEL-INDEPENDENT EVIDENCE FOR DARK ENERGY EVOLUTION FROM BARYON ACOUSTIC OSCILLATIONS

    SciTech Connect

    Sahni, V.; Shafieloo, A.; Starobinsky, A. A. E-mail: arman@apctp.org

    2014-10-01

    Baryon acoustic oscillations (BAOs) allow us to determine the expansion history of the universe, thereby shedding light on the nature of dark energy. Recent observations of BAOs in the Sloan Digital Sky Survey (SDSS) DR9 and DR11 have provided us with statistically independent measurements of H(z) at redshifts of 0.57 and 2.34, respectively. We show that these measurements can be used to test the cosmological constant hypothesis in a model-independent manner by means of an improved version of the Om diagnostic. Our results indicate that the SDSS DR11 measurement of H(z) = 222 ± 7 km s{sup –1} Mpc{sup –1} at z = 2.34, when taken in tandem with measurements of H(z) at lower redshifts, imply considerable tension with the standard ΛCDM model. Our estimation of the new diagnostic Omh {sup 2} from SDSS DR9 and DR11 data, namely, Omh {sup 2} ≈ 0.122 ± 0.01, which is equivalent to Ω{sub 0m} h {sup 2} for the spatially flat ΛCDM model, is in tension with the value Ω{sub 0m} h {sup 2} = 0.1426 ± 0.0025 determined for ΛCDM from Planck+WP. This tension is alleviated in models in which the cosmological constant was dynamically screened (compensated) in the past. Such evolving dark energy models display a pole in the effective equation of state of dark energy at high redshifts, which emerges as a smoking gun test for these theories.

  18. Precision surface-acoustic-wave (SAW) oscillators.

    PubMed

    Parker, T E; Montress, G K

    1988-01-01

    The evolution of SAW oscillator technology over the past 17 years is described and a review of the current state of the art for high-performance SAW oscillators is presented. This review draws heavily upon the authors' own experience and efforts, which have focused upon the development of a wide variety of SAW oscillators in response to numerous high-performance military system requirements. PMID:18290160

  19. Acoustic Bloch oscillations in a two-dimensional phononic crystal.

    PubMed

    He, Zhaojian; Peng, Shasha; Cai, Feiyan; Ke, Manzhu; Liu, Zhengyou

    2007-11-01

    We report the observation of acoustic Bloch oscillations at megahertz frequency in a two-dimensional phononic crystal. By creating periodically arrayed cavities with a decreasing gradient in width along one direction in the phononic crystal, acoustic Wannier-Stark ladders are created in the frequency domain. The oscillatory motion of an incident Gaussian pulse inside the sample is demonstrated by both simulation and experiment.

  20. Single Molecule as a Local Acoustic Detector for Mechanical Oscillators

    NASA Astrophysics Data System (ADS)

    Tian, Yuxi; Navarro, Pedro; Orrit, Michel

    2014-09-01

    A single molecule can serve as a nanometer-sized detector of acoustic strain. Such a nanomicrophone has the great advantage that it can be placed very close to acoustic signal sources and high sensitivities can be achieved. We demonstrate this scheme by monitoring the fluorescence intensity of a single dibenzoterrylene molecule in an anthracene crystal attached to an oscillating tuning fork. The characterization of the vibration amplitude and of the detection sensitivity is a first step towards detection and control of nanomechanical oscillators through optical detection and feedback.

  1. THE BARYON ACOUSTIC OSCILLATION BROADBAND AND BROAD-BEAM ARRAY: DESIGN OVERVIEW AND SENSITIVITY FORECASTS

    SciTech Connect

    Pober, Jonathan C.; Parsons, Aaron R.; McQuinn, Matthew; Ali, Zaki; DeBoer, David R.; McDonald, Patrick; Aguirre, James E.; Bradley, Richard F.; Chang, Tzu-Ching; Morales, Miguel F.

    2013-03-15

    This work describes a new instrument optimized for a detection of the neutral hydrogen 21 cm power spectrum between redshifts of 0.5 and 1.5: the Baryon Acoustic Oscillation Broadband and Broad-beam (BAOBAB) array. BAOBAB will build on the efforts of a first generation of 21 cm experiments that are targeting a detection of the signal from the Epoch of Reionization at z {approx} 10. At z {approx} 1, the emission from neutral hydrogen in self-shielded overdense halos also presents an accessible signal, since the dominant, synchrotron foreground emission is considerably fainter than at redshift 10. The principle science driver for these observations are baryon acoustic oscillations in the matter power spectrum which have the potential to act as a standard ruler and constrain the nature of dark energy. BAOBAB will fully correlate dual-polarization antenna tiles over the 600-900 MHz band with a frequency resolution of 300 kHz and a system temperature of 50 K. The number of antennas will grow in staged deployments, and reconfigurations of the array will allow for both traditional imaging and high power spectrum sensitivity operations. We present calculations of the power spectrum sensitivity for various array sizes, with a 35 element array measuring the cosmic neutral hydrogen fraction as a function of redshift, and a 132 element system detecting the BAO features in the power spectrum, yielding a 1.8% error on the z {approx} 1 distance scale, and, in turn, significant improvements to constraints on the dark energy equation of state over an unprecedented range of redshifts from {approx}0.5 to 1.5.

  2. Bloch oscillations of THz acoustic phonons in coupled nanocavity structures.

    PubMed

    Lanzillotti-Kimura, N D; Fainstein, A; Perrin, B; Jusserand, B; Mauguin, O; Largeau, L; Lemaître, A

    2010-05-14

    Nanophononic Bloch oscillations and Wannier-Stark ladders have been recently predicted to exist in specifically tailored structures formed by coupled nanocavities. Using pump-probe coherent phonon generation techniques we demonstrate that Bloch oscillations of terahertz acoustic phonons can be directly generated and probed in these complex nanostructures. In addition, by Fourier transforming the time traces we had access to the proper eigenmodes in the frequency domain, thus evidencing the related Wannier-Stark ladder. The observed Bloch oscillation dynamics are compared with simulations based on a model description of the coherent phonon generation and photoelastic detection processes.

  3. Quantum ion-acoustic wave oscillations in metallic nanowires

    SciTech Connect

    Moradi, Afshin

    2015-05-15

    The low-frequency electrostatic waves in metallic nanowires are studied using the quantum hydrodynamic model, in which the electron and ion components of the system are regarded as a two-species quantum plasma system. The Poisson equation as well as appropriate quantum boundary conditions give the analytical expressions of dispersion relations of the surface and bulk quantum ion-acoustic wave oscillations.

  4. Oscillations of a deformed liquid drop in an acoustic field

    NASA Astrophysics Data System (ADS)

    Shi, Tao; Apfel, Robert E.

    1995-07-01

    The oscillations of an axially symmetric liquid drop in an acoustic standing wave field in air have been studied using the boundary integral method. The interaction between the drop oscillation and sound field has been included in this analysis. Our computations focus on the frequency shift of small-amplitude oscillations of an acoustically deformed drop typical of a drop levitated in air. In the presence or absence of gravity, the trend and the magnitude of the frequency shift have been given in terms of drop size, drop deformation, and the strength of the sound field. Our calculations are compared with experiments performed on the United States Microgravity Laboratory (USML-1) and with ground-based measurements, and are found to be in good agreement within the accuracy of the experimental data.

  5. Constraints on the Dvali-Gabadadze-Porrati Model from Recent Supernova Observations and Baryon Acoustic Oscillations

    NASA Astrophysics Data System (ADS)

    Guo, Zong-Kuan; Zhu, Zong-Hong; Alcaniz, J. S.; Zhang, Yuan-Zhong

    2006-07-01

    Although there is mounting observational evidence that the expansion of our universe is undergoing a late-time acceleration, the mechanism for this acceleration is yet unknown. In the so-called Dvali-Gabadadze-Porrati (DGP) model this phenomenon is attributed to gravitational ``leakage'' into extra dimensions. In this work, we mainly focus our attention on the constraints on the model from the ``gold sample'' of Type Ia supernovae (SNe Ia), the first-year data from the Supernova Legacy Survey (SNLS), and the baryon acoustic oscillation (BAO) peak found in the Sloan Digital Sky Survey (SDSS). At 99.73% confidence level, the combination of the three databases provides Ωm=0.270+0.018-0.017 and Ωrc=0.216+0.012-0.013 (hence, a spatially closed universe with Ωk=-0.350+0.080-0.083), which seems to be in contradiction with the most recent WMAP results indicating a flat universe. Based on this result, we also estimated the transition redshift (at which the universe switches from deceleration to acceleration) to be 0.70

  6. Redshift-space Enhancement of Line-of-sight Baryon Acoustic Oscillations in the Sloan Digital Sky Survey Main-galaxy Sample

    NASA Astrophysics Data System (ADS)

    Tian, H. J.; Neyrinck, Mark C.; Budavári, Tamás; Szalay, Alexander S.

    2011-02-01

    We show that redshift-space distortions of galaxy correlations have a strong effect on correlation functions with distinct, localized features, like the signature of the baryon acoustic oscillations (BAO). Near the line of sight, the features become sharper as a result of redshift-space distortions. We demonstrate this effect by measuring the correlation function in Gaussian simulations and the Millennium simulation. We also analyze the SDSS DR7 main-galaxy sample, splitting the sample into slices 2fdg5 on the sky in various rotations. Measuring two-dimensional correlation functions in each slice, we do see a sharp bump along the line of sight. Using Mexican-hat wavelets, we localize it to (110 ± 10) h -1 Mpc. Averaging only along the line of sight, we estimate its significance at a particular wavelet scale and location at 2.2σ. In a flat angular weighting in the (π, rp ) coordinate system, the noise level is suppressed, pushing the bump's significance to 4σ. We estimate that there is about a 0.2% chance of getting such a signal anywhere in the vicinity of the BAO scale from a power spectrum lacking a BAO feature. However, these estimates of the significances make some use of idealized Gaussian simulations, and thus are likely a bit optimistic.

  7. Redshift-Space Enhancement of Line-of-Sight Baryon Acoustic Oscillations in the Sloan Digital Sky Survey Main-Galaxy Sample

    NASA Astrophysics Data System (ADS)

    Tian, Haijun; Neyrinck, Mark C.; Budavari, Tamas; SZALAY, AlEXANDER

    2015-08-01

    We show that redshift-space distortions of galaxy correlations have a strong effect on correlation functions with distinct, localized features, like the signature of the baryon acoustic oscillations (BAO). Near the line of sight, the features become sharper as a result of redshift-space distortions. We demonstrate this effect by measuring the correlation function in Gaussian simulations and the Millennium simulation. We also analyze the SDSS DR7 main-galaxy sample, splitting the sample into slices 2.5 on the sky in various rotations. Measuring two-dimensional correlation functions in each slice, we do see a sharp bump along the line of sight. Using Mexican-hat wavelets, we localize it to (110 ± 10) Mpc/h. Averaging only along the line of sight, we estimate its significance at a particular wavelet scale and location at 2.2σ. In a flat angular weighting in the (π,rp) coordinate system, the noise level is suppressed, pushing the bump’s significance to 4σ . We estimate that there is about a 0.2% chance of getting such a signal anywhere in the vicinity of the BAO scale from a power spectrum lacking a BAO feature. However, these estimates of the significances make some use of idealized Gaussian simulations, and thus are likely a bit optimistic.

  8. Direct observation of acoustic oscillations in InAs nanowires.

    PubMed

    Mariager, Simon O; Khakhulin, Dmitry; Lemke, Henrik T; Kjaer, Kasper S; Guerin, Laurent; Nuccio, Laura; Sørensen, Claus B; Nielsen, Martin M; Feidenhans'l, Robert

    2010-07-14

    Time-resolved X-ray diffraction and optical reflectivity are used to directly measure three different acoustic oscillations of InAs nanowires. The oscillations are excited by a femtosecond laser pulse and evolve at three different time scales. We measure the absolute scale of the initial radial expansion of the fundamental breathing eigenmode and determine the frequency by transient optical reflectivity. For the extensional eigenmode we measure the oscillations of the average radial and axial lattice constants and determine the amplitude of oscillations and the average extension. Finally we observe a bending motion of the nanowires. The frequencies of the eigenmodes are in good agreements with predictions made by continuum elasticity theory and we find no difference in the speed of sound between the wurtzite nanowires and cubic bulk crystals, but the measured strain is influenced by the interaction between different modes. The wurtzite crystal structure of the nanowires however has an anisotropic thermal expansion.

  9. Magnetophonon oscillations caused by acoustic phonons in bulk conductors

    NASA Astrophysics Data System (ADS)

    Raichev, O. E.

    2016-09-01

    The interaction of electrons with acoustic phonons under a magnetic field leads to a remarkable kind of magnetophonon oscillation of transport coefficients, recently discovered in two-dimensional electron systems. The present study shows that similar oscillations exist in bulk conductors and provides a theory of this phenomenon for the case of spherical Fermi surfaces. The resonance peaks occur when the product of the Fermi surface diameter by the sound velocity is a multiple of the cyclotron frequency. Theoretical predictions may facilitate the experimental observation of the phenomenon.

  10. Vertical vibration and shape oscillation of acoustically levitated water drops

    SciTech Connect

    Geng, D. L.; Xie, W. J.; Yan, N.; Wei, B.

    2014-09-08

    We present the vertical harmonic vibration of levitated water drops within ultrasound field. The restoring force to maintain such a vibration mode is provided by the resultant force of acoustic radiation force and drop gravity. Experiments reveal that the vibration frequency increases with the aspect ratio for drops with the same volume, which agrees with the theoretical prediction for those cases of nearly equiaxed drops. During the vertical vibration, the floating drops undergo the second order shape oscillation. The shape oscillation frequency is determined to be twice the vibration frequency.

  11. Vertical vibration and shape oscillation of acoustically levitated water drops

    NASA Astrophysics Data System (ADS)

    Geng, D. L.; Xie, W. J.; Yan, N.; Wei, B.

    2014-09-01

    We present the vertical harmonic vibration of levitated water drops within ultrasound field. The restoring force to maintain such a vibration mode is provided by the resultant force of acoustic radiation force and drop gravity. Experiments reveal that the vibration frequency increases with the aspect ratio for drops with the same volume, which agrees with the theoretical prediction for those cases of nearly equiaxed drops. During the vertical vibration, the floating drops undergo the second order shape oscillation. The shape oscillation frequency is determined to be twice the vibration frequency.

  12. Quasi-normal acoustic oscillations in the transonic Bondi flow

    NASA Astrophysics Data System (ADS)

    Chaverra, Eliana; Sarbach, Olivier

    2016-01-01

    We analyze the dynamics of nonspherical acoustic perturbations of the transonic Bondi flow, describing the steady radial accretion of a polytropic perfect fluid into a gravity center. The propagation of such perturbations can be described by a wave equation on the curved effective background geometry determined by the acoustic metric introduced by Unruh in the context of experimental black hole evaporation. We show that for the transonic Bondi flow, Unruh's acoustic metric describes an analogue black hole and that the acoustic perturbations undergo quasi-normal oscillations. The associated quasi-normal frequencies are computed and they are proven to scale like the surface gravity of the acoustic black hole. This provides an explanation for results given in an earlier work, where it was shown that the acoustic perturbations of a relativistic fluid accreted by a nonrotating black hole possess quasi-normal modes, and where it was found empirically that the associated frequencies scaled like the surface gravity of the analogue black hole in the limit where the radius of the sonic horizon is much larger than the Schwarzschild radius.

  13. Oscillating load-induced acoustic emission in laboratory experiment

    USGS Publications Warehouse

    Ponomarev, Alexander; Lockner, David A.; Stroganova, S.; Stanchits, S.; Smirnov, V.

    2010-01-01

    Spatial and temporal patterns of acoustic emission (AE) were studied. A pre-fractured cylinder of granite was loaded in a triaxial machine at 160 MPa confining pressure until stick-slip events occurred. The experiments were conducted at a constant strain rate of 10−7 s−1 that was modulated by small-amplitude sinusoidal oscillations with periods of 175 and 570 seconds. Amplitude of the oscillations was a few percent of the total load and was intended to simulate periodic loading observed in nature (e.g., earth tides or other sources). An ultrasonic acquisition system with 13 piezosensors recorded acoustic emissions that were generated during deformation of the sample. We observed a correlation between AE response and sinusoidal loading. The effect was more pronounced for higher frequency of the modulating force. A time-space spectral analysis for a “point” process was used to investigate details of the periodic AE components. The main result of the study was the correlation of oscillations of acoustic activity synchronized with the applied oscillating load. The intensity of the correlated AE activity was most pronounced in the “aftershock” sequences that followed large-amplitude AE events. We suggest that this is due to the higher strain-sensitivity of the failure area when the sample is in a transient, unstable mode. We also found that the synchronization of AE activity with the oscillating external load nearly disappeared in the period immediately after the stick-slip events and gradually recovered with further loading.

  14. Electromagnetically actuated micromanipulator using an acoustically oscillating bubble

    NASA Astrophysics Data System (ADS)

    Kwon, J. O.; Yang, J. S.; Lee, S. J.; Rhee, K.; Chung, S. K.

    2011-11-01

    A novel non-invasive micromanipulation technique has been developed where a microrobot swimming in an aqueous medium manipulates micro-objects, through electromagnetic actuation using an acoustically oscillating bubble attached to the microrobot as a grasping tool. This micromanipulation concept was experimentally verified; an investigation of electromagnetic actuation and acoustic excitation was also performed. Two-dimensional propulsion of a magnetic piece was demonstrated through electromagnetic actuation, using three pairs of electric coils surrounding the water chamber, and confirming that the propulsion speed of the magnetic piece was linearly proportional to the applied current intensity. Micro-object manipulation was separately demonstrated using an air bubble with glass beads (80 µm diameter) and a steel ball (800 µm diameter) in an aqueous medium. Upon acoustic excitation of the bubble by a piezo-actuator around its resonant frequency, the generated radiation force attracted and captured the neighboring glass beads and steel ball. The grasping force was indirectly measured by exposing the glass beads captured by the oscillating bubble to a stream generated by an auto-syringe pump in a mini-channel. By measuring the maximum speed of the streaming flow when the glass beads detached from the oscillating bubble and flowed downstream, the grasping force was calculated as 50 nN, based on Stokes' drag approximation. Finally, a fish egg was successfully manipulated with the integration of electromagnetic actuation and acoustic excitation, using a mini-robot consisting of a millimeter-sized magnetic piece with a bubble attached to its bottom. This novel micromanipulation may be an efficient tool for both micro device assembly and single-cell manipulation.

  15. Measurement of baryon acoustic oscillations in the Lyman-α forest fluctuations in BOSS data release 9

    SciTech Connect

    Slosar, Anže; Iršič, Vid; Kirkby, David; Blomqvist, Michael; Bailey, Stephen; Carithers, Bill; Busca, Nicolás G.; Aubourg, Éric; Bautista, Julian E.; Bhardwaj, Vaishali; Bolton, Adam S.; Brownstein, Joel; Dawson, Kyle S.; Bovy, Jo; Croft, Rupert A.C.; Ho, Shirley; Font-Ribera, Andreu; and others

    2013-04-01

    We use the Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 9 (DR9) to detect and measure the position of the Baryonic Acoustic Oscillation (BAO) feature in the three-dimensional correlation function in the Lyman-α flux fluctuations at a redshift z{sub eff} = 2.4. The feature is clearly detected at significance between 3 and 5 sigma (depending on the broadband model and method of error covariance matrix estimation) and is consistent with predictions of the standard ΛCDM model. We assess the biases in our method, stability of the error covariance matrix and possible systematic effects. We fit the resulting correlation function with several models that decouple the broadband and acoustic scale information. For an isotropic dilation factor, we measure 100 × (α{sub iso} − 1) = −1.6{sup +2.0+4.3+7.4}{sub −2.0−4.1−6.8} (stat.) ±1.0 (syst.) (multiple statistical errors denote 1,2 and 3 sigma confidence limits) with respect to the acoustic scale in the fiducial cosmological model (flat ΛCDM with Ω{sub m} = 0.27, h = 0.7). When fitting separately for the radial and transversal dilation factors we find marginalised constraints 100 × (α{sub ||} − 1) = −1.3{sup +3.5+7.6+12.3}{sub −3.3−6.7−10.2} (stat.) ±2.0 (syst.) and 100 × (α{sub p}erpendicular − 1) = −2.2{sup +7.4+17}{sub −7.1−15} (stat.) ±3.0 (syst.). The dilation factor measurements are significantly correlated with cross-correlation coefficient of ∼ −0.55. Errors become significantly non-Gaussian for deviations over 3 standard deviations from best fit value. Because of the data cuts and analysis method, these measurements give tighter constraints than a previous BAO analysis of the BOSS DR9 Lyman-α sample, providing an important consistency test of the standard cosmological model in a new redshift regime.

  16. The Acoustic Simple Harmonic Oscillator: Experimental Verification and Applications

    NASA Astrophysics Data System (ADS)

    Matteson, Sam

    2009-04-01

    In his famous volume, The Sensations of Tone, published in 1877, Hermann Helmholtz introduced a resonator that was central to his investigations of acoustics. This talk revisits the device that Helmholtz described and examines it as a manifestation of an acoustic simple harmonic oscillator (SHO). The presentation demonstrates that an enclosed volume which communicates with the outside world via a narrow tube exhibits a single strong frequency response in analogy to a mechanical SHO, along with weaker resonances of the air in the short pipe that comprises the ``neck.'' The investigations, furthermore, report results of a straightforward experiment that confirms the SHO model (with damping) and that is very accessible to undergraduate students using inexpensive equipment and internet-obtainable freeware. The current work also extends the analysis to include applications of the Helmholtz Resonator to several folk instruments, namely, the ocarina, whistling, and the ``bottle band.''

  17. Thermal Acoustic Oscillation: Causes, Detection, Analysis, and Prevention

    NASA Technical Reports Server (NTRS)

    Christie, R. J.; Hartwig, J. W.

    2014-01-01

    Thermal Acoustic Oscillations (TAO) can occur in cryogenic systems and produce significant sources of heat. This source of heat can increase the boil off rate of cryogenic propellants in spacecraft storage tanks and reduce mission life. This paper discusses the causes of TAO, how it can be detected, what analyses can be done to predict it, and how to prevent it from occurring.The paper provides practical insight into what can aggravate instability, practical methods for mitigation, and when TAO does not occur. A real life example of a cryogenic system with an unexpected heat source is discussed, along with how TAO was confirmed and eliminated.

  18. Impact of acoustic oscillations on thermal tornado stability

    NASA Astrophysics Data System (ADS)

    Belousova, A. O.; Golovanov, A. N.; Matveev, I. V.

    2012-09-01

    This paper presents physical modeling of thermal tornado under lab conditions. For the tested range of 0÷300 Hz, selective frequencies were discovered which facilitate the tornado decay. Data analysis was complemented by velocity profile measurement using LDV system LD-05M. The results on velocity pulsation at selected points were recalculated into coefficient of correlation between velocities and function cos(2π fΔ t i ) describing the acoustic oscillations. In the theoretical part of this paper, we present solution of dispersive equation of Euler's model and resulting boundary of stability for tornado existence. Satisfactory agreement between experiment and calculation has been observed.

  19. Damping criteria for thermal acoustic oscillations in slush and liquid hydrogen systems

    NASA Astrophysics Data System (ADS)

    Gu, Y. F.; Timmerhaus, K. D.

    Techniques for damping thermal acoustic oscillations in cryogenic systems are analyzed with emphasis on a number of the damping criteria. Theoretically, thermal acoustic oscillations can be damped by either reducing or increasing the radius of the tube, i.e., by increasing either the viscous or inertial resistance in the oscillation. It is found that increasing the tube radius will only provide the desired damping if the temperature ratio for the system is lower than the asymptotic value of the right-hand stability curve. Thermal acoustic oscillations may be damped by changing the temperature ratio along the tube. A minimum temperature ratio for initiating thermal acoustic oscillations in both normal boiling point and triple-point parahydrogen systems is about 5 when the open end of the tube is located above the liquid surface. Changing the length ratio of the warm section to the cold section is another option for damping thermal acoustic oscillations.

  20. A NEW STATISTIC FOR ANALYZING BARYON ACOUSTIC OSCILLATIONS

    SciTech Connect

    Xu, X.; Eisenstein, D. J.; Eckel, J.; Mehta, K.; Metchnik, M.; Pinto, P.; White, M.; Padmanabhan, N.; Seo, H.-J.

    2010-08-01

    We introduce a new statistic {omega}{sub l}(r{sub s}) for measuring and analyzing large-scale structure and particularly the baryon acoustic oscillations. {omega}{sub l}(r{sub s}) is a band-filtered, configuration space statistic that is easily implemented and has advantages over the traditional power spectrum and correlation function estimators. Unlike these estimators, {omega}{sub l}(r{sub s}) can localize most of the acoustic information into a single dip at the acoustic scale while avoiding sensitivity to the poorly constrained large-scale power (i.e., the integral constraint) through the use of a localized and compensated filter. It is also sensitive to anisotropic clustering through pair counting and does not require any binning of data. We measure the shift in the acoustic peak due to nonlinear effects using the monopole {omega}{sub 0}(r{sub s}) derived from subsampled dark matter (DM) catalogs as well as from mock galaxy catalogs created via halo occupation distribution modeling. All of these are drawn from 44 realizations of 1024{sup 3} particle DM simulations in a 1 h {sup -1} Gpc box at z = 1. We compare these shifts with those obtained from the power spectrum and conclude that the results agree. We therefore expect that distance measurements obtained from {omega}{sub 0}(r{sub s}) and P(k) will be consistent with each other. We also show that it is possible to extract the same amount of acoustic information by fitting over a finite range using either {omega}{sub 0}(r{sub s}) or P(k) derived from equal volume surveys.

  1. An investigation of thermally driven acoustical oscillations in helium systems

    SciTech Connect

    Fuerst, J.D.

    1990-08-01

    The phenomenon of thermal-acoustic oscillation is seen to arise spontaneously in gas columns subjected to steep temperature gradients, particularly in tubes connecting liquid helium reservoirs with the ambient environment. This if often the arrangement for installed cryogenic instrumentation and is accompanied by undesirably large heat transfer rates to the cold region. Experimental data are collected and matched to theoretical predictions of oscillatory behavior; these results are in good agreement with the analytical model and with previously collected data. The present experiment places the open ends of oscillating tubes of the various lengths and cross sections in communication with flowing helium in the subcooled, 2-phase, or superheated state while the other ends are maintained at some controlled, elevated temperature. Assorted cold end conditions are achieved through adjustments to the Fermilab Tevatron satellite test refrigerator to which the test cryostat is connected. The warm, closed ends of the tubes are maintained by isothermal baths of liquid nitrogen, ice water, and boiling water. The method is contrasted to previous arrangements whereby tubes are run from room temperature into or adjacent to a stagnant pool of liquid helium. Additionally, the effect of pulsations in the flowing helium stream is explored through operation of the refrigerator's wet and dry expanders during data collection. These data confirm the theory to which try were compared and support its use in the design of cryogenic sensing lines for avoidance of thermoacoustic oscillation.

  2. Acoustic analogue of electronic BLOCH oscillations and resonant Zener tunneling in ultrasonic superlattices.

    PubMed

    Sanchis-Alepuz, Helios; Kosevich, Yuriy A; Sánchez-Dehesa, José

    2007-03-30

    We demonstrate the existence of Bloch oscillations of acoustic fields in sound propagation through a superlattice of water cavities and layers of methyl methacrylate. To obtain the acoustic equivalent of a Wannier-Stark ladder, we employ a set of cavities with different thicknesses. Bloch oscillations are observed as time-resolved oscillations of transmission in a direct analogy to electronic Bloch oscillations in biased semiconductor superlattices. Moreover, for a particular gradient of cavity thicknesses, an overlap of two acoustic minibands occurs, which results in resonant Zener-like transmission enhancement.

  3. Acoustic Tests of Lorentz Symmetry Using Quartz Oscillators

    NASA Astrophysics Data System (ADS)

    Lo, Anthony; Haslinger, Philipp; Mizrachi, Eli; Anderegg, Loïc; Müller, Holger; Hohensee, Michael; Goryachev, Maxim; Tobar, Michael E.

    2016-01-01

    We propose and demonstrate a test of Lorentz symmetry based on new, compact, and reliable quartz oscillator technology. Violations of Lorentz invariance in the matter and photon sector of the standard model extension generate anisotropies in particles' inertial masses and the elastic constants of solids, giving rise to measurable anisotropies in the resonance frequencies of acoustic modes in solids. A first realization of such a "phonon-sector" test of Lorentz symmetry using room-temperature stress-compensated-cut crystals yields 120 h of data at a frequency resolution of 2.4 ×10-15 and a limit of c˜Q n=(-1.8 ±2.2 )×10-14 GeV on the most weakly constrained neutron-sector c coefficient of the standard model extension. Future experiments with cryogenic oscillators promise significant improvements in accuracy, opening up the potential for improved limits on Lorentz violation in the neutron, proton, electron, and photon sector.

  4. Effects of acoustic wave resonance oscillation on immobilized enzyme

    NASA Astrophysics Data System (ADS)

    Nishiyama, Hiroshi; Watanabe, Tomoya; Inoue, Yasunobu

    2014-03-01

    In aiming at developing a new method to artificially activate enzyme catalysts immobilized on surface, the effects of resonance oscillation of bulk acoustic waves were studied. Glucose oxidase (GOD) was immobilized by a covalent coupling method on a ferroelectric lead zirconate titanate (PZT) device that was able to generate thickness-extensional resonance oscillation (TERO). Glucose oxidation by the GOD enzyme was studied in a microreactor. The generation of TERO immediately increased the catalytic activity of immobilized GOD by a factor of 2-3. With turn-off of TERO, no significant activity decrease occurred, and 80-90% of the enhanced activity was maintained while the reaction proceeded. The almost complete reversion of the activity to the original low level before TERO generation was observed when the immobilized GOD was exposed to a glucose substrate-free solution. These results indicated that the presence of glucose substrate was essential for TERO-induced GOD activation and preservation of the increased activity level. The influences of reaction temperature, glucose concentration, pH, and rf electric power on the TERO activation showed that TERO strengthened the interactions of the immobilized enzyme with glucose substrate and hence promoted the formation of an activation complex.

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

    NASA Astrophysics Data System (ADS)

    Lin, Po-Cheng; I, Lin

    2016-02-01

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

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

    PubMed

    Lin, Po-Cheng; I, Lin

    2016-02-01

    We experimentally demonstrate self-excited oscillation and shedding of millimeter-sized water drops, acoustically levitated in a single-node standing waves cavity, by decreasing the steady acoustic wave intensity below a threshold. The perturbation of the acoustic field by drop motion is a possible source for providing an effective negative damping for sustaining the growing amplitude of the self-excited motion. Its further interplay with surface tension, drop inertia, gravity and acoustic intensities, select various self-excited modes for different size of drops and acoustic intensity. The large drop exhibits quasiperiodic motion from a vertical mode and a zonal mode with growing coupling, as oscillation amplitudes grow, until falling on the floor. For small drops, chaotic oscillations constituted by several broadened sectorial modes and corresponding zonal modes are self-excited. The growing oscillation amplitude leads to droplet shedding from the edges of highly stretched lobes, where surface tension no longer holds the rapid expanding flow. PMID:26986279

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

    PubMed

    Lin, Po-Cheng; I, Lin

    2016-02-01

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

  8. Efficient construction of mock catalogs for baryon acoustic oscillation surveys

    NASA Astrophysics Data System (ADS)

    Sunayama, Tomomi; Padmanabhan, Nikhil; Heitmann, Katrin; Habib, Salman; Rangel, Esteban

    2016-05-01

    Precision measurements of the large scale structure of the Universe require large numbers of high fidelity mock catalogs to accurately assess, and account for, the presence of systematic effects. We introduce and test a scheme for generating mock catalogs rapidly using suitably derated N-body simulations. Our aim is to reproduce the large scale structure and the gross properties of dark matter halos with high accuracy, while sacrificing the details of the halo's internal structure. By adjusting global and local time-steps in an N-body code, we demonstrate that we recover halo masses to better than 0.5% and the power spectrum to better than 1% both in real and redshift space for k=1hMpc-1, while requiring a factor of 4 less CPU time. We also calibrate the redshift spacing of outputs required to generate simulated light cones. We find that outputs separated by Δ z=0.05 allow us to interpolate particle positions and velocities to reproduce the real and redshift space power spectra to better than 1% (out to k=1hMpc-1). We apply these ideas to generate a suite of simulations spanning a range of cosmologies, motivated by the Baryon Oscillation Spectroscopic Survey (BOSS) but broadly applicable to future large scale structure surveys including eBOSS and DESI. As an initial demonstration of the utility of such simulations, we calibrate the shift in the baryonic acoustic oscillation peak position as a function of galaxy bias with higher precision than has been possible so far. This paper also serves to document the simulations, which we make publicly available.

  9. Efficient construction of mock catalogs for baryon acoustic oscillation surveys

    NASA Astrophysics Data System (ADS)

    Sunayama, Tomomi; Padmanabhan, Nikhil; Heitmann, Katrin; Habib, Salman; Rangel, Esteban

    2016-05-01

    Precision measurements of the large scale structure of the Universe require large numbers of high fidelity mock catalogs to accurately assess, and account for, the presence of systematic effects. We introduce and test a scheme for generating mock catalogs rapidly using suitably derated N-body simulations. Our aim is to reproduce the large scale structure and the gross properties of dark matter halos with high accuracy, while sacrificing the details of the halo's internal structure. By adjusting global and local time-steps in an N-body code, we demonstrate that we recover halo masses to better than 0.5% and the power spectrum to better than 1% both in real and redshift space for k=1hMpc‑1, while requiring a factor of 4 less CPU time. We also calibrate the redshift spacing of outputs required to generate simulated light cones. We find that outputs separated by Δ z=0.05 allow us to interpolate particle positions and velocities to reproduce the real and redshift space power spectra to better than 1% (out to k=1hMpc‑1). We apply these ideas to generate a suite of simulations spanning a range of cosmologies, motivated by the Baryon Oscillation Spectroscopic Survey (BOSS) but broadly applicable to future large scale structure surveys including eBOSS and DESI. As an initial demonstration of the utility of such simulations, we calibrate the shift in the baryonic acoustic oscillation peak position as a function of galaxy bias with higher precision than has been possible so far. This paper also serves to document the simulations, which we make publicly available.

  10. Dust-ion-acoustic wave oscillation in metallic multiwalled carbon nanotubes

    SciTech Connect

    Fathalian, Ali; Nikjo, Shahram

    2010-10-15

    In this paper, a charged multiwalled carbon nanotube (MWCNT), which is surrounded by charged nanoparticles, is modeled as a cylindrical shell of electron-ion-dust plasma. By employing the classical electrodynamics formulations and linearized hydrodynamic model, the dispersion relation of the dust-ion-acoustic wave oscillations in the composed system is investigated. We obtain a new low-frequency electrostatic excitation in the MWCNTs, i.e., dust-ion-acoustic wave oscillations.

  11. Broadband distortion modeling in Lyman-α forest BAO fitting

    NASA Astrophysics Data System (ADS)

    Blomqvist, Michael; Kirkby, David; Bautista, Julian E.; Arinyo-i-Prats, Andreu; Busca, Nicolás G.; Miralda-Escudé, Jordi; Slosar, Anže; Font-Ribera, Andreu; Margala, Daniel; Schneider, Donald P.; Vazquez, Jose A.

    2015-11-01

    In recent years, the Lyman-α absorption observed in the spectra of high-redshift quasars has been used as a tracer of large-scale structure by means of the three-dimensional Lyman-α forest auto-correlation function at redshift zsimeq 2.3, but the need to fit the quasar continuum in every absorption spectrum introduces a broadband distortion that is difficult to correct and causes a systematic error for measuring any broadband properties. We describe a k-space model for this broadband distortion based on a multiplicative correction to the power spectrum of the transmitted flux fraction that suppresses power on scales corresponding to the typical length of a Lyman-α forest spectrum. Implementing the distortion model in fits for the baryon acoustic oscillation (BAO) peak position in the Lyman-α forest auto-correlation, we find that the fitting method recovers the input values of the linear bias parameter bF and the redshift-space distortion parameter βF for mock data sets with a systematic error of less than 0.5%. Applied to the auto-correlation measured for BOSS Data Release 11, our method improves on the previous treatment of broadband distortions in BAO fitting by providing a better fit to the data using fewer parameters and reducing the statistical errors on βF and the combination bF(1+βF) by more than a factor of seven. The measured values at redshift z=2.3 are βF=1.39+0.11 +0.24 +0.38-0.10 -0.19 -0.28 and bF(1+βF)=-0.374+0.007 +0.013 +0.020-0.007 -0.014 -0.022 (1σ, 2σ and 3σ statistical errors). Our fitting software and the input files needed to reproduce our main results are publicly available.

  12. Experimental and theoretical demonstration of acoustic Bloch oscillations in porous silicon structures

    SciTech Connect

    Lazcano, Z.; Arriaga, J.; Aliev, G. N.

    2014-04-21

    We report the theoretical calculations and the experimental demonstration of acoustic Bloch oscillations and Wannier-Stark ladders in linear tilted multilayer structures based on porous silicon. The considered structures consist of layers with constant porosity alternated by layers with a linear gradient in the parameter η=1/v{sub L}{sup 2} along the growth direction in order to tilt the acoustic band gap. The purpose of this gradient is to mimic the tilted electronic miniband structure of a superlattice semiconductor under an external electric field. In this way, acoustic Wannier-Stark ladders of equidistant modes are formed and they were experimentally confirmed in the transmission spectrum around 1.2 GHz. Their frequency separation defines the period of the acoustic Bloch oscillations. We fabricated three different structures with the same thicknesses but different values in the η parameter to observe the effect on the period of the Bloch oscillations. We measured the acoustic transmission spectra in the frequency domain, and by using the Fourier transform, we obtained the transmission in the time domain. The transmission spectra of the fabricated samples show acoustic Bloch oscillations with periods of 27, 24, and 19 ns. The experimental results are in good agreement with the transfer matrix calculations. The observed phenomenon is the acoustic counterpart of the well known electronic Bloch oscillations.

  13. The Rhythm of Perception: Acoustic Rhythmic Entrainment Induces Subsequent Perceptual Oscillation

    PubMed Central

    Hickok, Gregory; Farahbod, Haleh; Saberi, Kourosh

    2015-01-01

    Acoustic rhythms are pervasive in speech, music, and environmental sounds. Evidence for neural codes representing periodic information has recently emerged, which seem a likely neural basis for the ability to detect rhythm and rhythmic information has been found to modulate auditory system excitability, providing a potential mechanism for parsing the acoustic stream. Here we explore the effects of a previous rhythmic stimulus on subsequent auditory perception. We found that a low-frequency (3 Hz) amplitute modulated signal induces a subsequent oscillation of perceptual detectability of a brief non-periodic acoustic stimulus (1 kHz tone); the frequency but not phase of the perceptual oscillation matches the entrained stimulus-driven rhythmic oscillation. This provides evidence that rhythmic contexts have a direct influence on subsequent auditory perception of discrete acoustic events. Rhythm coding is likely a fundamental feature of auditory system design that predates the development of explicit human enjoyment of rhythm in music or poetry. PMID:25968248

  14. The sensitivity of BAO dark energy constraints to general isocurvature perturbations

    SciTech Connect

    Kasanda, S. Muya; Zunckel, C.; Moodley, K.; Bassett, B.A.; Okouma, P. E-mail: caroline.zunckel@gmail.com E-mail: bruce.a.bassett@gmail.com

    2012-07-01

    Baryon Acoustic Oscillation (BAO) surveys will be a leading method for addressing the dark energy challenge in the next decade. We explore in detail the effect of allowing for small amplitude admixtures of general isocurvature perturbations in addition to the dominant adiabatic mode. We find that non-adiabatic initial conditions leave the sound speed unchanged but instead excite different harmonics. These harmonics couple differently to Silk damping, altering the form and evolution of acoustic waves in the baryon-photon fluid prior to decoupling. This modifies not only the scale on which the sound waves imprint onto the baryon distribution, which is used as the standard ruler in BAO surveys, but also the shape, width and height of the BAO peak. We discuss these effects in detail and show how more general initial conditions impact our interpretation of cosmological data in dark energy studies. We find that the inclusion of these additional isocurvature modes leads to a decrease in the Dark Energy Task Force figure of merit (FoM) by 46% i.e., FoM{sub ISO} = 0.54 × FoM{sub AD} and 53% for the BOSS and ADEPT experiments respectively when considered in conjunction with PLANK data. We also show that the incorrect assumption of adiabaticity has the potential to bias our estimates of the dark energy parameters by 2.7σ (2.2σ) for a single correlated isocurvature mode (CDM isocurvature), and up to 4.9σ (5.7σ) for three correlated isocurvature modes in the case of the BOSS (ADEPT) experiment. We find that the use of the large scale structure data in conjunction with CMB data improves our ability to measure the contributions of different modes to the initial conditions by as much as 95% for certain modes in the fully correlated case.

  15. Effect of wind tunnel acoustic modes on linear oscillating cascade aerodynamics

    NASA Technical Reports Server (NTRS)

    Buffum, Daniel H.; Fleeter, Sanford

    1993-01-01

    The aerodynamics of a biconvex airfoil cascade oscillating in torsion is investigated using the unsteady aerodynamic influence coefficient technique. For subsonic flow and reduced frequencies as large as 0.9, airfoil surface unsteady pressures resulting from oscillation of one of the airfoils are measured using flush-mounted high-frequency-response pressure transducers. The influence coefficient data are examined in detail and then used to predict the unsteady aerodynamics of a cascade oscillating at various interblade phase angles. These results are correlated with experimental data obtained in the traveling-wave mode of oscillation and linearized analysis predictions. It is found that the unsteady pressure disturbances created by an oscillating airfoil excite wind tunnel acoustic modes which have detrimental effects on the experimental data. Acoustic treatment is proposed to rectify this problem.

  16. Numerical investigation of amplitude-dependent dynamic response in acoustic metamaterials with nonlinear oscillators.

    PubMed

    Manimala, James M; Sun, C T

    2016-06-01

    The amplitude-dependent dynamic response in acoustic metamaterials having nonlinear local oscillator microstructures is studied using numerical simulations on representative discrete mass-spring models. Both cubically nonlinear hardening and softening local oscillator cases are considered. Single frequency, bi-frequency, and wave packet excitations at low and high amplitude levels were used to interrogate the models. The propagation and attenuation characteristics of harmonic waves in a tunable frequency range is found to correspond to the amplitude and nonlinearity-dependent shifts in the local resonance bandgap for such nonlinear acoustic metamaterials. A predominant shift in the propagated wave spectrum towards lower frequencies is observed. Moreover, the feasibility of amplitude and frequency-dependent selective filtering of composite signals consisting of individual frequency components which fall within propagating or attenuating regimes is demonstrated. Further enrichment of these wave manipulation mechanisms in acoustic metamaterials using different combinations of nonlinear microstructures presents device implications for acoustic filters and waveguides.

  17. Numerical investigation of amplitude-dependent dynamic response in acoustic metamaterials with nonlinear oscillators.

    PubMed

    Manimala, James M; Sun, C T

    2016-06-01

    The amplitude-dependent dynamic response in acoustic metamaterials having nonlinear local oscillator microstructures is studied using numerical simulations on representative discrete mass-spring models. Both cubically nonlinear hardening and softening local oscillator cases are considered. Single frequency, bi-frequency, and wave packet excitations at low and high amplitude levels were used to interrogate the models. The propagation and attenuation characteristics of harmonic waves in a tunable frequency range is found to correspond to the amplitude and nonlinearity-dependent shifts in the local resonance bandgap for such nonlinear acoustic metamaterials. A predominant shift in the propagated wave spectrum towards lower frequencies is observed. Moreover, the feasibility of amplitude and frequency-dependent selective filtering of composite signals consisting of individual frequency components which fall within propagating or attenuating regimes is demonstrated. Further enrichment of these wave manipulation mechanisms in acoustic metamaterials using different combinations of nonlinear microstructures presents device implications for acoustic filters and waveguides. PMID:27369163

  18. Theoretical Estimation of the Acoustic Energy Generation and Absorption Caused by Jet Oscillation

    NASA Astrophysics Data System (ADS)

    Takahashi, Kin'ya; Iwagami, Sho; Kobayashi, Taizo; Takami, Toshiya

    2016-04-01

    We investigate the energy transfer between the fluid field and acoustic field caused by a jet driven by an acoustic particle velocity field across it, which is the key to understanding the aerodynamic sound generation of flue instruments, such as the recorder, flute, and organ pipe. Howe's energy corollary allows us to estimate the energy transfer between these two fields. For simplicity, we consider the situation such that a free jet is driven by a uniform acoustic particle velocity field across it. We improve the semi-empirical model of the oscillating jet, i.e., exponentially growing jet model, which has been studied in the field of musical acoustics, and introduce a polynomially growing jet model so as to apply Howe's formula to it. It is found that the relative phase between the acoustic oscillation and jet oscillation, which changes with the distance from the flue exit, determines the quantity of the energy transfer between the two fields. The acoustic energy is mainly generated in the downstream area, but it is consumed in the upstream area near the flue exit in driving the jet. This theoretical examination well explains the numerical calculation of Howe's formula for the two-dimensional flue instrument model in our previous work [http://doi.org/10.1088/0169-5983/46/6/061411, Fluid Dyn. Res. 46, 061411 (2014)] as well as the experimental result of Yoshikawa et al. [http://doi.org/10.1016/j.jsv.2012.01.026, J. Sound Vib. 331, 2558 (2012)].

  19. First Detection of the Acoustic Oscillation Phase Shift Expected from the Cosmic Neutrino Background.

    PubMed

    Follin, Brent; Knox, Lloyd; Millea, Marius; Pan, Zhen

    2015-08-28

    The unimpeded relativistic propagation of cosmological neutrinos prior to recombination of the baryon-photon plasma alters gravitational potentials and therefore the details of the time-dependent gravitational driving of acoustic oscillations. We report here a first detection of the resulting shifts in the temporal phase of the oscillations, which we infer from their signature in the cosmic microwave background temperature power spectrum. PMID:26371637

  20. Coherent acoustic phonon oscillation accompanied with backward acoustic pulse below exciton resonance in a ZnO epifilm on oxide-buffered Si(1 1 1)

    NASA Astrophysics Data System (ADS)

    Lin, Ja-Hon; Shen, Yu-Kai; Liu, Wei-Rein; Lu, Chia-Hui; Chen, Yao-Hui; Chang, Chun-peng; Lee, Wei-Chin; Hong, Minghwei; Kwo, Jueinai-Raynien; Hsu, Chia-Hung; Hsieh, Wen-Feng

    2016-08-01

    Unlike coherent acoustic phonons (CAPs) generated from heat induced thermal stress by the coated Au film, we demonstrated the oscillation from c-ZnO epitaxial film on oxide buffered Si through a degenerate pump-probe technique. As the excited photon energy was set below the exciton resonance, the electronic stress that resulted from defect resonance was used to induce acoustic wave. The damped oscillation revealed a superposition of a high frequency and long decay CAP signal with a backward propagating acoustic pulse which was generated by the absorption of the penetrated pump beam at the Si surface and selected by the ZnO layer as the acoustic resonator.

  1. Coherent acoustic phonon oscillation accompanied with backward acoustic pulse below exciton resonance in a ZnO epifilm on oxide-buffered Si(1 1 1)

    NASA Astrophysics Data System (ADS)

    Lin, Ja-Hon; Shen, Yu-Kai; Liu, Wei-Rein; Lu, Chia-Hui; Chen, Yao-Hui; Chang, Chun-peng; Lee, Wei-Chin; Hong, Minghwei; Kwo, Jueinai-Raynien; Hsu, Chia-Hung; Hsieh, Wen-Feng

    2016-08-01

    Unlike coherent acoustic phonons (CAPs) generated from heat induced thermal stress by the coated Au film, we demonstrated the oscillation from c-ZnO epitaxial film on oxide buffered Si through a degenerate pump–probe technique. As the excited photon energy was set below the exciton resonance, the electronic stress that resulted from defect resonance was used to induce acoustic wave. The damped oscillation revealed a superposition of a high frequency and long decay CAP signal with a backward propagating acoustic pulse which was generated by the absorption of the penetrated pump beam at the Si surface and selected by the ZnO layer as the acoustic resonator.

  2. How does non-linear dynamics affect the baryon acoustic oscillation?

    SciTech Connect

    Sugiyama, Naonori S.; Spergel, David N. E-mail: dns@astro.princeton.edu

    2014-02-01

    We study the non-linear behavior of the baryon acoustic oscillation in the power spectrum and the correlation function by decomposing the dark matter perturbations into the short- and long-wavelength modes. The evolution of the dark matter fluctuations can be described as a global coordinate transformation caused by the long-wavelength displacement vector acting on short-wavelength matter perturbation undergoing non-linear growth. Using this feature, we investigate the well known cancellation of the high-k solutions in the standard perturbation theory. While the standard perturbation theory naturally satisfies the cancellation of the high-k solutions, some of the recently proposed improved perturbation theories do not guarantee the cancellation. We show that this cancellation clarifies the success of the standard perturbation theory at the 2-loop order in describing the amplitude of the non-linear power spectrum even at high-k regions. We propose an extension of the standard 2-loop level perturbation theory model of the non-linear power spectrum that more accurately models the non-linear evolution of the baryon acoustic oscillation than the standard perturbation theory. The model consists of simple and intuitive parts: the non-linear evolution of the smoothed power spectrum without the baryon acoustic oscillations and the non-linear evolution of the baryon acoustic oscillations due to the large-scale velocity of dark matter and due to the gravitational attraction between dark matter particles. Our extended model predicts the smoothing parameter of the baryon acoustic oscillation peak at z = 0.35 as ∼ 7.7Mpc/h and describes the small non-linear shift in the peak position due to the galaxy random motions.

  3. Surface acoustic wave stabilized oscillators: Additional aging results

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Updated aging data for SAW oscillators with aluminum transducers on ST-cut quartz, for gold transducers on ST-cut quartz, and for aluminum transducers on SiO2/LiTaO3. Devices with gold transducers age differently (both and shape of curve) from those having a aluminum transducers indicating the transducer metallization can represent an important aging mechanism.

  4. Helioseismology and asteroseismology: looking for gravitational waves in acoustic oscillations

    SciTech Connect

    Lopes, Ilídio; Silk, Joseph E-mail: ilopes@uevora.pt

    2014-10-10

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

  5. Helioseismology and Asteroseismology: Looking for Gravitational Waves in Acoustic Oscillations

    NASA Astrophysics Data System (ADS)

    Lopes, Ilídio; Silk, Joseph

    2014-10-01

    Current helioseismology observations allow the determination of the frequencies and surface velocity amplitudes of solar acoustic modes with exceptionally high precision. In some cases, the frequency accuracy is better than one part in a million. We show that there is a distinct possibility that quadrupole acoustic modes of low order could be excited by gravitational waves (GWs), if the GWs have a strain amplitude in the range 10-20 h -20 with h -20 ~ 1 or h -20 ~ 103, as predicted by several types of GW sources, such as galactic ultracompact binaries or extreme mass ratio inspirals and coalescence of black holes. If the damping rate at low order is 10-3η N μHz, with η N ~ 10-3-1, as inferred from the theory of stellar pulsations, then GW radiation will lead to a maximum rms surface velocity amplitude of quadrupole modes of the order of h_{-20}\\eta _N^{-1}\\sim 10-9-10-3 cm s-1, on the verge of what is currently detectable via helioseismology. The frequency and sensitivity range probed by helioseismological acoustic modes overlap with, and complement, the capabilities of eLISA for the brightest resolved ultracompact galactic binaries.

  6. Design guidelines for avoiding thermo-acoustic oscillations in helium piping systems

    SciTech Connect

    Gupta, Prabhat Kumar; Rabehl, Roger

    2015-04-02

    Thermo-acoustic oscillations are a commonly observed phenomenon in helium cryogenic systems, especially in tubes connecting hot and cold areas. The open ends of these tubes are connected to the lower temperature (typically at 4.5 K), and the closed ends of these tubes are connected to the high temperature (300 K). Cryogenic instrumentation installations provide ideal conditions for these oscillations to occur due to the steep temperature gradient along the tubing. These oscillations create errors in measurements as well as an undesirable heat load to the system. The work presented here develops engineering guidelines to design oscillation-free helium piping. This work also studies the effect of different piping inserts and shows how the proper geometrical combinations have to be chosen to avoid thermo-acoustic oscillations. The effect of an 80 K intercept is also studied and shows that thermo-oscillations can be dampened by placing the intercept at an appropriate location. As a result, the design of helium piping based on the present work is also verified with the experimental results available in open literature.

