WorldWideScience

Sample records for wave velocity findings

  1. Wave propagation and group velocity

    CERN Document Server

    Brillouin, Léon

    1960-01-01

    Wave Propagation and Group Velocity contains papers on group velocity which were published during the First World War and are missing in many libraries. It introduces three different definitions of velocities: the group velocity of Lord Rayleigh, the signal velocity of Sommerfeld, and the velocity of energy transfer, which yields the rate of energy flow through a continuous wave and is strongly related to the characteristic impedance. These three velocities are identical for nonabsorbing media, but they differ considerably in an absorption band. Some examples are discussed in the last chapter

  2. Phase velocity and attenuation of plane waves in dissipative elastic ...

    African Journals Online (AJOL)

    An iteration method to find the roots of a complex transcendental equation is under scanner. This method identified as functional iteration method is being used mainly in wave propagation problems to calculate the phase velocity and the attenuation of plane harmonic waves in dissipative elastic plates. Few mathematical ...

  3. Wave measurements using GPS velocity signals.

    Science.gov (United States)

    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.

  4. Wave Velocity Estimation in Heterogeneous Media

    KAUST Repository

    Asiri, Sharefa M.

    2016-03-21

    In this paper, modulating functions-based method is proposed for estimating space-time dependent unknown velocity in the wave equation. The proposed method simplifies the identification problem into a system of linear algebraic equations. Numerical simulations on noise-free and noisy cases are provided in order to show the effectiveness of the proposed method.

  5. Traveling waves in an optimal velocity model of freeway traffic

    Science.gov (United States)

    Berg, Peter; Woods, Andrew

    2001-03-01

    Car-following models provide both a tool to describe traffic flow and algorithms for autonomous cruise control systems. Recently developed optimal velocity models contain a relaxation term that assigns a desirable speed to each headway and a response time over which drivers adjust to optimal velocity conditions. These models predict traffic breakdown phenomena analogous to real traffic instabilities. In order to deepen our understanding of these models, in this paper, we examine the transition from a linear stable stream of cars of one headway into a linear stable stream of a second headway. Numerical results of the governing equations identify a range of transition phenomena, including monotonic and oscillating travelling waves and a time- dependent dispersive adjustment wave. However, for certain conditions, we find that the adjustment takes the form of a nonlinear traveling wave from the upstream headway to a third, intermediate headway, followed by either another traveling wave or a dispersive wave further downstream matching the downstream headway. This intermediate value of the headway is selected such that the nonlinear traveling wave is the fastest stable traveling wave which is observed to develop in the numerical calculations. The development of these nonlinear waves, connecting linear stable flows of two different headways, is somewhat reminiscent of stop-start waves in congested flow on freeways. The different types of adjustments are classified in a phase diagram depending on the upstream and downstream headway and the response time of the model. The results have profound consequences for autonomous cruise control systems. For an autocade of both identical and different vehicles, the control system itself may trigger formations of nonlinear, steep wave transitions. Further information is available [Y. Sugiyama, Traffic and Granular Flow (World Scientific, Singapore, 1995), p. 137].

  6. Relationship between stress wave velocities of green and dry veneer

    Science.gov (United States)

    Brian K. Brashaw; Xiping Wang; Robert J. Ross; Roy F. Pellerin

    2004-01-01

    This paper evaluates the relationship between the stress wave velocities of green and dry southern pine and Douglas-fir veneers. A commercial stress wave timer and a laboratory signal analysis system were used to measure the transit time required for an induced stress wave to travel the longitudinal length of each veneer. Stress wave transit times were measured in the...

  7. S-Wave Velocity Across Central Mexico Using High Resolution Surface Wave Tomography

    Science.gov (United States)

    Iglesias, A.; Clayton, R. W.; Pérez-Campos, X.; Singh, S. K.; Pacheco, J. F.; García, D.; Valdés-González, C.

    2008-12-01

    The shear wave velocity structure across central Mexico is determined by surface wave dispersion from a dense linear seismic experiment "Mesoamerican Subduction Experiment" (MASE). MASE consisted of 100 portable broadband stations deployed along a line crossing Central Mexico from the Pacific Coast to almost the Gulf of Mexico. Regional records were used to obtain Rayleigh-wave group velocity maps for periods from 5 to 50 s and they show a dramatic variation of velocity (~40%), especially for periods larger of 20 s. Local dispersion curves were reconstructed for each station and inverted to find S-wave velocity by using a simulated annealing algorithm. The results, from inversion, show a significant change, particularly in the lower crust, between the backarc, volcanic arc and forearc regions. The crust in the forearc is thicker and faster than the backarc region. Just below the active Trans Mexican Volcanic Belt (TMVB) (300 km from the coast) is presently a low velocity spot (~3.4 km/s) suggesting presence of anomalous material (probably related to a mantle wedge) as deep as 50 km. The results also show a poorly resolved slab and wedge which correspond to the ones in a model reported recently. The results are supported with consistency checks and resolution tests.

  8. Wave velocity characteristic for Kenaf natural fibre under impact damage

    Science.gov (United States)

    Zaleha, M.; Mahzan, S.; Fitri, Muhamad; Kamarudin, K. A.; Eliza, Y.; Tobi, A. L. Mohd

    2017-01-01

    This paper aims to determining the wave velocity characteristics for kenaf fibre reinforced composite (KFC) and it includes both experimental and simulation results. Lead zirconate titanate (PZT) sensor were proposed to be positioned to corresponding locations on the panel. In order to demonstrate the wave velocity, an impacts was introduced onto the panel. It is based on a classical sensor triangulation methodology, combines with experimental strain wave velocity analysis. Then the simulation was designed to replicate panel used in the experimental impacts test. This simulation was carried out using ABAQUS. It was shown that the wave velocity propagates faster in the finite element simulation. Although the experimental strain wave velocity and finite element simulation results do not match exactly, the shape of both waves is similar.

  9. Perturbational and nonperturbational inversion of Rayleigh-wave velocities

    Science.gov (United States)

    Haney, Matt; Tsai, Victor C.

    2017-01-01

    The inversion of Rayleigh-wave dispersion curves is a classic geophysical inverse problem. We have developed a set of MATLAB codes that performs forward modeling and inversion of Rayleigh-wave phase or group velocity measurements. We describe two different methods of inversion: a perturbational method based on finite elements and a nonperturbational method based on the recently developed Dix-type relation for Rayleigh waves. In practice, the nonperturbational method can be used to provide a good starting model that can be iteratively improved with the perturbational method. Although the perturbational method is well-known, we solve the forward problem using an eigenvalue/eigenvector solver instead of the conventional approach of root finding. Features of the codes include the ability to handle any mix of phase or group velocity measurements, combinations of modes of any order, the presence of a surface water layer, computation of partial derivatives due to changes in material properties and layer boundaries, and the implementation of an automatic grid of layers that is optimally suited for the depth sensitivity of Rayleigh waves.

  10. Non-collinear wave mixing for a bulk wave phase velocity measurement in an isotropic solid

    NARCIS (Netherlands)

    Demcenko, A.

    2013-01-01

    A measurement method is presented to estimate the bulk wave phase velocity in an isotropic solid when longitudinal or shear wave velocity is known. This method is based on the non-collinear plane wave interaction theory and it does not need to estimate the phase time-of-flight and wave propagation

  11. Group velocity of cylindrical guided waves in anisotropic laminate composites.

    Science.gov (United States)

    Glushkov, Evgeny; Glushkova, Natalia; Eremin, Artem; Lammering, Rolf

    2014-01-01

    An explicit expression for the group velocity of wave packets, propagating in a laminate anisotropic composite plate in prescribed directions, is proposed. It is based on the cylindrical guided wave asymptotics derived from the path integral representation for wave fields generated in the composites by given localized sources. The expression derived is theoretically confirmed by the comparison with a known representation for the group velocity vector of a plane guided wave. Then it is experimentally validated against laser vibrometer measurements of guided wave packets generated by a piezoelectric wafer active sensor in a composite plate.

  12. P1138Cardiac shear wave velocity in healthy individuals.

    Science.gov (United States)

    Strachinaru, M; Geleijnse, M L; Bosch, J G; De Jong, N; Van Der Steen, Afw; Van Dalen, B M; Vos, H J

    2016-12-01

    The closure of the valves generates shear waves in the heart walls. The propagation velocity of shear waves relates to stiffness. This could potentially be used to estimate the stiffness of the myocardium, with huge potential implications in pathologies characterized by a deterioration of the diastolic properties of the left ventricle. In an earlier phantom study we already validated shear wave tracking with a clinical ultrasound system in cardiac mode. In this study we aimed to measure the shear waves velocity in normal individuals. 12 healthy volunteers, mean age=37±10, 33% females, were investigated using a clinical scanner (Philips iE33), equipped with a S5-1 probe, using a clinical tissue Doppler (TDI) application. ECG and phonocardiogram (PCG) were synchronously recorded. We achieved a TDI frame rate of >500Hz by carefully tuning normal system settings. Data were processed offline in Philips Qlab 8 to extract tissue velocity along a virtual M-mode line in the basal third of the interventricular septum, in parasternal long axis view. This tissue velocity showed a propagating wave pattern after closure of the valves. The slope of the wave front velocity in a space-time panel was measured to obtain the shear wave propagation velocity. The velocity of the shear waves induced by the closure of the mitral valve (1st heart sound) and aortic valve (2nd heart sound) was averaged over 4 heartbeats for every subject. Shear waves were visible after each closure of the heart valves, synchronous to the heart sounds. The figure shows one heart cycle of a subject, with the mean velocity along a virtual M-mode line in the upper panel, synchronous to the ECG signal (green line) and phonocardiogram (yellow line) in the lower panel. The slope of the shear waves is marked with dotted lines and the onset of the heart sounds with white lines. In our healthy volunteer group the mean velocity of the shear wave induced by mitral valve closure was 4.8±0.7m/s, standard error of 0.14 m

  13. Surface Wave Velocity-Stress Relationship in Uniaxially Loaded Concrete

    DEFF Research Database (Denmark)

    Shokouhi, Parisa; Zoëga, Andreas; Wiggenhauser, Herbert

    2012-01-01

    loading cycles revealed that the velocities show a stress-memory effect in good agreement with the Kaiser effect. Comparing the velocities measured during loading and unloading, the effects of stress and damage on the measured velocities could be differentiated. Moreover, the stress dependency of surface......The sonic surface wave (or Rayleigh wave) velocity measured on prismatic concrete specimens under uniaxial compression was found to be highly stress-dependent. At low stress levels, the acoustoelastic effect and the closure of existing microcracks results in a gradual increase in surface wave...... velocities. At higher stress levels, concrete suffers irrecoverable damage: the existing microcracks widen and coalesce and new microcracks form. This progressive damage process leads first to the flattening and eventually the drop in the velocity-stress curves. Measurements on specimens undergoing several...

  14. Shear wave velocity structure in North America from large-scale waveform inversions of surface waves

    Science.gov (United States)

    Alsina, D.; Woodward, R.L.; Snieder, R.K.

    1996-01-01

    A two-step nonlinear and linear inversion is carried out to map the lateral heterogeneity beneath North America using surface wave data. The lateral resolution for most areas of the model is of the order of several hundred kilometers. The most obvious feature in the tomographic images is the rapid transition between low velocities in the technically active region west of the Rocky Mountains and high velocities in the stable central and eastern shield of North America. The model also reveals smaller-scale heterogeneous velocity structures. A high-velocity anomaly is imaged beneath the state of Washington that could be explained as the subducting Juan de Fuca plate beneath the Cascades. A large low-velocity structure extends along the coast from the Mendocino to the Rivera triple junction and to the continental interior across the southwestern United States and northwestern Mexico. Its shape changes notably with depth. This anomaly largely coincides with the part of the margin where no lithosphere is consumed since the subduction has been replaced by a transform fault. Evidence for a discontinuous subduction of the Cocos plate along the Middle American Trench is found. In central Mexico a transition is visible from low velocities across the Trans-Mexican Volcanic Belt (TMVB) to high velocities beneath the Yucatan Peninsula. Two elongated low-velocity anomalies beneath the Yellowstone Plateau and the eastern Snake River Plain volcanic system and beneath central Mexico and the TMVB seem to be associated with magmatism and partial melting. Another low-velocity feature is seen at depths of approximately 200 km beneath Florida and the Atlantic Coastal Plain. The inversion technique used is based on a linear surface wave scattering theory, which gives tomographic images of the relative phase velocity perturbations in four period bands ranging from 40 to 150 s. In order to find a smooth reference model a nonlinear inversion based on ray theory is first performed. After

  15. Calculating wave-generated bottom orbital velocities from surface-wave parameters

    Science.gov (United States)

    Wiberg, P.L.; Sherwood, C.R.

    2008-01-01

    Near-bed wave orbital velocities and shear stresses are important parameters in many sediment-transport and hydrodynamic models of the coastal ocean, estuaries, and lakes. Simple methods for estimating bottom orbital velocities from surface-wave statistics such as significant wave height and peak period often are inaccurate except in very shallow water. This paper briefly reviews approaches for estimating wave-generated bottom orbital velocities from near-bed velocity data, surface-wave spectra, and surface-wave parameters; MATLAB code for each approach is provided. Aspects of this problem have been discussed elsewhere. We add to this work by providing a method for using a general form of the parametric surface-wave spectrum to estimate bottom orbital velocity from significant wave height and peak period, investigating effects of spectral shape on bottom orbital velocity, comparing methods for calculating bottom orbital velocity against values determined from near-bed velocity measurements at two sites on the US east and west coasts, and considering the optimal representation of bottom orbital velocity for calculations of near-bed processes. Bottom orbital velocities calculated using near-bed velocity data, measured wave spectra, and parametric spectra for a site on the northern California shelf and one in the mid-Atlantic Bight compare quite well and are relatively insensitive to spectral shape except when bimodal waves are present with maximum energy at the higher-frequency peak. These conditions, which are most likely to occur at times when bottom orbital velocities are small, can be identified with our method as cases where the measured wave statistics are inconsistent with Donelan's modified form of the Joint North Sea Wave Project (JONSWAP) spectrum. We define the 'effective' forcing for wave-driven, near-bed processes as the product of the magnitude of forcing times its probability of occurrence, and conclude that different bottom orbital velocity statistics

  16. Cardiac Shear Wave Velocity Detection in the Porcine Heart.

    Science.gov (United States)

    Vos, Hendrik J; van Dalen, Bas M; Heinonen, Ilkka; Bosch, Johan G; Sorop, Oana; Duncker, Dirk J; van der Steen, Antonius F W; de Jong, Nico

    2017-04-01

    Cardiac muscle stiffness can potentially be estimated non-invasively with shear wave elastography. Shear waves are present on the septal wall after mitral and aortic valve closure, thus providing an opportunity to assess stiffness in early systole and early diastole. We report on the shear wave recordings of 22 minipigs with high-frame-rate echocardiography. The waves were captured with 4000 frames/s using a programmable commercial ultrasound machine. The wave pattern was extracted from the data through a local tissue velocity estimator based on one-lag autocorrelation. The wave propagation velocity was determined with a normalized Radon transform, resulting in median wave propagation velocities of 2.2 m/s after mitral valve closure and 4.2 m/s after aortic valve closure. Overall the velocities ranged between 0.8 and 6.3 m/s in a 95% confidence interval. By dispersion analysis we found that the propagation velocity only mildly increased with shear wave frequency. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  17. Wave velocities in a pre-stressed anisotropic elastic medium

    Indian Academy of Sciences (India)

    Modified Christoffel equations are derived for three-dimensional wave propagation in a general anisotropic medium under initial stress.The three roots of a cubic equation define the phase velocities of three quasi-waves in the medium.Analytical expressions are used to calculate the directional derivatives of phase ...

  18. Deep Shear Wave Velocity of Southern Bangkok and Vicinity

    Science.gov (United States)

    Wongpanit, T.; Hayashi, K.; Pananont, P.

    2017-09-01

    Bangkok is located on the soft marine clay in the Lower Chao Phraya Basin which can amplify seismic wave and can affect the shaking of buildings during an earthquake. Deep shear wave velocity of the sediment in the basin are useful for study the effect of the soft sediment on the seismic wave and can be used for earthquake engineering design and ground shaking estimation, especially for a deep basin. This study aims to measure deep shear wave velocity and create 2D shear wave velocity profile down to a bedrock in the southern Bangkok by the Microtremor measurements with 2 seismographs using Spatial Autocorrelation (2-SPAC) technique. The data was collected during a day time on linear array geometry with offsets varying between 5-2,000 m. Low frequency of natural tremor (0.2-0.6 Hz) was detected at many sites, however, very deep shear wave data at many sites are ambiguous due to man-made vibration noises in the city. The results show that shear wave velocity of the sediment in the southern Bangkok is between 100-2,000 ms-1 and indicate that the bedrock depth is about 600-800 m, except at Bang Krachao where bedrock depth is unclear.

  19. Rayleigh-Wave Group-Velocity Tomography of Saudi Arabia

    Science.gov (United States)

    Tang, Zheng; Mai, P. Martin; Chang, Sung-Joon; Zahran, Hani

    2017-04-01

    We use surface-wave tomography to investigate the lithospheric structure of the Arabian plate, which is traditionally divided into the Arabian shield in the west and the Arabian platform in the east. The Arabian shield is a complicated mélange of crustal material, composed of several Proterozoic terrains separated by ophiolite-bearing suture zones and dotted by outcropping Cenozoic volcanic rocks. The Arabian platform is primarily covered by very thick Paleozoic, Mesozoic and Cenozoic sediments. We develop high-resolution tomographic images from fundamental-mode Rayleigh-wave group-velocities across Saudi Arabia, utilizing the teleseismic data recorded by the permanent Saudi National Seismic Network (SNSN). Our study extends previous efforts on surface wave work by increasing ray path density and improving spatial resolution. Good quality dispersion measurements for roughly 3000 Rayleigh-wave paths have been obtained and utilized for the group-velocity tomography. We have applied the Fast Marching Surface Tomography (FMST) scheme of Rawlinson (2005) to obtain Rayleigh-wave group-velocity images for periods from 8 s to 40 s on a 0.8° 0.8° grid and at resolutions approaching 2.5° based on the checkerboard tests. Our results indicate that short-period group-velocity maps (8-15 s) correlate well with surface geology, with slow velocities delineating the main sedimentary features including the Arabian platform, the Persian Gulf and Mesopotamia. For longer periods (20-40 s), the velocity contrast is due to the differences in crustal thickness and subduction/collision zones. The lower velocities are sensitive to the thicker continental crust beneath the eastern Arabia and the subduction/collision zones between the Arabian and Eurasian plate, while the higher velocities in the west infer mantle velocity.

  20. Study on P-wave and S-wave velocity in dry and wet sandstones of Tushka region, Egypt

    Directory of Open Access Journals (Sweden)

    Mohamed A. Kassab

    2015-03-01

    The derived equations can be used for the prediction of P-wave velocity of wet rock samples from the P-wave velocity of dry rock samples, and the S-wave velocity of wet rock samples can be predicted from the S-wave velocity of dry rock samples. A strong linear correlation between P-wave velocity and S-wave velocity of dry rock samples and between P-wave velocity and S-wave velocity of wet rock samples was found. The resulting linear equations can be used for the estimation of S-wave velocity from the P-wave velocity in the case of both dry and wet rock samples.

  1. The Shear Wave Velocity on Elastography Correlates with the Clinical Symptoms and Histopathological Features of Keloids

    OpenAIRE

    Aya, Rino; Yamawaki, Satoko; Yoshikawa, Katsuhiro; Katayama, Yasuhiro; Enoshiri, Tatsuki; Naitoh, Motoko; Suzuki, Shigehiko

    2015-01-01

    Background: Keloids present as red, painful lesions causing serious functional and cosmetic problems; however, there is no consensus regarding tools for objectively evaluating keloids. To demonstrate the utility of shear wave elastography in keloids, we investigated the correlations between clinical symptoms, ultrasound shear wave velocity, and histopathological findings. Methods: Three patients with keloids containing both red hypertrophic and mature areas were evaluated using the shear wave...

  2. Superluminal X-wave propagation: energy localization and velocity.

    Science.gov (United States)

    Mugnai, D; Mochi, I

    2006-01-01

    The electromagnetic propagation of a Bessel-X wave is analyzed on the basis of a vectorial treatment in order to obtain information about the propagation of energy flux and the velocity of the energy. Knowledge of these quantities is of great interest since they are connected to the production of localized electromagnetic energy and to the topic of superluminality, respectively. The electric and magnetic fields are obtained in the far-field approximation by considering a realistic situation able to generate a Bessel-X wave. The vectorial treatment confirms the capability of this kind of wave to localize energy, while, quite surprisingly, even if the group velocity is superluminal, the energy velocity is equal to the light speed.

  3. Anisotropic S-wave velocity structure from joint inversion of surface wave group velocity dispersion: A case study from India

    Science.gov (United States)

    Mitra, S.; Dey, S.; Siddartha, G.; Bhattacharya, S.

    2016-12-01

    We estimate 1-dimensional path average fundamental mode group velocity dispersion curves from regional Rayleigh and Love waves sampling the Indian subcontinent. The path average measurements are combined through a tomographic inversion to obtain 2-dimensional group velocity variation maps between periods of 10 and 80 s. The region of study is parametrised as triangular grids with 1° sides for the tomographic inversion. Rayleigh and Love wave dispersion curves from each node point is subsequently extracted and jointly inverted to obtain a radially anisotropic shear wave velocity model through global optimisation using Genetic Algorithm. The parametrization of the model space is done using three crustal layers and four mantle layers over a half-space with varying VpH , VsV and VsH. The anisotropic parameter (η) is calculated from empirical relations and the density of the layers are taken from PREM. Misfit for the model is calculated as a sum of error-weighted average dispersion curves. The 1-dimensional anisotropic shear wave velocity at each node point is combined using linear interpolation to obtain 3-dimensional structure beneath the region. Synthetic tests are performed to estimate the resolution of the tomographic maps which will be presented with our results. We envision to extend this to a larger dataset in near future to obtain high resolution anisotrpic shear wave velocity structure beneath India, Himalaya and Tibet.

  4. Reconfigurable Wave Velocity Transmission Lines for Phased Arrays

    Science.gov (United States)

    Host, Nick; Chen, Chi-Chih; Volakis, John L.; Miranda, Felix

    2013-01-01

    Phased array antennas showcase many advantages over mechanically steered systems. However, they are also more complex, heavy and most importantly costly. This presentation paper presents a concept which overcomes these detrimental attributes by eliminating all of the phase array backend (including phase shifters). Instead, a wave velocity reconfigurable transmission line is used in a series fed array arrangement to allow phase shifting with one small (100mil) mechanical motion. Different configurations of the reconfigurable wave velocity transmission line are discussed and simulated and experimental results are presented.

  5. Wave equation based microseismic source location and velocity inversion

    Science.gov (United States)

    Zheng, Yikang; Wang, Yibo; Chang, Xu

    2016-12-01

    The microseismic event locations and velocity information can be used to infer the stress field and guide hydraulic fracturing process, as well as to image the subsurface structures. How to get accurate microseismic event locations and velocity model is the principal problem in reservoir monitoring. For most location methods, the velocity model has significant relation with the accuracy of the location results. The velocity obtained from log data is usually too rough to be used for location directly. It is necessary to discuss how to combine the location and velocity inversion. Among the main techniques for locating microseismic events, time reversal imaging (TRI) based on wave equation avoids traveltime picking and offers high-resolution locations. Frequency dependent wave equation traveltime inversion (FWT) is an inversion method that can invert velocity model with source uncertainty at certain frequency band. Thus we combine TRI with FWT to produce improved event locations and velocity model. In the proposed approach, the location and model information are interactively used and updated. Through the proposed workflow, the inverted model is better resolved and the event locations are more accurate. We test this method on synthetic borehole data and filed data of a hydraulic fracturing experiment. The results verify the effectiveness of the method and prove it has potential for real-time microseismic monitoring.

  6. Analyses of Current And Wave Forces on Velocity Caps

    DEFF Research Database (Denmark)

    Christensen, Erik Damgaard; Buhrkall, Jeppe; Eskesen, Mark C. D.

    2015-01-01

    leads the water into another pipe or tunnel system. A pressure gradient generated by the water level difference between the sea and basin drives the flow through the tunnel system. The tunnel system is often in the order of a couple kilometers long. Based on CFD analyses (computational fluid dynamics......Velocity caps are often used in connection with for instance offshore intake sea water for the use of for cooling water for power plants or as a source for desalinization plants. The intakes can also be used for river intakes. The velocity cap is placed on top of a vertical pipe. The vertical pipe......) this paper investigates the current and wave forces on the velocity cap and the vertical cylinder. The Morison’s force model was used in the analyses of the extracted force time series in from the CFD model. Further the distribution of the inlet velocities around the velocity cap was also analyzed in detail...

  7. An upper-mantle S-wave velocity model for Northern Europe from Love and Rayleigh group velocities

    Science.gov (United States)

    Weidle, Christian; Maupin, Valérie

    2008-12-01

    A model of upper-mantle S-wave velocity and transverse anisotropy beneath northwestern Europe is presented, based on regional surface wave observations. Group velocities for both Love and Rayleigh surface waves are measured on waveform data from international and regional data archives (including temporary deployments) and then inverted for group velocity maps, using a method accounting for Fresnel zone sensitivity. The group velocity variations are larger than in global reference maps, and we are able to resolve unprecedented details. We then apply a linear inversion scheme to invert for local 1-D shear wave velocity profiles which are consequently assembled to a 3-D model. By choosing conservative regularization parameters in the 2-D inversion, we ensure the smoothness of the group velocity maps and hence of the resulting 3-D shear wave speed model. To account for the different tectonic regimes in the study region and investigate the sensitivity of the 1-D inversions to inaccuracies in crustal parameters, we analyse inversions with different reference models of increasing complexity (pure 1-D, 3-D crust/1-D mantle and pure 3-D). We find that all inverted models are very consistent at depths below 70 km. At shallower depths, the constraints put by the reference models, primarily Moho depth which we do not invert for, remain the main cause for uncertainty in our inversion. The final 3-D model shows large variations in S-wave velocity of up to +/-12 per cent. We image an intriguing low-velocity anomaly in the depth range 70-150 km that extends from the Iceland plume beneath the North Atlantic and in a more than 400 km wide channel under Southern Scandinavia. Beneath Southern Norway, the negative perturbations are around 10 per cent with respect to ak135, and a shallowing of the anomaly is indicated which could be related to the sustained uplift of Southern Scandinavia in Neogene times. Furthermore, our upper-mantle model reveals good alignment to ancient plate

  8. Wave-equation Migration Velocity Analysis Using Plane-wave Common Image Gathers

    KAUST Repository

    Guo, Bowen

    2017-06-01

    Wave-equation migration velocity analysis (WEMVA) based on subsurface-offset, angle domain or time-lag common image gathers (CIGs) requires significant computational and memory resources because it computes higher dimensional migration images in the extended image domain. To mitigate this problem, a WEMVA method using plane-wave CIGs is presented. Plane-wave CIGs reduce the computational cost and memory storage because they are directly calculated from prestack plane-wave migration, and the number of plane waves is often much smaller than the number of shots. In the case of an inaccurate migration velocity, the moveout of plane-wave CIGs is automatically picked by a semblance analysis method, which is then linked to the migration velocity update by a connective function. Numerical tests on two synthetic datasets and a field dataset validate the efficiency and effectiveness of this method.

  9. The stress-induced surface wave velocity variations in concrete

    Science.gov (United States)

    Spalvier, Agustin; Bittner, James; Evani, Sai Kalyan; Popovics, John S.

    2017-02-01

    This investigation studies the behavior of surface wave velocity in concrete specimens subjected to low levels of compressive and tensile stress in beams from applied flexural loads. Beam specimen is loaded in a 4-point-load bending configuration, generating uniaxial compression and tension stress fields at the top and bottom surfaces of the beam, respectively. Surface waves are generated through contactless air-coupled transducers and received through contact accelerometers. Results show a clear distinction in responses from compression and tension zones, where velocity increases in the former and decreases in the latter, with increasing load levels. These trends agree with existing acoustoelastic literature. Surface wave velocity tends to decrease more under tension than it tends to increase under compression, for equal load levels. It is observed that even at low stress levels, surface wave velocity is affected by acoustoelastic effects, coupled with plastic effects (stress-induced damage). The acoustoelastic effect is isolated by means of considering the Kaiser effect and by experimentally mitigating the viscoelastic effects of concrete. Results of this ongoing investigation contribute to the overall knowledge of the acoustoelastic behavior of concrete. Applications of this knowledge may include structural health monitoring of members under flexural loads, improved high order modelling of materials, and validation of results seen in dynamic acoustoelasticity testing.

  10. Shear wave velocity structure of the Bushveld Complex, South Africa

    CSIR Research Space (South Africa)

    Kgaswane, EM

    2012-07-01

    Full Text Available The structure of the crust in the environs of the Bushveld Complex has been investigated by jointly inverting high-frequency teleseismic receiver functions and 2–60 s period Rayleigh wave group velocities for 16 broadband seismic stations located...

  11. Rayleigh Wave Velocity Measurements Using Broad Band Frequency Sources.

    Science.gov (United States)

    1981-07-01

    Heukelom 4I and Foster 1960, Chang and Ballard 1973, Ballard and McLean 1975). The procedure for measuring the Rayleigh wave velocity has consisted... Heukelom , W., and Foster, C. R. 1960. "Dynamic Testing of Pavements," Journal, Soil Mechanics and Foundations Division, American Society of Civil Engineers

  12. Rayleigh wave velocities and structural informations in Central Northern Italy

    Directory of Open Access Journals (Sweden)

    E. MANTOVANI

    1978-06-01

    Full Text Available Rayleigh wave dispersion has been observed along the three profiles
    Trieste-Olbia, Olbia-Bologna and Olbia-Bolzano, in central-northern Italy.
    The interpretation of phase velocities indicates a crustal thickness increasing
    from East (25-30 km, Trieste-Olbia to West (30-35 km, Olbia-Bolzano.
    For each profile two values of the Moho depth are acceptable; the shallower
    one is associated with a set of models which have low velocity
    material (¡3=4.3 lcm/s just under or within a few km from the Moho;
    the deeper one still accepts low velocity material ((3=4.4 km/s under
    the Moho but does not exclude the presence of an almost normal LID
    above the low velocity channel.

  13. Estimation of seabed shear-wave velocity profiles using shear-wave source data.

    Science.gov (United States)

    Dong, Hefeng; Nguyen, Thanh-Duong; Duffaut, Kenneth

    2013-07-01

    This paper estimates seabed shear-wave velocity profiles and their uncertainties using interface-wave dispersion curves extracted from data generated by a shear-wave source. The shear-wave source generated a seismic signature over a frequency range between 2 and 60 Hz and was polarized in both in-line and cross-line orientations. Low-frequency Scholte- and Love-waves were recorded. Dispersion curves of the Scholte- and Love-waves for the fundamental mode and higher-order modes are extracted by three time-frequency analysis methods. Both the vertically and horizontally polarized shear-wave velocity profiles in the sediment are estimated by the Scholte- and Love-wave dispersion curves, respectively. A Bayesian approach is utilized for the inversion. Differential evolution, a global search algorithm is applied to estimate the most-probable shear-velocity models. Marginal posterior probability profiles are computed by Metropolis-Hastings sampling. The estimated vertically and horizontally polarized shear-wave velocity profiles fit well with the core and in situ measurements.

  14. Hammering Yucca Flat, Part Two: Shear-Wave Velocity

    Science.gov (United States)

    Finlay, T. S.; Abbott, R. E.; Knox, H. A.; Tang, D. G.; James, S. R.; Haney, M. M.; Hampshire, J. B., II

    2015-12-01

    In preparation for the next phase of the Source Physics Experiment (SPE), we conducted an active-source seismic survey of Yucca Flat, Nevada, on the Nevada National Security Site. Results from this survey will be used to inform the geologic models associated with the SPE project. For this study, we used a novel 13,000 kilogram weight-drop seismic source to interrogate an 18-km North-South transect of Yucca Flat. Source points were spaced every 200 meters and were recorded by 350 to 380 3-component 2-Hz geophones with variable spacings of 10, 20, and 100 meters. We utilized the Refraction-Microtremor (ReMi) technique to create multiple 1D dispersion curves, which were then inverted for shear-wave velocity profiles using the Dix inversion method (Tsai and Haney, 2015). Each of these 1D velocity models was subsequently stitched together to create a 2D profile over the survey area. The dispersion results indicate a general decrease in surface-wave phase velocity to the south. This result is supported by slower shear-wave velocity sediments and increasing basin depth towards the survey's southern extent. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  15. Investigation of gravity waves using horizontally resolved radial velocity measurements

    Science.gov (United States)

    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

    Directory of Open Access Journals (Sweden)

    G. Stober

    2013-10-01

    Full Text Available 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.

  17. Pulse-wave morphology and pulse-wave velocity in healthy human volunteers

    DEFF Research Database (Denmark)

    Frimodt-Møller, M; Nielsen, A H; Kamper, A-L

    2006-01-01

    OBJECTIVE: Applanation tonometry for pulse-wave analysis (PWA) and determination of pulse-wave velocity (PWV) is a non-invasive method for assessment of the central aortic pressure waveform and indices of arterial stiffness. The objective of this study was to examine the influence of eating...

  18. Sensitivities of surface wave velocities to the medium parameters in a radially anisotropic spherical Earth and inversion strategies

    Directory of Open Access Journals (Sweden)

    Sankar N. Bhattacharya

    2015-11-01

    Full Text Available Sensitivity kernels or partial derivatives of phase velocity (c and group velocity (U with respect to medium parameters are useful to interpret a given set of observed surface wave velocity data. In addition to phase velocities, group velocities are also being observed to find the radial anisotropy of the crust and mantle. However, sensitivities of group velocity for a radially anisotropic Earth have rarely been studied. Here we show sensitivities of group velocity along with those of phase velocity to the medium parameters VSV, VSH , VPV, VPH , h and density in a radially anisotropic spherical Earth. The peak sensitivities for U are generally twice of those for c; thus U is more efficient than c to explore anisotropic nature of the medium. Love waves mainly depends on VSH while Rayleigh waves is nearly independent of VSH . The sensitivities show that there are trade-offs among these parameters during inversion and there is a need to reduce the number of parameters to be evaluated independently. It is suggested to use a nonlinear inversion jointly for Rayleigh and Love waves; in such a nonlinear inversion best solutions are obtained among the model parameters within prescribed limits for each parameter. We first choose VSH, VSV and VPH within their corresponding limits; VPV and h can be evaluated from empirical relations among the parameters. The density has small effect on surface wave velocities and it can be considered from other studies or from empirical relation of density to average P-wave velocity.

  19. Whistler Waves Driven by Anisotropic Strahl Velocity Distributions: Cluster Observations

    Science.gov (United States)

    Vinas, A.F.; Gurgiolo, C.; Nieves-Chinchilla, T.; Gary, S. P.; Goldstein, M. L.

    2010-01-01

    Observed properties of the strahl using high resolution 3D electron velocity distribution data obtained from the Cluster/PEACE experiment are used to investigate its linear stability. An automated method to isolate the strahl is used to allow its moments to be computed independent of the solar wind core+halo. Results show that the strahl can have a high temperature anisotropy (T(perpindicular)/T(parallell) approximately > 2). This anisotropy is shown to be an important free energy source for the excitation of high frequency whistler waves. The analysis suggests that the resultant whistler waves are strong enough to regulate the electron velocity distributions in the solar wind through pitch-angle scattering

  20. Waves in cell monolayer without proliferation: density determines cell velocity and wave celerity

    CERN Document Server

    Tlili, S; Li, B; Cardoso, O; Ladoux, B; Delanoë-Ayari, H; Graner, F

    2016-01-01

    Collective cell migration contributes to morphogenesis, wound healing or tumor metastasis. Culturing epithelial monolayers on a substrate is an in vitro configuration suitable to quantitatively characterize such tissue migration by measuring cell velocity, density and cell-substrate interaction force. Inhibiting cell division, we limit cell density increase and favor steady cell migration, while by using long narrow strips we stabilise the migrating front shape, so that we observe migration over a day or more. In the monolayer bulk, the cell velocity is a function of the cell density, namely it increases as a linear function of the cell radius. At least ten periods of propagating velocity waves are detected with a high signal-to-noise ratio, enabling for their quantitative spatio-temporal analysis. Cell density displays waves, in phase opposition with the velocity, as predicted by mass conservation; similarly, cell-substrate force appear to display small amplitude waves, in phase quadrature with respect to ve...

  1. Flow velocity measurement with the nonlinear acoustic wave scattering

    Energy Technology Data Exchange (ETDEWEB)

    Didenkulov, Igor, E-mail: din@appl.sci-nnov.ru [Institute of Applied Physics, 46 Ulyanov str., Nizhny Novgorod, 603950 (Russian Federation); Lobachevsky State University of Nizhny Novgorod, 23 Gagarin ave., Nizhny Novgorod, 603950 (Russian Federation); Pronchatov-Rubtsov, Nikolay, E-mail: nikvas@rf.unn.ru [Lobachevsky State University of Nizhny Novgorod, 23 Gagarin ave., Nizhny Novgorod, 603950 (Russian Federation)

    2015-10-28

    A problem of noninvasive measurement of liquid flow velocity arises in many practical applications. To this end the most often approach is the use of the linear Doppler technique. The Doppler frequency shift of signal scattered from the inhomogeneities distributed in a liquid relatively to the emitted frequency is proportional to the sound frequency and velocities of inhomogeneities. In the case of very slow flow one needs to use very high frequency sound. This approach fails in media with strong sound attenuation because acoustic wave attenuation increases with frequency and there is limit in increasing sound intensity, i.e. the cavitation threshold. Another approach which is considered in this paper is based on the method using the difference frequency Doppler Effect for flows with bubbles. This method is based on simultaneous action of two high-frequency primary acoustic waves with closed frequencies on bubbles and registration of the scattered by bubbles acoustic field at the difference frequency. The use of this method is interesting since the scattered difference frequency wave has much lower attenuation in a liquid. The theoretical consideration of the method is given in the paper. The experimental examples confirming the theoretical equations, as well as the ability of the method to be applied in medical diagnostics and in technical applications on measurement of flow velocities in liquids with strong sound attenuation is described. It is shown that the Doppler spectrum form depends on bubble concentration velocity distribution in the primary acoustic beams crossing zone that allows one to measure the flow velocity distribution.

  2. SHOCK-WAVE VELOCITY AND SHOCK PRESSURE FOR LOW-DENSITY POWDERS - A NOVEL-APPROACH

    NARCIS (Netherlands)

    DIJKEN, DK; DEHOSSON, JTM

    1994-01-01

    A novel approach is presented to predict the shock wave velocity as well as the shock wave pressure in powder materials. It is shown that the influence of the specific volume behind the shock wave on shock wave velocity and shock pressure decreases with decreasing initial powder density. The new

  3. Shock wave velocity and shock pressure for low density powders : A novel approach

    NARCIS (Netherlands)

    Dijken, D.K.; Hosson, J.Th.M. De

    1994-01-01

    A novel approach is presented to predict the shock wave velocity as well as the shock wave pressure in powder materials. It is shown that the influence of the specific volume behind the shock wave on shock wave velocity and shock pressure decreases with decreasing initial powder density. The new

  4. Blood pulse wave velocity measured by photoacoustic microscopy

    Science.gov (United States)

    Yeh, Chenghung; Hu, Song; Maslov, Konstantin; Wang, Lihong V.

    2013-03-01

    Blood pulse wave velocity (PWV) is an important indicator for vascular stiffness. In this letter, we present electrocardiogram-synchronized photoacoustic microscopy for in vivo noninvasive quantification of the PWV in the peripheral vessels of mice. Interestingly, strong correlation between blood flow speed and ECG were clearly observed in arteries but not in veins. PWV is measured by the pulse travel time and the distance between two spot of a chose vessel, where simultaneously recorded electrocardiograms served as references. Statistical analysis shows a linear correlation between the PWV and the vessel diameter, which agrees with known physiology. Keywords: photoacoustic microscopy, photoacoustic spectroscopy, bilirubin, scattering medium.

  5. Analysis shear wave velocity structure obtained from surface wave methods in Bornova, Izmir

    Energy Technology Data Exchange (ETDEWEB)

    Pamuk, Eren, E-mail: eren.pamuk@deu.edu.tr; Akgün, Mustafa, E-mail: mustafa.akgun@deu.edu.tr [Department of Geophysical Engineering, Dokuz Eylul University, Izmir (Turkey); Özdağ, Özkan Cevdet, E-mail: cevdet.ozdag@deu.edu.tr [Dokuz Eylul University Rectorate, Izmir (Turkey)

    2016-04-18

    Properties of the soil from the bedrock is necessary to describe accurately and reliably for the reduction of earthquake damage. Because seismic waves change their amplitude and frequency content owing to acoustic impedance difference between soil and bedrock. Firstly, shear wave velocity and depth information of layers on bedrock is needed to detect this changing. Shear wave velocity can be obtained using inversion of Rayleigh wave dispersion curves obtained from surface wave methods (MASW- the Multichannel Analysis of Surface Waves, ReMi-Refraction Microtremor, SPAC-Spatial Autocorrelation). While research depth is limeted in active source study, a passive source methods are utilized for deep depth which is not reached using active source methods. ReMi method is used to determine layer thickness and velocity up to 100 m using seismic refraction measurement systems.The research carried out up to desired depth depending on radius using SPAC which is utilized easily in conditions that district using of seismic studies in the city. Vs profiles which are required to calculate deformations in under static and dynamic loads can be obtained with high resolution using combining rayleigh wave dispersion curve obtained from active and passive source methods. In the this study, Surface waves data were collected using the measurements of MASW, ReMi and SPAC at the İzmir Bornova region. Dispersion curves obtained from surface wave methods were combined in wide frequency band and Vs-depth profiles were obtained using inversion. Reliability of the resulting soil profiles were provided by comparison with theoretical transfer function obtained from soil paremeters and observed soil transfer function from Nakamura technique and by examination of fitting between these functions. Vs values are changed between 200-830 m/s and engineering bedrock (Vs>760 m/s) depth is approximately 150 m.

  6. CONNECTION BETWEEN THE SHOCK WAVE SPEED AND II TYPE RADIO BURSTS DRIFT VELOCITY

    OpenAIRE

    E. A. Isaeva; Kravetz, R. O.

    2016-01-01

    The substantial arguments of strong connection between shock wave speed and drift velocity of II type radio bursts in 25-180 MHz range are presented. The studied sample has included 112 proton events that were accompanied with coronal shock waves. To evaluate drift velocity and shock wave speed there was used original records of dynamic spectra from radio spectrograph in 25- 180 MHz range. The velocities of shock waves were evaluated with the power mode model of solar corona density falloff.

  7. A continuous record of intereruption velocity change at Mount St. Helens from coda wave interferometry

    Science.gov (United States)

    Hotovec-Ellis, Alicia J.; Gomberg, Joan S.; Vidale, John; Creager, Ken C.

    2014-01-01

    In September 2004, Mount St. Helens volcano erupted after nearly 18 years of quiescence. However, it is unclear from the limited geophysical observations when or if the magma chamber replenished following the 1980–1986 eruptions in the years before the 2004–2008 extrusive eruption. We use coda wave interferometry with repeating earthquakes to measure small changes in the velocity structure of Mount St. Helens volcano that might indicate magmatic intrusion. By combining observations of relative velocity changes from many closely located earthquake sources, we solve for a continuous function of velocity changes with time. We find that seasonal effects dominate the relative velocity changes. Seismicity rates and repeating earthquake occurrence also vary seasonally; therefore, velocity changes and seismicity are likely modulated by snow loading, fluid saturation, and/or changes in groundwater level. We estimate hydrologic effects impart stress changes on the order of tens of kilopascals within the upper 4 km, resulting in annual velocity variations of 0.5 to 1%. The largest nonseasonal change is a decrease in velocity at the time of the deep Mw = 6.8 Nisqually earthquake. We find no systematic velocity changes during the most likely times of intrusions, consistent with a lack of observable surface deformation. We conclude that if replenishing intrusions occurred, they did not alter seismic velocities where this technique is sensitive due to either their small size or the finite compressibility of the magma chamber. We interpret the observed velocity changes and shallow seasonal seismicity as a response to small stress changes in a shallow, pressurized system.

  8. Experimental Investigation of Wave Velocity-Permeability Model for Granite Subjected to Different Temperature Processing

    Directory of Open Access Journals (Sweden)

    Guanghui Jiang

    2017-01-01

    Full Text Available Understanding the change of permeability of rocks before and after heating is of great significance for exploitation of hydrocarbon resources and disposal of nuclear waste. The rock permeability under high temperature cannot be measured with most of the existing methods. In this paper, quality, wave velocity, and permeability of granite specimen from Maluanshan tunnel are measured after high temperature processing. Quality and wave velocity of granite decrease and permeability of granite increases with increasing temperature. Using porosity as the medium, a new wave velocity-permeability model is established with modified wave velocity-porosity formula and Kozeny-Carman formula. Under some given wave velocities and corresponding permeabilities through experiment, the permeabilities at different temperatures and wave velocities can be obtained. By comparing the experimental and the theoretical results, the proposed formulas are verified. In addition, a sensitivity analysis is performed to examine the effect of particle size, wave velocities in rock matrix, and pore fluid on permeability: permeability increases with increasing particle size, wave velocities in rock matrix, and pore fluid; the higher the rock wave velocity, the lower the effect of wave velocities in rock matrix and pore fluid on permeability.

  9. Stress wave velocity patterns in the longitudinal-radial plane of trees for defect diagnosis

    Science.gov (United States)

    Guanghui Li; Xiang Weng; Xiaocheng Du; Xiping Wang; Hailin Feng

    2016-01-01

    Acoustic tomography for urban tree inspection typically uses stress wave data to reconstruct tomographic images for the trunk cross section using interpolation algorithm. This traditional technique does not take into account the stress wave velocity patterns along tree height. In this study, we proposed an analytical model for the wave velocity in the longitudinal–...

  10. Shear-wave velocity model from Rayleigh wave group velocities centered on the Sacramento/San Joaquin Delta

    Science.gov (United States)

    Fletcher, Jon Peter B.; Erdem, Jemile

    2017-01-01

    Rayleigh wave group velocities obtained from ambient noise tomography are inverted for an upper crustal model of the Central Valley, California, centered on the Sacramento/San Joaquin Delta. Two methods were tried; the first uses SURF96, a least-squares routine. It provides a good fit to the data, but convergence is dependent on the starting model. The second uses a genetic algorithm, whose starting model is random. This method was tried at several nodes in the model and compared to the output from SURF96. The genetic code is run five times and the variance of the output of all five models can be used to obtain an estimate of error. SURF96 produces a more regular solution mostly because it is typically run with a smoothing constraint. Models from the genetic code are generally consistent with the SURF96 code sometimes producing lower velocities at depth. The full model, calculated using SURF96, employed a 2-pass strategy, which used a variable damping scheme in the first pass. The resulting model shows low velocities near the surface in the Central Valley with a broad asymmetrical sedimentary basin located close to the western edge of the Central Valley near 122°W longitude. At shallow depths the Rio Vista Basin is found nestled between the Pittsburgh/Kirby Hills and Midland faults, but a significant basin also seems to exist to the west of the Kirby Hills fault. There are other possible correlations between fast and slow velocities in the Central Valley and geologic features such as the Stockton Arch, oil or gas producing regions and the fault-controlled western boundary of the Central Valley.

  11. On the Origin of High Shear Wave Velocities in the Deep Roots of Cratons

    Science.gov (United States)

    Zeng, L.; Duncan, M. S.; Garber, J. M.; Hernandez, J. A.; Maurya, S.; Zhang, H.; Faul, U.; McCammon, C. A.; Montagner, J. P.; Moresi, L. N.; Romanowicz, B. A.; Rudnick, R. L.; Stixrude, L. P.

    2016-12-01

    Some seismic models derived from tomographic studies indicate very high shear wave velocities around 150 km depth, which cannot be explained by standard cratonic peridotite compositions derived from kimberlites, even under the assumption of very cold geotherms (i.e. 28mW/m3 surface heat flux). We present the results of a multi-disciplinary study conducted at the CIDER Summer 2016 program in Santa Barbara (CA), in which we have reviewed various geophysical and petrological constraints on the nature of cratonic roots (seismic velocities, electrical conductivity, gravity, lithologies) and explored a range of possible solutions. We find that matching the high shear wave velocities requires a large proportion of eclogite that is not matched by observed eclogite proportions in kimberlite samples. The high shear velocity of diamond makes it a viable candidate to account for such high velocities, in a proportion that is compatible with the global carbon budget. Our most recent results will be presented as well as suggestions for possible mechanisms for diamond formation and emplacement.

  12. Crustal velocity structure of the Apennines (Italy from P-wave travel time tomography

    Directory of Open Access Journals (Sweden)

    A. Amato

    1996-06-01

    Full Text Available In this paper we provide P-wave velocity images of the crust underneath the Apennines (Italy, focusing on the lower crustal structure and the Moho topography. We inverted P-wave arrival times of earthquakes which occurred from 1986 to 1993 within the Apenninic area. To overcome inversion instabilities due to noisy data (we used bulletin data we decided to resolve a minimum number of velocity parameters, inverting for only two layers in the crust and one in the uppermost mantle underneath the Moho. A partial inversion of only 55% of the overall dataset yields velocity images similar to those obtained with the whole data set, indicating that the depicted tomograms are stable and fairly insensitive to the number of data used. We find a low-velocity anomaly in the lower crust extending underneath the whole Apenninic belt. This feature is segmented by a relative high-velocity zone in correspondence with the Ortona-Roccamonfina line, that separates the northern from the southern Apenninic arcs. The Moho has a variable depth in the study area, and is deeper (more than 37 km in the Adriatic side of the Northern Apennines with respect to the Tyrrhenian side, where it is found in the depth interval 22-34 km.

  13. Spectral analysis of surface waves method to assess shear wave velocity within centrifuge models

    Science.gov (United States)

    Murillo, Carol Andrea; Thorel, Luc; Caicedo, Bernardo

    2009-06-01

    The method of the spectral analysis of surface waves (SASW) is tested out on reduced scale centrifuge models, with a specific device, called the mini Falling Weight, developed for this purpose. Tests are performed on layered materials made of a mixture of sand and clay. The shear wave velocity VS determined within the models using the SASW is compared with the laboratory measurements carried out using the bender element test. The results show that the SASW technique applied to centrifuge testing is a relevant method to characterize VS near the surface.

  14. On measuring surface wave phase velocity from station–station cross-correlation of ambient signal

    DEFF Research Database (Denmark)

    Boschi, Lapo; Weemstra, Cornelis; Verbeke, Julie

    2012-01-01

    We apply two different algorithms to measure surface wave phase velocity, as a function of frequency, from seismic ambient noise recorded at pairs of stations from a large European network. The two methods are based on consistent theoretical formulations, but differ in the implementation: one...... method involves the time-domain cross-correlation of signal recorded at different stations; the other is based on frequency-domain cross-correlation, and requires finding the zero-crossings of the real part of the cross-correlation spectrum. Furthermore, the time-domain method, as implemented here......, writing out explicitly the relationships between the surface wave Green’s function, ambient-noise cross-correlation and phase and group velocities....

  15. Robustness of waves with a high phase velocity

    Energy Technology Data Exchange (ETDEWEB)

    Tajima, T., E-mail: ttajima@uci.edu [Department of Physics and Astronomy, University of California at Irvine, Irvine, CA, 92697 (United States); Tri Alpha Energy, Inc., P.O. Box 7010, Rancho Santa Margarita, CA 92688 (United States); Necas, A., E-mail: anecas@trialphaenergy.com [Tri Alpha Energy, Inc., P.O. Box 7010, Rancho Santa Margarita, CA 92688 (United States)

    2016-03-25

    Norman Rostoker pioneered research of (1) plasma-driven accelerators and (2) beam-driven fusion reactors. The collective acceleration, coined by Veksler, advocates to drive above-ionization plasma waves by an electron beam to accelerate ions. The research on this, among others, by the Rostoker group incubated the idea that eventually led to the birth of the laser wakefield acceleration (LWFA), by which a large and robust accelerating collective fields may be generated in plasma in which plasma remains robust and undisrupted. Besides the emergence of LWFA, the Rostoker research spawned our lessons learned on the importance of adiabatic acceleration of ions in collective accelerators, including the recent rebirth in laser-driven ion acceleration efforts in a smooth adiabatic fashion by a variety of ingenious methods. Following Rostoker’s research in (2), the beam-driven Field Reversed Configuration (FRC) has accomplished breakthroughs in recent years. The beam-driven kinetic plasma instabilities have been found to drive the reactivity of deuteron-deuteron fusion beyond the thermonuclear yield in C-2U plasma that Rostoker started. This remarkable result in FRCs as well as the above mentioned LWFA may be understood with the aid of the newly introduced idea of the “robustness hypothesis of waves with a high phase velocity”. It posits that when the wave driven by a particle beam (or laser pulse) has a high phase velocity, its amplitude is high without disrupting the supporting bulk plasma. This hypothesis may guide us into more robust and efficient fusion reactors and more compact accelerators.

  16. Mantle Shear-Wave Velocity Structure beneath the Hawaiian Hot Spot

    National Research Council Canada - National Science Library

    Cecily J. Wolfe; Sean C. Solomon; Gabi Laske; John A. Collins; Robert S. Detrick; John A. Orcutt; David Bercovici; Erik H. Hauri

    2009-01-01

    .... Three-dimensional images of shear-wave velocity beneath the Hawaiian Islands, obtained from a network of sea-floor and land seismometers, show an upper-mantle low-velocity anomaly that is elongated...

  17. Feasibility of waveform inversion of Rayleigh waves for shallow shear-wave velocity using a genetic algorithm

    Science.gov (United States)

    Zeng, C.; Xia, J.; Miller, R.D.; Tsoflias, G.P.

    2011-01-01

    Conventional surface wave inversion for shallow shear (S)-wave velocity relies on the generation of dispersion curves of Rayleigh waves. This constrains the method to only laterally homogeneous (or very smooth laterally heterogeneous) earth models. Waveform inversion directly fits waveforms on seismograms, hence, does not have such a limitation. Waveforms of Rayleigh waves are highly related to S-wave velocities. By inverting the waveforms of Rayleigh waves on a near-surface seismogram, shallow S-wave velocities can be estimated for earth models with strong lateral heterogeneity. We employ genetic algorithm (GA) to perform waveform inversion of Rayleigh waves for S-wave velocities. The forward problem is solved by finite-difference modeling in the time domain. The model space is updated by generating offspring models using GA. Final solutions can be found through an iterative waveform-fitting scheme. Inversions based on synthetic records show that the S-wave velocities can be recovered successfully with errors no more than 10% for several typical near-surface earth models. For layered earth models, the proposed method can generate one-dimensional S-wave velocity profiles without the knowledge of initial models. For earth models containing lateral heterogeneity in which case conventional dispersion-curve-based inversion methods are challenging, it is feasible to produce high-resolution S-wave velocity sections by GA waveform inversion with appropriate priori information. The synthetic tests indicate that the GA waveform inversion of Rayleigh waves has the great potential for shallow S-wave velocity imaging with the existence of strong lateral heterogeneity. ?? 2011 Elsevier B.V.

  18. Absorbing boundary conditions for low group velocity electromagnetic waves in photonic crystals.

    Science.gov (United States)

    Askari, Murtaza; Momeni, Babak; Reinke, Charles M; Adibi, Ali

    2011-03-20

    We present an efficient method for the absorption of slow group velocity electromagnetic waves in photonic crystal waveguides (PCWs). We show that adiabatically matching the low group velocity waves to high group velocity waves of the PCW and extending the PCW structure into the perfectly matched layer (PML) region results in a 15 dB reduction of spurious reflections from the PML. We also discuss the applicability of this method to structures other than PCWs.

  19. Shear wave velocity models retrieved using Rg wave dispersion data in shallow crust in some regions of southern Ontario, Canada

    Science.gov (United States)

    Ma, Shutian; Motazedian, Dariush; Corchete, Victor

    2013-04-01

    Many crucial tasks in seismology, such as locating seismic events and estimating focal mechanisms, need crustal velocity models. The velocity models of shallow structures are particularly important in the simulation of ground motions. In southern Ontario, Canada, many small shallow earthquakes occur, generating high-frequency Rayleigh ( Rg) waves that are sensitive to shallow structures. In this research, the dispersion of Rg waves was used to obtain shear-wave velocities in the top few kilometers of the crust in the Georgian Bay, Sudbury, and Thunder Bay areas of southern Ontario. Several shallow velocity models were obtained based on the dispersion of recorded Rg waves. The Rg waves generated by an m N 3.0 natural earthquake on the northern shore of Georgian Bay were used to obtain velocity models for the area of an earthquake swarm in 2007. The Rg waves generated by a mining induced event in the Sudbury area in 2005 were used to retrieve velocity models between Georgian Bay and the Ottawa River. The Rg waves generated by the largest event in a natural earthquake swarm near Thunder Bay in 2008 were used to obtain a velocity model in that swarm area. The basic feature of all the investigated models is that there is a top low-velocity layer with a thickness of about 0.5 km. The seismic velocities changed mainly within the top 2 km, where small earthquakes often occur.

