Sample records for wave attenuation measurements

  1. Rainfall attenuation of centimeter waves: Comparison of theory and measurement

    Microsoft Academic Search

    1965-01-01

    Numerical results for attenuation of centimeter waves by rainfall have been computed from J. W. Ryde's formula. These correct, and considerably extend, the previously published Ryde results. Comparison with available measurements suggests that the agreement is not entirely satisfactory; there is a tendency for measured attenuations to exceed the maximum possible levels predicted by the theory.

  2. Surface wave attenuation measurement for application to pavement characterization

    NASA Astrophysics Data System (ADS)

    Popovics, John S.; Song, Won-Joon; Achenbach, Jan D.

    1998-03-01

    There is a need for non-destructive evaluation (NDE) techniques which can effectively determine the extent of damage (cracking) in concrete structures. Non-destructive, one-sided surface wave attenuation measurement is a very sensitive and practical tool for such characterization. A technique for practical determination of frequency-dependent surface wave attenuation is introduced and demonstrated to be sensitive to damage in free concrete slabs. A theoretical model for the attenuation response in undamaged free slabs is introduced and shown to accurately predict experimentally obtained responses in concrete within certain frequency limits. The theoretical model is then used to investigate the practical application of the attenuation technique to concrete pavement NDE in terms of slab depth and subbase conditions. Theoretically obtained data are presented for a variety of pavement types. Based on the presented results of the theoretical model, conclusions concerning practical application of the technique to pavement inspection are given.

  3. Electromagnetic wave attenuation measurements in a ring-shaped inductively coupled air plasma

    NASA Astrophysics Data System (ADS)

    Wei, Xiaolong; Xu, Haojun; Li, Jianhai; Lin, Min; Su; Chen

    2015-05-01

    An aerocraft with the surface, inlet and radome covered large-area inductive coupled plasma (ICP) can attenuate its radar echo effectively. The shape, thickness, and electron density ( N e ) distribution of ICP are critical to electromagnetic wave attenuation. In the paper, an air all-quartz ICP generator in size of 20 × 20 × 7 cm3 without magnetic confinement is designed. The discharge results show that the ICP is amorphous in E-mode and ring-shaped in H-mode. The structure of ICP stratifies into core region and edge halo in H-mode, and its width and thickness changes from power and pressure. Such phenomena are explained by the distribution of RF magnetic field, the diffusion of negative ions plasma and the variation of skin depth. In addition, the theoretical analysis shows that the N e achieves nearly uniform within the electronegative core and sharply steepens in the edge. The N e of core region is diagnosed by microwave interferometer under varied conditions (pressure in range of 10-50 Pa, power in 300-700 W). Furthermore, the electromagnetic wave attenuation measurements were carried out with the air ICP in the frequencies of 4-5 GHz. The results show that the interspaced ICP is still effective to wave attenuation, and the wave attenuation increases with the power and pressure. The measured attenuation is approximately in accordance with the calculation data of finite-different time-domain simulations.

  4. Laboratory measurements of wave attenuation through model and live vegetation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surge and waves generated by hurricanes and tropical storms often cause severe damage and loss of life in coastal areas. It is widely recognized that wetlands along coastal fringes reduce storm surge and waves. Yet, the potential role and primary mechanisms of wave mitigation by wetland vegetation a...

  5. The upper mantle degree 2: Constraints and inferences from global mantle wave attenuation measurements

    NASA Astrophysics Data System (ADS)

    Romanowicz, Barbara

    1990-07-01

    We present the results of an analysis of global lateral variations in anelasticity of the upper mantle, as measured from very long period Rayleigh waves observed on the GEOSCOPE network. Four consecutive wave trains are used on each record to eliminate uncertainty on the amplitude at the source and to take into account, in a linear manner, focussing effects due to lateral variations in elastic parameters. Local estimates of attenuation are obtained using an inversion method based on the introduction of a correlation length, as an alternative to spherical harmonics expansion. Comparison of phase velocity and attenuation maps obtained at various periods shows a strong correlation of high-Q and high-velocity regions (respectively low Q and low velocity) both for great circle and minor arc data, at periods around 200 s. The detailed analysis of the degree 2 pattern, well resolved in the attenuation maps around this period, shows that it originates in the depth range 250-500 km and indicates that of the upper mantle degree 2 pattern observed in shear velocity is likely to be of thermal origin, possibly related to the topmost part of the large-scale convective system. Corrections for dispersion due to anelastic attenuation in degree 2 lead to significant decrease of corresponding lateral variations in shear velocity and a better agreement in phase and amplitude of the upper mantle degree 2 pattern with that observed in the geoid. This study shows that it is important to consider correcting presently available upper mantle tomographic models for the effects of intrinsic attenuation at long periods, before performing any comparison with short-period data or other geophysical parameters.

  6. New experimental approach to measure seismic wave attenuation of rocks at low frequencies

    NASA Astrophysics Data System (ADS)

    Madonna, C.; Boutareaud, S.; Burlini, L.; Habiger, R.

    2009-04-01

    Here we present a new experimental approach to accurately characterize attenuation on fluid-bearing rock samples. A prototype of apparatus has been built and developed in order to measure attenuation (1/Q) of seismic P-waves passing through a rock sample in the low frequency regime (0.1Hz - 50Hz), by the stress-strain method in an internally heated gas apparatus (Paterson-rig). Stress is measured with a high-sensitivity load cell (resolution 1N). Strain is measured with high sensitive LVDTs of 1mm full range (resolution 1e-7mm). The quality factor Q (i.e. the reciprocal of attenuation) is obtained from the time shift between the mechanically applied sinusoidal stress at the bottom of the sample, and the sinusoidal strain's response measured on the top sample. We report basic sketch of the apparatus, explain the technical difficulties and lastest improvements. In addition, we present the preliminary results on aluminium (1/Q close to 0) and Fontainbleau-sandstone saturated with oil, and their corresponding digital signal processing. This new technique can be used to accurately establish a catalog of 1/Q values as a function of in-situ rock properties. In particular, future studies using this apparatus will be used to investigate the effect of different fluid properties on 1/Q.

  7. Shear wave velocity and attenuation in the upper layer of ocean bottoms from long-range acoustic field measurements.

    PubMed

    Zhou, Ji-Xun; Zhang, Xue-Zhen

    2012-12-01

    Several physics-based seabed geoacoustic models (including the Biot theory) predict that compressional wave attenuation ?(2) in sandy marine sediments approximately follows quadratic frequency dependence at low frequencies, i.e., ?(2)?kf(n) (dB/m), n=2. A recent paper on broadband geoacoustic inversions from low frequency (LF) field measurements, made at 20 locations around the world, has indicated that the frequency exponent of the effective sound attenuation n?1.80 in a frequency band of 50-1000 Hz [Zhou et al., J. Acoust. Soc. Am. 125, 2847-2866 (2009)]. Carey and Pierce hypothesize that the discrepancy is due to the inversion models' neglect of shear wave effects [J. Acoust. Soc. Am. 124, EL271-EL277 (2008)]. The broadband geoacoustic inversions assume that the seabottom is an equivalent fluid and sound waves interact with the bottom at small grazing angles. The shear wave velocity and attenuation in the upper layer of ocean bottoms are estimated from the LF field-inverted effective bottom attenuations using a near-grazing bottom reflection expression for the equivalent fluid model, derived by Zhang and Tindle [J. Acoust. Soc. Am. 98, 3391-3396 (1995)]. The resultant shear wave velocity and attenuation are consistent with the SAX99 measurement at 25 Hz and 1000 Hz. The results are helpful for the analysis of shear wave effects on long-range sound propagation in shallow water. PMID:23231101

  8. Attenuation of compressional waves in peridotite measured as a function of temperature at 200 MPa

    Microsoft Academic Search

    Hiroki Sato; I. Selwyn Sacks; Tsutomu Murase; Gregory Muncill; Hiroyuki Fukuyama

    1988-01-01

    A technique has been developed to determine attenuation in rocks at high temperature using a gas-media, high-pressure apparatus. A pulse transmission technique and a spectral ratio method are used to study compressional seismic properties of rocks. Seismic waves are transmitted to and from the sample through buffer rods of mullite. The effect of seismic wave reflections within the sample assembly

  9. Diffraction, attenuation, and source corrections for nonlinear Rayleigh wave ultrasonic measurements.

    PubMed

    Torello, David; Thiele, Sebastian; Matlack, Kathryn H; Kim, Jin-Yeon; Qu, Jianmin; Jacobs, Laurence J

    2015-02-01

    This research considers the effects of diffraction, attenuation, and the nonlinearity of generating sources on measurements of nonlinear ultrasonic Rayleigh wave propagation. A new theoretical framework for correcting measurements made with air-coupled and contact piezoelectric receivers for the aforementioned effects is provided based on analytical models and experimental considerations. A method for extracting the nonlinearity parameter ?11 is proposed based on a nonlinear least squares curve-fitting algorithm that is tailored for Rayleigh wave measurements. Quantitative experiments are conducted to confirm the predictions for the nonlinearity of the piezoelectric source and to demonstrate the effectiveness of the curve-fitting procedure. These experiments are conducted on aluminum 2024 and 7075 specimens and a ?11(7075)/?11(2024) measure of 1.363 agrees well with previous literature and earlier work. The proposed work is also applied to a set of 2205 duplex stainless steel specimens that underwent various degrees of heat-treatment over 24h, and the results improve upon conclusions drawn from previous analysis. PMID:25287976

  10. Measurements of frequency dependent shear wave attenuation in sedimentary basins using induced earthquakes

    NASA Astrophysics Data System (ADS)

    Richter, Tom; Wegler, Ulrich

    2015-04-01

    Modeling of peak ground velocity caused by induced earthquakes requires detailed knowledge about seismic attenuation properties of the subsurface. Especially shear wave attenuation is important, because shear waves usually show the largest amplitude in high frequency seismograms. We report intrinsic and scattering attenuation coefficients of shear waves near three geothermal reservoirs in Germany for frequencies between 2 Hz and 50 Hz. The geothermal plants are located in the sedimentary basins of the upper Rhine graben (Insheim and Landau) and the Molasse basin (Unterhaching). The method optimizes the fit between Green's functions for the acoustic, isotropic radiative transfer theory and observed energy densities of induced earthquakes. The inversion allows the determination of scattering and intrinsic attenuation, site corrections, and spectral source energies for the investigated frequency bands. We performed the inversion at the three sites for events with a magnitude between 0.7 and 2. We determined a transport mean free path of 70 km for Unterhaching. For Landau and Insheim the transport mean free path depends on frequency. It ranges from 2 km (at 2 Hz) to 30 km (at 40 Hz) for Landau and from 9 km to 50 km for Insheim. The quality factor for intrinsic attenuation is constant for frequencies smaller than 10 Hz at all three sites. It is around 100 for Unterhaching and 200 for Landau and Insheim with higher values above 10 Hz.

  11. Global teleseismic S wave attenuation

    NASA Astrophysics Data System (ADS)

    Hwang, Y.; Ritsema, J. E.

    2009-12-01

    We have measured 140,000 teleseismic S wave spectra from 150 deep (focal depth > 200 km) earthquakes recorded at 890 broadband global and regional network stations up to 0.7 Hz. We have analyzed these data to constrain the (1) epicentral distance and (2) spatial variation of the shear wave attenuation parameter tS*. tS* increases by about 2 s between 30° and 98°. The increase in tS* is consistent (correlation coefficient of 0.9) with global QS profiles (Dziewonski and Anderson, 1981; Durek and Ekström, 1996; Lawrence and Wysession, 2006). However, there are well resolved departures in the distance dependence of tS*. Most notably, tS* is lower than PREM-predicted values between 58°-64°. This indicates a reduction in shear attenuation from the global average at ~1600 km depth beneath Central America, eastern Asia, and Alaska. These regions have previously been identified as downwelling mantle regions on the basis of seismic tomography (Grand et al., 1997), plate reconstructions (Ricard et al., 1993), and waveform analysis (Lay et al., 2004). Stations terms of tS* represent the spatial variation of attenuation in the upper mantle. Using multi-channel cross-correlation and least-squares inversion of differential spectra we resolve high attenuation in the upper mantle beneath western North America, western Europe, and eastern Africa. Attenuation is low beneath eastern North America, the Baltic regions, and central and southern Africa. This variation correlates well with global variations in heat flow (Pollack et al., 1993) and crustal age (Mooney et al., 1995).

  12. The upper mantle degree 2: constraints and inference from global mantle wave attenuation measurements

    Microsoft Academic Search

    Barbara Romanowicz

    1990-01-01

    We present the results of an analysis of global lateral variations in anelasticity of the upper mantle, as measured from very long period Rayleigh waves observed on the GEOSCOPE network. Four consecutive wave trains are used on each record to eliminate uncertainty on the amplitude at the source and to take into account, in a linear manner, focussing effects due

  13. Measurements of ultrasonic phase velocities and attenuation of slow waves in cellular aluminum foams as cancellous bone-mimicking phantoms.

    PubMed

    Zhang, Chan; Le, Lawrence H; Zheng, Rui; Ta, Dean; Lou, Edmond

    2011-05-01

    The water-saturated aluminum foams with an open network of interconnected ligaments were investigated by ultrasonic transmission technique for the suitability as cancellous bone-mimicking phantoms. The phase velocities and attenuation of nine samples covering three pores per inch (5, 10, and 20 PPI) and three aluminum volume fractions (5, 8, and 12% AVF) were measured over a frequency range of 0.7-1.3 MHz. The ligament thickness and pore sizes of the phantoms and low-density human cancellous bones are similar. A strong slow wave and a weak fast wave are observed for all samples while the latter is not visible without significant amplification (100x). This study reports the characteristics of slow wave, whose speeds are less than the sound speed of the saturating water and decrease mildly with AVF and PPI with an average 1469 m/s. Seven out of nine samples show positive dispersion and the rest show minor negative dispersion. Attenuation increases with AVF, PPI, and frequency except for the 20 PPI samples, which exhibit non-increasing attenuation level with fluctuations due to scattering. The phase velocities agree with Biot's porous medium theory. The RMSE is 16.0 m/s (1%) at n = 1.5. Below and above this value, the RMSE decreases mildly and rises sharply, respectively. PMID:21568432

  14. Teleseismic Body Wave Attenuation and Diffraction

    NASA Astrophysics Data System (ADS)

    Hwang, Yong Keun

    Using available digital seismic stations deployed since the 1980's, the largest data set based on broadband waveforms among studies on body-wave attenuation (t*) and quality factor (Q) are used in this thesis. The use of nearly 300,000 measurements of body-wave spectral ratio from globally distributed stations renders better constraints of t* and Q variations with higher spatial and depth resolutions in the mantle than have been previously available. The maps of body-wave t* correlate well with the variations of t* computed from the most recent surface-wave Q model QRFSI12 indicating that body-wave and surface-wave t* reflect the same intrinsic attenuation even though these waves sample the upper mantle entirely differently. The high correlation between body-wave t* maps and the t* inferred from a thermal interpretation of shear-wave velocity tomography S20RTS suggests that temperature controls both variations in attenuation and velocity in the upper mantle. The distance variations of P- and S-wave t* (t*P and t*S) are inverted for a radial profile of the quality factor Qmu in the lower mantle. On average, t* P and t*S increase by about 0.2 s and 0.7 s, respectively, between epicentral distances of 30° and 97°. The body-wave spectra are explained best if Qmu, increases in the lower mantle with the rate of 0.1/km. The relatively strong increase of t*S compare to t*P (t*S ? 4 t*P) suggests that intrinsic attenuation is the cause of the overall trend in our data. The ratio of P- and S-wave quality factor determined in this thesis (QP/Qmu = 2.27) confirms that intrinsic attenuation occurs mostly in shear and that bulk attenuation is negligible in the mantle. Finally, the delay of seismic waves which traversed numerical mantle plumes are calculated in this thesis for the first time. High-resolution numerical simulations of mantle plume are used to investigate the effects of numerical plumes on waveforms. The measurements of wave front delay demonstrate that the delay of shear-waves by plume tails at depths larger than 1000 km are immeasurably small (< 0.2 s) at seismic periods commonly used in waveform analysis.

  15. Measurement and parameterization of wave attenuation and scattering in the Marginal Ice Zone using Sentinel-1 SAR data

    NASA Astrophysics Data System (ADS)

    Collard, F.; Ardhuin, F.; Guitton, G.; Dumont, D.; Nicot, P.; Accenti, M.; Girard-Ardhuin, F.

    2014-12-01

    Sentinel-1A launched by the European Space Agency in April 2014 will complete its full calibration and validation phase including Level2 products early in 2015 but image quality is already good enought for scientific exploitation of observed wave modulations. The larger frequency bandwidth and new acquisition modes are providing a much improved capability for imaging ocean waves in the open water and in the ice compared to Envisat. Here we estimate wave spectra in the Arctic assuming a spatially uniform modulation transfer function where the backscatter over ice is homogeneous, matching the wave heights in open ocean and ice at the ice edge. These wave properties are used to estimate attenuation scales for wavelength longer than twice the radar image resolution. These estimated attenuations are compared to model results based on WAVEWATCH III, where attenuation and scattering uses a combination of friction below the ice and scattering adapted from Dumont et al. (2011) and Williams et al. (2013).

  16. Measuring sea ice permeability as a function of the attenuation and phase velocity shift of an acoustic wave

    NASA Astrophysics Data System (ADS)

    Hudier, E. J.; Bahoura, M.

    2012-12-01

    Sea ice is a two-phase porous medium consisting of a solid matrix of pure ice and a salty liquid phase. At spring when ice permeability increases, it has been observed that pressure gradients induced at the ice-water interface upstream and downstream of pressure ridge keels can cause sea water and brine to be forced through the ice water boundary. It suggests that salt and heat fluxes through the bottom ice layers may be a major factor controlling the decay of an ice sheet. Knowing how water flows through the ice matrix is fundamental to a modeling of ocean-ice heat exchanges integrating the advective import/export of latent heat that result from melting/freezing within the ice. Permeability is the measurement of the ease with which fluids flow through a porous medium, however one of the most tricky to measure without altering the porosity of the sampled medium. To further complicate the challenge, horizontal and vertical permeability of the ice, referred as ice anisotropy, is significant. Acoustic wave propagation through porous media have been theorized to relate the acoustic velocity and attenuation to the physical properties of the tested material. It is a non-invasive technique, and as such could provide more reliable measurements of sea ice permeability than anything presently used. Simulations combining the Biot's and squirt flow mechanisms are performed to investigate the effect of permeability on the attenuation and phase velocity as a function of frequency. We first present the attenuation dispersion curves for an isotropic sea ice, then low-frequency and high-frequency limits are determined. Optimal frequency range and resolution requirements are evaluated for testing.

  17. Ultrasonic Velocity and Attenuation of Longitudinal Waves in Rocks

    Microsoft Academic Search

    Michel Auberger; John S. Rinehart

    1961-01-01

    Hughes' pulse technique for measuring longitudinal velocities has been adapted and extended to measure attenuation of longitudinal waves in the frequency range from 250 to 1000 kc\\/s. Data for velocity and attenuation in eight different rocks (three granites, one porphyry, two sandstones, one limestone, and one marble) are given at eight different frequencies ranging from 250 to 1000 kc\\/s. The

  18. Attenuated Fractional Wave Equations With Anisotropy.

    PubMed

    Meerschaert, Mark M; McGough, Robert J

    2014-10-01

    This paper develops new fractional calculus models for wave propagation. These models permit a different attenuation index in each coordinate to fully capture the anisotropic nature of wave propagation in complex media. Analytical expressions that describe power law attenuation and anomalous dispersion in each direction are derived for these fractional calculus models. PMID:25278739

  19. The attenuation of strong shock waves 

    E-print Network

    Kirkpatrick, Ronald Crecelius

    1963-01-01

    26 II. Shock Front Velocity Energy Losses 35 41 LIST OF FIGURES ~Fi ure ~Pa e Lossless Shock Wave Attenuation The Parameter 1 for Shock Waves in Nitrogen The Parameter l for Shock Waves in a Perfect Gas 13 Shock Tube Electrode Configuration.... 18. 19. Shock Wave Propagation in Air Shock Wave Propagation in Nitrogen Shock Wave Propagation in Argon Shock Wave Propagation in Helium Shock Velocity Dependence on Distance for Air Shock Velocity Dependence on Distance for Nitrogen 33 33...

  20. Signature of seismic wave attenuation during fracture network formation

    NASA Astrophysics Data System (ADS)

    Barnhoorn, Auke; Zhubayev, Alimzhan; Houben, Maartje; Hardebol, Nico; Smeulders, David

    2015-04-01

    Seismic waves are significantly affected by the presence of fractures and faults. Fractures alter the arrival time of a seismic wave and the amplitude of the seismic wave. Attenuation of a seismic wave is the reduction of wave amplitude due to the presence of e.g. fractures. Attenuation of acoustic compressional P- and shear S-waves have been measured in laboratory studies on different rock types. These studies generally show a decrease in attenuation with an increase in stress. This decrease in attenuation is attributed to progressive crack closure of pre-existing cracks. The stress-dependent decrease in attenuation reported in these studies all occur within the elastic deformation field, i.e. below yield stress levels and thus no additional cracks/micro-fractures have yet been formed. At stress levels just above the yield strength the first fractures start to form. With increasing stress, fractures nucleate, grow and coalesce until a connected network of fractures has developed at which failure of the rock sample occurs. The change in attenuation during the fracturing process however has seldom been investigated. In analogy to fracture closure, where attenuation generally decreases, fracture formation should cause again an increase in attenuation. Here we report an experimental study on shales from Whitby (UK), where s-wave attenuation was measured in the laboratory during an increase in stress towards fracture formation until complete failure of the shale samples. Before yield stress conditions, as expected an increase in stress caused a gradual decrease in attenuation. At the transition from elastic to inelastic deformation behaviour, the first microfractures start to form and attenuation starts to increase again. This reversal in attenuation behaviour could potentially be used as an indicator that failure of a rock mass under stress is imminent (imminence of seismicity). The measured seismic velocities do not depict the transition from elastic to inelastic deformation behavior. After peak stress conditions, a fully connected network of fractures is gradually formed and attenuation of the s-waves starts to be more complex. Changes in attenuation depend here on how individual fractures connect with each other and thereby influence the seismic waves.

  1. Wave attenuation in thick graphite\\/epoxy composites

    Microsoft Academic Search

    A. K. Mal; Y. Bar-Cohen

    1992-01-01

    The mechanics of wave attenuation in thick graphite\\/epoxy composites is examined in order to facilitate interpretation of the wave amplitudes recorded in ultrasonic experiments. The values of a small number of parameters are determined through comparison between calculated and measured waveforms for four specimens. The agreement between the measured and calculated waveforms are shown to be excellent in all four

  2. Guided wave attenuation in pipes buried in sand

    NASA Astrophysics Data System (ADS)

    Leinov, Eli; Cawley, Peter; Lowe, Michael JS

    2015-03-01

    Long-range ultrasonic guided wave testing of pipelines is used routinely for detection of corrosion defects in a variety of industries, e.g. petrochemical and energy. When the method is applied to pipelines that are buried in soil, test ranges tend to be significantly compromised compared to those achieved for pipelines above ground because of the attenuation of the guided wave, due to energy leaking into the embedding soil. The attenuation characteristics of guided wave propagation in a pipe buried in sand are investigated using a full scale experimental rig. The apparatus consists of an 8"-diameter, 6-meters long steel pipe embedded over 3 meters in a rectangular container filled with sand and fitted with an air-bladder for the application of overburden pressure. Measurements of the attenuation of the T(0,1) and L(0,2) guided wave modes over a range of sand conditions, including loose, compacted, water saturated and drained, are presented. Attenuation values are found to be in the range of 1-5.5 dB/m. The application of overburden pressure modifies the compaction of the sand and increases the attenuation. The attenuation decreases in the fully water-saturated sand, while it increases in drained sand to values comparable with those obtained for the compacted sand. The attenuation behavior of the torsional guided wave mode is found not to be captured by a uniform soil model; comparison with predictions obtained with the Disperse software suggest that this is likely to be due to a layer of sand adhering to the surface of the pipe.

  3. The attenuation of strong shock waves

    E-print Network

    Kirkpatrick, Ronald Crecelius

    1963-01-01

    in that same region after the passage of the shock wave. This is illustrated in Figure 1 and expressed by equation (1) in A p j Tj f ~ ~ (so-j-7o jps u Figure 1. LOSSLESS SHOCK WAVE ATTENUATION which E is the energy supporting the shock wave, A... High Voltage P. ower Supply '7. 5p f C apacitor Shorting Switch Ignition Trigger Circuit Regulated Gas Supply Shock Tube Gas Vacuum Pump Accumulator Vacuum Gage Figure 5, SCHEMATIC OF SHOCK TUBE SYSTEM 22 luminous gas behind the shock...

  4. Review of methods to attenuate shock/blast waves

    NASA Astrophysics Data System (ADS)

    Igra, O.; Falcovitz, J.; Houas, L.; Jourdan, G.

    2013-04-01

    Quick and reliable shock wave attenuation is the goal of every protection facility and therefore it is not surprising that achieving this has drawn much attention during the past hundred years. Different options have been suggested; their usefulness varying from a reasonable protection to the opposite, a shock enhancement. An example for a suggestion for shock mitigation that turned out to be an enhancement of the impinging shock wave was the idea to cover a protected object with a foam layer. While the pressure behind the reflected shock wave from the foam frontal surface was smaller than that recorded in a similar reflection from a rigid wall [25], the pressure on the “protected” surface, attached to the foam's rear-surface, was significantly higher than that recorded in a similar reflection from a bare, rigid wall [11]. In protecting humans and installations from destructive shock and/or blast waves the prime goal is to reduce the wave amplitude and the rate of pressure increase across the wave front. Both measures result in reducing the wave harmful effects. During the past six decades several approaches for achieving the desired protection have been offered in the open literature. We point out in this review that while some of the suggestions offered are practical, others are impractical. In our discussion we focus on recent schemes for shock/blast wave attenuation, characterized by the availability of reliable measurements (notably pressure and optical diagnostics) as well as high-resolution numerical simulations.

  5. Separating thermal coagulation and cavitation effects in HIFU attenuation measurements

    NASA Astrophysics Data System (ADS)

    Reed, Justin; Bailey, Michael; Anand, Ajay; Kaczkowski, Peter

    2003-10-01

    HIFU can be used to destroy tumors. The conversion of acoustic energy into heat causes protein coagulation (Lesion) in tissue. Attenuation measurements have been proposed to monitor the progression of thermal therapy. The goal of this work is to study and separate the effects of cavitation and thermal coagulation in attenuation measurements. A HIFU transducer was used to treat Bovine liver. A receiving transducer mounted across from the transmitting HIFU transducer measured attenuation during the treatment. A pressure chamber provided static pressure greater than the pressure amplitude of the HIFU wave, which suppressed cavitation. rf data from a commercial ultrasound scanner was also obtained. A large increase in attenuation was observed with cavitation present, while a subtle increase in attenuation was observed with cavitation suppressed. Attenuation estimated from the RF data showed an increase in attenuation downstream of the location of the lesion with cavitation present, while a subtle increase in attenuation was observed at the location of the lesion with cavitation suppressed. It has been found that attenuation measurements are greatly affected by the presence of cavitation, and the actual effect of thermal coagulation on attenuation is quite small. [Work supported by NIH, NSF, NSBRI.

  6. Attenuation of seismic waves in Central Egypt

    NASA Astrophysics Data System (ADS)

    Morsy, Mamdouh Abbas; Abed, Azza M.

    2013-06-01

    Attenuation of seismic waves in central Egypt had never been studied before. The results of the research on the seismic attenuation are based upon the information collected by the seismological network from 1998 to 2011. 855 earthquakes were selected from the Egyptian seismological catalog, with their epicenter distances between 15 and 150 km, their magnitudes ranging from 2 and 4.1 and focal depths reaching up to 30 km. The first systematic study of attenuation derived from the P-, S- and coda wave in the frequency range 1-24 Hz is presented. In the interpretation of the results both single and multiple scattering in a half space are considered. The single scattering model proposed by Sato (1977) was used. Two methods, the coda (Qc) and the Multiple Lapse Time Window (MLTW) method are used. The aim of this study is to validate these interpretations in the region and to try to identify the effects of attenuation due to intrinsic (Qi) and scattering attenuation (Qsc). The mean Qc value calculated was Qc = (39 ± 1)f1.0±0.009. The average Qc at 1.5 Hz is (53 ± 6) and Qc = (900 ± 195) at 24 Hz with Qo ranging between 23 and 107, where ? ranging between 0.9 and 1.3. The quality factor (Q) was estimated from spectra of P- and S-waves by applying a spectral ratio technique. The results show variations in Qp and QS as a function of frequency, according to the power law Q = 56?1.1. The seismic albedo is 0.7 at all stations and it mean that the earthquake activity is due to tectonic origin. The attenuation and frequency dependency for different paths and the correlation of the results with the geotectonic of the region are presented. The Qc values were calculated and correlated with the geology and tectonics of the area. The relatively low Qo and the high frequency dependency agree with the values of a region characterized by a low tectonic activity and vise versa.

  7. Bubbles attenuate elastic waves at seismic frequencies: First experimental evidence

    NASA Astrophysics Data System (ADS)

    Tisato, Nicola; Quintal, Beatriz; Chapman, Samuel; Podladchikov, Yury; Burg, Jean-Pierre

    2015-05-01

    The migration of gases from deep to shallow reservoirs can cause damageable events. For instance, some gases can pollute the biosphere or trigger explosions and eruptions. Seismic tomography may be employed to map the accumulation of subsurface bubble-bearing fluids to help mitigating such hazards. Nevertheless, how gas bubbles modify seismic waves is still unclear. We show that saturated rocks strongly attenuate seismic waves when gas bubbles occupy part of the pore space. Laboratory measurements of elastic wave attenuation at frequencies <100 Hz are modeled with a dynamic gas dissolution theory demonstrating that the observed frequency-dependent attenuation is caused by wave-induced-gas-exsolution-dissolution (WIGED). This result is incorporated into a numerical model simulating the propagation of seismic waves in a subsurface domain containing CO2-gas bubbles. This simulation shows that WIGED can significantly modify the wavefield and illustrates how accounting for this physical mechanism can potentially improve the monitoring and surveying of gas bubble-bearing fluids in the subsurface.

  8. Theoretical investigations on site attenuation - Propagation characteristics inside the measuring site for the radio interference

    Microsoft Academic Search

    T. Kawana; S. Miyajima

    1978-01-01

    Theoretical investigations are presented on the site attenuation of the measuring site in which radio interference waves radiated from electrical equipment are measured. The general formula for calculation of site attenuation was obtained from these investigations and the reference values were calculated by this formula. Comparing these values with the site attenuation values actually measured in an open field, good

  9. Influences of obstacle geometries on shock wave attenuation

    NASA Astrophysics Data System (ADS)

    Sha, S.; Chen, Z.; Jiang, X.

    2014-11-01

    The interactions of planar shock waves with obstacles of different geometries were investigated numerically using large eddy simulation and a high-order numerical scheme. The immersed boundary method was also employed to handle complex boundary geometries. The development and variations of shock wave structures during the interaction processes were discussed. The influences of the upper side, windward and leeward geometries of the obstacles on shock wave attenuation were also examined. Our numerical results showed that the shock wave attenuation is inversely related to the width of the upper side of the obstacles. For the windward sides of the obstacles, negative slopes have better effects on shock wave attenuation than do other values. In addition, the influence of the leeward slope on shock wave attenuation is weaker than that of the upside and windward slopes. Finally, obstacle shapes with a high efficiency for shock wave attenuation have been obtained and validated.

  10. 5. SOUND ATTENUATION 5.1 NATURE OF SOUND WAVE

    E-print Network

    Cambridge, University of

    5. SOUND ATTENUATION 5.1 NATURE OF SOUND WAVE Historically, acoustic is the scientific study of sound. Sound can be considered as a wave phenomenon. A sound wave is a longitudinal wave where particles the sound wave, the particles of the medium through which the sound moves is vibrating in a back and forth

  11. A heterogeneous nonlinear attenuating full-wave model of ultrasound.

    PubMed

    Pinton, Gianmarco F; Dahl, Jeremy; Rosenzweig, Stephen; Trahey, Gregg E

    2009-03-01

    A full-wave equation that describes nonlinear propagation in a heterogeneous attenuating medium is solved numerically with finite differences in the time domain (FDTD). Three-dimensional solutions of the equation are verified with water tank measurements of a commercial diagnostic ultrasound transducer and are shown to be in excellent agreement in terms of the fundamental and harmonic acoustic fields and the power spectrum at the focus. The linear and nonlinear components of the algorithm are also verified independently. In the linear nonattenuating regime solutions match results from Field II, a well established software package used in transducer modeling, to within 0.3 dB. Nonlinear plane wave propagation is shown to closely match results from the Galerkin method up to 4 times the fundamental frequency. In addition to thermoviscous attenuation we present a numerical solution of the relaxation attenuation laws that allows modeling of arbitrary frequency dependent attenuation, such as that observed in tissue. A perfectly matched layer (PML) is implemented at the boundaries with a numerical implementation that allows the PML to be used with high-order discretizations. A -78 dB reduction in the reflected amplitude is demonstrated. The numerical algorithm is used to simulate a diagnostic ultrasound pulse propagating through a histologically measured representation of human abdominal wall with spatial variation in the speed of sound, attenuation, nonlinearity, and density. An ultrasound image is created in silico using the same physical and algorithmic process used in an ultrasound scanner: a series of pulses are transmitted through heterogeneous scattering tissue and the received echoes are used in a delay-and-sum beam-forming algorithm to generate a images. The resulting harmonic image exhibits characteristic improvement in lesion boundary definition and contrast when compared with the fundamental image. We demonstrate a mechanism of harmonic image quality improvement by showing that the harmonic point spread function is less sensitive to reverberation clutter. PMID:19411208

  12. Extensional wave attenuation and velocity in partially-saturated sand in the sonic frequency range

    SciTech Connect

    Liu, Z.; Rector, J.W.; Nihei, K.T.; Tomutsa, L.; Myer, L.R.; Nakagawa, S.

    2002-06-17

    Extensional wave attenuation and velocity measurements on a high permeability Monterey sand were performed over a range of gas saturations for imbibition and degassing conditions. These measurements were conducted using extensional wave pulse propagation and resonance over a 1 - 9 kHz frequency range for a hydrostatic confining pressure of 8.3 MPa. Analysis of the extensional wave data and the corresponding X-ray CT images of the gas saturation show strong attenuation resulting from the presence of the gas (QE dropped from 300 for the dry sand to 30 for the partially-saturated sand), with larger attenuation at a given saturation resulting from heterogeneous gas distributions. The extensional wave velocities are in agreement with Gassmann theory for the test with near-homogeneous gas saturation and with a patchy saturation model for the test with heterogeneous gas saturation. These results show that partially-saturated sands under moderate confining pressure can produce strong intrinsic attenuation for extensional waves.

  13. Seismic wave attenuation and yield determination at regional distances

    Microsoft Academic Search

    B. J. Mitchell; O. W. Nuttli; J. K. Xie; H. Al-Shukri; A. Correig

    1989-01-01

    Work was completed on yield determination at the Soviet test site on Novaya Zemlya. Magnitudes and yields, determined for 30 explosions using Lg amplitudes recorded in northwestern Europe, ranged between 2.5 and 4900 kt, the largest since April 1976 being about 145 kt. Studies were completed on seismic wave attenuation of surface waves at intermediate periods and of Lg waves

  14. Attenuation in invasive blood pressure measurement systems

    Microsoft Academic Search

    A. Ercole

    2006-01-01

    Equations are presented relating measured and actual arterial blood pressures in terms of the model impedances. The reactive properties of such a partial obstruction may lead to an IABP trace that is superficially similar in appearance to the case of an over-damped measur- ement system. However, this phenomenon should be termed 'attenuation' rather than 'damping' and is probably more common.

  15. Teleseismic Body-Wave Attenuation beneath the Western and Central United States

    NASA Astrophysics Data System (ADS)

    Yang, B.; Reed, C. A.; Liu, K. H.; Gao, S. S.

    2014-12-01

    Attenuation of seismic waves is the consequence of anelasticity of the Earth's layers along the path of propagation. Joint analyses of seismic velocity with attenuation anomalies can significantly reduce the non-uniqueness in the interpretation of velocity images and result in a better understanding of the Earth's interior structure, composition, and dynamics. Employing a Bayesian approach with a common spectrum simultaneous inversion for attenuation factors (Gao, 1997), we have processed over 14,000 teleseismic body-wave seismograms recorded by all publicly available broadband seismic stations in the western and central United States. Preliminary results show extensive low-attenuation areas beneath the central United States probably related to fragments of the ancient Farallon slab, while less pronounced regions of likely cold material underlie the Colorado Plateau. High-attenuation anomalies are discovered in association with the Snake River Plain and the Rio Grande Rift. We apply station-averaged parameters and P-S attenuation ratios and compare our findings with published shear-wave splitting results to examine the presence of partial melt and asthenospheric upwelling. Additionally, we examine the azimuthal variation of attenuation measurements to constrain the possible existence of attenuation anisotropy and attempt to constrain the source depth of anisotropy through tomographic methods.

  16. Anisotropic changes in P-wave velocity and attenuation during deformation and fluid infiltration of granite

    USGS Publications Warehouse

    Stanchits, S.A.; Lockner, D.A.; Ponomarev, A.V.

    2003-01-01

    Fluid infiltration and pore fluid pressure changes are known to have a significant effect on the occurrence of earthquakes. Yet, for most damaging earthquakes, with nucleation zones below a few kilometers depth, direct measurements of fluid pressure variations are not available. Instead, pore fluid pressures are inferred primarily from seismic-wave propagation characteristics such as Vp/Vs ratio, attenuation, and reflectivity contacts. We present laboratory measurements of changes in P-wave velocity and attenuation during the injection of water into a granite sample as it was loaded to failure. A cylindrical sample of Westerly granite was deformed at constant confining and pore pressures of 50 and 1 MPa, respectively. Axial load was increased in discrete steps by controlling axial displacement. Anisotropic P-wave velocity and attenuation fields were determined during the experiment using an array of 13 piezoelectric transducers. At the final loading steps (86% and 95% of peak stress), both spatial and temporal changes in P-wave velocity and peak-to-peak amplitudes of P and S waves were observed. P-wave velocity anisotropy reached a maximum of 26%. Transient increases in attenuation of up to 483 dB/m were also observed and were associated with diffusion of water into the sample. We show that velocity and attenuation of P waves are sensitive to the process of opening of microcracks and the subsequent resaturation of these cracks as water diffuses in from the surrounding region. Symmetry of the orientation of newly formed microcracks results in anisotropic velocity and attenuation fields that systematically evolve in response to changes in stress and influx of water. With proper scaling, these measurements provide constraints on the magnitude and duration of velocity and attenuation transients that can be expected to accompany the nucleation of earthquakes in the Earth's crust.

  17. Dispersion and attenuation of acoustic waves in randomly heterogeneous media

    NASA Astrophysics Data System (ADS)

    Parra, J. O.; Hackert, C. L.; Ababou, R.; Sablik, M. J.

    1999-10-01

    We derive the effective displacement relation for acoustic waves in a spatially random heterogeneous one-dimensional medium. This relationship is expressed in terms of parameters ?R and ?A which represent the standard deviations of the randomly varying density ?( x) and the randomly varying Young's modulus ?( x), of the medium. In this way, we build the contributions into the total displacement relationship for the spatially random heterogeneous medium and apply this result to determine the dispersion and attenuation of acoustic waves propagating in the random heterogeneous medium. Attenuation and dispersion of waves propagating in media with randomly varying properties has been the subject of much study. Most of this work has neglected the effects of intrinsic dispersion and attenuation in order to concentrate on the effects of the medium inhomogeneities. We demonstrate how intrinsic attenuation may be easily included in the theoretical development, and explore the combined effects of scattering-based and intrinsic attenuation and dispersion on wave propagation. We apply the solution to model interwell acoustic waves propagating in the Kankakee formation at the Buckhorn Test Site, IL. The modeling results show that the strong dispersion in the frequency range of 500-2000 Hz is due to the reservoir heterogeneity. Alternatively, the velocity dispersion for frequencies greater than 2000 Hz corresponds to the intrinsic properties of the reservoir.

  18. Stochastic solution to a time-fractional attenuated wave equation.

    PubMed

    Meerschaert, Mark M; Straka, Peter; Zhou, Yuzhen; McGough, Robert J

    2012-10-01

    The power law wave equation uses two different fractional derivative terms to model wave propagation with power law attenuation. This equation averages complex nonlinear dynamics into a convenient, tractable form with an explicit analytical solution. This paper develops a random walk model to explain the appearance and meaning of the fractional derivative terms in that equation, and discusses an application to medical ultrasound. In the process, a new strictly causal solution to this fractional wave equation is developed. PMID:23258950

  19. Ultrasound attenuation measurement the presence scatterer variation

    E-print Network

    Drummond, Tom

    Ultrasound attenuation measurement the presence scatterer variation for reduction shadowing.cam.ac.uk #12; #12; Abstract Pulse­echo ultrasound display relies many assumptions which known incorrect. De­ parture these makes interpretation conventional ultrasound images di#cult, and visu­ alisations harder

  20. Ultrasonic attenuation of 700MHz surface acoustic waves in thin films of superconducting NbN

    Microsoft Academic Search

    H. P. Fredricksen; M. Levy; J. R. Gavaler; M. Ashkin

    1983-01-01

    The temperature dependence of the ultrasonic attenuation of 700-MHz surface acoustic waves has been measured for nine films of superconducting NbN varying in thickness from 0.02 to 0.3 mum. The films, sputter deposited on LiNbO3 substrates, exhibited attenuation changes in the superconducting state which were very similar in each case. These changes did not, however, follow the predictions of Bardeen,

  1. Shear wave anisotropy from aligned inclusions: ultrasonic frequency dependence of velocity and attenuation

    NASA Astrophysics Data System (ADS)

    de Figueiredo, J. J. S.; Schleicher, J.; Stewart, R. R.; Dayur, N.; Omoboya, B.; Wiley, R.; William, A.

    2013-04-01

    To understand their influence on elastic wave propagation, anisotropic cracked media have been widely investigated in many theoretical and experimental studies. In this work, we report on laboratory ultrasound measurements carried out to investigate the effect of source frequency on the elastic parameters (wave velocities and the Thomsen parameter ?) and shear wave attenuation) of fractured anisotropic media. Under controlled conditions, we prepared anisotropic model samples containing penny-shaped rubber inclusions in a solid epoxy resin matrix with crack densities ranging from 0 to 6.2 per cent. Two of the three cracked samples have 10 layers and one has 17 layers. The number of uniform rubber inclusions per layer ranges from 0 to 100. S-wave splitting measurements have shown that scattering effects are more prominent in samples where the seismic wavelength to crack aperture ratio ranges from 1.6 to 1.64 than in others where the ratio varied from 2.72 to 2.85. The sample with the largest cracks showed a magnitude of scattering attenuation three times higher compared with another sample that had small inclusions. Our S-wave ultrasound results demonstrate that elastic scattering, scattering and anelastic attenuation, velocity dispersion and crack size interfere directly in shear wave splitting in a source-frequency dependent manner, resulting in an increase of scattering attenuation and a reduction of shear wave anisotropy with increasing frequency.

  2. Dust concentration measurement probe using beta attenuation

    Microsoft Academic Search

    S. E. Slezak; R. O. Buckius

    1983-01-01

    A small probe utilizing the attenuation of the beta emissions from promethium-147 has been constructed and calibrated for measuring the suspension concentration of dusts in the range of 0.1 to 2.0 kg\\/m3. The absorption of beta particles (negatively charged electrons) is related to the amount of matter through which the particles pass. The probe discussed here measures the beta absorption

  3. Experimental and Numerical Investigation of Pressure Wave Attenuation due to Bubbly Layers

    NASA Astrophysics Data System (ADS)

    Jayaprakash, Arvind; Fourmeau, Tiffany; Hsiao, Chao-Tsung; Chahine, Georges; Dynaflow Inc. Team

    2013-03-01

    In this work, the effects of dispersed microbubbles on a steep pressure wave and its attenuation are investigated both numerically and experimentally. Numerical simulations were carried out using a compressible Euler equation solver, where the liquid-gas mixture was modeled using direct numerical simulations involving discrete deforming bubbles. To reduce computational costs a 1D configuration is used and the bubbles are assumed distributed in layers and the initial pressure profile is selected similar to that of a one-dimensional shock tube problem. Experimentally, the pressure pulse was generated using a submerged spark electric discharge, which generates a large vapor bubble, while the microbubbles in the bubbly layer are generated using electrolysis. High speed movies were recorded in tandem with high fidelity pressure measurements. The dependence of pressure wave attenuation on the bubble radii, the void fraction, and the bubbly layer thickness were parametrically studied. It has been found that the pressure wave attenuation can be seen as due to waves reflecting and dispersing in the inter-bubble regions, with the energy absorbed by bubble volume oscillations and re-radiation. Layer thickness and small bubble sizes were also seen as having a strong effect on the attenuation with enhanced attenuation as the bubble size is reduced for the same void fraction. In this work, the effects of dispersed microbubbles on a steep pressure wave and its attenuation are investigated both numerically and experimentally. Numerical simulations were carried out using a compressible Euler equation solver, where the liquid-gas mixture was modeled using direct numerical simulations involving discrete deforming bubbles. To reduce computational costs a 1D configuration is used and the bubbles are assumed distributed in layers and the initial pressure profile is selected similar to that of a one-dimensional shock tube problem. Experimentally, the pressure pulse was generated using a submerged spark electric discharge, which generates a large vapor bubble, while the microbubbles in the bubbly layer are generated using electrolysis. High speed movies were recorded in tandem with high fidelity pressure measurements. The dependence of pressure wave attenuation on the bubble radii, the void fraction, and the bubbly layer thickness were parametrically studied. It has been found that the pressure wave attenuation can be seen as due to waves reflecting and dispersing in the inter-bubble regions, with the energy absorbed by bubble volume oscillations and re-radiation. Layer thickness and small bubble sizes were also seen as having a strong effect on the attenuation with enhanced attenuation as the bubble size is reduced for the same void fraction. This study was supported by the Department of Energy, under SBIR Phase II Contract DE-FG02-07ER84839.

  4. Attenuation of weak shock waves along pseudo-perforated walls

    Microsoft Academic Search

    A. Sasoh; K. Matsuoka; K. Nakashio; E. Timofeev; K. Takayama; P. Voinovich; T. Saito; S. Hirano; S. Ono; Y. Makino

    1998-01-01

    .   In order to attenuate weak shock waves in ducts, effects of pseudo-perforated walls were investigated. Pseudo-perforated\\u000a walls are defined as wall perforations having a closed cavity behind it. Shock wave diffraction and reflection created by\\u000a these perforations were visualized in a shock tube by using holographic interferometer, and also by numerical simulation.\\u000a Along the pseudo-perforated wall, an incident shock

  5. Attenuation of acoustic waves in glacial ice and salt domes

    E-print Network

    Price, P B

    2005-01-01

    Two classes of natural solid media (glacial ice and salt domes) are under consideration as media in which to deploy instruments for detection of neutrinos with energy >1e18 eV. Though insensitive to 1e11 to 1e16 eV neutrinos for which observatories (e.g., AMANDA and IceCube) that utilize optical Cherenkov radiation detectors are designed, radio and acoustic methods are suited for searches for the very low fluxes of neutrinos with energies >1017 eV. This is because, due to the very long attenuation lengths of radio and acoustic waves in ice and salt, detection modules can be spaced very far apart. In this paper, I calculate the absorption and scattering coefficients as a function of frequency and grain size for acoustic waves in glacial ice and salt domes and show that experimental measurements on laboratory samples and in glacial ice and salt domes are consistent with theory. For South Pole ice with grain size 0.2 cm at -51 degrees C, scattering lengths are calculated to be 2000 km and 25 km at 10 kHz and 30 ...

  6. Shock waves attenuation by granular filters

    Microsoft Academic Search

    A Britan; G Ben-Dor; O Igra; H Shapiro

    2001-01-01

    Proper design of protecting filters mitigates the effect of blast and shock waves and thereby makes such filters effective protection against both accidental and planned explosions. The main goal of the present study was to clarify the filter performance in reducing the loading on structures as well as reducing the strength of the transmitted shock. While most of the granular

  7. Attenuation of sound waves in drill strings

    Microsoft Academic Search

    Douglas S. Drumheller

    1993-01-01

    During drilling of deep wells, digital data are often transmitted from sensors located near the drill bit to the surface. Development of a new communication system with increased data capacity is of paramount importance to the drilling industry. Since steel drill strings are used, transmission of these data by elastic carrier waves traveling within the drill pipe is possible, but

  8. Gravitons to Photons -- attenuation of gravitational waves

    E-print Network

    Preston Jones; Douglas Singleton

    2015-05-19

    In this essay we examine the response of an Unruh-DeWitt detector (a quantum two-level system) to a gravitational wave background. The spectrum of the Unruh-Dewitt detector is of the same form as some scattering processes or three body decays such as muon-electron scattering {\\it i.e.} $\\mu ^- + e^- \\rightarrow \

  9. Attenuation of acoustic waves in glacial ice and salt domes P. B. Price

    E-print Network

    Price, P. Buford

    Attenuation of acoustic waves in glacial ice and salt domes P. B. Price Physics Department and salt domes, are under consideration as media in which to deploy instruments for detection of neutrinos domes and show that experimental measurements on laboratory samples and in glacial ice and salt domes

  10. Extensional wave attenuation and velocity in partially saturated sand in the sonic frequency range

    SciTech Connect

    Liu, Z.; Rector, J.W.; Nihei, K.T.; Tomutsa, L.; Myer, L.R.; Nakagawa, S.

    2001-08-10

    Extensional wave attenuation and velocity measurements on a high permeability Monterey sand were performed over a range of gas saturations for imbibition and degassing conditions. These measurements were conducted using extensional wave pulse propagation and resonance over a 1-9 kHz frequency range for a hydrostatic confining pressure of 8.3 MPa. Analysis of the extensional wave data and the corresponding X-ray CT images of the gas saturation show strong attenuation resulting from the presence of the gas (Q{sub E} dropped from 300 for the dry sand to 30 for the partially-saturated sand), with larger attenuation at a given saturation resulting from heterogeneous gas distributions. The extensional wave velocities are in agreement with Gassmann theory for the test with near-homogeneous gas saturation and with a patchy saturation model for the test with heterogeneous gas saturation. These results show that partially-saturated sands under moderate confining pressure can produce strong intrinsic attenuation for extensional waves.

  11. Body Wave Crustal Attenuation Characteristics in the Garhwal Himalaya, India

    NASA Astrophysics Data System (ADS)

    Negi, Sanjay S.; Paul, Ajay; Joshi, Anand; Kamal

    2015-06-01

    We estimate frequency-dependent attenuation of P and S waves in Garhwal Himalaya using the extended coda normalization method for the central frequencies 1.5, 2, 3, 4, 6, 8, 10, 12, and 16 Hz, with earthquake hypocentral distance ranging from 27 to 200 km. Forty well-located local earthquake waveforms were used to study the seismic attenuation characteristics of the Garhwal Himalaya, India, as recorded by eight stations operated by Wadia Institute of Himalayan Geology, Dehradun, India, from 2007 to 2012. We find frequency-dependent P and S wave quality factors as defined by the relations Q P = 56 ± 8 f 0.91±0.002 and Q S = 151 ± 8 f 0.84±0.002 by fitting a power-law frequency dependence model for the estimated values over the whole region. Both the Q P and Q S values indicate strong attenuation in the crust of Garhwal Himalaya. The ratio of Q S/ Q P > 1 obtained for the entire analyzed frequency range suggests that the scattering loss is due to a random and high degree of heterogeneities in the earth medium, playing an important role in seismic wave attenuation in the Himalayan crust.

  12. Ultrasound attenuation as a quantitative measure of fracture healing

    NASA Astrophysics Data System (ADS)

    Gheduzzi, Sabina; Humphrey, Victor F.; Dodd, Simon P.; Cunningham, James L.; Miles, Anthony W.

    2004-10-01

    The monitoring of fracture healing still relies upon the judgment of callus formation and on the manual assessment of the stiffness of the fracture. A diagnostic tool capable of quantitatively measuring healing progression of a fracture would allow the fine-tuning of the treatment regime. Ultrasound attenuation measurements were adopted as a possible method of assessing the healing process in human long bones. The method involves exciting ultrasonic waves at 200 kHz in the bone and measuring the reradiation along the bone and across the fracture zone. Seven cadaveric femora were tested in vitro in intact form and after creating a transverse fracture by sawing through the cortex. The effects of five different fracture types were investigated. A partial fracture, corresponding to a 50% cut through the cortex, a closed fracture, and fractures of widths varying between 1, 2, and 4 mm were investigated. The introduction of a fracture was found to produce a dramatic effect on the amplitude of the signal. Ultrasound attenuation was found to be sensitive to the presence of a fracture, even when the fracture was well reduced. It would therefore appear feasible to adopt attenuation across a fracture as a quantitative measurement of fracture healing.

  13. Ultrasonic plate waves for biochemical measurements

    Microsoft Academic Search

    B. I. Costellot; B. A. Martin; R. M. Whitet

    1989-01-01

    Flexural plate waves can propagate nonradiatively along liquid-immersed plates provided the plate-wave velocity is lower than the speed of sound in the liquid. This low-loss condition has been exploited to measure biochemical processes in liquids. Proteins or other biomolecules that adsorb to the plate surface lower the plate wave velocity, while the viscosity of the liquid causes attenuation of the

  14. Attenuation of acoustic waves in glacial ice and salt domes

    E-print Network

    P. B. Price

    2005-06-27

    Two classes of natural solid media (glacial ice and salt domes) are under consideration as media in which to deploy instruments for detection of neutrinos with energy >1e18 eV. Though insensitive to 1e11 to 1e16 eV neutrinos for which observatories (e.g., AMANDA and IceCube) that utilize optical Cherenkov radiation detectors are designed, radio and acoustic methods are suited for searches for the very low fluxes of neutrinos with energies >1017 eV. This is because, due to the very long attenuation lengths of radio and acoustic waves in ice and salt, detection modules can be spaced very far apart. In this paper, I calculate the absorption and scattering coefficients as a function of frequency and grain size for acoustic waves in glacial ice and salt domes and show that experimental measurements on laboratory samples and in glacial ice and salt domes are consistent with theory. For South Pole ice with grain size 0.2 cm at -51 degrees C, scattering lengths are calculated to be 2000 km and 25 km at 10 kHz and 30 kHz, respectively, and the absorption length is calculated to be 9 km at frequencies above 100 Hz. For NaCl (rock salt) with grain size 0.75 cm, scattering lengths are calculated to be 120 km and 1.4 km at 10 kHz and 30 kHz, and absorption lengths are calculated to be 30,000 km and 3300 km at 10 kHz and 30 kHz. Existing measurements are consistent with theory. For ice, absorption is the limiting factor; for salt, scattering is the limiting factor.

  15. Study of transmission line attenuation in broad band millimeter wave frequency range

    NASA Astrophysics Data System (ADS)

    Pandya, Hitesh Kumar B.; Austin, M. E.; Ellis, R. F.

    2013-10-01

    Broad band millimeter wave transmission lines are used in fusion plasma diagnostics such as electron cyclotron emission (ECE), electron cyclotron absorption, reflectometry and interferometry systems. In particular, the ECE diagnostic for ITER will require efficient transmission over an ultra wide band, 100 to 1000 GHz. A circular corrugated waveguide transmission line is a prospective candidate to transmit such wide band with low attenuation. To evaluate this system, experiments of transmission line attenuation were performed and compared with theoretical loss calculations. A millimeter wave Michelson interferometer and a liquid nitrogen black body source are used to perform all the experiments. Atmospheric water vapor lines and continuum absorption within this band are reported. Ohmic attenuation in corrugated waveguide is very low; however, there is Bragg scattering and higher order mode conversion that can cause significant attenuation in this transmission line. The attenuation due to miter bends, gaps, joints, and curvature are estimated. The measured attenuation of 15 m length with seven miter bends and eighteen joints is 1 dB at low frequency (300 GHz) and 10 dB at high frequency (900 GHz), respectively.

  16. Dust concentration measurement probe using beta attenuation

    NASA Astrophysics Data System (ADS)

    Slezak, S. E.; Buckius, R. O.

    1983-05-01

    A small probe utilizing the attenuation of the beta emissions from promethium-147 has been constructed and calibrated for measuring the suspension concentration of dusts in the range of 0.1 to 2.0 kg/m3. The absorption of beta particles (negatively charged electrons) is related to the amount of matter through which the particles pass. The probe discussed here measures the beta absorption through a 3.8-cm path length at sample rates up to 20 samples per second. The small size of the probe (16 cm overall) allows real-time in situ local measurements of the suspension of a dust. The basic theory of operation and details of the probe operation are presented. Data from the probe for use in dust flammability experiments are also presented.

  17. Frequency-dependent attenuation of S-waves in the Kanto region, Japan

    NASA Astrophysics Data System (ADS)

    Yoshimoto, K.; Okada, M.

    2009-09-01

    Apparent, scattering, and intrinsic S-wave attenuations (QS-1, Qscat-1 and Qint-1) of the upper lithosphere in the Kanto region of Japan were measured in the 1- to 32-Hz frequency range using Multiple Lapse Time Window Analysis (MLTWA) for 115 borehole seismograms of local earthquakes. A new set of time windows for MLTWA, in which multiple isotropic scattering is assumed, was proposed and employed to estimate the frequency dependence of S-wave attenuation parameters. Scattering attenuation was found to dominate intrinsic attenuation in the S-wave attenuation mechanism at low frequencies (<2 Hz), whereas the opposite relation was observed at high frequencies. The transition is caused by the different frequency dependences of Qscat-1(? f -1.5) and Qint-1(? f -0.7) at this frequency. Interestingly, Qscat-1 is almost frequency independent at frequencies >8 Hz, which implies the self-similar nature of short-wavelength heterogeneities in the upper lithosphere. In terms of the upper lithosphere of the Kanto region, these results may indicate that the random heterogeneities characterized by the Gaussian autocorrelation function with a fractional fluctuation ? ? 10% and a correlation length a ? 2 km are superimposed on the weak background self-similar heterogeneity.

  18. Attenuation of an air shock wave by perforated baffles

    SciTech Connect

    Klapovskii, V.E.; Grigor'ev, G.S.; Logvenov, A.Y.; Mineev, V.N.; Vershinin, V.Y.

    1984-03-01

    One of the ways of attenuating an air shock wave (ASW) is to use a perforated shield; the parameters of the ASW behind a perforated baffle in the form of a steel sheet with holes are determined by the amplitude of the incident ASW and the sheet perforation coefficient. The authors examine the effects of the perforated shield structure on the ASW behind it and examples are given where the results can be used in the design of test chambers.

  19. Attenuation of Coda Waves in the Saurashtra Region, Gujarat (India)

    Microsoft Academic Search

    Babita Sharma; Dinesh Kumar; S. S. Teotia; B. K. Rastogi; Arun K. Gupta; Srichand Prajapati

    2011-01-01

    The attenuation characteristics based on coda waves of two areas—Jamnagar and Junagarh of Saurashtra, Gujarat (India)—have\\u000a been investigated in the present study. The frequency dependent relationships have been developed for both the areas using\\u000a single back scattering model. The broadband waveforms of the vertical components of 33 earthquakes (Mw 1.5–3.5) recorded at\\u000a six stations of the Jamnagar area, and broadband

  20. Seismic wave attenuation and dispersion in thin layer sequences

    E-print Network

    Edwards, Clifford Murray

    1975-01-01

    be attributed to wave propagation through cyclic sequences consisting of thin layers with no absorption. iv Multiples tend to disperse the seismogram in the time domain, In frequency bands in which dispersion is pronounced, notches appear in the amplitude... Truncation 22 Group Velocities The Notch Attenuation Models Investigated Equal Thickness Layers Models With Two Layer Thicknesses 'Stratified System Between Half Spaces Distribution of Layer Thicknesses With Only Two Veloci. ties Conclusions...

  1. Shock wave attenuation by perforated plates with various hole sizes

    Microsoft Academic Search

    C. Kingery; R. Pearson; G. Coulter

    1977-01-01

    Results are presented for a set of experiments designed to determine the attenuation of shock waves passing through perforated plates as a function of peak overpressure and hole size for a given percentage of plate area vented. The venting hole size was varied from 1\\/8 inch (0.32 cm) to 2-13\\/16 inches (7.14 cm) as the vented area was varied from

  2. Wave attenuation over coastal salt marshes under storm surge conditions

    NASA Astrophysics Data System (ADS)

    Möller, Iris; Kudella, Matthias; Rupprecht, Franziska; Spencer, Tom; Paul, Maike; van Wesenbeeck, Bregje K.; Wolters, Guido; Jensen, Kai; Bouma, Tjeerd J.; Miranda-Lange, Martin; Schimmels, Stefan

    2014-10-01

    Coastal communities around the world face an increasing risk from flooding as a result of rising sea level, increasing storminess and land subsidence. Salt marshes can act as natural buffer zones, providing protection from waves during storms. However, the effectiveness of marshes in protecting the coastline during extreme events when water levels are at a maximum and waves are highest is poorly understood. Here we experimentally assess wave dissipation under storm surge conditions in a 300-metre-long wave flume tank that contains a transplanted section of natural salt marsh. We find that the presence of marsh vegetation causes considerable wave attenuation, even when water levels and waves are highest. From a comparison with experiments without vegetation, we estimate that up to 60% of observed wave reduction is attributed to vegetation. We also find that although waves progressively flatten and break vegetation stems and thereby reduce dissipation, the marsh substrate remained stable and resistant to surface erosion under all conditions. The effectiveness of storm wave dissipation and the resilience of tidal marshes even at extreme conditions suggest that salt marsh ecosystems can be a valuable component of coastal protection schemes.

  3. Determination of seismic attenuation from surface and downhole measurements

    Microsoft Academic Search

    Shengjie Sun

    2000-01-01

    Attenuation is a potentially very important seismic attribute for seismic exploration and reservoir characterization. In order for attenuation to be utilized successfully as an attribute, it must first be reliably extracted from the seismic data and separated from scattering effects. Existing methods meet fatal difficulties in measuring attenuation from both surface seismic data and vertical seismic profile (VSP) data. Intrinsic

  4. Attenuation of Correlation by Measurement Unreliability and Two Approaches for Correcting the Attenuation.

    ERIC Educational Resources Information Center

    Fan, Xitao

    This study focused on the issue of measurement reliability and its attenuation on correlation between two composites and two seemingly different approaches for correcting the attenuation. As expected, Monte Carlo simulation results show that correlation coefficients uncorrected for measurement error are systematically biased downward. For the data…

  5. Seismic Wave Attenuation Estimated from Tectonic Tremor and Radiated Energy in Tremor for Various Subduction Zones

    NASA Astrophysics Data System (ADS)

    Yabe, S.; Baltay, A.; Ide, S.; Beroza, G. C.