  7. Design guidelines for avoiding thermo-acoustic oscillations in helium piping systems

    DOE PAGES

    Gupta, Prabhat Kumar; Rabehl, Roger

    2015-04-02

    Thermo-acoustic oscillations are a commonly observed phenomenon in helium cryogenic systems, especially in tubes connecting hot and cold areas. The open ends of these tubes are connected to the lower temperature (typically at 4.5 K), and the closed ends of these tubes are connected to the high temperature (300 K). Cryogenic instrumentation installations provide ideal conditions for these oscillations to occur due to the steep temperature gradient along the tubing. These oscillations create errors in measurements as well as an undesirable heat load to the system. The work presented here develops engineering guidelines to design oscillation-free helium piping. This workmore » also studies the effect of different piping inserts and shows how the proper geometrical combinations have to be chosen to avoid thermo-acoustic oscillations. The effect of an 80 K intercept is also studied and shows that thermo-oscillations can be dampened by placing the intercept at an appropriate location. As a result, the design of helium piping based on the present work is also verified with the experimental results available in open literature.« less

  8. Measurement of acoustic glitches in solar-type stars from oscillation frequencies observed by Kepler

    SciTech Connect

    Mazumdar, A.; Monteiro, M. J. P. F. G.; Cunha, M. S.; Ballot, J.; Antia, H. M.; Basu, S.; Houdek, G.; Silva Aguirre, V.; Christensen-Dalsgaard, J.; Metcalfe, T. S.; Mathur, S.; García, R. A.; Verner, G. A.; Chaplin, W. J.; Sanderfer, D. T.; Seader, S. E.; Smith, J. C.

    2014-02-10

    For the very best and brightest asteroseismic solar-type targets observed by Kepler, the frequency precision is sufficient to determine the acoustic depths of the surface convective layer and the helium ionization zone. Such sharp features inside the acoustic cavity of the star, which we call acoustic glitches, create small oscillatory deviations from the uniform spacing of frequencies in a sequence of oscillation modes with the same spherical harmonic degree. We use these oscillatory signals to determine the acoustic locations of such features in 19 solar-type stars observed by the Kepler mission. Four independent groups of researchers utilized the oscillation frequencies themselves, the second differences of the frequencies and the ratio of the small and large separation to locate the base of the convection zone and the second helium ionization zone. Despite the significantly different methods of analysis, good agreement was found between the results of these four groups, barring a few cases. These results also agree reasonably well with the locations of these layers in representative models of the stars. These results firmly establish the presence of the oscillatory signals in the asteroseismic data and the viability of several techniques to determine the location of acoustic glitches inside stars.

  9. Theoretical Estimation of the Acoustic Energy Generation and Absorption Caused by Jet Oscillation

    NASA Astrophysics Data System (ADS)

    Takahashi, Kin'ya; Iwagami, Sho; Kobayashi, Taizo; Takami, Toshiya

    2016-04-01

    We investigate the energy transfer between the fluid field and acoustic field caused by a jet driven by an acoustic particle velocity field across it, which is the key to understanding the aerodynamic sound generation of flue instruments, such as the recorder, flute, and organ pipe. Howe's energy corollary allows us to estimate the energy transfer between these two fields. For simplicity, we consider the situation such that a free jet is driven by a uniform acoustic particle velocity field across it. We improve the semi-empirical model of the oscillating jet, i.e., exponentially growing jet model, which has been studied in the field of musical acoustics, and introduce a polynomially growing jet model so as to apply Howe's formula to it. It is found that the relative phase between the acoustic oscillation and jet oscillation, which changes with the distance from the flue exit, determines the quantity of the energy transfer between the two fields. The acoustic energy is mainly generated in the downstream area, but it is consumed in the upstream area near the flue exit in driving the jet. This theoretical examination well explains the numerical calculation of Howe's formula for the two-dimensional flue instrument model in our previous work [Fluid Dyn. Res. 46, 061411 (2014)] as well as the experimental result of Yoshikawa et al. [J. Sound Vib. 331, 2558 (2012)].

  10. Quantum Ion-Acoustic Oscillations in Single-Walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Khan, S. A.; Iqbal, Z.; Wazir, Z.; Aman-ur-Rehman

    2016-05-01

    Quantum ion-acoustic oscillations in single-walled carbon nanotubes are studied by employing a quantum hydrodynamics model. The dispersion equation is obtained by Fourier transformation, which exhibits the existence of quantum ion-acoustic wave affected by change of density balance due to presence of positive or negative heavy species as stationary ion clusters and wave potential at equilibrium. The numerical results are presented, and the role of quantum degeneracy, nanotube geometry, electron exchange-correlation effects, and concentration and polarity of heavy species on wave dispersion is pointed out for typical systems of interest.

  11. Surface acoustic wave opto-mechanical oscillator and frequency comb generator

    NASA Astrophysics Data System (ADS)

    Savchenkov, A. A.; Matsko, A. B.; Ilchenko, V. S.; Seidel, D.; Maleki, L.

    2011-09-01

    We report on realization of an efficient triply resonant coupling between two long lived optical modes and a high frequency surface acoustic wave (SAW) mode of the same monolithic crystalline whispering gallery mode resonator. The coupling results in an opto-mechanical oscillation and generation of a monochromatic SAW. A strong nonlinear interaction of this mechanical mode with other equidistant SAW modes leads to mechanical hyperparametric oscillation and generation of a SAW pulse train and associated frequency comb in the resonator. We visualized the comb by observing the modulation of the light escaping the resonator.

  12. Wavelet analysis of baryon acoustic structures in the galaxy distribution

    NASA Astrophysics Data System (ADS)

    Arnalte-Mur, P.; Labatie, A.; Clerc, N.; Martínez, V. J.; Starck, J.-L.; Lachièze-Rey, M.; Saar, E.; Paredes, S.

    2012-06-01

    Context. Baryon acoustic oscillations (BAO) are imprinted in the density field by acoustic waves travelling in the plasma of the early universe. Their fixed scale can be used as a standard ruler to study the geometry of the universe. Aims: The BAO have been previously detected using correlation functions and power spectra of the galaxy distribution. We present a new method to detect the real-space structures associated with BAO. These baryon acoustic structures are spherical shells of relatively small density contrast, surrounding high density central regions. Methods: We design a specific wavelet adapted to search for shells, and exploit the physics of the process by making use of two different mass tracers, introducing a specific statistic to detect the BAO features. We show the effect of the BAO signal in this new statistic when applied to the Λ - cold dark matter (ΛCDM) model, using an analytical approximation to the transfer function. We confirm the reliability and stability of our method by using cosmological N-body simulations from the MareNostrum Institut de Ciències de l'Espai (MICE). Results: We apply our method to the detection of BAO in a galaxy sample drawn from the Sloan Digital Sky Survey (SDSS). We use the "main" catalogue to trace the shells, and the luminous red galaxies (LRG) as tracers of the high density central regions. Using this new method, we detect, with a high significance, that the LRG in our sample are preferentially located close to the centres of shell-like structures in the density field, with characteristics similar to those expected from BAO. We show that stacking selected shells, we can find their characteristic density profile. Conclusions: We delineate a new feature of the cosmic web, the BAO shells. As these are real spatial structures, the BAO phenomenon can be studied in detail by examining those shells. Full Table 1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc

  13. Acoustic resonant oscillations between the atmosphere and the solid earth during the 1991 Mt. Pinatubo eruption

    NASA Astrophysics Data System (ADS)

    Watada, Shingo; Kanamori, Hiroo

    2010-12-01

    Long-period harmonic Rayleigh waves were observed on seismometers during the 1991 Mt. Pinatubo eruption in the Philippines. The amplitude spectrum of the Rayleigh waves shows two distinct peaks at periods of about 230 and 270 s. In the Earth's atmosphere, long-wavelength standing acoustic waves are bounded in a low-sound-velocity channel between the thermosphere and the ground. The Rayleigh waves and the fundamental and first overtone of atmospheric acoustic waves trapped in the low-sound-velocity channels have approximately the same horizontal wavelength and frequency at periods of 230 and 270 s, respectively, i.e., the atmosphere and the solid earth satisfy the condition for acoustic resonant oscillations. The standing atmospheric long-wavelength acoustic waves set off by the eruption selectively excited seismic spheroidal modes near the resonant period through acoustic resonant coupling and resulted in harmonic Rayleigh waves. In contrast, gravity waves and Lamb waves (atmospheric boundary waves) do not couple to the ground efficiently and are not easily observed as ground disturbance on seismograms during volcanic eruptions.

  14. Exploring bubble oscillation and mass transfer enhancement in acoustic-assisted liquid-liquid extraction with a microfluidic device

    PubMed Central

    Xie, Yuliang; Chindam, Chandraprakash; Nama, Nitesh; Yang, Shikuan; Lu, Mengqian; Zhao, Yanhui; Mai, John D.; Costanzo, Francesco; Huang, Tony Jun

    2015-01-01

    We investigated bubble oscillation and its induced enhancement of mass transfer in a liquid-liquid extraction process with an acoustically-driven, bubble-based microfluidic device. The oscillation of individually trapped bubbles, of known sizes, in microchannels was studied at both a fixed frequency, and over a range of frequencies. Resonant frequencies were analytically identified and were found to be in agreement with the experimental observations. The acoustic streaming induced by the bubble oscillation was identified as the cause of this enhanced extraction. Experiments extracting Rhodanmine B from an aqueous phase (DI water) to an organic phase (1-octanol) were performed to determine the relationship between extraction efficiency and applied acoustic power. The enhanced efficiency in mass transport via these acoustic-energy-assisted processes was confirmed by comparisons against a pure diffusion-based process. PMID:26223474

  15. Rayleigh criterion and acoustic energy balance in unconfined self-sustained oscillating flames

    SciTech Connect

    Durox, D.; Schuller, T.; Noiray, N.; Birbaud, A.L.; Candel, S.

    2009-01-15

    Instabilities of confined combustion systems are often discussed in terms of the Rayleigh criterion, which provides a necessary condition for unstable operation and is commonly used to distinguish driving and damping regions. The analysis is also carried out in some cases by making use of an acoustic energy balance in which the Rayleigh term acts as a source. The case of unconfined flames is less well documented but of importance in practical systems used in heating and drying. This study is motivated by problems of self-sustained oscillations of radiant burners for domestic or industrial processes and of various other types of open flames. Application of the Rayleigh criterion and of the balance of acoustic energy to oscillations arising in such unconfined systems is examined. The objective is to see if the Rayleigh condition is fulfilled and to show how the different perturbed variables are linked to each other to develop an unstable oscillation. These issues are investigated by experiments in two geometries. The first case relates to a single ''V''- or ''M''-shaped flame formed by a burner behaving like a Helmholtz resonator. The second geometry features a collection of conical flames (CCF) established by a multipoint injector. This system is fed by a manifold that features a set of plane modes and resonates like an organ pipe at frequencies corresponding to odd multiples of the quarter wave. The Rayleigh criterion and a related result written in the form of an acoustic energy balance are used to define conditions of instability. A link is established between the pressure signal radiated by the burner and the total heat release rate perturbation yielding the phase lag between these two variables and providing conditions for unstable operation. Systematic experiments carried out in the two burner geometries and model predictions are in good agreement indicating that the Rayleigh source term is positive and that the criterion is well fulfilled by the wavefield

  16. Rayleigh criterion and acoustic energy balance in unconfined self-sustained oscillating flames

    SciTech Connect

    Durox, D.; Schuller, T.; Noiray, N.; Birbaud, A.L.; Candel, S.

    2008-11-15

    Instabilities of confined combustion systems are often discussed in terms of the Rayleigh criterion, which provides a necessary condition for unstable operation and is commonly used to distinguish driving and damping regions. The analysis is also carried out in some cases by making use of an acoustic energy balance in which the Rayleigh term acts as a source. The case of unconfined flames is less well documented but of importance in practical systems used in heating and drying. This study is motivated by problems of self-sustained oscillations of radiant burners for domestic or industrial processes and of various other types of open flames. Application of the Rayleigh criterion and of the balance of acoustic energy to oscillations arising in such unconfined systems is examined. The objective is to see if the Rayleigh condition is fulfilled and to show how the different perturbed variables are linked to each other to develop an unstable oscillation. These issues are investigated by experiments in two geometries. The first case relates to a single ''V''- or ''M''-shaped flame formed by a burner behaving like a Helmholtz resonator. The second geometry features a collection of conical flames (CCF) established by a multipoint injector. This system is fed by a manifold that features a set of plane modes and resonates like an organ pipe at frequencies corresponding to odd multiples of the quarter wave. The Rayleigh criterion and a related result written in the form of an acoustic energy balance are used to define conditions of instability. A link is established between the pressure signal radiated by the burner and the total heat release rate perturbation yielding the phase lag between these two variables and providing conditions for unstable operation. Systematic experiments carried out in the two burner geometries and model predictions are in good agreement indicating that the Rayleigh source term is positive and that the criterion is well fulfilled by the wavefield

  17. The measurement of geodesic acoustic mode magnetic field oscillations in J-TEXT tokamak

    NASA Astrophysics Data System (ADS)

    Lan, T.; Wu, J.; Shen, H. G.; Deng, T. J.; Liu, A. D.; Xie, J. L.; Li, H.; Liu, W. D.; Yu, C. X.; Sun, Y.; Liu, H.; Chen, Z. P.; Zhuang, G.

    2014-10-01

    Geodesic acoustic mode (GAM) magnetic field oscillations have been investigated using three-dimension magnetic probe and Langmuir probe arrays in the edge of J-TEXT tokamak. The probe arrays are placed on the two top windows of tokamak, separated toroidally. Inside the LCFS, GAM shows apparent oscillations in floating potential. In contrast, GAM magnetic field oscillations are not significant in raw magnetic fields signals. Using toroidal correlation technique, the GAM magnetic field oscillations are distinguished from ambient magnetic field. The amplitudes of three dimension GAM magnetic field fluctuations, as well as the dependence with local plasma parameters such as safety factor and plasma beta, are coincident with theoretical predictions. And its toroidal symmetry mode structure, i.e. n = 0, is identified. Furthermore, the GAM current sheet, in which GAM oscillates, is firstly verified with magnetic probes arrays in different radial positions, which may help us to understand the radial structure of GAM. Supported by NNSFC (Nos. 10990210, 10990211, 10335060, 10905057 and 11375188), CPSF (No. 20080440104), YIF (No. WK2030040019) and KIPCAS (No. kjcx-yw-n28).

  18. Acoustic landmarks drive delta-theta oscillations to enable speech comprehension by facilitating perceptual parsing.

    PubMed

    Doelling, Keith B; Arnal, Luc H; Ghitza, Oded; Poeppel, David

    2014-01-15

    A growing body of research suggests that intrinsic neuronal slow (<10 Hz) oscillations in auditory cortex appear to track incoming speech and other spectro-temporally complex auditory signals. Within this framework, several recent studies have identified critical-band temporal envelopes as the specific acoustic feature being reflected by the phase of these oscillations. However, how this alignment between speech acoustics and neural oscillations might underpin intelligibility is unclear. Here we test the hypothesis that the 'sharpness' of temporal fluctuations in the critical band envelope acts as a temporal cue to speech syllabic rate, driving delta-theta rhythms to track the stimulus and facilitate intelligibility. We interpret our findings as evidence that sharp events in the stimulus cause cortical rhythms to re-align and parse the stimulus into syllable-sized chunks for further decoding. Using magnetoencephalographic recordings, we show that by removing temporal fluctuations that occur at the syllabic rate, envelope-tracking activity is reduced. By artificially reinstating these temporal fluctuations, envelope-tracking activity is regained. These changes in tracking correlate with intelligibility of the stimulus. Together, the results suggest that the sharpness of fluctuations in the stimulus, as reflected in the cochlear output, drive oscillatory activity to track and entrain to the stimulus, at its syllabic rate. This process likely facilitates parsing of the stimulus into meaningful chunks appropriate for subsequent decoding, enhancing perception and intelligibility.

  19. Acoustic landmarks drive delta-theta oscillations to enable speech comprehension by facilitating perceptual parsing

    PubMed Central

    Doelling, Keith; Arnal, Luc; Ghitza, Oded; Poeppel, David

    2013-01-01

    A growing body of research suggests that intrinsic neuronal slow (< 10 Hz) oscillations in auditory cortex appear to track incoming speech and other spectro-temporally complex auditory signals. Within this framework, several recent studies have identified critical-band temporal envelopes as the specific acoustic feature being reflected by the phase of these oscillations. However, how this alignment between speech acoustics and neural oscillations might underpin intelligibility is unclear. Here we test the hypothesis that the ‘sharpness’ of temporal fluctuations in the critical band envelope acts as a temporal cue to speech syllabic rate, driving delta-theta rhythms to track the stimulus and facilitate intelligibility. We interpret our findings as evidence that sharp events in the stimulus cause cortical rhythms to re-align and parse the stimulus into syllable-sized chunks for further decoding. Using magnetoencephalographic recordings, we show that by removing temporal fluctuations that occur at the syllabic rate, envelope-tracking activity is reduced. By artificially reinstating these temporal fluctuations, envelope-tracking activity is regained. These changes in tracking correlate with intelligibility of the stimulus. Together, the results suggest that the sharpness of fluctuations in the stimulus, as reflected in the cochlear output, drive oscillatory activity to track and entrain to the stimulus, at its syllabic rate. This process likely facilitates parsing of the stimulus into meaningful chunks appropriate for subsequent decoding, enhancing perception and intelligibility. PMID:23791839

  20. EVIDENCE OF MULTIPLE SLOW ACOUSTIC OSCILLATIONS IN THE STELLAR FLARING LOOPS OF PROXIMA CENTAURI

    SciTech Connect

    Srivastava, A. K.; Pandey, J. C.; Lalitha, S.

    2013-12-01

    We present the first observational evidence of multiple slow acoustic oscillations in the post-flaring loops of the corona of Proxima Centauri using XMM-Newton observations. We find the signature of periodic oscillations localized in the decay phase of the flare in its soft (0.3-10.0 keV) X-ray emissions. Using the standard wavelet tool, we find multiple periodicities of 1261 s and 687 s. These bursty oscillations persist for durations of 90 minutes and 50 minutes, respectively, for more than three cycles. The intensity oscillations with a period of 1261 s may be the signature of the fundamental mode of slow magnetoacoustic waves with a phase speed of 119 km s{sup –1} in a loop of length 7.5 × 10{sup 9} cm, which is initially heated, producing the flare peak temperature of 33 MK and later cooled down in the decay phase and maintained at an average temperature of 7.2 MK. The other period of 687 s may be associated with the first overtone of slow magnetoacoustic oscillations in the flaring loop. The fundamental mode oscillations show dissipation with a damping time of 47 minutes. The period ratio P {sub 1}/P {sub 2} is found to be 1.83, indicating that such oscillations are most likely excited in longitudinal density stratified stellar loops. We estimate the density scale height of the stellar loop system as ∼23 Mm, which is smaller than the hydrostatic scale height of the hot loop system, and implies the existence of non-equilibrium conditions.

  1. Evidence of Multiple Slow Acoustic Oscillations in the Stellar Flaring Loops of Proxima Centauri

    NASA Astrophysics Data System (ADS)

    Srivastava, A. K.; Lalitha, S.; Pandey, J. C.

    2013-12-01

    We present the first observational evidence of multiple slow acoustic oscillations in the post-flaring loops of the corona of Proxima Centauri using XMM-Newton observations. We find the signature of periodic oscillations localized in the decay phase of the flare in its soft (0.3-10.0 keV) X-ray emissions. Using the standard wavelet tool, we find multiple periodicities of 1261 s and 687 s. These bursty oscillations persist for durations of 90 minutes and 50 minutes, respectively, for more than three cycles. The intensity oscillations with a period of 1261 s may be the signature of the fundamental mode of slow magnetoacoustic waves with a phase speed of 119 km s-1 in a loop of length 7.5 × 109 cm, which is initially heated, producing the flare peak temperature of 33 MK and later cooled down in the decay phase and maintained at an average temperature of 7.2 MK. The other period of 687 s may be associated with the first overtone of slow magnetoacoustic oscillations in the flaring loop. The fundamental mode oscillations show dissipation with a damping time of 47 minutes. The period ratio P 1/P 2 is found to be 1.83, indicating that such oscillations are most likely excited in longitudinal density stratified stellar loops. We estimate the density scale height of the stellar loop system as ~23 Mm, which is smaller than the hydrostatic scale height of the hot loop system, and implies the existence of non-equilibrium conditions.

  2. Isocurvature modes and Baryon Acoustic Oscillations II: gains from combining CMB and Large Scale Structure

    SciTech Connect

    Carbone, Carmelita; Mangilli, Anna; Verde, Licia E-mail: anna.mangilli@icc.ub.edu

    2011-09-01

    We consider cosmological parameters estimation in the presence of a non-zero isocurvature contribution in the primordial perturbations. A previous analysis showed that even a tiny amount of isocurvature perturbation, if not accounted for, could affect standard rulers calibration from Cosmic Microwave Background observations such as those provided by the Planck mission, affect Baryon Acoustic Oscillations interpretation, and introduce biases in the recovered dark energy properties that are larger than forecasted statistical errors from future surveys. Extending on this work, here we adopt a general fiducial cosmology which includes a varying dark energy equation of state parameter and curvature. Beside Baryon Acoustic Oscillations measurements, we include the information from the shape of the galaxy power spectrum and consider a joint analysis of a Planck-like Cosmic Microwave Background probe and a future, space-based, Large Scale Structure probe not too dissimilar from recently proposed surveys. We find that this allows one to break the degeneracies that affect the Cosmic Microwave Background and Baryon Acoustic Oscillations combination. As a result, most of the cosmological parameter systematic biases arising from an incorrect assumption on the isocurvature fraction parameter f{sub iso}, become negligible with respect to the statistical errors. We find that the Cosmic Microwave Background and Large Scale Structure combination gives a statistical error σ(f{sub iso}) ∼ 0.008, even when curvature and a varying dark energy equation of state are included, which is smaller that the error obtained from Cosmic Microwave Background alone when flatness and cosmological constant are assumed. These results confirm the synergy and complementarity between Cosmic Microwave Background and Large Scale Structure, and the great potential of future and planned galaxy surveys.

  3. Suppression of Acoustic Oscillation in Hearing Aids: System and Circuit Design

    NASA Astrophysics Data System (ADS)

    Wang, Rongtai

    1995-01-01

    Two types of techniques for the suppression of acoustic oscillation in hearing aids have been studied, namely feed forward suppression and feedback cancellation. For feed forward suppression we introduce the maximum phase equalization (MPE) method based on the minimum phase theory. This method provides us with a higher degree of flexibility in selecting appropriate auxiliary techniques to suppress the acoustic oscillations. Examples of these auxiliary techniques have been described. But there is a limitation on the maximum usable gain increase by using feed forward techniques. For feedback cancellation techniques we present the knowledge based adaptive feedback cancellation (KBAFC) algorithm. This algorithm is fundamentally different from any previous technique. First, the KBAFC algorithm is based on the observation that although the hearing aid open loop transfer function does vary due to the change of the acoustic environment, however the structural behavior of the open loop transfer function remains invariant for a hearing aid in normal use. This property has been confirmed by experiments. In all previous feedback cancellation algorithms, such knowledge of the open loop transfer function is ignored. Second, in the KBAFC algorithm, since the structural behavior of the open loop transfer function is known, digital IIR and analog filters can be used. Additionally, a set of pure tones can be used as a probe signal. As a result, the computation complexity is reduced and the hearing aid is quiet. While in all previous feedback cancellation algorithms, since the open loop transfer function is considered to be a completely unknown, usually a FIR filter is used as a cancellation filter, and white noise is used as the probe signal. As a result, the computation complexity is large and the hearing aid is noisier. In order to verify the KBAFC algorithm, a prototype is implemented. The test results shows that by using the KBAFC algorithm the maximum cancellation can be larger

  4. Solar cycle variations in the powers and damping rates of low-degree solar acoustic oscillations

    NASA Astrophysics Data System (ADS)

    Broomhall, A.-M.; Pugh, C. E.; Nakariakov, V. M.

    2015-12-01

    Helioseismology uses the Sun's natural resonant oscillations to study the solar interior. The properties of the solar oscillations are sensitive to the Sun'2019;s magnetic activity cycle. Here we examine variations in the powers, damping rates, and energy supply rates of the most prominent acoustic oscillations in unresolved, Sun-as-a-star data, obtained by the Birmingham Solar Oscillations Network (BiSON) during solar cycles 22, 23, and the first half of 24. The variations in the helioseismic parameters are compared to the 10.7 cm flux, a well-known global proxy of solar activity. As expected the oscillations are most heavily damped and the mode powers are at a minimum at solar activity maximum. The 10.7 cm flux was linearly regressed using the fractional variations of damping rates and powers observed during cycle 23. In general, good agreement is found between the damping rates and the 10.7 cm flux. However, the linearly regressed 10.7 cm flux and fractional variation in powers diverge in cycles 22 and 24, indicating that the relationship between the mode powers and the 10.7 cm flux is not consistent from one cycle to the next. The energy supply rate of the oscillations, which is usually approximately constant, also decreases at this time. We have determined that this discrepancy is not because of the first-order bias introduced by an increase in the level of background noise or gaps in the data. Although we cannot categorically rule out an instrumental origin, the divergence observed in cycle 24, when the data were of high quality and the data coverage was over 80%, raises the possibility that the effect may be solar in origin.

  5. Energy analysis during acoustic bubble oscillations: relationship between bubble energy and sonochemical parameters.

    PubMed

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

    2014-01-01

    In this work, energy analysis of an oscillating isolated spherical bubble in water irradiated by an ultrasonic wave has been theoretically studied for various conditions of acoustic amplitude, ultrasound frequency, static pressure and liquid temperature in order to explain the effects of these key parameters on both sonochemistry and sonoluminescence. The Keller-Miksis equation for the temporal variation of the bubble radius in compressible and viscous medium has been employed as a dynamics model. The numerical calculations showed that the rate of energy accumulation, dE/dt, increased linearly with increasing acoustic amplitude in the range of 1.5-3.0 atm and decreased sharply with increasing frequency in the range 200-1000 kHz. There exists an optimal static pressure at which the power w is highest. This optimum shifts toward a higher value as the acoustic amplitude increases. The energy of the bubble slightly increases with the increase in liquid temperature from 10 to 60 °C. The results of this study should be a helpful means to explain a variety of experimental observations conducted in the field of sonochemistry and sonoluminescence concerning the effects of operational parameters. PMID:23683796

  6. MEASURING BARYON ACOUSTIC OSCILLATIONS ON 21 cm INTENSITY FLUCTUATIONS AT MODERATE REDSHIFTS

    SciTech Connect

    Mao Xiaochun

    2012-06-20

    After reionization, emission in the 21 cm hyperfine transition provides a direct probe of neutral hydrogen distributed in galaxies. Different from galaxy redshift surveys, observation of baryon acoustic oscillations in the cumulative 21 cm emission may offer an attractive method for constraining dark energy properties at moderate redshifts. Keys to this program are techniques to extract the faint cosmological signal from various contaminants, such as detector noise and continuum foregrounds. In this paper, we investigate the possible systematic and statistical errors in the acoustic scale estimates using ground-based radio interferometers. Based on the simulated 21 cm interferometric measurements, we analyze the performance of a Fourier-space, light-of-sight algorithm in subtracting foregrounds, and further study the observing strategy as a function of instrumental configurations. Measurement uncertainties are presented from a suite of simulations with a variety of parameters, in order to have an estimate of what behaviors will be accessible in the future generation of hydrogen surveys. We find that 10 separate interferometers, each of which contains {approx}300 dishes, observing an independent patch of the sky and producing an instantaneous field of view (FOV) of {approx}100 deg{sup 2}, can be used to make a significant detection of acoustic features over a period of a few years. Compared to optical surveys, the broad bandwidth, wide FOV, and multi-beam observation are all unprecedented capabilities of low-frequency radio experiments.

  7. Surface acoustic BLOCH oscillations, the Wannier-Stark ladder, and Landau-Zener tunneling in a solid.

    PubMed

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

    2010-04-23

    We present the experimental observation of Bloch oscillations, the Wannier-Stark ladder, and Landau-Zener tunneling of surface acoustic waves in perturbed grating structures on a solid substrate. A model providing a quantitative description of our experimental observations, including multiple Landau-Zener transitions of the anticrossed surface acoustic Wannier-Stark states, is developed. The use of a planar geometry for the realization of the Bloch oscillations and Landau-Zener tunneling allows a direct access to the elastic field distribution. The vertical surface displacement has been measured by interferometry.

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

    PubMed Central

    Zinin, Pavel V.; Allen, John S.

    2009-01-01

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

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

    PubMed

    Zinin, Pavel V; Allen, John S

    2009-02-01

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

  10. The 21-cm BAO signature of enriched low-mass galaxies during cosmic reionization

    NASA Astrophysics Data System (ADS)

    Cohen, Aviad; Fialkov, Anastasia; Barkana, Rennan

    2016-06-01

    Studies of the formation of the first stars have established that they formed in small haloes of ˜105-106 M⊙ via molecular hydrogen cooling. Since a low level of ultraviolet radiation from stars suffices to dissociate molecular hydrogen, under the usually assumed scenario this primordial mode of star formation ended by redshift z ˜ 15 and much more massive haloes came to dominate star formation. However, metal enrichment from the first stars may have allowed the smaller haloes to continue to form stars. In this Letter, we explore the possible effect of star formation in metal-rich low-mass haloes on the redshifted 21-cm signal of neutral hydrogen from z = 6 to 40. These haloes are significantly affected by the supersonic streaming velocity, with its characteristic baryon acoustic oscillation (BAO) signature. Thus, enrichment of low-mass galaxies can produce a strong signature in the 21-cm power spectrum over a wide range of redshifts, especially if star formation in the small haloes was more efficient than suggested by current simulations. We show that upcoming radio telescopes can easily distinguish among various possible scenarios.

  11. Inertial-acoustic oscillations of black hole accretion discs with large-scale poloidal magnetic fields

    NASA Astrophysics Data System (ADS)

    Yu, Cong; Lai, Dong

    2015-07-01

    We study the effect of large-scale magnetic fields on the non-axisymmetric inertial-acoustic modes (also called p modes) trapped in the innermost regions of accretion discs around black holes (BHs). These global modes could provide an explanation for the high-frequency quasi-periodic oscillations (HFQPOs) observed in BH X-ray binaries. There may be observational evidence for the presence of such large-scale magnetic fields in the discs since episodic jets are observed in the same spectral state when HFQPOs are detected. We find that a large-scale poloidal magnetic field can enhance the corotational instability and increase the growth rate of the purely hydrodynamic overstable p modes. In addition, we show that the frequencies of these overstable p modes could be further reduced by such magnetic fields, making them agree better with observations.

  12. Prediction of thermal acoustic oscillations (TAOs) in the CLAES solid CO2/neon system

    NASA Technical Reports Server (NTRS)

    Spradley, I. E.; Yuan, S. W. K.

    1991-01-01

    Results are presented of a study initiated to investigate the possibility that the existence of thermal acoustic oscillations (TAOs) in the Cryogenic Limb Atmospheric Etalon Spectrometer (CLAES) neon plumbing system ground configuration could be the cause of higher-than-predicted heat rates measured during thermal ground testing. Tests were conducted between warm boundary temperatures ranging from 40 to 100 K, which simulated the actual test conditions of the CLAES CO2/neon system. TAOs were observed between 6 and 106 Torr, which agreed with the analytical predictions, and verified the possible existence of TAOs in the CLAES system during ground testing. The presence of TAOs was eventually confirmed in the CLAES system during a subsequent thermal test and were determined to have caused the higher heat rates measured during the prior thermal test.

  13. An experimental study on resonance of oscillating air/vapor bubbles in water using a two-frequency acoustic apparatus

    NASA Astrophysics Data System (ADS)

    Ohsaka, K.

    2003-05-01

    A two-frequency acoustic apparatus is employed to study the growth behavior of vapor-saturated bubbles driven in a volumetric mode. A unique feature of the apparatus is its capability of trapping a bubble by an ultrasonic standing wave while independently driving it into oscillations by a second lower-frequency acoustic wave. It is observed that the growing vapor bubbles exhibit a periodic shape transition between the volumetric and shape modes due to resonant coupling. In order to explain this observation, we performed an experimental investigation on resonant coupling of air bubbles and obtained the following results: First, the induced shape oscillations are actually a mixed mode that contains the volume component, thus, vapor bubbles can grow while they exhibit shape oscillations. Second, the acoustically levitated bubbles are deformed and therefore, degeneracy in resonant frequency is partially removed. As a result, the vapor bubbles exhibit the shape oscillations in both the axisymmetric mode and asymmetric (three-dimensional) modes. Nonlinear effects in addition to the frequency shift and split due to deformation creates overlapping of the coupling ranges for different modes, which leads to the continuous shape oscillations above a certain bubble radius as the bubble grows.

  14. A spatiotemporally controllable chemical gradient generator via acoustically oscillating sharp-edge structures.

    PubMed

    Huang, Po-Hsun; Chan, Chung Yu; Li, Peng; Nama, Nitesh; Xie, Yuliang; Wei, Cheng-Hsin; Chen, Yuchao; Ahmed, Daniel; Huang, Tony Jun

    2015-11-01

    The ability to generate stable, spatiotemporally controllable concentration gradients is critical for resolving the dynamics of cellular response to a chemical microenvironment. Here we demonstrate an acoustofluidic gradient generator based on acoustically oscillating sharp-edge structures, which facilitates in a step-wise fashion the rapid mixing of fluids to generate tunable, dynamic chemical gradients. By controlling the driving voltage of a piezoelectric transducer, we demonstrated that the chemical gradient profiles can be conveniently altered (spatially controllable). By adjusting the actuation time of the piezoelectric transducer, moreover, we generated pulsatile chemical gradients (temporally controllable). With these two characteristics combined, we have developed a spatiotemporally controllable gradient generator. The applicability and biocompatibility of our acoustofluidic gradient generator are validated by demonstrating the migration of human dermal microvascular endothelial cells (HMVEC-d) in response to a generated vascular endothelial growth factor (VEGF) gradient, and by preserving the viability of HMVEC-d cells after long-term exposure to an acoustic field. Our device features advantages such as simple fabrication and operation, compact and biocompatible device, and generation of spatiotemporally tunable gradients.

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

    NASA Astrophysics Data System (ADS)

    Marston, Philip L.

    2001-05-01

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

  16. THE BARYON OSCILLATION SPECTROSCOPIC SURVEY OF SDSS-III

    SciTech Connect

    Dawson, Kyle S.; Ahn, Christopher P.; Bolton, Adam S.; Schlegel, David J.; Bailey, Stephen; Anderson, Scott F.; Bhardwaj, Vaishali; Aubourg, Eric; Bautista, Julian E.; Beifiori, Alessandra; Berlind, Andreas A.; Bizyaev, Dmitry; Brewington, Howard; Blake, Cullen H.; Blanton, Michael R.; Blomqvist, Michael; Borde, Arnaud; Brandt, W. N.; and others

    2013-01-01

    The Baryon Oscillation Spectroscopic Survey (BOSS) is designed to measure the scale of baryon acoustic oscillations (BAO) in the clustering of matter over a larger volume than the combined efforts of all previous spectroscopic surveys of large-scale structure. BOSS uses 1.5 million luminous galaxies as faint as i = 19.9 over 10,000 deg{sup 2} to measure BAO to redshifts z < 0.7. Observations of neutral hydrogen in the Ly{alpha} forest in more than 150,000 quasar spectra (g < 22) will constrain BAO over the redshift range 2.15 < z < 3.5. Early results from BOSS include the first detection of the large-scale three-dimensional clustering of the Ly{alpha} forest and a strong detection from the Data Release 9 data set of the BAO in the clustering of massive galaxies at an effective redshift z = 0.57. We project that BOSS will yield measurements of the angular diameter distance d{sub A} to an accuracy of 1.0% at redshifts z = 0.3 and z = 0.57 and measurements of H(z) to 1.8% and 1.7% at the same redshifts. Forecasts for Ly{alpha} forest constraints predict a measurement of an overall dilation factor that scales the highly degenerate D{sub A} (z) and H {sup -1}(z) parameters to an accuracy of 1.9% at z {approx} 2.5 when the survey is complete. Here, we provide an overview of the selection of spectroscopic targets, planning of observations, and analysis of data and data quality of BOSS.

  17. 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.

  18. Particle Mesh Simulations of the Lyα Forest and the Signature of Baryon Acoustic Oscillations in the Intergalactic Medium

    NASA Astrophysics Data System (ADS)

    White, Martin; Pope, Adrian; Carlson, Jordan; Heitmann, Katrin; Habib, Salman; Fasel, Patricia; Daniel, David; Lukic, Zarija

    2010-04-01

    We present a set of ultra-large particle-mesh simulations of the Lyα forest targeted at understanding the imprint of baryon acoustic oscillations in the inter-galactic medium. We use nine dark matter only simulations which can, for the first time, simultaneously resolve the Jeans scale of the intergalactic gas while covering the large volumes required to adequately sample the acoustic feature. Mock absorption spectra are generated using the fluctuating Gunn-Peterson approximation which have approximately correct flux probability density functions and small-scale power spectra. On larger scales, there is clear evidence in the redshift-space correlation function for an acoustic feature, which matches a linear theory template with constant bias. These spectra, which we make publicly available, can be used to test pipelines, plan future experiments, and model various physical effects. As an illustration, we discuss the basic properties of the acoustic signal in the forest, the scaling of errors with noise and source number density, modified statistics to treat mean flux evolution and mis-estimation, and non-gravitational sources such as fluctuations in the photoionizing background and temperature fluctuations due to He II reionization.

  19. Superhorizon fluctuations and acoustic oscillations in relativistic heavy-ion collisions

    SciTech Connect

    Mishra, Ananta P.; Mohapatra, Ranjita K.; Saumia, P. S.; Srivastava, Ajit M.

    2008-06-15

    We focus on the initial-state spatial anisotropies, originating at the thermalization stage, for central collisions in relativistic heavy-ion collisions. We propose that a plot of the root-mean-square values of the flow coefficients {radical}(v{sub n}{sup 2}){identical_to}v{sub n}{sup rms}, calculated in a laboratory fixed coordinate system, for a large range of n from 1 to about 30, can give nontrivial information about the initial stages of the system and its evolution. We also argue that for all wavelengths {lambda} of the anisotropy (at the surface of the plasma region) much larger than the acoustic horizon size H{sub s}{sup fr} at the freeze-out stage, the resulting values of v{sub n}{sup rms} should be suppressed by a factor of order 2H{sub s}{sup fr}/{lambda}. For noncentral collisions, these arguments naturally imply a certain amount of suppression of the elliptic flow. Further, by assuming that initial flow velocities are negligible at thermalization stage, we discuss the possibility that the resulting flow could show imprints of coherent oscillations in the plot of v{sub n}{sup rms} for subhorizon modes. For gold-gold collision at 200 GeV/nucleon center-of-mass energy, these features are expected to occur for n{>=}5, with n<4 modes showing suppression due to being superhorizon. This has strong similarities with the physics of the anisotropies of the cosmic microwave background radiation (CMBR) resulting from inflationary density fluctuations in the universe (despite important differences such as the absence of gravity effects for the heavy-ion case). It seems possible that the statistical fluctuations due to finite multiplicity may not be able to mask such features in the flow data or at least a nontrivial overall shape of the plot of v{sub n}{sup rms} may be inferred. In that case, the successes of analysis of CMBR anisotropy power spectrum to get cosmological parameters can be applied for relativistic heavy-ion collisions to learn about various relevant

  20. Corotational instability, magnetic resonances and global inertial-acoustic oscillations in magnetized black hole accretion discs

    NASA Astrophysics Data System (ADS)

    Fu, Wen; Lai, Dong

    2011-01-01

    Low-order, non-axisymmetric p-modes (also referred as inertial-acoustic modes) in hydrodynamic accretion discs around black holes are plausible candidates for high-frequency quasi-periodic oscillations (QPOs) observed in a number of accreting black hole systems. These modes are trapped in the innermost region of the accretion disc, and are subject to global instabilities due to wave absorption at the corotation resonance (where the wave pattern frequency ω/m equals the disc rotation rate Ω), when the fluid vortensity, ζ=κ2/(2ΩΣ) (where κ and Σ are the radial epicyclic frequency and disc surface density, respectively), has a positive gradient. We investigate the effects of disc magnetic fields on the wave absorption at corotation and the related wave super-reflection of the corotation barrier, and on the overstability of disc p-modes. In general, in the presence of magnetic fields, the p-modes have the character of inertial-fast magnetosonic waves in their propagation zone. For discs with a pure toroidal field, the corotation resonance is split into two magnetic resonances, where the wave frequency in the corotating frame of the fluid, ?, matches the slow magnetosonic wave frequency. Significant wave energy/angular momentum absorption occurs at both magnetic resonances, but with opposite signs, such that one of them enhances the super-reflection while the other diminishes it. The combined effect of the two magnetic resonances is to reduce the super-reflection and the growth rate of the overstable p-modes. Our calculations show that even a subthermal toroidal field (with the magnetic pressure less than the gas pressure) may suppress the overstability of hydrodynamic (B= 0) p-modes. For accretion discs with mixed (toroidal and vertical) magnetic fields, two additional Alfvén resonances appear, where ? matches the local Alfvén wave frequency. The effect of these additional resonances is to further reduce or diminish the growth rate of p-modes. Our results

  1. 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.

  2. Revisiting the BaO2/BaO redox cycle for solar thermochemical energy storage.

    PubMed

    Carrillo, A J; Sastre, D; Serrano, D P; Pizarro, P; Coronado, J M

    2016-03-21

    The barium peroxide-based redox cycle was proposed in the late 1970s as a thermochemical energy storage system. Since then, very little attention has been paid to such redox couples. In this paper, we have revisited the use of reduction-oxidation reactions of the BaO2/BaO system for thermochemical heat storage at high temperatures. Using thermogravimetric analysis, reduction and oxidation reactions were studied in order to find the main limitations associated with each process. Furthermore, the system was evaluated through several charge-discharge stages in order to analyse its possible degradation after repeated cycling. Through differential scanning calorimetry the heat stored and released were also determined. Oxidation reaction, which was found to be slower than reduction, was studied in more detail using isothermal tests. It was observed that the rate-controlling step of BaO oxidation follows zero-order kinetics, although at high temperatures a deviation from Arrhenius behaviour was observed probably due to hindrances to anionic oxygen diffusion caused by the formation of an external layer of BaO2. This redox couple was able to withstand several redox cycles without deactivation, showing reaction conversions close to 100% provided that impurities are previously eliminated through thermal pre-treatment, demonstrating the feasibility of this system for solar thermochemical heat storage.

  3. 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.

  4. Preliminary investigation of acoustic oscillations in an H2-O2 fired Hall generator

    NASA Technical Reports Server (NTRS)

    Phillips, B.

    1981-01-01

    Burner pressure oscillations and interelectrode voltage oscillations measured in an open-cycle supersonic flow Hall generator are presented. The ionized gas for the channel was supplied by seeding the approximately 1 lb/sec of hydrogen-oxygen combustion products with cesium. Since both the burner and the channel were located within magnetic fields exceeding 4 Tesla during operation, an infinite probe pressure measurement technique was used to measure burner pressure oscillations. Calibration of the burner pressure transducer using a resonance tube technique is presented. Evidence is presented for the existence of the first longitudinal mode of oscillations (5000 Hz) within the burner. Interelectrode voltage oscillations were simultaneously measured at two separate axial stations. The magnitude change and the phase shift between the two signals was interpreted as a decaying magnetoacoustic wave driven by the burner that propagates at local gas plus sonic velocities. The amplitude of the electrical voltage oscillations at the start of the power producing region of the channel varied with the magnetic field. This variation is compared with the results of a simple perturbation analysis. Arguments are presented for using an unsteady model for analyzing wave processes in channels.

  5. Comment on "Acoustical observation of bubble oscillations induced by bubble popping"

    NASA Astrophysics Data System (ADS)

    Blanc, É.; Ollivier, F.; Antkowiak, A.; Wunenburger, R.

    2015-03-01

    We have reproduced the experiment of acoustic monitoring of spontaneous popping of single soap bubbles standing in air reported by Ding et al. [2aa Phys. Rev. E 75, 041601 (2007), 10.1103/PhysRevE.75.041601]. By using a single microphone and two different signal acquisition systems recording in parallel the signal at the microphone output, among them the system used by Ding et al., we have experimentally evidenced that the acoustic precursors of bubble popping events detected by Ding et al. actually result from an acausal artifact of the signal processing performed by their acquisition system which lies outside of its prescribed working frequency range. No acoustic precursor of popping could be evidenced with the microphone used in these experiments, whose sensitivity is 1 V Pa-1 and frequency range is 500 Hz-100 kHz.

  6. Comment on "Acoustical observation of bubble oscillations induced by bubble popping".

    PubMed

    Blanc, É; Ollivier, F; Antkowiak, A; Wunenburger, R

    2015-03-01

    We have reproduced the experiment of acoustic monitoring of spontaneous popping of single soap bubbles standing in air reported by Ding et al. [2aaPhys. Rev. E 75, 041601 (2007)]. By using a single microphone and two different signal acquisition systems recording in parallel the signal at the microphone output, among them the system used by Ding et al., we have experimentally evidenced that the acoustic precursors of bubble popping events detected by Ding et al. actually result from an acausal artifact of the signal processing performed by their acquisition system which lies outside of its prescribed working frequency range. No acoustic precursor of popping could be evidenced with the microphone used in these experiments, whose sensitivity is 1VPa-1 and frequency range is 500 Hz-100 kHz. PMID:25871255

  7. Effect of standing transverse acoustic oscillations on fuel-oxidant mixing in cylindrical combustion chambers

    NASA Technical Reports Server (NTRS)

    Mickelsen, William R

    1957-01-01

    Vapor fuel-oxidant mixing is analyzed for standing transverse acoustic fields simulating those existing in screeching or screaming combustors. The additional mixing due to the acoustic field is shown to be a function of sound pressure and frequency, stream velocity, and turbulence. The effects of these parameters are shown graphically for a realistic range of combustor conditions. The fuel-oxidant ratio at various combustor stations is shown to have a cyclic fluctuation which is in phase with the pressure fluctuations. Possible mechanisms contributing to screech and scream are discussed.

  8. Power-law cosmology, SN Ia, and BAO

    SciTech Connect

    Dolgov, Aleksander; Halenka, Vitali; Tkachev, Igor E-mail: vithal@umich.edu

    2014-10-01

    We revise observational constraints on the class of models of modified gravity which at low redshifts lead to a power-law cosmology. To this end we use available public data on Supernova Ia and on baryon acoustic oscillations. We show that the expansion regime a(t) ∼ t{sup β} with β close to 3/2 in a spatially flat universe is a good fit to these data.

  9. Mock Quasar-Lyman-α forest data-sets for the SDSS-III Baryon Oscillation Spectroscopic Survey

    SciTech Connect

    Bautista, Julian E.; Busca, Nicolas G.; Pieri, Matthew M.; Miralda-Escudé, Jordi; Gontcho, Satya Gontcho A.; Feng, Yu; Ho, Shirley; Ge, Jian; Noterdaeme, Pasquier; Pâris, Isabelle; Rossi, Graziano

    2015-05-01

    We describe mock data-sets generated to simulate the high-redshift quasar sample in Data Release 11 (DR11) of the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). The mock spectra contain Lyα forest correlations useful for studying the 3D correlation function including Baryon Acoustic Oscillations (BAO). They also include astrophysical effects such as quasar continuum diversity and high-density absorbers, instrumental effects such as noise and spectral resolution, as well as imperfections introduced by the SDSS pipeline treatment of the raw data. The Lyα forest BAO analysis of the BOSS collaboration, described in Delubac et al. 2014, has used these mock data-sets to develop and cross-check analysis procedures prior to performing the BAO analysis on real data, and for continued systematic cross checks. Tests presented here show that the simulations reproduce sufficiently well important characteristics of real spectra. These mock data-sets will be made available together with the data at the time of the Data Release 11.

  10. Collective acoustic modes as renormalized damped oscillators: Unified description of neutron and x-ray scattering data from classical fluids

    SciTech Connect

    Bafile, Ubaldo; Guarini, Eleonora

    2006-06-15

    In the Q range where inelastic x-ray and neutron scattering are applied to the study of acoustic collective excitations in fluids, various models of the dynamic structure factor S(Q,{omega}) generalize in different ways the results obtained from linearized-hydrodynamics theory in the Q{yields}0 limit. Here we show that the models most commonly fitted to experimental S(Q,{omega}) spectra can be given a unified formulation. In this way, direct comparisons among the results obtained by fitting different models become now possible to a much larger extent than ever. We also show that a consistent determination of the dispersion curve and of the propagation Q range of the excitations is possible, whichever model is used. We derive an exact formula which describes in all cases the dispersion curve and allows for the first quantitative understanding of its shape, by assigning specific and distinct roles to the various structural, thermal, and damping effects that determine the Q dependence of the mode frequencies. The emerging picture describes the acoustic modes as Q-dependent harmonic oscillators whose characteristic frequency is explicitly renormalized in an exact way by the relaxation processes, which also determine, through the widths of both the inelastic and the elastic lines, the whole shape of collective-excitation spectra.

  11. Collective acoustic modes as renormalized damped oscillators: Unified description of neutron and x-ray scattering data from classical fluids

    NASA Astrophysics Data System (ADS)

    Bafile, Ubaldo; Guarini, Eleonora; Barocchi, Fabrizio

    2006-06-01

    In the Q range where inelastic x-ray and neutron scattering are applied to the study of acoustic collective excitations in fluids, various models of the dynamic structure factor S(Q,ω) generalize in different ways the results obtained from linearized-hydrodynamics theory in the Q→0 limit. Here we show that the models most commonly fitted to experimental S(Q,ω) spectra can be given a unified formulation. In this way, direct comparisons among the results obtained by fitting different models become now possible to a much larger extent than ever. We also show that a consistent determination of the dispersion curve and of the propagation Q range of the excitations is possible, whichever model is used. We derive an exact formula which describes in all cases the dispersion curve and allows for the first quantitative understanding of its shape, by assigning specific and distinct roles to the various structural, thermal, and damping effects that determine the Q dependence of the mode frequencies. The emerging picture describes the acoustic modes as Q -dependent harmonic oscillators whose characteristic frequency is explicitly renormalized in an exact way by the relaxation processes, which also determine, through the widths of both the inelastic and the elastic lines, the whole shape of collective-excitation spectra.

  12. Collective acoustic modes as renormalized damped oscillators: unified description of neutron and x-ray scattering data from classical fluids.

    PubMed

    Bafile, Ubaldo; Guarini, Eleonora; Barocchi, Fabrizio

    2006-06-01

    In the Q range where inelastic x-ray and neutron scattering are applied to the study of acoustic collective excitations in fluids, various models of the dynamic structure factor S(Q, omega) generalize in different ways the results obtained from linearized-hydrodynamics theory in the Q-->0 limit. Here we show that the models most commonly fitted to experimental S(Q, omega) spectra can be given a unified formulation. In this way, direct comparisons among the results obtained by fitting different models become now possible to a much larger extent than ever. We also show that a consistent determination of the dispersion curve and of the propagation Q range of the excitations is possible, whichever model is used. We derive an exact formula which describes in all cases the dispersion curve and allows for the first quantitative understanding of its shape, by assigning specific and distinct roles to the various structural, thermal, and damping effects that determine the Q dependence of the mode frequencies. The emerging picture describes the acoustic modes as Q-dependent harmonic oscillators whose characteristic frequency is explicitly renormalized in an exact way by the relaxation processes, which also determine, through the widths of both the inelastic and the elastic lines, the whole shape of collective-excitation spectra. PMID:16906814

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

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

  15. Suppression of nonlinear oscillations in combustors with partial length acoustic liners

    NASA Technical Reports Server (NTRS)

    Espander, W. R.; Mitchell, C. E.; Baer, M. R.

    1975-01-01

    An analytical model is formulated for a three-dimensional nonlinear stability problem in a rocket motor combustion chamber. The chamber is modeled as a right circular cylinder with a short (multi-orifice) nozzle, and an acoustic linear covering an arbitrary portion of the cylindrical periphery. The combustion is concentrated at the injector and the gas flow field is characterized by a mean Mach number. The unsteady combustion processes are formulated using the Crocco time lag model. The resulting equations are solved using a Green's function method combined with numerical evaluation techniques. The influence of acoustic liners on the nonlinear waveforms is predicted. Nonlinear stability limits and regions where triggering is possible are also predicted for both lined and unlined combustors in terms of the combustion parameters.

  16. Nonlinear Resonant Oscillations of Gas in Optimized Acoustical Resonators and the Effect of Central Blockage

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    Optimizing resonator shapes for maximizing the ratio of maximum to minimum gas pressure at an end of the resonator is investigated numerically. It is well known that the resonant frequencies and the nonlinear standing waveform in an acoustical resonator strongly depend on the resonator geometry. A quasi-Newton type scheme was used to find optimized axisymmetric resonator shapes achieving the maximum pressure compression ratio with an acceleration of constant amplitude. The acoustical field was solved using a one-dimensional model, and the resonance frequency shift and hysteresis effects were obtained through an automation scheme based on continuation method. Results are presented for optimizing three types of geometry: a cone, a horn-cone and a half cosine- shape. For each type, different optimized shapes were found when starting with different initial guesses. Further, the one-dimensional model was modified to study the effect of an axisymmetric central blockage on the nonlinear standing wave.