  20. Imaging of surface wave phase velocities from array phase observations

    Science.gov (United States)

    Weidle, Christian; Maupin, Valerie

    2010-05-01

    While temporary deployments some 10 years ago were largely based on short-period seismometers, the availability of broadband instruments in instrument pools increased strongly in recent years and as such modern temporary deployments for passive seismological recordings often consist to a large extent, if not exclusively, of broadband instruments. This opens for new analysis approaches as the broadband seismic wavefield is obtained at a relatively high spatial sampling relative to the wavelength. In an attempt to infer surface wave phase velocity anomalies beneath Southern Norway based on data from a temporary network of 41 broadband instruments, we present a new approach to overcome the limitations of two-station phase measurements (on the great circle with the source) and instead exploit the two-dimensional nature of the wavefield by taking into account phase measurements at all stations of the array from a single event. This is based on the assumption that the wavefield is at least piecewise linear within the study region. By triangulation of the network region and linear estimation of the phase gradient in each triangle we get without further a priori assumptions a coarse image of the phase velocity variations within our network. The image can be significantly refined for a single event recording by stacking multiple images based on arbitrary subsets of the available data. Phase velocity anomalies measured from single event recordings can be biased and blurred by non-plane arriving wavefield, reflections and diffractions of heterogeneities. Therefore, by averaging over velocity fields from different events with varying backazimuths, artefacts are reduced and the recovered image significantly improved. Another way to improve the recovered structures is to take into account the spatial variation of the amplitude field. However, while the phase between two neighboring stations may be (at least close to) linear, the amplitude may not, hence estimation of the second

  1. Electromechanical wave imaging and electromechanical wave velocity estimation in a large animal model of myocardial infarction

    Science.gov (United States)

    Costet, Alexandre; Melki, Lea; Sayseng, Vincent; Hamid, Nadira; Nakanishi, Koki; Wan, Elaine; Hahn, Rebecca; Homma, Shunichi; Konofagou, Elisa

    2017-12-01

    Echocardiography is often used in the clinic for detection and characterization of myocardial infarction. Electromechanical wave imaging (EWI) is a non-invasive ultrasound-based imaging technique based on time-domain incremental motion and strain estimation that can evaluate changes in contractility in the heart. In this study, electromechanical activation is assessed in infarcted heart to determine whether EWI is capable of detecting and monitoring infarct formation. Additionally, methods for estimating electromechanical wave (EW) velocity are presented, and changes in the EW propagation velocity after infarct formation are studied. Five (n  =  5) adult mongrels were used in this study. Successful infarct formation was achieved in three animals by ligation of the left anterior descending (LAD) coronary artery. Dogs were survived for a few days after LAD ligation and monitored daily with EWI. At the end of the survival period, dogs were sacrificed and TTC (tetrazolium chloride) staining confirmed the formation and location of the infarct. In all three dogs, as soon as day 1 EWI was capable of detecting late-activated and non-activated regions, which grew over the next few days. On final day images, the extent of these regions corresponded to the location of infarct as confirmed by staining. EW velocities in border zones of infarct were significantly lower post-infarct formation when compared to baseline, whereas velocities in healthy tissues were not. These results indicate that EWI and EW velocity might help with the detection of infarcts and their border zones, which may be useful for characterizing arrhythmogenic substrate.

  2. Acoustic Wave Velocity as a Selection Trait in Eucalyptus nitens

    Directory of Open Access Journals (Sweden)

    David Blackburn

    2014-04-01

    Full Text Available Previous studies in Eucalyptus nitens have revealed favourable genetic correlations exist between acoustic wave velocity (AWV in standing trees and modulus of elasticity (MOE, which can determine the suitability of trees for structural timber and/or engineered wood products. This study investigates the strength and stability of genetic variation in standing tree AWV across a range of environments in Tasmania, where there are a number of large plantation estates and breeding trials. Trees under study were from open-pollinated progeny trials established in 1993. Across sites, for standing tree AWV the ranking of E. nitens races did not change and within-race additive genetic correlations were strong (0.61 to 0.99. Heritabilities (0.16 to 0.74 and coefficients of additive genetic variation (2.6 to 4.8 were moderate for this trait. Correlations between standing tree AWV and both basic density and diameter at breast height (DBH were favourable. Results indicate that there is potential to improve MOE in E. nitens through the exploitation of genetic variation in AWV among and within races, the expression of genetic variation in AWV is relatively stable across different growing environments, and past selection for basic density and growth in pulpwood breeding programs is unlikely to have adversely affected MOE.

  3. Estimated Pulse Wave Velocity Calculated from Age and Mean Arterial Blood Pressure

    DEFF Research Database (Denmark)

    Greve, S. V.; Laurent, Stéphane; Olsen, M. H.

    2016-01-01

    In a recently published paper, Greve et al [J Hypertens 2016;34:1279-1289] investigate whether the estimated carotid-femoral pulse wave velocity (ePWV), calculated using an equation derived from the relationship between carotid-femoral pulse wave velocity (cfPWV), age, and blood pressure, predicts...

  4. HF Radar Observation of Velocity Fields Induced by Tsunami Waves in the Kii Channel, Japan

    OpenAIRE

    日向, 博文; 藤, 良太郎; 藤井, 智史; 藤田, 裕一; 花土, 弘; 片岡, 智哉; 水谷, 雅裕; 高橋, 智幸

    2012-01-01

    High frequency ocean surface radar observation reveals the velocity fields of propagating tsunami waves and subsequent 30-40 minute period natural oscillation in the Kii Channel, Japan induced by the March 11, 2011 moment magnitude 9.0 Tohoku-Oki earthquake. Technical issues of the ocean surface radar sysytem concerning the detection of tsunami waves and natural oscillation velocities are also discussed.

  5. Estimation of near-surface shear-wave velocities and quality factors using multichannel analysis of surface-wave methods

    Science.gov (United States)

    Xia, Jianghai

    2014-04-01

    This overview article gives a picture of multichannel analysis of high-frequency surface (Rayleigh and Love) waves developed mainly by research scientists at the Kansas Geological Survey, the University of Kansas and China University of Geosciences (Wuhan) during the last eighteen years by discussing dispersion imaging techniques, inversion systems, and real-world examples. Shear (S)-wave velocities of near-surface materials can be derived from inverting the dispersive phase velocities of high-frequency surface waves. Multichannel analysis of surface waves—MASW used phase information of high-frequency Rayleigh waves recorded on vertical component geophones to determine near-surface S-wave velocities. The differences between MASW results and direct borehole measurements are approximately 15% or less and random. Studies show that inversion with higher modes and the fundamental mode simultaneously can increase model resolution and an investigation depth. Multichannel analysis of Love waves—MALW used phase information of high-frequency Love waves recorded on horizontal (perpendicular to the direction of wave propagation) component geophones to determine S-wave velocities of shallow materials. Because of independence of compressional (P)-wave velocity, the MALW method has some attractive advantages, such as 1) Love-wave dispersion curves are simpler than Rayleigh wave's; 2) dispersion images of Love-wave energy have a higher signal to noise ratio and more focused than those generated from Rayleigh waves; and 3) inversion of Love-wave dispersion curves is less dependent on initial models and more stable than Rayleigh waves.

  6. Towards a new tool to develop a 3-D shear-wave velocity model from converted waves

    Science.gov (United States)

    Colavitti, Leonardo; Hetényi, György

    2017-04-01

    The main target of this work is to develop a new method in which we exploit converted waves to construct a fully 3-D shear-wave velocity model of the crust. A reliable 3-D model is very important in Earth sciences because geological structures may vary significantly in their lateral dimension. In particular, shear-waves provide valuable complementary information with respect to P-waves because they usually guarantee a much better correlation in terms of rock density and mechanical properties, reducing the interpretation ambiguities. Therefore, it is fundamental to develop a new technique to improve structural images and to describe different lithologies in the crust. In this study we start from the analysis of receiver functions (RF, Langston, 1977), which are nowadays largely used for structural investigations based on passive seismic experiments, to map Earth discontinuities at depth. The RF technique is also commonly used to invert for velocity structure beneath single stations. Here, we plan to combine two strengths of RF method: shear-wave velocity inversion and dense arrays. Starting from a simple 3-D forward model, synthetic RFs are obtained extracting the structure along a ray to match observed data. During the inversion, thanks to a dense stations network, we aim to build and develop a multi-layer crustal model for shear-wave velocity. The initial model should be chosen simple to make sure that the inversion process is not influenced by the constraints in terms of depth and velocity posed at the beginning. The RFs inversion represents a complex problem because the amplitude and the arrival time of different phases depend in a non-linear way on the depth of interfaces and the characteristics of the velocity structure. The solution we envisage to manage the inversion problem is the stochastic Neighbourhood Algorithm (NA, Sambridge, 1999a, b), whose goal is to find an ensemble of models that sample the good data-fitting regions of a multidimensional parameter

  7. Left ventricular ejection time, not heart rate, is an independent correlate of aortic pulse wave velocity.

    Science.gov (United States)

    Salvi, Paolo; Palombo, Carlo; Salvi, Giovanni Matteo; Labat, Carlos; Parati, Gianfranco; Benetos, Athanase

    2013-12-01

    Several studies showed a positive association between heart rate and pulse wave velocity, a sensitive marker of arterial stiffness. However, no study involving a large population has specifically addressed the dependence of pulse wave velocity on different components of the cardiac cycle. The aim of this study was to explore in subjects of different age the link between pulse wave velocity with heart period (the reciprocal of heart rate) and the temporal components of the cardiac cycle such as left ventricular ejection time and diastolic time. Carotid-femoral pulse wave velocity was assessed in 3,020 untreated subjects (1,107 men). Heart period, left ventricular ejection time, diastolic time, and early-systolic dP/dt were determined by carotid pulse wave analysis with high-fidelity applanation tonometry. An inverse association was found between pulse wave velocity and left ventricular ejection time at all ages (heart period was also found, with the exception of the youngest subjects (P = 0.20). A significant positive correlation was also found between pulse wave velocity and dP/dt (P heart period no longer became significant. Our data demonstrate that pulse wave velocity is more closely related to left ventricular systolic function than to heart period. This may have methodological and pathophysiological implications.

  8. Arterial pulse wave propagation velocity in healthy dogs by pulse wave Doppler ultrasound.

    Science.gov (United States)

    Nogueira, Rodrigo B; Pereira, Lucas A; Basso, Alice F; da Fonseca, Ingrid S; Alves, Lorena A

    2017-03-01

    The aim of this study was to prospectively evaluate the carotid-femoral pulse wave velocity (PWV) values in healthy dogs using pulse wave Doppler ultrasound. A secondary aim was to determine the feasibility of this method and to report the intra- and interobserver reproducibilities of the PWV in conscious dogs. The data were studied in 30 healthy, adult, male (n = 15) and female (n = 15) dogs. The time interval marked between the R wave peak of the electrocardiogram and the intersection of the blood flow wave upstroke of the Doppler spectrum with the baseline of zero frequency was determined for the carotid (T1) and for the femoral (T2) arteries. The distance covered by the pulse wave (L) was determined. The PWV was then calculated using the following formula: L/T2 - T1. The mean values of PWV calculated from the total sample (n = 30) evaluated were 13.41 ± 2.20 m/s. No significant statistical difference was observed for the PWV measurements between males (14.82 ± 3.18 m/s) and females (12.64 ± 2.45 m/s). The analysis revealed no intra nor interobserver differences. A reasonable reproducibility of the PWV measurements was showed by intraclass correlation coefficients (ICC), and the coefficients of variation (CV). These data demonstrate that noninvasive vascular Doppler analysis is a feasible and reproducible method to determine the carotid-femoral PWV in dogs.

  9. Background velocity inversion by phase along reflection wave paths

    KAUST Repository

    Yu, Han

    2014-08-05

    A background velocity model containing the correct lowwavenumber information is desired for both the quality of the migration image and the success of waveform inversion. We propose to invert for the low-wavenumber part of the velocity model by minimizing the phase difference between predicted and observed reflections. The velocity update is exclusively along the reflection wavepaths and, unlike conventional FWI, not along the reflection ellipses. This allows for reconstructing the smoothly varying parts of the background velocity model. Tests with synthetic data show both the benefits and limitations of this method.

  10. Association of Brachial-Ankle Pulse Wave Velocity with Asymptomatic Intracranial Arterial Stenosis in Hypertension Patients.

    Science.gov (United States)

    Wang, Yan; Zhang, Jin; Qain, Yuesheng; Tang, Xiaofeng; Ling, Huawei; Chen, Kemin; Li, Yan; Gao, Pingjin; Zhu, Dingliang

    2016-08-01

    Intracranial arterial stenosis is a common cause of ischemic stroke in Asians. We therefore sought to explore the relationship of brachial-ankle pulse wave velocity and intracranial arterial stenosis in 834 stroke-free hypertensive patients. Intracranial arterial stenosis was evaluated through computerized tomographic angiography. Brachial-ankle pulse wave velocity was measured by an automated cuff device. The top decile of brachial-ankle pulse wave velocity was significantly associated with intracranial arterial stenosis (P = .027, odds ratio = 1.82; 95% confidence interval: 1.07-3.10). The patients with the top decile of brachial-ankle pulse wave velocity showed 56% higher risk for the presence of intracranial arterial stenosis to the whole population, which was more significant in patients younger than 65 years old. We also found that brachial-ankle pulse wave velocity related to both intracranial arterial stenosis and homocysteine. Our study showed the association of brachial-ankle pulse wave velocity with asymptomatic intracranial arterial stenosis in hypertension patients, especially in relative younger subjects. Brachial-ankle pulse wave velocity might be a relatively simple and repeatable measurement to detect hypertension patients in high risk of intracranial arterial stenosis. Copyright © 2016. Published by Elsevier Inc.

  11. Rayleigh wave phase velocity and error maps up to the fifth overtone

    Science.gov (United States)

    Durand, Stéphanie; Debayle, Eric; Ricard, Yanick

    2015-05-01

    We present a global data set of phase velocity maps for Rayleigh waves, with their errors. These maps are obtained from the tomographic inversion of phase velocity curves measured in the period range 40-250 s by Debayle and Ricard (2012), completed with new measurements at longer periods, between 150 and 360 s. The full data set includes ˜22,000,000 phase velocity measurements combined to build 60 phase velocity maps covering the period range 40-360 s for the fundamental mode and up to the fifth overtone. Each phase velocity map is provided with its a posteriori error, resulting in a unique data set which can be combined with other seismic measurements (surface waves, normal modes, and body waves) in regional and global tomographic studies. A preliminary inversion of this data set shows that it provides constraints on the shear velocity structure down to 1000 km depth.

  12. Estimation of aortic compliance using magnetic resonance pulse wave velocity measurement

    Energy Technology Data Exchange (ETDEWEB)

    Boese, J.M.; Bock, M.; Schoenberg, S.O.; Schad, L.R. [Deutsches Krebsforschungszentrum, Radiologische Diagnostik und Therapie, D-69120 Heidelberg (Germany)

    2000-06-01

    A method for compliance estimation employing magnetic resonance pulse wave velocity measurement is presented. Time-resolved flow waves are recorded at several positions along the vessel using a phase contrast sequence, and pulse wave velocity is calculated from the delay of the wave onsets. Using retrospective cardiac gating in combination with an optically decoupled electrocardiogram acquisition, a high temporal resolution of 3 ms can be achieved. A phantom set-up for the simulation of pulsatile flow in a compliant vessel is described. In the phantom, relative errors of pulse wave velocity estimation were found to be about 15%, whereas in a volunteer, larger errors were found that might be caused by vessel branches. Results of pulse wave velocity estimation agree with directaortic distension measurements which rely on a peripheral estimate of aortic pressure and are therefore less accurate. Studies in 12 volunteers show values of pulse wave velocity consistent with the literature; in particular the well-known increase in pulse wave velocity with age was observed. Preliminary results show that the method can be applied to aortic aneurysms. (author)

  13. Influence of Aggregate Gradation on the Longitudinal Wave Velocity Changes in Unloaded Concrete

    Science.gov (United States)

    Teodorczyk, Michał

    2017-10-01

    Diagnosis is an important factor in the assessment of structural and operational condition of a concrete structure. Among diagnostic methods, non-destructive testing methods play a special role. Acoustic emission evaluation based on the identification and location of destructive processes is one of such methods. The 3D location of AE events and moment tensor of fracture analysis are calculated by longitudinal wave velocity. Therefore, determining the velocity of longitudinal wave of concrete and the impact of the material and destructive factors are of essential importance. This paper reports the investigation of the effect of aggregate gradation on the change in wave velocity of unloaded concrete. The investigation was carried out on six 150 x 150 x 600 mm elements. Three elements contained aggregate fraction 8/16 mm and the other three were made with aggregate fraction 2/16 mm. Two acoustic emission sensors were used on the surface of the elements, and the wave was generated by the Hsu – Nielsen source. Longitudinal wave velocities for each group of elements were calculated and statistical test of significance was used for the comparison of two means. The results of the test indicated a substantial effect of the aggregate grain size on the change in longitudinal wave velocity. The average wave velocity in the concrete containing 8/16 mm fraction was 4672 m/s. In the concrete with 2/16 mm fraction, the velocity decreased to 4373 m/s. The velocity of the wave decreases at larger quantities of aggregate. The propagating longitudinal wave encounters more aggregate grains on its way and is reflected, also from air voids, multiple times and so its velocity is noticeably lower in the concrete with the 2/16 fraction. Thus, to be able to accurately locate AE events and analyse moment tensor during concrete structure testing, the aggregate grain size used in the concrete should be taken into account.

  14. Comparison of atherosclerotic indicators between cardio ankle vascular index and brachial ankle pulse wave velocity.

    Science.gov (United States)

    Horinaka, Shigeo; Yabe, Akihisa; Yagi, Hiroshi; Ishimura, Kimihiko; Hara, Hitoshi; Iemua, Tomoyuki; Matsuoka, Hiroaki

    2009-01-01

    Aortic pulse wave velocity has been used for evaluating atherosclerosis. Recently, the development of the volume plethysmographic method has made it possible to easily measure the index of the pulse wave velocity. The brachial ankle pulse wave velocity and cardio ankle vascular index are used for estimating the extent of atherosclerosis. The diagnostic usefulness of these indexes in predicting coronary artery disease was examined. The brachial ankle pulse wave velocity, the cardio ankle vascular index, and the high-sensitivity C-reactive protein were measured in 696 patients who had chest pain and underwent coronary angiography. Measurement values of brachial ankle pulse wave velocity were compared with those of cardio ankle vascular index in terms of the baseline covariates and the number of major coronary vessels involved (vessel disease). The brachial ankle pulse wave velocity was significantly correlated with age, systolic blood pressure, and diastolic blood pressure but not with the high-sensitivity C-reactive protein. The cardio ankle vascular index was correlated only with age and the high-sensitivity C-reactive protein. The average of both brachial ankle pulse wave velocity and cardio ankle vascular index values was greater in 3 vessel disease group than in 0 vessel disease group. The receiver operating characteristic curve showed that the diagnostic accuracy of coronary artery disease was significantly higher in the cardio ankle vascular index than in the brachial ankle pulse wave velocity (area under the curve +/- standard error: 0.691 +/- 0.025 vs. 0.584 +/- 0.026; P cardio ankle vascular index are useful and that cardio ankle vascular index may have some advantages in its application to patients taking blood pressure-lowering medication because of the minimum effect of blood pressure on its measurement values. The cardio ankle vascular index has increased performance over brachial ankle pulse wave velocity in predicting the coronary artery disease.

  15. Estimation of the p-wave velocity profile of elastic real data based on surface wave inversion

    NARCIS (Netherlands)

    Ponomarenko, A.V.; Kashtan, B.M.; Troyan, V.N.; Mulder, W.A.

    2013-01-01

    Recently, we proposed an analytical approach to invert for a smoothly varying near-surface P-wave velocity profile that has a squared slowness linearly decreasing with depth. The exact solution for such a velocity profile in the acoustic approximation can be expressed in terms of Airy functions and

  16. Aortic pulse wave velocity measurement in systemic sclerosis patients

    Directory of Open Access Journals (Sweden)

    M. Sebastiani

    2012-12-01

    Full Text Available Background. Systemic sclerosis (SSc is characterized by endothelial dysfunction and widespread microangiopathy. However, a macrovascular damage could be also associated. Aortic pulse wave velocity (aPWV is known to be a reliable indicator of arterial stiffness and a useful prognostic predictor of cardiovascular events. Moreover, aPWV may be easily measured by non-invasive, user-friendly tool. Aim of our study was to evaluate aPWV alterations in a series of SSc patients. Methods. The aPWV was evaluated in 35 consecutive female SSc patients and 26 sex- and age-matched healthy controls. aPWV alterations were correlated with cardiopulmonary involvement. Results. A significant increase of aPWV was observed in SSc patients compared to controls (9.4±3.2 m/s vs 7.3±1 m/s; P=0.002. In particular, 14/35 (40% SSc patients and only 1/26 (4% controls (P=0.0009 showed increased aPWV (>9 m/s cut-off value. Moreover, echocardiography evaluation showed an increased prevalence of right atrial and ventricular dilatation (atrial volume: 23.6±6.2 mL vs 20.3±4.3 mL, P=0.026; ventricular diameter 19.5±4.9 mm vs 15.9±1.6 mm; P=0.001 associated to higher values of pulmonary arterial systolic pressure (PAPs in SSc patients (31.5±10.4 mmHg vs 21.6±2.9 mmHg; P50 years old. Furthermore, altered aPWV was more frequently associated with limited cutaneous pattern, longer disease duration (≥5 years, and/or presence of anticentromere antibody (ACA. Conclusions. A significantly higher prevalence of abnormally increased aPWV was evidenced in SSc patients compared to healthy controls. The possibility of more pronounced and diffuse vascular damage in a particular SSc subset (ACA-positive subjects with limited cutaneous scleroderma and longer disease duration might be raised.

  17. Theory and experiment on electromagnetic-wave-propagation velocities in stacked superconducting tunnel structures

    DEFF Research Database (Denmark)

    Sakai, S.; Ustinov, A. V.; Kohlstedt, H.

    1994-01-01

    focused on. Furthermore, under the assumption that all parameters of the layers are equal, analytic solutions for a generic N-fold stack are presented. The velocities of the waves in two- and three-junction stacks by Nb-Al-AlOx-Nb systems are experimentally obtained by measuring the cavity resonance......Characteristic velocities of the electromagnetic waves propagating in vertically stacked Josephson transmission are theoretically discussed. An equation for solving n velocities of the waves in an n Josephson-junction stack is derived. The solutions of two- and threefold stacks are especially...

  18. Shear-wave velocity structure of young Atlantic Lithosphere from dispersion analysis and waveform modelling of Rayleigh waves

    Science.gov (United States)

    Grevemeyer, Ingo; Lange, Dietrich; Schippkus, Sven

    2016-04-01

    The lithosphere is the outermost solid layer of the Earth and includes the brittle curst and brittle uppermost mantle. It is underlain by the asthenosphere, the weaker and hotter portion of the mantle. The boundary between the brittle lithosphere and the asthenosphere is call the lithosphere-asthenosphere boundary, or LAB. The oceanic lithosphere is created at spreading ridges and cools and thickens with age. Seismologists define the LAB by the presence of a low shear wave velocity zone beneath a high velocity lid. Surface waves from earthquakes occurring in young oceanic lithosphere should sample lithospheric structure when being recorded in the vicinity of a mid-ocean ridge. Here, we study group velocity and dispersion of Rayleigh waves caused by earthquakes occurring at transform faults in the Central Atlantic Ocean. Earthquakes were recorded either by a network of wide-band (up to 60 s) ocean-bottom seismometers (OBS) deployed at the Mid-Atlantic Ridge near 15°N or at the Global Seismic Network (GSN) Station ASCN on Ascension Island. Surface waves sampling young Atlantic lithosphere indicate systematic age-dependent changes of group velocities and dispersion of Rayleigh waves. With increasing plate age maximum group velocity increases (as a function of period), indicating cooling and thickening of the lithosphere. Shear wave velocity is derived inverting the observed dispersion of Rayleigh waves. Further, models derived from the OBS records were refined using waveform modelling of vertical component broadband data at periods of 15 to 40 seconds, constraining the velocity structure of the uppermost 100 km and hence in the depth interval of the mantle where lithospheric cooling is most evident. Waveform modelling supports that the thickness of lithosphere increases with age and that velocities in the lithosphere increase, too.

  19. Integration of SH seismic reflection and Love-wave dispersion data for shear wave velocity determination over quick clays

    Science.gov (United States)

    Comina, Cesare; Krawczyk, Charlotte M.; Polom, Ulrich; Socco, Laura Valentina

    2017-09-01

    Quick clay is a water-saturated formation originally formed through flocculation and deposition in a marine to brackish environment. It is subsequently leached to low salinity by freshwater flow. If its strength decreases, then the flocculated structure collapses leading to landslides of varying destructiveness. Leaching can result in a reduction of the undisturbed shear strength of these clays and suggestions exist that a reduction in shear wave velocities is also possible. Integration of SH seismic reflection and Love-wave dispersion data was undertaken, in an area near the Göta River in southwest Sweden, to evaluate the potential of shear wave velocity imaging for detecting quick clays. Seismic reflection processing evidenced several geologically interesting interfaces related to the probable presence of quick clays (locally confirmed by boreholes) and sand-gravelly layers strongly contributing to water circulation within them. Dispersion data were extracted with a Gaussian windowing approach and inverted with a laterally constrained inversion using a priori information from the seismic reflection imaging. The inversion of dispersion curves has evidenced the presence of a low velocity layer (lvl, with a velocity reduction of ca. 30 per cent) probably associable to quick clays. This velocity reduction is enough to produce detectable phase-velocity differences in the field data and to achieve a better velocity resolution if compared to reflection seismic velocity analyses. The proposed approach has the potential of a comprehensive determination of the shear wave velocity distribution in the shallow subsurface. A sensitivity analysis of Love-wave dispersion data is also presented underlining that, despite limited dispersion of the data set and the velocity-reducing effect of quick-clay leaching, the proposed interpretation procedure arises as a valuable approach in quick clay and other lvl identification.

  20. The effects of frequency on the elastic wave velocity in rocks at high temperatures under pressure

    Science.gov (United States)

    Matsushima, S.

    1986-04-01

    P- and S-wave velocities in nepheline basalt, Hamada, as well as diabase, Maryland, were measured experimentally to 1000°C and 2.5 GPa. A remarkable frequency dependence of large velocity-decrease was observed for both P- and S-waves at temperatures above 500°C. Remarkable velocity-characteristics, which cannot be explained by the existing theories, were: (1) Velocities were decreased considerably at 1-3 MHz. Above 3 MHz, samples showed elastic behavior like that of a perfect solid, and below 1 MHz, velocity-decrease decayed gradually. (2) Both P- and S-wave velocities decreased in the same way and almost to the same degree. (3) The higher the temperature, the more remarkably velocities decreased, at least up to the experimental limit temperature. A hypothesis of the relaxation of stress waves by the fluid-flow in the inclusions is proposed. Examples of geophysical applications are given for the attenuation and travel-time anomalies in the volcanic region and the P- and S-wave velocity-decrease in the upper mantle beneath continents.

  1. Characterization of guided wave velocity and attenuation in anisotropic materials from wavefield measurements

    Science.gov (United States)

    Williams, Westin B.; Michaels, Thomas E.; Michaels, Jennifer E.

    2016-02-01

    The behavior of guided waves propagating in anisotropic composite panels can be substantially more complicated than for isotropic, metallic plates. The angular dependency of wave propagation characteristics need to be understood and quantified before applying methods for damage detection and characterization. This study experimentally investigates the anisotropy of wave speed and attenuation for the fundamental A0-like guided wave mode propagating in a solid laminate composite panel. A piezoelectric transducer is the wave source and a laser Doppler vibrometer is used to measure the outward propagating waves along radial lines originating at the source transducer. Group velocity, phase velocity and attenuation are characterized as a function of angle for a single center frequency. The methods shown in this paper serve as a framework for future adaptation to damage imaging methods using guided waves for structural health monitoring.

  2. The wave phase velocity in superconducting transmission lines near T{sub c}

    Energy Technology Data Exchange (ETDEWEB)

    Kuzhakhmetov, A.R.; Lobov, G.D.; Shtykov, V.V.; Zhgoon, S.A. [Moscow Power Engineering Inst. (Russian Federation). Radio Engineering Dept.

    1998-06-01

    A peculiarity in behavior of electromagnetic waves phase velocity ({nu}{sub ph}), propagating in superconducting planar transmission lines, in the vicinity of the transition temperature (T{sub c}) was observed in experiment and deduced theoretically. (orig.) 5 refs.

  3. A numerical method for predicting Rayleigh surface wave velocity in anisotropic crystals

    Science.gov (United States)

    Cherry, Matthew R.; Sathish, Shamachary; Grandhi, Ramana

    2017-12-01

    A numerical method was developed for calculating the Rayleigh Surface Wave (RSW) velocity in arbitrarily oriented single crystals in 360 degrees of propagation. This method relies on the results from modern analysis of RSW behavior with the Stroh formalism to restrict the domain in which to search for velocities by first calculating the limiting velocity. This extension of existing numerical methods also leads to a natural way of determining both the existence of the RSW as well as the possibility of encountering a pseudo-surface wave. Furthermore, the algorithm is applied to the calculation of elastic properties from measurement of the surface wave velocity in multiple different directions on a single crystal sample. The algorithm was tested with crystal symmetries and single crystal elastic moduli from literature. It was found to be very robust and efficient in calculating RSW velocity curves in all cases.

  4. Near-surface shear-wave velocity measurements in unlithified sediment

    Science.gov (United States)

    Richards, B.T.; Steeples, D.; Miller, R.; Ivanov, J.; Peterie, S.; Sloan, S.D.; McKenna, J.R.

    2011-01-01

    S-wave velocity can be directly correlated to material stiffness and lithology making it a valuable physical property that has found uses in construction, engineering, and environmental projects. This study compares different methods for measuring S-wave velocities, investigating and identifying the differences among the methods' results, and prioritizing the different methods for optimal S-wave use at the U. S. Army's Yuma Proving Grounds YPG. Multichannel Analysis of Surface Waves MASW and S-wave tomography were used to generate S-wave velocity profiles. Each method has advantages and disadvantages. A strong signal-to-noise ratio at the study site gives the MASW method promising resolution. S-wave first arrivals are picked on impulsive sledgehammer data which were then used for the tomography process. Three-component downhole seismic data were collected in-line with a locking geophone, providing ground truth to compare the data and to draw conclusions about the validity of each data set. Results from these S-wave measurement techniques are compared with borehole seismic data and with lithology data from continuous samples to help ascertain the accuracy, and therefore applicability, of each method. This study helps to select the best methods for obtaining S-wave velocities for media much like those found in unconsolidated sediments at YPG. ?? 2011 Society of Exploration Geophysicists.

  5. AORTIC PULSE WAVE VELOCITY MEASURED BY PULSE WAVE IMAGING (PWI): A COMPARISON WITH APPLANATION TONOMETRY.

    Science.gov (United States)

    Vappou, Jonathan; Luo, Jianwen; Okajima, Kazue; Di Tullio, Marco; Konofagou, Elisa

    2011-06-01

    Arterial stiffness is a well-established indicator of cardiovascular disease outcome. Pulse Wave Velocity (PWV) is a surrogate for arterial stiffness that is measured either globally using carotid to femoral applanation tonometry or locally using biomedical imaging methods. Pulse Wave Imaging (PWI) is an ultrasound-based method for both qualitative visualisation of pulse wave propagation and quantitative estimation of arterial stiffness. The objective of this study is to assess the PWI performance in PWV estimation by comparing local abdominal aortic PWV values obtained by PWI to the carotid-femoral PWV measured by applanation tonometry. A total of 18 subjects (age 18-66, 32.5±14.5) with no history of cardiovascular disease were consecutively tested by both PWI and tonometry. The correlation coefficient r between values found by the two methods was found to be equal to 0.68. A linear regression yielded PWVPWI = 1.02* PWVtonometry +0.15. Tukey mean-difference plots indicated that PWVPWI was significantly lower than PWVtonometry (-0.3 m/s) at lower PWV values (PWV≤7 m/s), whereas PWVPWI was significantly higher (+1.4 m/s) than PWVtonometry at higher PWV values (PWV>7 m/s). Despite the regional nature of the PWVPWI measurements, as opposed to the global PWVtonometry measurements, abdominal PWVPWI and carotid-femoral PWVtonometry values were found to be similar, with an average bias equal to 0.25 m/s. Such a bias and its variation with PWV may be partially explained by both physiological variations of PWV along the arterial tree and by the increasing uncertainty of the PWV estimate by PWI as PWV increases.

  6. Migration velocity analysis using pre-stack wave fields

    KAUST Repository

    Alkhalifah, Tariq Ali

    2016-08-25

    Using both image and data domains to perform velocity inversion can help us resolve the long and short wavelength components of the velocity model, usually in that order. This translates to integrating migration velocity analysis into full waveform inversion. The migration velocity analysis part of the inversion often requires computing extended images, which is expensive when using conventional methods. As a result, we use pre-stack wavefield (the double-square-root formulation) extrapolation, which includes the extended information (subsurface offsets) naturally, to make the process far more efficient and stable. The combination of the forward and adjoint pre-stack wavefields provides us with update options that can be easily conditioned to improve convergence. We specifically use a modified differential semblance operator to split the extended image into a residual part for classic differential semblance operator updates and the image (Born) modelling part, which provides reflections for higher resolution information. In our implementation, we invert for the velocity and the image simultaneously through a dual objective function. Applications to synthetic examples demonstrate the features of the approach.

  7. On the time varying horizontal water velocity of single, multiple, and random gravity wave trains

    NARCIS (Netherlands)

    Wells, D.R.

    1964-01-01

    In this dissertation some characteristics of the horizontal water velocity for single, multiple, and random gravity wave trains are studied. This work consists of two parts, an analogue study and hydraulic measurements. An important aspect in this work is to suggest the horizontal water velocity

  8. Analyses of Current And Wave Forces on Velocity Caps

    OpenAIRE

    Christensen, Erik Damgaard; Buhrkall, Jeppe; Eskesen, Mark C. D.; Jensen, Bjarne

    2015-01-01

    Velocity caps are often used in connection with for instance offshore intake sea water for the use of for cooling water for power plants or as a source for desalinization plants. The intakes can also be used for river intakes. The velocity cap is placed on top of a vertical pipe. The vertical pipe leads the water into another pipe or tunnel system. A pressure gradient generated by the water level difference between the sea and basin drives the flow through the tunnel system. The tunnel system...

  9. Crustal velocity structure of the Deccan Volcanic Province, Indian Peninsula, from observed surface wave dispersion

    Directory of Open Access Journals (Sweden)

    Gaddale Suresh

    2014-08-01

    Full Text Available Through inversion of fundamental mode group velocities of Love and Rayleigh waves, we study the crustal and subcrustal structure across the central Deccan Volcanic Province (DVP, which is one of the world’s largest terrestrial flood basalts. Our analysis is based on broadband seismograms recorded at seismological station Bhopal (BHPL in the central India from earthquakes located near west coast of India, with an average epicentral distance about 768 km. The recording station and epicentral zone are situated respectively on the northern and southern edges of DVP with wave paths across central DVP. The period of group velocity data ranges from 5 to 60 s for Rayleigh waves and 5 to 45 s for Love waves. Using the genetic algorithm, the observed data have been inverted to obtain the crust and subcrustal velocity structure along the wavepaths. Using this procedure, a similar velocity structure was also obtained earlier for the northwestern DVP, which is in the west of the present study region. Comparison of results show that the crustal thickness decreases westward from central DVP (39.6 km to northwestern DVP (37.8 km along with the decrease of thickness of upper crust; while the thickness of lower crust remains nearly same. From east to west S-wave velocity in the upper crust decreases by 2 to 3 per cent, while P-wave velocity in the whole crust and subcrust decreases by 3 to 6 per cent. The P- and S-wave velocities are positively correlated with crustal thickness and negatively correlated with earth’s heat flow. It appears that the elevated crustal and subcrustal temperature in the western side is the main factor for low velocities on this side.

  10. Velocity flow field and water level measurements in shoaling and breaking water waves

    CSIR Research Space (South Africa)

    Mukaro, R

    2010-01-01

    Full Text Available In this paper we report on the laboratory investigations of breaking water waves. Measurements of the water levels and instantaneous fluid velocities were conducted in water waves breaking on a sloping beach within a glass flume. Instantaneous water...

  11. PIV measurements of velocities and accelerations under breaking waves on a slope

    DEFF Research Database (Denmark)

    Vested, Malene Hovgaard; Carstensen, Stefan; Christensen, Erik Damgaard

    2017-01-01

    Understanding the physics of breaking waves is an ongoing research topic, not only due to human curiosity, but also due to the influence breaking waves have on offshore structures. In recent years, the development in experimental methods has facilitated a new insight into the physics of breaking...... waves. In this study, we have investigated the wave kinematics under steep and breaking waves on a laboratory beach with a slope of 1/25. The velocity field was measured by use of Particle Image Velocimetry (PIV) at a sample rate of 96Hz. The high sample rate allowed for the accelerations...

  12. The elastic wave velocity response of methane gas hydrate formation in vertical gas migration systems

    Science.gov (United States)

    Bu, Q. T.; Hu, G. W.; Ye, Y. G.; Liu, C. L.; Li, C. F.; Best, A. I.; Wang, J. S.

    2017-06-01

    Knowledge of the elastic wave velocities of hydrate-bearing sediments is important for geophysical exploration and resource evaluation. Methane gas migration processes play an important role in geological hydrate accumulation systems, whether on the seafloor or in terrestrial permafrost regions, and their impact on elastic wave velocities in sediments needs further study. Hence, a high-pressure laboratory apparatus was developed to simulate natural continuous vertical migration of methane gas through sediments. Hydrate saturation (S h) and ultrasonic P- and S-wave velocities (V p and V s) were measured synchronously by time domain reflectometry (TDR) and by ultrasonic transmission methods respectively during gas hydrate formation in sediments. The results were compared to previously published laboratory data obtained in a static closed system. This indicated that the velocities of hydrate-bearing sediments in vertical gas migration systems are slightly lower than those in closed systems during hydrate formation. While velocities increase at a constant rate with hydrate saturation in the closed system, P-wave velocities show a fast-slow-fast variation with increasing hydrate saturation in the vertical gas migration system. The observed velocities are well described by an effective-medium velocity model, from which changing hydrate morphology was inferred to cause the fast-slow-fast velocity response in the gas migration system. Hydrate forms firstly at the grain contacts as cement, then grows within the pore space (floating), then finally grows into contact with the pore walls again. We conclude that hydrate morphology is the key factor that influences the elastic wave velocity response of methane gas hydrate formation in vertical gas migration systems.

  13. Longitudinal and shear wave velocities in pure tungsten and tungsten fiber-reinforced tungsten composites

    Science.gov (United States)

    Lee, H. T.; Ando, S.; Coenen, J. W.; Mao, Y.; Riesch, J.; Gietl, H.; Kasada, R.; Hamaji, Y.; Ibano, K.; Ueda, Y.

    2017-12-01

    Longitudinal and shear wave velocities in pure tungsten and tungsten fiber-reinforced tungsten (Wf/W) composites were studied by laser ultrasonic measurements. The samples were produced from powders or powder/fiber mixtures by spark plasma sintering process. It was found that sintering temperature, as a processing parameter, has the largest effect. Higher sintering temperatures result in faster wave velocities. For example, longitudinal wave velocities and their standard deviations in sintered W at 1800 °C and 2000 °C were 4834 ± 53 m s-1 and 5043 ± 47 m s-1. In comparison, the average longitudinal wave velocity for a polycrystalline reference W was 5227 ± 5 m s-1. The values for Wf/W composites fall between the two sintered samples. However, the thicker Yttria (Y2O3) fiber/matrix interface resulted in faster wave velocities. The elastic moduli were calculated from the sound velocities using average density measurements. The standard relations for isotropic, homogeneous material were used. It was found that the shear, bulk, Young’s modulus are 80%-90% of the values for polycrystalline tungsten, while the temperature dependency from 25 °C to 450 °C is similar.

  14. Resolution potential of surface wave phase velocity measurements at small arrays

    Science.gov (United States)

    Bodin, Thomas; Maupin, Valérie

    2008-02-01

    The deployment of temporary arrays of broadband seismological stations over dedicated targets is common practice. Measurement of surface wave phase velocity across a small array and its depth-inversion gives us information about the structure below the array which is complementary to the information obtained from body-wave analysis. The question is however: what do we actually measure when the array is much smaller than the wave length, and how does the measured phase velocity relates to the real structure below the array? We quantify this relationship by performing a series of numerical simulations of surface wave propagation in 3-D structures and by measuring the apparent phase velocity across the array on the synthetics. A principal conclusion is that heterogeneities located outside the array can map in a complex way onto the phase velocities measured by the array. In order to minimize this effect, it is necessary to have a large number of events and to average measurements from events well-distributed in backazimuth. A second observation is that the period of the wave has a remarkably small influence on the lateral resolution of the measurement, which is dominantly controlled by the size of the array. We analyse if the artefacts created by heterogeneities can be mistaken for azimuthal variations caused by anisotropy. We also show that if the amplitude of the surface waves can be measured precisely enough, phase velocities can be corrected and the artefacts which occur due to reflections and diffractions in 3-D structures greatly reduced.

  15. Lagrangian temperature and vertical velocity fluctuations due to gravity waves in the lower stratosphere

    Science.gov (United States)

    Podglajen, Aurélien; Hertzog, Albert; Plougonven, Riwal; Legras, Bernard

    2016-04-01

    Wave-induced Lagrangian fluctuations of temperature and vertical velocity in the lower stratosphere are quantified using measurements from superpressure balloons (SPBs). Observations recorded every minute along SPB flights allow the whole gravity wave spectrum to be described and provide unprecedented information on both the intrinsic frequency spectrum and the probability distribution function of wave fluctuations. The data set has been collected during two campaigns coordinated by the French Space Agency in 2010, involving 19 balloons over Antarctica and 3 in the deep tropics. In both regions, the vertical velocity distributions depart significantly from a Gaussian behavior. Knowledge on such wave fluctuations is essential for modeling microphysical processes along Lagrangian trajectories. We propose a new simple parameterization that reproduces both the non-Gaussian distribution of vertical velocities (or heating/cooling rates) and their observed intrinsic frequency spectrum.

  16. Elastic wave velocity of granite during triaxial compression under controlled pore pressure

    Science.gov (United States)

    Zaima, K.; Katayama, I.

    2016-12-01

    Elastic wave velocity is one of important physical properties to investigate structure in the Earth's interior. Because of a markedly change in elastic wave velocity at the presence of fluid, the geothermal fluid reservoir is frequently detected through seismic tomography. Previous laboratory experiments have carried to investigate effect of confining pressure (e.g. Nur and Simmons, 1969), axial stress during deformation (e.g. Lockner et al, 1977), fluid saturation (e.g. Nur and Simmons, 1969). However, there are few studies examining elastic wave velocity change on fracture process under controlled pore pressure. In this study, we examined change of elastic wave velocity and amplitude during triaxial compression under pore pressure as a fundamental research on estimating of artificial geothermal reservoir on hot dry rock system. We used Aji granite with a cylindrical shape. On dry condition, confining pressure was 20 MPa, and on wet condition, we used water as a pore fluid and confining pressure was 20 MPa and pore pressure was 10 MPa. We adopted pulse transmission method for measurements of elastic wave velocity and amplitude. We observed a systematic change of elastic wave velocity possibly due to closure, growth and formation of cracks during deformation. While elastic wave velocity was increased due to closure of preexisting cracks at the primary stage of deformation, it decreased markedly at the late stage of deformation. Vp/Vs tends to increase during deformation on wet condition while it decreases on dry condition. These data are consistent with theoretical model by O'Connell and Budiansky (1974), in which fluid filled cracks increase Vp/Vs but open (dry) cracks have an opposite influence. Based on the theoretical model, crack density tends to be suppressed during deformation under wet experiments. During deformation, amplitude was decreased with increasing cracks in the specimens, in which P wave has relatively small amplitude compared to wet condition

  17. Anisotropy of S wave velocity in the lowermost mantle using broad-band data recorded at Syowa in Antarctica

    Science.gov (United States)

    Usui, Y.; Hiramatsu, Y.; Furumoto, M.; Kanao, M.

    2003-12-01

    We investigate the velocity structure of the lowermost mantle (D") beneath the Antarctic Ocean. We analyze seismograms from 16 deep earthquakes in south Pacific subduction zones from 1990 to 2001 recorded by STS-1 broad-band seismographs at Syowa station in Antarctica. The source-receiver combinations span distances range 85\\deg-95\\deg with associated S waves passing through D" beneath the Antarctic ocean. Differential travel times of split S waves are estimated to be up to 2s, showing that longitudinal components (SV) energy arrives earlier than transverse components (SH) energy. The absence of significant splitting for S waves with turning points more than four hundred kilometers above the core-mantle boundary (CMB) indicates that anisotropy is localized within the D" region. Differential travel times among S, ScS and SKS phases and waveform modeling are used to construct the velocity structure in D". We calculate synthetic waveforms by the Direct Solution Method (DSM: Geller and Ohminato, 1994; Geller and Takeuchi, 1995). SH shows a double arrival at the epicentral distance near 89\\deg. However SV in this range remains a single arrival. Isotropic model_@can not explain these observation. We find that synthetics for transverse isotropic models with SH velocity discontinuity (SYYM model) explain well the observed differential travel times and waveforms. The thickness of the anisotropic zone, where SH wave is faster up to 2.0% than SV wave, estimated to be about 350 km. This study region corresponds to the high velocity region at the lowermost mantle by tomographic studies (Kuo et al., 2000; Masters et al., 2000). This kind of transverse anisotropy correlates with high velocity regions where paleo-slabs may descend into the lower mantle (Kendall and Silver, 1996; Garnero and Lay, 1997). We conclude that these observations may be explained by an anisotropic D" layer and D" layer anisotropy is attributed to the paleo-slab material subducted during 120Myr-180Myr.

  18. P Wave and S Wave Acoustic Velocities of Partial Molten Peridotite at Mantle P-T and MHz Frequencies

    Science.gov (United States)

    Weidner, D. J.; Li, L.; Whitaker, M. L.; Triplett, R.

    2016-12-01

    The speed that acoustic waves travel in a partially molten peridotite are crucial parameters to detect not only the presence of melt in the Earth's deep interior, but also understand many issues about the structure and dynamics of the mantle. Technical challenges have hindered such measurements in the laboratory. Here we report the experimental results on the ultrasonic acoustic wave velocities in a partial molten peridotite using multi-anvil high pressure apparatus located at beamline BM6 Advance Photon Source. We use the newly installed ultrasonic equipment using the pulse-echo-overlap method coupled with D-DIA device. X-ray radiography is used to measure sample length at high P-T. The X-ray diffraction spectrum is used to determine the pressure and sample conditions. Precise measurements of P and S wave velocities are obtained at 60 and 35 MHz respectively and are nearly simultaneous. We use a double reflector method to enable measurement of elastic wave velocities of cold-pressed polycrystalline sample which is sintered in situ at high P-T. Experiments were carried out up to 3 GPa and 1500 oC. Our preliminary results indicate that the KLB1 peridotite sample experienced a few percent decrease of both p and s wave velocities as partial melting occurs. The data define a small decrease in the bulk modulus as well as the shear modulus upon melting. This implies that dynamic melting is a significant process at megahertz frequencies.

  19. Velocity autocorrelation function in supercooled liquids: Long-time tails and anomalous shear-wave propagation.

    Science.gov (United States)

    Peng, H L; Schober, H R; Voigtmann, Th

    2016-12-01

    Molecular dynamic simulations are performed to reveal the long-time behavior of the velocity autocorrelation function (VAF) by utilizing the finite-size effect in a Lennard-Jones binary mixture. Whereas in normal liquids the classical positive t^{-3/2} long-time tail is observed, we find in supercooled liquids a negative tail. It is strongly influenced by the transfer of the transverse current wave across the period boundary. The t^{-5/2} decay of the negative long-time tail is confirmed in the spectrum of VAF. Modeling the long-time transverse current within a generalized Maxwell model, we reproduce the negative long-time tail of the VAF, but with a slower algebraic t^{-2} decay.

  20. Wave-Related Reynolds Number Parameterizations of CO2 and DMS Transfer Velocities

    Science.gov (United States)

    Brumer, Sophia E.; Zappa, Christopher J.; Blomquist, Byron W.; Fairall, Christopher W.; Cifuentes-Lorenzen, Alejandro; Edson, James B.; Brooks, Ian M.; Huebert, Barry J.

    2017-10-01

    Predicting future climate hinges on our understanding of and ability to quantify air-sea gas transfer. The latter relies on parameterizations of the gas transfer velocity k, which represents physical mass transfer mechanisms and is usually parameterized as a nonlinear function of wind forcing. In an attempt to reduce uncertainties in k, this study explores empirical parameterizations that incorporate both wind speed and sea state dependence via wave-wind and breaking Reynolds numbers, RH and RB. Analysis of concurrent eddy covariance gas transfer and measured wavefield statistics supplemented by wave model hindcasts shows for the first time that wave-related Reynolds numbers collapse four open ocean data sets that have a wind speed dependence of CO2 transfer velocity ranging from lower than quadratic to cubic. Wave-related Reynolds number and wind speed show comparable performance for parametrizing dimethyl sulfide (DMS) which, because of its higher solubility, is less affected by bubble-mediated exchange associated with wave breaking.

  1. Low-velocity fault-zone guided waves: Numerical investigations of trapping efficiency

    Science.gov (United States)

    Li, Y.-G.; Vidale, J.E.

    1996-01-01

    Recent observations have shown that shear waves trapped within low-velocity fault zones may be the most sensitive measure of fault-zone structure (Li et al., 1994a, 1994b). Finite-difference simulations demonstrate the effects of several types of complexity on observations of fault-zone trapped waves. Overlying sediments with a thickness more than one or two fault-zone widths and fault-zone step-overs more than one or two fault widths disrupt the wave guide. Fault kinks and changes in fault-zone width with depth leave readily observable trapped waves. We also demonstrate the effects of decreased trapped wave excitation with increasing hypocentral offset from the fault and the effects of varying the contrast between the velocity in the fault zone and surrounding hard rock. Careful field studies may provide dramatic improvements in our knowledge of fault-zone structure.

  2. PIV measurements of velocities and accelerations under breaking waves on a slope

    Science.gov (United States)

    Vested, Malene; Carstensen, Stefan; Damgaard Christensen, Erik

    2017-04-01

    Understanding the physics of breaking waves is an ongoing research topic, not only due to human curiosity, but also due to the influence breaking waves have on offshore structures. In recent years, the development in experimental methods has facilitated a new insight into the physics of breaking waves. In this study, we have investigated the wave kinematics under steep and breaking waves on a laboratory beach with a slope of 1/25. The velocity field was measured by use of Particle Image Velocimetry (PIV) at a sample rate of 96Hz. The high sample rate allowed for the accelerations to be determined directly from the sampled velocities. It was found that both velocities and accelerations differ from the ones predicted from common wave theories such as streamfunction theory. This was especially evident at the top part of the wave close to the surface. This was not surprising, since the breaking event is a highly non-linear process. The results presented here may facilitate computations of the impact force on offshore structures and furthermore be used for validation of CFD models while altogether shedding light on the mechanisms behind breaking waves.

  3. 3-D Seismic Velocity Structure of the Hawaii Hotspot from Joint Inversion of Body Wave and Surface Wave data

    Science.gov (United States)

    Cheng, C.; Allen, R. M.; Porritt, R. W.

    2012-12-01

    The Hawaii hotspot and the associated chain of islands have been long regarded as the case example of a deep-rooted mantle plume. However the efforts to detect a thermal plume seismically have been inconclusive. In this study we combine the complementary sensitivities of body- and surface-waves in order to improve resolution of mantle structure beneath Hawaii. Adding surface-wave constraints to the body wave inversion improves the resolution of the crustal and upper mantle structure. We used data from the deployment of temporary broadband ocean-bottom seismometers (OBS) of the Hawaiian Plume-Lithosphere Undersea Melt Experiment (PLUME) together with data from the on-shore stations in order to make the most complete dataset available. In a first step, we obtained stable and reliable OBS orientations over a range of earthquake back-azimuths using teleseismic P-wave particle motions. Due to the high noise of the OBS data in some frequency bands, we began by filtering in the period band of 0.04-1Hz. Using the proper channel orientations, we measured ~800 S-wave relative arrival times (direct S and SKS phases) on the SV component using muti-channel cross correlation. We applied the two-plane wave tomography method to generate surface wave phase velocity information. We use surface waves from 71 events with magnitude greater than 5.8 to generate phase velocity maps from 25 sec to 100 sec. These maps clearly show the low velocities beneath the islands surrounded by relatively high phase velocity. The pure S wave inversion result shows the 3-D structure beneath the PLUME array to a depth of 1000km and reveals a several-hundred-kilometer-wide region of low velocities beneath Hawaii that dips to the southeast. The low velocities continue downward through the mantle transition zone and extend into the uppermost lower-mantle where our resolution begins to degrade. These images are consistent with the interpretation that the Hawaiian hotspot is the result of an upwelling high

  4. Effect of gas on shear wave velocity of sandy soils densified with explosives

    Directory of Open Access Journals (Sweden)

    Carlos Alberto Vega-Posada

    2017-01-01

    Full Text Available Context: Shear wave velocity tests (Vs are commonly used to estimate the increase in resistance of explosive densified soils. In some historical cases, Vs tests performed after the soil improvement process do not show a significant increase in soil resistance, even though the soil surface sits more than 0.50 m. It is believed that this response is due to the presence of gas on the soil mass. Method: This paper presents the results of monotonic triaxial tests performed on samples of dense gaseous sandy soils to evaluate the effect of occluded gas on the response to the shear wave velocity in densified sands with explosives. For sand sampling, it was collected from a loose sand deposit located in South Carolina, USA. These samples were densified in-situ with explosives, and consolidated to the in-situ effective stress conditions, which are considered representative in the conditions of effort at the moment of the densification with explosives. Results: Triaxial tests were performed under global non-drained conditions. The results of these tests show that gas causes the shear wave velocity values obtained for the gaseous sands to approximate the shear wave velocity values obtained in the saturated samples tested under drained conditions. In addition, behavior tends to be more pronounced as the soil is denser. Conclusions: These response may offer some insights as to why the shear wave velocity does not increase significantly in densified soils with explosives, even though the density increases considerably.

  5. In-situ changes in the elastic wave velocity of rock with increasing temperature using high-resolution coda wave interferometry

    Science.gov (United States)

    Griffiths, Luke; Heap, Michael; Lengliné, Olivier; Schmittbuhl, Jean; Baud, Patrick

    2017-04-01

    Rock undergoes fluctuations in temperature in various settings in Earth's crust, including areas of volcanic or geothermal activity, or industrial environments such as hydrocarbon or geothermal reservoirs. Changes in temperature can cause thermal stresses that can result in the formation of microcracks, which affect the mechanical, physical, and transport properties of rocks. Of the affected physical properties, the elastic wave velocity of rock is particularly sensitive to microcracking. Monitoring the evolution of elastic wave velocity during the thermal stressing of rock therefore provides valuable insight into thermal cracking processes. One monitoring technique is Coda Wave Interferometry (CWI), which infers high-resolution changes in the medium from changes in multiple-scattered elastic waves. We have designed a new experimental setup to perform CWI whilst cyclically heating and cooling samples of granite (cylinders of 20 mm diameter and 40 mm length). In our setup, the samples are held between two pistons within a tube furnace and are heated and cooled at a rate of 1 °C/min to temperatures of up to 300 °C. Two high temperature piezo-transducers are each in contact with an opposing face of the rock sample. The servo-controlled uniaxial press compensates for the thermal expansion and contraction of the pistons and the sample, keeping the coupling between the transducers and the sample, and the axial force acting on the sample, constant throughout. Our setup is designed for simultaneous acoustic emission monitoring (AE is commonly used as a proxy for microcracking), and so we can follow thermal microcracking precisely by combining the AE and CWI techniques. We find that during the first heating/cooling cycle, the onset of thermal microcracking occurs at a relatively low temperature of around 65 °C. The CWI shows that elastic wave velocity decreases with increasing temperature and increases during cooling. Upon cooling, back to room temperature, there is an

  6. Approximation of wave action flux velocity in strongly sheared mean flows

    Science.gov (United States)

    Banihashemi, Saeideh; Kirby, James T.; Dong, Zhifei

    2017-08-01

    Spectral wave models based on the wave action equation typically use a theoretical framework based on depth uniform current to account for current effects on waves. In the real world, however, currents often have variations over depth. Several recent studies have made use of a depth-weighted current U˜ due to [Skop, R. A., 1987. Approximate dispersion relation for wave-current interactions. J. Waterway, Port, Coastal, and Ocean Eng. 113, 187-195.] or [Kirby, J. T., Chen, T., 1989. Surface waves on vertically sheared flows: approximate dispersion relations. J. Geophys. Res. 94, 1013-1027.] in order to account for the effect of vertical current shear. Use of the depth-weighted velocity, which is a function of wavenumber (or frequency and direction) has been further simplified in recent applications by only utilizing a weighted current based on the spectral peak wavenumber. These applications do not typically take into account the dependence of U˜ on wave number k, as well as erroneously identifying U˜ as the proper choice for current velocity in the wave action equation. Here, we derive a corrected expression for the current component of the group velocity. We demonstrate its consistency using analytic results for a current with constant vorticity, and numerical results for a measured, strongly-sheared current profile obtained in the Columbia River. The effect of choosing a single value for current velocity based on the peak wave frequency is examined, and we suggest an alternate strategy, involving a Taylor series expansion about the peak frequency, which should significantly extend the range of accuracy of current estimates available to the wave model with minimal additional programming and data transfer.

  7. Shear Wave Velocity Structure of Southern African Crust: Evidence for Compositional Heterogeneity within Archaean and Proterozoic Terrains

    Energy Technology Data Exchange (ETDEWEB)

    Kgaswane, E M; Nyblade, A A; Julia, J; Dirks, P H H M; Durrheim, R J; Pasyanos, M E

    2008-11-11

    Crustal structure in southern Africa has been investigated by jointly inverting receiver functions and Rayleigh wave group velocities for 89 broadband seismic stations spanning much of the Precambrian shield of southern Africa. 1-D shear wave velocity profiles obtained from the inversion yield Moho depths that are similar to those reported in previous studies and show considerable variability in the shear wave velocity structure of the lower part of the crust between some terrains. For many of the Archaean and Proterozoic terrains in the shield, S velocities reach 4.0 km/s or higher over a substantial part of the lower crust. However, for most of the Kimberley terrain and adjacent parts of the Kheis Province and Witwatersrand terrain, as well as for the western part of the Tokwe terrain, mean shear wave velocities of {le} 3.9 km/s characterize the lower part of the crust along with slightly ({approx}5 km) thinner crust. These findings indicate that the lower crust across much of the shield has a predominantly mafic composition, except for the southwest portion of the Kaapvaal Craton and western portion of the Zimbabwe Craton, where the lower crust is intermediate-to-felsic in composition. The parts of the Kaapvaal Craton underlain by intermediate-to-felsic lower crust coincide with regions where Ventersdorp rocks have been preserved, and thus we suggest that the intermediate-to-felsic composition of the lower crust and the shallower Moho may have resulted from crustal melting during the Ventersdorp tectonomagmatic event at c. 2.7 Ga and concomitant crustal thinning caused by rifting.