    2013-12-01

    Ground motion prediction is an essential component of earthquake hazard assessment. Seismic wave attenuation with distance is an important, yet difficult to constrain, factor for such estimation. Using the empirical method of ground motion prediction equations (GMPEs), seismic wave attenuation with distance, which includes both the effect of anelastic attenuation and scattering, can be estimated from the distance decay of peak ground velocity (PGV) or peak ground acceleration (PGA) of ordinary earthquakes; however, in some regions where plate-boundary earthquakes are infrequent, such as Cascadia and Nankai, there are fewer data with which to constrain the empirical parameters. In both of those subduction zones, tectonic tremor occurs often. In this study, we use tectonic tremor to estimate the seismic wave attenuation with distance, and in turn use the attenuation results to estimate the radiated seismic energy of tremor. Our primary interest is in the variations among subduction zones. Ground motion attenuation and the distribution of released seismic energy from tremors are two important subduction zone characteristics. Therefore, it is very interesting to see whether there are variations of these parameters in different subduction zones, or regionally within the same subduction zone. It is also useful to estimate how much energy is released by tectonic tremor from accumulated energy to help understand subduction dynamics and the difference between ordinary earthquakes and tremor. We use the tectonic tremor catalog of Ide (2012) in Nankai, Cascadia, Mexico and southern Chile. We measured PGV and PGA of individual tremor bursts at each station. We assume a simple GMPE relationship and estimate seismic attenuation and relative site amplification factors from the data. In the Nankai subduction zone, there are almost no earthquakes on the plate interface, but intra-slab earthquakes occur frequently. Both the seismic wave attenuation with distance and the site response obtained from intra-slab earthquakes is almost the same as that determined from tectonic tremor. This means the attenuation parameter should be well estimated from tremor. Furthermore, we find substantial along-strike variation in the estimated attenuation parameter in the Nankai subduction zone, allowing us to infer with-in region differences in behavior.

  6. Attenuation of shock waves in copper and stainless steel

    SciTech Connect

    Harvey, W.B.

    1986-06-01

    By using shock pins, data were gathered on the trajectories of shock waves in stainless steel (SS-304L) and oxygen-free-high-conductivity copper (OFHC-Cu). Shock pressures were generated in these materials by impacting the appropriate target with thin (approx.1.5 mm) flying plates. The flying plates in these experiments were accelerated to high velocities (approx.4 km/s) by high explosives. Six experiments were conducted, three using SS-304L as the target material and three experiments using OFHC-Cu as the target material. Peak shock pressures generated in the steel experiments were approximately 109, 130, and 147 GPa and in the copper experiments, the peak shock pressures were approximately 111, 132, and 143 GPa. In each experiment, an attenuation of the shock wave by a following release wave was clearly observed. An extensive effort using two characteristic codes (described in this work) to theoretically calculate the attenuation of the shock waves was made. The efficacy of several different constitutive equations to successfully model the experiments was studied by comparing the calculated shock trajectories to the experimental data. Based on such comparisons, the conclusion can be drawn that OFHC-Cu enters a melt phase at about 130 GPa on the principal Hugoniot. There was no sign of phase changes in the stainless-steel experiments. In order to match the observed attenuation of the shock waves in the SS-304L experiments, it was necessary to include strength effects in the calculations. It was found that the values for the parameters in the strength equations were dependent on the equation of state used in the modeling of the experiments. 66 refs., 194 figs., 77 tabs.

  7. Anelastic Attenuation and Elastic Scattering of Seismic Waves in the Los Angeles Region

    NASA Astrophysics Data System (ADS)

    Song, X.; Jordan, T. H.

    2013-12-01

    The accuracy of earthquake simulations needed for physics-based seismic hazard analysis depends on good information about crustal structure. For low-frequency (f < 0.3 Hz) simulations, the most important structural parameters are the seismic wave velocities, but as the frequencies increase, seismic wave attenuation becomes more important. We compare attenuation models that have been recently used in the CyberShake hazard model (Graves et al., 2011) and other simulation studies for the Los Angeles region (Olsen et al., 2009; Taborda & Bielak, 2013) with constraints from local earthquake data out to 10 Hz, which include those from Hauksson & Shearer's (2006) attenuation tomography as well as our own measurements. We show that the velocity-attenuation scaling relationship for shear waves employed by CyberShake (QS = 50VS, where VS is in km/s) provides a good approximation to the average crustal structure at f = 0.3 Hz, but it does not capture the lateral variations in QS at shallow depths. Moreover, this frequency-independent model is inconsistent with the high QS values observed throughout most of the crust at f > 1 Hz. The data indicate a frequency-dependent attenuation of the form QS ~ f ?, where 0.5 ? ? ? 0.8. Anomalously low QS factors are observed at very shallow depths, which can be explained by a combination of anelastic attenuation and elastic scattering. The scattering parameters are roughly consistent with small-scale, near-surface heterogeneities observed in well-logs and seismic reflection surveys in the Los Angeles basin. High-frequency scattering may also play a role in explaining Hauksson & Shearer's (2006) observation that the QP/QS ratio is anomalously low (~ unity). We summarize the observations in a new attenuation and scattering model for the CyberShake region that is laterally heterogeneous and frequency dependent.

  8. Seismic Attenuation Technology for the Advanced Virgo Gravitational Wave Detector

    NASA Astrophysics Data System (ADS)

    Beker, M. G.; Blom, M.; van den Brand, J. F. J.; Bulten, H. J.; Hennes, E.; Rabeling, D. S.

    The current interferometric gravitational wave detectors are being upgraded to what are termed 'second generation' devices. Sensitivities will be increased by an order of magnitude and these new instruments are expected to uncover the ?eld of gravitational astronomy. A main challenge in this endeavor is the mitigation of noise induced by seismic motion. Detailed studies with Virgo show that seismic noise can be reinjected into the dark fringe signal. For example, laser beam jitter and backscattered light limit the sensitivity of the interferometer. Here, we focus on seismic attenuators based on compact inverted pendulums in combination with geometric anti-prings to obtain 40 dB of attenuation above 4 Hz in six degrees of freedom. Low frequency resonances (< 0.5 Hz) are damped by using a control system based on input from LVDTs and geophones. Such systems are under development for the seismic attenuation of optical benches operated both in air and vacuum. The design and realization of the seismic attenuation system for the Virgo external injection bench, including its control scheme, will be discussed and stand-alone performance presented.

  9. Fiber Attenuation To measure the attenuation coefficient of a multi-mode fiber, and to

    E-print Network

    Collins, Gary S.

    Fiber Attenuation Purpose: To measure the attenuation coefficient of a multi-mode fiber, and to see the effect of mode scrambling on the fiber output. Equipment: · optics table, or 2'x2' breadboard · 4 1 -20 (340C) · short rod For the fiber- · F-MLD-500 fiber (~500 meters) · fiber coupler · 20X objective lens

  10. Electric field analysis in the earth considering attenuation of electromagnetic waves propagated in lossy media

    SciTech Connect

    Mackawa, T.; Shimada, T.; Inoue, S.; Jitsumori, A. (Mitsubishi Electric Corp., 8-1-1 Tsukaguchi-honmachi, Amagasaki, Hyogo 661 (JP)); Okumura, N. (Japan National Oil Corp., 1-1-2 Hamada, Chiba 260 (JP)); Akizuki, K. (Waseda Univ., 3-4-1 Okubo, Shinjuku-ku, Tokyo 160 (JP))

    1992-03-01

    In the field of oil well drilling. EM-MWD (Electromagnetic Measurement While Drilling) offers many advantages. The EM-MWD system can transmit measured data from the well bottom to the surface with high speed using electromagnetic waves. Developing the EM-MWD technology requires analysis of the electric field around a drill string. A new computer simulation method has been developed. The method considers attenuation of electromagnetic waves propagated in lossy media, the earth, using features of analysis models. This paper reports that the simulation method can be applied to waveform simulation. This method has been verified by field experiment using a borehole of 500m depth.

  11. Imaging Rayleigh Wave Attenuation and Phase Velocity beneath North America with USArray

    NASA Astrophysics Data System (ADS)

    Bao, X.; Dalton, C. A.; Jin, G.; Gaherty, J. B.

    2014-12-01

    The EarthScope USArray provides an opportunity to obtain detailed images of the continental upper mantle of United States at a novel scale. The majority of mantle models derived from USArray data contain spatial variations in velocity; however, little is known about the attenuation structure of the North American upper mantle. Joint interpretation of seismic attenuation and velocity models can improve upon the interpretations based only on velocity, and provide important constraints on the temperature, composition, melt content, and volatile content of the mantle. In this study, Rayleigh wave travel time and amplitude are measured using an interstation cross-correlation version of the Generalized Seismological Data Functional algorithm, which takes advantage of waveform similarity at nearby stations. Our data are from 670 large teleseismic earthquakes that occurred from 2006 to 2014 and were recorded by 1,764 Transportable Array stations. More than 4.8 million measurements at periods between 20 and 100 s are collected into our database. Isolating the signal of attenuation in the amplitude observations is challenging because amplitudes are sensitive to a number of factors in addition to attenuation, such as focusing/defocusing and local site amplification. We generate several Rayleigh wave attenuation maps at each period, using several different approaches to account for source and receiver effects on amplitude. This suite of attenuation maps allows us to distinguish between the robust features in the maps and the features that are sensitive to the treatment of source and receiver effects. We apply Helmholtz surface-wave tomography (Lin et al., 2012) to determine velocity and attenuation maps. A significant contrast in velocity and attenuation is observed in the transition between the western and central United States along the Rocky Mountain front. We find low Q values in the western US, along the eastern coast, and the Gulf plain. These areas are also characterized by low wave speed in the phase-velocity maps. The lateral variations in Q may indicate possible temperature variations in the upper mantle of the continental interior. Our Q maps in the western US show good agreement with those presented by Lin et al. (2012). Both models contain low Q (< 100) beneath the Colorado Plateau and the West Coast for 60 s.

  12. Temporal change in coda wave attenuation observed during an eruption of Mount St. Helens

    SciTech Connect

    Fehler, M.; Roberts, P.; Fairbanks, T.

    1988-05-10

    During the past few years there have been numerous reports of changes in coda wave attenuation occurring before major earthquakes. These observations are important because they may provide insight into stress-related structural changes taking place in the focal region prior to the occurrence of large earthquakes. The results of these studies led us to suspect that temporal changes in coda wave attenuation might also accompany volcanic eruptions. By measuring power decay envelopes for earthquakes at Mount St. Helens recorded before, during, and after an eruption that took place during September 3--6, 1981, we found that coda Q/sup -1/ for frequencies between 6 and 30 Hz was 20--30% higher before the eruption than after. The change is attributed to an increase in the density of open microcracks in the rock associated with inflation of the volcano prior to the eruption. Q/sup -1/ was found to be only weakly dependent on frequency and displayed a slight peak near 10 Hz. The weak frequency dependence is attributed to the dominance of intrinsic attenuation over scattering attenuation, since it is generally accepted that intrinsic attenuation is constant with frequency, whereas scattering attenuation decreases strongly at higher frequencies. The weak frequency dependence of Q/sup -1/ at Mount St. Helens contrasts with results reported for studies in nonvolcanic regions. The peak in Q/sup -1/ near 10 Hz at Mount St. Helens is attributed to the scale length of heterogeneity responsible for generating backscattered waves. Results for nonvolcanic regions have shown this peak to occur near 0.5 Hz. Thus a smaller scale length of heterogeneity is required to explain the 10-Hz peak at Mount St. Helens. copyright American Geophysical Union 1988

  13. Attenuation of shock waves propagating in polyurethane foams

    Microsoft Academic Search

    K. Kitagawa; M. Yasuhara; K. Takayama

    2006-01-01

    Shock wave attenuation in polyurethane foams is investigated experimentally and numerically. This study is a part of research\\u000a project regarding shock propagation in polyurethane foams with high-porosities\\u000a $$\\\\phi_{g}$$  =  0.951 ~ 0.977 and low densities of ?c  =  27.6 ~55.8 kg\\/m3. Sixty Millimeter long cylindrical foams with various cell numbers and foam insertion condition were installed in a horizontal\\u000a shock tube

  14. Numerical investigation of wave attenuation by vegetation using a 3D RANS model

    NASA Astrophysics Data System (ADS)

    Marsooli, Reza; Wu, Weiming

    2014-12-01

    Vegetation has been recognized as an important natural shoreline protection against storm surges and waves. Understanding of wave-vegetation interaction is essential for assessing the ability of vegetation patches, such as wetlands, to mitigate storm damages. In this study the wave attenuation by vegetation is investigated numerically using a 3-D model which solves the Reynolds-Averaged Navier-Stokes equations (RANS) by means of a finite-volume method based on collocated hexahedron mesh. A mixing length model is used for turbulence closure of the RANS equations. The water surface boundary is tracked using the Volume-of-Fluid (VOF) method with the Compressive Interface Capturing Scheme for Arbitrary Meshes (CICSAM) to solve the VOF advection equation. The presence of vegetation is taken into account by adding the vegetation drag and inertia forces to the momentum equations. The model is validated by several laboratory experiments of short wave propagation through vegetation over flat and sloping beds. The comparisons show good agreement between the measured data and calculated results, but the swaying motion of flexible vegetation which is neglected in this study can influence the accuracy of the wave height predictions. The model is then applied to one of the validation tests with different vegetation properties, revealing that the wave height attenuation by vegetation depends not only on the wave conditions, but also the vegetation characteristics such as vegetation height and density.

  15. Separating thermal coagulation and cavitation effects in HIFU attenuation measurements

    Microsoft Academic Search

    Justin Reed; Michael Bailey; Ajay Anand; Peter Kaczkowski

    2003-01-01

    HIFU can be used to destroy tumors. The conversion of acoustic energy into heat causes protein coagulation (Lesion) in tissue. Attenuation measurements have been proposed to monitor the progression of thermal therapy. The goal of this work is to study and separate the effects of cavitation and thermal coagulation in attenuation measurements. A HIFU transducer was used to treat Bovine

  16. Direct determination of the attenuation coefficient for radionuclide volume measurements

    Microsoft Academic Search

    A. M. Keller; T. R. Simon; T. C. Smitherman; C. R. Malloy; G. J. Dehmer

    1987-01-01

    Correcting for the attenuation of photons between the cardiac chambers and chest surface is crucial for accurate nongeometric ventricular volume determinations from equilibrium radionuclide angiograms. Previous techniques have assumed that the attenuation coefficient of water for \\/sup 99m\\/Tc (0.15\\/cm) should be used for this correction. In this study, this assumption was tested directly by measuring attenuation of the activity of

  17. The propagation and attenuation of complex acoustic waves in treated circular and annular ducts

    NASA Technical Reports Server (NTRS)

    Reethof, G.

    1976-01-01

    The propagation of plane waves and higher order acoustic modes in a circular multisectioned duct was studied. A unique source array consisting of two concentric rings of sources, providing phase and amplitude control in the radial, as well as circumferential direction, was developed to generate plane waves and both spinning and nonspinning higher order modes. Measurements of attenuation and radial mode shapes were taken with finite length liners between the hard wall sections of an anechoically terminated duct. Materials tested as liners included a glass fiber material and both sintered fiber metals and perforated sheet metals with a honeycomb backing. The fundamental acoustic properties of these materials were studied with emphasis on the attenuation of sound by the liners and the determination of local versus extended reaction behavior for the boundary condition. The experimental results were compared with a mathematical model for the multisectioned duct.

  18. Seismic wave attenuation and yield determination at regional distances

    NASA Astrophysics Data System (ADS)

    Mitchell, B. J.; Nuttli, O. W.; Xie, J. K.; Al-Shukri, H.; Correig, A.

    1989-05-01

    Work was completed on yield determination at the Soviet test site on Novaya Zemlya. Magnitudes and yields, determined for 30 explosions using Lg amplitudes recorded in northwestern Europe, ranged between 2.5 and 4900 kt, the largest since April 1976 being about 145 kt. Studies were completed on seismic wave attenuation of surface waves at intermediate periods and of Lg waves at 1 Hz in several regions of the world. Limits were determined for the degree of frequency dependence of Q sub beta which can occur in the crust in stable and tectonically active regions. A stochastic convolution model was proposed for Lg coda at distances greater than 200 km which considers the effects of dispersion scattering and mode conversions at those distances. A back projection tomographic method was developed to regionalize large scale lateral variations of coda Q for Lg waves which traverse long continental paths. A seismically active region in the New Madrid seismic zone was found to be characterized by lower than normal Q values. In the western United States it was found that Q values in the upper mantle vary laterally, becoming smaller from east to west. Crust of the Basin and Range province has a low-Q upper crust overlying a lower crust with higher Q values.

  19. Wave Velocity Attenuation and Sediment Retention among Different Vegetation Types in a Pacific Northwest Estuary

    NASA Astrophysics Data System (ADS)

    Lemein, T.; Cox, D. T.; Albert, D.; Blackmar, P.

    2012-12-01

    Feedbacks between vegetation, wave climate, and sedimentation create stable ecosystem states within estuaries that provide ecosystem services such as wildlife habitat, erosion control, and pollution filtration. Flume and field studies conducted with cordgrass (Spartina spp.) and sea grasses (Zostera spp., Halodule spp.) have demonstrated that the presence of vegetation reduces wave energy and increases sediment retention. Since the spatial distribution of plant species and the presence of unique plant species differ between estuaries, there is a need to understand how individual plant species, or groups of species with similar morphology, influence wave characteristics and sedimentation. Within Tillamook Bay, Oregon, three species of emergent vascular vegetation species (Carex lyngbyei, Eleocharis sp., Schoenoplectus pungens) and one species of submergent vascular vegetation species (Zostera marina) are present in the high wave energy portion of the estuary at the border of open water and the start of vegetation. These species represent three distinct growth forms (emergent reeds, emergent grasses, submergent grasses) and occur at varying densities relative to each other, as well as within the estuary. Using paired acoustic Doppler velocimeters (ADVs), we quantify the relative attenuation of wave velocity between vegetation types and densities within the estuary and compare these results with published attenuation rates from flume and field studies in different environments. The effect of decreased wave velocity on sediment retention is measured using permanent sediment markers within and outside of vegetation stands and paired with ADV data. Sediment retention is predicted to vary seasonally with seasonal vegetation composition changes and remain constant in unvegetated areas. From this experiment we expect to identify like groups of plant species whose attenuation characteristics are the same, allowing for models of wave-vegetation-sediment interaction to be created with multiple vegetation types.

  20. Measurements of spectral attenuation coefficients in the lower Chesapeake Bay

    NASA Technical Reports Server (NTRS)

    Houghton, W. M.

    1983-01-01

    The spectral transmission was measured for water samples taken in the lower Chesapeake Bay to allow characterization of several optical properties. The coefficients of total attenuation, particle attenuation, and absorption by dissolved organic matter were determined over a wavelength range from 3500 A to 8000 A. The data were taken over a 3 year period and at a number of sites so that an indication of spatial and temporal variations could be obtained. The attenuations determined in this work are, on the average, 10 times greater than those obtained by Hulburt in 1944, which are commonly accepted in the literature for Chesapeake Bay attenuation.

  1. Lg waves attenuation studies over the Iranian Plateau and Zagros

    NASA Astrophysics Data System (ADS)

    Kaviani, A.; Sandvol, E. A.; Rumpker, G.; Ku, W.; Gok, R.

    2012-12-01

    Waveforms from regional events collected over the last 15 years by the permanent seismological networks and temporary deployments deployed within the Iranian plateau provide a unique and unprecedented opportunity to investigate the crustal and mantle attenuation characteristics by analysis of the regional phases including Lg and Pg waves. We have investigated the crustal attenuation using Lg waveforms available from 305 stations consisting of 101 permanent and 204 temporary stations. This study is performed within the framework of a larger project aimed at developing high-resolution seismic attenuation models for the Iranian plateau and the Zagros mountains using different data and approaches. We have combined the Iranian data set with data from numerous networks across Turkey, Georgia, Azerbaijan, Syria, Jordan, and Saudi Arabia. This combination provides us with waveforms from over 550 stations spanning most of the Northern Middle East. Simultaneous inversion of the Lg Q values calculated using two-station paths gives us a model of Lg Q that extends from the western Anatolian plate to the eastern edge of the Iranian plateau. Prior studies have suggested strong complexity in the crustal and uppermost mantle attenuation structure beneath much of the Iranian plateau and the surrounding regions. Lg waves propagating over different paths in this region show strong variations in amplitude and frequency content due to this very complex structure. We have created a frequency dependent Lg Q model that covers most of the Iranian plateau using instrument corrected two station method that eliminates the contributions from the source. Our model maps Lg Q around 200 for most part of the central Iranian plateau and Alborz mountains whereas it is lower than 150 for the western Anatolian plateau. Relatively high Q values (>300) are observed in the Zagros belt that abruptly changes across the Zagros suture. We have also found unexpected results, including a high Q zone that surrounds the Caspian Sea. We argue that it originates from energy that is bending around the south Caspian Sea oceanic crust as well as efficient Lg propagation through the Alborz mountain crust.

  2. Imaging the attenuation structure beneath the northwestern margin of Colorado Plateau: Integrating seismic body-wave observations and forward modeling

    NASA Astrophysics Data System (ADS)

    Bellis, C.; Lin, P.; Holtzman, B. K.; Gaherty, J. B.; Roy, M.

    2013-12-01

    The upper mantle beneath the Colorado Plateau (CP) is characterized by high seismic velocities in the plateau interior and lower seismic velocities beneath the plateau margins, below the Basin and Range to the west and the Rio Grande Rift to the east. The seismic velocity contrast across the margins has been interpreted as a thermal- mechanical modification of the sub-CP lithospheric keel, by various mechanisms. Using teleseismic P- and S-wave spectra from the La Ristra 1.5 Array and EarthScope USArray Transportable Array (TA), we measure t*, the seismic parameter representing integrated attenuation along a ray path, across the western margin of the CP. For wave fields from two sets of earthquakes to the Northwest and Southeast of the CP, we measured the spectra of P- and S-waves at each station, relative to the spectra of the reference stations and extracted the differential attenuation factor (dt*) across the frequency band 0.2-4 Hz for P waves and 0.1-1.5 Hz for S waves for each event-station pair. To first order, both tp* and ts* varies from higher in the Basin and Range to lower on the CP, which suggests that coherent variations in attenuation are present across the Northwestern margin of the CP. However, the gradients of dt* for the two sets of NW and SE wave fields are significantly different, with a sharper gradient observed for the NW set. One of our primary questions concerns the origin of these variations: to what extent do they reflect the spatial distribution of intrinsic attenuation structure or wave propagation effects such as focusing and defocusing. To address these questions, our approach is to first build 1- and 2-D models for hypothetical spatial variations in state and compositional variables (T, water and melt content), and then calculate attenuation structures based on experimentally derived power-law frequency-dependent anelastic models. These structures are transferred into our anelastic finite difference wave propagation code, from which we measure t*. From 1D forward models of viscoelastic wave propagation, we show that teleseismic t* measurements are very sensitive to intrinsic attenuation structure at the lithosphere scale (upper 400 km) beneath the array. From 2D models that represent hypothetical structures of the western margin of the CP, wave propagation effects can also be explored. Comparison of 1D and 2D models will help us understand trade-offs between wave propagation effects and intrinsic attenuation on the measured t* variations across the CP.

  3. P-wave attenuation tomography of Mount St. Helens: preliminary results from coda-normalized spectra

    NASA Astrophysics Data System (ADS)

    de Siena, L.; Hicks, S.; Waite, G. P.; Moran, S. C.

    2010-12-01

    The P-wave velocity structure of Mount St. Helens has been recently imaged with local earthquake tomography, using the data recorded since its eruption in 1980. Part of this dataset has been processed to obtain a preliminary frequency dependent Qp image of the crust below the volcanic cone. We extended the so-called coda-normalization method, usually applied to S-waves, to the measurement of path-dependent P-wave attenuation. A scattering model has been developed in order to select the best time-window to measure the P-wave spectral amplitude on each trace. The objective is to average the effect of the source radiation pattern with the properties of early coda. The weighting matrix in the final inversion is dependent on the source radiation pattern and the spectral amplitude of noise. The Discrete Picard Condition and the Discrepancy Principle have been applied to investigate the maximum resolution available in each part of the medium. Truncated Singular Value Decomposition as well as Zeroth-, first- and second-order Tikhonov regularization techniques have been investigated by using the multi-resolution inversion code (MuReATA). The interpretation of the preliminary results is carried out by using cluster analysis on velocity and attenuation measurements.

  4. On the specifics of measuring attenuation and velocity of ultrasound in media with microstructure

    Microsoft Academic Search

    N. Ye. Nikitina

    2010-01-01

    We examine specific problems of measuring attenuation and velocity of ultrasound in engineering materials using the pulse method of exciting and receiving elastic oscillations. These problems are related to the influence of the internal structure of metals and alloys on the propagation in them of elastic longitudinal and shear waves in the megahertz frequency range. Using the example of a

  5. Surface multiple attenuation operators in the plane-wave domain: Theory and applications

    NASA Astrophysics Data System (ADS)

    Liu, Faqi

    1999-11-01

    This dissertation conducts the study of wave theory based multiple attenuation methods in the plane wave domain. The first part includes a detailed event based description of the forward modeling of a complete seismogram, which plays a key role in the derivation of different multiple attenuation equations. With the aid of some synthetic examples, the second part of this dissertation theoretically addresses different multiple attenuation methods. The most important part of this study is that all the initially unrelated methods reported in the literature are derived from a single forward modeling equation. I classified these methods into two fundamental groups: a prediction and subtraction based group and a deconvolution based group. In the former category, the prediction of multiples is performed by optimization, which requires the knowledge of either a source function or the reflectivity of the structure. Multiple attenuation methods in the second group make use of the convolutional model of a seismic reflection, where the multiple free data are represented as a deconvolution of the downgoing incident wavefield from the upgoing reflection. This approach has the potential application to multi-component ocean bottom seismometer data, where the dual sensor measurements, namely pressure and vertical velocity, provide an efficient way for the decomposition of pressure to its upgoing and downgoing wave components. The third part of the research consists of the evaluation of three different multiple attenuation methods and their applications to real data. The first method is designed for fairly flat layered earth model, which aims at the attenuation of the water layer multiples. The second one is a 2-D method that handles the lateral variation of the structure by coupling different upgoing and downgoing plane waves, which results in an elegant equation in a matrix form. In most geological settings, these matrices show band limited structure with narrow band width in the plane wave domain, which significantly increases the efficiency of the method. These two methods belong to the prediction and subtraction approach. The third method is a representative of the deconvolution approach, it decomposes the pressure to its upgoing and downgoing components by using the hydrophone and geophone data. For a optimal separation, I design a filter to calibrate the geophone data so that the variant coupling of the hydrophone and geophone together with different noise can be properly taken care. Examples on both synthetic and real data show that the methods are stable and successful. Theoretically, they all can be extended to 3-D cases.

  6. Blast-wave density measurements

    Microsoft Academic Search

    D. V. Ritzel

    1986-01-01

    Applications of a densitometer to obtain time-resolved data on the total density in blast-wave flows are described. A beta-source (promethium-147) is separated by a gap from a scintillator and a photomultiplier tube (PMT). Attenuation of the radiation beam by the passing blast wave is due to the total density in the gap volume during the wave passage. Signal conditioning and

  7. Attenuation law of planar shock waves propagating through dust-gas suspensions

    Microsoft Academic Search

    F. Aizik; G. Ben-Dor; T. Elperin; O. Igra; M. Mond; H. Gronig

    1995-01-01

    Olim et al. has proposed a general law for describing the instantaneous shock wave Mach number as it attenuates while propagating through dust-gas suspensions. Owing to the inadequacy of Olim's proposal, this study is aimed at finding the functional dependence of both the attenuation coefficient and Mach number on the initial shock wave Mach number, the diameter of the solid

  8. Shear wave speed and attenuation in water-saturated glass beads and sand

    E-print Network

    Paris-Sud XI, Université de

    Shear wave speed and attenuation in water-saturated glass beads and sand N. P. Chotiros and M. J dependence of shear wave attenuation in water-saturated glass beads and sand contains distinguishable, in the frequency band from 200 Hz to 2 kHz, indicated that the constant-Q model may be applicable to dry sand

  9. Application of sound-absorbent plastic to weak-shock-wave attenuators

    Microsoft Academic Search

    Katsuhisa Ootsuta; Kei Matsuoka; Akihiro Sasoh; Kazuyoshi Takayama

    1998-01-01

    A device for attenuating weak shock waves propagating in a duct has been developed utilizing sound-absorbent plastic which is usually used for attenuating sound waves. The device has a tube made of the sound-absorbent plastic installed coaxially to a surrounding metal tube with a clearance between them. The clearance acts as an air layer to enhance the performance of the

  10. Nonlinear attenuation of S-waves and Love waves within ambient rock

    NASA Astrophysics Data System (ADS)

    Sleep, Norman H.; Erickson, Brittany A.

    2014-04-01

    obtain scaling relationships for nonlinear attenuation of S-waves and Love waves within sedimentary basins to assist numerical modeling. These relationships constrain the past peak ground velocity (PGV) of strong 3-4 s Love waves from San Andreas events within Greater Los Angeles, as well as the maximum PGV of future waves that can propagate without strong nonlinear attenuation. During each event, the shaking episode cracks the stiff, shallow rock. Over multiple events, this repeated damage in the upper few hundred meters leads to self-organization of the shear modulus. Dynamic strain is PGV divided by phase velocity, and dynamic stress is strain times the shear modulus. The frictional yield stress is proportional to depth times the effective coefficient of friction. At the eventual quasi-steady self-organized state, the shear modulus increases linearly with depth allowing inference of past typical PGV where rock over the damaged depth range barely reaches frictional failure. Still greater future PGV would cause frictional failure throughout the damaged zone, nonlinearly attenuating the wave. Assuming self-organization has taken place, estimated maximum past PGV within Greater Los Angeles Basins is 0.4-2.6 m s-1. The upper part of this range includes regions of accumulating sediments with low S-wave velocity that may have not yet compacted, rather than having been damaged by strong shaking. Published numerical models indicate that strong Love waves from the San Andreas Fault pass through Whittier Narrows. Within this corridor, deep drawdown of the water table from its currently shallow and preindustrial levels would nearly double PGV of Love waves reaching Downtown Los Angeles.

  11. BROADBAND ATTENUATION MEASUREMENTS OF PHOSPHOLIPID-SHELLED ULTRASOUND CONTRAST AGENTS

    PubMed Central

    Raymond, Jason L.; Haworth, Kevin J.; Bader, Kenneth B.; Radhakrishnan, Kirthi; Griffin, Joseph K.; Huang, Shao-Ling; McPherson, David D.; Holland, Christy K.

    2014-01-01

    The aim of this study was to characterize the frequency-dependent acoustic attenuation of three phospholipid-shelled ultrasound contrast agents (UCAs): Definity, MicroMarker and echogenic liposomes. A broadband through-transmission technique allowed for measurement over 2 to 25 MHz with a single pair of transducers. Viscoelastic shell parameters of the UCAs were estimated using a linearized model developed by N. de Jong, L. Hoff, T. Skotland and N. Bom (Ultrasonics 1992; 30:95–103). The effect of diluent on the attenuation of these UCA suspensions was evaluated by performing attenuation measurements in 0.5% (w/v) bovine serum albumin and whole blood. Changes in attenuation and shell parameters of the UCAs were investigated at room temperature (25°C) and physiologic temperature (37°C). The attenuation of the UCAs diluted in 0.5% (w/v) bovine serum albumin was found to be identical to the attenuation of UCAs in whole blood. For each UCA, attenuation was higher at 37°C than at 25°C, underscoring the importance of conducting characterization studies at physiologic temperature. Echogenic liposomes exhibited a larger increase in attenuation at 37°C versus 25°C than either Definity or MicroMarker. PMID:24262056

  12. Excitation and Attenuation of Hypersonic Waves in Quartz

    Microsoft Academic Search

    H. E. Bömmel; K. Dransfeld

    1960-01-01

    A method for the generation and detection of hypersonic waves, which has only been briefly described earlier, together with some absorption measurements in quartz, is discussed in some detail. Further measurements of the hypersonic absorption in quartz at different crystal orientations and after neutron irradiation are reported. The results are in qualitative agreement with a phonon-phonon relaxation process.

  13. Direct determination of the attenuation coefficient for radionuclide volume measurements

    SciTech Connect

    Keller, A.M.; Simon, T.R.; Smitherman, T.C.; Malloy, C.R.; Dehmer, G.J.

    1987-01-01

    Correcting for the attenuation of photons between the cardiac chambers and chest surface is crucial for accurate nongeometric ventricular volume determinations from equilibrium radionuclide angiograms. Previous techniques have assumed that the attenuation coefficient of water for /sup 99m/Tc (0.15/cm) should be used for this correction. In this study, this assumption was tested directly by measuring attenuation of the activity of a radioactive source within the right and left cardiac chambers. The balloon of a flow-directed catheter, filled with /sup 99m/Tc, was used as a source and its depth within the body was measured with biplane fluoroscopy. In ten patients, a total of 36 measurements of attenuation were made. With linear regression analysis, the overall calculated attenuation coefficient, mu, was 0.12/cm (standard error of slope = 0.01, R = 0.93). Although the mean value of mu varied from 0.08 to 0.13 for four different intracardiac locations these differences were not significant. These direct measurements indicate that the attenuation of photons in the heart is not equivalent to that of water and suggest that an attenuation coefficient of 0.12/cm should be used in analyzing ventricular activity.

  14. Direct determination of the attenuation coefficient for radionuclide volume measurements.

    PubMed

    Keller, A M; Simon, T R; Smitherman, T C; Malloy, C R; Dehmer, G J

    1987-01-01

    Correcting for the attenuation of photons between the cardiac chambers and chest surface is crucial for accurate nongeometric ventricular volume determinations from equilibrium radionuclide angiograms. Previous techniques have assumed that the attenuation coefficient of water for 99mTc (0.15/cm) should be used for this correction. In this study, this assumption was tested directly by measuring attenuation of the activity of a radioactive source within the right and left cardiac chambers. The balloon of a flow-directed catheter, filled with 99mTc, was used as a source and its depth within the body was measured with biplane fluoroscopy. In ten patients, a total of 36 measurements of attenuation were made. With linear regression analysis, the overall calculated attenuation coefficient, mu, was 0.12/cm (standard error of slope = 0.01, R = 0.93). Although the mean value of mu varied from 0.08 to 0.13 for four different intracardiac locations these differences were not significant. These direct measurements indicate that the attenuation of photons in the heart is not equivalent to that of water and suggest that an attenuation coefficient of 0.12/cm should be used in analyzing ventricular activity. PMID:3794802

  15. Attenuation of capillary and gravity waves at sea by monomolecular organic surface films

    NASA Astrophysics Data System (ADS)

    Hühnerfuss, Heinrich; Alpers, Werner; Garrett, William D.; Lange, Philipp A.; Stolte, Siegfried

    1983-11-01

    During the MARSEN 79 experiment, attenuation of capillary and gravity water waves by two oleyl alcohol and one methyl oleate surface films (`slicks') was investigated. A slight influence of an oleyl alcohol slick occurs at frequencies between 0.5 Hz and 0.7 Hz and above 0.7 Hz (wavelength L = 3.2 m) wave attenuation becomes significant. A methyl oleate slick causes only a slight wave damping in the frequency range ƒ<5 Hz (L>6.7 cm). In the capillary wave range ƒ?14 Hz the wave-damping characteristics for the two surface film substances are comparable. In the high-frequency capillary wave range ƒ>20 Hz, however, methyl oleate surface films act more strongly on the wave field, as was demonstrated by additional wind-wave tunnel experiments. The different wave attenuation characteristics of these two surface active compounds are attributed to different interaction between their hydrophilic part and the adjacent water layer.

  16. A direct measurement of skull attenuation for quantitative SPECT

    SciTech Connect

    Turkington, T.G.; Gilland, D.R.; Jaszczak, R.J.; Greer, K.L.; Coleman, R.E. (Duke Univ. Medical Center, Durham, NC (United States). Dept. of Radiology); Smith, M.F. (Duke Univ., Durham, NC (United States). Dept. of Biomedical Engineering)

    1993-08-01

    The attenuation of 140 keV photons was measured in three empty skulls by placing a [sup 99m]Tc line source inside each one and acquiring projection data. These projections were compared to projections of the line source alone to determine the transmission through each point in the skull surrounding the line source. The effective skull thickness was calculated for each point using an assumed dense bone attenuation coefficient. The relative attenuation for this thickness of bone was compared to that of an equivalent amount of soft tissue to evaluate the increased attenuation of photons in brain SPECT relative to a uniform soft tissue approximation. For the skull regions surrounding most of the brain, the effective bone thickness varied considerably, but was generally less than 6 mm, resulting in a relative attenuation increases of less than 6%.

  17. Attenuation and velocity structure from diffuse coda waves: Constraints from underground array data

    NASA Astrophysics Data System (ADS)

    Galluzzo, Danilo; La Rocca, Mario; Margerin, Ludovic; Del Pezzo, Edoardo; Scarpa, Roberto

    2015-03-01

    An analysis of coda waves excited in the 0.2-20 Hz frequency band and recorded by the underground array Underseis (central Italy) has been performed to constrain both seismic attenuation at regional scale and velocity structure in the Mount Gran Sasso area. Attenuation was estimated with the MLTWA method, and shows a predominance of scattering phenomena over intrinsic absorption. The values of Qi and Qs are compatible with other estimates obtained in similar tectonic environments. Array methods allowed for a detailed study of the propagation characteristics, demonstrating that earthquake coda at frequencies greater than about 6 Hz is composed of only body waves. Coherence and spectral characteristics of seismic waves measured along the coda of local and regional earthquakes indicate that the wavefield becomes fully diffuse only in the late coda. The frequency-dependent energy partitioning between horizontal and vertical components has been also estimated and compared with synthetic values computed in a layered half-space under the diffuse field assumption. This comparison confirms that, for frequencies higher than 6 Hz, the coda appears as a sum of body waves coming from all directions while, in the low frequency range (0.2-2 Hz), the observations can be well explained by a coda wavefield composed of an equipartition mixture of surface and body waves traveling in a multiple-layered medium. A Monte-Carlo inversion has been performed to obtain a set of acceptable velocity models of the upper crust. The present results show that a broadband coda wavefield recorded in an underground environment is useful to constrain both the regional attenuation and the velocity structure of the target area, thereby complementing the results of classical array analysis of the wavefield.

  18. ORNL system for measurement of telephone-line attenuation

    SciTech Connect

    Rochelle, R.W.; Williams, I.E.

    1988-06-01

    The purpose of modifying the TS-100 Automated Tempest Test System software was to use the equipment for making radio-frequency attenuation measurements between an input port and an output port of a telephone network. One set of tests was performed to simulate the electromagnetic radiation from a secure computer terminal and its coupling to telephone lines within a building. Another set of tests was conducted to determine the procedures for measuring attenuation on telephone lines between buildings that are all within the secure zone. The measurements indicate that attenuation between the terminal and the telephone is a function of many variables; however, attenuation in the cable between the buildings is proportional to the length of the cable between the buildings. 1 ref., 2 figs.

  19. Compressional wave velocity and attenuation at ultrasonic and sonic frequencies in near-surface sedimentary rocks

    SciTech Connect

    Best, A.I. [Univ. of Reading (United Kingdom). Postgraduate Research Inst. for Sedimentology] [Univ. of Reading (United Kingdom). Postgraduate Research Inst. for Sedimentology; Sams, M.S. [Imperial College of Science, Technology and Medicine, London (United Kingdom). Dept. of Geology] [Imperial College of Science, Technology and Medicine, London (United Kingdom). Dept. of Geology

    1997-03-01

    Laboratory ultrasonic measurements of compressional wave velocity and attenuation were made as a function of effective pressure on samples of limestone, sandstone and siltstone taken from a shallow borehole test site. The results indicate that the sandstones are pervaded by grain contact microcracks which dramatically affect their compressional wave attenuations. Clean sandstone shows a compressional wave quality factor (Q{sub p}) of 24 {+-} 2 at 5 MPa effective pressure (close to the estimated in situ burial pressure) and a Q{sub p} of 83 {+-} 29 at 60 MPa. The Q{sub p} of limestones and siltstones at the site show negligible and small increases with pressure in the laboratory, respectively. The strong pressure dependence of Q{sub p} in clean sandstone was used to infer the presence of in situ microcracks. Sediment velocities measured in the laboratory at about 1 MHz were compared with those from the full waveform sonic log at about 10 kHz implies that they must also be highly attenuating over a significant part of the frequency range 10 kHz to 1 MHz, to account for the magnitude of the observed velocity dispersion. Assuming the laboratory Q{sub p} values measured at 5 MPa remain constant down to 10 kHz predicts the observed dispersion quite well. Furthermore, the sonic log velocities of sandstones, limestones and siltstones (after normalizing each lithology for porosity and clay content) were found to reflect the same pressure (depth) trends observed in the laboratory. The results provide evidence for the existence of in situ microcracks in near-surface sediments.

  20. Ultrasonic attenuation of surface acoustic waves in a thin film of superconducting Nb 3Sn

    NASA Astrophysics Data System (ADS)

    Fredricksen, H. P.; Salvo, H. L.; Levy, M.; Hammond, R. H.; Geballe, T. H.

    1980-02-01

    The attenuation of 660 MHz surface acoustic waves propagating in a thin film of Nb 3Sn 5000 Å thick has been measured as a function of temperature from 4.2 K to 16 K. The A 15 Nb 3Sn, electron-beam codeposited on YZ lithium niobate and annealed at 700°C, was studied using 5.1 ?m wavelength interdigital electrodes. The film revealed a transition temperature of 14.2 ± 0.1 K and using the BCS theory, an energy gap 2 ?(0) = 3.5 kBTc.

  1. Studies on Shock Attenuation in Plastic Materials and Applications in Detonation Wave Shaping

    NASA Astrophysics Data System (ADS)

    Khurana, Ritu; Gautam, P. C.; Rai, Rajwant; Kumar, Anil; Sharma, A. C.; Singh, Manjit, Dr

    2012-07-01

    Pressure in plastic materials attenuates due to change of impedance, phase change in the medium and plastic deformation. A lot of theoretical and experimental efforts have been devoted to the attenuation of shock wave produced by the impact of explosive driven flyer plate. However comparatively less work has been done on the attenuation of shock waves due to contact explosive detonation. Present studies deal with the attenuation of explosive driven shock waves in various plastic materials and its applications in design of Hybrid Detonation Wave Generator In present work shock attenuating properties of different polymers such as Perspex, Teflon, nylon, polypropylene and viton has been studied experimentally using rotating mirror streak camera and electrical position pins. High explosive RDX/TNT and OCTOL of diameter 75-100mm and thickness 20 to 50mm were detonated to induce shock wave in the test specimens. From experimental determined shock velocity at different locations the attenuation in shock pressure was calculated. The attenuation of shock velocity with thickness in the material indicates exponential decay according to relation US = UOexp(-ax). In few of the experiments manganin gauge of resistance 50 ohms was used to record stress time profile across shock wave. The shock attenuation data of Viton has successfully been used in the design of hybrid detonation wave generator using Octol as high explosive. While selecting a material it was ensured that the attenuated shock remains strong enough to initiate an acceptor explosive. Theoretical calculation were supported by Autodyne 2D hydro-code simulation which were validated with the experiments conducted using high speed streak photography and electrical shock arrival pins. Shock attenuation data of Perspex was used to establishing card gap test and wedge test in which test items is subjected to known pressure pulse by selecting the thickness of the plastic material.

  2. Shear-wave attenuation and velocity studies in southeastern Asia

    NASA Astrophysics Data System (ADS)

    Jemberie, Alemayehu Lakew

    Models of shear-wave Q (Qmu) have been obtained for southeastern Asia using two methods. The first method inverts attenuation coefficients of the fundamental Rayleigh mode obtained using a standard two-station technique. The second method matches theoretical amplitude spectra for the fundamental and higher-mode Rayleigh waves computed for previously obtained velocity and assumed Qmu models, and earthquakes with known source depths and focal mechanisms, to observed spectra. The latter method provides much better regional coverage than the first and allows us to map lateral variations of Qmu at various levels in the crust and uppermost mantle. For the single-station, multi-mode method, I assumed an Earth model consisting of three layers, layer 1 being 10 km, layer 2 being 20 km, and layer 3 being 30 km in thickness. Qmu in layer 1 achieves lowest values (about 40) in the southern part of the Tibetan Plateau and in the Tarim basin and is highest (about 250) in southeastern China. The Qmu map of layer 2 indicates that the highest Qmu values (about 150) he in the central part of China and in parts of the Sino-Korean platform. The lowest Q mu value (about 50) occurs in Tibet and the Pamir thrust system. Layer 2 exhibits an overall increase in Qmu going from south to north. For layer 3 the resolution of crustal variations in Qmu, is poorer than layers 1 and 2. Available results, however, indicate that Qmu, is highest (about 180) under southern Mongolia and the Tarim basin, somewhat lower (100) beneath the southern portion of the Baikal Rift, and lowest (80) under the Pamir thrust system.

  3. Non-destructive Inspection of Chloride Ion in Concrete Structures Using Attenuated Total Reflection of Millimeter Waves

    NASA Astrophysics Data System (ADS)

    Tripathi, Saroj R.; Inoue, Hiroo; Hasegawa, Tsuyoshi; Kawase, Kodo

    2013-02-01

    The chloride induced corrosion of reinforcing steel bar is one of the major causes of deterioration of concrete structures. Therefore, it is essential to periodically monitor the level of chloride ion (Cl-) concentration in concrete structures. In this work, we developed millimeter wave attenuated total reflection measurement setup in order to determine the Cl- concentration in concrete structures. We prepared concrete samples with different compositions and varying Cl- concentrations and we measured their attenuated total reflectance at 65 GHz. We observed that the reflectance decreases almost linearly with the increase in Cl- concentration indicating that this technique could be used to inspect the Cl- concentration in concrete structures nondestructively.

  4. Material hardness and ageing measurement using guided ultrasonic waves.

    PubMed

    Korde, Nilesh; Kundu, Tribikram

    2013-02-01

    Elastic properties of materials can be easily determined from the ultrasonic wave velocity measurement. However, material hardness cannot be obtained from the ultrasonic wave speed. Heat treatment and ageing affect the microstructure of many materials changing their hardness and strength. It has been already established that ultrasonic attenuation and dispersion are also affected by the material microstructure. It is investigated in this paper if the attenuation of ultrasonic guided waves can be correlated with the material ageing or duration of heat treatment and material hardness. To this aim six identical aluminum 2024 alloy plate specimens were subjected to different durations of heat treatment at 150°C and were inspected nondestructively propagating Lamb waves through the specimens. Attenuation of the Lamb wave was found to be inversely related to the hardness. Rockwell hardness test was performed to corroborate the ultrasonic observations. In comparison to the Rockwell hardness test the ultrasonic inspection was found to be more sensitive to the heat treatment duration and material ageing. From these results it is concluded that guided wave inspection method is a reliable and probably more desirable alternative for characterizing the hardness and microstructure of heat treated materials. Earlier investigations correlated the bulk wave attenuation with the material ageing while this work is the first attempt to correlate the guided wave attenuation to the material hardness and ageing. PMID:23047018

  5. Time-reverse modelling of acoustic wave propagation in attenuating media

    NASA Astrophysics Data System (ADS)

    Zhu, Tieyuan

    2014-04-01

    Time-reverse modelling (TRM) of acoustic wave propagation has been widely implemented in seismic migration and time-reversal source imaging. The basic assumption of this modelling is that the wave equation is time-invariant in non-attenuating media. In the Earth, attenuation often invalidates this assumption of time-invariance. To overcome this problem, I propose a TRM approach that compensates for attenuation and dispersion effects during the wave propagation in attenuating media. This approach is based on a viscoacoustic wave equation which explicitly separates attenuation and dispersion following a constant-Q model. Compensating for attenuation and dispersion during TRM is achieved by reversing the sign of the attenuation operator coefficient while leaving the counterpart dispersion parameter unchanged in this viscoacoustic wave equation. A low-pass filter is included to avoid amplifying high-frequency noise during TRM. I demonstrate the effects of the filter on the attenuation and the phase velocity by comparing with theoretical solutions in a 1-D Pierre shale homogeneous medium. Three synthetic examples are used to demonstrate the feasibility of attenuation compensation during TRM. The first example uses a 1-D homogeneous model to demonstrate the accuracy of the numerical implementation of the methodology. The second example shows the applicability of source location using a 2-D layering model. The last example uses a 2-D cross-well synthetic experiment to show that the methodology can also be implemented in conjunction with reverse-time migration to image subsurface reflectors. When attenuation compensation is included, I find improved estimation of the source location, the excitation timing of the point source, the magnitude of the focused source wavelet and the reflectivity image of reflectors, particularly for deep structures underneath strongly attenuating zones.

  6. Attenuation of Scalar Fluxes Measured with Spatially-displaced Sensors

    NASA Astrophysics Data System (ADS)

    Horst, T. W.; Lenschow, D. H.

    2009-02-01

    Observations from the Horizontal Array Turbulence Study (HATS) field program are used to examine the attenuation of measured scalar fluxes caused by spatial separation between the vertical velocity and scalar sensors. The HATS data show that flux attenuation for streamwise, crosswind, and vertical sensor displacements are each a function of a dimensionless, stability-dependent parameter n m multiplied by the ratio of sensor displacement to measurement height. The scalar flux decays more rapidly with crosswind displacements than for streamwise displacements and decays more rapidly for stable stratification than for unstable stratification. The cospectral flux attenuation model of Kristensen et al. agrees well with the HATS data for streamwise sensor displacements, although it is necessary to include a neglected quadrature spectrum term to explain the observation that flux attenuation is often less with the scalar sensor downwind of the anemometer than for the opposite configuration. A simpler exponential decay model provides good estimates for crosswind sensor displacements, as well as for streamwise sensor displacements with stable stratification. A model similar to that of Lee and Black correctly predicts flux attenuation for a combination of streamwise and crosswind displacements, i.e. as a function of wind direction relative to the sensor displacement. The HATS data for vertical sensor displacements extend the near-neutral results of Kristensen et al. to diabatic stratification and confirm their finding that flux attenuation is less with the scalar sensor located below the anemometer than if the scalar sensor is displaced an equal distance either horizontally or above the anemometer.

  7. Extracting the Green's function of attenuating heterogeneous acoustic media from uncorrelated waves

    Microsoft Academic Search

    Roel Snieder

    2007-01-01

    The Green's function of acoustic or elastic wave propagation can, for loss-less media, be retrieved by correlating the wave field that is excited by random sources and is recorded at two locations. Here the generalization of this idea to attenuating acoustic waves in an inhomogeneous medium is addressed, and it is shown that the Green's function can be retrieved from

  8. A three-dimensional model of wave attenuation in the marginal ice zone

    Microsoft Academic Search

    L. G. Bennetts; M. A. Peter; V. A. Squire; M. H. Meylan

    2010-01-01

    A three-dimensional model of wave scattering by a large array of floating thin elastic plates is used to predict the rate of ocean wave attenuation in the marginal ice zone in terms of the properties of the ice cover and the incoming wavefield. This is regarded as a small step toward assimilating interactions of ocean waves with areas of sea

  9. Stress Wave attenuation in SiC3D/Al Composite

    NASA Astrophysics Data System (ADS)

    Chunyuan, Yuan; Yangwei, Wang; Guoju, Li; Xu, Zhang; Jubin, Gao

    2013-03-01

    SiC3D/Al composite is a kind of special composite with interpenetrating network microstructure. The attenuation properties of stress wave propagation along the SiC3D/Al composite are studied by a Split Hopkinson Pressure Bar system & FEM simulations, and the attenuation mechanism is discussed in this paper. Results show that the attenuation rate of the stress wave in the composite is up to 1.73MPa·mm-1. The reduction of the amplitude of waves is caused by that plenty of interfaces between SiC and Al within the composite acting with stress waves. When the incident plane wave reaches the SiC3D/Al interface, reflection wave and transmission wave propagates in different directions along the irregular interface between SiC phase and aluminium phase due to the impedance mismatch of them, which leads to the divergence of stress wave. At the same time, some stress micro-focuses occurs in the aluminium phase for the complex wave superimposition, and some plastic deformation may take place within such micro-regions, which results in the consumption of stress wave energy. In conclusion, the stress wave attenuation is derived from divergence and consumption of stress wave.

  10. Subduction zone guided waves: 3D modelling and attenuation effects

    NASA Astrophysics Data System (ADS)

    Garth, T.; Rietbrock, A.

    2013-12-01

    Waveform modelling is an important tool for understanding complex seismic structures such as subduction zone waveguides. These structures are often simplified to 2D structures for modelling purposes to reduce computational costs. In the case of subduction zone waveguide affects, 2D models have shown that dispersed arrivals are caused by a low velocity waveguide, inferred to be subducted oceanic crust and/or hydrated outer rise normal faults. However, due to the 2D modelling limitations the inferred seismic properties such as velocity contrast and waveguide thickness are still debated. Here we test these limitations with full 3D waveform modelling. For waveguide effects to be observable the waveform must be accurately modelled to relatively high frequencies (> 2 Hz). This requires a small grid spacing due to the high seismic velocities present in subduction zones. A large area must be modelled as well due to the long propagation distances (400 - 600 km) of waves interacting with subduction zone waveguides. The combination of the large model area and small grid spacing required means that these simulations require a large amount of computational resources, only available at high performance computational centres like the UK National super computer HECTOR (used in this study). To minimize the cost of modelling for such a large area, the width of the model area perpendicular to the subduction trench (the y-direction) is made as small as possible. This reduces the overall volume of the 3D model domain. Therefore the wave field is simulated in a model ';corridor' of the subduction zone velocity structure. This introduces new potential sources of error particularly from grazing wave side reflections in the y-direction. Various dampening methods are explored to reduce these grazing side reflections, including perfectly matched layers (PML) and more traditional exponential dampening layers. Defining a corridor model allows waveguide affects to be modelled up to at least 2 Hz (needed for dispersion analysis) for the large model area that is considered. Simulations with a variety of quality factors (Q) at different parts of the subduction zone have been run to investigate how seismic attenuation affects the observed dispersed waveforms. We show that the low Q in the mantle wedge can improve the fit of the dispersed waveforms. A low Q in the low velocity waveguide structure however means that the delayed high frequency energy has very low amplitude, and so is not seen clearly at the surface. The Q of the low velocity crustal waveguide must therefore be greater than 250, suggesting that melting does not occur in the subducted oceanic crust at depths of 220 km or less. The velocity contrast seen at these depths must therefore be due to compositional variations. Benchmarking 2D elastic models with the 3D case shows that 2D models give a good approximation of 3D subduction zone waveguide structure. Visco-elastic simulations show that attenuation in the mantle wedge affects the observed dispersion, but the low velocity waveguide itself does not have significantly reduced Q. This work is an example of how the increasing computing power coupled with well-defined model boundaries can allow high resolution 3D modelling to be applied to specific structures of interest.

  11. The Velocity and Attenuation of Acoustic Emission Waves in SiC/SiC Composites Loaded in Tension

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Gyekenyesi, Andrew L.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    The behavior of acoustic waves produced by microfracture events and from pencil lead breaks was studied for two different silicon carbide fiber-reinforced silicon carbide matrix composites. The two composite systems both consisted of Hi-Nicalon (trademark) fibers and carbon interfaces but had different matrix compositions that led to considerable differences in damage accumulation and acoustic response. This behavior was primarily due to an order of magnitude difference in the interfacial shear stress for the two composite systems. Load/unload/reload tensile tests were performed and measurements were made over the entire stress range in order to determine the stress-dependence of acoustic activity for increasing damage states. It was found that using the extensional wave velocities from acoustic emission (AE) events produced from pencil lead breaks performed outside of the transducers enabled accurate measurements of the stiffness of the composite. The extensional wave velocities changed as a function of the damage state and the stress where the measurement was taken. Attenuation for AE waveforms from the pencil lead breaks occurred only for the composite possessing the lower interfacial shear stress and only at significantly high stresses. At zero stress after unloading from a peak stress, no attenuation occurred for this composite because of crack closure. For the high interfacial stress composite no attenuation was discernable at peak or zero stress over the entire stress-range of the composite. From these observations, it is believed that attenuation of AE waveforms is dependent on the magnitude of matrix crack opening.

  12. Upper mantle attenuation and velocity structure from measurements of differential S phases

    NASA Astrophysics Data System (ADS)

    Reid, F. J. L.; Woodhouse, J. H.; van Heijst, H. J.

    2001-06-01

    Although much progress has been made in determining the 3-D distribution of seismic wave velocities in the Earth, substantially less is known about the 3-D distribution of intrinsic attenuation. In this study variations in attenuation and shear velocity of the Earth's mantle are constrained using measurements of differential traveltime and attenuation. The data are broad-band displacement SH seismograms filtered to have energy in the period range 8-20s. The seismograms are obtained from over 600 globally distributed earthquakes of magnitude, Mw, 5.5 or greater. Differential traveltimes and differential t* values from multiple S phases are estimated by a waveform-fitting method, resulting in approximately 4300 measurements for SS-S in the distance range 50°-105° and 1000 measurements for SSS-SS in the distance range 90°-179°. Each measurement consists of a differential traveltime and a corresponding differential t*. The differential traveltimes and t* values are inverted to obtain models of the lateral variation of shear velocity and lateral variation of q?, where q?=1/Q?. The models explain the data well but have limited depth resolution. The velocity models show good correlation with previous studies; in particular, low velocities are observed underlying mid-oceanic ridges and convergent margins and high velocities are found for continental regions. The q? models show shield regions to be less attenuating than PREM, with ridges appearing as highly attenuating features. The models have limited depth resolution and to address this problem we also present a shear velocity model obtained from the combination of body wave and surface wave data sets.

  13. Scattering versus intrinsic attenuation in the near surface: Measurements from permanent down-hole geophones

    NASA Astrophysics Data System (ADS)

    Mangriotis, Maria-Daphne

    The study of attenuation, equivalently of the quality (Q) factor, in the near-surface has three main applications. Firstly, low Q values, which are fairly common in near-surface materials, aside from decreasing seismic energy, also distort the waveforms; treatment of this disturbance effect with inverse-Q filters requires reliable Q estimates. Secondly, attenuation is a seismic parameter which improves interpretation of seismograms, as it is correlated with lithological properties. Thirdly, establishing near-surface Q is important in assessing site effects on strong ground motion events in applications of earthquake modeling and seismic engineering design. In view of these applications, theoretical treatments of attenuation, as well as laboratory and field tests, aim at estimating Q as a function of frequency and strain level. To determine the applicability of using different types of Q measurements, laboratory vs. in-situ measurements, to predict Q behavior across the different frequency bands and strain-levels of interest, it is necessary to model and separate the attenuation mechanisms into scattering (heterogeneity of elastic properties causing energy to be redistributed in space) and intrinsic (energy absorption due to conversion to heat) components. The objective of the presented study was to separate scattering versus intrinsic attenuation in the near-surface from a shallow VSP experiment conducted in the Lawrence Livermore National Laboratory (LLNL) facility using permanent down-hole geophones and a vertical impact source. Given that the VSP array was above the watertable, the Q characterization lies within the vadose zone. The first arrival of the vertically-incident transmitted P-wave was used to estimate the P-wave attenuation in the field data. Scattering attenuation estimates were established for a selected range of elastic models, which addressed both the effect of the variance of the elastic properties (density and velocity), as well as the effect of the structure of the variation, i.e. 1D versus 3D heterogeneity, on scattering. The elastic profiles were constructed from a superposition of interval values determined from log information (for the density profile) and first-break arrivals (for the velocity profile) and a high-frequency random component with variance range typical of sedimentary basins. The results for the scattering Q estimates related to one-way transmission and multiple reflections are in the order of 20 to 100, as obtained from 1D analytical and elastic finite-difference models. Given the short propagation pathlengths in the experiment, the results show that attenuation due to lateral heterogeneity is non-significant. In addition, given the experimental geometry of shallow VSP studies, it is shown that the scattering estimates are affected from the presence of the near-field, local impedance, and interference effects, which are termed 'pseudo-Q' factors. The pseudo-Q factors result in a biased estimate for scattering Q derived from both time-domain and frequency-domain methods. Hence, to accurately model the scattering vs. intrinsic components of attenuation, the bias due to the pseudo-Q factors was accounted for. The intrinsic attenuation was deduced from comparison of the field data Q estimates, which contain scattering attenuation, intrinsic attenuation and effects from pseudo-Q factors with the elastic synthetic Q estimates. Results yield very low intrinsic Q values, in the order of 4 to 15, for the low and high scattering attenuation estimates respectively. The intrinsic attenuation is attributed to the interaction of the free gas present in the vadose zone with the compressional wave, which is the only known mechanism that can lead to absorption at seismic frequencies (White, 1975; Dutta and Seriff, 1979). Visco-elastic modeling shows that aside from amplitude decay, an intrinsic attenuation mechanism is required to produce the pulse broadening observed in the field data. For a typical set of conditions in the vadose zone, analytical modeling shows that it is possible for the effect

  14. Improved techniques for measuring x-ray mass attenuation coefficients

    NASA Astrophysics Data System (ADS)

    de Jonge, Martin D.; Tran, Chanh Q.; Chantler, Christopher T.; Barnea, Zwi N. M...

    2006-04-01

    We apply the x-ray extended-range technique (XERT) to measure mass attenuation coefficients over one order of magnitude more accurately than previously reported in the literature. We describe the application of the XERT to the investigation of systematic effects due to harmonic energy components in the x-ray beam, scattering and fluorescence from the absorbing sample, the bandwidth of the x-ray beam, and thickness variations across the absorber. The high-accuracy measurements are used for comparison with different calculations of mass attenuation coefficients, and to identify particular regions where these calculations fail.

  15. A web-based tutorial for ultrasonic attenuation measurement

    NASA Astrophysics Data System (ADS)

    Margetan, Frank J.; Barnard, Dan; Orman, David; Feygin, Alex; Pavel, Brittney

    2014-02-01

    An ultrasonic attenuation-versus-frequency curve can serve as an "ultrasonic signature" which may be correlated with microstructural properties of interest such as grain size in metals or porosity level in composites. Attenuation also plays a role in ultrasonic inspections and is consequently a key input into many inspection simulation models. A web-based self-tutorial on practical attenuation measurements is under development. The focus is on pulse/echo immersion measurements made using a broadband transducer to deduce attenuation within the transducer's useable bandwidth. Two approaches are considered: one using a calibration specimen having a known attenuation curve, and one without. In the first approach a back-wall (BW) echo in the calibration specimen is compared with a BW echo in the test specimen. In the second approach various BW reverberation echoes in the test specimen are compared with one another or with a front-wall echo. The web-based tutorial incorporates three classes of materials. The first includes written documentation and videos describing the measurement setups, the data-acquisition and analysis procedures, and the underlying models use to analyze the raw UT data. Secondly, general purpose "stand-alone" data-analysis software is supplied that is designed to be used with any ultrasonic inspection system that can output A-scan data as a text file. This includes both FORTRAN software and Excel spreadsheet calculators that accept A-scan text data as inputs. Thirdly, we supply demonstration software where the data acquisition and analysis procedures are integrated with a specific class of commercial ultrasonic test instruments, namely those running UTEX Winpect control software. This paper provides an overview of the measurement methods and tutorial materials. We also present early results from round-robin trials in which selected metal and composite specimens are being sent to participating partners for attenuation measurement.