  17. Nonlinear Resonant Oscillations of Gas in Optimized Acoustical Resonators and the Effect of Central Blockage

    NASA Technical Reports Server (NTRS)

    Li, Xiaofan; Finkbeiner, Joshua; Raman, Ganesh; Daniels, Christopher; Steinetz, Bruce M.

    2003-01-01

    Optimizing resonator shapes for maximizing the ratio of maximum to minimum gas pressure at an end of the resonator is investigated numerically. It is well known that the resonant frequencies and the nonlinear standing waveform in an acoustical resonator strongly depend on the resonator geometry. A quasi-Newton type scheme was used to find optimized axisymmetric resonator shapes achieving the maximum pressure compression ratio with an acceleration of constant amplitude. The acoustical field was solved using a one-dimensional model, and the resonance frequency shift and hysteresis effects were obtained through an automation scheme based on continuation method. Results are presented for optimizing three types of geometry: a cone, a horn-cone and a half cosine-shape. For each type, different optimized shapes were found when starting with different initial guesses. Further, the one-dimensional model was modified to study the effect of an axisymmetric central blockage on the nonlinear standing wave.

  18. Reconstructing Baryon Oscillations : Enhancing the Dark Energy Reach of Future Redshift Surveys

    NASA Astrophysics Data System (ADS)

    Padmanabhan, Nikhil

    The baryon acoustic oscillation (BAO) method is a key component of any Stage IV dark energy program, including a possible NASA Joint Dark Energy Mission. Sound waves in the plasma of the early Universe get frozen into the matter distribution when the Universe transitions into a neutral state, imprinting a characteristic feature in the galaxy correlation function. This feature can be used as a standard ruler to constrain the expansion history of the Universe, and probe the redshift evolution of the dark energy. However, the statistical precision of the method is limited by large scale velocity flows, which smooth out the acoustic feature and reduce its contrast. We propose to develop "reconstruction" algorithms which undo this smoothing, and increase the statistical accuracy of the BAO method. A first such algorithm already exists, and has been demonstrated to work, both theoretically as well as on N]body simulations. However, current implementations of this algorithm use symmetry properties of the simulations, which are not realized in real survey data. The first goal of this proposal is to extend this algorithm to work on realistic survey data with irregular boundaries and missing data. We have demonstrated such an algorithm in principle, and plan to further refine it, applying to more realistic simulations. We also plan on exploring different "interpolation" schemes to fill in missing data, testing to ensure that they do not bias the standard ruler. The second goal of this proposal is to characterize the requirements that reconstruction would place on the design of future surveys. The first of these, and the most relevant for a possible JDEM mission, is to understand the requirement on the contiguity of the survey] whether reconstruction works with gaps in the survey, and what scales and spatial frequencies of gaps can be tolerated. We also plan to understand how reconstruction degrades for low number density tracers, and if reconstruction is sensitive to galaxy

  19. [EFFECTS OF MUSIC-ACOUSTIC SIGNALS, ONLINE CONTROLLED BY EEG OSCILLATORS OF THE SUBJECT].

    PubMed

    Fedotchev, A I; Bondar, A T; Bakhchina, A V; Parin, S B; Polevaya, S A; Radchenko, G S

    2015-08-01

    The effects of 2 variants of the method of musical EEG neurofeedback, in which the dominant spectral components of subject's EEG (EEG oscillators) are online converted to music-like signals similar by timbre to flute sounds, have been studied. In the first case, these music-like signals were smoothly varying by the pitch and intensity in accordance with the current amplitude of the EEG oscillator. In the second case, the same variations of flute-like sound were accompanied by such musical element as rhythm. After the single exposure, the modifications of subject's brain activity and positive changes in psycho-physiological state of the subject have been found. Particularly pronounced effects were observed under rhythmically organized music-like stimuli.

  20. [EFFECTS OF MUSIC-ACOUSTIC SIGNALS, ONLINE CONTROLLED BY EEG OSCILLATORS OF THE SUBJECT].

    PubMed

    Fedotchev, A I; Bondar, A T; Bakhchina, A V; Parin, S B; Polevaya, S A; Radchenko, G S

    2015-08-01

    The effects of 2 variants of the method of musical EEG neurofeedback, in which the dominant spectral components of subject's EEG (EEG oscillators) are online converted to music-like signals similar by timbre to flute sounds, have been studied. In the first case, these music-like signals were smoothly varying by the pitch and intensity in accordance with the current amplitude of the EEG oscillator. In the second case, the same variations of flute-like sound were accompanied by such musical element as rhythm. After the single exposure, the modifications of subject's brain activity and positive changes in psycho-physiological state of the subject have been found. Particularly pronounced effects were observed under rhythmically organized music-like stimuli. PMID:26591592

  1. Asymptotic theory of intermediate- and high-degree solar acoustic oscillations

    NASA Technical Reports Server (NTRS)

    Brodsky, M.; Vorontsov, S. V.

    1993-01-01

    A second-order asymptotic approximation is developed for adiabatic nonradial p-modes of a spherically symmetric star. The exact solutions of adiabatic oscillations are assumed in the outermost layers, where the asymptotic description becomes invalid, which results in a eigenfrequency equation with model-dependent surface phase shift. For lower degree modes, the phase shift is a function of frequency alone; for high-degree modes, its dependence on the degree is explicitly taken into account.

  2. Resolving the source of the solar acoustic oscillations: What will be possible with DKIST?

    NASA Astrophysics Data System (ADS)

    Rast, Mark; Martinez Pillet, Valentin

    2016-05-01

    The solar p-modes are likely excited by small-scale convective dynamics in the solar photosphere, but the detailed source properties are not known. Theoretical models differ and observations are yet unable to differentiate between them. Resolving the underlying source events is more than a curiosity. It is important to the veracity of global helioseismic measurements (including local spectral methods such as ring diagram analysis) because global p-mode line shapes and thus accurate frequency determinations depend critically on the relationship between intensity and velocity during the excitation events. It is also fundamental to improving the accuracy of the local time-distance measurements because in these kernel calculations depend on knowledge of the source profile and the properties of the excitation noise. The Daniel K. Inouye Solar Telescope (DKIST) will have the spatial resolution and spectral range needed to resolve the solar acoustic excitation events in both time and space (horizontally and with height) using multi-wavelength observations. Inversions to determine the dynamic and thermodynamic evolution of the discrete small-scale convective events that serve as acoustic sources may also be possible, though determination of the pressure fluctuations associated with the sources is a challenge. We describe the DKIST capabilities anticipated and the preliminary work needed to prepare for them.

  3. Evolving BioAssay Ontology (BAO): modularization, integration and applications

    PubMed Central

    2014-01-01

    The lack of established standards to describe and annotate biological assays and screening outcomes in the domain of drug and chemical probe discovery is a severe limitation to utilize public and proprietary drug screening data to their maximum potential. We have created the BioAssay Ontology (BAO) project (http://bioassayontology.org) to develop common reference metadata terms and definitions required for describing relevant information of low-and high-throughput drug and probe screening assays and results. The main objectives of BAO are to enable effective integration, aggregation, retrieval, and analyses of drug screening data. Since we first released BAO on the BioPortal in 2010 we have considerably expanded and enhanced BAO and we have applied the ontology in several internal and external collaborative projects, for example the BioAssay Research Database (BARD). We describe the evolution of BAO with a design that enables modeling complex assays including profile and panel assays such as those in the Library of Integrated Network-based Cellular Signatures (LINCS). One of the critical questions in evolving BAO is the following: how can we provide a way to efficiently reuse and share among various research projects specific parts of our ontologies without violating the integrity of the ontology and without creating redundancies. This paper provides a comprehensive answer to this question with a description of a methodology for ontology modularization using a layered architecture. Our modularization approach defines several distinct BAO components and separates internal from external modules and domain-level from structural components. This approach facilitates the generation/extraction of derived ontologies (or perspectives) that can suit particular use cases or software applications. We describe the evolution of BAO related to its formal structures, engineering approaches, and content to enable modeling of complex assays and integration with other ontologies and

  4. Formation of single-phase BaO nanoclusters

    SciTech Connect

    Du, Yingge; Kim, Dong Jun; Varga, Tamas; Wang, Zhitao; Szanyi, Janos; Lyubinetsky, Igor

    2011-06-01

    Combined analysis employing in-situ X-rays photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and ex-situ X-ray diffraction (XRD) has demonstrated the feasibility to deposit single-phase barium oxide overlayers by a direct sublimation of BaO material from an effusion cell. Furthermore, in situ scanning tunneling microscopy (STM) has confirmed that the BaO grows as nanoclusters with dimensions down to ~2 nm.

  5. Evolving BioAssay Ontology (BAO): modularization, integration and applications.

    PubMed

    Abeyruwan, Saminda; Vempati, Uma D; Küçük-McGinty, Hande; Visser, Ubbo; Koleti, Amar; Mir, Ahsan; Sakurai, Kunie; Chung, Caty; Bittker, Joshua A; Clemons, Paul A; Brudz, Steve; Siripala, Anosha; Morales, Arturo J; Romacker, Martin; Twomey, David; Bureeva, Svetlana; Lemmon, Vance; Schürer, Stephan C

    2014-01-01

    The lack of established standards to describe and annotate biological assays and screening outcomes in the domain of drug and chemical probe discovery is a severe limitation to utilize public and proprietary drug screening data to their maximum potential. We have created the BioAssay Ontology (BAO) project (http://bioassayontology.org) to develop common reference metadata terms and definitions required for describing relevant information of low-and high-throughput drug and probe screening assays and results. The main objectives of BAO are to enable effective integration, aggregation, retrieval, and analyses of drug screening data. Since we first released BAO on the BioPortal in 2010 we have considerably expanded and enhanced BAO and we have applied the ontology in several internal and external collaborative projects, for example the BioAssay Research Database (BARD). We describe the evolution of BAO with a design that enables modeling complex assays including profile and panel assays such as those in the Library of Integrated Network-based Cellular Signatures (LINCS). One of the critical questions in evolving BAO is the following: how can we provide a way to efficiently reuse and share among various research projects specific parts of our ontologies without violating the integrity of the ontology and without creating redundancies. This paper provides a comprehensive answer to this question with a description of a methodology for ontology modularization using a layered architecture. Our modularization approach defines several distinct BAO components and separates internal from external modules and domain-level from structural components. This approach facilitates the generation/extraction of derived ontologies (or perspectives) that can suit particular use cases or software applications. We describe the evolution of BAO related to its formal structures, engineering approaches, and content to enable modeling of complex assays and integration with other ontologies and

  6. Evolving BioAssay Ontology (BAO): modularization, integration and applications.

    PubMed

    Abeyruwan, Saminda; Vempati, Uma D; Küçük-McGinty, Hande; Visser, Ubbo; Koleti, Amar; Mir, Ahsan; Sakurai, Kunie; Chung, Caty; Bittker, Joshua A; Clemons, Paul A; Brudz, Steve; Siripala, Anosha; Morales, Arturo J; Romacker, Martin; Twomey, David; Bureeva, Svetlana; Lemmon, Vance; Schürer, Stephan C

    2014-01-01

    The lack of established standards to describe and annotate biological assays and screening outcomes in the domain of drug and chemical probe discovery is a severe limitation to utilize public and proprietary drug screening data to their maximum potential. We have created the BioAssay Ontology (BAO) project (http://bioassayontology.org) to develop common reference metadata terms and definitions required for describing relevant information of low-and high-throughput drug and probe screening assays and results. The main objectives of BAO are to enable effective integration, aggregation, retrieval, and analyses of drug screening data. Since we first released BAO on the BioPortal in 2010 we have considerably expanded and enhanced BAO and we have applied the ontology in several internal and external collaborative projects, for example the BioAssay Research Database (BARD). We describe the evolution of BAO with a design that enables modeling complex assays including profile and panel assays such as those in the Library of Integrated Network-based Cellular Signatures (LINCS). One of the critical questions in evolving BAO is the following: how can we provide a way to efficiently reuse and share among various research projects specific parts of our ontologies without violating the integrity of the ontology and without creating redundancies. This paper provides a comprehensive answer to this question with a description of a methodology for ontology modularization using a layered architecture. Our modularization approach defines several distinct BAO components and separates internal from external modules and domain-level from structural components. This approach facilitates the generation/extraction of derived ontologies (or perspectives) that can suit particular use cases or software applications. We describe the evolution of BAO related to its formal structures, engineering approaches, and content to enable modeling of complex assays and integration with other ontologies and

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

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  8. Acoustic and Slow Sausage Oscillations in the Stratified Solar Photosphere: Hinode Observations and Phase Relationships

    NASA Astrophysics Data System (ADS)

    Tsap, Y. T.; Stepanov, A. V.; Kopylova, Y. G.

    2016-09-01

    Based on the linearized magnetohydrodynamic (MHD) equations within the framework of the thin flux tube approximation, the phase relationships between the disturbed quantities of evanescent acoustic and slow sausage MHD modes excited in the adiabatically stratified solar atmosphere are considered. It has been shown that the sign of the phase differences (equal to ±π/2) between the velocity and other disturbed quantities such as pressure, density, magnetic field, and temperature, depends on the wave frequency ω. The obtained phase relationships agree well with SOT/Hinode observations obtained by Fujimura and Tsuneta (Astrophys. J. 702, 1443, 2009) when ω≈ωc, where ωc is the cutoff frequency. The role of various modes excited in the solar atmosphere in the light of the chromospheric and coronal heating problems are discussed.

  9. Electrodynamic soil plate oscillator: Modeling nonlinear mesoscopic elastic behavior and hysteresis in nonlinear acoustic landmine detection

    NASA Astrophysics Data System (ADS)

    Korman, M. S.; Duong, D. V.; Kalsbeck, A. E.

    2015-10-01

    An apparatus (SPO), designed to study flexural vibrations of a soil loaded plate, consists of a thin circular elastic clamped plate (and cylindrical wall) supporting a vertical soil column. A small magnet attached to the center of the plate is driven by a rigid AC coil (located coaxially below the plate) to complete the electrodynamic soil plate oscillator SPO design. The frequency dependent mechanical impedance Zmech (force / particle velocity, at the plate's center) is inversely proportional to the electrical motional impedance Zmot. Measurements of Zmot are made using the complex output to input response of a Wheatstone bridge that has an identical coil element in one of its legs. Near resonance, measurements of Zmot (with no soil) before and after a slight point mass loading at the center help determine effective mass, spring, damping and coupling constant parameters of the system. "Tuning curve" behavior of real{ Zmot } and imaginary{ Zmot } at successively higher vibration amplitudes of dry sifted masonry sand are measured. They exhibit a decrease "softening" in resonance frequency along with a decrease in the quality Q factor. In soil surface vibration measurements a bilinear hysteresis model predicts the tuning curve shape for this nonlinear mesoscopic elastic SPO behavior - which also models the soil vibration over an actual plastic "inert" VS 1.6 buried landmine. Experiments are performed where a buried 1m cube concrete block supports a 12 inch deep by 30 inch by 30 inch concrete soil box for burying a VS 1.6 in dry sifted masonry sand for on-the-mine and off-the-mine soil vibration experiments. The backbone curve (a plot of the peak amplitude vs. corresponding resonant frequency from a family of tuning curves) exhibits mostly linear behavior for "on target" soil surface vibration measurements of the buried VS 1.6 or drum-like mine simulants for relatively low particle velocities of the soil. Backbone curves for "on target" measurements exhibit

  10. A high-overtone bulk acoustic wave resonator-oscillator-based 4.596 GHz frequency source: Application to a coherent population trapping Cs vapor cell atomic clock

    NASA Astrophysics Data System (ADS)

    Daugey, Thomas; Friedt, Jean-Michel; Martin, Gilles; Boudot, Rodolphe

    2015-11-01

    This article reports on the design and characterization of a high-overtone bulk acoustic wave resonator (HBAR)-oscillator-based 4.596 GHz frequency source. A 2.298 GHz signal, generated by an oscillator constructed around a thermally controlled two-port aluminum nitride-sapphire HBAR resonator with a Q-factor of 24 000 at 68 °C, is frequency multiplied by 2-4.596 GHz, half of the Cs atom clock frequency. The temperature coefficient of frequency of the HBAR is measured to be -23 ppm/ °C at 2.298 GHz. The measured phase noise of the 4.596 GHz source is -105 dB rad2/Hz at 1 kHz offset and -150 dB rad2/Hz at 100 kHz offset. The 4.596 GHz output signal is used as a local oscillator in a laboratory-prototype Cs microcell-based coherent population trapping atomic clock. The signal is stabilized onto the atomic transition frequency by tuning finely a voltage-controlled phase shifter implemented in the 2.298 GHz HBAR-oscillator loop, preventing the need for a high-power-consuming direct digital synthesis. The short-term fractional frequency stability of the free-running oscillator is 1.8 × 10-9 at one second integration time. In locked regime, the latter is improved in a preliminary proof-of-concept experiment at the level of 6.6 × 10-11 τ-1/2 up to a few seconds and found to be limited by the signal-to-noise ratio of the detected CPT resonance.

  11. A high-overtone bulk acoustic wave resonator-oscillator-based 4.596 GHz frequency source: Application to a coherent population trapping Cs vapor cell atomic clock.

    PubMed

    Daugey, Thomas; Friedt, Jean-Michel; Martin, Gilles; Boudot, Rodolphe

    2015-11-01

    This article reports on the design and characterization of a high-overtone bulk acoustic wave resonator (HBAR)-oscillator-based 4.596 GHz frequency source. A 2.298 GHz signal, generated by an oscillator constructed around a thermally controlled two-port aluminum nitride-sapphire HBAR resonator with a Q-factor of 24,000 at 68 °C, is frequency multiplied by 2-4.596 GHz, half of the Cs atom clock frequency. The temperature coefficient of frequency of the HBAR is measured to be -23 ppm/ °C at 2.298 GHz. The measured phase noise of the 4.596 GHz source is -105 dB rad(2)/Hz at 1 kHz offset and -150 dB rad(2)/Hz at 100 kHz offset. The 4.596 GHz output signal is used as a local oscillator in a laboratory-prototype Cs microcell-based coherent population trapping atomic clock. The signal is stabilized onto the atomic transition frequency by tuning finely a voltage-controlled phase shifter implemented in the 2.298 GHz HBAR-oscillator loop, preventing the need for a high-power-consuming direct digital synthesis. The short-term fractional frequency stability of the free-running oscillator is 1.8 × 10(-9) at one second integration time. In locked regime, the latter is improved in a preliminary proof-of-concept experiment at the level of 6.6 × 10(-11) τ(-1/2) up to a few seconds and found to be limited by the signal-to-noise ratio of the detected CPT resonance.

  12. A high-overtone bulk acoustic wave resonator-oscillator-based 4.596 GHz frequency source: Application to a coherent population trapping Cs vapor cell atomic clock

    SciTech Connect

    Daugey, Thomas; Friedt, Jean-Michel; Martin, Gilles; Boudot, Rodolphe

    2015-11-15

    This article reports on the design and characterization of a high-overtone bulk acoustic wave resonator (HBAR)-oscillator-based 4.596 GHz frequency source. A 2.298 GHz signal, generated by an oscillator constructed around a thermally controlled two-port aluminum nitride-sapphire HBAR resonator with a Q-factor of 24 000 at 68 °C, is frequency multiplied by 2–4.596 GHz, half of the Cs atom clock frequency. The temperature coefficient of frequency of the HBAR is measured to be −23 ppm/ °C at 2.298 GHz. The measured phase noise of the 4.596 GHz source is −105 dB rad{sup 2}/Hz at 1 kHz offset and −150 dB rad{sup 2}/Hz at 100 kHz offset. The 4.596 GHz output signal is used as a local oscillator in a laboratory-prototype Cs microcell-based coherent population trapping atomic clock. The signal is stabilized onto the atomic transition frequency by tuning finely a voltage-controlled phase shifter implemented in the 2.298 GHz HBAR-oscillator loop, preventing the need for a high-power-consuming direct digital synthesis. The short-term fractional frequency stability of the free-running oscillator is 1.8 × 10{sup −9} at one second integration time. In locked regime, the latter is improved in a preliminary proof-of-concept experiment at the level of 6.6 × 10{sup −11} τ{sup −1/2} up to a few seconds and found to be limited by the signal-to-noise ratio of the detected CPT resonance.

  13. The extended Baryon Oscillation Spectroscopic Survey: a cosmological forecast

    NASA Astrophysics Data System (ADS)

    Zhao, Gong-Bo; Wang, Yuting; Ross, Ashley J.; Shandera, Sarah; Percival, Will J.; Dawson, Kyle S.; Kneib, Jean-Paul; Myers, Adam D.; Brownstein, Joel R.; Comparat, Johan; Delubac, Timothée; Gao, Pengyuan; Hojjati, Alireza; Koyama, Kazuya; McBride, Cameron K.; Meza, Andrés; Newman, Jeffrey A.; Palanque-Delabrouille, Nathalie; Pogosian, Levon; Prada, Francisco; Rossi, Graziano; Schneider, Donald P.; Seo, Hee-Jong; Tao, Charling; Wang, Dandan; Yèche, Christophe; Zhang, Hanyu; Zhang, Yuecheng; Zhou, Xu; Zhu, Fangzhou; Zou, Hu

    2016-04-01

    We present a science forecast for the extended Baryon Oscillation Spectroscopic Survey (eBOSS) survey. Focusing on discrete tracers, we forecast the expected accuracy of the baryonic acoustic oscillation (BAO), the redshift-space distortion (RSD) measurements, the fNL parameter quantifying the primordial non-Gaussianity, the dark energy and modified gravity parameters. We also use the line-of-sight clustering in the Lyman α forest to constrain the total neutrino mass. We find that eBOSS luminous red galaxies, emission line galaxies and clustering quasars can achieve a precision of 1, 2.2 and 1.6 per cent, respectively, for spherically averaged BAO distance measurements. Using the same samples, the constraint on fσ8 is expected to be 2.5, 3.3 and 2.8 per cent, respectively. For primordial non-Gaussianity, eBOSS alone can reach an accuracy of σ(fNL) ˜ 10-15. eBOSS can at most improve the dark energy figure of merit by a factor of 3 for the Chevallier-Polarski-Linder parametrization, and can well constrain three eigenmodes for the general equation-of-state parameter. eBOSS can also significantly improve constraints on modified gravity parameters by providing the RSD information, which is highly complementary to constraints obtained from weak lensing measurements. A principal component analysis shows that eBOSS can measure the eigenmodes of the effective Newton's constant to 2 per cent precision; this is a factor of 10 improvement over that achievable without eBOSS. Finally, we derive the eBOSS constraint (combined with Planck, Dark Energy Survey and BOSS) on the total neutrino mass, σ(Σmν) = 0.03 eV (68 per cent CL), which in principle makes it possible to distinguish between the two scenarios of neutrino mass hierarchies.

  14. BAO Plate Archive and Armenian Virtual Observatory (ArVO)

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M. 1; Astsatryan, H. V. 2; Magakian, T. Yu. 1; Sargsyan, L. A. 1; Gigoyan, K. S. 1; Erastova, L. K. 1; Gyulzadyan, M. V. 1; Sinamyan, P. K. 1; Paronyan, G. M. 1; Knyazyan, A. V. 2; Mikayelyan, G. A. 1; Farmanyan, S. V. 1; Hovhannisyan, L. R. 1; Nikoghosyan, E. H. 1; Abrahamyan, H. V. 1; Andreasyan, H. R. 1; Azatyan, N. M. 1; Khachatryan, K. G. 1; Kostandyan, G. R. 1; Vardanyan, A. V. 1

    2016-09-01

    A review on Byurakan Astrophysical Observatory (BAO) Plate Archive and Armenian Virtual Observatory (ArVO) projects is given. BAO Plate Archive consists of 37,500 photographic plates and films, obtained with 2.6m telescope, 1m and 0.5m Schmidt telescopes and other smaller ones during 1947-1991. The famous Markarian Survey (or the First Byurakan Survey, FBS) 2000 plates were digitized in 2002-2005 and the Digitized FBS (DFBS, www.aras.am/Dfbs/dfbs.html) was created. New science projects have been conducted based on this low-dispersion spectroscopic material. Several other smaller digitization projects have been carried out as well, such as part of Second Byurakan Survey (SBS) plates, photographic chain plates in Coma, where the blazar ON 231 is located and 2.6m film spectra of FBS Blue Stellar Objects. However, most of the plates and films are not digitized. In 2015, we have started a project on the whole BAO Plate Archive digitization, creation of electronic database and its scientific usage. Armenian Virtual Observatory (ArVO, www.aras.am/Arvo/arvo.htm) database will accommodate all new data. The project runs in collaboration with the Armenian Institute of Informatics and Automation Problems (IIAP) and will continue during 3 years in 2015-2017. The final result will be an Electronic Database and online Interactive Sky map to be used for further research projects. ArVO will provide all standards and tools for efficient usage of the scientific output and its integration in international databases.

  15. First cosmological constraints on dark energy from the radial baryon acoustic scale.

    PubMed

    Gaztañaga, Enrique; Miquel, Ramon; Sánchez, Eusebio

    2009-08-28

    We present cosmological constraints arising from the first measurement of the radial (line-of-sight) baryon acoustic oscillations (BAO) scale in the large scale structure traced by the galaxy distribution. Here we use these radial BAO measurements at z = 0.24 and z = 0.43 to derive new constraints on dark energy and its equation of state for a flat universe, without any other assumptions on the cosmological model: w = -1.14 + or - 0.39 (assumed constant), Omega(m) = 0.24(-0.05);(+0.06). If we drop the assumption of flatness and include previous cosmic microwave background and supernova data, we find w = -0.974 + or - 0.058, Omega(m) = 0.271 + or - 0.015, and Omega(k) = -0.002 + or - 0.006, in good agreement with a flat cold dark matter cosmology with a cosmological constant. To our knowledge, these are the most stringent constraints on these parameters to date under our stated assumptions.

  16. REGARDING THE LINE-OF-SIGHT BARYONIC ACOUSTIC FEATURE IN THE SLOAN DIGITAL SKY SURVEY AND BARYON OSCILLATION SPECTROSCOPIC SURVEY LUMINOUS RED GALAXY SAMPLES

    SciTech Connect

    Kazin, Eyal A.; Blanton, Michael R.; Scoccimarro, Roman; McBride, Cameron K.; Berlind, Andreas A.

    2010-08-20

    We analyze the line-of-sight baryonic acoustic feature in the two-point correlation function {xi} of the Sloan Digital Sky Survey luminous red galaxy (LRG) sample (0.16 < z < 0.47). By defining a narrow line-of-sight region, r{sub p} < 5.5 h {sup -1} Mpc, where r{sub p} is the transverse separation component, we measure a strong excess of clustering at {approx}110 h {sup -1} Mpc, as previously reported in the literature. We also test these results in an alternative coordinate system, by defining the line of sight as {theta} < 3{sup 0}, where {theta} is the opening angle. This clustering excess appears much stronger than the feature in the better-measured monopole. A fiducial {Lambda}CDM nonlinear model in redshift space predicts a much weaker signature. We use realistic mock catalogs to model the expected signal and noise. We find that the line-of-sight measurements can be explained well by our mocks as well as by a featureless {xi} = 0. We conclude that there is no convincing evidence that the strong clustering measurement is the line-of-sight baryonic acoustic feature. We also evaluate how detectable such a signal would be in the upcoming Baryon Oscillation Spectroscopic Survey (BOSS) LRG volume. Mock LRG catalogs (z < 0.6) suggest that (1) the narrow line-of-sight cylinder and cone defined above probably will not reveal a detectable acoustic feature in BOSS; (2) a clustering measurement as high as that in the current sample can be ruled out (or confirmed) at a high confidence level using a BOSS-sized data set; (3) an analysis with wider angular cuts, which provide better signal-to-noise ratios, can nevertheless be used to compare line-of-sight and transverse distances, and thereby constrain the expansion rate H(z) and diameter distance D{sub A}(z).

  17. Transient dynamic analysis of the Bao'An Stadium

    NASA Astrophysics Data System (ADS)

    Knight, David; Whitefield, Rowan; Nhieu, Eric; Tahmasebinia, Faham; Ansourian, Peter; Alonso-Marroquin, Fernando

    2016-08-01

    Bao'An Stadium is a unique structure that utilises 54m span cantilevers with tensioned members to support the roof. This report involves a simplified finite element model of Bao'An stadium using Strand7 to analyse the effects of deflections, buckling and earthquake loading. Modelling the cantilevers of the original structure with a double curvature was problematic due to unrealistic deflections and no total mass participation using the Spectral Response Solver. To rectify this, a simplified symmetrical stadium was created and the cable free length attribute was used to induce tension in the inner ring and bottom chord members to create upwards deflection. Further, in place of the Spectral Response Solver, the Transient Linear Dynamic Solver was inputted with an El-Centro earthquake. The stadium's response to a 0.20g earthquake and self-weight indicated the deflections satisfied AS1170.0, the loading in the columns was below the critical buckling load, and all structural members satisfied AS4100.

  18. BAO Plate Archive Project: Digitization, Electronic Database and Research Programmes

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.; Abrahamyan, H. V.; Andreasyan, H. R.; Azatyan, N. M.; Farmanyan, S. V.; Gigoyan, K. S.; Gyulzadyan, M. V.; Khachatryan, K. G.; Knyazyan, A. V.; Kostandyan, G. R.; Mikayelyan, G. A.; Nikoghosyan, E. H.; Paronyan, G. M.; Vardanyan, A. V.

    2016-06-01

    The most important part of the astronomical observational heritage are astronomical plate archives created on the basis of numerous observations at many observatories. Byurakan Astrophysical Observatory (BAO) plate archive consists of 37,000 photographic plates and films, obtained at 2.6m telescope, 1m and 0.5m Schmidt type and other smaller telescopes during 1947-1991. In 2002-2005, the famous Markarian Survey (also called First Byurakan Survey, FBS) 1874 plates were digitized and the Digitized FBS (DFBS) was created. New science projects have been conducted based on these low-dispersion spectroscopic material. A large project on the whole BAO Plate Archive digitization, creation of electronic database and its scientific usage was started in 2015. A Science Program Board is created to evaluate the observing material, to investigate new possibilities and to propose new projects based on the combined usage of these observations together with other world databases. The Executing Team consists of 11 astronomers and 2 computer scientists and will use 2 EPSON Perfection V750 Pro scanners for the digitization, as well as Armenian Virtual Observatory (ArVO) database will be used to accommodate all new data. The project will run during 3 years in 2015-2017 and the final result will be an electronic database and online interactive sky map to be used for further research projects, mainly including high proper motion stars, variable objects and Solar System bodies.

  19. A Grammar of Bao'an Tu, a Mongolic Language of Northwest China

    ERIC Educational Resources Information Center

    Fried, Robert Wayne

    2010-01-01

    The present study is a grammatical overview of the Bao'an Tu language (one of the varieties included in the designation "ISO6393-3:PEH", also known as "Tongren Monguor", "Southwestern Monguor", or "Tongren Tu"). Bao'an Tu is spoken by approximately 4,000 people who live on the Qinghai-Tibetan Plateau in Tongren County, Huangnan Prefecture, Qinghai…

  20. Gaseous bubble oscillations in anisotropic non-Newtonian fluids under influence of high-frequency acoustic field

    NASA Astrophysics Data System (ADS)

    Golykh, R. N.

    2016-06-01

    Progress of technology and medicine dictates the ever-increasing requirements (heat resistance, corrosion resistance, strength properties, impregnating ability, etc.) for non-Newtonian fluids and materials produced on their basis (epoxy resin, coating materials, liquid crystals, etc.). Materials with improved properties obtaining is possible by modification of their physicochemical structure. One of the most promising approaches to the restructuring of non-Newtonian fluids is cavitation generated by high-frequency acoustic vibrations. The efficiency of cavitation in non-Newtonian fluid is determined by dynamics of gaseous bubble. Today, bubble dynamics in isotropic non-Newtonian fluids, in which cavitation bubble shape remains spherical, is most full investigated, because the problem reduces to ordinary differential equation for spherical bubble radius. However, gaseous bubble in anisotropic fluids which are most wide kind of non-Newtonian fluids (due to orientation of macromolecules) deviates from spherical shape due to viscosity dependence on shear rate direction. Therefore, the paper presents the mathematical model of gaseous bubble dynamics in anisotropic non-Newtonian fluids. The model is based on general equations for anisotropic non-Newtonian fluid flow. The equations are solved by asymptotic decomposition of fluid flow parameters. It allowed evaluating bubble size and shape evolution depending on rheological properties of liquid and acoustic field characteristics.

  1. Local perturbations of the upper layers of a sun-like star: The impact on the acoustic oscillation spectrum

    SciTech Connect

    Brito, Ana; Lopes, Ilídio E-mail: ilidio.lopes@ist.utl.pt

    2014-02-10

    In the last decade, the quality and the amount of observational asteroseismic data that has been made available by space based missions had a tremendous upgrowth. The determination of asteroseismic parameters to estimate the fundamental physical processes occurring in stars' interiors can be done today in a way that has never been possible before. In this work, we propose to compute the seismic observable β, which is a proxy of the phase shift of the acoustic modes propagating in the envelope of the Sun-like stars. This seismic parameter β can be used to identify rapid variation regions usually known as glitches. We show that a small variation in the structure, smaller than 1% in the sound speed, produces a glitch in the acoustic potential that could explain the oscillatory character of β. This method allows us to determine the location and the thickness of the glitch with precision. We applied this idea to the Sun-like star α Centauri A and found a glitch located at approximately 0.94 R (1400 s) and with a thickness of 0.2% of the stars' radius. This is fully consistent with the data and also validates other seismic tests.

  2. The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: baryon acoustic oscillations in the correlation function of LOWZ and CMASS galaxies in Data Release 12

    NASA Astrophysics Data System (ADS)

    Cuesta, Antonio J.; Vargas-Magaña, Mariana; Beutler, Florian; Bolton, Adam S.; Brownstein, Joel R.; Eisenstein, Daniel J.; Gil-Marín, Héctor; Ho, Shirley; McBride, Cameron K.; Maraston, Claudia; Padmanabhan, Nikhil; Percival, Will J.; Reid, Beth A.; Ross, Ashley J.; Ross, Nicholas P.; Sánchez, Ariel G.; Schlegel, David J.; Schneider, Donald P.; Thomas, Daniel; Tinker, Jeremy; Tojeiro, Rita; Verde, Licia; White, Martin

    2016-04-01

    We present distance scale measurements from the baryon acoustic oscillation signal in the constant stellar mass and low-redshift sample samples from the Data Release 12 of the Baryon Oscillation Spectroscopic Survey. The total volume probed is 14.5 Gpc3, a 10 per cent increment from Data Release 11. From an analysis of the spherically averaged correlation function, we infer a distance to z = 0.57 of D_V(z)r^fid_d/r_d = 2028± 21 Mpc and a distance to z = 0.32 of D_V(z)r^fid_d/r_d = 1264± 22 Mpc assuming a cosmology in which r^fid_d = 147.10 Mpc. From the anisotropic analysis, we find an angular diameter distance to z = 0.57 of D_A(z)r^fid_d/r_d = 1401± 21 Mpc and a distance to z = 0.32 of 981 ± 20 Mpc, a 1.5 and 2.0 per cent measurement, respectively. The Hubble parameter at z = 0.57 is H(z)r_d/r^fid_d = 100.3± 3.7 km s-1 Mpc-1 and its value at z = 0.32 is 79.2 ± 5.6 km s-1 Mpc-1, a 3.7 and 7.1 per cent measurement, respectively. These cosmic distance scale constraints are in excellent agreement with a Λ cold dark matter model with cosmological parameters released by the recent Planck 2015 results.

  3. Large-Scale Distribution of Total Mass versus Luminous Matter from Baryon Acoustic Oscillations: First Search in the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey Data Release 10

    NASA Astrophysics Data System (ADS)

    Soumagnac, M. T.; Barkana, R.; Sabiu, C. G.; Loeb, A.; Ross, A. J.; Abdalla, F. B.; Balan, S. T.; Lahav, O.

    2016-05-01

    Baryon acoustic oscillations in the early Universe are predicted to leave an as yet undetected signature on the relative clustering of total mass versus luminous matter. A detection of this effect would provide an important confirmation of the standard cosmological paradigm and constrain alternatives to dark matter as well as nonstandard fluctuations such as compensated isocurvature perturbations (CIPs). We conduct the first observational search for this effect, by comparing the number-weighted and luminosity-weighted correlation functions, using the SDSS-III BOSS Data Release 10 CMASS sample. When including CIPs in our model, we formally obtain evidence at 3.2 σ of the relative clustering signature and a limit that matches the existing upper limits on the amplitude of CIPs. However, various tests suggest that these results are not yet robust, perhaps due to systematic biases in the data. The method developed in this Letter used with more accurate future data such as that from DESI, is likely to confirm or disprove our preliminary evidence.

  4. Large-Scale Distribution of Total Mass versus Luminous Matter from Baryon Acoustic Oscillations: First Search in the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey Data Release 10.

    PubMed

    Soumagnac, M T; Barkana, R; Sabiu, C G; Loeb, A; Ross, A J; Abdalla, F B; Balan, S T; Lahav, O

    2016-05-20

    Baryon acoustic oscillations in the early Universe are predicted to leave an as yet undetected signature on the relative clustering of total mass versus luminous matter. A detection of this effect would provide an important confirmation of the standard cosmological paradigm and constrain alternatives to dark matter as well as nonstandard fluctuations such as compensated isocurvature perturbations (CIPs). We conduct the first observational search for this effect, by comparing the number-weighted and luminosity-weighted correlation functions, using the SDSS-III BOSS Data Release 10 CMASS sample. When including CIPs in our model, we formally obtain evidence at 3.2σ of the relative clustering signature and a limit that matches the existing upper limits on the amplitude of CIPs. However, various tests suggest that these results are not yet robust, perhaps due to systematic biases in the data. The method developed in this Letter used with more accurate future data such as that from DESI, is likely to confirm or disprove our preliminary evidence.

  5. Large-Scale Distribution of Total Mass versus Luminous Matter from Baryon Acoustic Oscillations: First Search in the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey Data Release 10.

    PubMed

    Soumagnac, M T; Barkana, R; Sabiu, C G; Loeb, A; Ross, A J; Abdalla, F B; Balan, S T; Lahav, O

    2016-05-20

    Baryon acoustic oscillations in the early Universe are predicted to leave an as yet undetected signature on the relative clustering of total mass versus luminous matter. A detection of this effect would provide an important confirmation of the standard cosmological paradigm and constrain alternatives to dark matter as well as nonstandard fluctuations such as compensated isocurvature perturbations (CIPs). We conduct the first observational search for this effect, by comparing the number-weighted and luminosity-weighted correlation functions, using the SDSS-III BOSS Data Release 10 CMASS sample. When including CIPs in our model, we formally obtain evidence at 3.2σ of the relative clustering signature and a limit that matches the existing upper limits on the amplitude of CIPs. However, various tests suggest that these results are not yet robust, perhaps due to systematic biases in the data. The method developed in this Letter used with more accurate future data such as that from DESI, is likely to confirm or disprove our preliminary evidence. PMID:27258862

  6. Electronic structures and optical spectra of BaO from first principles

    SciTech Connect

    Wu, Chang-Wei; Pan, Bo; Wang, Neng-Ping

    2015-08-21

    We present the results of first-principles study for the electronic structure and optical absorption spectrum of the alkaline-earth metal oxide BaO. The quasiparticle band structure is evaluated within the Hedin's GW approximation [Phys. Rev. 139, A796 (1965)]. Thereafter, the electron-hole interaction is taken into consideration and the Bethe-Salpeter equation for the electron-hole two-particle Green function is solved. The calculated quasiparticle band gap of BaO is 4.1 eV, which is in good agreement with the experimental result. The calculated optical absorption spectrum of BaO is also in agreement with the experimental data. In particular, the calculated excitation energy for the lowest exciton peak in the optical absorption spectrum of BaO reproduces very well the corresponding experimental result.

  7. The SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Overview and early data

    DOE PAGES

    Kyle S. Dawson

    2016-02-04

    In a six-year program started in 2014 July, the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) will conduct novel cosmological observations using the BOSS spectrograph at Apache Point Observatory. These observations will be conducted simultaneously with the Time Domain Spectroscopic Survey (TDSS) designed for variability studies and the Spectroscopic Identification of eROSITA Sources (SPIDERS) program designed for studies of X-ray sources. In particular, eBOSS will measure with percent-level precision the distance-redshift relation with baryon acoustic oscillations (BAO) in the clustering of matter. eBOSS will use four different tracers of the underlying matter density field to vastly expand the volume covered bymore » BOSS and map the large-scale-structures over the relatively unconstrained redshift range 0.6 < z < 2.2. Using more than 250,000 new, spectroscopically confirmed luminous red galaxies at a median redshift z = 0.72, we project that eBOSS will yield measurements of the angular diameter distance dA(z) to an accuracy of 1.2% and measurements of H(z) to 2.1% when combined with the z > 0.6 sample of BOSS galaxies. With ~195,000 new emission line galaxy redshifts, we expect BAO measurements of dA(z) to an accuracy of 3.1% and H(z) to 4.7% at an effective redshift of z = 0.87. A sample of more than 500,000 spectroscopically confirmed quasars will provide the first BAO distance measurements over the redshift range 0.9 < z < 2.2, with expected precision of 2.8% and 4.2% on dA(z) and H(z), respectively. Finally, with 60,000 new quasars and re-observation of 60,000 BOSS quasars, we will obtain new Lyα forest measurements at redshifts z > 2.1; these new data will enhance the precision of dA(z) and H(z) at z > 2.1 by a factor of 1.44 relative to BOSS. Furthermore, eBOSS will provide improved tests of General Relativity on cosmological scales through redshift-space distortion measurements, improved tests for non-Gaussianity in the primordial density

  8. The SDSS-IV Extended Baryon Oscillation Spectroscopic Survey: Overview and Early Data

    NASA Astrophysics Data System (ADS)

    Dawson, Kyle S.; Kneib, Jean-Paul; Percival, Will J.; Alam, Shadab; Albareti, Franco D.; Anderson, Scott F.; Armengaud, Eric; Aubourg, Éric; Bailey, Stephen; Bautista, Julian E.; Berlind, Andreas A.; Bershady, Matthew A.; Beutler, Florian; Bizyaev, Dmitry; Blanton, Michael R.; Blomqvist, Michael; Bolton, Adam S.; Bovy, Jo; Brandt, W. N.; Brinkmann, Jon; Brownstein, Joel R.; Burtin, Etienne; Busca, N. G.; Cai, Zheng; Chuang, Chia-Hsun; Clerc, Nicolas; Comparat, Johan; Cope, Frances; Croft, Rupert A. C.; Cruz-Gonzalez, Irene; da Costa, Luiz N.; Cousinou, Marie-Claude; Darling, Jeremy; de la Macorra, Axel; de la Torre, Sylvain; Delubac, Timothée; du Mas des Bourboux, Hélion; Dwelly, Tom; Ealet, Anne; Eisenstein, Daniel J.; Eracleous, Michael; Escoffier, S.; Fan, Xiaohui; Finoguenov, Alexis; Font-Ribera, Andreu; Frinchaboy, Peter; Gaulme, Patrick; Georgakakis, Antonis; Green, Paul; Guo, Hong; Guy, Julien; Ho, Shirley; Holder, Diana; Huehnerhoff, Joe; Hutchinson, Timothy; Jing, Yipeng; Jullo, Eric; Kamble, Vikrant; Kinemuchi, Karen; Kirkby, David; Kitaura, Francisco-Shu; Klaene, Mark A.; Laher, Russ R.; Lang, Dustin; Laurent, Pierre; Le Goff, Jean-Marc; Li, Cheng; Liang, Yu; Lima, Marcos; Lin, Qiufan; Lin, Weipeng; Lin, Yen-Ting; Long, Daniel C.; Lundgren, Britt; MacDonald, Nicholas; Geimba Maia, Marcio Antonio; Malanushenko, Elena; Malanushenko, Viktor; Mariappan, Vivek; McBride, Cameron K.; McGreer, Ian D.; Ménard, Brice; Merloni, Andrea; Meza, Andres; Montero-Dorta, Antonio D.; Muna, Demitri; Myers, Adam D.; Nandra, Kirpal; Naugle, Tracy; Newman, Jeffrey A.; Noterdaeme, Pasquier; Nugent, Peter; Ogando, Ricardo; Olmstead, Matthew D.; Oravetz, Audrey; Oravetz, Daniel J.; Padmanabhan, Nikhil; Palanque-Delabrouille, Nathalie; Pan, Kaike; Parejko, John K.; Pâris, Isabelle; Peacock, John A.; Petitjean, Patrick; Pieri, Matthew M.; Pisani, Alice; Prada, Francisco; Prakash, Abhishek; Raichoor, Anand; Reid, Beth; Rich, James; Ridl, Jethro; Rodriguez-Torres, Sergio; Carnero Rosell, Aurelio; Ross, Ashley J.; Rossi, Graziano; Ruan, John; Salvato, Mara; Sayres, Conor; Schneider, Donald P.; Schlegel, David J.; Seljak, Uros; Seo, Hee-Jong; Sesar, Branimir; Shandera, Sarah; Shu, Yiping; Slosar, Anže; Sobreira, Flavia; Streblyanska, Alina; Suzuki, Nao; Taylor, Donna; Tao, Charling; Tinker, Jeremy L.; Tojeiro, Rita; Vargas-Magaña, Mariana; Wang, Yuting; Weaver, Benjamin A.; Weinberg, David H.; White, Martin; Wood-Vasey, W. M.; Yeche, Christophe; Zhai, Zhongxu; Zhao, Cheng; Zhao, Gong-bo; Zheng, Zheng; Ben Zhu, Guangtun; Zou, Hu

    2016-02-01

    In a six-year program started in 2014 July, the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) will conduct novel cosmological observations using the BOSS spectrograph at Apache Point Observatory. These observations will be conducted simultaneously with the Time Domain Spectroscopic Survey (TDSS) designed for variability studies and the Spectroscopic Identification of eROSITA Sources (SPIDERS) program designed for studies of X-ray sources. In particular, eBOSS will measure with percent-level precision the distance-redshift relation with baryon acoustic oscillations (BAO) in the clustering of matter. eBOSS will use four different tracers of the underlying matter density field to vastly expand the volume covered by BOSS and map the large-scale-structures over the relatively unconstrained redshift range 0.6 < z < 2.2. Using more than 250,000 new, spectroscopically confirmed luminous red galaxies at a median redshift z = 0.72, we project that eBOSS will yield measurements of the angular diameter distance dA(z) to an accuracy of 1.2% and measurements of H(z) to 2.1% when combined with the z > 0.6 sample of BOSS galaxies. With ∼195,000 new emission line galaxy redshifts, we expect BAO measurements of dA(z) to an accuracy of 3.1% and H(z) to 4.7% at an effective redshift of z = 0.87. A sample of more than 500,000 spectroscopically confirmed quasars will provide the first BAO distance measurements over the redshift range 0.9 < z < 2.2, with expected precision of 2.8% and 4.2% on dA(z) and H(z), respectively. Finally, with 60,000 new quasars and re-observation of 60,000 BOSS quasars, we will obtain new Lyα forest measurements at redshifts z > 2.1 these new data will enhance the precision of dA(z) and H(z) at z > 2.1 by a factor of 1.44 relative to BOSS. Furthermore, eBOSS will provide improved tests of General Relativity on cosmological scales through redshift-space distortion measurements, improved tests for non-Gaussianity in the primordial density field, and

  9. Modeling scale-dependent bias on the baryonic acoustic scale with the statistics of peaks of Gaussian random fields

    NASA Astrophysics Data System (ADS)

    Desjacques, Vincent; Crocce, Martin; Scoccimarro, Roman; Sheth, Ravi K.

    2010-11-01

    Models of galaxy and halo clustering commonly assume that the tracers can be treated as a continuous field locally biased with respect to the underlying mass distribution. In the peak model pioneered by Bardeen et al. [Astrophys. J. 304, 15 (1986)ASJOAB0004-637X10.1086/164143], one considers instead density maxima of the initial, Gaussian mass density field as an approximation to the formation site of virialized objects. In this paper, the peak model is extended in two ways to improve its predictive accuracy. First, we derive the two-point correlation function of initial density peaks up to second order and demonstrate that a peak-background split approach can be applied to obtain the k-independent and k-dependent peak bias factors at all orders. Second, we explore the gravitational evolution of the peak correlation function within the Zel’dovich approximation. We show that the local (Lagrangian) bias approach emerges as a special case of the peak model, in which all bias parameters are scale independent and there is no statistical velocity bias. We apply our formulas to study how the Lagrangian peak biasing, the diffusion due to large scale flows, and the mode coupling due to nonlocal interactions affect the scale dependence of bias from small separations up to the baryon acoustic oscillation (BAO) scale. For 2σ density peaks collapsing at z=0.3, our model predicts a ˜5% residual scale-dependent bias around the acoustic scale that arises mostly from first order Lagrangian peak biasing (as opposed to second order gravity mode coupling). We also search for a scale dependence of bias in the large scale autocorrelation of massive halos extracted from a very large N-body simulation provided by the MICE Collaboration. For halos with mass M≳1014M⊙/h, our measurements demonstrate a scale-dependent bias across the BAO feature which is very well reproduced by a prediction based on the peak model.

  10. Perturbation theory, effective field theory, and oscillations in the power spectrum

    NASA Astrophysics Data System (ADS)

    Vlah, Zvonimir; Seljak, Uroš; Yat Chu, Man; Feng, Yu

    2016-03-01

    We explore the relationship between the nonlinear matter power spectrum and the various Lagrangian and Standard Perturbation Theories (LPT and SPT). We first look at it in the context of one dimensional (1-d) dynamics, where 1LPT is exact at the perturbative level and one can exactly resum the SPT series into the 1LPT power spectrum. Shell crossings lead to non-perturbative effects, and the PT ignorance can be quantified in terms of their ratio, which is also the transfer function squared in the absence of stochasticity. At the order of PT we work, this parametrization is equivalent to the results of effective field theory (EFT), and can thus be expanded in terms of the same parameters. We find that its radius of convergence is larger than the SPT loop expansion. The same EFT parametrization applies to all SPT loop terms and if stochasticity can be ignored, to all N-point correlators. In 3-d, the LPT structure is considerably more complicated, and we find that LPT models with parametrization motivated by the EFT exhibit running with k and that SPT is generally a better choice. Since these transfer function expansions contain free parameters that change with cosmological model their usefulness for broadband power is unclear. For this reason we test the predictions of these models on baryonic acoustic oscillations (BAO) and other primordial oscillations, including string monodromy models, for which we ran a series of simulations with and without oscillations. Most models are successful in predicting oscillations beyond their corresponding PT versions, confirming the basic validity of the model. We show that if primordial oscillations are localized to a scale q, the wiggles in power spectrum are approximately suppressed as exp[-k2Σ2(q)/2], where Σ(q) is rms displacement of particles separated by q, which saturates on large scales, and decreases as q is reduced. No oscillatory features survive past k ~ 0.5h/Mpc at z = 0.

  11. Nonlinear Acoustics in Fluids

    NASA Astrophysics Data System (ADS)

    Lauterborn, Werner; Kurz, Thomas; Akhatov, Iskander

    At high sound intensities or long propagation distances at in fluids sufficiently low damping acoustic phenomena become nonlinear. This chapter focuses on nonlinear acoustic wave properties in gases and liquids. The origin of nonlinearity, equations of state, simple nonlinear waves, nonlinear acoustic wave equations, shock-wave formation, and interaction of waves are presented and discussed. Tables are given for the nonlinearity parameter B/A for water and a range of organic liquids, liquid metals and gases. Acoustic cavitation with its nonlinear bubble oscillations, pattern formation and sonoluminescence (light from sound) are modern examples of nonlinear acoustics. The language of nonlinear dynamics needed for understanding chaotic dynamics and acoustic chaotic systems is introduced.

  12. Spectroscopic and theoretical studies of the low-lying states of BaO+

    NASA Astrophysics Data System (ADS)

    Bartlett, Joshua H.; VanGundy, Robert A.; Heaven, Michael C.

    2015-07-01

    The BaO+ cation is of interest from the perspectives of electronic structure and the potential for cooling to ultra-cold temperatures. Spectroscopic data for the ion have been obtained using a two-color photoionization technique. The ionization energy for BaO was found to be 6.8123(3) eV. The ground state of BaO+ was identified as X2Σ+, and both vibrational and rotational constants were determined. Vibrationally resolved spectra were recorded for A2Π, the first electronically excited state. These data yielded the term energy, vibrational frequency, and the spin-orbit interaction constant. Relativistic electronic structure calculations were carried out using multi-reference configuration interaction (MRCI), coupled cluster and density functional theory methods. Transition moments for the pure vibrational and A2Π-X2Σ+ transitions were predicted using the MRCI method.