  8. 3D velocity distribution of P- and S-waves in a biotite gneiss, measured in oil as the pressure medium: Comparison with velocity measurements in a multi-anvil pressure apparatus and with texture-based calculated data

    Science.gov (United States)

    Lokajíček, T.; Kern, H.; Svitek, T.; Ivankina, T.

    2014-06-01

    Ultrasonic measurements of the 3D velocity distribution of P- and S-waves were performed on a spherical sample of a biotite gneiss from the Outokumpu scientific drill hole. Measurements were done at room temperature and pressures up to 400 and 70 MPa, respectively, in a pressure vessel with oil as a pressure medium. A modified transducer/sample assembly and the installation of a new mechanical system allowed simultaneous measurements of P- and S-wave velocities in 132 independent directions of the sphere on a net in steps of 15°. Proper signals for P- and S-waves could be recorded by coating the sample surface with a high-viscosity shear wave gel and by temporal point contacting of the transmitter and receiver transducers with the sample surface during the measurements. The 3D seismic measurements revealed a strong foliation-related directional dependence (anisotropy) of P- and S-wave velocities, which is confirmed by measurements in a multi-anvil apparatus on a cube-shaped specimen of the same rock. Both experimental approaches show a marked pressure sensitivity of P- and S-wave velocities and velocity anisotropies. With increasing pressure, P- and S-wave velocities increase non-linearly due to progressive closure of micro-cracks. The reverse is true for velocity anisotropy. 3D velocity calculations based on neutron diffraction measurements of crystallographic preferred orientation (CPO) of major minerals show that the intrinsic bulk anisotropy is basically caused by the CPO of biotite constituting about 23 vol.% of the rock. Including the shape of biotite grains and oriented low-aspect ratio microcracks into the modelling increases bulk anisotropy. An important finding from this study is that the measurements on the sample sphere and on the sample cube displayed distinct differences, particularly in shear wave velocities. It is assumed that the differences are due to the different geometries of the samples and the configuration of the transducer-sample assembly

  9. Relationships between the anisotropy of longitudinal wave velocity and hydroxyapatite crystallite orientation in bovine cortical bone.

    Science.gov (United States)

    Yamamoto, Kazufumi; Nakatsuji, Tomohiro; Yaoi, Yuichiro; Yamato, Yu; Yanagitani, Takahiko; Matsukawa, Mami; Yamazaki, Kaoru; Matsuyama, Yukihiro

    2012-03-01

    Quantitative ultrasound (QUS) is now widely used for evaluating bone in vivo, because obtained ultrasonic wave properties directly reflect the visco-elasticity. Bone tissue is composed of minerals like hydroxyapatite (HAp) and a collagen matrix. HAp crystallites orientation is thus one parameter of bone elasticity. In this study, we experimentally investigated the anisotropy of ultrasonic wave velocity and the HAp crystallites orientation in the axial-radial and axial-tangential planes in detail, using cylindrical specimens obtained from the cortical bone of three bovine femurs. Longitudinal bulk wave propagation was investigated by using a conventional ultrasonic pulse system. We used the one cycle of sinusoidal pulse which was emitted from wide band transmitter. The nominal frequency of the pulse was 1MHz. First, we investigated the anisotropy of longitudinal wave velocity, measuring the anisotropy of velocity in two planes using cylindrical specimens obtained from identical bone areas. The wave velocity changed due to the rotation angle, showing the maximum value in the direction a little off the bone axis. Moreover, X-ray pole figure measurements also indicated that there were small tilts in the HAp crystallites orientation from the bone axis. The tilt angles were similar to those of the highest velocity direction. There were good correlations between velocity and HAp crystallites orientation obtained in different directions. However, a comparatively low correlation was found in posterior bone areas, which shows the stronger effects of bone microstructure. In the radial-tangential plane, where the HAp crystallites hardly ever align, weak anisotropy of velocity was found which seemed to depend on the bone microstructure. Copyright © 2011 Elsevier B.V. All rights reserved.

  10. Shear Wave Velocity for Evaluation of State of Cohesionless Soils with Fines

    Science.gov (United States)

    Lipiński, Mirosław J.; Wdowska, Małgorzata K.; Jaroń, Łukasz

    2017-10-01

    The paper concerns evaluation of cohesionless soils containing fines. In clean sands, state of soil is usually quantified by relative density DR with use of field techniques like static or dynamic probes. However, in cohesionless soils containing considerable amount of fines, relative density alone, which is based solely on void ratio values, is not representative. This results from the fact that in case of cohesionless soil there is no unique intrinsic compressibility line, like it is in case of cohesive soils. Thus state of soil depends not only on void ratio but also state of stress. For this reason it is necessary to look for an alternative means to quantify state of soils with fines. The paper concerns possibility of evaluation of state of soil containing various amount of fines on the basis of shear wave velocity measurement. The idea rests on the fact that void ratio and state of stress are the major factors which contribute to a state of soil and shear wave velocity as well. When measured shear wave velocities are normalised with respect to stresses the resulting values might be strictly correlated to void ratio. To validate this approach, an experimental test programme (based on series of sophisticated triaxial tests) was carried out on four kinds of sandy material containing various amount of fines up to 60%. The experimental data made possible to establish basic correlation between soil states and shear wave velocity for each kind of soil. Normalized shear wave velocity was compared with void ratio and state parameter as well. The obtained results revealed that determination of void ratio on the basis of shear wave velocity in a certain range of fines can be much more adequate than for clean sands. However, if the fines content exceeds certain value, the obtained correlation is no longer as good.

  11. APPLICATION OF A HEURISTIC METHOD FOR THE ESTIMATION OF S-WAVE VELOCITY STRUCTURE

    Directory of Open Access Journals (Sweden)

    Alfaro Castillo Andrés José

    2006-08-01

    Full Text Available The assessment of local site effects is one of the most important subjects in Engineering Seismology. In order to perform an assessment, it is necessary to determine the S-wave velocity structure of the site. Additionally, in some basins, it is very important to know the deep sedimentary structure, due to the amplification phenomena of low frequency waves. There are several techniques to achieve this purpose; probably the most inexpensive technique is using the vertical component of microtremors measured with an array of seismographs. The phase velocity of Rayleigh waves is inverted to an S-wave velocity (Vs profile  using optimization techniques. Most of the time, least square methods have been applied in the inversion.Recently, heuristic methods have also been used for the estimation of the S-wave velocity structure from microtremor.In this study seven arrays of microtremors in the city of Tsukuba city were performed, located to the NE edge of Kanto Basin, in order to estimate the deep S-wave velocity structure. The spatial autocorrelationmethod SPAC was used to determine phase velocity dispersion curves in the frequency range from 0.3-2.5 Hz. The determination of Vs profiles reached a depth of 750 m. Two methods were used to estimate the Swavevelocity structure: Inversion method and a heuristic method via the combination of Downhill Simplex Algorithm with a Very Fast Simulated Annealing Method. Comparisons with Vs from the existent resultsfrom PS-logging tests at the center of the array showed the reliability of the heuristic method.

  12. Site response, shallow shear-wave velocity, and wave propagation at the San Jose, California, dense seismic array

    Science.gov (United States)

    Hartzell, S.; Carver, D.; Williams, R.A.; Harmsen, S.; Zerva, A.

    2003-01-01

    Ground-motion records from a 52-element dense seismic array near San Jose, California, are analyzed to obtain site response, shallow shear-wave velocity, and plane-wave propagation characteristics. The array, located on the eastern side of the Santa Clara Valley south of the San Francisco Bay, is sited over the Evergreen basin, a 7-km-deep depression with Miocene and younger deposits. Site response values below 4 Hz are up to a factor of 2 greater when larger, regional records are included in the analysis, due to strong surface-wave development within the Santa Clara Valley. The pattern of site amplification is the same, however, with local or regional events. Site amplification increases away from the eastern edge of the Santa Clara Valley, reaching a maximum over the western edge of the Evergreen basin, where the pre-Cenozoic basement shallows rapidly. Amplification then decreases further to the west. This pattern may be caused by lower shallow shear-wave velocities and thicker Quaternary deposits further from the edge of the Santa Clara Valley and generation/trapping of surface waves above the shallowing basement of the western Evergreen basin. Shear-wave velocities from the inversion of site response spectra based on smaller, local earthquakes compare well with those obtained independently from our seismic reflection/refraction measurements. Velocities from the inversion of site spectra that include larger, regional records do not compare well with these measurements. A mix of local and regional events, however, is appropriate for determination of site response to be used in seismic hazard evaluation, since large damaging events would excite both body and surface waves with a wide range in ray parameters. Frequency-wavenumber, plane-wave analysis is used to determine the backazimuth and apparent velocity of coherent phases at the array. Conventional, high-resolution, and multiple signal characterization f-k power spectra and stacked slowness power spectra are

  13. Measurement of elastic modulus and ultrasonic wave velocity by piezoelectric resonator

    Science.gov (United States)

    Erhart, Jiří

    2015-01-01

    A piezoelectric ceramic resonator is used for the ‘electrical’ measurement of elastic properties, i.e. Young’s modulus and ultrasonic wave velocity in metallic materials. Piezoelectric response is precisely calculated for the piezoelectric ceramic ring fixed at the end of a metallic rod. The piezoelectric ring serves as both an actuator as well as a sensor. The experimental setup and method of measurement using higher overtones is explained in detail and practically demonstrated for a set of different metallic materials. Young’s moduli and ultrasonic wave velocities are measured within 3% relative error. The presented method is suitable for an advanced engineering class or physics laboratory training.

  14. Comparison of pulsed wave and color Doppler myocardial velocity imaging in healthy dogs.

    Science.gov (United States)

    Wess, G; Killich, M; Hartmann, K

    2010-01-01

    Tissue velocity imaging (TVI) is increasingly used in small animal cardiology. Tissue velocity of the myocardial wall can be measured by pulsed wave (PW) or color Doppler (CD) imaging methods. Currently, the same reference ranges are used for PW TVI and CD TVI methods. However, if and how both methods correlate, and whether they can be used interchangeably, have not been assessed in small animals. To compare the results of PW TVI and CD TVI measurements. Seventy-one healthy dogs. Longitudinal myocardial velocity profiles were recorded from the 4-chamber left apical view. Peak maximal systolic (S), early (E), and late diastolic (A) velocities were measured off-line in a blinded fashion in the septal and lateral left ventricular wall by PW TVI and CD TVI. Differences between peak PW TVI and CD TVI waves were analyzed by a paired t-test. Regression analysis and Bland-Altman difference plots also were used to assess agreement between methods. There was a significant correlation between PW TVI and CD TVI (P waves measured by PW TVI were significantly higher than the CD TVI values (P < .001). Peak systolic and diastolic PW velocities were approximately 2.20 cm/s higher than corresponding mean CD TVI velocities. PW TVI measurements are significantly higher compared with CD TVI measurements. Theses differences are clinically relevant. These methods should not be used interchangeably, and different reference ranges for PW TVI and CD TVI should be used.

  15. Detailed three-dimensional shear wave velocity structure of the northwestern United States from Rayleigh wave tomography

    Science.gov (United States)

    Wagner, Lara; Forsyth, Donald W.; Fouch, Matthew J.; James, David E.

    2010-11-01

    Since the mid-Miocene, the northwestern United States has experienced extensive flood basalt volcanism, followed by the formation of two time-progressive tracks of silicic volcanism: the Yellowstone/Snake River Plains (YSRP) and the High Lava Plains (HLP). The YSRP track progresses towards the northeast, parallel to North American plate motion, and has therefore often been attributed to a deep mantle plume source. However, the HLP track progresses to the northwest over the same time frame in a direction not consistent with any regional plate motion. The causes of the mid-Miocene flood basalts and the tracks of the YSRP and HLP are a matter of ongoing debate. We present results of Rayleigh wave phase velocity inversions and inversions for 3-D shear wave velocity structure of the northwestern United States using data collected from the High Lava Plains seismic experiment and the EarthScope USArray Transportable Array (TA). The large number of stations used in these inversions allows us to show an unprecedented level of detail in the seismic velocity structures of this tectonically complex area. Our velocity images indicate that low S-wave velocities in the uppermost mantle do not well match the track of HLP volcanism. While at the surface the Newberry caldera appears to anchor the NW end of the HLP hotspot track, the seismic results show that it lies in a separate, north-south trending low velocity band just east of the Cascades that is distinct from the main HLP trace. The ultra-low S-wave velocities beneath the YSRP track extend locally to at least 175 km depth and are by far the most prominent seismic anomalies in the region. Along axis, the YSRP hotspot track is characterized by a discrete low velocity channel in the upper mantle that shallows, narrows and intensifies to the northeast, but then deepens rapidly to the north beneath Yellowstone. The shallowing of the low velocity anomaly to the northeast is consistent with a stationary heat source beneath a moving

  16. Using second-sound shock waves to probe the intrinsic critical velocity of liquid helium II

    Science.gov (United States)

    Turner, T. N.

    1983-01-01

    A critical velocity truly intrinsic to liquid helium II is experimentally sought in the bulk fluid far from the apparatus walls. Termed the 'fundamental critical velocity,' it necessarily is caused by mutual interactions which operate between the two fluid components and which are activated at large relative velocities. It is argued that flow induced by second-sound shock waves provides the ideal means by which to activate and isolate the fundamental critical velocity from other extraneous fluid-wall interactions. Experimentally it is found that large-amplitude second-sound shock waves initiate a breakdown in the superfluidity of helium II, which is dramatically manifested as a limit to the maximum attainable shock strength. This breakdown is shown to be caused by a fundamental critical velocity. Secondary effects include boiling for ambient pressures near the saturated vapor pressure or the formation of helium I boundary layers at higher ambient pressures. When compared to the intrinsic critical velocity discovered in highly restricted geometries, the shock-induced critical velocity displays a similar temperature dependence and is the same order of magnitude.

  17. Heart-Carotid Pulse Wave Velocity a Useful Index of Atherosclerosis in Chinese Hypertensive Patients

    OpenAIRE

    Li, Chunyue; Xiong, Huahua; Pirbhulal, Sandeep; Wu, Dan; Li, Zhenzhou; Huang, Wenhua; Zhang, Heye; Wu, Wanqing

    2015-01-01

    Abstract This study was designed to investigate the relationship between heart-carotid pulse wave velocity (hcPWV) and carotid intima-media thickness (CIMT) in hypertensive patients, and also to examine the effect of pre-ejection period (PEP) on it. Doppler ultrasound device was used to measure CIMT in left common carotid artery. Hypertensive patients were divided into normal (n?=?36, CIMT ?0.8?mm) and thickened (n?=?31, CIMT?>?0.8?mm) group. Electrocardiogram R-wave-based carotid pulse wave ...

  18. Circumferential-wave phase velocities for empty, fluid-immersed spherical metal shells

    DEFF Research Database (Denmark)

    Überall, Herbert; Ahyi, A. C.; Raju, P. K.

    2002-01-01

    In earlier studies of acoustic scattering resonances and of the dispersive phase velocities of surface waves that generate them [see, e.g., Talmant et al., J. Acoust. Soc. Am. 86, 278–289 (1989) for spherical aluminum shells] we have demonstrated the effectiveness and accuracy of obtaining phase......-loaded, evacuated spherical metal shells of aluminum, stainless steel, and tungsten carbide. In particular, the characteristic upturn of the dispersion curves of low-order shell-borne circumferential waves (A or A0 waves) which takes place on spherical shells when the frequency tends towards very low values...

  19. Angle-domain Migration Velocity Analysis using Wave-equation Reflection Traveltime Inversion

    KAUST Repository

    Zhang, Sanzong

    2012-11-04

    The main difficulty with an iterative waveform inversion is that it tends to get stuck in a local minima associated with the waveform misfit function. This is because the waveform misfit function is highly non-linear with respect to changes in the velocity model. To reduce this nonlinearity, we present a reflection traveltime tomography method based on the wave equation which enjoys a more quasi-linear relationship between the model and the data. A local crosscorrelation of the windowed downgoing direct wave and the upgoing reflection wave at the image point yields the lag time that maximizes the correlation. This lag time represents the reflection traveltime residual that is back-projected into the earth model to update the velocity in the same way as wave-equation transmission traveltime inversion. The residual movemout analysis in the angle-domain common image gathers provides a robust estimate of the depth residual which is converted to the reflection traveltime residual for the velocity inversion. We present numerical examples to demonstrate its efficiency in inverting seismic data for complex velocity model.

  20. S-wave velocity below Europe from delay-time and waveform inversions

    NARCIS (Netherlands)

    Zielhuis, A.

    1992-01-01

    The upper mantle of Europe has been the subject of many tomographic studies of variations in P-wave velocity (e.g., Romanowicz 1980; Hovland et al., 1981; Spakman, 1988, 1991; and Spakman et aI., in preparation). In particular the studies of Spakman (1988, 1991) and Spakman et aI. (in preparation)

  1. S-wave velocity below Europe from delay-time and waveform inversions

    NARCIS (Netherlands)

    Zielhuis, A.

    1992-01-01

    The upper mantle of Europe has been the subject of many tomographic studies of variations in P-wave velocity (e.g., Romanowicz 1980; Hovland et al., 1981; Spakman, 1988, 1991; and Spakman et aI., in preparation). In particular the studies of Spakman (1988, 1991) and Spakman et aI. (in

  2. P-wave velocity test for assessment of geotechnical properties of ...

    Indian Academy of Sciences (India)

    -wave velocity test, a non-destructive and easy method to apply in both field and laboratory conditions, has increasingly been conducted to determine the geotechnical properties of rock materials. The aim of this study is to predict the rock properties including the uniaxial compressive strength, Schmidt hardness, modulus ...

  3. P-wave velocity test for assessment of geotechnical properties of ...

    Indian Academy of Sciences (India)

    Administrator

    wave velocity changes with porosity and degree of saturation. ..... Hudson J A, Jones E T W and New B M 1980 Q. J. Eng. Geol. 13 33. International Society for Rock Mechanics 1981 ISRM Sug- gested Methods. 211. Kahraman S 2001 Int. J.

  4. Correlating P-wave Velocity with the Physico-Mechanical Properties of Different Rocks

    Science.gov (United States)

    Khandelwal, Manoj

    2013-04-01

    In mining and civil engineering projects, physico-mechanical properties of the rock affect both the project design and the construction operation. Determination of various physico-mechanical properties of rocks is expensive and time consuming, and sometimes it is very difficult to get cores to perform direct tests to evaluate the rock mass. The purpose of this work is to investigate the relationships between the different physico-mechanical properties of the various rock types with the P-wave velocity. Measurement of P-wave velocity is relatively cheap, non-destructive and easy to carry out. In this study, representative rock mass samples of igneous, sedimentary, and metamorphic rocks were collected from the different locations of India to obtain an empirical relation between P-wave velocity and uniaxial compressive strength, tensile strength, punch shear, density, slake durability index, Young's modulus, Poisson's ratio, impact strength index and Schmidt hammer rebound number. A very strong correlation was found between the P-wave velocity and different physico-mechanical properties of various rock types with very high coefficients of determination. To check the sensitivity of the empirical equations, Students t test was also performed, which confirmed the validity of the proposed correlations.

  5. An integrated shear-wave velocity model for the Groningen gas field, The Netherlands

    NARCIS (Netherlands)

    Kruiver, Pauline P.; van Dedem, Ewoud; Romijn, Remco; de Lange, Ger; Korff, M.; Stafleu, Jan; Gunnink, Jan L.; Rodriguez-Marek, Adrian; Bommer, Julian J.; van Elk, Jan; Doornhof, Dirk

    2017-01-01

    A regional shear-wave velocity (VS) model has been developed for the Groningen gas field in the Netherlands as the basis for seismic microzonation of an area of more than 1000 km2. The VS model, extending to a depth of almost 1 km, is an essential input to the

  6. Coda wave interferometry for the measurement of thermally induced ultrasonic velocity variations in CFRP laminates

    Science.gov (United States)

    Livings, Richard; Dayal, Vinay; Barnard, Dan

    2016-02-01

    Ultrasonic velocity measurement is a well-established method to measure properties and estimate strength as well as detect and locate damage. Determination of accurate and repeatable ultrasonic wave velocities can be difficult due to the influence of environmental and experimental factors. Diffuse fields created by a multiple scattering environment have been shown to be sensitive to homogeneous strain fields such as those caused by temperature variations, and Coda Wave Interferometry has been used to measure the thermally induced ultrasonic velocity variation in concrete, aluminum, and the Earth's crust. In this work, we analyzed the influence of several parameters of the experimental configuration on the measurement of thermally induced ultrasonic velocity variations in a carbon-fiber reinforced polymer plate. Coda Wave Interferometry was used to determine the relative velocity change between a baseline signal taken at room temperature and the signal taken at various temperatures. The influence of several parameters of the experimental configuration, such as the material type, the receiver aperture size, and fiber orientation on the results of the processing algorithm was evaluated in order to determine the optimal experimental configuration.---This work is supported by the NSF Industry/University Cooperative Research Program of the Center for Nondestructive Evaluation at Iowa State University.

  7. Developing regionalized models of lithospheric thickness and velocity structure across Eurasia and the Middle East from jointly inverting P-wave and S-wave receiver functions with Rayleigh wave group and phase velocities

    Energy Technology Data Exchange (ETDEWEB)

    Julia, J; Nyblade, A; Hansen, S; Rodgers, A; Matzel, E

    2009-07-06

    In this project, we are developing models of lithospheric structure for a wide variety of tectonic regions throughout Eurasia and the Middle East by regionalizing 1D velocity models obtained by jointly inverting P-wave and S-wave receiver functions with Rayleigh wave group and phase velocities. We expect the regionalized velocity models will improve our ability to predict travel-times for local and regional phases, such as Pg, Pn, Sn and Lg, as well as travel-times for body-waves at upper mantle triplication distances in both seismic and aseismic regions of Eurasia and the Middle East. We anticipate the models will help inform and strengthen ongoing and future efforts within the NNSA labs to develop 3D velocity models for Eurasia and the Middle East, and will assist in obtaining model-based predictions where no empirical data are available and for improving locations from sparse networks using kriging. The codes needed to conduct the joint inversion of P-wave receiver functions (PRFs), S-wave receiver functions (SRFs), and dispersion velocities have already been assembled as part of ongoing research on lithospheric structure in Africa. The methodology has been tested with synthetic 'data' and case studies have been investigated with data collected at an open broadband stations in South Africa. PRFs constrain the size and S-P travel-time of seismic discontinuities in the crust and uppermost mantle, SRFs constrain the size and P-S travel-time of the lithosphere-asthenosphere boundary, and dispersion velocities constrain average S-wave velocity within frequency-dependent depth-ranges. Preliminary results show that the combination yields integrated 1D velocity models local to the recording station, where the discontinuities constrained by the receiver functions are superimposed to a background velocity model constrained by the dispersion velocities. In our first year of this project we will (i) generate 1D velocity models for open broadband seismic stations

  8. Improved aortic pulse wave velocity assessment from multislice two-directional in-plane velocity-encoded magnetic resonance imaging.

    Science.gov (United States)

    Westenberg, Jos J M; de Roos, Albert; Grotenhuis, Heynric B; Steendijk, Paul; Hendriksen, Dennis; van den Boogaard, Pieter J; van der Geest, Rob J; Bax, Jeroen J; Jukema, J Wouter; Reiber, Johan H C

    2010-11-01

    To evaluate the accuracy and reproducibility of aortic pulse wave velocity (PWV) assessment by in-plane velocity-encoded magnetic resonance imaging (MRI). In 14 patients selected for cardiac catheterization on suspicion of coronary artery disease and 15 healthy volunteers, PWV was assessed with multislice two-directional in-plane velocity-encoded MRI (PWV(i.p.)) and compared with conventionally assessed PWV from multisite one-directional through-plane velocity-encoded MRI (PWV(t.p.)). In patients, PWV was also obtained from intraarterially acquired pressure-time curves (PWV(pressure)), which is considered the gold standard reference method. In volunteers, PWV(i.p.) and PWV(t.p.) were obtained in duplicate in the same examination to test reproducibility. In patients, PWV(i.p.) showed stronger correlation and similar variation with PWV(pressure) than PWV(t.p.) (Pearson correlation r = 0.75 vs. r = 0.58, and coefficient of variation [COV] = 10% vs. COV = 12%, respectively). In volunteers, repeated PWV(i.p.) assessment showed stronger correlation and less variation than repeated PWV(t.p.) (proximal aorta: r = 0.97 and COV = 10% vs. r = 0.69 and COV = 17%; distal aorta: r = 0.94 and COV = 12% vs. r = 0.90 and COV = 16%; total aorta: r = 0.97 and COV = 7% vs. r = 0.90 and COV = 13%). PWV(i.p.) is an improvement over conventional PWV(t.p.) by showing higher agreement as compared to the gold standard (PWV(pressure)) and higher reproducibility for repeated MRI assessment. © 2010 Wiley-Liss, Inc.

  9. Laser photoacoustic technique for ultrasonic surface acoustic wave velocity evaluation on porcelain

    Science.gov (United States)

    Qian, K.; Tu, S. J.; Gao, L.; Xu, J.; Li, S. D.; Yu, W. C.; Liao, H. H.

    2016-10-01

    A laser photoacoustic technique has been developed to evaluate the surface acoustic wave (SAW) velocity of porcelain. A Q-switched Nd:YAG laser at 1064 nm was focused by a cylindrical lens to initiate broadband SAW impulses, which were detected by an optical fiber interferometer with high spatial resolution. Multiple near-field surface acoustic waves were observed on the sample surface at various locations along the axis perpendicular to the laser line source as the detector moved away from the source in the same increments. The frequency spectrum and dispersion curves were obtained by operating on the recorded waveforms with cross-correlation and FFT. The SAW phase velocities of the porcelain of the same source are similar while they are different from those of different sources. The marked differences of Rayleigh phase velocities in our experiment suggest that this technique has the potential for porcelain identification.

  10. Second sound shock waves and critical velocities in liquid helium 2. Ph.D. Thesis

    Science.gov (United States)

    Turner, T. N.

    1979-01-01

    Large amplitude second-sound shock waves were generated and the experimental results compared to the theory of nonlinear second-sound. The structure and thickness of second-sound shock fronts are calculated and compared to experimental data. Theoretically it is shown that at T = 1.88 K, where the nonlinear wave steepening vanishes, the thickness of a very weak shock must diverge. In a region near this temperature, a finite-amplitude shock pulse evolves into an unusual double-shock configuration consisting of a front steepened, temperature raising shock followed by a temperature lowering shock. Double-shocks are experimentally verified. It is experimentally shown that very large second-sound shock waves initiate a breakdown in the superfluidity of helium 2, which is dramatically displayed as a limit to the maximum attainable shock strength. The value of the maximum shock-induced relative velocity represents a significant lower bound to the intrinsic critical velocity of helium 2.

  11. Associations between plasma fibulin-1, pulse wave velocity and diabetes in patients with coronary heart disease

    DEFF Research Database (Denmark)

    Hansen, Maria Lyck; Rasmussen, Lars Melholt

    2015-01-01

    BACKGROUND: Diabetes is related to increased risk of cardiovascular disease, and arterial stiffness and its consequences may be the factor connecting the two. Arterial stiffness is often measured by carotid-femoral pulse wave velocity (cf-PWV), but no plasma biomarker reflecting arterial stiffness...... undergoing coronary artery bypass grafting. METHODS: Pulse wave velocity (PWV) and pulse wave analysis including augmentation index (Aix75) was measured in 273 patients, who subsequently underwent a coronary by-pass operation. Plasma samples were drawn and information was gathered on diabetes status, HbA1c...... indices are not directly related in patients with cardiac disease, despite the fact that both measures are increased among patients with diabetes....

  12. Condition Assessment of PC Tendon Duct Filling by Elastic Wave Velocity Mapping

    Directory of Open Access Journals (Sweden)

    Kit Fook Liu

    2014-01-01

    Full Text Available Imaging techniques are high in demand for modern nondestructive evaluation of large-scale concrete structures. The travel-time tomography (TTT technique, which is based on the principle of mapping the change of propagation velocity of transient elastic waves in a measured object, has found increasing application for assessing in situ concrete structures. The primary aim of this technique is to detect defects that exist in a structure. The TTT technique can offer an effective means for assessing tendon duct filling of prestressed concrete (PC elements. This study is aimed at clarifying some of the issues pertaining to the reliability of the technique for this purpose, such as sensor arrangement, model, meshing, type of tendon sheath, thickness of sheath, and material type as well as the scale of inhomogeneity. The work involved 2D simulations of wave motions, signal processing to extract travel time of waves, and tomography reconstruction computation for velocity mapping of defect in tendon duct.

  13. Shear-wave velocity of slope sediments near Hudson Canyon from analysis of ambient noise

    Science.gov (United States)

    Miller, N. C.; Ten Brink, U. S.; Collins, J. A.; McGuire, J. J.; Flores, C. H.

    2014-12-01

    We present new ambient noise data that help constrain the shear strength of marine sediments on the continental slope north of Hudson Canyon on the U.S. Atlantic margin. Sediment shear strength is a key parameter in models of potentially tsunamigenic, submarine slope failures, but shear strength is difficult to measure in situ and is expected to evolve in time with changes in pore pressure. The ambient noise data were recorded by 11 short-period, ocean-bottom seismometers and hydrophones deployed in a ~1 by 1.5 km array for ~6 months on the continental slope. These high frequency (~0.1 - 50 Hz), narrow-aperture data are expected to record noise propagating as interface waves and/or resonating in the upper ~500 m of sediment. Propagation of interface waves is controlled by the shear-wave velocity of the sediment, which we measure by calculating lag-times in cross-correlations of waveforms recorded by pairs of receivers. These measurements of shear-wave velocity will be used to constrain shear strength. The data also appear to record wind-generated noise resonating in layered sediment. We expect this resonance to also be sensitive to shear-wave velocity, and spectral analysis and modeling of harmonics may provide a second constraint on sediment shear strength. Both the correlogram- and spectral-based measurements can be made using hour- to day-long segments of data, enabling us to constrain temporal evolution of shear-wave velocity and potential forcing mechanisms (e.g., tidal and storm loading and submarine groundwater discharge) through the ~6 month deployment.

  14. Rayleigh wave group velocity tomography of Gujarat region, Western India and its implications to mantle dynamics

    Science.gov (United States)

    Dixit, Mayank; Singh, A. P.; Mishra, O. P.

    2017-07-01

    In the present study, fundamental Rayleigh waves with varying period from 10 to 80 s are used to obtain group velocity maps in the northwest Deccan Volcanic Province of India. About 350 paths are obtained using 53 earthquakes (4.8 ≤ M ≥ 7.9) recorded by the SeisNetG (Seismic Network of Gujarat). Individual dispersion curves of group velocity of Rayleigh wave for each source-station path are estimated using multiple filter technique. These curves are used to determine lateral distribution of Rayleigh wave group velocity by tomographic inversion method. Our estimated Rayleigh group velocity at varying depths showed conspicuous corroboration with three tectonic blocks [Kachchh Rift Basin (KRB), Saurashtra Horst (SH), and Mainland Gujarat (MG)] in the region. The seismically active KRB with a thicker crust is characterized as a low velocity zone at a period varying from 10 to 30 s as indicative of mantle downwarping or sagging of the mantle beneath the KRB, while the SH and MG are found to be associated with higher group velocities, indicating the existence of the reduced crustal thickness. The trend of higher group velocity was found prevailed adjacent to the Narmada and Cambay rift basins that also correspond to the reduced crust, suggesting the processes of mantle upwarping or uplifting due to mantle upwelling. The low velocities at periods longer than 40 s beneath the KRB indicate thicker lithosphere. The known Moho depth correlates well with the observed velocities at a period of about 30 s in the Gujarat region. Our estimates of relatively lower group velocities at periods varying from 70 to 80 s may correspond to the asthenospheric flow beneath the region. It is interesting to image higher group velocity for the thinner crust beneath the Arabian Sea adjacent to the west coast of Gujarat at the period of 40 s that may correspond to the upwarped or upwelled mantle beneath the Arabian Sea. Our results have better resolution estimated by a radius of equivalent

  15. Stress wave velocity and dynamic modulus of elasticity of yellow-poplar ranging from 100 to 10 percent moisture content

    Science.gov (United States)

    Jody D. Gray; Shawn T. Grushecky; James P. Armstrong

    2008-01-01

    Moisture content has a significant impact on mechanical properties of wood. In recent years, stress wave velocity has been used as an in situ and non-destructive method for determining the stiffness of wooden elements. The objective of this study was to determine what effect moisture content has on stress wave velocity and dynamic modulus of elasticity. Results...

  16. Superresolution Imaging Using Resonant Multiples and Plane-wave Migration Velocity Analysis

    KAUST Repository

    Guo, Bowen

    2017-08-28

    Seismic imaging is a technique that uses seismic echoes to map and detect underground geological structures. The conventional seismic image has the resolution limit of λ/2, where λ is the wavelength associated with the seismic waves propagating in the subsurface. To exceed this resolution limit, this thesis develops a new imaging method using resonant multiples, which produces superresolution images with twice or even more the spatial resolution compared to the conventional primary reflection image. A resonant multiple is defined as a seismic reflection that revisits the same subsurface location along coincident reflection raypath. This reverberated raypath is the reason for superresolution imaging because it increases the differences in reflection times associated with subtle changes in the spatial location of the reflector. For the practical implementation of superresolution imaging, I develop a post-stack migration technique that first enhances the signal-to-noise ratios (SNRs) of resonant multiples by a moveout-correction stacking method, and then migrates the post-stacked resonant multiples with the associated Kirchhoff or wave-equation migration formula. I show with synthetic and field data examples that the first-order resonant multiple image has about twice the spatial resolution compared to the primary reflection image. Besides resolution, the correct estimate of the subsurface velocity is crucial for determining the correct depth of reflectors. Towards this goal, wave-equation migration velocity analysis (WEMVA) is an image-domain method which inverts for the velocity model that maximizes the similarity of common image gathers (CIGs). Conventional WEMVA based on subsurface-offset, angle domain or time-lag CIGs requires significant computational and memory resources because it computes higher dimensional migration images in the extended image domain. To mitigate this problem, I present a new WEMVA method using plane-wave CIGs. Plane-wave CIGs reduce the

  17. Age-related changes of regional pulse wave velocity in the descending aorta using Fourier velocity encoded M-mode.

    Science.gov (United States)

    Taviani, Valentina; Hickson, Stacey S; Hardy, Christopher J; McEniery, Carmel M; Patterson, Andrew J; Gillard, Jonathan H; Wilkinson, Ian B; Graves, Martin J

    2011-01-01

    Aortic pulse wave velocity (PWV) is an independent determinant of cardiovascular risk. Although aortic stiffening with age is well documented, the interaction between aging and regional aortic PWV is still a debated question. We measured global and regional PWV in the descending aorta of 56 healthy subjects aged 25-76 years using a one-dimensional, interleaved, Fourier velocity encoded pulse sequence with cylindrical excitation. Repeatability across two magnetic resonance examinations (n = 19) and accuracy against intravascular pressure measurements (n = 4) were assessed. The global PWV was found to increase nonlinearly with age. The thoracic aorta was found to stiffen the most with age (PWV [thoracic, 20-40 years] = 4.7 ± 1.1 m/s; PWV [thoracic, 60-80 years] = 7.9 ± 1.5 m/s), followed by the mid- (PWV [mid-abdominal, 20-40 years] = 4.9 ± 1.3 m/s; PWV [mid-abdominal, 60-80 years] = 7.4 ± 1.9 m/s) and distal abdominal aorta (PWV [distal abdominal, 20-40 years] = 4.8 ± 1.4 m/s; PWV [distal abdominal, 60-80 years] = 5.7 ± 1.4 m/s). Good agreement was found between repeated magnetic resonance measurements and between magnetic resonance PWVs and the gold-standard. Fourier velocity encoded M-mode allowed to measure global and regional PWV in the descending aorta. There was a preferential stiffening of the thoracic aorta with age, which may be due to progressive fragmentation of elastin fibers in this region. © 2010 Wiley-Liss, Inc.

  18. Seismic wave velocity of rocks in the Oman ophiolite: constraints for petrological structure of oceanic crust

    Science.gov (United States)

    Saito, S.; Ishikawa, M.; Shibata, S.; Akizuki, R.; Arima, M.; Tatsumi, Y.; Arai, S.

    2010-12-01

    Evaluation of rock velocities and comparison with velocity profiles defined by seismic refraction experiments are a crucial approach for understanding the petrological structure of the crust. In this study, we calculated the seismic wave velocities of various types of rocks from the Oman ophiolite in order to constrain a petrological structure of the oceanic crust. Christensen & Smewing (1981, JGR) have reported experimental elastic velocities of rocks from the Oman ophiolite under oceanic crust-mantle conditions (6-430 MPa). However, in their relatively low-pressure experiments, internal pore-spaces might affect the velocity and resulted in lower values than the intrinsic velocity of sample. In this study we calculated the velocities of samples based on their modal proportions and chemical compositions of mineral constituents. Our calculated velocities represent the ‘pore-space-free’ intrinsic velocities of the sample. We calculated seismic velocities of rocks from the Oman ophiolite including pillow lavas, dolerites, plagiogranites, gabbros and peridotites at high-pressure-temperature conditions with an Excel macro (Hacker & Avers 2004, G-cubed). The minerals used for calculations for pillow lavas, dolerites and plagiogranites were Qtz, Pl, Prh, Pmp, Chl, Ep, Act, Hbl, Cpx and Mag. Pl, Hbl, Cpx, Opx and Ol were used for the calculations for gabbros and peridotites. Assuming thermal gradient of 20° C/km and pressure gradient of 25 MPa/km, the velocities were calculated in the ranges from the atmospheric pressure (0° C) to 200 MPa (160° C). The calculation yielded P-wave velocities (Vp) of 6.5-6.7 km/s for the pillow lavas, 6.6-6.8 km/s for the dolerites, 6.1-6.3 km/s for the plagiogranites, 6.9-7.5 km/s for the gabbros and 8.1-8.2 km/s for the peridotites. On the other hand, experimental results reported by Christensen & Smewing (1981, JGR) were 4.5-5.9 km/s for the pillow lavas, 5.5-6.3 km/s for the dolerites, 6.1-6.3 km/s for the plagiogranites, 6

  19. Heart-Carotid Pulse Wave Velocity a Useful Index of Atherosclerosis in Chinese Hypertensive Patients.

    Science.gov (United States)

    Li, Chunyue; Xiong, Huahua; Pirbhulal, Sandeep; Wu, Dan; Li, Zhenzhou; Huang, Wenhua; Zhang, Heye; Wu, Wanqing

    2015-12-01

    This study was designed to investigate the relationship between heart-carotid pulse wave velocity (hcPWV) and carotid intima-media thickness (CIMT) in hypertensive patients, and also to examine the effect of pre-ejection period (PEP) on it. Doppler ultrasound device was used to measure CIMT in left common carotid artery. Hypertensive patients were divided into normal (n = 36, CIMT ≤0.8 mm) and thickened (n = 31, CIMT > 0.8 mm) group. Electrocardiogram R-wave-based carotid pulse wave velocity (rcPWV) and aortic valve-carotid pulse wave velocity (acPWV) were calculated as the ratio of the travel length to the pulse transit time with or without PEP, respectively. CIMT has significant relations with rcPWV (r = 0.611, P blood pressure, diastolic blood pressure, fasting blood glucose, total cholesterol, high-density lipoprotein cholesterol, antihypertensive medication, and plaque occurrence. However, similar results were not found in normal group. Since CIMT has been considered as an index of atherosclerosis, our results suggested that both rcPWV and acPWV could be useful indexes of atherosclerosis in thickened CIMT hypertensive patients. Additionally, if hcPWV is computed with heart-carotid pulse transit time, including PEP could improve the accuracy of atherosclerosis assessment in hypertensive patients.

  20. In vivo noninvasive method for measuring local wave velocity in femoral arteries of pig

    Science.gov (United States)

    Zhang, Xiaoming; Kinnick, Randall; Pislaru, Cristina; Fatemi, Mostafa; Greenleaf, James

    2005-09-01

    We have proposed generating a bending wave in the arterial wall using ultrasound radiation force and measuring the wave velocity along the arterial wall [Zhang et al., IEEE Trans. Ultrason. Ferroelectr. Freq. Control 52, 642-652 (2005)]. Here, we report the results of in vivo studies on pigs. The pig was anesthetized, and a micromanometer tip catheter was inserted into the femoral artery to measure luminal pressure. A water bath was created on the animal's groin to allow unimpeded access of the ultrasound beams to the femoral artery. The femoral artery was first located using a 13-MHz linear-array transducer. Then, a vibro-acoustography image was obtained to ensure precise positioning of the excitation force relative to the artery. The artery was excited by the force transducer and the resulting vibration of the arterial wall was measured by a sensing Doppler transceiver. Measured wave velocity was 3.1 m/s at 300 Hz. With this new method wave velocity over a distance of 5 mm, and therefore stiffness of arteries, can be measured locally and non-invasively. Measurement time is short in a few tens of milliseconds, which allows pressure dependence and pharmacological effect on the wall properties to be measured at different cardiac times.

  1. PICASSO: Shear velocities in the Western Mediterranean from Rayleigh Wave tomography

    Science.gov (United States)

    Palomeras, I.; Thurner, S.; Levander, A.

    2012-12-01

    The Western Mediterranean has been affected by complex subduction and slab rollback, simultaneously with compression due to African-European convergence. The deformed region occupies a wide area from the intra-continental Atlas mountain belt in Morocco to the southern Iberian Massif in Spain. Evolutionary models of the Western Mediterranean invoke extensive slab rollback and compression in the Cenozoic, as well as likely upper mantle delamination scenarios during formation of the Alboran domain, the Betics, Rif, and Atlas Mountains. PICASSO (Program to Investigate Convective Alboran Sea System Overturn) is a multidisciplinary, international investigation of the Alboran System and surrounding areas. In this study we have analyzed data from the 95 PICASSO broadband stations with data from the Spanish IberArray and Siberia Array in Spain and Morocco, the University of Muenster array in the Atlas Mountains and the permanent Spanish and Portuguese networks. We present Rayleigh wave tomography results made from 168 teleseimic events recorded by 237 stations from April 2009 to April 2011. We measured Rayleigh phase velocities using the two-plane-wave method to remove complications due to multi-pathing, and finite-frequency kernels to improve lateral resolution. Phase velocities were then inverted for shear velocity structure on a grid of 0.5 by 0.5 degree to form a well-resolved 3D shear velocity model to 230 km depth. Our results show low S-velocities (2.9 km/s) in the crust beneath the Gibraltar Strait. Low upper mantle S-velocities are mapped beneath the Middle and High Atlas at ~60 km depth suggesting an elevated asthenosphere beneath these young mountain belts, in agreement with receiver functions analysis (Thurner et al, this session). Beneath the Western Alboran Sea, upper-mantle velocities change laterally from high velocities (>4.5 km/s) in the east to lower velocities to the west (~4.3 km/s). The Rayleigh wave tomography is consistent with P-tomography that

  2. Planar time-resolved PIV for velocity and pressure retrieval in atmospheric boundary layer over surface waves.

    Science.gov (United States)

    Troitskaya, Yuliya; Kandaurov, Alexander; Sergeev, Daniil; Bopp, Maximilian; Caulliez, Guillemette

    2017-04-01

    Air-sea coupling in general is important for weather, climate, fluxes. Wind wave source is crucially important for surface waves' modeling. But the wind-wave growth rate is strongly uncertain. Using direct measurements of pressure by wave-following Elliott probe [1] showed, weak and indefinite dependence of wind-wave growth rate on the wave steepness, while Grare et.al. [2] discuss the limitations of direct measurements of pressure associated with the inability to measure the pressure close to the surface by contact methods. Recently non-invasive methods for determining the pressure on the basis of technology of time-resolved PIV are actively developed [3]. Retrieving air flow velocities by 2D PIV techniques was started from Reul et al [4]. The first attempt for retrieving wind pressure field of waves in the laboratory tank from the time-resolved PIV measurements was done in [5]. The experiments were performed at the Large Air-Sea Interaction Facility (LASIF) - MIO/Luminy (length 40 m, cross section of air channel 3.2 x 1.6 m). For 18 regimes with wind speed up to 14 m/s including presence of puddle waves, a combination of time resolved PIV technique and optical measurements of water surface form was applied to detailed investigation of the characteristics of the wind flow over the water surface. Ammonium chloride smoke was used for flow visualization illuminated by two 6 Wt blue diode lasers combined into a vertical laser plane. Particle movement was captured with high-speed camera using Scheimpflug technique (up to 20 kHz frame rate with 4-frame bursts, spatial resolution about 190 μm, field of view 314x12 mm). Velocity air flow field was retrieved by PIV images processing with adaptive cross-correlation method on the curvilinear grid following surface wave form. The resulting time resolved instantaneous velocity fields on regular grid allowed us to obtain momentum fluxes directly from measured air velocity fluctuations. The average wind velocity patterns were

  3. [Pulse wave velocity as an early marker of diastolic heart failure in patients with hypertension].

    Science.gov (United States)

    Moczulska, Beata; Kubiak, Monika; Bryczkowska, Anna; Malinowska, Ewa

    2017-04-21

    According to the WHO, hypertension is one of the major causes of death worldwide. It leads to a number of severe complications. Diastolic heart failure, that is heart failure with preserved ejection fraction (HFPEF), is especially common. New, but simple, indices for the early detection of patients who have not yet developed complications or are in their early developmental stages are still searched for. The aim of this study is to examine the correlation between pulse wave velocity (PWV) and markers of diastolic heart failure (DHF) assessed in echocardiography in patients with hypertension and no symptoms of heart failure. The study was comprised of 65 patients with treated hypertension. Patients with symptoms of heart failure, those with diabetes and smokers were excluded. Arterial stiffness was measured with the Mobil-O-Graph NG PWA. Pulse wave velocity (PWV) was estimated. The following markers of diastolic heart failure were assessed in the echocardiographic examination: E/A ratio - the ratio of the early (E) to late (A) ventricular filling velocities, DT - decceleration time, E/E' - the ratio of mitral peak velocity of early filling (E) to early diastolic mitral annular velocity E' in tissue Doppler echocardiography. PWV was statistically significantly higher in the DHF group. In the group of patients with heart failure, the average E/A ratio was significantly lower as compared to the group with no heart failure. Oscillometric measurement of pulse wave velocity is non-invasive, lasts a few minutes and does not require the presence of a specialist. It allows for an early detection of patients at risk of diastolic heart failure even within the conditions of primary health care.

  4. Measurements of electrical impedance and elastic wave velocity of reservoir rock under fluid-flow test

    Science.gov (United States)

    Sawayama, Kazuki; Kitamura, Keigo; Fujimitsu, Yasuhiro

    2017-04-01

    The estimation of water saturation under the ground is essential in geothermal fields, particularly for EGS (enhanced geothermal system). To estimate water saturation, recently, electromagnetic exploration using Magnetotelluric (MT) method has been applied in the geothermal fields. However, the relationship between electrical impedance obtained from this method and water saturation in the reservoir rock has not been well known. Our goal is to elucidate this basic relationship by fluid-flow experiments. As our first step to this goal, we developed the technique to measure and analyze the electrical impedance of the cracked rock in the geothermal reservoir. The fluid-flow test has been conducted as following procedures. At first, reservoir rock sample (pyroxene andesite, Makizono lava formation, Japan) was filled with nitrogen gas (Pp = 10 MPa) under 20 MPa of confining pressure. This nitrogen gas imitates the overheated steam in the geothermal fields. Then, brine (1wt.%-KCl, 1.75 S/m) which imitates the artificial recharge to the reservoir was injected to the samples. After flow rate of drainage fluid becomes stable, injection pressure was increased (11, 12, 14, 16, 18 MPa) and decreased (18, 16, 14, 12, 11 MPa) to vary the water saturation in the samples. During the test, water saturation, permeability, electrical impedance (10-2-105 Hz of frequency) and elastic wave velocity were measured. As a result of andesite, electrical impedance dramatically decreased from 105 to 103 Ω and P-wave velocity increased by 2% due to the brine injection. This remarkable change of the electrical impedance could be due to the replacement of pre-filled nitrogen gas to the brine. After the brine injection, electrical impedance decreased with injection pressure (small change of water saturation) by up to 40% while P-wave velocity was almost constant (less than 1%). This decrease of electrical impedance with injection pressure could be related to the flow to the narrow path (microcrack

  5. ABCA1-dependent serum cholesterol efflux capacity inversely correlates with pulse wave velocity in healthy subjects.

    Science.gov (United States)

    Favari, Elda; Ronda, Nicoletta; Adorni, Maria Pia; Zimetti, Francesca; Salvi, Paolo; Manfredini, Matteo; Bernini, Franco; Borghi, Claudio; Cicero, Arrigo F G

    2013-01-01

    The capacity of HDL to induce cell cholesterol efflux is considered one of its main antiatherogenic properties. Little is known about the impact of such HDL function on vascular physiology. We investigated the relationship between ABCA1-dependent serum cholesterol efflux capacity (CEC), an HDL functionality indicator, and pulse wave velocity (PWV), an indicator of arterial stiffness. Serum of 167 healthy subjects was used to conduct CEC measurement, and carotid-femoral PWV was measured with a high-fidelity tonometer. J774 macrophages, labeled with [(3)H]cholesterol and stimulated to express ABCA1, were exposed to sera; the difference between cholesterol efflux from stimulated and unstimulated cells provided specific ABCA1-mediated CEC. PWV is inversely correlated with ABCA1-dependent CEC (r = -0.183; P = 0.018). Moreover, controlling for age, sex, body mass index, mean arterial pressure, serum LDL, HDL-cholesterol, and fasting plasma glucose, PWV displays a significant negative regression on ABCA1-dependent CEC (β = -0.204; 95% confidence interval, -0.371 to -0.037). The finding that ABCA1-dependent CEC, but not serum HDL cholesterol level (r = -0.002; P = 0.985), is a significant predictor of PWV in healthy subjects points to the relevance of HDL function in vascular physiology and arterial stiffness prevention.

  6. Effects of Obesity and Hypertension on Pulse Wave Velocity in Children.

    Science.gov (United States)

    Kulsum-Mecci, Nazia; Goss, Charles; Kozel, Beth A; Garbutt, Jane M; Schechtman, Kenneth B; Dharnidharka, Vikas R

    2017-03-01

    Pulse wave velocity (PWV) is a biomarker of arterial stiffness. Findings from prior studies are conflicting regarding the impact of obesity on PWV in children. The authors measured carotid-femoral PWV in 159 children aged 4 to 18 years, of whom 95 were healthy, 25 were obese, 15 had hypertension (HTN), and 24 were both obese and hypertensive. Mean PWV increased with age but did not differ by race or sex. In adjusted analyses in children 10 years and older (n=102), PWV was significantly higher in children with hypertension (PWV±standard deviation, 4.9±0.7 m/s), obesity (5.0±0.9 m/s), and combined obesity-hypertension (5.2±0.6 m/s) vs healthy children (4.3±0.7 m/s) (each group, Pobesity and HTN both significantly and independently increased PWV, while African American children did not have a higher PWV than Caucasian children. ©2016 Wiley Periodicals, Inc.

  7. A Method for Determination of in Run-Up Front Velocities on Dikes in Oblique and Short-Crested Waves

    DEFF Research Database (Denmark)

    Andersen, Thomas Lykke; Nørgaard, Jørgen Harck; Burcharth, Hans F.

    2011-01-01

    This paper presents a physical model test study to improve description of run-up events on dikes in oblique long and short-crested waves in terms of flow depth, flow velocities and overtopping. The paper focus on the flow velocities and a new method is proposed for determining flow velocities...

  8. Characteristics of light reflected from a dense ionization wave with a tunable velocity

    OpenAIRE

    Zhidkov, A.; Esirkepov, T.; Fujii, T; Nemoto, K; Koga, J; Bulanov, S. V.

    2009-01-01

    An optically-dense ionization wave (IW) produced by two femtosecond laser pulses focused cylindrically and crossing each other is shown to be an efficient coherent x-ray converter. The resulting velocity of a quasi-plane IW in the vicinity of pulse intersection increases with the angle between the pulses from the group velocity of ionizing pulses to infinity allowing an easy tuning the wavelength of x-rays. The x-ray spectra of a converted, lower frequency coherent light change from the monoc...

  9. Characteristics of light reflected from a dense ionization wave with a tunable velocity.

    Science.gov (United States)

    Zhidkov, A; Esirkepov, T; Fujii, T; Nemoto, K; Koga, J; Bulanov, S V

    2009-11-20

    An optically dense ionization wave (IW) produced by two femtosecond (approximately 10/30 fs) laser pulses focused cylindrically and crossing each other may become an efficient coherent x-ray converter in accordance with the Semenova-Lampe theory. The resulting velocity of a quasiplane IW in the vicinity of pulse intersection changes with the angle between the pulses from the group velocity of ionizing pulses to infinity allowing a tuning of the wavelength of x rays and their bunching. The x-ray spectra after scattering of a lower frequency and long coherent light pulse change from the monochromatic to high order harmoniclike with the duration of the ionizing pulses.

  10. The velocity of the arterial pulse wave: a viscous-fluid shock wave in an elastic tube.

    Science.gov (United States)

    Painter, Page R

    2008-07-29

    The arterial pulse is a viscous-fluid shock wave that is initiated by blood ejected from the heart. This wave travels away from the heart at a speed termed the pulse wave velocity (PWV). The PWV increases during the course of a number of diseases, and this increase is often attributed to arterial stiffness. As the pulse wave approaches a point in an artery, the pressure rises as does the pressure gradient. This pressure gradient increases the rate of blood flow ahead of the wave. The rate of blood flow ahead of the wave decreases with distance because the pressure gradient also decreases with distance ahead of the wave. Consequently, the amount of blood per unit length in a segment of an artery increases ahead of the wave, and this increase stretches the wall of the artery. As a result, the tension in the wall increases, and this results in an increase in the pressure of blood in the artery. An expression for the PWV is derived from an equation describing the flow-pressure coupling (FPC) for a pulse wave in an incompressible, viscous fluid in an elastic tube. The initial increase in force of the fluid in the tube is described by an increasing exponential function of time. The relationship between force gradient and fluid flow is approximated by an expression known to hold for a rigid tube. For large arteries, the PWV derived by this method agrees with the Korteweg-Moens equation for the PWV in a non-viscous fluid. For small arteries, the PWV is approximately proportional to the Korteweg-Moens velocity divided by the radius of the artery. The PWV in small arteries is also predicted to increase when the specific rate of increase in pressure as a function of time decreases. This rate decreases with increasing myocardial ischemia, suggesting an explanation for the observation that an increase in the PWV is a predictor of future myocardial infarction. The derivation of the equation for the PWV that has been used for more than fifty years is analyzed and shown to yield

  11. The velocity of the arterial pulse wave: a viscous-fluid shock wave in an elastic tube

    Directory of Open Access Journals (Sweden)

    Painter Page R

    2008-07-01

    Full Text Available Abstract Background The arterial pulse is a viscous-fluid shock wave that is initiated by blood ejected from the heart. This wave travels away from the heart at a speed termed the pulse wave velocity (PWV. The PWV increases during the course of a number of diseases, and this increase is often attributed to arterial stiffness. As the pulse wave approaches a point in an artery, the pressure rises as does the pressure gradient. This pressure gradient increases the rate of blood flow ahead of the wave. The rate of blood flow ahead of the wave decreases with distance because the pressure gradient also decreases with distance ahead of the wave. Consequently, the amount of blood per unit length in a segment of an artery increases ahead of the wave, and this increase stretches the wall of the artery. As a result, the tension in the wall increases, and this results in an increase in the pressure of blood in the artery. Methods An expression for the PWV is derived from an equation describing the flow-pressure coupling (FPC for a pulse wave in an incompressible, viscous fluid in an elastic tube. The initial increase in force of the fluid in the tube is described by an increasing exponential function of time. The relationship between force gradient and fluid flow is approximated by an expression known to hold for a rigid tube. Results For large arteries, the PWV derived by this method agrees with the Korteweg-Moens equation for the PWV in a non-viscous fluid. For small arteries, the PWV is approximately proportional to the Korteweg-Moens velocity divided by the radius of the artery. The PWV in small arteries is also predicted to increase when the specific rate of increase in pressure as a function of time decreases. This rate decreases with increasing myocardial ischemia, suggesting an explanation for the observation that an increase in the PWV is a predictor of future myocardial infarction. The derivation of the equation for the PWV that has been used for

  12. The effect of superluminal phase velocity on electron acceleration in a powerful electromagnetic wave

    Science.gov (United States)

    Robinson, A. P. L.; Arefiev, A. V.; Khudik, V. N.

    2015-08-01

    In this paper, we examine the effect that electromagnetic dispersion has on the motion of an electron in a relativistically strong plane wave. We obtain an analytic solution for the electron momentum and check this solution against direct numerical integration of the equations of motion. The solution shows that even a relatively small difference between the phase velocity of the wave, vp, and the speed of light, c, can significantly alter the electron dynamics if the normalized wave amplitude a0 exceeds √{2 c /(vp-c ) } . At this amplitude, the maximum longitudinal electron momentum scales only linearly with a0, as opposed to a02 . We also show that at this amplitude the impact of an accelerating longitudinal electric field and electron pre-acceleration is negated by the superluminous phase velocity of the wave. This has implications for the potential of Direct Laser Acceleration of electrons. We point out that electromagnetic dispersion can arise from both propagation in a plasma and from propagating the laser in what is effectively a wave-guiding structure, and that this latter source of dispersion is likely to be more significant.