  16. Differential shear wave attenuation and its lateral variation in the North Atlantic region

    NASA Technical Reports Server (NTRS)

    Sheehan, Anne F.; Solomon, Sean C.

    1992-01-01

    A digital data base of over 150 seismograms and a spectral radio technique are used to measure SS-S differential attenuation in the North Atlantic region. Differential attenuation is positively correlated with SS-S travel time residual, and both differential attentuation and travel time residual decrease with increasing seafloor age. Models are developed for seismic Q in which lateral variations include contributions from the asthenospheric low-Q zone as well as from lithospheric cooling. The Q models obtained under this assumption are in good agreement with those obtained from surface wave studies and are therefore preferred over those models with lateral variations confined to the upper 125 km. Systematic long-wavelength (1000-7000 km) variations in differential attenuation, corrected for seafloor age, are evident along the axis of the Mid-Atlantic Ridge. These variations can be qualitatively correlated with long-wavelength variations in SS-S differential travel time residuals and are attributed to along-axis differences in upper mantle temperature.

  17. On the specifics of measuring attenuation and velocity of ultrasound in media with microstructure

    Microsoft Academic Search

    N. Ye. Nikitina

    2010-01-01

    We examine specific problems of measuring attenuation and velocity of ultrasound in engineering materials using the pulse\\u000a method of exciting and receiving elastic oscillations. These problems are related to the influence of the internal structure\\u000a of metals and alloys on the propagation in them of elastic longitudinal and shear waves in the megahertz frequency range.\\u000a Using the example of a

  18. Ultrasonic attenuation - Q measurements on 70215,29. [lunar rock

    NASA Technical Reports Server (NTRS)

    Warren, N.; Trice, R.; Stephens, J.

    1974-01-01

    Ultrasonic attenuation measurements have been made on an aluminum alloy, obsidian, and rock samples including lunar sample 70215,29. The measurement technique is based on a combination of the pulse transmission method and the forced resonance method. The technique is designed to explore the problem of defining experimentally, the Q of a medium or sample in which mode conversion may occur. If modes are coupled, the measured attenuation is strongly dependent on individual modes of vibration, and a range of Q-factors may be measured over various resonances or from various portions of a transient signal. On 70215,29, measurements were made over a period of a month while the sample outgassed in hard varuum. During this period, the highest measured Q of this sample increased from a few hundred into the range of 1000-1300.

  19. Determination of the profile of the attenuation factor in an aerosol using two-wave sounding

    SciTech Connect

    Korshunov, V.A.

    1986-12-01

    One of the more important problems in laser sounding of the atmosphere is the determination of the spatial distribution of the aerosol which is created by local sources of either artificial or natural origin. In such a case, the aerosol medium generally has the form of a cloud or a stream which is elongated along the direction of the wind. In this study, the authors consider the possibility of determining the profile of the aerosol attenuation factor using two-wave laser sounding without the use of a priori information on the unknown profile and without applying data on independent measurements. The authors assume that there is knowledge of the lidar ratios and of the ratios of the attenuation factors at the sounding wavelengths. Using the above assumptions on the aerosol medium, the authors derive a geometric expression of the experiment using two wavelengths for the equations for laser location. The results of the calculations show that the solution guarantees small errors of electric field intensity in comparison with the one-wave solutions.

  20. Seismic tomography of compressional wave attenuation structure for K?¯lauea Volcano, Hawai`i

    NASA Astrophysics Data System (ADS)

    Lin, Guoqing; Shearer, Peter M.; Amelung, Falk; Okubo, Paul G.

    2015-04-01

    We present a frequency-independent three-dimensional (3-D) compressional wave attenuation model (indicated by the reciprocal of quality factor Qp) for K?¯lauea Volcano in Hawai`i. We apply the simul2000 tomographic algorithm to the attenuation operator t* values for the inversion of Qp perturbations through a recent 3-D seismic velocity model and earthquake location catalog. The t* values are measured from amplitude spectra of 26708 P wave arrivals of 1036 events recorded by 61 seismic stations at the Hawaiian Volcanology Observatory. The 3-D Qp model has a uniform horizontal grid spacing of 3 km, and the vertical node intervals range between 2 and 10 km down to 35 km depth. In general, the resolved Qp values increase with depth, and there is a correlation between seismic activity and low-Qp values. The area beneath the summit caldera is dominated by low-Qp anomalies throughout the entire resolved depth range. The Southwest Rift Zone and the East Rift Zone exhibit very high Qp values at about 9 km depth, whereas the shallow depths are characterized with low-Qp anomalies comparable with those in the summit area. The seismic zones and fault systems generally display relatively high Qp values relative to the summit. The newly developed Qp model provides an important complement to the existing velocity models for exploring the magmatic system and evaluating and interpreting intrinsic physical properties of the rocks in the study area.

  1. Acoustic Measurement of Suspended Fine Particle Concentrations by Attenuation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of sediment concentration is important in the study of streams and rivers. The work presented explores the appropriate frequency and transducer spacing for acoustic measurement of suspended particles in the range of 0.1 – 64 microns. High frequency (20 MHz) acoustic signal attenuation wa...

  2. Satellite measurements of ocean waves

    NASA Technical Reports Server (NTRS)

    Stewart, R. H.

    1974-01-01

    Satellite measurements of the directional spectrum of ocean waves are beneficial to theoretical wave research, ocean engineering, and marine activities. Wave measurements from satellites by active microwave systems also help to analyze those processes that govern the transfer of heat, water vapor, and momentum across the air-sea interface.

  3. 55-Gallon Drum Attenuation Corrections for Waste Assay Measurements

    SciTech Connect

    Casella, V.R.

    2002-04-03

    The present study shows how the percent attenuation for low-level waste (LLW), carbon-steel 55-gallon drums (44 and 46 mil) and for transuranic (TRU) DOT Type 7A 55-gallon drums (approximately 61 mil) changes with gamma energy from 60 keV to 1400 keV. Attenuation for these drums is in the range of 5 to 15 percent at energies from 400 to 1400 keV and from 15 to 35 percent at energies from 120 to 400 keV. At 60 keV, these drums attenuate 70-80 percent of the gamma rays. Correction factors were determined in order to correct for gamma attenuation of a TRU drum if a calibration is performed with a LLW drum. These correction factors increase the activities of the TRU drum by from 10 percent to 2 percent in the energy range of 165 to 1400 keV, with an increase of about 50 percent at 60 keV. Correction factors for TRU drums and for analyses without a drum were used to adjust the percent yield for frequently measured gamma rays, so that the assay libraries could be modified to provide the drum attenuation corrections.

  4. Measurement of acoustic attenuation in South Pole ice

    NASA Astrophysics Data System (ADS)

    IceCube Collaboration; Abbasi, R.; Abdou, Y.; Abu-Zayyad, T.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Andeen, K.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S. W.; Bay, R.; Bazo Alba, J. L.; Beattie, K.; Beatty, J. J.; Bechet, S.; Becker, J. K.; Becker, K.-H.; Benabderrahmane, M. L.; Berdermann, J.; Berghaus, P.; Berley, D.; Bernardini, E.; Bertrand, D.; Besson, D. Z.; Bissok, M.; Blaufuss, E.; Boersma, D. J.; Bohm, C.; Böser, S.; Botner, O.; Bradley, L.; Braun, J.; Buitink, S.; Carson, M.; Chirkin, D.; Christy, B.; Clem, J.; Clevermann, F.; Cohen, S.; Colnard, C.; Cowen, D. F.; D'Agostino, M. V.; Danninger, M.; de Clercq, C.; Demirörs, L.; Depaepe, O.; Descamps, F.; Desiati, P.; de Vries-Uiterweerd, G.; Deyoung, T.; Díaz-Vélez, J. C.; Dreyer, J.; Dumm, J. P.; Duvoort, M. R.; Ehrlich, R.; Eisch, J.; Ellsworth, R. W.; Engdegård, O.; Euler, S.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Feusels, T.; Filimonov, K.; Finley, C.; Foerster, M. M.; Fox, B. D.; Franckowiak, A.; Franke, R.; Gaisser, T. K.; Gallagher, J.; Ganugapati, R.; Geisler, M.; Gerhardt, L.; Gladstone, L.; Glüsenkamp, T.; Goldschmidt, A.; Goodman, J. A.; Grant, D.; Griesel, T.; Groß, A.; Grullon, S.; Gunasingha, R. M.; Gurtner, M.; Gustafsson, L.; Ha, C.; Hallgren, A.; Halzen, F.; Han, K.; Hanson, K.; Helbing, K.; Herquet, P.; Hickford, S.; Hill, G. C.; Hoffman, K. D.; Homeier, A.; Hoshina, K.; Hubert, D.; Huelsnitz, W.; Hülß, J.-P.; Hulth, P. O.; Hultqvist, K.; Hussain, S.; Imlay, R. L.; Ishihara, A.; Jacobsen, J.; Japaridze, G. S.; Johansson, H.; Joseph, J. M.; Kampert, K.-H.; Kappes, A.; Karg, T.; Karle, A.; Kelley, J. L.; Kemming, N.; Kenny, P.; Kiryluk, J.; Kislat, F.; Klein, S. R.; Knops, S.; Köhne, J.-H.; Kohnen, G.; Kolanoski, H.; Köpke, L.; Koskinen, D. J.; Kowalski, M.; Kowarik, T.; Krasberg, M.; Krings, T.; Kroll, G.; Kuehn, K.; Kuwabara, T.; Labare, M.; Lafebre, S.; Laihem, K.; Landsman, H.; Lauer, R.; Lehmann, R.; Lennarz, D.; Lünemann, J.; Madsen, J.; Majumdar, P.; Maruyama, R.; Mase, K.; Matis, H. S.; Matusik, M.; Meagher, K.; Merck, M.; Mészáros, P.; Meures, T.; Middell, E.; Milke, N.; Montaruli, T.; Morse, R.; Movit, S. M.; Nahnhauer, R.; Nam, J. W.; Naumann, U.; Nießen, P.; Nygren, D. R.; Odrowski, S.; Olivas, A.; Olivo, M.; Ono, M.; Panknin, S.; Paul, L.; Pérez de Los Heros, C.; Petrovic, J.; Piegsa, A.; Pieloth, D.; Porrata, R.; Posselt, J.; Price, P. B.; Prikockis, M.; Przybylski, G. T.; Rawlins, K.; Redl, P.; Resconi, E.; Rhode, W.; Ribordy, M.; Rizzo, A.; Rodrigues, J. P.; Roth, P.; Rothmaier, F.; Rott, C.; Roucelle, C.; Ruhe, T.; Rutledge, D.; Ruzybayev, B.; Ryckbosch, D.; Sander, H.-G.; Sarkar, S.; Schatto, K.; Schlenstedt, S.; Schmidt, T.; Schneider, D.; Schukraft, A.; Schultes, A.; Schulz, O.; Schunck, M.; Seckel, D.; Semburg, B.; Seo, S. H.; Sestayo, Y.; Seunarine, S.; Silvestri, A.; Slipak, A.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Stephens, G.; Stezelberger, T.; Stokstad, R. G.; Stoyanov, S.; Strahler, E. A.; Straszheim, T.; Sullivan, G. W.; Swillens, Q.; Taboada, I.; Tamburro, A.; Tarasova, O.; Tepe, A.; Ter-Antonyan, S.; Tilav, S.; Toale, P. A.; Tosi, D.; Tur?an, D.; van Eijndhoven, N.; Vandenbroucke, J.; van Overloop, A.; van Santen, J.; Voigt, B.; Walck, C.; Waldenmaier, T.; Wallraff, M.; Walter, M.; Wendt, C.; Westerhoff, S.; Whitehorn, N.; Wiebe, K.; Wiebusch, C. H.; Wikström, G.; Williams, D. R.; Wischnewski, R.; Wissing, H.; Woschnagg, K.; Xu, C.; Xu, X. W.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zarzhitsky, P.; IceCube Collaboration

    2011-01-01

    Using the South Pole Acoustic Test Setup (SPATS) and a retrievable transmitter deployed in holes drilled for the IceCube experiment, we have measured the attenuation of acoustic signals by South Pole ice at depths between 190 m and 500 m. Three data sets, using different acoustic sources, have been analyzed and give consistent results. The method with the smallest systematic uncertainties yields an amplitude attenuation coefficient ? = 3.20 ± 0.57 km-1 between 10 and 30 kHz, considerably larger than previous theoretical estimates. Expressed as an attenuation length, the analyses give a consistent result for ? ? 1/? of ˜300 m with 20% uncertainty. No significant depth or frequency dependence has been found.

  5. Crosswell seismic studies in gas hydrate-bearing sediments: P wave velocity and attenuation tomography

    NASA Astrophysics Data System (ADS)

    Bauer, K.; Haberland, Ch.; Pratt, R. G.; Ryberg, T.; Weber, M. H.; Mallik Working Group

    2003-04-01

    We present crosswell seismic data from the Mallik 2002 Production Research Well Program, an international research project on Gas Hydrates in the Northwest Territories of Canada. The program participants include 8 partners; The Geological Survey of Canada (GSC), The Japan National Oil Corporation (JNOC), GeoForschungsZentrum Potsdam (GFZ), United States Geological Survey (USGS), United States Department of the Energy (USDOE), India Ministry of Petroleum and Natural Gas (MOPNG)/Gas Authority of India (GAIL) and the Chevron-BP-Burlington joint venture group. The crosswell seismic measurements were carried out by making use of two 1160 m deep observation wells (Mallik 3L-38 and 4L-38) both 45 m from and co-planar with the 1188 m deep production research well (5L-38). A high power piezo-ceramic source was used to generate sweeped signals with frequencies between 100 and 2000 Hz recorded with arrays of 8 hydrophones per depth level. A depth range between 800 and 1150 m was covered, with shot and receiver spacings of 0.75 m. High quality data could be collected during the survey which allow for application of a wide range of crosswell seismic methods. The initial data analysis included suppression of tube wave energy and picking of first arrivals. A damped least-squares algorithm was used to derive P-wave velocities from the travel time data. Next, t* values were derived from the decay of the amplitude spectra, which served as input parameters for a damped least-squares attenuation tomography. The initial results of the P-wave velocity and attenuation tomography reveal significant features reflecting the stratigraphic environment and allow for detection and eventually quantification of gas hydrate bearing sediments. A prominent correlation between P velocity and attenuation was found for the gas hydrate layers. This contradicts to the apparently more meaningful inverse correlation as it was determined for the gas hydrates at the Blake Ridge but supports the results from the Mallik 2L-38 sonic log data. The P velocities and attenuation values, if combined with other information can be important for the quantitative evaluation of the gas hydrate saturation, and may further constrain petrophysical models of the hydrate bearing sediment formation.

  6. Measuring Distance with Sound Waves

    NSDL National Science Digital Library

    AMPS GK-12 Program,

    Students learn about sound waves and use them to measure distances between objects. They explore how engineers incorporate ultrasound waves into medical sonogram devices and ocean sonar equipment. Students learn about properties, sources and applications of three types of sound waves, known as the infra-, audible- and ultra-sound frequency ranges. They use ultrasound waves to measure distances and understand how ultrasonic sensors are engineered.

  7. Application of sound-absorbent plastic to weak-shock-wave attenuators

    NASA Astrophysics Data System (ADS)

    Ootsuta, Katsuhisa; Matsuoka, Kei; Sasoh, Akihiro; Takayama, Kazuyoshi

    1998-04-01

    A device for attenuating weak shock waves propagating in a duct has been developed utilizing sound-absorbent plastic which is usually used for attenuating sound waves. The device has a tube made of the sound-absorbent plastic installed coaxially to a surrounding metal tube with a clearance between them. The clearance acts as an air layer to enhance the performance of the shock wave attenuation. When a weak shock wave propagates through this device, the pressure gradient of the shock wave is gradually smeared and hence its overpressure is decreased. The performance of the device was examined using a 1/250-scaled train tunnel simulator which simulated the discharge of weak shock waves created by high-speed entry of trains to tunnels. The overpressure of the shock waves ranged up to 5 kPa. The shock wave overpressure was decreased by 90% with the present attenuator attached. This device can be applied to various industrial noise suppressions which are associated with unsteady compressible flows.

  8. Shock-Wave Attenuation and Energy-Dissipation Potential of Granular Materials

    E-print Network

    Grujicic, Mica

    Shock-Wave Attenuation and Energy-Dissipation Potential of Granular Materials Mica Grujicic, B shocks in granular materials is analyzed using a conventional shock-physics approach. Within this approach, both compression shocks and decompression waves are treated as (stress, specific volume, particle

  9. Interferometric ground-roll removal: Attenuation of scattered surface waves in single-sensor data

    E-print Network

    Interferometric ground-roll removal: Attenuation of scattered surface waves in single-sensor data of these scattered surface waves exist and can be separated into two categories: acquisition-based suppression-driven Herman and Perkins, 2006 inverse-scattering series. The use of extensive stacked arrays in acquisition

  10. Measurment and Interpretation of Seismic Attenuation for Hydrocarbon Exploration

    SciTech Connect

    Michael Batzle; Luca Duranti; James Rector; Steve Pride

    2007-12-31

    This research project is the combined effort of several leading research groups. Advanced theoretical work is being conducted at the Lawrence Berkeley National Laboratory. Here, the fundamental controls on loss mechanisms are being examined, primarily by use of numerical models of heterogeneous porous media. At the University of California, Berkeley, forward modeling is combined with direct measurement of attenuation. This forward modeling provides an estimate of the influence of 1/Q on the observed seismic signature. Direct measures of losses in Vertical Seismic Profiles (VSPs) indicate mechanisms to separate scattering versus intrinsic losses. At the Colorado School of Mines, low frequency attenuation measurements are combined with geologic models of deep water sands. ChevronTexaco is our corporate cosponsor and research partner. This corporation is providing field data over the Genesis Field, Gulf of Mexico. In addition, ChevronTexaco has rebuilt and improved their low frequency measurement system. Soft samples representative of the Genesis Field can now be measured for velocities and attenuations under reservoir conditions. Throughout this project we have: Assessed the contribution of mechanical compaction on time-lapse monitoring; Developed and tested finite difference code to model dispersion and attenuation; Heterogeneous porous materials were modeled and 1/Q calculated vs. frequency; 'Self-affine' heterogeneous materials with differing Hurst exponent modeled; Laboratory confirmation was made of meso-scale fluid motion influence on 1/Q; Confirmed theory and magnitude of layer-based scattering attenuation at Genesis and at a shallow site in California; Scattering Q's of between 40 and 80 were obtained; Measured very low intrinsic Q's (2-20) in a partially saturated vadose zone VSP; First field study to separate scattering and intrinsic attenuation in real data set; Revitalized low frequency device at ChevronTexaco's Richmond lab completed; First complete frequency dependent measurements on Berea sandstones from dry to various saturations (brine and decane); Frequency dependent forward modeling code is running, and tested on a couple of Cases--derives frequency dependent reflectivity from porosity based logs; Genesis seismic data obtained but is on hold until forward modeling is complete; Boundary and end effects modeled for soft material measurements at CSM; and Numerous papers published or submitted and presentations made.

  11. Anisotropic dispersion and attenuation due to wave-induced fluid flow: Quasi-static finite element modeling in poroelastic solids

    Microsoft Academic Search

    F. Wenzlau; J. B. Altmann; T. M. Müller

    2010-01-01

    Heterogeneous porous media such as hydrocarbon reservoir rocks are effectively described as anisotropic viscoelastic solids. They show characteristic velocity dispersion and attenuation of seismic waves within a broad frequency band, and an explanation for this observation is the mechanism of wave-induced pore fluid flow. Various theoretical models quantify dispersion and attenuation of normal incident compressional waves in finely layered porous

  12. Upper mantle and crustal P-wave attenuation beneath the North Korea region

    NASA Astrophysics Data System (ADS)

    Cleveland, M.; Randall, G. E.; Patton, H. J.; Phillips, W. S.

    2014-12-01

    Accurate estimation of the magnitude of crustal seismic sources is dependent upon a strong understanding of the anelastic P-wave attenuation in the crust and upper mantle. In this study, we estimate the crustal/upper mantle average attenuation (t*) for the region around North Korea by expanding upon methods described by Ichinose et al. [2013]. We estimate t* by modeling the observed spectra and spectral ratio of regional and teleseismic P- and pP-phases of large, deep (> 500 km) earthquakes rupturing beneath the North Korea region. We use seismograms, acquired from the IRIS data archive, from operational stations at the time of each earthquake. Because of a trade-off between the variables, we use multi-variable optimization to estimate the best-fitting corner frequency (fc) and t* for each spectrum. In addition to using a more quantitative and global approach than earlier studies, we introduce new measurement approaches enabling a better understanding of the uncertainty in the measured t* value and its trade-off with fc.

  13. Attenuation zones of periodic pile barriers and its application in vibration reduction for plane waves

    NASA Astrophysics Data System (ADS)

    Huang, Jiankun; Shi, Zhifei

    2013-09-01

    The periodic theory of solid-state physics is introduced to study the reduction characteristics of periodic pile barriers. The attenuation zones of a two-dimensional infinite periodic pile barrier subjected to plane waves are analyzed by plane wave expansion method. Influences of soil parameters and pile configurations on the first no-directional attenuation zone are discussed. The screening effectiveness of finite periodic pile barriers is simulated by the finite element method. The present theoretical results are in well agreement with experimental data, which validates the existence of attenuation zones in the periodic structures. The results show that vibrations with frequencies in the attenuation zones can be reduced significantly. The present investigation provides a new concept for designing pile barriers to block mid-frequency vibration.

  14. Effects of fracture contact areas on seismic attenuation due to wave-induced fluid flow

    NASA Astrophysics Data System (ADS)

    Germán Rubino, J.; Müller, Tobias M.; Milani, Marco; Holliger, Klaus

    2014-05-01

    Wave-induced fluid flow (WIFF) between fractures and the embedding matrix is considered to be a predominant seismic attenuation mechanism in fractured rocks. That is, due to the strong compressibility contrast between fractures and embedding matrix, seismic waves induce strong fluid pressure gradients, followed by local fluid flow between such regions, which in turn produces significant energy dissipation. Natural fractures can be conceptualized as two surfaces in partial contact, containing very soft and highly permeable material in the inner region. It is known that the characteristics of the fracture contact areas control the mechanical properties of the rock sample, since as the contact area increases, the fracture becomes stiffer. Correspondingly, the detailed characteristics of the contact area of fractures are expected to play a major role in WIFF-related attenuation. To study this topic, we consider a simple model consisting of a horizontal fracture located at the center of a porous rock sample and represented by a number of rectangular cracks of constant height separated by contact areas. The cracks are modelled as highly compliant, porous, and permeable heterogeneities, which are hydraulically connected to the background material. We include a number of rectangular regions of background material separating the cracks, which represent the presence of contact areas of the fracture. In order to estimate the WIFF effects, we apply numerical oscillatory relaxation tests based on the quasi-static poro-elastic equations. The equivalent undrained, complex plane-wave modulus, which allows to estimate seismic attenuation and velocity dispersion for the vertical direction of propagation, is expressed in terms of the imposed displacement and the resulting average vertical stress at the top boundary. In order to explore the effects of the presence of fracture contact areas on WIFF effects, we perform an exhaustive sensitivity analysis considering different characteristics for the regions of contact. This study enabled us to observe that in the case of regular distributions of contact areas seismic attenuation and dispersion levels increase with decreasing size or increasing separation of the contact areas. In addition, we corroborated that for the same fraction of contact area, seismic attenuation and dispersion are weaker for regular distributions of contact areas and stronger when they are located within a narrow cluster. Our numerical approach also allowed us to explore the vertical solid displacement gap across fractures. We found that this parameter is strongly affected by the geometrical details of the fracture contact areas and turned out to be complex-valued and frequency-dependent due to WIFF effects. Finally, using laboratory measurements of changes in fracture contact area as a function of the applied stress, we proposed a model illustrating the effects related to the evolution of the contact area with increasing stress. The corresponding results suggest that seismic attenuation and phase velocity may constitute useful attributes to extract information on the prevailing effective stress of fractured media.

  15. Seismic wave attenuation in Israel region estimated from the multiple lapse time window analysis and S-wave coda decay rate

    NASA Astrophysics Data System (ADS)

    Meirova, Tatiana; Pinsky, Vladimir

    2014-04-01

    For the first time, a regional seismic attenuation for the Israel region is quantitatively estimated as a combination of intrinsic and scattering attenuations. We use a multiple lapse time windows analysis (MLTWA) to determinate the relative contributions of intrinsic absorption and scattering processes to the total regional attenuation in the crust. A single isotropic scattering model assuming a uniform half-space lithosphere is used to fit MLTWA predicted and measured energies from the records of 232 regional earthquakes recorded at 17 short-period and 5 broad-band local seismic stations. Analysis is performed for a set of 10 frequencies between 0.5 and 10 Hz. The frequency-dependent quality factor Q obtained by MLTWA ranges between Q = 77f0.96 in the Northern Israel and Q = 132f0.96 in Southern Israel. Independent estimates of regional coda Q value based on S-wave coda decay rate obtained by averaging of five broad-band Israel Seismic Network stations are approximated by the relation Qc = 126f1.05. As a whole, our findings indicate that in the Israel region, intrinsic absorption prevails over scattering attenuation. Separate analysis for three tectonically different regions in Israel region-Galilee-Lebanon, Judea-Samaria and Eastern Sinai-shows a regional dependence of attenuation parameters. The variation of attenuation characteristics implies different physical mechanisms of seismic attenuation in the Israel region and is related to the differences of structure in the Earth's crust beneath Israel. Such variation in the attenuation patterns is in agreement with the assumption that Northern Israel is tectonically more active than Southern Israel and that in the northern and central parts of Israel the upper crust is more heterogeneous than in the southern part.

  16. Study on energy attenuation of ultrasonic guided waves going through girth welds.

    PubMed

    Yibo, Li; Liying, Sun; Zhidong, Song; Yuankai, Zhang

    2006-12-22

    Ultrasonic guided wave is introduced as a new non-destructive long range pipe inspection method. It can be used to inspect pipe which is inaccessible to other conventional NDT methods, and rapid, long distance inspection can be achieved. An investigation of the guided ultrasonic waves traveling along pipe with special geometry characteristics, such as elbow, several girth welds, and some artificial defects is described. In this paper, factors that may cause attenuation of ultrasonic guided waves are discussed and energy attenuation of longitudinal and torsional guided waves is studied on an experimental pipe having seven girth welds. Good agreement has been obtained between the experiments and the predictions. In the end, the detection sensitivity and locating precision of two guided waves, namely longitudinal and torsional, were compared on defects, such as notch, burr and branch. PMID:17070566

  17. Blast-wave density measurements

    NASA Astrophysics Data System (ADS)

    Ritzel, D. V.

    Applications of a densitometer to obtain time-resolved data on the total density in blast-wave flows are described. A beta-source (promethium-147) is separated by a gap from a scintillator and a photomultiplier tube (PMT). Attenuation of the radiation beam by the passing blast wave is due to the total density in the gap volume during the wave passage. Signal conditioning and filtering methods permit the system to output linearized data. Results are provided from use of the system to monitor blast waves emitted by detonation of a 10.7 m diameter fiberglass sphere containing 609 tons of ammonium nitrate/fuel oil at a 50.6 m height. Blast wave density data are provided for peak overpressure levels of 245, 172 and 70 kPa and distances of 183, 201 and 314 m from ground zero. Data resolution was of high enough quality to encourage efforts to discriminate dust and gasdynamic phenomena within passing blast waves.

  18. Toward Improved Methods of Estimating Attenuation, Phase and Group velocity of surface waves observed on Shallow Seismic Records

    Microsoft Academic Search

    M. S. Diallo; M. Holschneider; M. Kulesh; F. Scherbaum; M. Ohrnberger; E. Lück

    2004-01-01

    This contribution is concerned with the estimate of attenuation and dispersion characteristics of surface waves observed on a shallow seismic record. The analysis is based on a initial parameterization of the phase and attenuation functions which are then estimated by minimizing a properly defined merit function. To minimize the effect of random noise on the estimates of dispersion and attenuation

  19. Millimeter-wave propagation measurements at the Ballistic Research Laboratory

    Microsoft Academic Search

    H. Bruce Wallace

    1988-01-01

    Results of measurements made with radars from 35 to 217 GHz of near-earth propagation in rain, fog, snow, and humidity are presented. The effects of water vapor are characterized by an attenuation coefficient that is a function of vapor pressure or absolute humidity. Backscatter contributes significantly to the adverse effect of rain on mm-wave radars because the droplet sizes become

  20. An evaluation of two millimeter wave propagation models for horizontal atmospheric attenuation at 70-115 GHZ

    NASA Astrophysics Data System (ADS)

    Vogel, Gerard N.

    1988-02-01

    An evaluation is performed for two millimeter wave propagation models: the LIEBE model, developed at the Institute for Telecommunications, Boulder, CO, under the guidance of Dr. H. Liebe; and the EOSAEL model, developed at the U. S. Army Atmospheric Laboratory at White Sands Missile Range, NM. This evaluation is conducted for horizontal attenuation due to both clear atmosphere and hydrometer effects under typical surface meteorological conditions, and within the frequency range 70-115 GHz. Intercomparisons of model theories and predictions show slight differences for molecular oxygen and fog attenuations, but significant differences for water vapor and rain attenuations. Results indicate that, while the qualitative agreement between either the EOSAEL or LIEBE model predictions, and measurements, for horizontal attenuation due to oxygen, water vapor, fog and rain is certainly satisfactory, there is a definite need for improvement. Overall, no clear preference for either the EOSAEL or LIEBE model for operational use is ascertained. Data comparisons suggest that, for several attenuation types, model preference is dependent on either the frequency or meteorological conditions.

  1. Sensitivity of seismic measurements to frequency-dependent attenuation and upper mantle structure: An initial approach

    NASA Astrophysics Data System (ADS)

    Bellis, C.; Holtzman, B.

    2014-07-01

    This study addresses the sensitivity of seismic attenuation measurements to dissipative mechanisms and structure in the Earth's upper mantle. The Andrade anelastic model fits experimental attenuation data with a mild power law frequency dependence and can be scaled from laboratory to Earth conditions. We incorporate this anelastic model into 400km 1-D thermal profiles of the upper mantle. These continuous-spectrum models are approximated by multiple relaxation mechanisms that are implemented within a finite-difference scheme to perform wave propagation simulations in 1-D domains. In two sets of numerical experiments, we evaluate the measurable signature of the intrinsic attenuation structure. The two sets are defined by thermal profiles with added step functions of temperature, varying in (i) amplitude and depth or (ii) amplitude and sharpness. The corresponding synthetic data are processed using both the conventional t* approach, i.e., a linear regression of the displacement frequency spectrum, and an alternative nonlinear fit to identify the integrated value of attenuation and its frequency dependence. The measured sensitivity patterns are analyzed to assess the effects of the anelastic model and its spatial distribution on seismic data (in the absence of scattering effects). We have two straightforward results: (1) the frequency dependence power law is recoverable from the measurements; (2) t* is sensitive to both the depth and the amplitude of the step, and it is insensitive to the sharpness of the step, in the 0.25 to 2 Hz band. There is much potential for gaining information about the upper mantle thermodynamic state from careful interpretation of attenuation.

  2. Near-surface seismic attenuation of P-waves in West Texas

    E-print Network

    Al-Zahrani, Said Awdhah

    1992-01-01

    NEAR-SURFACE SEISMIC ATTENUATION OF P-WAVES IN WEST TEXAS A Thesis by SAID AWDHAH AL-ZAHRANI Submitted to the Office of Graduate Studies of Texas ARM University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE... August 1992 Major Subject: Geophysics NEAR-SURFACE SEISMIC ATTENUATION OF P-WAVES IN WEST TEXAS A Thesis by SAID AWDHAH AL-ZAHRANI Approved as to style and content by: Steven H. arder (Chair of Committee) rry W. S neer (Me ber) I S. Watkins...

  3. Multiple attenuation to reflection seismic data using Radon filter and Wave Equation Multiple Rejection (WEMR) method

    NASA Astrophysics Data System (ADS)

    Erlangga, Mokhammad Puput

    2015-04-01

    Separation between signal and noise, incoherent or coherent, is important in seismic data processing. Although we have processed the seismic data, the coherent noise is still mixing with the primary signal. Multiple reflections are a kind of coherent noise. In this research, we processed seismic data to attenuate multiple reflections in the both synthetic and real seismic data of Mentawai. There are several methods to attenuate multiple reflection, one of them is Radon filter method that discriminates between primary reflection and multiple reflection in the ?-p domain based on move out difference between primary reflection and multiple reflection. However, in case where the move out difference is too small, the Radon filter method is not enough to attenuate the multiple reflections. The Radon filter also produces the artifacts on the gathers data. Except the Radon filter method, we also use the Wave Equation Multiple Elimination (WEMR) method to attenuate the long period multiple reflection. The WEMR method can attenuate the long period multiple reflection based on wave equation inversion. Refer to the inversion of wave equation and the magnitude of the seismic wave amplitude that observed on the free surface, we get the water bottom reflectivity which is used to eliminate the multiple reflections. The WEMR method does not depend on the move out difference to attenuate the long period multiple reflection. Therefore, the WEMR method can be applied to the seismic data which has small move out difference as the Mentawai seismic data. The small move out difference on the Mentawai seismic data is caused by the restrictiveness of far offset, which is only 705 meter. We compared the real free multiple stacking data after processing with Radon filter and WEMR process. The conclusion is the WEMR method can more attenuate the long period multiple reflection than the Radon filter method on the real (Mentawai) seismic data.

  4. Experimental investigation of wave attenuation through model and live vegetation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hurricanes and tropical storms often cause severe damage and loss of life in coastal areas. It is widely recognized that wetlands along coastal fringes reduce storm surge and waves. Yet, the potential role and primary mechanisms of wave mitigation by wetland vegetation are not fully understood. K...

  5. Shallow Seismic Attenuation and Shear Waves Splitting In The Short Period Range of Deception Island Volcano (antarctica)

    NASA Astrophysics Data System (ADS)

    Martínez-Arévalo, C.; Bianco, F.; Ibáñez, J. M.; del Pezzo, E.

    The occurrence of a seismic series in Deception Island volcano (Antarctica), com- posed by hundreds of local volcano-tectonic earthquakes, has permitted us to study the seismic attenuation of such a volcanic environment in the short-distance and high- frequency range. This study has been performed using P, S and coda waves and ap- plying different, frequency dependent and independent, techniques. The methods used for this analysis have been: Spectral and Broadening of the Pulse, for direct P and S waves, Coda Normalization for S-waves and Single Back-Scattering model for coda waves. The results show that, in general, Q values are significantly smaller, for all the frequency range used (6-30 Hz), than those found in other volcanic and tectonic areas. The attenuation for P-waves is greater than for S-waves in the frequency in- dependent methods, with a Qb/QP ratio that ranges between 1.9 and 3.2. Comparing the Q factor obtained for S-waves we have observed clear differences as a function of the method used; the Coda Normalization Method has supplied significantly higher Q values (Qd) than the other two methods (Qb). These Qd values are similar to the Q factor for coda waves (Qc). We have interpreted this discrepancy as an effect of the methods: Coda Normalization and Single Back-Scattering methods eliminate the con- tribution of the near surface attenuation in their Q values. Comparing both Qb and Qd we have estimated the near surface attenuation under the recording site, named Qk. On the other hand, we have observed that Qd has an anomalous frequency dependence, with a minimum value at 21 Hz. This pattern is interpreted as an effect of strong scat- tering of the seismic waves in the source area of the earthquakes. Qc values depend clearly with frequency and lapse time, and the lapse time dependence is interpreted as a depth dependence of the seismic attenuation in Deception Island volcano. The de- rived Q values have allowed us to separate the contribution of intrinsic and scattering attenuation, deriving that the scattering attenuation is predominant over the intrinsic effects. Finally, in order to investigate how the heterogeneous medium of the volcanic island could produce other effects, we have measured the splitting of the shear waves of the same data set. The observations reveal that the arrival delay of the shear waves horizontal components varies between 0.02 and 0.14 seconds, a big amount if we take into account the short hypocentral distances (less than 5 km). The study of the polar- 1 ization direction indicates a main E-W direction. All these evidences reveal the strong heterogeneous structure of Deception Island volcano. 2

  6. Improved techniques for measuring x-ray mass attenuation coefficients

    NASA Astrophysics Data System (ADS)

    de Jonge, Martin D.; Tran, Chanh Q.; Chantler, Christopher T.; Barnea, Zwi

    2004-10-01

    We have applied the x-ray extended-range technique (XERT) to measure mass attenuation coefficients over one order of magnitude more accurately than previously reported in the literature. We describe here the application of the XERT to the investigation of a number of systematic effects which has enabled us to ensure that these recent measurements are free from systematic error. In particular we describe our techniques for quantifying the effects of harmonic components in the x-ray beam, scattering and fluorescence from the absorbing sample, the bandwidth of the x-ray beam, and thickness variations across the absorber.

  7. Effect of subsurface hydrological properties on velocity and attenuation of compressional and shear wave in fluid-saturated viscoelastic porous media

    NASA Astrophysics Data System (ADS)

    Ghasemzadeh, Hasan; Abounouri, Amir Ali

    2012-08-01

    SummaryOver the past years there has been a growing interest in the use of seismic waves to gain required information about the Earth's subsurface. Despite all achievements, the problem of accurately linking field measurement of seismic attributes to subsurface hydrological properties such as porosity and intrinsic permeability is still ambiguous. The goal of the present paper is to provide a comprehensive study on the effect of subsurface hydrological properties on seismic attributes such as wave attenuation and velocity. This is achieved by using dispersion relations obtained from equations of wave motion that are derived from Biot's theory of poroelasticity. Since the attenuation predicted from Biot's theory is only due to relative motion of the solid and fluid phases, viscoelasticity effects are introduced to consider the attenuation caused by grain to grain contact. The dispersion relations for body waves including fast wave, slow wave and shear wave are valid in both low and high frequency ranges where viscous and inertia effects are dominant, respectively. Numerical simulations are performed on sand samples over a wide range of frequencies (1 Hz to 1 MHz). For samples with constant porosity, but different intrinsic permeabilities, it is demonstrated that the velocity of slow wave is higher for the more permeable sample over the full frequency range. The velocity of fast wave and shear wave is higher for the more permeable sample, but the difference is significant only at intermediate frequencies (10-100,000 Hz). However, the corresponding peak velocity and attenuation of each of the wave modes are almost equal for different intrinsic permeability values and, therefore, independent of intrinsic permeability. Another series of numerical simulations are carried out on sand samples with different porosity values. It is shown that the most porous sand has higher slow wave and shear wave velocity, but lower fast wave velocity. Also, the peak attenuation of fast wave and shear wave gets larger as sand porosity increases, but slow wave behavior is opposite. Remarkable result is that all wave modes become more dispersive when porosity increases. Thus, neglecting the dependence of wave velocity on frequency can lead to significant miscalculation of wave velocity for sand samples with high porosity values.

  8. DTS Measurements Waves Model Toroidal field discussion Experimental magnetostrophic waves

    E-print Network

    Low, Robert

    DTS Measurements Waves Model Toroidal field discussion Experimental magnetostrophic waves T #12;DTS Measurements Waves Model Toroidal field discussion The Earth Magnetostrophic waves Hartmann meeting, Coventry 15-16 February 2007 #12;DTS Measurements Waves Model Toroidal field discussion The Earth

  9. FAST TRACK PAPER: Characteristic frequencies of seismic attenuation due to wave-induced fluid flow in fractured porous media

    Microsoft Academic Search

    Miroslav Brajanovski; Tobias M. Müller; Boris Gurevich

    2006-01-01

    We analyse compressional wave attenuation in fluid saturated porous material with porous inclusions having different compressibilities and very different spatial scales in comparison with the background. Such a medium exhibits significant attenuation due to wave-induced fluid flow across the interface between inclusion and background. For the representative element containing two layers (one of them representing inclusion), we show that overall

  10. Wave energy attenuation and shoreline alteration characteristics of submerged breakwaters 

    E-print Network

    Krafft, Katherine Margaret

    1993-01-01

    in this research was sometimes deficient in resolving exactly the fundamental frequency of a periodic wave, comparison of results for the two methods was generally favorable. ACKNOWLEDGEMENTS Many thanks are extended to my advisor, Dr. J. B. Herbich... - frequency X ? distance from original shoreline, (assuming a constant slope of 1: 15) Xt - centered and padded time series data CHAPTER I INTRODUCTION 1. 1 General The dynamic behavior of waves on a shore in conjunction with inadequate littoral drift...

  11. Attenuation of P, S, and coda waves in Koyna region, India

    Microsoft Academic Search

    Babita Sharma; S. S. Teotia; Dinesh Kumar

    2007-01-01

    The attenuation properties of the crust in the Koyna region of the Indian shield have been investigated using 164 seismograms\\u000a from 37 local earthquakes that occurred in the region. The extended coda normalization method has been used to estimate the\\u000a quality factors for P waves $$ {\\\\left( {Q_{\\\\alpha } } \\\\right)} $$ and S waves $$ {\\\\left( {Q_{\\\\beta } }

  12. Shear wave attenuation and dispersion in melt-bearing olivine polycrystals

    E-print Network

    Shear wave attenuation and dispersion in melt-bearing olivine polycrystals: 1. Specimen fabrication 2003; accepted 7 January 2004; published 23 June 2004. [1] Five melt-bearing polycrystalline olivine behavior of melt-free materials, a broad dissipation peak is observed for each of the melt-bearing

  13. Shear wave attenuation and dispersion in melt-bearing olivine polycrystals

    E-print Network

    Shear wave attenuation and dispersion in melt-bearing olivine polycrystals: 2. Microstructural forced oscillation tests of melt-bearing olivine aggregates reported by Jackson et al. [2004. While the nanometer scale grain boundary structure in the melt-bearing aggregates is essentially

  14. A study of tensile damage and attenuation effect of perforated concrete defense layer on stress waves

    Microsoft Academic Search

    Zhi-liang Wang; Yong-chi Li; J. G. Wang; R. F. Shen

    2007-01-01

    Civil defense shelters are often constructed beneath the ground to provide protection against blast loadings. Concrete is widely used as the material for the defense layer of the shelters. This paper adopts a continuum damage model of brittle media to numerically investigate the dynamic fracture and attenuation effect of perforated concrete defense layer on stress waves from planar charge. The

  15. A temporal change in coda wave attenuation observed during an eruption of Mount St. Helens

    Microsoft Academic Search

    Michael Fehler; Peter Roberts; Tom Fairbanks

    1988-01-01

    During the past few years there have been numerous reports of changes in coda wave attenuation occurring before major earthquakes. These observations are important because they may provide insight into stress-related structural changes taking place in the focal region prior to the occurrence of large earthquakes. The results of these studies led us to suspect that temporal changes in coda

  16. Plastic yielding as a frequency and amplitude independent mechanism of seismic wave attenuation

    E-print Network

    Podladchikov, Yuri

    for micro- fracturing. INTRODUCTION The attenuation of elastic waves has received a good deal of atten- tion and Deresiewicz, 1953; Knopoff and MacDonald, 1960; Walsh, 1966 , grain contact adhesion hysteresis Sharma and Mindlin and Deresiewicz 1953 assume two identi- cal elastic homogeneous spherical particles in contact

  17. Attenuation, transport and diffusion of scalar waves in textured random media

    Microsoft Academic Search

    L. Margerin

    2006-01-01

    Most theoretical investigations of seismic wave scattering rely on the assumption that the underlying medium is statistically isotropic. However, deep seismic soundings of the crust as well as geological observations often reveal the existence of elongated or preferentially oriented scattering structures. In this paper, we develop mean field and radiative transfer theories to describe the attenuation and multiple scattering of

  18. Shear wave velocity, seismic attenuation, and thermal structure of the continental upper mantle

    USGS Publications Warehouse

    Artemieva, I.M.; Billien, M.; Leveque, J.-J.; Mooney, W.D.

    2004-01-01

    Seismic velocity and attenuation anomalies in the mantle are commonly interpreted in terms of temperature variations on the basis of laboratory studies of elastic and anelastic properties of rocks. In order to evaluate the relative contributions of thermal and non-thermal effects on anomalies of attenuation of seismic shear waves, QS-1, and seismic velocity, VS, we compare global maps of the thermal structure of the continental upper mantle with global QS-1 and Vs maps as determined from Rayleigh waves at periods between 40 and 150 S. We limit the comparison to three continental mantle depths (50, 100 and 150 km), where model resolution is relatively high. The available data set does not indicate that, at a global scale, seismic anomalies in the upper mantle are controlled solely by temperature variations. Continental maps have correlation coefficients of <0.56 between VS and T and of <0.47 between QS and T at any depth. Such low correlation coefficients can partially be attributed to modelling arrefacts; however, they also suggest that not all of the VS and QS anomalies in the continental upper mantle can be explained by T variations. Global maps show that, by the sign of the anomaly, VS and QS usually inversely correlate with lithospheric temperatures: most cratonic regions show high VS and QS and low T, while most active regions have seismic and thermal anomalies of the opposite sign. The strongest inverse correlation is found at a depth of 100 km, where the attenuation model is best resolved. Significantly, at this depth, the contours of near-zero QS anomalies approximately correspond to the 1000 ??C isotherm, in agreement with laboratory measurements that show a pronounced increase in seismic attenuation in upper mantle rocks at 1000-1100 ??C. East-west profiles of VS, QS and T where continental data coverage is best (50??N latitude for North America and 60??N latitude for Eurasia) further demonstrate that temperature plays a dominant, but non-unique, role in determining the value of lithospheric VS and QS. At 100 km depth, where the resolution of seismic models is the highest, we compare observed seismic VS and QS with theoretical VST and QST values, respectively, that are calculated solely from temperature anomalies and constrained by experimental data on temperature dependencies of velocity and attenuation. This comparison shows that temperature variations alone are sufficient to explain seismic VS and QS in ca 50 per cent of continental regions. We hypothesize that compositional anomalies resulting from Fe depletion can explain the misfit between seismic and theoretical VS in cratonic lithosphere. In regions of active tectonics, temperature effects alone cannot explain seismic VS and QS in the lithosphere. It is likely that partial melts and/or fluids may affect seismic parameters in these regions. This study demonstrates that lithospheric temperature plays the dominant role in controlling VS and QS anomalies, but other physical parameters, such as compositional variations, fluids, partial melting and scattering, may also play a significant role in determining VS and QS variations in the continental mantle. ?? 2004 RAS.

  19. Measurement of Acoustic Attenuation and Absorption Coefficients using Thermometry

    NASA Astrophysics Data System (ADS)

    Morris, Hugh; Rivens, Ian; Shaw, Adam; ter Haar, Gail

    2007-05-01

    Accurate knowledge of both the attenuation and the absorption coefficient of tissue are required when planning an optimal high intensity focused ultrasound treatment. A novel technique for simple measurement of this parameters has been developed in which a thin-film thermocouple (TFT) is placed between two layers of tissue of different thicknesses. The sample can be rotated about an axis through the junction of the TFT so that it can be insonated from either side leaving the tissue adjacent to the junction unchanged, but changing the overlying thickness. The attenuation and absorption coefficients can be calculated from the heating curves measured in the two orientations. Experiments have been carried out in both tissue mimicking material (TMM) and in ex vivo liver tissue. Weakly focused transducers, resonant at 1.05 MHz, 2.4 MHz and 3.55 MHz were used at free-field spatial peak intensities of 9-14 W/cm2. The temperature rise was measured as a function of time using a TFT. These thermocouples are not subject to the viscous heating artefact that is common to other thermocouple devices and so are advantageous for this purpose. Alignment was achieved with a 3D automated gantry system, which was controlled with specialised software. Timing and data acquisition were also controlled with this software. All experiments were carried out in degassed water. Results for TMM and degassed excised bovine liver are presented.

  20. Representative Elementary Length to Measure Soil Mass Attenuation Coefficient

    PubMed Central

    Borges, J. A. R.; Pires, L. F.; Costa, J. C.

    2014-01-01

    With increasing demand for better yield in agricultural areas, soil physical property representative measurements are more and more essential. Nuclear techniques such as computerized tomography (CT) and gamma-ray attenuation (GAT) have been widely employed with this purpose. The soil mass attenuation coefficient (?s) is an important parameter for CT and GAT analysis. When experimentally determined (?es), the use of suitable sized samples enable to evaluate it precisely, as well as to reduce measurement time and costs. This study investigated the representative elementary length (REL) of sandy and clayey soils for ?es measurements. Two radioactive sources were employed (241Am and 137Cs), three collimators (2–4?mm diameters), and 14 thickness (x) samples (2–15?cm). Results indicated ideal thickness intervals of 12–15 and 2–4?cm for the sources 137Cs and 241Am, respectively. The application of such results in representative elementary area (REA) evaluations in clayey soil clods via CT indicated that ?es average values obtained for x?>?4?cm and source 241Am might induce to the use of samples which are not large enough for soil bulk density evaluations (?s). As a consequence, ?s might be under- or overestimated, generating inaccurate conclusions about the physical quality of the soil under study. PMID:24672338

  1. Representative elementary length to measure soil mass attenuation coefficient.

    PubMed

    Borges, J A R; Pires, L F; Costa, J C

    2014-01-01

    With increasing demand for better yield in agricultural areas, soil physical property representative measurements are more and more essential. Nuclear techniques such as computerized tomography (CT) and gamma-ray attenuation (GAT) have been widely employed with this purpose. The soil mass attenuation coefficient (?(s)) is an important parameter for CT and GAT analysis. When experimentally determined (?(es)), the use of suitable sized samples enable to evaluate it precisely, as well as to reduce measurement time and costs. This study investigated the representative elementary length (REL) of sandy and clayey soils for ?(es) measurements. Two radioactive sources were employed ((241)Am and (137)Cs), three collimators (2-4 mm diameters), and 14 thickness (x) samples (2-15 cm). Results indicated ideal thickness intervals of 12-15 and 2-4 cm for the sources (137)Cs and (241)Am, respectively. The application of such results in representative elementary area (REA) evaluations in clayey soil clods via CT indicated that ?(es) average values obtained for x > 4 cm and source (241)Am might induce to the use of samples which are not large enough for soil bulk density evaluations (?(s)). As a consequence, ?(s) might be under- or overestimated, generating inaccurate conclusions about the physical quality of the soil under study. PMID:24672338

  2. Blast wave attenuation by lightly destructable granular materials

    E-print Network

    Texas at Arlington, University of

    is to coat the surface with a sacrificial layer. In [3] full-scale experiments were carried out to investigate the behaviour of a covering of aluminum foam under the effect of a blast wave. In our study steel chamber V BK - 2, 4.5m in diameter and 7m in length. The sand/cement cylinder was placed 95cm

  3. Wave attenuation over coastal salt marshes under storm surge conditions

    E-print Network

    Möller, Iris; Kudella, Matthias; Rupprecht, Franziska; Spencer, Tom; Paul, Maike; van Wesenbeeck, Bregje K.; Wolters, Guido; Jensen, Kai; Bouma, Tjeerd J.; Miranda-Lange, Martin; Schimmels, Stefan

    2014-09-29

    requirements11) perspectives. This has resulted in a re-evaluation of coastal flood and erosion risk 35 reduction methods5. Natural coastal landforms, including sand dunes, mudflats and salt marshes, are 36 now widely recognised as potential barriers to wave... dissipation by vegetated beds commonly rely on knowledge of the drag coefficient 87 CD incorporated into a friction factor that takes account of vegetation stem density, height, and 88 diameter. The complex nature of salt marsh vegetation precludes the a...

  4. INDIRECT MEASUREMENT OF BIOLOGICAL ACTIVITY TO MONITOR NATURAL ATTENUATION

    EPA Science Inventory

    The remediation of ground water contamination by natural attenuation, specifically biodegradation, requires continual monitoring. This research is aimed at improving methods for evaluating the long-term performance of Monitored Natural Attenuation (MNA), specifically changes in ...

  5. Characteristics of vibrational wave propagation and attenuation in submarine fluid-filled pipelines

    NASA Astrophysics Data System (ADS)

    Yan, Jin; Zhang, Juan

    2015-04-01

    As an important part of lifeline engineering in the development and utilization of marine resources, the submarine fluid-filled pipeline is a complex coupling system which is subjected to both internal and external flow fields. By utilizing Kennard's shell equations and combining with Helmholtz equations of flow field, the coupling equations of submarine fluid-filled pipeline for n=0 axisymmetrical wave motion are set up. Analytical expressions of wave speed are obtained for both s=1 and s=2 waves, which correspond to a fluid-dominated wave and an axial shell wave, respectively. The numerical results for wave speed and wave attenuation are obtained and discussed subsequently. It shows that the frequency depends on phase velocity, and the attenuation of this mode depends strongly on material parameters of the pipe and the internal and the external fluid fields. The characteristics of PVC pipe are studied for a comparison. The effects of shell thickness/radius ratio and density of the contained fluid on the model are also discussed. The study provides a theoretical basis and helps to accurately predict the situation of submarine pipelines, which also has practical application prospect in the field of pipeline leakage detection.

  6. Measurement of ultrasonic scattering attenuation in austenitic stainless steel welds: realistic input data for NDT numerical modeling.

    PubMed

    Ploix, Marie-Aude; Guy, Philippe; Chassignole, Bertrand; Moysan, Joseph; Corneloup, Gilles; El Guerjouma, Rachid

    2014-09-01

    Multipass welds made of 316L stainless steel are specific welds of the primary circuit of pressurized water reactors in nuclear power plants. Because of their strong heterogeneous and anisotropic nature due to grain growth during solidification, ultrasonic waves may be greatly deviated, split and attenuated. Thus, ultrasonic assessment of the structural integrity of such welds is quite complicated. Numerical codes exist that simulate ultrasonic propagation through such structures, but they require precise and realistic input data, as attenuation coefficients. This paper presents rigorous measurements of attenuation in austenitic weld as a function of grain orientation. In fact attenuation is here mainly caused by grain scattering. Measurements are based on the decomposition of experimental beams into plane-wave angular spectra and on the modeling of the ultrasonic propagation through the material. For this, the transmission coefficients are calculated for any incident plane wave on an anisotropic plate. Two different hypotheses on the welded material are tested: first it is considered as monoclinic, and then as triclinic. Results are analyzed, and validated through comparison to theoretical predictions of related literature. They underline the great importance of well-describing the anisotropic structure of austenitic welds for UT modeling issues. PMID:24759567

  7. Millimeter-wave propagation measurements at the Ballistic Research Laboratory

    NASA Astrophysics Data System (ADS)

    Wallace, H. Bruce

    1988-05-01

    Results of measurements made with radars from 35 to 217 GHz of near-earth propagation in rain, fog, snow, and humidity are presented. The effects of water vapor are characterized by an attenuation coefficient that is a function of vapor pressure or absolute humidity. Backscatter contributes significantly to the adverse effect of rain on mm-wave radars because the droplet sizes become comparable to signal wavelengths. Path losses from fogs, haze, or clouds, are caused by both absorption and scattering by water droplets. Attenuation due to falling snow is difficult to link to and single characteristics.

  8. Tracking accelerated aging of composites with ultrasonic attenuation measurements

    SciTech Connect

    Chinn, D.J.; Durbin, P.F.; Thomas, G.H.; Groves, S.E.

    1996-10-01

    Composite materials are steadily replacing traditional materials in many industries. For many carbon composite materials, particularly in aerospace applications, durability is a critical design parameter which must be accurately characterized. Lawrence Livermore National Laboratory (LLNL) and Boeing Commercial Airplane Group have established a cooperative research and development agreement (CRADA) to assist in the high speed research program at Boeing. LLNL`s expertise in fiber composites, computer modeling, mechanical testing, chemical analysis and nondestructive evaluation (ND) will contribute to the study of advanced composite materials in commercial aerospace applications. Through thermo-mechanical experiments with periodic chemical analysis and nondestructive evaluation, the aging mechanisms in several continuous fiber polymer composites will be studied. Several measurement techniques are being studied for their correlation with aging. This paper describes through-transmission ultrasonic attenuation measurements of isothermally aged composite materials and their use as a tracking parameter for accelerated aging.

  9. Ionospheric wave spectrum measurements

    NASA Technical Reports Server (NTRS)

    Harker, K. J.; Ilic, D. B.; Crawford, F. W.

    1979-01-01

    The local spectrum S(k, omega) of either potential or electron-density fluctuations can be used to determine macroscopic-plasma characteristics such as the local density and temperature, transport coefficients, and drift current. This local spectrum can be determined by measuring the cross-power spectrum. The paper examines the practicality of using the cross-power spectrum analyzer on the Space Shuttle to measure ionospheric parameters. Particular attention is given to investigating the integration time required to measure the cross-power spectral density to a desired accuracy.

  10. Attenuation of shock waves propagating through nano-structured porous materials

    NASA Astrophysics Data System (ADS)

    Al-Qananwah, Ahmad K.; Koplik, Joel; Andreopoulos, Yiannis

    2013-07-01

    Porous materials have long been known to be effective in energy absorption and shock wave attenuation. These properties make them attractive in blast mitigation strategies. Nano-structured materials have an even greater potential for blast mitigation because of their high surface-to-volume ratio, a geometric parameter which substantially attenuates shock wave propagation. A molecular dynamics approach was used to explore the effects of this remarkable property on the behavior of traveling shocks impacting on solid materials. The computational setup included a moving piston, a gas region and a target solid wall with and without a porous structure. The gas and porous solid were modeled by Lennard-Jones-like and effective atom potentials, respectively. The shock wave is resolved in space and time and its reflection from a solid wall is gradual, due to the wave's finite thickness, and entails a self-interaction as the reflected wave travels through the incoming incident wave. Cases investigated include a free standing porous structure, a porous structure attached to a wall and porous structures with graded porosity. The effects of pore shape and orientation have been also documented. The results indicate that placing a nano-porous material layer in front of the target wall reduced the stress magnitude and the energy deposited inside the solid by about 30 percent, while at the same time substantially decreasing the loading rate.

  11. Numerical Analysis of Pulsed Pressure Waves in Attenuative and Dispersive Media.

    NASA Astrophysics Data System (ADS)

    Wismer, Margaret Gertrude

    This thesis examines the behavior of pulsed pressure waves as they propagate through dissipative fluids whose attenuation is characterized by a frequency power law. This means that the degree of attenuation increases as the frequency of a sinusoidal input signal increases where the rate of change is a physical property of the substance. Previously published experimental data indicates that this form of attenuation is typical of many viscous materials including biological tissues and fluids, adhesive glues, etc. The model developed to describe this behavior is based on the assumption that the pulsed waves have finite amplitude and can therefore be uniquely represented in the Fourier frequency domain in which the attenuation is equal to the imaginary part of the complex wavenumber. To ensure causality of the system impulse response, it is shown that the real part of the wavenumber must be nonlinearly dependent on frequency. This means that the physical system must be dispersive as well as attenuative and consequently pulsed waves are distorted as they propagate. Based on the complex wavenumber, a dispersive version of the wave equation which satisfies continuity conditions at material interfaces is derived. A spatial and temporal discretization of this equation allows for the analysis of realistic imaging regions. Due to noninteger powers of frequency in the wavenumber a continuous time version of the wave equation is not easily obtained making traditional finite difference time domain operators inapplicable. The interdependence of imaginary and real parts of the wavenumber, however, makes it possible to combine the corresponding terms in the wave equation into a single factor. This factor can then be mapped into discrete time frequency. In this domain noninteger exponents can be eliminated via a power series expansion and the resulting equations transform naturally to discrete time operators. The validity of this method is verified by comparing the results with those obtained through a numerical frequency domain implementation. The algorithm is demonstrated in two dimensions by simulating pulsed pressure waves radiating from a finite aperture through an adhesive bond layer in which case a thin dispersive layer is sandwiched between two lossless fluids.

  12. Effect of phase change on shock wave attenuation in GeO2 and T. J. Ahrens

    E-print Network

    Stewart, Sarah T.

    wave velocity decreases to a value below 2.5 km/s the speed of the bulk wave, at the HEL . 3 A shockEffect of phase change on shock wave attenuation in GeO2 C. Liua) and T. J. Ahrens Seismological shock regime with ramp 4 GPa Hugoniot elastic limit HEL precursor. Shock propagation velocity decreases

  13. Seismic-wave attenuation and yield determination at regional distances. Final report, 1 May 1987-30 April 1989

    Microsoft Academic Search

    B. J. Mitchell; O. W. Nuttli; J. K. Xie; H. Al-Shukri; A. Correig

    1989-01-01

    Work was completed on yield determination at the Soviet test site on Novaya Zemlya. Magnitudes and yields, determined for 30 explosions using Lg amplitudes recorded in northwestern Europe, ranged between 2.5 and 4900 kt, the largest since April 1976 being about 145 kt. Studies were completed on seismic wave attenuation of surface waves at intermediate periods and of Lg waves

  14. Reflection of attenuated waves at the surface of a porous solid saturated with two immiscible viscous fluids

    NASA Astrophysics Data System (ADS)

    Sharma, M. D.; Kumar, M.

    2011-01-01

    The mathematical model for wave motion in a porous solid saturated by two immiscible fluids is solved for the propagation of harmonic plane waves along a general direction in 3-D space. The solution is obtained in the form of Christoffel equations, which are solved further to calculate the complex velocities and polarisations of three longitudinal waves and one transverse wave. For any of these four attenuated waves, a general inhomogeneous propagation is considered through a particular specification of complex slowness vector. Inhomogeneity of an attenuated wave is represented through a finite non-dimensional parameter. For an arbitrarily chosen value of this inhomogeneity parameter, phase velocity and attenuation of a wave are calculated from the specification of its slowness vector. This specification enables to separate the contribution from homogeneous propagation of attenuated wave to the total attenuation. The phenomenon of reflection is studied to calculate the partition of wave-induced energy incident at the plane boundary of the porous solid. A parameter is used to define the partial opening of pores at the surface of porous solid. An arbitrary value of this parameter allows to study the variations in the energy partition with the opening of surface pores from fully closed to perfectly open. Another parameter is used to vary the saturation in pores from whole liquid to whole gas. Numerical examples are considered to discuss the effects of propagation direction, inhomogeneity parameter, opening of surface pores and saturating pore-fluid on the partition of incident energy.

  15. The measurement of attenuation from vertical seismic profiles 

    E-print Network

    Davis, Francis Erwin

    1983-01-01

    vertical seismic profiles. These attenua ior, strmates were correlatec with litholocic informatio. , determined =rom well logs, core analyszs, and cuttings. Att nuaiton wa. s found tc correlate with shal s, wrth a direct correlation bet een attenuation... to borehole irregularities affecting sonic log travel times, thus creating artificial reflections on the synthetic seismogram. Interference from other seismic events can mask attenuation and will limit the spatial resolution of the attenuation estimate...

  16. The wave equation with viscoelastic attenuation and its application in problems of shallow-sea acoustics

    NASA Astrophysics Data System (ADS)

    Petrov, P. S.; Zakharenko, A. D.; Trofimov, M. Yu.