  13. Solar Oscillations

    NASA Technical Reports Server (NTRS)

    Duvall, Thomas

    2004-01-01

    Oscillations were first detected in the solar photosphere in 1962 by Leighton and students. In 1970 it was calculated that these oscillations, with a period near five minutes, were the manifestations of acoustic waves trapped in the interior. The subsequent measurements of the frequencies of global oscillation modes from the spatio-temporal power spectrum of the waves made possible the refinement of solar interior models. Over the years, increased understanding of the nuclear reaction rates, the opacity, the equation of state, convection, and gravitational settling have resulted. Mass flows shift the frequencies of modes leading to very accurate measurements of the interior rotation as a function of radius and latitude. In recent years, analogues of terrestrial seismology have led to a tomography of the interior, including measurements of global north-south flows and flow and wave speed measurements below features such as sunspots. The future of helioseismology seems bright with the approval of NASA's Solar Dynamics Observatory mission, to be launched in 2008.

  14. Acoustic tooth cleaner

    NASA Technical Reports Server (NTRS)

    Heyman, J. S. (Inventor)

    1982-01-01

    An acoustic oral hygiene unit is described that uses acoustic energy to oscillate mild abrasive particles in a water suspension which is then directed in a low pressure stream onto the teeth. The oscillating abrasives scrub the teeth clean removing food particles, plaque, calculous, and other foreign material from tooth surfaces, interproximal areas, and tooth-gingiva interface more effectively than any previous technique. The relatively low power output and the basic design makes the invention safe and convenient for everyday use in the home without special training. This invention replaces all former means of home dental prophylaxis, and requires no augmentation to fulfill all requirements for daily oral hygienic care.

  15. A theory of generalized Bloch oscillations.

    PubMed

    Duggen, Lars; Lew Yan Voon, L C; Lassen, Benny; Willatzen, Morten

    2016-04-20

    Bloch oscillations of electrons are shown to occur for cases when the energy spectrum does not consist of the traditional evenly-spaced ladders and the potential gradient does not result from an external electric field. A theory of such generalized Bloch oscillations is presented and an exact calculation is given to confirm this phenomenon. Our results allow for a greater freedom of design for experimentally observing Bloch oscillations. For strongly coupled oscillator systems displaying Bloch oscillations, it is further demonstrated that reordering of oscillators leads to destruction of Bloch oscillations. We stipulate that the presented theory of generalized Bloch oscillations can be extended to other systems such as acoustics and photonics.

  16. Acoustical heat pumping engine

    DOEpatents

    Wheatley, John C.; Swift, Gregory W.; Migliori, Albert

    1983-08-16

    The disclosure is directed to an acoustical heat pumping engine without moving seals. A tubular housing holds a compressible fluid capable of supporting an acoustical standing wave. An acoustical driver is disposed at one end of the housing and the other end is capped. A second thermodynamic medium is disposed in the housing near to but spaced from the capped end. Heat is pumped along the second thermodynamic medium toward the capped end as a consequence both of the pressure oscillation due to the driver and imperfect thermal contact between the fluid and the second thermodynamic medium.

  17. Acoustical heat pumping engine

    DOEpatents

    Wheatley, J.C.; Swift, G.W.; Migliori, A.

    1983-08-16

    The disclosure is directed to an acoustical heat pumping engine without moving seals. A tubular housing holds a compressible fluid capable of supporting an acoustical standing wave. An acoustical driver is disposed at one end of the housing and the other end is capped. A second thermodynamic medium is disposed in the housing near to but spaced from the capped end. Heat is pumped along the second thermodynamic medium toward the capped end as a consequence both of the pressure oscillation due to the driver and imperfect thermal contact between the fluid and the second thermodynamic medium. 2 figs.

  18. A simple violin oscillator

    NASA Technical Reports Server (NTRS)

    Jones, R. T.

    1976-01-01

    For acoustic tests the violin is driven laterally at the bridge by a small speaker of the type commonly found in pocket transistor radios. An audio oscillator excites the tone which is picked up by a sound level meter. Gross patterns of vibration modes are obtained by the Chladni method.

  19. Work Function Reduction by BaO: Growth of Crystalline Barium Oxide on Ag(001) and Ag(111) Surfaces

    SciTech Connect

    Droubay, Timothy C.; Kong, Lingmei; Chambers, Scott A.; Hess, Wayne P.

    2015-02-01

    Ultrathin films of barium oxide were grown on Ag(001) and Ag(111) using the evaporation of Ba metal in an O2 atmosphere by molecular beam epitaxy. Ultraviolet photoemission spectroscopy reveals that films consisting of predominantly BaO or BaO2 result in Ag(001) work function reductions of 1.74 eV and 0.64 eV, respectively. On the Ag(001) surface, Ba oxide growth is initiated by two-dimensional nucleation of epitaxial BaO, followed by a transition to three-dimensional dual-phase nucleation of epitaxial BaO and BaO2. Three-dimensional islands of primarily BaO2(111) nucleate epitaxially on the Ag(111) substrate leaving large patches of Ag uncovered. We find no indication of chemical reaction or charge transfer between the films and the Ag substrates. These data suggest that the origin of the observed work function reduction is largely due to a combination of BaO surface relaxation and an electrostatic compressive effect.

  20. Co2FeAl based magnetic tunnel junctions with BaO and MgO/BaO barriers

    NASA Astrophysics Data System (ADS)

    Rogge, J.; Hetaba, W.; Schmalhorst, J.; Bouchikhaoui, H.; Stender, P.; Baither, D.; Schmitz, G.; Hütten, A.

    2015-07-01

    We succeed to integrate BaO as a tunneling barrier into Co2FeAl based magnetic tunnel junctions (MTJs). By means of Auger electron spectroscopy it could be proven that the applied annealing temperatures during BaO deposition and afterwards do not cause any diffusion of Ba neither into the lower Heusler compound lead nor into the upper Fe counter electrode. Nevertheless, a negative tunnel magnetoresistance (TMR) ratio of -10% is found for Co2FeAl (24 nm) / BaO (5 nm) / Fe (7 nm) MTJs, which can be attributed to the preparation procedure and can be explained by the formation of Co- and Fe-oxides at the interfaces between the Heusler and the crystalline BaO barrier by comparing with theory. Although an amorphous structure of the BaO barrier seems to be confirmed by high-resolution transmission electron microscopy (TEM), it cannot entirely be ruled out that this is an artifact of TEM sample preparation due to the sensitivity of BaO to moisture. By replacing the BaO tunneling barrier with an MgO/BaO double layer barrier, the electric stability could effectively be increased by a factor of five. The resulting TMR effect is found to be about +20% at room temperature, although a fully antiparallel state has not been realized.

  1. Acoustic cryocooler

    DOEpatents

    Swift, Gregory W.; Martin, Richard A.; Radenbaugh, Ray

    1990-01-01

    An acoustic cryocooler with no moving parts is formed from a thermoacoustic driver (TAD) driving a pulse tube refrigerator (PTR) through a standing wave tube. Thermoacoustic elements in the TAD are spaced apart a distance effective to accommodate the increased thermal penetration length arising from the relatively low TAD operating frequency in the range of 15-60 Hz. At these low operating frequencies, a long tube is required to support the standing wave. The tube may be coiled to reduce the overall length of the cryocooler. One or two PTR's are located on the standing wave tube adjacent antinodes in the standing wave to be driven by the standing wave pressure oscillations. It is predicted that a heat input of 1000 W at 1000 K will maintian a cooling load of 5 W at 80 K.

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

    PubMed

    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. PMID:27661695

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

    PubMed

    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.

  4. Theoretical description based on general and exact nonextensive dispersion relations of plasma oscillation data and verification of new acoustic plasma waves

    SciTech Connect

    Ebrahimi, V.; Esfandyari-Kalejahi, A.

    2014-09-15

    In this paper, first we represent the differences between spatial and temporal dispersions and their dependence on the measurement techniques for electrostatic waves in unmagnetized collisionless plasma. Then, three different experimental data are compared to the solutions of exact nonextensive dispersion relations for electron-ion and pair plasma. The results confirm the existence of new acoustic plasma waves. Furthermore, these comparisons yield a Maxwellian and a nonextensive plasma with nonextensive parameter q larger than one, and a Maxwellian plasma with some abnormal dispersion properties.

  5. Contour mode resonators with acoustic reflectors

    DOEpatents

    Olsson, Roy H.; Fleming, James G.; Tuck, Melanie R.

    2008-06-10

    A microelectromechanical (MEM) resonator is disclosed which has a linear or ring-shaped acoustic resonator suspended above a substrate by an acoustic reflector. The acoustic resonator can be formed with a piezoelectric material (e.g. aluminum nitride, zinc oxide or PZT), or using an electrostatically-actuated material. The acoustic reflector (also termed an acoustic mirror) uses alternating sections of a relatively low acoustic impedance Z.sub.L material and a relatively high acoustic impedance Z.sub.H material to isolate the acoustic resonator from the substrate. The MEM resonator, which can be formed on a silicon substrate with conventional CMOS circuitry, has applications for forming oscillators, rf filters, and acoustic sensors.

  6. Acoustic bubble removal method

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.; Elleman, D. D.; Wang, T. G. (Inventor)

    1983-01-01

    A method is described for removing bubbles from a liquid bath such as a bath of molten glass to be used for optical elements. Larger bubbles are first removed by applying acoustic energy resonant to a bath dimension to drive the larger bubbles toward a pressure well where the bubbles can coalesce and then be more easily removed. Thereafter, submillimeter bubbles are removed by applying acoustic energy of frequencies resonant to the small bubbles to oscillate them and thereby stir liquid immediately about the bubbles to facilitate their breakup and absorption into the liquid.

  7. BAO Plate Archive digitization, creation of electronic database and its scientific usage

    NASA Astrophysics Data System (ADS)

    Mickaelian, Areg M.

    2015-08-01

    Astronomical plate archives created on the basis of numerous observations at many observatories are important part of the astronomical heritage. Byurakan Astrophysical Observatory (BAO) plate archive consists of 37,500 photographic plates and films, obtained at 2.6m telescope, 1m and 0.5m Schmidt telescopes and other smaller ones during 1947-1991. In 2002-2005, the famous Markarian Survey (First Byurakan Survey, FBS) 2000 plates were digitized and the Digitized FBS (DFBS, http://www.aras.am/Dfbs/dfbs.html) was created. New science projects have been conducted based on these low-dispersion spectroscopic material. In 2015, we have started a project on the whole BAO Plate Archive digitization, creation of electronic database and its scientific usage. A Science Program Board is created to evaluate the observing material, to investigate new possibilities and to propose new projects based on the combined usage of these observations together with other world databases. The Executing Team consists of 9 astronomers and 3 computer scientists and will use 2 EPSON Perfection V750 Pro scanners for the digitization, as well as Armenian Virtual Observatory (ArVO) database to accommodate all new data. The project will run during 3 years in 2015-2017 and the final result will be an electronic database and online interactive sky map to be used for further research projects.

  8. Braided oscillators

    NASA Astrophysics Data System (ADS)

    Yildiz, A.

    2002-03-01

    A generalized oscillator algebra is proposed and the braided Hopf algebra structure for this generalized oscillator is investigated. Using the solutions for the braided Hopf algebra structure, two types of braided Fibonacci oscillators are introduced. This leads to two types of braided Biedenharn-Macfarlane oscillators as special cases of the Fibonacci oscillators. We also find the braided Hopf algebra solutions for the three dimensional braided space. One of these, as a special case, gives the Hopf algebra given in the literature.

  9. Digital Technology in the protection of cultural heritage Bao Fan Temple mural digital mapping survey

    NASA Astrophysics Data System (ADS)

    Zheng, Y.

    2015-08-01

    Peng Xi county, Sichuan province, the Bao Fan temple mural digitization survey mapping project: we use three-dimensional laserscanning, multi-baseline definition digital photography, multi-spectral digital image acquisition and other technologies for digital survey mapping. The purpose of this project is to use modern mathematical reconnaissance mapping means to obtain accurate mural shape, color, quality and other data. Combined with field investigation and laboratory analysis results, and based on a comprehensive survey and study, a comprehensive analysis of the historical Bao Fan Temple mural artistic and scientific value was conducted. A study of the mural's many qualities (structural, material, technique, preservation environment, degradation, etc.) reveal all aspects of the information carried by the Bao Fan Temple mural. From multiple angles (archeology, architecture, surveying, conservation science and other disciplines) an assessment for the Bao Fan Temple mural provides basic data and recommendations for conservation of the mural. In order to achieve the conservation of cultural relics in the Bao Fan Temple mural digitization survey mapping process, we try to apply the advantages of three-dimensional laser scanning equipment. For wall murals this means obtaining three-dimensional scale data from the scan of the building and through the analysis of these data to help determine the overall condition of the settlement as well as the deformation of the wall structure. Survey analysis provides an effective set of conclusions and suggestions for appropriate mural conservation. But before data collection, analysis and research need to first to select the appropriate scanning equipment, set the appropriate scanning accuracy and layout position of stations necessary to determine the scope of required data. We use the fine features of the three-dimensional laser scanning measuring arm to scan the mural surface deformation degradation to reflect the actual state of

  10. Determination of dark energy by the Einstein Telescope: Comparing with CMB, BAO, and SNIa observations

    SciTech Connect

    Zhao, W.; Baskaran, D.; Van Den Broeck, C.; Li, T. G. F.

    2011-01-15

    A design study is currently in progress for a third-generation gravitational-wave (GW) detector called the Einstein Telescope (ET). An important kind of source for ET will be the inspiral and merger of binary neutron stars up to z{approx}2. If binary neutron star mergers are the progenitors of short-hard {gamma}-ray bursts, then some fraction of them will be seen both electromagnetically and through GW, so that the luminosity distance and the redshift of the source can be determined separately. An important property of these 'standard sirens' is that they are self-calibrating: the luminosity distance can be inferred directly from the GW signal, with no need for a cosmic distance ladder. Thus, standard sirens will provide a powerful independent check of the {Lambda}CDM model. In previous work, estimates were made of how well ET would be able to measure a subset of the cosmological parameters (such as the dark energy parameter w{sub 0}) it will have access to, assuming that the others had been determined to great accuracy by alternative means. Here we perform a more careful analysis by explicitly using the potential Planck cosmic microwave background data as prior information for these other parameters. We find that ET will be able to constrain w{sub 0} and w{sub a} with accuracies {Delta}w{sub 0}=0.099 and {Delta}w{sub a}=0.302, respectively. These results are compared with projected accuracies for the JDEM baryon acoustic oscillations project and the SNAP type Ia supernovae observations.

  11. Method and means for measuring acoustic emissions

    DOEpatents

    Renken, Jr., Claus J.

    1976-01-06

    The detection of acoustic emissions emanating from an object is achieved with a capacitive transducer coupled to the object. The capacitive transducer is charged and then allowed to discharge with the rate of discharge being monitored. Oscillations in the rate of discharge about the normally exponential discharge curve for the capacitive transducer indicate the presence of acoustic emissions.

  12. Combustor oscillating pressure stabilization and method

    DOEpatents

    Gemmen, R.S.; Richards, G.A.; Yip, M.T.J.; Robey, E.H.; Cully, S.R.; Addis, R.E.

    1998-08-11

    High dynamic pressure oscillations in hydrocarbon-fueled combustors typically occur when the transport time of the fuel to the flame front is at some fraction of the acoustic period. These oscillations are reduced to acceptably lower levels by restructuring or repositioning the flame front in the combustor to increase the transport time. A pilot flame front located upstream of the oscillating flame and pulsed at a selected frequency and duration effectively restructures and repositions the oscillating flame in the combustor to alter the oscillation-causing transport time. 7 figs.

  13. Combustor oscillating pressure stabilization and method

    DOEpatents

    Gemmen, Randall S.; Richards, George A.; Yip, Mui-Tong Joseph; Robey, Edward H.; Cully, Scott R.; Addis, Richard E.

    1998-01-01

    High dynamic pressure oscillations in hydrocarbon-fueled combustors typically occur when the transport time of the fuel to the flame front is at some fraction of the acoustic period. These oscillations are reduced to acceptably lower levels by restructuring or repositioning the flame front in the combustor to increase the transport time. A pilot flame front located upstream of the oscillating flame and pulsed at a selected frequency and duration effectively restructures and repositions the oscillating flame in the combustor to alter the oscillation-causing transport time.

  14. Acoustical standards in engineering acoustics

    NASA Astrophysics Data System (ADS)

    Burkhard, Mahlon D.

    2001-05-01

    The Engineering Acoustics Technical Committee is concerned with the evolution and improvement of acoustical techniques and apparatus, and with the promotion of new applications of acoustics. As cited in the Membership Directory and Handbook (2002), the interest areas include transducers and arrays; underwater acoustic systems; acoustical instrumentation and monitoring; applied sonics, promotion of useful effects, information gathering and transmission; audio engineering; acoustic holography and acoustic imaging; acoustic signal processing (equipment and techniques); and ultrasound and infrasound. Evident connections between engineering and standards are needs for calibration, consistent terminology, uniform presentation of data, reference levels, or design targets for product development. Thus for the acoustical engineer standards are both a tool for practices, for communication, and for comparison of his efforts with those of others. Development of many standards depends on knowledge of the way products are put together for the market place and acoustical engineers provide important input to the development of standards. Acoustical engineers and members of the Engineering Acoustics arm of the Society both benefit from and contribute to the Acoustical Standards of the Acoustical Society.

  15. Acoustic Neuroma

    MedlinePlus

    An acoustic neuroma is a benign tumor that develops on the nerve that connects the ear to the brain. The tumor ... press against the brain, becoming life-threatening. Acoustic neuroma can be difficult to diagnose, because the symptoms ...

  16. Ion Acoustic Waves in Ultracold Neutral Plasmas

    SciTech Connect

    Castro, J.; McQuillen, P.; Killian, T. C.

    2010-08-06

    We photoionize laser-cooled atoms with a laser beam possessing spatially periodic intensity modulations to create ultracold neutral plasmas with controlled density perturbations. Laser-induced fluorescence imaging reveals that the density perturbations oscillate in space and time, and the dispersion relation of the oscillations matches that of ion acoustic waves, which are long-wavelength, electrostatic, density waves.

  17. First observations of 14CO2 at the Boulder Atmospheric Observatory (BAO)

    NASA Astrophysics Data System (ADS)

    Lafranchi, B. W.; Petron, G.; Andrews, A. E.; Miller, J. B.; Lehman, S. J.; Montzka, S. A.; Miller, B. R.; Guilderson, T. P.

    2010-12-01

    Atmospheric radiocarbon (14C) represents an important observational constraint on emissions of fossil-fuel derived carbon into the atmosphere due to the near absence of 14C in fossil fuel reservoirs. The high sensitivity and precision that accelerator mass spectrometry (AMS) affords in atmospheric 14C analysis has greatly increased the potential for using such measurements to facilitate carbon cycle studies and the validation of greenhouse gas emissions inventories. Here we report on the first ever 14CO2 observations from the Boulder Atmospheric Observatory (BAO), located 35 km north of Denver, CO. The BAO tower is one of 8 tall towers in the NOAA/ESRL greenhouse gas flask sampling network that has recently begun sampling for atmospheric 14C, as well as other trace gases. We will present observations of Δ14C in whole air samples collected between June 2009 and March 2010 at BAO (300 m a.g.l.). Values ranged from -10‰ to +46 ‰ corresponding to estimated fossil fuel CO2 (CO2ff) mixing ratios as high as 10 ppm above the background. Strong correlations between [CO2] and Δ14C suggest that much of the day-to-day variability in [CO2] is driven primarily by changes in [CO2ff] reaching the site. This variability is expected to be a function of the fossil fuel emission strength, regional transport, and boundary layer height. An analysis of differences in Δ14C with day of week provides a simple means to disentangle changes in the emission source strength of CO2ff from natural meteorological variability. Performing this analysis, we find that on average the site experiences slightly less fossil fuel emissions on weekends than on weekdays, presumably due to changes in anthropogenic emission patterns. Lastly, we will examine the correlations of Δ14C with traces gases, such as benzene, CO, and acetylene, in order to better assess the potential for using these relationships to interpolate [CO2ff] to faster time-scales, to extrapolate over a longer observational period, and

  18. Acoustic Imaging in Helioseismology

    NASA Astrophysics Data System (ADS)

    Chou, Dean-Yi; Chang, Hsiang-Kuang; Sun, Ming-Tsung; LaBonte, Barry; Chen, Huei-Ru; Yeh, Sheng-Jen; Team, The TON

    1999-04-01

    The time-variant acoustic signal at a point in the solar interior can be constructed from observations at the surface, based on the knowledge of how acoustic waves travel in the Sun: the time-distance relation of the p-modes. The basic principle and properties of this imaging technique are discussed in detail. The helioseismic data used in this study were taken with the Taiwan Oscillation Network (TON). The time series of observed acoustic signals on the solar surface is treated as a phased array. The time-distance relation provides the phase information among the phased array elements. The signal at any location at any time can be reconstructed by summing the observed signal at array elements in phase and with a proper normalization. The time series of the constructed acoustic signal contains information on frequency, phase, and intensity. We use the constructed intensity to obtain three-dimensional acoustic absorption images. The features in the absorption images correlate with the magnetic field in the active region. The vertical extension of absorption features in the active region is smaller in images constructed with shorter wavelengths. This indicates that the vertical resolution of the three-dimensional images depends on the range of modes used in constructing the signal. The actual depths of the absorption features in the active region may be smaller than those shown in the three-dimensional images.

  19. Acoustic Seal

    NASA Technical Reports Server (NTRS)

    Steinetz, Bruce M. (Inventor)

    2006-01-01

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

  20. Acoustic seal

    NASA Technical Reports Server (NTRS)

    Steinetz, Bruce M. (Inventor)

    2006-01-01

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

  1. Co{sub 2}FeAl based magnetic tunnel junctions with BaO and MgO/BaO barriers

    SciTech Connect

    Rogge, J.; Schmalhorst, J.; Hütten, A.; Hetaba, W.

    2015-07-15

    We succeed to integrate BaO as a tunneling barrier into Co{sub 2}FeAl based magnetic tunnel junctions (MTJs). By means of Auger electron spectroscopy it could be proven that the applied annealing temperatures during BaO deposition and afterwards do not cause any diffusion of Ba neither into the lower Heusler compound lead nor into the upper Fe counter electrode. Nevertheless, a negative tunnel magnetoresistance (TMR) ratio of -10% is found for Co{sub 2}FeAl (24 nm) / BaO (5 nm) / Fe (7 nm) MTJs, which can be attributed to the preparation procedure and can be explained by the formation of Co- and Fe-oxides at the interfaces between the Heusler and the crystalline BaO barrier by comparing with theory. Although an amorphous structure of the BaO barrier seems to be confirmed by high-resolution transmission electron microscopy (TEM), it cannot entirely be ruled out that this is an artifact of TEM sample preparation due to the sensitivity of BaO to moisture. By replacing the BaO tunneling barrier with an MgO/BaO double layer barrier, the electric stability could effectively be increased by a factor of five. The resulting TMR effect is found to be about +20% at room temperature, although a fully antiparallel state has not been realized.

  2. Neurodynamic oscillators

    NASA Technical Reports Server (NTRS)

    Espinosa, Ismael; Gonzalez, Hortensia; Quiza, Jorge; Gonazalez, J. Jesus; Arroyo, Ruben; Lara, Ritaluz

    1995-01-01

    Oscillation of electrical activity has been found in many nervous systems, from invertebrates to vertebrates including man. There exists experimental evidence of very simple circuits with the capability of oscillation. Neurons with intrinsic oscillation have been found and also neural circuits where oscillation is a property of the network. These two types of oscillations coexist in many instances. It is nowadays hypothesized that behind synchronization and oscillation there is a system of coupled oscillators responsible for activities that range from locomotion and feature binding in vision to control of sleep and circadian rhythms. The huge knowledge that has been acquired on oscillators from the times of Lord Rayleigh has made the simulation of neural oscillators a very active endeavor. This has been enhanced with more recent physiological findings about small neural circuits by means of intracellular and extracellular recordings as well as imaging methods. The future of this interdisciplinary field looks very promising; some researchers are going into quantum mechanics with the idea of trying to provide a quantum description of the brain. In this work we describe some simulations using neuron models by means of which we form simple neural networks that have the capability of oscillation. We analyze the oscillatory activity with root locus method, cross-correlation histograms, and phase planes. In the more complicated neural network models there is the possibility of chaotic oscillatory activity and we study that by means of Lyapunov exponents. The companion paper shows an example of that kind.

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

    NASA Technical Reports Server (NTRS)

    Lyell, Margaret J.

    1992-01-01

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

  4. Topological Acoustics

    NASA Astrophysics Data System (ADS)

    Yang, Zhaoju; Gao, Fei; Shi, Xihang; Lin, Xiao; Gao, Zhen; Chong, Yidong; Zhang, Baile

    2015-03-01

    The manipulation of acoustic wave propagation in fluids has numerous applications, including some in everyday life. Acoustic technologies frequently develop in tandem with optics, using shared concepts such as waveguiding and metamedia. It is thus noteworthy that an entirely novel class of electromagnetic waves, known as "topological edge states," has recently been demonstrated. These are inspired by the electronic edge states occurring in topological insulators, and possess a striking and technologically promising property: the ability to travel in a single direction along a surface without backscattering, regardless of the existence of defects or disorder. Here, we develop an analogous theory of topological fluid acoustics, and propose a scheme for realizing topological edge states in an acoustic structure containing circulating fluids. The phenomenon of disorder-free one-way sound propagation, which does not occur in ordinary acoustic devices, may have novel applications for acoustic isolators, modulators, and transducers.

  5. Topological acoustics.

    PubMed

    Yang, Zhaoju; Gao, Fei; Shi, Xihang; Lin, Xiao; Gao, Zhen; Chong, Yidong; Zhang, Baile

    2015-03-20

    The manipulation of acoustic wave propagation in fluids has numerous applications, including some in everyday life. Acoustic technologies frequently develop in tandem with optics, using shared concepts such as waveguiding and metamedia. It is thus noteworthy that an entirely novel class of electromagnetic waves, known as "topological edge states," has recently been demonstrated. These are inspired by the electronic edge states occurring in topological insulators, and possess a striking and technologically promising property: the ability to travel in a single direction along a surface without backscattering, regardless of the existence of defects or disorder. Here, we develop an analogous theory of topological fluid acoustics, and propose a scheme for realizing topological edge states in an acoustic structure containing circulating fluids. The phenomenon of disorder-free one-way sound propagation, which does not occur in ordinary acoustic devices, may have novel applications for acoustic isolators, modulators, and transducers.

  6. Weapons bay acoustic environment

    NASA Astrophysics Data System (ADS)

    Shaw, L. L.; Shimovetz, R. M.

    1994-09-01

    An aircraft weapons bay exposed to freestream flow experiences an intense aeroacoustic environment in and around the bay. Experience has taught that the intensity of this environment can be severe enough to result in damage to a store, its internal equipment, or the structure of the weapons bay itself. To ensure that stores and sensitive internal equipment can withstand this hazardous environment and successfully complete the mission, they must be qualified to the most severe sound pressure levels anticipated for the mission. If the qualification test levels are too high, the store and its internal equipment will be over designed, resulting in unnecessary costs and possible performance penalties. If the qualification levels are below those experienced in flight, the store or its internal equipment may catastrophically fail during performance of the mission. Thus, it is desirable that the expected levels in weapons bays be accurately predicted. A large number of research efforts have been directed toward understanding flow-induced cavity oscillations. However, the phenomena are still not adequately understood to allow one to predict the fluctuating pressure levels for various configurations and flow conditions. This is especially true at supersonic flow speeds, where only a small amount of data are available. This paper will give a background of flow induced cavity oscillations and discuss predictions, control and suppression, and the future of weapons bay acoustic environments. A large number of research efforts have been directed toward understanding flow-induced cavity oscillations. However, the phenomena are still not adequately understood to allow one to predict the fluctuating pressure levels for various configurations and flow conditions. This is especially true at supersonic flow speeds, where only a small amount of data are available. This paper will give a background of flow induced cavity oscillations and discuss predictions, control and suppression, and

  7. Musical Acoustics

    NASA Astrophysics Data System (ADS)

    Gough, Colin

    This chapter provides an introduction to the physical and psycho-acoustic principles underlying the production and perception of the sounds of musical instruments. The first section introduces generic aspects of musical acoustics and the perception of musical sounds, followed by separate sections on string, wind and percussion instruments.

  8. Acoustic metafluids.

    PubMed

    Norris, Andrew N

    2009-02-01

    Acoustic metafluids are defined as the class of fluids that allow one domain of fluid to acoustically mimic another, as exemplified by acoustic cloaks. It is shown that the most general class of acoustic metafluids are materials with anisotropic inertia and the elastic properties of what are known as pentamode materials. The derivation uses the notion of finite deformation to define the transformation of one region to another. The main result is found by considering energy density in the original and transformed regions. Properties of acoustic metafluids are discussed, and general conditions are found which ensure that the mapped fluid has isotropic inertia, which potentially opens up the possibility of achieving broadband cloaking. PMID:19206861

  9. A structural model guide for geothermal exploration in Ancestral Mount Bao, Leyte, Philippines

    NASA Astrophysics Data System (ADS)

    Lagmay, M. A.

    2001-12-01

    The Tongonan Geothermal Field, located on the eroded flank of Ancestral Mount Bao (AMB) volcano, is the largest producing geothermal field in the Philippines. It produces about 640 MW of energy supplying power to the grid of Luzon, Visayas, and Mindano, the three major islands of the Philippines. The Tongonan geothermal field is host to several major power plants that tap geothermal power from the northern flank of the AMB volcano. I present a structural model guide for delineating exploration targets in other flanks of the ~1,200 km2 area of the AMB volcano. The model limits the exploration area, where more detailed investigations involving geophysical, and geochemical methods can be applied. This structural model guide is based on analogue sand cone experiments, their comparison with the natural prototype (i.e. AMB volcano), and the observation of the geographic positions of producing geothermal power plants within the Tongonan Geothermal Field. Based on this structural model, I suggest an ideal exploration target on the south-southeastern flank of the AMB, directly overlying the left-lateral Philippine fault.

  10. A structural model guide for geothermal exploration in Ancestral Mount Bao, Leyte, Philippines

    NASA Astrophysics Data System (ADS)

    Lagmay, Alfredo Mahar Francisco A.; Tengonciang, Arlene Mae P.; Marcos, Herbert V.; Pascua, Chelo S.

    2003-03-01

    The Tongonan Geothermal Field is the largest producing geothermal field in the Philippines having an installed capacity of 700 MW. It hosts several major power plants that tap geothermal power from the northern flank of the eroded Ancestral Mount Bao (AMB) volcano in Leyte Island, Philippines. A structural model guide is presented to delineate exploration targets in other flanks of the 1200 km 2 area of the AMB volcano. If applied, the model constrains the coverage of geothermal exploration to areas where more detailed investigations involving geological, geophysical, and geochemical methods can be conducted. Analog sand cone experiments and their comparison with the deformation of the AMB volcano were used to interpret wells within the Tongonan Geothermal Field. The study shows that existing producing wells in Tongonan straddle the crypto-Philippine fault, a N34°W (azimuth=326°) trending master fault inferred to traverse the base of the AMB volcano. This master fault induced fracture-controlled permeability where fluids in the Tongonan Geothermal Field circulate. The structural model suggests that the south-southeastern flank of the AMB directly above the southern extension of the master Philippine fault is an ideal geothermal target amenable to detailed exploration.

  11. Interaction Between Dark Energy and Dark Matter: Observational Constraints from Ohd, BAO, CMB and SNe Ia

    NASA Astrophysics Data System (ADS)

    Cao, Shuo; Liang, Nan

    2013-12-01

    In order to test if there is energy transfer between dark energy (DE) and dark matter (DM), we investigate cosmological constraints on two forms of nontrivial interaction between the DM sector and the sector responsible for the acceleration of the universe, in light of the newly revised observations including OHD, CMB, BAO and SNe Ia. More precisely, we find the same tendencies for both phenomenological forms of the interaction term Q = 3γHρ, i.e. the parameter γ to be a small number, |γ| ≈ 10-2. However, concerning the sign of the interaction parameter, we observe that γ > 0 when the interaction between dark sectors is proportional to the energy density of dust matter, whereas the negative coupling (γ < 0) is preferred by observations when the interaction term is proportional to DE density. We further discuss two possible explanations to this incompatibility and apply a quantitative criteria to judge the severity of the coincidence problem. Results suggest that the γmIDE model with a positive coupling may alleviate the coincidence problem, since its coincidence index C is smaller than that for the γdIDE model, the interacting quintessence and phantom models by four orders of magnitude.

  12. Reactivity of a Thick BaO Film Supported on Pt(111): Adsorption and Reaction of NO2, H2O and CO2

    SciTech Connect

    Mudiyanselage, Kumudu; Yi, Cheol-Woo W.; Szanyi, Janos

    2009-09-15

    Reactions of NO2, H2O, and CO2 with a thick (> 20 MLE) BaO film supported on Pt(111) were studied with temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). NO2 reacts with a thick BaO to form surface nitrite-nitrate ion pairs at 300 K, while only nitrates form at 600 K. In the thermal decomposition process of nitrite–nitrate ion pairs, first nitrites decompose and desorb as NO. Then nitrates decompose in two steps : at lower temperature with the release of NO2 and at higher temperature, nitrates dissociate to NO + O2. The thick BaO layer converts completely to Ba(OH)2 following the adsorption of H2O at 300 K. Dehydration/dehydroxylation of this hydroxide layer can be fully achieved by annealing to 550 K. CO2 also reacts with BaO to form BaCO3 that completely decomposes to regenerate BaO upon annealing to 825 K. However, the thick BaO film cannot be converted completely to Ba(NOx)2 or BaCO3 under the experimental conditions employed in this study.

  13. Acoustically enhanced heat exchange and drying apparatus

    DOEpatents

    Bramlette, T.T.; Keller, J.O.

    1987-07-10

    A heat transfer drying apparatus includes an acoustically augmented heat transfer chamber for receiving material to be dried. The chamber includes a first heat transfer gas inlet, a second heat transfer gas inlet, a material inlet, and a gas outlet which also serves as a dried material and gas outlet. A non-pulsing first heat transfer gas source provides a first drying gas to the acoustically augmented heat transfer chamber through the first heat transfer gas inlet. A valveless, continuous second heat transfer gas source provides a second drying gas to the acoustically augmented heat transfer chamber through the second heat transfer gas inlet. The second drying gas also generates acoustic waves which bring about acoustical coupling with the gases in the acoustically augmented heat transfer chamber. The second drying gas itself oscillates at an acoustic frequency of approximately 180 Hz due to fluid mechanical motion in the gas. The oscillations of the second heat transfer gas coupled to the first heat transfer gas in the acoustically augmented heat transfer chamber enhance heat and mass transfer by convection within the chamber. 3 figs.

  14. Light diffraction by acoustically induced domains in nematic liquid crystals

    SciTech Connect

    Kapustina, O. A.

    2006-05-15

    The phenomenon of light diffraction by a system of linear domains formed in planar layers of nematic liquid crystals in an oscillating Couette flow, acoustically induced at sound frequencies, is investigated.

  15. High Q Miniature Sapphire Acoustic Resonator

    NASA Technical Reports Server (NTRS)

    Wang, Rabi T.; Tjoelker, R. L.

    2010-01-01

    We have demonstrated high Q measurements in a room temperature Miniature Sapphire Acoustic Resonator (MSAR). Initial measurements of bulk acoustic modes in room temperature sapphire at 39 MHz have demonstrated a Q of 8.8 x 10(exp 6). The long term goal of this work is to integrate such a high Q resonator with small, low noise quartz oscillator electronics, providing a fractional frequency stability better than 1 x 10(exp -14) @ 1s.

  16. Acoustic trauma

    MedlinePlus

    Acoustic trauma is a common cause of sensory hearing loss . Damage to the hearing mechanisms within the inner ... Symptoms include: Partial hearing loss that most often involves ... The hearing loss may slowly get worse. Noises, ringing in ...

  17. Acoustic Neuroma

    MedlinePlus

    ... slow growing tumor which arise primarily from the vestibular portion of the VIII cranial nerve and lie ... you have a "brain tumor" called acoustic neuroma (vestibular schwannoma). You think you are the only one ...

  18. Underwater Acoustics.

    ERIC Educational Resources Information Center

    Creasey, D. J.

    1981-01-01

    Summarizes the history of underwater acoustics and describes related research studies and teaching activities at the University of Birmingham (England). Also includes research studies on transducer design and mathematical techniques. (SK)

  19. Room Acoustics

    NASA Astrophysics Data System (ADS)

    Kuttruff, Heinrich; Mommertz, Eckard

    The traditional task of room acoustics is to create or formulate conditions which ensure the best possible propagation of sound in a room from a sound source to a listener. Thus, objects of room acoustics are in particular assembly halls of all kinds, such as auditoria and lecture halls, conference rooms, theaters, concert halls or churches. Already at this point, it has to be pointed out that these conditions essentially depend on the question if speech or music should be transmitted; in the first case, the criterion for transmission quality is good speech intelligibility, in the other case, however, the success of room-acoustical efforts depends on other factors that cannot be quantified that easily, not least it also depends on the hearing habits of the listeners. In any case, absolutely "good acoustics" of a room do not exist.

  20. Constraints on kinematic model from recent cosmic observations: SN Ia, BAO and observational Hubble data

    SciTech Connect

    Xu, Lixin; Li, Wenbo; Lu, Jianbo E-mail: liwenbo10@yahoo.com.cn

    2009-07-01

    In this paper, linear first order expansion of deceleration parameter q(z) = q{sub 0}+q{sub 1}(1−a) (M{sub 1}), constant jerk j = j{sub 0} (M{sub 2}) and third order expansion of luminosity distance (M{sub 3}) are confronted with cosmic observations: SCP 307 SN Ia, BAO and observational Hubble data (OHD). Likelihood is implemented to find the best fit model parameters. All these models give the same prediction of the evolution of the universe which is undergoing accelerated expansion currently and experiences a transition from decelerated expansion to accelerated expansion. But, the transition redshift depends on the concrete parameterized form of the model assumed. M{sub 1} and M{sub 2} give value of transition redshift about z{sub t} ∼ 0.6. M{sub 3} gives a larger one, say z{sub t} ∼ 1. The χ{sup 2}/dof implies almost the same goodness of the models. But, for its badness of evolution of deceleration parameter at high redshift z > 1, M{sub 3} can not be reliable. M{sub 1} and M{sub 2} are compatible with ΛCDM model at the 2σ and 1σ confidence levels respectively. M{sub 3} is not compatible with ΛCDM model at 2σ confidence level. From M{sub 1} and M{sub 2} models, one can conclude that the cosmic data favor a cosmological model having j{sub 0} < −1.

  1. Power oscillator

    DOEpatents

    Gitsevich, Aleksandr

    2001-01-01

    An oscillator includes an amplifier having an input and an output, and an impedance transformation network connected between the input of the amplifier and the output of the amplifier, wherein the impedance transformation network is configured to provide suitable positive feedback from the output of the amplifier to the input of the amplifier to initiate and sustain an oscillating condition, and wherein the impedance transformation network is configured to protect the input of the amplifier from a destructive feedback signal. One example of the oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency. Various control circuits may be employed to match the driving frequency of the oscillator to a plurality of tuning states of the lamp.

  2. Raindrop oscillations

    NASA Technical Reports Server (NTRS)

    Beard, K. V.

    1982-01-01

    A model of the change in shape of a raindrop is presented. Raindrops measured by two orthogonal cameras were classified by shape and orientation to determine the nature of the oscillation. A physical model based on potential energy was then developed to study the amplitude variation of oscillating drops. The model results show that oscillations occur about the equilibrium axis ratio, but the time average axis ratio if significantly more spherical for large amplitudes because of asymmetry in the surface potential energy. A generalization of the model to oscillations produced by turbulence yields average axis ratios that are consistent with the camera measurements. The model results for average axis ratios were applied to rainfall studies with a dual polarized radar.

  3. Near-term measurements with 21 cm intensity mapping: Neutral hydrogen fraction and BAO at z<2

    SciTech Connect

    Masui, Kiyoshi Wesley; McDonald, Patrick; Pen, Ue-Li

    2010-05-15

    It is shown that 21 cm intensity mapping could be used in the near term to make cosmologically useful measurements. Large scale structure could be detected using existing radio telescopes, or using prototypes for dedicated redshift survey telescopes. This would provide a measure of the mean neutral hydrogen density, using redshift space distortions to break the degeneracy with the linear bias. We find that with only 200 hours of observing time on the Green Bank Telescope, the neutral hydrogen density could be measured to 25% precision at redshift 0.54acoustic oscillations, giving a cosmological distance measure at 3.5% precision. These observation time requirements could be greatly reduced with the construction of multiple pixel receivers. Similar results are possible using prototypes for dedicated cylindrical telescopes on month time scales, or Square Kilometre Array pathfinder aperture arrays on day time scales. Such measurements promise to improve our understanding of these quantities while beating a path for future generations of hydrogen surveys.

  4. THE SDSS-III BARYON OSCILLATION SPECTROSCOPIC SURVEY: QUASAR TARGET SELECTION FOR DATA RELEASE NINE

    SciTech Connect

    Ross, Nicholas P.; Kirkpatrick, Jessica A.; Carithers, William C.; Ho, Shirley; Myers, Adam D.; Sheldon, Erin S.; Yeche, Christophe; Aubourg, Eric; Strauss, Michael A.; Lee, Khee-Gan; Bovy, Jo; Blanton, Michael R.; Hogg, David W.; Richards, Gordon T.; Brandt, W. N.; Croft, Rupert A. C.; Da Silva, Robert; Dawson, Kyle; Eisenstein, Daniel J.; Hennawi, Joseph F.; and others

    2012-03-01

    The SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), a five-year spectroscopic survey of 10,000 deg{sup 2}, achieved first light in late 2009. One of the key goals of BOSS is to measure the signature of baryon acoustic oscillations (BAOs) in the distribution of Ly{alpha} absorption from the spectra of a sample of {approx}150,000 z > 2.2 quasars. Along with measuring the angular diameter distance at z Almost-Equal-To 2.5, BOSS will provide the first direct measurement of the expansion rate of the universe at z > 2. One of the biggest challenges in achieving this goal is an efficient target selection algorithm for quasars in the redshift range 2.2 < z < 3.5, where their colors tend to overlap those of the far more numerous stars. During the first year of the BOSS survey, quasar target selection (QTS) methods were developed and tested to meet the requirement of delivering at least 15 quasars deg{sup -2} in this redshift range, with a goal of 20 out of 40 targets deg{sup -2} allocated to the quasar survey. To achieve these surface densities, the magnitude limit of the quasar targets was set at g {<=} 22.0 or r {<=} 21.85. While detection of the BAO signature in the distribution of Ly{alpha} absorption in quasar spectra does not require a uniform target selection algorithm, many other astrophysical studies do. We have therefore defined a uniformly selected subsample of 20 targets deg{sup -2}, for which the selection efficiency is just over 50% ({approx}10 z > 2.20 quasars deg{sup -2}). This 'CORE' subsample will be fixed for Years Two through Five of the survey. For the remaining 20 targets deg{sup -2}, we will continue to develop improved selection techniques, including the use of additional data sets beyond the Sloan Digital Sky Survey (SDSS) imaging data. In this paper, we describe the evolution and implementation of the BOSS QTS algorithms during the first two years of BOSS operations (through 2011 July), in support of the science investigations based on

  5. Acoustic Characteristics of Simulated Respiratory-Induced Vocal Tremor

    ERIC Educational Resources Information Center

    Lester, Rosemary A.; Story, Brad H.

    2013-01-01

    Purpose: The purpose of this study was to investigate the relation of respiratory forced oscillation to the acoustic characteristics of vocal tremor. Method: Acoustical analyses were performed to determine the characteristics of the intensity and fundamental frequency (F[subscript 0]) for speech samples obtained by Farinella, Hixon, Hoit, Story,…

  6. Acoustic Measurement Of Periodic Motion Of Levitated Object

    NASA Technical Reports Server (NTRS)

    Watkins, John L.; Barmatz, Martin B.

    1992-01-01

    Some internal vibrations, oscillations in position, and rotations of acoustically levitated object measured by use of microphone already installed in typical levitation chamber for tuning chamber to resonance and monitoring operation. Levitating acoustic signal modulated by object motion of lower frequency. Amplitude modulation detected and analyzed spectrally to determine amplitudes and frequencies of motions.

  7. Miniature Sapphire Acoustic Resonator - MSAR

    NASA Technical Reports Server (NTRS)

    Wang, Rabi T.; Tjoelker, Robert L.

    2011-01-01

    A room temperature sapphire acoustics resonator incorporated into an oscillator represents a possible opportunity to improve on quartz ultrastable oscillator (USO) performance, which has been a staple for NASA missions since the inception of spaceflight. Where quartz technology is very mature and shows a performance improvement of perhaps 1 dB/decade, these sapphire acoustic resonators when integrated with matured quartz electronics could achieve a frequency stability improvement of 10 dB or more. As quartz oscillators are an essential element of nearly all types of frequency standards and reference systems, the success of MSAR would advance the development of frequency standards and systems for both groundbased and flight-based projects. Current quartz oscillator technology is limited by quartz mechanical Q. With a possible improvement of more than x 10 Q with sapphire acoustic modes, the stability limit of current quartz oscillators may be improved tenfold, to 10(exp -14) at 1 second. The electromagnetic modes of sapphire that were previously developed at JPL require cryogenic temperatures to achieve the high Q levels needed to achieve this stability level. However sapphire fs acoustic modes, which have not been used before in a high-stability oscillator, indicate the required Q values (as high as Q = 10(exp 8)) may be achieved at room temperature in the kHz range. Even though sapphire is not piezoelectric, such a high Q should allow electrostatic excitation of the acoustic modes with a combination of DC and AC voltages across a small sapphire disk (approximately equal to l mm thick). The first evaluations under this task will test predictions of an estimated input impedance of 10 kilohms at Q = 10(exp 8), and explore the Q values that can be realized in a smaller resonator, which has not been previously tested for acoustic modes. This initial Q measurement and excitation demonstration can be viewed similar to a transducer converting electrical energy to

  8. 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

  9. 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. PMID:27365040

  10. Programmable Oscillator

    NASA Technical Reports Server (NTRS)

    Quirk, Kevin J.; Patawaran, Ferze D.; Nguyen, Danh H.; Lee, Clement G.; Nguyen, Huy

    2011-01-01

    A programmable oscillator is a frequency synthesizer with an output phase that tracks an arbitrary function. An offset, phase-locked loop circuit is used in combination with an error control feedback loop to precisely control the output phase of the oscillator. To down-convert the received signal, several stages of mixing may be employed with the compensation for the time-base distortion of the carrier occurring at any one of those stages. In the Goldstone Solar System Radar (GSSR), the compensation occurs in the mixing from an intermediate frequency (IF), whose value is dependent on the station and band, to a common IF used in the final stage of down-conversion to baseband. The programmable oscillator (PO) is used in the final stage of down-conversion to generate the IF, along with a time-varying phase component that matches the time-base distortion of the carrier, thus removing it from the final down-converted signal.

  11. Stable local oscillator microcircuit.

    SciTech Connect

    Brocato, Robert Wesley

    2006-10-01

    This report gives a description of the development of a Stable Local Oscillator (StaLO) Microcircuit. The StaLO accepts a 100MHz input signal and produces output signals at 1.2, 3.3, and 3.6 GHz. The circuit is built as a multi-chip module (MCM), since it makes use of integrated circuit technologies in silicon and lithium niobate as well as discrete passive components. The StaLO uses a comb generator followed by surface acoustic wave (SAW) filters. The comb generator creates a set of harmonic components of the 100MHz input signal. The SAW filters are narrow bandpass filters that are used to select the desired component and reject all others. The resulting circuit has very low sideband power levels and low phase noise (both less than -40dBc) that is limited primarily by the phase noise level of the input signal.

  12. Acoustic forcing of a liquid drop

    NASA Technical Reports Server (NTRS)

    Lyell, M. J.

    1992-01-01

    The development of systems such as acoustic levitation chambers will allow for the positioning and manipulation of material samples (drops) in a microgravity environment. This provides the capability for fundamental studies in droplet dynamics as well as containerless processing work. Such systems use acoustic radiation pressure forces to position or to further manipulate (e.g., oscillate) the sample. The primary objective was to determine the effect of a viscous acoustic field/tangential radiation pressure forcing on drop oscillations. To this end, the viscous acoustic field is determined. Modified (forced) hydrodynamic field equations which result from a consistent perturbation expansion scheme are solved. This is done in the separate cases of an unmodulated and a modulated acoustic field. The effect of the tangential radiation stress on the hydrodynamic field (drop oscillations) is found to manifest as a correction to the velocity field in a sublayer region near the drop/host interface. Moreover, the forcing due to the radiation pressure vector at the interface is modified by inclusion of tangential stresses.

  13. Acoustic levitation and manipulation for space applications

    NASA Technical Reports Server (NTRS)

    Wang, T. G.

    1979-01-01

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

  14. Artificial Swimmers Propelled by Acoustically Activated Flagella.

    PubMed

    Ahmed, Daniel; Baasch, Thierry; Jang, Bumjin; Pane, Salvador; Dual, Jürg; Nelson, Bradley J

    2016-08-10

    Recent studies have garnered considerable interest in the field of propulsion to maneuver micro- and nanosized objects. Acoustics provide an alternate and attractive method to generate propulsion. To date, most acoustic-based swimmers do not use structural resonances, and their motion is determined by a combination of bulk acoustic streaming and a standing-wave field. The resultant field is intrinsically dependent on the boundaries of their resonating chambers. Though acoustic based propulsion is appealing in biological contexts, existing swimmers are less efficient, especially when operating in vivo, since no predictable standing-wave can be established in a human body. Here we describe a new class of nanoswimmer propelled by the small-amplitude oscillation of a flagellum-like flexible tail in standing and, more importantly, in traveling acoustic waves. The artificial nanoswimmer, fabricated by multistep electrodeposition techniques, compromises a rigid bimetallic head and a flexible tail. During acoustic excitation of the nanoswimmer the tail structure oscillates, which leads to a large amplitude propulsion in traveling waves. FEM simulation results show that the structural resonances lead to high propulsive forces. PMID:27459382

  15. Pattern-formation under acoustic driving forces

    NASA Astrophysics Data System (ADS)

    Valverde, Jose Manuel

    2015-07-01

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

  16. Nonlinear Acoustics Used To Reduce Leakage Flow

    NASA Technical Reports Server (NTRS)

    Daniels, Christopher C.; Steinetz, Bruce M.

    2004-01-01

    Leakage and wear are two fundamental problems in all traditional turbine seals that contribute to an engine's inefficiency. The solutions to seal leakage and wear conflict in the conventional design space. Reducing the clearance between the seal and rotating shaft reduces leakage but increases wear because of increased contact incidents. Increasing the clearance to reduce the contact between parts reduces wear but increases parasitic leakage. The goal of this effort is to develop a seal that restricts leakage flow using acoustic pressure while operating in a noncontacting manner, thereby increasing life. In 1996, Dr. Timothy Lucas announced his discovery of a method to produce shock-free high-amplitude pressure waves. For the first time, the formation of large acoustic pressures was possible using dissonant resonators. A pre-prototype acoustic seal developed at the NASA Glenn Research Center exploits this fundamental acoustic discovery: a specially shaped cavity oscillated at the contained fluid's resonant frequency produces high-amplitude acoustic pressure waves of a magnitude approaching those required of today's seals. While the original researchers are continuing their development of acoustic pumps, refrigeration compressors, and electronic thermal management systems using this technology, the goal of researchers at Glenn is to apply these acoustic principles to a revolutionary sealing device. When the acoustic resonator shape is optimized for the sealing device, the flow from a high-pressure cavity to a low-pressure cavity will be restricted by a series of high-amplitude standing pressure waves of higher pressure than the pressure to be sealed. Since the sealing resonator cavity will not touch the adjacent sealing structures, seal wear will be eliminated, improving system life. Under a cooperative agreement between Glenn and the Ohio Aerospace Institute (OAI), an acoustic-based pre-prototype seal was demonstrated for the first time. A pressurized cavity was

  17. Acoustic detection and ranging using solvable chaos

    NASA Astrophysics Data System (ADS)

    Corron, Ned J.; Stahl, Mark T.; Chase Harrison, R.; Blakely, Jonathan N.