  13. Velocity gradients in the Earth's upper mantle: insights from higher mode surface waves

    Science.gov (United States)

    Fishwick, Stewart; Maupin, Valerie; Afonso, Juan Carlos

    2016-04-01

    The majority of seismic tomographic models of the uppermost mantle beneath Precambrian regions show a positive velocity gradient from the Moho to depths of around 100 km. It is becoming increasingly well recognised that this gradient is not readily compatible with simple models of a craton with constant composition and a steady-state geotherm and more complex compositional variations are invoked to explain this feature. At these depths most of the models are dominated by data from fundamental mode surface waves, and the combination of the sensitivity kernels alongside the choice of model parameterisation means that the velocity gradient could be an artefact of the particular inversion. Indeed, recent work using thermodynamically consistent velocity models suggests that in some cases there is not a requirement of this style of gradient. We investigate this aspect of the mantle structure further by returning to the Sa phase. This phase can be considered as the build up of a wave packet due to the overlapping group velocities of higher modes at periods of around 8 - 30 s. Using the Australian shield as a test-case we compare waveforms built from three different styles of velocity model. Firstly, the 1D model AU3 (Gaherty & Jordan, 1995) which did incorporate the Sa phase as part of the waveform in their modelling. Secondly, recent tomographic models of the Australian continent are used, which include no a priori information from the phase. Thirdly, a thermodynamically consistent velocity model that fits the broad dispersion characteristics of the tomography is tested. Finally, these synthetic waveforms are compared to real data crossing the Australian shield. The results illustrate small, but clear, variations in waveform dependent on the velocity structure. Complicating factors in any analysis involve the importance of having good knowledge of the crustal structure and a very accurate source depth (particularly if this is similar to the average crustal thickness).

  14. High Frame Rate Vector Velocity Estimation using Plane Waves and Transverse Oscillation

    DEFF Research Database (Denmark)

    Jensen, Jonas; Stuart, Matthias Bo; Jensen, Jørgen Arendt

    2015-01-01

    is obtained by filtering the beamformed RF images in the Fourier domain using a Gaussian filter centered at a desired oscillation frequency. Performance of the method is quantified through measurements with the experimental scanner SARUS and the BK 2L8 linear array transducer. Constant parabolic flow......This paper presents a method for estimating 2-D vector velocities using plane waves and transverse oscillation. The approach uses emission of a low number of steered plane waves, which result in a high frame rate and continuous acquisition of data for the whole image. A transverse oscillating field...

  15. Flute mode waves near the lower hybrid frequency excited by ion rings in velocity space

    Science.gov (United States)

    Cattell, C.; Hudson, M.

    1982-01-01

    Discrete emissions at the lower hybrid frequency are often seen on the S3-3 satellite. Simultaneous observation of perpendicularly heated ions suggests that these ions may provide the free energy necessary to drive the instability. Studies of the dispersion relation for flute modes excited by warm ion rings in velocity space show that waves are excited with real frequencies near the lower hybrid frequency and with growth rates ranging from about 0.01 to 1 times the ion cyclotron frequency. Numerical results are therefore consistent with the possibility that the observed ions are the free energy source for the observed waves.

  16. Near-surface fault detection by migrating back-scattered surface waves with and without velocity profiles

    KAUST Repository

    Yu, Han

    2016-04-26

    We demonstrate that diffraction stack migration can be used to discover the distribution of near-surface faults. The methodology is based on the assumption that near-surface faults generate detectable back-scattered surface waves from impinging surface waves. We first isolate the back-scattered surface waves by muting or FK filtering, and then migrate them by diffraction migration using the surface wave velocity as the migration velocity. Instead of summing events along trial quasi-hyperbolas, surface wave migration sums events along trial quasi-linear trajectories that correspond to the moveout of back-scattered surface waves. We have also proposed a natural migration method that utilizes the intrinsic traveltime property of the direct and the back-scattered waves at faults. For the synthetic data sets and the land data collected in Aqaba, where surface wave velocity has unexpected perturbations, we migrate the back-scattered surface waves with both predicted velocity profiles and natural Green\\'s function without velocity information. Because the latter approach avoids the need for an accurate velocity model in event summation, both the prestack and stacked migration images show competitive quality. Results with both synthetic data and field records validate the feasibility of this method. We believe applying this method to global or passive seismic data can open new opportunities in unveiling tectonic features.

  17. Pulse wave velocity 24-hour monitoring with one-site measurements by oscillometry

    Directory of Open Access Journals (Sweden)

    Posokhov IN

    2013-02-01

    Full Text Available Igor N PosokhovHemodynamic Laboratory Ltd, Nizhniy Novgorod, RussiaAbstract: This review describes issues for the estimation of pulse wave velocity (PWV under ambulatory conditions using oscillometric systems. The difference between the principles of measuring the PWV by the standard method and by oscillometry is shown, and information on device validation studies is summarized. It was concluded that currently oscillometry is a method that is very convenient to use in the 24-hour monitoring of the PWV, is relatively accurate, and is reasonably comfortable for the patient. Several indices with the same principles as those in the analysis of blood pressure in ambulatory monitoring of blood pressure, namely the assessment of load, variability, and circadian rhythm, are proposed.Keywords: pulse wave velocity, 24-hour monitoring, oscillometry

  18. Estimated Pulse Wave Velocity Calculated from Age and Mean Arterial Blood Pressure

    DEFF Research Database (Denmark)

    Greve, S. V.; Laurent, Stéphane; Olsen, M. H.

    2016-01-01

    In a recently published paper, Greve et al [J Hypertens 2016;34:1279-1289] investigate whether the estimated carotid-femoral pulse wave velocity (ePWV), calculated using an equation derived from the relationship between carotid-femoral pulse wave velocity (cfPWV), age, and blood pressure, predicts...... cardiovascular disease (CVD) as good as the measured cfPWV. Because ePWV predicts CVD as good as cfPWV, some might wonder whether ePWV could be replaced by cfPWV, which is a time-consuming measurement requiring an expensive apparatus. This question is addressed in this mini-review. (C) 2016 S. Karger AG, Basel...

  19. [Penultimate pulse wave velocity, better than baseline pulse wave velocity, predicted mortality in Italian ESRD cohort study - a case for daily hemodialysis for ESRD patients with accelerated pulse wave velocity changes].

    Science.gov (United States)

    Onuigbo, Macaulay; Onuigbo, Nnonyelum; Bellasi, Antonio; Russo, Domenico; Di Iorio, Biagio Raffaele

    2013-01-01

    Cardiac disease remains the major cause of death among ESRD patients. Indeed, the risk of cardiovascular events in ESRD is reported to be at least 3.4 fold higher than that of the general population. Moreover, annual mortality rates among ESRD patients on hemodialysis approximate 20%, with cardiovascular disease accounting for almost half of this mortality profile. Despite this knowledge, so far we have been unable to identify treatable pathogenetic factors among ESRD patients to help reverse these poor cardiovascular outcomes. The difficulty to prognosticate cardiovascular mortality in ESRD remains elusive. However, in 2011, our group, for the first time, had demonstrated that cyclic variations of arterial stiffness as measured by pulse wave velocity (PWV) before and after hemodialysis determined mortality differences within an ESRD cohort. We have therefore examined the impact of individual patient-level translational PWV changes over time on mortality outcomes in an Italian ESRD cohort. Prospective observational study, 2007-2010, in an Italian ESRD cohort who underwent in-center outpatient conventional thrice weekly hemodialysis. PWV was measured by the foot-to-foot method and repeated after six months. Coronary artery calcification (CAC) was measured at 0, 12 and 24 months. Routine clinical data and patient demographics were recorded and mortality outcomes were analyzed. Between 2007 and 2010, 466 Italian ESRD patients, 229 males and 237 females, age 19-97 (65.6) years, were followed up for 28.9 months. 128 patients (74M:54F) died. The major causes of death were acute myocardial infarction (AMI) in 47 (37%) patients (age 70, 26M:21F) and sudden death (SD) in 29 (23%) patients (age 72, 19M:10F). Paired PWV data was available in 308 surviving patients and in 106 patients who died. Baseline PWV was lower in surviving vs dead patients 8.46 +/- 1.8 vs 9.43 +/- 3.75 (p=0.0005). Repeat PWV values were unchanged in the 308 survivors (8.46 +/- 1.8 vs 8.53 +/- 1.85, p=0

  20. A Numerical Method for Predicting Rayleigh Surface Wave Velocity in Anisotropic Crystals (Postprint)

    Science.gov (United States)

    2017-09-05

    crystal elastic moduli from literature . It was found to be very robust and efficient in calculating RSW velocity curves in all cases. 15. SUBJECT...crystal sample. The algorithm was tested with crystal symmetries and single crystal elastic moduli from literature . It was found to be very robust and...using them in the context of materials characterization. Another important concept in the analysis of surface waves is the surface impedance matrix

  1. Effects of Mechanical Pumping on the Arterial Pulse Wave Velocity: Peripheral Artery and Micro-Vessels

    Science.gov (United States)

    2001-10-25

    EFFECTS OF MECHANICAL PUMPING ON THE ARTERIAL PULSE WAVE VELOCITY : PERIPHERAL ARTERY AND MICRO -VESSELS Shu-Mei Wu*†, Yio-Wha Shau**, Bor-Shyh...was contributed from the results of BA-RA, the PWV for the micro -vessels (BA-finger) on the contrary was increased. Keywords- Mechanical Pumping ...arterial conduit (brachial artery-radial artery; BA-RA) and the micro -vessels (RA-ring finger) to mechanical pumping was evaluated. II

  2. Influence of shear wave velocity reversals on one-dimensional site response of spatially varied profiles

    OpenAIRE

    Pehlivan, M; Hashash, YMA; Harmon, JA; Rathje, EM; Stewart, JP; Silva, SJ; Campbell, KW; Nikolaou, S

    2015-01-01

    Spatial variability and uncertainties that exist in natural deposits are often modeled in one-dimensional (1D) site response analysis through multiple spatially varied shear wave velocity (VS) profiles. These spatially varied VS profiles usually exhibit VS reversals that might not be observed in the natural deposits. This study investigates the consequences of allowing VS reversals in spatially varied VS on the 1D site response characteristics. Two sets of sixty (60) spatially varied VS profi...

  3. Deep water velocities and particle displacements induced by acoustic-gravity waves from submarine earthquakes

    Science.gov (United States)

    Oliveira, T. C. A.; Kadri, U.

    2016-02-01

    An uplift of the ocean bottom caused by a submarine earthquake can generate Acoustic-Gravity Waves (AGW), progressive compression-type waves that travel at near the speed of sound in water. The role of AGW for oceans hydrodynamics has recently became a topic of increasing scientific interest. Kadri [Deep ocean water transport by acoustic-gravity waves, J.Geo. Res. Oceans, 119, (2014)] showed theoretically that AGW can contribute to deep ocean currents and circulation. We analyze and simulate the fundamental AGW modes generated by a submarine earthquake. We consider the first five AGW modes and show that they may all induce comparable temporal variations in water particle velocities at different depths in regions far from the epicenter. Results of temporal variations of horizontal and vertical fluid parcel velocities induced by AGW confirm chaotic flow trajectories at different water depths. A realistic example based on the 2004 Indian Ocean earthquake shows that vertical water particle displacements of O(10-2 ) m can be generated at 1 Km depth in a 4 km water depth ocean. We show that the velocity field depends on the presence of the leading AGW modes. Each AGW mode becomes evanescent at a critical time, at which energy is transferred to the next higher modes. Consequently, the main pattern of the velocity field changes as the leading mode change. As an example, for a reference point located at 1000 Km from the epicenter, the first five AGW become evanescent after 1.6, 4.6, 7.7, 10.8 and 13.8 hours, respectively. Our analysis and simulations shed light on the spatio-temporal evolution of the deep water velocities and particle displacements induced by AGW that radiate during submarine earthquakes. Thus, this work is a contribution to understand the role of high moment magnitude submarine earthquakes in deep water mixing mechanism.

  4. Correlates of Osteoprotegerin and Association with Aortic Pulse Wave Velocity in Patients with Chronic Kidney Disease

    Science.gov (United States)

    Leonard, Mary B.; Townsend, Raymond R.; Appel, Lawrence; Wolf, Myles; Budoff, Matt J.; Chen, Jing; Lustigova, Eva; Gadegbeku, Crystal A.; Glenn, Melanie; Hanish, Asaf; Raj, Dominic; Rosas, Sylvia E.; Seliger, Stephen L.; Weir, Matthew R.; Parekh, Rulan S.

    2011-01-01

    Summary Background and objectives Osteoprotegerin (OPG), a cytokine that regulates bone resorption, has been implicated in the process of vascular calcification and stiffness. Design, setting, participants, & measurements Serum OPG was measured in 351 participants with chronic kidney disease (CKD) from one site of the Chronic Renal Insufficiency Cohort Study. Cortical bone mineral content (BMC) was measured by quantitative computed tomography in the tibia. Multivariable linear regression was used to test the association between serum OPG and traditional cardiovascular risk factors, measures of abnormal bone and mineral metabolism, and pulse wave velocity. Results Higher serum OPG levels were associated with older age, female gender, greater systolic BP, lower estimated GFR, and lower serum albumin. OPG was not associated with measures of abnormal bone or mineral metabolism including serum phosphorus, albumin-corrected serum calcium, intact parathyroid hormone, bone-specific alkaline phosphatase, or cortical BMC. Among 226 participants with concurrent aortic pulse wave velocity measurements, increasing tertiles of serum OPG were associated with higher aortic pulse wave velocity after adjustment for demographics, traditional vascular risk factors, and nontraditional risk factors such as estimated GFR, albuminuria, serum phosphate, corrected serum calcium, presence of secondary hyperparathyroidism, serum albumin, and C-reactive protein or after additional adjustment for cortical BMC in a subset (n = 161). Conclusions These data support a strong relationship between serum OPG and arterial stiffness independent of many potential confounders including traditional cardiovascular risk factors, abnormal bone and mineral metabolism, and inflammation. PMID:21940840

  5. Wave Structure and Velocity Profiles in Downwards Gas-Liquid Annular Flows

    Science.gov (United States)

    Zadrazil, Ivan; Hewitt, Geoff; Matar, Omar; Markides, Christos

    2012-11-01

    A downwards flow of gas in the core of a vertical pipe, and of liquid in the annulus between the pipe wall and the gas phase is referred to as a ``downwards annular flow'' (DAF). DAFs are conventionally described in terms of short-lived, small-amplitude ``ripples,'' and large-amplitude, high-speed ``disturbances.'' We use a combination of Laser Induced Fluorescence (LIF), Particle Image and Tracking Velocimetry (PIV, PTV) to study DAFs. We demonstrate through these techniques that the liquid films become progressively more complex with increasing liquid Reynolds number (ReL), while a similar increase of complexity is observed for increasing gas Reynolds number (ReG). Disturbance waves are observed for low and high ReL, and ripples for intermediate ReL. Additionally, a high degree of rolling breakdown of disturbance waves is observed in falling films at the highest ReL, which is a source of bubble entrainment into the film body. Our results will comprise: (i) statistical data on film thickness, and (ii) wave frequency, velocity, wavelength. In addition, a qualitative (e.g. re-circulation zones) and quantitative (e.g. mean/rms velocity profiles) velocity characterisation of the film flows will be presented.

  6. Blood pulse wave velocity and pressure sensing via fiber based and free space based optical sensors

    Science.gov (United States)

    Sirkis, Talia; Beiderman, Yevgeny; Agdarov, Sergey; Beiderman, Yafim; Zalevsky, Zeev

    2017-02-01

    Continuous noninvasive measurement of vital bio-signs, such as cardiopulmonary parameters, is an important tool in evaluation of the patient's physiological condition and health monitoring. On the demand of new enabling technologies, some works have been done in continuous monitoring of blood pressure and pulse wave velocity. In this paper, we introduce two techniques for non-contact sensing of vital bio signs. In the first approach the optical sensor is based on single mode in-fibers Mach-Zehnder interferometer (MZI) to detect heartbeat, respiration and pulse wave velocity (PWV). The introduced interferometer is based on a new implanted scheme. It replaces the conventional MZI realized by inserting of discontinuities in the fiber to break the total internal reflection and scatter/collect light. The proposed fiber sensor was successfully incorporated into shirt to produce smart clothing. The measurements obtained from the smart clothing could be obtained in comfortable manner and there is no need to have an initial calibration or a direct contact between the sensor and the skin of the tested individual. In the second concept we show a remote noncontact blood pulse wave velocity and pressure measurement based on tracking the temporal changes of reflected secondary speckle patterns produced in human skin when illuminated by a laser beams. In both concept experimental validation of the proposed schemes is shown and analyzed.

  7. The impact of intraocular pressure on elastic wave velocity estimates in the crystalline lens

    Science.gov (United States)

    Park, Suhyun; Yoon, Heechul; Larin, Kirill V.; Emelianov, Stanislav Y.; Aglyamov, Salavat R.

    2017-02-01

    Intraocular pressure (IOP) is believed to influence the mechanical properties of ocular tissues including cornea and sclera. The elastic properties of the crystalline lens have been mainly investigated with regard to presbyopia, the age-related loss of accommodation power of the eye. However, the relationship between the elastic properties of the lens and IOP remains to be established. The objective of this study is to measure the elastic wave velocity, which represents the mechanical properties of tissue, in the crystalline lens ex vivo in response to changes in IOP. The elastic wave velocities in the cornea and lens from seven enucleated bovine globe samples were estimated using ultrasound shear wave elasticity imaging. To generate and then image the elastic wave propagation, an ultrasound imaging system was used to transmit a 600 µs pushing pulse at 4.5 MHz center frequency and to acquire ultrasound tracking frames at 6 kHz frame rate. The pushing beams were separately applied to the cornea and lens. IOP in the eyeballs was varied from 5 to 50 mmHg. The results indicate that while the elastic wave velocity in the cornea increased from 0.96  ±  0.30 m s-1 to 6.27  ±  0.75 m s-1 as IOP was elevated from 5 to 50 mmHg, there were insignificant changes in the elastic wave velocity in the crystalline lens with the minimum and the maximum speeds of 1.44  ±  0.27 m s-1 and 2.03  ±  0.46 m s-1, respectively. This study shows that ultrasound shear wave elasticity imaging can be used to assess the biomechanical properties of the crystalline lens noninvasively. Also, it was observed that the dependency of the crystalline lens stiffness on the IOP was significantly lower in comparison with that of cornea.

  8. Rayleigh wave phase velocities and upper mantle structure in the Apennines

    Directory of Open Access Journals (Sweden)

    St. MUELLER

    1976-06-01

    Full Text Available The dispersion of the phase velocities of the surface Rayleigh
    waves on the path between the station pair Torino-L'Aquila in the
    Apennines has been observed with long period seismic stations for twin
    earthquakes.
    The inversion was provided by the "Hedgehog" program of non-linear
    inversion analysis.
    The interpretation supports the notion that in the Apennines low-velocity
    material in the mantle is found within a few km of the Moho and may
    lie immediately below the Moho; however the alternative model of a highvelocity
    lid and very low-velocity channel cannot be completely rejected.

  9. Increased pulse-wave velocity in patients with anxiety: implications for autonomic dysfunction.

    Science.gov (United States)

    Yeragani, Vikram Kumar; Tancer, Manuel; Seema, K P; Josyula, Krishnapriya; Desai, Nagaraj

    2006-07-01

    Decreased vagal function is associated with vascular dysfunction. In this study, we compared vascular indices and correlated heart rate and QT variability measures with vascular indices in patients with anxiety disorders and normal controls. We compared age- and sex-matched controls (n=23) and patients with anxiety (n=25) using the Vascular Profiler (VP-1000; Colin Medical Instruments, Japan), approved by the US Food and Drug Administration. Using this machine, we obtained ankle and brachial blood pressure (BP) in both arms (brachial), both legs (ankle), and carotid artery, and lead I electrocardiogram (ECG) and phonocardiogram. Using these signals, pulse-wave velocity (PWV), and arterial stiffness index % and preejection period can be calculated. We also obtained ECG sampled at 1000 Hz in lead II configuration in supine posture to obtain beat-to-beat interbeat interval (R-R) and QT interval variability for 256 s. Patients with anxiety had significantly higher carotid mean arterial pressure (MAP) %, brachial-ankle PWV (BAPWV), arterial stiffness index %, MAP, and diastolic BP of the extremities compared to controls. We found significant negative correlations (r values from .4 to .65; P<.05 to .007) between R-R interval high-frequency (0.15-0.5 Hz) power (which is an indicator of cardiac vagal function), and increased BAPWV and systolic BP of the extremities only in patients. We were unable to find such correlations in controls. We also found significant positive correlations between QT variability index (a probable indicator of cardiac sympathetic function) and MAP of the extremities and BAPWV only in the patient group. These findings suggest an important association between decreased vagal and increased sympathetic function, and decreased arterial compliance and possible atherosclerotic changes and increased BP in patients with anxiety.

  10. Seismic velocity site characterization of 10 Arizona strong-motion recording stations by spectral analysis of surface wave dispersion

    Science.gov (United States)

    Kayen, Robert E.; Carkin, Brad A.; Corbett, Skye C.

    2017-10-19

    Vertical one-dimensional shear wave velocity (VS) profiles are presented for strong-motion sites in Arizona for a suite of stations surrounding the Palo Verde Nuclear Generating Station. The purpose of the study is to determine the detailed site velocity profile, the average velocity in the upper 30 meters of the profile (VS30), the average velocity for the entire profile (VSZ), and the National Earthquake Hazards Reduction Program (NEHRP) site classification. The VS profiles are estimated using a non-invasive continuous-sine-wave method for gathering the dispersion characteristics of surface waves. Shear wave velocity profiles were inverted from the averaged dispersion curves using three independent methods for comparison, and the root-mean-square combined coefficient of variation (COV) of the dispersion and inversion calculations are estimated for each site.

  11. The lithospheric shear-wave velocity structure of Saudi Arabia: Young volcanism in an old shield

    KAUST Repository

    Tang, Zheng

    2016-05-11

    We investigate the lithospheric shear-wave velocity structure of Saudi Arabia by conducting H-κ stacking analysis and jointly inverting teleseismic P-receiver functions and fundamental-mode Rayleigh wave group velocities at 56 broadband stations deployed by the Saudi Geological Survey (SGS). The study region, the Arabian plate, is traditionally divided into the western Arabian shield and the eastern Arabian platform: The Arabian shield itself is a complicated mélange of crustal material, composed of several Proterozoic terrains separated by ophiolite-bearing suture zones and dotted by outcropping Cenozoic volcanic rocks (locally known as harrats). The Arabian platform is primarily covered by 8 to 10 km of Paleozoic, Mesozoic and Cenozoic sedimentary rocks. Our results reveal high Vp/Vs ratios in the region of Harrat Lunayyir, which are interpreted as solidified magma intrusions from old magmatic episodes in the shield. Our results also indicate slow velocities and large upper mantle lid temperatures below the southern and northern tips of the Arabian shield, when compared with the values obtained for the central shield. We argue that our inferred patterns of lid velocity and temperature are due to heating by thermal conduction from the Afar plume (and, possibly, the Jordan plume), and that volcanism in western Arabia may result from small-scale adiabatic ascent of magma diapirs.

  12. Shear-Wave Velocity Structure Around the Korean Peninsula Using the Rayleigh Wave Signature of the North Korea Underground Nuclear Explosion on May 25, 2009

    Science.gov (United States)

    Kim, G.; Shin, J.; Chi, H. C.; Sheen, D.; Park, J.; Cho, C.

    2011-12-01

    The crustal structure around the Korean Peninsula was investigated by analyzing the Rayleigh waves generated from the 2nd North Korea underground nuclear explosion on May 25, 2009. Group velocity dispersion curves were measured from vertical component waveforms of 20 broadband stations in the range of 194 to 1183 km from the test site. The measured dispersion curves were inverted to get shear-wave velocity models for depths from 0 to 50 km. The dispersion curves and the velocity models clearly show lateral variations in the crustal structure, which could be more clearly classified into the North Korea-Northeast China group, the Western Margin of the East Sea group, and the Japan Basin group. For each group, an averaged dispersion curve and an averaged velocity model were measured. The averaged shear-wave velocity model of the North Korea-Northeast China group shows that the mean shear-wave velocity of the Moho discontinuity, which is known to be located at approximately 35 km, is 4.37 km/s with a standard deviation of 0.15 km/s. The averaged shear-wave velocity model of the Japan Basin group shows a mean shear-wave velocity of 4.26 km/s with a standard deviation of 0.14 km/s in the layer between 16 and 22 km. The averaged shear-wave velocity model of the Western Margin of the East Sea group shows characteristics of a transition zone between the North Korea-Northeast China group, which represents continental crust, and the Japan Basin group, which represents oceanic crust. The mean shear-wave velocity in the layer between 16 and 22 km is 4.12 km/s with a standard deviation of 0.05 km/s.

  13. Validity and reproducibility of arterial pulse wave velocity measurement using new device with oscillometric technique: A pilot study

    Directory of Open Access Journals (Sweden)

    Patnaik Amar

    2005-08-01

    Full Text Available Abstract Background Availability of a range of techniques and devices allow measurement of many variables related to the stiffness of large or medium sized arteries. There is good evidence that, pulse wave velocity is a relatively simple measurement and is a good indicator of changes in arterial properties. The pulse wave velocity calculated from pulse wave recording by other methods like doppler or tonometry is tedious, time-consuming and above all their reproducibility depends on the operator skills. It requires intensive resource involvement. For epidemiological studies these methods are not suitable. The aim of our study was to clinically evaluate the validity and reproducibility of a new automatic device for measurement of pulse wave velocity that can be used in such studies. Methods In 44 subjects including normal healthy control and patients with coronary artery disease, heart brachial, heart ankle, brachial ankle and carotid femoral pulse wave velocities were recorded by using a new oscillometric device. Lead I and II electrocardiogram and pressure curves were simultaneously recorded. Two observers recorded the pulse wave velocity for validation and one observer recorded the velocity on two occasions for reproducibility. Results and Discussion Pulse wave velocity and arterial stiffness index were recorded in 24 control and 20 coronary artery disease patients. All the velocities were significantly high in coronary artery disease patients. There was highly significant correlation between the values noted by the two observers with low standard deviation. The Pearson's correlation coefficient for various velocities ranged from (r = 0.88–0.90 with (p Conclusion The new device "PeriScope" based on oscillometric technique has been found to be a simple, non-invasive and reproducible device for the assessment of pulse wave velocity and can be used to determine arterial stiffness in large population based studies.

  14. Surface Wave Multipathing and its Influence on Phase Velocities Measured by Small Networks

    Science.gov (United States)

    Maupin, V.

    2011-12-01

    Networks of temporary broadband seismological stations are commonly deployed over dedicated targets. Measurement of surface wave phase velocity across the network and its depth-inversion gives us information about the structure below the network which is complementary to the information obtained from body-wave analysis. For small networks, we face however the fundamental problem that the dimensions of the heterogeneities to image are not large compared to the wavelengths of the surface waves used to image them. In addition, multipathing is very common is teleseismic surface waves at moderate frequencies and the complexity of the incoming wavefield has to be taken into account during the tomographic process. We perform a series of numerical simulations of surface wave propagation in 3-D structures using complex incoming wavefields in order to analyse how the nature of the incoming wavefield plays together with the 3-D structure to determine phases and amplitudes at the different stations of a network. We analyse how different tomographic methods cope with the complex wavefield, the consequences on the resolution of the resulting tomographic models and we try to provide recommendations for data selection. The numerical simulations are done using a multiple-scattering mode coupling scheme. The amount of multipathing is taken from a recent study using teleseismic surface waves recorded on a temporary network in Southern Norway. The period range of 20 to 200s and the 450km x 600km dimension of the network is also taken form the same study.

  15. Effect of viscosity on the wave propagation: Experimental determination of compression and expansion pulse wave velocity in fluid-fill elastic tube.

    Science.gov (United States)

    Stojadinović, Bojana; Tenne, Tamar; Zikich, Dragoslav; Rajković, Nemanja; Milošević, Nebojša; Lazović, Biljana; Žikić, Dejan

    2015-11-26

    The velocity by which the disturbance travels through the medium is the wave velocity. Pulse wave velocity is one of the main parameters in hemodynamics. The study of wave propagation through the fluid-fill elastic tube is of great importance for the proper biophysical understanding of the nature of blood flow through of cardiovascular system. The effect of viscosity on the pulse wave velocity is generally ignored. In this paper we present the results of experimental measurements of pulse wave velocity (PWV) of compression and expansion waves in elastic tube. The solutions with different density and viscosity were used in the experiment. Biophysical model of the circulatory flow is designed to perform measurements. Experimental results show that the PWV of the expansion waves is higher than the compression waves during the same experimental conditions. It was found that the change in viscosity causes a change of PWV for both waves. We found a relationship between PWV, fluid density and viscosity. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. On-chip laser Doppler vibrometer for arterial pulse wave velocity measurement.

    Science.gov (United States)

    Li, Yanlu; Segers, Patrick; Dirckx, Joris; Baets, Roel

    2013-07-01

    Pulse wave velocity (PWV) is an important marker for cardiovascular risk. The Laser Doppler vibrometry has been suggested as a potential technique to measure the local carotid PWV by measuring the transit time of the pulse wave between two locations along the common carotid artery (CCA) from skin surface vibrations. However, the present LDV setups are still bulky and difficult to handle. We present in this paper a more compact LDV system integrated on a CMOS-compatible silicon-on-insulator substrate. In this system, a chip with two homodyne LDVs is utilized to simultaneously measure the pulse wave at two different locations along the CCA. Measurement results show that the dual-LDV chip can successfully conduct the PWV measurement.

  17. Joint analysis of shear wave velocity from SH-wave refraction and MASW techniques for SPT-N estimation

    Directory of Open Access Journals (Sweden)

    Sawasdee Yordkayhun

    2014-06-01

    Full Text Available Horizontally polarized shear wave (SH refraction and multichannel analysis of surface wave (MASW methods have been carried out in Hatyai City, southern Thailand, a pilot study for site classification, part of the National Earthquake Hazards Reduction Program (NEHRP. The objectives of this study are the comparison of the efficiencies of different shear wave velocity (Vs determination techniques and the use of Vs measurements of the prediction of standard penetration resistance (SPT-N. Good correlation between all Vs profiles and SPT-N values and local lithology are observed. However, there are systematic differences between SH-refraction based-Vs and MASW based-Vs, which might be explained by possible converted waves, limitations of the assumptions used, poor quality of the acquired data, and limitations of the inversion procedures of the methods applied. From the integrated use of Vs from both methods an empirical formula to describe the correlation between Vs and SPT-N values has been proposed and can be used to estimate geotechnical parameters in areas where no borehole or geophysical investigation exist.

  18. Rayleigh-wave Group Velocity Tomography in the Vicinity of the Hawaiian Hotspot

    Science.gov (United States)

    Strader, A. E.; Laske, G.; Orcutt, J. A.; Wolfe, C. J.; Collins, J. A.; Solomon, S. C.; Detrick, R. S.; Bercovici, D.; Hauri, E. H.

    2009-12-01

    We present maps of long-period Rayleigh wave group velocity maps for the area spanned by the Hawaiian PLUME (Plume-Lithosphere Undersea Mantle Experiment) project. Specifically, we used observations from the second deployment of ocean-bottom and land broadband instruments that operated from April 2006 through May 2007. The recording network consisted of13 land stations with ten temporary and three observatory instruments and 38 ocean bottom sites that were equipped with 4-component broad-band instruments. With an average station spacing of approximately 200 km, this network had an aperture of nearly 1300 km. For this study, we used an efficient interactive screen tool that employs a multiple filtering technique to measure the frequency-dependent group velocity. The spectra are pre-whitened to reduce biasing effects at frequencies with strong dispersion. We established that the technique provides reliable results for the two-station approach used here, at frequencies between 7 and 60 mHz. Our analysis includes records from 182 shallow earthquakes with focal depth h00.01×1020 Nm, and surface wave magnitudes MS≥5.6. Six smaller events also have signal levels suitable for analysis. For initial dispersion quality and consistency checks, we inspected local group velocity maps obtained from 555 path-averaged group velocity curves for paths that cross the PLUME network. Occam-smoothed matrix inversions are performed for maps with 1° in latitude and longitude. The data are highly consistent at frequencies above 10 mHz. At frequencies below 25 mHz, there is an anomaly downstream of the island of Hawaii that intensifies with decreasing frequency. This result suggests a deep-seated structural anomaly. Group velocities at frequencies above 40 mHz also map with high fidelity. However, in an initial inversion for three-dimensional mantle shear velocity structure we discarded such data, as they are highly sensitive to bathymetry (which is well known and can be corrected for

  19. Automatic Wave Equation Migration Velocity Analysis by Focusing Subsurface Virtual Sources

    KAUST Repository

    Sun, Bingbing

    2017-11-03

    Macro velocity model building is important for subsequent pre-stack depth migration and full waveform inversion. Wave equation migration velocity analysis (WEMVA) utilizes the band-limited waveform to invert for the velocity. Normally, inversion would be implemented by focusing the subsurface offset common image gathers (SOCIGs). We re-examine this concept with a different perspective: In subsurface offset domain, using extended Born modeling, the recorded data can be considered as invariant with respect to the perturbation of the position of the virtual sources and velocity at the same time. A linear system connecting the perturbation of the position of those virtual sources and velocity is derived and solved subsequently by Conjugate Gradient method. In theory, the perturbation of the position of the virtual sources is given by the Rytov approximation. Thus, compared to the Born approximation, it relaxes the dependency on amplitude and makes the proposed method more applicable for real data. We demonstrate the effectiveness of the approach by applying the proposed method on both isotropic and anisotropic VTI synthetic data. A real dataset example verifies the robustness of the proposed method.

  20. Rayleigh Wave Group Velocity Tomography of Siberia, China and the Vicinity

    Science.gov (United States)

    Wu, F. T.; Levshin, A. L.; Kozhevnikov, V. M.

    Rayleigh waves are used in a tomographic inversion to obtain group velocity maps of East Asia (40° E-160° E and 20° N-70° N). The period range studied is 30 to 70 seconds. Seismograms used for this study were recorded at CDSN stations, at a temporary broadband seismic array in Tibet, at several SRO stations, and Kirnos-equipped stations established in Asia by the former Soviet Union, in Siberia, in the Sakhalin and in Mongolia. Altogether more than 1200 paths were available in the tomographic inversion. The study area includes the Angara craton, the geologically ancient core of Asia, and the subsequently accreted units, the Altaids (a Paleozoic collision complex), the Sino-Korean platform (a chain of Archaen terranes separated by belts of active structures), the south China platform (a collage of Precambrian, Paleozoic and Mesozoic metamorphic and igneous terranes), as well as the Tibetan plateau (an active tectonic feature created in late Cenozoic through collision of the Indian subcontinent and the Asian continent). Many of these main units are recognizable in the tomographic images as distinctive units; Tibet appears as a prominent low velocity (about -15% from the average) structure, with western and central Tibet often appearing as the areas with the lowest velocities, the Central Asian fold-belt, and the Angara craton are consistently high group velocity areas. Some lesser tectonic features are also recognizable. For example, Lake Baikal is seen as a high velocity feature at periods greater than 40 seconds. However, the high group velocity feature does not stop near the southern end of Lake Baikal; it extends south-southwestward across Mongolia. The North China Plain, a part of the platform where extensional tectonics dominate, is an area of high velocities as a result of relatively thin crust. The south China block, the least tectonically active region of China, is generally an area of high velocity. For periods longer than 40 seconds, a NNE trending

  1. Vertical structure of internal wave induced velocity for mode I and II solitary waves in two- and three-layer fluid

    Science.gov (United States)

    Gigiyatullin, Ayrat; Kurkin, Andrey; Kurkina, Oxana; Rouvinskaya, Ekaterina; Rybin, Artem

    2017-04-01

    With the use of the Gardner equation, or its variable-coefficient forms, the velocity components of fluid particles in the vertical section induced by a passage of internal waves can be estimated in weakly nonlinear limit. The horizontal velocity gives the greatest contribution into the local current speed. This is a typical property of long waves. This feature of an internal wave field may greatly contribute to the local sediment transport and/or resuspension. The velocity field induced by mode I and II internal solitary waves are studied. The contribution from second-order terms in asymptotic expansion into the horizontal velocity is estimated for the models of two- and three-layer fluid density stratification for solitons of positive and negative polarity, as well as for breathers of different shapes and amplitudes. The influence of the nonlinear correction manifests itself firstly in the shape of the lines of zero horizontal velocity: they are curved and the shape depends on the soliton amplitude and polarity while for the leading-order wave field they are horizontal. Also the wavefield accounting for the nonlinear correction for mode I waves has smaller maximal absolute values of negative velocities (near-surface for the soliton of elevation, and near-bottom for the soliton of depression) and larger maximums of positive velocities. Thus for the solitary internal waves of positive polarity weakly nonlinear theory overestimates the near-bottom velocities and underestimates the near-surface current. For solitary waves of negative polarity, which are the most typical for hydrological conditions of low and middle latitudes, the situation is the opposite. Similar estimations are produced for mode II waves, which possess more complex structure. The presented results of research are obtained with the support of the Russian Foundation for Basic Research grant 16-35-00413.

  2. P-Wave Velocity Tomography from Local Earthquakes in Western Mexico

    Science.gov (United States)

    Ochoa-Chávez, Juan A.; Escudero, Christian R.; Núñez-Cornú, Francisco J.; Bandy, William L.

    2016-10-01

    In western Mexico, the subduction of the Rivera and Cocos plates beneath the North America plate has deformed and fragmented the overriding plate, forming several structural rifts and crustal blocks. To obtain a reliable subsurface image of the continental crust and uppermost mantle in this complex area, we used P-wave arrivals of local earthquakes along with the Fast Marching Method tomography technique. We followed an inversion scheme consisting of (1) the use of a high-quality earthquake catalog and corrected phase picks, (2) the selection of earthquakes using a maximum location error threshold, (3) the estimation of an improved 1-D reference velocity model, and (4) the use of checkerboard testing to determine the optimum configuration of the velocity nodes and inversion parameters. Surprisingly, the tomography results show a very simple δVp distribution that can be described as being controlled by geologic structures formed during two stages of the separation of the Rivera and Cocos plates. The earlier period represents the initial stages of the separation of the Rivera and Cocos plates beneath western Mexico; the later period represents the more advanced stage of rifting where the Rivera and Cocos plates had separated sufficiently to allow melt to accumulate below the Colima Volcanic complex. During the earlier period (14 or 10-1.6 Ma), NE-SW-oriented structures/lineaments (such as the Southern Colima Rift) were formed as the two plates separated. During the second period (1.6 Ma to the present), the deformation is attributed to magma, generated within and above the tear zone between the Rivera and Cocos plates, rising beneath the region of the Colima Volcanic Complex. The rising magma fractured the overlying crust, forming a classic triple-rift junction geometry. This triple-rift system is confined to the mid- to lower crust perhaps indicating that this rifting process is still in an early stage. This fracturing, along with fluid circulation and associated

  3. Shallow shear-wave velocity profiles and site response characteristics from microtremor array measurements in Metro Manila, the Philippines

    Science.gov (United States)

    Grutas, Rhommel; Yamanaka, Hiroaki

    2012-07-01

    This paper presents the outcome of reconnaissance surveys in metropolitan Manila (Metro Manilla), the Philippines, with the aim of mapping shallow shear-wave velocity structures. Metro Manila is a seismically active and densely populated region that is in need of detailed investigation of the subsurface structures, to assess local site effects in seismic hazard estimation. We conducted microtremor array observations and used the spatial autocorrelation method to estimate the shear-wave profiles at 32 sites in major geological settings in Metro Manila. We applied a hybrid genetic simulated annealing algorithm to invert phase velocity data from the spatial autocorrelation method to generate shear-wave velocity models near the global best-fit solution. The comparison between the inferred shear-wave velocity profiles and PS logging showed good agreement in terms of the fundamental mode of Rayleigh waves and site responses. Then, we utilised the inferred shear-wave velocity profiles to compute the site amplifications with reference to the motion in engineering bedrock. Subsequently, the site amplifications have been grouped, based on NEHRP site classes. The amplification factor has also been compared with the average shear-wave velocity of the upper 30m at each site, to produce a power-law regression equation that can be used as a starting basis for further site-effects evaluation in the metropolis.

  4. A study of CO2 flooding on wave velocities in the Naharkatiya oil reservoir of Upper Assam Basin

    Directory of Open Access Journals (Sweden)

    Subrata Borgohain Gogoi

    2017-03-01

    Full Text Available This paper studies the compressional-wave and shear-wave velocities in the laboratory in six conventional core plugs. These plugs were obtained from a depth of more than 3000 m from the producing horizons of Naharkatiya oil reservoir of Upper Assam Basin, India. The porosities of the conventional core plugs were from 9.67 to 25.8% and that of unconsolidated sand pack was 47%. These plugs and sand pack were saturated with n-hexadecane before CO2 flooding. It was observed that during flooding compressional-wave velocities decreased more than the shear wave velocities. These decreases in wave velocity depend on confining pressure, pore pressure, porosity and temperature of the plugs. Increasing pore pressure at constant confining pressure not only keeps the pores and cracks open but also reduces the confining pressure effect and increases the CO2 density. Higher pore pressures causes larger decrease in both compressional and shear wave velocities. In case of conventional core plugs which are consolidated, having lower porosities tends to decrease the CO2 effect. In unconsolidated sand pack the flooding effect is large even though porosity is high because the bulk modulus of the sand is low. The experimental and the theoretical analyses in this paper show that the decrease in compressional-wave velocities caused by CO2 flooding makes it possible to track CO2 front movements and monitor CO2 flooding process in the reservoir.

  5. Lack of circadian variation of pulse wave velocity measurements in healthy volunteers.

    Science.gov (United States)

    Drager, Luciano F; Diegues-Silva, Luzia; Diniz, Patrícia M; Lorenzi-Filho, Geraldo; Krieger, Eduardo M; Bortolotto, Luiz A

    2011-01-01

    Arterial stiffness is an independent marker of cardiovascular events. Pulse wave velocity (PWV) is a validated method to detect arterial stiffness that can be influenced by several factors including age and blood pressure. However, it is not clear whether PWV could be influenced by circadian variations. In the present study, the authors measured blood pressure and carotid-femoral PWV measurements in 15 young healthy volunteers in 4 distinct periods: 8 am, noon, 4 pm, and 8 pm. No significant variations of systolic (P=.92), mean (P=.77), and diastolic (P=.66) blood pressure among 8 am (113±15, 84±8, 69±6 mm Hg), noon (114±13, 83±8, 68±6 mm Hg), 4 pm (114±13, 85±8, 70±7 mm Hg), and 8 pm (113±7, 83±10, 68±7 mm Hg), respectively, were observed. Similarly, carotid-femoral PWV did not change among the periods (8 am: 7.6 ± 1.4 m/s, noon: 7.4±1.1 m/s, 4 pm: 7.6±1.0 m/s, 8 pm, 7.6±1.3 m/s; P=.85). Considering all measurements, mean blood pressure significantly correlated with PWV (r=.31; P=.016). In young healthy volunteers, there is no significant circadian variation of carotid-femoral PWV. These findings support the concept that it does not appear mandatory to perform PWV measurements at exactly the same period of the day. © 2010 Wiley Periodicals, Inc.

  6. Spatial Parallelism of a 3D Finite Difference, Velocity-Stress Elastic Wave Propagation Code

    Energy Technology Data Exchange (ETDEWEB)

    MINKOFF,SUSAN E.

    1999-12-09

    Finite difference methods for solving the wave equation more accurately capture the physics of waves propagating through the earth than asymptotic solution methods. Unfortunately. finite difference simulations for 3D elastic wave propagation are expensive. We model waves in a 3D isotropic elastic earth. The wave equation solution consists of three velocity components and six stresses. The partial derivatives are discretized using 2nd-order in time and 4th-order in space staggered finite difference operators. Staggered schemes allow one to obtain additional accuracy (via centered finite differences) without requiring additional storage. The serial code is most unique in its ability to model a number of different types of seismic sources. The parallel implementation uses the MP1 library, thus allowing for portability between platforms. Spatial parallelism provides a highly efficient strategy for parallelizing finite difference simulations. In this implementation, one can decompose the global problem domain into one-, two-, and three-dimensional processor decompositions with 3D decompositions generally producing the best parallel speed up. Because i/o is handled largely outside of the time-step loop (the most expensive part of the simulation) we have opted for straight-forward broadcast and reduce operations to handle i/o. The majority of the communication in the code consists of passing subdomain face information to neighboring processors for use as ''ghost cells''. When this communication is balanced against computation by allocating subdomains of reasonable size, we observe excellent scaled speed up. Allocating subdomains of size 25 x 25 x 25 on each node, we achieve efficiencies of 94% on 128 processors. Numerical examples for both a layered earth model and a homogeneous medium with a high-velocity blocky inclusion illustrate the accuracy of the parallel code.

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

    Science.gov (United States)

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

    2018-01-01

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

  8. Shear wave velocity versus quality factor: results from seismic noise recordings

    Science.gov (United States)

    Boxberger, Tobias; Pilz, Marco; Parolai, Stefano

    2017-08-01

    The assessment of the shear wave velocity (vs) and shear wave quality factor (Qs) for the shallow structure below a site is necessary to characterize its site response. In the past, methods based on the analysis of seismic noise have been shown to be very efficient for providing a sufficiently accurate estimation of the vs versus depth at reasonable costs for engineering seismology purposes. In addition, a slight modification of the same method has proved to be able to provide realistic Qs versus depth estimates. In this study, data sets of seismic noise recorded by microarrays of seismic stations in different geological environments of Europe and Central Asia are used to calculate both vs and Qs versus depth profiles. Analogous to the generally adopted approach in seismic hazard assessment for mapping the average shear wave velocity in the uppermost 30 m (vs30) as a proxy of the site response, this approach was also applied to the quality factor within the uppermost 30 m (Qs30). A slightly inverse correlation between both parameters is found based on a methodological consistent determination for different sites. Consequently, a combined assessment of vs and Qs by seismic noise analysis has the potential to provide a more comprehensive description of the geological structure below a site.

  9. Comparison of Ambient Noise Methods to Find Surface - Wave Dispersion Curves at Pacaya Volcano, Guatemala

    Science.gov (United States)

    Pawar, Prathamesh Vijay

    The application of ambient noise analysis to active volcanic systems represents a recent technique to model seismic structure without distinct sources. All the existing methods are based on the fact that surface waves are dispersive and most of them require a large number of available days and inter-station distances larger than 2-3 wavelengths. We apply multiple techniques to seismic data recorded during a temporary deployment of 19 seismic stations in January 2015 at Pacaya volcano, Guatemala, a dataset with some distinct differences from those typically used for ambient noise analysis. Despite having less than a week of data and relatively close inter-station spacing, we find a good agreement between the approaches. In particular, we find that the SPAC method (Aki, 1957) is applicable not only for a seismic array, but also for single pairs of stations. It may be particularly favorable in those conditions characterized by small set of data and small inter-station distances. We also noted linear relationship between phase velocity and inter-station distance might suggest a contribution of body/scattered waves within the surface waves and it is probably due to the seismic station configuration in proximity of the Pacaya vent.

  10. Three-dimensional S-wave velocity model of the Bohemian Massif from Bayesian ambient noise tomography

    Science.gov (United States)

    Valentová, Lubica; Gallovič, František; Maierová, Petra

    2017-10-01

    We perform two-step surface wave tomography of phase-velocity dispersion curves obtained by ambient noise cross-correlations in the Bohemian Massif. In the first step, the inter-station dispersion curves were inverted for each period (ranging between 4 and 20 s) separately into phase-velocity maps using 2D adjoint method. In the second step, we perform Bayesian inversion of the set of the phase-velocity maps into an S-wave velocity model. To sample the posterior probability density function, the parallel tempering algorithm is employed providing over 1 million models. From the model samples, not only mean model but also its uncertainty is determined to appraise the reliable features. The model is correlated with known main geologic structures of the Bohemian Massif. The uppermost low-velocity anomalies are in agreement with thick sedimentary basins. In deeper parts (4-20 km), the S-wave velocity anomalies correspond, in general, to main tectonic domains of the Bohemian Massif. The exception is a stable low-velocity body in the middle of the high-velocity Moldanubian domain and high-velocity body resembling a promontory of the Moldanubian into the Teplá-Barrandian domain. The most pronounced (high-velocity) anomaly is located beneath the Eger Rift that is a part of a Tertiary rift system across Europe.

  11. Love wave phase velocity models of the southeastern margin of Tibetan Plateau from a dense seismic array

    Science.gov (United States)

    Han, Fengqin; Jia, Ruizhi; Fu, Yuanyuan V.

    2017-08-01

    Love wave dispersion maps across the southeastern margin of the Tibetan Plateau are obtained using earthquake data recorded by the temporary ChinArray and permanent China Digital Seismic Array. Fundamental mode Love wave phase velocity curves are measured by inverting Love wave amplitude and phase with the two-plane-wave method. The phase velocity maps with resolution better than 150 km are presented at periods of 20-100 s, which is unprecedented in the study area. The maps agree well with each other and show clear correlations with major tectonic structures. The Love wave phase velocity could provide new information about structures in the crust and upper mantle beneath the southeast margin of Tibetan Plateau, like the radial anisotropy.

  12. Upper-mantle velocities below the Scandinavian Mountains from P- and S- wave traveltime tomography

    DEFF Research Database (Denmark)

    Hejrani, Babak; Balling, N.; Jacobsen, B. H.

    2017-01-01

    More than 20000 arrival-times of teleseismic P- and S-waves were measured over a period of more than 10 years in five separate temporary and two permanent seismic networks covering the Scandinavian (Scandes) Mountains and adjacent areas of the Baltic Shield. The relative traveltime residuals were...... inverted to 3D tomograms of P- and S- velocities and the VP/VS ratio. Resolution analysis documents that good 3D resolution is available under the dense network south of 64° latitude (Southern Scandes Mountains), and patchier, but highly useful resolution is available further north, where station coverage...... is more uneven. A pronounced upper-mantle velocity boundary (UMVB), transecting the study region is defined. It runs from SE Norway (east of the Oslo Graben) across the mountains to the Norwegian coast near Trondheim (around the Møre-Trøndelag Fault Complex), from where it follows the coast and runs...

  13. Investigating Near Surface S-Wave Velocity Properties Using Ambient Noise in Southwestern Taiwan

    Directory of Open Access Journals (Sweden)

    Chun-Hsiang Kuo

    2015-01-01

    Full Text Available Ambient noise is typically used to estimate seismic site effects and velocity profiles instead of earthquake recordings, especially in areas with limited seismic data. The dominant Horizontal to Vertical Spectral Ratio (HVSR frequency of ambient noise is correlated to Vs30, which is the average S-wave velocity in the top 30 m. Vs30 is a widely used parameter for defining seismic amplification in earthquake engineering. HVSR can detect the vertical discontinuity of velocities, that is, the interfaces between hard bedrock and soft sediments. In southwestern Taiwan most strong motion stations are located in the plains and show a dominant frequency lower than 3 Hz. Several stations near the coast have low dominant frequencies of less than 1 Hz. The dominant frequencies are higher than 4 Hz at piedmont stations. The stations in the mountains with dominant frequencies over 8 Hz are typically located on very hard sites. This study analyzed the HVSR characteristics under different seismic site conditions considering the Vs30 from previous study (Kuo et al. 2012. The result implies that HVSRs are a better tool than Vs30 to classify the sites where bedrock is deeper than 30 m. Furthermore, we found a linear correlation between Vs30 and dominant HVSR frequency which could be used as a proxy of Vs30. The Vs30 map in this area was derived using the Engineering Geological Database for Taiwan Strong Motion Instrumentation Program (EGDT. The comparable distribution pattern between the dominant frequency and Vs30 demonstrate that HVSR can recognize S-wave velocity properties at the shallow subsurface.

  14. Short-term effects of a standardized glucose load on region-specific aortic pulse wave velocity assessed by MRI

    NARCIS (Netherlands)

    Jonker, Jacqueline T.; Tjeerdema, Nathanja; Hensen, Liselotte C. R.; Lamb, Hildo J.; Romijn, Johannes A.; Smit, Johannes W. A.; Westenberg, Jos J. M.; de Roos, Albert

    2014-01-01

    Purpose To assess the short-term effects of a standardized oral glucose load on regional aortic pulse wave velocity (PWV) using two-directional in-plane velocity encoded MRI. Materials and Methods A randomized, controlled intervention was performed in 16 male subjects (mean +/- standard deviation:

  15. Estimating a continuous p-wave velocity profile with constant squared-slowness gradient models from seismic field data

    NARCIS (Netherlands)

    Ponomarenko, A.V.; Kashtan, B.M.; Troyan, V.N.; Mulder, W.A.

    2015-01-01

    We inverted seismic field data for a continuous, laterally invariant P-wave velocity profile. Instead of the usual approach that involves horizontal layers with piecewise constant densities and velocities, we consider models of one or two layers with a constant gradient of the squared slowness above

  16. Nuclear Magnetic Resonance and Elastic Wave Velocity of Chalk Saturated with Brines Containing Divalent Ions

    DEFF Research Database (Denmark)

    Katika, Konstantina; Alam, Mohammad Monzurul; Fabricius, Ida Lykke

    divided into groups of three and each group was saturated either with deionized water, calcite equilibrated water, or sodium chloride, magnesium chloride and calcium chloride solutions of the same ionic strength. Saturation with solutions that contain divalent ions caused major shifts in the distribution...... of the relaxation time. Core samples saturated with calcium chloride solution relaxed slower and those saturated with magnesium chloride solution relaxed faster than the rest of the samples. Along with the changes in relaxation the samples experienced smaller velocities of elastic waves when saturated with MgCl2...

  17. Shear-wave velocity structure of the Tongariro Volcanic Centre, New Zealand: Fast Rayleigh and slow Love waves indicate strong shallow anisotropy

    Science.gov (United States)

    Godfrey, Holly J.; Fry, Bill; Savage, Martha K.

    2017-04-01

    Models of the velocity structure of volcanoes can help define possible magma pathways and contribute to calculating more accurate earthquake locations, which can help with monitoring volcanic activity. However, shear-wave velocity of volcanoes is difficult to determine from traditional seismic techniques, such as local earthquake tomography (LET) or refraction/reflection surveys. Here we use the recently developed technique of noise cross correlation of continuous seismic data to investigate the subsurface shear-wave velocity structure of the Tongariro Volcanic Centre (TgVC) of New Zealand, focusing on the active Ruapehu and Tongariro Volcanoes. We observe both the fundamental and first higher-order modes of Rayleigh and Love waves within our noise dataset, made from stacks of 15 min cross-correlation functions. We manually pick group velocity dispersion curves from over 1900 correlation functions, of which we consider 1373 to be high quality. We subsequently invert a subset of the fundamental mode Rayleigh- and Love-wave dispersion curves both independently and jointly for one dimensional shear-wave velocity (Vs) profiles at Ruapehu and Tongariro Volcanoes. Vs increases very slowly at a rate of approximately 0.2 km/s per km depth beneath Ruapehu, suggesting that progressive hydrothermal alteration mitigates the effects of compaction driven velocity increases. At Tongariro, we observe larger Vs increases with depth, which we interpret as different layers within Tongariro's volcanic system above altered basement greywacke. Slow Vs, on the order of 1-2 km/s, are compatible with P-wave velocities (using a Vp/Vs ratio of 1.7) from existing velocity profiles of areas within the TgVC, and the observations of worldwide studies of shallow volcanic systems that used ambient noise cross-correlation methods. Most of the measured group velocities of fundamental mode Love-waves across the TgVC are 0.1-0.4 km/s slower than those of fundamental mode Rayleigh-waves in the

  18. Consistency of students’ conceptions of wave propagation: Findings from a conceptual survey in mechanical waves

    Directory of Open Access Journals (Sweden)

    Apisit Tongchai

    2011-07-01

    Full Text Available We recently developed a multiple-choice conceptual survey in mechanical waves. The development, evaluation, and demonstration of the use of the survey were reported elsewhere [A. Tongchai et al., Developing, evaluating and demonstrating the use of a conceptual survey in mechanical waves, Int. J. Sci. Educ. 31, 2437 (2009ISEDEB0950-069310.1080/09500690802389605]. We administered the survey to 902 students from seven different groups ranging from high school to second year university. As an outcome of that analysis we were able to identify several conceptual models which the students seemed to be using when answering the questions in the survey. In this paper we attempt to investigate the strength with which the students were committed to these conceptual models, as evidenced by the consistency with which they answered the questions. For this purpose we focus on the patterns of student responses to questions in one particular subtopic, wave propagation. This study has three main purposes: (1 to investigate the consistency of student conceptions, (2 to explore the relative usefulness of different analysis techniques, and (3 to determine what extra information a study of consistency can give about student understanding of basic concepts. We used two techniques: first, categorizing and counting, which is widely used in the science education community, and second, model analysis, recently introduced into physics education research. The manner in which categorizing and counting is used is very diverse while model analysis has been employed only in prescriptive ways. Research studies have reported that students often use their conceptual models inconsistently when solving a series of questions that test the same idea. Our results support their conclusions. Moreover, our findings suggest that students who have had more experiences in physics learning seem to use the scientifically accepted models more consistently. Further, the two analysis techniques

  19. Simultaneous Multiphase PIV of Capillary Waves on a High Velocity Liquid Jet

    Science.gov (United States)

    Andre, Matthieu; Bardet, Philippe

    2013-11-01

    Relaxation of a laminar boundary layer below the free surface of a jet is inviscidly unstable and can roll-up which generates millimeter size waves. The latter largely modify important characteristics of jets such as heat and mass transfers between phases and can lead to breakup, or air entrainment. Two dimensional linear stability analysis predicts the initial disturbance wavelength and growth rate for inviscid flows; it does not take into account the effects of viscosity, non-linearity, or actual boundary layer profile. Because of the small temporal and spatial scales associated with this flow, few experimental data are available. Data acquisition is further complicated by the presence of a free surface with steep waves. The current experiment consists in a 20.3 mm × 146.0 mm water slab laminar jet flowing onto a transparent open-channel at a Reynolds number of 2.9 × 104 to 1.4 × 105. Two high speed cameras are employed to obtain velocity fields simultaneously in the liquid and in the gas phase with Particle Image Velocimetry (PIV). Fluorescent dye is added in the liquid in order to improve interface detection. Each phase is recorded at 10 kHz, leading to a temporal resolution of 100 μs and high magnification lenses give a spatial resolution of 200 μm. The results confirm the mechanism of formation of the short surface waves. Generation of surface vorticity is identified in high curvature regions. Knowledge of the velocities in both phases allows studying vorticity flux through the free surface. The latter stage of wave growth can be accompanied by the formation of a vortex pair in the liquid and air entrapment.