    2012-11-01

    A suitable tool for the simulation of low frequency acoustic pulse signals propagating in a shallow sea is the numerical integration of the nonstationary wave equation. The main feature of such simulation problems is that in this case the sound waves propagate in the geoacoustic waveguide formed by the upper layers of the bottom and the water column. By this reason, the correct dependence of the attenuation of sound waves in the bottom on their frequency must be taken into account. In this paper we obtain an integro-differential equation for the sound waves in the viscoelastic fluid, which allows to simulate the arbitrary dependence of acoustic wave attenuation on frequency in the time domain computations. The procedure of numerical solution of this equation based on its approximation by a system of differential equations is then considered and the methods of artificial limitation of computational domain are described. We also construct a simple finite-difference scheme for the proposed equation suitable for the numerical solution of nonstationary problems arising in the shallow-sea acoustics.

  17. Comparison of OLYMPUS beacon and radiometric attenuation measurements at Blacksburg, Virginia

    NASA Technical Reports Server (NTRS)

    Snider, J. B.; Jacobson, M. D.; Beeler, R. H.; Hazen, D. A.

    1991-01-01

    Measurements of attenuation of the 20 and 30 GHz beacons onboard the OLYMPUS satellite are compared to simultaneous observations of atmospheric attenuation by a multichannel microwave radiometer along the same path. Departures from high correlation between the two measurements are believed to be related to differences in antenna beamwidths. Mean equivalent zenith attenuations derived from the slant path data are compared to zenith observations made at previous locations.

  18. Investigating Global Shear-Wave Attenuation and Radial Anisotropy in the Earth's Mantle using Free Oscillations

    NASA Astrophysics Data System (ADS)

    Moulik, P.; Ekstrom, G.

    2011-12-01

    A self-consistent radial and lateral description of the Earth's elastic and anelastic heterogeneity has implications for understanding the internal geodynamic processes with their thermal, chemical and compositional contexts. We investigate the extent and amplitude of radial anisotropy and attenuation in the Earth's mantle using observations of eigenfrequencies, quality factors (Q) and splitting functions of free oscillations collected from the literature. We observe that the convergence to a best-fit 1-D shear attenuation model using the Q data requires an iterative framework of recalculating the sensitivity kernels. This non-linearity is due to the dependence of the anelastic kernels on the intrinsic attenuation structure of the reference model in addition to the expected theoretical dependence on the elastic structure. We perform forward modeling of the splitting coefficients while accounting for shear-wave anisotropy (Mochizuki 1986) and using the 3-D anisotropic mantle model S362ANI (Kustowski et al., 2008), which was constrained using surface-wave phase anomalies, long-period waveforms, and body-wave travel times. We use these calculations to investigate the sensitivity of the mode splitting functions to radial anisotropy at different depths in the Earth. The differences in the synthetic predictions of the 2-D splitting functions while including and excluding the anisotropic part of S362ANI are observed to be significant for some modes, indicating that splitting functions can provide useful additional constraints on mantle anisotropy. Corrections to the splitting coefficients are implemented to remove the effects of the lateral heterogeneities in the crust using the spherical harmonic expansion of the different layers and discontinuities in CRUST 2.0 (Bassin et al., 2000). An iterative inversion is being developed using the eigenfrequencies and quality factors as constraints on the spherically averaged radial (1-D) elastic and attenuation structure and the splitting coefficients as additional constraints on the lateral (3-D) variations in elastic structure.

  19. Characteristics of the near-bottom suspended sediment field over the continental shelf off northern California based on optical attenuation measurements during STRESS and SMILE

    NASA Astrophysics Data System (ADS)

    Trowbridge, J. H.; Butman, B.; Limeburner, R.

    1994-08-01

    Time-series measurements of current velocity, optical attenuation and surface wave intensity obtained during the Sediment Transport Events on Shelves and Slopes (STRESS) experiments, combined with shipboard measurements of conductivity, temperature and optical attenuation obtained during the Shelf Mixed Layer Experiment (SMILE), provide a description of the sediment concentration field over the central and outer shelf off northern California. The questions addressed are: (1) existence and characteristics of bottom nepheloid layers and their relationship to bottom mixed layers; (2) characteristics of temporal fluctuations in sediment concentration and their relationship to waves and currents; (3) spatial scales over which suspended sediment concentrations vary horizontally; and (4) vertical distribution of suspended sediment.

  20. Characteristics of the near-bottom suspended sediment field over the continental shelf off northern California based on optical attenuation measurements during STRESS and SMILE

    USGS Publications Warehouse

    Trowbridge, J.H.; Butman, B.; Limeburner, R.

    1994-01-01

    Time-series measurements of current velocity, optical attenuation and surface wave intensity obtained during the Sediment Transport Events on Shelves and Slopes (STRESS) experiments, combined with shipboard measurements of conductivity, temperature and optical attenuation obtained during the Shelf Mixed Layer Experiment (SMILE), provide a description of the sediment concentration field over the central and outer shelf off northern California. The questions addressed are: (1) existence and characteristics of bottom nepheloid layers and their relationship to bottom mixed layers; (2) characteristics of temporal fluctuations in sediment concentration and their relationship to waves and currents; (3) spatial scales over which suspended sediment concentrations vary horizontally; and (4) vertical distribution of suspended sediment. ?? 1994.

  1. Physical Models of Seismic-Attenuation Measurements on Lab Samples

    NASA Astrophysics Data System (ADS)

    Coulman, T. J.; Morozov, I. B.

    2012-12-01

    Seismic attenuation in Earth materials is often measured in the lab by using low-frequency forced oscillations or static creep experiments. The usual assumption in interpreting and even designing such experiments is the "viscoelastic" behavior of materials, i.e., their description by the notions of a Q-factor and material memory. However, this is not the only theoretical approach to internal friction, and it also involves several contradictions with conventional mechanics. From the viewpoint of mechanics, the frequency-dependent Q becomes a particularly enigmatic property attributed to the material. At the same time, the behavior of rock samples in seismic-attenuation experiments can be explained by a strictly mechanical approach. We use this approach to simulate such experiments analytically and numerically for a system of two cylinders consisting of a rock sample and elastic standard undergoing forced oscillations, and also for a single rock sample cylinder undergoing static creep. The system is subject to oscillatory compression or torsion, and the phase-lag between the sample and standard is measured. Unlike in the viscoelastic approach, a full Lagrangian formulation is considered, in which material anelasticity is described by parameters of "solid viscosity" and a dissipation function from which the constitutive equation is derived. Results show that this physical model of anelasticity predicts creep results very close to those obtained by using empirical Burger's bodies or Andrade laws. With nonlinear (non-Newtonian) solid viscosity, the system shows an almost instantaneous initial deformation followed by slow creep towards an equilibrium. For Aheim Dunite, the "rheologic" parameters of nonlinear viscosity are ?=0.79 and ?=2.4 GPa-s. Phase-lag results for nonlinear viscosity show Q's slowly decreasing with frequency. To explain a Q increasing with frequency (which is often observed in the lab and in the field), one has to consider nonlinear viscosity with ? < 0.5 and/or include thermoelastic effects. The model also shows how the Q values measured on the samples depend on the shapes and dimensions of the elements of the experimental system.; Non-linear creep approximating the anelastic part of Burgers' model for Aheim dunite (Chopra, 1997). Non-linear model parameters are ?=0.79, ?=2.4 GPa-s, and the Burger's model parameters are: ?=15.75 GPa and viscosity ?=2040 GPa-s.

  2. Heterogeneous lower mantle shear attenuation from ScS-S differential t* measurements via instantaneous frequency under Central America

    NASA Astrophysics Data System (ADS)

    Durand, S.; Ford, S. R.; Matas, J.; Romanowicz, B. A.; Ricard, Y. R.; Montagner, J.; Lekic, V.

    2011-12-01

    Heterogeneities in lower mantle shear attenuation can be inferred from differential t* measurements between the ScS and S seismic phases, denoted ?t* {ScS-S}. A classical approach for measuring differential t* utilizes spectral ratio method. In this study, a different method, based on instantaneous frequency, is used. The instantaneous frequency of a phase is the average of the signal Fourier frequency spectrum at the arrival-time of the phase. Making the assumption that waves propagating in an anelastic medium see their dominant period decrease, the ?t* {ScS-S} is then obtained by attenuating the seismic phase with a greater instantaneous frequency using a t* operator until it matches the seismic phase with the lesser instantaneous frequency. The instantaneous frequency matching method is applied to high quality broadband seismic data from 1994 to 2009 with core reflection localized beneath Central America and for seismic paths close to a reference plane. This allows us to map variations in attenuation along a slice of the mantle. The range of measured ?t* {ScS-S} indicates heterogeneities in Central America lower mantle shear attenuation. We then do a least square inversion of the ?t* {ScS-S} to find a 2-D map of Q? in this slice of mantle. It reveals the presence of a very attenuating zone, dln(Q)=-90%, extending from 800-2000 km depth where the Farallon slab has been detected with tomography. Finally, we measure differential travel times by cross-correlating the S and ScS seismic phases and compare to the measured ?t* {ScS-S}. Interestingly, the comparison suggests that attenuation and velocity structure may not be correlated.

  3. The Use of Ultrasonic Seismic Wave Attenuation (Q) for Better Subsurface Imaging, Energy Exploration, and Tracking of Sequestrated Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Delaney, D.; Purcell, C. C.; Mur, A. J.; Haljasmaa, I.; Soong, Y.; Harbert, W.

    2012-12-01

    Parameters related to seismic and ultrasonic elastic waves traveling through a porous rock material with compliant pores, cracks and isometric pores are subject to variations which are dependent on the physical properties of the rock such as density, porosity, permeability, frame work moduli, fluid moduli, micro structural variation, and effective pressure. Our goal is to understand these variations through experiments completed using Berea sandstone, rhyolites, coal, and carbonate samples. Understanding these lithologies are relevant to enhanced oil recovery, enhanced geothermal, and CO2 storage activities. Working in the COREFLOW laboratory at the National Energy Technology Laboratory (NETL) of the United States Department of Energy (DOE) we performed several experiments on these rock types with various different pore filling fluids, effective pressures, and temperatures. We measured P, S1 and S2 ultrasonic velocities using an New England Research (NER) Autolab 1500 device and calculated the lame parameters (Bulk modulus (K), Young's modulus (E), Lamè's first parameter (?), Shear modulus (G), Poisson's ratio ( ), P-wave modulus (M)). Using an aluminum reference core and the P, S1, and S2 ultrasonic waveform data collected, we employed the spectral ratio method to estimate Q. This method uses the ratio of the amplitude-frequency spectrum (obtained via fast Fourier Transform and processed using Matlab) of the rock core compared with the amplitude-frequency spectrum of the aluminum reference core to calculate the quality factor (Q). The quality factor is a dimensionless value that represents the attenuation of a seismic wave as it travels through a rock. Seismic attenuation is dependent on wave velocity, the path length or time the wave is in the rock, and of course the physical properties of the rock through which the wave travels. Effective pressures used in our experiments varied between 0.01 MPa and 50 MPa and temperatures varied between 21 C to 80 C which allowed us to more accurately represent subsurface conditions. Pore filling fluids consisted of deionized water, oil, gas, and supercritical CO2. We have found that Q for the P, S1, and S2 seismic waves is strongly dependent on and proportional to the effective pressure of the rock. Also our experiments indicate that the presence of different pore filling fluids such as water, oil, and CO2 alter the value of Q. Carbonate samples were tested dry (atmospheric gas as pore fluid) and with deionized water, oil, and CO2. With the substitution of each of these fluids into the dry rock core sample, we see the value of Q shift as much as 20% lower for the P, S1, and S2 seismic waves. Our experiments indicate that the presence of oil, water, or CO2 lowers the value of Q of a rock. For all effective pressures we see this shift in the value of Q, it would seem that with the introduction of these pore-filling fluids the quality factor value is typically lowered, however at higher effective pressures (about 40 MPa) the shift in Q is less. By understanding how seismic waves attenuate we can better understand what collected seismic signals traveled through. This knowledge and understanding of seismic wave attenuation could prove to be a powerful tool for better subsurface imaging, tracking of sequestrated CO2, and energy exploration.

  4. Estimates of ocean wave heights and attenuation in sea ice using the SAR wave mode on Sentinel-1A

    NASA Astrophysics Data System (ADS)

    Ardhuin, Fabrice; Collard, Fabrice; Chapron, Bertrand; Girard-Ardhuin, Fanny; Guitton, Gilles; Mouche, Alexis; Stopa, Justin

    2015-04-01

    Swell evolution from the open ocean into sea ice is poorly understood, in particular the amplitude attenuation expected from scattering and dissipation. New synthetic aperture radar (SAR) data from Sentinel-1 wave mode reveal intriguing patterns of bright oscillating lines shaped like instant noodles. We investigate cases in which the oscillations are in the azimuth direction, around a straight line in the range direction. This observation is interpreted as the distortion by the SAR processing of crests from a first swell, due to the presence of a second swell. As deviations from a straight line should be proportional to the orbital velocity towards the satellite, swell height can be estimated, from 1.5 to 5 m in the present case. This evolution of this 13 s period swell across the ice pack is consistent with an exponential attenuation on a length scale of 200 km.

  5. Experimental measurements of seismic attenuation in microfracture sedimentary rock

    SciTech Connect

    Peacock, S.; McCann, C.; Sothcott, J.; Astin, T.R. (Univ. of Reading (United Kingdom). Research Inst. for Sedimentology)

    1994-09-01

    In a previous paper (Peacock et al., 1994), the authors related ultrasonic velocities in water-saturated Carrara Marble to crack densities in polished sections to verify Hudson's (1980, 1981, 1986) theory for velocities in cracked rock. They describe the empirical relationships between attenuation and crack density that they established during these experiments in the hope of clarifying the mechanism of attenuation in rocks with fluid-filled cracks. Relating seismic velocity and attenuation to crack density is important in predicting the productivity of fractured petroleum reservoirs such as the North Sea Brent Field. It also allows cracks to be used as stress indicators throughout the shallow crust (Crampin and Lovell, 1991).

  6. Technological cost-reduction pathways for attenuator wave energy converters in the marine hydrokinetic environment.

    SciTech Connect

    Bull, Diana L; Ochs, Margaret Ellen

    2013-09-01

    This report considers and prioritizes the primary potential technical costreduction pathways for offshore wave activated body attenuators designed for ocean resources. This report focuses on technical research and development costreduction pathways related to the device technology rather than environmental monitoring or permitting opportunities. Three sources of information were used to understand current cost drivers and develop a prioritized list of potential costreduction pathways: a literature review of technical work related to attenuators, a reference device compiled from literature sources, and a webinar with each of three industry device developers. Data from these information sources were aggregated and prioritized with respect to the potential impact on the lifetime levelized cost of energy, the potential for progress, the potential for success, and the confidence in success. Results indicate the five most promising costreduction pathways include advanced controls, an optimized structural design, improved power conversion, planned maintenance scheduling, and an optimized device profile.

  7. A Split of Direction of Propagation and Attenuation of P Waves in the Po Valley

    NASA Astrophysics Data System (ADS)

    Daminelli, R.; Tento, A.; Marcellini, A.

    2013-12-01

    On July 17, 2011 a ML 4.8 earthquake occurred in the PO valley at a 48 km epicentral distance from a seismic station located at Palazzo Te (Mantova). The station is situated on deep quaternary sediments: the uppermost layers are mainly composed of clay and silty clay with interbedded sands; the Robertson index is 1.4wave particle motion, that appears rather difficult to explain if we assume the homogeneity of the P waves (that means attenuation is scalar). Note that the degree of nonlinearity is very low given that the maximum strain can be roughly estimated as 10-5 on the basis of maximum ground velocity of the P wave train considered and the Vp. On the contrary we show that P wave particle motion can be fully (and easily) described by a Homogeneous Isotropic Linear Viscoelastic model (HILV). HILV, as in the 2009 Borcherdt formulation adopted here, allows two different directions of propagation and attenuation; in other words attenuation becomes a vector that is not necessarily parallel to the propagation vector. The results evidence that the incidence angle and the inhomogeneity angle (it is the angle between propagation and attenuation vectors and it is closely related to Q factor) are in good agreement with the geological conditions of the site. Finally, we observed that these results are very similar to the ones obtained when we analyzed two explosions recorded by a seismic station in Milano, also situated in the Po valley at some 140 km from Mantova (Marcellini & Tento, 2011). Borcherdt, R.D. (2009) 'Viscoelastic Waves in Layered Media', Cambridge University Press, Cambridge, United Kingdom, 305 pp. Marcellini, A. and A. Tento (2011) ' Explosive Sources Prove the Validity of Homogeneous Isotropic Linear Viscoelastic Models', BSSA, Vol. 101, No. 4, pp. 1576-1583.

  8. Dislocation Damping and Anisotropic Seismic-wave Attenuation in the Earth's Upper Mantle

    NASA Astrophysics Data System (ADS)

    Farla, R. J. M.; Jackson, I.; Fitz Gerald, J. D.; Faul, U. H.; Zimmerman, M. E.

    2012-04-01

    Seismic anisotropy, attributed to olivine lattice preferred orientation, suggests that tectonic deformation in the Earth's shallow upper mantle involves dislocation creep. Reversible glide of dislocations, generated by the prevailing/fossil tectonic stress, may result in anelastic relaxation that contributes to the reduction of seismic wave speeds and associated attenuation. To test this hypothesis, pure polycrystalline olivine specimens were synthesised by isostatic hot-pressing of synthetic powders of Fo90 composition. The hot-pressed material is dense (< 1% porosity), fine-grained, essentially dry and melt-free olivine. Other, more coarse-grained material was prepared in the same way from crushed natural (San Carlos) olivine. These contrasting materials provided the opportunity to distinguish between the influences of grain size, dislocation density and minor impurities. Selected specimens were deformed by dislocation creep either in compression or torsion and characterised for dislocation density via oxidative decoration and backscattered electron imaging. The shear modulus and associated strain-energy dissipation in both hot-pressed and pre-deformed specimens were measured at seismic frequencies and low strain amplitudes under conditions of simultaneous high pressure and temperature with torsional forced-oscillation methods. On the basis of a prior study of dislocation recovery, a maximum temperature of 1100C was chosen to allow sustained forced-oscillation testing under conditions of relatively stable dislocation microstructure. The high-temperature dissipation background, attributed in undeformed fine-grained materials to grain-boundary sliding, and the associated partial relaxation of the shear modulus, are systematically enhanced in the pre-deformed materials - suggesting a role for the dislocations introduced during the prior deformation. The enhancement is systematically greater for prior torsional deformation than for prior deformation in compression. This observation is consistent with the prediction from a simple model of resolved shear stress that dislocations generated by prior torsional deformation are more favourably oriented for glide during the subsequent torsional oscillation measurements. Such dislocation damping is expected to become more significant relative to grainsize-sensitive effects for the larger grain sizes of the Earth's mantle. Moreover, it is predicted that dislocation damping in the Earth's mantle will be anisotropic - being greatest for those shear-wave propagation directions and polarisations with shear stress aligned with the prevailing/fossil tectonic stress.

  9. Measurement of photon attenuation from different cardiac chambers

    Microsoft Academic Search

    A. M. Keller; T. R. Simon; C. R. Malloy; G. J. Dehmer; T. C. Smitherman

    1985-01-01

    Accounting for the attenuation (AT) of photons within cardiac chambers is crucial to accurate non-geometric volume determinations from gated blood pool scintigraphy. Previous techniques to determine AT for each patient have assumed an attenuation factor of 0.15\\/cm for Tc-99m, the value of water. To verify this, the authors determined the AT at various tissue distances (TD) in vivo. As a

  10. Teleseismic Body Wave Attenuation in the Upper Mantle beneath the United States

    NASA Astrophysics Data System (ADS)

    Cafferky, S.; Schmandt, B.

    2014-12-01

    EarthScope seismic data provide opportunities to examine mantle properties on a continental scale as the Transportable Array (TA) nears the end of its traverse across the contiguous United States. We use P- and S-wave amplitude spectra from all >M5.7 deep earthquakes recorded by the TA to examine seismic attenuation patterns in the upper mantle. More than 2 million inter-station P-wave spectral ratios were inverted for maps of relative tP* variations across the U.S. in multiple frequency bands between 0.08 - 2 Hz. We plan to have corresponding S-wave results by meeting time. Maps of tP* are strongly correlated (>0.8) for frequency bands of 0.08 - 2 Hz, 0.25 - 2 Hz, 0.08 - 1 Hz, and 0.25 - 1 Hz. The broader the frequency band examined (e.g. 0.08 - 2 Hz), the lower the magnitude in variations of tP*; however, those broader frequency bands still exhibited geographic patterns similar to the narrow frequency bands. We compare our maps' tP* with seismic velocity models and constraints on crustal scattering to assess the physical origin of apparent attenuation. In the tectonically active and high heat flow domain of the western U.S., tP* variations are moderately correlated with thermal variations predicted by tomography studies of seismic velocity. However, contrast in tP* between western Cordillera and the cratonic interior is weaker than predicted by tomography. Additionally some areas of high attenuation are correlated with Precambrian tectonic boundaries within the Laurentian craton. The weak contrast between the western and eastern U.S. and correlations with Precambrian tectonics suggest that elastic scattering due to small-scale (~10 - 100 km) heterogeneity or compositional variations in the lithosphere are major contributors to tP* estimates from deep earthquake spectral ratios. Moderate correlation of tP* with estimates of mantle temperature within the western U.S. suggests deep earthquake spectral ratios do carry some evidence of intrinsic attenuation, but separating the effects of elastic scattering and intrinsic attenuation remains a challenge.

  11. The effect of in-stream structures on flood wave attenuation in Western Carpathians of Slovakia

    NASA Astrophysics Data System (ADS)

    Majerova, M.

    2010-12-01

    In-stream structures were built as a part of the erosion and sediment flux control on mountainous streams in Slovakia. These structures, steps, drop structures, and check dams, affect the flow regime and flood wave attenuation. Flood magnitude for ten and hundred-year flood events decreased by 0.21-29% depending on the flow and type of structures used. The largest decrease in flood duration was 39%. Relative change in flow depth and velocity, representing local stream conditions, ranged from 16 to 52%, and 12 to 106% respectively. These changes were modeled with 1D model, HEC-RAS, version 4.0, using unsteady flow simulations. Observed water surface was used for the calibration. Roughness was calculated using Chow and Cowan equations which were based on field observations. The flood events were modeled on Breznicky Creek, Sutovsky Creek, and Ilanovsky Creek in Kremnica Mountains, Little Fatra and Low Tatras as part of the Western Carpathian Mountains. Two scenarios were analyzed for ten and hundred-year flood events: 1) streams in their natural state, and 2) streams which have been altered by different in-stream structures. The results of this study are consistent with practice of torrent control for steps, small in-stream structures, and results from stream study in Czech Republic. The steps, used for local erosion control and habitat improvement, did not change the flood wave attenuation significantly. For drop structures and check dams, actual available water storage created by structures influenced the overall flood wave attenuation change. Quantification of flood magnitude and time duration under different flow regimes with different types of in-stream structures provides necessary information for flood risk management.

  12. Measurements and Linear Wave Theory Based Simulations of Vegetated Wave Hydrodynamics for Practical Applications 

    E-print Network

    Anderson, Mary Elizabeth

    2011-10-21

    Wave attenuation by vegetation is a highly dynamic process and its quantification is important for accurately understanding and predicting coastal hydrodynamics. However, the influence of vegetation on wave dissipation is not yet fully established...

  13. Correlation Attenuation Due to Measurement Error: A New Approach Using the Bootstrap Procedure

    ERIC Educational Resources Information Center

    Padilla, Miguel A.; Veprinsky, Anna

    2012-01-01

    Issues with correlation attenuation due to measurement error are well documented. More than a century ago, Spearman proposed a correction for attenuation. However, this correction has seen very little use since it can potentially inflate the true correlation beyond one. In addition, very little confidence interval (CI) research has been done for…

  14. Disturbance attenuation and H?-control via measurement feedback in nonlinear systems

    Microsoft Academic Search

    A. Isidori; A. Astolfi

    1992-01-01

    A solution to the problem of disturbance attenuation via measurement feedback with internal stability is presented for an affine nonlinear system. It is shown that the concept of disturbance attenuation, in the sense of truncated L2 norms, can be given an interpretation in terms of the response to periodic inputs in the sense of RMS amplitude, even in the nonlinear

  15. Attenuation corrections for in-cylinder NO LIF measurements in a heavy-duty Diesel engine

    Microsoft Academic Search

    K. Verbiezen; R. J. H. Klein-Douwel; A. P. van Vliet; A. J. Donkerbroek; W. L. Meerts; N. J. Dam; J. J. Ter Meulen

    2006-01-01

    Quantification of the nitric oxide (NO) concentration inside the cylinder of a Diesel engine by means of laser-induced fluorescence (LIF) measurements requires, amongst others, knowledge of the attenuation of the ultraviolet radiation involved. We present a number of laser diagnostic techniques to assess this attenuation, enabling a correction for laser intensity and detection efficiency of the raw NO LIF data.

  16. SHEAR WAVE DISPERSION MEASURES LIVER STEATOSIS

    PubMed Central

    Barry, Christopher T.; Mills, Bradley; Hah, Zaegyoo; Mooney, Robert A.; Ryan, Charlotte K.; Rubens, Deborah J.; Parker, Kevin J.

    2012-01-01

    Crawling waves, which are interfering shear wave patterns, can be generated in liver tissue over a range of frequencies. Some important biomechanical properties of the liver can be determined by imaging the crawling waves using Doppler techniques and analyzing the patterns. We report that the dispersion of shear wave velocity and attenuation, that is, the frequency dependence of these parameters, are strongly correlated with the degree of steatosis in a mouse liver model, ex vivo. The results demonstrate the possibility of assessing liver steatosis using noninvasive imaging methods that are compatible with color Doppler scanners and, furthermore, suggest that liver steatosis can be separated from fibrosis by assessing the dispersion or frequency dependence of shear wave propagations. PMID:22178165

  17. Predicting Wave Glider Speed from Environmental Measurements

    E-print Network

    Sukhatme, Gaurav S.

    Predicting Wave Glider Speed from Environmental Measurements Ryan N. Smith, Jnaneshwar Das, Graham spatiotemporal resolutions. This paper focuses on the newly developed Wave Glider platform from Liquid Robotics ocean waves, the Liquid Robotics Wave Glider (see Fig. 1) provides a persistent ocean presence

  18. Satellite wave measurements for coastal engineering applications

    Microsoft Academic Search

    Harald E. Krogstad; Stephen F. Barstow

    1999-01-01

    Measurements from the GEOSAT, ERS-1 and 2 and Topex\\/Poseidon satellites have now accumulated to over 15 years of global ocean wave and wind data. Extraction of wave height, wind speed and wave period from the satellite altimeters and directional wave spectra from the synthetic aperture radars are reviewed along with recent validation and calibration efforts. Applications of the data to

  19. Wave measurement and modeling in Chesapeake Bay

    Microsoft Academic Search

    Weiqi Lin; Lawrence P. Sanford; Steven E. Suttles

    2002-01-01

    Three recently measured wind and wave data sets in the northern part of Chesapeake Bay (CB) are presented. Two of the three data sets were collected in late 1995. The third one was collected in July of 1998. The analyzed wind and wave data show that waves were dominated by locally generated, fetch limited young wind seas. Significant wave heights

  20. Lg Wave Attenuation in the Isparta Angle and Anatolian Plateau (Turkey)

    NASA Astrophysics Data System (ADS)

    Sahin, Sakir; Bao, Xueyang; Turkelli, Niyazi; Sandvol, Eric; Teoman, Ugur; Kahraman, Metin

    2013-03-01

    We estimate Lg wave attenuation using local and regional seismic phases in the Isparta Angle and the Anatolian Plateau (Turkey). The Isparta Angle (IA) is a tectonically active zone forming the boundary between the African Plate and the Anatolian Plateau, and is currently undergoing N-S extensional deformation. The Anatolian Plateau contains many intra-continental faults including the North Anatolian Fault Zone and the East Anatolian Fault Zone as well as the Menderes Massif. A large waveform data set was compiled from a variety of local and regional seismic networks including 121 digital seismic stations (broad-band and short period) between 1999 and 2008 spanning the IA, the Anatolian Plateau and Azerbaijan. The data set was used to determine the nature of Lg wave propagation and characterize the nature of seismic attenuation within the crust of these regions. Lg waveforms were used to calculate the frequency-dependent Lg- Q o and Lg- ? . A wide range of Lg- Q o values was obtained between ~52 ± 6 and 524 ± 227. Low Lg- Q o values (~90-155) are calculated towards the north of IA, Iskenderun Gulf and its vicinity, Bingöl-Karl?ova, Izmit and its vicinity. Lg- Q o values are especially low (<90) along the Menderes Massif and the Aksehir-Simav Fault Zones. This may be due to intrinsic attenuation of Lg associated with the partially molten crust and young volcanism. The high Lg- Q o values (~350) are probably caused by the crust not being subject to large amounts of extensional deformation like the Antalya Gulf and apparently being thick enough to support Lg propagation. Relatively higher values along the border of this subduction zone and plate boundary might be related to the Taurus Mountain belts and Bitlis-Zagros Suture Zone. The lateral frequency dependency Lg- ? is also consistent with high tectonic activity in this region.

  1. Measurement of Attenuation and Speed of Sound in Soils

    Microsoft Academic Search

    Michael L. Oelze; William D. O'Brien; Robert G. Darmody

    2002-01-01

    required. These basic properties of the soil can then be evaluated to assess the acoustic imaging tradeoffs for The potential application of this work is the detection and imaging detecting and characterizing buried artifacts. The acous- of buried objects using acoustic methodology. To image buried arti- facts, it is vital to know speed and attenuation of sound in the particular

  2. An in situ measurement of the radio-frequency attenuation in ice at Summit Station, Greenland

    E-print Network

    J. Avva; J. M. Kovac; C. Miki; D. Saltzberg; A. G. Vieregg

    2014-09-30

    We report an in situ measurement of the electric field attenuation length at radio frequencies for the bulk ice at Summit Station, Greenland, made by broadcasting radio-frequency signals vertically through the ice and measuring the relative power in the return ground bounce signal. We find the depth-averaged field attenuation length to be 947 +92/-85 meters at 75 MHz. While this measurement has clear radioglaciological applications, the radio clarity of the ice also has implications for the detection of ultra-high energy (UHE) astrophysical particles via their radio emission in dielectric media such as ice. The measured attenuation length at Summit Station is comparable to previously measured radio-frequency attenuation lengths at candidate particle detector sites around the world, and strengthens the case for Summit Station as the most promising northern site for UHE neutrino detection.

  3. Shallow seismic attenuation and shear-wave splitting in the short period range of Deception Island volcano (Antarctica)

    NASA Astrophysics Data System (ADS)

    Martínez-Arévalo, Carmen; Bianco, Francesca; Ibáñez, Jesús M.; Del Pezzo, Edoardo

    2003-11-01

    The occurrence of a seismic series in Deception Island volcano (Antarctica), composed of hundreds of local volcano-tectonic earthquakes, has permitted us to study the seismic attenuation of such a volcanic environment in the short-distance and high-frequency range. This study has been performed using P-waves, S-waves and coda-waves and applying different, frequency dependent and independent, techniques. The methods used for this analysis have been: spectral and broadening-of-the-pulse, for direct P- and S-waves, coda normalization for S-waves, and single back-scattering model for coda-waves. The results show that, in general, Q values are significantly smaller for the entire frequency range used (6-30 Hz) than those found in other volcanic and tectonic areas. The attenuation for P-waves is greater than for S-waves in the frequency independent methods, with a Q ?/ QP ratio that ranges between 1.9 and 3.2. Comparing the Q-factor obtained for S-waves we have observed clear differences as a function of the method used; the coda normalization method has supplied significantly higher Q values ( Q d) than the other two methods ( Q ?). We have interpreted this discrepancy as an effect of the methods: coda normalization and single back-scattering methods eliminate the contribution of the near-surface attenuation in their Q values. Comparing both Q ? and Q d we have estimated the near-surface attenuation under the recording site, named Q ?. On the other hand, we have observed that Q d has anomalous frequency dependence, with a minimum value at 21 Hz. This pattern is interpreted as an effect of strong scattering of the seismic waves in the source area of the earthquakes. Q c values depend clearly with frequency and lapse time and the lapse time dependence could be interpreted as a depth dependence of the seismic attenuation in Deception Island volcano, Antarctica. The obtained Q values have allowed us to separate the contribution of intrinsic and scattering attenuation, deriving that the scattering attenuation is predominant over the intrinsic effects. Finally, in order to investigate how the heterogeneous medium of the volcanic island could produce other effects, we have checked whether it produces polarization of the shear-waves. The preliminary results of the polarization direction indicate a main E-W strain direction. All these evidences reveal the strongly heterogeneous structure of Deception Island volcano.

  4. A simple model of ultrasound propagation in a cavitating liquid. Part I: Theory, nonlinear attenuation and traveling wave generation.

    PubMed

    Louisnard, O

    2012-01-01

    The bubbles involved in sonochemistry and other applications of cavitation oscillate inertially. A correct estimation of the wave attenuation in such bubbly media requires a realistic estimation of the power dissipated by the oscillation of each bubble, by thermal diffusion in the gas and viscous friction in the liquid. Both quantities and calculated numerically for a single inertial bubble driven at 20 kHz, and are found to be several orders of magnitude larger than the linear prediction. Viscous dissipation is found to be the predominant cause of energy loss for bubbles small enough. Then, the classical nonlinear Caflish equations describing the propagation of acoustic waves in a bubbly liquid are recast and simplified conveniently. The main harmonic part of the sound field is found to fulfill a nonlinear Helmholtz equation, where the imaginary part of the squared wave number is directly correlated with the energy lost by a single bubble. For low acoustic driving, linear theory is recovered, but for larger drivings, namely above the Blake threshold, the attenuation coefficient is found to be more than 3 orders of magnitude larger then the linear prediction. A huge attenuation of the wave is thus expected in regions where inertial bubbles are present, which is confirmed by numerical simulations of the nonlinear Helmholtz equation in a 1D standing wave configuration. The expected strong attenuation is not only observed but furthermore, the examination of the phase between the pressure field and its gradient clearly demonstrates that a traveling wave appears in the medium. PMID:21764348

  5. Acoustic shear wave displacement measurement using ultrasound

    Microsoft Academic Search

    Vinayak Dutt; Randall R. Kinnick; James F. Greenleaf

    1996-01-01

    Echo ultrasound can be used to detect and measure acoustic shear waves. Earlier it has been shown that a phase contrast based magnetic resonance imaging technique can be used for cyclic shear wave displacement measurement. Echo ultrasound presents an alternate method for imaging of such shear waves. The ultrasound based method uses the phase of quadrature echo signals to estimate

  6. Characterization of plastically deformed steel utilizing ultrasonic velocity and attenuation measurements

    Microsoft Academic Search

    P. D. Panetta; G. A. Alers

    2001-01-01

    There is a desire to detect plastically deformed regions in structures to monitor their integrity. The ultimate goal of this work is to develop an ultrasonic technique that can serve as a tool to detect and characterize plastically deformed regions in large structures. It is well known that the velocity and attenuation coefficient of propagating ultrasonic waves are sensitive to

  7. Effective x-ray attenuation measurements with full field digital mammography

    SciTech Connect

    Heine, John J.; Behera, Madhusmita [The H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, Florida 33612-4799 (United States)

    2006-11-15

    This work shows that effective x-ray attenuation coefficients may be estimated by applying Beer's Law to phantom image data acquired with the General Electric Senographe 2000D full field digital mammography system. Theoretical developments are provided indicating that an approximate form of the Beer's relation holds for polychromatic x-ray beams. The theoretical values were compared with experimentally determined measured values, which were estimated at various detector locations. The measured effective attenuation coefficients are in agreement with those estimated with theoretical developments and numerical integration. The work shows that the measured quantities show little spatial variation. The main ideas are demonstrated with polymethylmethacrylate and breast tissue equivalent phantom imaging experiments. The work suggests that the effective attenuation coefficients may be used as known values for radiometric standardization applications that compensate for the image acquisition influences. The work indicates that it is possible to make quantitative attenuation coefficient measurements from a system designed for clinical purposes.

  8. Ultrasonic attenuation in pearlitic steel.

    PubMed

    Du, Hualong; Turner, Joseph A

    2014-03-01

    Expressions for the attenuation coefficients of longitudinal and transverse ultrasonic waves are developed for steel with pearlitic microstructure. This type of lamellar duplex microstructure influences attenuation because of the lamellar spacing. In addition, longitudinal attenuation measurements were conducted using an unfocused transducer with 10 MHz central frequency on the cross section of a quenched railroad wheel sample. The dependence of longitudinal attenuation on the pearlite microstructure is observed from the changes of longitudinal attenuation from the quenched tread surface to deeper locations. The results show that the attenuation value is lowest and relatively constant within the quench depth, then increases linearly. The experimental results demonstrate a reasonable agreement with results from the theoretical model. Ultrasonic attenuation provides an important non-destructive method to evaluate duplex microstructure within grains which can be implemented for quality control in conjunction with other manufacturing processes. PMID:24268679

  9. Computer signal processing for ultrasonic attenuation and velocity measurements for material property characterizations

    NASA Technical Reports Server (NTRS)

    Vary, A.

    1979-01-01

    Instrumentation and computer programming concepts that were developed for ultrasonic materials characterization are described. Methods that facilitate velocity and attenuation measurements are outlined. The apparatus described is based on a broadband, buffered contact probe using a pulse-echo approach for simultaneously measuring velocity and attenuation. Instrumentation, specimen condition, and signal acquisition and acceptance criteria are discussed. Typical results with some representative materials are presented.

  10. Computer signal processing for ultrasonic attenuation and velocity measurements for material property characterizations

    NASA Technical Reports Server (NTRS)

    Vary, A.

    1979-01-01

    This report deals with instrumentation and computer programming concepts that have been developed for ultrasonic materials characterization. Methods that facilitate velocity and attenuation measurements are described. The apparatus described is based on a broadband, buffered contact probe using a pulse-echo approach for simultaneously measuring velocity and attenuation. Instrumentation, specimen condition, and signal acquisition and acceptance criteria are discussed. Typical results with some representative materials are presented.

  11. Measurement of photon attenuation from different cardiac chambers

    SciTech Connect

    Keller, A.M.; Simon, T.R.; Malloy, C.R.; Dehmer, G.J.; Smitherman, T.C.

    1985-05-01

    Accounting for the attenuation (AT) of photons within cardiac chambers is crucial to accurate non-geometric volume determinations from gated blood pool scintigraphy. Previous techniques to determine AT for each patient have assumed an attenuation factor of 0.15/cm for Tc-99m, the value of water. To verify this, the authors determined the AT at various tissue distances (TD) in vivo. As a point source they used the balloon of a 5 French Swan-Ganz catheter which could reproducibly be filled with a constant amount of Tc-99m and could be placed within the left or right cardiac chambers. The exact location of the balloon, once inflated, and the TD from the balloon to the collimator of a small field-of-view Anger camera was determined using biplane orthogonal fluoroscopy. AT was determined by counting the inflated Tc-99m filled balloon in air and dividing that value by the counts of the same balloon within the heart. The authors positioned the balloon in the apex of the right and left ventricle, the ascending aorta and at the junction of the right atrium and inferior vena cava to give a total of 36 simultaneous observations of AT and TD. For our data the slope of the regression of the natural log of AT versus TD, when forced through zero, was 0.102, the calculated attenuation factor. The authors conclude that the attenuation factor that should be used for determining cardiac volumes with gated blood pool scans is 0.102/cm, not the value for water.

  12. Dependence of CT attenuation values on scanner type using in vivo measurements

    NASA Astrophysics Data System (ADS)

    Prasad, Mithun; Meza, Alicia; Kim, Hyun J.; Brown, Matthew S.; Abtin, Fereidoun; Goldin, Jonathan G.; McNitt-Gray, Michael F.

    2008-03-01

    One of the key measures of response to treatment for patients in multicenter clinical trials is the lung density measured in Hounsfield Units (HU) from Computer Tomography (CT) scans. The purpose of this work is to determine the dependence of CT attenuation values on scanner type by using in vivo measurements made from homogeneous anatomic areas. In vivo measurements were made in areas within the trachea, aorta, fat and muscle regions of CT scans obtained from subjects scanned as part of a multicenter treatment trial. Scans were selected so that exams from all four major manufacturers were included in the study. For each anatomic region of interest, the mean and standard deviation values were computed to investigate attenuation dependence on scanners. For example, trachea mean (standard deviation) measurements for exams from GE, Siemens, Philips and Toshiba scanners were -986 HU(+/-15), - 993 HU(+/-9), -988HU(+/-8), -1046(+/-10) respectively. Inter-scanner variability was observed for each scanner showing significant differences (all p-values <0.005). Previous work in examining attenuation dependence on scanners has been performed using anthropomorphic phantoms. The novelty of this work is the use of in vivo measurements from homogeneous regions in order to examine scanner effects on CT attenuation values. Our results show that CT attenuation values for the anatomic regions vary between scanners and hence, dependence of CT attenuation values on scanners is observed.

  13. Intrinsic and attenuative dispersion characteristics of direct P-waves in and near the source area of the 1999 M W 7.6 Chi-Chi, Taiwan, earth- quake before and after the mainshock

    Microsoft Academic Search

    Xiqiang Liu; Chauhuei Chen; Yanwen Zhou; Junhao Qu

    2009-01-01

    Based on the measurement of the arrival time of maxima magnitude from band-pass filtering signals which were determined using\\u000a a new Morlet wavelet multiple-filter method, we develop a method for measuring intrinsic and attenuative dispersion of the\\u000a first cycle direct P-wave. We determine relative group delays of spectral components of direct P-waves for 984 ray paths from\\u000a SML and ALS

  14. Full-scale measurements of wave load and wave kinematics

    SciTech Connect

    Nielsen, K.G.; Bryndum, M.B. [Danish Hydraulic Inst., Hoersholm (Denmark); Dal, E.G.; Pedersen, B. [LICengineering A/S, Hellerup (Denmark); Andreasen, K.K. [Maersk Olie og Gas AS, Esbjerg (Denmark)

    1995-12-31

    A system for full-scale measurements of wave kinematics and wave loading was installed fin the late summer of 1994 at the Tyra East platform, operated by Maersk Olie og Gas AS in the Danish North Sea. Measurements commenced in october 1994 and are planned to continue throughout the winter of 1994/95. The measurement system consists of two parts: a 57 m long wire/cable (called the Load and Response Measuring System, LMS) which is capable of measuring hydrodynamic loads and structural response, and a subsurface acoustic system measuring the wave kinematics and the surface elevation (called the Wave Kinematics Measurement System, WMS), utilizing the incoherent Doppler technique. From the results of the LMS the action of vortex shedding will be detected and analyzed and the wave loads will be determined. From the results of the WMS the kinematics in the wave zone will be determined. In combination the results of both systems may be used in the validation of wave load models. In continuation of the present project, it is the intention that the data from the full-scale measurements will be compared and analyzed for a comparison with existing theory and calculation models. Those results will be presented at a later stage.

  15. Microwave and Millimeter-Wave Attenuation in Sand and Dust Storms

    Microsoft Academic Search

    Xiao-Ying Dong; Hsing-Yi Chen; Dong-Hui Guo

    2011-01-01

    The attenuation and phase delay due to sand and dust storms are obtained by using the effective material property tech- nique and general formulation of the complex propagation factor. The validity of attenuation is verified by Ghobrial et al.'s formula. Attenuations obtained for various frequencies are shown in this letter. It is found that the attenuation decreases sharply as the

  16. Differential shear-wave attenuation (deltat) across the East Pacific Rise

    SciTech Connect

    Schlue, J.W.

    1981-08-01

    SS phases from earthquakes on fracture zones near the Easter Island Cordillera and the West Chile Rise which are recorded in the United States have reflection points on either side of the East Pacific Rise (EPR) near the equator. The east-west records from seven WWSSN stations of seven events in this region were used to obtain spectral amplitudes of horizontally polarized S and SS waves. SS-to-S amplitude ratios were formed, and differential attenuation (deltat) computed within the frequency band 0.01 to 0.11 Hz. The values of deltat vary between -0.1 sec and +35.8 sec for the 23 station-event paris used. However, the change in deltat with distance from the axis of the EPR does not reflect the smooth variation expected using a model of a simple cooling slab.

  17. VHF/UHF wave attenuation in a city with regularly spaced buildings

    NASA Astrophysics Data System (ADS)

    Blaunstein, N.; Levin, M.

    1996-03-01

    In this work a theoretical and experimental investigation analyzing VHF/UHF radio wave propagation in a suburban environment with a grid-type street plan is presented for the purpose of personal communication services prediction. A waveguide with randomly distributed gaps (slits) between the sides of buildings is considered as a model of straight streets with two- and three-story buildings. The average field intensity and path loss at the street level, taking into account the reflection from the ground, multireflection, and diffraction from the walls and building edges, are investigated in line-of-sight (LOS) conditions using a new three-dimensional multislit waveguide model. This model gives good agreement with the two-rays model and with an experimentally found law of field intensity attenuation at the street level with high and low building density up to 1-2 km from the source.

  18. Attenuation of seismic waves and the universal rheological model of the Earth's mantle

    NASA Astrophysics Data System (ADS)

    Birger, B. I.

    2007-08-01

    Analysis of results of laboratory studies on creep of mantle rocks, data on seismic wave attenuation in the mantle, and rheological micromechanisms shows that the universal, i.e., relevant to all time scales, rheological model of the mantle can be represented as four rheological elements connected in series. These elements account for elasticity, diffusion rheology, high temperature dislocation rheology, and low temperature dislocation rheology. The diffusion rheology element is described in terms of a Newtonian viscous fluid. The high temperature dislocation rheology element is described by the rheological model previously proposed by the author. This model is a combination of a power-law non-Newtonian fluid model for stationary flows and the linear hereditary Andrade model for flows associated with small strains. The low temperature dislocation rheology element is described by the linear hereditary Lomnitz model.

  19. In situ acoustic and laboratory ultrasonic sound speed and attenuation measured in heterogeneous soft seabed sediments: Eel River shelf, California

    USGS Publications Warehouse

    Gorgas, T.J.; Wilkens, R.H.; Fu, S.S.; Neil, Frazer L.; Richardson, M.D.; Briggs, K.B.; Lee, H.

    2002-01-01

    We compared in situ and laboratory velocity and attenuation values measured in seafloor sediments from the shallow water delta of the Eel River, California. This region receives a substantial volume of fluvial sediment that is discharged annually onto the shelf. Additionally, a high input of fluvial sediments during storms generates flood deposits that are characterized by thin beds of variable grain-sizes between the 40- and 90-m isobaths. The main objectives of this study were (1) to investigate signatures of seafloor processes on geoacoustic and physical properties, and (2) to evaluate differences between geoacoustic parameters measured in situ at acoustic (7.5 kHz) and in the laboratory at ultrasonic (400 kHz) frequencies. The in situ acoustic measurements were conducted between 60 and 100 m of water depth. Wet-bulk density and porosity profiles were obtained to 1.15 m below seafloor (m bsf) using gravity cores of the mostly cohesive fine-grained sediments across- and along-shelf. Physical and geoacoustic properties from six selected sites obtained on the Eel margin revealed the following. (1) Sound speed and wet-bulk density strongly correlated in most cases. (2) Sediment compaction with depth generally led to increased sound speed and density, while porosity and in situ attenuation values decreased. (3) Sound speed was higher in coarser- than in finer-grained sediments, on a maximum average by 80 m s-1. (4) In coarse-grained sediments sound speed was higher in the laboratory (1560 m s-1) than in situ (1520 m s-1). In contrast, average ultrasonic and in situ sound speed in fine-grained sediments showed only little differences (both approximately 1480 m s-1). (5) Greater attenuation was commonly measured in the laboratory (0.4 and 0.8 dB m-1 kHz-1) than in situ (0.02 and 0.65 dB m-1 kHz-1), and remained almost constant below 0.4 m bsf. We attributed discrepancies between laboratory ultrasonic and in situ acoustic measurements to a frequency dependence of velocity and attenuation. In addition, laboratory attenuation was most likely enhanced due to scattering of sound waves at heterogeneities that were on the scale of ultrasonic wavelengths. In contrast, high in situ attenuation values were linked to stratigraphic scattering at thin-bed layers that form along with flood deposits. ?? 2002 Published by Elsevier Science B.V.

  20. CTS attenuation and cross polarization measurements at 11.7 GHz

    NASA Technical Reports Server (NTRS)

    Vogel, W. J.

    1979-01-01

    Attenuation and cross-polarization isolation at 11.7 GHz, measured at Austin, Texas by receiving the circularly polarized emissions from the CTS satellite are presented. A 12 month summary for Feb 78 to Jan 79 is presented. For .016 percent of the time the attenuation was greater than 10 dB, the isolation was less than 21 dB and the rainrate exceeded 55 mm/hr. Ice depolarization was observed frequently.

  1. Attenuation corrections for in-cylinder NO LIF measurements in a heavy-duty Diesel engine

    Microsoft Academic Search

    K. Verbiezen; R. J. H. Klein-Douwel; A. P. van Vliet; A. J. Donkerbroek; W. L. Meerts; N. J. Dam; J. J. ter Meulen

    2006-01-01

    Quantification of the nitric oxide (NO) concentration inside the cylinder of a Diesel engine by means of laser-induced fluorescence\\u000a (LIF) measurements requires, amongst others, knowledge of the attenuation of the ultraviolet radiation involved. We present\\u000a a number of laser diagnostic techniques to assess this attenuation, enabling a correction for laser intensity and detection\\u000a efficiency of the raw NO LIF data.

  2. A Simultaneous Multi-phase Approach to Determine P-wave and S-wave Attenuation of the Crust and Upper Mantle

    SciTech Connect

    Pasyanos, M E; Walter, W R; Matzel, E M

    2009-02-26

    We have generalized the methodology of our regional amplitude tomography from the Lg phase to the four primary regional phases (Pn, Pg, Sn, Lg). Differences in the geometrical spreading, source term, site term, and travel paths are accounted for, while event source parameters such as seismic moment are consistent among phases. In the process, we have developed the first regional attenuation model that uses the amplitudes of four regional phases to determine a comprehensive P-wave and S-wave attenuation model of the crust and upper mantle. When applied to an area encompassing the Middle East, eastern Europe, western Asia, south Asia, and northeast Africa for the 1-2 Hz passband, we find large differences in the attenuation of the lithosphere across the region. The tectonic Tethys collision zone has high attenuation, while stable outlying regions have low attenuation. While crust and mantle Q variations are often consistent, we do find several notable areas where they differ considerably, but are appropriate given the region's tectonic history. Lastly, the relative values of Qp and Qs indicate that scattering Q is likely the dominant source of attenuation in the crust at these frequencies.

  3. Determination of Rain Rate from a Spaceborne Radar Using Measurements of Total Attenuation

    Microsoft Academic Search

    Robert Meneghini; Jerome Eckerman; David Atlas

    1983-01-01

    Several experimental and theoretical studies have shown that path-integrated rain rates can be determined by means of a direct measurement of attenuation. For ground-based radars, this is done by measuring the backscattering cross section of a fixed target in the presence and absence of rain along the radar beam. A ratio of the two measurements yields a factor proportional to

  4. Attenuation of standing waves in a large water tank using arrays of large tethered encapsulated bubbles.

    PubMed

    Lee, Kevin M; Wilson, Preston S; Wochner, Mark S

    2014-04-01

    The use of bubble resonance effects to attenuate low-frequency underwater sound was investigated experimentally in a large water tank. A compact electromechanical sound source was used to excite standing wave fields at frequencies ranging between 50 and 200 Hz in the tank. The source was then surrounded by a stationary array of tethered encapsulated air bubbles, and reduction in standing wave amplitude by as much as 26?dB was observed. The bubbles consisted of either thin-shelled latex balloons with approximately 5?cm radii or thicker-shelled vinyl boat fenders with 6.9?cm radii. The effects of changing the material and thickness of the bubble shells were found to be in qualitative agreement with predictions from Church's model for sound propagation in a liquid containing encapsulated bubbles [J. Acoust. Soc. Am. 97, 1510-1521 (1995)]. Although demonstrated here for low frequency noise abatement within a tank, which is useful for quieting acoustic test facilities and large tanks used for marine life husbandry, the eventual aim of this work is to use stationary arrays of large tethered encapsulated bubbles to abate low frequency underwater noise from anthropogenic sources in the marine environment. PMID:25234970

  5. Measurement of lower-hybrid-driven current profile by Abel inversion of electron-cyclotron wave transmission spectra

    SciTech Connect

    Fidone, I.; Giruzzi, G. (Association Euratom-CEA Sur la Fusion, Departement de Recherches sur la Fusion Controlee, Centre d'Etudes Nucleaires de Cadarache, 13108 Saint-Paul-lez-Durance, Cedex (France)); Caron, X.; Meyer, R.L. (Laboratoire de Physique des Milieux Ionises, U. A. CNRS 835, Universite de Nancy I, B. P. 239, 54506 Vandoeuvre-les-Nancy (France))

    1991-10-01

    A method for measuring the radial profile of the lower-hybrid-driven current in a low-density tokamak plasma using electron-cyclotron wave attenuation is discussed. This diagnostic scheme is reminiscent of the transmission interferometry approach, commonly used in tokamaks to measure the plasma density, but now the wave amplitude instead of the phase is measured. Wave attenuation of the ordinary mode at {omega}{sub {ital p}} {much lt} {omega} {lt} {omega}{sub {ital c}} along vertical chords is measured; at these frequencies, the waves are absorbed by the superthermal tail sustained by lower-hybrid waves and the local wave absorption coefficient is proportional to the noninductive current density. The radial profile of this current is obtained from Abel inversion. An application to the Tore Supra tokamak is presented.

  6. Wave-front estimation from wave-front slope measurements

    Microsoft Academic Search

    W. H. Southwell

    1980-01-01

    The problem of wave-front estimation from wave-front slope measurements has been examined from a least-squares curve fitting model point of view. It is shown that the slope measurement sampling geometry influences the model selection for the phase estimation. Successive over-relax- ation (SOR) is employed to numerically solve the exact zonal phase estimation problem. A new zonal phase gradient model is

  7. Magellan radio occultation measurements of atmospheric waves on Venus

    NASA Technical Reports Server (NTRS)

    Hinson, David P.; Jenkins, J. M.

    1995-01-01

    Radio occultation experiments were conducted at Venus on three consecutive orbits of the Magellan spacecraft in October 1991. Each occultation occurred over the same topography (67 deg N, 127 deg E) and at the same local time (22 hr 5 min), but the data are sensitive to zonal variations because the atmosphere rotates significantly during one orbit. Through comparisons between observations and predictions of standard wave theory, we have demonstrated that small-scale oscillations in retrieved temperature profiles as well as scintillations in received signal intensity are caused by a spectrum of vertically propagating internal gravity waves. There is a strong similarity between the intensity scintillations observed here and previous measurements, which pertain to a wide range of locations and experiment dates. This implies that the same basic phenomenon underlies all the observations and hence that gravity waves are a persistent, global feature of Venus' atmosphere. We obtained a fairly complete characterization of a gravity wave that appears above the middle cloud in temperature measurements on all three orbits. The amplitude and vertical wavelength are about 4 K and 2.5 km respectively, at 65 km. A model for radiative damping implies that the wave intrinsic frequency is approximately 2 x 10(exp 4) rad/sec, the corresponding ratio between horizontal and vertical wavelengths is approximately 100. The wave is nearly stationary relative to the surface or the Sun. Radiative attenuation limits the wave amplitude at altitudes above approximately 65 km, leading to wave drag on the mean zonal winds of about +0.4 m/sec per day (eastward). The sign, magnitude, and location of this forcing suggest a possible role in explaining the decrease with height in the zonal wind speed that is believed to occur above the cloud tops. Temperature oscillations with larger vertical wavelengths (5-10 km) were also observed on all three orbits, but we are able unable to interpret these unambiguously.

  8. Temperature measurements of the low-attenuation radiographic ice ball during CT-guided renal cryoablation.

    PubMed

    Permpongkosol, Sompol; Link, Richard E; Kavoussi, Louis R; Solomon, Stephen B

    2008-01-01

    During renal cryoablation a low-attenuation area on CT develops around the cryoprobe. Knowledge of the temperature of the growing low-attenuation area can guide therapy and ensure lethal temperatures. Herein, we report thermocouple results and correlating CT images during the development of the low-attenuation "radiographic ice ball." Five patients who underwent percutaneous CT-guided renal cryoablation were identified who had thermocouples inserted and serial intraprocedural CT images that included images with thermocouple measurements of 0 degrees and sub-0 degrees C. Thermocouples had been percutaneously placed just beyond the edge of the tumors either to ensure adequate cooling or to ensure safety to adjacent critical structures. Renal cryotherapy under CT guidance produced a growing low-attenuation area corresponding to the radiographic ice ball. When the thermocouple measured 0 degrees C, CT images showed the thermocouple tip at the edge of the low-attenuation ice ball. At lower temperatures the tip was within the low-attenuation ice ball. We conclude that knowledge of the temperature at the ice ball edge during cryoablation can be used to predict the extent of tissue necrosis and thus provide an estimate of cryotherapy effectiveness during the procedure. Further work is necessary to establish a firm relationship between the thermal conditions and the zone of damage. PMID:17987248

  9. Methods for intercomparison of wave measurements

    Microsoft Academic Search

    Harald E. Krogstad; Judith Wolf; Stephen P. Thompson; Lucy R. Wyatt

    1999-01-01

    The paper reviews methods for quality assessment and intercomparison of ocean wave data. The sampling variability for conventional time series recordings is summarized and compared to less common area measuring measurements. The sampling variability affects the scatter seen in simultaneous observations, and variability in excess of the sampling variability signifies real differences between the instruments. Various means of intercomparing wave

  10. Toward global measurements of ocean wave spectra

    Microsoft Academic Search

    F. Jackson; W. Walton; P. Baker

    1982-01-01

    The development of a microwave radar technique for global, satellite measurement of ocean wave directional spectra has been a NASA goal for some years now. Our work at NASA Goddard, both experimental and theoretical, leads us to believe that we have found a simple, accurate, and economical solution to the global waves measurement problem. With some relatively minor modifications, these

  11. Measurement of the seismic attenuation performance of the VIRGO Superattenuator

    Microsoft Academic Search

    S. Braccini; L. Barsotti; C. Bradaschia; G. Cella; A. Di Virgilio; I. Ferrante; F. Fidecaro; I. Fiori; F. Frasconi; A. Gennai; A. Giazotto; F. Paoletti; R. Passaquieti; D. Passuello; R. Poggiani; E. Campagna; G. Guidi; G. Losurdo; F. Martelli; M. Mazzoni; B. Perniola; F. Piergiovanni; R. Stanga; F. Vetrano; A. Viceré; L. Brocco; S. Frasca; E. Majorana; A. Pai; C. Palomba; P. Puppo; P. Rapagnani; F. Ricci; G. Ballardin; R. Barillé; R. Cavalieri; E. Cuoco; V. Dattilo; D. Enard; R. Flaminio; A. Freise; S. Hebri; L. Holloway; P. La Penna; M. Loupias; J. Marque; C. Moins; A. Pasqualetti; P. Ruggi; R. Taddei; Z. Zhang; F. Acernese; S. Avino; F. Barone; E. Calloni; R. De Rosa; L. Di Fiore; A. Eleuteri; L. Giordano; L. Milano; S. Pardi; K. Qipiani; I. Ricciardi; G. Russo; S. Solimeno; D. Babusci; G. Giordano; P. Amico; L. Bosi; L. Gammaitoni; F. Marchesoni; M. Punturo; F. Travasso; H. Vocca; C. Boccara; J. Moreau; V. Loriette; V. Reita; J. M. Mackowski; N. Morgado; L. Pinard; A. Remillieux; M. Barsuglia; M. A. Bizouard; V. Brisson; F. Cavalier; A. C. Clapson; M. Davier; P. Hello; S. Krecklbergh; F. Beauville; D. Buskulic; R. Gouaty; D. Grosjean; F. Marion; A. Masserot; B. Mours; E. Tournefier; D. Tombolato; D. Verkindt; M. Yvert; S. Aoudia; F. Bondu; A. Brillet; E. Chassande-Mottin; F. Cleva; J. P. Coulon; B. Dujardin; J. D. Fournier; H. Heitmann; C. N. Man; A. Spallicci; J. Y. Vinet

    2005-01-01

    The gravitational wave detector VIRGO aims at extending the detection band down to a few Hertz by isolating the mirrors of the interferometer from seismic noise. This result is achieved by hanging each mirror through an elastic suspension (Superattenuator), designed to filter mechanical vibrations in all the degrees of freedom. An experimental upper limit of the mirror residual seismic noise

  12. Vibration and wave propagation attenuation for metamaterials by periodic piezoelectric arrays with high-order resonant circuit shunts

    NASA Astrophysics Data System (ADS)

    Zhou, Wanlu; Wu, You; Zuo, Lei

    2015-06-01

    Beam or plate metamaterials with periodic piezoelectric arrays have attracted more and more attention in recent years for wave propagation attenuation and the corresponding vibration reduction. Conventional designs use resistive shunt (R-shunt) and resistor-inductor shunt (RL-shunt). An innovative metamaterial with a high-order resonant shunt circuit is proposed and investigated for vibration and wave propagation attenuation in this paper. The proposed high-order resonant shunt circuit can introduce two local resonances in series around the tuning frequency to broaden the attenuation bandwidth, or can create two separate resonances to achieve two separate bandgaps. Finite element modeling of the beam metamaterial with wave propagation and vibration in the transverse direction is established. Simulations have been conducted to compare the vibration attenuation performances among R-shunt, RL-shunt, and the proposed high-order shunt. An impedance-based method has been presented for the parameter design of electrical components in the proposed high-order shunt for bandgaps at two desired frequencies.

  13. Viscosity measurement based on shear-wave laser speckle contrast analysis

    NASA Astrophysics Data System (ADS)

    Cheng, Yi; Li, Sinan; Eckersley, Robert J.; Elson, Daniel S.; Tang, Meng-Xing

    2013-12-01

    Tissue viscosity is correlated with tissue pathological changes and provides information for tissue characterization. In this study, we report an optical method to track continuous shear-wave propagation at centimeter depths in an optically turbid medium. Shear-wave attenuation coefficients were measured at multiple frequencies using shear-wave laser speckle contrast analysis (SW-LASCA) to quantitatively estimate tissue viscosity using the Voigt model. Shear waves were generated within tissue-mimicking phantoms by an amplitude-modulated ultrasound (modulation frequency: 100 to 600 Hz) and tracked by time-resolved laser speckle contrast difference received on a charged-coupled device camera. Averaged contrast difference over a selected time window was related to shear-wave amplitude and used to calculate the shear-wave attenuation coefficient. Phantoms of varying viscosities (0.1 and 0.3 Pa s) were studied. Attenuation coefficients for different shear-wave frequencies (100 to 600 Hz) were calculated. Derived viscosity values had a maximum standard deviation of 9%, and these values were consistent with the independent measurements reported in a previous study using nonoptical methods.

  14. Measurements and Linear Wave Theory Based Simulations of Vegetated Wave Hydrodynamics for Practical Applications

    E-print Network

    Anderson, Mary Elizabeth

    2011-10-21

    ratio (Hs/h) may dominate over vegetation characteristics such as density or structure. For transects with the greatest proportion of Spartina anglica, when Hs/h exceeded 0.55, further increase in maximum observed wave attenuation ceased, suggesting...