    2013-06-01

    Acoustic experiments demonstrate a novel approach to ranging and detection that exploits the properties of a solvable chaotic oscillator. This nonlinear oscillator includes an ordinary differential equation and a discrete switching condition. The chaotic waveform generated by this hybrid system is used as the transmitted waveform. The oscillator admits an exact analytic solution that can be written as the linear convolution of binary symbols and a single basis function. This linear representation enables coherent reception using a simple analog matched filter and without need for digital sampling or signal processing. An audio frequency implementation of the transmitter and receiver is described. Successful acoustic ranging measurements in the presence of noise and interference from a second chaotic emitter are presented to demonstrate the viability of the approach.

  18. Acoustic detection and ranging using solvable chaos.

    PubMed

    Corron, Ned J; Stahl, Mark T; Harrison, R Chase; Blakely, Jonathan N

    2013-06-01

    Acoustic experiments demonstrate a novel approach to ranging and detection that exploits the properties of a solvable chaotic oscillator. This nonlinear oscillator includes an ordinary differential equation and a discrete switching condition. The chaotic waveform generated by this hybrid system is used as the transmitted waveform. The oscillator admits an exact analytic solution that can be written as the linear convolution of binary symbols and a single basis function. This linear representation enables coherent reception using a simple analog matched filter and without need for digital sampling or signal processing. An audio frequency implementation of the transmitter and receiver is described. Successful acoustic ranging measurements in the presence of noise and interference from a second chaotic emitter are presented to demonstrate the viability of the approach. PMID:23822484

  19. Acoustic transducer for acoustic microscopy

    DOEpatents

    Khuri-Yakub, B.T.; Chou, C.H.

    1990-03-20

    A shear acoustic transducer-lens system is described in which a shear polarized piezoelectric material excites shear polarized waves at one end of a buffer rod having a lens at the other end which excites longitudinal waves in a coupling medium by mode conversion at selected locations on the lens. 9 figs.

  20. Acoustic transducer for acoustic microscopy

    DOEpatents

    Khuri-Yakub, Butrus T.; Chou, Ching H.

    1990-01-01

    A shear acoustic transducer-lens system in which a shear polarized piezoelectric material excites shear polarized waves at one end of a buffer rod having a lens at the other end which excites longitudinal waves in a coupling medium by mode conversion at selected locations on the lens.

  1. Acoustic velocity measurements in materials using a regenerative method

    DOEpatents

    Laine, Edwin F.

    1986-01-01

    Acoustic energy is propagated through earth material between an electro-acoustic generator and a receiver which converts the received acoustic energy into electrical signals. A closed loop is formed by a variable gain amplifier system connected between the receiver and the generator. The gain of the amplifier system is increased until sustained oscillations are produced in the closed loop. The frequency of the oscillations is measured as an indication of the acoustic propagation velocity through the earth material. The amplifier gain is measured as an indication of the acoustic attenuation through the earth materials. The method is also applicable to the non-destructive testing of structural materials, such as steel, aluminum and concrete.

  2. Acoustic-velocity measurements in materials using a regenerative method

    DOEpatents

    Laine, E.F.

    1982-09-30

    Acoustic energy is propatated through earth material between an electro-acoustic generator and a receiver which converts the received acoustic energy into electrical signals. A closed loop is formed by a variable gain amplifier system connected between the receiver and the generator. The gain of the amplifier system is increased until sustained oscillations are produced in the closed loop. The frequency of the oscillations is measured as an indication of the acoustic propagation velocity through the earth material. The amplifier gain is measured as an indication of the acoustic attenuation through the earth materials. The method is also applicable to the non-destructive testing of structural materials, such as steel, aluminum and concrete.

  3. STABILIZED OSCILLATOR

    DOEpatents

    Jessen, P.L.; Price, H.J.

    1958-03-18

    This patent relates to sine-wave generators and in particular describes a generator with a novel feedback circuit resulting in improved frequency stability. The generator comprises two triodes having a common cathode circuit connected to oscillate at a frequency and amplitude at which the loop galn of the circutt ls unity, and another pair of triodes having a common cathode circuit arranged as a conventional amplifier. A signal is conducted from the osciliator through a frequency selective network to the amplifier and fed back to the osciliator. The unique feature of the feedback circuit is the amplifier operates in the nonlinear portion of its tube characteristics thereby providing a relatively constant feedback voltage to the oscillator irrespective of the amplitude of its input signal.

  4. Antiperiodic oscillations

    PubMed Central

    Freire, Joana G.; Cabeza, Cecilia; Marti, Arturo; Pöschel, Thorsten; Gallas, Jason A. C.

    2013-01-01

    The investigation of regular and irregular patterns in nonlinear oscillators is an outstanding problem in physics and in all natural sciences. In general, regularity is understood as tantamount to periodicity. However, there is now a flurry of works proving the existence of “antiperiodicity”, an unfamiliar type of regularity. Here we report the experimental observation and numerical corroboration of antiperiodic oscillations. In contrast to the isolated solutions presently known, we report infinite hierarchies of antiperiodic waveforms that can be tuned continuously and that form wide spiral-shaped stability phases in the control parameter plane. The waveform complexity increases towards the focal point common to all spirals, a key hub interconnecting them all. PMID:23739041

  5. FEL Oscillators

    SciTech Connect

    George Neil

    2003-05-12

    FEL Oscillators have been around since 1977 providing not only a test bed for the physics of Free Electron Lasers and electron/photon interactions but as a workhorse of scientific research. More than 30 FEL oscillators are presently operating around the world spanning a wavelength range from the mm region to the ultraviolet using DC and rf linear accelerators and storage rings as electron sources. The characteristics that have driven the development of these sources are the desire for high peak and average power, high micropulse energies, wavelength tunability, timing flexibility, and wavelengths that are unavailable from more conventional laser sources. Substantial user programs have been performed using such sources encompassing medicine, biology, solid state research, atomic and molecular physics, effects of non-linear fields, surface science, polymer science, pulsed laser vapor deposition, to name just a few.

  6. Neutrino oscillations.

    PubMed

    Thomson, Mark

    2002-05-15

    The wave theory of light, and in particular the principle of interference, was formulated by Thomas Young in 1801. In the 20th century, the principle of interference was extended to the quantum mechanical wave functions describing matter. The phenomenon of quantum mechanical interference of different neutrino states, neutrino oscillations, has provided one of the most exciting developments in high energy particle physics of the last decade. Observations of the flavour oscillations of neutrinos produced by distant sources, such as from the core of the Sun, provide compelling evidence that neutrinos have mass. This article describes the main features and the most significant experimental observations of this unusual application of the principle of interference.

  7. Spike oscillations

    NASA Astrophysics Data System (ADS)

    Heinzle, J. Mark; Uggla, Claes; Lim, Woei Chet

    2012-11-01

    According to Belinskiǐ, Khalatnikov and Lifshitz (BKL), a generic spacelike singularity is characterized by asymptotic locality: Asymptotically, toward the singularity, each spatial point evolves independently from its neighbors, in an oscillatory manner that is represented by a sequence of Bianchi type I and II vacuum models. Recent investigations support this conjecture but with a modification: Apart from local BKL behavior there also exists formation of spatial structures (“spikes”) at, and in the neighborhood of, certain spatial surfaces that break asymptotic locality; the complete description of a generic spacelike singularity involves spike oscillations, which are described by sequences of Bianchi type I and certain inhomogeneous vacuum models. In this paper we describe how BKL and spike oscillations arise from concatenations of exact solutions in a Hubble-normalized state space setting, suggesting the existence of hidden symmetries and showing that the results of BKL are part of a greater picture.

  8. Condition of resonant break-up of gas bubbles by an acoustic wave in liquid

    NASA Astrophysics Data System (ADS)

    Vanovskiy, V. V.; Petrov, A. G.

    2016-07-01

    The linear theory of damping of radial vibrations of a bubble in a liquid is constructed by taking into account the key dissipative mechanisms: thermal, viscous, and acoustic. The basic approximation of homobaricity made helps to obtain the results in a convenient and simple form. The results obtained for damping are used further in the description of the forced resonant oscillations of a bubble in an acoustic wave with the frequency equal to the eigenfrequency of the radial oscillation mode and twice as high as the frequency of the deformation oscillation mode (resonance 2:2:1). It is shown that the amplitude of deformation oscillations, which is reasonably large for breaking, is developed at a relatively small pressure amplitude of the exciting acoustic wave, and subharmonics arise in the acoustic-emission spectrum. The condition of bubble break-up is obtained for a fast and slow start of the acoustic wave.

  9. Medical Acoustics

    NASA Astrophysics Data System (ADS)

    Beach, Kirk W.; Dunmire, Barbrina

    Medical acoustics can be subdivided into diagnostics and therapy. Diagnostics are further separated into auditory and ultrasonic methods, and both employ low amplitudes. Therapy (excluding medical advice) uses ultrasound for heating, cooking, permeablizing, activating and fracturing tissues and structures within the body, usually at much higher amplitudes than in diagnostics. Because ultrasound is a wave, linear wave physics are generally applicable, but recently nonlinear effects have become more important, even in low-intensity diagnostic applications.

  10. Combustion instability coupling with feed system acoustics

    NASA Technical Reports Server (NTRS)

    Priem, Richard J.; Breisacher, Kevin J.

    1988-01-01

    High frequency combustion instability has recently been observed by Rocketdyne in a 40K thrust methane/LOX combustion chamber. The oscillations had frequencies as high as 14,000 Hz with pressure amplitudes in the LOX dome of 500 psi at a chamber pressures of 2,000 psi. At this frequency the wave length associated with a period of oscillation is 2.3 inches in LOX and 1.4 inches in methane. These distances are comparable to the lengths of the injector elements which requires that acoustic waves be considered in the feed systems rather than using lumped parameters as is normally considered for feed system coupled oscillations. To expand the capability of existing models, the Feiler and Heidmann feed system coupled instability model was modified to include acoustic oscillations in the feed system. Similarly the vaporization controlled instability model of Heidmann and Wieber was modified to include flow oscillations that would be produced by feed system coupling. The major elements that control oscillations in a rocket combustion chamber are shown and discussed.

  11. MTCI acoustic agglomeration particulate control

    SciTech Connect

    Chandran, R.R.; Mansour, M.N.; Scaroni, A.W.; Koopmann, G.H.; Loth, J.L.

    1994-10-01

    The overall objective of this project is to demonstrate pulse combination induced acoustic enhancement of coal ash agglomeration and sulfur capture at conditions typical of direct coal-fired turbines and PFBC hot gas cleanup. MTCI has developed an advanced compact pulse combustor island for direct coal-firing in combustion gas turbines. This combustor island comprises a coal-fired pulse combustor, a combined ash agglomeration and sulfur capture chamber (CAASCC), and a hot cyclone. In the MTCI proprietary approach, the pulse combustion-induced high intensity sound waves improve sulfur capture efficiency and ash agglomeration. The resulting agglomerates allow the use of commercial cyclones and achieve very high particulate collection efficiency. In the MTCI proprietary approach, sorbent particles are injected into a gas stream subjected to an intense acoustic field. The acoustic field serves to improve sulfur capture efficiency by enhancing both gas film and intra-particle mass transfer rates. In addition, the sorbent particles act as dynamic filter foci, providing a high density of stagnant agglomerating centers for trapping the finer entrained (in the oscillating flow field) fly ash fractions. A team has been formed with MTCI as the prime contractor and Penn State University and West Virginia University as subcontractors to MTCI. MTCI is focusing on hardware development and system demonstration, PSU is investigating and modeling acoustic agglomeration and sulfur capture, and WVU is studying aerovalve fluid dynamics. Results are presented from all three studies.

  12. A thermodynamic study of BaO + BaCl2 + Cr2O3 fluxes used for the removal of phosphorus from chromium-containing iron melts

    NASA Astrophysics Data System (ADS)

    Inouye, T. K.; Fujiwara, H.; Ichise, E.; Iwase, M.

    1994-10-01

    Electrochemical measurements with solid-oxide galvanic cell of the type Mo/Mo + MoO2//ZrO2(MgO)//{Cu + Cr}alloy + (Cr2O3)slag/Mo were conducted at 1473 K in order to obtain the activities of Cr2O3 in BaO + BaCl2 + Cr2O3 slags used for dephosphorization of chromium-containing iron melts. Based on the activity measurements, it is concluded that in the system BaO + BaCl2 + Cr2 O3 at 1473 K, there are 1 two-phase region in saturation with pure Cr2O3(s) and 3 three-phase regions. The activities of Cr2O3 within such three-phase regions decrease with an increase in BaO/BaCl2 mole ratios. The Cr2O3 activities in BaO + BaCl2 + Cr2O3 fluxes are, in general, greater than those in CaO + CaCl2 + Cr2O3, corresponding to much more effective dephosphorization by BaO + BaCl2 + Cr2O3 fluxes rather than CaO + CaCl2 + Cr2O3 slag.

  13. Acoustic modes in fluid networks

    NASA Technical Reports Server (NTRS)

    Michalopoulos, C. D.; Clark, Robert W., Jr.; Doiron, Harold H.

    1992-01-01

    Pressure and flow rate eigenvalue problems for one-dimensional flow of a fluid in a network of pipes are derived from the familiar transmission line equations. These equations are linearized by assuming small velocity and pressure oscillations about mean flow conditions. It is shown that the flow rate eigenvalues are the same as the pressure eigenvalues and the relationship between line pressure modes and flow rate modes is established. A volume at the end of each branch is employed which allows any combination of boundary conditions, from open to closed, to be used. The Jacobi iterative method is used to compute undamped natural frequencies and associated pressure/flow modes. Several numerical examples are presented which include acoustic modes for the Helium Supply System of the Space Shuttle Orbiter Main Propulsion System. It should be noted that the method presented herein can be applied to any one-dimensional acoustic system involving an arbitrary number of branches.

  14. Combustion oscillation control by cyclic fuel injection

    SciTech Connect

    Richards, G.A.; Yip, M.J.; Robey, E.; Cowell, L.; Rawlins, D.

    1995-04-01

    A number of recent articles have demonstrated the use of active control to mitigate the effects of combustion instability in afterburner and dump combustor applications. In these applications, cyclic injection of small quantities of control fuel has been proposed to counteract the periodic heat release that contributes to undesired pressure oscillations. This same technique may also be useful to mitigate oscillations in gas turbine combustors, especially in test rig combustors characterized by acoustic modes that do not exist in the final engine configuration. To address this issue, the present paper reports on active control of a subscale, atmospheric pressure nozzle/combustor arrangement. The fuel is natural gas. Cyclic injection of 14% control fuel in a premix fuel nozzle is shown to reduce oscillating pressure amplitude by a factor of 0.30 (i.e., {approximately}10 dB) at 300 Hz. Measurement of the oscillating heat release is also reported.

  15. Parametrically excited sectorial oscillation of liquid drops floating in ultrasound.

    PubMed

    Shen, C L; Xie, W J; Wei, B

    2010-04-01

    We report experiments in which the nonaxisymmetric sectorial oscillations of water drops have been excited using acoustic levitation and an active modulation method. The observed stable sectorial oscillations are up to the seventh mode. These oscillations are excited by parametric resonance. The oblate initial shape of the water drops is essential to this kind of excitations. The oscillation frequency increases with mode number but decreases with equatorial radius for each mode number. The data can be well described by a modified Rayleigh equation, without the use of additional parameters. PMID:20481825

  16. Acoustic Tooth Cleaner

    NASA Technical Reports Server (NTRS)

    Heyman, J. S.

    1984-01-01

    Acoustically-energized water jet aids in plaque breakdown. Acoustic Wand includes acoustic transducer 1/4 wave plate, and tapered cone. Together elements energize solution of water containing mild abrasive injected into mouth to help prevent calculous buildup.

  17. The acoustic characteristics of turbomachinery cavities

    NASA Technical Reports Server (NTRS)

    Lucas, M. J.; Noreen, R.; Southerland, L. D.; Cole, J., III; Junger, M.

    1995-01-01

    Internal fluid flows are subject not only to self-sustained oscillations of the purely hydrodynamic type but also to the coupling of the instability with the acoustic mode of the surrounding cavity. This situation is common to turbomachinery, since flow instabilities are confined within a flow path where the acoustic wavelength is typically smaller than the dimensions of the cavity and flow speeds are low enough to allow resonances. When acoustic coupling occurs, the fluctuations can become so severe in amplitude that it may induce structural failure of engine components. The potential for catastrophic failure makes identifying flow-induced noise and vibration sources a priority. In view of the complexity of these types of flows, this report was written with the purpose of presenting many of the methods used to compute frequencies for self-sustained oscillations. The report also presents the engineering formulae needed to calculate the acoustic resonant modes for ducts and cavities. Although the report is not a replacement for more complex numerical or experimental modeling techniques, it is intended to be used on general types of flow configurations that are known to produce self-sustained oscillations. This report provides a complete collection of these models under one cover.

  18. Optical and acoustical dynamics of microbubble contrast agents inside neutrophils.

    PubMed Central

    Dayton, P A; Chomas, J E; Lum, A F; Allen, J S; Lindner, J R; Simon, S I; Ferrara, K W

    2001-01-01

    Acoustically active microbubbles are used for contrast-enhanced ultrasound assessment of organ perfusion. In regions of inflammation, contrast agents are captured and phagocytosed by activated neutrophils adherent to the venular wall. Using direct optical observation with a high-speed camera and acoustical interrogation of individual bubbles and cells, we assessed the physical and acoustical responses of both phagocytosed and free microbubbles. Optical analysis of bubble radial oscillations during insonation demonstrated that phagocytosed microbubbles experience viscous damping within the cytoplasm and yet remain acoustically active and capable of large volumetric oscillations during an acoustic pulse. Fitting a modified version of the Rayleigh-Plesset equation that describes mechanical properties of thin shells to optical radius-time data of oscillating bubbles provided estimates of the apparent viscosity of the intracellular medium. Phagocytosed microbubbles experienced a viscous damping approximately sevenfold greater than free microbubbles. Acoustical comparison between free and phagocytosed microbubbles indicated that phagocytosed microbubbles produce an echo with a higher mean frequency than free microbubbles in response to a rarefaction-first single-cycle pulse. Moreover, this frequency increase is predicted using the modified Rayleigh-Plesset equation. We conclude that contrast-enhanced ultrasound can detect distinct acoustic signals from microbubbles inside of neutrophils and may provide a unique tool to identify activated neutrophils at sites of inflammation. PMID:11222315

  19. A test device for premixed gas turbine combustion oscillations

    SciTech Connect

    Richards, G.A.; Gemmen, R.S.; Yip, M.J.

    1996-03-01

    This report discusses design and operation of a single-nozzle test combustor for studying lean, premixed combustion oscillations from gas turbine fuel nozzles. It was used to study oscillations from a prototype fuel nozzle that produced oscillations during testing in a commercial engine. Similar, but not identical, oscillations were recorded in the test device. Basic requirements of the device design were that the flame geometry be maintained and acoustic losses be minimized; this was achieved by using a Helmholtz resonator as the combustor geometry. Surprisingly, the combustor oscillated strongly at several frequencies, without modification of the resonator. Brief survey of operating conditions suggests that it may be helpful to characterize oscillating behavior in terms of reference velocity and inlet air temperature with the rig backpressure playing a smaller role. The preliminary results do not guarantee that the single-nozzle test device will reproduce arbitrary oscillations that occur on a complete engine test. Nozzle/nozzle interactions may complicate the response, and oscillations controlled by acoustic velocities transverse to the nozzle axis may not be reproduced in a test device that relies on a bulk Helmholtz mode. Nevertheless, some oscillations can be reproduced, and the single-nozzle test device allows both active and passive control strategies to be tested relatively inexpensively.

  20. Acoustic transducer

    DOEpatents

    Drumheller, D.S.

    1997-12-30

    An acoustic transducer is described comprising a one-piece hollow mandrel into the outer surface of which is formed a recess with sides perpendicular to the central axis of the mandrel and separated by a first distance and with a bottom parallel to the central axis and within which recess are a plurality of washer-shaped discs of a piezoelectric material and at least one disc of a temperature-compensating material with the discs being captured between the sides of the recess in a pre-stressed interference fit, typically at 2,000 psi of compressive stress. The transducer also includes a power supply and means to connect to a measurement device. The transducer is intended to be used for telemetry between a measurement device located downhole in an oil or gas well and the surface. The transducer is of an construction that is stronger with fewer joints that could leak fluids into the recess holding the piezoelectric elements than is found in previous acoustic transducers. 4 figs.

  1. Acoustic transducer

    DOEpatents

    Drumheller, Douglas S.

    1997-01-01

    An acoustic transducer comprising a one-piece hollow mandrel into the outer surface of which is formed a recess with sides perpendicular to the central axis of the mandrel and separated by a first distance and with a bottom parallel to the central axis and within which recess are a plurality of washer-shaped discs of a piezoelectric material and at least one disc of a temperature-compensating material with the discs being captured between the sides of the recess in a pre-stressed interference fit, typically at 2000 psi of compressive stress. The transducer also includes a power supply and means to connect to a measurement device. The transducer is intended to be used for telemetry between a measurement device located downhole in an oil or gas well and the surface. The transducer is of an construction that is stronger with fewer joints that could leak fluids into the recess holding the piezoelectric elements than is found in previous acoustic transducers.

  2. Correlation of signals of thermal acoustic radiation

    NASA Astrophysics Data System (ADS)

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

    2003-03-01

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

  3. Oscillator detector

    SciTech Connect

    Potter, B.M.

    1980-05-13

    An alien liquid detector employs a monitoring element and an oscillatory electronic circuit for maintaining the temperature of the monitoring element substantially above ambient temperature. The output wave form, eg., frequency of oscillation or wave shape, of the oscillatory circuit depends upon the temperaturedependent electrical characteristic of the monitoring element. A predetermined change in the output waveform allows water to be discriminated from another liquid, eg., oil. Features of the invention employing two thermistors in two oscillatory circuits include positioning one thermistor for contact with water and the other thermistor above the oil-water interface to detect a layer of oil if present. Unique oscillatory circuit arrangements are shown that achieve effective thermistor action with an economy of parts and energizing power. These include an operational amplifier employed in an astable multivibrator circuit, a discrete transistor-powered tank circuit, and use of an integrated circuit chip.

  4. Reactions of NO2 with BaO/Pt(111) Model Catalysts: The Effects of BaO Film Thickness and NO2 Pressure on the Formation of Ba(NOx)2 Species

    SciTech Connect

    Mudiyanselage, Kumudu; Yi, Cheol-Woo; Szanyi, Janos

    2011-05-31

    The adsorption and reaction of NO2 on BaO (<1, ~3, and >20 monolayer equivalent (MLE))/Pt(111) model systems were studied with temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and infrared reflection absorption spectroscopy (IRAS) under ultra-high vacuum (UHV) as well as elevated pressure conditions. NO2 reacts with sub-monolayer BaO (<1 MLE) to form nitrites only, whereas the reaction of NO2 with BaO (~3 MLE)/Pt(111) produces mainly nitrites and a small amount of nitrates under UHV conditions (PNO2 ~ 1.0 × 10-9 Torr) at 300 K. In contrast, a thick BaO(>20 MLE) layer on Pt(111) reacts with NO2 to form nitrite-nitrate ion pairs under the same conditions. At elevated NO2 pressures (≥ 1.0 × 10-5 Torr), however, BaO layers at all these three coverages convert to amorphous barium nitrates at 300 K. Upon annealing to 500 K, these amorphous barium nitrate layers transform into crystalline phases. The thermal decomposition of the thus-formed Ba(NOx)2 species is also influenced by the coverage of BaO on the Pt(111) substrate: at low BaO coverages, these species decompose at significantly lower temperatures in comparison with those formed on thick BaO films due to the presence of Ba(NOx)2/Pt interface where the decomposition can proceed at lower temperatures. However, the thermal decomposition of the thick Ba(NO3)2 films follows that of bulk nitrates. Results obtained from these BaO/Pt(111) model systems under UHV and elevated pressure conditions clearly demonstrate that both the BaO film thickness and the applied NO2 pressure are critical in the Ba(NOx)2 formation and subsequent thermal decomposition processes.

  5. An acoustofluidic micromixer based on oscillating sidewall sharp-edges†

    PubMed Central

    Huang, Po-Hsun; Xie, Yuliang; Ahmed, Daniel; Rufo, Joseph; Nama, Nitesh; Chen, Yuchao; Chan, Chung Yu; Huang, Tony Jun

    2014-01-01

    Rapid and homogeneous mixing inside a microfluidic channel is demonstrated via the acoustic streaming phenomenon induced by the oscillation of sidewall sharp-edges. By optimizing the design of the sharp-edges, excellent mixing performance and fast mixing speed can be achieved in a simple device, making our sharp-edge-based acoustic micromixer a promising candidate for a wide variety of applications. PMID:23896797

  6. Determination of decay coefficients for combustors with acoustic absorbers

    NASA Technical Reports Server (NTRS)

    Mitchell, C. E.; Espander, W. R.; Baer, M. R.

    1972-01-01

    An analytical technique for the calculation of linear decay coefficients in combustors with acoustic absorbers is presented. Tuned circumferential slot acoustic absorbers were designed for the first three transverse modes of oscillation, and decay coefficients for these absorbers were found as a function of backing distance for seven different chamber configurations. The effectiveness of the absorbers for off-design values of the combustion response and acoustic mode is also investigated. Results indicate that for tuned absorbers the decay coefficient increases approximately as the cube of the backing distance. For most off-design situations the absorber still provides a damping effect. However, if an absorber designed for some higher mode of oscillation is used to damp lower mode oscillations, a driving effect is frequently found.

  7. Surface-Controlled Drop Oscillations in Space

    NASA Technical Reports Server (NTRS)

    Holt, R. Glynn; Tian, Yuren; Janovsky, Joseph; Apfel, Robert E.

    1996-01-01

    Large liquid drops were deformed by an acoustic standing wave in a resonant air chanber called the Drop Physics Module, which was carried on Space Shuttle Columbia as part of the second United States Microgravity Laboratory mission. When this deforming force was suddenly reduced, the drops executed free oscillations about a perfect sherical equilibrium. Results are presented for pure water and aqueous solutions of soluble surfactants. [PACS: 43.25.U, 47.55Dz, 68.10.Cr, 83.10.-y].

  8. Acoustic emission descriptors

    NASA Astrophysics Data System (ADS)

    Witos, Franciszek; Malecki, Ignacy

    The authors present selected problems associated with acoustic emission interpreted as a physical phenomenon and as a measurement technique. The authors examine point sources of acoustic emission in isotropic, homogeneous linearly elastic media of different shapes. In the case of an unbounded medium the authors give the analytical form of the stress field and the wave shift field of the acoustic emission. In the case of a medium which is unbounded plate the authors give a form for the equations which is suitable for numerical calculation of the changes over time of selected acoustic emission values. For acoustic emission as a measurement technique, the authors represent the output signal as the resultant of a mechanical input value which describes the source, the transient function of the medium, and the transient function of specific components of the measurement loop. As an effect of this notation, the authors introduce the distinction between an acoustic measurement signal and an acoustic measurement impulse. The authors define the basic parameters of an arbitrary impulse. The authors extensively discuss the signal functions of acoustic emission impulses and acoustic emission signals defined in this article as acoustic emission descriptors (or signal functions of acoustic emission impulses) and advanced acoustic emission descriptors (which are either descriptors associated with acoustic emission applications or the signal functions of acoustic emission signals). The article also contains the results of experimental research on three different problems in which acoustic emission descriptors associated with acoustic emission pulses, acoustic emission applications, and acoustic emission signals are used. These problems are respectively: a problem of the amplitude-load characteristics of acoustic emission pulses in carbon samples subjected to compound uniaxial compression, the use of acoustic emission to predict the durability characteristics of conveyor belts, and

  9. Acoustic transducer

    DOEpatents

    Drumheller, Douglas S.

    2000-01-01

    An active acoustic transducer tool for use down-hole applications. The tool includes a single cylindrical mandrel including a shoulder defining the boundary of a narrowed portion over which is placed a sandwich-style piezoelectric tranducer assembly. The piezoelectric transducer assembly is prestressed by being placed in a thermal interference fit between the shoulder of the mandrel and the base of an anvil which is likewise positioned over the narrower portion of the mandrel. In the preferred embodiment, assembly of the tool is accomplished using a hydraulic jack to stretch the mandrel prior to emplacement of the cylindrical sandwich-style piezoelectric transducer assembly and anvil. After those elements are positioned and secured, the stretched mandrel is allowed to return substantially to its original (pre-stretch) dimensions with the result that the piezoelectric transducer elements are compressed between the anvil and the shoulder of the mandrel.

  10. Constraining anisotropic baryon oscillations

    NASA Astrophysics Data System (ADS)

    Padmanabhan, Nikhil; White, Martin

    2008-06-01

    We present an analysis of anisotropic baryon acoustic oscillations and elucidate how a mis-estimation of the cosmology, which leads to incorrect values of the angular diameter distance, dA, and Hubble parameter, H, manifest themselves in changes to the monopole and quadrupole power spectrum of biased tracers of the density field. Previous work has focused on the monopole power spectrum, and shown that the isotropic dilation combination dA2H-1 is robustly constrained by an overall shift in the scale of the baryon feature. We extend this by demonstrating that the quadrupole power spectrum is sensitive to an anisotropic warping mode dAH, allowing one to break the degeneracy between dA and H. We describe a method for measuring this warping, explicitly marginalizing over the form of redshift-space distortions. We verify this method on N-body simulations and estimate that dAH can be measured with a fractional accuracy of ˜(3/V)% where the survey volume is estimated in h-3Gpc3.

  11. Acoustic telemetry.

    SciTech Connect

    Drumheller, Douglas Schaeffer; Kuszmaul, Scott S.

    2003-08-01

    Broadcasting messages through the earth is a daunting task. Indeed, broadcasting a normal telephone conversion through the earth by wireless means is impossible with todays technology. Most of us don't care, but some do. Industries that drill into the earth need wireless communication to broadcast navigation parameters. This allows them to steer their drill bits. They also need information about the natural formation that they are drilling. Measurements of parameters such as pressure, temperature, and gamma radiation levels can tell them if they have found a valuable resource such as a geothermal reservoir or a stratum bearing natural gas. Wireless communication methods are available to the drilling industry. Information is broadcast via either pressure waves in the drilling fluid or electromagnetic waves in the earth and well tubing. Data transmission can only travel one way at rates around a few baud. Given that normal Internet telephone modems operate near 20,000 baud, these data rates are truly very slow. Moreover, communication is often interrupted or permanently blocked by drilling conditions or natural formation properties. Here we describe a tool that communicates with stress waves traveling through the steel drill pipe and production tubing in the well. It's based on an old idea called Acoustic Telemetry. But what we present here is more than an idea. This tool exists, it's drilled several wells, and it works. Currently, it's the first and only acoustic telemetry tool that can withstand the drilling environment. It broadcasts one way over a limited range at much faster rates than existing methods, but we also know how build a system that can communicate both up and down wells of indefinite length.

  12. Acoustic spin pumping in magnetoelectric bulk acoustic wave resonator

    NASA Astrophysics Data System (ADS)

    Polzikova, N. I.; Alekseev, S. G.; Pyataikin, I. I.; Kotelyanskii, I. M.; Luzanov, V. A.; Orlov, A. P.

    2016-05-01

    We present the generation and detection of spin currents by using magnetoelastic resonance excitation in a magnetoelectric composite high overtone bulk acoustic wave (BAW) resonator (HBAR) formed by a Al-ZnO-Al-GGG-YIG-Pt structure. Transversal BAW drives magnetization oscillations in YIG film at a given resonant magnetic field, and the resonant magneto-elastic coupling establishes the spin-current generation at the Pt/YIG interface. Due to the inverse spin Hall effect (ISHE) this BAW-driven spin current is converted to a dc voltage in the Pt layer. The dependence of the measured voltage both on magnetic field and frequency has a resonant character. The voltage is determined by the acoustic power in HBAR and changes its sign upon magnetic field reversal. We compare the experimentally observed amplitudes of the ISHE electrical field achieved by our method and other approaches to spin current generation that use surface acoustic waves and microwave resonators for ferromagnetic resonance excitation, with the theoretically expected values.

  13. Containerless solidification of acoustically levitated Ni-Sn eutectic alloy

    NASA Astrophysics Data System (ADS)

    Geng, D. L.; Xie, W. J.; Wei, B.

    2012-10-01

    Containerless solidification of Ni-18.7at%Sn eutectic alloy has been achieved with a single-axis acoustic levitator. The temperature, motion, and oscillation of the sample were monitored by a high speed camera. The temperature of the sample can be determined from its image brightness, although the sample moves vertically and horizontally during levitation. The experimentally observed frequency of vertical motion is in good agreement with theoretical prediction. The sample undergoes shape oscillation before solidification finishes. The solidification microstructure of this alloy consists of a mixture of anomalous eutectic plus regular lamellar eutectic. This indicates the achievement of rapid solidification under acoustic levitation condition.

  14. Underwater acoustic wave generation by filamentation of terawatt ultrashort laser pulses.

    PubMed

    Jukna, Vytautas; Jarnac, Amélie; Milián, Carles; Brelet, Yohann; Carbonnel, Jérôme; André, Yves-Bernard; Guillermin, Régine; Sessarego, Jean-Pierre; Fattaccioli, Dominique; Mysyrowicz, André; Couairon, Arnaud; Houard, Aurélien

    2016-06-01

    Acoustic signals generated by filamentation of ultrashort terawatt laser pulses in water are characterized experimentally. Measurements reveal a strong influence of input pulse duration on the shape and intensity of the acoustic wave. Numerical simulations of the laser pulse nonlinear propagation and the subsequent water hydrodynamics and acoustic wave generation show that the strong acoustic emission is related to the mechanism of superfilamention in water. The elongated shape of the plasma volume where energy is deposited drives the far-field profile of the acoustic signal, which takes the form of a radially directed pressure wave with a single oscillation and a very broad spectrum.

  15. Underwater acoustic wave generation by filamentation of terawatt ultrashort laser pulses.

    PubMed

    Jukna, Vytautas; Jarnac, Amélie; Milián, Carles; Brelet, Yohann; Carbonnel, Jérôme; André, Yves-Bernard; Guillermin, Régine; Sessarego, Jean-Pierre; Fattaccioli, Dominique; Mysyrowicz, André; Couairon, Arnaud; Houard, Aurélien

    2016-06-01

    Acoustic signals generated by filamentation of ultrashort terawatt laser pulses in water are characterized experimentally. Measurements reveal a strong influence of input pulse duration on the shape and intensity of the acoustic wave. Numerical simulations of the laser pulse nonlinear propagation and the subsequent water hydrodynamics and acoustic wave generation show that the strong acoustic emission is related to the mechanism of superfilamention in water. The elongated shape of the plasma volume where energy is deposited drives the far-field profile of the acoustic signal, which takes the form of a radially directed pressure wave with a single oscillation and a very broad spectrum. PMID:27415357

  16. Phase mixing and nonlinearity in geodesic acoustic modes

    SciTech Connect

    Hung, C. P.; Hassam, A. B.

    2013-09-15

    Phase mixing and nonlinear resonance detuning of geodesic acoustic modes in a tokamak plasma are examined. Geodesic acoustic modes (GAMs) are tokamak normal modes with oscillations in poloidal flow constrained to lie within flux surfaces. The mode frequency is sonic, dependent on the local flux surface temperature. Consequently, mode oscillations between flux surfaces get rapidly out of phase, resulting in enhanced damping from the phase mixing. Damping rates are shown to scale as the negative 1/3 power of the large viscous Reynolds number. The effect of convective nonlinearities on the normal modes is also studied. The system of nonlinear GAM equations is shown to resemble the Duffing oscillator, which predicts resonance detuning of the oscillator. Resonant amplification is shown to be suppressed nonlinearly. All analyses are verified by numerical simulation. The findings are applied to a recently proposed GAM excitation experiment on the DIII-D tokamak.

  17. Phase mixing and nonlinearity in geodesic acoustic modes

    NASA Astrophysics Data System (ADS)

    Hung, C. P.; Hassam, A. B.

    2013-09-01

    Phase mixing and nonlinear resonance detuning of geodesic acoustic modes in a tokamak plasma are examined. Geodesic acoustic modes (GAMs) are tokamak normal modes with oscillations in poloidal flow constrained to lie within flux surfaces. The mode frequency is sonic, dependent on the local flux surface temperature. Consequently, mode oscillations between flux surfaces get rapidly out of phase, resulting in enhanced damping from the phase mixing. Damping rates are shown to scale as the negative 1/3 power of the large viscous Reynolds number. The effect of convective nonlinearities on the normal modes is also studied. The system of nonlinear GAM equations is shown to resemble the Duffing oscillator, which predicts resonance detuning of the oscillator. Resonant amplification is shown to be suppressed nonlinearly. All analyses are verified by numerical simulation. The findings are applied to a recently proposed GAM excitation experiment on the DIII-D tokamak.

  18. Numerical simulation of pressure oscillations in a ramjet combustor

    NASA Technical Reports Server (NTRS)

    Jou, Wen-Huei; Menon, Suresh

    1989-01-01

    Large-eddy simulations of compressible cold flow in a ramjet combustor configuration were performed. The objectives were to investigate the mechanisms for vortex-acoustic interaction in such a device and to develop a simulation method that can be extended to cases with combustion heat release to study combustion instability. From the simulation, it was found that the separated shear layer rolls up into concentrated vortices that merge to form large coherent structures. These vortices interact with the choked nozzle downstream to produce an axial acoustic dipole. The spectrum of the pressure fluctuation at the base of the backward-facing step shows that there are two types of oscillations: an acoustic resonant mode and a vortex-acoustic coupled mode. Based on the flow physics observed in the simulations, a simple one-dimensional model for the vortex-acoustic coupled mode was proposed. The eigenvalue problem based on this model was solved to obtain the frequency of the coupled mode.

  19. Motion measurement of acoustically levitated object

    NASA Technical Reports Server (NTRS)

    Watkins, John L. (Inventor); Barmatz, Martin B. (Inventor)

    1993-01-01

    A system is described for determining motion of an object that is acoustically positioned in a standing wave field in a chamber. Sonic energy in the chamber is sensed, and variation in the amplitude of the sonic energy is detected, which is caused by linear motion, rotational motion, or drop shape oscillation of the object. Apparatus for detecting object motion can include a microphone coupled to the chamber and a low pass filter connected to the output of the microphone, which passes only frequencies below the frequency of sound produced by a transducer that maintains the acoustic standing wave field. Knowledge about object motion can be useful by itself, can be useful to determine surface tension, viscosity, and other information about the object, and can be useful to determine the pressure and other characteristics of the acoustic field.

  20. Acoustic streaming and Sun's meridional circulation

    NASA Astrophysics Data System (ADS)

    Valverde, Jose Manuel

    2016-09-01

    A vast number of physical processes involving oscillations of a bounded viscous fluid are relevantly influenced by acoustic streaming. When this happens a steady circulation of fluid develops in a thin boundary adjacent to the interface. Some examples are refracted sound waves, a fluid inside a spherical cavity undergoing torsional oscillations or a pulsating liquid droplet. Steady streaming around circular interfaces consists of a hemispherically symmetric recirculation of fluid from the equatorial plane to the polar axes closely resembling the meridional circulation pattern observed in the Sun's convection zone that determines the solar cycle. In this paper, it is argued that the acoustic pulsations exhibited by the Sun would lead to acoustic streaming in the boundary of the convection zone. A simple estimation using a typical dominant frequency of 3 mHz and the observed surface oscillation amplitude yields a steady streaming velocity us ∼ 10 m s‑1, which is on the order of the meridional circulation velocity observed in the Sun's convection zone.

  1. Acoustic streaming and Sun's meridional circulation

    NASA Astrophysics Data System (ADS)

    Valverde, Jose Manuel

    2016-09-01

    A vast number of physical processes involving oscillations of a bounded viscous fluid are relevantly influenced by acoustic streaming. When this happens a steady circulation of fluid develops in a thin boundary adjacent to the interface. Some examples are refracted sound waves, a fluid inside a spherical cavity undergoing torsional oscillations or a pulsating liquid droplet. Steady streaming around circular interfaces consists of a hemispherically symmetric recirculation of fluid from the equatorial plane to the polar axes closely resembling the meridional circulation pattern observed in the Sun's convection zone that determines the solar cycle. In this paper, it is argued that the acoustic pulsations exhibited by the Sun would lead to acoustic streaming in the boundary of the convection zone. A simple estimation using a typical dominant frequency of 3 mHz and the observed surface oscillation amplitude yields a steady streaming velocity us ˜ 10 m s‑1, which is on the order of the meridional circulation velocity observed in the Sun's convection zone.

  2. Acoustic streaming and Sun's meridional circulation

    NASA Astrophysics Data System (ADS)

    Valverde, Jose Manuel

    2016-09-01

    A vast number of physical processes involving oscillations of a bounded viscous fluid are relevantly influenced by acoustic streaming. When this happens a steady circulation of fluid develops in a thin boundary adjacent to the interface. Some examples are refracted sound waves, a fluid inside a spherical cavity undergoing torsional oscillations or a pulsating liquid droplet. Steady streaming around circular interfaces consists of a hemispherically symmetric recirculation of fluid from the equatorial plane to the polar axes closely resembling the meridional circulation pattern observed in the Sun's convection zone that determines the solar cycle. In this paper, it is argued that the acoustic pulsations exhibited by the Sun would lead to acoustic streaming in the boundary of the convection zone. A simple estimation using a typical dominant frequency of 3 mHz and the observed surface oscillation amplitude yields a steady streaming velocity us ˜ 10 m s-1, which is on the order of the meridional circulation velocity observed in the Sun's convection zone.

  3. Biogeochemical characteristics of Kuan-Tzu-Ling, Chung-Lun and Bao-Lai hot springs in southern Taiwan.

    PubMed

    Maity, Jyoti Prakash; Liu, Chia-Chuan; Nath, Bibhash; Bundschuh, Jochen; Kar, Sandeep; Jean, Jiin-Shuh; Bhattacharya, Prosun; Liu, Jiann-Hong; Atla, Shashi B; Chen, Chien-Yen

    2011-01-01

    Hot springs are the important natural sources of geothermally heated groundwater from the Earth's crust. Kuan-Tzu-Ling (KTL), Chung-Lun (CL) and Bao-Lai (BL) are well-known hot springs in southern Taiwan. Fluid and mud (sediments) samples were collected from the eruption points of three hot springs for detailed biogeochemical characterization. The fluid sample displays relatively high concentrations of Na(+) and Cl(-) compared with K(+), Mg(2+), Ca(2+), NO(2) (-), and SO(4) (2-), suggesting a possible marine origin. The concentrations of Fe, Cr, Mn, Ni, V and Zn were significantly higher in the mud sediments compared with fluids, whereas high concentrations of As, Ba, Cu, Se, Sr and Rb were observed in the fluids. This suggests that electronegative elements were released during sediment-water interactions. High As concentration in the fluids was observed to be associated with low redox (Eh) conditions. The FTIR spectra of the humic acid fractions of the sediments showed the presence of possible functional groups of secondary amines, ureas, urethanesm (amide), and silicon. The sulfate-reducing deltaproteobacterium 99% similar to Desulfovibrio psychrotolerans (GU329907) were rich in the CL hot spring while mesophilic, proteolytic, thiosulfate- and sulfur-reducing bacterium that 99% similar to Clostridium sulfidigenes (GU329908) were rich in the BL hot spring.

  4. S-Band Shallow Bulk Acoustic Wave (SBAW) microwave source

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Techniques necessary to fabricate a high performance S-band microwave single source using state-of-the-art shallow bulk acoustic wave (SBAW) were explored. The bulk wave structures of the AlN/Al 2O3 were investigated for both the R plane and basal plane of sapphire. A 1.072 GHz SBAW delay line and oscillators were developed. A method of selecting and setting oscillator output frequency by selecting substrate orientation angle was also established.

  5. Fermi Liquid in a Torsional Oscillator

    NASA Astrophysics Data System (ADS)

    Virtanen, T. H.; Thuneberg, E. V.

    2012-12-01

    We study the transverse acoustic impedance of normal Fermi liquid inside a torsionally oscillating cylindrical container. We use Landau's Fermi liquid theory, and our approach is applicable to both normal 3He and mixtures of 3He in superfluid 4He. The fluid causes dissipation and a change of the resonant frequency of the oscillator. Usually, a liquid medium increases the moment of inertia of the oscillator, but we show that for a suitable choice of container radius and driving frequency, the Fermi liquid can actually decrease the inertia and increase the resonant frequency. Results of numerical calculations for all values of mean free path l are shown and comparison is made to both hydrodynamic theory and simple kinetic theory in the ballistic limit.

  6. Terahertz Antiferromagnetic Spin Hall Nano-Oscillator

    NASA Astrophysics Data System (ADS)

    Cheng, Ran; Xiao, Di; Brataas, Arne

    2016-05-01

    We consider the current-induced dynamics of insulating antiferromagnets in a spin Hall geometry. Sufficiently large in-plane currents perpendicular to the Néel order trigger spontaneous oscillations at frequencies between the acoustic and the optical eigenmodes. The direction of the driving current determines the chirality of the excitation. When the current exceeds a threshold, the combined effect of spin pumping and current-induced torques introduces a dynamic feedback that sustains steady-state oscillations with amplitudes controllable via the applied current. The ac voltage output is calculated numerically as a function of the dc current input for different feedback strengths. Our findings open a route towards terahertz antiferromagnetic spin-torque oscillators.

  7. Properties of acoustic sources in the Sun

    NASA Technical Reports Server (NTRS)

    Kumar, Pawan

    1994-01-01

    The power spectrum of solar acoustic oscillations shows peaks extending out to frequencies much greater than the acoustic cutoff frequency of approximately 5.3 mHz, where waves are no longer trapped. Kumar & Lu (1991) proposed that these peaks arise from the interference of traveling waves which are generated by turbulent convection. According to this model, the frequencies of the peaks in the power spectrum depend on the static structure of the Sun as well as the radial location of the sources. Kumar & Lu used this idea to determine the depth of the acoustic sources. However, they ignored dissipative effects and found that the theoretically computed power spectrum was falling off much more rapidly than the observed spectrum. In this paper, we include the interaction of radiation with acoustic waves in the computation of the power spectrum. We find that the theoretically calculated power spectra, when radiative damping is included are in excellent agreement with the observed power spectra over the entire observed frequency range of 5.3 to 7.5 mHz above the acoustic cutoff frequency. Moreover, by matching the peak frequencies in the observed and theoretical spectra we find the mean depth of acoustic sources to be 140 +/- 60 km below the photosphere. We show that the spectrum of solar turbulence near the top of the solar convection zone is consistent with the Kolmogorov spectrum, and that the observed high frequency power spectrum provides strong evidence that the acoustic sources in the Sun are quadrupolar. The data, in fact, rules out dipole sources as significant contributors to acoustic wave generation in the Sun. The radial extent of the sources is poorly determined and is estimated to be less than about 550 km.

  8. Acoustic hemostasis

    NASA Astrophysics Data System (ADS)

    Crum, Lawrence; Beach, Kirk; Carter, Stephen; Chandler, Wayne; Curra, Francesco; Kaczkowski, Peter; Keilman, George; Khokhlova, Vera; Martin, Roy; Mourad, Pierre; Vaezy, Shahram

    2000-07-01

    In cases of severe injury, physicians speak of a "golden hour"—a brief grace period in which quickly applied, proper therapy can save the life of the patient. Much of this mortality results from exsanguination, i.e., bleeding to death—often from internal hemorrhage. The inability of a paramedic to treat breaches in the vascular system deep within the body or to stem the loss of blood from internal organs is a major reason for the high level of mortality associated with blunt trauma. We have undertaken an extensive research program to treat the problem of internal bleeding. Our approach is as follows: (a) We use scanning ultrasound to identify internal bleeding and hemorrhage, (b) we use ultrasound imaging to locate specific breaches in the vascular system, both from damaged vessels and gross damage to the capillary bed, and (c) we use High Intensity Focused Ultrasound (HIFU) to treat the damaged region and to induce hemostasis. We present a general review of this research with some emphasis on the role of nonlinear acoustics.

  9. Acoustic disturbances in a gas with an axial temperature gradient

    NASA Astrophysics Data System (ADS)

    Lariononv, V. M.

    2016-01-01

    Linear analysis acoustic disturbances in one-dimensional gas flow with a longitudinal gradient of the sound speed provided. Known wave equation for the acoustic velocity is used. In the case of linear distribution of the sound speed in the hot part of the flow equation has an exact analytic solution. This allows to define the expression describing the propagation acoustic disturbances in a gas with varying mean temperature and density. The results can be used to calculate the resonance frequencies of the gas oscillations in the laboratory and industrial combustors.

  10. Acoustic stabilization of electric arc instabilities in nontransferred plasma torches

    SciTech Connect

    Rat, V.; Coudert, J. F.

    2010-03-08

    Electric arc instabilities in dc plasma torches lead to nonhomogeneous treatments of nanosized solid particles or liquids injected within thermal plasma jets. This paper shows that an additional acoustic resonator mounted on the cathode cavity allows reaching a significant damping of these instabilities, particularly the Helmholtz mode of arc oscillations. The acoustic resonator is coupled with the Helmholtz resonator of the plasma torch limiting the amplitude of arc voltage variations. It is also highlighted that this damping is dependent on friction effects in the acoustic resonator.

  11. Resonant acoustic transducer and driver system for a well drilling string communication system

    DOEpatents

    Chanson, Gary J.; Nicolson, Alexander M.

    1981-01-01

    The acoustic data communication system includes an acoustic transmitter and receiver wherein low frequency acoustic waves, propagating in relatively loss free manner in well drilling string piping, are efficiently coupled to the drill string and propagate at levels competitive with the levels of noise generated by drilling machinery also present in the drill string. The transmitting transducer incorporates a mass-spring piezoelectric transmitter and amplifier combination that permits self-oscillating resonant operation in the desired low frequency range.

  12. Acoustic source for generating an acoustic beam

    DOEpatents

    Vu, Cung Khac; Sinha, Dipen N.; Pantea, Cristian

    2016-05-31

    An acoustic source for generating an acoustic beam includes a housing; a plurality of spaced apart piezo-electric layers disposed within the housing; and a non-linear medium filling between the plurality of layers. Each of the plurality of piezoelectric layers is configured to generate an acoustic wave. The non-linear medium and the plurality of piezo-electric material layers have a matching impedance so as to enhance a transmission of the acoustic wave generated by each of plurality of layers through the remaining plurality of layers.

  13. Bounds on the Fourier coefficients for the periodic solutions of non-linear oscillator equations

    NASA Technical Reports Server (NTRS)

    Mickens, R. E.

    1988-01-01

    The differential equations describing nonlinear oscillations (as seen in mechanical vibrations, electronic oscillators, chemical and biochemical reactions, acoustic systems, stellar pulsations, etc.) are investigated analytically. The boundedness of the Fourier coefficients for periodic solutions is demonstrated for two special cases, and the extrapolation of the results to higher-dimensionsal systems is briefly considered.

  14. Canonical Acoustics and Its Application to Surface Acoustic Wave on Acoustic Metamaterials

    NASA Astrophysics Data System (ADS)

    Shen, Jian Qi

    2016-08-01

    In a conventional formalism of acoustics, acoustic pressure p and velocity field u are used for characterizing acoustic waves propagating inside elastic/acoustic materials. We shall treat some fundamental problems relevant to acoustic wave propagation alternatively by using canonical acoustics (a more concise and compact formalism of acoustic dynamics), in which an acoustic scalar potential and an acoustic vector potential (Φ ,V), instead of the conventional acoustic field quantities such as acoustic pressure and velocity field (p,u) for characterizing acoustic waves, have been defined as the fundamental variables. The canonical formalism of the acoustic energy-momentum tensor is derived in terms of the acoustic potentials. Both the acoustic Hamiltonian density and the acoustic Lagrangian density have been defined, and based on this formulation, the acoustic wave quantization in a fluid is also developed. Such a formalism of acoustic potentials is employed to the problem of negative-mass-density assisted surface acoustic wave that is a highly localized surface bound state (an eigenstate of the acoustic wave equations). Since such a surface acoustic wave can be strongly confined to an interface between an acoustic metamaterial (e.g., fluid-solid composite structures with a negative dynamical mass density) and an ordinary material (with a positive mass density), it will give rise to an effect of acoustic field enhancement on the acoustic interface, and would have potential applications in acoustic device design for acoustic wave control.

  15. What Is an Acoustic Neuroma

    MedlinePlus

    ... Acoustic Neuroma An acoustic neuroma, also called a vestibular schwannoma, is a rare benign tumor of the ... Acoustic Neuroma? An acoustic neuroma, known as a vestibular schwannoma, is a benign (non-cancerous) growth that ...

  16. Characterization of oscillations during premix gas turbine combustion

    SciTech Connect

    Richards, G.A.; Janus, M.C.