  20. Assessing the P-wave attenuation and phase velocity characteristics of fractured media based on creep and relaxation tests

    Science.gov (United States)

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

    2014-05-01

    , the corresponding results obtained from creep and relaxation tests must be equivalent. For most analyses of media characterized by patchy saturation or double-porosity-type structures these two definitions are equivalent. It is, however, not clear whether this equivalence remains true in the presence of strong material contrasts as those prevailing in fractured rocks. In this work, we explore this question for periodically fractured media. To this end, we build a medium composed of infinite replicas of a unit volume containing one fracture. This unit volume coincides with the smallest possible volume that is statistically representative of the whole. Then, we perform several creep and relaxation tests on samples composed of an increasing number of these unit volumes. We find that the wave field signatures determined from relaxation tests are independent from the number of unit volumes. Conversely, the P-wave attenuation and phase velocity characteristics inferred from creep tests are different and vary with the number of unit volumes considered. Quite interestingly, the creep test results converge with those of the relaxation tests as the number of unit volumes increases. These findings are expected to have direct implications for corresponding laboratory measurements as well as for our understanding of seismic wave propagation in fractured media.

  1. Influence of apparent wave velocity on seismic performance of a super-long-span triple-tower suspension bridge

    Directory of Open Access Journals (Sweden)

    Hao Wang

    2015-06-01

    Full Text Available As one of the main characteristics of seismic waves, apparent wave velocity has great influence on seismic responses of long-span suspension bridges. Understanding these influences is important for seismic design. In this article, the critical issues concerning the traveling wave effect analysis are first reviewed. Taizhou Bridge, the longest triple-tower suspension bridge in the world, is then taken as an example for this investigation. A three-dimensional finite element model of the bridge is established in ABAQUS, and the LANCZOS eigenvalue solver is employed to calculate the structural dynamic characteristics. Traveling wave effect on seismic responses of these long-span triple-tower suspension bridges is investigated. Envelopes of seismic shear force and moment in the longitudinal direction along the three towers, relative displacements between the towers and the girder, and reaction forces at the bottoms of the three towers under different apparent wave velocities are calculated and presented in detail. The results show that the effect of apparent wave velocity on the seismic responses of triple-tower suspension bridge fluctuates when the velocity is lower than 2000 m/s, and the effects turn stable when the velocity becomes larger. In addition, the effects of traveling wave are closely related to spectral characteristics and propagation direction of the seismic wave, and seismic responses of components closer to the source are relatively larger. Therefore, reliable estimation of the seismic input and apparent wave velocity according to the characteristics of the bridge site are significant for accurate prediction of seismic responses. This study provides critical reference for seismic analysis and design of long-span triple-tower suspension bridges.

  2. Extreme bottom velocities induced by wind wave and currents in the Gulf of Gdańsk

    Science.gov (United States)

    Cieślikiewicz, Witold; Dudkowska, Aleksandra; Gic-Grusza, Gabriela; Jędrasik, Jan

    2017-11-01

    The principal goal of this study is to get some preliminary insights about the intensity of water movement generated by wind waves, and due to the currents in the bottom waters of Gulf of Gdańsk, during severe storms. The Gulf of Gdańsk is located in the southern Baltic Sea. This paper presents the results of analysis of wave and current-induced velocities during extreme wind conditions, which are determined based on long-term historical records. The bottom velocity fields originated from wind wave and wind currents, during analysed extreme wind events, are computed independently of each other. The long-term wind wave parameters for the Baltic Sea region are derived from the 44-year hindcast wave database generated in the framework of the project HIPOCAS funded by the European Union. The output from the numerical wave model WAM provides the boundary conditions for the model SWAN operating in high-resolution grid covering the area of the Gulf of Gdańsk. Wind current velocities are calculated with the M3D hydrodynamic model developed in the Institute of Oceanography of the University of Gdańsk based on the POM model. The three dimensional current fields together with trajectories of particle tracers spreading out of bottom boundary layer are modelled, and the calculated fields of bottom velocities are presented in the form of 2D maps. During northerly winds, causing in the Gulf of Gdańsk extreme waves and most significant wind-driven circulation, the wave-induced bottom velocities are greater than velocities due to currents. The current velocities in the bottom layer appeared to be smaller by an order of magnitude than the wave-induced bottom orbital velocities. Namely, during most severe northerly storms analysed, current bottom velocities ranged about 0.1-0.15 m/s, while the root mean square of wave-induced near-seabed velocities reached maximum values of up to 1.4 m/s in the southern part of Gulf of Gdańsk.

  3. Northern Korean Peninsula 1-D velocity model from surface wave dispersion and full-waveform data

    Science.gov (United States)

    Lee, S. J.; Rhie, J.; Kim, S.; Kang, T. S.; Cho, C.

    2016-12-01

    Monitoring seismic activities in the northern Korean Peninsula is important not only for understanding the characteristics of earthquakes but also for watching nuclear tests. To better monitor those natural and man-made seismic activities, reliable seismic velocity models are required. However, the seismic velocity structure of the region is not known well due to the lack of available seismic data directly measured in the region. This study presents 1-D velocity models of the region using two different datasets comprised of two-year-long continuous waveform and the 2013 North Korea nuclear test event waveform recorded at stations surrounding the region. Two reference 1-D models for the inland and offshore areas (Western East Sea) were estimated by 1-D inversion of surface wave dispersion measurements from ambient noise cross-correlations of the continuous waveform. To investigate the variations in the velocity models, many 1-D models for the paths between the 2013 nuclear test site and stations in China and South Korea were constructed by forward waveform modeling. The velocity variations are not significant for both models representing the inland and offshore paths, respectively. The 1-D models for the inland paths are similar to the models constructed for the southern Korean Peninsula. Interestingly, waveforms sampling through the offshore paths are not well explained by simple 1-D isotropic models. The preliminary result indicates that there exists radial anisotropy with SH being faster than SV by 3-5% in the upper mantle beneath the offshore northern Korean Peninsula, although further studies are necessary to explain the origin of anisotropy. A proper characterization of propagation effects along the offshore paths would be useful for monitoring future nuclear tests because many seismic stations in the eastern South Korea record waveforms sampling the offshore region from the nuclear test site to those stations.

  4. An experimental study of wave propagation and velocity distributions in a vertically driven time-dependent granular gas

    Science.gov (United States)

    Perez, John Anthony

    Averaged over appropriate space and time scales the dynamics of highly fluidized granular systems are often reminiscent of molecular fluid flows. As a result, theoretical efforts to describe these systems have borrowed heavily from continuum mechanics, particularly hydrodynamics. This has led to various proposed granular hydrodynamic theories which have been used to simulate granular materials in various states of confinement and excitation. These studies suggest that a continuum model for granular gasses can accurately reproduce the mean density, velocity and temperature profiles for an experimental granular gas. This thesis contributes to this body of work by presenting an experimental study of the hydrodynamic fields and velocity distributions within a vertically driven quasi-2D granular gas. We have taken pictures as fast as possible of a time-dependent granular gas using a high-speed CCD camera. We have extracted the positions and velocities of 57-564 particles per frame over 400 GB of raw images collected at 3700 fps. We used this data to compute the density, velocity and temperature fields as functions of time and space to a very high resolution. This approach led to the discovery of novel substructures within the hydrodynamic fields which would have been overlooked had we chosen to average over a drive cycle as earlier studies have done. In particular, the high spatial resolution available from our measurements reveals a serrated substructure in the shock waves which has not been reported before. This substructure is the result of collisional momentum transport . One of the current issues in formulating a granular continuum model is how to incorporate local and non-local dependencies between stress and strain correctly. In this thesis we demonstrate that the collisional transfer of momentum produces a non-local effect in the stress tensor which plays a major role in determining the mean flow. Current models have incorporated only the collisional or

  5. Consistency of students’ conceptions of wave propagation: Findings from a conceptual survey in mechanical waves

    Directory of Open Access Journals (Sweden)

    Chernchok Soankwan

    2011-07-01

    Full Text Available We recently developed a multiple-choice conceptual survey in mechanical waves. The development, evaluation, and demonstration of the use of the survey were reported elsewhere [ A. Tongchai et al. Int. J. Sci. Educ. 31 2437 (2009]. We administered the survey to 902 students from seven different groups ranging from high school to second year university. As an outcome of that analysis we were able to identify several conceptual models which the students seemed to be using when answering the questions in the survey. In this paper we attempt to investigate the strength with which the students were committed to these conceptual models, as evidenced by the consistency with which they answered the questions. For this purpose we focus on the patterns of student responses to questions in one particular subtopic, wave propagation. This study has three main purposes: (1 to investigate the consistency of student conceptions, (2 to explore the relative usefulness of different analysis techniques, and (3 to determine what extra information a study of consistency can give about student understanding of basic concepts. We used two techniques: first, categorizing and counting, which is widely used in the science education community, and second, model analysis, recently introduced into physics education research. The manner in which categorizing and counting is used is very diverse while model analysis has been employed only in prescriptive ways. Research studies have reported that students often use their conceptual models inconsistently when solving a series of questions that test the same idea. Our results support their conclusions. Moreover, our findings suggest that students who have had more experiences in physics learning seem to use the scientifically accepted models more consistently. Further, the two analysis techniques have different advantages and disadvantages. Our findings show that model analysis can be used in more diverse ways, provides

  6. Six-channel ECG-based pulse wave velocity for assessing whole-body arterial stiffness.

    Science.gov (United States)

    Wu, Hsien-Tsai; Hsu, Po-Chun; Liu, An-Bang; Chen, Zong-Li; Huang, Ruay-Ming; Chen, Ching-Pin; Tang, Chieh-Ju; Sun, Cheuk-Kwan

    2012-06-01

    Despite the proposal of different means of non-invasive arterial stiffness assessment, none offers simultaneous information on whole-body peripheral arterial condition. We investigated the validity of applying a six-channel electrocardiogram-based pulse wave velocity (ECG-PWV) measurement system for this purpose. The study consisted of two parts. Part One enrolled hypertensive (Group 1, n = 32) and normal (Group 2, n = 32) subjects, whereas Part Two recruited diabetic (Group 3, n = 50) and normal (Group 4, n = 50) subjects. To validate the application of ECG-PWV in assessing peripheral arterial stiffness in different parts of body, ECG-PWV data were compared with three other parameters including the cardio-ankle vascular index (CAVI), pulse wave velocity-digital volume pulse (PWV-DVP) and intima-media thickness (IMT). ECG-PWV in healthy subjects in Part One correlated significantly with CAVI and PWV-DVP (p blood sugar, serum creatinine and ECG-PWV from the foot. However, no significant difference was noted in PWV-DVP between two groups. Six-channel ECG-PWV measurement system showed remarkable correlation with IMT in hypertensive subjects and with key anthropometric and biochemical parameters in diabetic patients, suggesting its validity in assessing whole-body arterial stiffness in subjects with peripheral arterial diseases within 10 min.

  7. Prediction of shear wave velocity using empirical correlations and artificial intelligence methods

    Science.gov (United States)

    Maleki, Shahoo; Moradzadeh, Ali; Riabi, Reza Ghavami; Gholami, Raoof; Sadeghzadeh, Farhad

    2014-06-01

    Good understanding of mechanical properties of rock formations is essential during the development and production phases of a hydrocarbon reservoir. Conventionally, these properties are estimated from the petrophysical logs with compression and shear sonic data being the main input to the correlations. This is while in many cases the shear sonic data are not acquired during well logging, which may be for cost saving purposes. In this case, shear wave velocity is estimated using available empirical correlations or artificial intelligent methods proposed during the last few decades. In this paper, petrophysical logs corresponding to a well drilled in southern part of Iran were used to estimate the shear wave velocity using empirical correlations as well as two robust artificial intelligence methods knows as Support Vector Regression (SVR) and Back-Propagation Neural Network (BPNN). Although the results obtained by SVR seem to be reliable, the estimated values are not very precise and considering the importance of shear sonic data as the input into different models, this study suggests acquiring shear sonic data during well logging. It is important to note that the benefits of having reliable shear sonic data for estimation of rock formation mechanical properties will compensate the possible additional costs for acquiring a shear log.

  8. Prediction of shear wave velocity using empirical correlations and artificial intelligence methods

    Directory of Open Access Journals (Sweden)

    Shahoo Maleki

    2014-06-01

    Full Text Available Good understanding of mechanical properties of rock formations is essential during the development and production phases of a hydrocarbon reservoir. Conventionally, these properties are estimated from the petrophysical logs with compression and shear sonic data being the main input to the correlations. This is while in many cases the shear sonic data are not acquired during well logging, which may be for cost saving purposes. In this case, shear wave velocity is estimated using available empirical correlations or artificial intelligent methods proposed during the last few decades. In this paper, petrophysical logs corresponding to a well drilled in southern part of Iran were used to estimate the shear wave velocity using empirical correlations as well as two robust artificial intelligence methods knows as Support Vector Regression (SVR and Back-Propagation Neural Network (BPNN. Although the results obtained by SVR seem to be reliable, the estimated values are not very precise and considering the importance of shear sonic data as the input into different models, this study suggests acquiring shear sonic data during well logging. It is important to note that the benefits of having reliable shear sonic data for estimation of rock formation mechanical properties will compensate the possible additional costs for acquiring a shear log.

  9. Measuring curvature and velocity vector fields for waves of cardiac excitation in 2-D media.

    Science.gov (United States)

    Kay, Matthew W; Gray, Richard A

    2005-01-01

    Excitable media theory predicts the effect of electrical wavefront morphology on the dynamics of propagation in cardiac tissue. It specifies that a convex wavefront propagates slower and a concave wavefront propagates faster than a planar wavefront. Because of this, wavefront curvature is thought to be an important functional mechanism of cardiac arrhythmias. However, the curvature of wavefronts during an arrhythmia are generally unknown. We introduce a robust, automated method to measure the curvature vector field of discretely characterized, arbitrarily shaped, two-dimensional (2-D) wavefronts. The method relies on generating a smooth, continuous parameterization of the shape of a wave using cubic smoothing splines fitted to an isopotential at a specified level, which we choose to be -30 mV. Twice differentiating the parametric form provides local curvature vectors along the wavefront and waveback. Local conduction velocities are computed as the wave speed along lines normal to the parametric form. In this way, the curvature and velocity vector field for wavefronts and wavebacks can be measured. We applied the method to data sampled from a 2-D numerical model and several examples are provided to illustrate its usefulness for studying the dynamics of cardiac propagation in 2-D media.

  10. Correlation between Shear Wave Velocity and Porosity in Porous Solids and Rocks

    Directory of Open Access Journals (Sweden)

    J. Kováčik

    2013-01-01

    Full Text Available The shear wave velocity dependence on porosity was modelled using percolation theory model for the shear modulus porosity dependence. The obtained model is not a power law dependence (no simple scaling with porosity, but a more complex equation. Control parameters of this equation are shear wave velocity of bulk solid, percolation threshold of the material and the characteristic power law exponent for shear modulus porosity dependence. This model is suitable for all porous materials, mortars and porous rocks filled with liquid or gas. In the case of pores filled with gas the model can be further simplified: The term for the ratio of the gas density to the density of solid material can be omitted in the denominator (the ratio is usually in the range of (10−4, 10−3 for all solids. This simplified equation was then tested on the experimental data set for porous ZnO filled with air. Due to lack of reasonable data the scientists are encouraged to test the validity of proposed model using their experimental data.

  11. Estimation of S-wave Velocity Structures by Using Microtremor Array Measurements for Subsurface Modeling in Jakarta

    Directory of Open Access Journals (Sweden)

    Mohamad Ridwan

    2014-12-01

    Full Text Available Jakarta is located on a thick sedimentary layer that potentially has a very high seismic wave amplification. However, the available information concerning the subsurface model and bedrock depth is insufficient for a seismic hazard analysis. In this study, a microtremor array method was applied to estimate the geometry and S-wave velocity of the sedimentary layer. The spatial autocorrelation (SPAC method was applied to estimate the dispersion curve, while the S-wave velocity was estimated using a genetic algorithm approach. The analysis of the 1D and 2D S-wave velocity profiles shows that along a north-south line, the sedimentary layer is thicker towards the north. It has a positive correlation with a geological cross section derived from a borehole down to a depth of about 300 m. The SPT data from the BMKG site were used to verify the 1D S-wave velocity profile. They show a good agreement. The microtremor analysis reached the engineering bedrock in a range from 359 to 608 m as depicted by a cross section in the north-south direction. The site class was also estimated at each site, based on the average S-wave velocity until 30 m depth. The sites UI to ISTN belong to class D (medium soil, while BMKG and ANCL belong to class E (soft soil.

  12. Shear-wave velocity of marine sediments offshore Taiwan using ambient seismic noise

    Science.gov (United States)

    Lin, Yu-Tse; Lin, Jing-Yi; Kuo-Chen, Hao; Yeh, Yi-Chin; Cheng, Win-Bin

    2017-04-01

    Seismic ambient noise technology has many advantages over the traditional two-station method. The most important one is that noise is happening all the time and it can be widely and evenly distributed. Thus, the Green's Function of any station pair can be obtained through the data cross-correlation process. Many related studies have been performed to estimate the velocity structures based on the inland area. Only a few studies were reported for the marine area due to the relatively shorter recording time of ocean bottom seismometers (OBS) deployment and the high cost of the marine experiment. However, the understanding about the shear-wave velocity (Vs) of the marine sediments is very crucial for the hazard assessment related to submarine landslides, particularly with the growing of submarine resources exploration. In this study, we applied the ambient noise technique to four OBS seismic networks located offshore Taiwan in the aim of getting more information about the noise sources and having the preliminary estimation for the Vs of the marine sediments. Two of the seismic networks were deployed in the NE part of Taiwan, near the Ryukyu subduction system, whereas the others were in the SW area, on the continental margin rich in gas hydrate. Generally, ambient seismic noise could be associated with wind, ocean waves, rock fracturing and anthropogenic activity. In the southwestern Taiwan, the cross-correlation function obtained from two seismic networks indicate similar direction, suggestion that the source from the south part of the network could be the origin of the noise. However, the two networks in the northeastern Taiwan show various source direction, which could be caused by the abrupt change of bathymetry or the volcanic degassing effect frequently observed by the marine geophysical method in the area. The Vs determined from the dispersion curve shows a relatively higher value for the networks in the Okinawa Trough (OT) off NE Taiwan than that in the

  13. Pulse-wave propagation in straight-geometry vessels for stiffness estimation: theory, simulations, phantoms and in vitro findings.

    Science.gov (United States)

    Shahmirzadi, Danial; Li, Ronny X; Konofagou, Elisa E

    2012-11-01

    Pulse wave imaging (PWI) is an ultrasound-based method for noninvasive characterization of arterial stiffness based on pulse wave propagation. Reliable numerical models of pulse wave propagation in normal and pathological aortas could serve as powerful tools for local pulse wave analysis and a guideline for PWI measurements in vivo. The objectives of this paper are to (1) apply a fluid-structure interaction (FSI) simulation of a straight-geometry aorta to confirm the Moens-Korteweg relationship between the pulse wave velocity (PWV) and the wall modulus, and (2) validate the simulation findings against phantom and in vitro results. PWI depicted and tracked the pulse wave propagation along the abdominal wall of canine aorta in vitro in sequential Radio-Frequency (RF) ultrasound frames and estimates the PWV in the imaged wall. The same system was also used to image multiple polyacrylamide phantoms, mimicking the canine measurements as well as modeling softer and stiffer walls. Finally, the model parameters from the canine and phantom studies were used to perform 3D two-way coupled FSI simulations of pulse wave propagation and estimate the PWV. The simulation results were found to correlate well with the corresponding Moens-Korteweg equation. A high linear correlation was also established between PWV² and E measurements using the combined simulation and experimental findings (R² =  0.98) confirming the relationship established by the aforementioned equation.

  14. Shear wave velocity-based evaluation and design of stone column improved ground for liquefaction mitigation

    Science.gov (United States)

    Zhou, Yanguo; Sun, Zhengbo; Chen, Jie; Chen, Yunmin; Chen, Renpeng

    2017-04-01

    The evaluation and design of stone column improvement ground for liquefaction mitigation is a challenging issue for the state of practice. In this paper, a shear wave velocity-based approach is proposed based on the well-defined correlations of liquefaction resistance (CRR)-shear wave velocity ( V s)-void ratio ( e) of sandy soils, and the values of parameters in this approach are recommended for preliminary design purpose when site specific values are not available. The detailed procedures of pre- and post-improvement liquefaction evaluations and stone column design are given. According to this approach, the required level of ground improvement will be met once the target V s of soil is raised high enough (i.e., no less than the critical velocity) to resist the given earthquake loading according to the CRR- V s relationship, and then this requirement is transferred to the control of target void ratio (i.e., the critical e) according to the V s- e relationship. As this approach relies on the densification of the surrounding soil instead of the whole improved ground and is conservative by nature, specific considerations of the densification mechanism and effect are given, and the effects of drainage and reinforcement of stone columns are also discussed. A case study of a thermal power plant in Indonesia is introduced, where the effectiveness of stone column improved ground was evaluated by the proposed V s-based method and compared with the SPT-based evaluation. This improved ground performed well and experienced no liquefaction during subsequent strong earthquakes.

  15. Whole-mantle P-wave velocity structure and azimuthal anisotropy

    Science.gov (United States)

    Yamamoto, Y.; Zhao, D.

    2009-12-01

    There are some hotspot volcanoes on Earth, such as Hawaii and Iceland. The mantle plume hypothesis was proposed forty years ago to explain hotspot volcanoes (e.g., Wilson, 1963; Morgan, 1971). Seismic tomography is a powerful technique to detect mantle plumes and determine their detailed structures. We determined a new whole-mantle 3-D P-wave velocity model (Tohoku model) using a global tomography method (Zhao, 2004, 2009). A flexible-grid approach with a grid interval of ~200 km is adopted to conduct the tomographic inversion. Our model shows that low-velocity (low-V) anomalies with diameters of several hundreds of kilometers are visible from the core-mantle boundary (CMB) to the surface under the major hotspot regions. Under South Pacific where several hotspots including Tahiti exist, there is a huge low-V anomaly from the CMB to the surface. This feature is consistent with the previous models. We conducted extensive resolution tests in order to understand whether this low-V anomaly shows a single superplume or a plume cluster. Unfortunately this problem is still not resolved because the ray path coverage in the mantle under South Pacific is not good enough. A network of ocean bottom seismometers is necessary to solve this problem. To better understand the whole-mantle structure and dynamics, we also conducted P-wave tomographic inversions for the 3-D velocity structure and azimuthal anisotropy. At each grid node there are three unknown parameters: one represents the isotropic velocity, the other two represent the azimuthal anisotropy. Our results show that in the shallow part of the mantle (fast velocity direction (FVD) is almost the same as the plate motion direction. For example, the FVD in the western Pacific is NWW-SEE, which is normal to the Japan trench axis. In the Tonga subduction zone, the FVD is also perpendicular to the trench axis. Under the Tibetan region the FVD is NE-SW, which is parallel to the direction of the India-Asia collision. In the deeper

  16. Effect of curvature and thickness on elastic wave velocity in cornea-like structures by FEM and OCE

    Science.gov (United States)

    Han, Zhaolong; Li, Jiasong; Singh, Manmohan; Vantipalli, Srilatha; Aglyamov, Salavat R.; Wu, Chen; Liu, Chih-hao; Twa, Michael D.; Larin, Kirill V.

    2016-03-01

    Wave models, which have been utilized in the past to reconstruct corneal biomechanical properties based on the propagation of an elastic wave, were often developed assuming a thin-plate geometry. However, the curvature and thickness of the cornea are not considered when utilizing these models. In this work, optical coherence elastography (OCE) experiments were conducted on tissue-mimicking agar phantoms and contact lenses along with finite element (FE) modeling of four kinds of cornea-like structures to understand the effects of curvature and thickness on the group velocity of an elastic wave. As the radius of curvature increased from 19.1 to 47.7 mm, the group velocity of the elastic wave obtained by both FE and OCE from a spherical shell section model decreased from ~2.8 m/s to ~2.2 m/s. When the thickness of the agar phantom increased from 1.9 mm to 5.6 mm, the elastic wave velocity increased from ~3.0 m/s to ~4.1 m/s. Both the FE and OCE results show that the group velocity of the elastic wave decreased with radius of curvature but increased with thickness. Therefore, the curvature and thickness must be considered when developing accurate wave models for quantifying biomechanical properties of the cornea.

  17. Estimation of seismic velocity in the subducting crust of the Pacific slab beneath Hokkaido, northern Japan by using guided waves

    Science.gov (United States)

    Shiina, T.; Nakajima, J.; Toyokuni, G.; Kita, S.; Matsuzawa, T.

    2014-12-01

    A subducting crust contains a large amount of water as a form of hydrous minerals (e.g., Hacker et al., 2003), and the crust plays important roles for water transportation and seismogenesis in subduction zones at intermediate depths (e.g., Kirby et al., 1996; Iwamori, 2007). Therefore, the investigation of seismic structure in the crust is important to understand ongoing physical processes with subduction of oceanic lithosphere. A guided wave which propagates in the subducting crust is recorded in seismograms at Hokkaido, northern Japan (Shiina et al., 2014). Here, we estimated P- and S-wave velocity in the crust with guided waves, and obtained P-wave velocity of 6.6-7.3 km/s and S-wave velocity of 3.6-4.2 km/s at depths of 50-90 km. Moreover, Vp/Vs ratio in the crust is calculated to be 1.80-1.85 in that depth range. The obtained P-wave velocity about 6.6km/s at depths of 50-70 km is consistent with those estimated in Tohoku, northeast Japan (Shiina et al., 2013), and this the P-wave velocity is lower than those expected from models of subducting crustal compositions, such as metamorphosed MORB model (Hacker et al., 2003). In contrast, at greater depths (>80 km), the P-wave velocity marks higher velocity than the case of NE Japan and the velocity is roughly comparable to those of the MORB model. The obtained S-wave velocity distribution also shows characteristics similar to P waves. This regional variation may be caused by a small variation in thermal regime of the Pacific slab beneath the two regions as a result of the normal subduction in Tohoku and oblique subduction in Hokkaido. In addition, the effect of seismic anisotropy in the subducting crust would not be ruled out because rays used in the analysis in Hokkaido propagate mostly in the trench-parallel direction, while those in Tohoku are sufficiently criss-crossed.

  18. Robust segmentation methods with an application to aortic pulse wave velocity calculation.

    Science.gov (United States)

    Babin, Danilo; Devos, Daniel; Pižurica, Aleksandra; Westenberg, Jos; Vansteenkiste, Ewout; Philips, Wilfried

    2014-04-01

    Aortic stiffness has proven to be an important diagnostic and prognostic factor of many cardiovascular diseases, as well as an estimate of overall cardiovascular health. Pulse wave velocity (PWV) represents a good measure of the aortic stiffness, while the aortic distensibility is used as an aortic elasticity index. Obtaining the PWV and the aortic distensibility from magnetic resonance imaging (MRI) data requires diverse segmentation tasks, namely the extraction of the aortic center line and the segmentation of aortic regions, combined with signal processing methods for the analysis of the pulse wave. In our study non-contrasted MRI images of abdomen were used in healthy volunteers (22 data sets) for the sake of non-invasive analysis and contrasted magnetic resonance (MR) images were used for the aortic examination of Marfan syndrome patients (8 data sets). In this research we present a novel robust segmentation technique for the PWV and aortic distensibility calculation as a complete image processing toolbox. We introduce a novel graph-based method for the centerline extraction of a thoraco-abdominal aorta for the length calculation from 3-D MRI data, robust to artifacts and noise. Moreover, we design a new projection-based segmentation method for transverse aortic region delineation in cardiac magnetic resonance (CMR) images which is robust to high presence of artifacts. Finally, we propose a novel method for analysis of velocity curves in order to obtain pulse wave propagation times. In order to validate the proposed method we compare the obtained results with manually determined aortic centerlines and a region segmentation by an expert, while the results of the PWV measurement were compared to a validated software (LUMC, Leiden, the Netherlands). The obtained results show high correctness and effectiveness of our method for the aortic PWV and distensibility calculation. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. Laser Light Scattering Diagnostic for Measurement of Flow Velocity in Vicinity of Propagating Shock Waves

    Science.gov (United States)

    Seasholtz, Richard G.; Buggele, Alvin E.

    2002-01-01

    A laser light scattering diagnostic for measurement of dynamic flow velocity at a point is described. The instrument is being developed for use in the study of propagating shock waves and detonation waves in pulse detonation engines under development at the NASA Glenn Research Center (GRC). The approach uses a Fabry-Perot interferometer to measure the Doppler shift of laser light scattered from small (submicron) particles in the flow. The high-speed detection system required to resolve the transient response as a shock wave crosses the probe volume uses fast response photodetectors, and a PC based data acquisition system. Preliminary results of measurements made in the GRC Mach 4, 10 by 25 cm supersonic wind tunnel are presented. Spontaneous condensation of water vapor in the flow is used as seed. The tunnel is supplied with continuous air flow at up to 45 psia and the flow is exhausted into the GRC laboratory-wide altitude exhaust system at pressures down to 0.3 psia.

  20. 3D P-Wave Velocity Structure of the Deep Galicia Rifted Margin

    Science.gov (United States)

    Bayrakci, Gaye; Minshull, Timothy; Davy, Richard; Sawyer, Dale; Klaeschen, Dirk; Papenberg, Cord; Reston, Timothy; Shillington, Donna; Ranero, Cesar

    2015-04-01

    The combined wide-angle reflection-refraction and multi-channel seismic (MCS) experiment, Galicia 3D, was carried out in 2013 at the Galicia rifted margin in the northeast Atlantic Ocean, west of Spain. The main geological features within the 64 by 20 km (1280 km²) 3D box investigated by the survey are the peridotite ridge (PR), the fault bounded, rotated basement blocks and the S reflector, which has been interpreted to be a low angle detachment fault. 44 short period four-component ocean bottom seismometers and 28 ocean bottom hydrophones were deployed in the 3D box. 3D MCS profiles sampling the whole box were acquired with two airgun arrays of 3300 cu.in. fired alternately every 37.5 m. We present the results from 3D first-arrival time tomography that constrains the P-wave velocity in the 3D box, for the entire depth sampled by reflection data. Results are validated by synthetic tests and by the comparison with Galicia 3D MCS lines. The main outcomes are as follows: 1- The 3.5 km/s iso-velocity contour mimics the top of the acoustic basement observed on MCS profiles. Block bounding faults are imaged as velocity contrasts and basement blocks exhibit 3D topographic variations. 2- On the southern profiles, the top of the PR rises up to 5.5 km depth whereas, 20 km northward, its basement expression (at 6.5 km depth) nearly disappears. 3- The 6.5 km/s iso-velocity contour matches the topography of the S reflector where the latter is visible on MCS profiles. Within a depth interval of 0.6 km (in average), velocities beneath the S reflector increase from 6.5 km/s to 7 km/s, which would correspond to a decrease in the degree of serpentinization from ~45 % to ~30 % if these velocity variations are caused solely by variations in hydration. At the intersections between the block bounding normal faults and the S reflector, this decrease happens over a larger depth interval (> 1 km), suggesting that faults act as conduit for the water flow in the upper mantle.

  1. Creep of porous rocks and measurements of elastic wave velocities under different hydrous conditions

    Science.gov (United States)

    Eslami, J.; Grgic, D.; Hoxha, D.

    2009-04-01

    The long-term mechanical behavior of rocks is of prime importance for many geological hazards (e.g., landslides, rock falls, and volcanoes) as well as for the stability of man-made structures (underground mines, road cuts, and open pits). In some shallow environments, rocks exist in partially saturated conditions which can evolve with time according to variations in the relative humidity hr of the atmosphere (e.g., natural slopes, open cut excavations). In underground mines, rocks are also partially saturated because of artificial ventilation. These variations in liquid saturation may have a large impact on mechanical behavior since they imply variations in capillary pressure and, depending on the porosity and on the shape of the porous network, variations in the effective stresses. Therefore, knowledge of static fatigue under saturated and partially saturated conditions is important for estimating the long-term stability of such rock structures. Many studies have already shown that time-dependent weakening is much more important for a saturated rock than for a dry one and that the time to failure may decrease by several orders of magnitude for saturated rocks as compared to dry rocks. In addition, the weakening effect of water is more significant in long-term experiments than in short-term ones (instantaneous loading). A physical explanation for these results may be the enhancement of subcritical crack growth by stress corrosion at crack tips which is often considered to be the main cause of time-dependent behavior of rocks. The failure of brittle rocks during compression tests is preceded by the formation, growth, and coalescence of microcracks. Elastic wave velocities are reduced due to the presence of open microcraks and fractures and may be used to monitor the progressive damage of rocks. The specific experimental setup available in our lab allows the simultaneous measurement of five velocities (with different polarizations and directions) and two directions

  2. Calculation Analysis of Pressure Wave Velocity in Gas and Drilling Mud Two-Phase Fluid in Annulus during Drilling Operations

    Directory of Open Access Journals (Sweden)

    Yuanhua Lin

    2013-01-01

    Full Text Available Investigation of propagation characteristics of a pressure wave is of great significance to the solution of the transient pressure problem caused by unsteady operations during management pressure drilling operations. With consideration of the important factors such as virtual mass force, drag force, angular frequency, gas influx rate, pressure, temperature, and well depth, a united wave velocity model has been proposed based on pressure gradient equations in drilling operations, gas-liquid two-fluid model, the gas-drilling mud equations of state, and small perturbation theory. Solved by adopting the Runge-Kutta method, calculation results indicate that the wave velocity and void fraction have different values with respect to well depth. In the annulus, the drop of pressure causes an increase in void fraction along the flow direction. The void fraction increases first slightly and then sharply; correspondingly the wave velocity first gradually decreases and then slightly increases. In general, the wave velocity tends to increase with the increase in back pressure and the decrease of gas influx rate and angular frequency, significantly in low range. Taking the virtual mass force into account, the dispersion characteristic of the pressure wave weakens obviously, especially at the position close to the wellhead.

  3. Insights into anisotropy development and weakening of ice from in situ P wave velocity monitoring during laboratory creep

    Science.gov (United States)

    Vaughan, M. J.; Prior, D. J.; Jefferd, M.; Brantut, N.; Mitchell, T. M.; Seidemann, M.

    2017-09-01

    Polycrystalline ice weakens significantly after a few percent strain, during high homologous temperature deformation. Weakening is correlated broadly with the development of a crystallographic preferred orientation (CPO). We deformed synthetic polycrystalline ice at -5°C under uniaxial compression, while measuring ultrasonic P wave velocities along several raypaths through the sample. Changes in measured P wave velocities (Vp) and in the velocities calculated from microstructural measurements of CPO (by cryo-electron backscatter diffraction) both show that velocities along trajectories parallel and perpendicular to shortening decrease with increasing strain, while velocities on diagonal trajectories increase. Thus, in these experiments, velocity data provide a continuous measurement of CPO evolution in creeping ice. Samples reach peak stresses after 1% shortening. Weakening corresponds to the start of CPO development, as indicated by divergence of P wave velocity changes for different raypaths, and initiates at ≈3% shortening. Selective growth by strain-induced grain boundary migration (GBM) of grains favorably oriented for basal slip may initiate weakening through the formation of an interconnected network of these grains by 3% shortening. After weakening initiates, CPO continues to develop by GBM and nucleation processes. The resultant CPO has an open cone (small circle) configuration, with the cone axis parallel to shortening. The development of this CPO causes significant weakening under uniaxial compression, where the shear stresses resolved on the basal planes (Schmid factors) are high.

  4. P-wave velocity changes in freezing hard low-porosity rocks: a laboratory-based time-average model

    Directory of Open Access Journals (Sweden)

    D. Draebing

    2012-10-01

    Full Text Available P-wave refraction seismics is a key method in permafrost research but its applicability to low-porosity rocks, which constitute alpine rock walls, has been denied in prior studies. These studies explain p-wave velocity changes in freezing rocks exclusively due to changing velocities of pore infill, i.e. water, air and ice. In existing models, no significant velocity increase is expected for low-porosity bedrock. We postulate, that mixing laws apply for high-porosity rocks, but freezing in confined space in low-porosity bedrock also alters physical rock matrix properties. In the laboratory, we measured p-wave velocities of 22 decimetre-large low-porosity (< 10% metamorphic, magmatic and sedimentary rock samples from permafrost sites with a natural texture (> 100 micro-fissures from 25 °C to −15 °C in 0.3 °C increments close to the freezing point. When freezing, p-wave velocity increases by 11–166% perpendicular to cleavage/bedding and equivalent to a matrix velocity increase from 11–200% coincident to an anisotropy decrease in most samples. The expansion of rigid bedrock upon freezing is restricted and ice pressure will increase matrix velocity and decrease anisotropy while changing velocities of the pore infill are insignificant. Here, we present a modified Timur's two-phase-equation implementing changes in matrix velocity dependent on lithology and demonstrate the general applicability of refraction seismics to differentiate frozen and unfrozen low-porosity bedrock.

  5. Ratio of left ventricular peak E-wave velocity to flow propagation velocity assessed by color M-mode Doppler echocardiography in first myocardial infarction

    DEFF Research Database (Denmark)

    Møller, J E; Søndergaard, E; Seward, J B

    2000-01-01

    OBJECTIVES: To determine the ability of the ratio of peak E-wave velocity to flow propagation velocity (E/Vp) measured with color M-mode Doppler echocardiography to predict in-hospital heart failure and cardiac mortality in an unselected consecutive population with first myocardial infarction (MI......). BACKGROUND: Several experimental studies indicate color M-mode echocardiography to be a valuable tool in the evaluation of diastolic function, but data regarding the clinical value are lacking. METHODS: Echocardiography was performed within 24 h of arrival at the coronary care unit in 110 consecutive...... compared with patients with E/Vp or =1.5 to be the single best predictor of in-hospital clinical heart failure when compared with age, heart rate, E-wave deceleration time (Dt), left ventricular (LV) ejection fraction, wall...

  6. High resolution wireless body area network with statistically synchronized sensor data for tracking pulse wave velocity.

    Science.gov (United States)

    Li, Kejia; Warren, Steve

    2012-01-01

    Wireless body area networks (WBANs) will take on more diverse forms in terms of their sensor combinations and communication protocols as their presence is extended to a greater number of monitoring scenarios. This paper presents an application layer protocol that solves issues caused by sensor nodes that must compete for high speed, real-time communication with the receiver. Such applications emphasize the delivery of large amounts of raw data from different sensor nodes in a time-synchronized manner, rather than channels that experience intermittent operation. An example of tracking pulse wave velocity (PWV) is introduced in this paper, where high-precision PWVs are estimated with the help of timeline recovery and feature extraction processes in MATLAB.

  7. Relations between diabetes, blood pressure and aortic pulse wave velocity in haemodialysis patients

    DEFF Research Database (Denmark)

    Peters, Christian Daugaard; Kjærgaard, Krista Dybtved; Dzeko, Mirela

    Diabetes (DM) is common in haemodialysis (HD) patients and affects both blood pressure (BP) and arterial stiffness. Carotid femoral pulse wave velocity (PWV) reflects the stiffness of the aorta and is regarded as a strong risk factor for cardiovascular (CV) mortality in HD patients. However, PWV...... (HD) and 32 HD patients with DM (HD+DM). The SphygmoCor system was used for estimation of PWV. HD-duration, age, gender and BP medication were similar in the two groups. Mean DM-duration was 23±11 years and 25(78%) had type 2 DM. HD+DM had higher BMI (26±5 vs. 29±5 kg/m2, p=0.02), systolic BP (142......±20 vs. 152±21 mmHg, p=0.02) and pulse pressure (65±17 vs. 80±18 mmHg, p

  8. Blood pressure and pulse wave velocity as metrics for evaluating pathologic ageing of the cardiovascular system.

    Science.gov (United States)

    Nilsson, Peter M; Khalili, Payam; Franklin, Stanley S

    2014-02-01

    The influence of chronological ageing on the components of the cardiovascular system is of fundamental importance for understanding how hemodynamics change and the cardiovascular risk increases with age, the most important risk marker. An increase in peripheral vascular resistance associated with increased stiffness of central elastic arteries represents hallmarks of this ageing effect on the vasculature, referred to as early vascular ageing (EVA). In clinical practice, it translates into increased brachial and central systolic blood pressure and corresponding pulse pressure in subjects above 50 years of age, as well as increased carotid-femoral pulse wave velocity (c-f PWV)--a marker of arterial stiffness. A c-f PWV value ≥ 10 m/s is threshold for increased risk according. Improved lifestyle and control of risk factors via appropriate drug therapy are of importance in providing vascular protection related to EVA. One target group might be members of risk families including subjects with early onset cardiovascular disease.

  9. Upper-mantle P- and S- wave velocities across the Northern Tornquist Zone from traveltime tomography

    DEFF Research Database (Denmark)

    Hejrani, Babak; Balling, N.; Jacobsen, B. H.

    2015-01-01

    This study presents P- and S-wave velocity variations for the upper mantle in southern Scandinavia and northern Germany based on teleseismic traveltime tomography. Tectonically, this region includes the entire northern part of the prominent Tornquist Zone which follows along the transition from old...... Precambrian shield units to the east to younger Phanerozoic deep sedimentary basins to the southwest. We combine data from several separate temporary arrays/profiles (276 stations) deployed over a period of about 15 yr and permanent networks (31 stations) covering the areas of Denmark, northern Germany......, southern Sweden and southern Norway. By performing an integrated P- and S-traveltime analysis, we obtain the first high-resolution combined 3-D VP and VS models, including variations in the VP/VS ratio, for the whole of this region of study. Relative station mean traveltime residuals vary within ±1 s for P...

  10. Quantitative Assessment of In-situ Salt Karstification Using Shear Wave Velocity, Dead Sea

    Science.gov (United States)

    Ezersky, Michael; Legchenko, Anatoly

    2014-09-01

    The Dead Sea (DS) coastal areas have been dramatically affected by sinkhole formation since around 1990. Such sinkholes along both Israeli and Jordanian shores are linked to karst cavities that form through slow salt dissolution. A quantitative estimate of such in-situ salt karstification would be an important indicator of sinkhole hazard. One of the indications of salt karstification is its increased hydraulic conductivity, caused by the development of dissolution cavities forming conducting channels within the salt layer. We measured the hydraulic conductivity (K) versus shear-wave velocity (Vs) of DS salt in situ for estimating the actual salt karstification in areas of sinkhole development. These parameters were measured with the Magnetic Resonance Sounding (MRS) and Multichannel Analysis of Surface Waves (MASW) methods, respectively. Understanding of the field relationships was augmented by similar inter-relations obtained in the laboratory on samples of DS salt. In-situ salt velocities Vs vary from 750 m/s to over 1650 m/s, while hydraulic conductivity (K) in the same zones varies between about 10- 4 m/s to slightly over 10- 8 m/s. Both field and laboratory K and Vs values fit the exponential function ln(K) = - 0.0045 ∗ Vs - 5.416 with a determination coefficient (R2) of 0.88. A classification based on Vs and K was generated for salt conditions and the corresponding degrees of sinkhole hazard, which was verified in the Mineral Beach sinkhole development area. The mapping of sinkhole sites shows that they form within highly conductive zones with K ≥ 5.5 ∗ 10- 5. It is suggested that this methodology, with some modification, can be used for evaluating the conductive properties of karstified rock and associated sinkhole hazards.

  11. Role of birth weight and postnatal growth on pulse wave velocity in teenagers.

    Science.gov (United States)

    Salvi, Paolo; Revera, Miriam; Joly, Laure; Reusz, George; Iaia, Maurizio; Benkhedda, Salim; Chibane, Ahcene; Parati, Gianfranco; Benetos, Athanase; Temmar, Mohamed

    2012-10-01

    Low birth weight and accelerated postnatal growth appear to play a significant role in the pathogenesis of hypertension and cardiovascular disease in adulthood. The aim of the present study was to characterize the factors determining pulse wave velocity (PWV) in teenagers and, in particular, to verify the relationship with birth weight, postnatal growth, timing of adiposity rebound, lifestyle, and hemodynamic parameters. Carotid-femoral and carotid-radial pulse wave velocities of 558 healthy teenagers (age range: 16.2-19.9 years) were determined by means of a PulsePen tonometer. Birth weight and gestational age were obtained from obstetrical records, and data regarding postnatal growth were obtained from pediatric clinical records. No change in aortic PWV was found in association with birth weight, postnatal growth, and timing of adiposity rebound. However, the study showed a strong association between accelerated growth from 0 to 12 months and carotid-radial PWV (trend: p = .02). Subjects with birth weight values <2,500 g showed higher values of upper limb PWV (p < .05) and higher values of diastolic and mean arterial pressure (p < .05). Stepwise regression analysis revealed that mean arterial pressure, age, and height were the main independent factors determining aortic PWV in this young population. These results suggest that there is no linear correlation between birth weight and hemodynamic parameters in teenagers; however, subjects characterized by very low birth weight and accelerated postnatal weight gain appear to demonstrate increased upper limb PWV and diastolic and mean arterial pressure values. Copyright © 2012 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

  12. Aortic distensibility measured by pulse-wave velocity is not modified in patients with Chagas' disease

    Directory of Open Access Journals (Sweden)

    Arteaga Edmundo

    2006-06-01

    Full Text Available Abstract Background Experimental studies demonstrate that infection with trypanosoma cruzi causes vasculitis. The inflammatory lesion process could hypothetically lead to decreased distensibility of large and small arteries in advanced Chagas' disease. We tested this hypothesis. Methods and results We evaluated carotid-femoral pulse-wave velocity (PWV in 53 Chagas' disease patients compared with 31 healthy volunteers (control group. The 53 patients were classified into 3 groups: 1 16 with indeterminate form of Chagas' disease; 2 18 with Chagas' disease, electrocardiographic abnormalities, and normal systolic function; 3 19 with Chagas' disease, systolic dysfunction, and mild-to-moderate congestive heart failure. No difference was noted between the 4 groups regarding carotid-femoral PWV (8.4 ± 1.1 vs 8.2 ± 1.5 vs 8.2 ± 1.4 vs 8.7 ± 1.6 m/s, P = 0.6 or pulse pressure (39.5 ± 7.6 vs 39.3 ± 8.1 vs 39.5 ± 7.4 vs 39.7 ± 6.9 mm Hg, P = 0.9. A positive, significant, similar correlation occurred between PWV and age in patients with Chagas' disease (r = 0.42, P = 0.002, in controls (r = 0.48, P = 0.006, and also between PWV and systolic blood pressure in both groups (patients with Chagas' disease, r = 0.38, P = 0.005; healthy subjects, r = 0.36, P = 0.043. Conclusion Carotid femoral pulse-wave velocity is not modified in patients with Chagas' disease, suggesting that elastic properties of large arteries are not affected in this disorder.

  13. Numerical assessment and comparison of pulse wave velocity methods aiming at measuring aortic stiffness.

    Science.gov (United States)

    Obeid, Hasan; Soulat, Gilles; Mousseaux, Elie; Laurent, Stéphane; Stergiopulos, Nikos; Boutouyrie, Pierre; Segers, Patrick

    2017-10-31

    Pulse waveform analyses have become established components of cardiovascular research. Recently several methods have been proposed as tools to measure aortic pulse wave velocity (aPWV). The carotid-femoral pulse wave velocity (cf-PWV), the current clinical gold standard method for the noninvasive assessment of aPWV, uses the carotid-to-femoral pulse transit time difference (cf-PTT) and an estimated path length to derive cf-PWV. The heart-ankle PWV (ha-PWV), brachial-ankle PWV (ba-PWV) and finger-toe (ft-PWV) are also methods presuming to approximate aPWV based on time delays between physiological cardiovascular signals at two locations (~heart-ankle PTT, ha-PTT; ~brachial-ankle PTT, ba-PTT; ~finger-toe PTT, ft-PTT) and a path length typically derived from the subject's height. To test the validity of these methods, we used a detailed 1D arterial network model (143 arterial segments) including the foot and hand circulation. The arterial tree dimensions and properties were taken from the literature and completed with data from patient scans. We calculated PTTs with all the methods mentioned above. The calculated PTTs were compared with the aortic PTT (aPTT), which is considered as the absolute reference method in this study. The correlation between methods and aPTT was good and significant, cf-PTT (R 2  =  0.97; P  methods, but absolute values differed because of the different path lengths used. In conclusion, our computer model-based analyses demonstrate that for PWV methods based on peripheral signals, pulse transit time differences closely correlate with the aortic transit time, supporting the use of these methods in clinical practice.

  14. Arterial pulse wave velocity, inflammatory markers, pathological GH and IGF states, cardiovascular and cerebrovascular disease

    Directory of Open Access Journals (Sweden)

    Michael R Graham

    2008-12-01

    Full Text Available Michael R Graham1, Peter Evans2, Bruce Davies1, Julien S Baker11Health and Exercise Science Research Unit, Faculty of Health Sport and Science, University of Glamorgan, Pontypridd, Wales, United Kingdom; 2Royal Gwent Hospital, Newport, Gwent, United KingdomAbstract: Blood pressure (BP measurements provide information regarding risk factors associated with cardiovascular disease, but only in a specific artery. Arterial stiffness (AS can be determined by measurement of arterial pulse wave velocity (APWV. Separate from any role as a surrogate marker, AS is an important determinant of pulse pressure, left ventricular function and coronary artery perfusion pressure. Proximal elastic arteries and peripheral muscular arteries respond differently to aging and to medication. Endogenous human growth hormone (hGH, secreted by the anterior pituitary, peaks during early adulthood, declining at 14% per decade. Levels of insulin-like growth factor-I (IGF-I are at their peak during late adolescence and decline throughout adulthood, mirror imaging GH. Arterial endothelial dysfunction, an accepted cause of increased APWV in GH deficiency (GHD is reversed by recombinant human (rh GH therapy, favorably influencing the risk for atherogenesis. APWV is a noninvasive method for measuring atherosclerotic and hypertensive vascular changes increases with age and atherosclerosis leading to increased systolic blood pressure and increased left ventricular hypertrophy. Aerobic exercise training increases arterial compliance and reduces systolic blood pressure. Whole body arterial compliance is lowered in strength-trained individuals. Homocysteine and C-reactive protein are two infl ammatory markers directly linked with arterial endothelial dysfunction. Reviews of GH in the somatopause have not been favorable and side effects of treatment have marred its use except in classical GHD. Is it possible that we should be assessing the combined effects of therapy with rhGH and rh

  15. Evaluation of Different CH4-CO2 Replacement Processes in Hydrate-Bearing Sediments by Measuring P-Wave Velocity

    Directory of Open Access Journals (Sweden)

    Bei Liu

    2013-11-01

    Full Text Available The replacement of methane with carbon dioxide in natural gas hydrate-bearing sediments is considered a promising technology for simultaneously recovering natural gas and entrapping CO2. During the CH4-CO2 replacement process, the variations of geophysical property of the hydrate reservoir need to be adequately known. Since the acoustic wave velocity is an important geophysical property, in this work, the variations of P-wave velocity of hydrate-bearing sediments were measured during different CH4-CO2 replacement processes using pure gaseous CO2 and CO2/N2 gas mixtures. Our experimental results show that P-wave velocity continually decreased during all replacement processes. Compared with injecting pure gaseous CO2, injection of CO2/N2 mixture can promote the replacement process, however, it is found that the sediment experiences a loss of stiffness during the replacement process, especially when using CO2/N2 gas mixtures.

  16. The Study on S-Wave Velocity Structure of Upper Crust in Three Gorges Region of Yangtze River

    Science.gov (United States)

    Li, X.; Zhu, P.; Zhou, Q.

    2014-12-01

    The profile of S-wave velocity structure along Badong-Maoping-Tumen is presented using the ambient noise data observed at 10 stations from mobile broadband seismic array which is located at Three Gorges Region. All of available vertical component time series during April and May,2011 have been cross-correlated to estimate the empirical Green functions. Group velocity dispersion curves were measured by applying multiple filtering technique. Using these dispersion curves,we obtain high resolution pure-path dispersions at 0.5-10 second periods. The S-wave velocity structure,which was reconstructed by inverting the pure-path dispersions,reveals the velocity variations of upper crust at Three Gorges Region. Main conclusions are as follows:(1)The velocity variations in the study region have a close relationship with the geological structure and the velocity profile suggests a anticline unit which core area is Huangling block;(2)The relative fast velocity variations beneath Jiuwanxi and its surrounding areas may correspond to the geological structure and earthquake activity there;(3) The high velocity of the upper crustal in Sandouping indicates that the Reservoir Dam of Three Gorges is located at a tectonic stable region.

  17. Independent association between brachial-ankle pulse wave velocity and global longitudinal strain of left ventricle.

    Science.gov (United States)

    Kim, Hack-Lyoung; Seo, Jae-Bin; Chung, Woo-Young; Kim, Sang-Hyun; Kim, Myung-A; Zo, Joo-Hee

    2015-12-01

    Data regarding the influence of arterial stiffness on left ventricular (LV) long-axis function has been scarce. This study was performed to investigate the association between brachial-ankle pulse wave velocity (baPWV) and LV global longitudinal strain (GLS). A total of 248 subjects (mean age 59.2 ± 12.3 years; 50% were men) without structural heart problems were retrospectively evaluated. LV GLS was measured by 2-dimensional speckle-tracking echocardiography. baPWV measurements were made on the same day of echocardiography. The incidences of hypertension, diabetes mellitus, and dyslipidemia were 51.2, 19.4, and 22.2%, respectively. The mean value of baPWV was 1557 ± 285 cm/s. In simple linear regression analysis, baPWV had a significant positive association with LV GLS (β = 0.215, P = 0.001). In multiple linear regression analysis, baPWV was independently associated with LV GLS even after controlling for potential confounders, including age, gender, body mass index, systolic blood pressure, heart rate, HbA1c, total cholesterol, estimated glomerular filtration rate, left ventricular mass index, E/A, septal e' velocity and pulmonary artery systolic pressure (β = 0.211, P = 0.028). The results of this study suggest that baPWV may be independently associated with LV GLS, supporting the evidence of a close interaction between arterial stiffness and LV function. Increased arterial stiffness may result in impaired LV longitudinal function.

  18. P-wave velocity anisotropy related to sealed fractures reactivation tracing the structural diagenesis in carbonates

    Science.gov (United States)

    Matonti, C.; Guglielmi, Y.; Viseur, S.; Garambois, S.; Marié, L.

    2017-05-01

    Fracture properties are important in carbonate reservoir characterization, as they are responsible for a large part of the fluid transfer properties at all scales. It is especially true in tight rocks where the matrix transfer properties only slightly contribute to the fluid flow. Open fractures are known to strongly affect seismic velocities, amplitudes and anisotropy. Here, we explore the impact of fracture evolution on the geophysical signature and directional Vp anisotropy of fractured carbonates through diagenesis. For that purpose, we studied a meter-scale, parallelepiped quarry block of limestone using a detailed structural and diagenetic characterization, and numerous Vp measurements. The block is affected by two en-échelon fracture clusters, both being formed in opening mode (mode 1) and cemented, but only one being reactivated in shear. We compared the diagenetic evolution of the fractures, which are almost all 100% filled with successive calcite cements, with the P-wave velocities measured across this meter-scale block of carbonate, which recorded the tectonic and diagenetic changes of a South Provence sedimentary basin. We found that a directional Vp anisotropy magnitude as high as 8-16% correlates with the reactivated fractures' cluster dip angle, which is explained by the complex filling sequence and softer material present inside the fractures that have been reactivated during the basin's tectonic inversion. We show that although a late karstification phase preferentially affected these reactivated fractures, it only amplified the pre-existing anisotropy due to tectonic shear. We conclude that Vp anisotropy measurements may help to identify the fracture sealing/opening processes associated with polyphased tectonic history, the anisotropy being independent of the current stress-state. This case shows that velocity anisotropies induced by fractures resulted here from a cause that is different from how these features have often been interpreted

  19. Ultrasonic measurements of the elastic wave velocities of peridotite KLB-1 at mantle P and T

    Science.gov (United States)

    Wang, X.; Liu, W.; Herzberg, C. T.; Li, B.

    2012-12-01

    In situ measurements of sound velocities and densities on individual phases of Earth minerals at high pressure and temperature have provided important data to interpret the seismic structure at depths. When using these data to test compositional models of the mantle (e.g., pyrolite and piclogite), seismic properties of the mineralogical aggregates have to be calculated by using averaging schemes based on the proportion and elasticity of each phase. More importantly, the chemical interactions among various mantle phases are difficult to be accurately included. Since the composition of peridotite KLB-1 closely matches the composition of pyrolite, measurement of it's velocities at relevant mantle conditions will provide the most direct comparison with seismic data. In this study, well-sintered KLB-1 aggregates suitable for ultrasonic measurements were hot-pressed at various P-T conditions up to those of the transition zone. The recovered samples were characterized by X-ray diffraction, optical, and scanning electron microscopy (SEM) and found to be uniform in grain size (around 10 micron), free of macrocracks and to have bulk densities close to theoretical values (small amount of pores/microcracks observable in SEM scale). P and S wave velocities have been accurately measured up to 7 GPa and 800°C using a combined ultrasonic and X-radiation technique with direct measurement of sample length at high P and T. The success of this experiment makes it possible to extend these measurements to the conditions of the transition zone on aggregate samples to directly discriminate the composition of the Earth's mantle.

  20. Shallow P- and S-wave velocities and site resonances in the St. Louis region, Missouri-Illinois

    Science.gov (United States)

    Williams, R.A.; Odum, J.K.; Stephenson, W.J.; Herrmann, Robert B.

    2007-01-01

    As part of the seismic hazard-mapping efforts in the St. Louis metropolitan area we determined the compressional and shear-wave velocities (Vp and Vs) to about a 40-m depth at 17 locations in this area. The Vs measurements were made using high-resolution seismic refraction and reflection methods. We find a clear difference in the Vs profiles between sites located on the river floodplains and those located in the upland urban areas of St. Louis. Vs30 (average Vs to 30-m depth) values in floodplain areas range from 200 to 290 m/s (NEHRP category D) and contrast with sites on the upland areas of St. Louis, which have Vs30 values ranging from 410 to 785 m/s (NEHRP categories C and B). The lower Vs30 values and earthquake recordings in the floodplains suggest a greater potential for stronger and more prolonged ground shaking in an earthquake. Spectral analysis of a M3.6 earthquake recorded on the St. Louis-area ANSS seismograph network indicates stronger shaking and potentially damaging S-wave resonant frequencies at NEHRP category D sites compared to ground motions at a rock site located on the Saint Louis University campus. ?? 2007, Earthquake Engineering Research Institute.