  15. Quantum nondemolition measurements. [by gravitational wave antennas

    NASA Technical Reports Server (NTRS)

    Braginskii, V. B.; Vorontsov, Iu. I.; Thorne, K. S.

    1980-01-01

    The article describes new electronic techniques required for quantum nondemolition measurements and the theory underlying them. Consideration is given to resonant-bar gravitational-wave antennas. Position measurements are discussed along with energy measurements and back-action-evading measurements. Thermal noise in oscillators and amplifiers is outlined. Prospects for stroboscopic measurements are emphasized.

  16. On the excess attenuation of sound in the atmosphere

    NASA Technical Reports Server (NTRS)

    Deloach, R.

    1975-01-01

    The attenuation suffered by an acoustic plane wave propagating from an elevated source to the ground, in excess of absorption losses, was studied. Reported discrepancies between attenuation measurements made in the field and theories which only account for absorption losses are discussed. It was concluded that the scattering of sound by turbulence results in a nonnegligible contribution to the total attenuation.

  17. Analysis of phase noise effect on microwave attenuation precision measurement using a heterodyne receiver

    Microsoft Academic Search

    T. Y. Wu; S. W. Chua; Y. L. Lu

    2010-01-01

    The phase noise effect on microwave attenuation precision measurement using a lock-in amplifier (LIA) is studied. A frequency domain phase noise modeling is used to analyse the phase sensitive detection made by the LIA. The error bound for the magnitude and phase of LIA measurement has been established. The theoretical prediction of the maximum magnitude and phase fluctuation in LIA

  18. The role of the reflection coefficient in precision measurement of ultrasonic attenuation

    NASA Technical Reports Server (NTRS)

    Generazio, E. R.

    1984-01-01

    Ultrasonic attenuation measurements using contact, pulse-echo techniques are sensitive to surface roughness and couplant thickness variations. This can reduce considerable inaccuracies in the measurement of the attenuation coefficient for broadband pulses. Inaccuracies arise from variations in the reflection coefficient at the buffer-couplant-sample interface. The reflection coefficient is examined as a function of the surface roughness and corresponding couplant thickness variations. Interrelations with ultrasonic frequency are illustrated. Reliable attenuation measurements are obtained only when the frequency dependence of the reflection coefficient is incorporated in signal analysis. Data are given for nickel 200 samples and a silicon nitride ceramic bar having surface roughness variations in the 0.3 to 3.0 microns range for signal bandwidths in the 50 to 100 MHz range.

  19. Seismic Wave Amplification, Attenuation, and Scattering at the UZ-16 Borehole, Yucca Mountain, Nevada

    NASA Astrophysics Data System (ADS)

    Preston, L.; Smith, K.

    2006-12-01

    The UE#25 UZ-16 borehole array at Yucca Mountain, Nevada (designated site for the nation's high-level nuclear waste repository), provides a prime opportunity to investigate near surface effects on seismic waveforms as a function of depth. The borehole 3-component geophone array consists of 96 depth levels of 4.5 Hz sensors from about 30 m to 500 m depth below the surface. Currently we are recording at 18 approximately equally spaced depth levels and the array was recently augmented with three 3-component matching surface sensors (totaling 63 16-bit 200 sps data channels). The time stamped continuous digital data stream is telemetered in real-time to the Nevada Seismological Laboratory where it is visually inspected and event data is subset and integrated with regional network data when necessary; system check calibrations have been performed on all recorded sensors. Therefore, we have high resolution time-depth local and regional earthquake waveform histories from 500 m to the surface within the Yucca Mountain block. Due to the thick cover of Miocene volcanic tuffs at Yucca Mountain, the borehole does not penetrate into the underlying Paleozoic basement but samples tuff horizons of varying thicknesses and properties. Ground motion design criteria for the repository and surface facilities are based, in part, on characterizing the near surface velocities and the amplification, intrinsic attenuation, and scattering of seismic waves from local earthquakes. We present results from several investigations of local earthquake recordings including spectral ratios and attenuation as a function of depth and characterize scattering in the tuff layers. Preliminary results indicate differences in spectral ratios depending on component, with E-W components indicating higher ratios relative to N-S and Z components as compared to the bottom most geophone, most likely due to the structural fabric of Yucca Mountain. Also, most observed amplification from spectral ratios (from about 3 Hz to 15 Hz) appears to occur within the top 60 m of the borehole with the surface geophones demonstrating the largest amplifications, as expected. Preliminary results indicate coda energy amplification, as a function of depth, within the first 5 s after the primary S-wave arrival.

  20. Attenuation corrections for in-cylinder NO LIF measurements in a heavy-duty Diesel engine

    NASA Astrophysics Data System (ADS)

    Verbiezen, K.; Klein-Douwel, R. J. H.; van Vliet, A. P.; Donkerbroek, A. J.; Meerts, W. L.; Dam, N. J.; Ter Meulen, J. J.

    2006-04-01

    Quantification of the nitric oxide (NO) concentration inside the cylinder of a Diesel engine by means of laser-induced fluorescence (LIF) measurements requires, amongst others, knowledge of the attenuation of the ultraviolet radiation involved. We present a number of laser diagnostic techniques to assess this attenuation, enabling a correction for laser intensity and detection efficiency of the raw NO LIF data. Methods discussed include overall laser beam transmission, bidirectional laser scattering (bidirectional LIF), spectrally resolved fluorescence imaging, and Raman scattering by N2. A combination of techniques is necessary to obtain the complete attenuation of laser beam and NO fluorescence. The overall laser beam transmission measurements and bidirectional LIF measurements (the latter yielding spatially resolved transmission) provide evidence of a non-uniform attenuation distribution, with predominant attenuation within or near the piston bowl. Fluorescence imaging of multiple vibrational bands through a spectrograph is shown to be a powerful method for obtaining spatially resolved data on the transmission losses of fluorescence. Special attention is paid to the role of CO2 and O2 as UV light absorbers, and the consequences to different excitation-detection schemes for NO.

  1. Electric field analysis in the Earth considering attenuation of electromagnetic waves propagated in lossy media

    Microsoft Academic Search

    T. Maekawa; T. Shimada; S. Inoue; A. Jitsumori; N. Okumura; K. Akizuki

    1992-01-01

    It is pointed out that, in the field of oil well drilling, EM-MWD (electromagnetic measurement while drilling) offers many advantages. The EM-MWD system can transmit measured data from the well bottom to the surface at high speed using electromagnetic waves. Developing the EM-MWD technology requires analysis of the electric field around a drill string. A novel computer simulation method has

  2. Improvement of the seismic noise attenuation performance of the Monolithic Geometric Anti-Spring filters for gravitational wave interferometric detectors

    NASA Astrophysics Data System (ADS)

    Stochino, Alberto; DeSalvo, Riccardo; Huang, Yumei; Sannibale, Virginio

    2007-10-01

    The Monolithic Geometric Anti-Spring (GAS) filter is one of the most efficient vertical seismic isolation devices for Gravitational Wave (GW) interferometers. However, the attenuation of this filter was previously limited to around 60 dB due to the high frequency saturation associated with the filter's distributed mass—a problem typical of passive mechanical filters. We show that it is possible to circumvent this limit using a compensation wand based on the Center Of Percussion (COP) effect. When this device is mounted in parallel with the blade springs of a GAS filter, attenuation improves to 80 dB in the region above 10 Hz. Using this device it is therefore possible to design simpler attenuation chains consisting of fewer stages.

  3. Decoherence measure by gravitational wave interferometers

    E-print Network

    Yasushi Mino

    2008-08-14

    We consider the possibility to measure the quantum decoherence using gravitational wave interferometers. Gravitational wave interferometers create the superposition state of photons and measure the interference of the photon state. If the decoherence occurs, the interference of the photon state vanishes and it can be measured by the interferometers. As examples of decoherence mechanisms, we consider 1) decoherence by spontaneous localization, 2) gravitational decoherence and 3) decoherence by extra-dimensional gravity.

  4. Seabed Wave Boundary Layer Measurements and Analysis

    Microsoft Academic Search

    K. F. Lambrakos

    1982-01-01

    Velocity measurements made at two elevations off a rough sea floor in 18.3 m of water depth in the Strait of Juan de Fuca suggest the presence of a wave boundary layer. The wave velocities measured at 0.69 m off bottom are, overall, larger in magnitude and also shifted in time relative to the velocities measured at 1.85 m. These

  5. Effect of Viscous Cross Coupling between two Immiscible Fluids on Elastic Wave Propagation and Attenuation in Unsaturated Porous Media

    NASA Astrophysics Data System (ADS)

    Lo, WeiCheng; Lee, JheWei; Lee, ChengHaw

    2015-04-01

    A central issue in the theoretical treatment of a multiphase system is the proper mathematical description of momentum transfer across fluid-solid and fluid-fluid interfaces. Although recent studies have advanced our knowledge on modeling the coupling behavior between a porous framework and the fluids permeating it, the effect of viscous resistance caused by two-fluid flow on elastic wave behavior in unsaturated porous media still remains unaddressed. In the present study, we generalize the theory of dynamic poroelasticity to incorporate viscous cross coupling arising from the velocity difference between two adjacent fluids for examining the dynamic behavior of fluid flow in deformable porous media related to harmonic wave perturbation. The corresponding dispersion relations that characterize three compressional waves and one shear wave are precisely formulated, with the coefficients featuring all elasticity, inertial coupling, and viscous coupling parameters, for describing how wave number changes as excitation frequency is stipulated. To evaluate quantitatively this as-yet unknown effect, numerical simulations are implemented to solve the dispersion relations for Columbia fine sandy loam bearing an oil-water mixture with respect to three representative wave excitation frequencies. Our results show that the phase speed and attenuation coefficient of the third compressional wave which has the smallest speed is strongly sensitive to the presence of viscous cross coupling, as expected for this wave being attributed primarily to the out-of-phase motion of the two pore fluids. Viscous cross coupling also exerts an impact on the attenuation coefficient of the shear wave and the first compressional wave whose speed is greatest, which exhibits two opposite trends at different ranges of low and high water contents. A sensitivity analysis is further conducted to provide information on the importance of the coupling parameter, revealing that the effect becomes more significant as the coupling is stronger.

  6. Internal Wave Measurements From a Midwater Float

    Microsoft Academic Search

    James Lowell Cairns

    1975-01-01

    An instrument package has been developed that drifts along freely with the water while it repeatedly profiles ocean temperature. Profiling during drifting reduces the Doppler and line structure effects that usually contaminate internal wave measurements. Six days o1' exceptionally clean internal wave records were acquired 470 km offshore of San Diego, Calitbrnia, in June 1973 at a nominal depth of

  7. Plasma wave measurements with STEREO S/WAVES: Calibration, potential model, and preliminary results

    E-print Network

    California at Berkeley, University of

    Plasma wave measurements with STEREO S/WAVES: Calibration, potential model, and preliminary results] The S/WAVES experiments on the two STEREO spacecraft measure waves, both in situ plasma waves measurements of plasma density, sufficiently rapid to be on the time scale of Langmuir wave fluctuations

  8. Insights from ScS-S measurements on deep mantle attenuation

    NASA Astrophysics Data System (ADS)

    Durand, S.; Matas, J.; Ford, S.; Ricard, Y.; Romanowicz, B.; Montagner, J.-P.

    2013-07-01

    We apply a recently developed method based on the instantaneous frequency to analyze broadband seismic data recorded by the transportable USArray. We measure in the frequency band [0.018-0.2] Hz about 700 high-quality differential ScS-S anelastic delay times, ?tScS-S?, sampling the mantle below Central America and below Alaska that we compare to elastic delay times, ?t, obtained by cross-correlating the S and ScS signals. We confirm that the instantaneous frequency matching method is more robust than the classical spectral ratio method. By a series of careful analyses of the effects of signal-to-noise ratio, source mechanism characteristics and possible phase interferences on measurements of differential anelastic delay times, we demonstrate that in order to obtain accurate values of ?tScS-S* the seismic records must be rigorously selected. In spite of the limited number of data that satisfy our quality criteria, we recover, using an additional stacking procedure, a clear dependence of ?tScS-S? on the epicentral distance in the two regions. The absence of correlation between the obtained anelastic and elastic delay-times indicates a complex compositional-thermal origin of the attenuation structure, or effects of scattering by small scale structure, in accordance with possible presence of subducted material. The regional 1-D inversions of our measurements indicate a non-uniform lower mantle attenuation structure: a zone with high attenuation in the mid-lower mantle (Q??250) and a low attenuation layer at its base (Q??450). A comparison of our results with low-frequency normal-model Q models is consistent with frequency-dependent attenuation with Q???? and ?=0.1-0.2 (i.e. less attenuation at higher frequencies), although possible effects of lateral variations in Q in the deep mantle add some uncertainty to these values.

  9. Diffraction correction for precision surface acoustic wave velocity measurements

    E-print Network

    Nagy, Peter B.

    Diffraction correction for precision surface acoustic wave velocity measurements Alberto Ruiz M wave dispersion measurements can be used to nondestructively characterize shot-peened, laser shock dispersion measurements. A simple diffraction correction model was developed for surface waves

  10. CTS attenuation and cross polarization measurements at 11.7 GHz

    NASA Technical Reports Server (NTRS)

    Vogel, W. J.

    1978-01-01

    The results of data obtained at The University of Texas at Austin during a total of 551 days of righthand circularly polarized transmission at 11.7 GHz from the CTS satellite are presented. Measured were attenuation, cross-polarization and rain rate. Results indicate that ice depolarization can be of significant importance.

  11. Broadband optoacoustic measurements of ultrasound attenuation in severely plastically deformed nickel

    Microsoft Academic Search

    Victor V. Kozhushko; Günther Paltauf; Heinz Krenn; Stephan Scheriau; Reinhard Pippan

    2010-01-01

    Laser optoacoustics and immersion techniques allowed a broadband ultrasound spectroscopy which was used for measuring the attenuation of severely plastically deformed nickel. A disk shaped specimen of nickel of about 33 mm diameter and 2.5 mm thickness was prepared by the high pressure torsion method. The produced equivalent shear strain linearly increased from a minimum at the center up to

  12. Photogrammetric Measurements of CEV Airbag Landing Attenuation Systems

    NASA Technical Reports Server (NTRS)

    Barrows, Danny A.; Burner, Alpheus W.; Berry, Felecia C.; Dismond, Harriett R.; Cate, Kenneth H.

    2008-01-01

    High-speed photogrammetric measurements are being used to assess the impact dynamics of the Orion Crew Exploration Vehicle (CEV) for ground landing contingency upon return to earth. Test articles representative of the Orion capsule are dropped at the NASA Langley Landing and Impact Research (LandIR) Facility onto a sand/clay mixture representative of a dry lakebed from elevations as high as 62 feet (18.9 meters). Two different types of test articles have been evaluated: (1) half-scale metal shell models utilized to establish baseline impact dynamics and soil characterization, and (2) geometric full-scale drop models with shock-absorbing airbags which are being evaluated for their ability to cushion the impact of the Orion CEV with the earth s surface. This paper describes the application of the photogrammetric measurement technique and provides drop model trajectory and impact data that indicate the performance of the photogrammetric measurement system.

  13. A model for P-wave attenuation and dispersion in a porous medium permeated by aligned fractures

    NASA Astrophysics Data System (ADS)

    Brajanovski, Miroslav; Gurevich, Boris; Schoenberg, Michael

    2005-10-01

    Fractures in a porous rock can be modelled as very thin and highly porous layers in a porous background. First, a dispersion equation for a P wave propagating in periodically layered poroelastic medium is obtained using propagator matrix approach applied to Biot equations of poroelasticity with periodic coefficients. Then in the limit of low stiffness and thickness this dispersion equation yields an expression for the effective P-wave modulus of the fractured porous material. When both pores and fractures are dry, this material is equivalent to a transversely isotropic elastic porous material with linear-slip interfaces. When saturated with a liquid this material exhibits significant attenuation and velocity dispersion due to wave-induced fluid flow between pores and fractures. In the low-frequency limit the material properties are equal to those obtained by anisotropic Gassmann (or Brown-Korringa) theory applied to a porous material with linear-slip interfaces. At low frequencies inverse quality factor scales with the first power of frequency ?. At high frequencies the effective elastic properties are equal to those for isolated fluid-filled fractures in a solid (non-porous) background, and inverse quality factor scales with ?-1/2. The magnitude of both attenuation and dispersion strongly depends on both the degree of fracturing and background porosity of the medium. The characteristic frequency of the attenuation and dispersion depends on the background permeability, fluid viscosity, as well as fracture density and spacing.

  14. OSCR wave measurements-some preliminary results

    Microsoft Academic Search

    Lucy R. Wyatt; Louise J. Ledgard

    1996-01-01

    OSCR is an HF radar system that has been developed for high spatial resolution coastal surface current measurement. This paper describes preliminary results that demonstrate that wave measurement can be successfully obtained from suitably processed OSCR data. Comparisons with data from a WAVEC directional buoy are presented and show encouraging agreement. Some of the limitations to the measurement process are

  15. Investigation of the tone-burst tube for duct lining attenuation measurement

    NASA Technical Reports Server (NTRS)

    Soffel, A. R.; Morrow, P. F.

    1972-01-01

    The tone burst technique makes practical the laboratory evaluation of potential inlet and discharge duct treatments. Tone burst apparatus requires only simple machined parts and standard components. Small, simply made, lining samples are quickly and easily installed in the system. Two small electromagnetric loudspeaker drivers produce peak sound pressure level of over 166 db in the 3-square-inch sample duct. Air pump available in most laboratories can produce air flows of over plus and minus Mach 0.3 in the sample duct. The technique uses short shaped pulses of sound propagated down a progressive wave tube containing the sample duct. The peak pressure level output of the treated duct is compared with the peak pressure level output of a substituted reference duct. The difference between the levels is the attenuation or insertion loss of the treated duct. Evaluations of resonant absorber linings by the tone burst technique check attenuation values predicted by empirical formulas based on full scale ducts.

  16. Noncontact measurement of ultrasonic attenuation during rotating fatigue test of steel

    SciTech Connect

    Ogi, H.; Hirao, M.; Minoura, K. [Faculty of Engineering Science, Osaka University, Machikaneyama 1-3, Toyonaka, Osaka 560 (Japan)] [Faculty of Engineering Science, Osaka University, Machikaneyama 1-3, Toyonaka, Osaka 560 (Japan)

    1997-04-01

    Acoustic resonance technique has been applied to monitor the fatigue damage process of steel pipes exposed to rotating bending fatigue. The technique incorporates a superheterodyne spectrometer and an electromagnetic acoustic transducer (EMAT). The EMAT was newly developed for this purpose, and uses the magnetostrictive mechanism of ferromagnetic metals and excites and detects axial shear waves traveling around the sample pipe with axial polarization. Noncontact ultrasonic spectroscopy permits the accurate determination of the resonant frequency and the attenuation coefficient throughout the fatigue life. The attenuation coefficient shows a sharp peak around 80{percent}{endash}90{percent} of the life. The evolution is interpreted as reflecting dislocation multiplication, depinning, and formation of cell structures, which is supported by transmission electron microscopy observations. {copyright} {ital 1997 American Institute of Physics.}

  17. Ten-element photodetector for optical power and attenuation measurements

    SciTech Connect

    Kuebarsepp, Toomas; White, Malcolm

    2010-07-01

    The properties of what is, to the best of our knowledge, the first ten-element polarization-dependent transmission trap detector consisting of silicon photodiodes are described. The responsivity and the transmittance of the photodetector were measured at laser wavelengths of 476.2 and 647.1nm. In particular, the effect of the polarization state of the incident radiation on the transmittance was determined. Differences in transmittance of an order of magnitude were observed between s and p polarization. These values were compared with theoretical values calculated using the Fresnel reflection formulas. The difference between the calculated and measured values was less than {+-}3x10{sup -7}. The spatial nonuniformity of the response was measured to be less than {+-}3x10{sup -4}. The transmittance was measured to be spatially uniform across a 5mmx5mm area of the trap detector aperture to within {+-}1.5x10{sup -6} for s-polarized input and within {+-}1.5x10{sup -7} for p-polarized input.

  18. New method to measure the attenuation of hadrons in extensive air showers

    SciTech Connect

    Apel, W. D.; Badea, F.; Bekk, K.; Bozdog, H.; Daumiller, K.; Doll, P.; Engel, R.; Engler, J.; Finger, M.; Gils, H. J.; Haungs, A.; Heck, D.; Huege, T.; Isar, P. G.; Klages, H. O.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Nehls, S.; Oehlschlaeger, J. [Institut fuer Kernphysik, Forschungszentrum Karlsruhe, 76021 Karlsruhe (Germany)] (and others)

    2009-07-15

    Extensive air showers are generated through interactions of high-energy cosmic rays impinging the Earth's atmosphere. A new method is described to infer the attenuation of hadrons in air showers. The numbers of electrons and muons, registered with the scintillator array of the KASCADE experiment, are used to estimate the energy of the shower inducing primary particle. A large hadron calorimeter is used to measure the hadronic energy reaching observation level. The ratio of energy reaching ground level to the energy of the primary particle is used to derive an attenuation length of hadrons in air showers. In the energy range from 10{sup 6} to 3x10{sup 7} GeV the attenuation length obtained increases from 170 to 210 g/cm{sup 2}. The experimental results are compared to predictions of simulations based on contemporary high-energy interaction models.

  19. Wave-induced fluid flow in random porous media: Attenuation and ...

    E-print Network

    2005-04-20

    compressional wave P-wave which accounts for the effect of wave-induced flow. ...... gating in media with varying thermal conductivity is caused by conversion into a ... for many situations where wave field energy is dissipated. 2740. J. Acoust.

  20. The measurement of attenuation from vertical seismic profiles

    E-print Network

    Davis, Francis Erwin

    1983-01-01

    method for measuring attenuat'on from vertrcal seismic profiles was found to be dependent upon the ability to correct for interference and/or source changes, Also, at enuation values calculated via this method are extremely sensitive to window duration...) for the homogeneous Pierre shale. Several holes were drilled to various depths and geophones were clamped in to guarantee good coupling. Each geophone recorded the passage of seismic energy from the same shot, eliminating concern over source variability. Spectra...

  1. Wave Measurements Using GPS Velocity Signals

    PubMed Central

    Doong, Dong-Jiing; Lee, Beng-Chun; Kao, Chia Chuen

    2011-01-01

    This study presents the idea of using GPS-output velocity signals to obtain wave measurement data. The application of the transformation from a velocity spectrum to a displacement spectrum in conjunction with the directional wave spectral theory are the core concepts in this study. Laboratory experiments were conducted to verify the accuracy of the inversed displacement of the surface of the sea. A GPS device was installed on a moored accelerometer buoy to verify the GPS-derived wave parameters. It was determined that loss or drifting of the GPS signal, as well as energy spikes occurring in the low frequency band led to erroneous measurements. Through the application of moving average skill and a process of frequency cut-off to the GPS output velocity, correlations between GPS-derived, and accelerometer buoy-measured significant wave heights and periods were both improved to 0.95. The GPS-derived one-dimensional and directional wave spectra were in agreement with the measurements. Despite the direction verification showing a 10° bias, this exercise still provided useful information with sufficient accuracy for a number of specific purposes. The results presented in this study indicate that using GPS output velocity is a reasonable alternative for the measurement of ocean waves. PMID:22346618

  2. Attenuation measurements of passive linear and nonlinear hearing protectors for impulse noise

    Microsoft Academic Search

    William J. Murphy; Chucri A. Kardous

    2003-01-01

    As a part of a NIOSH Health Hazard Evaluation of law-enforcement personnel, the attenuation of several types of earplugs were measured in response to impulse noise produced by small-arms gunfire. The earplugs were primarily flanged premolded plugs produced by EAR\\/Aearo and Bilsom\\/Baccou-Dalloz. Measurements for the North Sonic Ear Valve, EAR Classic earplugs, and EAR Ultra 9000 passive nonlinear ear muff

  3. Superheterodyne Measurement of Microwave Attenuation at a 10kHz Intermediate Frequency

    Microsoft Academic Search

    Richard F. Clark

    1969-01-01

    The excellent relative frequency stability of the output of two microwave oscillators phase-locked to a common reference signal permits the use of an audio intermediate frequency in the superheterodyne measurement of microwave attenuation. The phase-lock feature also permits the measurement of microwave phase at the audio frequency. The choice of the audio instead of the more conventional 30-MHz intermediate frequency

  4. Geodynamic Environment by Satellite Geodesy, Seismic Attenuation and S-wave Splitting. Example from Vrancea Seismogenic Zone, SE Carpathians

    NASA Astrophysics Data System (ADS)

    Mocanu, Victor; Russo, Raymond; Ambrosius, Boudewijn

    2010-05-01

    In the Vrancea seismogenic zone (SE Carpathians), where very strong earthquakes (Mw > 7) are reported several times a century, the seismotectonics is very complex. It develops beneath the contact between the Moldavian East European Platform, the Scythian Platform, and the Moesian Platform, to the east and southeast, and terranes of the Transylvania Basin lying within the Carpathian arc. Several hypothesis have been considered by scientists in order to explain the clustered foci of crustal and intermediate events (as deep as 200 km). However, until now, there is no tectonic scenario which could explain all geological and geophysical observations. We try to integrate long-term permanent and campaign GPS outcomes with contributions from seismic attenuation and S-wave splitting results. GPS contributions mainly refer to determination of velocity vectors. 15 campaigns and seven permanent stations are being used in order to determine the detailed kinematics of an area characterized by very small velocities (1-2 mm/y), bringing the satellite technique to almost its limit. The results suggest a counterclockwise mantle flow around the Vrancea seismogenic zone, which is a high velocity body developed in an almost vertical position, developing deeper than 200 km. This results is also supported by seismic attenuation studies. We found that models like delamination and subduction could be supported by seismic attenuation studies in this zone. The delamination model implies strong upwelling and horizontal inflow of asthenosphere into the gap between the delaminating and remnant lithosphere. The other model implies downwelling and perhaps lateral-horizontal inflow along the slab detachment or tear. The models imply different distributions of density and rheological properties associated with the different lithosphere - asthenosphere structures. We use the ratio of spectral amplitudes of P and S waves from vertical and transverse seismograms to estimate the S to P ratio in the frequency domain, and then we calculate Qs, the relative shear wave attenuation via two complementary techniques: We find that stations located near and above the Vrancea zone and in the Transylvanian Basin, attenuation is high (low Q). Stations situated on the East European, Moesian, and Scythian Platforms are characterized by higher Qs (low attenuation). We interpret the high attenuation in the Vrancea and Transylvanian Basin is the result of shallow hot asthenosphere present in this area. Observations of source-side shear wave splitting clearly show that upper mantle anisotropy is strongly variable in the region of the tightly curved Carpathian Arc: shear waves taking off from Vrancea along paths that sample the East and Southern Carpathians have fast anisotropy axes parallel to these ranges, whereas those leaving the source region to traverse the upper mantle beneath the Transylvanian Basin (i.e., mantle wedge side) trend NE-SW. Shear waves sampling the East European and Scythian Platforms are separable into two groups, one characterized by fast shear trends to the NE-SW, and a second, deeper group, with trends to NW-SE; also, the majority of null splits occur along paths leaving Vrancea in these NE-E azimuths. Deeper fabric with E-W trend marking asthenospheric flow beneath the craton's base. This more complex anisotropy beneath the western edge of the East European Platform would account for both the variability of observed splitting of waves that sample this volume.

  5. Roadside tree attenuation measurements at UHF for land mobile satellite systems

    NASA Technical Reports Server (NTRS)

    Goldhirsh, Julius; Vogel, Wolfhard J.

    1987-01-01

    Tree attenuation results at 870 MHz are described for experiments conducted in October 1985 and March 1986 in Central Maryland. These experiments employed a helicopter as a source platform and a van with receiver and data acquisition instrumentation. Tree attenuation results were obtained for the cases in which the van was stationary and in motion. The experiments were performed for the purpose of providing the designers of planned land mobile satellite systems with important elements in the determination of link parameter requirements; namely, the expected fading statistics due to roadside trees for both mobile and stationary vehicles. Single tree attenuation results gave worst case median fades as high as 15 dB although roadside tree values were noted to produce fades in excess of 20 dB for small percentages of time. The cumulative fade distributions and their relative contributions as a function of path elevation angle, right side versus left side driving, and different road types are derived from the field measurements. Upon comparing the attenuations from bare deciduous trees (March 1986) with those due to trees in full foliage (October 1985), the increase in dB attenuations were, in general, less than 25 percent for the dynamic cases, and less than 40 percent for the worst case static configuration. This result demonstrates that the dominant fading is caused by the wooded tree branches as opposed to the leaves on these branches. The tail end of the observed fade distributions was observed to follow lognormal distributions with respect to dB attenuation.

  6. Concurrent measurements of the directional spectra of microseismic energy and surface gravity waves

    NASA Astrophysics Data System (ADS)

    Nye, T.; Yamamoto, T.

    1994-07-01

    This paper presents concurrent measurements of surface wave directional spectra and double-frequency, long-wave microseisms. Long-wave energy rapidly develops during periods of shifting winds which create bidirectional sea states. Theoretically, nonlinear sum interactions of opposing wavenumber vectors of approximately the same frequency create long-wave energy at twice the frequency, which is only slightly attenuated in shallow water. Bidirectional sea states have been found using a buried ocean bottom seismometer measuring system from which the long wave energy has been measured at double frequencies. This system was incorporated into the Office of Naval Research sponsored Sources of Ambient Microseismic Ocean Noise (SAMSON) experiment for 3 months off the Army Corps of Engineers' Field Research Facility near Duck, North Carolina in the fall of 1990. Four working sensors produced directional spectra results from nearly 22 gigabytes of recorded data, which was collected 2 km offshore of the FRF under 12-13 m of water and approximately 1 m of sediment. Because of the insignificant attenuation the measured energy levels of the double frequency microseisms at the seafloor are of the same order of magnitude as the single-frequency, surface wave energy induced seafloor motion. Various data sets were analyzed that confirmed Longuet-Higgins' theory, which proposes that the propagation direction of double-frequency microseisms occurs in the direction of the vector sum of the opposing single-frequency seas.

  7. An explicit formula for the coherent SH waves' attenuation coefficient in random porous materials with low porosities.

    PubMed

    Zhang, Jun; Ye, Wenjing

    2015-09-01

    In this paper, the attenuation coefficient of coherent SH waves in random porous material with uniformly randomly distributed elliptical cavities of different aspect ratios is studied. Based on an analysis of the mechanism for attenuation, a simple macro model for the attenuation coefficient is proposed. The macro model says that the attenuation coefficient can be expressed as a function of the mean scattering cross section and the number density of cavities at low porosities. Then, large-scale numerical simulations using the pre-corrected Fast Fourier Transform (pFFT) algorithm accelerated Boundary Element Method (BEM) are conducted to specify this macro model. Finally, this macro model is compared with four theoretical models derived for composite/porous materials with circular inclusions at the porosity p=3.17% and 5%. Results show this macro model agree well with three of them. Compared to the existing theoretical models, the form of this macro model is simple and has a clear physical meaning. In addition, it is applicable to cases with relatively complex cavities. PMID:25983311

  8. Surface wave attenuation from ambient noise correlation: methods and applications to 1D and 2D arrays

    NASA Astrophysics Data System (ADS)

    Li, J.; Zhou, L.; Song, X.; Weaver, R. L.

    2014-12-01

    It can be shown that the field-field correlation function of an imperfectly diffuse wave field is equal to the (time derivative of) Green's function times the specific intensity of the noise (Weaver, 2013). The theoretical understanding permits the interpretation of correlation amplitudes and promises to facilitate the retrieval of attenuation, site amplification factors, and scattering strengths from the noise correlation. In order to develop methods for extracting attenuation from ambient noise and apply to real data (particularly in Tibetan Plateau), we propose approaches with detailed formulations for a linear array and a more general 2D station network. A particular problem in retrieving amplitudes from noise is that seismic ambient noise source is not uniform and changes with time. We tested numerical simulations with azimuthally and temporally varying noise source, and have started to add internal scattering in the simulations. Our simulations validate that amplitudes and attenuations can indeed be extracted from noise correlations for a linear array or for a more general 2D array. We propose a temporal flattening procedure, which is effective in speeding up convergence while preserving relative amplitudes. For real data, we propose an "asynchronous" temporal flattening procedure that does not require all stations to have the data at the same time. Tests on real data suggest attenuations extracted are comparable with those from earthquakes.

  9. Continuous measurement with traveling wave probes

    E-print Network

    Andrew Silberfarb; Ivan H. Deutsch

    2003-08-01

    We consider the use of a traveling wave probe to continuously measure the quantum state of an atom in free space. Unlike the more familiar cavity QED geometry, the traveling wave is intrinsically a multimode problem. Using an appropriate modal decomposition we determine the effective measurement strength for different atom-field interactions and different initial states of the field. These include the interaction of a coherent-state pulse with an atom, the interaction of a Fock-state pulse with an atom, and the use of Faraday rotation of a polarized laser probe to perform a QND measurement on an atomic spin.

  10. Evaluation of high frequency radar wave measurement

    Microsoft Academic Search

    L. R Wyatt; S. P Thompson; R. R Burton

    1999-01-01

    The spatial coverage, temporal availability and spectral and parameter accuracy of wave measurements using radars operating at the upper end of the high frequency (HF) radio band are discussed. The two radars used are the Ocean Surface Current Radar (OSCR) developed in the UK and the Wellen Radar (WERA) developed in Germany. The measurements show that useful accuracy is obtainable

  11. Snowpack snow water equivalent measurement using the attenuation of cosmic gamma radiation

    SciTech Connect

    Osterhuber, R. [Univ. of California, Soda Springs, CA (United States). Central Sierra Snow Lab.; Fehrke, F. [California Dept. of Water Resources, Sacramento, CA (United States); Condreva, K. [Sandia National Labs., Livermore, CA (United States)

    1998-05-01

    Incoming, background cosmic radiation constantly fluxes through the earth`s atmosphere. The high energy gamma portion of this radiation penetrates many terrestrial objects, including the winter snowpack. The attenuation of this radiation is exponentially related to the mass of the medium through which it penetrates. For the past three winters, a device measuring cosmic gamma radiation--and its attenuation through snow--has been installed at the Central Sierra Snow Laboratory, near Donner Pass, California. This gamma sensor, measuring energy levels between 5 and 15 MeV, has proved to be an accurate, reliable, non-invasive, non-mechanical instrument with which to measure the total snow water equivalent of a snowpack. This paper analyzes three winters` worth of data and discusses the physics and practical application of the sensor for the collection of snow water equivalent data from a remote location.

  12. Attenuation of wind waves by monomolecular sea slicks and the Marangoni effect

    Microsoft Academic Search

    Heinrich Hühnerfuss; Wolfgang Walter; Philipp A. Lange; Werner Alpers

    1987-01-01

    Previous observations of wind wave damping by monomolecular surface films (``slicks'') have shown a pronounced energy detraction (``dip'') in the short gravity wave range of the wind wave spectra. In this work, wind wave tunnel experiments with mechanically generated water waves have supplied experimental evidence which clearly shows that this dip is predominantly caused by the film-induced ``Marangoni effect.''

  13. A simple model of ultrasound propagation in a cavitating liquid. Part I: Theory, nonlinear attenuation and traveling wave generation

    E-print Network

    Louisnard, Olivier

    2013-01-01

    The bubbles involved in sonochemistry and other applications of cavitation oscillate inertially. A correct estimation of the wave attenuation in such bubbly media requires a realistic estimation of the power dissipated by the oscillation of each bubble, by thermal diffusion in the gas and viscous friction in the liquid. Both quantities and calculated numerically for a single inertial bubble driven at 20 kHz, and are found to be several orders of magnitude larger than the linear prediction. Viscous dissipation is found to be the predominant cause of energy loss for bubbles small enough. Then, the classical nonlinear Caflish equations describing the propagation of acoustic waves in a bubbly liquid are recast and simplified conveniently. The main harmonic part of the sound field is found to fulfill a nonlinear Helmholtz equation, where the imaginary part of the squared wave number is directly correlated with the energy lost by a single bubble. For low acoustic driving, linear theory is recovered, but for larger ...

  14. Filter Paper: Solution to High Self-Attenuation Corrections in HEPA Filter Measurements

    SciTech Connect

    Oberer, R.B.; Harold, N.B.; Gunn, C.A.; Brummett, M.; Chaing, L.G.

    2005-10-01

    An 8 by 8 by 6 inch High Efficiency Particulate Air (HEPA) filter was measured as part of a uranium holdup survey in June of 2005 as it has been routinely measured every two months since 1998. Although the survey relies on gross gamma count measurements, this was one of a few measurements that had been converted to a quantitative measurement in 1998. The measurement was analyzed using the traditional Generalized Geometry Holdup (GGH) approach, using HMS3 software, with an area calibration and self-attenuation corrected with an empirical correction factor of 1.06. A result of 172 grams of {sup 235}U was reported. The actual quantity of {sup 235}U in the filter was approximately 1700g. Because of this unusually large discrepancy, the measurement of HEPA filters will be discussed. Various techniques for measuring HEPA filters will be described using the measurement of a 24 by 24 by 12 inch HEPA filter as an example. A new method to correct for self attenuation will be proposed for this measurement Following the discussion of the 24 by 24 by 12 inch HEPA filter, the measurement of the 8 by 8 by 6 inch will be discussed in detail.

  15. Weak Measurement and (Bohmian) Conditional Wave Functions

    E-print Network

    Travis Norsen; Ward Struyve

    2013-10-07

    It was recently pointed out (and demonstrated experimentally) by Lundeen et al. that the wave function of a particle (more precisely, the wave function possessed by each member of an ensemble of identically-prepared particles) can be "directly measured" using weak measurement. Here it is shown that if this same technique is applied, with appropriate post-selection, to one particle from a (perhaps entangled) multi-particle system, the result is precisely the so-called "conditional wave function" of Bohmian mechanics. Thus, a plausibly operationalist method for defining the wave function of a quantum mechanical sub-system corresponds to the natural definition of a sub-system wave function which Bohmian mechanics (uniquely) makes possible. Similarly, a weak-measurement-based procedure for directly measuring a sub-system's density matrix should yield, under appropriate circumstances, the Bohmian "conditional density matrix" as opposed to the standard reduced density matrix. Experimental arrangements to demonstrate this behavior -- and also thereby reveal the non-local dependence of sub-system state functions on distant interventions -- are suggested and discussed.

  16. The contribution of activated processes to Q. [stress corrosion cracking in seismic wave attenuation

    NASA Technical Reports Server (NTRS)

    Spetzler, H. A.; Getting, I. C.; Swanson, P. L.

    1980-01-01

    The possible role of activated processes in seismic attenuation is investigated. In this study, a solid is modeled by a parallel and series configuration of dashpots and springs. The contribution of stress and temperature activated processes to the long term dissipative behavior of this system is analyzed. Data from brittle rock deformation experiments suggest that one such process, stress corrosion cracking, may make a significant contribution to the attenuation factor, Q, especially for long period oscillations under significant tectonic stress.

  17. Precision of Raman depolarization and optical attenuation measurements of sound tooth enamel

    Microsoft Academic Search

    Michael G. Sowa; Dan P. Popescu; Jeffrey Werner; Mark Hewko; Alex C.-T. Ko; Jeri Payette; Cecilia C. S. Dong; Blaine Cleghorn; Lin-P’ing Choo-Smith

    2007-01-01

    The demineralization of enamel that is associated with early caries formation affects the optical properties of the enamel.\\u000a Polarized Raman spectroscopy and optical coherence tomography have been used to detect these changes and potentially offer\\u000a a means to detect and monitor early caries development. The total optical attenuation coefficient as measured by optical coherence\\u000a tomography and the polarization anisotropy of

  18. The Effect of Internal Waves on Surface Wind Waves 1. Experimental Measurements

    Microsoft Academic Search

    B. A. Hughes; H. L. Grant

    1978-01-01

    Internal waves were generated by a ship using the 'dead water' effect in areas where the water contains a strong near-surface density gradient. The effects of these internal waves on wind waves were examined. The principal measurements were slope statistics of the wind waves and horizontal currents in the internal waves. The effects on the wind waves were always observable

  19. High frequency ultrasound measurements of the attenuation and backscatter from biological tissues

    NASA Astrophysics Data System (ADS)

    Maruvada, Subha

    There are now diagnostic ultrasonic imaging devices that operate at very high frequencies (VHF) of 20 MHz and beyond for clinical applications in ophthalmology, dermatology, and vascular surgery. To be able to better interpret these images and to further the development of these devices, knowledge of ultrasonic attenuation and scattering of biological tissues in this high frequency range is crucial. Though currently VHF ultrasound is applied mostly to the eye and skin tissue, in this thesis, VHF experiments were performed on porcine red blood cell suspensions and bovine myocardium, liver, and kidney because these tissues are easy to obtain, are similar in structure to their human counterparts and have been used in ultrasound experiments by many investigators but in a lower frequency range. Attenuation and backscatter coefficients of porcine blood and bovine tissues were measured, respectively, using substitution methods. Unfocused and focused transducers were employed in the experiments and corresponding results were compared. This dissertation presents the results of measurements of acoustic attenuation and backscatter from various biological materials (bovine myocardium, liver, and kidney, and porcine blood) in a wide frequency range (10 to 90 MHz) and compares them to previous lower frequency results. Based on the methods used to calculate the acoustic parameters, the frequency limits of the measurements are also defined.

  20. Sparse signal reconstruction from polychromatic X-ray CT measurements via mass attenuation discretization

    SciTech Connect

    Gu, Renliang; Dogandži?, Aleksandar [Iowa State University, Center for Nondestructive Evaluation, 1915 Scholl Road, Ames, IA 50011 (United States)

    2014-02-18

    We propose a method for reconstructing sparse images from polychromatic x-ray computed tomography (ct) measurements via mass attenuation coefficient discretization. The material of the inspected object and the incident spectrum are assumed to be unknown. We rewrite the Lambert-Beer’s law in terms of integral expressions of mass attenuation and discretize the resulting integrals. We then present a penalized constrained least-squares optimization approach for reconstructing the underlying object from log-domain measurements, where an active set approach is employed to estimate incident energy density parameters and the nonnegativity and sparsity of the image density map are imposed using negative-energy and smooth ?{sub 1}-norm penalty terms. We propose a two-step scheme for refining the mass attenuation discretization grid by using higher sampling rate over the range with higher photon energy, and eliminating the discretization points that have little effect on accuracy of the forward projection model. This refinement allows us to successfully handle the characteristic lines (Dirac impulses) in the incident energy density spectrum. We compare the proposed method with the standard filtered backprojection, which ignores the polychromatic nature of the measurements and sparsity of the image density map. Numerical simulations using both realistic simulated and real x-ray ct data are presented.

  1. X-ray attenuation of adipose breast tissue: in-vitro and in-vivo measurements using spectral imaging

    NASA Astrophysics Data System (ADS)

    Fredenberg, Erik; Erhard, Klaus; Berggren, Karl; Dance, David R.; Young, Kenneth C.; Cederström, Björn; Johansson, Henrik; Lundqvist, Mats; Moa, Elin; Homan, Hanno; Willsher, Paula; Kilburn-Toppin, Fleur; Wallis, Matthew

    2015-03-01

    The development of new x-ray imaging techniques often requires prior knowledge of tissue attenuation, but the sources of such information are sparse. We have measured the attenuation of adipose breast tissue using spectral imaging, in vitro and in vivo. For the in-vitro measurement, fixed samples of adipose breast tissue were imaged on a spectral mammography system, and the energy-dependent x-ray attenuation was measured in terms of equivalent thicknesses of aluminum and poly-methyl methacrylate (PMMA). For the in-vivo measurement, a similar procedure was applied on a number of spectral screening mammograms. The results of the two measurements agreed well and were consistent with published attenuation data and with measurements on tissue-equivalent material.

  2. Internal reflection beneath capillary water waves: a method for measuring wave slope

    E-print Network

    Saylor, John R.

    Internal reflection beneath capillary water waves: a method for measuring wave slope J. R. Saylor of America Key words: Wave slope measurement, internal reflection, capillary waves. 1. Introduction The waves Ray-tracing simulations were performed to explore total internal reflection of light rays beneath

  3. Additional attenuation of natural VLF electromagnetic waves observed by the DEMETER spacecraft resulting from preseismic activity

    NASA Astrophysics Data System (ADS)

    PíšA, David; N?Mec, FrantišEk; SantolíK, Ond?Ej; Parrot, Michel; Rycroft, Michael

    2013-08-01

    We use VLF electromagnetic wave data measured by the DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite at an altitude of about 700 km to check for the presence of statistically significant changes of natural wave intensity (due to signals from lightning) related to preseismic activity. All the relevant data acquired by DEMETER during almost 6.5 years of the mission have been analyzed using a robust two-step data-processing schema. This enables us to compare data from the vicinity of about 8400 earthquakes with an unperturbed background distribution based on data collected during the whole DEMETER mission and to evaluate the statistical significance of the observed effects. We confirm previously reported results of a small but statistically significant decrease of the wave intensity (by ˜2 dB) at frequencies of about 1.7 kHz. The effect is observed for a few hours before the times of the main shocks; it occurs during the night. The effect is stronger between March and August, at higher latitudes and for the positions of hypocenters below the sea. We suggest an explanation based on changed properties of the lower boundary of the ionosphere, which leads to a decrease of the intensity of lightning-generated whistlers observed at the spacecraft altitude. This effect might result from a lowering of the ionosphere associated with an increase in the electrical conductivity of the lower troposphere due to an additional ionization of air molecules at the Earth's surface prior to earthquakes.

  4. Shallow angle LIDAR for wave measurement

    Microsoft Academic Search

    J. M. K. Horwood; R. W. F. Thurley; M. R. Belmont; J. Baker

    2005-01-01

    The Exeter University Marine Dynamics Group has developed a shallow angle LIDAR for wave measurement purposes. This paper introduces the system and illustrates some metrology issues specific to this method. The LIDAR system uses a 532 nm (green) Q switched, high repetition rate, nanosecond pulsed laser. The system is designed to be scanned along a line or over an area.

  5. Radiometric Measurements of the Microwave Emissivity of Reproducible Breaking Waves

    E-print Network

    Reising, Steven C.

    Radiometric Measurements of the Microwave Emissivity of Reproducible Breaking Waves Sharmila measurements of breaking waves on the open ocean showed that the emission due to wave breaking varies measurements on the open ocean. Therefore, the authors conducted a wave basin experiment in which reproducible

  6. Spinal axis irradiation with electrons: Measurements of attenuation by the spinal processes

    SciTech Connect

    Muller-Runkel, R.; Vijayakumar, S.

    1986-07-01

    Electrons may be used beneficially for spinal axis irradiation in medulloblastoma children to avoid some of the long-term sequelae induced by megavoltage photons. However, the attenuation by the intervening bone ought to be considered. Three-dimensional computer treatment planning with inhomogeneity correction for electron beams is not yet generally available, and alternate methods are needed to evaluate the attenuation by the complex bony structure of the spine. Here, we present our experimental data showing the alteration in the electron isodoses due to the intervening spinous processes. Film dosimetric measurements were made in the vertebral columns obtained from autopsies of a goat, a dog, and a child. Our results show that electron beam therapy for the spinal axis is a viable option.

  7. Centimeter and millimeter wave attenuation and brightness temperature due to atmospheric oxygen and water vapor

    NASA Technical Reports Server (NTRS)

    Smith, E. K.

    1982-01-01

    Calculations are presented for atmospheric absorption and radiation emission for several atmospheric conditions and elevation angles. The calculations are for frequencies in the 1 to 340 GHz frequency range. The calculations are compared to those from other models. Agreement is found to within 15% for absorption coefficient (7.5 g/m/cubed water vapor at 290 K) and approximately the same for total zenithal attenuation. The attenuation and gaseous emission noise curves defined by the International Radio Consultative Committee are found to have minor inconsistencies.

  8. An Empirical Assessment of Exposure Measurement Error and Effect Attenuation in Bipollutant Epidemiologic Models

    PubMed Central

    Baxter, Lisa K.; Chang, Howard H.

    2014-01-01

    Background: Using multipollutant models to understand combined health effects of exposure to multiple pollutants is becoming more common. However, complex relationships between pollutants and differing degrees of exposure error across pollutants can make health effect estimates from multipollutant models difficult to interpret. Objectives: We aimed to quantify relationships between multiple pollutants and their associated exposure errors across metrics of exposure and to use empirical values to evaluate potential attenuation of coefficients in epidemiologic models. Methods: We used three daily exposure metrics (central-site measurements, air quality model estimates, and population exposure model estimates) for 193 ZIP codes in the Atlanta, Georgia, metropolitan area from 1999 through 2002 for PM2.5 and its components (EC and SO4), as well as O3, CO, and NOx, to construct three types of exposure error: ?spatial (comparing air quality model estimates to central-site measurements), ?population (comparing population exposure model estimates to air quality model estimates), and ?total (comparing population exposure model estimates to central-site measurements). We compared exposure metrics and exposure errors within and across pollutants and derived attenuation factors (ratio of observed to true coefficient for pollutant of interest) for single- and bipollutant model coefficients. Results: Pollutant concentrations and their exposure errors were moderately to highly correlated (typically, > 0.5), especially for CO, NOx, and EC (i.e., “local” pollutants); correlations differed across exposure metrics and types of exposure error. Spatial variability was evident, with variance of exposure error for local pollutants ranging from 0.25 to 0.83 for ?spatial and ?total. The attenuation of model coefficients in single- and bipollutant epidemiologic models relative to the true value differed across types of exposure error, pollutants, and space. Conclusions: Under a classical exposure-error framework, attenuation may be substantial for local pollutants as a result of ?spatial and ?total with true coefficients reduced by a factor typically < 0.6 (results varied for ?population and regional pollutants). Citation: Dionisio KL, Baxter LK, Chang HH. 2014. An empirical assessment of exposure measurement error and effect attenuation in bipollutant epidemiologic models. Environ Health Perspect 122:1216–1224;?http://dx.doi.org/10.1289/ehp.1307772 PMID:25003573

  9. Can We Measure the Wave Function of a SingleWave Packet of Light?

    E-print Network

    Utah, University of

    Can We Measure the Wave Function of a SingleWave Packet of Light? Brownian Motion and Continuous Wave Packet Collapse in RepeatedWeak Quantum Nondemolition Measurements ORLY ALTER AND YOSHIHISA, the wave function of the measured system collapses to the corresponding eigenstate, according

  10. Full wave modeling of therapeutic ultrasound: efficient time-domain implementation of the frequency power-law attenuation.

    PubMed

    Liebler, Marko; Ginter, Siegfried; Dreyer, Thomas; Riedlinger, Rainer E

    2004-11-01

    For the simulation of therapeutic ultrasound applications, a method including frequency-dependent attenuation effects directly in the time domain is highly desirable. This paper describes an efficient numerical time-domain implementation of the power-law attenuation model presented by Szabo [Szabo, J. Acoust. Soc. Am. 96, 491-500 (1994)]. Simulations of therapeutic ultrasound applications are feasible in conjunction with a previously presented finite differences time-domain (FDTD) algorithm for nonlinear ultrasound propagation [Ginter et al., J. Acoust. Soc. Am. 111, 2049-2059 (2002)]. Szabo implemented the empirical frequency power-law attenuation using a causal convolutional operator directly in the time-domain equation. Though a variety of time-domain models has been published in recent years, no efficient numerical implementation has been presented so far for frequency power-law attenuation models. Solving a convolutional integral with standard time-domain techniques requires enormous computational effort and therefore often limits the application of such models to 1D problems. In contrast, the presented method is based on a recursive algorithm and requires only three time levels and a few auxiliary data to approximate the convolutional integral with high accuracy. The simulation results are validated by comparison with analytical solutions and measurements. PMID:15603120

  11. High-frequency attenuation and backscatter measurements of rat blood between 30 and 60 MHz

    NASA Astrophysics Data System (ADS)

    Huang, Chih-Chung

    2010-10-01

    There has recently been a great deal of interest in noninvasive high-frequency ultrasound imaging of small animals such as rats due to their being the preferred animal model for gene therapy and cancer research. Improving the interpretation of the obtained images and furthering the development of the imaging devices require a detailed knowledge of the ultrasound attenuation and backscattering of biological tissue (e.g. blood) at high frequencies. In the present study, the attenuation and backscattering coefficients of the rat red blood cell (RBC) suspensions and whole blood with hematocrits ranging from 6% to 40% were measured between 30 and 60 MHz using a modified substitution approach. The acoustic parameters of porcine blood under the same conditions were also measured in order to compare differences in the blood properties between these two animals. For porcine blood, both whole blood and RBC suspension were stirred at a rotation speed of 200 rpm. Three different rotation speeds of 100, 200 and 300 rpm were carried out for rat blood experiments. The attenuation coefficients of both rat and porcine blood were found to increase linearly with frequency and hematocrit (the values of coefficients of determination (r2) are around 0.82-0.97 for all cases). The average attenuation coefficient of rat whole blood with a hematocrit of 40% increased from 0.26 Nepers mm-1 at 30 MHz to 0.47 Nepers mm-1 at 60 MHz. The maximum backscattering coefficients of both rat and porcine RBC suspensions were between 10% and 15% hematocrits at all frequencies. The fourth-power dependence of backscatter on frequency was approximately valid for rat RBC suspensions with hematocrits between 6% and 40%. However, the frequency dependence of the backscatter estimate deviates from a fourth-power law for porcine RBC suspension with hematocrit higher than 20%. The backscattering coefficient plateaued for hematocrits higher than 15% in porcine blood, but for rat blood it was maximal around a hematocrit of 20% at the same rotation speed, and shifted to a hematocrit of 10% at a higher speed. The backscattering properties of rat RBCs in plasma are similar to those of RBCs in saline at a higher rotation speed. The differences in attenuation and backscattering between rat and porcine blood may be attributed to RBCs' being smaller and the RBC aggregation level being lower for rat blood than for porcine blood.

  12. Satellite and ground based Measurements of Wave Interactions above Antarctica

    NASA Astrophysics Data System (ADS)

    Baumgaertner, A. J.; McDonald, A. J.

    Wave interactions are an important mechanism for the coupling of different regions in the middle atmosphere This study investigates the coupling of gravity waves planetary waves and tides in the stratosphere mesosphere and lower thermosphere above Antarctica using satellite and radar data CHAMP Challenging Minisatellite Payload radio occultation measurements is used to measure gravity wave activity in the Antarctic lower stratosphere while data from the EOS microwave limb sounder is employed to study waves with longer periods in the middle atmosphere These datasets are complemented by measurements from an MF radar at Scott Base which yields measures of gravity waves planetary waves and tides Wave activity is presented as a function of time altitude and geographic location and interactions are then investigated with a focus on coupling with atmospheric tides Amplitude changes and the generation of secondary waves are among the observed effects Climatologies based on periodogram analysis of MF radar winds are used to identify periods of strong wave-wave interactions

  13. Seismic-wave attenuation and yield determination at regional distances. Final report, 1 May 1987-30 April 1989

    SciTech Connect

    Mitchell, B.J.; Nuttli, O.W.; Xie, J.K.; Al-Shukri, H.; Correig, A.

    1989-05-25

    Work was completed on yield determination at the Soviet test site on Novaya Zemlya. Magnitudes and yields, determined for 30 explosions using Lg amplitudes recorded in northwestern Europe, ranged between 2.5 and 4900 kt, the largest since April 1976 being about 145 kt. Studies were completed on seismic wave attenuation of surface waves at intermediate periods and of Lg waves at 1 Hz in several regions of the world. Limits were determined for the degree of frequency dependence of Q (sub beta) which can occur in the crust in stable and tectonically active regions. A stochastic convolution model was proposed for Lg coda at distances > 200 km which considers the effects of dispersion scattering and mode conversions at those distances. A back-projection tomographic method was developed to regionalize large-scale lateral variations of coda Q for Lg waves which traverse long continental paths. A seismically active region in the New Madrid seismic zone was found to be characterized by lower than normal Q values. In the western United States, Q values in the upper mantle vary laterally, becoming smaller from east to west. Crust of the Basin and Range province has a low-Q upper crust overlying a lower crust with higher Q values.

  14. Energy and phase velocity considerations required for attenuation and velocity measurements of anisotropic composites.

    PubMed

    Carroll, N L; Humphrey, V F; Smith, J D

    2002-05-01

    Viscoelastic fibre-reinforced composite materials have a number of possible advantages for use in underwater acoustic applications. In order to exploit these materials it is important to be able to measure their complex stiffness matrix in order to determine their acoustic response. Ultrasonic transmission measurements on parallel-sided samples, employing broadband pulsed transducers at 2.25 MHz and an immersion method, have been used to determine the viscoelastic properties of a glass-reinforced composite with uniaxially aligned fibres. The composite measured was constructed from Cytecfiberite's CYCOM 919 E-glass. The theory of acoustic propagation in anisotropic materials shows that the direction of energy propagation is, in general, different from that given by Snell's Law. At 15 degrees incidence, Snell's Law implies a refracted angle of 40 +/- 2 degrees, whereas the energy direction is observed to be 70 +/- 2 degrees. Despite this, the experimental data indicates that the position of the receiving transducer has relatively little effect on the apparent phase velocity measured. The phase velocities measured at positions determined from the refracted angle and energy direction are 3647 and 3652 +/- 50 m s(-1), respectively. However, the amplitude of the received signal, and hence estimate of attenuation, is highly sensitive to the receiver position. This indicates that the acoustic Poynting vector must be considered in order to precisely determine the correct position of the receiving transducer for attenuation measurements. The beam displacement for a 17.6 mm sample at 15 degrees incidence is 9.5 and 40 mm by Snell's Law and Poynting's Theorem, respectively. Measured beam displacements have been compared with predictions derived from material stiffness coefficients. These considerations are important in recovering the complex stiffness matrix. PMID:12159995

  15. Teleseismic shear wave splitting measurements in noisyenvironments

    NASA Astrophysics Data System (ADS)

    Restivo, Andrea; Helffrich, George

    1999-06-01

    High noise levels hamper teleseismic shear wave splitting measurements, which bandpass filtering does not always help. To investigate how robust splitting measurements are to noise, we analysed a set of synthetic records with known splitting parameters and added fixed levels of noise. In the presence of weak anisotropy, single-waveform splitting measurements are unreliable when operating with noisy data sets. A practical rule in terms of S/N ratio and splitting delay time parameters is that splitting is confidently detectable at S/N>8, regardless of the wave's original polarization orientation. However, for the evidence of weak anisotropy to be detectable and measurable at an S/N value of 4, the backazimuth separation of the phases from the fast polarization direction needs to be higher than 20 deg. Stacks of individual measurements consistently yield reliable results down to S/N values of 4. Applying stacking to data from DSB (Dublin, Ireland), the fast polarization direction phi and lag time deltat are 58 deg and 0.95 s. This orientation reflects surface trends of deformation in the area, as found elsewhere in the UK. Our result thus reinforces the proposed model that the detected anisotropy in the British Isles originates from lithospheric coherent deformation preserved from the last main tectonic episode.

  16. Thermoreflectance temperature measurement with millimeter wave

    NASA Astrophysics Data System (ADS)

    Pradere, C.; Caumes, J.-P.; BenKhemis, S.; Pernot, G.; Palomo, E.; Dilhaire, S.; Batsale, J.-C.

    2014-06-01

    GigaHertz (GHz) thermoreflectance technique is developed to measure the transient temperature of metal and semiconductor materials located behind an opaque surface. The principle is based on the synchronous detection, using a commercial THz pyrometer, of a modulated millimeter wave (at 110 GHz) reflected by the sample hidden behind a shield layer. Measurements were performed on aluminum, copper, and silicon bulks hidden by a 5 cm thick Teflon plate. We report the first measurement of the thermoreflectance coefficient which exhibits a value 100 times higher at 2.8 mm radiation than those measured at visible wavelengths for both metallic and semiconductor materials. This giant thermoreflectance coefficient ?, close to 10-3 K-1 versus 10-5 K-1 for the visible domain, is very promising for future thermoreflectance applications.

  17. Thermoreflectance temperature measurement with millimeter wave

    SciTech Connect

    Pradere, C., E-mail: christophe.pradere@ensam.eu; Caumes, J.-P.; BenKhemis, S.; Palomo, E.; Batsale, J.-C. [I2M (Institut de Mécanique et d’Ingénierie de Bordeaux) UMR CNRS 5295, TREFLE Department, Esplanade des Arts et Métiers, F-33405 Talence Cedex (France); Pernot, G.; Dilhaire, S. [LOMA UMR 5798: CNRS-UB1, 351 Cours de la Libération, 33405 Talence Cedex (France)

    2014-06-15

    GigaHertz (GHz) thermoreflectance technique is developed to measure the transient temperature of metal and semiconductor materials located behind an opaque surface. The principle is based on the synchronous detection, using a commercial THz pyrometer, of a modulated millimeter wave (at 110 GHz) reflected by the sample hidden behind a shield layer. Measurements were performed on aluminum, copper, and silicon bulks hidden by a 5 cm thick Teflon plate. We report the first measurement of the thermoreflectance coefficient which exhibits a value 100 times higher at 2.8 mm radiation than those measured at visible wavelengths for both metallic and semiconductor materials. This giant thermoreflectance coefficient ?, close to 10{sup ?3} K{sup ?1} versus 10{sup ?5} K{sup ?1} for the visible domain, is very promising for future thermoreflectance applications.

  18. Wave-front measurement errors from restricted concentric subdomains

    E-print Network

    Wave-front measurement errors from restricted concentric subdomains Kenneth A. Goldberg and Kevin errors. In nearly all cases, the measured rms wave-front error and the magnitudes of the individual subdomain. In this way, systematic wave-front measurement errors intro- duced by subregion selection

  19. Communication: Singularity-free hybrid functional with a Gaussian-attenuating exact exchange in a plane-wave basis

    NASA Astrophysics Data System (ADS)

    Song, Jong-Won; Giorgi, Giacomo; Yamashita, Koichi; Hirao, Kimihiko

    2013-06-01

    Integrable singularity in the exact exchange calculations in hybrid functionals is an old and well-known problem in plane-wave basis. Recently, we developed a hybrid functional named Gaussian-attenuating Perdew-Burke-Ernzerhof (Gau-PBE), which uses a Gaussian function as a modified Coulomb potential for the exact exchange. We found that the modified Coulomb potential of Gaussian function enables the exact exchange calculation in plane-wave basis to be singularity-free and, as a result, the Gau-PBE functional shows faster energy convergence on k and q grids for the exact exchange calculations. Also, a tight comparison (same k and q meshes) between Gau-PBE and two other hybrid functionals, i.e., PBE0 and HSE06, indicates Gau-PBE functional as the least computational time consuming. The Gau-PBE functional employed in conjunction with a plane wave basis provides bandgaps with higher accuracy than the PBE0 and HSE06 in agreement with bandgaps previously calculated using Gaussian-type-orbitals.

  20. Attenuation measurements of passive linear and nonlinear hearing protectors for impulse noise

    NASA Astrophysics Data System (ADS)

    Murphy, William J.; Kardous, Chucri A.