    1998-04-01

    The use of premix combustion in stationary gas turbines can produce very low levels of NO{sub x} emissions. This benefit is widely recognized, but turbine developers routinely encounter problems with combustion oscillations during the testing of new premix combustors. Because of the associated pressure fluctuations, combustion oscillations must be eliminated in a final combustor design. Eliminating these oscillations is often time-consuming and costly because there is no single approach to solve an oscillation problem. Previous investigations of combustion stability have focused on rocket applications, industrial furnaces, and some aeroengine gas turbines. Comparatively little published data is available for premixed combustion at conditions typical of an industrial gas turbine. In this paper, the authors report experimental observations of oscillations produced by a fuel nozzle typical of industrial gas turbines. Tests are conducted in a specially designed combustor capable of providing the acoustic feedback needed to study oscillations. Tests results are presented for pressures up to 10 atmospheres, theoretical considerations, it is expected that oscillations can be characterized by a nozzle reference velocity, with operating pressure playing a smaller role. This expectation is compared to observed data that shows both the benefits and limitations of characterizing the combustor oscillating behavior in terms of a reference velocity rather than other engine operating parameters. This approach to characterizing oscillations is then used to evaluate how geometric changes to the fuel nozzle will affect the boundary between stable and oscillating combustion.

  17. Self-exited gas oscillations in Helmholtz resonator type combustor

    NASA Astrophysics Data System (ADS)

    Larionov, V. M.; Saifullin, E. R.; Semenova, E. V.

    2016-01-01

    When the length of the resonance tube is much less and order of the acoustic wavelength is studied. Experimental set-up with a multiport burner is considered. The "energy balance" method is used to calculate the frequency and amplitude of the gas oscillations. The results of measurements and calculations show that increasing the length of the resonance tube causes the excitation oscillation with a first lower frequency. Further, there are no oscillations. When the length of the resonance tube becomes the order of the wavelength, the second resonant frequency is excited. The calculation results are in good agreement with the experimental data.

  18. Combustor oscillation attenuation via the control of fuel-supply line dynamics

    DOEpatents

    Richards, George A.; Gemmen, Randall S.

    1998-01-01

    Combustion oscillation control in combustion systems using hydrocarbon fuels is provided by acoustically tuning a fuel-delivery line to a desired phase of the combustion oscillations for providing a pulse of a fuel-rich region at the oscillating flame front at each time when the oscillation produced pressure in the combustion chamber is in a low pressure phase. The additional heat release produced by burning such fuel-rich regions during low combustion chamber pressure effectively attenuates the combustion oscillations to a selected value.

  19. Combustor oscillation attenuation via the control of fuel-supply line dynamics

    DOEpatents

    Richards, G.A.; Gemmen, R.S.

    1998-09-22

    Combustion oscillation control in combustion systems using hydrocarbon fuels is provided by acoustically tuning a fuel-delivery line to a desired phase of the combustion oscillations for providing a pulse of a fuel-rich region at the oscillating flame front at each time when the oscillation produced pressure in the combustion chamber is in a low pressure phase. The additional heat release produced by burning such fuel-rich regions during low combustion chamber pressure effectively attenuates the combustion oscillations to a selected value. 9 figs.

  20. Symptoms of Acoustic Neuroma

    MedlinePlus

    ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ...

  1. Acoustic Neuroma Educational Video

    MedlinePlus

    ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ...

  2. Acoustic emission frequency discrimination

    NASA Technical Reports Server (NTRS)

    Sugg, Frank E. (Inventor); Graham, Lloyd J. (Inventor)

    1988-01-01

    In acoustic emission nondestructive testing, broadband frequency noise is distinguished from narrow banded acoustic emission signals, since the latter are valid events indicative of structural flaws in the material being examined. This is accomplished by separating out those signals which contain frequency components both within and beyond (either above or below) the range of valid acoustic emission events. Application to acoustic emission monitoring during nondestructive bond verification and proof loading of undensified tiles on the Space Shuttle Orbiter is considered.

  3. Acoustic flame detector for gas chromatography.

    PubMed

    Thurbide, K B; Wentzell, P D; Aue, W A

    1996-09-01

    A novel gas chromatography detector is described that uses acoustic signals from a partly premixed hydrogen-air flame burning on top of a capillary. The device, referred to as the acoustic flame detector (AFD), is based on the measurement of the frequency of acoustic transients generated at the burner under a range of operating conditions. The presence of trace amounts of analyte in the flame was found to increase the frequency of these sonic bursts from the baseline level of ∼100 Hz. The response of the AFD for n-dodecane, measured as the shift in frequency, was determined to be linear over ∼3 orders of magnitude, with a minimum detectable level of about 1-5 ng C/s using the current system. The sensitivity correlates roughly with carbon content, except for certain organometallics (Sn, Mn), which gave substantially enhanced signals. Some tailing was observed but became serious only for particular types of organometallics. The noise of the system was predominantly of the 1/f type. The effects of flow conditions, burner geometry, and flame gas constituents were investigated. The oscillations could be followed by acoustic, visual, electrical, and optical means. The AFD mechanism is shown to involve oscillatory chemical kinetics, in which the flame front (the inner cone) temporarily enters a few millimeters into the capillary during each cycle, thereby creating the acoustic signal.

  4. Accuracy of cosmological parameters using the baryon acoustic scale

    SciTech Connect

    Thepsuriya, Kiattisak; Lewis, Antony E-mail: antony@cosmologist.info

    2015-01-01

    Percent-level measurements of the comoving baryon acoustic scale standard ruler can be used to break degeneracies in parameter constraints from the CMB alone. The sound horizon at the epoch of baryon drag is often used as a proxy for the scale of the peak in the matter density correlation function, and can conveniently be calculated quickly for different cosmological models. However, the measurements are not directly constraining this scale, but rather a measurement of the full correlation function, which depends on the detailed evolution through decoupling. We assess the level of reliability of parameter constraints based on a simple approximation of the acoustic scale compared to a more direct determination from the full numerical two-point correlation function. Using a five-parameter fitting technique similar to recent BAO data analyses, we find that for standard ΛCDM models and extensions with massive neutrinos and additional relativistic degrees of freedom, the approximation is at better than 0.15% for most parameter combinations varying over reasonable ranges.

  5. Tutorial on architectural acoustics

    NASA Astrophysics Data System (ADS)

    Shaw, Neil; Talaske, Rick; Bistafa, Sylvio

    2002-11-01

    This tutorial is intended to provide an overview of current knowledge and practice in architectural acoustics. Topics covered will include basic concepts and history, acoustics of small rooms (small rooms for speech such as classrooms and meeting rooms, music studios, small critical listening spaces such as home theatres) and the acoustics of large rooms (larger assembly halls, auditoria, and performance halls).

  6. Application of surface acoustic wave devices to radio telemetry

    NASA Technical Reports Server (NTRS)

    Strasilla, U.

    1983-01-01

    Three experimental Surface Acoustic Wave Resonators (SAWR) are developed and evaluated. A desired center frequency is obtained by correct spacing of the Inter-Digital Transducers (IDT). Transmitting and receiving IDT's must be close for adequate coupling and a sufficient number of reflectors are required to create a high quality standing wave. A review of oscillator theory is given and current technology evaluated.

  7. Self-sustained oscillation limit of tube bundle resonant noise. (Phase 1: Evaluation equation of oscillation limit)

    SciTech Connect

    Nishimura, M.; Fujita, K.; Hasegawa, N.

    1995-12-01

    Self-sustained oscillation limit of tube bundle resonant noise is studied in this paper. Excited acoustic energy and dissipating one in tube bundle are derived theoretically. In the exciting stage, the acoustic field is considered to be fed back to the flow field as the inlet flow fluctuation. And the acoustic damping is considered to induce the dissipating energy. Based on the energy balance of both and dimensional analysis, a new simple evaluation equation of self-sustained oscillation limit is proposed concerning on tube bundle resonant noise. A typical experimental results are evaluated based on this equation. The results are roughly good, but this suggests that model analysis of both exciting energy and dissipating one is necessary for more precise evaluation.

  8. Voltage-controlled oscillator

    NASA Technical Reports Server (NTRS)

    Durand, J. L.

    1971-01-01

    Oscillator generates symmetrical triangular waveform when inverting and noninverting inputs are equal. Oscillator portion of circuit has integrated circuit, high-performance operational amplifier wired as differential integrator, and two silicon controlled rectifiers.

  9. Saturation in coupled oscillators

    NASA Astrophysics Data System (ADS)

    Roman, Ahmed; Hanna, James

    2015-03-01

    We consider a weakly nonlinear system consisting of a resonantly forced oscillator coupled to an unforced oscillator. It has long been known that, for quadratic nonlinearities and a 2:1 resonance between the oscillators, a perturbative solution of the dynamics exhibits a phenomenon known as saturation. At low forcing, the forced oscillator responds, while the unforced oscillator is quiescent. Above a critical value of the forcing, the forced oscillator's steady-state amplitude reaches a plateau, while that of the unforced oscillator increases without bound. We show that, contrary to established folklore, saturation is not unique to quadratically nonlinear systems. We present conditions on the form of the nonlinear couplings and resonance that lead to saturation. Our results elucidate a mechanism for localization or diversion of energy in systems of coupled oscillators, and suggest new approaches for the control or suppression of vibrations in engineered systems.

  10. Violent Folding of a Flame Front in a Flame-Acoustic Resonance

    NASA Astrophysics Data System (ADS)

    Petchenko, Arkady; Bychkov, Vitaly; Akkerman, V.'Yacheslav; Eriksson, Lars-Erik

    2006-10-01

    The first direct numerical simulations of violent flame folding because of the flame-acoustic resonance are performed. Flame propagates in a tube from an open end to a closed one. Acoustic amplitude becomes extremely large when the acoustic mode between the flame and the closed tube end comes in resonance with intrinsic flame oscillations. The acoustic oscillations produce an effective acceleration field at the flame front leading to a strong Rayleigh-Taylor instability during every second half period of the oscillations. The Rayleigh-Taylor instability makes the flame front strongly corrugated with elongated jets of heavy fuel mixture penetrating the burnt gas and even with pockets of unburned matter separated from the flame front.

  11. Acoustic waves in random ensembles of magnetic fluxes

    SciTech Connect

    Ryutova, M.P.

    1995-10-10

    To analyze the observational data and provide the appropriate diagnostic procedure for photospheric manifestation of solar oscillations it is necessary to take into account strong inhomogeneity of solar atmosphere with respect to distribution of magnetic fields. We study the collective phenomena in the propagation of acoustic waves and unsteady wave-packets through quite regions, sunspots and plages, including time-dependent response of these regions to solar oscillations, the energy transfer mechanisms, frequency shift effects and reradiation of the acoustic waves in higher layers of atmosphere. We show that the dynamics of differently magnetized regions, their dispersion properties, and their response to the propagation of acoustic waves are completely different. We describe the effects caused by the specific distribution and randomness of magnetic flux tubes, which can be observed and which can provide the tools for diagnostic goals.

  12. LES and acoustic analysis of thermo-acoustic instabilities in a partially premixed model combustor

    NASA Astrophysics Data System (ADS)

    Hernández, Ignacio; Staffelbach, Gabriel; Poinsot, Thierry; Román Casado, Juan C.; Kok, Jim B. W.

    2013-01-01

    Numerical simulations were performed using Large Eddy Simulation (LES) and acoustic analysis tools to study thermo-acoustic instabilities in a methane/air academic burner installed at the University of Twente (The Netherlands). It operates under fuel-lean partially premixed conditions at atmospheric pressure, and was built to study thermo-acoustic instabilities in conditions representative of gas turbine Lean Premixed systems: gaseous fuel is injected upstream of the combustor and has a limited time to mix with air. Even though the objective is to burn in a premixed mode, the actual regime corresponds to a partially premixed flame where strong equivalence ratio variations are created especially during combustion instabilities. Capturing these modes with LES is a challenge: here, simulations for both stable and unstable regimes are performed. In the unstable case, the limit cycle oscillations (LCO) are characterized and compared to experimental results. Reasonable agreement is found between simulations and experiments.

  13. Spinning Photons and Twisting Oscillators

    NASA Astrophysics Data System (ADS)

    Shi, Hao

    2014-03-01

    Optomechanics is the study of the interaction between electromagnetic radiation and mechanical motion. A typical optomechanical system involves an optical resonator coupled to a mechanical degree of freedom. Some of the most striking experimental achievements include preparation of macroscopic mechanical oscillators in their quantum ground states, the detection of optomechanical quantum back-action, and generation of optomechanically induced transparency and slow light. Most optomechanical systems rely on linear coupling between the radiation and the displacement of the mechanical oscillator. I will begin this talk instead by discussing the basic quantum mechanics of a generic quadratically coupled optomechanical system. I will also mention our efforts in extending optomechanics to torsional and rotational systems. Specifically, I will describe our theoretical proposal to couple a windmill-shaped dielectric to cavity Laguerre Gaussian modes. Subsequently, I will suggest a method for coupling LG modes to surface acoustic waves on a cavity mirror as a new platform for storage of photons carrying orbital angular momentum. Finally, I will discuss our most recent study of the prospects of cooling full rotational motion to the quantum regime. Supported by Research Corporation for Science Advancement.

  14. Spinning Photons and Twisting Oscillators

    NASA Astrophysics Data System (ADS)

    Shi, Hao

    2014-05-01

    Optomechanics is the study of the interaction between optical radiation and mechanical motion. Typically, an optomechanical system is composed of an optical resonator coupled to a mechanical degree of freedom. Some of the most striking experimental achievements include the quantum ground state preparation for a macroscopic oscillator, the detection of optomechanical quantum back-action, and generation of optomechanically induced transparency and slow light. Most optomechanical systems depend on linear coupling between the optical field and the displacement of the mechanical oscillator. In this talk, I will start instead by discussing the basic quantum mechanics of a generic quadratically coupled optomechanical system, followed by our efforts towards extending optomechanics to torsional and rotational systems. Specifically, I will describe our theoretical proposal to couple a windmill-shaped dielectric to cavity Laguerre Gaussian modes. In addition, I will present an optoacoustic system, composed of a LG mode coupled t surface acoustic waves of a spherical mirror, as a new platform for storage of photons carrying orbital angular momentum. Finally, I will discuss our most recent investigation of the prospects of cooling full rotational motion to the quantum regime.

  15. ACOUSTICAL STANDARDS NEWS.

    PubMed

    Stremmel, Neil; Struck, Christopher J

    2016-07-01

    American National Standards (ANSI Standards) developed by Accredited Standards Committees S1, S2, S3, S3/SC 1, and S12 in the areas of acoustics, mechanical vibration and shock, bioacoustics, animal bioacoustics, and noise, respectively, are published by the Acoustical Society of America (ASA). In addition to these standards, ASA publishes a catalog of Acoustical American National Standards. To receive a copy of the latest Standards catalog, please contact Neil Stremmel.Comments are welcomed on all material in Acoustical Standards News.This Acoustical Standards News section in JASA, as well as the National Catalog of Acoustical Standards and other information on the Standards Program of the Acoustical Society of America, are available via the ASA home page: http://acousticalsociety.org. PMID:27475185

  16. Covariant harmonic oscillators and coupled harmonic oscillators

    NASA Technical Reports Server (NTRS)

    Han, Daesoo; Kim, Young S.; Noz, Marilyn E.

    1995-01-01

    It is shown that the system of two coupled harmonic oscillators shares the basic symmetry properties with the covariant harmonic oscillator formalism which provides a concise description of the basic features of relativistic hadronic features observed in high-energy laboratories. It is shown also that the coupled oscillator system has the SL(4,r) symmetry in classical mechanics, while the present formulation of quantum mechanics can accommodate only the Sp(4,r) portion of the SL(4,r) symmetry. The possible role of the SL(4,r) symmetry in quantum mechanics is discussed.

  17. SHOCK-EXCITED OSCILLATOR

    DOEpatents

    Creveling, R.

    1957-12-17

    S> A shock-excited quartz crystal oscillator is described. The circuit was specifically designed for application in micro-time measuring work to provide an oscillator which immediately goes into oscillation upon receipt of a trigger pulse and abruptly ceases oscillation when a second pulse is received. To achieve the instant action, the crystal has a prestressing voltage applied across it. A monostable multivibrator receives the on and off trigger pulses and discharges a pulse through the crystal to initiate or terminate oscillation instantly.

  18. Discrete monotron oscillator

    SciTech Connect

    Carlsten, B.E.; Haynes, W.B.

    1996-08-01

    The authors theoretically and numerically investigate the operation and behavior of the discrete monotron oscillator, a novel high-power microwave source. The discrete monotron differs from conventional monotrons and transit time oscillators by shielding the electron beam from the monotron cavity`s RF fields except at two distinct locations. This makes the discrete monotron act more like a klystron than a distributed traveling wave device. As a result, the oscillator has higher efficiency and can operate with higher beam powers than other single cavity oscillators and has more stable operation without requiring a seed input signal than mildly relativistic, intense-beam klystron oscillators.

  19. Electric Properties of [(BaO)1.00(XO)x](Ti0.95Zr0.05)O2 (X = Ca, Sr, Ba) Ceramics Fired under Reduced Atmosphere

    NASA Astrophysics Data System (ADS)

    Sakai, Yuichi; Futakuchi, Tomoaki; Adachi, Masatoshi

    2009-09-01

    Ba(Ti0.95Zr0.05)O3 doped with CaO, SrO, or BaO was investigated in order to develop materials suitable for lead-free actuators with resistance to reduction. The grain sizes of [(BaO)1.00(XO)x](Ti0.95Zr0.05)O2 (X = Ca, Sr, Ba; x = 0-0.05) ceramics decreased with increasing amount of dopant concentration x. The grain sizes of the ceramics with a dopant concentration x in the range of 0.005 to 0.05 are approximately 1-2 µm. The crystalline phases of the ceramics with a dopant concentration x = 0.01 or less were perovskite single phases. CaO, SrO, or BaO doping concentrations of x = 0.005 or more were effective for preventing the reduction of Ba(Ti0.95Zr0.05)O3 during firing under 3% H2-N2 atmosphere. The remanent polarizations and dynamic piezoelectric constants of the ceramics decreased with increasing dopant concentration of CaO, SrO, or BaO. The dynamic piezoelectric constant of the ceramics with BaO dopant concentration x of 0.005 was approximately 640 pm/V. The Curie temperature was approximately 109 °C in this composition.

  20. The effect of pressure oscillations on fuel droplet ignition

    NASA Astrophysics Data System (ADS)

    Eigenbrod, Christian; Klinkov, Konstantin; Fachini, Fernando F.

    Combustion-driven instabilities have an important influence on the performance and noise char-acteristics of gas turbines. Thermo-acoustic oscillations can increase not only emissions of noise or pollutants such as unburnt hydrocarbons or nitric oxides, but can also lead to very high levels of pressure pulsations, resulting in structural damage of the machine. Identified mechanisms capable of driving combustion instabilities include complex flow and flame interactions: fuel feed line -acoustic coupling, equivalence-ratio oscillations, oscillatory vaporization and mix-ing, oscillatory flame-area variation, vortex shedding. In order to clarify different aspects of acoustics -combustion interference it is necessary to study the simplified models. At ZARM, Bremen the effect of acoustic oscillation on single droplet ignition was studied experimentally and numerically. The experimental facility allows to investigate the ignition of a single droplet under spherical conditions (absence of natural convection) and variable pressure and temperature of the ambient gas. The suspended fuel droplet with initial diameter of 0.7 mm is placed in a furnace, two opposite walls of which are motor-driven pistons. The scale of the oscillation of gas parameters in the furnace corresponds to that in real gas-turbines under condition of a thermo-acoustic resonance. In the present work parameters of the ignition of a single n-heptane droplet under mean pressure (p0) up to 5 bar and temperature 700 K was examined. The computational model is 1-dimensional and includes processes of vaporization, multi-component diffusion and extended chemical reactions including the low-temperature branch. The model was firstly validated through the single droplet experiments achieving good agreement. Then the physical parameters were varied in order to match conditions of real gas-turbines. In this case droplet diameter was about 0.04-0.1 mm, initial pressure of the gas up to 20 bar and temperature up to 700 K

  1. Surface-controlled drop oscillations in space

    NASA Astrophysics Data System (ADS)

    Holt, R. Glynn

    2001-05-01

    A series of experiments probing the effects of surfactants was performed by Bob Apfel and his research group in the 1990s. Several laboratory experiments were carried out in uni-axial acoustic levitators. Two experiments were carried out in a triple-axis levitator called the Drop Physics Module, which was carried on Space Shuttle Columbia as part of the First and Second United States Microgravity Laboratory missions. Liquid drops containing aqueous solutions of soluble surfactants were acoustically positioned and deformed (and in some cases rotated) in order to excite shape mode oscillations. The results of these experiments allowed the inference of surface rheological properties (Gibb's elasticity, surface viscosity coefficients) as functions of surfactant type and concentration. The highlights of this effort will be presented in a semi-technical fashion. [Work supported by NASA.

  2. 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.

  3. Nature's Autonomous Oscillators

    NASA Technical Reports Server (NTRS)

    Mayr, H. G.; Yee, J.-H.; Mayr, M.; Schnetzler, R.

    2012-01-01

    Nonlinearity is required to produce autonomous oscillations without external time dependent source, and an example is the pendulum clock. The escapement mechanism of the clock imparts an impulse for each swing direction, which keeps the pendulum oscillating at the resonance frequency. Among nature's observed autonomous oscillators, examples are the quasi-biennial oscillation and bimonthly oscillation of the Earth atmosphere, and the 22-year solar oscillation. The oscillations have been simulated in numerical models without external time dependent source, and in Section 2 we summarize the results. Specifically, we shall discuss the nonlinearities that are involved in generating the oscillations, and the processes that produce the periodicities. In biology, insects have flight muscles, which function autonomously with wing frequencies that far exceed the animals' neural capacity; Stretch-activation of muscle contraction is the mechanism that produces the high frequency oscillation of insect flight, discussed in Section 3. The same mechanism is also invoked to explain the functioning of the cardiac muscle. In Section 4, we present a tutorial review of the cardio-vascular system, heart anatomy, and muscle cell physiology, leading up to Starling's Law of the Heart, which supports our notion that the human heart is also a nonlinear oscillator. In Section 5, we offer a broad perspective of the tenuous links between the fluid dynamical oscillators and the human heart physiology.

  4. Acoustic Translation of an Acoustically Levitated Sample

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    Acoustic-levitation apparatus uses only one acoustic mode to move sample from one region of chamber to another. Sample heated and cooled quickly by translation between hot and cold regions of levitation chamber. Levitated sample is raised into furnace region by raising plunger. Frequency of sound produced by transducers adjusted by feedback system to maintain (102) resonant mode, which levitates sample midway between transducers and plunger regardless of plunger position.

  5. Dynamic Weakening by Acoustic Fluidization during Stick-Slip Motion.

    PubMed

    Giacco, F; Saggese, L; de Arcangelis, L; Lippiello, E; Pica Ciamarra, M

    2015-09-18

    The unexpected weakness of some faults has been attributed to the emergence of acoustic waves that promote failure by reducing the confining pressure through a mechanism known as acoustic fluidization, also proposed to explain earthquake remote triggering. Here we validate this mechanism via the numerical investigation of a granular fault model system. We find that the stick-slip dynamics is affected only by perturbations applied at a characteristic frequency corresponding to oscillations normal to the fault, leading to gradual dynamical weakening as failure is approaching. Acoustic waves at the same frequency spontaneously emerge at the onset of failure in the absence of perturbations, supporting the relevance of acoustic fluidization in earthquake triggering. PMID:26431017

  6. Liquid Helium Acoustic Microscope.

    NASA Astrophysics Data System (ADS)

    Steer, Andrew Paul

    Available from UMI in association with The British Library. In an acoustic microscope, images are generated by monitoring the intensity of the ultrasonic reflection, or echo, from the surface of a sample. In order to achieve this a pulse of acoustic energy is produced by the excitation of a thin film transducer. The pulse thus generated propagates through a crystal and is incident upon the acoustic lens surface, which is the boundary between the crystal and an acoustic coupling liquid. The acoustic lens is a converging element, and brings the ultrasonic beam to a focus within the liquid. A sample, placed at the focus, can act as a reflector, and the returned pulse then contains information regarding the acoustic reflectivity of this specimen. Acoustic pulses are repeatedly launched and detected while the acoustic lens is scanned over the surface of the sample. In this manner an acoustic image is constructed. Acoustic losses in room temperature liquid coupling media represent a considerable source of difficulty in the recovery of acoustic echo signals. At the frequencies of operation required in a microscope which is capable of high resolution, the ultrasonic attenuation is not only large but increases with the square of frequency. In superfluid liquid helium at temperatures below 0.1 K, however, the ultrasonic attenuation becomes negligible. Furthermore, the low sound velocity in liquid helium results in an increase in resolution, since the acoustic wavelength is proportional to velocity. A liquid helium acoustic microscope has been designed and constructed. Details of the various possible detection methods are given, and comparisons are made between them. Measurements of the performance of the system that was adopted are reported. The development of a cooled preamplifier is also described. The variation of reflected signal with object distance has been measured and compared with theoretical predictions. This variation is important in the analysis of acoustic

  7. Acoustic Levitator Maintains Resonance

    NASA Technical Reports Server (NTRS)

    Barmatz, M. B.; Gaspar, M. S.

    1986-01-01

    Transducer loading characteristics allow resonance tracked at high temperature. Acoustic-levitation chamber length automatically adjusted to maintain resonance at constant acoustic frequency as temperature changes. Developed for containerless processing of materials at high temperatures, system does not rely on microphones as resonance sensors, since microphones are difficult to fabricate for use at temperatures above 500 degrees C. Instead, system uses acoustic transducer itself as sensor.

  8. Dynamics of acoustically levitated disk samples.

    PubMed

    Xie, W J; Wei, B

    2004-10-01

    The acoustic levitation force on disk samples and the dynamics of large water drops in a planar standing wave are studied by solving the acoustic scattering problem through incorporating the boundary element method. The dependence of levitation force amplitude on the equivalent radius R of disks deviates seriously from the R3 law predicted by King's theory, and a larger force can be obtained for thin disks. When the disk aspect ratio gamma is larger than a critical value gamma(*) ( approximately 1.9 ) and the disk radius a is smaller than the critical value a(*) (gamma) , the levitation force per unit volume of the sample will increase with the enlargement of the disk. The acoustic levitation force on thin-disk samples ( gammaacoustic field for stable levitation of a large water drop is to adjust the reflector-emitter interval H slightly above the resonant interval H(n) . The simulation shows that the drop is flattened and the central parts of its top and bottom surface become concave with the increase of sound pressure level, which agrees with the experimental observation. The main frequencies of the shape oscillation under different sound pressures are slightly larger than the Rayleigh frequency because of the large shape deformation. The simulated translational frequencies of the vertical vibration under normal gravity condition agree with the theoretical analysis. PMID:15600551

  9. Dynamics of acoustically levitated disk samples

    NASA Astrophysics Data System (ADS)

    Xie, W. J.; Wei, B.

    2004-10-01

    The acoustic levitation force on disk samples and the dynamics of large water drops in a planar standing wave are studied by solving the acoustic scattering problem through incorporating the boundary element method. The dependence of levitation force amplitude on the equivalent radius R of disks deviates seriously from the R3 law predicted by King’s theory, and a larger force can be obtained for thin disks. When the disk aspect ratio γ is larger than a critical value γ*(≈1.9) and the disk radius a is smaller than the critical value a*(γ) , the levitation force per unit volume of the sample will increase with the enlargement of the disk. The acoustic levitation force on thin-disk samples (γ⩽γ*) can be formulated by the shape factor f(γ,a) when a⩽a*(γ) . It is found experimentally that a necessary condition of the acoustic field for stable levitation of a large water drop is to adjust the reflector-emitter interval H slightly above the resonant interval Hn . The simulation shows that the drop is flattened and the central parts of its top and bottom surface become concave with the increase of sound pressure level, which agrees with the experimental observation. The main frequencies of the shape oscillation under different sound pressures are slightly larger than the Rayleigh frequency because of the large shape deformation. The simulated translational frequencies of the vertical vibration under normal gravity condition agree with the theoretical analysis.

  10. Acoustic dispersive prism

    PubMed Central

    Esfahlani, Hussein; Karkar, Sami; Lissek, Herve; Mosig, Juan R.

    2016-01-01

    The optical dispersive prism is a well-studied element, which allows separating white light into its constituent spectral colors, and stands in nature as water droplets. In analogy to this definition, the acoustic dispersive prism should be an acoustic device with capability of splitting a broadband acoustic wave into its constituent Fourier components. However, due to the acoustical nature of materials as well as the design and fabrication difficulties, there is neither any natural acoustic counterpart of the optical prism, nor any artificial design reported so far exhibiting an equivalent acoustic behaviour. Here, based on exotic properties of the acoustic transmission-line metamaterials and exploiting unique physical behaviour of acoustic leaky-wave radiation, we report the first acoustic dispersive prism, effective within the audible frequency range 800 Hz–1300 Hz. The dispersive nature, and consequently the frequency-dependent refractive index of the metamaterial are exploited to split the sound waves towards different and frequency-dependent directions. Meanwhile, the leaky-wave nature of the structure facilitates the sound wave radiation into the ambient medium. PMID:26739504

  11. Localized acoustic surface modes

    NASA Astrophysics Data System (ADS)

    Farhat, Mohamed; Chen, Pai-Yen; Bağcı, Hakan

    2016-04-01

    We introduce the concept of localized acoustic surface modes. We demonstrate that they are induced on a two-dimensional cylindrical rigid surface with subwavelength corrugations under excitation by an incident acoustic plane wave. Our results show that the corrugated rigid surface is acoustically equivalent to a cylindrical scatterer with uniform mass density that can be represented using a Drude-like model. This, indeed, suggests that plasmonic-like acoustic materials can be engineered with potential applications in various areas including sensing, imaging, and cloaking.

  12. Low frequency acoustic microscope

    DOEpatents

    Khuri-Yakub, Butrus T.

    1986-11-04

    A scanning acoustic microscope is disclosed for the detection and location of near surface flaws, inclusions or voids in a solid sample material. A focused beam of acoustic energy is directed at the sample with its focal plane at the subsurface flaw, inclusion or void location. The sample is scanned with the beam. Detected acoustic energy specularly reflected and mode converted at the surface of the sample and acoustic energy reflected by subsurface flaws, inclusions or voids at the focal plane are used for generating an interference signal which is processed and forms a signal indicative of the subsurface flaws, inclusions or voids.

  13. Vertical vibration dynamics of acoustically levitated drop containing two immiscible liquids

    NASA Astrophysics Data System (ADS)

    Zang, Duyang; Zhai, Zhicong; Li, Lin; Lin, Kejun; Li, Xiaoguang; Geng, Xingguo

    2016-09-01

    We have studied the levitation and oscillation dynamics of complex drops containing two immiscible liquids. Two types of drops, core-shell drop and abnormal-shaped drop, have been obtained depending on the levitation procedures. The oscillation dynamics of the drops have been studied using a high speed camera. It has been found that the oscillation of the abnormal-shaped drop has a longer oscillation period and decays much faster than that of the core-shell drop, which cannot be accounted for by the air resistance itself. The acoustic streaming induced by ultrasound may bring an additional force against the motion of the drop due to the Bernoulli effect. This is responsible for the enhanced damping during the oscillation in acoustic levitation.

  14. Electronic and Optical Properties of BaO, BaS, BaSe, BaTe and BaPo Compounds Under Hydrostatic Pressure

    NASA Astrophysics Data System (ADS)

    Drablia, S.; Meradji, H.; Ghemid, S.; Boukhris, N.; Bouhafs, B.; Nouet, G.

    We have performed first-principle full-potential (linear) augmented plane wave plus local orbital calculations (FP-L/APW + l0) with density functional theory (DFT) in local density approximation (LDA) and generalized gradient approximation (GGA), with the aim to determine and predict the electronic and optical properties of rocksalt BaO, BaS, BaSe, BaTe and BaPo compounds. First we present the main features of the electronic properties of these compounds, where the electronic band structure shows that the fundamental energy gap is indirect (Γ-X) for all compounds except for BaO which is direct (X-X). The different interband transitions have been determined from the imaginary part of the dielectric function. The real and imaginary parts of the dielectric function and the reflectivity are calculated. We have presented the assignment of the different optical transitions existing in these compounds from the imaginary part of the dielectric function spectra with respect to their correspondence in the electronic band. We have also calculated the pressure and volume dependence of the optical properties for these compounds.

  15. Acoustic Levitation With Less Equipment

    NASA Technical Reports Server (NTRS)

    Barmatz, M. B.; Jacobi, N.

    1983-01-01

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

  16. Synchronization of Coupled Oscillators on a Two-Dimensional Plane.

    PubMed

    Guo, Dameng; Fu, Yong Qing; Zheng, Bo

    2016-08-01

    The effect of the transfer rate of signal molecules on coupled chemical oscillators arranged on a two-dimensional plane was systematically investigated in this paper. A microreactor equipped with a surface acoustic wave (SAW) mixer was applied to adjust the transfer rate of the signal molecules in the microreactor. The SAW mixer with adjustable input powers provided a simple means to generate different mixing rates in the microreactor. A robust synchronization of the oscillators was found at an input radio frequency power of 20 dBm, with which the chemical waves were initiated at a fixed site of the oscillator system. With increasing input power, the frequency of the chemical waves was increased, which agreed well with the prediction given by the time-delayed phase oscillator model. Results from the finite element simulation agreed well with the experimental results. PMID:27124217

  17. Synchronization of Coupled Oscillators on a Two-Dimensional Plane.

    PubMed

    Guo, Dameng; Fu, Yong Qing; Zheng, Bo

    2016-08-01

    The effect of the transfer rate of signal molecules on coupled chemical oscillators arranged on a two-dimensional plane was systematically investigated in this paper. A microreactor equipped with a surface acoustic wave (SAW) mixer was applied to adjust the transfer rate of the signal molecules in the microreactor. The SAW mixer with adjustable input powers provided a simple means to generate different mixing rates in the microreactor. A robust synchronization of the oscillators was found at an input radio frequency power of 20 dBm, with which the chemical waves were initiated at a fixed site of the oscillator system. With increasing input power, the frequency of the chemical waves was increased, which agreed well with the prediction given by the time-delayed phase oscillator model. Results from the finite element simulation agreed well with the experimental results.

  18. RSRM Chamber Pressure Oscillations: Transit Time Models and Unsteady CFD

    NASA Technical Reports Server (NTRS)

    Nesman, Tom; Stewart, Eric

    1996-01-01

    Space Shuttle solid rocket motor low frequency internal pressure oscillations have been observed since early testing. The same type of oscillations also are present in the redesigned solid rocket motor (RSRM). The oscillations, which occur during RSRM burn, are predominantly at the first three motor cavity longitudinal acoustic mode frequencies. Broadband flow and combustion noise provide the energy to excite these modes at low levels throughout motor burn, however, at certain times during burn the fluctuating pressure amplitude increases significantly. The increased fluctuations at these times suggests an additional excitation mechanism. The RSRM has inhibitors on the propellant forward facing surface of each motor segment. The inhibitors are in a slot at the segment field joints to prevent burning at that surface. The aft facing segment surface at a field joint slot burns and forms a cavity of time varying size. Initially the inhibitor is recessed in the field joint cavity. As propellant burns away the inhibitor begins to protrude into the bore flow. Two mechanisms (transit time models) that are considered potential pressure oscillation excitations are cavity-edge tones, and inhibitor hole-tones. Estimates of frequency variation with time of longitudinal acoustic modes, cavity edge-tones, and hole-tones compare favorably with frequencies measured during motor hot firing. It is believed that the highest oscillation amplitudes occur when vortex shedding frequencies coincide with motor longitudinal acoustic modes. A time accurate computational fluid dynamic (CFD) analysis was made to replicate the observations from motor firings and to observe the transit time mechanisms in detail. FDNS is the flow solver used to detail the time varying aspects of the flow. The fluid is approximated as a single-phase ideal gas. The CFD model was an axisymmetric representation of the RSRM at 80 seconds into burn.Deformation of the inhibitors by the internal flow was determined

  19. Acoustic levitator for containerless measurements on low temperature liquids

    SciTech Connect

    Benmore, Chris J; Weber, Richard; Neuefeind, Joerg C; Rey, Charles A A

    2009-01-01

    A single-axis acoustic levitator was constructed and used to levitate liquid and solid drops at temperatures from -40 to +40 C. The levitator consisted of: (i) two acoustic transducers mounted on a rigid vertical support that was bolted to an optical breadboard, (ii) a acoustic power supply that controlled acoustic intensity, relative phase of the drive to the transducers, and could modulate the acoustic forces at frequencies up to 1kHz, (iii) a video camera, and (iv) a system for providing a stream of controlled temperature gas flow over the sample. The acoustic transducers were operated at their resonant frequency of ~ 22 kHz and could produce sound pressure levels up to 160 dB. The force applied by the acoustic field could be modulated using a frequency generator to excite oscillations in the sample. Sample temperature was controlled using a modified Cryostream Plus and measured using thermocouples and an infrared thermal imager. The levitator was installed at x-ray beamline 11 ID-C at the Advanced Photon Source and used to investigate the structure of supercooled liquids.

  20. Acoustic levitator for structure measurements on low temperature liquid droplets.

    PubMed

    Weber, J K R; Rey, C A; Neuefeind, J; Benmore, C J

    2009-08-01

    A single-axis acoustic levitator was constructed and used to levitate liquid and solid drops of 1-3 mm in diameter at temperatures in the range -40 to +40 degrees C. The levitator comprised (i) two acoustic transducers mounted on a rigid vertical support that was bolted to an optical breadboard, (ii) an acoustic power supply that controlled acoustic intensity, relative phase of the drive to the transducers, and could modulate the acoustic forces at frequencies up to 1 kHz, (iii) a video camera, and (iv) a system for providing a stream of controlled temperature gas flow over the sample. The acoustic transducers were operated at their resonant frequency of approximately 22 kHz and could produce sound pressure levels of up to 160 dB. The force applied by the acoustic field could be modulated to excite oscillations in the sample. Sample temperature was controlled using a modified Cryostream Plus and measured using thermocouples and an infrared thermal imager. The levitator was installed at x-ray beamline 11 ID-C at the Advanced Photon Source and used to investigate the structure of supercooled liquids.

  1. Acoustic levitator for structure measurements on low temperature liquid droplets.

    PubMed

    Weber, J K R; Rey, C A; Neuefeind, J; Benmore, C J

    2009-08-01

    A single-axis acoustic levitator was constructed and used to levitate liquid and solid drops of 1-3 mm in diameter at temperatures in the range -40 to +40 degrees C. The levitator comprised (i) two acoustic transducers mounted on a rigid vertical support that was bolted to an optical breadboard, (ii) an acoustic power supply that controlled acoustic intensity, relative phase of the drive to the transducers, and could modulate the acoustic forces at frequencies up to 1 kHz, (iii) a video camera, and (iv) a system for providing a stream of controlled temperature gas flow over the sample. The acoustic transducers were operated at their resonant frequency of approximately 22 kHz and could produce sound pressure levels of up to 160 dB. The force applied by the acoustic field could be modulated to excite oscillations in the sample. Sample temperature was controlled using a modified Cryostream Plus and measured using thermocouples and an infrared thermal imager. The levitator was installed at x-ray beamline 11 ID-C at the Advanced Photon Source and used to investigate the structure of supercooled liquids. PMID:19725664

  2. Global tools for thermo-acoustic instabilities in gas turbines

    NASA Astrophysics Data System (ADS)

    Nicoud, Franck; Benoit, Laurent

    2003-11-01

    The trend to operate gas turbine in leaner regime in order to decrease the pollutant emission increases the opportunities for thermo-acoustic instabilities. Suppress these oscillations at the design level requires a better understanding of the physical phenomena involved. A key point is the knowledge of the acoustic eigenmodes under industrial conditions (complex geometry, variable speed of sound, unsteady combustion). A classical approach consists in representing the flow domain as a network of 1D acoustic tubes connected to each other thanks to jump relationships. We present a different strategy where the 3D acoustic equations are solved for the pressure in the frequency domain with pulsation dependent impedance as acoustic boundary conditions. The effect of the flame on the acoustics is accounting for by modelling the unsteady heat release via the classical n-τ model. The interaction index n and the time delay τ depend on space and can be assessed experimentally or by means of Large-Eddy Simulations. The reactive acoustic equations in the frequency domain lead to a non-linear eigenvalue problem that is being solved thanks to asymptotic expansion in n. Results are presented in order to demonstrate the capability of the method to account for unsteady flames and complex geometries.

  3. Paradoxes of neutrino oscillations

    SciTech Connect

    Akhmedov, E. Kh.; Smirnov, A. Yu.

    2009-08-15

    Despite the theory of neutrino oscillations being rather old, some of its basic issues are still being debated in the literature. We discuss a number of such issues, including the relevance of the 'same energy' and 'same momentum' assumptions, the role of quantum-mechanical uncertainty relations in neutrino oscillations, the dependence of the coherence and localization conditions that ensure the observability of neutrino oscillations on neutrino energy and momentum uncertainties, the question of (in)dependence of the oscillation probabilities on the neutrino production and detection processes, and the applicability limits of the stationary-source approximation. We also develop a novel approach to calculation of the oscillation probability in the wave-packet approach, based on the summation/integration conventions different from the standard one, which allows a new insight into the 'same energy' vs. 'same momentum' problem. We also discuss a number of apparently paradoxical features of the theory of neutrino oscillations.

  4. Development of fluidic oscillators as flow control actuators

    NASA Astrophysics Data System (ADS)

    Gregory, James Winborn

    applying the paint to various flowfields. The polymer/ceramic formulation is used to record the 12-kHz oscillating shock wave and propagating acoustic waves generated by a Hartmann oscillator. Polymer/ceramic PSP is also used to measure the acoustic mode shapes in a rectangular resonance cavity driven by a speaker at 145 dB. These results compare favorably to the analytical solution for the same geometry.

  5. Nonparametric study of the evolution of the cosmological equation of state with SNeIa, BAO, and high-redshift GRBs

    SciTech Connect

    Postnikov, S.; Dainotti, M. G.; Hernandez, X.; Capozziello, S. E-mail: mdainott@stanford.edu E-mail: xavier@astros.unam.mx

    2014-03-10

    We study the dark energy equation of state as a function of redshift in a nonparametric way, without imposing any a priori w(z) (ratio of pressure over energy density) functional form. As a check of the method, we test our scheme through the use of synthetic data sets produced from different input cosmological models that have the same relative errors and redshift distribution as the real data. Using the luminosity-time L{sub X} -T{sub a} correlation for gamma-ray burst (GRB) X-ray afterglows (the Dainotti et al. correlation), we are able to utilize GRB samples from the Swift satellite as probes of the expansion history of the universe out to z ≈ 10. Within the assumption of a flat Friedmann-Lemaître-Robertson-Walker universe and combining supernovae type Ia (SNeIa) data with baryonic acoustic oscillation constraints, the resulting maximum likelihood solutions are close to a constant w = –1. If one imposes the restriction of a constant w, we obtain w = –0.99 ± 0.06 (consistent with a cosmological constant) with the present-day Hubble constant as H {sub 0} = 70.0 ± 0.6km s{sup –1} Mpc{sup –1} and density parameter as Ω{sub Λ0} = 0.723 ± 0.025, while nonparametric w(z) solutions give us a probability map that is centered at H {sub 0} = 70.04 ± 1km s{sup –1} Mpc{sup –1} and Ω{sub Λ0} = 0.724 ± 0.03. Our chosen GRB data sample with a full correlation matrix allows us to estimate the amount, as well as quality (errors), of data needed to constrain w(z) in the redshift range extending an order of magnitude beyond the farthest SNeIa measured.

  6. Oscillations in stellar atmospheres

    NASA Technical Reports Server (NTRS)

    Costa, A.; Ringuelet, A. E.; Fontenla, J. M.

    1989-01-01

    Atmospheric excitation and propagation of oscillations are analyzed for typical pulsating stars. The linear, plane-parallel approach for the pulsating atmosphere gives a local description of the phenomenon. From the local analysis of oscillations, the minimum frequencies are obtained for radially propagating waves. The comparison of the minimum frequencies obtained for a variety of stellar types is in good agreement with the observed periods of the oscillations. The role of the atmosphere in the globar stellar pulsations is thus emphasized.

  7. Self-oscillation

    NASA Astrophysics Data System (ADS)

    Jenkins, Alejandro

    2013-04-01

    Physicists are very familiar with forced and parametric resonance, but usually not with self-oscillation, a property of certain dynamical systems that gives rise to a great variety of vibrations, both useful and destructive. In a self-oscillator, the driving force is controlled by the oscillation itself so that it acts in phase with the velocity, causing a negative damping that feeds energy into the vibration: no external rate needs to be adjusted to the resonant frequency. The famous collapse of the Tacoma Narrows bridge in 1940, often attributed by introductory physics texts to forced resonance, was actually a self-oscillation, as was the swaying of the London Millennium Footbridge in 2000. Clocks are self-oscillators, as are bowed and wind musical instruments. The heart is a “relaxation oscillator”, i.e., a non-sinusoidal self-oscillator whose period is determined by sudden, nonlinear switching at thresholds. We review the general criterion that determines whether a linear system can self-oscillate. We then describe the limiting cycles of the simplest nonlinear self-oscillators, as well as the ability of two or more coupled self-oscillators to become spontaneously synchronized (“entrained”). We characterize the operation of motors as self-oscillation and prove a theorem about their limit efficiency, of which Carnot’s theorem for heat engines appears as a special case. We briefly discuss how self-oscillation applies to servomechanisms, Cepheid variable stars, lasers, and the macroeconomic business cycle, among other applications. Our emphasis throughout is on the energetics of self-oscillation, often neglected by the literature on nonlinear dynamical systems.

  8. Workshop on Harmonic Oscillators

    NASA Technical Reports Server (NTRS)

    Han, D. (Editor); Kim, Y. S. (Editor); Zachary, W. W. (Editor)

    1993-01-01

    Proceedings of a workshop on Harmonic Oscillators held at the College Park Campus of the University of Maryland on March 25 - 28, 1992 are presented. The harmonic oscillator formalism is playing an important role in many branches of physics. This is the simplest mathematical device which can connect the basic principle of physics with what is observed in the real world. The harmonic oscillator is the bridge between pure and applied physics.

  9. Drift effects on electromagnetic geodesic acoustic modes

    NASA Astrophysics Data System (ADS)

    Sgalla, R. J. F.

    2015-02-01

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

  10. Drift effects on electromagnetic geodesic acoustic modes

    SciTech Connect

    Sgalla, R. J. F.

    2015-02-15

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

  11. Experimental determination of the dynamics of an acoustically levitated sphere

    NASA Astrophysics Data System (ADS)

    Pérez, Nicolás; Andrade, Marco A. B.; Canetti, Rafael; Adamowski, Julio C.

    2014-11-01

    Levitation of solids and liquids by ultrasonic standing waves is a promising technique to manipulate materials without contact. When a small particle is introduced in certain areas of a standing wave field, the acoustic radiation force pushes the particle to the pressure node. This movement is followed by oscillations of the levitated particle. Aiming to investigate the particle oscillations in acoustic levitation, this paper presents the experimental and numerical characterization of the dynamic behavior of a levitated sphere. To obtain the experimental response, a small sphere is lifted by the acoustic radiation force. After the sphere lift, it presents a damped oscillatory behavior, which is recorded by a high speed camera. To model this behavior, a mass-spring-damper system is proposed. In this model, the acoustic radiation force that acts on the sphere is theoretically predicted by the Gor'kov theory and the viscous forces are modeled by two damping terms, one term proportional to the square of the velocity and another term proportional to the particle velocity. The proposed model was experimentally verified by using different values of sound pressure amplitude. The comparison between numerical and experimental results shows that the model can accurately describe the oscillatory behavior of the sphere in an acoustic levitator.

  12. Experimental determination of the dynamics of an acoustically levitated sphere

    SciTech Connect

    Pérez, Nicolás; Andrade, Marco A. B.; Canetti, Rafael; Adamowski, Julio C.

    2014-11-14

    Levitation of solids and liquids by ultrasonic standing waves is a promising technique to manipulate materials without contact. When a small particle is introduced in certain areas of a standing wave field, the acoustic radiation force pushes the particle to the pressure node. This movement is followed by oscillations of the levitated particle. Aiming to investigate the particle oscillations in acoustic levitation, this paper presents the experimental and numerical characterization of the dynamic behavior of a levitated sphere. To obtain the experimental response, a small sphere is lifted by the acoustic radiation force. After the sphere lift, it presents a damped oscillatory behavior, which is recorded by a high speed camera. To model this behavior, a mass-spring-damper system is proposed. In this model, the acoustic radiation force that acts on the sphere is theoretically predicted by the Gor'kov theory and the viscous forces are modeled by two damping terms, one term proportional to the square of the velocity and another term proportional to the particle velocity. The proposed model was experimentally verified by using different values of sound pressure amplitude. The comparison between numerical and experimental results shows that the model can accurately describe the oscillatory behavior of the sphere in an acoustic levitator.

  13. Acoustic telemetry: The new MWD system

    SciTech Connect

    Tochikawa, T.; Sakai, T.; Taniguchi, R.; Shimada, T.

    1996-12-31

    A new MWD system utilizing acoustic telemetry system has been researched, based on the principle of elastic wave propagation and magnetostrictive technology. The system is intended for data transmission through jointed drill strings with much higher reliability and transmitting efficiency. In order to achieve a good acoustical propagation characteristics through the drillstring the elastic wave signal requirements have had to be less than 1 kHz. The development of an optimum oscillator that generates such a low elastic wave frequency under harsh drilling conditions has been one of the technical breakthroughs. In this regard, one of the features of the system is the use of a magnetostrictive material as an oscillator in the transmitter. Utilzing the phenomena in which a magnetostrictive material as an oscillator in the transmitter. Utilizing the phenomena in which a magnetostrictive material drastically distorts by applying magnetic field to it, the oscillator generates and elastic wave for propagation and transmission through the drill strings. Several field tests have proven that the system could transmit canned data from the depth of 1914 meters and data demodulation at the surface free from troubles while drilling forty nine (49) degrees deviated well. These results provide a comprehensive understanding of wave propagation characteristics which the authors are assured that practical MWD equipment with higher than normal transmission rates can be developed and commercialized. Since the system can offer several unique features especially in terms of miniaturization and non-dependence on drilling fluids it can be applied to the emerging technologies such as slim-hole drilling, coiled tubing drilling, local communication on the bottom hole assembly. Furthermore it can offer wider application for the drilling environment such as underbalanced drilling.

  14. Acoustics Critical Readiness Review

    NASA Technical Reports Server (NTRS)

    Ballard, Kenny

    2010-01-01

    This presentation reviews the status of the acoustic equipment from the medical operations perspective. Included is information about the acoustic dosimeters, sound level meter, and headphones that are planned for use while on orbit. Finally there is information about on-orbit hearing assessments.

  15. Introduction to acoustic emission

    NASA Technical Reports Server (NTRS)

    Possa, G.

    1983-01-01

    Typical acoustic emission signal characteristics are described and techniques which localize the signal source by processing the acoustic delay data from multiple sensors are discussed. The instrumentation, which includes sensors, amplifiers, pulse counters, a minicomputer and output devices is examined. Applications are reviewed.

  16. Orbital motions of bubbles in an acoustic field

    NASA Astrophysics Data System (ADS)

    Shirota, Minori; Yamashita, Ko; Inamura, Takao

    2012-09-01

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

  17. Numerical simulations of ionospheric oscillations caused by coseismic atmospheric waves

    NASA Astrophysics Data System (ADS)

    Matsumura, M.; Shinagawa, H.; Tsugawa, T.; Saito, A.; Otsuka, Y.; Iyemori, T.

    2012-12-01

    Following the Mw=9.0 Tohoku earthquake on March 11, 2011, oscillations of total electric content (TEC) were observed in the ionosphere. They propagated with velocities of 140-780m/s from the tsunami source point, and had circular wave fronts [Tsugawa et al., 2011]. The purpose of this study is to simulate these oscillations and to elucidate the generation mechanism of them. In this study, we describe numerical simulations using a coupled model of a two-dimensional tsunami and a three-dimensional atmosphere and ionosphere. Velocity of the sea surface displacement generated by tsunami is implemented in the atmosphere-ionosphere model as the lower boundary condition. The simulations elucidate followings: (1) Oscillations of 420-780m/s are caused by secondary acoustic and gravity waves generated in the thermosphere. They are generated by primary acoustic waves triggered by the sea-surface displacement at the tsunami source point. (2) Oscillations of 140-290m/s are caused by gravity waves generated by tsunami and the tsunami source. They propagate to the thermosphere and attenuate over F1 region. This indicates that the TEC oscillations of 140-290m/s are mainly contributed by F1 or E region.

  18. Virtual acoustics displays

    NASA Technical Reports Server (NTRS)

    Wenzel, Elizabeth M.; Fisher, Scott S.; Stone, Philip K.; Foster, Scott H.