  1. On the estimation of total arterial compliance from aortic pulse wave velocity.

    Science.gov (United States)

    Vardoulis, Orestis; Papaioannou, Theodore G; Stergiopulos, Nikolaos

    2012-12-01

    Total arterial compliance (C(T)) is a main determinant of cardiac afterload, left ventricular function and arterio-ventricular coupling. C(T) is physiologically more relevant than regional aortic stiffness. However, direct, in vivo, non-invasive, measurement of C(T) is not feasible. Several methods for indirect C(T) estimation require simultaneous recording of aortic flow and pressure waves, limiting C(T) assessment in clinical practice. In contrast, aortic pulse wave velocity (aPWV) measurement, which is considered as the "gold standard" method to assess arterial stiffness, is noninvasive and relatively easy. Our aim was to establish the relation between aPWV and C(T). In total, 1000 different hemodynamic cases were simulated, by altering heart rate, compliance, resistance and geometry using an accurate, distributed, nonlinear, one-dimensional model of the arterial tree. Based on Bramwell-Hill theory, the formula C(T) = k • aPWV(-2) was found to accurately estimate C(T) from aPWV. Coefficient k was determined both analytically and by fitting C(T) vs. aPWV data. C(T) estimation may provide an additional tool for cardiovascular risk (CV) assessment and better management of CV diseases. C(T) could have greater impact in assessing elderly population or subjects with elevated arterial stiffness, where aPWV seem to have limited prognostic value. Further clinical studies should be performed to validate the formula in vivo.

  2. Pulse wave velocity is associated with cognitive impairment in hemodialysis patients.

    Science.gov (United States)

    Angermann, Susanne; Baumann, Marcus; Wassertheurer, Siegfried; Mayer, Christopher Clemens; Steubl, Dominik; Hauser, Christine; Suttmann, Yana; Reichelt, Anna-Lena; Satanovskij, Robin; Lorenz, Georg; Lukas, Moritz; Haller, Bernhard; Heemann, Uwe; Grimmer, Timo; Schmaderer, Christoph

    2017-07-01

    Cognitive impairment in hemodialysis patients is common and associated with adverse outcomes. So far, the underlying pathogenesis remains unclear. Therefore, we examined the potential relationship between cognitive impairment and three different categories of risk factors with particular focus on arterial stiffness measured by pulse wave velocity (PWV). A total of 201 chronic hemodialysis patients underwent cognitive testing under standardized conditions using the Montreal Cognitive Assessment (MoCA). Demographic data including cardiovascular risk factors, dialysis-associated factors as well as factors related to chronic kidney disease (CKD) were analyzed. To account for arterial stiffness, PWV was measured by ambulatory blood pressure monitoried with an oscillometric device that records brachial blood pressure along with pulse waves. In our cohort, 60.2% of patients showed pathological MoCA test results indicating cognitive impairment. PWV was significantly associated with cognitive impairment apart from age, educational level, diabetes, and hypercholesterolemia. High prevalence of cognitive impairment in hemodialysis patients was confirmed. For the first time, an association between cognitive impairment and arterial stiffness was detected in a larger cohort of hemodialysis patients. Concerning the underlying pathogenesis of cognitive impairment, current results revealed a potential involvement of arterial stiffness, which has to be further evaluated in future studies. © 2017 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.

  3. Seismic Velocity Structure and Depth-Dependence of Anisotropy in the Red Sea and Arabian Shield from Surface Wave Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, S; Gaherty, J; Schwartz, S; Rodgers, A; Al-Amri, A

    2007-07-25

    We investigate the lithospheric and upper mantle structure as well as the depth-dependence of anisotropy along the Red Sea and beneath the Arabian Peninsula using receiver function constraints and phase velocities of surface waves traversing two transects of stations from the Saudi Arabian National Digital Seismic Network. Frequency-dependent phase delays of fundamental-mode Love and Rayleigh waves, measured using a cross-correlation procedure, require very slow shear velocities and the presence of anisotropy throughout the upper mantle. Linearized inversion of these data produce path-averaged 1D radially anisotropic models with about 4% anisotropy in the lithosphere, increasing to about 4.8% anisotropy across the lithosphere-asthenosphere boundary (LAB). Models with reasonable crustal velocities in which the mantle lithosphere is isotropic cannot satisfy the data. The lithospheric lid, which ranges in thickness from about 70 km near the Red Sea coast to about 90 km beneath the Arabian Shield, is underlain by a pronounced low-velocity zone with shear velocities as low as 4.1 km/s. Forward models, which are constructed from previously determined shear-wave splitting estimates, can reconcile surface and body wave observations of anisotropy. The low shear velocity values are similar to many other continental rift and oceanic ridge environments. These low velocities combined with the sharp velocity contrast across the LAB may indicate the presence of partial melt beneath Arabia. The anisotropic signature primarily reflects a combination of plate- and density-driven flow associated with active rifting processes in the Red Sea.

  4. Stereoscopy of dust density waves under microgravity: Velocity distributions and phase-resolved single-particle analysis

    Energy Technology Data Exchange (ETDEWEB)

    Himpel, Michael, E-mail: himpel@physik.uni-greifswald.de; Killer, Carsten; Melzer, André [Institute of Physics, Ernst-Moritz-Arndt-University, 17489 Greifswald (Germany); Bockwoldt, Tim; Piel, Alexander [IEAP, Christian-Albrechts-Universität Kiel, D-24098 Kiel (Germany); Ole Menzel, Kristoffer [ABB Switzerland Ltd, Corporate Research Center, 5405 Dättwil (Switzerland)

    2014-03-15

    Experiments on dust-density waves have been performed in dusty plasmas under the microgravity conditions of parabolic flights. Three-dimensional measurements of a dust density wave on a single particle level are presented. The dust particles have been tracked for many oscillation periods. A Hilbert analysis is applied to obtain trajectory parameters such as oscillation amplitude and three-dimensional velocity amplitude. While the transverse motion is found to be thermal, the velocity distribution in wave propagation direction can be explained by harmonic oscillations with added Gaussian (thermal) noise. Additionally, it is shown that the wave properties can be reconstructed by means of a pseudo-stroboscopic approach. Finally, the energy dissipation mechanism from the kinetic oscillation energy to thermal motion is discussed and presented using phase-resolved analysis.

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

    Science.gov (United States)

    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 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

  6. Measurement of regional pulse wave velocity using very high frame rate ultrasound.

    Science.gov (United States)

    Hasegawa, Hideyuki; Hongo, Kazue; Kanai, Hiroshi

    2013-04-01

    Pulse wave velocity (PWV) is the propagation velocity of the pressure wave along the artery due to the heartbeat. The PWV becomes faster with progression of arteriosclerosis and, thus, can be used as a diagnostic index of arteriosclerosis. Measurement of PWV is known as a noninvasive approach for diagnosis of arteriosclerosis and is widely used in clinical situations. In the traditional PWV method, the average PWV is calculated between two points, the carotid and femoral arteries, at an interval of several tens of centimeters. However, PWV depends on part of the arterial tree, i.e., PWVs in the distal arteries are faster than those in the proximal arteries. Therefore, measurement of regional PWV is preferable. To evaluate regional PWV in the present study, the minute vibration velocity of the human carotid arterial wall was measured at intervals of 0.2 mm at 72 points in the arterial longitudinal direction by the phased-tracking method at a high temporal resolution of 3472 Hz, and PWV was estimated by applying the Hilbert transform to those waveforms. In the present study, carotid arteries of three healthy subjects were measured in vivo. The PWVs in short segments of 14.4 mm in the arterial longitudinal direction were estimated to be 5.6, 6.4, and 6.7 m/s, which were in good agreement with those reported in the literature. Furthermore, for one of the subjects, a component was clearly found propagating from the periphery to the direction of the heart, i.e., a well known component reflected by the peripheral arteries. By using the proposed method, the propagation speed of the reflection component was also separately estimated to be -8.4 m/s. The higher magnitude of PWV for the reflection component was considered to be the difference in blood pressure at the arrivals of the forward and reflection components. Such a method would be useful for more sensitive evaluation of the change in elasticity due to progression of arteriosclerosis by measuring the regional PWV

  7. The association between pulse wave velocity and cognitive function: the Sydney Memory and Ageing Study.

    Directory of Open Access Journals (Sweden)

    Joel Singer

    Full Text Available OBJECTIVES: Pulse wave velocity (PWV is a measure of arterial stiffness and its increase with ageing has been associated with damage to cerebral microvessels and cognitive impairment. This study examined the relationship between carotid-femoral PWV and specific domains of cognitive function in a non-demented elderly sample. METHOD: Data were drawn from the Sydney Memory and Ageing Study, a cohort study of non-demented community-dwelling individuals aged 70-90 years, assessed in successive waves two years apart. In Wave 2, PWV and cognitive function were measured in 319 participants. Linear regression was used to analyse the cross-sectional relationship between arterial stiffness and cognitive function in the whole sample, and separately for men and women. Analysis of covariance was used to assess potential differences in cognition between subjects with PWV measurements in the top and bottom tertiles of the cohort. Covariates were age, education, body mass index, pulse rate, systolic blood pressure, cholesterol, depression, alcohol, smoking, hormone replacement therapy, apolipoprotein E ε4 genotype, use of anti-hypertensive medications, history of stroke, transient ischemic attack, myocardial infarction, angina, diabetes, and also sex for the whole sample analyses. RESULTS: There was no association between PWV and cognition after Bonferroni correction for multiple testing. When examining this association for males and females separately, an association was found in males, with higher PWV being associated with lower global cognition and memory, however, a significant difference between PWV and cognition between males and females was not found. CONCLUSION: A higher level of PWV was not associated with lower cognitive function in the whole sample.

  8. Feasibility of pulse wave velocity estimation from low frame rate US sequences in vivo

    Science.gov (United States)

    Zontak, Maria; Bruce, Matthew; Hippke, Michelle; Schwartz, Alan; O'Donnell, Matthew

    2017-03-01

    The pulse wave velocity (PWV) is considered one of the most important clinical parameters to evaluate CV risk, vascular adaptation, etc. There has been substantial work attempting to measure the PWV in peripheral vessels using ultrasound (US). This paper presents a fully automatic algorithm for PWV estimation from the human carotid using US sequences acquired with a Logic E9 scanner (modified for RF data capture) and a 9L probe. Our algorithm samples the pressure wave in time by tracking wall displacements over the sequence, and estimates the PWV by calculating the temporal shift between two sampled waves at two distinct locations. Several recent studies have utilized similar ideas along with speckle tracking tools and high frame rate (above 1 KHz) sequences to estimate the PWV. To explore PWV estimation in a more typical clinical setting, we used focused-beam scanning, which yields relatively low frame rates and small fields of view (e.g., 200 Hz for 16.7 mm filed of view). For our application, a 200 Hz frame rate is low. In particular, the sub-frame temporal accuracy required for PWV estimation between locations 16.7 mm apart, ranges from 0.82 of a frame for 4m/s, to 0.33 for 10m/s. When the distance is further reduced (to 0.28 mm between two beams), the sub-frame precision is in parts per thousand (ppt) of the frame (5 ppt for 10m/s). As such, the contributions of our algorithm and this paper are: 1. Ability to work with low frame-rate ( 200Hz) and decreased lateral field of view. 2. Fully automatic segmentation of the wall intima (using raw RF images). 3. Collaborative Speckle Tracking of 2D axial and lateral carotid wall motion. 4. Outlier robust PWV calculation from multiple votes using RANSAC. 5. Algorithm evaluation on volunteers of different ages and health conditions.

  9. Shear wave velocities in deformed Al-stishovite and seismic heterogeneities in the mid-mantle

    Science.gov (United States)

    Sanchez-Valle, C.; Rosa, A. D.; Bolfan-Casanova, N.; Evans, S.; Merkel, S.

    2012-12-01

    Seismic observations show extensive evidence for negative shear wave anomalies of 2 to 6% in the shallow to middle parts of the lower mantle (800 to 1850 km depths) in the vicinity of subduction zones [e.g., 1-4]. Although the origin of these anomalies is still under debate, shear softening related to the stishovite (rutile structure) to post-stishovite (CaCl2 structure) in subducted MORB may be a plausible explanation for these features [5]. The broad range of depths over which the heterogeneities span may be related to compositional effects on the transition pressure [5,6]. To better deciphering the observed seismic heterogeneities, a more detailed evaluation of the seismic properties of deformed stishovite due to mantle flow is required. In this contribution, we report investigations of the effect of texture development on the shear wave velocities of Al-bearing stishovite containing 5wt% of Al2O3, a plausible composition for subducted slabs. Experiments were conducted using synchrotron radial x-ray diffraction at ESRF ID09A and a panoramic diamond anvil cell as deformation apparatus. The samples were synthesized at 20 GPa and 1700 °C in a multianvil apparatus. The recovered Al-Stishovite crystals were reduced to fine-grained powders and loaded in x-ray transparent boron gaskets for experiments up to 50 GPa. Upon compression, changes in the texture are observed across the stishovite to post-stishovite transition. The results from the deformation experiments are used with available elasticity data obtained by Brillouin scattering spectroscopy in similar samples [5] to evaluate the effect of texture on the shear wave anomalies in stishovite. Ultimately, the implications of these results for the interpretation of seismic heterogeneities in the mid-mantle will be discussed. [1] Stunff et al., (1995); [2]Kaneshima and Helffrich (1999); [3] Vinnik et al., (2001); [4] Niu et al., (2003); [5] Lakshtanov et al., (2007); [6] Nomura et al. [2010].

  10. Liquefaction assessment based on combined use of CPT and shear wave velocity measurements

    Science.gov (United States)

    Bán, Zoltán; Mahler, András; Győri, Erzsébet

    2017-04-01

    Soil liquefaction is one of the most devastating secondary effects of earthquakes and can cause significant damage in built infrastructure. For this reason liquefaction hazard shall be considered in all regions where moderate-to-high seismic activity encounters with saturated, loose, granular soil deposits. Several approaches exist to take into account this hazard, from which the in-situ test based empirical methods are the most commonly used in practice. These methods are generally based on the results of CPT, SPT or shear wave velocity measurements. In more complex or high risk projects CPT and VS measurement are often performed at the same location commonly in the form of seismic CPT. Furthermore, VS profile determined by surface wave methods can also supplement the standard CPT measurement. However, combined use of both in-situ indices in one single empirical method is limited. For this reason, the goal of this research was to develop such an empirical method within the framework of simplified empirical procedures where the results of CPT and VS measurements are used in parallel and can supplement each other. The combination of two in-situ indices, a small strain property measurement with a large strain measurement, can reduce uncertainty of empirical methods. In the first step by careful reviewing of the already existing liquefaction case history databases, sites were selected where the records of both CPT and VS measurement are available. After implementing the necessary corrections on the gathered 98 case histories with respect to fines content, overburden pressure and magnitude, a logistic regression was performed to obtain the probability contours of liquefaction occurrence. Logistic regression is often used to explore the relationship between a binary response and a set of explanatory variables. The occurrence or absence of liquefaction can be considered as binary outcome and the equivalent clean sand value of normalized overburden corrected cone tip

  11. A lithospheric velocity model for the flat slab region of Argentina from joint inversion of Rayleigh wave phase velocity dispersion and teleseismic receiver functions

    Science.gov (United States)

    Ammirati, Jean-Baptiste; Alvarado, Patricia; Beck, Susan

    2015-07-01

    In the central Andes, the Nazca plate displays large along strike variations in dip with a near horizontal subduction angle between 28 and 32°S referred to the Pampean flat slab segment. The upper plate above the Pampean flat slab has high rates of crustal seismicity and active basement cored uplifts. The SIEMBRA experiment, a 43-broad-band-seismic-station array was deployed to better characterize the Pampean flat slab region around 31°S. In this study, we explore the lithospheric structure above the flat slab as a whole and its relation to seismicity. We use the SIEMBRA data to perform a joint inversion of teleseismic receiver functions and Rayleigh wave phase velocity dispersion to constrain the shear wave velocity variations in the lithosphere. Our joint inversion results show: (1) the presence of several upper-plate mid-crustal discontinuities and their lateral extent that are probably related to the terrane accretion history; (2) zones of high shear wave velocity in the upper-plate lower crust associated with a weak Moho signal consistent with the hypothesis of partial eclogitization in the lower crust; (3) the presence of low shear-wave velocities at ˜100 km depth interpreted as the subducting oceanic crust. Finally, in order to investigate the relation of the lithospheric structure to seismicity, we determine an optimal velocity-depth model based on the joint inversion results and use it to perform regional moment tensor inversions (SMTI) of crustal and slab earthquakes. The SMTI for 18 earthquakes that occurred between 2007 and 2009 in the flat slab region below Argentina, indicates systematically shallower focal depths for slab earthquakes (compared with inversions using previous velocity models). This suggests that the slab seismicity is concentrated mostly between 90 and 110 km depths within the subducting Nazca plate's oceanic crust and likely related to dehydration. In addition, the slab earthquakes exhibit extensional focal mechanisms suggesting

  12. Relationship between changes in the velocity of longitudinal seismic waves and certain geological-engineering parameters of rock in the Central Kyzylkum

    Energy Technology Data Exchange (ETDEWEB)

    Tallyabaev, R.A.

    1979-01-01

    An examination is made of the interconnection between the longitudinal velocity of seismic waves and certain physico-mechanical properties of rock. Tables are presented for calculated values for seismic wave velocities in relation to various types of rock. The relationship between the longitudinal velocity of seismic waves of sandy-gravel-clay rock and the porosity coefficient was found to be inversely proportional. 4 references, 1 figure.

  13. Acoustic and Shear-Wave Velocities in Hydrate-Bearing Sediments Offshore Southwestern Taiwan: Tomography, Converted Waves Analysis and Reverse-Time Migration of OBS Records

    Directory of Open Access Journals (Sweden)

    Philippe Schnurle

    2006-01-01

    Full Text Available A 2.5-D combined seismic reflection and refraction survey has been conducted in the accretionary complex offshore of southwestern Taiwan where BSRs (Bottom Simulating Reflectors are highly concentrated and geochemical signals for the presence of gas hydrate are strong. In this study, we perform velocity analysis of the 6 4-component OBS (Ocean-Bottom Seismometer records along the southernmost transect of this seismic experiment. We utilize 3 independent methods in order to accurately determine the acoustic and shear-wave velocities of the sediments: 1-D Root Mean Square (RMS analysis of the P-P and P-S reflected events on individual datumed components, 2-D inversion of the P-P and P-S reflected and refracted events along the in-line transect, and 3-D acoustic inversion of the first arrivals. The principal sources of bias in the determination of the velocities are the 3-dimentional nature of the topography and the complexity of the underlying structures. The three methods result in consistent velocity profiles. Rapid lateral and vertical variations of the velocities are observed. We then investigate the large scale gas hydrate content through rock physic modeling: at the vertical of each OBS, shear-waves velocities are utilized to estimate the water-filled porosities, and the acoustic velocities predicted for a set of gas hydrate, quartz and clay contents are compared to the observed profiles.

  14. Wind-wave, velocity, and turbidity time-series data from Liberty Island (station LVB), Sacramento-San Joaquin Delta, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Time series data of water surface elevation, wave height, turbidity, and current and wave velocity were collected in Liberty Island beginning in August 2015 as part...

  15. Classification of Low Velocity Impactors Using Spiral Sensing of Acousto-Ultrasonic Waves

    Science.gov (United States)

    Agbasi, Chijioke Raphael

    The non-linear elastodynamics of a flat plate subjected to low velocity foreign body impacts is studied, resembling the space debris impacts on the space structure. The work is based on a central hypothesis that in addition to identifying the impact locations, the material properties of the foreign objects can also be classified using acousto-ultrasonic signals (AUS). Simultaneous localization of impact point and classification of impact object is quite challenging using existing state-of-the-art structural health monitoring (SHM) approaches. Available techniques seek to report the exact location of impact on the structure, however, the reported information is likely to have errors from nonlinearity and variability in the AUS signals due to materials, geometry, boundary conditions, wave dispersion, environmental conditions, sensor and hardware calibration etc. It is found that the frequency and speed of the guided wave generated in the plate can be quantized based on the impactor's relationship with the plate (i.e. the wave speed and the impactor's mechanical properties are coupled). In this work, in order to characterize the impact location and mechanical properties of imapctors, nonlinear transient phenomenon is empirically studied to decouple the understanding using the dominant frequency band (DFB) and Lag Index (LI) of the acousto-ultrasonic signals. Next the understanding was correlated with the elastic modulus of the impactor to predict transmitted force histories. The proposed method presented in this thesis is especially applicable for SHM where sensors cannot be widely or randomly distributed. Thus a strategic organization and localization of the sensors is achieved by implementing the geometric configuration of Theodorous Spiral Sensor Cluster (TSSC). The performance of TSSC in characterizing the impactor types are compared with other conventional sensor clusters (e.g. square, circular, random etc.) and it is shown that the TSSC is advantageous over

  16. Correlation Between P-wave Velocity and Strength Index for Shale to Predict Uniaxial Compressive Strength Value

    Directory of Open Access Journals (Sweden)

    Awang H.

    2017-01-01

    Full Text Available Seismic refraction survey is a non destructive method used in site investigation to identify the seismic velocity subsurface strata. Although it is widely known, the reliability of the result is still doubtable for some reason as well as due to an engineer’s ignorant, which insist on using conventional method rather than new advanced method causing the lack of usage in geophysical method for testing. This study aims to produce a correlation between P-wave velocity value and point load strength index value for shale. Both field and laboratory tests were carried out. In order to obtain the P-wave value, seismic refraction method was conducted as a field test at Precint 4, Putrajaya, Malaysia to achieve the Pwave velocity value of the shale bed. Ten samples of shale were collected from the field and laboratory tests were conducted. The tests are divided into three sections, namely non-destructive laboratory test, physical properties test and mechanical properties test. Ultrasonic Velocity Test via PUNDIT test was conducted as non-destructive laboratory test to acknowledge the P-wave velocity value in laboratory. Both field and laboratory P-wave velocity value were then compared and the result delivers are reliable due to it is within the range. For physical properties test, the rock density and porosity were acknowledged. Meanwhile, Point Load Test was conducted as mechanical properties. Correlation for both Pwave velocity value and point load strength value were achieved via producing an empirical relationship as the end result. Prediction of uniaxial compressive strength (UCS value was made via converting the point load strength value to UCS value using a correlation. By acknowledging this empirical relationship, it shows that geophysical methods are able to produce a reliable result. Hence more and widely used of geophysical method will be profound in the future.

  17. Analysis of epidural pressure pulse wave (EDP-PW) and common carotid blood velocity (CBFV) in acute intracranial hypertension.

    Science.gov (United States)

    Shigemori, M; Tokutomi, T; Kawaba, T; Nakashima, H; Kuramoto, S

    1986-06-01

    The changes in the two consistent components of epidural pressure pulse wave (EDP-PW), P1 and P2 waves, and mean velocity of common carotid blood flow (CBFV) were studied in 21 patients with acute intracranial hypertension to investigate the origin of th the amplitude change in these components. The amplitudes of P2 wave increased progressively with the rise of EDP, but those of P1 wave remained nearly invariable at EDP of more than 20-30 mmHg which is incompatible with the changes in CBFV. Jugular vein compression caused in rapid rise of EDP and a proportionate increase in the magnitudes of both waves. Hyperventilation and mannitol administration caused a disproportionate reduction in the amplitudes of P2 wave with a fall of EDP. But mannitol at high EDP (more than 40 mmHg) caused a mild fall of EDP and some increase in the amplitudes of P2 wave. These results indicate that the variations in the amplitudes of P1 wave reflect the changes in vascular resistance of the large intracranial conductive arteries, while those of P2 wave result from the changes in the volume of the cerebral bulk. The increase in the amplitudes of P2 wave induced by mannitol at high EDP may suggest a defective autoregulation of the cerebral vessels.

  18. Estimation of femoral bone density from trabecular direct wave and cortical guided wave ultrasound velocities measured at the proximal femur in vivo

    DEFF Research Database (Denmark)

    Barkmann, Reinhard; Dencks, Stefanie; Bremer, Alexander

    2008-01-01

    Bone mineral density (BMD) of the proximal femur is a predictor of hip fracture risk. We developed a Quantitative Ultrasound (QUS) scanner for measurements at this site with similar performance (FemUS). In this study we tested if ultrasound velocities of direct waves through trabecular bone and o...

  19. 3-D P- and S-wave velocity structure along the central Alpine Fault, South Island, New Zealand

    Science.gov (United States)

    Guo, B.; Thurber, C. H.; Roecker, S. W.; Townend, J.; Rawles, C.; Chamberlain, C. J.; Boese, C. M.; Bannister, S.; Feenstra, J.; Eccles, J. D.

    2017-05-01

    The Deep Fault Drilling Project (DFDP) on the central Alpine Fault, South Island, New Zealand, has motivated a broad range of geophysical and geological studies intended to characterize the fault system in the locality of the drill site at various scales. In order to better understand the structural features of the central Alpine Fault, we have developed 3-D P- and S-wave velocity (VP and VS) models of the region by double-difference tomography using data sets from multiple seismic networks. In previous work, the quality of the S-wave model has been poor due to the small number of available S-wave picks. We have utilized a new high-accuracy automatic S-wave picker to increase the number of usable S-wave arrivals by more than a factor of two, thereby substantially improving the VS model. Compared to previous studies, our new higher-resolution VP model based on more observations shows a clear VP contrast (higher VP on the southeast hanging wall side) at depths of 5-10 km near the DFDP drill sites. With our better resolved VS model, in the same region, we detect a sharply defined high VS body (VS > 3.7 km s-1) within the hanging wall. Our earthquake relocations reveal the presence of clusters within and around low-velocity zones in the hanging wall southeast of the Alpine Fault. Together with the improved earthquake locations, the P- and S-wave tomography results reveal the Alpine Fault to be marked by a velocity contrast throughout most of the study region. The fault dips southeastwards at about 50° from 5 to 15 km depth, as inferred from the velocity structure, seismicity and observations of fault zone guided waves.

  20. Identifying Coronary Artery Disease in Asymptomatic Middle-Aged Sportsmen : The Additional Value of Pulse Wave Velocity

    NARCIS (Netherlands)

    Braber, Thijs L.; Prakken, Niek H. J.; Mosterd, Arend; Mali, Willem P. Th. M.; Doevendans, Pieter A. F. M.; Bots, Michiel L.; Velthuis, Birgitta K.

    2015-01-01

    Background Cardiovascular screening may benefit middle-aged sportsmen, as coronary artery disease (CAD) is the main cause of exercise-related sudden cardiac death. Arterial stiffness, as measured by pulse wave velocity (PWV), may help identify sportsmen with subclinical CAD. We examined the

  1. Identifying coronary artery disease in asymptomatic middle-aged sportsmen : The additional value of pulse wave velocity

    NARCIS (Netherlands)

    Braber, Thijs L.; Prakken, Niek H J; Mosterd, Arend|info:eu-repo/dai/nl/156271583; Mali, Willem P Th M; Doevendans, Pieter A F M|info:eu-repo/dai/nl/164248366; Bots, Michiel L.|info:eu-repo/dai/nl/110610032; Velthuis, Birgitta K.|info:eu-repo/dai/nl/176956301

    2015-01-01

    Background: Cardiovascular screening may benefit middle-aged sportsmen, as coronary artery disease (CAD) is the main cause of exercise-related sudden cardiac death. Arterial stiffness, as measured by pulse wave velocity (PWV), may help identify sportsmen with subclinical CAD. We examined the

  2. Derivation of site-specific relationships between hydraulic parameters and p-wave velocities based on hydraulic and seismic tomography

    Energy Technology Data Exchange (ETDEWEB)

    Brauchler, R.; Doetsch, J.; Dietrich, P.; Sauter, M.

    2012-01-10

    In this study, hydraulic and seismic tomographic measurements were used to derive a site-specific relationship between the geophysical parameter p-wave velocity and the hydraulic parameters, diffusivity and specific storage. Our field study includes diffusivity tomograms derived from hydraulic travel time tomography, specific storage tomograms, derived from hydraulic attenuation tomography, and p-wave velocity tomograms, derived from seismic tomography. The tomographic inversion was performed in all three cases with the SIRT (Simultaneous Iterative Reconstruction Technique) algorithm, using a ray tracing technique with curved trajectories. The experimental set-up was designed such that the p-wave velocity tomogram overlaps the hydraulic tomograms by half. The experiments were performed at a wellcharacterized sand and gravel aquifer, located in the Leine River valley near Göttingen, Germany. Access to the shallow subsurface was provided by direct-push technology. The high spatial resolution of hydraulic and seismic tomography was exploited to derive representative site-specific relationships between the hydraulic and geophysical parameters, based on the area where geophysical and hydraulic tests were performed. The transformation of the p-wave velocities into hydraulic properties was undertaken using a k-means cluster analysis. Results demonstrate that the combination of hydraulic and geophysical tomographic data is a promising approach to improve hydrogeophysical site characterization.

  3. Lapse-time-dependent coda-wave depth sensitivity to local velocity perturbations in 3-D heterogeneous elastic media

    Science.gov (United States)

    Obermann, Anne; Planès, Thomas; Hadziioannou, Céline; Campillo, Michel

    2016-10-01

    In the context of seismic monitoring, recent studies made successful use of seismic coda waves to locate medium changes on the horizontal plane. Locating the depth of the changes, however, remains a challenge. In this paper, we use 3-D wavefield simulations to address two problems: first, we evaluate the contribution of surface- and body-wave sensitivity to a change at depth. We introduce a thin layer with a perturbed velocity at different depths and measure the apparent relative velocity changes due to this layer at different times in the coda and for different degrees of heterogeneity of the model. We show that the depth sensitivity can be modelled as a linear combination of body- and surface-wave sensitivity. The lapse-time-dependent sensitivity ratio of body waves and surface waves can be used to build 3-D sensitivity kernels for imaging purposes. Second, we compare the lapse-time behaviour in the presence of a perturbation in horizontal and vertical slabs to address, for instance, the origin of the velocity changes detected after large earthquakes.

  4. Crustal surface wave velocity structure of the east Albany-Fraser Orogen, Western Australia, from ambient noise recordings

    Science.gov (United States)

    Sippl, C.; Kennett, B. L. N.; Tkalčić, H.; Gessner, K.; Spaggiari, C. V.

    2017-09-01

    Group and phase velocity maps in the period range 2-20 s for the Proterozoic east Albany-Fraser Orogen, Western Australia, are extracted from ambient seismic noise recorded with the 70-station ALFREX array. This 2 yr temporary installation provided detailed coverage across the orogen and the edge of the Neoarchean Yilgarn Craton, a region where no passive seismic studies of this scale have occurred to date. The surface wave velocities are rather high overall (>3 km s-1 nearly everywhere), as expected for exposed Proterozoic basement rocks. No clear signature of the transition between Yilgarn Craton and Albany-Fraser Orogen is observed, but several strong anomalies corresponding to more local geological features were obtained. A prominent, NE-elongated high-velocity anomaly in the northern part of the array is coincident with a Bouguer gravity high caused by the upper crustal metamorphic rocks of the Fraser Zone. This feature disappears towards longer periods, which hints at an exclusively upper crustal origin for this anomaly. Further east, the limestones of the Cenozoic Eucla Basin are clearly imaged as a pronounced low-velocity zone at short periods, but the prevalence of low velocities to periods of ≥5 s implies that the uppermost basement in this area is likewise slow. At longer periods, slightly above-average surface wave velocities are imaged below the Eucla Basin.

  5. Applanation tonometry: a reliable technique to assess aortic pulse wave velocity in spinal cord injury.

    Science.gov (United States)

    Currie, K D; Hubli, M; Krassioukov, A V

    2014-04-01

    Within-subject repeated measures. To determine the intra- and inter-tester reliability of aortic pulse wave velocity (aPWV) measurements collected using applanation tonometry in individuals with spinal cord injury (SCI). Inpatient Rehabilitation Centre and outpatient Clinic in Vancouver, BC, Canada. Fifteen men and three women with traumatic SCI (age: 46±16 years; C3-L1; American Spinal Injury Association Impairment Scale A-D; 2-284 months post injury) participated in two testing sessions separated by an average of 2 days. During each testing session, aPWV measurements were collected in the supine position following 10 min of rest. Arterial blood pressure waveforms were collected simultaneously by two trained raters at the carotid and femoral arterial sites using applanation tonometry. Heart rate was continuously measured using a single-lead electrocardiogram, whereas brachial blood pressures were measured at 5-min intervals using an automated device. Intra- and inter-tester aPWV measurements demonstrated almost perfect reliability with intraclass correlation coefficients of 0.91 and 0.98 (Pblood pressure between intra- and inter-testing sessions. Applanation tonometry measurements of aPWV are reliable in individuals with SCI. In addition, the SDDs were smaller than a clinically relevant value, suggesting that this measurement is suitable for repeated measures study designs in SCI.

  6. Factors associated with brachial-ankle pulse wave velocity in the general population.

    Science.gov (United States)

    Sonoda, H; Takase, H; Dohi, Y; Kimura, G

    2012-12-01

    The present study investigated factors that modify or affect arterial stiffness as assessed by brachial-ankle pulse wave velocity (baPWV) in the general population. Subjects had previously participated in a physical checkup program (n=911), and baPWV and urinary albumin and sodium excretion were also measured. Urine albumin was expressed as the ratio of urine albumin to urine creatinine. Individual salt intake was assessed by estimating 24-h urinary salt excretion and expressed as the ratio of estimated salt intake to body weight. The mean blood pressure and baPWV were 127.1±15.2/77.0±9.5 mm Hg and 15.9±3.3 m s(-1), respectively. Univariate analysis demonstrated that baPWV correlated with various factors including age, blood pressure, electrocardiogram voltage (SV(1)+RV(5)), urine albumin and salt intake. Multivariate regression analysis revealed that electrocardiogram voltage (Pblood pressure (P<0.0001), urine albumin (P<0.001) and salt intake (P<0.001), independently correlated with baPWV after adjustment for other possible factors. Similar results were obtained for participants not taking any medication. These results suggest that the baPWV value is independently associated with individual salt intake and cardiac and renal damage, and could be a useful procedure for identifying individuals with concealed risk of cardiovascular disease.

  7. Serum Osteopontin Level Correlates with Carotid-Femoral Pulse Wave Velocity in Geriatric Persons

    Directory of Open Access Journals (Sweden)

    Chung-Jen Lee

    2014-01-01

    Full Text Available Osteopontin (OPN is involved in the regulation of vascular calcification processes. The aim of this study was to evaluate the relationship between fasting serum OPN concentration and carotid-femoral pulse wave velocity (cfPWV in geriatric persons. Fasting blood samples were obtained from 93 geriatric persons. cfPWV were performed by SphygmoCor system. Serum OPN levels were measured using a commercially available enzyme-linked immunosorbent assay. Geriatric adults who had diabetes (P=0.007 or dyslipidemia (P=0.029 had higher cfPWV levels than those without diabetes or dyslipidemia. The univariable linear regression analysis showed that age (P=0.002, waist circumference (P=0.048, body mass index (P=0.004, systolic blood pressure (P=0.001, diastolic blood pressure (P=0.036, pulse pressure (P=0.017, creatinine (P=0.002, and log-OPN level (P=0.001 were positively correlated with cfPWV levels, while the high-density lipoprotein cholesterol (HDL-cholesterol level (P=0.007 and glomerular filtration rate (P=0.001 were negatively correlated with cfPWV levels among the geriatric adults. Multivariable forward stepwise linear regression analysis of the significant variables also showed that log-OPN (β=0.233, R2=0.123, regression coefficient: 1.868, P=0.011 was still an independent predictor of cfPWV levels in geriatric persons.

  8. Association between pulse wave velocity and hot flashes/sweats in middle-aged women.

    Science.gov (United States)

    Yang, Ruwei; Zhou, Yang; Li, Changbin; Tao, Minfang

    2017-10-23

    As women age and go through menopause, they suffer a higher incidence of cardiovascular morbidity and mortality. Previous studies have shown that a relationship exists between hot flashes/sweats and an increased risk of cardiovascular disease. However, the association between hot flashes/sweats and arterial stiffness is unclear. We aim to explore the relationship between hot flashes/sweats and arterial stiffness using the modified Kupperman index (KMI) questionnaire and measure the brachial-ankle pulse wave velocity (baPWV). The prevalence of hot flashes in our research was reported to be 41.77%. There was a statistically significant difference between the mean baPWV among groups that experienced different severities of hot flashes/sweats according to one-way ANOVA test (p hot flashes/sweats based on linear regression after adjusting for established cardiovascular confounders (95% CI: (5.86, 43.23), p = 0.01). To the best of our knowledge, this study is the first investigation to propose that baPWV may serve both as an objective index for evaluating the severity of hot flashes/sweats and as a predictor of arterial stiffness beyond Cardiac Vascular Disease (CVD) risk factors in middle-aged women.

  9. Cystatin C is better than albuminuria as a predictor of pulse wave velocity in hypertensive patients.

    Science.gov (United States)

    Ozkok, Abdullah; Akpinar, Timur Selcuk; Tufan, Fatih; Kaya, Omer; Bozbey, Hamza Ugur; Atas, Riza; Toz, Bahtiyar; Atay, Kadri; Yilmaz, Emre; Besiroglu, Mehmet; Nas, Kamil; Hadrovic, Nur; Illyés, Miklós; Ecder, Tevfik

    2014-01-01

    Arterial stiffness is important in the evaluation of the cardiovascular risk in both general population and hypertensive patients. In this study, we aimed to investigate the associations of both serum cystatin C levels and albuminuria with arterial stiffness in healthy controls and hypertensive patients. Seventy-six healthy controls (male/female = 44/32) and 76 hypertensive patients (male/female = 43/33) were enrolled. Arterial stiffness parameters such as augmentation index (AIx) and pulse wave velocity (PWV) were non-invasively measured with the Arteriograph (Tensiomed Ltd., Budapest, Hungary). AIx (31.92 ± 14.31 vs. 27.95 ± 11.03, p = 0.03) and PWV (9.84 ± 1.62 vs. 8.87 ± 2.04, p albuminuria was significantly associated with PWV in hypertensive patients. Serum cystatin C may be better than albuminuria as a predictor of arterial stiffness in hypertensive patients.

  10. Atmospheric anomalies over Mt.Etna using GPS signal delays and tomography of radio wave velocities

    Directory of Open Access Journals (Sweden)

    G. Puglisi

    2007-06-01

    Full Text Available Due to the prominent topography of Mt. Etna, the use of satellite geodetic techniques may significantly suffer from atmospheric heterogeneities. This problem mainly affects the DInSAR technique. To overcome these drawbacks the present study attempts to make headway in measuring and interpreting atmospheric anomalies. We used the GAMIT software to obtain the ZTD (Zenith Total Delay values for the GPS sessions performed on 1996-97, during ERS-2 passes at Mt. Etna. GAMIT software also allows to characterize the statistical behaviour of the tropospheric effects, by using residuals for each station-satellite pair, and to locate the atmospheric anomalies, present mostly at low altitudes. The attempt at using these results to produce a tomography of radio waves velocity of the troposphere suggests that the number of GPS stations used to investigate atmosphere is a critical point in such a study. The three stations are too few to invert anomalies eventually existing in the lower atmosphere. This result is a good starting point for better direct future study to verify the applicability of this tomographic technique to a geodetic network with a higher number of stations, with the aim of characterizing the lower atmosphere of Mt. Etna for a more accurate monitoring of ground deformations.

  11. Evidence for thermospheric gravity waves in the southern polar cap from ground-based vertical velocity and photometric observations

    Directory of Open Access Journals (Sweden)

    J. L. Innis

    Full Text Available Zenith-directed Fabry-Perot Spectrometer (FPS and 3-Field Photometer (3FP observations of the λ630 nm emission (~240 km altitude were obtained at Davis station, Antarctica, during the austral winter of 1999. Eleven nights of suitable data were searched for significant periodicities common to vertical winds from the FPS and photo-metric variations from the 3FP. Three wave-like events were found, each of around one or more hours in duration, with periods around 15 minutes, vertical velocity amplitudes near 60 ms–1 , horizontal phase velocities around 300 ms–1 , and horizontal wavelengths from 240 to 400 km. These characteristics appear consistent with polar cap gravity waves seen by other workers, and we conclude this is a likely interpretation of our data. Assuming a source height near 125 km altitude, we determine the approximate source location by calculating back along the wave trajectory using the gravity wave property relating angle of ascent and frequency. The wave sources appear to be in the vicinity of the poleward border of the auroral oval, at magnetic local times up to 5 hours before local magnetic midnight.

    Key words. Meteorology and atmospheric dynamics (thermospheric dynamics; waves and tides

  12. Seismic Velocity Estimation in the Middle East from Multiple Waveform Functionals: P & S Receiver Functions, Waveform Fitting, and Surface Wave Dispersion

    Science.gov (United States)

    2010-09-01

    senstivity to the uppermost mantle shear wave structure and to velocity contrasts across the Moho (Gangopadhyay et al., 2007). The amplitudes and signal-to...uppermost mantle shear wave structure and to velocity contrasts across the Moho (Gangopadhyay et al., 2007). Mutually satisfying constraints imposed by

  13. Lithospheric Shear Velocity Structure of South Island, New Zealand from Rayleigh Wave Tomography of Amphibious Array Data

    Science.gov (United States)

    Ball, J. S.; Sheehan, A. F.; Stachnik, J. C.; Lin, F. C.; Collins, J. A.

    2015-12-01

    We present the first 3D shear velocity model extending well offshore of New Zealand's South Island, imaging the lithosphere beneath Campbell and Challenger plateaus. Our model is constructed via linearized inversion of both teleseismic (18 -70 s period) and ambient noise-based (8 - 25 s period) Rayleigh wave dispersion measurements. We augment an array of 29 ocean-bottom instruments deployed off the South Island's east and west coasts in 2009-2010 with 28 New Zealand land-based seismometers. The ocean-bottom seismometers and 4 of the land seismometers were part of the Marine Observations of Anisotropy Near Aotearoa (MOANA) experiment, and the remaining land seismometers are from New Zealand's permanent GeoNet array. Major features of our shear wave velocity (Vs) model include a low-velocity (Vs<4.3km/s) body extending to at least 75km depth beneath the Banks and Otago peninsulas, a high-velocity (Vs~4.7km/s) upper mantle anomaly underlying the Southern Alps to a depth of 100km, and discontinuous lithospheric velocity structure between eastern and western Challenger Plateau. Using the 4.5km/s contour as a proxy for the lithosphere-asthenosphere boundary, our model suggests that the lithospheric thickness of Challenger Plateau is substantially greater than that of Campbell Plateau. The high-velocity anomaly we resolve beneath the central South Island exhibits strong spatial correlation with subcrustal earthquake hypocenters along the Alpine Fault (Boese et al., 2013). The ~400km-long low velocity zone we image beneath eastern South Island underlies Cenozoic volcanics and mantle-derived helium observations (Hoke et al., 2000) on the surface. The NE-trending low-velocity zone dividing Challenger Plateau in our model underlies a prominent magnetic discontinuity (Sutherland et al., 1999). The latter feature has been interpreted to represent a pre-Cretaceous crustal boundary, which our results suggest may involve the entire mantle lithosphere.

  14. Shear wave elastography findings of de Quervain tenosynovitis.

    Science.gov (United States)

    Turkay, Rustu; Inci, Ercan; Aydeniz, Banu; Vural, Meltem

    2017-10-01

    Our aim was to evaluate the feasibility of using shear wave elastography (SWE) to assess first extensor compartment tendons rigidity and its alterations with tenosynovitis. We performed B-mode ultrasound and SWE to total number of 80 participants. All participants were evaluated clinically to call the diagnosis of de Quervain tenosynovitis or to rule out the diagnosis. We composed 2 groups. Group 1 included 40 healthy volunteers (33 females and 7 male participants with ages ranging from 24 to 60 years, median age was 37.5 years) and group 2 had 40 de Quervain patients (32 females and 8 male patients with ages ranging from 25 to 51 years, median age was 34 years). SWE measurements were repeated 3 times and arithmetic average was used for the final SWE value. The median SWE value of healthy group (group 1) was 72kPa and the de Quervain patient group (group 2) was 29kPa. Two groups demonstrated statistically significant difference (p<0.001). The ROC curve analysis was performed and the SWE value of 40.5kPA was calculated as a cut-off value for the diagnosis of de Quervain tenosynovitis with 95% specificity and 85% sensitivity. SWE modality can provide useful data regarding de Quervain tenosynovitis. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Deep ReMi Imaging - Mapping Shear-Wave Velocities to 1 km Depth and Greater Using Refraction Microtremor

    Science.gov (United States)

    Louie, J. N.; Pancha, A.; Munger, D.; Law, C.; Adams, D.; Mick, T. M.; Pullammanappallil, S. K.

    2016-12-01

    The Refraction Microtremor (ReMi) surface-wave technique, in use since 2002, has become a standard tool for assessing urban shear-wave velocities for engineering applications. ReMi is effective for site-class studies as well as assessing ground conditions, including 1D and 2D velocity-depth profiling to shallow depths of approximately 100 m. Over the last few years, we have successfully extended the application of the method to depths greater than 1 km. The use of deep ReMi, which relies primarily on ambient noise, for estimation of shear-wave velocities to kilometer depths, allows for mapping the thickness and velocity of deep urban basins. Accurate 3D modeling and calibration of recorded earthquake ground motions in urban areas is one use of deep ReMi results. Such models have the potential to be an essential part of seismic hazard evaluation. We present results from several deep ReMi studies conducted in the Reno-area and Tahoe basins of Nevada and California. Wireless instruments coupled with low-frequency geophones deployed in 3-km-long arrays across the densely populated urban environment acquired data in 2012, 2014, and 2015. In addition to mapping basement as deep as 900 m, the lateral velocity variations reveal deep-seated fault structure in the initial studies. A study of the Reno-area basin in 2016 employed arrays of 90 IRIS-PASSCAL Texans, 15 and 22 km long. This data set appears to constrain a sub-basin interface between Tertiary volcanics and Mesozoic basement at 1-2 km depth. Characterization of shear velocity at greater than 100 m depth, to basement, along with previously unknown faults, is vital towards quantifying earthquake ground motion and seismic hazard potential in geologically complex urban basins. Our measurements will allow Nevada communities to become more resilient against natural hazards.

  16. Shock wave velocity measuring system based on vernier VISAR-type interferometers

    Science.gov (United States)

    Gubskii, K. L.; Koshkin, D. S.; Antonov, A. S.; Mikhailuk, A. V.; Pirog, V. A.; Kuznetsov, A. P.

    2015-11-01

    The paper presents a multi-line diagnostic system for measuring the surface velocity in shock physics experiments. This system is designed for simultaneous measurement of surface velocity at multiple points. It is free from ambiguity caused by harmonic dependence of interference signals on the velocity and has a time resolution of 0.8 ns.

  17. Antireflection coating of barriers to enhance electron tunnelling: exploring the matter wave analogy of superluminal optical phase velocity.

    Science.gov (United States)

    Zhao, Zijun C; McKenzie, David R

    2017-10-06

    The tunnelling of electrons through barriers is important in field emission sources and in interconnects within electronic devices. Here we use the analogy between the electromagnetic wave equation and the Schrodinger equation to find potential barriers that, when added before an existing barrier, increase the transmission probability. A single pre-barrier of negative potential behaves as a dielectric "antireflection coating", as previously reported. However, we obtain an unexpected and much greater enhancement of transmission when the pre-barrier has a positive potential of height smaller than the energy of the incident electron, an unfamiliar optical case, corresponding to media with superluminal phase velocities as in dilute free electron media and anomalous dispersion at X-ray frequencies. We use a finite difference time domain algorithm to evaluate the transmission through a triangular field emission barrier with a pre-barrier that meets the new condition. We show that the transmission is enhanced for an incident wavepacket, producing a larger field emission current than for an uncoated barrier. Examples are given of available materials to enhance transmission in practical applications. The results are significant for showing how to increase electron transmission in field emission and at interconnects between dissimilar materials in all types of electronic devices.

  18. ABCA1-dependent serum cholesterol efflux capacity inversely correlates with pulse wave velocity in healthy subjects[S

    Science.gov (United States)

    Favari, Elda; Ronda, Nicoletta; Adorni, Maria Pia; Zimetti, Francesca; Salvi, Paolo; Manfredini, Matteo; Bernini, Franco; Borghi, Claudio; Cicero, Arrigo F. G.

    2013-01-01

    The capacity of HDL to induce cell cholesterol efflux is considered one of its main antiatherogenic properties. Little is known about the impact of such HDL function on vascular physiology. We investigated the relationship between ABCA1-dependent serum cholesterol efflux capacity (CEC), an HDL functionality indicator, and pulse wave velocity (PWV), an indicator of arterial stiffness. Serum of 167 healthy subjects was used to conduct CEC measurement, and carotid-femoral PWV was measured with a high-fidelity tonometer. J774 macrophages, labeled with [3H]cholesterol and stimulated to express ABCA1, were exposed to sera; the difference between cholesterol efflux from stimulated and unstimulated cells provided specific ABCA1-mediated CEC. PWV is inversely correlated with ABCA1-dependent CEC (r = −0.183; P = 0.018). Moreover, controlling for age, sex, body mass index, mean arterial pressure, serum LDL, HDL-cholesterol, and fasting plasma glucose, PWV displays a significant negative regression on ABCA1-dependent CEC (β = −0.204; 95% confidence interval, −0.371 to −0.037). The finding that ABCA1-dependent CEC, but not serum HDL cholesterol level (r = −0.002; P = 0.985), is a significant predictor of PWV in healthy subjects points to the relevance of HDL function in vascular physiology and arterial stiffness prevention. PMID:23103472

  19. Shear wave velocity structure in the lithosphere and asthenosphere across the Southern California continent and Pacific plate margin using inversion of Rayleigh wave data from the ALBACORE project.

    Science.gov (United States)

    Price, A. C.; Weeraratne, D. S.; Kohler, M. D.; Rathnayaka, S.; Escobar, L., Sr.

    2015-12-01

    The North American and Pacific plate boundary is a unique example of past subduction of an oceanic spreading center which has involved oceanic plate capture and inception of a continental transform boundary that juxtaposes continental and oceanic lithosphere on a single plate. The amphibious ALBACORE seismic project (Asthenospheric and Lithospheric Broadband Architecture from the California Offshore Region Experiment) deployed 34 ocean bottom seismometers (OBS) on 15-35 Ma seafloor and offers a unique opportunity to compare the LAB in continental and oceanic lithosphere in one seismic study. Rayleigh waves were recorded simultaneously by our offshore array and 82 CISN network land stations from 2010-2011. Here we predict phase velocities for a starting shear wave velocity model for each of 5 regions in our study area and compare to observed phase velocities from our array in a least-squares sense that produces the best fit 1-D shear wave velocity structure for each region. Preliminary results for the deep ocean (seafloor 25-32 Ma) indicates high velocities reaching 4.5 km/s at depths of 50 km associated with the lithosphere for seafloor 25-32 Ma. A negative velocity gradient is observed below this which reaches a minimum of 4.0 km/s at 160 km depth. The mid-ocean region (age 13-25 Ma) indicates a slightly lower magnitude and shallower LVZ. The Inner Borderland displays the highest lithospheric velocities offshore reaching 4.8 km/s at 40 km depth indicating underplating. The base of the LVZ in the Borderland increases sharply from 4.0 km/s to 4.5 km/s at 80-150 km depth indicating partial melt and compositional changes. The LVZ displays a very gradual positive velocity gradient in all other regions such as the deep seafloor and continent reaching 4.5 km/s at 300 km depth. The deep ocean, Borderlands, and continental region each have unique lithospheric velocities, LAB depths, and LVZ character that indicate stark differences in mantle structure that occur on a

  20. CONTRIBUTION OF VELOCITY VORTICES AND FAST SHOCK REFLECTION AND REFRACTION TO THE FORMATION OF EUV WAVES IN SOLAR ERUPTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hongjuan; Liu, Siqing; Gong, Jiancun [Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190 (China); Wu, Ning [School of Tourism and Geography, Yunnan Normal University, Kunming, Yunnan 650031 (China); Lin, Jun [Yunnan Observatories, Chinese Academy of Sciences, Kunming, Yunnan 650011 (China)

    2015-06-01

    We numerically study the detailed evolutionary features of the wave-like disturbance and its propagation in the eruption. This work is a follow-up to Wang et al., using significantly upgraded new simulations. We focus on the contribution of the velocity vortices and the fast shock reflection and refraction in the solar corona to the formation of the EUV waves. Following the loss of equilibrium in the coronal magnetic structure, the flux rope exhibits rapid motions and invokes the fast-mode shock at the front of the rope, which then produces a type II radio burst. The expansion of the fast shock, which is associated with outward motion, takes place in various directions, and the downward expansion shows the reflection and the refraction as a result of the non-uniform background plasma. The reflected component of the fast shock propagates upward and the refracted component propagates downward. As the refracted component reaches the boundary surface, a weak echo is excited. The Moreton wave is invoked as the fast shock touches the bottom boundary, so the Moreton wave lags the type II burst. A secondary echo occurs in the area where reflection of the fast shock encounters the slow-mode shock, and the nearby magnetic field lines are further distorted because of the interaction between the secondary echo and the velocity vortices. Our results indicate that the EUV wave may arise from various processes that are revealed in the new simulations.

  1. Platelet to Lymphocyte Percentage Ratio Is Associated With Brachial-Ankle Pulse Wave Velocity in Hemodialysis.

    Science.gov (United States)

    Chen, Szu-Chia; Lee, Mei-Yueh; Huang, Jiun-Chi; Tsai, Yi-Chun; Mai, Hsiu-Chin; Su, Ho-Ming; Chang, Jer-Ming; Chen, Hung-Chun

    2016-02-01

    Increased arterial stiffness in patients receiving hemodialysis (HD) is highly prevalent and is associated with cardiovascular morbidity and mortality. In HD, inflammation is one of the major causes of increased arterial stiffness. Activation of platelets and decreased lymphocyte percentage (LYMPH%) may exhibit inflammation. The aim of this study is to examine the relationship between platelet to LYMPH% ratio and arterial stiffness in HD patients.A total of 220 patients receiving HD were enrolled in this study. The brachial-ankle pulse wave velocity (baPWV) was measured using an ankle-brachial index form device. Multivariate linear regression analysis was performed to investigate the relations of the platelet to LYMPH% ratio and baPWV. The value of the platelet to LYMPH% ratio was 59.2 ± 33.3 (10 cells/L/%). After multivariate stepwise analysis, diabetes (β: 163.973, P = 0.02), high systolic blood pressure (per 1 mm Hg, β: 9.010, P < 0.001), high platelet to LYMPH% ratio (per 10 cells/L/%, β: 3.334, P < 0.01), and low albumin (per 0.1 mg/dL, β: -55.912, P < 0.001) were independently associated with an increased baPWV. Furthermore, high white blood cells (per 10 cells/L, β: 3.941, P < 0.001), high neutrophil percentage (per 1%, β: 1.144, P < 0.001), and high CRP (per 1 mg/L, β: 9.161, P = 0.03) were independently associated with an increased platelet to LYMPH% ratio.An increased platelet to LYMPH% ratio is associated with an increased baPWV in HD patients. An easy and inexpensive laboratory measure of platelet to LYMPH% ratio may provide an important information regarding arterial stiffness in patients with HD.

  2. Determinants of Brachial-Ankle Pulse Wave Velocity in Chinese Patients with Rheumatoid Arthritis

    Directory of Open Access Journals (Sweden)

    Ping Li

    2013-01-01

    Full Text Available Objective. To investigate the relationship between Brachial-ankle pulse wave velocity (baPWV, and its associated risk factors in Chinese patients with RA. Methods. 138 Chinese RA patients and 150 healthy subjects were included. baPWV of all the participants was measured. RA related factors were determined, as well as traditional cardiovascular risk factors. Results. baPWV was significant higher in RA group (1705.44 ± 429.20 cm/s compared to the healthy control group (1386.23 ± 411.09 cm/s (P<0.001. Compared with low baPWV group, high baPWV group patients were significantly older (P = 0.008 and taller (P = 0.033. Serum cholesterol (P = 0.035, triglycerides (P = 0.004, and LDL level (P = 0.006 were significantly higher in high baPWV group patients compared with low baPWV group patients. The baPWV of RA patients was positively correlated with age (r = 0.439, P<0.001, and serum cholesterol level (r = 0.231, P = 0.035, serum triglycerides level (r = 0.293, P<0.001, serum LDL level (r = 0.323, P = 0.003. Meanwhile, baPWV negatively correlated with the height of RA patients (r = −0.253, P = 0.043. Multivariate regression analysis showed that baPWV of RA group was independently associated with age and serum triglycerides level. Conclusions. The old age and high level of serum triglycerides may be the major determinants of arterial stiffness in Chinese RA patients.

  3. Carotid-femoral pulse wave velocity in a healthy adult sample: The ELSA-Brasil study.

    Science.gov (United States)

    Baldo, Marcelo Perim; Cunha, Roberto S; Molina, Maria Del Carmen B; Chór, Dora; Griep, Rosane H; Duncan, Bruce B; Schmidt, Maria Inês; Ribeiro, Antonio L P; Barreto, Sandhi M; Lotufo, Paulo A; Bensenor, Isabela M; Pereira, Alexandre C; Mill, José Geraldo

    2018-01-15

    Aging declines essential physiological functions, and the vascular system is strongly affected by artery stiffening. We intended to define the age- and sex-specific reference values for carotid-to-femoral pulse wave velocity (cf-PWV) in a sample free of major risk factors. The ELSA-Brasil study enrolled 15,105 participants aged 35-74years. The healthy sample was achieved by excluding diabetics, those over the optimal and normal blood pressure levels, body mass index ≤18.5 or ≥25kg/m2, current and former smokers, and those with self-report of previous cardiovascular disease. After exclusions, the sample consisted of 2158 healthy adults (1412 women). Although cf-PWV predictors were similar between sex (age, mean arterial pressure (MAP) and heart rate), cf-PWV was higher in men (8.74±1.15 vs. 8.31±1.13m/s; adjusted for age and MAP, PBrasil population (n=15,105) increased by twice the age-related slope of cf-PWV growth, regardless of sex (0.0919±0.182 vs. 0.0504±0.153m/s per year for men, 0.0960±0.173 vs. 0.0606±0.139m/s per year for women). cf-PWV is different between men and women and even in an optimal and normal range of MAP and free of other classical risk factors for arterial stiffness, reference values for cf-PWV should take into account MAP levels. Also, the presence of major risk factors in the general population doubles the age-related rise in cf-PWV. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Evaluation of carotid-femoral pulse wave velocity: influence of timing algorithm and heart rate.