    2003-04-01

    As a part of a NIOSH Health Hazard Evaluation of law-enforcement personnel, the attenuation of several types of earplugs were measured in response to impulse noise produced by small-arms gunfire. The earplugs were primarily flanged premolded plugs produced by EAR/Aearo and Bilsom/Baccou-Dalloz. Measurements for the North Sonic Ear Valve, EAR Classic earplugs, and EAR Ultra 9000 passive nonlinear ear muff were conducted. The EAR premolded earplugs were the Combat Arms passive linear and nonlinear, HiFi and Ultratech earplugs. The Bilsom devices were the 555, 655 NST, and 655 ISL earplugs. The Combat Arms and 655 ISL earplugs both utilize a cartridge developed by the French German Research Institute de Saint Louis that provides nonlinear attenuation. The peak reduction of these devices ranged between 10 and 28 dB. The slope of peak reduction with peak level for the Ultra9000 device was about 0.5 dB/dB, while the slopes for most earplugs were about 0.1 to 0.3 dB/dB for weapons impulses between 159- and 170-dB peak level. The peak reductions ranged from 6 dB for the North Ear valve to 30 dB for the EAR Classic foam earplug.

  1. S-wave attenuation in northeastern Sonora, Mexico, near the faults that ruptured during the earthquake of 3 May 1887 Mw 7.5.

    PubMed

    Villalobos-Escobar, Gina P; Castro, Raúl R

    2014-01-01

    We used a new data set of relocated earthquakes recorded by the Seismic Network of Northeastern Sonora, Mexico (RESNES) to characterize the attenuation of S-waves in the fault zone of the 1887 Sonora earthquake (M w 7.5). We determined spectral attenuation functions for hypocentral distances (r) between 10 and 140 km using a nonparametric approach and found that in this fault zone the spectral amplitudes decay slower with distance at low frequencies (f?attenuation functions obtained for 23 frequencies (0.4???f???63.1 Hz) permit us estimating the average quality factor Q S ?=?(141 ± 1.1 )f ((0.74 ± 0.04)) and a geometrical spreading term G(r) =?1/r (0.21). The values of Q estimated for S-wave paths traveling along the fault system that rupture during the 1887 event, in the north-south direction, are considerably lower than the average Q estimated using source-station paths from multiple stations and directions. These results indicate that near the fault zone S waves attenuate considerably more than at regional scale, particularly at low frequencies. This may be the result of strong scattering near the faults due to the fractured upper crust and higher intrinsic attenuation due to stress concentration near the faults. PMID:25674476

  2. Measurements of wave-variance and velocity spectra in breaking waves

    Microsoft Academic Search

    H.-T. Liu; J.-T. Liu

    1987-01-01

    Displacements of mechanical waves superposed onto wind waves were measured with a laser displacement gauge in a wind-wave tank. The effects of wave breaking, especially the spilling breaking type, on the wave-variance spectra are investigated. In the absence of wave breaking, the quasi-equilibrium spectrum consists of an f -7\\/3 subrange in the capillary regime, and its spectral density increases with

  3. Measurements of wave-variance and velocity spectra in breaking waves

    Microsoft Academic Search

    H.-T. Liu; J.-T. Liu

    1987-01-01

    Displacements of mechanical waves superposed onto wind waves were measured with a laser displacement gauge in a wind-wave tank. The effects of wave breaking, especially the spilling breaking type, on the wave-variance spectra are investigated. In the absence of wave breaking, the quasi-equilibrium spectrum consists of an f-7\\/3 subrange in the capillary regime, and its spectral density increases with increasing

  4. Microscopic Observation of Mechanism for Shear Wave Attenuation in Nylon-66

    NASA Astrophysics Data System (ADS)

    Li, Ting

    2005-07-01

    Gupta[1] found rapid shear attenuation near the impact surface for PMMA target. However, the physical mechanism remains unknown. In this article, nylon-66 was chosen for experimental investigation by using a keyed gas gun and EMV method, since nylon-66 has the spherical grain structure, which can be observed under a polarized microscope. The similar rapid shear attenuation occurs in the present study when the impact velocity and inclination angle reach a critical value. The polarized micro-observation of recovered samples shows that near the impact surface there is a melting layer of thickness about 6-8?m, which causes the decay of the shear component propagating into the sample. The interesting thing is that there is a discontinuous crystalline layer about 2-3?m thick above the melting layer, which indicates the melting may not directly caused by the friction on the impact surface and the heat produces inside of the sample and near the surface. Further observation discloses an adiabatic shear band near the surface to cause the material failure. [1]Gupta Y M, J. Appl. Phys. 51(1980), 5352.

  5. Lee-Yang measures and wave functions

    E-print Network

    Dimitar K. Dimitrov

    2013-11-04

    We establish necessary and sufficient conditions for a Borel measure to be a Lee-Yang one which means that its Fourier transform possesses only real zeros. Equivalently, we answer a question of P\\'olya who asked for a characterisation of those positive positive, even and sufficiently fast decaying kernels whose Fourier transforms have only real zeros. The characterisation is given in terms of Wronskians of polynomials that are orthogonal with respect to the measure. The results show that Fourier transforms of a rather general class of measures can be approximated by symmetrized Slater determinants composed by orthogonal polynomials, that is, by some wave functions which are symmetric like the Boson ones. Brief comments on possible interpretation and applications of the main results in quantum and statistical mechanics, to Toda lattices and the general solution of the heat equation, are given. We discuss briefly the possibility of represent the Riemann $\\xi$ function as a partition function of a statistical mechanics system.

  6. High-resolution surface wave tomography in oceanic and continental regions: Simultaneous inversion for shear wave velocity, azimuthal anisotropy and attenuation

    NASA Astrophysics Data System (ADS)

    Yang, Yingjie

    The primary goal of this thesis is to understand the structure, dynamics, deformation and evolution of the Earth's lithosphere and mantle in both oceanic and continental settings by surface wave tomography. In chapter 1, we revised 2-D Born-approximation sensitivity kernels of surface waves for the global case to that for a regional case. We found that the kernels can accurately predict the perturbation of the wavefield. Based on the 2-D sensitivity kernels, we developed a surface wave tomography method and tested the inversion method by using synthesized data obtained from numerical simulations. We found the method can almost completely recover the input checkerboard structure when the size of anomalies is larger than one wavelength. In chapter 2, we applied the tomography method developed in chapter 1 to fundamental mode Rayleigh waves in southern California. Two-dimensional phase velocities are used to invert for three-dimensional S-wave velocities of the upper mantle. The pattern of velocity anomalies indicates that there is active small-scale convection in the asthenosphere beneath southern California and that the dominant form of convection is 3-D lithospheric drips and asthenospheric upwellings, rather than 2-D sheets or slabs. Azimuthal anisotropy is obtained in a joint inversion including lateral variations of phase velocities. The strength of anisotropy is ˜1.7% at periods shorter than 67s and decreases to ˜1% at longer periods. In chapter 3, we invert Rayleigh waves recorded at ocean-bottom seismometers (OBSs) in very young (less than 10 Ma) seafloor for shear wave velocity (Vs) and attenuation (Qmu). A high velocity lid with negative gradient in the uppermost mantle overlying a low velocity zone is observed. Our Q mu models exhibit a sharp change over the depth range of 40 to 60 km with higher values above 40 km. The change of Qmu and S-wave velocity with depth is partly due to the sharp change of water content in the upper mantle as a result of the extraction of water by large fractional melting above ˜65 km. ˜1% partial melting in the low velocity zone is required to satisfy the minimum value of shear wave velocity.

  7. Measurement and fitting techniques for the assessment of material nonlinearity using nonlinear Rayleigh waves

    NASA Astrophysics Data System (ADS)

    Torello, David; Kim, Jin-Yeon; Qu, Jianmin; Jacobs, Laurence J.

    2015-03-01

    This research considers the effects of diffraction, attenuation, and the nonlinearity of generating sources on measurements of nonlinear ultrasonic Rayleigh wave propagation. A new theoretical framework for correcting measurements made with air-coupled and contact piezoelectric receivers for the aforementioned effects is provided based on analytical models and experimental considerations. A method for extracting the nonlinearity parameter ?11 is proposed based on a nonlinear least squares curve-fitting algorithm that is tailored for Rayleigh wave measurements. Quantitative experiments are conducted to confirm the predictions for the nonlinearity of the piezoelectric source and to demonstrate the effectiveness of the curve-fitting procedure. These experiments are conducted on aluminum 2024 and 7075 specimens and a ?117075/?112024 measure of 1.363 agrees well with previous literature and earlier work.

  8. Measurements of mass attenuation coefficient, effective atomic number and electron density of some amino acids

    NASA Astrophysics Data System (ADS)

    Kore, Prashant S.; Pawar, Pravina P.

    2014-05-01

    The mass attenuation coefficients of some amino acids, such as DL-aspartic acid-LR(C4H7NO4), L-glutamine (C4H10N2O3), creatine monohydrate LR(C4H9N3O2H2O), creatinine hydrochloride (C4H7N3O·HCl) L-asparagine monohydrate(C4H9N3O2H2O), L-methionine LR(C5H11NO2S), were measured at 122, 356, 511, 662, 1170, 1275 and 1330 keV photon energies using a well-collimated narrow beam good geometry set-up. The gamma-rays were detected using NaI (Tl) scintillation detection system with a resolution of 0.101785 at 662 keV. The attenuation coefficient data were then used to obtain the effective atomic numbers (Zeff), and effective electron densities (Neff) of amino acids. It was observed that the effective atomic number (Zeff) and effective electron densities (Neff) initially decrease and tend to be almost constant as a function of gamma-ray energy. Zeff and Neff experimental values showed good agreement with the theoretical values with less than 1% error for amino acids.

  9. Phase speed and attenuation in bubbly liquids inferred from impedance measurements near the individual bubble resonance frequency.

    PubMed

    Wilson, Preston S; Roy, Ronald A; Carey, William M

    2005-04-01

    In the ocean, natural and artificial processes generate clouds of bubbles that scatter and attenuate sound. Measurements have shown that at the individual bubble resonance frequency, sound propagation in this medium is highly attenuated and dispersive. The existing theory to explain this behavior is deemed adequate away from resonance. However, due to excessive attenuation near resonance, little experimental data exists for a comparison with model predictions. An impedance tube was developed specifically for exploring this regime. The effective medium phase speed and attenuation were inferred from measurements of the surface impedance of a layer of bubbly liquid composed of air bubbles and distilled water, for void fractions from 6.2 x 10(-5) to 5.4 x 10(-4) and bubble sizes centered around 0.62 mm in radius. Improved measurement speed, accuracy, and precision is possible with the new instrument, and both instantaneous and time-averaged measurements were obtained. The phase speed and attenuation at resonance was observed to be sensitive to the bubble population statistics and agreed with an existing model [J. Acoust. Soc. Am. 85, 732-746 (1989)], within the uncertainty of the bubble population parameters. Agreement between the model and the data reported here is better than for the data that was available when the model was originally published. PMID:15898635

  10. Global Love wave overtone measurements K. Visser,1

    E-print Network

    Utrecht, Universiteit

    Global Love wave overtone measurements K. Visser,1 S. Lebedev,1 J. Trampert,1 and B. L. N. Kennett2. [1] Love wave phase velocities for fundamental and higher modes are difficult to measure because forty thousand Love wave seismograms from the GDSN and GEOSCOPE global networks from 1994 ­ 2004. Our

  11. In situ measurements of attenuation coefficient for evaluating the hardness of cataract lens by a high frequency ultrasonic needle transducer

    Microsoft Academic Search

    Chih-Chung Huang; Ruimin Chen; Po-Hsiang Tsui; Qifa Zhou; Mark S. Humayun; K. Kirk Shung

    2009-01-01

    A cataract is a clouding of the lens in the eye that affects vision. Phacoemulsification is the mostly common surgical method for treating cataracts, and determining the optimal phacoemulsification energy is dependent on measuring the hardness of the lens. This study explored the use of an ultrasound needle transducer for in situ minimally invasive measurements of ultrasound attenuation coefficient to

  12. Shock Wave Therapy Effectively Attenuates Inflammation in Rat Carotid Artery following Endothelial Denudation by Balloon Catheter

    Microsoft Academic Search

    Pei-Lin Shao; Chaw-Chi Chiu; Chun-Man Yuen; Sarah Chua; Li-Teh Chang; Jiunn-Jye Sheu; Cheuk-Kwan Sun; Chiung-Jen Wu; Ching-Jen Wang; Hon-Kan Yip

    2010-01-01

    Background: This study investigates the effectiveness of extracorporeal shock wave (ECSW) in ameliorating inflammatory mediator expression and neointimal formation in a rat model of vascular injury. Methods and Results: Male Sprague-Dawley rats with left carotid artery (LCA) injury induced by balloon dilatation (BD; group 1) were compared with group 2 [LCA injury plus ECSW-181 (defined as 181 total shocks given

  13. A model for P-wave attenuation and dispersion in a porous medium ...

    E-print Network

    lll

    2005-09-05

    fluid-saturated porous medium composed of two constituents, b and c can be ... 376. M. Brajanovski, B. Gurevich and M. Schoenberg. The results presented in this .... 9 ??µ?. K2 g . (30). As with the frequency-dependent P-wave modulus, the

  14. Evaluation of coastal wave attenuation due to viscous fluid sediment at Jefferson County, Texas 

    E-print Network

    Tuttle, Meghan I

    2000-01-01

    echosounder and collected soil samples. Testing concluded that a dual frequency fathometer is employable in the surf zone, but that low frequency data must be collected in water depths greater than two meters of water. The observed wave data is employed...

  15. Physical modeling and analysis of P-wave attenuation anisotropy in transversely isotropic media

    E-print Network

    Boise State University

    can provide sensitive attributes for fracture detection and lithology discrimination. This pa- per-preserving migration, and seismic fracture detec- tion. INTRODUCTION Most existing publications on seismic anisotropy and amplitudes of seismic waves. It is likely; howev- er, that anisotropic formations are also characterized

  16. Phase velocity dispersion and attenuation of seismic waves due to trapped fluids in residual-saturated porous media

    NASA Astrophysics Data System (ADS)

    Steeb, H.; Kurzeja, P.; Frehner, M.; Schmalholz, S. M.

    2012-04-01

    Propagation of seismic waves in partially saturated porous media depends on various material properties, e.g. saturation, porosity, elastic properties of the skeleton, viscous properties of the pore fluids and, additionally, capillary pressure and effective permeability. If the wetting fluid is in a discontinuous state, i.e. residual-saturated configuration, phase velocities and frequency-dependent attenuation additionally depend on microscopical (pore-scale) properties such as droplet and/or ganglia size. To model wave propagation in residual-saturated porous media, we developed a three-phase model based on an enriched continuum mixture theory capturing the strong coupling between the micro- and the macroscale. The three-phase model comprises the porous solid skeleton, a continuous fluid part and a discontinuous fluid part. The discontinuous part describes the movement of blobs/clusters of the wetting fluid and is based on an oscillator rheology. On the microscale, the oscillators are determined by their mass, damping and eigenfrequency. Amongst others, these properties depend on the microscopic geometry and surface tension. To embed the microscopic oscillators into a macroscopic poroelastic description of the non-wetting fluid and the skeleton, a scale bridging between both spatial scales is applied conserving density, eigenfrequency and damping. This homogenization approach accounts for the discontinuous character of the wetting fluid. Furthermore, probability density functions are used to describe the size distribution of different kinds of fluid clusters. The discontinuous fluid part is linked to the continuous solid phase by momentum exchange in the form of pinned or sliding oscillators. The non-wetting continuous fluid phase exhibits similar behavior as the poroelastic model introduced by Biot. The final model delivers insight into the behavior of propagating waves on the macroscale, influenced by different properties of the microscopic oscillating fluid clusters. Furthermore, the dispersion relations allow for a comparison with continuous models, such as the Biot model, and for the calculation of characteristic values, which might be helpful for the comparison with experimental studies. We define a dimensionless parameter that determines if the overall motion of the residual fluid is dominated by oscillations (underdamped, resonance) or not (overdamped). Our results show that the residual fluid has a significant impact on the velocity dispersion and attenuation, no matter if it oscillates or not. For long wavelengths, our model coincides with the Biot-Gassmann equations. We show under which conditions and how the classical biphasic models can be used to approximate the dynamic behavior of residual-saturated porous media.

  17. Non-contact ultrasonic spectroscopy measurement of elastic constants and ultrasonic attenuation

    SciTech Connect

    Schwarz, R.B.; Kuokkala, V.T.; Srinivasan, S.; Visscher, W.M.

    1991-01-01

    We have developed an ultrasonic spectroscopy method for measuring the elastic constants of solids in hostile environments and over a broad temperature regime. The sample is cut as a rectangular parallelepiped, approximately 1 mm{sup 3} in volume. One or two of the sample surfaces are coated with a thin film of a magnetostrictive material such as nickel. The sample is placed coaxially with two solenoids. One solenoid is used to generate an AC magnetic field of small amplitude which stretches the films. By sweeping the frequency of this field, the sample is excited successively into its various mechanical resonance modes. The second solenoid detects the mechanical resonances. The elastic constants are then deduced from the spectrum of mechanical resonances measured at constant temperature. The internal friction is deduced from the width of the resonance peaks. Because the technique is strictly non-contact (the sample may be encapsulated in a fused silica tube), it is deal for measuring elastic constants in hostile environments or under controlled atmospheres. In its present version the system allows us to measure the elastic constants and ultrasonic attenuation of a given sample between 80 and 100 K. The operation of the system is exemplified by measurements on amorphous Ni{sub 80}P{sub 20} and crystalline Ti{sub 60}Cr{sub 40}. 17 refs., 6 figs.

  18. Spectral light absorption and attenuation measurements from a towed undulating vehicle

    NASA Astrophysics Data System (ADS)

    Barth, John A.; Bogucki, Darek J.

    2000-02-01

    Measurements from a nine-wavelength light absorption and attenuation instrument mounted on a towed, undulating vehicle (SeaSoar) capable of rapidly profiling the water column - complete up-down cycles in 1.5-12 min depending on the maximum sampling depth - are used to characterize strong spatial variations in the distributions of upper-ocean bio-optical properties. Water sampled from adjacent to the conductivity and temperature sensors located in the nose of the vehicle is pumped through the 25-cm dual optical flow tubes of a Western Environmental Technology Laboratories (WET Labs) ac-9 instrument mounted on top of SeaSoar. A three-stage algorithm for post-processing the optical data to insure high-quality measurements concurrent with conductivity-temperature-depth data is described. After synchronizing the optical, navigational and conductivity-temperature-depth data streams, the method relies on finding the optimal time delay between when a water parcel is sampled first by the temperature and conductivity sensors and then by the absorption and attenuation optics. After applying the calculated time-dependent lag, a correction for the dependence of light absorption on temperature and salinity and a scattering correction to absorption are made. The final processed optical data from SeaSoar compare well with the same parameters sampled by a slowly lowered vertical profiling package deployed from a nearby stationary vessel. A 2-h, 30-km long cross-shelf section consisting of 184 vertical profiles separated by 150-200 m reveals strong horizontal variations on short spatial scales (1 km or less) of the vertical distributions of bio-optical properties.

  19. Protective measurements of the wave function of a single system

    E-print Network

    Lev Vaidman

    2014-02-27

    My view on the meaning of the quantum wave function and its connection to protective measurements is described. The wave function and only the wave function is the ontology of the quantum theory. Protective measurements support this view although they do not provide a decisive proof. A brief review of the discovery and the criticism of protective measurements is presented. Protective measurements with postselection are discussed.

  20. VHF\\/UHF wave attenuation in a city with regularly spaced buildings

    Microsoft Academic Search

    N. Blaunstein; M. Levin

    1996-01-01

    In this work a theoretical and experimental investigation analyzing VHF\\/UHF radio wave propagation in a suburban environment with a grid-type street plan is presented for the purpose of personal communication services prediction. A waveguide with randomly distributed gaps (slits) between the sides of buildings is considered as a model of straight streets with two- and three-story buildings. The average field

  1. Full Wave Analysis of RF Signal Attenuation in a Lossy Cave using a High Order Time Domain Vector Finite Element Method

    SciTech Connect

    Pingenot, J; Rieben, R; White, D

    2004-12-06

    We present a computational study of signal propagation and attenuation of a 200 MHz dipole antenna in a cave environment. The cave is modeled as a straight and lossy random rough wall. To simulate a broad frequency band, the full wave Maxwell equations are solved directly in the time domain via a high order vector finite element discretization using the massively parallel CEM code EMSolve. The simulation is performed for a series of random meshes in order to generate statistical data for the propagation and attenuation properties of the cave environment. Results for the power spectral density and phase of the electric field vector components are presented and discussed.

  2. Measurement of Organics Using Three FTIR Techniques: Absorption, Attenuated Total Reflectance, and Diffuse Reflectance

    NASA Astrophysics Data System (ADS)

    Gebel, M. E.; Kaleuati, M. A.; Finlayson-Pitts, B. J.

    2003-06-01

    This paper describes an undergraduate junior- and senior-level instrumental analysis experiment that uses three infrared analysis techniques: conventional transmission spectroscopy, attenuated total reflection (ATR) spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Using transmission spectroscopy, methyl t-butyl ether, MTBE, in a state-supplied certification gasoline was measured to be 11.3 ± 0.4 % (v/v, 2s), in agreement with the stated MTBE content of 10.9% (v/v). Measurements were also carried out on various brands of commercial gasoline and MTBE was found to vary from 9.2 to 12.2% (v/v). ATR was used to measure the ethanol content of different brands of vodka, which ranged from 36 to 40 % (v/v) in agreement with the labeled concentration of 40% (v/v). This part of the experiment highlights the significant advantages of using ATR for the analysis of aqueous solutions that cannot be carried out using normal transmission spectroscopy. Finally, DRIFTS measurements were made of total hydrocarbons in six soil samples. The results ranged from below the detection limit of 120 ppm (w/w) for soil from a path at a residential home to 915 ppm (w/w) for a sample from the center planter of a gas station. This part of the experiment illustrates the advantages of using DRIFTS to analyze solids compared to making pellets or mulls. This experiment is carried out during one seven-hour laboratory period.

  3. Correcting Four Similar Correlational Measures for Attenuation Due to Errors of Measurement in the Dependent Variable: Eta, Epsilon, Omega, and Intraclass r.

    ERIC Educational Resources Information Center

    Stanley, Julian C.; Livingston, Samuel A.

    Besides the ubiquitous Pearson product-moment r, there are a number of other measures of relationship that are attenuated by errors of measurement and for which the relationship between true measures can be estimated. Among these are the correlation ratio (eta squared), Kelley's unbiased correlation ratio (epsilon squared), Hays' omega squared,…

  4. In vivo evidence of methamphetamine induced attenuation of brain tissue oxygenation as measured by EPR oximetry

    PubMed Central

    Weaver, John; Yang, Yirong; Purvis, Rebecca; Weatherwax, Theodore; Rosen, Gerald M.; Liu, Ke Jian

    2014-01-01

    Abuse of methamphetamine (METH) is a major and significant societal problem in the US, as a number of studies have suggested that METH is associated with increased cerebrovascular events, hemorrhage or vasospasm. Although cellular and molecular mechanisms involved in METH-induced toxicity are not completely understood, changes in brain O2 may play an important role and contribute to METH-induced neurotoxicity including dopaminergic receptor degradation. Given that O2 is the terminal electron acceptor for many enzymes that are important in brain function, the impact of METH on brain tissue pO2 in vivo remains largely uncharacterized. This study investigated striatal tissue pO2 changes in male C57BL/6 mice (16–20g) following METH administration using EPR oximetry, a highly sensitive modality to measure pO2 in vivo, in situ and in real time. We demonstrate that 20 min after a single injection of METH (8 mg/kg i.v.), the striatal pO2 was reduced to 81% of the pretreatment level and exposure to METH for 3 consecutive days further attenuated striatal pO2 to 64%. More importantly, pO2 did not recover fully to control levels even 24 hrs after administration of a single dose of METH. and continual exposure to METH exacerbates the condition. We also show a reduction in cerebral blood flow associated with a decreased brain pO2 indicating an ischemic condition. Our findings suggests that administration of METH can attenuate brain tissue pO2, which may lead to hypoxic insult, thus a risk factor for METH-induced brain injury and the development of stroke in young adults. PMID:24412707

  5. In vivo evidence of methamphetamine induced attenuation of brain tissue oxygenation as measured by EPR oximetry.

    PubMed

    Weaver, John; Yang, Yirong; Purvis, Rebecca; Weatherwax, Theodore; Rosen, Gerald M; Liu, Ke Jian

    2014-03-01

    Abuse of methamphetamine (METH) is a major and significant societal problem in the US, as a number of studies have suggested that METH is associated with increased cerebrovascular events, hemorrhage or vasospasm. Although cellular and molecular mechanisms involved in METH-induced toxicity are not completely understood, changes in brain O? may play an important role and contribute to METH-induced neurotoxicity including dopaminergic receptor degradation. Given that O? is the terminal electron acceptor for many enzymes that are important in brain function, the impact of METH on brain tissue pO? in vivo remains largely uncharacterized. This study investigated striatal tissue pO? changes in male C57BL/6 mice (16-20 g) following METH administration using EPR oximetry, a highly sensitive modality to measure pO? in vivo, in situ and in real time. We demonstrate that 20 min after a single injection of METH (8 mg/kg i.v.), the striatal pO? was reduced to 81% of the pretreatment level and exposure to METH for 3 consecutive days further attenuated striatal pO? to 64%. More importantly, pO? did not recover fully to control levels even 24 h after administration of a single dose of METH and continual exposure to METH exacerbates the condition. We also show a reduction in cerebral blood flow associated with a decreased brain pO? indicating an ischemic condition. Our findings suggests that administration of METH can attenuate brain tissue pO?, which may lead to hypoxic insult, thus a risk factor for METH-induced brain injury and the development of stroke in young adults. PMID:24412707

  6. Hydrometeor Size Distribution Measurements by Imaging the Attenuation of a Laser Spot

    NASA Technical Reports Server (NTRS)

    Lane, John

    2013-01-01

    The optical extinction of a laser due to scattering of particles is a well-known phenomenon. In a laboratory environment, this physical principle is known as the Beer-Lambert law, and is often used to measure the concentration of scattering particles in a fluid or gas. This method has been experimentally shown to be a usable means to measure the dust density from a rocket plume interaction with the lunar surface. Using the same principles and experimental arrangement, this technique can be applied to hydrometeor size distributions, and for launch-pad operations, specifically as a passive hail detection and measurement system. Calibration of a hail monitoring system is a difficult process. In the past, it has required comparison to another means of measuring hydrometeor size and density. Using a technique recently developed for estimating the density of surface dust dispersed during a rocket landing, measuring the extinction of a laser passing through hail (or dust in the rocket case) yields an estimate of the second moment of the particle cloud, and hydrometeor size distribution in the terrestrial meteorological case. With the exception of disdrometers, instruments that measure rain and hail fall make indirect measurements of the drop-size distribution. Instruments that scatter microwaves off of hydrometeors, such as the WSR-88D (Weather Surveillance Radar 88 Doppler), vertical wind profilers, and microwave disdrometers, measure the sixth moment of the drop size distribution (DSD). By projecting a laser onto a target, changes in brightness of the laser spot against the target background during rain and hail yield a measurement of the DSD's second moment by way of the Beer-Lambert law. In order to detect the laser attenuation within the 8-bit resolution of most camera image arrays, a minimum path length is required. Depending on the intensity of the hail fall rate for moderate to heavy rainfall, a laser path length of 100 m is sufficient to measure variations in optical extinction using a digital camera. For hail fall only, the laser path may be shorter because of greater scattering due to the properties of hailstones versus raindrops. A photodetector may replace the camera in automated installations. Laser-based rain and hail measurement systems are available, but they are based on measuring the interruption of a thin laser beam, thus counting individual hydrometeors. These systems are true disdrometers since they also measure size and velocity. The method reported here is a simple method, requiring far less processing, but it is not a disdrometer.

  7. Delamination of southern Puna lithosphere revealed by body wave attenuation tomography

    NASA Astrophysics Data System (ADS)

    Liang, Xiaofeng; Sandvol, Eric; Kay, Suzanne; Heit, Benjamin; Yuan, Xiaohui; Mulcahy, Patrick; Chen, Chen; Brown, Larry; Comte, Diana; Alvarado, Patricia

    2014-01-01

    The southern Puna Plateau has been proposed to result from a major Pliocene delamination event that has previously been inferred from geochemical, geological, and some preliminary geophysical data. Seventy-five seismic stations were deployed across the southern Puna Plateau in 2007-2009 by scientists from the U.S., Germany, Chile, and Argentina to test the delamination model for the region. The Puna passive seismic stations were located between 25 and 28°S. Using the seismic waveform data collected from the PUNA experiment, we employ attenuation tomography methods to resolve both compressional and shear quality factors (Qp and Qs, respectively) in the crust and uppermost mantle. The images clearly show a high-Q Nazca slab subducting eastward beneath the Puna plateau and another high-Q block with a westward dip beneath the Eastern Cordillera. We suggest that the latter is a piece of delaminated South American lithosphere. A significant low-Q zone lies between the Nazca slab and the South American lithosphere and extends southward from the northern margin of the seismic array at 25°S before vanishing around 27.5°S. This low-Q zone extends farther west in the crust and uppermost mantle at the southern end of the seismic array. The low-Q zone reaches ~100 km depth beneath the northern part of the array but only ~50 km depth in the south. Lateral variations of the low-Q zone reflect the possible mechanism conversion between mantle upwelling related to delamination and dehydration. The depth of the Nazca slab as defined by Q images decreases from north to south beneath the plateau, which is consistent with the steep-flat transition of the angle of the subducting slab as defined by previous earthquake studies.

  8. Measurement of semi-rigid coaxial cables at cryogenic temperature -thermal conductance and attenuation-

    NASA Astrophysics Data System (ADS)

    Kasai, Soichi; Kushino, Akihiro

    2013-03-01

    We are developing semi-rigid coaxial cables for low temperature experiments which require fast readout with low noise. Coaxial cables used at low temperature are made of low thermal conductivity materials, such as stainless-steel, cupro-nickel and polytetrafluoroethylene to suppress heat penetration through cables. As the thermal conductivity of such alloys is affected by the thermal and mechanical treatment in forming process, we have to measure thermal property of coaxial cables after forming. The low thermal conductance of 5.5 cm specimen was measured by the steady-state heat-flow method with 1m long and thin niobium-titanium wiring for thermometers and heaters. Signal attenuation of coaxial cables was measured at 3K stage of an adiabatic demagnetization refrigerator. In order to cool center electrical conductor, the cables with 1m long length were coiled, and surrounded by copper blocks then attached to 3K stage. We successfully observed superconducting transition of center conductor of superconducting niobium-titanium coaxial cables with this method.

  9. The precise measurement of the attenuation coefficients of various IR optical materials applicable to immersion grating

    NASA Astrophysics Data System (ADS)

    Kaji, Sayumi; Sarugaku, Yuki; Ikeda, Yuji; Kobayashi, Naoto; Nakanishi, Kenshi; Kondo, Sohei; Yasui, Chikako; Kawakita, Hideyo

    2014-07-01

    Immersion grating is a next-generation diffraction grating which has the immersed the diffraction surface in an optical material with high refractive index of n > 2, and can provide higher spectral resolution than a classical reflective grating. Our group is developing various immersion gratings from the near- to mid-infrared region (Ikeda et al.1, 2, 3, 4, Sarugaku et al.5, and Sukegawa et al.6). The internal attenuation ?att of the candidate materials is especially very important to achieve the high efficiency immersion gratings used for astronomical applications. Nevertheless, because there are few available data as ?att < 0.01cm-1 in the infrared region, except for measurements of CVD-ZnSe, CVD-ZnS, and single-crystal Si in the short near-infrared region reported by Ikeda et al.7, we cannot select suitable materials as an immersion grating in an aimed wavelength range. Therefore, we measure the attenuation coefficients of CdTe, CdZnTe, Ge, Si, ZnSe, and ZnS that could be applicable to immersion gratings. We used an originally developed optical unit attached to a commercial FTIR which covers the wide wavelength range from 1.3?m to 28?m. This measurement system achieves the high accuracy of (triangle)?att ~ 0.01cm-1. As a result, high-resistivity single-crystal CdZnTe, single-crystal Ge, single-crystal Si, CVD-ZnSe, and CVD-ZnS show ?att < 0.01cm-1 at the wavelength range of 5.5 - 19.0?m, 2.0 - 10.5?m, 1.3 - 5.4?m, 1.7 - 13.2?m, and 1.9 - 9.2?m, respectively. This indicates that these materials are good candidates for high efficiency immersion grating covering those wavelength ranges. We plan to make similar measurement under the cryogenic condition as T <= 10K for the infrared, especially mid-infrared applications.

  10. Microwave velocity measurements of marginal detonation waves

    Microsoft Academic Search

    D H Edwards; G Hooper; R J Meddins

    1970-01-01

    A prerequisite to a study of a detonation wave structure is the establishment of an equilibrium frontal configuration, which is repeatable at equi-spaced distances along the detonation tube, together with a constant average wave velocity. A microwave interferometer is described which is capable of giving a continuous monitor of the velocity of a marginal planar detonation wave propagating in a

  11. Surface-wave attenuation and its lateral variation in the crust of the southwestern United States

    NASA Astrophysics Data System (ADS)

    Sholy, Beshara Ibrahim

    Shear wave Q (Qmu) models are obtained for a broad region of the southwestern United States. A single station method that compares observed amplitude spectra of fundamental and higher-mode Rayleigh waves to theoretically predicted spectra for assumed Qmu models is used to determine Q mu as a function of depth. Velocity structure and initial Qmu models are assumed for event-station pairs in which the events have known source depths and focal mechanisms. 164 event-station paths obtained from 33 earthquakes and 32 stations provide good path coverage for the region. The coverage is adequate to map lateral variations of Qmu at various depths in the continental crust of the southwestern United States. Two Qmu earth models of the crust are presented. Both models have three horizontal crustal layers of varying thickness overlying a uniform half-space. The analyses reveal that the Qmu variations correlate with changes in surface tectonics of the region. Average Qmu values for the upper crust for the whole region are found to vary between 55 and 75. These low values are expected for the seismically active and highly fractured crust of California and for the rifted Basin and Range province. Higher average Qmu values (103--116) are found at mid-crustal and lower-crustal depths. Qmu variations patterns are compared to geological and geophysical parameters of the southwestern United States, and found to partially correlate with heat flow patterns of the region.

  12. Measurement of Current Polarization by Doppler-Shifted Spin Waves

    E-print Network

    Measurement of Current Polarization by Doppler-Shifted Spin Waves P R O J E C T L E A D E R devices to measure spin wave propagation at sub-micrometer wavelengths in current- carrying ferromagnetic To develop methods for measuring the spin polarization of current in ferromagnetic metals, which is a pivotal

  13. Analysis of freak wave measurements in the Sea of Japan

    Microsoft Academic Search

    Nobuhito Mori; Paul C Liu; Takashi Yasuda

    2002-01-01

    This paper presents an analysis of a set of available freak wave measurements gathered from several periods of continuous wave recordings made in the Sea of Japan during 1986–1990 by the Ship Research Institute of Japan. The analysis provides an ideal opportunity to catch a glimpse of the statistics of freak waves in the ocean. The results show that a

  14. Measurements of shoaling internal waves and turbulence in an estuary

    E-print Network

    Measurements of shoaling internal waves and turbulence in an estuary Clark Richards,1 Daniel 2012; accepted 30 October 2012. [1] The shoaling of horizontally propagating internal waves may energetics, and two main features were studied. First, during a period of shoaling internal waves, turbulence

  15. Measurements of shoaling internal waves and turbulence in an estuary

    E-print Network

    Kelley, Dan

    Measurements of shoaling internal waves and turbulence in an estuary Clark Richards,1 Daniel internal waves may represent an important source of mixing and transport in estuaries and coastal seas of the turbulent energetics, and two main features were studied. First, during a period of shoaling internal waves

  16. Millimeter-wave channel measurements for indoor wireless communications

    Microsoft Academic Search

    G. A. Kalivas; M. El-Tanany; S. A. Mahmoud

    1992-01-01

    Propagation losses for the indoor radio channel at 21.6 GHz and 37.2 GHz are examined. The propagation measurements carried out are used to quantitatively present, through enveloped distribution, the effects of spatial fading, which is due to multipath propagation, and temporal fading, which is due to people moving in the building. Attenuation is given in the form of the exponent

  17. The MOSDEF Survey: Measurements of Balmer Decrements and the Dust Attenuation Curve at Redshifts z~1.4-2.6

    E-print Network

    Reddy, Naveen A; Shapley, Alice E; Freeman, William R; Siana, Brian; Coil, Alison L; Mobasher, Bahram; Price, Sedona H; Sanders, Ryan L; Shivaei, Irene

    2015-01-01

    We present results on the dust attenuation curve of z~2 galaxies using early observations from the MOSFIRE Deep Evolution Field (MOSDEF) survey. Our sample consists of 224 star-forming galaxies with nebular spectroscopic redshifts in the range z= 1.36-2.59 and high S/N measurements of, or upper limits on, the H-alpha and H-beta emission lines obtained with Keck/MOSFIRE. We construct composite SEDs of galaxies in bins of specific SFR and Balmer optical depth in order to directly constrain the dust attenuation curve from the UV through near-IR for typical star-forming galaxies at high redshift. Our results imply an attenuation curve that is very similar to the SMC extinction curve at wavelengths redward of 2500 Angstroms. At shorter wavelengths, the shape of the curve is identical to that of the Calzetti relation, but with a lower normalization (R_V). Hence, the new attenuation curve results in SFRs that are ~20% lower, and log stellar masses that are 0.16 dex lower, than those obtained with the Calzetti attenu...

  18. Measurements of Inertial Limit Alfven Wave Dispersion for Finite Perpendicular Wave Number C. A. Kletzing,1,* D. J. Thuecks,1

    E-print Network

    California at Los Angles, University of

    Measurements of Inertial Limit Alfve´n Wave Dispersion for Finite Perpendicular Wave Number C. A verified the correct E=B ratio for these waves [6,7]. Measurements of Alfve´n waves in the laboratory were temperature was measured with a swept Langmuir probe and found to be 1.9 eV in the region where the waves were

  19. Wind and wave measurements using complex ERS-2 SAR wave mode data

    Microsoft Academic Search

    Susanne Lehner; Johannes Schulz-Stellenfleth; Birgit Schättler; Helko Breit; Jochen Horstmann

    2000-01-01

    A global dataset of complex synthetic aperture (SAR) images is processed from wave mode raw data acquired by the ERS-2 satellite. Using these data, different algorithms for wind and wave measurements recently developed in view of future ENVISAT ASAR data are analyzed on a statistical basis. Different aspects of complex SAR wave mode processing with the DLR processor BSAR are

  20. Measurement of wind waves by means of a buoy accelerometer wave gauge

    Microsoft Academic Search

    A. V. Babanin; P. P. Verkeev; B. B. Krivinsky; V. G. Proshchenko

    1993-01-01

    An accelerometer buoy wave gauge developed in the Marine Hydrophysical Institute of the Ukrainian Academy of Sciences is described. This allows measurement of acceleration and the sea surface elevation in the system of reference connected with a buoy. The integral and frequency spectral characteristics of waves can be computed from the records of the wave gauge signal. The use of

  1. A COMPARISON OF MEASURED AND CALCULATED GAMMA RAY ATTENUATION FOR A COMMON COUNTING GEOMETRY

    SciTech Connect

    Gaylord, R F

    2004-02-26

    In order to perform quantitative gamma spectroscopy, it is necessary to know the sample-specific detection efficiency for photons as a function of energy. The detection efficiency, along with the branching ratio for the isotope and gamma ray of interest, is used to convert observed counts/second to actual disintegrations/second, and, hence, has a large effect on the accuracy of the measurement. In cases where the geometry of the source is simple and reproducible, such as a point source, small vial of solid, or jar of liquid, geometry-specific standards may be counted to determine the detection efficiency. In cases where the samples are large, irregular, or unique, this method generally cannot be used. For example, it is impossible to obtain a NIST-traceable standard glovebox or 55-gallon drum. In these cases, a combination of measured absolute detector efficiency and calculated sample-specific correction factors is commonly used. The correction factors may be calculated via Monte Carlo simulation of the item (the method used by Canberra's ISOCS system), or via semi-empirical calculation of matrix and container attenuations based on the thickness and composition of the container and radioactive matrix (ISOTOPIC by EG&G Ortec uses this method). The accuracy of these correction factors for specific geometries is often of vital interest when assessing the quality of gamma spectroscopy data. During the Building 251 Risk-Reduction Project, over 100 samples of high activity actinides will be characterized via gamma spectroscopy, typically without removing the material from the current storage containers. Most of the radioactive materials in B-251 are stored in cylindrical stainless steel canisters (called USV containers, after the Underground Storage Vaults they are commonly stored in), 13 cm in diameter, by 28 cm high, with walls that are 1.8 mm thick. While the actual samples have a variety of configurations inside the USV container, a very common configuration is the material (usually as an oxide powder pellet of approximately 2 cm diameter by {approx}2 mm thick) in a squat glass jar, with the jar placed in a thin steel food-pack can, which is then placed in the bottom of the USV canister. During data acquisition, the USV containers are typically rotated at approximately 4 rpm on a turntable to eliminate errors due to the material not being centered in the can, or attenuation not being isotropic. An aluminum plate is placed over the container, secured by three vertical rods, to securely hold the container. Pictures of both the containers, and this typical counting configuration are shown below.

  2. Non-linear random wave kinematics models verified against measurements in steep waves

    SciTech Connect

    Stansberg, C.T. [Norwegian Marine Technology Research Inst. A/S, Trondheim (Norway); Gudmestad, O.T. [Den Norske Stats Olijeselskap A.S., Stavanger (Norway)

    1996-12-31

    Measurements from an earlier experiment on random wave kinematics are compared to four different numerical wave models. The models are: Second-order random wave model, Hybrid wave model, Wheeler stretching, and a modified Wheeler stretching method. Wave elevation, horizontal fluid particle velocities and corresponding accelerations in steep individual waves are included in the comparison. Spatial velocity profiles, as well as time history profiles showing the kinematics at certain fixed vertical levels, are shown. It is found that the second order and the hybrid wave models generally predict the measured kinematics (velocities as well as accelerations) reasonably well. The Wheeler stretching method predicts velocities quite well at the free surface of crest peaks, while it underpredicts the velocities further below in the wave zone fluid. With the modified Wheeler stretching procedure this is improved.

  3. Comparing shear-wave velocity profiles inverted from multichannel surface wave with borehole measurements

    Microsoft Academic Search

    Jianghai Xia; Richard D. Miller; Choon B. Park; James A. Hunter; James B. Harris; Julian Ivanov

    2002-01-01

    Recent field tests illustrate the accuracy and consistency of calculating near-surface shear (S)-wave velocities using multichannel analysis of surface waves (MASW). S-wave velocity profiles (S-wave velocity vs. depth) derived from MASW compared favorably to direct borehole measurements at sites in Kansas, British Columbia, and Wyoming. Effects of changing the total number of recording channels, sampling interval, source offset, and receiver

  4. Attenuation length measurements of a liquid scintillator with LabVIEW and reliability evaluation of the device

    NASA Astrophysics Data System (ADS)

    Gao, Long; Yu, Bo-Xiang; Ding, Ya-Yun; Zhou, Li; Wen, Liang-Jian; Xie, Yu-Guang; Wang, Zhi-Gang; Cai, Xiao; Sun, Xi-Lei; Fang, Jian; Xue, Zhen; Zhang, Ai-Wu; Lü, Qi-Wen; Sun, Li-Jun; Ge, Yong-Shuai; Liu, Ying-Biao; Niu, Shun-Li; Hu, Tao; Cao, Jun; Lü, Jun-Guang

    2013-07-01

    An attenuation length measurement device was constructed using an oscilloscope and LabVIEW for signal acquisition and processing. The performance of the device has been tested in a variety of ways. The test results show that the set-up has a good stability and high precision (sigma/mean reached 0.4 percent). Besides, the accuracy of the measurement system will decrease by about 17 percent if a filter is used. The attenuation length of a gadolinium-loaded liquid scintillator (Gd-LS) was measured as 15.10±0.35 m where Gd-LS was heavily used in the Daya Bay Neutrino Experiment. In addition, one method based on the Beer-Lambert law was proposed to investigate the reliability of the measurement device, the R-square reached 0.9995. Moreover, three purification methods for Linear Alkyl Benzene (LAB) production were compared in the experiment.

  5. Frequency-dependent squeeze-amplitude attenuation and squeeze-angle rotation by electromagnetically induced transparency for gravitational-wave interferometers

    Microsoft Academic Search

    Eugeniy E. Mikhailov; Keisuke Goda; Thomas Corbitt; Nergis Mavalvala

    2006-01-01

    We study the effects of frequency-dependent squeeze-amplitude attenuation and squeeze-angle rotation by electromagnetically induced transparency (EIT) on gravitational-wave (GW) interferometers. We propose the use of low-pass, bandpass, and high-pass EIT filters, an S-shaped EIT filter, and an intracavity EIT filter to generate frequency-dependent squeezing for injection into the antisymmetric port of GW interferometers. We find that the EIT filters have

  6. Changes in clot lysis levels of reteplase and streptokinase following continuous wave ultrasound exposure, at ultrasound intensities following attenuation from the skull bone

    Microsoft Academic Search

    Bjarne Madsen Härdig; Jonas Carlson; Anders Roijer

    2008-01-01

    BACKGROUND: Ultrasound (US) has been used to enhance thrombolytic therapy in the treatment of stroke. Considerable attenuation of US intensity is however noted if US is applied over the temporal bone. The aim of this study was therefore to explore possible changes in the effect of thrombolytic drugs during low-intensity, high-frequency continuous-wave ultrasound (CW-US) exposure. METHODS: Clots were made from

  7. Measurement of the Gouy phase anomaly for electron waves

    NASA Astrophysics Data System (ADS)

    Petersen, T. C.; Paganin, D. M.; Weyland, M.; Simula, T. P.; Eastwood, S. A.; Morgan, M. J.

    2013-10-01

    We measure the Gouy phase anomaly for matter waves using in-line holography to retrieve the full complex field of an astigmatic electron wave function. Sequential phase shifts of ?/2 rad are observed for electron trajectories along the optic axis that pass through each line-focus caustic of subnanometer transverse width. Our observations demonstrate that anomalous phase shifts of matter waves in the vicinity of caustics can be robustly measured using phase retrieval, extending the current scope of singular electron optics.

  8. Short distance attenuation measurements at 900 MHz and 1.8 GHz using low antenna heights for microcells

    Microsoft Academic Search

    PHILIP HARLEY

    1989-01-01

    Short-distance, low-antenna-height signal attenuation measurements are presented in connection with their use in the design of future microcell cellular radio networks. Measurements presented are based on the propagation along busy city streets in a direction radial to a fixed antenna site. Antenna heights between 5 m and 20 m were chosen for the fixed site, while 1.5 m was chosen

  9. Long-Term Change of Sound Wave Propagation Attenuation Due to the Effects of Ocean Acidification

    NASA Astrophysics Data System (ADS)

    Gotoh, S.; Tsuchiya, T.; Hiyoshi, Y.

    2014-12-01

    In recent years, the concentration of carbon dioxide in the atmosphere is increasing due to global warming. And, the ocean acidification advances because this melts into seawater, pH decrease in seawater are concerned. The sound wave to propagate seawater, pH is known to affect absorption loss (?) by chemical buffer effects of the seawater. However, conventionally, ? has not been investigated much in the calculation of pH. Therefore, when calculating the propagation distance in the sonar equation, pH =8~8.1 (Weak alkaline) are used empirically. Therefore we used an actual value of pH of 30 years from 1984 in the sea near the Japan, and investigated change over the years of absorption loss (?) at some frequency. As a result, we found that ? value decreases gradually in the past 30 years, as high-latitude decreases. Further, the future, assuming that ocean acidification is more advanced, and to simulate a change of the absorption loss and propagation loss in end of this century using the pH value reported from the "Intergovernmental Panel on Climate Change" (IPCC). As a result, it was just suggested that ? decreased more in the end of this century and affected the submarine detection. In addition, in recent years, we examined the effects of noise that offshore wind power construction proceeds in each country emits gives to the underwater sound. As a result, in the end of this century, an underwater noise increases about 17%, and underwater sound environmental degradation of the sea is concerned.

  10. Chemical amplification--cavity attenuated phase shift spectroscopy measurements of atmospheric peroxy radicals.

    PubMed

    Wood, Ezra C; Charest, John R

    2014-10-21

    We describe a new instrument for the quantification of atmospheric peroxy radicals (HO2, CH3O2, C2H5O2, etc.) using the chemical amplification method. Peroxy radicals are mixed with high concentrations of NO and CO, causing a chain reaction that produces a measurable increase in NO2 which is quantified by cavity attenuated phase shift (CAPS) spectroscopy, a highly sensitive spectroscopic detection technique. The instrument utilizes two identical reaction chambers, each with a dedicated CAPS NO2 sensor. Similar to all dual-channel chemical amplifiers, one reaction chamber operates in amplification or "ROx" mode and the other in background or "Ox" mode. The peroxy radical mixing ratio is determined by the difference between the two channels' NO2 readings divided by a laboratory-determined chain length. Each reaction chamber alternates between ROx and Ox mode on an anti-synchronized schedule, eliminating the effect of CAPS baseline offsets on the calculated peroxy radical concentrations. The chain length is determined by a new calibration method: peroxyacetyl and methyl peroxy radicals are produced by the photolysis of acetone and quantified as NO2 following reaction with excess NO. We demonstrate the performance of the instrument with results from ambient sampling in Amherst and several diagnostics of its precision. The detection limit while sampling ambient air at a relative humidity (RH) of 40% is 0.6 ppt (1 min average, signal-to-noise ratio =2), with an estimated accuracy of 25% (2?). PMID:25260158

  11. High-Frequency Acoustic Wave Measurements in Air

    Microsoft Academic Search

    J. D. Fox; B. T. Khuri-Yakub; G. S. Kino

    1983-01-01

    We have constructed focused and unfocused acoustic transducers for excitation of waves in air. These transducers operate at 1 and 2 MHz , respectively, and employ a quarter wavelength matching layer. we can transmit waves over distances of 1-40 cm . We have constructed systems for phase measurements and for pulse transit time measurements. At 1 MHz , the typical

  12. High frequency measurement of P- and S-wave velocities on crystalline rock massif surface - methodology of measurement

    NASA Astrophysics Data System (ADS)

    Vilhelm, Jan; Slavík, Lubomír

    2014-05-01

    For the purpose of non-destructive monitoring of rock properties in the underground excavation it is possible to perform repeated high-accuracy P- and S-wave velocity measurements. This contribution deals with preliminary results gained during the preparation of micro-seismic long-term monitoring system. The field velocity measurements were made by pulse-transmission technique directly on the rock outcrop (granite) in Bedrichov gallery (northern Bohemia). The gallery at the experimental site was excavated using TBM (Tunnel Boring Machine) and it is used for drinking water supply, which is conveyed in a pipe. The stable measuring system and its automatic operation lead to the use of piezoceramic transducers both as a seismic source and as a receiver. The length of measuring base at gallery wall was from 0.5 to 3 meters. Different transducer coupling possibilities were tested namely with regard of repeatability of velocity determination. The arrangement of measuring system on the surface of the rock massif causes better sensitivity of S-transducers for P-wave measurement compared with the P-transducers. Similarly P-transducers were found more suitable for S-wave velocity determination then P-transducers. The frequency dependent attenuation of fresh rock massif results in limited frequency content of registered seismic signals. It was found that at the distance between the seismic source and receiver from 0.5 m the frequency components above 40 kHz are significantly attenuated. Therefore for the excitation of seismic wave 100 kHz transducers are most suitable. The limited frequency range should be also taken into account for the shape of electric impulse used for exciting of piezoceramic transducer. The spike pulse generates broad-band seismic signal, short in the time domain. However its energy after low-pass filtration in the rock is significantly lower than the energy of seismic signal generated by square wave pulse. Acknowledgments: This work was partially supported by the Technology Agency of the Czech Republic, project No. TA 0302408

  13. Study of Dual-Wavelength PIA Estimates: Ratio of Ka- and Ku-band Attenuations Obtained from Measured DSD Data

    NASA Astrophysics Data System (ADS)

    Liao, L.; Meneghini, R.; Tokay, A.

    2014-12-01

    Accurate attenuation corrections to the measurements of the Ku- and Ka-band dual-wavelength precipitation radar (DPR) aboard the Global Precipitation Measurement (GPM) satellite is crucial for estimates of precipitation rate and microphysical properties of hydrometeors. Surface reference technique (SRT) provides a means to infer path-integrated attenuation (PIA) by comparing differences of normalized surface cross sections (?0) between rain and rain-free areas. Although single-wavelength SRT has been widely used in attenuation correction for airborne/spaceborne radar applications, its accuracy relies on the variance of ?0 in rain-free region. Dual-wavelength surface reference technique (DSRT) has shown promising ways to improve accuracy in PIA estimates over single-wavelength as a result of that the variance of the difference of PIA between two wavelengths (?PIA) is much smaller than the variance of ?0 at single wavelength arising from high correlation of ?0 between Ku- and Ka-bands. However, derivation of PIA at either wavelength from DSRT requires an assumption of the ratio of Ka- and Ku-band PIAs (p). Inappropriate assumption of this ratio will lead to the bias of PIA estimates. In this study the ratio p will be investigated through measured DSD data. The attenuation coefficients at Ku and Ka bands are first computed directly from measured DSD spectra, and then regression analysis is performed to the data points (Ku- and Ka-band attenuation coefficients) in obtaining p values for rain. Taking an advantage of large collection of the DSD measurements from various GPM Ground Validation (GPM GV) programs, the results of the ratio p will be examined from different climatological regimes. Because PIA is affected by all types of hydrometeors contained in the columns of radar measurements, the synthetic profiles composed of different types of hydrometeors are constructed using measured DSD to look into impacts of different phase hydrometeors on the p values. To generate these profiles fully-, partially- and un-correlated DSD data are employed in an attempt to describe wide dynamic range of microphysical structures of hydrometeors. Bright-band model is employed to take into account of mixed-phase region, and additional attenuations due to cloud water are also included in the profiles.

  14. Ultrasonic Attenuation in Lanthanum Monochalcogenides

    Microsoft Academic Search

    Raja Ram Yadav; Devraj Singh

    2001-01-01

    Ultrasonic attenuation due to phonon-phonon interaction and thermoelastic relaxation are studied in Lanthanum Monochalcogenides in direction at different higher temperatures. For evaluation of ultrasonic absorption coefficients the second and third order elastic constants (SOEC) and (TOEC) are also calculated. Shear wave attenuation shows maximum along propagation direction with polarized along and the attenuation increases at higher temperatures. Thermo-elastic loss is

  15. Wind-wave tank measurements of bound and freely propagating short gravity-capillary waves

    Microsoft Academic Search

    Martin Gade; Werner Alpers; Stanislav A. Ermakov; Heinrich Hühnerfuss; Philipp A. Lange

    1998-01-01

    Measurements of the surface elevation and slope and of the backscattered radar power at X and Ka band were carried out in a wind-wave tank with mechanically generated gravity waves as well as with wind waves on slick-free and slick-covered water surfaces. The measured radar Doppler shifts show that on a slick-free water surface, bound gravity-capillary (X and Ka band

  16. Sub-wavelength position measurements with running wave driving fields

    E-print Network

    J. Evers; S. Qamar

    2009-01-29

    A scheme for sub-wavelength position measurements of quantum particles is discussed, which operates with running-wave laser fields as opposed to standing wave fields proposed in previous setups. The position is encoded in the phase of the applied fields rather than in the spatially modulated intensity of a standing wave. Therefore, disadvantages of standing wave schemes such as cases where the atom remains undetected since it is at a node of the standing wave field are avoided. Reversing the directions of parts of the driving laser fields allows to switch between different magnification levels, and thus to optimize the localization.

  17. An improvement to the full-foil mapping technique for high accuracy measurement of X-ray mass attenuation coefficients

    NASA Astrophysics Data System (ADS)

    Rae, Nicholas A.; Glover, Jack L.; Chantler, Christopher T.

    2010-07-01

    The limiting uncertainty in recent high accuracy measurements of the mass attenuation coefficient is the measurement of the integrated column density. An improvement in the design of the absorption foil holder is described which reduces the integrated column density uncertainty. The new design allows the edges of the foil to be more accurately mapped by the X-ray beam by reducing the largest source of uncertainty in the foil mapping: the uncertainty in the points along the foil edge. The method is shown to reduce the uncertainty in measurements of the mass attenuation coefficient of zinc foils. The reduced uncertainty in the full-foil mapping will allow the X-ray Extended Range Technique (XERT) to be applied to small non-metallic absorption foils more accurately.

  18. Attenuation Tomography of the Upper Mantle

    NASA Astrophysics Data System (ADS)

    Adenis, A.; Debayle, E.; Ricard, Y. R.

    2014-12-01

    We present a 3-D model of surface wave attenuation in the upper mantle. The model is constrained by a large data set of fundamental and higher Rayleigh mode observations. This data set consists of about 1,800,000 attenuation curves measured in the period range 50-300s by Debayle and Ricard (2012). A careful selection allows us to reject data for which measurements are likely biased by the poor knowledge of the scalar seismic moment or by a ray propagation too close to a node of the source radiation pattern. For each epicenter-station path, elastic focusing effects due to seismic heterogeneities are corrected using DR2012 and the data are turned into log(1/Q). The selected data are then combined in a tomographic inversion using the non-linear least square formalism of Tarantola and Valette (1982). The obtained attenuation maps are in agreement with the surface tectonic for periods and modes sensitive to the top 200km of the upper mantle. Low attenuation regions correlate with continental shields while high attenuation regions are located beneath young oceanic regions. The attenuation pattern becomes more homogeneous at depths greater than 200 km and the maps are dominated by a high quality factor signature beneath slabs. We will discuss the similarities and differences between the tomographies of seismic velocities and of attenuations.

  19. Dual shear wave induced laser speckle contrast signal and the improvement in shear wave speed measurement.

    PubMed

    Li, Sinan; Cheng, Yi; Eckersley, Robert J; Elson, Daniel S; Tang, Meng-Xing

    2015-06-01

    Shear wave speed is quantitatively related to tissue viscoelasticity. Previously we reported shear wave tracking at centimetre depths in a turbid optical medium using laser speckle contrast detection. Shear wave progression modulates displacement of optical scatterers and therefore modulates photon phase and changes the laser speckle patterns. Time-resolved charge-coupled device (CCD)-based speckle contrast analysis was used to track shear waves and measure the time-of-flight of shear waves for speed measurement. In this manuscript, we report a new observation of the laser speckle contrast difference signal for dual shear waves. A modulation of CCD speckle contrast difference was observed and simulation reproduces the modulation pattern, suggesting its origin. Both experimental and simulation results show that the dual shear wave approach generates an improved definition of temporal features in the time-of-flight optical signal and an improved signal to noise ratio with a standard deviation less than 50% that of individual shear waves. Results also show that dual shear waves can correct the bias of shear wave speed measurement caused by shear wave reflections from elastic boundaries. PMID:26114021

  20. Dual shear wave induced laser speckle contrast signal and the improvement in shear wave speed measurement

    PubMed Central

    Li, Sinan; Cheng, Yi; Eckersley, Robert J; Elson, Daniel S; Tang, Meng-Xing

    2015-01-01

    Shear wave speed is quantitatively related to tissue viscoelasticity. Previously we reported shear wave tracking at centimetre depths in a turbid optical medium using laser speckle contrast detection. Shear wave progression modulates displacement of optical scatterers and therefore modulates photon phase and changes the laser speckle patterns. Time-resolved charge-coupled device (CCD)-based speckle contrast analysis was used to track shear waves and measure the time-of-flight of shear waves for speed measurement. In this manuscript, we report a new observation of the laser speckle contrast difference signal for dual shear waves. A modulation of CCD speckle contrast difference was observed and simulation reproduces the modulation pattern, suggesting its origin. Both experimental and simulation results show that the dual shear wave approach generates an improved definition of temporal features in the time-of-flight optical signal and an improved signal to noise ratio with a standard deviation less than 50% that of individual shear waves. Results also show that dual shear waves can correct the bias of shear wave speed measurement caused by shear wave reflections from elastic boundaries.

  1. New constraints on the properties of the Yellowstone mantle plume from P and S wave attenuation tomography

    Microsoft Academic Search

    David C. Adams; Eugene D. Humphreys

    2010-01-01

    We estimate attenuation (t*) for teleseismic P and S arrivals to seismometers in the Yellowstone Intermountain Seismic Array; tomographically invert these data for upper mantle Qp-1 and Qs-1 structure; and, with the aid of the upper mantle velocity model of Waite et al. (2006), interpret the results for mantle temperature, partial melt, and water content. Because attenuation analysis is susceptible

  2. Regional body-wave attenuation using a coda source normalization method: Application to MEDNET records of earthquakes in Italy

    Microsoft Academic Search

    William R. Walter; Kevin Mayeda; Luca Malagnini; Laura Scognamiglio

    2007-01-01

    We develop a new methodology to determine apparent attenuation for the regional seismic phases Pn, Pg, Sn, and Lg using coda-derived source spectra. The apparent Q, combining path and site attenuation, is determined from the difference between the geometrical spreading-corrected amplitude and the independently determined source spectra derived from the coda methodology. We apply the technique to 50 earthquakes with

  3. Direct measurements of neutral wave characteristics in the thermosphere

    NASA Technical Reports Server (NTRS)

    Potter, W. E.; Kayser, D. C.; Mauersberger, K.

    1976-01-01

    The elliptical and circular phases of the Atmosphere Explorer-C satellite have provided the basis for a study of the neutral wave characteristics in the thermosphere using data collected by the open source mass spectrometer used to measure both reactive (O,N) and nonreactive (O2, N2, He, Ar) constituents. The phase relationships between the constituents are discussed and the results of a wave occurrence and amplitude survey covering 338 despun orbits in which the local time and latitude characteristics of the waves are presented are discussed. Conclusions based on this survey are tested in a study of waves measured at high latitudes during a geomagnetic storm.

  4. A ``gentle'' nodal suspension for measurements of the acoustic attenuation in materials

    NASA Astrophysics Data System (ADS)

    Cesarini, E.; Lorenzini, M.; Campagna, E.; Martelli, F.; Piergiovanni, F.; Vetrano, F.; Losurdo, G.; Cagnoli, G.

    2009-05-01

    Loss angle measurements in ultralow mechanical loss materials is normally affected by a large systematic error due to the excess losses introduced by the suspension system used to hold the samples. Crystals such as sapphire and silicon or amorphous materials such as fused silica can have loss angles in the range of 10-10-10-7; such materials are of extreme interest in the detection of small displacements as it is required in quantum measurements, frequency stabilization, Micro Electro-Mechanical Systems (MEMS), and gravitational wave research. In the system proposed here the sample is suspended in equilibrium on top of a sphere, touching on one of the nodal points of vibration. The advantage of this system, as compared to others used so far, is twofold: (i) one surface only of the sample is touched and the contact surface is minimized because of the absence of applied forces; (ii) some relevant parameters of the suspension can be measured and eventually varied, giving the experimentalist the possibility to identify whether the measured loss is limited by the suspension system in use or it is an intrinsic property of the sample under investigation. The measurements of a 75 mm diameter and 3 mm thickness disk of Suprasil®311 gave a loss angle ? of 5×10-8.