    1991-01-01

    The real time acoustic display capabilities are described which were developed for the Virtual Environment Workstation (VIEW) Project at NASA-Ames. The acoustic display is capable of generating localized acoustic cues in real time over headphones. An auditory symbology, a related collection of representational auditory 'objects' or 'icons', can be designed using ACE (Auditory Cue Editor), which links both discrete and continuously varying acoustic parameters with information or events in the display. During a given display scenario, the symbology can be dynamically coordinated in real time with 3-D visual objects, speech, and gestural displays. The types of displays feasible with the system range from simple warnings and alarms to the acoustic representation of multidimensional data or events.

  19. Acoustic ground impedance meter

    NASA Technical Reports Server (NTRS)

    Zuckerwar, A. J. (Inventor)

    1984-01-01

    A method and apparatus are presented for measuring the acoustic impedance of a surface in which the surface is used to enclose one end of the chamber of a Helmholz resonator. Acoustic waves are generated in the neck of the resonator by a piston driven by a variable speed motor through a cam assembly. The acoustic waves are measured in the chamber and the frequency of the generated acoustic waves is measured by an optical device. These measurements are used to compute the compliance and conductance of the chamber and surface combined. The same procedure is followed with a calibration plate having infinite acoustic impedance enclosing the chamber of the resonator to compute the compliance and conductance of the chamber alone. Then by subtracting, the compliance and conductance for the surface is obtained.

  20. Ocean acoustic hurricane classification.

    PubMed

    Wilson, Joshua D; Makris, Nicholas C

    2006-01-01

    Theoretical and empirical evidence are combined to show that underwater acoustic sensing techniques may be valuable for measuring the wind speed and determining the destructive power of a hurricane. This is done by first developing a model for the acoustic intensity and mutual intensity in an ocean waveguide due to a hurricane and then determining the relationship between local wind speed and underwater acoustic intensity. From this it is shown that it should be feasible to accurately measure the local wind speed and classify the destructive power of a hurricane if its eye wall passes directly over a single underwater acoustic sensor. The potential advantages and disadvantages of the proposed acoustic method are weighed against those of currently employed techniques. PMID:16454274

  1. Ocean acoustic hurricane classification.

    PubMed

    Wilson, Joshua D; Makris, Nicholas C

    2006-01-01

    Theoretical and empirical evidence are combined to show that underwater acoustic sensing techniques may be valuable for measuring the wind speed and determining the destructive power of a hurricane. This is done by first developing a model for the acoustic intensity and mutual intensity in an ocean waveguide due to a hurricane and then determining the relationship between local wind speed and underwater acoustic intensity. From this it is shown that it should be feasible to accurately measure the local wind speed and classify the destructive power of a hurricane if its eye wall passes directly over a single underwater acoustic sensor. The potential advantages and disadvantages of the proposed acoustic method are weighed against those of currently employed techniques.

  2. Cochlear bionic acoustic metamaterials

    NASA Astrophysics Data System (ADS)

    Ma, Fuyin; Wu, Jiu Hui; Huang, Meng; Fu, Gang; Bai, Changan

    2014-11-01

    A design of bionic acoustic metamaterial and acoustic functional devices was proposed by employing the mammalian cochlear as a prototype. First, combined with the experimental data in previous literatures, it is pointed out that the cochlear hair cells and stereocilia cluster are a kind of natural biological acoustic metamaterials with the negative stiffness characteristics. Then, to design the acoustic functional devices conveniently in engineering application, a simplified parametric helical structure was proposed to replace actual irregular cochlea for bionic design, and based on the computational results of such a bionic parametric helical structure, it is suggested that the overall cochlear is a local resonant system with the negative dynamic effective mass characteristics. There are many potential applications in the bandboard energy recovery device, cochlear implant, and acoustic black hole.

  3. Acoustic Remote Sensing

    NASA Astrophysics Data System (ADS)

    Dowling, David R.; Sabra, Karim G.

    2015-01-01

    Acoustic waves carry information about their source and collect information about their environment as they propagate. This article reviews how these information-carrying and -collecting features of acoustic waves that travel through fluids can be exploited for remote sensing. In nearly all cases, modern acoustic remote sensing involves array-recorded sounds and array signal processing to recover multidimensional results. The application realm for acoustic remote sensing spans an impressive range of signal frequencies (10-2 to 107 Hz) and distances (10-2 to 107 m) and involves biomedical ultrasound imaging, nondestructive evaluation, oil and gas exploration, military systems, and Nuclear Test Ban Treaty monitoring. In the past two decades, approaches have been developed to robustly localize remote sources; remove noise and multipath distortion from recorded signals; and determine the acoustic characteristics of the environment through which the sound waves have traveled, even when the recorded sounds originate from uncooperative sources or are merely ambient noise.

  4. Acoustic suspension system

    NASA Technical Reports Server (NTRS)

    Lee, M. C.; Wang, T. G. (Inventor)

    1983-01-01

    An acoustic levitation system is described, with single acoustic source and a small reflector to stably levitate a small object while the object is processed as by coating or heating it. The system includes a concave acoustic source which has locations on opposite sides of its axis that vibrate towards and away from a focal point to generate a converging acoustic field. A small reflector is located near the focal point, and preferably slightly beyond it, to create an intense acoustic field that stably supports a small object near the reflector. The reflector is located about one-half wavelength from the focal point and is concavely curved to a radius of curvature (L) of about one-half the wavelength, to stably support an object one-quarter wavelength (N) from the reflector.

  5. Acoustic integrated extinction

    PubMed Central

    Norris, Andrew N.

    2015-01-01

    The integrated extinction (IE) is defined as the integral of the scattering cross section as a function of wavelength. Sohl et al. (2007 J. Acoust. Soc. Am. 122, 3206–3210. (doi:10.1121/1.2801546)) derived an IE expression for acoustic scattering that is causal, i.e. the scattered wavefront in the forward direction arrives later than the incident plane wave in the background medium. The IE formula was based on electromagnetic results, for which scattering is causal by default. Here, we derive a formula for the acoustic IE that is valid for causal and non-causal scattering. The general result is expressed as an integral of the time-dependent forward scattering function. The IE reduces to a finite integral for scatterers with zero long-wavelength monopole and dipole amplitudes. Implications for acoustic cloaking are discussed and a new metric is proposed for broadband acoustic transparency. PMID:27547100

  6. Acoustic droplet vaporization for diagnostic and therapeutic applications

    NASA Astrophysics Data System (ADS)

    Kripfgans, Oliver Daniel

    A technology, termed Acoustic Droplet Vaporization (ADV), is developed whereby superheated droplets are caused to vaporize by application of an ultrasonic field. The droplet emulsion (90% <6 um diameter) is made by mixing saline, albumin, and perfluorocarbon at high speed. It has been observed that an acoustic pressure threshold exists above which the droplets vaporize into bubbles approximately 25-times the original droplet diameter. For frequencies between 1.5 and 8 MHz, the threshold decreases from 4.5 to 0.75 MPa peak rarefactional pressure. The single pulse efficiency of ADV has been measured as 26%. This technology might be useful for tissue occlusion in cancer treatment as well as for aberration correction in acoustic imaging. To demonstrate these potential applications, gas bubbles were made in vivo in animal models by ADV. It was found that ADV could be used to temporarily form large gas bubbles (>30 um) in vivo, which at large number density occluded targeted tissues and reduced the blood flow by 34%. Alternatively, for a very sparse droplet population, gas bubbles could serve as potential point beacons for phase aberration correction given their backscatter amplitudes of 24 dB above tissue background. Other possible applications include drug delivery, indicator for cryo therapy, pressure/radiation beacons, hyperthermia, and cavitation nuclei. ADV of individual droplets showed that during acoustic irradiation, droplets perform dipole-type oscillations and that such oscillations increased in amplitude with acoustic intensity. Smaller droplets required more acoustic intensity for vaporization than larger droplets; however, independent of droplet diameter, a maximum oscillation amplitude of 1.3 um, was required. This threshold corresponds to a Reynolds number of ˜5 x 104. Vaporization started either as a spot on the axis of oscillation close to a pole of the droplet, or homogeneously throughout the droplet's imaged cross-section. It is concluded that

  7. Active-bridge oscillator

    DOEpatents

    Wessendorf, Kurt O.

    2001-01-01

    An active bridge oscillator is formed from a differential amplifier where positive feedback is a function of the impedance of one of the gain elements and a relatively low value common emitter resistance. This use of the nonlinear transistor parameter h stabilizes the output and eliminates the need for ALC circuits common to other bridge oscillators.

  8. Investigating Magnetic Oscillations.

    ERIC Educational Resources Information Center

    Brueningsen, Christopher A.

    1993-01-01

    Studies magnetic oscillation using an air track. Ceramic magnets are attached to the cart and also are used as dampeners in place of the springs. The resulting oscillations are fairly sinusoidal and is a good example of simple harmonic motion. (MVL)

  9. Oscillating Chemical Reactions

    ERIC Educational Resources Information Center

    Hawkins, M. D.; And Others

    1975-01-01

    Describes several oscillating chemical reactions which can be used in undergraduate chemistry laboratories. In one such reaction, ferroin oscillates from red (reducing solution) to blue (oxidizing solution) for about an hour at a frequency which can readily be shown to depend on such factors as the temperature, type of solvent, and concentration…

  10. HIGH POWER PULSED OSCILLATOR

    DOEpatents

    Singer, S.; Neher, L.K.

    1957-09-24

    A high powered, radio frequency pulse oscillator is described for generating trains of oscillations at the instant an input direct voltage is impressed, or immediately upon application of a light pulse. In one embodiment, the pulse oscillator comprises a photo-multiplier tube with the cathode connected to the first dynode by means of a resistor, and adjacent dynodes are connected to each other through adjustable resistors. The ohmage of the resistors progressively increases from a very low value for resistors adjacent the cathode to a high value adjacent the plate, the last dynode. Oscillation occurs with this circuit when a high negative voltage pulse is applied to the cathode and the photo cathode is bombarded. Another embodiment adds capacitors at the resistor connection points of the above circuit to increase the duration of the oscillator train.

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

    PubMed Central

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

    2016-01-01

    Low-energy collective electronic excitations exhibiting sound-like linear dispersion have been intensively studied both experimentally and theoretically for a long time. However, coherent acoustic plasmon modes appearing in time-domain measurements are rarely observed due to Landau damping by the single-particle continua. Here we report on the observation of coherent acoustic Dirac plasmon (CADP) modes excited in indirectly (electrostatically) opposite-surface coupled films of the topological insulator Bi2Se3. Using transient second-harmonic generation, a technique capable of independently monitoring the in-plane and out-of-plane electron dynamics in the films, the GHz-range oscillations were observed without corresponding oscillations in the transient reflectivity. These oscillations were assigned to the transverse magnetic and transverse electric guided CADP modes induced by the evanescent guided Lamb acoustic waves and remained Landau undamped due to fermion tunnelling between the opposite-surface Dirac states. PMID:27687867

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  13. Acoustic sniper localization system

    NASA Astrophysics Data System (ADS)

    Prado, Gervasio; Dhaliwal, Hardave; Martel, Philip O.

    1997-02-01

    Technologies for sniper localization have received increased attention in recent months as American forces have been deployed to various trouble spots around the world. Among the technologies considered for this task acoustics is a natural choice for various reasons. The acoustic signatures of gunshots are loud and distinctive, making them easy to detect even in high noise background environments. Acoustics provides a passive sensing technology with excellent range and non line of sight capabilities. Last but not least, an acoustic sniper location system can be built at a low cost with off the shelf components. Despite its many advantages, the performance of acoustic sensors can degrade under adverse propagation conditions. Localization accuracy, although good, is usually not accurate enough to pinpoint a sniper's location in some scenarios (for example which widow in a building or behind which tree in a grove). For these more demanding missions, the acoustic sensor can be used in conjunction with an infra red imaging system that detects the muzzle blast of the gun. The acoustic system can be used to cue the pointing system of the IR camera in the direction of the shot's source.

  14. Acoustic cooling engine

    DOEpatents

    Hofler, Thomas J.; Wheatley, John C.; Swift, Gregory W.; Migliori, Albert

    1988-01-01

    An acoustic cooling engine with improved thermal performance and reduced internal losses comprises a compressible fluid contained in a resonant pressure vessel. The fluid has a substantial thermal expansion coefficient and is capable of supporting an acoustic standing wave. A thermodynamic element has first and second ends and is located in the resonant pressure vessel in thermal communication with the fluid. The thermal response of the thermodynamic element to the acoustic standing wave pumps heat from the second end to the first end. The thermodynamic element permits substantial flow of the fluid through the thermodynamic element. An acoustic driver cyclically drives the fluid with an acoustic standing wave. The driver is at a location of maximum acoustic impedance in the resonant pressure vessel and proximate the first end of the thermodynamic element. A hot heat exchanger is adjacent to and in thermal communication with the first end of the thermodynamic element. The hot heat exchanger conducts heat from the first end to portions of the resonant pressure vessel proximate the hot heat exchanger. The hot heat exchanger permits substantial flow of the fluid through the hot heat exchanger. The resonant pressure vessel can include a housing less than one quarter wavelength in length coupled to a reservoir. The housing can include a reduced diameter portion communicating with the reservoir. The frequency of the acoustic driver can be continuously controlled so as to maintain resonance.

  15. Acoustic mapping velocimetry

    NASA Astrophysics Data System (ADS)

    Muste, M.; Baranya, S.; Tsubaki, R.; Kim, D.; Ho, H.; Tsai, H.; Law, D.

    2016-05-01

    Knowledge of sediment dynamics in rivers is of great importance for various practical purposes. Despite its high relevance in riverine environment processes, the monitoring of sediment rates remains a major and challenging task for both suspended and bed load estimation. While the measurement of suspended load is currently an active area of testing with nonintrusive technologies (optical and acoustic), bed load measurement does not mark a similar progress. This paper describes an innovative combination of measurement techniques and analysis protocols that establishes the proof-of-concept for a promising technique, labeled herein Acoustic Mapping Velocimetry (AMV). The technique estimates bed load rates in rivers developing bed forms using a nonintrusive measurements approach. The raw information for AMV is collected with acoustic multibeam technology that in turn provides maps of the bathymetry over longitudinal swaths. As long as the acoustic maps can be acquired relatively quickly and the repetition rate for the mapping is commensurate with the movement of the bed forms, successive acoustic maps capture the progression of the bed form movement. Two-dimensional velocity maps associated with the bed form migration are obtained by implementing algorithms typically used in particle image velocimetry to acoustic maps converted in gray-level images. Furthermore, use of the obtained acoustic and velocity maps in conjunction with analytical formulations (e.g., Exner equation) enables estimation of multidirectional bed load rates over the whole imaged area. This paper presents a validation study of the AMV technique using a set of laboratory experiments.

  16. Study of Two-Dimensional Compressible Non-Acoustic Modeling of Stirling Machine Type Components

    NASA Technical Reports Server (NTRS)

    Tew, Roy C., Jr.; Ibrahim, Mounir B.

    2001-01-01

    A two-dimensional (2-D) computer code was developed for modeling enclosed volumes of gas with oscillating boundaries, such as Stirling machine components. An existing 2-D incompressible flow computer code, CAST, was used as the starting point for the project. CAST was modified to use the compressible non-acoustic Navier-Stokes equations to model an enclosed volume including an oscillating piston. The devices modeled have low Mach numbers and are sufficiently small that the time required for acoustics to propagate across them is negligible. Therefore, acoustics were excluded to enable more time efficient computation. Background information about the project is presented. The compressible non-acoustic flow assumptions are discussed. The governing equations used in the model are presented in transport equation format. A brief description is given of the numerical methods used. Comparisons of code predictions with experimental data are then discussed.

  17. Ultrastable Cryogenic Microwave Oscillators

    NASA Astrophysics Data System (ADS)

    Mann, Anthony G.

    Ultrastable cryogenic microwave oscillators are secondary frequency standards in the microwave domain. The best of these oscillators have demonstrated a short term frequency stability in the range 10-14 to a few times 10-16. The main application for these oscillators is as flywheel oscillators for the next generation of passive atomic frequency standards, and as local oscillators in space telemetry ground stations to clean up the transmitter close in phase noise. Fractional frequency stabilities of passive atomic frequency standards are now approaching 3 x10^-14 /τ where τ is the measurement time, limited only by the number of atoms that are being interrogated. This requires an interrogation oscillator whose short-term stability is of the order of 10-14 or better, which cannot be provided by present-day quartz technology. Ultrastable cryogenic microwave oscillators are based on resonators which have very high electrical Q-factors. The resolution of the resonator's linewidth is typically limited by electronics noise to about 1ppm and hence Q-factors in excess of 108 are required. As these are only attained in superconducting cavities or sapphire resonators at low temperatures, use of liquid helium cooling is mandatory, which has so far restricted these oscillators to the research or metrology laboratory. Recently, there has been an effort to dispense with the need for liquid helium and make compact flywheel oscillators for the new generation of primary frequency standards. Work is under way to achieve this goal in space-borne and mobile liquid-nitrogen-cooled systems. The best cryogenic oscillators developed to date are the ``whispering gallery'' (WG) mode sapphire resonator-oscillators of NASA's Jet Propulsion Laboratory (JPL) and the University of Western Australia (UWA), as well as Stanford University's superconducting cavity stabilized oscillator (SCSO). All of these oscillators have demonstrated frequency

  18. Calibration of acoustic transients.

    PubMed

    Burkard, Robert

    2006-05-26

    This article reviews the appropriate stimulus parameters (click duration, toneburst envelope) that should be used when eliciting auditory brainstem responses from mice. Equipment specifications required to calibrate these acoustic transients are discussed. Several methods of calibrating the level of acoustic transients are presented, including the measurement of peak equivalent sound pressure level (peSPL) and peak sound pressure level (pSPL). It is hoped that those who collect auditory brainstem response thresholds in mice will begin to use standardized methods of acoustic calibration, so that hearing thresholds across mouse strains obtained in different laboratories can more readily be compared.

  19. PRSEUS Acoustic Panel Fabrication

    NASA Technical Reports Server (NTRS)

    Nicolette, Velicki; Yovanof, Nicolette P.; Baraja, Jaime; Mathur, Gopal; Thrash, Patrick; Pickell, Robert

    2011-01-01

    This report describes the development of a novel structural concept, Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS), that addresses the demanding fuselage loading requirements for the Hybrid Wing or Blended Wing Body (BWB) airplane configuration with regards to acoustic response. A PRSEUS panel was designed and fabricated and provided to NASA-LaRC for acoustic response testing in the Structural Acoustics Loads and Transmission (SALT) facility). Preliminary assessments of the sound transmission characteristics of a PRSEUS panel subjected to a representative Hybrid Wing Body (HWB) operating environment were completed for the NASA Environmentally Responsible Aviation (ERA) Program.

  20. Acoustic rotation control

    NASA Technical Reports Server (NTRS)

    Elleman, D. D.; Croonquist, A. P.; Wang, T. G. (Inventor)

    1983-01-01

    A system is described for acoustically controlled rotation of a levitated object, which avoids deformation of a levitated liquid object. Acoustic waves of the same wavelength are directed along perpendicular directions across the object, and with the relative phases of the acoustic waves repeatedly switched so that one wave alternately leads and lags the other by 90 deg. The amount of torque for rotating the object, and the direction of rotation, are controlled by controlling the proportion of time one wave leads the other and selecting which wave leads the other most of the time.

  1. Acoustic well cleaner

    DOEpatents

    Maki, Jr., Voldi E.; Sharma, Mukul M.

    1997-01-21

    A method and apparatus are disclosed for cleaning the wellbore and the near wellbore region. A sonde is provided which is adapted to be lowered into a borehole and which includes a plurality of acoustic transducers arranged around the sonde. Electrical power provided by a cable is converted to acoustic energy. The high intensity acoustic energy directed to the borehole wall and into the near wellbore region, redissolves or resuspends the material which is reducing the permeability of the formation and/or restricting flow in the wellbore.

  2. Underwater acoustic omnidirectional absorber

    NASA Astrophysics Data System (ADS)

    Naify, Christina J.; Martin, Theodore P.; Layman, Christopher N.; Nicholas, Michael; Thangawng, Abel L.; Calvo, David C.; Orris, Gregory J.

    2014-02-01

    Gradient index media, which are designed by varying local element properties in given geometry, have been utilized to manipulate acoustic waves for a variety of devices. This study presents a cylindrical, two-dimensional acoustic "black hole" design that functions as an omnidirectional absorber for underwater applications. The design features a metamaterial shell that focuses acoustic energy into the shell's core. Multiple scattering theory was used to design layers of rubber cylinders with varying filling fractions to produce a linearly graded sound speed profile through the structure. Measured pressure intensity agreed with predicted results over a range of frequencies within the homogenization limit.

  3. Acoustic signals generated in inclined granular flows

    NASA Astrophysics Data System (ADS)

    Tan, Danielle S.; Jenkins, James T.; Keast, Stephen C.; Sachse, Wolfgang H.

    2015-10-01

    Spontaneous avalanching in specific deserts produces a low-frequency sound known as "booming." This creates a puzzle, because avalanches down the face of a dune result in collisions between sand grains that occur at much higher frequencies. Reproducing this phenomenon in the laboratory permits a better understanding of the underlying mechanisms for the generation of such lower frequency acoustic emissions, which may also be relevant to other dry granular flows. Here we report measurements of low-frequency acoustical signals, produced by dried "sounding" sand (sand capable of booming in the desert) flowing down an inclined chute. The amplitude of the signal diminishes over time but reappears upon drying of the sand. We show that the presence of this sound in the experiments may provide supporting evidence for a previously published "waveguide" explanation for booming. Also, we propose a model based on kinetic theory for a sheared inclined flow in which the flowing layer exhibits "breathing" modes superimposed on steady shearing. The predicted oscillation frequency is of a similar order of magnitude as the measurements, indicating that small perturbations can sustain oscillations of a low frequency. However, the frequency is underestimated, which indicates that the stiffness has been underestimated. Also, the model predicts a discrete spectrum of frequencies, instead of the broadband spectrum measured experimentally.

  4. Nonlinear Oscillations and Flow of Gas Within Closed and Open Conical Resonators

    NASA Technical Reports Server (NTRS)

    Daniels, Christopher; Finkbeiner, Joshua; Steinetz, Bruce; Li, Xiaofan; Raman, Ganesh

    2004-01-01

    A dissonant acoustic resonator with a conical shaped cavity was tested in four configurations: (A) baseline resonator with closed ends and no blockage; (B) closed resonator with internal blockage; (C) ventilated resonator with no blockage; and (D) ventilated resonator with an applied pressure differential. These tests were conducted to investigate the effects of blockage and ventilation holes on dynamic pressurization. Additionally, the investigation was to determine the ability of acoustic pressurization to impede flow through the resonator. In each of the configurations studied, the entire resonator was oscillated at the gas resonant frequency while dynamic pressure, static pressure, and temperature of the fluid were measured. In the final configuration, flow through the resonator was recorded for three oscillation conditions. Ambient condition air was used as the working fluid. The baseline results showed a marked reduction in the amplitude of the dynamic pressure waveforms over previously published studies due to the use of air instead of refrigerant as the working fluid. A change in the resonant frequency was recorded when blockages of differing geometries were used in the closed resonator, while acoustic pressure amplitudes were reduced from baseline measurements. A sharp reduction in the amplitude of the acoustic pressure waves was expected and recorded when ventilation ports were added. With elevated pressure applied to one end of the resonator, flow was reduced by oscillating the cavity at the fluid fundamental resonant frequency compared to cases without oscillation and oscillation off-resonance.

  5. Acoustic mode driven by fast electrons in TJ-II Electron Cyclotron Resonance plasmas

    NASA Astrophysics Data System (ADS)

    Sun, B. J.; Ochando, M. A.; López-Bruna, D.

    2016-08-01

    Intense harmonic oscillations in radiation signals (δ I/I∼ 5{%}) are commonly observed during Electron Cyclotron Resonance (ECR) heating in TJ-II stellarator plasmas at low line-averaged electron density, 0.15 < \\bar{n}e < 0.6 ×1019 \\text{m}-3 . The frequency agrees with acoustic modes. The poloidal modal structure is compatible with Geodesic Acoustic Modes (GAM) but an n \

  6. Controllable Solid Propulsion Combustion and Acoustic Knowledge Base Improvements

    NASA Technical Reports Server (NTRS)

    McCauley, Rachel; Fischbach, Sean; Fredrick, Robert

    2012-01-01

    Controllable solid propulsion systems have distinctive combustion and acoustic environments that require enhanced testing and analysis techniques to progress this new technology from development to production. In a hot gas valve actuating system, the movement of the pintle through the hot gas exhibits complex acoustic disturbances and flow characteristics that can amplify induced pressure loads that can damage or detonate the rocket motor. The geometry of a controllable solid propulsion gas chamber can set up unique unsteady flow which can feed acoustic oscillations patterns that require characterization. Research in this area aids in the understanding of how best to design, test, and analyze future controllable solid rocket motors using the lessons learned from past government programs as well as university research and testing. This survey paper will give the reader a better understanding of the potentially amplifying affects propagated by a controllable solid rocket motor system and the knowledge of the tools current available to address these acoustic disturbances in a preliminary design. Finally the paper will supply lessons learned from past experiences which will allow the reader to come away with understanding of what steps need to be taken when developing a controllable solid rocket propulsion system. The focus of this survey will be on testing and analysis work published by solid rocket programs and from combustion and acoustic books, conference papers, journal articles, and additionally from subject matter experts dealing currently with controllable solid rocket acoustic analysis.

  7. Chromospheric Heating by Acoustic Waves Compared to Radiative Cooling

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    Acoustic and magnetoacoustic waves are among the possible candidate mechanisms that heat the upper layers of the solar atmosphere. A weak chromospheric plage near the large solar pore NOAA 11005 was observed on 2008 October 15, in the Fe i 617.3 nm and Ca ii 853.2 nm lines of the Interferometric Bidimemsional Spectrometer attached to the Dunn Solar Telescope. In analyzing the Ca ii observations (with spatial and temporal resolutions of 0.″4 and 52 s) the energy deposited by acoustic waves is compared to that released by radiative losses. The deposited acoustic flux is estimated from the power spectra of Doppler oscillations measured in the Ca ii line core. The radiative losses are calculated using a grid of seven one-dimensional hydrostatic semi-empirical model atmospheres. The comparison shows that the spatial correlation of the maps of radiative losses and acoustic flux is 72%. In a quiet chromosphere, the contribution of acoustic energy flux to radiative losses is small, only about 15%. In active areas with a photospheric magnetic-field strength between 300 and 1300 G and an inclination of 20°-60°, the contribution increases from 23% (chromospheric network) to 54% (a plage). However, these values have to be considered as lower limits and it might be possible that the acoustic energy flux is the main contributor to the heating of bright chromospheric network and plages.

  8. Linear models of acoustic waves in sunspot umbrae

    NASA Technical Reports Server (NTRS)

    Gurman, J. B.; Leibacher, J. W.

    1984-01-01

    The two-dimensional, linear hydrodynamics of quiet solar and umbral model atmospheres in a plane-parallel, adiabatic approximation are investigated. The 5.5-8.5 mHz oscillations observed in umbral chromospheres and transition regions are interpreted as acoustic waves propagating parallel, or nearly parallel, to the temperature gradient. These waves are not totally internally reflected by the steep temperature gradient and, thus, are not trapped. Partial reflections, however, are effective in modulating the transmission as a function of frequency. The resonant transmission mechanism of Zugzda, Locans, and Staude (1983) is found to produce a spectrum of resonances in the transmission of acoustic waves in any atmosphere with a temperature minimum. Since the observed umbral oscillations display power in only a narrow range of frequencies, characteristics of the umbral models, wave propagation, and observations that would tend to suppress the higher frequency resonances are examined.

  9. Dynamics of single inclusions in channels with constrictions in the acoustic field

    NASA Astrophysics Data System (ADS)

    Maksimov, A. Yu.; Gubaidullin, A. A.

    2016-10-01

    The process of mobilization of viscous droplets, trapped in the channel with a sinusoidal constriction under the influence of an external acoustic field have been studied. The dependence of the amplitude of acoustic impact from the frequency has been found. The problem of the free longitudinal oscillations of a droplet in the absence of viscous friction forces in the channels with the constrictions was considered. The influence of surface tension, droplet volume and shape of constrictions on the natural frequency of the longitudinal oscillations of a droplet pinned at the constriction of the capillary were studied.

  10. Evaluation of Start Transient Oscillations with the J-2X Engine Gas Generator Assembly

    NASA Technical Reports Server (NTRS)

    Hulka, J. R.; Morgan, C. J.; Casiano, M. J.

    2015-01-01

    During development of the gas generator for the liquid oxygen/liquid hydrogen propellant J-2X rocket engine, distinctive and oftentimes high-amplitude pressure oscillations and hardware vibrations occurred during the start transient of nearly every workhorse gas generator assembly test, as well as during many tests of engine system hardware. These oscillations appeared whether the steady-state conditions exhibited stable behavior or not. They occurred similarly with three different injector types, and with every combustion chamber configuration tested, including chamber lengths ranging over a 5:1 range, several different nozzle types, and with or without a side branch line simulating a turbine spin start gas supply line. Generally, two sets of oscillations occurred, one earlier in the start transient and at higher frequencies, and the other almost immediately following and at lower frequencies. Multiple dynamic pressure measurements in the workhorse combustion chambers indicated that the oscillations were associated with longitudinal acoustic modes of the combustion chambers, with the earlier and higher frequency oscillation usually related to the second longitudinal acoustic mode and the later and lower frequency oscillation usually related to the first longitudinal acoustic mode. Given that several early development gas generator assemblies exhibited unstable behavior at frequencies near the first longitudinal acoustic modes of longer combustion chambers, the start transient oscillations are presumed to provide additional insight into the nature of the combustion instability mechanisms. Aspects of the steadystate oscillations and combustion instabilities from development and engine system test programs have been reported extensively in the three previous JANNAF Liquid Propulsion Subcommittee meetings (see references below). This paper describes the hardware configurations, start transient sequence operations, and transient and dynamic test data during the start

  11. Compact acoustic refrigerator

    SciTech Connect

    Bennett, G.A.

    1991-12-31

    This invention is comprised of a compact acoustic refrigeration system that actively cools components, e.g., electrical circuits, in a borehole environment. An acoustic engine includes first thermodynamic elements for generating a standing acoustic wave in a selected medium. An acoustic refrigerator includes second thermodynamic elements located in the standing wave for generating a relatively cold temperature at a first end of the second thermodynamic elements and a relatively hot temperature at a second end of the second thermodynamic elements. A resonator volume cooperates with the first and second thermodynamic elements to support the standing wave. To accommodate the high heat fluxes required for heat transfer to/from the first and second thermodynamic elements, first heat pipes transfer heat from the heat load to the second thermodynamic elements and second heat pipes transfer heat from first and second thermodynamic elements to the borehole environment.

  12. Acoustics lecturing in Mexico

    NASA Astrophysics Data System (ADS)

    Beristain, Sergio

    2002-11-01

    Some thirty years ago acoustics lecturing started in Mexico at the National Polytechnic Institute in Mexico City, as part of the Bachelor of Science degree in Communications and Electronics Engineering curricula, including the widest program on this field in the whole country. This program has been producing acoustics specialists ever since. Nowadays many universities and superior education institutions around the country are teaching students at the B.Sc. level and postgraduate level many topics related to acoustics, such as Architectural Acoustics, Seismology, Mechanical Vibrations, Noise Control, Audio, Audiology, Music, etc. Also many institutions have started research programs in related fields, with participation of medical doctors, psychologists, musicians, engineers, etc. Details will be given on particular topics and development.

  13. Compact acoustic refrigerator

    DOEpatents

    Bennett, G.A.

    1992-11-24

    A compact acoustic refrigeration system actively cools components, e.g., electrical circuits, in a borehole environment. An acoustic engine includes first thermodynamic elements for generating a standing acoustic wave in a selected medium. An acoustic refrigerator includes second thermodynamic elements located in the standing wave for generating a relatively cold temperature at a first end of the second thermodynamic elements and a relatively hot temperature at a second end of the second thermodynamic elements. A resonator volume cooperates with the first and second thermodynamic elements to support the standing wave. To accommodate the high heat fluxes required for heat transfer to/from the first and second thermodynamic elements, first heat pipes transfer heat from the heat load to the second thermodynamic elements and second heat pipes transfer heat from first and second thermodynamic elements to the borehole environment. 18 figs.

  14. Acoustic imaging system

    DOEpatents

    Smith, Richard W.

    1979-01-01

    An acoustic imaging system for displaying an object viewed by a moving array of transducers as the array is pivoted about a fixed point within a given plane. A plurality of transducers are fixedly positioned and equally spaced within a laterally extending array and operatively directed to transmit and receive acoustic signals along substantially parallel transmission paths. The transducers are sequentially activated along the array to transmit and receive acoustic signals according to a preestablished sequence. Means are provided for generating output voltages for each reception of an acoustic signal, corresponding to the coordinate position of the object viewed as the array is pivoted. Receptions from each of the transducers are presented on the same display at coordinates corresponding to the actual position of the object viewed to form a plane view of the object scanned.

  15. Acoustic Neuroma Association

    MedlinePlus

    ... Platinum Sponsors More from this sponsor... Platinum Sponsor Gold Sponsor University of Colorado Acoustic Neuroma Program Rocky Mountain Gamma Knife Center Gold Sponsor NYU Langone Medical Center Departments of Neurosurgery ...

  16. Acoustic-Levitation Chamber

    NASA Technical Reports Server (NTRS)

    Barmatz, M. B.; Granett, D.; Lee, M. C.

    1984-01-01

    Uncontaminated environments for highly-pure material processing provided within completely sealed levitation chamber that suspends particles by acoustic excitation. Technique ideally suited for material processing in low gravity environment of space.

  17. Multimode Acoustic Research

    NASA Technical Reports Server (NTRS)

    Barmatz, M.

    1985-01-01

    There is a need for high temperature containerless processing facilities that can efficiently position and manipulate molten samples in the reduced gravity environment of space. The goal of the research is to develop sophisticated high temperature manipulation capabilities such as selection of arbitrary axes rotation and rapid sample cooling. This program will investigate new classes of acoustic levitation in rectangular, cylindrical and spherical geometries. The program tasks include calculating theoretical expressions of the acoustic forces in these geometries for the excitation of up to three acoustic modes (multimodes). These calculations are used to: (1) determine those acoustic modes that produce stable levitation, (2) isolate the levitation and rotation capabilities to produce more than one axis of rotation, and (3) develop methods to translate samples down long tube cylindrical chambers. Experimental levitators will then be constructed to verify the stable levitation and rotation predictions of the models.

  18. Compact acoustic refrigerator

    DOEpatents

    Bennett, Gloria A.

    1992-01-01

    A compact acoustic refrigeration system actively cools components, e.g., electrical circuits (22), in a borehole environment. An acoustic engine (12, 14) includes first thermodynamic elements (12) for generating a standing acoustic wave in a selected medium. An acoustic refrigerator (16, 26, 28) includes second thermodynamic elements (16) located in the standing wave for generating a relatively cold temperature at a first end of the second thermodynamic elements (16) and a relatively hot temperature at a second end of the second thermodynamic elements (16). A resonator volume (18) cooperates with the first and second thermodynamic elements (12, 16) to support the standing wave. To accommodate the high heat fluxes required for heat transfer to/from the first and second thermodynamic elements (12, 16), first heat pipes (24, 26) transfer heat from the heat load (22) to the second thermodynamic elements (16) and second heat pipes (28, 32) transfer heat from first and second thermodynamic elements (12, 16) to the borehole environment.

  19. Simulating acoustic waves in spotted stars

    NASA Astrophysics Data System (ADS)

    Papini, Emanuele; Birch, Aaron C.; Gizon, Laurent; Hanasoge, Shravan M.

    2015-05-01

    Acoustic modes of oscillation are affected by stellar activity, however it is unclear how starspots contribute to these changes. Here we investigate the nonmagnetic effects of starspots on global modes with angular degree ℓ ≤ 2 in highly active stars, and characterize the spot seismic signature on synthetic light curves. We perform 3D time-domain simulations of linear acoustic waves to study their interaction with a model starspot. We model the spot as a 3D change in the sound speed stratification with respect to a convectively stable stellar background, built from solar Model S. We perform a parametric study by considering different depths and perturbation amplitudes. Exact numerical simulations allow the investigation of the wavefield-spot interaction beyond first order perturbation theory. The interaction of the axisymmetric modes with the starspot is strongly nonlinear. As mode frequency increases, the frequency shifts for radial modes exceed the value predicted by linear theory, while the shifts for the ℓ = 2,m = 0 modes are smaller than predicted by linear theory, with avoided-crossing-like patterns forming between the m = 0 and m = 1 mode frequencies. The nonlinear behavior increases with increasing spot amplitude and/or decreasing depth. Linear theory still reproduces the correct shifts for nonaxisymmetric modes. In the nonlinear regime the mode eigenfunctions are not pure spherical harmonics, but rather a mixture of different spherical harmonics. This mode mixing, together with the frequency changes, may lead to misidentification of the modes in the observed acoustic power spectra.

  20. Acoustic Streaming in Microgravity: Flow Stability and Heat Transfer Enhancement

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.

    1999-01-01

    Experimental results are presented for drops and bubbles levitated in a liquid host, with particular attention given to the effect of shape oscillations and capillary waves on the local flow fields. Some preliminary results are also presented on the use of streaming flows for the control of evaporation rate and rotation of electrostatically levitated droplets in 1 g. The results demonstrate the potential for the technological application of acoustic methods to active control of forced convection in microgravity.

  1. Numerical Techniques in Acoustics

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J. (Compiler)

    1985-01-01

    This is the compilation of abstracts of the Numerical Techniques in Acoustics Forum held at the ASME's Winter Annual Meeting. This forum was for informal presentation and information exchange of ongoing acoustic work in finite elements, finite difference, boundary elements and other numerical approaches. As part of this forum, it was intended to allow the participants time to raise questions on unresolved problems and to generate discussions on possible approaches and methods of solution.

  2. Wavefront modulation and subwavelength diffractive acoustics with an acoustic metasurface

    NASA Astrophysics Data System (ADS)

    Xie, Yangbo; Wang, Wenqi; Chen, Huanyang; Konneker, Adam; Popa, Bogdan-Ioan; Cummer, Steven A.

    2014-11-01

    Metasurfaces are a family of novel wavefront-shaping devices with planar profile and subwavelength thickness. Acoustic metasurfaces with ultralow profile yet extraordinary wave manipulating properties would be highly desirable for improving the performance of many acoustic wave-based applications. However, designing acoustic metasurfaces with similar functionality to their electromagnetic counterparts remains challenging with traditional metamaterial design approaches. Here we present a design and realization of an acoustic metasurface based on tapered labyrinthine metamaterials. The demonstrated metasurface can not only steer an acoustic beam as expected from the generalized Snell’s law, but also exhibits various unique properties such as conversion from propagating wave to surface mode, extraordinary beam-steering and apparent negative refraction through higher-order diffraction. Such designer acoustic metasurfaces provide a new design methodology for acoustic signal modulation devices and may be useful for applications such as acoustic imaging, beam steering, ultrasound lens design and acoustic surface wave-based applications.

  3. Wavefront modulation and subwavelength diffractive acoustics with an acoustic metasurface.

    PubMed

    Xie, Yangbo; Wang, Wenqi; Chen, Huanyang; Konneker, Adam; Popa, Bogdan-Ioan; Cummer, Steven A

    2014-11-24

    Metasurfaces are a family of novel wavefront-shaping devices with planar profile and subwavelength thickness. Acoustic metasurfaces with ultralow profile yet extraordinary wave manipulating properties would be highly desirable for improving the performance of many acoustic wave-based applications. However, designing acoustic metasurfaces with similar functionality to their electromagnetic counterparts remains challenging with traditional metamaterial design approaches. Here we present a design and realization of an acoustic metasurface based on tapered labyrinthine metamaterials. The demonstrated metasurface can not only steer an acoustic beam as expected from the generalized Snell's law, but also exhibits various unique properties such as conversion from propagating wave to surface mode, extraordinary beam-steering and apparent negative refraction through higher-order diffraction. Such designer acoustic metasurfaces provide a new design methodology for acoustic signal modulation devices and may be useful for applications such as acoustic imaging, beam steering, ultrasound lens design and acoustic surface wave-based applications.

  4. Acoustic detection of pneumothorax

    NASA Astrophysics Data System (ADS)

    Mansy, Hansen A.; Royston, Thomas J.; Balk, Robert A.; Sandler, Richard H.

    2003-04-01

    This study aims at investigating the feasibility of using low-frequency (<2000 Hz) acoustic methods for medical diagnosis. Several candidate methods of pneumothorax detection were tested in dogs. In the first approach, broadband acoustic signals were introduced into the trachea during end-expiration and transmitted waves were measured at the chest surface. Pneumothorax was found to consistently decrease pulmonary acoustic transmission in the 200-1200-Hz frequency band, while less change was observed at lower frequencies (p<0.0001). The ratio of acoustic energy between low (<220 Hz) and mid (550-770 Hz) frequency bands was significantly different in the control (healthy) and pneumothorax states (p<0.0001). The second approach measured breath sounds in the absence of an external acoustic input. Pneumothorax was found to be associated with a preferential reduction of sound amplitude in the 200- to 700-Hz range, and a decrease of sound amplitude variation (in the 300 to 600-Hz band) during the respiration cycle (p<0.01 for each). Finally, chest percussion was implemented. Pneumothorax changed the frequency and decay rate of percussive sounds. These results imply that certain medical conditions may be reliably detected using appropriate acoustic measurements and analysis. [Work supported by NIH/NHLBI #R44HL61108.

  5. 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. PMID:26723303

  6. 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.

  7. A compact acoustic recorder

    NASA Astrophysics Data System (ADS)

    Stein, Ronald

    1989-09-01

    The design and operation of a portable compact acoustic recorder is discussed. Designed to be used in arctic conditions for applications that require portable equipment, the device is configured to fit into a lightweight briefcase. It will operate for eight hours at -40 F with heat provided by a hot water bottle. It has proven to be an effective scientific tool in the measurement of underwater acoustic signals in arctic experiments. It has also been used successfully in warmer climates, e.g., in recording acoustic signals from small boats with no ac power. The acoustic recorder's cost is moderate since it is based on a Sony Walkman Professional (WM-D6C) tape recorder playback unit. A speaker and battery assembly and a hydrophone interface electronic assembly complete the system electronics. The interface assembly supplies a number of functions, including a calibration tone generator, an audio amplifier, and a hydrophone interface. Calibrated acoustic recordings can be made by comparing the calibration tone amplitude with the acoustic signal amplitude. The distortion of the recording is minimized by using a high quality, consumer tape recorder.

  8. Acoustic communication by ants

    NASA Astrophysics Data System (ADS)

    Hickling, Robert

    2002-05-01

    Many ant species communicate acoustically by stridulating, i.e., running a scraper over a washboard-like set of ridges. Ants appear to be insensitive to airborne sound. Consequently, myrmecologists have concluded that the stridulatory signals are transmitted through the substrate. This has tended to diminish the importance of acoustic communication, and it is currently believed that ant communication is based almost exclusively on pheromones, with acoustic communication assigned an almost nonexistent role. However, it can be shown that acoustic communication between ants is effective only if the medium is air and not the substrate. How, then, is it possible for ants to appear deaf to airborne sound and yet communicate through the air? An explanation is provided in a paper [R. Hickling and R. L. Brown, ``Analysis of acoustic communication by ants,'' J. Acoust. Soc. Am. 108, 1920-1929 (2000)]. Ants are small relative to the wavelengths they generate. Hence, they create a near field, which is characterized by a major increase in sound velocity (particle velocity of sound) in the vicinity of the source. Hair sensilla on the ants' antennae respond to sound velocity. Thus, ants are able to detect near-field sound from other ants and to exclude extraneous airborne sound.

  9. Oscillations of Quasars.

    PubMed

    McVittie, G C

    1964-10-01

    Rotation in addition to free gravitational motion can produce oscillations in a large spherical mass of gas. The theory may provide an explanation of the variations of brightness in such objects as 3C273.

  10. A novel photonic oscillator

    NASA Technical Reports Server (NTRS)

    Yao, X. S.; Maleki, L.

    1995-01-01

    We report a novel oscillator for photonic RF systems. This oscillator is capable of generating high-frequency signals up to 70 GHz in both electrical and optical domains and is a special voltage-controlled oscillator with an optical output port. It can be used to make a phase-locked loop (PLL) and perform all functions that a PLL is capable of for photonic systems. It can be synchronized to a reference source by means of optical injection locking, electrical injection locking, and PLL. It can also be self-phase locked and self-injection locked to generate a high-stability photonic RF reference. Its applications include high-frequency reference regeneration and distribution, high-gain frequency multiplication, comb-frequecy and square-wave generation, carrier recovery, and clock recovery. We anticipate that such photonic voltage-controlled oscillators (VCOs) will be as important to photonic RF systems as electrical VCOs are to electrical RF systems.

  11. Entraining synthetic genetic oscillators

    NASA Astrophysics Data System (ADS)

    Wagemakers, Alexandre; Buldú, Javier M.; Sanjuán, Miguel A. F.; de Luis, Oscar; Izquierdo, Adriana; Coloma, Antonio

    2009-09-01

    We propose a new approach for synchronizing a population of synthetic genetic oscillators, which consists in the entrainment of a colony of repressilators by external modulation. We present a model where the repressilator dynamics is affected by periodic changes in temperature. We introduce an additional plasmid in the bacteria in order to correlate the temperature variations with the enhancement of the transcription rate of a certain gene. This can be done by introducing a promoter that is related to the heat shock response. This way, the expression of that gene results in a protein that enhances the overall oscillations. Numerical results show coherent oscillations of the population for a certain range of the external frequency, which is in turn related to the natural oscillation frequency of the modified repressilator. Finally we study the transient times related with the loss of synchronization and we discuss possible applications in biotechnology of large-scale production coupled to synchronization events induced by heat shock.

  12. High frequency nanotube oscillator

    DOEpatents

    Peng, Haibing; Zettl, Alexander K.

    2012-02-21

    A tunable nanostructure such as a nanotube is used to make an electromechanical oscillator. The mechanically oscillating nanotube can be provided with inertial clamps in the form of metal beads. The metal beads serve to clamp the nanotube so that the fundamental resonance frequency is in the microwave range, i.e., greater than at least 1 GHz, and up to 4 GHz and beyond. An electric current can be run through the nanotube to cause the metal beads to move along the nanotube and changing the length of the intervening nanotube segments. The oscillator can operate at ambient temperature and in air without significant loss of resonance quality. The nanotube is can be fabricated in a semiconductor style process and the device can be provided with source, drain, and gate electrodes, which may be connected to appropriate circuitry for driving and measuring the oscillation. Novel driving and measuring circuits are also disclosed.

  13. A nonlinear oscillator

    SciTech Connect

    Tomlin, R.

    1990-01-27

    A nonlinear oscillator design was imported from Cornell modified, and built for the purpose of simulating the chaotic states of a forced pendulum. Similar circuits have been investigated in the recent nonlinear explosion.

  14. Oscillating fluid power generator

    SciTech Connect

    Morris, David C

    2014-02-25

    A system and method for harvesting the kinetic energy of a fluid flow for power generation with a vertically oriented, aerodynamic wing structure comprising one or more airfoil elements pivotably attached to a mast. When activated by the moving fluid stream, the wing structure oscillates back and forth, generating lift first in one direction then in the opposite direction. This oscillating movement is converted to unidirectional rotational movement in order to provide motive power to an electricity generator. Unlike other oscillating devices, this device is designed to harvest the maximum aerodynamic lift forces available for a given oscillation cycle. Because the system is not subjected to the same intense forces and stresses as turbine systems, it can be constructed less expensively, reducing the cost of electricity generation. The system can be grouped in more compact clusters, be less evident in the landscape, and present reduced risk to avian species.

  15. Ultrastable Multigigahertz Photonic Oscillator

    NASA Technical Reports Server (NTRS)

    Logan, Ronald T., Jr.

    1996-01-01

    Novel photonic oscillator developed to serve as ultrastable source of microwave and millimeter-wave signals. In system, oscillations generated photonically, then converted to electronic form. Includes self-mode-locked semiconductor laser producing stream of pulses, detected and fed back to laser as input. System also includes fiber-optic-delay-line discriminator, which detects fluctuations of self-mode-locking frequency and generates error signal used in negative-feedback loop to stabilize pulse-repetition frequency.

  16. Current oscillations in nanopores

    NASA Astrophysics Data System (ADS)

    Hyland, Brittany

    We develop a simple phenomenological model to describe current oscillations in single, conically shaped nanopores. The model utilizes aspects of reaction rate theory, electrochemical oscillators, and nonlinear dynamical systems. Time series of experimental data were analyzed and compared to time series simulated using the model equations. There is good qualitative agreement between experiment and simulation, though the model needs to be improved in order to obtain better quantitative agreement.

  17. Mathematical model of acoustic speech production with mobile walls of the vocal tract

    NASA Astrophysics Data System (ADS)

    Lyubimov, N. A.; Zakharov, E. V.

    2016-03-01

    A mathematical speech production model is considered that describes acoustic oscillation propagation in a vocal tract with mobile walls. The wave field function satisfies the Helmholtz equation with boundary conditions of the third kind (impedance type). The impedance mode corresponds to a threeparameter pendulum oscillation model. The experimental research demonstrates the nonlinear character of how the mobility of the vocal tract walls influence the spectral envelope of a speech signal.

  18. Oscillating edge-flames

    NASA Astrophysics Data System (ADS)

    Buckmaster, J.; Zhang, Yi

    1999-09-01

    It has been known for some years that when a near-limit flame spreads over a liquid pool of fuel, the edge of the flame can oscillate. It is also known that when a near-asphyxiated candle-flame burns in zero gravity, the edge of the (hemispherical) flame can oscillate violently prior to extinction. We propose that these oscillations are nothing more than a manifestation of the large Lewis number instability well known in chemical reactor studies and in combustion studies, one that is exacerbated by heat losses. As evidence of this we examine an edge-flame confined within a fuel-supply boundary and an oxygen-supply boundary, anchored by a discontinuity in data at the fuel-supply boundary. We show that when the Lewis number of the fuel is 2, and the Lewis number of the oxidizer is 1, oscillations of the edge occur when the Damköhler number is reduced below a critical value. During a single oscillation period there is a short premixed propagation stage and a long diffusion stage, behaviour that has been observed in flame spread experiments. Oscillations do not occur when both Lewis numbers are equal to 1.

  19. Periodically oscillating plasma sphere

    SciTech Connect

    Park, J.; Nebel, R.A.; Stange, S.; Murali, S. Krupakar

    2005-05-15

    The periodically oscillating plasma sphere, or POPS, is a novel fusion concept first proposed by D. C. Barnes and R. A. Nebel [Fusion Technol. 38, 28 (1998)]. POPS utilizes the self-similar collapse of an oscillating ion cloud in a spherical harmonic oscillator potential well formed by electron injection. Once the ions have been phase-locked, their coherent motion simultaneously produces very high densities and temperatures during the collapse phase of the oscillation. A requirement for POPS is that the electron injection produces a stable harmonic oscillator potential. This has been demonstrated in a gridded inertial electrostatic confinement device and verified by particle simulation. Also, the POPS oscillation has been confirmed experimentally through observation that the ions in the potential well exhibit resonance behavior when driven at the POPS frequency. Excellent agreement between the observed POPS frequencies and the theoretical predictions has been observed for a wide range of potential well depths and three different ion species. Practical applications of POPS require large plasma compressions. These large compressions have been observed in particle simulations, although space charge neutralization remains a major issue.

  20. Oscillating asymmetric dark matter

    SciTech Connect

    Tulin, Sean; Yu, Hai-Bo; Zurek, Kathryn M. E-mail: haiboyu@umich.edu

    2012-05-01

    We study the dynamics of dark matter (DM) particle-antiparticle oscillations within the context of asymmetric DM. Oscillations arise due to small DM number-violating Majorana-type mass terms, and can lead to recoupling of annihilation after freeze-out and washout of the DM density. Asymmetric DM oscillations 'interpolate' between symmetric and asymmetric DM freeze-out scenarios, and allow for a larger DM model-building parameter space. We derive the density matrix equations for DM oscillations and freeze-out from first principles using nonequilibrium field theory, and our results are qualitatively different than in previous studies. DM dynamics exhibits particle-vs-antiparticle 'flavor' effects, depending on the interaction type, analogous to neutrino oscillations in a medium. 'Flavor-sensitive' DM interactions include scattering or annihilation through a new vector boson, while 'flavor-blind' interactions include scattering or s-channel annihilation through a new scalar boson. In particular, we find that flavor-sensitive annihilation does not recouple when coherent oscillations begin, and that flavor-blind scattering does not lead to decoherence.