    Science.gov (United States)

    Millasseau, Sandrine C; Stewart, Andrew D; Patel, Sundip J; Redwood, Simon R; Chowienczyk, Philip J

    2005-02-01

    Carotid-femoral pulse wave velocity (PWV), a measure of arterial stiffness, is determined from the time taken for the arterial pulse to propagate from the carotid to the femoral artery. Propagation time is measured variously from the foot of the waveform or point of maximum upslope. We investigated whether these methods give comparable values of PWV at rest, during beta-adrenergic stimulation, and pacing-induced tachycardia. In subjects at rest (n=43), values obtained using the foot-to-foot method (SphygmoCor system) were 1.7+/-0.75 m/s (mean+/-SD) greater than those obtained using the maximum slope (Complior system) at a mean value of 12 m/s. Isoprotenerol (0.5 to 1.5 microg/min; n=10), and pacing (in subjects with permanent pacemakers; n=11) increased heart rate but had differential effects on systolic blood pressure and pulse pressure. The increase in heart rate produced by isoprotenerol (18+/-3 bpm) and pacing (40 bpm) was associated with an increase in PWV measured using both systems (increases of 0.7+/-0.2 m/s and 0.9+/-0.2 m/s for SphygmoCor and Complior, respectively, during isoprotenerol and increases of 2.1+/-0.5 m/s and 1.1+/-0.2 m/s for SphygmoCor and Complior, respectively, during pacing, each P<0.001). Reanalysis of waveforms recorded from the Complior system using the foot-to-foot method produced similar values of PWV to those obtained with the SphygmoCor, confirming that the difference between these systems was attributable to the timing algorithm rather than other aspects of signal acquisition. Carotid-femoral PWV is critically dependent on the method used to determine propagation time, but this does not account for variation of PWV with heart rate.

  5. Relationships between Brachial-Ankle Pulse Wave Velocity and Peripheral Neuropathy in Type 2 Diabetes

    Directory of Open Access Journals (Sweden)

    Byung Kil Ha

    2012-12-01

    Full Text Available BackgroundBrachial-ankle pulse wave velocity (baPWV is known to be a good surrogate marker of clinical atherosclerosis. Atherosclerosis is a major predictor for developing neuropathy. The goal of this study was to determine the relationship between baPWV and diabetic peripheral neuropathy (DPN in patients with type 2 diabetes.MethodsA retrospective cross-sectional study was conducted involving 692 patients with type 2 diabetes. The correlation between increased baPWV and DPN, neurological symptoms, and neurological assessment was analyzed. DPN was examined using the total symptom score (TSS, ankle reflexes, the vibration test, and the 10-g monofilament test. DPN was defined as TSS ≥2 and an abnormal neurological assessment. Data were expressed as means±standard deviation for normally distributed data and as median (interquartile range for non-normally distributed data. Independent t-tests or chi-square tests were used to make comparisons between groups, and a multiple logistic regression test was used to evaluate independent predictors of DPN. The Mantel-Haenszel chi-square test was used to adjust for age.ResultsPatients with DPN had higher baPWV and systolic blood pressure, and were more likely to be older and female, when compared to the control group. According to univariate analysis of risk factors for DPN, the odds ratio of the baPWV ≥1,600 cm/sec was 1.611 (95% confidence interval [CI], 1.072 to 2.422; P=0.021 and the odds ratio in female was 1.816 (95% CI, 1.195 to 2.760; P=0.005.ConclusionIncreased baPWV was significantly correlated with peripheral neuropathy in patients with type 2 diabetes.

  6. Prenatal influences on size, velocity and tempo of infant growth: findings from three contemporary cohorts.

    Directory of Open Access Journals (Sweden)

    Costanza Pizzi

    Full Text Available Studying prenatal influences of early life growth is relevant to life-course epidemiology as some of its features have been linked to the onset of later diseases.We studied the association between prenatal maternal characteristics (height, age, parity, education, pre-pregnancy body mass index (BMI, smoking, gestational diabetes and hypertension and offspring weight trajectories in infancy using SuperImposition by Translation And Rotation (SITAR models, which parameterize growth in terms of three biologically interpretable parameters: size, velocity and tempo. We used data from three contemporary cohorts based in Portugal (GXXI, n=738, Italy (NINFEA, n=2,925, and Chile (GOCS, n=959.Estimates were generally consistent across the cohorts for maternal height, age, parity and pre-pregnancy overweight/obesity. Some exposures only affected one growth parameter (e.g. maternal height (per cm: 0.4% increase in size (95% confidence interval (CI:0.3; 0.5, others were either found to affect size and velocity (e.g. pre-pregnancy underweight vs normal weight: smaller size (-4.9%, 95% CI:-6.5; -3.3, greater velocity (5.9%, 95% CI:1.9;10.0, or to additionally influence tempo (e.g. pre-pregnancy overweight/obesity vs normal weight: increased size (7.9%, 95% CI:4.9;10.8, delayed tempo (0.26 months, 95% CI:0.11;0.41, decreased velocity (-4.9%, 95% CI: -10.8;0.9.By disentangling the growth parameters of size, velocity and tempo, we found that prenatal maternal characteristics, especially maternal smoking, pre-pregnancy overweight and underweight, parity and gestational hypertension, are associated with different aspects of infant weight growth. These results may offer insights into the mechanisms governing infant growth.

  7. Prenatal influences on size, velocity and tempo of infant growth: findings from three contemporary cohorts.

    Science.gov (United States)

    Pizzi, Costanza; Cole, Tim J; Richiardi, Lorenzo; dos-Santos-Silva, Isabel; Corvalan, Camila; De Stavola, Bianca

    2014-01-01

    Studying prenatal influences of early life growth is relevant to life-course epidemiology as some of its features have been linked to the onset of later diseases. We studied the association between prenatal maternal characteristics (height, age, parity, education, pre-pregnancy body mass index (BMI), smoking, gestational diabetes and hypertension) and offspring weight trajectories in infancy using SuperImposition by Translation And Rotation (SITAR) models, which parameterize growth in terms of three biologically interpretable parameters: size, velocity and tempo. We used data from three contemporary cohorts based in Portugal (GXXI, n=738), Italy (NINFEA, n=2,925), and Chile (GOCS, n=959). Estimates were generally consistent across the cohorts for maternal height, age, parity and pre-pregnancy overweight/obesity. Some exposures only affected one growth parameter (e.g. maternal height (per cm): 0.4% increase in size (95% confidence interval (CI):0.3; 0.5)), others were either found to affect size and velocity (e.g. pre-pregnancy underweight vs normal weight: smaller size (-4.9%, 95% CI:-6.5; -3.3), greater velocity (5.9%, 95% CI:1.9;10.0)), or to additionally influence tempo (e.g. pre-pregnancy overweight/obesity vs normal weight: increased size (7.9%, 95% CI:4.9;10.8), delayed tempo (0.26 months, 95% CI:0.11;0.41), decreased velocity (-4.9%, 95% CI: -10.8;0.9)). By disentangling the growth parameters of size, velocity and tempo, we found that prenatal maternal characteristics, especially maternal smoking, pre-pregnancy overweight and underweight, parity and gestational hypertension, are associated with different aspects of infant weight growth. These results may offer insights into the mechanisms governing infant growth.

  8. Reproducibility of shear wave velocity measurements by acoustic radiation force impulse imaging of the liver: a study in healthy volunteers.

    Science.gov (United States)

    Guzmán-Aroca, Florentina; Reus, Manuel; Berná-Serna, Juan D; Serrano, Laura; Serrano, Cristina; Gilabert, Amparo; Cepero, Angela

    2011-07-01

    The purposes of this study were to investigate interobserver reproducibility using acoustic radiation force impulse imaging and to develop an acoustic radiation force impulse scoring system. Fifty healthy volunteers with normal liver function test values were selected for the study. Shear wave velocity measurements, expressed in meters per second, were taken in a deep portion of liver segment 6. Two observers with different levels of experience performed the measurements independently and blindly. All of the measurements taken by the 2 observers were valid, even in volunteers with a body mass index of greater than 28 kg/m(2). The results point to very good interobserver reproducibility of shear wave velocity measurements, with an intraclass coefficient correlation of 0.86 (P measurements using the acoustic radiation force impulse technique and a standardized protocol are accurate and reproducible.

  9. Upper mantle compositional variations and discontinuity topography imaged beneath Australia from Bayesian inversion of surface-wave phase velocities and thermochemical modeling

    DEFF Research Database (Denmark)

    Khan, A.; Zunino, Andrea; Deschamps, F.

    2013-01-01

    Here we discuss the nature of velocity heterogeneities seen in seismic tomography images of Earth's mantle whose origins and relation to thermochemical variations are yet to be understood. We illustrate this by inverting fundamental-mode and higher-order surface-wave phase velocities for radial...... inference approach whereby robust uncertainty estimates are obtained. We find that both compositional and thermal anomalies are required if observations are to be satisfied. Mantle thermochemical variations extend to 250 km depth beneath western and central Australia and are characterized by increased Mg....../Fe and Mg/Si values relative to surrounding mantle. Correlated herewith are thermal variations that closely follow surface tectonics. We also observe a strong contribution to lateral variations in structure and topography across the “410 km” seismic discontinuity from thermochemically induced phase...

  10. 3D isotropic shear wave velocity structure of the lithosphere-asthenosphere system underneath the Alpine-Mediterranean Mobile belt

    Science.gov (United States)

    El-Sharkawy, Amr; Weidle, Christian; Christiano, Luigia; Lebedev, Sergei; Meier, Thomas

    2017-04-01

    The Alpine-Mediterranean mobile belt is, tectonically, one of the most complicated and active regions in the world. Since the Mesozoic, collisions between Gondwana-derived continental blocks and Eurasia, due to the closure of a number of rather small ocean basins, have shaped the Mediterranean geology. During the late Mesozoic, it was dominated by subduction zones (e.g., in Anatolia, the Dinarides, the Carpathians, the Alps, the Apennines, and the Betics), which inverted the extensional regime, consuming the previously formed oceanic lithosphere, the adjacent passive continental margins and presumably partly also continental lithosphere. The location, distribution, and evolution of these subduction zones were mainly controlled by the continental or oceanic nature, density, and thickness of the lithosphere inherited from the Mesozoic rift after the European Variscan Orogeny. Despite the numerous studies that have attempted to characterize the lithosphere-asthenosphere structure in that area, details of the lithospheric structure and dynamics, as well as flow in the asthenosphere are, however, poorly known. A 3D shear-wave velocity structure of the lithosphere-asthenosphere system in the Mediterranean is investigated using new tomographic images obtained from surface wave tomography. An automated algorithm for inter-station phase velocity measurements is applied here to obtain both Rayleigh and Love fundamental mode phase velocities. We utilize a database consisting of more than 4000 seismic events recorded by more than 2000 broadband seismic stations within the area, provided by the European Integrated Data Archive (WebDc/EIDA) and IRIS. Moreover, for the first time, data from the Egyptian National Seismological Network (ENSN), recorded by up to 25 broad band seismic stations, are also included in the analysis. For each station pair, approximately located on the same great circle path, the recorded waveforms are cross correlated and the dispersion curves of

  11. Development of site class and site coefficient maps of Semarang, Indonesia using field shear wave velocity data

    OpenAIRE

    Partono Windu; Irsyam Masyhur; Prabandiyani Retno Wardani Sri

    2017-01-01

    The new Indonesian National Code for seismic resistance design (SNI-03-1726-2012) issued recently utilizes seismic response spectra for the whole area of the country. Site class and site coefficient are two parameters needed for designing response spectra. Site class can be estimated using average standard penetration test (N-SPT), average shear wave velocity (Vs) and average un-drained shear strength (Su) of top 30 meter soil deposit. Site coefficients can be predicted using probabilistic se...

  12. ABCA1-dependent serum cholesterol efflux capacity inversely correlates with pulse wave velocity in healthy subjects[S

    OpenAIRE

    Favari, Elda; Ronda, Nicoletta; Adorni, Maria Pia; Zimetti, Francesca; Salvi, Paolo; Manfredini, Matteo; Bernini, Franco; Borghi, Claudio; Cicero, Arrigo F. G.

    2013-01-01

    The capacity of HDL to induce cell cholesterol efflux is considered one of its main antiatherogenic properties. Little is known about the impact of such HDL function on vascular physiology. We investigated the relationship between ABCA1-dependent serum cholesterol efflux capacity (CEC), an HDL functionality indicator, and pulse wave velocity (PWV), an indicator of arterial stiffness. Serum of 167 healthy subjects was used to conduct CEC measurement, and carotid-femoral PWV was measured with a...

  13. Estimating method for a phase-velocity of Rayleigh waves on multi-layered media and its application to inversion problem; Rayleigh ha no bunsan kyokusen no kinji keisanho no teian to chika kozo suitei eno oyo

    Energy Technology Data Exchange (ETDEWEB)

    Konno, K. [Shibaura Institute of Technology, Tokyo (Japan)

    1997-10-15

    An attempt was made to approximate a dispersion curve being a function of S-wave velocity, P-wave velocity, density and layer thickness by using only the S-wave velocity and the layer thickness. Then, this approximation method was utilized for an attempt of deriving the S-wave velocity structure directly from the observed dispersion curve. Lastly, the derived S-wave velocity structure was attempted to be utilized as an initial model for inversion analysis. The pseudo-phase velocity derived by using this proposed method becomes functions for only the cycle, S-wave velocity and layer thickness, converges into the S-wave velocity of the lowermost layer at the extreme of a long cycle, and agrees with the S-wave velocity of the surface layer in the short cycle side. The pseudo-dispersion curve approximates the dispersion curve of Rayleigh waves more closely than that of Love waves. If depths and pseudo-wave lengths are in rough agreement in a region in which amplitude of the base mode Rayleigh waves is distributed largely, the pseudo-phase velocity resembles to the theoretical phase velocity. S-wave velocity at a ground depth which corresponds to a length of the Rayleigh wave could be estimated to some extent by differentiating the wavelength with regard to the cycle. 7 refs., 19 figs., 1 tab.

  14. Prediction of Compressional, Shear, and Stoneley Wave Velocities from Conventional Well Log Data Using a Committee Machine with Intelligent Systems

    Science.gov (United States)

    Asoodeh, Mojtaba; Bagheripour, Parisa

    2012-01-01

    Measurement of compressional, shear, and Stoneley wave velocities, carried out by dipole sonic imager (DSI) logs, provides invaluable data in geophysical interpretation, geomechanical studies and hydrocarbon reservoir characterization. The presented study proposes an improved methodology for making a quantitative formulation between conventional well logs and sonic wave velocities. First, sonic wave velocities were predicted from conventional well logs using artificial neural network, fuzzy logic, and neuro-fuzzy algorithms. Subsequently, a committee machine with intelligent systems was constructed by virtue of hybrid genetic algorithm-pattern search technique while outputs of artificial neural network, fuzzy logic and neuro-fuzzy models were used as inputs of the committee machine. It is capable of improving the accuracy of final prediction through integrating the outputs of aforementioned intelligent systems. The hybrid genetic algorithm-pattern search tool, embodied in the structure of committee machine, assigns a weight factor to each individual intelligent system, indicating its involvement in overall prediction of DSI parameters. This methodology was implemented in Asmari formation, which is the major carbonate reservoir rock of Iranian oil field. A group of 1,640 data points was used to construct the intelligent model, and a group of 800 data points was employed to assess the reliability of the proposed model. The results showed that the committee machine with intelligent systems performed more effectively compared with individual intelligent systems performing alone.

  15. A combined analysis of basaltic melting and shear wave velocity anomalies to constrain dynamic support of western North America

    Science.gov (United States)

    Klöcking, Marthe; White, Nicky; Maclennan, John; Fitton, Godfrey

    2017-04-01

    The region of western North America that encompasses the Basin and Range Province, the Snake River Plain and the Colorado Plateau is about 2 km higher than cratonic North America. This topographic difference broadly coincides with variations in lithospheric thickness (i.e. 260 samples from volcanic centers throughout western North America for major, trace and rare earth elements using ICP-MS and XRF techniques. For asthenospheric samples, we observe a correlation between slow shear wave velocity anomalies and basaltic geochemistry. Using a combination of petrologic observations, forward and inverse modeling of major and rare earth elements, and shear wave velocity anomalies from tomographic models, we determine depth of melting and melt fraction. We explore the possibility that volatiles, anomalous source composition and/or temperature can give rise to basaltic magmatism and regional uplift. We then calculate mantle temperatures from shear wave velocity profiles beneath each volcanic field. In this way, we exploit a variety of approaches to constrain lithospheric thickness and mantle potential temperature. Our combined geochemical and geophysical results yield excess temperatures of 50-80 °C beneath a 60 km thin lithospheric plate. A dynamic topographic model of progressive lithospheric erosion over anomalously hot upper mantle can account for regional uplift as well as the temporal and spatial distribution of magmatism across western North America.

  16. USING ELASTIC WAVE VELOCITY ON CLASSIFICATION WEATHERING ROCK MATERIALS AND PREDICTION OF ENGINEERING PROPERTIES IN KURTUN GRANODIORITE

    Directory of Open Access Journals (Sweden)

    Şener CERYAN

    2007-02-01

    Full Text Available A great number of landslides occurred in weathered granites outcropped the area in which Kurtun Dams with reservoirs and Gümüshane-Giresun highways pass trough. For this, weathering effect on the rock materials of the Kurtun granodiorite was investigated. In this study, both physical and mineralogical changes on the granitic materials due to weathering are described separately using P- wave velocity in rocks materials. Mineralogical Change Parameter and Physical Parameter defined based on P- wave velocity in rocks materials are applied on the samples from the selected weathering profiles, for the estimation of the effects of weathering on the physicomechanical properties of rock materials. The relative variation of mechanical properties and these indices display a statistically significant correlation. Besides, it is shown that P wave velocity in the solid parts of the samples. and Quantitative Weathering index originally defined Ceryan (1999a as based on slake-durability index, Mineralogical Change Parameter and Physical Parameter can be used together to evaluate the effect of weathering on the mechanical behavior of rocks material from Kürtün granodiorite.

  17. Characterization of wind velocities in the upstream induction zone of a wind turbine using scanning continuous-wave lidars

    DEFF Research Database (Denmark)

    Simley, Eric; Angelou, Nikolas; Mikkelsen, Torben Krogh

    2016-01-01

    Technical University’s Risø campus is investigated using a scanning Light Detection and Ranging (lidar) system. Three short-range continuous-wave “WindScanner” lidars are positioned in the field around the V27 turbine allowing detection of all three components of the wind velocity vectors within...... in the induction zone are studied by more rapidly scanning along individual lines perpendicular to the rotor at different radial distances from the hub. The mean velocity measurements reveal that the longitudinal velocity reductions become greater closer to the rotor plane and closer to the center of the rotor...... 9% and 3% of the freestream longitudinal wind speed were measured for the abovementioned high and low CP values, respectively. Turbulence statistics, calculated using 2.5-min time series, suggest that the standard deviation of the longitudinal wind component decreases close to the rotor, while...

  18. 3-D crustal P-wave velocity tomography of the Italian region using local and regional seismicity data

    Directory of Open Access Journals (Sweden)

    F. M. Mele

    1995-06-01

    Full Text Available A tomographic experiment was performed in the Italian region using local and regional arrivaI times of p and S seismological phases selected from the Italian National Bulletin in the time interval 1984-1991. We deter- mined a 3-D crustal P-wave velocity model using a simultaneous inversion method that iteratively re1ocates the hypocenters and computes the unknown model parameters. A fast two-point ray tracing algorithm was adopted to compute the ray paths and travel times of P", S", P g' Sg phases with good accuracy. Synthetic tests were performed using the "true" hypocenter and station distribution to rough1y evaluate the extension of the areas most densely spanned by the ray paths; the agreement between synthetic and computed models is more satisfactory at Moho depths than in the upper crust. The qua1ity of the model resulting from inversion of real data is examined by the ca1culation of the Spread Function (Toomey and Foulger, 1989. The 3-D crustal P-wave velocity mode1 of the Italian region shows remarkab1e trends at Moho depths: the areas east of the Apennines call for positive adjustments of the initial velocity va1ue, while the west region shows negative ad- justments. The correspondence among the main features of the velocity field, the map of Moho isobaths and the map of the gravity anoma1ies is also outlined.

  19. High frame-rate blood vector velocity imaging using plane waves: simulations and preliminary experiments

    DEFF Research Database (Denmark)

    Udesen, J.; Gran, F.; Hansen, K.L.

    2008-01-01

    Conventional ultrasound methods for acquiring color images of blood velocity are limited by a relatively low frame-rate and are restricted to give velocity estimates along the ultrasound beam direction only. To circumvent these limitations, the method presented in this paper uses 3 techniques: 1...... carotid artery of a healthy male was scanned with a scan sequence that satisfies the limits set by the Food and Drug Administration. Vector velocity images were obtained with a frame-rate of 100 Hz where 40 speckle images are used for each vector velocity image. It was found that the blood flow...

  20. High Frame-Rate Blood Vector Velocity Imaging Using Plane Waves: Simulations and Preliminary Experiments

    DEFF Research Database (Denmark)

    Udesen, Jesper; Gran, Fredrik; Hansen, Kristoffer Lindskov

    2008-01-01

    Conventional ultrasound methods for acquiring color images of blood velocity are limited by a relatively low frame-rate and are restricted to give velocity estimates along the ultrasound beam direction only. To circumvent these limitations, the method presented in this paper uses 3 techniques: 1...... carotid artery of a healthy male was scanned with a scan sequence that satisfies the limits set by the Food and Drug Administration. Vector velocity images were obtained with a frame-rate of 100 Hz where 40 speckle images are used for each vector velocity image. It was found that the blood flow...

  1. Dispersion Energy Analysis of Rayleigh and Love Waves in the Presence of Low-Velocity Layers in Near-Surface Seismic Surveys

    Science.gov (United States)

    Mi, Binbin; Xia, Jianghai; Shen, Chao; Wang, Limin

    2017-10-01

    High-frequency surface-wave analysis methods have been effectively and widely used to determine near-surface shear (S) wave velocity. To image the dispersion energy and identify different dispersive modes of surface waves accurately is one of key steps of using surface-wave methods. We analyzed the dispersion energy characteristics of Rayleigh and Love waves in near-surface layered models based on numerical simulations. It has been found that if there is a low-velocity layer (LVL) in the half-space, the dispersion energy of Rayleigh or Love waves is discontinuous and ``jumping'' appears from the fundamental mode to higher modes on dispersive images. We introduce the guided waves generated in an LVL (LVL-guided waves, a trapped wave mode) to clarify the complexity of the dispersion energy. We confirm the LVL-guided waves by analyzing the snapshots of SH and P-SV wavefield and comparing the dispersive energy with theoretical values of phase velocities. Results demonstrate that LVL-guided waves possess energy on dispersive images, which can interfere with the normal dispersion energy of Rayleigh or Love waves. Each mode of LVL-guided waves having lack of energy at the free surface in some high frequency range causes the discontinuity of dispersive energy on dispersive images, which is because shorter wavelengths (generally with lower phase velocities and higher frequencies) of LVL-guided waves cannot penetrate to the free surface. If the S wave velocity of the LVL is higher than that of the surface layer, the energy of LVL-guided waves only contaminates higher mode energy of surface waves and there is no interlacement with the fundamental mode of surface waves, while if the S wave velocity of the LVL is lower than that of the surface layer, the energy of LVL-guided waves may interlace with the fundamental mode of surface waves. Both of the interlacements with the fundamental mode or higher mode energy may cause misidentification for the dispersion curves of surface

  2. Developing Regionalized Models of Lithospheric Thickness and Velocity Structure Across Eurasia and the Middle East from Jointly Inverting P-Wave and S-Wave Receiver Functions with Rayleigh Wave Group and Phase Velocities

    Science.gov (United States)

    2011-09-01

    constant sub- Moho velocity and velocity gradient. Because the mantle lithosphere is parameterized as infinitely thick with a constant velocity...increase up to 4.5 km/s at Moho depths. The mantle is PREM-like and does not display any velocity decrease suggestive of a lithosphere-asthenosphere...models were inverted down to a depth of 250 km and constrained to be PREM below. The low-velocity channel is bounded by the red dotted lines, the Moho is

  3. Geological variation in S-wave velocity structures in Northern Taiwan and implications for seismic hazards based on ambient noise analysis

    Science.gov (United States)

    Lai, Ya-Chuan; Huang, Bor-Shouh; Huang, Yu-Chih; Yao, Huajian; Hwang, Ruey-Der; Huang, Yi-Ling; Chang, Wen-Yen

    2014-12-01

    Ambient noise analysis in Northern Taiwan revealed obvious lateral variations related to major geological units. The empirical Green's functions extracted from interstation ambient noise were regarded as Rayleigh waves, from which we analyzed the group velocities for period from 3 to 6 s. According to geological features, we divided Northern Taiwan into seven subregions, for which regionalized group velocities were derived by using the pure-path method. On average, the group velocities in mountain areas were higher than those in the plain areas. We subsequently inverted the S-wave velocity structure for each subregion down to 6 km in depth. Following the analysis, we proposed the first models of geology-dependent shallow S-wave structures in Northern Taiwan. Overall, the velocity increased substantially from west to east; specifically, the mountain areas, composed of metamorphic rocks, exhibited higher velocities than did the coastal plain and basin, which consist of soft sediment. At a shallow depth, the Western Coastal Plain, Taipei Basin, and Ilan Plain displayed a larger velocity gradient than did other regions. At the top 3 km of the model, the average velocity gradient was 0.39 km/s per km for the Western Coastal Plain and 0.15 km/s per km for the Central Range. These S-wave velocity models with large velocity gradients caused the seismic waves to become trapped easily in strata and, thus, the ground motion was amplified. The regionalized S-wave velocity models derived from ambient noises can provide useful information regarding seismic wave propagation and for assessing seismic hazards in Northern Taiwan.

  4. Factors related to pulse wave velocity and augmentation index in chronic hemodialysis patients.

    Science.gov (United States)

    Celik, Gülperi; Demirci, Meltem Sezis; Tumuklu, Murat; Ascı, Gulay; Sipahi, Savas; Toz, Huseyin; Bascı, Ali; Ok, Ercan

    2011-01-01

    Augmentation index (AIx) and pulse wave velocity (PWV) are early markers of atherosclerotic vascular changes and also have been shown to be predictive of cardiovascular disease and total mortality. The aim of our study was to evaluate the relationship between PWV and AIx-HR75, which is the corrected form of AIx according to a heart rate of 75 beats/min, echocardiographic parameters and biochemical parameters in chronic hemodialysis (HD) patients. AIx-HR75 and PWV were measured in 556 HD patients by applanation tonometry using the SphygmoCor device. The mean PWV and AIx-HR75 values of the study group were 10.2 ± 2.4 and 28.4 ± 10.2 m/s. A positive correlation was found between PWV and AIx-HR75 (r = 0.214, p = 0.000). AIx-HR75 correlated with age (r = 0.093, p = 0.028), body surface area (BSA) (r = -0.194, p = 0.000), mean arterial pressure (MAP) (r = 0.335, p = 0.000), pulse pressure (PP) (r = 0.212, p = 0.000), cardiothoracic index (r = 0.155, p = 0.016), and presence of left ventricular hypertrophy (r = 0.152, p = 0.001). PWV correlated with MAP (r = 0.208, p = 0.000), PP (r = 0.098, r = 0.021), left ventricular mass (r = 0.105, p = 0.023), and predialysis sodium level (r = -0.105, p = 0.023). In the multivariate analyses, PWV was associated with MAP (t = 3.78, p = 0.000), presence of diabetes (t = 3.20, p = 0.001), and predialysis sodium level (t = -2.06, p = 0.040), and AIx-HR75 was associated with age (t = 2.48, p = 0.014), female sex (t = 3.98, p = 0.000), BSA (t = -2.15, p = 0.033), and MAP (t = 7.02, p = 0.000). There is a strong association between MAP and arterial stiffness parameters in HD patients. We feel that efficient control of blood pressure could lead to reduced arterial stiffness in HD patients.

  5. [Review on Application of Optical Scattering Spectroscopy for Elastic Wave Velocity Study on Materials in Earth's Interior].

    Science.gov (United States)

    Jiang, Jian-jun; Li, He-ping; Dai, Li-dong; Hu, Hai-ying; Wang, Yan; Zhao, Chao-shuai

    2015-09-01

    In-situ experimental results on the elastic wave velocity of Earth materials at high pressure and high temperature in combination with data from seismic observation can help to inverse the chemical composition, state and migration of materials in Earth's interior, providing an important approach to explore information of deep earth. Applying the Brillouin scattering into the Diamond Anvil Cell (DAC) to obtain the in situ elastic wave velocities of minerals, is the important approach to investigate elastic properties of Earth's Interior. With the development of DAC technology, on the one hand, the high temperature and high pressure experimental environment to simulate different layers of the earth can be achieved; on the other hand, the optical properties of DAC made many kinds of optical analysis and test methods have been widely applied in this research field. In order to gain the elastic wave velocity under high temperature and high pressure, the accurate experimental pressure and heating temperature of the sample in the cavity should be measured and calibrated first, then the scattering signal needs to dealt with, using the Brillouin frequency shift to calculate the velocity in the sample. Combined with the lattice constants obtained from X ray technique, by a solid elastic theory, all the elastic parameters of minerals can be solved. In this paper, firstly, application of methods based on optical spectrum such as Brillouin and Raman scattering in elasticity study on materials in Earth's interior, and the basic principle and research progress of them in the velocity measurement, pressure and temperature calibration are described in detail. Secondly, principle and scope of application of two common methods of spectral pressure calibration (fluorescence and Raman spectral pressure standard) are analyzed, in addition with introduce of the application of two conventional means of temperature calibration (blackbody radiation and Raman temperature scale) in

  6. Sediment and Crustal Shear Velocity Structure offshore New Zealand from Seafloor Compliance, Receiver Functions and Rayleigh Wave Dispersion

    Science.gov (United States)

    Ball, J. S.; Sheehan, A. F.; Stachnik, J. C.; Lin, F.; Collins, J. A.

    2013-12-01

    We have developed a joint Monte Carlo inversion of teleseismic receiver functions, seafloor compliance, and Rayleigh wave dispersion and apply it here to ocean bottom seismic (OBS) data from offshore New Zealand. With this method we estimate sediment and crustal thickness and shear velocity structure beneath the Bounty Trough and the Tasman Sea flanking the South Island of New Zealand. Teleseismic receiver functions and surface wave dispersion measurements provide complementary constraints on shear velocity structure and interface depths beneath seismic stations. At ocean bottom seismic (OBS) stations the interpretation of these measurements is complicated by strong sediment reverberations that obscure deeper impedance contrasts such as the Moho. In principle, the seafloor's response to ocean loading from infragravity waves (seafloor compliance) can be used to determine shallow shear velocity information. This velocity information can subsequently be used to better model the receiver function reverberations, allowing deeper interfaces of tectonic interest to be resolved. Data for this study were acquired in 2009-2010 by the Marine Observations of Anisotropy Near Aotearoa (MOANA) experiment, which deployed 30 broadband OBS and differential pressure gauges (DPGs) off the South Island of New Zealand. High-frequency (5Hz) receiver functions were estimated using multitaper cross-correlation for events in a 30-90 degree epicentral distance range. Coherence-weighted stacks binned by epicentral distance were produced in the frequency domain to suppress noise. Seafloor compliance was measured using multitaper pressure and acceleration spectra averaged from 120 days of continuous data without large transient events. Seafloor compliance measurements on the order of 10-9 Pa-1 are sensitive to shear velocity structure in the uppermost 5km of the crust and sediments. Rayleigh dispersion measurements were obtained at periods of 6-27s from ambient noise cross correlation. Sediment

  7. An Analysis of Pulsed Wave Ultrasound Systems for Blood Velocity Estimation

    DEFF Research Database (Denmark)

    Jensen, J. A.

    1995-01-01

    of the received signal. The time evolution and distribution of velocity can then be found by using samples from a number of pulse-echo lines. Making a short-time Fourier transform of the data reveals the velocity distribution in the range gate over time. Such systems are called Doppler ultrasound systems implying...

  8. Defining the relation between mechanical properties and ultrasonic wave velocity in spheroidal cast iron manufactured in the foundry Metal-Odlew s.c.

    Directory of Open Access Journals (Sweden)

    W. Orłowicz

    2009-01-01

    Full Text Available This work presents results of ultrasonic evaluation of mechanical properties of spheroidal cast iron manufactured under the productionconditions of Metal-Odlew s.c. Tests were conducted on wedge casts which were used as samples for tensile tests, a map of distribution of longitudinal ultrasound wave velocity was determined for the cast wedges. The tensile tests were conducted and values of longitudinalultrasound wave velocity were determined in the place where the sample was broken. Relations between the mechanical properties and the velocity of longitudinal ultrasonic wave cL were determined.

  9. Influence of Pore-Fluid Pressure on Elastic Wave Velocity and Electrical Conductivity in Water-Saturated Rocks

    Science.gov (United States)

    Higuchi, A.; Watanabe, T.

    2013-12-01

    Pore-fluid pressure in seismogenic zones can play a key role in the occurrence of earthquakes (e.g., Sibson, 2009). Its evaluation via geophysical observations can lead to a good understanding of seismic activities. The evaluation requires a thorough understanding of the influence of the pore-fluid pressure on geophysical observables like seismic velocity and electrical conductivity. We have studied the influence of pore-fluid pressure on elastic wave velocity and electrical conductivity in water-saturated rocks. Fine grained (100-500μm) biotite granite (Aji, Kagawa pref., Japan) was used as rock samples. The density is 2.658-2.668 g/cm3, and the porosity 0.68-0.87%. The sample is composed of 52.8% plagioclase, 36.0% Quartz, 3.0% K-feldspar, 8.2% biotite. SEM images show that a lot of grain boundaries are open. Few intracrystalline cracks were observed. Following the method proposed by David and Zimmerman (2012), the distribution function of crack aspect ratio was evaluated from the pressure dependence of compressional and shear wave velocities in a dry sample. Cylindrical sample has dimensions of 25 mm in diameter and 30 mm in length, and saturated with 0.01 mol/l KCl aqueous solution. Compressional and shear wave velocities were measured with the pulse transmission technique (PZT transducers, f=2 MHz), and electrical conductivity the two-electrode method (Ag-AgCl electrodes, f=1 Hz-100 kHz). Simultaneous measurements of velocities and conductivity were made using a 200 MPa hydrostatic pressure vessel, in which confining and pore-fluid pressures can be separately controlled. The pore-fluid is electrically insulated from the metal work of the pressure vessel by using a newly designed plastic device (Watanabe and Higuchi, 2013). The confining pressure was progressively increased up to 25 MPa, while the pore-fluid pressure was kept at 0.1 MPa. It took five days or longer for the electrical conductivity to become stationary after increasing the confining pressure

  10. Association of type 2 diabetes mellitus and ratio of transmitral E wave velocity to early diastole mitral velocity with cardiovascular events in chronic kidney disease.

    Science.gov (United States)

    Chen, Po-Chih; Huang, Jiun-Chi; Chen, Szu-Chia; Wu, Pei-Yu; Lee, Jia-Jung; Chiu, Yi-Wen; Chang, Jer-Ming; Chen, Hung-Chun; Huang, Yeou-Lih

    2017-11-07

    The association between DM and left ventricular diastolic dysfunction, assessed using the ratio of peak early transmitral filling wave velocity (E) to early diastolic velocity of mitral annulus (Ea), with cardiovascular (CV) outcomes in patients with chronic kidney disease (CKD) remains uncertain. This study included 356 CKD stage 3-5 patients underwent echocardiography. All patients were classified into four groups based on the presence of DM and E/Ea ≤ or > 9. CV events included CV death, hospitalization for heart failure, unstable angina or nonfatal myocardial infarction, sustained ventricular arrhythmia, transient ischemic attack, and stroke. There were 58 CV events during the mean observation period of 25.0 months. A combination of the presence of DM and E/Ea > 9 (vs. a combination of non-DM and E/Ea ≤ 9) was associated with CV events in unadjusted model (hazard ratio [HR], 6.990; 95% confidence interval [CI], 2.753-17.744; p Ea ratio (p = 0.033) improved the prediction of CV events, compared to the E/Ea ratio (p = 0.018), left atrial diameter (p = 0.016) and left ventricular mass index (p = 0.001) in the patients with DM. The combination of DM and left ventricular diastolic dysfunction was associated with CV events in patients with CKD stage 3-5. Assessments of DM status and E/Ea ratio may facilitate identifying high-risk patient population of unfavorable CV outcomes.

  11. Shear velocity model for the westernmost Mediterranean from ambient noise and ballistic finite-frequency Rayleigh wave tomography

    Science.gov (United States)

    Palomeras, I.; Villasenor, A.; Thurner, S.; Levander, A.; Gallart, J.; Harnafi, M.

    2014-12-01

    The westernmost Mediterranean comprises the Iberian Peninsula and Morocco, separated by the Alboran Sea and the Algerian Basin. From north to south this region consists of the Pyrenees, resulting from Iberia-Eurasia collision; the Iberian Massif, which has been undeformed since the end of the Paleozoic; the Central System and Iberian Chain, regions with intracontinental Oligocene-Miocene deformation; the Gibraltar Arc (Betics, Rif and Alboran terranes), resulting from post-Oligocene subduction roll-back; and the Atlas Mountains. We analyzed data from recent broad-band array deployments and permanent stations in the area (IberArray and Siberia arrays, the PICASSO array, the University of Munster array, and the Spanish, Portuguese and Moroccan National Networks) to characterize its lithospheric structure. The combined array of 350 stations has an average interstation spacing of ~60 km. We calculated the Rayleigh waves phase velocities from ambient noise (periods 4 to 40 s) and teleseismic events (periods 20 to 167 s). We inverted the phase velocities to obtain a shear velocity model for the lithosphere to ~200 km depth. Our results correlate well with the surface expression of the main structural units with higher crustal velocity for the Iberian Massif than for the Alpine Iberia and Atlas Mountains. The Gibraltar Arc has lower crustal shear velocities than the regional average at all crustal depths. It also shows an arc shaped anomaly with high upper mantle velocities (>4.6 km/s) at shallow depths (<65 km) interpreted as the subducting Alboran slab. The hanging slab is depressing the crust of the Gibraltar arc to ~55 km depth, as seen in receiver function data and active source seismic profiles. Low upper mantle velocities (<4.2 km/s) are observed beneath the Atlas, the northeastern end of the Betic Mountains and the Late Cenozoic volcanic fields in Iberia and Morocco, indicative of high temperatures at relatively shallow depths, and suggesting that the lithosphere

  12. Phase and group velocity tracing analysis of projected wave packet motion along oblique radar beams – qualitative analysis of QP echoes

    Directory of Open Access Journals (Sweden)

    F. S. Kuo

    2007-02-01

    Full Text Available The wave packets of atmospheric gravity waves were numerically generated, with a given characteristic wave period, horizontal wave length and projection mean wind along the horizontal wave vector. Their projection phase and group velocities along the oblique radar beam (vpr and vgr, with different zenith angle θ and azimuth angle φ, were analyzed by the method of phase- and group-velocity tracing. The results were consistent with the theoretical calculations derived by the dispersion relation, reconfirming the accuracy of the method of analysis. The RTI plot of the numerical wave packets were similar to the striation patterns of the QP echoes from the FAI irregularity region. We propose that the striation range rate of the QP echo is equal to the radial phase velocity vpr, and the slope of the energy line across the neighboring striations is equal to the radial group velocity vgr of the wave packet; the horizontal distance between two neighboring striations is equal to the characteristic wave period τ. Then, one can inversely calculate all the properties of the gravity wave responsible for the appearance of the QP echoes. We found that the possibility of some QP echoes being generated by the gravity waves originated from lower altitudes cannot be ruled out.

  13. Identifying coronary artery disease in men with type 2 diabetes: osteoprotegerin, pulse wave velocity, and other biomarkers of cardiovascular risk.

    LENUS (Irish Health Repository)

    Davenport, Colin

    2012-02-01

    OBJECTIVES: In patients with type 2 diabetes, high serum levels of osteoprotegerin (OPG) have been associated with a greater risk of cardiovascular events. However, it remains unclear how well OPG performs when compared with traditional biomarkers of cardiovascular risk such as high-sensitivity C-reactive protein (hsCRP). Furthermore, OPG levels are also high in the presence of diabetes-related microvascular disease, and it is unclear whether OPG can distinguish microvascular disease from large-vessel atherosclerosis. The first aim of this study was to compare OPG levels against other biomarkers of cardiovascular risk in the identification of patients with documented multivessel coronary artery disease (CAD). The second aim was to compare OPG levels in patients with microvascular complications (microalbuminuria) against those with established CAD. METHODS: Three groups of male patients with type 2 diabetes were recruited: patients without microvascular complications or large-vessel atherosclerosis (n = 24), patients with microalbuminuria only (n = 23), and patients with microalbuminuria and documented multivessel CAD (n = 25). OPG, hsCRP, interleukin 6, urate, and pulse wave velocity were measured. RESULTS: Serum OPG levels were significantly higher in patients with a combination of microalbuminuria and CAD than in those with microalbuminuria alone. There were no significant differences in any of the other biomarkers between the groups. CONCLUSION: OPG was found to be superior to the other biomarkers studied in identifying patients with documented CAD. The presence of CAD was a greater determinant of serum OPG levels than microalbuminuria in our population. These findings support the use of OPG as a biomarker of cardiovascular risk.

  14. Time-lapse changes of P- and S-wave velocities and shear wave splitting in the first year after the 2011 Tohoku earthquake, Japan: shallow subsurface

    Science.gov (United States)

    Sawazaki, Kaoru; Snieder, Roel

    2013-04-01

    We detect time-lapse changes in P- and S-wave velocities (hereafter, VP and VS, respectively) and shear wave splitting parameters associated with the 2011 Tohoku earthquake, Japan, at depths between 0 and 504 m. We estimate not only medium parameters but also the 95 per cent confidence interval of the estimated velocity change by applying a new least squares inversion scheme to the deconvolution analysis of KiK-net vertical array records. Up to 6 per cent VS reduction is observed at more than half of the analysed KiK-net stations in northeastern Japan with over 95 per cent confidence in the first month after the main shock. There is a considerable correlation between the S-wave traveltime delay and the maximum horizontal dynamic strain (MDS) by the main shock motion when the strain exceeds 5 × 10- 4 on the ground surface. This correlation is not clearly observed for MDS at the borehole bottom. On the contrary, VP and shear wave splitting parameters do not show systematic changes after the Tohoku earthquake. These results indicate that the time-lapse change is concentrated near the ground surface, especially in loosely packed soil layers. We conclude that the behaviour of VP, VS and shear wave splitting parameters are explained by the generation of omnidirectional cracks near the ground surface and by the diffusion of water in the porous subsurface. Recovery of VS should be related to healing of the crack which is proportional to the logarithm of the lapse time after the main shock and/or to decompaction after shaking.

  15. Intraseasonal vertical velocity variation caused by the equatorial wave in the central equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Horii, T.; Masumoto, Y.; Ueki, I.; PrasannaKumar, S.; Mizuno, K.

    for African-Asian-Australian Monsoon Analysis and Prediction, in October-November 2006. Using an array of four subsurface moored acoustic Doppler current profilers, we estimated vertical velocity by applying the continuity equation. Results indicated...

  16. 2-D inversion of P-wave polarization data to obtain maps of velocity gradient

    Science.gov (United States)

    Jing, Xili; Li, Li

    2017-11-01

    Gradient mapping is a technique employed in the interpretation of tomographic velocity images for delineating geological structures. In this paper, a tomographic method is proposed for determining relative velocity gradient field from seismic polarization directions. This inverse problem is iteratively resolved by the damped least squares method. With Hamiltonian formulation of ray theory and under the assumption that the medium is weakly inhomogeneous, the problem formulation for polarization direction is approximately expressed as a function of relative velocity gradient. Explicit expressions of the Frechet derivatives of polarization directions with respect to model parameters are given. The proposed tomographic method is illustrated by conducting synthetic experiments for showing the ability of our method to recover relative velocity gradient field as well as its potential applicability to complex media. The test results demonstrate that the proposed method is a promising approach for imaging geological structures.

  17. Estimation of shallow S-wave velocity structure and site response characteristics by microtremor array measurements in Tekirdag region, NW Turkey

    National Research Council Canada - National Science Library

    Karagoz, Ozlem; Chimoto, Kosuke; Citak, Seckin; Ozel, Oguz; Yamanaka, Hiroaki; Hatayama, Ken

    2015-01-01

    ...). We collected microtremor array data at 44 sites in Tekirdag, Marmara Ereglisi, Corlu, and Muratlı. The phase velocities of Rayleigh waves were estimated from the microtremor data using a Spatial Autocorrelation method...

  18. Comparison of an oscillometric method with cardiac magnetic resonance for the analysis of aortic pulse wave velocity.

    Science.gov (United States)

    Feistritzer, Hans-Josef; Reinstadler, Sebastian J; Klug, Gert; Kremser, Christian; Seidner, Benjamin; Esterhammer, Regina; Schocke, Michael F; Franz, Wolfgang-Michael; Metzler, Bernhard

    2015-01-01

    Pulse wave velocity (PWV) is the proposed gold-standard for the assessment of aortic elastic properties. The aim of this study was to compare aortic PWV determined by a recently developed oscillometric device with cardiac magnetic resonance imaging (CMR). PWV was assessed in 40 volunteers with two different methods. The oscillometric method (PWVOSC) is based on a transfer function from the brachial pressure waves determined by oscillometric blood pressure measurements with a common cuff (Mobil-O-Graph, I.E.M. Stolberg, Germany). CMR was used to determine aortic PWVCMR with the use of the transit time method based on phase-contrast imaging at the level of the ascending and abdominal aorta on a clinical 1.5 Tesla scanner (Siemens, Erlangen, Germany). The median age of the study population was 34 years (IQR: 24-55 years, 11 females). A very strong correlation was found between PWVOSC and PWVCMR (r = 0.859, p wave velocity assessed by transformation of the brachial pressure waveform showed an acceptable agreement with the CMR-derived transit time method.

  19. Study of the dynamic behavior of earthflows through the analysis of shear wave velocity in the landslide's body

    Science.gov (United States)

    Bertello, Lara

    2015-04-01

    Over the first year of my PhD, I carried out a literature search about earthflows features and dynamics and conducted periodic ReMi-MASW campaigns to assess the temporal variation of shear velocity for several landslides that were recently reactivated. Literature search was conducted to review recent works related to shear wave velocity as an indicator for rheological changes in clay materials (Mainsant et al., 2012). From January to August 2014 I carried out numerous ReMi-MASW surveys to characterize several active earthflows in the Emilia-Romagna Apennines. I did these measures both inside and outside the landslide's bodies, usually during the first ten days after the reactivation. At first, these measures indicate low shear waves velocity inside the landslide and high velocity outside. This is due to the different consistence of the materials, to the different water content and to the void index. Then I repeated the measures over time in the same places on the same landslide, in order to detect the variability of Vs over time in correlations with the landslide's movements. Periodic ReMi-MASW survey were conducted on the following landslides: • The Montevecchio (FC) earthflow was reactivated the 1th of February 2014 (estimated volume of 240.000 m³) and increased the movement's velocity around the 7th of February 2014, after intense precipitations. Analyzing the data collected inside the landslide's body, I observed an increase of Vs over time, due to the decrease of landslide velocity; • The Silla (BO) complex landslide reactivated the 10th of February 2014 (estimated volume of 900.000 m³), and moved downslope with a maximum velocity in the order of several m/hour. Studying the data, it is possible to notice how the Vs increase over time only in the lower portion of the landslide. In fact the upper portion is still active, so the Vs remained unchanged over time. • the Puzzola-Grizzana Morandi (BO) complex landslide. This landslide was reactivated the 10th

  20. Circumferential-wave phase velocities for empty, fluid-immersed spherical metal shells

    DEFF Research Database (Denmark)

    Überall, Herbert; Claude Ahyi, A.; Raju, P. K.

    2001-01-01

    frequency/elasticity-theory connection, and we obtain comparative dispersion-curve results for water-loaded, evacuated spherical shells of various metals. In particular, the characteristic upturn of the dispersion curves of low-order shell-borne circumferential waves (A or A0 waves) which takes place...... on spherical shells when the frequency tends towards low values, is demonstrated here for all the metals under consideration....

  1. Equivalent pore radius and velocity of elastic waves in shale. Skjold Flank-1 Well, Danish North Sea

    DEFF Research Database (Denmark)

    Mbia, Ernest Ncha; Fabricius, Ida Lykke; Oji, Collins O.

    2013-01-01

    logging data.We used cuttings samples and available well logs to characterize Cenozoic, Cretaceous and Jurassic shale sections in the Skjold Flank-1 well of Danish North Sea. Logging data and well reports were used to select 31 shale cuttings samples and experimental data for porosity, grain density...... relationships were used to calculate equivalent pore radius for the Cenozoic, Cretaceous and Jurassic shale sections in Skjold Flank-1 well from elastic moduli. Elastic moduli were calculated from sonic velocity and density logs. The calculated equivalent pore radius logs vary from 27nm at 500m to 13nm at 2000m...... experiments on cuttings or core samples. In this study we demonstrate that elastic moduli as calculated from bulk density and velocity of elastic waves relate to equivalent pore radius of the studied shale intervals. This relationship establishes the possibility of calculating equivalent pore radius from...

  2. Continuous monitoring of shear wave velocity at the Montevecchio earthflow (Forlì-Cesena Province, Northern Apennines)

    Science.gov (United States)

    Bertello, Lara; Berti, Matteo; Castellaro, Silvia

    2016-04-01

    The Montevecchio landslide is located about 20 km to the south - west of Cesena (Northern Italy). The landslide has a length of nearly 700 m, a maximum width of 50 m in the accumulation zone and the depth of the slip surface is around 10 m. This landslide was triggered several times in the last few years. At first on the 1th of February 2014 and at the end of February 2014 some remedial works started. From February to May 2014, the velocity of the landslide was around meters/day. At the end of May 2014, two monitoring systems were installed in the main track of the earthflow channel. The System 1 consists of a rain gauge, a pressure sensor at the depth of 1 meter, a time-lapse camera Brinno (taking photos every 30 minutes), a laser system and four geophones at 4.5Hz with a spacing of 2 meters. The System 2 consists of three GPS rover placed in the earthflow channel and the master station outside the landslide. During the 2015, the Montevecchio earth flow reactivated three times. The last reactivation was during the night between the 24th and the 25th of May. Analyzing the data acquired from the geophones, the trend of the shear wave velocity over time was detected. The data correspond to an acquisition of the ambient seismic noise (passive mode) with a sampling frequency of 300 Hz for 2min every hours and all them are collected in a Flash Memory Drive. A drop in Vs is found from the 21th-22th of May, in correspondence with a rainfall event. The video collected by the time-lapse camera shows that the landslide started to move downslope with a velocity of about 10 cm/d. Before this rainfall, the landslide was moving at a very low speed (less than 1 cm/day) and shear wave velocities were relatively high. The displacement rate increased on the 27th of May after the second rainfall event (30 mm/d) and reached the value of 10 m/day. The velocity remained apparently constant for several days, but we should consider that the data collected from the 27th of May to the 1th

  3. Why Did Bluetongue Spread the Way It Did? Environmental Factors Influencing the Velocity of Bluetongue Virus Serotype 8 Epizootic Wave in France

    Science.gov (United States)

    Pioz, Maryline; Guis, Hélène; Crespin, Laurent; Gay, Emilie; Calavas, Didier; Durand, Benoît; Abrial, David; Ducrot, Christian

    2012-01-01

    Understanding where and how fast an infectious disease will spread during an epidemic is critical for its control. However, the task is a challenging one as numerous factors may interact and drive the spread of a disease, specifically when vector-borne diseases are involved. We advocate the use of simultaneous autoregressive models to identify environmental features that significantly impact the velocity of disease spread. We illustrate this approach by exploring several environmental factors influencing the velocity of bluetongue (BT) spread in France during the 2007–2008 epizootic wave to determine which ones were the most important drivers. We used velocities of BT spread estimated in 4,495 municipalities and tested sixteen covariates defining five thematic groups of related variables: elevation, meteorological-related variables, landscape-related variables, host availability, and vaccination. We found that ecological factors associated with vector abundance and activity (elevation and meteorological-related variables), as well as with host availability, were important drivers of the spread of the disease. Specifically, the disease spread more slowly in areas with high elevation and when heavy rainfall associated with extreme temperature events occurred one or two months prior to the first clinical case. Moreover, the density of dairy cattle was correlated negatively with the velocity of BT spread. These findings add substantially to our understanding of BT spread in a temperate climate. Finally, the approach presented in this paper can be used with other infectious diseases, and provides a powerful tool to identify environmental features driving the velocity of disease spread. PMID:22916249

  4. Association of pulse wave velocity with total lung capacity: A cross-sectional analysis of the BOLD London study.

    Science.gov (United States)

    Amaral, André F S; Patel, Jaymini; Gnatiuc, Louisa; Jones, Meinir; Burney, Peter G J

    2015-12-01

    Low lung function, measured using spirometry, has been associated with mortality from cardiovascular disease, but whether this is explained by airflow obstruction or restriction is a question that remains unanswered. To assess the association of total lung capacity (TLC), forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) with several cardio-metabolic and inflammatory markers. In the follow up of the Burden of Lung Disease (BOLD) study in London, acceptable post-bronchodilator spirometric, pulse rate, pulse wave velocity and blood pressure data were obtained from 108 participants. Blood samples for measurement of cardio-metabolic and inflammatory markers were also collected from these participants. Association of lung function and volume with the different biomarkers was examined in multivariable linear regression models adjusted for potential confounders. Following adjustment for age, sex, height, and ethnicity, TLC (adjusted coefficient = -1.53; 95% CI: -2.57, -0.49) and FVC (adjusted coefficient = -2.66; 95% CI: -4.98, -0.34) were inversely associated with pulse wave velocity, and further adjustment for smoking status, pack-years and body mass index (BMI) did not materially change these results. FEV1 was inversely associated with systolic blood pressure, and adjustment for smoking status, pack-years and BMI made this association stronger (adjusted coefficient = -9.47; 95% CI: -15.62, -3.32). The inverse association of pulse wave velocity, which is a marker of cardiovascular disease, with TLC suggests that the association of the former with low FVC is independent of airflow obstruction. The association between FEV1 with systolic blood pressure after adjustment for FVC suggests an association with airflow obstruction rather than with restricted spirometry. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  5. S-wave velocity structure and tectonic implications of the northwestern sub-basin and Macclesfield of the South China Sea

    Science.gov (United States)

    Wei, Xiaodong; Ruan, Aiguo; Li, Jiabiao; Niu, Xiongwei; Wu, Zhenli; Ding, Weiwei

    2017-06-01

    Based on the optimum P-wave model, the S-wave velocity structure of a wide angle seismic profile (OBS2006-1), across the northwestern sub-basin (NWSB) and the Macclesfield, is simulated by a 2-D ray-tracing method. The results indicate the S-wave velocities in the upper and lower crust of the NWSB are 3.2-3.6 km/s and 3.6-4.0 km/s, with Vp/ Vs ratios of 1.82-1.88 and 1.74-1.82, respectively, which reflect typical oceanic crust characteristics. The S-wave velocity in the upper crust of the NWSB is a little higher in the NNW segment than that in the SSE segment, while the lateral variation of Vp/ Vs ratio is in the opposite. We suggest that the NWSB might have experienced asymmetrical magma flows during sea floor spreading, which may have blurred the magnetic anomaly lineation. The comparison of S-wave velocities along the northern margin of the SCS shows that the west section is different from the east section, and the northwestern margin has a non-volcanic crust structure. The S-wave structures and P-wave velocity models along the northern margin, Macclesfield and Reed Bank show that the Macclesfield might have a conjugate relationship with the Reed Bank.

  6. Diurnal Variation of Pulse Wave Velocity Assessed Non-Invasively by Applanation Tonometry in Young Healthy Men

    OpenAIRE

    Bodlaj, Gerd; Berg, Joerg; Biesenbach, Georg

    2007-01-01

    Purpose Pulse wave velocity (PWV) is at least partially controlled by vascular tone. Vascular tone and underlying physiological processes such as sympathetic activity, plasma catecholamin, and cortisol levels have been shown to follow diurnal variations. Materials and Methods Carotid-to-radial PWV was non-invasively assessed by applanation tonometry in 21 young (26.5 ? 2.3 years) healthy men at three different time points (8:00hr, 12:00hr, 17:00hr) during a day. Additionally, heart rate, syst...

  7. Microtremor exploration for shallow S-wave velocity profiles at stations in local strong motion network in Bursa, Yalova, and Kocaeli in north-western Turkey

    Science.gov (United States)

    Özmen, Özgür Tuna; Yamanaka, Hiroaki; Chimoto, Kosuke; Çeken, Ulubey; Alkan, Mehmet Akif; Tekin, Kudret; Ateş, Erkan

    2017-05-01

    We conducted microtremor array surveys for shallow S-wave velocity profiles at 20 sites in Bursa, Yalova and Kocaeli provinces in the north-western part of Turkey to provide fundamental data to assess the seismic hazard in the area. All of the measurement sites were positioned very close to strong motion stations belonging to the Disaster and Emergency Management Presidency of Turkey (AFAD) in order to further understand site amplification factors in strong motion records. Of the 20 study sites, two were located in Yalova, four in Bursa and 14 in Kocaeli. We temporarily installed two small arrays to obtain simultaneous records of vertical microtremors. Then, the spatial autocorrelation method was applied to retrieve Rayleigh wave phase velocity curves in a frequency range from 1 to 30 Hz from the array records. The phase velocities in the western part of the Kocaeli area are low across a wide frequency range, while relatively high phase velocities are found in the eastern part of the Kocaeli province. The phase velocities in the Yalova and Bursa provinces are widely distributed suggesting large variations in soil conditions. The observed phase velocity curve at each site was inverted to a one-dimensional (1D) S-wave velocity profile to a depth of 100 m, using a hybrid heuristic inversion method. All the S-wave velocity profiles in the eastern Kocaeli area are similar; however, the sites in the western Kocaeli and Yalova-Bursa areas have profiles with different features from the others. Finally, we discuss amplification factors for S-waves using the inverted profiles. The dominant fundamental periods of the amplification factors were distributed in a frequency range from 0.7 to 5 Hz. The profiles obtained are also used to map average S-wave velocities in the study area, with an addition of existing data at strong motion stations of the AFAD.