  5. Precipitation-attenuation studies based on measurements of ATS-6 20/30-GHz beacon signals at Clarksburg, Maryland

    NASA Technical Reports Server (NTRS)

    Fang, D. J.; Harris, J. M.

    1976-01-01

    Radiometric sky temperature and minute precipitation measurements were intended to broaden the data base required to advance the understanding of the propagation characteristics of the earth-satellite path at frequencies over 10 GHz. Analyses of the data collected from the measurement program have established a detailed correlation between the satellite signal and the signals from auxiliary ground-based measurements. The indirectly derived statistics agreed reasonably well (or can be reconciled) with the earlier published results. The correlations may therefore be used for indirectly estimating long term cumulative attenuation statistics in the absence of direct satellite signal measurements.

  6. Global models of seismic attenuation in the upper mantle

    NASA Astrophysics Data System (ADS)

    Selby, N.

    2003-04-01

    Measurement of the intrinsic attenuation characteristics of the Earth has proved to be one of the most difficult problems in global seismology. Essentially, this is because the amplitudes and frequency content of seismic waves, used to measure attenuation, are affected by errors in the determination of the magnitudes and source mechanisms of seismic disturbances, and by variations in the elastic structure of the Earth. Hence the relationship between `apparent' attenuation, measured by seismology, and intrinsic attenuation, which can be related to the anelastic properties of the Earth, is problematical. Here I review some recent tomographic global models of Q?, intrinsic shear attenuation, in the upper mantle, and compare these results with other published models. I also discuss the wider importance of anelasticity to problems in observational seismology.

  7. Interferometric measurement of the biphoton wave function

    E-print Network

    Federica A. Beduini; Joanna A. Zieli?ska; Vito G. Lucivero; Yannick A. de Icaza Astiz; Morgan W. Mitchell

    2014-07-29

    Interference between an unknown two-photon state (a "biphoton") and the two-photon component of a reference state gives a phase-sensitive arrival-time distribution containing full information about the biphoton temporal wave function. Using a coherent state as a reference, we observe this interference and reconstruct the wave function of single-mode biphotons from a low-intensity narrowband squeezed vacuum state.

  8. HF radar measurements of long ocean waves

    Microsoft Academic Search

    B. J. Lipa; D. E. Barrick; J. W. Maresca

    1981-01-01

    Sea-echo data from three separate narrow-beam HF radar experiments on the Pacific Ocean are analyzed here by techniques presented in Lipa and Barrick (1980). Only those wave spectral components whose periods exceeded 10 s were included. Close agreement of radar-deduced wave field parameters with surface observations confirms the validity of the second-order theoretical solution for the echo Doppler spectrum, upon

  9. Modified cavity attenuated phase shift (CAPS) method for airborne aerosol light extinction measurement

    NASA Astrophysics Data System (ADS)

    Perim de Faria, Julia; Bundke, Ulrich; Freedman, Andrew; Petzold, Andreas

    2015-04-01

    Monitoring the direct impact of aerosol particles on climate requires the consideration of at least two major factors: the aerosol single-scattering albedo, defined as the relation between the amount of energy scattered and extinguished by an ensemble of aerosol particles; and the aerosol optical depth, calculated from the integral of the particle extinction coefficient over the thickness of the measured aerosol layer. Remote sensing networks for measuring these aerosol parameters on a regular basis are well in place (e.g., AERONET, ACTRIS), whereas the regular in situ measurement of vertical profiles of atmospheric aerosol optical properties remains still an important challenge in quantifying climate change. The European Research Infrastructure IAGOS (In-service Aircraft for a Global Observing System; www.iagos.org) responds to the increasing requests for long-term, routine in situ observational data by using commercial passenger aircraft as measurement platform. However, scientific instrumentation for the measurement of atmospheric constituents requires major modifications before being deployable aboard in-service passenger aircraft. Recently, a compact and robust family of optical instruments based on the cavity attenuated phase shift (CAPS) technique has become available for measuring aerosol light extinction. In particular, the CAPS PMex particle optical extinction monitor has demonstrated sensitivity of less than 2 Mm-1 in 1 second sampling period; with a 60 s averaging time, a detection limit of less than 0.3 Mm-1 can be achieved. While this technique was successfully deployed for ground-based atmospheric measurements under various conditions, its suitability for operation aboard aircraft in the free and upper free troposphere still has to be demonstrated. Here, we report on the modifications of a CAPS PMex instrument for measuring aerosol light extinction on aircraft, and subsequent laboratory tests for evaluating the modified instrument prototype: (1) In a first set of tests, the robustness of the method was demonstrated down to pressure levels below 200 hPa, using air and CO2 as test gases. Rayleigh scattering cross-section values for both gases deviated by less than 5 % from literature data for all investigated pressure levels.(2) The measurement of aerosol particles at lower pressure levels required the modification of the air flow handling. A new flow scheme using mass flow controllers and a revised vacuum pump set-up was developed and successfully tested. The overall reduction of the instrument noise level to values less than 0.15 Mm-1 was achieved. (3) Polydisperse laboratory-generated ammonium sulphate particles and monodisperse polystyrene latex spheres where used to evaluate the instrument operation for the pressure range from 1000 hPa to less than 200 hPa against an optical particle counter. Reference aerosol extinction coefficients were calculated from measured size distributions, using Mie theory. We found less than 10 % deviation between the CAPS PMex instrument response and calcuated extinction coefficients over the investigated pressure range.

  10. New Laboratory-Based Attenuation Measurements on Ice to Support Tidal Heating Models

    NASA Astrophysics Data System (ADS)

    Castillo-Rogez, J.; Choukroun, M.; Young, J.; Zhong, F.; Engelhardt, H.; Barmatz, M.

    2008-12-01

    The response of icy satellite materials to tidal stress has important consequences on their geophysical, geological, and dynamical evolution. The major issue with modeling the tidal response of these objects is that the viscoelastic properties of planetary material are not constrained by laboratory measurements for the relevant frequency range 10e-7 to 10e-5 Hz. While the Maxwell model is usually applied in icy satellite tidal modeling, laboratory measurements for the Earth's mantle have shown that this model is not applicable at forcing frequencies away from the Maxwell frequency. Alternative models (e.g., Andrade, Cole) based on measurements on silicates or terrestrial ice sheets may be better suited to describe ice attenuation, but they have not been introduced in planetary science studies, in part because laboratory measurements are necessary in order to warrant their extrapolation to conditions applicable to icy satellites. The reason why the laboratory data needed for modeling tidal processes at icy satellites are missing is that it is a challenge to achieve measurements at the low stress, low frequencies, and cryogenic conditions relevant to these objects. In the JPL Ice Physical Properties Laboratory an Instron compression system has been implemented with the capability to measure the phase lag between strain and stress, i.e., the internal friction, of an icy sample at frequencies as low as Enceladus' tidal forcing frequency, temperatures as low as 90 K, and cyclic peak stress lower than 0.1 MPa, characteristic of tidal stress at Enceladus or Europa. We will present the first measurements obtained with this system on monocrystalline ice in the frequency range 6x10e-6 to 10e-2 Hz and temperature range 233 - 253 K. We observed a change in frequency-dependence of the friction coefficient at a frequency about the inverse of the Maxwell time. While the Andrade model can fit the phase lags measured over the entire frequency range, it fails to reproduce the effective moduli measured at frequencies higher than 10e-5 Hz. On the other hand, the model developed by Cole (Philos. Mag. A, 72, 231-248, 1995) can account for both the phase lag and effective moduli data, but we had to determine two different sets of parameters in order to characterize the ice viscoelasticity at frequencies higher than the inverse of the Maxwell time, and lower than this reference. We will also present preliminary measurements on polycrystalline ice. Acknowledgements: This work has been conducted at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Copyright 2008 California Institute of Technology. Government sponsorship acknowledged. Part of this work was also carried out in the Mars and Ice Simulation Laboratory at Caltech.

  11. Terahertz reflection response measurement using a phonon polariton wave

    NASA Astrophysics Data System (ADS)

    Inoue, Hayato; Katayama, Kenji; Shen, Qing; Toyoda, Taro; Nelson, Keith A.

    2009-03-01

    We developed a new technique for the measurement of terahertz reflection responses utilizing a propagating phonon polariton wave. Frequency tunable phonon polariton waves were generated by the recently developed continuously variable spatial frequency transient grating method [K. Katayama, H. Inoue, H. Sugiya, Q. Shen, T. Taro, and K. A. Nelson, Appl. Phys. Lett. 92, 031906 (2008)]. The phonon polariton wave traveled in a ferroelectric crystal in an in-plane direction with an inclined angle of 26°, and the wave reflected at the crystal edge where a sample was positioned. The reflected polariton wave was detected by the same method as that used for the generation of the polariton waves. By comparing the reflection intensities in the presence and absence of the sample, reflectivity of the polariton wave was calculated, and the refractive index and absorption in the terahertz region were obtained.

  12. Global Measurements of Stratospheric Mountain Waves from Space

    NASA Technical Reports Server (NTRS)

    Eckermann, Stephen D.; Preusse, Peter; Jackman, Charles H. (Technical Monitor)

    1999-01-01

    Temperatures acquired by the Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) during shuttle mission STS-66 have provided measurements of stratospheric mountain waves from space. Large-amplitude, long-wavelength mountain waves at heights of 15 to 30 kilometers above the southern Andes Mountains were observed and characterized, with vigorous wave breaking inferred above 30 kilometers. Mountain waves also occurred throughout the stratosphere (15 to 45 kilometers) over a broad mountainous region of central Eurasia. The global distribution of mountain wave activity accords well with predictions from a mountain wave model. The findings demonstrate that satellites can provide the global data needed to improve mountain wave parameterizations and hence global climate and forecast models.

  13. Broadband superheterodyne tracking circuits for millimeter-wave measurements

    SciTech Connect

    Doane, J.L.

    1980-03-01

    Superheterodyne stimulus-response measurements can be made with high dynamic range, but are often sensitive to oscillator frequency drift and noise. The usual techniques for reducing this sensitivity often become impractical at millimeter-wave frequencies and above. This paper describes a feedforward tracking technique and its application to single frequency millimeter-wave interferometry and Doppler-shift scattering measurements on tokamak plasmas. Swept frequency transmission measurements can also be made with high dynamic range using this technique.

  14. Broadband superheterodyne tracking circuits for millimeter-wave measurements.

    PubMed

    Doane, J L

    1980-03-01

    Superheterodyne stimulus-response measurements can be made with high dynamic range, but are often sensitive to oscillator frequency drift and noise. The usual techniques for reducing this sensitivity often become impractical at millimeter-wave frequencies and above. This paper describes a feedforward tracking technique and its application to single frequency millimeter-wave interferometry and Doppler-shift scattering measurements on tokamak plasmas. Swept frequency transmission measurements can also be made with high dynamic range using this technique. PMID:18647058

  15. Time-Resolved Measurements of Electron Number Density and Collision Frequency Using Microwave Attenuation and Phase Shift

    Microsoft Academic Search

    Mostofa Howlader; Yunqiang Yang; J. Reece Roth

    2003-01-01

    Microwave interferometry is a well-established non-perturbing plasma diagnostic technique. Compared with other diagnostic techniques, it is more robust and reliable in experimental applications. We describe an extended microwave interferometry technique to characterize the time-resolved electron number density and collision frequency of a fluorescent light tube plasma. This technique is based on a modern vector network analyzer and measures the attenuation

  16. Millimeter-wave polarimetric measurements of artificial and natural targets

    Microsoft Academic Search

    M. W. Whitt; F. T. Ulaby

    1988-01-01

    The millimeter-wave polarimeter (MMP), a scatterometer system uses the HP 8510A vector network analyzer for coherent processing of the received signal, provides the polarization and phase measurement capability needed to measure the complete scattering matrix of a given target. A calibration and measurement technique that was used with the MMP at 35 GHz to measure the scattering matrix for both

  17. Volumetric measurements of a spatially growing dust acoustic wave

    SciTech Connect

    Williams, Jeremiah D. [Physics Department, Wittenberg University, Springfield, Ohio 45504 (United States)

    2012-11-15

    In this study, tomographic particle image velocimetry (tomo-PIV) techniques are used to make volumetric measurements of the dust acoustic wave (DAW) in a weakly coupled dusty plasma system in an argon, dc glow discharge plasma. These tomo-PIV measurements provide the first instantaneous volumetric measurement of a naturally occurring propagating DAW. These measurements reveal over the measured volume that the measured wave mode propagates in all three spatial dimensional and exhibits the same spatial growth rate and wavelength in each spatial direction.

  18. Measurements of the Gravity Waves Velocity

    E-print Network

    V. A. Dubrovskiy

    2001-06-20

    Some results are presented of the Earth's microseismic background. It is assumed that background peaks should correspond to the resonance gravity-wave exchange in the system of two gravity-connected bodies. The microseismic spectrum is compared with the distribution of gravity potential of the nearest stars. A close peak-to-peak correspondence is found. This correspondence and resonance condition lead to an evaluation of the gravity-wave velocity. The resulting value is nine orders of magnitude more than the velocity of light. Some consequences of such result are discussed.

  19. Estimating directional wave spectrum based on stationary ship motion measurements

    Microsoft Academic Search

    Eduardo A. Tannuri; João V. Sparano; Alexandre N. Simos; José J. Da Cruz

    2003-01-01

    Useful information can be derived from on-board estimation of the directional wave spectrum of the sea, especially concerning feed forward control of dynamically positioned systems. This work discusses the feasibility of using stationary ship motion measurements for in-site directional wave spectrum estimation, focusing on the particular problems that may arise in the application of adapted estimation methods to this kind

  20. A New Wave Equation For a Continuous Nondemolition Measurement

    E-print Network

    V. P. Belavkin

    2005-12-17

    A stochastic model for nondemolition continuous measurement in a quantum system is given. It is shown that the posterior dynamics, including a continuous collapse of the wave function, is described by a nonlinear stochastic wave equation. For a particle in an electromagnetic field it reduces the Schroedinger equation with extra imaginary stochastic potentials.

  1. Ocean wave dispersion surface measured with airborne IR imaging system

    Microsoft Academic Search

    John P. Dugan; Henry H. Suzukawa; Charles P. Forsyth; Morton S. Farber

    1996-01-01

    Image sequences of the ocean have been collected at long range and low grazing angle with an airborne infrared system. The images are geographically registered, and 3D frequency-wavenumber spectra are calculated and shown to have a strong 2D dispersion surface that is characteristic of wind waves and swell. Wave directions compare well with in situ measurements, and their speeds are

  2. Measurement of Oblique Impact-generated Shear Waves

    NASA Technical Reports Server (NTRS)

    Dahl, J. M.; Schultz, P. H.

    2001-01-01

    Experimental strain measurements reveal that oblique impacts can generate shear waves with displacements as large as those in the P-wave. Large oblique impacts may thus be more efficient sources of surface disruption than vertical impacts. Additional information is contained in the original extended abstract.

  3. Full Wave Analysis of RF Signal Attenuation in a Lossy Rough Surface Cave using a High Order Time Domain Vector Finite Element Method

    SciTech Connect

    Pingenot, J; Rieben, R; White, D; Dudley, D

    2005-10-31

    We present a computational study of signal propagation and attenuation of a 200 MHz planar loop antenna in a cave environment. The cave is modeled as a straight and lossy random rough wall. To simulate a broad frequency band, the full wave Maxwell equations are solved directly in the time domain via a high order vector finite element discretization using the massively parallel CEM code EMSolve. The numerical technique is first verified against theoretical results for a planar loop antenna in a smooth lossy cave. The simulation is then performed for a series of random rough surface meshes in order to generate statistical data for the propagation and attenuation properties of the antenna in a cave environment. Results for the mean and variance of the power spectral density of the electric field are presented and discussed.

  4. Measurement of ocean wave spectra using polarimetric AIRSAR data

    NASA Technical Reports Server (NTRS)

    Schuler, D. L.

    1993-01-01

    A polarimetric technique for improving the visibility of waves, whose propagation direction has an azimuthal component, in RAR (real aperture radar) or SAR (synthetic aperture radar) images has been investigated. The technique shows promise as a means of producing more accurate 2-D polarimetric RAR ocean wave spectra. For SAR applications domination by velocity-bunching effects may limit its usefulness to long ocean swell. A modification of this technique involving measurement of polarization signature modulations in the image is useful for detecting waves in SAR images and, potentially, estimating RMS wave slopes.

  5. Percutaneous Penetration Enhancement in Vivo Measured by Attenuated Total Reflectance Infrared Spectroscopy

    Microsoft Academic Search

    Vivien H. W. Mak; Russell O. Potts; Richard H. Guy

    1990-01-01

    A novel application of attenuated total reflectance IR Spectroscopy (ATR-IR) was used to monitor the outer several microns of the stratum corneum (SC) and, thereby, demonstrate enhanced percutaneous absorption in vivo in man. 4-Cyanophenol (CP) as a model permeant yielded a unique IR signal, distinct from those of the stratum corneum and the vehicle components. CP was administered for 1,

  6. High frequency ultrasound measurements of the attenuation and backscatter from biological tissues

    Microsoft Academic Search

    Subha Maruvada

    2000-01-01

    There are now diagnostic ultrasonic imaging devices that operate at very high frequencies (VHF) of 20 MHz and beyond for clinical applications in ophthalmology, dermatology, and vascular surgery. To be able to better interpret these images and to further the development of these devices, knowledge of ultrasonic attenuation and scattering of biological tissues in this high frequency range is crucial.

  7. Measured and calculated acoustic attenuation rates of tuned resonator arrays for two surface impedance distribution models with flow

    NASA Technical Reports Server (NTRS)

    Parrott, Tony L.; Abrahamson, A. Louis; Jones, Michael G.

    1988-01-01

    An experiment was performed to validate two analytical models for predicting low frequency attenuation of duct liner configurations built from an array of seven resonators that could be individually tuned via adjustable cavity depths. These analytical models had previously been developed for high frequency aero-engine inlet duct liner design. In the low frequency application, the liner surface impedance distribution is unavoidably spatially varying by virtue of available fabrication techniques. The characteristic length of this spatial variation may be a significant fraction of the acoustic wavelength. Comparison of measured and predicted attenuation rates and transmission losses for both modal decomposition and finite element propagation models were in good to excellent agreement for a test frequency range that included the first and second cavity resonance frequencies. This was true for either of two surface impedance distribution modeling procedures used to simplify the impedance boundary conditions. In the presence of mean flow, measurements revealed a fine scale structure of acoustic hot spots in the attenuation and phase profiles. These details were accurately predicted by the finite element model. Since no impedance changes due to mean flow were assumed, it is concluded that this fine scale structure was due to convective effects of the mean flow interacting with the surface impedance nonuniformities.

  8. Direct Measurement of Wave Kernels in Time-Distance Helioseismology

    NASA Technical Reports Server (NTRS)

    Duvall, T. L., Jr.

    2006-01-01

    Solar f-mode waves are surface-gravity waves which propagate horizontally in a thin layer near the photosphere with a dispersion relation approximately that of deep water waves. At the power maximum near 3 mHz, the wavelength of 5 Mm is large enough for various wave scattering properties to be observable. Gizon and Birch (2002,ApJ,571,966)h ave calculated kernels, in the Born approximation, for the sensitivity of wave travel times to local changes in damping rate and source strength. In this work, using isolated small magnetic features as approximate point-sourc'e scatterers, such a kernel has been measured. The observed kernel contains similar features to a theoretical damping kernel but not for a source kernel. A full understanding of the effect of small magnetic features on the waves will require more detailed modeling.

  9. An inexpensive instrument for measuring wave exposure and water velocity

    USGS Publications Warehouse

    Figurski, J.D.; Malone, D.; Lacy, J.R.; Denny, M.

    2011-01-01

    Ocean waves drive a wide variety of nearshore physical processes, structuring entire ecosystems through their direct and indirect effects on the settlement, behavior, and survivorship of marine organisms. However, wave exposure remains difficult and expensive to measure. Here, we report on an inexpensive and easily constructed instrument for measuring wave-induced water velocities. The underwater relative swell kinetics instrument (URSKI) is a subsurface float tethered by a short (<1 m) line to the seafloor. Contained within the float is an accelerometer that records the tilt of the float in response to passing waves. During two field trials totaling 358 h, we confirmed the accuracy and precision of URSKI measurements through comparison to velocities measured by an in situ acoustic Doppler velocimeter and those predicted by a standard swell model, and we evaluated how the dimensions of the devices, its buoyancy, and sampling frequency can be modified for use in a variety of environments.

  10. Dielectric and Magnetic Measurements on Ferrite Ceramics at Millimeter Waves

    Microsoft Academic Search

    K. A. Korolev; Shu Chen; M. N. Afsar

    2007-01-01

    Transmittance measurements on 99.9% pure yttrium iron garnets, aluminum-substituted yttrium iron garnets, gadolinium-substituted yttrium iron garnets and nickel ferrite ceramics over a broad-band millimeter wave frequency range have been performed. The measurements have been done using a free-space, quasi optical millimeter wave spectrometer in transverse magnetic field up to 8 kOe. Magneto-optical approach has been successfully employed for the separation

  11. Spatio-Temporal Measurements of Short Wind Water Waves

    Microsoft Academic Search

    Roland Rocholz; Bernd Jähne

    2010-01-01

    Spatio-temporal measurements of wind-driven short-gravity capillary waves are reported for a wide range of experimental conditions, including wind, rain and surface slicks. The experiments were conducted in the Hamburg linear wind\\/wave flume in cooperation with the Institute of Oceanography at the University of Hamburg, Germany. Both components of the slope field were measured optically at a fetch of 14.4 m

  12. The MOSDEF Survey: Measurements of Balmer Decrements and the Dust Attenuation Curve at Redshifts z ~ 1.4–2.6

    NASA Astrophysics Data System (ADS)

    Reddy, Naveen A.; Kriek, Mariska; Shapley, Alice E.; Freeman, William R.; Siana, Brian; Coil, Alison L.; Mobasher, Bahram; Price, Sedona H.; Sanders, Ryan L.; Shivaei, Irene

    2015-06-01

    We present results on the dust attenuation curve of z ? 2 galaxies using early observations from the MOSFIRE Deep Evolution Field survey. Our sample consists of 224 star-forming galaxies with zspec = 1.36–2.59 and high signal-to-noise ratio measurements of H? and H? obtained with Keck/MOSFIRE. We construct composite spectral energy distributions (SEDs) of galaxies in bins of Balmer decrement to measure the attenuation curve. We find a curve that is similar to the SMC extinction curve at ? ? 2500 Å. At shorter wavelengths, the shape is identical to that of the Calzetti et al. relation, but with a lower normalization. Hence, the new attenuation curve results in star formation rates (SFRs) that are ? 20% lower, and stellar masses that are {? }{log}({M}*{/M}? )? 0.16 dex lower, than those obtained with the Calzetti relation. We find that the difference in the total attenuation of the ionized gas and stellar continuum correlates strongly with SFR, such that for dust-corrected SFRs ? 20 M? yr?1, assuming a Chabrier initial mass function, the nebular emission lines suffer an increasing degree of obscuration relative to the continuum. A simple model that can account for these trends is one in which the UV through optical stellar continuum is dominated by a population of less-reddened stars, while the nebular line and bolometric luminosities become increasingly dominated by dustier stellar populations for galaxies with large SFRs, as a result of the increased dust enrichment that accompanies such galaxies. Consequently, UV- and SED-based SFRs may underestimate the total SFR at even modest levels of ?20 M? yr?1. Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation.

  13. Measurements of the interaction of wave groups with shorter wind-generated waves

    NASA Technical Reports Server (NTRS)

    Chu, Jacob S.; Long, Steven R.; Phillips, O. M.

    1992-01-01

    Fields of statistically steady wind-generated waves produced in a wind wave facility were perturbed by the injection of groups of longer, mechanically generated waves with various slopes. The time histories of the surface displacements were measured at four fetches in ensembles consisting of 100 realizations of each set of experimental conditions; the data were stored and analyzed digitally. Four distinct stages in the overall interaction are identified and characterized. The properties of the wave energy front are documented, and a preliminary discussion is given of the dynamic processes involved in its formation.

  14. The success of extracorporeal shock-wave lithotripsy based on the stone-attenuation value from non-contrast computed tomography

    PubMed Central

    Massoud, Amr M.; Abdelbary, Ahmed M.; Al-Dessoukey, Ahmad A.; Moussa, Ayman S.; Zayed, Ahmed S.; Mahmmoud, Osama

    2014-01-01

    Objective To determine the utility of the urinary stone-attenuation value (SAV, in Hounsfield units, HU) from non-contrast computed tomography (NCCT) for predicting the success of extracorporeal shock-wave lithotripsy (ESWL). Patients and methods The study included 305 patients with renal calculi of ?30 mm and upper ureteric calculi of ?20 mm. The SAV was measured using NCCT. Numerical variables were compared using a one-way analysis of variance with posthoc multiple two-group comparisons. Univariate and multivariate regression analysis models were used to test the preferential effect of the independent variable(s) on the success of ESWL. Results Patients were grouped according to the SAV as group 1 (?500 HU, 81 patients), group 2 (501–1000 HU, 141 patients) and group 3 (>1000 HU, 83 patients). ESWL was successful in 253 patients (83%). The rate of stone clearance was 100% in group 1, 95.7% (135/141) in group 2 and 44.6% (37/83) in group 3 (P = 0.001). Conclusions The SAV value is an independent predictor of the success of ESWL and a useful tool for planning stone treatment. Patients with a SAV ?956 HU are not ideal candidates for ESWL. The inclusion criteria for ESWL of stones with a SAV <500 HU can be expanded with regard to stone size, site, age, renal function and coagulation profile. In patients with a SAV of 500–1000 HU, factors like a body mass index of >30 kg/m2 and a lower calyceal location make them less ideal for ESWL. PMID:26019941

  15. Measurement of X-ray mass attenuation coefficients in biological and geological samples in the energy range of 7-12keV.

    PubMed

    Trunova, Valentina; Sidorina, Anna; Kriventsov, Vladimir

    2014-10-17

    Information about X-ray mass attenuation coefficients in different materials is necessary for accurate X-ray fluorescent analysis. The X-ray mass attenuation coefficients for energy of 7-12keV were measured in biological (Mussel and Oyster tissues, blood, hair, liver, and Cabbage leaves) and geological (Baikal sludge, soil, and Alaskite granite) samples. The measurements were carried out at the EXAFS Station of Siberian Synchrotron Radiation Center (VEPP-3). Obtained experimental mass attenuation coefficients were compared with theoretical values calculated for some samples. PMID:25464176

  16. Analysis methods for multi-component wave measurements on board the DEMETER spacecraft

    Microsoft Academic Search

    O. Santolík; F. Nemec; M. Parrot; D. Lagoutte; L. Madrias; J. J. Berthelier

    2006-01-01

    We describe analysis methods to estimate parameters of electromagnetic waves based on the multi-component measurements of the DEMETER spacecraft. Using the fact that the wave magnetic field is perpendicular to the wave vector, the wave normal direction can be estimated by different methods. We use these plane-wave estimates to interpret measurements of the observed wave emissions. For instance, we use

  17. Measurements of Inertial Limit Alfven Wave Dispersion for Finite Perpendicular Wave Number

    SciTech Connect

    Kletzing, C. A.; Thuecks, D. J.; Skiff, F.; Bounds, S. R. [Department of Physics and Astronomy, University of Iowa 203 Van Allen Hall, Iowa City, Iowa, 52245 (United States); Vincena, S. [Department of Physics and Astronomy, University of California Los Angeles 1000 Veteran Avenue, Suite 15-70, Los Angeles, California, 90095-1696 (United States)

    2010-03-05

    Measurements of the dispersion relation for shear Alfven waves as a function of perpendicular wave number are reported for the inertial regime for which V{sub A}>V{sub Te}. The parallel phase velocity and damping are determined as k{sub perpendicular} varies and the measurements are compared to theoretical predictions. The comparison shows that the best agreement between theory and experiment is achieved for a fully complex plasma dispersion relation which includes the effects of electron collisions.

  18. Study of EMIC wave excitation using direct ion measurements

    NASA Astrophysics Data System (ADS)

    Min, Kyungguk; Liu, Kaijun; Bonnell, John W.; Breneman, Aaron W.; Denton, Richard E.; Funsten, Herbert O.; Jahn, Jöerg-Micha; Kletzing, Craig A.; Kurth, William S.; Larsen, Brian A.; Reeves, Geoffrey D.; Spence, Harlan E.; Wygant, John R.

    2015-04-01

    With data from Van Allen Probes, we investigate electromagnetic ion cyclotron (EMIC) wave excitation using simultaneously observed ion distributions. Strong He band waves occurred while the spacecraft was moving through an enhanced density region. We extract from helium, oxygen, proton, and electron mass spectrometer measurement the velocity distributions of warm heavy ions as well as anisotropic energetic protons that drive wave growth through the ion cyclotron instability. Fitting the measured ion fluxes to multiple sinm-type distribution functions, we find that the observed ions make up about 15% of the total ions, but about 85% of them are still missing. By making legitimate estimates of the unseen cold (below ˜2 eV) ion composition from cutoff frequencies suggested by the observed wave spectrum, a series of linear instability analyses and hybrid simulations are carried out. The simulated waves generally vary as predicted by linear theory. They are more sensitive to the cold O+ concentration than the cold He+ concentration. Increasing the cold O+ concentration weakens the He band waves but enhances the O band waves. Finally, the exact cold ion composition is suggested to be in a range when the simulated wave spectrum best matches the observed one.

  19. Comparing shear-wave velocity profiles inverted from multichannel surface wave with borehole measurements

    USGS Publications Warehouse

    Xia, J.; Miller, R.D.; Park, C.B.; Hunter, J.A.; Harris, J.B.; Ivanov, J.

    2002-01-01

    Recent field tests illustrate the accuracy and consistency of calculating near-surface shear (S)-wave velocities using multichannel analysis of surface waves (MASW). S-wave velocity profiles (S-wave velocity vs. depth) derived from MASW compared favorably to direct borehole measurements at sites in Kansas, British Columbia, and Wyoming. Effects of changing the total number of recording channels, sampling interval, source offset, and receiver spacing on the inverted S-wave velocity were studied at a test site in Lawrence, Kansas. On the average, the difference between MASW calculated Vs and borehole measured Vs in eight wells along the Fraser River in Vancouver, Canada was less than 15%. One of the eight wells was a blind test well with the calculated overall difference between MASW and borehole measurements less than 9%. No systematic differences were observed in derived Vs values from any of the eight test sites. Surface wave analysis performed on surface data from Wyoming provided S-wave velocities in near-surface materials. Velocity profiles from MASW were confirmed by measurements based on suspension log analysis. ?? 2002 Elsevier Science Ltd. All rights reserved.

  20. In situ measurements of impact-induced pressure waves in sandstone targets

    NASA Astrophysics Data System (ADS)

    Hoerth, Tobias; Schäfer, Frank; Nau, Siegfried; Kuder, Jürgen; Poelchau, Michael H.; Thoma, Klaus; Kenkmann, Thomas

    2014-10-01

    In the present study we introduce an innovative method for the measurement of impact-induced pressure waves within geological materials. Impact experiments on dry and water-saturated sandstone targets were conducted at a velocity of 4600 m/s using 12 mm steel projectiles to investigate amplitudes, decay behavior, and speed of the waves propagating through the target material. For this purpose a special kind of piezoresistive sensor capable of recording transient stress pulses within solid brittle materials was developed and calibrated using a Split-Hopkinson pressure bar. Experimental impact parameters (projectile size and speed) were kept constant and yielded reproducible signal curves in terms of rise time and peak amplitudes. Pressure amplitudes decreased by 3 orders of magnitude within the first 250 mm (i.e., 42 projectile radii). The attenuation for water-saturated sandstone is higher compared to dry sandstone which is attributed to dissipation effects caused by relative motion between bulk material and interstitial water. The proportion of the impact energy radiated as seismic energy (seismic efficiency) is in the order of 10-3. The present study shows the feasibility of real-time measurements of waves caused by hypervelocity impacts on geological materials. Experiments of this kind lead to a better understanding of the processes in the crater subsurface during a hypervelocity impact.

  1. The application of S-band polarimetric radar measurements to Ka-band attenuation prediction

    Microsoft Academic Search

    JOHN D. BEAVER; V. N. Bringi

    1997-01-01

    In September 1993, the National Aeronautics and Space Administration's Advanced Communications Technology Satellite (ACTS) was deployed into a geostationary orbit near 100° W longitude. The ACTS satellite employs two Ka-band beacons, one at 20.185 GHz and another at 27.505 GHz. Impairments due to rain attenuation and tropospheric scintillations will significantly affect new technologies for this spectrum. Heavy rain at Ka-band

  2. Measurement of the normalized broadband ultrasound attenuation in trabecular bone by using a bidirectional transverse transmission technique

    NASA Astrophysics Data System (ADS)

    Lee, Kang Il

    2015-01-01

    A new method for measuring the normalized broadband ultrasound attenuation (nBUA) in trabecular bone by using a bidirectional transverse transmission technique was proposed and validated with measurements obtained by using the conventional transverse transmission technique. There was no significant difference between the nBUA measurements obtained for 14 bovine femoral trabecular bone samples by using the bidirectional and the conventional transverse transmission techniques. The nBUA measured by using the two transverse transmission techniques showed strong positive correlations of r = 0.87 to 0.88 with the apparent bone density, consistent with the behavior in human trabecular bone invitro. We expect that the new method can be usefully applied for improved accuracy and precision in clinical measurements.

  3. Model-based tomographic optoacoustic reconstructions in acoustically attenuating media

    NASA Astrophysics Data System (ADS)

    Deán-Ben, X. Luís.; Razansky, Daniel

    2014-03-01

    Acoustic attenuation influences the transmission of the ultrasonic waves excited optoacoustically in biological samples, in a way that the amplitude of the waves is reduced as they propagate through acoustically attenuating tissues. Furthermore, being dependent on frequency, acoustic attenuation also causes broadening of the time-resolved optoacoustic signals, which in turn leads to blurring of features and overall deterioration of image quality. The effects of acoustic attenuation are more prominent for the high frequency components of the optoacoustic waves and they must be taken into account for high resolution imaging. In this work, we modify a model-based reconstruction algorithm to incorporate the effects of acoustic attenuation in tomographic optoacoustic imaging set-ups. As the waves propagate from the excitation until the measurement points, they undergo space and frequency dependent attenuation, which can be effectively accounted for using the suggested model-based approach. The simulation results obtained showcase a good performance of the introduced method in terms of resolution improvement.

  4. Physical measurements of breaking wave impact on a floating wave energy converter

    NASA Astrophysics Data System (ADS)

    Hann, Martyn R.; Greaves, Deborah M.; Raby, Alison

    2013-04-01

    Marine energy converter must both efficiently extract energy in small to moderate seas and also successfully survive storms and potential collisions. Extreme loads on devices are therefore an important consideration in their design process. X-MED is a SuperGen UKCMER project and is a collaboration between the Universities of Manchester, Edinburgh and Plymouth and the Scottish Association for Marine Sciences. Its objective is to extend the knowledge of extreme loads due to waves, currents, flotsam and mammal impacts. Plymouth Universities contribution to the X-MED project involves measuring the loading and response of a taut moored floating body due to steep and breaking wave impacts, in both long crested and directional sea states. These measurements are then to be reproduced in STAR-CCM+, a commercial volume of fluid CFD solver, so as to develop techniques to predict the wave loading on wave energy converters. The measurements presented here were conducted in Plymouth Universities newly opened COAST laboratories 35m long, 15.5m wide and 3m deep ocean basin. A 0.5m diameter taut moored hemispherical buoy was used to represent a floating wave energy device or support structure. The changes in the buoys 6 degree of freedom motion and mooring loads are presented due to focused breaking wave impacts, with the breaking point of the wave changed relative to the buoy.

  5. Ultrasonic attenuation and velocity in AS\\/3501-6 graphite fiber composite

    Microsoft Academic Search

    James H. Williams; Hamid Nayeb-Hashemi; Samson S. Lee

    1980-01-01

    The ultrasonic group velocity and attenuation were measured as a function of frequency for longitudinal and shear waves in the Hercules epoxy matrix (3501-6) and in the principal directions of the unidirectional Hercules graphite fiber epoxy composite (AS\\/3501-6). Tests were conducted in the frequency ranges 0.25–14 MHz and 0.5–3 MHz for longitudinal and shear wave modes, respectively. While the attenuation

  6. Laser Interferometric Measurements of Air-Coupled Lamb Waves

    NASA Astrophysics Data System (ADS)

    Garcia-Rodriguez, M.; Yañez, Y.; Garcia-Hernandez, M. J.; Salazar, J.; Turo, A.; Chavez, J. A.

    2010-05-01

    In this paper, experimental measurements of the vibration pattern that results when an air-coupled A0 Lamb wave mode propagates in a plate are presented. Lamb waves are generated using an air-coupled piezoelectric transducer array. The measurements were performed in 304 stainless steel using laser interferometry. Air coupled piezoelectric ultrasonic array transducers are a novel tool that could lead to interesting advances in the area of non-contact laminar material testing using Lamb wave's propagation techniques, and it is interesting to know the vibration pattern in the plate. Using this system, some snapshots of the interaction of the A0 Lamb wave mode with a crack-defect in the plate are also presented.

  7. Laser measurements of bacterial endospore destruction from shock waves

    NASA Astrophysics Data System (ADS)

    Lappas, Petros P.; McCartt, A. Daniel; Gates, Sean D.; Jeffries, Jay B.; Hanson, Ronald K.

    2013-12-01

    The effects of shock waves on bioaerosols containing endospores were measured by combined laser absorption and scattering. Experiments were conducted in the Stanford aerosol shock tube for post-shock temperatures ranging from 400 K to 1100 K. Laser intensity measurements through the test section of the shock tube at wavelengths of 266 and 665 nm provided real-time monitoring of the morphological changes (includes changes in shape, structure and optical properties) in the endospores. Scatter of the visible light measured the integrity of endospore structure, while absorption of the UV light provided a measure of biochemicals released when endospores ruptured. For post-shock temperatures above 750 K the structural breakdown of Bacillus atrophaeus (BA) endospores was observed. A simple theoretical model using laser extinction is presented for determining the fraction of endospores that are ruptured by the shock waves. In addition, mechanisms of endospore mortality preceding their disintegration due to shock waves are discussed.

  8. Monitoring the wave function by time continuous position measurement

    E-print Network

    Thomas Konrad; Andreas Rothe; Francesco Petruccione; Lajos Diósi

    2009-02-13

    We consider a single copy of a quantum particle moving in a potential and show that it is possible to monitor its complete wave function by only continuously measuring its position. While we assume that the potential is known, no information is available about its state initially. In order to monitor the wave function, an estimate of the wave function is propagated due to the influence of the potential and continuously updated according to the results of the position measurement. We demonstrate by numerical simulations that the estimation reaches arbitrary values of accuracy below 100 percent within a finite time period for the potentials we study. In this way our method grants, a certain time after the beginning of the measurement, an accurate real-time record of the state evolution including the influence of the continuous measurement. Moreover, it is robust against sudden perturbations of the system as for example random momentum kicks from environmental particles, provided they occur not too frequently.

  9. Interpretation of measurements of the polarization percentage for plasma waves

    NASA Astrophysics Data System (ADS)

    Pincon, J. L.; Marouan, Y.; Lefeuvre, F.

    1992-02-01

    The conditions of the application of the pure-state concept to the analysis of a plasma wave in a magnetoplasma are studied. Estimations of the Samson percentage of polarization are discussed. The best results are obtained with the minimum prediction error estimator. Simple physical interpretation is possible when the estimator is derived from the three magnetic-wave-field components only. There is an exception for electrostatic waves. Propagation modes and the region of the Clemmow-Mullaly-Allis diagram exist for which the percentage of polarization may be considered as a measure of the dispersion in k vectors.

  10. Measurement of Light-Cone Wave Functions by Diffractive Dissociation

    E-print Network

    Daniel Ashery

    2000-08-22

    Diffractive dissociation of particles can be used to study their light-cone wave function. Results from Fermilab experiment E791 for diffractive dissociation of 500 GeV/c $\\pi^-$ mesons into di-jets are presented. The results show that the $|q\\bar {q}>$ light-cone asymptotic wave function describes the data well for $Q^2 \\sim 10 ~{\\rm (GeV/c)^2}$ or more. Evidence for color transparency comes from a measurement of the $A$-dependence of the yield of the diffractive di-jets. It is proposed to carry out similar studies for the light-cone wave function of the photon.

  11. Slow-Wave Acoustic Isolation For Measurement Of Flow

    NASA Technical Reports Server (NTRS)

    Lynnworth, Lawrence C.; Aurilio, Marco

    1993-01-01

    Propagation of interfering signals delayed. Experiments demonstrated utility of slow-wave isolation between transmitting and receiving transducers in acoustic measurements of sound speed and/or flow velocity in ducts. Specifically, finding pertains to acoustic measurements of speeds of flow of low-molecular-weight gases at pressures low enough to be contained in thin-walled metal conduits.

  12. Diurnal variations of mesospheric ozone using millimeter-wave measurements

    Microsoft Academic Search

    W. J. Wilson; P. R. Schwartz

    1981-01-01

    In March 1979, millimeter-wave observations of the ozone emission line at 101737 MHz were made to measure the diurnal variations in mesospheric ozone. Changes in mesospheric ozone were measured diurnally for a 10-day period. The ozone column above approximately 76 km rapidly decreased after sunrise to half value within 1 hour and was then followed by a slower (approximately 8

  13. Measurement of waves in flows across a surface

    NASA Technical Reports Server (NTRS)

    Kendall, Jr., James M. (Inventor)

    1992-01-01

    A method and apparatus for sensing wave flow across a surface wherein at least two pressure levels are sensed and combined to provide a representation of waves within the flow. In the preferred embodiment holes bored through the aircraft surface at an interval of one-half the wavelength of the flow being measured introduce pressure perturbations into a cavity so they may acoustically interfere. The interfering waveform is sensed by at least one microphone disposed in the cavity.

  14. New consistency tests for high-accuracy measurements of X-ray mass attenuation coefficients by the X-ray extended-range technique

    SciTech Connect

    Chantler, C.T.; Islam, M.T.; Rae, N.A.; Tran, C.Q.; Glover, J.L.; Barnea, Z. (La Trobe); (Melbourne)

    2012-09-25

    An extension of the X-ray extended-range technique is described for measuring X-ray mass attenuation coefficients by introducing absolute measurement of a number of foils - the multiple independent foil technique. Illustrating the technique with the results of measurements for gold in the 38-50 keV energy range, it is shown that its use enables selection of the most uniform and well defined of available foils, leading to more accurate measurements; it allows one to test the consistency of independently measured absolute values of the mass attenuation coefficient with those obtained by the thickness transfer method; and it tests the linearity of the response of the counter and counting chain throughout the range of X-ray intensities encountered in a given experiment. In light of the results for gold, the strategy to be ideally employed in measuring absolute X-ray mass attenuation coefficients, X-ray absorption fine structure and related quantities is discussed.

  15. Measurement of viscosity of highly viscous non-Newtonian fluids by means of ultrasonic guided waves.

    PubMed

    Kazys, Rymantas; Mazeika, Liudas; Sliteris, Reimondas; Raisutis, Renaldas

    2014-04-01

    In order to perform monitoring of the polymerisation process, it is necessary to measure viscosity. However, in the case of non-Newtonian highly viscous fluids, viscosity starts to be dependent on the vibration or rotation frequency of the sensing element. Also, the sensing element must possess a sufficient mechanical strength. Some of these problems may be solved applying ultrasonic measurement methods, however until now most of the known investigations were devoted to measurements of relatively low viscosities (up to a few Pas) of Newtonian liquids. The objective of the presented work is to develop ultrasonic method for measurement of viscosity of high viscous substances during manufacturing process in extreme conditions. For this purpose the method based on application of guided Lamb waves possessing the predominant component of in-plane displacements (the S0 and the SH0 modes) and propagating in an aluminium planar waveguide immersed in a viscous liquid has been investigated. The simulations indicated that in the selected modes mainly in-plane displacements are dominating, therefore the attenuation of those modes propagating in a planar waveguide immersed in a viscous liquid is mainly caused by viscosity of the liquid. The simulation results were confirmed by experiments. All measurements were performed in the viscosity standard Cannon N2700000. Measurements with the S0 wave mode were performed at the frequency of 500kHz. The SH0 wave mode was exited and used for measurements at the frequency of 580kHz. It was demonstrated that by selecting the particular mode of guided waves (S0 or SH0), the operation frequency and dimensions of the aluminium waveguide it is possible to get the necessary viscosity measurement range and sensitivity. The experiments also revealed that the measured dynamic viscosity is strongly frequency dependent and as a characteristic feature of non-Newtonian liquids is much lower than indicated by the standards. Therefore, in order to get the absolute values of viscosity in this case an additional calibration procedure is required. Feasibility to measure variations of high dynamic viscosities in the range of (20-25,000) Pas was theoretically and experimentally proved. The proposed solution differently from the known methods in principle is more mechanically robust and better fitted for measurements in extreme conditions. PMID:24491274

  16. SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

    SciTech Connect

    Joel Walls; M.T. Taner; Gary Mavko; Jack Dvorkin

    2002-04-01

    Wave-induced variations of pore pressure in a partially-saturated reservoir result in oscillatory liquid flow. The viscous losses during this flow are responsible for wave attenuation. The same viscous effects determine the changes in the dynamic bulk modulus of the system versus frequency. These changes are necessarily linked to attenuation via the causality condition. We analytically quantify the frequency dependence of the bulk modulus of a partially saturated rock by assuming that saturation is patchy and then link these changes to the inverse quality factor. As a result, the P-wave attenuation is quantitatively linked to saturation and thus can serve as a saturation indicator.

  17. Airborne radar measurements of ocean wave spectra and wind speed during the grand banks ERS?1 SAR wave experiment

    Microsoft Academic Search

    D. Vandemark; F. C. Jackson; E. J. Walsh; B. Chapron

    1994-01-01

    Measurements of ocean directional wave spectra, significant wave height, and wind speed over the Grand Banks of Newfoundland were made using the combined capabilities of the radar ocean wave spectrometer (ROWS) and scanning radar altimeter (SRA). The instruments were flown aboard the NASA P?3A aircraft in support of the Grand Banks ERS?1 Synthetic Aperture Radar (SAR) Wave Experiment. The NASA

  18. Linear stochastic wave-equations for continuously measured quantum systems

    E-print Network

    Peter Goetsch; Robert Graham

    1994-05-17

    While the linearity of the Schr\\"odinger equation and the superposition principle are fundamental to quantum mechanics, so are the backaction of measurements and the resulting nonlinearity. It is remarkable, therefore, that the wave-equation of systems in continuous interaction with some reservoir, which may be a measuring device, can be cast into a linear form, even after the degrees of freedom of the reservoir have been eliminated. The superposition principle still holds for the stochastic wave-function of the observed system, and exact analytical solutions are possible in sufficiently simple cases. We discuss here the coupling to Markovian reservoirs appropriate for homodyne, heterodyne, and photon counting measurements. For these we present a derivation of the linear stochastic wave-equation from first principles and analyze its physical content.

  19. Measurements of radiated elastic wave energy from dynamic tensile cracks

    NASA Technical Reports Server (NTRS)

    Boler, Frances M.

    1990-01-01

    The role of fracture-velocity, microstructure, and fracture-energy barriers in elastic wave radiation during a dynamic fracture was investigated in experiments in which dynamic tensile cracks of two fracture cofigurations of double cantilever beam geometry were propagating in glass samples. The first, referred to as primary fracture, consisted of fractures of intact glass specimens; the second configuration, referred to as secondary fracture, consisted of a refracture of primary fracture specimens which were rebonded with an intermittent pattern of adhesive to produce variations in fracture surface energy along the crack path. For primary fracture cases, measurable elastic waves were generated in 31 percent of the 16 fracture events observed; the condition for radiation of measurable waves appears to be a local abrupt change in the fracture path direction, such as occurs when the fracture intersects a surface flaw. For secondary fractures, 100 percent of events showed measurable elastic waves; in these fractures, the ratio of radiated elastic wave energy in the measured component to fracture surface energy was 10 times greater than for primary fracture.

  20. Measurement of carbon nanotube microstructure relative density by optical attenuation and observation of size-dependent variations.

    PubMed

    Park, Sei Jin; Schmidt, Aaron J; Bedewy, Mostafa; Hart, A John

    2013-07-21

    Engineering the density of carbon nanotube (CNT) forest microstructures is vital to applications such as electrical interconnects, micro-contact probes, and thermal interface materials. For CNT forests on centimeter-scale substrates, weight and volume can be used to calculate density. However, this is not suitable for smaller samples, including individual microstructures, and moreover does not enable mapping of spatial density variations within the forest. We demonstrate that the relative mass density of individual CNT microstructures can be measured by optical attenuation, with spatial resolution equaling the size of the focused spot. For this, a custom optical setup was built to measure the transmission of a focused laser beam through CNT microstructures. The transmittance was correlated with the thickness of the CNT microstructures by Beer-Lambert-Bouguer law to calculate the attenuation coefficient. We reveal that the density of CNT microstructures grown by CVD can depend on their size, and that the overall density of arrays of microstructures is affected significantly by run-to-run process variations. Further, we use the technique to quantify the change in CNT microstructure density due to capillary densification. This is a useful and accessible metrology technique for CNTs in future microfabrication processes, and will enable direct correlation of density to important properties such as stiffness and electrical conductivity. PMID:23748864

  1. Wave Packet under Continuous Measurement via Bohmian Mechanics

    E-print Network

    Antonio B. Nassar

    2010-01-25

    A new quantum mechanical description of the dynamics of wave packet under continuous measurement is formulated via Bohmian mechanics. The solution to this equation is found through a wave packet approach which establishes a direct correlation between a classical variable with a quantum variable describing the dynamics of the center of mass and the width of the wave packet. The approach presented in this paper gives a comparatively clearer picture than approaches using restrited path integrals and master equation approaches. This work shows how the extremely irregular character of classical chaos can be reconciled with the smooth and wavelike nature of phenomena on the atomic scale. It is demonstrated that a wave packet under continuous quantum measurement displays both chaotic and non-chaotic features. The Lyapunov characteristic exponents for the trajectories of classical particle and the quantum wave packet center of mass are calculated and their chaoticities are demonstrated to be about the same. Nonetheless, the width of the wave packet exhibits a non-chaotic behavior and allows for the possibility to beat the standard quantum limit by means of transient, contractive states.

  2. Measurement of the x-ray mass attenuation coefficients of gold in the 38?50-keV energy range

    SciTech Connect

    Islam, M.T.; Rae, N.A.; Glover, J.L.; Barnea, Z.; de Jonge, M.D.; Tran, C.Q.; Wang, J.; Chantler, C.T. (Melbourne)

    2010-11-12

    We used synchrotron x rays to measure the x-ray mass attenuation coefficients of gold at nine energies from 38 to 50 keV with accuracies of 0.1%. Our results are much more accurate than previous measurements in this energy range. A comparison of our measurements with calculated mass attenuation coefficients shows that our measurements fall almost exactly midway between the XCOM and FFAST calculated theoretical values, which differ from one another in this energy region by about 4%, even though the range includes no absorption edge. The consistency and accuracy of these measurements open the way to investigations of the x-ray attenuation in the region of the L absorption edge of gold.

  3. 1D model of seismic wave attenuation in the crust and upper mantle in the north-eastern flanc of the Baikal rift system

    NASA Astrophysics Data System (ADS)

    Dobrynina, Anna; Sankov, Vladimir; Chechelnitsky, Vladimir

    2014-05-01

    The deep profiles of quality factor were obtained using coda-waves of local strong and moderate earthquakes (epicentral distances up to 50 km) occurred within north-eastern flanc of the Baikal rift system during 2002-2009. We used two methods: 1 - the coda envelope method [Experimental.., 1981; Kopnichev, 1991] and 2 - the sliding window method (lapse time window 10-15 sec with a step of 5 sec). Depth of coda-wave penetration was determined according to Pulli's formulae [1984], the velocity of coda-wave is 3.55 km/s (equal to shear wave velocity). For analysis we used the Q values at frequency 1 Hz since for this frequency the attenuation field heterogeneity is most evident [Aptikaeva and Kopnichev, 1991]. In result Q-profiles for eleven local areas were obtained. The Q-values vary from 50 to 170 for different profiles and depths. Herewith quality factor changes nonuniformly - the alternation of layers with high and low Q-values is observed. This phenomenon can be explained by existing velocity discontinuity. In particular for all profiles this alternation is confined to the depth about 100 km. Analysis VP-anomalies obtained in result of 2D teleseismic tomography along Baikal rift system [Mordvinova, 2009] shows the existence discontinuity on depth about 100 km under most of Baikal rift system structures. Analysis of 1D profiles of shear wave velocities in the crust and upper mantle after inversion of receiver functions [Anan'in et al., 2009] also shows presence of these discontinuity dividing high and low velocity layers. The comparison of Q-values and shear wave velocities [Anan'in et al., 2009] shown that in high velocity layers quality factor is higher too and vice versa. Multilayer quality factor model for the lithosphere in north-eastern flanc of the Baikal rift system with the alternation of layers with high and low attenuation determined by us together with analogous data obtained by Yu.F. Kopnichev [1992] for south-western flanc of the rift system can be one of inferential evidences of passive rifting mechanism in studied area. The reported study was supported by RFBR (research project N12-05-31038-mol_a) and by grant of President of Russian Federation (research project N MK-1171.2014.5).

  4. Evaluation of multilayered pavement structures from measurements of surface waves

    USGS Publications Warehouse

    Ryden, N.; Lowe, M.J.S.; Cawley, P.; Park, C.B.

    2006-01-01

    A method is presented for evaluating the thickness and stiffness of multilayered pavement structures from guided waves measured at the surface. Data is collected with a light hammer as the source and an accelerometer as receiver, generating a synthetic receiver array. The top layer properties are evaluated with a Lamb wave analysis. Multiple layers are evaluated by matching a theoretical phase velocity spectrum to the measured spectrum. So far the method has been applied to the testing of pavements, but it may also be applicable in other fields such as ultrasonic testing of coated materials. ?? 2006 American Institute of Physics.

  5. Mercurial magnetic field waves measured by orbiting satellite

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2012-06-01

    Researchers working with NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging ( MESSENGER) spacecraft report the frequent detections of Kelvin-Helmholtz (KH) waves at the edge of the innermost planet's magnetosphere. In six different sets of magnetic field measurements made by the orbiter as it passed through Mercury's magnetopause, the boundary that separates the planet's magnetosphere from the solar wind plasma in the magnetosheath, Sundberg et al. detected the magnetic field oscillations characteristic of fully developed KH waves. These waves form when fuids of different speeds travel alongside each other—in this case, the magnetosphere and magnetosheath plasmas—and promote mixing of the plasmas on larger spatial, and shorter time, scales than diffusive transport. The observations, which span the frst 88 days of MESSENGER's time in orbit, bring Mercury alongside Earth, Saturn, and Venus as planets for which such KH waves are of importance.

  6. Colored Dissolved Organic Matter in Shallow Estuaries: The Effects of Source and Transport on Light Attenuation and Measurement

    NASA Astrophysics Data System (ADS)

    Oestreich, W. K.; Ganju, N. K.; Pohlman, J.; Suttles, S. E.

    2014-12-01

    Light is of great importance to the health and ecological function of shallow estuaries. Primary production in such estuaries, which is typically dominated by seagrass, is contingent upon light penetration to the deeper part of the estuarine water column. A major component contributing to light attenuation in these systems is colored dissolved organic matter (CDOM). CDOM is most often measured via a proxy, fluorescing dissolved organic matter (fDOM), due to the ease of taking rapid, accurate fDOM measurements. Fluorescence data can then be converted to absorbance by CDOM for use in light attenuation models. However, this fDOM-CDOM conversion has proven to be quite variable between estuaries, and even between sites along a given estuary. We displayed and attempted to explain this variability through the study of three diverse estuaries: West Falmouth Harbor (MA), Barnegat Bay (NJ), and Chincoteague Bay (MD/VA). Land use surrounding these estuaries ranges from wastewater treatment to agricultural operations and residential communities. Measurements of fDOM and absorbance by CDOM (quantified via spectrophotometer measurement of 0.2?m-filtered samples) were taken along a gradient from terrestrial to oceanic end-members. These measurements yielded highly variable fDOM-CDOM relationships between estuaries. The mean ratio of absorption coefficient at 340nm (m-1) to fDOM (QSU) was much higher in West Falmouth Harbor (0.874) than in Barnegat Bay (0.227) and Chincoteague Bay (0.173). This fDOM-CDOM relationship was also observed to be variable between sites within West Falmouth Harbor and Barnegat Bay, but consistent throughout sites along Chincoteague Bay. This variability, both within and between estuaries, is likely due to differing CDOM sources as a result of differences in land use in the areas surrounding these estuaries. Stable carbon isotope analysis of DOC from each site and hydrodynamic model results will be used to differentiate sources and further elucidate the fDOM-CDOM relationship.

  7. Study of atmospheric parameters measurements using MM-wave radar in synergy with LITE-2

    NASA Technical Reports Server (NTRS)

    Andrawis, Madeleine Y.

    1994-01-01

    The Lidar In-Space Technology Experiment, (LITE), has been developed, designed, and built by NASA Langley Research Center, to be flown on the space shuttle 'Discovery' on September 9, 1994. Lidar, which stands for light detecting and ranging, is a radar system that uses short pulses of laser light instead of radio waves in the case of the common radar. This space-based lidar offers atmospheric measurements of stratospheric and tropospheric aerosols, the planetary boundary layer, cloud top heights, and atmospheric temperature and density in the 10-40 km altitude range. A study is being done on the use, advantages, and limitations of a millimeterwave radar to be utilized in synergy with the Lidar system, for the LITE-2 experiment to be flown on a future space shuttle mission. The lower atmospheric attenuation, compared to infrared and optical frequencies, permits the millimeter-wave signals to penetrate through the clouds and measure multi-layered clouds, cloud thickness, and cloud-base height. These measurements would provide a useful input to radiation computations used in the operational numerical weather prediction models, and for forecasting. High power levels, optimum modulation, data processing, and high antenna gain are used to increase the operating range, while space environment, radar tradeoffs, and power availability are considered. Preliminary, numerical calculations are made, using the specifications of an experimental system constructed at Georgia Tech. The noncoherent 94 GHz millimeter-wave radar system has a pulsed output with peak value of 1 kW. The backscatter cross section of the particles to be measured, that are present in the volume covered by the beam footprint, is also studied.

  8. Diffraction correction for precision surface acoustic wave velocity measurements

    NASA Astrophysics Data System (ADS)

    Ruiz M., Alberto; Nagy, Peter B.

    2002-09-01

    Surface wave dispersion measurements can be used to nondestructively characterize shot-peened, laser shock-peened, burnished, and otherwise surface-treated specimens. In recent years, there have been numerous efforts to separate the contribution of surface roughness from those of near-surface material variations, such as residual stress, texture, and increased dislocation density. As the accuracy of the dispersion measurements was gradually increased using state-of-the-art laser-ultrasonic scanning and sophisticated digital signal processing methods, it was recognized that a perceivable dispersive effect, similar to the one found on rough shot-peened specimens, is exhibited by untreated smooth surfaces as well. This dispersion effect is on the order of 0.1%, that is significantly higher than the experimental error associated with the measurements and comparable to the expected velocity change produced by near-surface compressive residual stresses in metals below their yield point. This paper demonstrates that the cause of this apparent dispersion is the diffraction of the surface acoustic wave (SAW) as it travels over the surface of the specimen. The results suggest that a diffraction correction may be introduced to increase the accuracy of surface wave dispersion measurements. A simple diffraction correction model was developed for surface waves and this correction was subsequently validated by laser-interferometric velocity measurements on aluminum specimens. copyright 2002 Acoustical Society of America.

  9. Ground Motion Attenuation and Shear-Wave Splitting Analyses for the November 2011 M5.7 Prague, Oklahoma Earthquake

    NASA Astrophysics Data System (ADS)

    Sumy, D. F.; Cochran, E. S.; Keranen, K. M.; Neighbors, C.; Atkinson, G. M.

    2014-12-01

    During November 2011, three M?5.0 earthquakes and thousands of aftershocks occurred on and near the Wilzetta fault, a structurally complex ~200 km long, Pennsylvanian-aged fault near Prague, Oklahoma, in close proximity to several active wastewater injection wells. All three M?5.0 earthquakes had strike-slip mechanisms consistent with rupture on three independent focal planes, suggesting activation of three different strands of the Wilzetta fault. Wastewater injection can cause a buildup of pore ?uid pressure along the fault, which decreases the fault strength and may induce earthquakes. Based on the proximity of earthquakes to active ?uid injection wells, the unilateral progression of aftershocks away from the initial M5.0 event, and shallow earthquake depths, Keranen et al. [2013] concluded that fluid injection was responsible for inducing the first M5.0 event. Furthermore, Sumy et al. [2014] found that the initial M5.0 event increased the Coulomb stress in the region of the M5.7 mainshock, triggering a cascade of earthquakes along the Wilzetta fault. Thus, while nearby wastewater injection directly induced the initial M5.0 event, this earthquake triggered successive failure along the Wilzetta fault; however, it remains unclear if the additional ruptured fault strands are also influenced by fluid injection. In this study, we explore instrumental ground motions and shear-wave splitting of the November 2011 Prague, Oklahoma sequence, in order to construct ground motion prediction equations (GMPEs) and understand the local stress regime, respectively. We examine ~1,000 earthquakes recorded by a total of 47 seismometers, located within ~150 km of the Wilzetta fault. With respect to GMPEs, initial results suggest that the ground motions are smaller than similar magnitude earthquakes of natural/tectonic origins, and these lower intensities may be a result of lower stress drops [e.g. Hough, 2014]. With respect to shear-wave splitting, we examine quality graded fast polarization and delay time measurements and observe fast directions oriented roughly E-W across the study area, which is consistent with the maximum principal stress of N80E determined from the focal mechanism inversion of Sumy et al. [2014].

  10. Split Hopkinson Resonant Bar Test for Sonic-Frequency Acoustic Velocity and Attenuation Measurements of Small, Isotropic Geologic Samples

    SciTech Connect

    Nakagawa, S.

    2011-04-01

    Mechanical properties (seismic velocities and attenuation) of geological materials are often frequency dependent, which necessitates measurements of the properties at frequencies relevant to a problem at hand. Conventional acoustic resonant bar tests allow measuring seismic properties of rocks and sediments at sonic frequencies (several kilohertz) that are close to the frequencies employed for geophysical exploration of oil and gas resources. However, the tests require a long, slender sample, which is often difficult to obtain from the deep subsurface or from weak and fractured geological formations. In this paper, an alternative measurement technique to conventional resonant bar tests is presented. This technique uses only a small, jacketed rock or sediment core sample mediating a pair of long, metal extension bars with attached seismic source and receiver - the same geometry as the split Hopkinson pressure bar test for large-strain, dynamic impact experiments. Because of the length and mass added to the sample, the resonance frequency of the entire system can be lowered significantly, compared to the sample alone. The experiment can be conducted under elevated confining pressures up to tens of MPa and temperatures above 100 C, and concurrently with x-ray CT imaging. The described Split Hopkinson Resonant Bar (SHRB) test is applied in two steps. First, extension and torsion-mode resonance frequencies and attenuation of the entire system are measured. Next, numerical inversions for the complex Young's and shear moduli of the sample are performed. One particularly important step is the correction of the inverted Young's moduli for the effect of sample-rod interfaces. Examples of the application are given for homogeneous, isotropic polymer samples and a natural rock sample.