  1. Experimental study on inter-particle acoustic forces.

    PubMed

    Garcia-Sabaté, Anna; Castro, Angélica; Hoyos, Mauricio; González-Cinca, Ricard

    2014-03-01

    A method for the experimental measurement of inter-particle forces (secondary Bjerknes force) generated by the action of an acoustic field in a resonator micro-channel is presented. The acoustic radiation force created by an ultrasonic standing wave moves suspended particles towards the pressure nodes and the acoustic pressure induces particle volume oscillations. Once particles are in the levitation plane, transverse and secondary Bjerknes forces become important. Experiments were carried out in a resonator filled with a suspension composed of water and latex particles of different size (5-15 μm) at different concentrations. Ultrasound was generated by means of a 2.5 MHz nominal frequency transducer. For the first time the acoustic force generated by oscillating particles acting on other particles has been measured, and the critical interaction distance in various cases has been determined. Inter-particle forces on the order of 10(-14) N have been measured by using this method. PMID:24606249

  2. Acoustic analog of a free-electron laser

    SciTech Connect

    Zavtrak, S.T.

    1995-12-31

    As well known, at the present time there are many types of laser the operation of which is based on the stimulated emission of light by an active medium. Lasers are generators of coherent electromagnetic waves in the range from ultraviolet to submillimeters. But acoustic analogs of such devices have not been created up to now in spite of the progress in laser technology. Meanwhile, an acoustic laser could have a lot of interesting applications. Recently a theoretical scheme for an acoustic laser was proposed by the present author. A liquid dielectric with dispersed particles was considered as an active medium. The pumping was created by an oscillating electric field deforming dispersed particle volumes. Different types of oils or distilled water can serve as a liquid dielectric with gas bubbles as dispersed particles. Gas bubbles in water can be created by an electrolysis. The phase bunching of the initially incoherent emitters (gas bubbles) was realized by acoustic radiation forces. This scheme is an analog of the free-electron laser (FEL). It was shown that two types of losses must be overcome for the beginning of a generation. The first type results from the energy dissipation in the active medium and the second one is caused by radiation losses at the boundaries of the resonator. The purposes of this report are: (1) to discuss the analogies between the acoustic laser and FEL; (2) to propose an effective scheme of an acoustic laser with a mechanical pumping (by a piezoelectric emitter of the piston type); (3) to consider the schemes of acoustic lasers with the different types of the resonators (rectangular and cylindrical); (4) to discuss the possibility of the creation of an impact acoustic laser (5) to discuss the experimental works which are planned to be carried out in cooperation with prof. L.A. Crum.

  3. Long-lived coherent traveling acoustic pulses induced by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Wang, Jincheng; Guo, Chunlei

    2007-11-01

    In this paper, we systematically study the generation and propagation of coherent acoustic pulses in a metal-dielectric system using a two-color femtosecond pump-probe technique at different probe angles. A long-lived acoustic oscillation is observed in a borosilicate glass coated with gold and shows different attenuations and amplitude at different probe wavelengths. Our study demonstrates that the two-color optical pump-probe technique can be used as a noninvasive tool to study acoustic properties of dielectric materials.

  4. On the motion of a small sphere in acoustic standing waves

    NASA Astrophysics Data System (ADS)

    Saito, Makoto; Kamimura, Heihachiro

    Analysis of the oscillatory motion of a small Stylofoam sphere in the acoustic resonant chamber is reported. The acoustic standing waves in the resonant chamber are assumed to consist of the first and second harmonics. It is found that the period of the oscillation of the sphere is given by the complete elliptic integral of the first kind, and the motion can be expressed by the sn function. The calculated results are compared with the experimental data and the King's calculation in which only the first harmonic of the acoustic waves is considered.

  5. Temporal characteristics of surface-acoustic-wave-driven luminescence from a lateral p-n junction

    NASA Astrophysics Data System (ADS)

    Gell, J. R.; Ward, M. B.; Shields, A. J.; Atkinson, P.; Bremner, S. P.; Anderson, D.; Kataoka, M.; Barnes, C. H. W.; Jones, G. A. C.; Ritchie, D. A.

    2007-07-01

    Short radio frequency pulses were used to study the surface-acoustic-wave-driven light emission from a molecular beam epitaxy regrown GaAs /AlGaAs lateral p-n junction. The luminescence provides a fast probe of the signals arriving at the junction allowing the authors to temporally separate the effect of the surface-acoustic-wave from pickup of the free space electromagnetic wave. Oscillations in the light intensity are resolved at the resonant frequency of the transducer, suggesting that the surface-acoustic-wave is transporting electrons across the junction in packets.

  6. Neuronal oscillations in sleep: insights from functional neuroimaging.

    PubMed

    Dang-Vu, Thien Thanh

    2012-09-01

    Recent functional neuroimaging studies have investigated brain activity patterns during sleep in humans, beyond the conventionally defined sleep stages. These works have characterized the neural activations related to the major brain oscillations of sleep, that is, spindles and slow waves during non-rapid-eye-movement sleep and ponto-geniculo-occipital waves during rapid-eye-movement sleep. These phasic events have been found associated with increases of brain activity in specific neural networks, which identify structures involved in the generation of sleep oscillations. Most importantly, these results confirm that, even during the deepest stages of sleep, neuronal network activities are sustained and organized by spontaneous brain oscillations of sleep. The understanding of the neural mechanisms underlying sleep oscillations is fundamental since increasing evidence suggests a pivotal role for these rhythms in the functional properties of sleep. In particular, interactions between the sleeping brain and the surrounding environment are closely modulated by neuronal oscillations of sleep. Functional neuroimaging studies have demonstrated that spindles distort the transmission of auditory information to the cortex, therefore isolating the brain from external disturbances during sleep. In contrast, slow waves evoked by acoustic stimulation--and also termed K-complexes--are associated with larger auditory cortex activation, thus reflecting an enhanced processing of external information during sleep. Future brain imaging studies of sleep should further explore the contribution of neuronal oscillations to the off-line consolidation of memory during sleep.

  7. The active-bridge oscillator

    SciTech Connect

    Wessendorf, K.O.

    1998-07-01

    This paper describes the Active-Bridge Oscillator (ABO), a new concept in high-stability oscillator design. The ABO is ab ridge-type oscillator design that is easly to design and overcomes many of the operational and design difficulties associated with standard bridge oscillator designs. The ABO will oscillate with a very stable output amplitude over a wide range of operating conditions without the use of an automatic-level-control (ALC). A standard bridge oscillator design requires an ALC to maintain the desired amplitude of oscillation. for this and other reasons, bridge oscilaltors are not used in mainstream designs. Bridge oscillators are generally relegated to relatively low-volume, high-performance applications. The Colpitts and Pierce designs are the most popular oscillators but are typically less stable than a bridge-type oscillator.

  8. Measuring acoustic habitats

    PubMed Central

    Merchant, Nathan D; Fristrup, Kurt M; Johnson, Mark P; Tyack, Peter L; Witt, Matthew J; Blondel, Philippe; Parks, Susan E

    2015-01-01

    1. Many organisms depend on sound for communication, predator/prey detection and navigation. The acoustic environment can therefore play an important role in ecosystem dynamics and evolution. A growing number of studies are documenting acoustic habitats and their influences on animal development, behaviour, physiology and spatial ecology, which has led to increasing demand for passive acoustic monitoring (PAM) expertise in the life sciences. However, as yet, there has been no synthesis of data processing methods for acoustic habitat monitoring, which presents an unnecessary obstacle to would-be PAM analysts. 2. Here, we review the signal processing techniques needed to produce calibrated measurements of terrestrial and aquatic acoustic habitats. We include a supplemental tutorial and template computer codes in matlab and r, which give detailed guidance on how to produce calibrated spectrograms and statistical analyses of sound levels. Key metrics and terminology for the characterisation of biotic, abiotic and anthropogenic sound are covered, and their application to relevant monitoring scenarios is illustrated through example data sets. To inform study design and hardware selection, we also include an up-to-date overview of terrestrial and aquatic PAM instruments. 3. Monitoring of acoustic habitats at large spatiotemporal scales is becoming possible through recent advances in PAM technology. This will enhance our understanding of the role of sound in the spatial ecology of acoustically sensitive species and inform spatial planning to mitigate the rising influence of anthropogenic noise in these ecosystems. As we demonstrate in this work, progress in these areas will depend upon the application of consistent and appropriate PAM methodologies. PMID:25954500

  9. Acoustic radiation from weakly wrinkled premixed flames

    SciTech Connect

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

    2006-01-01

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

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

    SciTech Connect

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

    2014-04-21

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

  11. Optical Heterodyne Investigation of the Microwave Frequency Acoustic Properties of Liquids.

    NASA Astrophysics Data System (ADS)

    Bonney, Rob

    An optical heterodyne interferometer with a state -of-the-art microwave frequency acoustic transducer was used to measure the acoustic properties of liquids and solutions at frequencies up to 1.5 GHz. Heterodyne detection with a strong optical local oscillator was used to detect a weak optical signal beam produced by Bragg deflection from an acoustic wave coupled into a liquid sample. The acoustic transducer had a frequency range of 0.2-1.5 GHz. Several liquid mixtures were measured for the first time, including aqueous dimethyl sulfoxide, and ethyl acetate in carbon disulphide. In some cases, previously unknown dispersions were characterized. A thermodynamic model (valid in the low frequency limit) involving the heat of mixing was used successfully to predict the variation of velocity with composition of liquid mixtures. With this model as a guide, an attempt was made to identify a liquid mixture which would make a superior medium for the acoustic microscope. The search produced results which supported theoretical predictions, but no superior medium was found. Solutions of biomolecules were also investigated due to interest in possible resonant acoustic modes in DNA. No dispersions or resonances were found in solutions of polyglycines, and results for DNA solutions were inconclusive. Applications of this work include general studies in liquid acoustics at very high frequencies, acoustic studies of DNA solutions, and characterization of media for such technological applications as acoustic microscopy or phase conjugation using stimulated Brillouin scattering.

  12. Neutrino Oscillation Physics

    SciTech Connect

    Kayser, Boris

    2012-06-01

    To complement the neutrino-physics lectures given at the 2011 International School on Astro Particle Physics devoted to Neutrino Physics and Astrophysics (ISAPP 2011; Varenna, Italy), at the 2011 European School of High Energy Physics (ESHEP 2011; Cheila Gradistei, Romania), and, in modified form, at other summer schools, we present here a written description of the physics of neutrino oscillation. This description is centered on a new way of deriving the oscillation probability. We also provide a brief guide to references relevant to topics other than neutrino oscillation that were covered in the lectures. Neutrinos and photons are by far the most abundant elementary particles in the universe. Thus, if we would like to comprehend the universe, we must understand the neutrinos. Of course, studying the neutrinos is challenging, since the only known forces through which these electrically-neutral leptons interact are the weak force and gravity. Consequently, interactions of neutrinos in a detector are very rare events, so that very large detectors and intense neutrino sources are needed to make experiments feasible. Nevertheless, we have confirmed that the weak interactions of neutrinos are correctly described by the Standard Model (SM) of elementary particle physics. Moreover, in the last 14 years, we have discovered that neutrinos have nonzero masses, and that leptons mix. These discoveries have been based on the observation that neutrinos can change from one 'flavor' to another - the phenomenon known as neutrino oscillation. We shall explain the physics of neutrino oscillation, deriving the probability of oscillation in a new way. We shall also provide a very brief guide to references that can be used to study some major neutrino-physics topics other than neutrino oscillation.

  13. Solar oscillation frequency and solar neutrino predictions

    SciTech Connect

    Cox, A.N.

    1990-07-05

    The light and velocity variations of the Sun and solar-like stars are unique among intrinsic variable stars. Unlike all other standard classes, such as Cepheids, B stars, and white dwarfs, the pulsation driving is caused by coupling with the acoustic noise in the upper convection zone. Each global pulsation mode is just another degree of freedom for the turbulent convection, and energy is shared equally between these g{sup {minus}}-modes and the solar oscillation modes. This driving and damping, together with the normal stellar pulsation mechanisms produce extremely low amplitude solar oscillations. Actually, the surface layer radiative damping is strong, and the varying oscillation mode amplitudes manifest the stochastic convection driving and the steady damping. Thus stability calculations for solar-like pulsations are difficult and mostly inconclusive, but calculations of pulsation periods are as straightforward as for all the other classes of intrinsic variable stars. The issue that is important for the Sun is its internal structure, because the mass, radius, and luminosity are extremely well known. Conventionally, we need the pulsation constants for each of millions of modes. Unknown parameters for constructing solar models are the composition and its material pressure, energy, and opacity, as well as the convection mixing length. We treat the nuclear energy and neutrino production formulas as sufficiently well known. The presence of weakly interacting massive particles (WIMPs) orbiting the solar center affects the predicted oscillation frequencies so that they do not agree with observations as well as those for models without WIMPs. 34 refs., 4 figs.

  14. Acoustic phonon dynamics in thin-films of the topological insulator Bi{sub 2}Se{sub 3}

    SciTech Connect

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

    2015-04-28

    Transient reflectivity traces measured for nanometer-sized films (6–40 nm) of the topological insulator Bi{sub 2}Se{sub 3} revealed GHz-range oscillations driven within the relaxation of hot carriers photoexcited with ultrashort (∼100 fs) laser pulses of 1.51 eV photon energy. These oscillations have been suggested to result from acoustic phonon dynamics, including coherent longitudinal acoustic phonons in the form of standing acoustic waves. An increase of oscillation frequency from ∼35 to ∼70 GHz with decreasing film thickness from 40 to 15 nm was attributed to the interplay between two different regimes employing traveling-acoustic-waves for films thicker than 40 nm and the film bulk acoustic wave resonator (FBAWR) modes for films thinner than 40 nm. The amplitude of oscillations decays rapidly for films below 15 nm thick when the indirect intersurface coupling in Bi{sub 2}Se{sub 3} films switches the FBAWR regime to that of the Lamb wave excitation. The frequency range of coherent longitudinal acoustic phonons is in good agreement with elastic properties of Bi{sub 2}Se{sub 3}.

  15. [Acoustic characteristics of classrooms].

    PubMed

    Koszarny, Zbigniew; Chyla, Andrzej

    2003-01-01

    Quality and usefulness of school rooms for transmission of verbal information depends on the two basic parameters: form and quantity of the reverberation time, and profitable line measurements of school rooms from the acoustic point of view. An analysis of the above-mentioned parameters in 48 class rooms and two gymnasiums in schools, which were built in different periods, shows that the most important problem is connected with too long reverberation time and inappropriate acoustic proportions. In schools built in the 1970s, the length of reverberation time is mostly within a low frequency band, while in schools built contemporarily, the maximum length of disappearance time takes place in a quite wide band of 250-2000 Hz. This exceeds optimal values for that kind of rooms at least twice, and five times in the newly built school. A long reverberation time is connected with a low acoustic absorption of school rooms. Moreover, school rooms are characterised by inappropriate acoustic proportions. The classrooms, in their relation to the height, are too long and too wide. It is connected with deterioration of the transmission of verbal information. The data show that this transmission is unequal. Automatically, it leads to a speech disturbance and difficulties with understanding. There is the need for adaptation of school rooms through increase of an acoustic absorption.

  16. Acoustic emission monitoring system

    DOEpatents

    Romrell, Delwin M.

    1977-07-05

    Methods and apparatus for identifying the source location of acoustic emissions generated within an acoustically conductive medium. A plurality of acoustic receivers are communicably coupled to the surface of the medium at a corresponding number of spaced locations. The differences in the reception time of the respective sensors in response to a given acoustic event are measured among various sensor combinations prescribed by the monitoring mode employed. Acoustic reception response encountered subsequent to the reception by a predetermined number of the prescribed sensor combinations are inhibited from being communicated to the processing circuitry, while the time measurements obtained from the prescribed sensor combinations are translated into a position measurement representative of the location on the surface most proximate the source of the emission. The apparatus is programmable to function in six separate and five distinct operating modes employing either two, three or four sensory locations. In its preferred arrangement the apparatus of this invention will re-initiate a monitoring interval if the predetermined number of sensors do not respond to a particular emission within a given time period.

  17. Overview of Solar Seismology: Oscillations as Probes of Internal Structure and Dynamics in the Sun

    NASA Technical Reports Server (NTRS)

    Toomre, J.

    1984-01-01

    The physical nature of solar oscillations is reviewed. The nomenclature of the subject and the techniques used to interpret the oscillations are discussed. Many of the acoustic and gravity waves that can be observed in the atmosphere of the Sun are actually resonant or standing modes of the interior; precise measurements of the frequencies of such modes allow deductions of the internal structure and dynamics of this star. The scientific objectives of such studies of solar seismic disturbances, or of solar seismology, are outlined. The reasons why it would be very beneficial to carry out further observations of solar oscillations both from ground based networks and from space will be discussed.

  18. Core-centering of compound drops in capillary oscillations: Observations on USML-1 experiments in space

    NASA Technical Reports Server (NTRS)

    Wang, Taylor G.; Anikumar, A. V.; Lee, C. P.; Lin, K. C.

    1994-01-01

    AA Using the existing inviscid theories, an attempt is made to explain the centering of the oscillating liquid shell. Experiments on liquid shells and liquid-core compound drops were conducted using acoustic levitation, in a low-gravity environment during a Space Shuttle flight. It was observed that their inner and outer interfaces became concentric when excited into capillary oscillations. Using the existing inviscid theories, and attempt is made to explain the centering of the oscillating liquid shell. It is concluded that viscosity needs to be considered in order to provide a realistic description of the centering process.

  19. Finite q-oscillator

    NASA Astrophysics Data System (ADS)

    Atakishiyev, Natig M.; Klimyk, Anatoliy U.; Wolf, Kurt Bernardo

    2004-05-01

    The finite q-oscillator is a model that obeys the dynamics of the harmonic oscillator, with the operators of position, momentum and Hamiltonian being functions of elements of the q-algebra suq(2). The spectrum of position in this discrete system, in a fixed representation j, consists of 2j + 1 'sensor'-points x_s={\\case12}[2s]_q, s\\in\\{-j,-j+1,\\ldots,j\\} , and similarly for the momentum observable. The spectrum of energies is finite and equally spaced, so the system supports coherent states. The wavefunctions involve dual q-Kravchuk polynomials, which are solutions to a finite-difference Schrödinger equation. Time evolution (times a phase) defines the fractional Fourier-q-Kravchuk transform. In the classical limit as q rarr 1 we recover the finite oscillator Lie algebra, the N = 2j rarr infin limit returns the Macfarlane-Biedenharn q-oscillator and both limits contract the generators to the standard quantum-mechanical harmonic oscillator.

  20. Oscillations of soap bubbles

    NASA Astrophysics Data System (ADS)

    Kornek, U.; Müller, F.; Harth, K.; Hahn, A.; Ganesan, S.; Tobiska, L.; Stannarius, R.

    2010-07-01

    Oscillations of droplets or bubbles of a confined fluid in a fluid environment are found in various situations in everyday life, in technological processing and in natural phenomena on different length scales. Air bubbles in liquids or liquid droplets in air are well-known examples. Soap bubbles represent a particularly simple, beautiful and attractive system to study the dynamics of a closed gas volume embedded in the same or a different gas. Their dynamics is governed by the densities and viscosities of the gases and by the film tension. Dynamic equations describing their oscillations under simplifying assumptions have been well known since the beginning of the 20th century. Both analytical description and numerical modeling have made considerable progress since then, but quantitative experiments have been lacking so far. On the other hand, a soap bubble represents an easily manageable paradigm for the study of oscillations of fluid spheres. We use a technique to create axisymmetric initial non-equilibrium states, and we observe damped oscillations into equilibrium by means of a fast video camera. Symmetries of the oscillations, frequencies and damping rates of the eigenmodes as well as the coupling of modes are analyzed. They are compared to analytical models from the literature and to numerical calculations from the literature and this work.

  1. Wave velocity dispersion and attenuation in media exhibiting internal oscillations

    NASA Astrophysics Data System (ADS)

    Frehner, Marcel; Steeb, Holger; Schmalholz, Stefan M.

    2010-05-01

    Understanding the dynamical and acoustical behavior of porous and heterogeneous rocks is of great importance in geophysics, e.g. earthquakes, and for various seismic engineering applications, e.g. hydrocarbon exploration. Within a heterogeneous medium oscillations with a characteristic resonance frequency, depending on the mass and internal length of the heterogeneity, can occur. When excited, heterogeneities can self-oscillate with their natural frequency. Another example of internal oscillations is the dynamical behavior of non-wetting fluid blobs or fluid patches in residually saturated pore spaces. Surface tension forces or capillary forces act as the restoring force that drives the oscillation. Whatever mechanism is involved, an oscillatory phenomena within a heterogeneous medium will have an effect on acoustic or seismic waves propagating through such a medium, i.e. wave velocity dispersion and frequency-dependent attenuation. We present two models for media exhibiting internal oscillations and discuss the frequency-dependent wave propagation mechanism. Both models give similar results: (1) The low-frequency (i.e. quasi-static) limit for the phase velocity is identical with the Gassmann-Wood limit and the high-frequency limit is larger than this value and (2) Around the resonance frequency a very strong phase velocity change and the largest attenuation occurs. (1) Model for a homogeneous medium exhibiting internal oscillations We present a continuum model for an acoustic medium exhibiting internal damped oscillations. The obvious application of this model is water containing oscillating gas bubbles, providing the material and model parameters for this study. Two physically based momentum interaction terms between the two inherent constituents are used: (1) A purely elastic term of oscillatory nature that scales with the volume of the bubbles and (2) A viscous term that scales with the specific surface of the bubble. The model is capable of taking into account

  2. ACOUSTICS IN ARCHITECTURAL DESIGN, AN ANNOTATED BIBLIOGRAPHY ON ARCHITECTURAL ACOUSTICS.

    ERIC Educational Resources Information Center

    DOELLE, LESLIE L.

    THE PURPOSE OF THIS ANNOTATED BIBLIOGRAPHY ON ARCHITECTURAL ACOUSTICS WAS--(1) TO COMPILE A CLASSIFIED BIBLIOGRAPHY, INCLUDING MOST OF THOSE PUBLICATIONS ON ARCHITECTURAL ACOUSTICS, PUBLISHED IN ENGLISH, FRENCH, AND GERMAN WHICH CAN SUPPLY A USEFUL AND UP-TO-DATE SOURCE OF INFORMATION FOR THOSE ENCOUNTERING ANY ARCHITECTURAL-ACOUSTIC DESIGN…

  3. Surface Acoustic Wave Microfluidics

    NASA Astrophysics Data System (ADS)

    Yeo, Leslie Y.; Friend, James R.

    2014-01-01

    Fluid manipulations at the microscale and beyond are powerfully enabled through the use of 10-1,000-MHz acoustic waves. A superior alternative in many cases to other microfluidic actuation techniques, such high-frequency acoustics is almost universally produced by surface acoustic wave devices that employ electromechanical transduction in wafer-scale or thin-film piezoelectric media to generate the kinetic energy needed to transport and manipulate fluids placed in adjacent microfluidic structures. These waves are responsible for a diverse range of complex fluid transport phenomena - from interfacial fluid vibration and drop and confined fluid transport to jetting and atomization - underlying a flourishing research literature spanning fundamental fluid physics to chip-scale engineering applications. We highlight some of this literature to provide the reader with a historical basis, routes for more detailed study, and an impression of the field's future directions.

  4. Acoustic particle separation

    NASA Technical Reports Server (NTRS)

    Barmatz, M. B.; Stoneburner, J. D.; Jacobi, N.; Wang, T. (Inventor)

    1985-01-01

    A method is described which uses acoustic energy to separate particles of different sizes, densities, or the like. The method includes applying acoustic energy resonant to a chamber containing a liquid of gaseous medium to set up a standing wave pattern that includes a force potential well wherein particles within the well are urged towards the center, or position of minimum force potential. A group of particles to be separated is placed in the chamber, while a non-acoustic force such as gravity is applied, so that the particles separate with the larger or denser particles moving away from the center of the well to a position near its edge and progressively smaller lighter particles moving progressively closer to the center of the well. Particles are removed from different positions within the well, so that particles are separated according to the positions they occupy in the well.

  5. Acoustic Levitation Containerless Processing

    NASA Technical Reports Server (NTRS)

    Whymark, R. R.; Rey, C. A.

    1985-01-01

    This research program consists of the development of acoustic containerless processing systems with applications in the areas of research in material sciences, as well as the production of new materials, solid forms with novel and unusual microstructures, fusion target spheres, and improved optical fibers. Efforts have been focused on the containerless processing at high temperatures for producing new kinds of glasses. Also, some development has occurred in the areas of containerlessly supporting liquids at room temperature, with applications in studies of fluid dynamics, potential undercooling of liquids, etc. The high temperature area holds the greatest promise for producing new kinds of glasses and ceramics, new alloys, and possibly unusual structural shapes, such as very uniform hollow glass shells for fusion target applications. High temperature acoustic levitation required for containerless processing has been demonstrated in low-g environments as well as in ground-based experiments. Future activities include continued development of the signals axis acoustic levitator.

  6. Acoustic energy shaping

    NASA Technical Reports Server (NTRS)

    Wang, T. G.; Elleman, D. D. (Inventor)

    1977-01-01

    A suspended mass is shaped by melting all or a selected portion of the mass and applying acoustic energy in varying amounts to different portions of the mass. In one technique for forming an optical waveguide slug, a mass of oval section is suspended and only a portion along the middle of the cross-section is heated to a largely fluid consistency. Acoustic energy is applied to opposite edges of the oval mass to press the unheated opposite edge portions together so as to form bulges at the middle of the mass. In another technique for forming a ribbon of silicon for constructing solar cells, a cylindrical thread of silicon is drawn from a molten mass of silicon, and acoustic energy is applied to opposite sides of the molten thread to flatten it into a ribbon.

  7. Passive broadband acoustic thermometry

    NASA Astrophysics Data System (ADS)

    Anosov, A. A.; Belyaev, R. V.; Klin'shov, V. V.; Mansfel'd, A. D.; Subochev, P. V.

    2016-04-01

    The 1D internal (core) temperature profiles for the model object (plasticine) and the human hand are reconstructed using the passive acoustothermometric broadband probing data. Thermal acoustic radiation is detected by a broadband (0.8-3.5 MHz) acoustic radiometer. The temperature distribution is reconstructed using a priori information corresponding to the experimental conditions. The temperature distribution for the heated model object is assumed to be monotonic. For the hand, we assume that the temperature distribution satisfies the heat-conduction equation taking into account the blood flow. The average error of reconstruction determined for plasticine from the results of independent temperature measurements is 0.6 K for a measuring time of 25 s. The reconstructed value of the core temperature of the hand (36°C) generally corresponds to physiological data. The obtained results make it possible to use passive broadband acoustic probing for measuring the core temperatures in medical procedures associated with heating of human organism tissues.

  8. Latticed pentamode acoustic cloak.

    PubMed

    Chen, Yi; Liu, Xiaoning; Hu, Gengkai

    2015-01-01

    We report in this work a practical design of pentamode acoustic cloak with microstructure. The proposed cloak is assembled by pentamode lattice made of a single-phase solid material. The function of rerouting acoustic wave round an obstacle has been demonstrated numerically. It is also revealed that shear related resonance due to weak shear resistance in practical pentamode lattices punctures broadband feature predicted based on ideal pentamode cloak. As a consequence, the latticed pentamode cloak can only conceal the obstacle in segmented frequency ranges. We have also shown that the shear resonance can be largely reduced by introducing material damping, and an improved broadband performance can be achieved. These works pave the way for experimental demonstration of pentamode acoustic cloak. PMID:26503821

  9. Latticed pentamode acoustic cloak

    PubMed Central

    Chen, Yi; Liu, Xiaoning; Hu, Gengkai

    2015-01-01

    We report in this work a practical design of pentamode acoustic cloak with microstructure. The proposed cloak is assembled by pentamode lattice made of a single-phase solid material. The function of rerouting acoustic wave round an obstacle has been demonstrated numerically. It is also revealed that shear related resonance due to weak shear resistance in practical pentamode lattices punctures broadband feature predicted based on ideal pentamode cloak. As a consequence, the latticed pentamode cloak can only conceal the obstacle in segmented frequency ranges. We have also shown that the shear resonance can be largely reduced by introducing material damping, and an improved broadband performance can be achieved. These works pave the way for experimental demonstration of pentamode acoustic cloak. PMID:26503821

  10. A New Wave of Acoustics.

    ERIC Educational Resources Information Center

    Beyer, Robert

    1981-01-01

    Surveys 50 years of acoustical studies by discussing selected topics including the ear, nonlinear representations, underwater sound, acoustical diagnostics, absorption, electrolytes, phonons, magnetic interaction, and superfluidity and the five sounds. (JN)

  11. Resonance frequencies of lipid-shelled microbubbles in the regime of nonlinear oscillations

    PubMed Central

    Doinikov, Alexander A.; Haac, Jillian F.; Dayton, Paul A.

    2009-01-01

    Knowledge of resonant frequencies of contrast microbubbles is important for the optimization of ultrasound contrast imaging and therapeutic techniques. To date, however, there are estimates of resonance frequencies of contrast microbubbles only for the regime of linear oscillation. The present paper proposes an approach for evaluating resonance frequencies of contrast agent microbubbles in the regime of nonlinear oscillation. The approach is based on the calculation of the time-averaged oscillation power of the radial bubble oscillation. The proposed procedure was verified for free bubbles in the frequency range 1–4 MHz and then applied to lipid-shelled microbubbles insonified with a single 20-cycle acoustic pulse at two values of the acoustic pressure amplitude, 100 kPa and 200 kPa, and at four frequencies: 1.5, 2.0, 2.5, and 3.0 MHz. It is shown that, as the acoustic pressure amplitude is increased, the resonance frequency of a lipid-shelled microbubble tends to decrease in comparison with its linear resonance frequency. Analysis of existing shell models reveals that models that treat the lipid shell as a linear viscoelastic solid appear may be challenged to provide the observed tendency in the behavior of the resonance frequency at increasing acoustic pressure. The conclusion is drawn that the further development of shell models could be improved by the consideration of nonlinear rheological laws. PMID:18977009

  12. Neural Oscillations Carry Speech Rhythm through to Comprehension

    PubMed Central

    Peelle, Jonathan E.; Davis, Matthew H.

    2012-01-01

    A key feature of speech is the quasi-regular rhythmic information contained in its slow amplitude modulations. In this article we review the information conveyed by speech rhythm, and the role of ongoing brain oscillations in listeners’ processing of this content. Our starting point is the fact that speech is inherently temporal, and that rhythmic information conveyed by the amplitude envelope contains important markers for place and manner of articulation, segmental information, and speech rate. Behavioral studies demonstrate that amplitude envelope information is relied upon by listeners and plays a key role in speech intelligibility. Extending behavioral findings, data from neuroimaging – particularly electroencephalography (EEG) and magnetoencephalography (MEG) – point to phase locking by ongoing cortical oscillations to low-frequency information (~4–8 Hz) in the speech envelope. This phase modulation effectively encodes a prediction of when important events (such as stressed syllables) are likely to occur, and acts to increase sensitivity to these relevant acoustic cues. We suggest a framework through which such neural entrainment to speech rhythm can explain effects of speech rate on word and segment perception (i.e., that the perception of phonemes and words in connected speech is influenced by preceding speech rate). Neuroanatomically, acoustic amplitude modulations are processed largely bilaterally in auditory cortex, with intelligible speech resulting in differential recruitment of left-hemisphere regions. Notable among these is lateral anterior temporal cortex, which we propose functions in a domain-general fashion to support ongoing memory and integration of meaningful input. Together, the reviewed evidence suggests that low-frequency oscillations in the acoustic speech signal form the foundation of a rhythmic hierarchy supporting spoken language, mirrored by phase-locked oscillations in the human brain. PMID:22973251

  13. Digital numerically controlled oscillator

    NASA Technical Reports Server (NTRS)

    Cellier, A.; Huey, D. C.; Ma, L. N. (Inventor)

    1980-01-01

    The frequency and phase of an output signal from an oscillator circuit are controlled with accuracy by a digital input word. Positive and negative alterations in output frequency are both provided for by translating all values of input words so that they are positive. The oscillator reference frequency is corrected only in one direction, by adding phase to the output frequency of the oscillator. The input control word is translated to a single algebraic sign and the digital 1 is added thereto. The translated input control word is then accumulated. A reference clock signal having a frequency at an integer multiple of the desired frequency of the output signal is generated. The accumulated control word is then compared with a threshold level. The output signal is adjusted in a single direction by dividing the frequency of the reference clock signal by a first integer or by an integer different from the first integer.

  14. The Fastest Quasiperiodic Oscillations

    NASA Astrophysics Data System (ADS)

    Kaaret, Philip

    Quasi-periodic oscillations (QPOs) at frequencies near 1000 Hz have been detected from a umber of neutron star x-ray binaries using RXTE. These fast oscillations are likely associated with rbital motion very close to the neutron star and and, thus, give us information about the behavior of the accretion disk in the strong gravitational field near the neutron star. The oscillation frequencies can also be used to place constraints on the properties of the neutron stars with the highest detected frequencies being the most constraining. We propose TOOs observations of selected neutron star x-ray binaries when found to be in states likely to produce kHz QPOs with frequencies exceeding 1200 Hz.

  15. Aspherical bubble dynamics and oscillation times

    SciTech Connect

    Vogel, A.; Noack, J.; Chapyak, E.J.; Godwin, R.P.

    1999-06-01

    The cavitation bubbles common in laser medicine are rarely perfectly spherical and are often located near tissue boundaries, in vessels, etc., which introduce aspherical dynamics. Here, novel features of aspherical bubble dynamics are explored by time-resolved photography and numerical simulations. The growth-collapse period of cylindrical bubbles of large aspect ratio (length:diameter {approximately}20) differs only slightly from twice the Rayleigh collapse time for a spherical bubble with an equivalent maximum volume. This fact justifies using the temporal interval between the acoustic signals emitted upon bubble creation and collapse to estimate the maximum bubble volume. As a result, hydrophone measurements can provide an estimate of the bubble size and energy even for aspherical bubbles. The change of the oscillation period of bubbles near solid walls and elastic (tissue-like) boundaries relative to that of isolated spherical bubbles is also investigated.

  16. Acoustic resonance in the combustion conduits of a steam locomotive

    SciTech Connect

    Ziada, S.; Oengoeren, A.; Vogel, H.H.

    1996-12-01

    The sound emission of a modern, oil fired steam rack locomotive increased sharply when the locomotive speed exceeded the design value of 12 km/hr. The results of pressure and noise measurements, together with an acoustical model of the combustion conduits indicated that the acoustic resonance modes of the combustion conduits are excited by the pressure pulsations generated by the exhaust from the steam cylinders at multiples of the piston frequency. Additionally, when the acoustic resonance is initiated, the resulting pulsations trigger the flame instability of the oil burners which, in turn, enhances the resonance. By means of the acoustical model, a Helmholtz resonator has been designed and optimized to reduce the acoustic response such that it does not excite the flame instability. A second set of measurements, after installing the resonator, has shown a reduction in the noise level by an amount exceeding 21 dBA. The paper focuses upon the identification of the excitation source and the implementation of the countermeasure which are of interest to other applications involving combustion oscillations.

  17. Modulated acoustic radiation pressure and stress-coupling projections

    NASA Astrophysics Data System (ADS)

    Marston, Philip L.; Thiessen, David B.

    2005-09-01

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

  18. Acoustic emission intrusion detector

    DOEpatents

    Carver, Donald W.; Whittaker, Jerry W.

    1980-01-01

    An intrusion detector is provided for detecting a forcible entry into a secured structure while minimizing false alarms. The detector uses a piezoelectric crystal transducer to sense acoustic emissions. The transducer output is amplified by a selectable gain amplifier to control the sensitivity. The rectified output of the amplifier is applied to a Schmitt trigger circuit having a preselected threshold level to provide amplitude discrimination. Timing circuitry is provided which is activated by successive pulses from the Schmitt trigger which lie within a selected time frame for frequency discrimination. Detected signals having proper amplitude and frequency trigger an alarm within the first complete cycle time of a detected acoustical disturbance signal.

  19. Electromechanical acoustic liner

    NASA Technical Reports Server (NTRS)

    Sheplak, Mark (Inventor); Cattafesta, III, Louis N. (Inventor); Nishida, Toshikazu (Inventor); Horowitz, Stephen Brian (Inventor)

    2007-01-01

    A multi-resonator-based system responsive to acoustic waves includes at least two resonators, each including a bottom plate, side walls secured to the bottom plate, and a top plate disposed on top of the side walls. The top plate includes an orifice so that a portion of an incident acoustical wave compresses gas in the resonators. The bottom plate or the side walls include at least one compliant portion. A reciprocal electromechanical transducer coupled to the compliant portion of each of the resonators forms a first and second transducer/compliant composite. An electrical network is disposed between the reciprocal electromechanical transducer of the first and second resonator.

  20. Densitometry By Acoustic Levitation

    NASA Technical Reports Server (NTRS)

    Trinh, Eugene H.

    1989-01-01

    "Static" and "dynamic" methods developed for measuring mass density of acoustically levitated solid particle or liquid drop. "Static" method, unknown density of sample found by comparison with another sample of known density. "Dynamic" method practiced with or without gravitational field. Advantages over conventional density-measuring techniques: sample does not have to make contact with container or other solid surface, size and shape of samples do not affect measurement significantly, sound field does not have to be know in detail, and sample can be smaller than microliter. Detailed knowledge of acoustic field not necessary.

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

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

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

  2. Gamma Oscillation in Schizophrenia

    PubMed Central

    O'Donnell, Brian F.; Youn, Soyoung; Kwon, Jun Soo

    2011-01-01

    Dysfunctional neural circuitry has been found to be involved in abnormalities of perception and cognition in patients with schizophrenia. Gamma oscillations are essential for integrating information within neural circuits and have therefore been associated with many perceptual and cognitive processes in healthy human subjects and animals. This review presents an overview of the neural basis of gamma oscillations and the abnormalities in the GABAergic interneuronal system thought to be responsible for gamma-range deficits in schizophrenia. We also review studies of gamma activity in sensory and cognitive processes, including auditory steady state response, attention, object representation, and working memory, in animals, healthy humans and patients with schizophrenia. PMID:22216037

  3. Advances in optoelectronic oscillators

    NASA Astrophysics Data System (ADS)

    Nguimdo, Romain M.; Saleh, Khaldoun; Lin, Guoping; Matinenghi, Romain; Chembo, Yanne K.

    2016-02-01

    Optoelectronic oscillators are used for a wide variety of applications in microwave photonics. We here report the latest advances in this technology from our research group, with emphasis on the analysis of phase noise performance. We present a stochastic modelling approach for phase noise performance analysis of optoelectronic oscillators based on whispering gallery mode resonators and/or optical fiber delay lines, and the theory is complemented with experimental measurements. We provide a detailed theoretical analysis which enables us to find the stationary states of the system as well as their stability. Our calculations also permit to find explicit formulas for the phase noise spectra, thereby allowing for their optimization.

  4. Micromechanical Oscillating Mass Balance

    NASA Technical Reports Server (NTRS)

    Altemir, David A. (Inventor)

    1997-01-01

    A micromechanical oscillating mass balance and method adapted for measuring minute quantities of material deposited at a selected location, such as during a vapor deposition process. The invention comprises a vibratory composite beam which includes a dielectric layer sandwiched between two conductive layers. The beam is positioned in a magnetic field. An alternating current passes through one conductive layers, the beam oscillates, inducing an output current in the second conductive layer, which is analyzed to determine the resonant frequency of the beam. As material is deposited on the beam, the mass of the beam increases and the resonant frequency of the beam shifts, and the mass added is determined.

  5. Post Treatment of Acoustic Neuroma

    MedlinePlus

    Home What is an AN What is an Acoustic Neuroma? Identifying an AN Symptoms Acoustic Neuroma Keywords Educational Video Pre-Treatment Treatment Options Summary Treatment Options Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions ...

  6. Variable-Position Acoustic Levitation

    NASA Technical Reports Server (NTRS)

    Barmatz, M. B.; Stoneburner, J. D.; Jacobi, N.; Wang, T. G.

    1983-01-01

    Method of acoustic levitation supports objects at positions other than acoustic nodes. Acoustic force is varied so it balances gravitational (or other) force, thereby maintaining object at any position within equilibrium range. Levitation method applicable to containerless processing. Such objects as table-tennis balls, hollow plastic spheres, and balsa-wood spheres levitated in laboratory by new method.

  7. Oscillating viscous boundary layer at high Reynolds number: Experiments and numerical calculations

    NASA Astrophysics Data System (ADS)

    Reyt, I.; Bailliet, H.; Foucault, E.; Valière, J.-Ch.

    2015-10-01

    Transition to turbulence for an acoustically oscillating flow (without any mean motion) in a resonant wave guide is considered. Departure from the laminar behaviour of the Stokes boundary layer formed in the near wall region is studied both experimentally and numerically for increasing acoustic levels. Laser Doppler Velocimetry is used to measure velocity profiles at different phases along the acoustic period and the experimental profile distortion is interpreted as the consequence of the development of a turbulent boundary layer. On the other hand, the oscillating flow is investigated numerically with a high order resolution one dimensional scheme for comparison with experimental results. The effective viscosity that models transition to turbulence is included and the velocity profile is integrated along the radial coordinate. Results from experiments and from numerical calculation are in very good agreement.

  8. Fundamentals of Acoustics. Psychoacoustics and Hearing. Acoustical Measurements

    NASA Technical Reports Server (NTRS)

    Begault, Durand R.; Ahumada, Al (Technical Monitor)

    1997-01-01

    These are 3 chapters that will appear in a book titled "Building Acoustical Design", edited by Charles Salter. They are designed to introduce the reader to fundamental concepts of acoustics, particularly as they relate to the built environment. "Fundamentals of Acoustics" reviews basic concepts of sound waveform frequency, pressure, and phase. "Psychoacoustics and Hearing" discusses the human interpretation sound pressure as loudness, particularly as a function of frequency. "Acoustic Measurements" gives a simple overview of the time and frequency weightings for sound pressure measurements that are used in acoustical work.

  9. Acoustic subwavelength imaging of subsurface objects with acoustic resonant metalens

    SciTech Connect

    Cheng, Ying; Liu, XiaoJun; Zhou, Chen; Wei, Qi; Wu, DaJian

    2013-11-25

    Early research into acoustic metamaterials has shown the possibility of achieving subwavelength near-field acoustic imaging. However, a major restriction of acoustic metamaterials is that the imaging objects must be placed in close vicinity of the devices. Here, we present an approach for acoustic imaging of subsurface objects far below the diffraction limit. An acoustic metalens made of holey-structured metamaterials is used to magnify evanescent waves, which can rebuild an image at the central plane. Without changing the physical structure of the metalens, our proposed approach can image objects located at certain distances from the input surface, which provides subsurface signatures of the objects with subwavelength spatial resolution.

  10. Coupled opto-electronic oscillator

    NASA Technical Reports Server (NTRS)

    Yao, X. Steve (Inventor); Maleki, Lute (Inventor)

    1999-01-01

    A coupled opto-electronic oscillator that directly couples a laser oscillation with an electronic oscillation to simultaneously achieve a stable RF oscillation at a high frequency and ultra-short optical pulsation by mode locking with a high repetition rate and stability. Single-mode selection can be achieved even with a very long opto-electronic loop. A multimode laser can be used to pump the electronic oscillation, resulting in a high operation efficiency. The optical and the RF oscillations are correlated to each other.

  11. Downstream boundary effects on the frequency of self-excited oscillations in transonic diffuser flows

    NASA Technical Reports Server (NTRS)

    Hsieh, T.; Coakley, T. J.

    1987-01-01

    An investigation of downstream boundary effects on the frequency of self-excited oscillations in two-dimensional, separated transonic diffuser flows has been conducted numerically by solving the compressible, Reynolds-averaged, thin-layer Navier-Stokes equation with a two-equation turbulence model. It was found that the unsteady diffuser flowfields are very sensitive to the location of the downstream boundary. Extension of the diffuser downstream boundary significantly reduces the frequency and amplitude of oscillations for pressure, velocity and shock. Computational results suggest that the mechanism causing the self-excited oscillation changes from viscous convective wave dominated oscillations to inviscid acoustic wave dominated oscillations when the location of downstream boundary varies from 8.66 to 134.7 throat height. The existence of a suction slot in the experimental setup obscures the physical downstream boundary and, therefore, presents a difficulty for quantitative comparisons between computation and experiment.

  12. Oscillating bubbles: a versatile tool for lab on a chip applications.

    PubMed

    Hashmi, Ali; Yu, Gan; Reilly-Collette, Marina; Heiman, Garrett; Xu, Jie

    2012-11-01

    With the fast development of acoustic and multiphase microfluidics in recent years, oscillating bubbles have drawn more-and-more attention due to their great potential in various Lab on a Chip (LOC) applications. Many innovative bubble-based devices have been explored in the past decade. In this article, we first briefly summarize current understanding of the physics of oscillating bubbles, and then critically summarize recent advancements, including some of our original work, on the applications of oscillating bubbles in microfluidic devices. We intend to highlight the advantages of using oscillating bubbles along with the challenges that accompany them. We believe that these emerging studies on microfluidic oscillating bubbles will be revolutionary to the development of next-generation LOC technologies.

  13. Designing an Acoustic Suspension Speaker System in the General Physics Laboratory: A Divergent experiment

    ERIC Educational Resources Information Center

    Horton, Philip B.

    1969-01-01

    Describes a student laboratory project involving the design of an "acoustic suspension speaker system. The characteristics of the loudspeaker used are measured as an extension of the inertia-balance experiment. The experiment may be extended to a study of Stelmholtz resonators, coupled oscillators, electromagnetic forces, thermodynamics and…

  14. 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.

  15. Vibration of a single microcapsule with a hard plastic shell in an acoustic standing wave field.

    PubMed

    Koyama, Daisuke; Kotera, Hironori; Kitazawa, Natsuko; Yoshida, Kenji; Nakamura, Kentaro; Watanabe, Yoshiaki

    2011-04-01

    Observation techniques for measuring the small vibration of a single microcapsule of tens of nanometers in an acoustic standing wave field are discussed. First, simultaneous optical observation of a microbubble vibration by two methods is investigated, using a high-speed video camera, which permits two-dimensional observation of the bubble vibration, and a laser Doppler vibrometer (LDV), which can observe small bubble vibration amplitudes at high frequency. Bubbles of tens of micrometers size were trapped at the antinode of an acoustic standing wave generated in an observational cell. Bubble vibration at 27 kHz could be observed and the experimental results for the two methods showed good agreement. The radial vibration of microcapsules with a hard plastic shell was observed using the LDV and the measurement of the capsule vibration with radial oscillation amplitude of tens of nanometers was successful. The acoustic radiation force acting on microcapsules in the acoustic standing wave was measured from the trapped position of the standing wave and the radial oscillation amplitude of the capsules was estimated from the theoretical equation of the acoustic radiation force, giving results in good agreement with the LDV measurements. The radial oscillation amplitude of a capsule was found to be proportional to the amplitude of the driving sound pressure. A larger expansion ratio was observed for capsules closer to the resonance condition under the same driving sound pressure and frequency.

  16. A thermodynamic study of BaO + BaCl[sub 2] + Cr[sub 2]O[sub 3] fluxes used for the removal of phosphorus from chromium-containing iron melts

    SciTech Connect

    Inouye, T.K.; Fujiwara, H.; Ichise, E.; Iwase, M. )

    1994-10-01

    Electrochemical measurements with solid-oxide galvanic cell of the type Mo/Mo + MoO[sub 2]//ZrO[sub 2](MgO)//(Cu + Cr)[sub alloy] + (Cr[sub 2]O[sub 3])[sub slag]/Mo were conducted at 1,473 K in order to obtain the activities of Cr[sub 2]O[sub 3] in BaO + BaCl[sub 2] + Cr[sub 2]O[sub 3] slags used for dephosphorization of chromium-containing iron melts. Based on the activity measurements, it is concluded that in the system BaO + BaCl[sub 2] + Cr[sub 2]O[sub 3] at 1,473 K, there are 1 two-phase region in saturation with pure Cr[sub 2]O[sub 3](s) and 3 three-phase regions. The activities of Cr[sub 2]O[sub 3] within such three-phase regions decrease with an increase in BaO/BaCl[sub 2] mole ratios. The Cr[sub 2]O[sub 3] activities in BaO + BaCl[sub 2] + Cr[sub 2]O[sub 3] fluxes are, in general, greater than those in CaO + CaCl[sub 2] + Cr[sub 2]O[sub 3], corresponding to much more effective dephosphorization by BaO + BaCl[sub 2] + Cr[sub 2]O[sub 3] fluxes rather than CaO + CaCl[sub 2] + Cr[sub 2]O[sub 3] slag.

  17. The planar jet-plate oscillator

    NASA Astrophysics Data System (ADS)

    Arthurs, David; Ziada, Samir

    2011-01-01

    The aeroacoustic noise generated by a high speed, planar gas jet impinging on a flat plate is investigated experimentally. The jet used in this study is typical of those commonly found in industrial applications such as in various coating control and heat transfer processes. Normal jet impingement on the plate is found to generate strong acoustic tones over a wide range of impingement distances and jet velocities. The characteristics of these tones, as a function of the jet velocity and impingement distance, are quantified. Phase and amplitude measurements of the pressure fluctuations on the impingement plate indicate that the acoustic tones are generated by an antisymmetric instability mode of the jet oscillation. The effect of plate inclination in both the transverse and span-wise directions, with respect to the incident jet, is also studied. The jet-plate tone is found to be much more sensitive to changes in the span-wise plate inclination than to changes in the transverse inclination, but in both cases, a complete suppression of the tone is found to be possible.

  18. NOx uptake on alkaline earth oxides (BaO, MgO, CaO and SrO) supported on γ-Al2O3

    SciTech Connect

    Verrier, Christelle LM; Kwak, Ja Hun; Kim, Do Heui; Peden, Charles HF; Szanyi, Janos

    2008-07-15

    NOx uptake experiments were performed on a series of alkaline earth oxide (AEO) (MgO, CaO, SrO, BaO) on γ-alumina materials. Temperature Programmed Desorption (TPD) conducted on He flow revealed the presence of two kinds of nitrate species: i.e. bulk and surface nitrates. The ratio of these two types of nitrate species strongly depends on the nature of the alkaline earth oxide. The amount of bulk nitrate species increases with the basicity of the alkaline earth oxide. This conclusion was supported by the results of infrared and 15N solid state NMR studies of NO2 adsorption. Due to the low melting point of the precursor used for the preparation of MgO/Al2O3 material (Mg(NO3)2), a significant amount of Mg was lost during sample activation (high temperature annealing) resulting in a material with properties were very similar to that of the γ-Al2O3 support. The effect of water on the NOx species formed in the exposure of the AEO-s to NO2 was also investigated. In agreement with our previous findings for the BaO/γ-Al2O3 system, an increase of the bulk nitrate species and the simultaneous decrease of the surface nitrate phase were observed for all of these materials.

  19. Short-time QiBaoMeiRan Formula Treatment Exerts Estrogenic Activities without Side Effects on Reproductive Tissues in Immature Mice

    PubMed Central

    Xu, Ying; Ma, Xiao-ping; An, Jin-na; Zhang, Zi-jia; Ding, Jie; Qu, Ya-kun; Liu, Zhen-li; Lin, Na

    2015-01-01

    The Chinese herbal preparation QiBaoMeiRan formula (QBMR) displayed estrogenic effects in ovariectomized rats after long-term administration in a previous study. The uterus and vagina are negatively influenced by estrogens in hormone therapy. While QBMR is known to be a phytoestrogen, its estrogenic effects and safety on reproductive tissues after short-term administration and its mechanism via estrogen receptor (ER) pathway haven’t been studied. Here, we characterized its estrogenic effects using immature mice together with in vitro studies for further molecular characterization. Immature mice were treated with QBMR at doses of 1.125, 2.25, and 4.5 g/kg for 7 days. 1.125 and 2.25 g/kg QBMR promoted the growth and development of uterus and vagina, and upregulated ERα and ERβ expression in reproductive tissues. QBMR had a stimulatory effect on proliferating cell nuclear antigen in vagina but not in uterus, and was without any influence on ki-67 antigen in uterus and vagina. QBMR significantly induced luciferase expression from the ERα/β-estrogen response element (ERE) luciferase reporter and upregulated ERα and ERβ expressions in MCF-7 cells, which were significantly inhibited by estrogen antagonist ICI182,780. This study demonstrated QBMR exerts estrogenic effects on reproductive tissues without side effects and through ER-ERE-dependent pathway. PMID:26644197

  20. Acoustics in Schools.

    ERIC Educational Resources Information Center

    Singer, Miriam J.

    This paper explores the issues associated with poor acoustics within schools. Additionally, it suggests remedies for existing buildings and those under renovation, as well as concerns for new construction. The paper discusses the effects of unwanted noise on students in terms of physiological, motivational, and cognitive influences. Issues are…