  11. The upper mantle structure of the central Rio Grande rift region from teleseismic P and S wave travel time delays and attenuation

    USGS Publications Warehouse

    Slack, P.D.; Davis, P.M.; Baldridge, W.S.; Olsen, K.H.; Glahn, A.; Achauer, U.; Spence, W.

    1996-01-01

    The lithosphere beneath a continental rift should be significantly modified due to extension. To image the lithosphere beneath the Rio Grande rift (RGR), we analyzed teleseismic travel time delays of both P and S wave arrivals and solved for the attenuation of P and S waves for four seismic experiments spanning the Rio Grande rift. Two tomographic inversions of the P wave travel time data are given: an Aki-Christofferson-Husebye (ACH) block model inversion and a downward projection inversion. The tomographic inversions reveal a NE-SW to NNE-SSW trending feature at depths of 35 to 145 km with a velocity reduction of 7 to 8% relative to mantle velocities beneath the Great Plains. This region correlates with the transition zone between the Colorado Plateau and the Rio Grande rift and is bounded on the NW by the Jemez lineament, a N52??E trending zone of late Miocene to Holocene volcanism. S wave delays plotted against P wave delays are fit with a straight line giving a slope of 3.0??0.4. This correlation and the absolute velocity reduction imply that temperatures in the lithosphere are close to the solidus, consistent with, but not requiring, the presence of partial melt in the mantle beneath the Rio Grande rift. The attenuation data could imply the presence of partial melt. We compare our results with other geophysical and geologic data. We propose that any north-south trending thermal (velocity) anomaly that may have existed in the upper mantle during earlier (Oligocene to late Miocene) phases of rifting and that may have correlated with the axis of the rift has diminished with time and has been overprinted with more recent structure. The anomalously low-velocity body presently underlying the transition zone between the core of the Colorado Plateau and the rift may reflect processes resulting from the modern (Pliocene to present) regional stress field (oriented WNW-ESE), possibly heralding future extension across the Jemez lineament and transition zone.

  12. Continuous subsurface velocity measurement with coda wave interferometry

    E-print Network

    Niu, Fenglin

    to 10À8 PaÀ1 [e.g., Birch, 1960, 1961; Simmons, 1964]. Such dependence is attributed to the opening, and B. Wang (2008), Continuous subsurface velocity measurement with coda wave interferometry, J. Geophys/closing of micro- cracks in response to changes in the stress normal to the crack surface [e.g., Walsh, 1965; Nur

  13. Selective continuous quantum measurements: Restricted path integrals and wave equations

    E-print Network

    Lajos Diosi

    1995-01-10

    We discuss both the restricted path integral (RPI) and the wave equation (WE) techniques in the theory of continuous quantum measurements. We intend to make Mensky's fresh review complete by transforming his "effective" WE with complex Hamiltonian into Ito-differential equations.

  14. Measurement of the Schrodinger wave of a single particle

    E-print Network

    Yakir Aharonov; Lev Vaidman

    1993-04-28

    We show that it is possible to measure Schrodinger wave of a single quantum system. This provides a strong argument for associating physical reality with the quantum state of a single system, and challenges the usual assumption that the quantum state has physical meaning only for an ensemble of identical systems.

  15. Modal wave-front estimation from phase derivative measurements

    Microsoft Academic Search

    Ronald Cubalchini

    1979-01-01

    Modal estimation of wave-front phase from phase derivatives is discussed. It is shown that it is desirable to minimize the number of modes estimated and the number of measurements used to maintain the quality of the estimates of low-order modes. It is also shown that mode cross coupling occurs when one tries to estimate modes higher than astigmatism.

  16. Histogram measurement of ADC nonlinearities using sine waves

    Microsoft Academic Search

    Jerome Blair

    1994-01-01

    This paper gives results concerning the measurement of differential and integral nonlinearity of ADC's using the histogram method with a sine wave input signal. We specify the amount of overdrive required as a function of the noise level and the desired accuracy and the number of samples required as a function of the desired accuracy, the desired confidence level, and

  17. Analysis of rain attenuation from experimental drop size distributions

    Microsoft Academic Search

    Jose M. Garcia-Rubia; Jose M. Riera; Ana Benarroch; Pedro Garcia

    2010-01-01

    The prediction and analysis of rain attenuation is gaining interest in the recent years, because of the increasing use of millimetre-wave radio communication systems. In these frequencies, propagation in the troposphere produces strong degradations in the presence of rain, with deep fades for even moderate rainfall rates. More detailed measurements of the rain phenomena can be obtained with the use

  18. Geophysical Prospecting 35, 187-196, 1987 IN SITU MEASUREMENTS OF SHEAR-WAVE

    E-print Network

    Snieder, Roel

    Geophysical Prospecting 35, 187-196, 1987 IN SITU MEASUREMENTS OF SHEAR-WAVE VELOCITY I N SEDIMENTS,R. and NOLET,G. 1987, In Situ Measurement of Shear-Wave Velocity in Sediments with Higher-Mode Rayleigh Waves properties of these Rayleigh waves were measured in the 2-D amplitude spectrum-orf,k-spectrum-and resulted

  19. Shack Hartmann wave-front measurement with a large F-number plastic microlens array

    E-print Network

    Yoon, Geunyoung

    Shack Hartmann wave-front measurement with a large F-number plastic microlens array Geun Young Yoon, with a constant peak intensity. One can improve the wave-front measurement accuracy by reducing the spot the wave-front sensor gives an appropriate defocus and astigmatism, and the laser wave front is measured

  20. Planetary and Space Science 54 (2006) 512527 Analysis methods for multi-component wave measurements

    E-print Network

    Santolik, Ondrej

    2006-01-01

    of electromagnetic waves based on the multi-component measurements of the DEMETER spacecraft. Using the fact by different methods. We use these plane-wave estimates to interpret measurements of the observed wave measurements. We show the first results of these analysis techniques for different types of wave emissions

  1. Electric Field Measurements of Directly Converted Lower Hybrid Waves at a Density Striation

    E-print Network

    California at Los Angles, University of

    1 Electric Field Measurements of Directly Converted Lower Hybrid Waves at a Density Striation S in that only the magnetic fields of the waves were measured. Recent experiments at the LAPD directly measure that whistler waves incident on a field-aligned density striation will produce lower hybrid waves via a linear

  2. PROOF COPY 015417JCP Onset of decoherence: Six-wave mixing measurements of vibrational

    E-print Network

    Apkarian, V. Ara

    PROOF COPY 015417JCP PROOF COPY 015417JCP Onset of decoherence: Six-wave mixing measurements October 2003; accepted 10 February 2004 Pump­probe, four-wave, and six-wave mixing measurements of I2 coherence on the ground electronic X-state; and parametric six-wave mixing SWM measure- ments are used

  3. Proceedings of the Combustion Institute, Volume 29, 2002/pp. 18091815 MEASUREMENTS OF INCOHERENT ACOUSTIC WAVE SCATTERING

    E-print Network

    Lieuwen, Timothy C.

    -0150, USA This paper presents measurements of acoustic wave scattering from turbulent, premixed flames. These measurements were obtained by directing highly coherent 5­15 kHz waves at a rim-stabilized, premixed flame and measuring the scattered waves. Specific attention is focused on the incoherent wave character- istics

  4. Measurements of the Linear Kinetic Plasma Response to Alfvén Waves

    NASA Astrophysics Data System (ADS)

    Schroeder, J. W. R.; Skiff, F.; Howes, G. G.; Kletzing, C. A.; Carter, T. A.; Dorfman, S.

    2014-10-01

    Alfvén waves likely account for a significant fraction of auroral electron acceleration. However, a direct test of electron acceleration by Alfvén waves has never been accomplished. Complex trajectories and limited resolutions have prevented in situ observations from completing thorough tests of existing theory. Until now, laboratory diagnostics have not been sensitive to the predicted small fluctuations in the tail of the electron distribution function fe. A novel diagnostic developed at the University of Iowa uses the absorption of a small-amplitude whistler wave to measure fe up to 1 keV with 0 . 1 % accuracy. Inertial Alfvén waves (vte /vA ~ 0 . 2) with ?B / B ~10-5 are launched in an overdense plasma at the Large Plasma Device (LaPD) with B0 = 1800 G. Under these conditions, only the whistler mode propagates parallel to the background magnetic field at frequencies just below the electron cyclotron frequency. Results show fluctuations in the tail of the distribution function at the frequency of the Alfvén wave. An analytic solution from the Boltzmann equation is used to describe experimental results. Further analysis of measurements is presented and is compared to theoretical predictions.

  5. Measurement of smoke concentration using degenerate four-wave mixing

    Microsoft Academic Search

    T C Cole; W A Cole; R W Pitz

    2002-01-01

    Degenerate four-wave mixing (DFWM) was successfully used to monitor a wide range of smoke concentrations (0.1-10 mg m?3) in sample cells. To the authors' knowledge, this is the first measurement of smoke by DFWM. The DFWM method is very sensitive, measuring down to ?0.1 ppb soot volume fraction. To verify the visible laser DFWM system, NO2 concentrations from 2 to

  6. Speed of sound and acoustic attenuation of compounds affected during optoacoustic monitoring of thermal therapies measured in the temperature range from 5°C to 60°C

    NASA Astrophysics Data System (ADS)

    Oruganti, Tanmayi; Petrova, Elena; Oraevsky, Alexander A.; Ermilov, Sergey A.

    2015-03-01

    Optoacoustic (photoacoustic) imaging is being adopted for monitoring tissue temperature during hypothermic and hyperthermic cancer treatments. The technique's accuracy benefits from the knowledge of speed of sound (SoS) and acoustic coefficient of attenuation (AcA) as they change with temperature in biological tissues, blood, and acoustic lens of an ultrasound probe. In these studies we measured SoS and AcA of different ex vivo tissues and blood components (plasma and erythrocyte concentrates) in the temperature range from 5°C to 60°C. We used the technique based on measurements of time-delay and spectral amplitude of pressure pulses generated by wideband planar acoustic waves propagating through the interrogated medium. Water was used as a reference medium with known acoustic properties. In order to validate our experimental technique, we measured the temperature dependence of SoS and AcA for aqueous NaCl solution of known concentration and obtained the results in agreement with published data. Similar to NaCl solution and pure water, SoS in blood and plasma was monotonously increasing with temperature. However, SoS of erythrocyte concentrates displayed abnormalities at temperatures above 45°C, suggesting potential effects from hemoglobin denaturation and/or hemolysis of erythrocytes. On the contrary to aqueous solutions, the SoS in polyvinyl-chloride (plastisol) - a material frequently used for mimicking optical and acoustic properties of tissues - decreased with temperature. We also measured SoS and AcA in silicon material of an acoustic lens and did not observe temperature-related changes of SoS.

  7. Huygens/ASI plasma wave analyzer capabilities for aerosol measurement

    NASA Technical Reports Server (NTRS)

    Borucki, William J.; Fulchignoni, Marcello

    1992-01-01

    The capabilities of the Huygens Atmospheric Structure Instrument (HASI) are described. These include measurement of atmospheric electrical conductivity by the plasma wave analyzer. How measurement of the atmospheric conductivity can lead to an estimate or the total surface area of the aerosols as a function of altitude is outlined. It is concluded that since the ASI is designed to measure the electrical conductivity as well as the pressure and temperature as a function of altitude, its results should provide a useful check on other instruments that are designed to measure the abundance of aerosols in a limited range of sizes.

  8. Towards a quantitative, measurement-based estimate of the uncertainty in photon mass attenuation coefficients at radiation therapy energies

    NASA Astrophysics Data System (ADS)

    Ali, E. S. M.; Spencer, B.; McEwen, M. R.; Rogers, D. W. O.

    2015-02-01

    In this study, a quantitative estimate is derived for the uncertainty in the XCOM photon mass attenuation coefficients in the energy range of interest to external beam radiation therapy—i.e. 100 keV (orthovoltage) to 25 MeV—using direct comparisons of experimental data against Monte Carlo models and theoretical XCOM data. Two independent datasets are used. The first dataset is from our recent transmission measurements and the corresponding EGSnrc calculations (Ali et al 2012 Med. Phys. 39 5990–6003) for 10–30 MV photon beams from the research linac at the National Research Council Canada. The attenuators are graphite and lead, with a total of 140 data points and an experimental uncertainty of ˜0.5% (k = 1). An optimum energy-independent cross section scaling factor that minimizes the discrepancies between measurements and calculations is used to deduce cross section uncertainty. The second dataset is from the aggregate of cross section measurements in the literature for graphite and lead (49 experiments, 288 data points). The dataset is compared to the sum of the XCOM data plus the IAEA photonuclear data. Again, an optimum energy-independent cross section scaling factor is used to deduce the cross section uncertainty. Using the average result from the two datasets, the energy-independent cross section uncertainty estimate is 0.5% (68% confidence) and 0.7% (95% confidence). The potential for energy-dependent errors is discussed. Photon cross section uncertainty is shown to be smaller than the current qualitative ‘envelope of uncertainty’ of the order of 1–2%, as given by Hubbell (1999 Phys. Med. Biol 44 R1–22).

  9. Towards a quantitative, measurement-based estimate of the uncertainty in photon mass attenuation coefficients at radiation therapy energies.

    PubMed

    Ali, E S M; Spencer, B; McEwen, M R; Rogers, D W O

    2015-02-21

    In this study, a quantitative estimate is derived for the uncertainty in the XCOM photon mass attenuation coefficients in the energy range of interest to external beam radiation therapy-i.e. 100 keV (orthovoltage) to 25 MeV-using direct comparisons of experimental data against Monte Carlo models and theoretical XCOM data. Two independent datasets are used. The first dataset is from our recent transmission measurements and the corresponding EGSnrc calculations (Ali et al 2012 Med. Phys. 39 5990-6003) for 10-30 MV photon beams from the research linac at the National Research Council Canada. The attenuators are graphite and lead, with a total of 140 data points and an experimental uncertainty of ?0.5% (k = 1). An optimum energy-independent cross section scaling factor that minimizes the discrepancies between measurements and calculations is used to deduce cross section uncertainty. The second dataset is from the aggregate of cross section measurements in the literature for graphite and lead (49 experiments, 288 data points). The dataset is compared to the sum of the XCOM data plus the IAEA photonuclear data. Again, an optimum energy-independent cross section scaling factor is used to deduce the cross section uncertainty. Using the average result from the two datasets, the energy-independent cross section uncertainty estimate is 0.5% (68% confidence) and 0.7% (95% confidence). The potential for energy-dependent errors is discussed. Photon cross section uncertainty is shown to be smaller than the current qualitative 'envelope of uncertainty' of the order of 1-2%, as given by Hubbell (1999 Phys. Med. Biol 44 R1-22). PMID:25622289

  10. Fundamental measurements in standing-wave and traveling-wave thermoacoustics

    NASA Astrophysics Data System (ADS)

    Petculescu, Gabriela

    The periodic compressions and expansions of the gas in an acoustic wave, combined with heat exchange with external reservoirs, generate a rich variety of thermoacoustic processes. A new class of heat pumps and prime-movers make use of these effects. In a traditional standing-wave thermoacoustic device, the energy conversion occurs in the stack, influencing the device efficiency. A major part of the dissertation focuses on fundamental measurements of stack properties. Different geometries and nonlinear effects are studied with a versatile volume-modulation technique yielding the complex compressibility, C(o) (equivalent to the cycle P-V diagram), for a variety of temperature gradients and frequencies. The thermoacoustic function FT, describing the fluid oscillatory temperature field in the stack, can be calculated from compressibility measurements with a zero temperature gradient. When a gradient is imposed on the stack, thermoacoustic gain can be empirically determined from the compressibility, for any stack geometry. The method was first tested with a circular geometry for which theoretical calculations were possible. Good agreement was found between theory and experiment. The technique was further adapted to look at the effect of high displacement amplitudes relative to the stack length, beyond the range of validity of the linear theory. The measurements were extended to look at pin-array stacks, which are particularly interesting because of their convex geometry, which enhances the ratio of useful power to viscous dissipation. Pins parallel and perpendicular to the acoustic axis were studied. The results of the zero temperature gradient experiment tested theoretical assumptions regarding thermal and viscous effects. With a nonzero gradient, thermoacoustic gain was measured and found to be the same for both geometries. Traveling-wave thermoacoustics is discussed in the last chapter. Earlier work showed that amplification of pure traveling waves is surmounted by viscous losses, unless the acoustic impedance in the regenerator is increased. Traveling and standing waves were produced in a resonator in a controlled ratio, with the regenerator placed at the velocity node of the standing wave. Traveling-wave amplification across the regenerator was significantly improved by the addition of the standing wave component. An optimal standing-wave-ratio, specific to a given regenerator/heat-exchanger geometry was observed.

  11. Reduction of the Buildup Contribution in Gamma Ray Attenuation Measurements and a New Way to Study This Experiment in a Student Laboratory

    ERIC Educational Resources Information Center

    Adamides, E.; Kavadjiklis, A.; Koutroubas, S.K.; Moshonas, N.; Tzedakis, A.; Yiasemides, K.

    2014-01-01

    In continuation of our investigation into the buildup phenomenon appearing in gamma ray attenuation measurements in laboratory experiments we study the dependence of the buildup factor on the area of the absorber in an effort to reduce the buildup of photons. Detailed measurements are performed for up to two mean free paths of [superscript 60]Co…

  12. Measurement of sound speed vs. depth in South Pole ice: pressure waves and shear waves

    SciTech Connect

    IceCube Collaboration; Klein, Spencer

    2009-06-04

    We have measured the speed of both pressure waves and shear waves as a function of depth between 80 and 500 m depth in South Pole ice with better than 1% precision. The measurements were made using the South Pole Acoustic Test Setup (SPATS), an array of transmitters and sensors deployed in the ice at the South Pole in order to measure the acoustic properties relevant to acoustic detection of astrophysical neutrinos. The transmitters and sensors use piezoceramics operating at {approx}5-25 kHz. Between 200 m and 500 m depth, the measured profile is consistent with zero variation of the sound speed with depth, resulting in zero refraction, for both pressure and shear waves. We also performed a complementary study featuring an explosive signal propagating vertically from 50 to 2250 m depth, from which we determined a value for the pressure wave speed consistent with that determined for shallower depths, higher frequencies, and horizontal propagation with the SPATS sensors. The sound speed profile presented here can be used to achieve good acoustic source position and emission time reconstruction in general, and neutrino direction and energy reconstruction in particular. The reconstructed quantities could also help separate neutrino signals from background.

  13. Validation of National Data Buoy Center Directional Wave Measurements Using Swell Waves from Distant Storms

    Microsoft Academic Search

    Theodore Mettlach; C.-C. Teng

    2006-01-01

    Accuracy of swell wave direction measurements derived from Datawell Hippy 40-second Mark II and National Data Buoy Center angular rate sensor (ARS) are determined using two NDBC west coast stations: 46042 in Monterey Bay and 46028 near Cape San Martin. These are located in deep water 66 nautical miles apart off the central coast of California. Hippy and ARS spectral

  14. Hydrogel-encapsulated soil: a tool to measure contaminant attenuation in situ.

    PubMed

    Spalding, Brian P; Brooks, Scott C; Watson, David B

    2010-04-15

    Hydrogel encapsulation presents a novel and powerful general method to observe many water-solid contaminant interactions in situ for a variety of aqueous media including groundwater, with a variety of nondestructive analytical methods, and with a variety of solids including contaminated soil. After intervals of groundwater immersion, polyacrylamide hydrogel-encapsulated solid specimens were retrieved, assayed nondestructively for uranium and other elements using X-ray fluorescence spectroscopy, and replaced in groundwater for continued reaction. Desorption dynamics of uranium from contaminated soils and other solids, when moved to uncontaminated groundwater, were fit to a general two-component kinetic retention model with slow-release and fast-release fractions for the total uranium. In a group of Oak Ridge soils with varying ambient uranium contamination (169-1360 mg/kg), the uranium fraction retained under long-term in situ kinetic behavior was strongly correlated (r(2) = 0.89) with residual uranium after laboratory sequential extraction of water-soluble and cation-exchangeable fractions of the soils. To illustrate how potential remedial techniques can be compared to natural attenuation, thermal stabilization of one soil increased the size of its long-term in situ retained fraction from 50% to 88% of the total uranium and increased the half-life of that long-term retained fraction from 990 to 40000 days. PMID:20230051

  15. Phase Velocity Method for Guided Wave Measurements in Composite Plates

    NASA Astrophysics Data System (ADS)

    Moreno, E.; Galarza, N.; Rubio, B.; Otero, J. A.

    Carbon Fiber Reinforced Polymer is a well-recognized material for aeronautic applications. Its plane structure has been widely used where anisotropic characteristics should be evaluated with flaw detection. A phase velocity method of ultrasonic guided waves based on a pitch-catch configuration is presented for this purpose. Both shear vertical (SV) and shear horizontal (SH) have been studied. For SV (Lamb waves) the measurements were done at different frequencies in order to evaluate the geometrical dispersion and elastic constants. The results for SV are discussed with an orthotropic elastic model. Finally experiments with lamination flaws are presented.

  16. A self-zeroing capacitance probe for water wave measurements

    NASA Technical Reports Server (NTRS)

    Long, Steven R.

    1992-01-01

    The wave probe developed at the Air-Sea Interaction Research Facility was designed to measure the surface elevation fluctuations of water waves. Design criteria included being linear in response, self-zeroing to the mean water level, having multiple operating ranges so that the instrument's maximum output could be matched to the maximum surface elevation over varying conditions, and be as noise-free as possible. The purpose of this publication is to provide a detailed description of the design and construction of this probe.

  17. Flood wave attenuation by a wetland following a beaver dam failure on a second order boreal stream

    Microsoft Academic Search

    Graham R. Hillman

    1998-01-01

    On June 8 1994, a beaver dam on Rocky Creek, a small stream in central Alberta, failed and released about 7500 m3 of water. The estimated peak of the resulting flood wave was 15 m3 s?1, which is 3.5 times the maximum discharge recorded for the creek over 23 years. The flood wave destroyed five hydrometric\\u000a stations, scoured some channel

  18. A simple rain attenuation model for earth-space radio links operating at 10-35 GHz

    NASA Technical Reports Server (NTRS)

    Stutzman, W. L.; Yon, K. M.

    1986-01-01

    The simple attenuation model has been improved from an earlier version and now includes the effect of wave polarization. The model is for the prediction of rain attenuation statistics on earth-space communication links operating in the 10-35 GHz band. Simple calculations produce attenuation values as a function of average rain rate. These together with rain rate statistics (either measured or predicted) can be used to predict annual rain attenuation statistics. In this paper model predictions are compared to measured data from a data base of 62 experiments performed in the U.S., Europe, and Japan. Comparisons are also made to predictions from other models.

  19. Precision measurements in ion traps using slowly moving standing waves

    E-print Network

    A. Walther; U. Poschinger; K. Singer; F. Schmidt-Kaler

    2011-05-09

    The present paper describes the experimental implementation of a measuring technique employing a slowly moving, near resonant, optical standing wave in the context of trapped ions. It is used to measure several figures of merit that are important for quantum computation in ion traps and which are otherwise not easily obtainable. Our technique is shown to offer high precision, and also in many cases using a much simpler setup than what is normally used. We demonstrate here measurements of i) the distance between two crystalline ions, ii) the Lamb-Dicke parameter, iii) temperature of the ion crystal, and iv) the interferometric stability of a Raman setup. The exact distance between two ions, in units of standing wave periods, is very important for motional entangling gates, and our method offers a practical way of calibrating this distance in the typical lab situation.

  20. Pressure measurements of a three wave journal air bearing

    NASA Technical Reports Server (NTRS)

    Dimofte, Florin; Addy, Harold E., Jr.

    1994-01-01

    In order to validate theoretical predictions of a wave journal bearing concept, a bench test rig was assembled at NASA Lewis Research Center to measure the steady-state performance of a journal air bearing. The tester can run up to 30,000 RPM and the spindle has a run out of less than 1 micron. A three wave journal bearing (50 mm diameter and 58 mm length) has been machined at NASA Lewis. The pressures at 16 ports along the bearing circumference at the middle of the bearing length were measured and compared to the theoretical prediction. The bearing ran at speeds up to 15,000 RPM and certain loads. Good agreement was found between the measured and calculated pressures.

  1. ULF wave measurements onboard the Interball auroral probe

    NASA Astrophysics Data System (ADS)

    Perraut, S.; Roux, A.; Darrouzet, F.; de Villedary, C.; Mogilevsky, M.; Lefeuvre, F.

    1998-09-01

    The IESP experiment implemented onboard the Interball auroral probe measures the six components (3B, 3E) of the waves in the ULF range: 0.1-10 Hz and from time to time 0-30 Hz. Two different kinds of waves have been observed in the auroral region at altitudes between 10 000 and 20 000 km: (1) electrostatic emissions which consist of quasi-monochromatic structures with frequencies above the oxygen gyrofrequency, superimposed on a wide band signal interpreted as a Doppler broadening, (2) electromagnetic wide band spectrum fluctuations. These emissions are interpreted as current-driven electromagnetic or electrostatic ion cyclotron waves. The electromagnetic/electrostatic character is controlled by the plasma parameter i and by the O+ concentration.

  2. Attenuation studies of booster-rocket propellants and their simulants

    SciTech Connect

    Weirick, L.J.

    1990-08-01

    A series of impact experiments on a composite propellant, an energetic propellant, and their simulants was recently completed using a light-gas gun. Previous experiments were done to obtain Hugoniot data, to investigate the pressure threshold at which a reaction occurs, and to measure spall damage at various impact velocities. The present studies measured the attenuation of shock waves in these materials, completing the shock characterization needed for material modeling. An initial impulse of 2.0 GPa magnitude and {approximately}0.6 {mu}s duration was imposed upon samples of various thicknesses. VISAR was used to measure the free-surface velocity at the back of the samples; these data were used to generate a curve of shock-wave attenuation versus sample thickness for each material. Results showed that all four materials attenuated the shock wave very similarly. Material thicknesses of 3.0, 7.62, 12.7, and 19.0 mm attenuated the shock wave {approximately}16%, 33%, 50%, and 66% respectively. 14 refs., 12 figs., 4 tabs.

  3. Evanescent wave absorption measurements of corroded materials using ATR and optical fibers

    NASA Astrophysics Data System (ADS)

    Namkung, Juock; Hoke, Mike; Schwartz, Andy

    2011-06-01

    The purpose of this research effort is to develop an in-situ corrosion sensing capability. The technique will permit detection of corrosion on and within aircraft structures. This includes component junctions that are susceptible to corrosion but which are not accessible for visual inspection. The prototype experimental configuration we are developing includes long wave infrared transmitting optical fiber probes interfaced with a Fourier Transform Infrared (FTIR) interferometer for evanescent wave absorption spectroscopic measurements. The mature and fielded technique will allow periodic remote sensing for detection of corrosion and for general onboard aircraft structural health monitoring. An experimental setup using an Attenuated Total Reflection (ATR) crystal integrated with an FTIR spectrometer has been assembled. Naturally occurring corrosion including Aluminum Hydroxide [Al(OH)3] is one of the main corrosion products of aluminum the principle structural metal of aircraft. Absorption spectra of our model corrosion product, pure Al(OH)3, have been collected with this ATR/FTIR experimental setup. The Al(OH)3spectra serve as reference spectral signatures. The spectra of corrosion samples from a simulated corrosion process have been collected and compared with the reference Al(OH)3 spectra. Also absorption spectra of naturally occurring corrosion collected from a fielded corroded aircraft part have been obtained and compared with the spectra from the simulated corrosion.

  4. Multiparameter full waveform inversion of multicomponent ocean-bottom-cable data from the Valhall field. Part 1: imaging compressional wave speed, density and attenuation

    NASA Astrophysics Data System (ADS)

    Prieux, Vincent; Brossier, Romain; Operto, Stéphane; Virieux, Jean

    2013-09-01

    Multiparameter full waveform inversion (FWI) is a challenging quantitative seismic imaging method for lithological characterization and reservoir monitoring. The difficulties in multiparameter FWI arise from the variable influence of the different parameter classes on the phase and amplitude of the data, and the trade-off between these. In this framework, choosing a suitable parametrization of the subsurface and designing the suitable FWI workflow are two key methodological issues in non-linear waveform inversion. We assess frequency-domain visco-acoustic FWI to reconstruct the compressive velocity (VP), the density (?) or the impedance (IP) and the quality factor (QP), from the hydrophone component, using a synthetic data set that is representative of the Valhall oil field in the North Sea. We first assess which of the (VP, ?) and (VP, IP) parametrizations provides the most reliable FWI results when dealing with wide-aperture data. Contrary to widely accepted ideas, we show that the (VP, ?) parametrization allows a better reconstruction of both the VP, ? and IP parameters, first because it favours the broad-band reconstruction of the dominant VP parameter, and secondly because the trade-off effects between velocity and density at short-to-intermediate scattering angles can be removed by multiplication, to build an impedance model. This allows for the matching of the reflection amplitudes, while the broad-band velocity model accurately describes the kinematic attributes of both the diving waves and reflections. Then, we assess different inversion strategies to recover the quality factor QP, in addition to parameters VP and ?. A difficulty related to attenuation estimation arises because, on the one hand the values of QP are on average one order of magnitude smaller than those of VP and ?, and on the other hands model perturbations relative to the starting models can be much higher for QP than for VP and ? during FWI. In this framework, we show that an empirical tuning of the FWI regularization, which is adapted to each parameter class, is a key issue to correctly account for the attenuation in the inversion. We promote a hierarchical approach where the dominant parameter VP is reconstructed first from the full data set (i.e. without any data preconditioning) to build a velocity model as kinematically accurate as possible before performing the joint update of the three parameter classes during a second step. This hierarchical imaging of compressive wave speed, density and attenuation is applied to a real wide-aperture ocean-bottom-cable data set from the Valhall oil field. Several geological features, such as accumulation of gas below barriers of claystone and soft quaternary sediment are interpreted in the FWI models of density and attenuation. The models of VP, ? and QP that have been developed by visco-acoustic FWI of the hydrophone data can be used as initial models to perform visco-elastic FWI of the geophone data for the joint update of the compressive and shear wave speeds.

  5. Attenuation and Velocity tomography can we join them?

    NASA Astrophysics Data System (ADS)

    Debski, Wojciech

    2013-04-01

    Velocity tomography, is now routinely used to image velocity distributions which are subsequently interpreted in terms of the Earth or rock-sample structure. This technique has been successfully used in detailed mapping of the Earth in various scales ranging from the whole globe until very local rock-mass structure, e.g. in mines. It is also used in geo-technical (tunnels, mines, water dams, etc.) and laboratory measurements. The second tomography technique, namely attenuation tomography, is used to image another physical property of rocks: the acoustic attenuation structure usually describe by the parameter Q. This technique is, however, much more difficult than velocity tomography because the attenuation of seismic/acoustic waves is a much more subtle effect than a variation of delays of energy arrival times due to velocity heterogeneities. There exist a lot of factors that can easily disturb attenuation measurements so it is difficult to obtain a reliable image of the attenuation structure. For this reason, a very high quality of data used for attenuation tomography must be ensured. Nevertheless, the additional effort necessary to obtain an image of Q is worthwhile because Q is regarded to be more sensitive to the rock structure than seismic/acoustic wave velocity. Imaging the Q distribution can be achieved by inverting various characteristics of the measured signals: amplitudes, spectra decay, pulse broadening or central frequency shift. The advantages and limitations of each of these approaches are well known. In this presentation we discuss the approach developed for the acoustic ultrasonic tomography imaging and called Enhanced Velocity Tomography and possibility of its using in a ``global seismological'' framework. It consists in a combination of both velocity and attenuation tomography into one scheme to maximize the advantage of the robustness of velocity and the sensitivity to the micro-structure of attenuation.

  6. Ocean Waves Measurement and Analysis, Fifth International Symposium WAVES 2005, 3rd-7th, July, 2005. Madrid, Spain Paper number: 197

    E-print Network

    Grilli, Stéphan T.

    Ocean Waves Measurement and Analysis, Fifth International Symposium WAVES 2005, 3rd-7th, July, 2005. Madrid, Spain Paper number: 197 #12;Ocean Waves Measurement and Analysis, Fifth International Symposium International Symposium WAVES 2005, 3rd-7th, July, 2005. Madrid, Spain #12;Ocean Waves Measurement and Analysis

  7. Rapid Response Measurements of Hurricane Waves and Storm Surge

    NASA Astrophysics Data System (ADS)

    Gravois, U.

    2010-12-01

    Andrew (1992), Katrina (2005), and Ike (2008) are recent examples of extensive damage that resulted from direct hurricane landfall. Some of the worst damages from these hurricanes are caused by wind driven waves and storm surge flooding. The potential for more hurricane disasters like these continues to increase as a result of population growth and real estate development in low elevation coastal regions. Observational measurements of hurricane waves and storm surge play an important role in future mitigation efforts, yet permanent wave buoy moorings and tide stations are more sparse than desired. This research has developed a rapid response method using helicopters to install temporary wave and surge gauges ahead of hurricane landfall. These temporary installations, with target depths from 10-15 m and 1-7 km offshore depending on the local shelf slope, increase the density of measurement points where the worst conditions are expected. The method has progressed to an operational state and has successfully responded to storms Ernesto (2006), Noel (2007), Fay (2008), Gustav (2008), Hanna (2008) and Ike (2008). The temporary gauges are pressure data loggers that measure at 1 Hz continuously for 12 days and are post-processed to extract surge and wave information. For the six storms studied, 45 out of 49 sensors were recovered by boat led scuba diver search teams, with 43 providing useful data for an 88 percent success rate. As part of the 20 sensor Hurricane Gustav response, sensors were also deployed in lakes and bays inLouisiana, east of the Mississippi river delta. Gustav was the largest deployment to date. Generally efforts were scaled back for storms that were not anticipated to be highly destructive. For example, the cumulative total of sensors deployed for Ernesto, Noel, Fay and Hanna was only 20. Measurement locations for Gustav spanned over 800 km of exposed coastline from Louisiana to Florida with sensors in close proximity to landfall near Cocodrie, Louisiana. Surge measurements between landfall and the Mississippi delta show 1.5 - 2 m of surge and values exceeding 2 m further from landfall north of the Mississippi delta. These observations demonstrate the importance of coastal geography on storm surge vulnerability. Waves measurements from Gustav show large waves of 5 m at all exposed locations from landfall to western Florida. Some smaller values were also recorded, likely to be due to depth limited breaking or sheltering from the Mississippi delta. Two weeks after Hurricane Gustav, major Hurricane Ike entered the Gulf of Mexico threatening Texas. Unfortunately the sensors already deployed for Gustav reached the 12 day memory limit and did not catch the most extreme conditions of Ike. However, 9 additional sensors were deployed for Ike spanning 360 km of the Texas coast. These measurements show surge east of the Galveston, Texas landfall exceeding 4.5 m and wave heights greater than 5 m. Hurricane Ike was by far the most destructive of the 6 storms measured and has spawned separate work relating the extent of building damage to these measurements.

  8. Upper mantle Q and thermal structure beneath Tanzania, East Africa from teleseismic P wave spectra

    Microsoft Academic Search

    Anupama Venkataraman; Andrew A. Nyblade; Jeroen Ritsema

    2004-01-01

    We measure P wave spectral amplitude ratios from deep-focus earthquakes recorded at broadband seismic stations of the Tanzania network to estimate regional variation of sublithospheric mantle attenuation beneath the Tanzania craton and the eastern branch of the East African Rift. One-dimensional profiles of QP adequately explain the systematic variation of P wave attenuation in the sublithospheric upper mantle: QP ~

  9. Upper mantle Q and thermal structure beneath Tanzania, East Africa from teleseismic P wave spectra

    Microsoft Academic Search

    Anupama Venkataraman; Andrew A. Nyblade; Jeroen Ritsema

    2004-01-01

    We measure P wave spectral amplitude ratios from deep-focus earthquakes recorded at broadband seismic stations of the Tanzania network to estimate regional variation of sublithospheric mantle attenuation beneath the Tanzania craton and the eastern branch of the East African Rift. One-dimensional profiles of QP adequately explain the systematic variation of P wave attenuation in the sublithospheric upper mantle: QP ?

  10. Measurement of modal amplitudes of guided waves in rails

    NASA Astrophysics Data System (ADS)

    Loveday, Philip W.

    2008-03-01

    One important application of guided wave ultrasound is that of rail condition monitoring where long lengths of rail can be monitored from permanently attached transducer locations. During the development of transducers for such a system it is advantageous to be able to measure the amplitude of the individual modes of propagation on a short length of rail in the laboratory. This paper describes a method of extracting modal amplitudes from measured time domain signals performed at a limited set of points on the waveguide. The method uses the wave propagation characteristics of the waveguide, predicted by a semi-analytical finite element model, to extract the modal amplitudes from experimental measurements. The frequency response at a set of measurement locations is described by a superposition (with unknown amplitude coefficients) of the frequency response of the modes that propagate in the frequency range of interest. Experimental time domain responses are measured and transformed to frequency responses. The amplitude of each mode is estimated using the pseudo-inverse to provide a minimum norm least-squares estimate. The technique is demonstrated on a rail excited by a piezoelectric patch transducer. A laser vibrometer was used to measure displacements at five points around the rail circumference at three distances giving a total of 15 measurements. Eight propagating modes were extracted from these measurements. The extracted modes were then used to predict the response at points further along the waveguide and these predictions were verified by further measurements indicating that the modes of propagation were accurately estimated. The technique requires that the distance between the measurement points be known but does not require that the distance from the transducer be known. This feature and the fact that only a few measurements are required make the method suitable for measuring the propagation of individual modes over long distances in the field.

  11. Brachial-ankle pulse wave velocity in the measurement of arterial stiffness: recent evidence and clinical applications.

    PubMed

    Munakata, Masanori

    2014-01-01

    Arterial stiffness is a vascular measure that has been reported to predict cardiovascular events. It is important to measure arterial stiffness in order to determine current vascular status and treatment strategy. Brachial-ankle pulse wave velocity (baPWV) is a unique measure of systemic arterial stiffness that is measured by brachial and tibial arterial wave analyses. Measurement of baPWV is easy and is reproducible. For more than a decade, this measure has been used broadly in East Asian countries. Meta-analysis of cohort studies conducted in the general population with hypertension, diabetes, or end-stage renal disease, and other high-risk individuals have shown that a 1 m/s increase in baPWV is associated with 12% increase in the risk of cardiovascular events. Thus, the Japanese Circulation Society has proposed that a baPWV of 1800 cm/s is a threshold for high-risk category. For baPWV to be clinically applicable, we must confirm that circulation of the lower limbs are normal by examining brachial ankle blood pressure index. In cases of peripheral arterial disease, the reliability of baPWV measurement is attenuated. To further confirm the clinical usefulness of this measure, we need to examine the hypothesis that baPWV-guided therapy could improve prognosis in high-risk patients. PMID:25392144

  12. Acoustic measurement of suspensions of clay and silt particles using single frequency attenuation and backscatter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of ultrasonic acoustic technology to measure the concentration of fine suspended sediments has the potential to greatly increase the temporal and spatial resolution of sediment measurements while reducing the need for personnel to be present at gauging stations during storm events. The conv...

  13. Eulerian measurements of horizontal accelerations in shoaling gravity waves

    NASA Technical Reports Server (NTRS)

    Elgar, Steve; Guza, R. T.; Freilich, M. H.

    1988-01-01

    Laboratory and field measurements of suspended sediment in the nearshore suggest that fluid accelerations are an important factor in sediment transport by oscillatory waves. Here, Eulerian accelerations of the cross-shore velocity are calculated from measurements of velocity obtained by an array of bottom-mounted electromagnetic flow meters spanning a natural surf zone. Large shoreward accelerations of brief duration are associated with the steep front faces of both near-breaking and breaking waves. Weaker offshore accelerations of longer duration occur during passage of the more gently sloped rear faces. The acceleration field is thus strongly skewed in the shoreward direction. Power spectra and bispectra indicate, as expected, that statistics of the acceleration field are significantly influenced by high-frequency motions but are rather insensitive to surf beat.

  14. Multiple component mode conversion coefficients via Lamb wave polarization measurements

    Microsoft Academic Search

    James T. Ayers; Nicoleta Apetre; Massimo Ruzzene

    2011-01-01

    The paper presents a method of quantifying the mode conversion of Lamb waves within a 1D structure from a notch-like asymmetric damage using both in-plane and out-of-plane velocity\\/displacement measurements. The method is applied to data recorded from a Scanning Laser Doppler Vibrometer, and likewise to numerical studies from a plane strain finite element model. A filtering procedure is implemented, and

  15. Optical Heterodyne Measurement of Neon Laser's Millimeter Wave Difference Frequency

    Microsoft Academic Search

    J. L. Hall; W. W. Morey

    1967-01-01

    We report detection and measurement of the millimeter wave difference frequency between two near laser lines at 1.152 ?. The two spectral transitions, separated by 2.26 Å, oscillate in pure neon in a single laser device, producing about 150 ?W total power in several longitudinal modes. The many resulting 51.3-kmc beat frequencies have been studied by optical heterodyne techniques. A

  16. Four-wave mixing wavelength conversion efficiency in semiconductor traveling-wave amplifiers measured to 65 nm of wavelength shift

    Microsoft Academic Search

    Jianhui Zhou; K. J. Vahala; M. A. Newkirk; B. I. Miller

    1994-01-01

    The efficiency of broadband optical wavelength conversion by four-wave mixing in semiconductor traveling-wave amplifiers is measured for wavelength shifts up to 65 nm using a tandem amplifier geometry. A quantity we call the relative conversion efficiency function, which determines the strength of the four-wave mixing nonlinearity, was extracted from the data. Using this quantity, gain requirements for lossless four-wave mixing

  17. Quantum Measurement Theory in Gravitational-Wave Detectors

    NASA Astrophysics Data System (ADS)

    Danilishin, Stefan L.; Khalili, Farid Ya.

    2012-04-01

    The fast progress in improving the sensitivity of the gravitational-wave detectors, we all have witnessed in the recent years, has propelled the scientific community to the point at which quantum behavior of such immense measurement devices as kilometer-long interferometers starts to matter. The time when their sensitivity will be mainly limited by the quantum noise of light is around the corner, and finding ways to reduce it will become a necessity. Therefore, the primary goal we pursued in this review was to familiarize a broad spectrum of readers with the theory of quantum measurements in the very form it finds application in the area of gravitational-wave detection. We focus on how quantum noise arises in gravitational-wave interferometers and what limitations it imposes on the achievable sensitivity. We start from the very basic concepts and gradually advance to the general linear quantum measurement theory and its application to the calculation of quantum noise in the contemporary and planned interferometric detectors of gravitational radiation of the first and second generation. Special attention is paid to the concept of the Standard Quantum Limit and the methods of its surmounting.

  18. Quantum Measurement Theory in Gravitational-Wave Detectors

    E-print Network

    Stefan L. Danilishin; Farid Ya. Khalili

    2012-05-09

    The fast progress in improving the sensitivity of the gravitational-wave (GW) detectors, we all have witnessed in the recent years, has propelled the scientific community to the point, when quantum behaviour of such immense measurement devices as kilometer-long interferometers starts to matter. The time, when their sensitivity will be mainly limited by the quantum noise of light is round the corner, and finding the ways to reduce it will become a necessity. Therefore, the primary goal we pursued in this review was to familiarize a broad spectrum of readers with the theory of quantum measurements in the very form it finds application in the area of gravitational-wave detection. We focus on how quantum noise arises in gravitational-wave interferometers and what limitations it imposes on the achievable sensitivity. We start from the very basic concepts and gradually advance to the general linear quantum measurement theory and its application to the calculation of quantum noise in the contemporary and planned interferometric detectors of gravitational radiation of the first and second generation. Special attention is paid to the concept of Standard Quantum Limit and the methods of its surmounting.

  19. Fiber Optic Attenuators

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Mike Buzzetti designed a fiber optic attenuator while working at Jet Propulsion Laboratory, intended for use in NASA's Deep Space Network. Buzzetti subsequently patented and received an exclusive license to commercialize the device, and founded Nanometer Technologies to produce it. The attenuator functions without introducing measurable back-reflection or insertion loss, and is relatively insensitive to vibration and changes in temperature. Applications include cable television, telephone networks, other signal distribution networks, and laboratory instrumentation.

  20. Accuracy and reliability of Chile's National Air Quality Information System for measuring particulate matter: Beta attenuation monitoring issue.

    PubMed

    Toro A, Richard; Campos, Claudia; Molina, Carolina; Morales S, Raul G E; Leiva-Guzmán, Manuel A

    2015-09-01

    A critical analysis of Chile's National Air Quality Information System (NAQIS) is presented, focusing on particulate matter (PM) measurement. This paper examines the complexity, availability and reliability of monitoring station information, the implementation of control systems, the quality assurance protocols of the monitoring station data and the reliability of the measurement systems in areas highly polluted by particulate matter. From information available on the NAQIS website, it is possible to confirm that the PM2.5 (PM10) data available on the site correspond to 30.8% (69.2%) of the total information available from the monitoring stations. There is a lack of information regarding the measurement systems used to quantify air pollutants, most of the available data registers contain gaps, almost all of the information is categorized as "preliminary information" and neither standard operating procedures (operational and validation) nor assurance audits or quality control of the measurements are reported. In contrast, events that cause saturation of the monitoring detectors located in northern and southern Chile have been observed using beta attenuation monitoring. In these cases, it can only be concluded that the PM content is equal to or greater than the saturation concentration registered by the monitors and that the air quality indexes obtained from these measurements are underestimated. This occurrence has been observed in 12 (20) public and private stations where PM2.5 (PM10) is measured. The shortcomings of the NAQIS data have important repercussions for the conclusions obtained from the data and for how the data are used. However, these issues represent opportunities for improving the system to widen its use, incorporate comparison protocols between equipment, install new stations and standardize the control system and quality assurance. PMID:25796098

  1. Comparison of sound speed and attenuation measured in a sandy sediment to predictions based on the Biot theory of porous media

    Microsoft Academic Search

    Kevin L. Williams; Darrell R. Jackson; Eric I. Thorsos; Dajun Tang; Steven G. Schock

    2002-01-01

    During the sediment acoustics experiment in 1999 (SAX99), several researchers measured sound speed and attenuation. Together, the measurements span the frequency range of about 125 Hz-400 kHz. The data are unique both for the frequency range spanned at a common location, and for the extensive environmental characterization that was carried out as part of SAX99. Environmental measurements were sufficient to

  2. Measurements of plasma wave spectra in Jupiter's magnetosphere

    NASA Technical Reports Server (NTRS)

    Scarf, F. L.; Gurnett, D. A.; Kurth, W. S.

    1981-01-01

    Compressed plots of E field averages for all of the 16-channel spectrum analyzer data from the Voyager 1 and 2 magnetosphere traversals are presented to provide an overall framework for the discussion. The importance of considering peaks as well as averages is illustrated by using 16-channel measurements from the first inbound and last outbound bow shock for Voyager 2. Selected wideband measurements from the waveform receivers are presented to demonstrate how many important wave bursts are variable in times less than or comparable to the 4-s scan period of the 16-channel analyzer.

  3. Diurnal variations of mesospheric ozone using millimeter-wave measurements

    NASA Technical Reports Server (NTRS)

    Wilson, W. J.; Schwartz, P. R.

    1981-01-01

    In March 1979, millimeter-wave observations of the ozone emission line at 101737 MHz were made to measure the diurnal variations in mesospheric ozone. Changes in mesospheric ozone were measured diurnally for a 10-day period. The ozone column above approximately 76 km rapidly decreased after sunrise to half value within 1 hour and was then followed by a slower (approximately 8 hours) decrease to an absolute minimum at 1600 hours. At sunset, the ozone column above approximately 76 km increased rapidly to its maximum value within 2 hours. In the 48-68 km altitude range, the ozone changes were gradual with a minimum near local noon (1200 hours).

  4. Utility of automated brachial ankle pulse wave velocity measurements in hypertensive patients

    Microsoft Academic Search

    Masanori Munakata; Nobuhiko Ito; Tohru Nunokawa; Kaoru Yoshinaga

    2003-01-01

    BackgroundWe examined whether pulse wave velocity (PWV), determined by brachial ankle arterial pressure wave measurements, using a newly developed, fully automated device could be a surrogate measure for carotid femoral PWV.

  5. Laboratory measurements of wave height variations and currents along a steep-sided channel 

    E-print Network

    Way, Francis

    2000-01-01

    for numerical model predictions of wave transformation. A frequently applied model, REFDIF1, was used to compare with the measurements. Orbital velocities and mean currents were also measured to document any wave and bathymetry induced changes in particle...

  6. Simulation of radiometric and attenuation measurements along Earth-satellite links in the 10-to 50-GHz band

    E-print Network

    Marzano, Frank Silvio

    observation point in order to simulate a ground-based station with a beacon receiver and a multichannel to derive a statistical estimation of the total path attenuation from surface rain rate and ground in the telecommunications field is related to the possibility of evaluating the attenuation statistics for given frequency

  7. Maximum Wave Run-up Measured on a Natural Beach Owing to Extreme Waves

    NASA Astrophysics Data System (ADS)

    Thornton, E. B.; MacMahan, J. H.

    2014-12-01

    Unique field data indicative of maximum run-up owing to extreme wave conditions with a 50 year return period are obtained from the distribution of sea-glass on 10-18 m high dunes. The hypothesis that sea-glass is an indicator of maximum run-up is verified by the observations that new sea-glass on a beach is found at the rackline, the highest point of run-up. The source of the sea-glass is a garbage dump on the dune in southern Monterey Bay from 1937-1951. It is estimated that the dump, located on an erosive shoreline, was falling into the ocean by at least 1960, so that the maximum run-up values have a return period of at least 50 years. Various empirical run-up models based both on extensive laboratory and field measurements are assessed to include contributions from sea-swell and infragravity waves, setup and tidal elevation, which are parameterized on wave height and surf parameter, P, which is a function of wave height, period and beach slope. Deep water hindcast waves (1958-2011) refracted to 4m water depth are used as input to the models. Beach and dune slopes averaged over the run-up region from mean water level to the maximum run-up ranged 0.1 - 0.63 (angle of repose). Reasonable comparison with model predicted run-up with distribution of sea-glass on the dune were obtained for P <2 events, but were underpredicted for large P. Large P events are associated with long period swell waves characteristic of the Pacific Ocean that are outside the empirical parameter space from which the model equations were derived, suggesting a possible deficiency in the models.

  8. Measurement of chest wall displacement based on terahertz wave

    NASA Astrophysics Data System (ADS)

    Li, Hui; Lv, Hao; Jiao, Teng; Lu, Guohua; Li, Sheng; Li, Zhao; Liu, Miao; Jing, Xijing; Wang, Jianqi

    2015-02-01

    Measurement of chest wall displacement is an important approach for measuring mechanics of chest wall, which has considerable significance for assessing respiratory system and diagnosing pulmonary diseases. However, existing optical methods for measuring chest wall displacement are inconvenient for some specific patients such as the female patients and the patients with bandaged chest. In this letter, we proposed a method for measuring chest wall displacement based on terahertz wave and established corresponding mathematic model and set up a terahertz measurement system. The main advantages of this method are that it can measure the chest wall displacement of the subjects without taking off clothes or arranging any markers. To validate this method and assess the performance of the terahertz system, in vitro, the displacement of a water module driven by a linear guide rail was measured by the terahertz system and compared with the actual displacement of the water module. The results showed that the waveforms measured with two methods have a good agreement, and the relative error is less than 5% and sufficiently good for measurement demands. In vivo, the synchronous experiment was performed on five human volunteers with the terahertz system and a respiratory belt transducer. The results demonstrate that this method has good performance and promising prospects for measuring chest wall displacement.

  9. Measurements of the thermal coefficient of optical attenuation at different depth regions of in vivo human skins using optical coherence tomography: a pilot study.

    PubMed

    Su, Ya; Yao, X Steve; Li, Zhihong; Meng, Zhuo; Liu, Tiegen; Wang, Longzhi

    2015-02-01

    We present detailed measurement results of optical attenuation's thermal coefficients (referenced to the temperature of the skin surface) in different depth regions of in vivo human forearm skins using optical coherence tomography (OCT). We first design a temperature control module with an integrated optical probe to precisely control the surface temperature of a section of human skin. We propose a method of using the correlation map to identify regions in the skin having strong correlations with the surface temperature of the skin and find that the attenuation coefficient in these regions closely follows the variation of the surface temperature without any hysteresis. We observe a negative thermal coefficient of attenuation in the epidermis. While in dermis, the slope signs of the thermal coefficient of attenuation are different at different depth regions for a particular subject, however, the depth regions with a positive (or negative) slope are different in different subjects. We further find that the magnitude of the thermal coefficient of attenuation coefficient is greater in epidermis than in dermis. We believe the knowledge of such thermal properties of skins is important for several noninvasive diagnostic applications, such as OCT glucose monitoring, and the method demonstrated in this paper is effective in studying the optical and biological properties in different regions of skin. PMID:25780740

  10. Attenuation of Biologically Effective UV Radiation in Tropical Atlantic Waters Measured with a Biochemical DNA Dosimeter

    Microsoft Academic Search

    Peter Boelen; Ingrid Obernosterer; Arie A. Vink; Anita G. J. Buma

    1999-01-01

    A biochemical dosimeter was developed to study the at- tenuation of biologically effective UV radiation in marine tropical waters. Small quartz vials were used containing a solution of DNA molecules; the vials were incubated at discrete water depths. Subsequently, DNA damage was determined in these samples, using an antibody directed against thymine dimers followed by chemiluminescent detection. Measurements of DNA

  11. Explosives detection through fast-neutron time-of-flight attenuation measurements

    Microsoft Academic Search

    J. C. Overley; M. S. Chmelik; R. J. Rasmussen; R. M. S. Schofield; H. W. Lefevre

    1995-01-01

    Computer simulations have been used to devise an algorithm for detection of explosives in luggage which is based upon measured projected number densities of H, C, N, and O. Other elements are lumped together as projection X. Dependence on luggage-thickness is reduced by normalizing the projection for each element by the total. Normalization constrains projections to a 4-dimensional space. Distributions

  12. Gamma Ray Attenuation Coefficient Measurement in Energies 1172 keV and 1332 keV for Neutron Absorbent Saturated Solutions

    SciTech Connect

    Jalali, Majid [Esfahan Nuclear Technology Center - ENTC (Iran, Islamic Republic of)

    2006-07-01

    The compounds, Na{sub 2}B{sub 4}O{sub 7}, H{sub 3}BO{sub 3}, CdCl{sub 2} and NaCl and their solutions, attenuate gamma rays in addition to neutron absorption. These compounds are widely used in shielding of neutron sources, reactor control and neutron converters. Mass attenuation coefficients of gamma related to saturated solutions of the above four compounds, in energies 1172 keV and 1332 keV have been measured by NaI detector and agree very well with the results obtained by Xcom code. Experiment and computation show that, H{sub 3}BO{sub 3} has the highest gamma ray attenuation coefficient among the aforementioned compounds. (author)

  13. Measurements of the Shear Alfven Wave Dispersion for Finite Perpendicular Wave Number C. A. Kletzing,* S. R. Bounds, and J. Martin-Hiner

    E-print Network

    California at Los Angles, University of

    Measurements of the Shear Alfve´n Wave Dispersion for Finite Perpendicular Wave Number C. A for the regime in which VA ' VTe. By measuring the parallel phase velocity of the waves, the measurements can for these waves has been derived by several authors, direct experimental measurements to verify the dispersion

  14. Infrared spectroscopy with heated attenuated total internal reflectance enabling precise measurement of thermally induced transitions in complex biological polymers.

    PubMed

    Warren, Frederick J; Perston, Benjamin B; Royall, Paul G; Butterworth, Peter J; Ellis, Peter R

    2013-04-16

    We report an improved tool for acquiring temperature-resolved fourier transform infrared (FT-IR) spectra of complex polymer systems undergoing thermal transitions, illustrated by application to several phenomena related to starch gelatinization that have proved difficult to study by other means. Starch suspensions from several botanical origins were gelatinized using a temperature-controlled attenuated total reflectance (ATR) crystal, with IR spectra collected every 0.25 °C. By following the 995/1022 cm(-1) peak ratio, clear transitions occurring between 59 and 70 °C were observed, for which the midpoints could be determined accurately by sigmoidal fits. The magnitude of the change in peak ratio was found to be strongly correlated to the enthalpy of gelatinization as measured by differential scanning calorimetry (DSC, R(2) = 0.988). An important advantage of the technique, compared to DSC, is that the signal-to-noise ratio is not reduced when measuring very broad transitions. This has the potential to allow more precise determination of the gelatinization parameters of high-amylose starches, for which gelatinization may take place over several tens of °C. PMID:23461675

  15. Investigation of gravity waves using horizontally resolved radial velocity measurements

    NASA Astrophysics Data System (ADS)

    Stober, G.; Sommer, S.; Rapp, M.; Latteck, R.

    2013-10-01

    The Middle Atmosphere Alomar Radar System (MAARSY) on the island of Andøya in Northern Norway (69.3° N, 16.0° E) observes polar mesospheric summer echoes (PMSE). These echoes are used as tracers of atmospheric dynamics to investigate the horizontal wind variability at high temporal and spatial resolution. MAARSY has the capability of pulse-to-pulse beam steering allowing for systematic scanning experiments to study the horizontal structure of the backscatterers as well as to measure the radial velocities for each beam direction. Here we present a method to retrieve gravity wave parameters from these horizontally resolved radial wind variations by applying velocity azimuth display and volume velocity processing. Based on the observations a detailed comparison of the two wind analysis techniques is carried out in order to determine the zonal and meridional wind as well as to measure first-order inhomogeneities. Further, we demonstrate the possibility to resolve the horizontal wave properties, e.g., horizontal wavelength, phase velocity and propagation direction. The robustness of the estimated gravity wave parameters is tested by a simple atmospheric model.

  16. Investigation of gravity waves using horizontally resolved radial velocity measurements

    NASA Astrophysics Data System (ADS)

    Stober, G.; Sommer, S.; Rapp, M.; Latteck, R.

    2013-06-01

    The Middle Atmosphere Alomar Radar System (MAARSY) on the island Andøya in Northern Norway (69.3° N, 16.0° E) observes polar mesospheric summer echoes (PMSE). These echoes are used as tracers of atmospheric dynamics to investigate the horizontal wind variability at high temporal and spatial resolution. MAARSY has the capability of a pulse-to-pulse beam steering allowing for systematic scanning experiments to study the horizontal structure of the backscatterers as well as to measure the radial velocities for each beam direction. Here we present a method to retrieve gravity wave parameters from these horizontally resolved radial wind variations by applying velocity azimuth display and volume velocity processing. Based on the observations a detailed comparison of the two wind analysis techniques is carried out in order to determine the zonal and meridional wind as well as to measure first order inhomogeneities. Further, we demonstrate the possibility to resolve the horizontal wave properties, e.g. horizontal wavelength, phase velocity and propagation direction. The robustness of the estimated gravity wave parameters is tested by a simple atmospheric model.

  17. Measurement and Modeling of Steep Ocean Wave Slopes

    NASA Technical Reports Server (NTRS)

    Chapron, B.; Vandemark, D.; Elfouhaily, T.

    2000-01-01

    Our study emphasizes the importance of identifying and quantifying the distribution variance, skewness and kurtosis from optical and microwave scattering observations. Recent field measurements of the sea slope distribution for intermediate-to-long scale gravity waves will be presented. These data were collected using an airborne laser range system designed to estimate the surface slope vector at horizontal scales of 1-2 m. The observed slope distribution tail indicates that the occurrence of steep waves substantially exceeds a Gaussian prediction. This measured peakedness is present over the wide range of sea state and wind speed conditions encountered. Data are further evaluated within the context of Cox and Munk's well-known sea slope investigations. Based on a re-evaluation of the Cox and Munk's reported parameters, we find a consistent picture develops wherein data are shown to consistently indicate non-Gaussian statistics. One fundamental application of such a non-Gaussian slope observation is its place in modifying predicted wave breaking probability to help to better quantify gas transfer processes at the sea surface.

  18. Monitoring Fatigue Damage Accumulation with Rayleigh Wave Harmonic Generation Measurements

    NASA Astrophysics Data System (ADS)

    Barnard, D. J.; Brasche, L. J. H.; Raulerson, D.; Degtyar, A. D.

    2003-03-01

    The use of nonlinear acoustics, and in particular harmonic generation, continues to gain interest as a means to characterize microstructural changes in engineering materials as a result of processing and in-service conditions. Typical measurements involve the propagation of a monochromatic longitudinal wave toneburst through the bulk of a sample in a through-transmission arrangement. This arrangement is not well suited for field applications, where two sided access is limited and parallel surfaces are rare. Harmonic generation measurements to monitor fatigue damage in acro engine alloys subject to fatigue will be presented. The use of Rayleigh waves has allowed one sided access and accommodates a small amount of surface curvature while restricting the probing wave to the surface where fatigue damage is typically initiated. Early results using uncalibrated receiving transducers on Ni-based alloys demonstrate a sensitivity to damage accumulation in low cycle fatigue, where damage is spread over the sample surface. Damage accumulation in high cycle fatigue is concentrated in small regions on the sample surface and so has not yet been revealed by changes in the generation of harmonics using the uncalibrated probes.

  19. Simultaneously measuring thickness, density, velocity and attenuation of thin layers using V(z,t) data from time-resolved acoustic microscopy.

    PubMed

    Chen, Jian; Bai, Xiaolong; Yang, Keji; Ju, Bing-Feng

    2015-02-01

    To meet the need of efficient, comprehensive and automatic characterization of the properties of thin layers, a nondestructive method using ultrasonic testing to simultaneously measure thickness, density, sound velocity and attenuation through V(z,t) data, recorded by time-resolved acoustic microscopy is proposed. The theoretical reflection spectrum of the thin layer at normal incidence is established as a function of three dimensionless parameters. The measured reflection spectrum R(?,?) is obtained from V(z,t) data and the measured thickness is derived from the signals when the lens is focused on the front and back surface of the thin layer, which are picked up from the V(z,t) data. The density, sound velocity and attenuation are then determined by the measured thickness and inverse algorithm utilizing least squares method to fit the theoretical and measured reflection spectrum at normal incidence. It has the capability of simultaneously measuring thickness, density, sound velocity and attenuation of thin layer in a single V(z,t) acquisition. An example is given for a thin plate immersed in water and the results are satisfactory. The method greatly simplifies the measurement apparatus and procedures, which improves the efficiency and automation for simultaneous measurement of basic mechanical and geometrical properties of thin layers. PMID:25448428

  20. Tests of collision operators using laboratory measurements of shear Alfven wave dispersion and D. J. Thuecks,

    E-print Network

    California at Los Angles, University of

    POP33461 Tests of collision operators using laboratory measurements of shear Alfv´en wave) Measurements of shear Alfv´en waves are used to test the predictions of a variety of different electron colli the dielectric tensor. Laboratory measurements of the parallel phase velocity and damping of shear Alfv´en waves