  8. Inversion of Love wave phase velocity using smoothness-constrained least-squares technique; Heikatsuka seiyakutsuki saisho jijoho ni yoru love ha iso sokudo no inversion

    Energy Technology Data Exchange (ETDEWEB)

    Kawamura, S. [Nippon Geophysical Prospecting Co. Ltd., Tokyo (Japan)

    1996-10-01

    Smoothness-constrained least-squares technique with ABIC minimization was applied to the inversion of phase velocity of surface waves during geophysical exploration, to confirm its usefulness. Since this study aimed mainly at the applicability of the technique, Love wave was used which is easier to treat theoretically than Rayleigh wave. Stable successive approximation solutions could be obtained by the repeated improvement of velocity model of S-wave, and an objective model with high reliability could be determined. While, for the inversion with simple minimization of the residuals squares sum, stable solutions could be obtained by the repeated improvement, but the judgment of convergence was very hard due to the smoothness-constraint, which might make the obtained model in a state of over-fitting. In this study, Love wave was used to examine the applicability of the smoothness-constrained least-squares technique with ABIC minimization. Applicability of this to Rayleigh wave will be investigated. 8 refs.

  9. Validated 3D Velocity Models in Asia from Joint Regional Body- and Surface-Wave Tomography

    Science.gov (United States)

    2009-02-17

    sedimentary basin structures across the region (e.g. Tarim , Ordos) persisting into the uppermost mantle. We show additional slices of the JWM model at 30...sedimentary basins or anomalous mantle structures, the assumed relationship may be wrong, leading to errors in the velocity model derived from the

  10. Wet and gassy zones in a municipal landfill from P- and S-wave velocity fields

    NARCIS (Netherlands)

    Konstantaki, L.A.; Ghose, R.; Draganov, D.S.; Heimovaara, T.J.

    2016-01-01

    The knowledge of the distribution of leachate and gas in a municipal landfill is of vital importance to the landfill operators performing improved landfill treatments and for environmental protection and efficient biogas extraction. We have explored the potential of using the velocity fields of

  11. Hyperbolic shock waves of the optical self-focusing with normal group-velocity dispersion

    DEFF Research Database (Denmark)

    Bergé, L.; Germaschewski, K.; Grauer, R.

    2002-01-01

    The theory of focusing light pulses in Kerr media with normal group-velocity dispersion in (2+1) and (3+1) dimensions is revisited. It is shown that pulse splitting introduced by this dispersion follows from shock fronts that develop along hyperbolas separating the region of transverse self...

  12. Microplasticity effect in low-velocity zone induced by seismic wave

    Science.gov (United States)

    Mashinskii, E. I.

    2012-08-01

    Microplasticity effects in loam caused by seismic wave of frequency about 1000 Hz are detected in the borehole-to-borehole measurements. Microplasticity manifestations on seismic record are presented as the ladder-like stepwise changes in amplitude course. The step (plateau) on seismic trace is time delay, its duration depends on the strain-amplitude value. Time delay changes the frequency characteristic of stress pulse, nonlinearly transforms wave front, and shifts the amplitude maximum along time axis. The microplastic process occurs owing to the anomalous realignment of the internal stresses on the microstructural defects in the area of small deformations. This is the useful contribution to wave propagation physics. The received results can also be used in solving the applied problems in material science, seismic prospecting, diagnostics, etc.

  13. Surface wave tomography of North America and the Caribbean using global and regional broad-band networks: Phase velocity maps and limitations of ray theory

    Science.gov (United States)

    Godey, S.; Snieder, R.; Villasenor, A.; Benz, H.M.

    2003-01-01

    We present phase velocity maps of fundamental mode Rayleigh waves across the North American and Caribbean plates. Our data set consists of 1846 waveforms from 172 events recorded at 91 broad-band stations operating in North America. We compute phase velocity maps in four narrow period bands between 50 and 150 s using a non-linear waveform inversion method that solves for phase velocity perturbations relative to a reference Earth model (PREM). Our results show a strong velocity contrast between high velocities beneath the stable North American craton, and lower velocities in the tectonically active western margin, in agreement with other regional and global surface wave tomography studies. We perform detailed comparisons with global model results, which display good agreement between phase velocity maps in the location and amplitude of the anomalies. However, forward modelling shows that regional maps are more accurate for predicting waveforms. In addition, at long periods, the amplitude of the velocity anomalies imaged in our regional phase velocity maps is three time larger than in global phase velocity models. This amplitude factor is necessary to explain the data accurately, showing that regional models provide a better image of velocity structures. Synthetic tests show that the raypath coverage used in this study enables one to resolve velocity features of the order of 800-1000 km. However, only larger length-scale features are observed in the phase velocity maps. The limitation in resolution of our maps can be attributed to the wave propagation theory used in the inversion. Ray theory does not account for off-great-circle ray propagation effects, such as ray bending or scattering. For wavelengths less than 1000 km, scattering effects are significant and may need to be considered.

  14. Generation of a pseudo-2D shear-wave velocity section by inversion of a series of 1D dispersion curves

    Science.gov (United States)

    Luo, Y.; Xia, J.; Liu, J.; Xu, Y.; Liu, Q.

    2008-01-01

    Multichannel Analysis of Surface Waves utilizes a multichannel recording system to estimate near-surface shear (S)-wave velocities from high-frequency Rayleigh waves. A pseudo-2D S-wave velocity (vS) section is constructed by aligning 1D models at the midpoint of each receiver spread and using a spatial interpolation scheme. The horizontal resolution of the section is therefore most influenced by the receiver spread length and the source interval. The receiver spread length sets the theoretical lower limit and any vS structure with its lateral dimension smaller than this length will not be properly resolved in the final vS section. A source interval smaller than the spread length will not improve the horizontal resolution because spatial smearing has already been introduced by the receiver spread. In this paper, we first analyze the horizontal resolution of a pair of synthetic traces. Resolution analysis shows that (1) a pair of traces with a smaller receiver spacing achieves higher horizontal resolution of inverted S-wave velocities but results in a larger relative error; (2) the relative error of the phase velocity at a high frequency is smaller than at a low frequency; and (3) a relative error of the inverted S-wave velocity is affected by the signal-to-noise ratio of data. These results provide us with a guideline to balance the trade-off between receiver spacing (horizontal resolution) and accuracy of the inverted S-wave velocity. We then present a scheme to generate a pseudo-2D S-wave velocity section with high horizontal resolution using multichannel records by inverting high-frequency surface-wave dispersion curves calculated through cross-correlation combined with a phase-shift scanning method. This method chooses only a pair of consecutive traces within a shot gather to calculate a dispersion curve. We finally invert surface-wave dispersion curves of synthetic and real-world data. Inversion results of both synthetic and real-world data demonstrate that

  15. Evidence for instability-waves in the velocity-field of a fully developed turbulent channel-flow

    Science.gov (United States)

    Hofbauer, M.

    1980-01-01

    The results from hot film measurements and quantitative visual investigations, performed in the turbulent flow of an oil-channel at a low Reynolds number (Re = 8000), are discussed. The main result of the hot film measurements is the power spectrum of the v-component of the fluctuating velocity. The power spectrum has regular maxima and minima. The frequencies corresponding to the maxima of the power spectrum are plotted as a function of the order n of the maxima. This graph demonstrates that the frequencies of the maxima are the harmonics of a fundamental frequency which are determined to be about 0.15 Hz. An estimation shows that the fundamental frequency is of the same order of magnitude as the roughly calculated unstable Tollmien-Schlichting frequencies of the mean turbulent velocity profile. This fundamental frequency is interpreted as the most excited frequency of Tollmien-Schlichting-like instability waves. The harmonics are believed to be due to a nonlinear amplification of the primarily excited instability waves. The evidence of regular oscillations in the near-wall region of the fully developed turbulent flow from the visual studies is examined.

  16. Site response, shallow shear-wave velocity, and damage in Los Gatos, California, from the 1989 Loma Prieta earthquake

    Science.gov (United States)

    Hartzell, S.; Carver, D.; Williams, R.A.

    2001-01-01

    Aftershock records of the 1989 Loma Prieta earthquake are used to calculate site response in the frequency band of 0.5-10 Hz at 24 locations in Los Gatos, California, on the edge of the Santa Clara Valley. Two different methods are used: spectral ratios relative to a reference site on rock and a source/site spectral inversion method. These two methods complement each other and give consistent results. Site amplification factors are compared with surficial geology, thickness of alluvium, shallow shear-wave velocity measurements, and ground deformation and structural damage resulting from the Loma Prieta earthquake. Higher values of site amplification are seen on Quaternary alluvium compared with older Miocene and Cretaceous units of Monterey and Franciscan Formation. However, other more detailed correlations with surficial geology are not evident. A complex pattern of alluvial sediment thickness, caused by crosscutting thrust faults, is interpreted as contributing to the variability in site response and the presence of spectral resonance peaks between 2 and 7 Hz at some sites. Within the range of our field measurements, there is a correlation between lower average shear-wave velocity of the top 30 m and 50% higher values of site amplification. An area of residential homes thrown from their foundations correlates with high site response. This damage may also have been aggravated by local ground deformation. Severe damage to commercial buildings in the business district, however, is attributed to poor masonry construction.

  17. Constraining P-wave velocity variations in the upper mantle beneath Southeast Asia

    NARCIS (Netherlands)

    Li, Chang; Hilst, R.D. van der; Toksöz, M. Nafi

    2006-01-01

    We have produced a P-wave model of the upper mantle beneath Southeast (SE) Asia from reprocessed short period International Seismological Centre (ISC) P and pP data, short period P data of the Annual Bulletin of Chinese Earthquakes (ABCE), and long period PP-P data.We used 3D sensitivity kernels

  18. Constraining spatial variations in P-wave velocity in the upper mantle beneath SE Asia

    NARCIS (Netherlands)

    Li, C.; Hilst, R.D. van der; Toksoz, N.M.

    2006-01-01

    We have produced a P-wave model of the upper mantle beneath Southeast (SE) Asia from reprocessed short period International Seismological Centre (ISC) P and pP data, short period P data of the Annual Bulletin of Chinese Earthquakes (ABCE), and long period PP-P data.We used 3D sensitivity kernels

  19. Group velocity effect on resonant, long-range wake-fields in slow wave structures

    CERN Document Server

    Smirnov, A V

    2002-01-01

    Synchronous wake-fields in a dispersive waveguide are derived in a general explicit form on the basis of a rigorous electro-dynamical approach using Fourier transformations. The fundamental role of group velocity in wake-field propagation, calculation of attenuation, amplitudes, form-factors and loss-factors is analyzed for single bunch radiation. Adiabatic tapering of the waveguide and bunch density variation is taken into account analytically for the time-domain fields. Effects of field 'compression/expansion' and group delays are demonstrated. The role of these effects is discussed for single bunch wake-fields, transient beam loading, BBU and HOMs. A novel waveguide structure with central rf coupling and both positive and negative velocities is proposed. It can be used effectively in both high-energy accelerators and single-section linacs.

  20. Imaging earth's interior: Tomographic inversions for mantle P-wave velocity structure

    Energy Technology Data Exchange (ETDEWEB)

    Pulliam, R.J.

    1991-07-01

    A formalism is developed for the tomographic inversion of seismic travel time residuals. The travel time equations are solved both simultaneously, for velocity model terms and corrections to the source locations, and progressively, for each set of terms in succession. The methods differ primarily in their treatment of source mislocation terms. Additionally, the system of equations is solved directly, neglecting source terms. The efficacy of the algorithms is explored with synthetic data as we perform simulations of the general procedure used to produce tomographic images of Earth's mantle from global earthquake data. The patterns of seismic heterogeneity in the mantle that would be returned reliably by a tomographic inversion are investigated. We construct synthetic data sets based on real ray sampling of the mantle by introducing spherical harmonic patterns of velocity heterogeneity and perform inversions of the synthetic data.

  1. Imaging earth`s interior: Tomographic inversions for mantle P-wave velocity structure

    Energy Technology Data Exchange (ETDEWEB)

    Pulliam, Robert Jay [Univ. of California, Berkeley, CA (United States)

    1991-07-01

    A formalism is developed for the tomographic inversion of seismic travel time residuals. The travel time equations are solved both simultaneously, for velocity model terms and corrections to the source locations, and progressively, for each set of terms in succession. The methods differ primarily in their treatment of source mislocation terms. Additionally, the system of equations is solved directly, neglecting source terms. The efficacy of the algorithms is explored with synthetic data as we perform simulations of the general procedure used to produce tomographic images of Earth`s mantle from global earthquake data. The patterns of seismic heterogeneity in the mantle that would be returned reliably by a tomographic inversion are investigated. We construct synthetic data sets based on real ray sampling of the mantle by introducing spherical harmonic patterns of velocity heterogeneity and perform inversions of the synthetic data.

  2. Constraints on structural evolution from correlations between hydraulic properties and P-wave velocities during brittle faulting of rocks

    Science.gov (United States)

    Ahrens, Benedikt; Duda, Mandy; Renner, Jörg

    2017-04-01

    One of the key challenges in geophysics concerns the derivation of structure and state of rocks and rock formations from constraints on the spatial distribution of their physical properties, as gained from laboratory experiments, borehole logging, and surveys at the surface covering scales from centimeters to kilometers. The use of information from the propagation of elastic waves constitutes the most common approach to derive the structure and state of rocks, if direct information on in-situ properties is limited (e.g., through boreholes) or inaccessible. Furthermore, the determination of hydraulic rock properties serves the dual purpose of constraining structure and providing the basis for predictions of the behavior of a system of interest during continued fluid injection or production, as associated with, e.g., exploitation of hydrocarbon reservoirs, operation of subsurface liquid-waste repositories, or geothermal energy provision. In-situ, wave observations potentially provide better coverage of rock volumes (in space and time) than hydraulic investigations and thus constraints on correlations between elastic and hydraulic properties bear the potential to improve subsurface characterization. In our laboratory study, we continuously monitored hydraulic properties and elastic wave velocities of porous Wilkeson sandstone samples during conventional triaxial deformation. Confining pressures applied in the tests cover the range from below to above the critical pressure for crack closure to control the state of pre-existing cracks. Hydraulic properties were determined using the oscillatory pore-pressure method owing to its benefits regarding continuous and highly resolved monitoring of permeability and specific storage capacity during deformation and even imminent localized failure. The magnitude of the deformation-associated variations in the monitored physical properties strongly depends on initial microstructure and degree of hydrostatically induced crack closure

  3. Improved septal contraction and coronary flow velocity after cardiac resynchronization therapy elucidated by strain imaging and pulsed wave Doppler echocardiography.

    Science.gov (United States)

    Kayano, Hiroyuki; Ueda, Hiroaki; Kawamata, Tomoaki; Miyoshi, Fumito; Toshida, Tsutomu; Watanabe, Norikazu; Hirano, Yuichi; Kawamura, Mitsuharu; Asano, Taku; Kou, Shyhaku; Tanno, Kaoru; Ozawa, Masaki; Kobayashi, Youichi; Katagiri, Takashi

    2006-02-01

    The effects of cardiac resynchronization therapy (CRT) with various atrioventricular conduction delay settings were investigated on cardiac hemodynamic changes involved in coronary flow velocity using color and pulsed wave Doppler modalities and myocardial regional contractility using a novel echocardiographic technique (strain imaging). Seven patients with advanced heart failure (left ventricular ejection fraction or = 140 msec) were treated with CRT. Color and pulsed wave Doppler imaging were performed from the apical four-chamber view to examine the cardiac functions such as stroke volume, cardiac output, mitral regurgitant volume and coronary flow velocity. Strain imaging was performed to quantify the asynchrony of both intraventricular and interventricular time delay between the septum and left ventricular free wall (posterior wall) and to assess the regional contractile function. Wall motion was also evaluated. Intraventricular and interventricular asynchrony were improved from 173 +/- 18 to 60 +/- 6 msec, and 69 +/- 25 to 12 +/- 3 msec, respectively. Stroke volume (55.2 +/- 6.2 to 76.8 +/- 10.8 ml; 39% up), cardiac output (3.9 +/- 0.3 to 5.4 +/- 0.5 I/min; 38% up) and coronary flow velocity (24 +/- 3 to 36 +/- 5 cm/sec; 50% up) were greatly increased and mitral regurgitant volume (59.7 +/- 18.0 to 38.9 +/- 11.3 ml; 35% down)was clearly decreased. Septal wall shortening was greatly increased from 10.2 +/- 2.3% to 17.0 +/- 1.8% and septal wall motion (radial thickening)was also improved simultaneously. Atrioventricular interval settings influenced all above parameters. CRT improved the cardiac hemodynamics involved in coronary flow significantly due to both resynchronization of inter and intra asynchrony, and improvement of the regional myocardial contraction in patients with severe congestive heart failure and complete left bundle branch block.

  4. P-wave velocity and density structure beneath Mt. Vesuvius: a magma body in the upper edifice?

    Directory of Open Access Journals (Sweden)

    Paolo Capuano

    2013-11-01

    Full Text Available A high-resolution image of the compressional wave velocity and density structure in the shallow edifice of Mount Vesuvius has been derived from simultaneous inversion of travel times and hypocentral parameters of local earthquakes and from gravity inversion. The robustness of the tomography solution has been improved by adding to the earthquake data a set of land based shots, used for constraining the travel time residuals. The results give a high resolution image of the P-wave velocity structure with details down to 300-500 m. The relocated local seismicity appears to extend down to 5 km depth below the central crater, distributed into two clusters, and separated by an anomalously high Vp region positioned at around 1 km depth. A zone with high Vp/Vs ratio in the upper layers is interpreted as produced by the presence of intense fluid circulation alternatively to the interpretation in terms of a small magma chamber inferred by petrologic studies. In this shallower zone the seismicity has the minimum energy, whilst most of the high-energy quakes (up to Magnitude 3.6 occur in the cluster located at greater depth. The seismicity appears to be located along almost vertical cracks, delimited by a high velocity body located along past intrusive body, corresponding to remnants of Mt. Somma. In this framework a gravity data inversion has been performed to study the shallower part of the volcano. Gravity data have been inverted using a method suitable for the application to scattered data in presence of relevant topography based on a discretization of the investigated medium performed by establishing an approximation of the topography by a triangular mesh. The tomography results, the retrieved density distribution, and the pattern of relocated seismicity exclude the presence of significant shallow magma reservoirs close to the central conduit. These should be located at depth higher than that of the base of the hypocenter volume, as evidenced by

  5. Crust-mantle coupling mechanism in Cameroon, West Africa, revealed by 3D S-wave velocity and azimuthal anisotropy

    Science.gov (United States)

    Ojo, Adebayo Oluwaseun; Ni, Sidao; Chen, Haopeng; Xie, Jun

    2018-01-01

    To understand the depth variation of deformation beneath Cameroon, West Africa, we developed a new 3D model of S-wave isotropic velocity and azimuthal anisotropy from joint analysis of ambient seismic noise and earthquake surface wave dispersion. We found that the Cameroon Volcanic Line (CVL) is well delineated by slow phase velocities in contrast with the neighboring Congo Craton, in agreement with previous studies. Apart from the Congo Craton and the Oubanguides Belt, the uppermost mantle revealed a relatively slow velocity indicating a thinned or thermally altered lithosphere. The direction of fast axis in the upper crust is mostly NE-SW, but trending approximately N-S around Mt. Oku and the southern CVL. The observed crustal azimuthal anisotropy is attributed to alignment of cracks and crustal deformation related to magmatic activities. A widespread zone of weak-to-zero azimuthal anisotropy in the mid-lower crust shows evidence for vertical mantle flow or isotropic mid-lower crust. In the uppermost mantle, the fast axis direction changed from NE-SW to NW-SE around Mt. Oku and northern Cameroon. This suggests a layered mechanism of deformation and revealed that the mantle lithosphere has been deformed. NE-SW fast azimuths are observed beneath the Congo Craton and are consistent with the absolute motion of the African plate, suggesting a mantle origin for the observed azimuthal anisotropy. Our tomographically derived fast directions are consistent with the local SKS splitting results in some locations and depths, enabling us to constrain the origin of the observed splitting. The different feature of azimuthal anisotropy in the upper crust and the uppermost mantle implies decoupling between deformation of crust and mantle in Cameroon.

  6. Normal values of aortic dimensions, distensibility, and pulse wave velocity in children and young adults: a cross-sectional study

    Directory of Open Access Journals (Sweden)

    Voges Inga

    2012-11-01

    Full Text Available Abstract Background Aortic enlargement and impaired bioelasticity are of interest in several cardiac and non-cardiac diseases as they can lead to cardiovascular complications. Cardiovascular magnetic resonance (CMR is increasingly accepted as a noninvasive tool in cardiovascular evaluation. Assessment of aortic anatomy and bioelasticity, namely aortic distensibility and pulse wave velocity (PWV, by CMR is accurate and reproducible and could help to identify anatomical and bioelastic abnormalities of the aorta. However, normal CMR values for healthy children and young adults are lacking. Methods Seventy-one heart-healthy subjects (age 16.4 ± 7.6 years, range 2.3 - 28.3 years were examined using a 3.0 Tesla CMR scanner. Aortic cross-sectional areas and aortic distensibility were measured at four positions of the ascending and descending thoracic aorta. PWV was assessed from aortic blood flow velocity measurements in a aortic segment between the ascending aorta and the proximal descending aorta. The Lambda-Mu-Sigma (LMS method was used to obtain percentile curves for aortic cross-sectional areas, aortic distensibility and PWV according to age. Results Aortic areas, PWV and aortic distensibility (aortic cross-sectional areas: r = 0.8 to 0.9, p  Conclusions This study provides percentile curves for cross-sectional areas, distensibility and pulse wave velocity of the thoracic aorta in children and young adolescents between their 3rd and 29th year of life. These data may serve as a reference for the detection of pathological changes of the aorta in cardiovascular disease.

  7. Dispersive SH waves in a cylindrical multiferroic composite with interfacial irregularity: Approximate analysis on coordinate-dependent phase velocity

    Science.gov (United States)

    Li, Yong-Dong; Liu, Shi-Lun; Jin, Ying; Wei, Hong-Xing; Guan, Yong

    2017-09-01

    Irregular interfaces may be formed between the neighboring ferromagnetic and ferroelectric layers of multiferroic composites during the hot-pressing process. They undoubtedly affects the mechanical behavior of multiferroic composites and this is a scientific problem deserving studying. In addition, phase velocity will be a function of coordinate if the interface is irregular, and this makes the governing equation so complicated that direct analytical solution is unobtainable. The present article proposes an approximate approach for analyzing SH waves in a cylindrical multiferroic composite with interfacial irregularity. The dispersion equation is analytically derived and numerically solved. After the validity range of the approximate treatment is clarified, parametric studies reveals that interfacial corrugations can give rise to an oscillatory distribution of phase velocity along the propagation direction. Because such oscillation can lead to unstable signal transmission, it should be avoided in engineering. Further discussion suggests three possible ways for suppressing the oscillation of phase velocity. The research results can provide references for optimizing the design, manufacture and application of multiferroic devices.

  8. Three-dimensional lithospheric S wave velocity model of the NE Tibetan Plateau and western North China Craton

    Science.gov (United States)

    Wang, Xingchen; Li, Yonghua; Ding, Zhifeng; Zhu, Lupei; Wang, Chunyong; Bao, Xuewei; Wu, Yan

    2017-08-01

    We present a new 3-D lithospheric Vs model for the NE Tibetan Plateau (NETP) and the western North China Craton (NCC). First, high-frequency receiver functions (RFs) were inverted using the neighborhood algorithm to estimate the sedimentary structure beneath each station. Then a 3D Vs model with unprecedented resolution was constructed by jointly inverting RFs and Rayleigh wave dispersions. A low-velocity sedimentary layer with thicknesses varying from 2 to 10 km is present in the Yinchuan-Hetao graben, Ordos block, and western Alxa block. Velocities from the middle-lower crust to the uppermost mantle are generally high in the Ordos block and low in the Alxa block, indicating that the Alxa block is not part of the NCC. The thickened crust in southwestern Ordos block and western Alxa block suggests that they have been modified. Two crustal low-velocity zones (LVZs) were detected beneath the Kunlun Fault (KF) zone and western Qilian Terrane (QLT). The origin of the LVZ beneath the KF zone may be the combined effect of shear heating, localized asthenosphere upwelling, and crustal radioactivity. The LVZ in the western QLT, representing an early stage of the LVZ that has developed in the KF zone, acts as a decollement to decouple the deformation between the upper and lower crust and plays a key role in seismogenesis. We propose that the crustal deformation beneath the NETP is accommodated by a combination of shear motion, thickening of the upper-middle crust, and removal of lower crust.

  9. Comparison of an Oscillometric Method with Cardiac Magnetic Resonance for the Analysis of Aortic Pulse Wave Velocity

    Science.gov (United States)

    Feistritzer, Hans-Josef; Reinstadler, Sebastian J.; Klug, Gert; Kremser, Christian; Seidner, Benjamin; Esterhammer, Regina; Schocke, Michael F.; Franz, Wolfgang-Michael; Metzler, Bernhard

    2015-01-01

    Objectives Pulse wave velocity (PWV) is the proposed gold-standard for the assessment of aortic elastic properties. The aim of this study was to compare aortic PWV determined by a recently developed oscillometric device with cardiac magnetic resonance imaging (CMR). Methods PWV was assessed in 40 volunteers with two different methods. The oscillometric method (PWVOSC) is based on a transfer function from the brachial pressure waves determined by oscillometric blood pressure measurements with a common cuff (Mobil-O-Graph, I.E.M. Stolberg, Germany). CMR was used to determine aortic PWVCMR with the use of the transit time method based on phase-contrast imaging at the level of the ascending and abdominal aorta on a clinical 1.5 Tesla scanner (Siemens, Erlangen, Germany). Results The median age of the study population was 34 years (IQR: 24–55 years, 11 females). A very strong correlation was found between PWVOSC and PWVCMR (r = 0.859, p < 0.001). Mean PWVOSC was 6.7 ± 1.8 m/s and mean PWVCMR was 6.1 ± 1.8 m/s (p < 0.001). Analysis of agreement between the two measurements using Bland-Altman method showed a bias of 0.57 m/s (upper and lower limit of agreement: 2.49 m/s and -1.34 m/s). The corresponding coefficient of variation between both measurements was 15%. Conclusion Aortic pulse wave velocity assessed by transformation of the brachial pressure waveform showed an acceptable agreement with the CMR-derived transit time method. PMID:25612307

  10. Comparison of an oscillometric method with cardiac magnetic resonance for the analysis of aortic pulse wave velocity.

    Directory of Open Access Journals (Sweden)

    Hans-Josef Feistritzer

    Full Text Available OBJECTIVES: Pulse wave velocity (PWV is the proposed gold-standard for the assessment of aortic elastic properties. The aim of this study was to compare aortic PWV determined by a recently developed oscillometric device with cardiac magnetic resonance imaging (CMR. METHODS: PWV was assessed in 40 volunteers with two different methods. The oscillometric method (PWVOSC is based on a transfer function from the brachial pressure waves determined by oscillometric blood pressure measurements with a common cuff (Mobil-O-Graph, I.E.M. Stolberg, Germany. CMR was used to determine aortic PWVCMR with the use of the transit time method based on phase-contrast imaging at the level of the ascending and abdominal aorta on a clinical 1.5 Tesla scanner (Siemens, Erlangen, Germany. RESULTS: The median age of the study population was 34 years (IQR: 24-55 years, 11 females. A very strong correlation was found between PWVOSC and PWVCMR (r = 0.859, p < 0.001. Mean PWVOSC was 6.7 ± 1.8 m/s and mean PWVCMR was 6.1 ± 1.8 m/s (p < 0.001. Analysis of agreement between the two measurements using Bland-Altman method showed a bias of 0.57 m/s (upper and lower limit of agreement: 2.49 m/s and -1.34 m/s. The corresponding coefficient of variation between both measurements was 15%. CONCLUSION: Aortic pulse wave velocity assessed by transformation of the brachial pressure waveform showed an acceptable agreement with the CMR-derived transit time method.

  11. Time evolution of electromagnetic wave packets through superlattices: evidence for superluminal velocities.

    Science.gov (United States)

    Pereyra, Pedro; Simanjuntak, Herbert P

    2007-05-01

    We study the space-time evolution of electromagnetic wave packets through optical superlattices. We present rigorous analytical solutions describing the multiple-scattering processes of Gaussian wave packets defined in the band gap and in the resonant energy regions. Following their space-time evolution, we obtain the Maxwell equations prediction for the time spent inside the superlattice. From a close and careful observation of the reflected and transmitted parts of Gaussian packets in a photonic band gap, we conclude unambiguously that the superluminal transmission and the Hartman effect are inherent properties of the electromagnetic theory. It is also shown that the theoretical predictions for the time spent inside an optical superlattice are in good agreement with the experimental results and the phase time predictions.

  12. Deriving inertial wave characteristics from surface drifter velocities: Frequency variability in the Tropical Pacific

    Science.gov (United States)

    Poulain, Pierre-Marie; Luther, Douglas S.; Patzert, William C.

    1992-11-01

    Two techniques have been developed for estimating statistics of inertial oscillations from satellite-tracked drifters. These techniques overcome the difficulties inherent in estimating such statistics from data dependent upon space coordinates that are a function of time. Application of these techniques to tropical surface drifter data collected during the NORPAX, EPOCS, and TOGA programs reveals a latitude-dependent, statistically significant "blue shift" of inertial wave frequency. The latitudinal dependence of the blue shift is similar to predictions based on "global" internal wave spectral models, with a superposition of frequency shifting due to modification of the effective local inertial frequency by the presence of strongly sheared zonal mean currents within 12° of the equator.

  13. Ground-motion site effects from multimethod shear-wave velocity characterization at 16 seismograph stations deployed for aftershocks of the August 2011 Mineral, Virginia earthquake

    Science.gov (United States)

    Stephenson, William J.; Odum, Jackson K.; McNamara, Daniel E.; Williams, Robert A.; Angster, Stephen J

    2014-01-01

    We characterize shear-wave velocity versus depth (Vs profile) at 16 portable seismograph sites through the epicentral region of the 2011 Mw 5.8 Mineral (Virginia, USA) earthquake to investigate ground-motion site effects in the area. We used a multimethod acquisition and analysis approach, where active-source horizontal shear (SH) wave reflection and refraction as well as active-source multichannel analysis of surface waves (MASW) and passive-source refraction microtremor (ReMi) Rayleigh wave dispersion were interpreted separately. The time-averaged shear-wave velocity to a depth of 30 m (Vs30), interpreted bedrock depth, and site resonant frequency were estimated from the best-fit Vs profile of each method at each location for analysis. Using the median Vs30 value (270–715 m/s) as representative of a given site, we estimate that all 16 sites are National Earthquake Hazards Reduction Program (NEHRP) site class C or D. Based on a comparison of simplified mapped surface geology to median Vs30 at our sites, we do not see clear evidence for using surface geologic units as a proxy for Vs30 in the epicentral region, although this may primarily be because the units are similar in age (Paleozoic) and may have similar bulk seismic properties. We compare resonant frequencies calculated from ambient noise horizontal:vertical spectral ratios (HVSR) at available sites to predicted site frequencies (generally between 1.9 and 7.6 Hz) derived from the median bedrock depth and average Vs to bedrock. Robust linear regression of HVSR to both site frequency and Vs30 demonstrate moderate correlation to each, and thus both appear to be generally representative of site response in this region. Based on Kendall tau rank correlation testing, we find that Vs30 and the site frequency calculated from average Vs to median interpreted bedrock depth can both be considered reliable predictors of weak-motion site effects in the epicentral region.

  14. Estimating front-wave velocity of infectious diseases: a simple, efficient method applied to bluetongue

    Directory of Open Access Journals (Sweden)

    Pioz Maryline

    2011-04-01

    Full Text Available Abstract Understanding the spatial dynamics of an infectious disease is critical when attempting to predict where and how fast the disease will spread. We illustrate an approach using a trend-surface analysis (TSA model combined with a spatial error simultaneous autoregressive model (SARerr model to estimate the speed of diffusion of bluetongue (BT, an infectious disease of ruminants caused by bluetongue virus (BTV and transmitted by Culicoides. In a first step to gain further insight into the spatial transmission characteristics of BTV serotype 8, we used 2007-2008 clinical case reports in France and TSA modelling to identify the major directions and speed of disease diffusion. We accounted for spatial autocorrelation by combining TSA with a SARerr model, which led to a trend SARerr model. Overall, BT spread from north-eastern to south-western France. The average trend SARerr-estimated velocity across the country was 5.6 km/day. However, velocities differed between areas and time periods, varying between 2.1 and 9.3 km/day. For more than 83% of the contaminated municipalities, the trend SARerr-estimated velocity was less than 7 km/day. Our study was a first step in describing the diffusion process for BT in France. To our knowledge, it is the first to show that BT spread in France was primarily local and consistent with the active flight of Culicoides and local movements of farm animals. Models such as the trend SARerr models are powerful tools to provide information on direction and speed of disease diffusion when the only data available are date and location of cases.

  15. Comparison of an empirical S-wave velocity model and a calculated stress-strain model for a rock mass disturbed by mining

    Science.gov (United States)

    Krawiec, Krzysztof; Czarny, Rafał

    2017-11-01

    In the article a comparison analysis is presented between a numerical model of the stress and deformation state in a rock mass and an S-wave velocity model obtained as a result of in situ measurement. The research was conducted using data from the Jastrzębie and Moszczenica coal mines. The part of the rock mass examined was strongly disturbed by multi-seam exploitation of coal. To obtain the S-wave velocity model 6 hours of ambient seismic noise data were recorded using 11 seismometers. The propagation of the Rayleigh surface wave between the seismometers was reconstructed utilising the seismic interferometry and the cross correlation technique. Estimation of a two dimensional model of the Swave velocity field was performed on the basis of dispersion curves of the Rayleigh wave phase velocity. The stress and deformation field were calculated assuming a plane state of stress with the use of the elastic-plastic Coulomb-Mohr strength criterion. Images of the vertical stress, horizontal stress, vertical strain and horizontal strain as well as the subsidence profile on the model surface were obtained as a result of the calculation. Analysis of the results shows correlation between the field of S-wave velocity and the modelled field of stress and strain.

  16. Comparison of an empirical S-wave velocity model and a calculated stress-strain model for a rock mass disturbed by mining

    Directory of Open Access Journals (Sweden)

    Krawiec Krzysztof

    2017-01-01

    Full Text Available In the article a comparison analysis is presented between a numerical model of the stress and deformation state in a rock mass and an S-wave velocity model obtained as a result of in situ measurement. The research was conducted using data from the Jastrzębie and Moszczenica coal mines. The part of the rock mass examined was strongly disturbed by multi-seam exploitation of coal. To obtain the S-wave velocity model 6 hours of ambient seismic noise data were recorded using 11 seismometers. The propagation of the Rayleigh surface wave between the seismometers was reconstructed utilising the seismic interferometry and the cross correlation technique. Estimation of a two dimensional model of the Swave velocity field was performed on the basis of dispersion curves of the Rayleigh wave phase velocity. The stress and deformation field were calculated assuming a plane state of stress with the use of the elastic-plastic Coulomb-Mohr strength criterion. Images of the vertical stress, horizontal stress, vertical strain and horizontal strain as well as the subsidence profile on the model surface were obtained as a result of the calculation. Analysis of the results shows correlation between the field of S-wave velocity and the modelled field of stress and strain.

  17. Shear Wave Velocity and Site Amplification Factors for 25 Strong-Motion Instrument Stations Affected by the M5.8 Mineral, Virginia, Earthquake of August 23, 2011

    Science.gov (United States)

    Kayen, Robert E.; Carkin, Brad A.; Corbett, Skye C.; Zangwill, Aliza; Estevez, Ivan; Lai, Lena

    2015-01-01

    Vertical one-dimensional shear wave velocity (Vs) profiles are presented for 25 strong-motion instrument sites along the Mid-Atlantic eastern seaboard, Piedmont region, and Appalachian region, which surround the epicenter of the M5.8 Mineral, Virginia, Earthquake of August 23, 2011. Testing was performed at sites in Pennsylvania, Maryland, West Virginia, Virginia, the District of Columbia, North Carolina, and Tennessee. The purpose of the study is to determine the detailed site velocity profile, the average velocity in the upper 30 meters of the profile (VS,30), the average velocity for the entire profile (VS,Z), and the National Earthquake Hazards Reduction Program (NEHRP) site classification. The Vs profiles are estimated using a non-invasive continuous-sine-wave method for gathering the dispersion characteristics of surface waves. A large trailer-mounted active source was used to shake the ground during the testing and produce the surface waves. Shear wave velocity profiles were inverted from the averaged dispersion curves using three independent methods for comparison, and the root-mean square combined coefficient of variation (COV) of the dispersion and inversion calculations are estimated for each site.

  18. Structure of the Crust beneath Cameroon, West Africa, from the Joint Inversion of Rayleigh Wave Group Velocities and Receiver Functions

    Energy Technology Data Exchange (ETDEWEB)

    Tokam, A K; Tabod, C T; Nyblade, A A; Julia, J; Wiens, D A; Pasyanos, M E

    2010-02-18

    Cameroon using 1-D shear wave velocity models obtained from the joint inversion of Rayleigh wave group velocities and P-receiver functions for 32 broadband seismic stations. From the 1-D shear wave velocity models, we obtain new insights into the composition and structure of the crust and upper mantle across Cameroon. After briefly reviewing the geological framework of Cameroon, we describe the data and the joint inversion method, and then interpret variations in crustal structure found beneath Cameroon in terms of the tectonic history of the region.

  19. Effects of cardiac timing and peripheral resistance on measurement of pulse wave velocity for assessment of arterial stiffness.

    Science.gov (United States)

    Xiao, Hanguang; Butlin, Mark; Tan, Isabella; Avolio, Alberto

    2017-07-20

    To investigate the effects of heart rate (HR), left ventricular ejection time (LVET) and wave reflection on arterial stiffness as assessed by pulse wave velocity (PWV), a pulse wave propagation simulation system (PWPSim) based on the transmission line model of the arterial tree was developed and was applied to investigate pulse wave propagation. HR, LVET, arterial elastic modulus and peripheral resistance were increased from 60 to 100 beats per minute (bpm), 0.1 to 0.45 seconds, 0.5 to 1.5 times and 0.5 to 1.5 times of the normal value, respectively. Carotid-femoral PWV (cfPWV) and brachial-ankle PWV (baPWV) were calculated by intersecting tangent method (cfPWVtan and baPWVtan), maximum slope (cfPWVmax and baPWVmax), and using the Moens-Korteweg equation ([Formula: see text] and [Formula: see text]). Results showed cfPWV and baPWV increased significantly with arterial elastic modulus but did not increase with HR when using a constant elastic modulus. However there were significant LVET dependencies of cfPWVtan and baPWVtan (0.17 ± 0.13 and 0.17 ± 0.08 m/s per 50 ms), and low peripheral resistance dependencies of cfPWVtan, cfPWVmax, baPWVtan and baPWVmax (0.04 ± 0.01, 0.06 ± 0.04, 0.06 ± 0.03 and 0.09 ± 0.07 m/s per 10% peripheral resistance), respectively. This study demonstrated that LVET dominates the effect on calculated PWV compared to HR and peripheral resistance when arterial elastic modulus is constant.

  20. Real-Time Vertical Temperature, and Velocity Profiles from a Wave Glider

    Science.gov (United States)

    2012-09-30

    Liquid Robotics navigated a Wave Glider from San Diego to Hawaii on a 82 day-long voyage that covered approximately 2500 nautical miles (http...Gawarkiewicz, G., et al. (2011), Circulation and Intrusions Northeast of Taiwan: Chasing and Predicting Uncertainty in the Cold Dome ., Oceanography, 24(4), 110...121. Lee, D.-K., and P. Niiler (2010), Influence of warm SST anomalies formed in the eastern Pacific subduction zone on recent El Nino events, J Mar Res, 68(3-4), 459-477.

  1. Video measurements of fluid velocities and water levels in breaking waves

    CSIR Research Space (South Africa)

    Govender, K

    2002-01-01

    Full Text Available of macroscopic particles, that un-expanded polystyrene beads, which were heated in water at a temperature of around 86‡C for approximately 30 s, were most suitable. These partially expanded beads, which are approximately 0.8 mm in diameter, function well... of a pair captured 1 ms apart, shows a scene containing both bubbles resulting from the wave breaking, and polystyrene seed particles. It was found that the structure of corresponding portions of the two images persists for the duration...

  2. Prediction of Compressional Wave Velocity Using Regression and Neural Network Modeling and Estimation of Stress Orientation in Bokaro Coalfield, India

    Science.gov (United States)

    Paul, Suman; Ali, Muhammad; Chatterjee, Rima

    2017-09-01

    Velocity of compressional wave (V P) of coal and non-coal lithology is predicted from five wells from the Bokaro coalfield (CF), India. Shear sonic travel time logs are not recorded for all wells under the study area. Shear wave velocity (Vs) is available only for two wells: one from east and other from west Bokaro CF. The major lithologies of this CF are dominated by coal, shaly coal of Barakar formation. This paper focuses on the (a) relationship between Vp and Vs, (b) prediction of Vp using regression and neural network modeling and (c) estimation of maximum horizontal stress from image log. Coal characterizes with low acoustic impedance (AI) as compared to the overlying and underlying strata. The cross-plot between AI and Vp/Vs is able to identify coal, shaly coal, shale and sandstone from wells in Bokaro CF. The relationship between Vp and Vs is obtained with excellent goodness of fit (R 2) ranging from 0.90 to 0.93. Linear multiple regression and multi-layered feed-forward neural network (MLFN) models are developed for prediction Vp from two wells using four input log parameters: gamma ray, resistivity, bulk density and neutron porosity. Regression model predicted Vp shows poor fit (from R 2 = 0.28) to good fit (R 2 = 0.79) with the observed velocity. MLFN model predicted Vp indicates satisfactory to good R2 values varying from 0.62 to 0.92 with the observed velocity. Maximum horizontal stress orientation from a well at west Bokaro CF is studied from Formation Micro-Imager (FMI) log. Breakouts and drilling-induced fractures (DIFs) are identified from the FMI log. Breakout length of 4.5 m is oriented towards N60°W whereas the orientation of DIFs for a cumulative length of 26.5 m is varying from N15°E to N35°E. The mean maximum horizontal stress in this CF is towards N28°E.

  3. Constructing a 3D Crustal Model Across the Entire Contiguous US Using Broadband Rayleigh Wave Phase Velocity and Ellipticity Measurements

    Science.gov (United States)

    Lin, F. C.; Schmandt, B.

    2015-12-01

    Imaging the crust and lithosphere structure beneath North America is one of the primary targets for the NSF-funded EarthScope project. In this study, we apply the recently developed ambient noise and surface wave tomography methods to construct a detailed 3D crustal model across the entire contiguous US using USArray data between January 2007 and May 2015. By using both Rayleigh wave phase velocity and ellipticity measurements between 8 and 100 sec period, the shear velocity structure can be well resolved within the five crustal layers we modeled: three upper crust, one middle crust, and one lower crust. Clear correlations are observed between the resolved velocity anomalies and known geological features at all depths. In the uppermost crust, slow Vs anomalies are observed within major sedimentary environments such as the Williston Basin, Denver Basin, and Mississippi embayment, and fast Vs anomalies are observed in environments with deeply exhumed bedrock outcrops at the surface including the Laurentian Highlands, Ouachita-Ozark Interior Highlands, and Appalachian Highlands. In the deeper upper crust, slow anomalies are observed in deep sedimentary basins such as the Green River Basin, Appalachian Basin, Southern Oklahoma Aulacogen, and areas surrounding the Gulf of Mexico. Fast anomalies, on the other hand, are observed in the Colorado Plateau, within the Great Plains between the Front Ranges and Midcontinental Rift, and east of the Appalachian Mountains. At this depth, the Midcontinental Rift and Grenville Front clearly correlate well with various velocity structure boundaries. In the middle crust, slow anomalies are mostly observed in the tectonically active areas in the western US, but relatively slow anomalies are also observed southeast of the Precambrian Rift Margins. At this depth, fast anomalies are observed beneath various deep sedimentary basins such as the Southern Oklahoma Aulacogen, Appalachian Basin, and Central Valley. In the lower crust, a clear

  4. Prediction of Compressional Wave Velocity Using Regression and Neural Network Modeling and Estimation of Stress Orientation in Bokaro Coalfield, India

    Science.gov (United States)

    Paul, Suman; Ali, Muhammad; Chatterjee, Rima

    2018-01-01

    Velocity of compressional wave ( V P) of coal and non-coal lithology is predicted from five wells from the Bokaro coalfield (CF), India. Shear sonic travel time logs are not recorded for all wells under the study area. Shear wave velocity ( Vs) is available only for two wells: one from east and other from west Bokaro CF. The major lithologies of this CF are dominated by coal, shaly coal of Barakar formation. This paper focuses on the (a) relationship between Vp and Vs, (b) prediction of Vp using regression and neural network modeling and (c) estimation of maximum horizontal stress from image log. Coal characterizes with low acoustic impedance (AI) as compared to the overlying and underlying strata. The cross-plot between AI and Vp/ Vs is able to identify coal, shaly coal, shale and sandstone from wells in Bokaro CF. The relationship between Vp and Vs is obtained with excellent goodness of fit ( R 2) ranging from 0.90 to 0.93. Linear multiple regression and multi-layered feed-forward neural network (MLFN) models are developed for prediction Vp from two wells using four input log parameters: gamma ray, resistivity, bulk density and neutron porosity. Regression model predicted Vp shows poor fit (from R 2 = 0.28) to good fit ( R 2 = 0.79) with the observed velocity. MLFN model predicted Vp indicates satisfactory to good R2 values varying from 0.62 to 0.92 with the observed velocity. Maximum horizontal stress orientation from a well at west Bokaro CF is studied from Formation Micro-Imager (FMI) log. Breakouts and drilling-induced fractures (DIFs) are identified from the FMI log. Breakout length of 4.5 m is oriented towards N60°W whereas the orientation of DIFs for a cumulative length of 26.5 m is varying from N15°E to N35°E. The mean maximum horizontal stress in this CF is towards N28°E.

  5. Ultrasonic Acoustic Wave Velocities of Neighborite (NaMgF3) Across Orthorhombic and Cubic Phase Boundary at High P-T

    Science.gov (United States)

    Weidner, D. J.; Li, L.; Whitaker, M. L.; Triplett, R.

    2016-12-01

    Neighborite perovskite (NaMgF3) is a close analogue to Mg or Ca silicate perovskite. It experience a second-order phase transition at high T which may have a significant effect on the acoustic velocities. Here we report the measurement of elastic wave velocities of neighborite perovskite using multi-anvil high pressure apparatus located in beamline BM6 Advance Photon Source. We use the newly installed ultrasonic equipment using pulse-echo-overlap method coupled with D-DIA device. X-ray radiograph is used to measure sample length at high P-T. X-ray diffraction spectrum is used to determine the pressure and sample conditions. Precise measurements of P and S wave velocities are at 60 and 35 MHz respectively and are nearly simultaneous. We use a double reflector method to enable measurement of elastic wave velocities of cold-pressed polycrystalline sample which is sintered in situ at high P-T. Experiments were carried out up to 3 GPa and 1100 oC. Our preliminary results indicated that at MHz frequencies the change in acoustic velocities across the orthorhombic-cubic phase boundaries is very smooth, with no indication of a velocity minimum at the transition, nor velocity increase for the cubic phase.

  6. Subsurface structure of the Nojima fault from dipole shear velocity/anisotropy and borehole Stoneley wave

    Energy Technology Data Exchange (ETDEWEB)

    Ito, H. [Geological Survey of Japan, Tsukuba (Japan); Yamamoto, H.; Brie, A.

    1996-10-01

    Fracture and permeability in the fault zone of the active fault drilling at the Nojima fault were evaluated from acoustic waveforms. There were several permeable intervals in the fault zone. There was strong Stoneley wave attenuation, very large S-Se below the fault and in the interval above the fault. In the fault zone, there were also several short intervals where S-Se was very large; 667 m-674 m and 706 m-710 m. In these intervals, the Stoneley attenuation was large, but there was no Stoneley reflection from within the interval. Reflections were observed at the upper and lower boundaries, going away from the bed up above, and down below. In this well, the shear wave was very strongly attenuated at and below the fault zone. The fast shear azimuth changed at the fault. The slowness anisotropy was fairly strong above the fault from 602 m to 612 m, but smaller below the fault. The changes in fast shear azimuth were much more pronounced near the fault, which suggested a strong influence of the fault. 6 refs., 5 figs.

  7. Borehole P- and S-wave velocity at thirteen stations in Southern California

    Science.gov (United States)

    Gibbs, James F.; Boore, David M.; Tinsley, John C.; Mueller, Charles S.

    2001-01-01

    The U.S. Geological Survey (USGS), as part of a program to acquire seismic velocity data at locations of strong-ground motion in earthquakes (e.g., Gibbs et al., 2000), has investigated thirteen additional sites in the Southern California region. Of the thirteen sites, twelve are in the vicinity of Whittier, California, and one is located in San Bernardino, California. Several deployments of temporary seismographs were made after the Whittier Narrows, California earthquake of 1 October 1987 (Mueller et al., 1988). A deployment, between 2 October and 9 November 1987, was the motivation for selection of six of the drill sites. Temporary portable seismographs at Hoover School (HOO), Lincoln School (LIN), Corps of Engineers Station (NAR), Olive Junior High School (OLV), Santa Anita Golf Course (SAG), and Southwestern Academy (SWA) recorded significant aftershock data. These portable sites, with the exception of Santa Anita Golf Course, were co-sited with strong-motion recorders. Stations at HOO, Lincoln School Whittier (WLB), Saint Paul High School (STP), Alisos Adult School (EXC), Cerritos College Gymnasium (CGM), Cerritos College Physical Science Building (CPS), and Cerritos College Police Building (CPB) were part of an array of digital strong-motion stations deployed from "bedrock" in Whittier to near the deepest part of the Los Angeles basin in Norwalk. Although development and siting of this new array (partially installed at the time of this writing) was generally motivated by the Whittier Narrows earthquake, these new sites (with the exception of HOO) were not part of any Whittier Narrows aftershock deployments. A similar new digital strong-motion site was installed at the San Bernardino Fire Station during the same time frame. Velocity data were obtained to depths of about 90 meters at two sites, 30 meters at seven sites, and 18 to 25 meters at four sites. Lithology data from the analysis of cuttings and samples was obtained from the two 90-meter deep holes and

  8. Mapping refuse profile in Singapore old dumping ground through electrical resistivity, S-wave velocity and geotechnical monitoring.

    Science.gov (United States)

    Yin, Ke; Tong, Huan Huan; Noh, Omar; Wang, Jing-Yuan; Giannis, Apostolos

    2015-03-01

    The purpose of this study was to track the refuse profile in Lorong Halus Dumping Ground, the largest landfill in Singapore, by electrical resistivity and surface wave velocity after 25 years of closure. Data were analyzed using an orthogonal set of plots by spreading 24 lines in two perpendicular geophone-orientation directions. Both geophysical techniques determined that refuse boundary depth was 13 ± 2 m. The refuse boundary revealed a certain degree of variance, mainly ascribed to the different principle of measurements, as well as the high heterogeneity of the subsurface. Discrepancy was higher in spots with greater heterogeneity. 3D analysis was further conducted detecting refuse pockets, leachate mounding and gas channels. Geotechnical monitoring (borehole) confirmed geophysical outcomes tracing different layers such as soil capping, decomposed refuse materials and inorganic wastes. Combining the geophysical methods with borehole monitoring, a comprehensive layout of the dumping site was presented showing the hot spots of interests.

  9. Measurements of acoustic particle velocity in a coaxial duct and its application to a traveling-wave thermoacoustic heat engine.

    Science.gov (United States)

    Morii, Jun; Biwa, Tetsushi; Yazaki, Taichi

    2014-09-01

    We present theoretical solutions, based on linear acoustic theory, for axial acoustic particle velocity in an annular region of a coaxial duct. The solutions are expressed in terms of two non-dimensional parameters h/δ(ν) and R; h and δ(ν), respectively, represent the half of the spacing between two concentric ducts and the characteristic length given by kinematic viscosity of the gas and angular frequency of acoustic oscillations, and R is the radius ratio of the ducts. The validity of the solutions was verified by direct measurements using a laser Doppler velocimeter. The present results are applied to measurements of the acoustic power distribution in a traveling wave thermoacoustic engine with a coaxial duct, which provides experimental evidence for acoustic power feedback in the coaxial duct.

  10. PULSE WAVE VELOCITY AND CENTRAL AORTIC PRESSURE IN OBESE CHILDREN ACCORDING TO THE NON-INVASIVE ARTERIOGRAPHY RESULTS

    Directory of Open Access Journals (Sweden)

    O. V. Kozhevnikova

    2013-01-01

    Full Text Available The article presents information value of non-invasive arteriography, which reveals early signs of cardiovascular pathology formation in children, using a large number of trials in children. The authors examined predictors of cardiovascular catastrophes’ development, confirmed in adults: aortic wall’s stiffness, central aortic pressure and pulse pressure – that have not been sufficiently studied in children yet. The article shows that the high-technology method of non-invasive arteriography allows revealing changes of these parameters in children on the preclinical stage. It also shows their correlation with body mass index, fatty hepatosis, direct correlation of weight gain with connection of pulse wave velocity and central blood pressure and importance of follow-up evaluation of these parameters. Heterogeneity of the group of obese children in terms of these parameters is a premise for development of individual approach to control and prevention of cardiovascular complications’ development risk in childhood.

  11. Upper-mantle P- and S-wave velocities below Scandinavia and East Greenland from teleseismic traveltime tomography

    DEFF Research Database (Denmark)

    Hejrani, Babak

    2014-01-01

    This dissertation deals with the resolution of P- and S-velocity variations in the upper mantle (down to 600 km) using teleseismic P- and S-wave arrival times. The natural laboratory is the land areas bordering the North Atlantic; the Scandinavian and East Greenland Caledonides and the Northern...... improved resolution when stations follow profiles. The method was tested on the SCANLIPS array across the Scandinavian Peninsula (Paper I). On the data side, I performed a complete reorganization of the in-house MATLAB-based system (Medhus et al., 2012a,b) for handling event extraction, filtering, cross....../VS put important constraints on the required compositional differences in mantle lithosphere and asthenosphere in the region. Second study focused on the Scandinavian Caledonides, using a dense network south of Trondheim (including SCANLIPS profile) and more sparse station coverage to the north. The UMVB...

  12. Impact of ADMA, endothelial progenitor cells and traditional cardiovascular risk factors on pulse wave velocity among prediabetic individuals

    Directory of Open Access Journals (Sweden)

    Protopsaltis Ioannis

    2012-11-01

    Full Text Available Abstract Background Central arterial stiffness represents a well-established predictor of cardiovascular disease. Decreased circulating endothelial progenitor cells (EPCs, increased asymmetric dimethyl-arginine (ADMA levels, traditional cardiovascular risk factors and insulin resistance have all been associated with increased arterial stiffness. The correlations of novel and traditional cardiovascular risk factors with central arterial stiffness in prediabetic individuals were investigated in the present study. Methods The study population consisted of 53 prediabetic individuals. Individuals were divided into groups of isolated impaired fasting glucose (IFG, isolated impaired glucose tolerance (IGT and combined IGT-IFG. Age, sex, family history of diabetes, smoking history, body mass index (BMI, waist to hip ratio (WHR, waist circumference (WC, blood pressure, lipid profile, levels of high sensitive C-reactive protein (hsCRP, glomerular filtration rate (GFR, and history of antihypertensive or statin therapy were obtained from all participants. Insulin resistance was evaluated using the Homeostatic Model Assessment (HOMA-IR. Carotid -femoral pulse wave velocity was used as an index of arterial stiffness. Circulating EPC count and ADMA serum levels were also determined. Results Among studied individuals 30 (56.6% subjects were diagnosed with isolated IFG, 9 (17% with isolated IGT (17% and 14 with combined IFG-IGT (26.4%. In univariate analysis age, mean blood pressure, fasting glucose, total cholesterol, LDL cholesterol, and ADMA levels positively correlated with pulse-wave velocity while exercise and GFR correlated negatively. EPC count did not correlate with PWV. In multivariate stepwise regression analysis PWV correlated independently and positively with LDL-Cholesterol (low density lipoprotein and ADMA levels and negatively with exercise. Conclusions Elevated ADMA and LDL-C levels are strongly associated with increased arterial stiffness among

  13. Probing the critical zone using passive- and active-source estimates of subsurface shear-wave velocities

    Science.gov (United States)

    Callahan, R. P.; Taylor, N. J.; Pasquet, S.; Dueker, K. G.; Riebe, C. S.; Holbrook, W. S.

    2016-12-01

    Geophysical imaging is rapidly becoming popular for quantifying subsurface critical zone (CZ) architecture. However, a diverse array of measurements and measurement techniques are available, raising the question of which are appropriate for specific study goals. Here we compare two techniques for measuring S-wave velocities (Vs) in the near surface. The first approach quantifies Vs in three dimensions using a passive source and an iterative residual least-squares tomographic inversion. The second approach uses a more traditional active-source seismic survey to quantify Vs in two dimensions via a Monte Carlo surface-wave dispersion inversion. Our analysis focuses on three 0.01 km2 study plots on weathered granitic bedrock in the Southern Sierra Critical Zone Observatory. Preliminary results indicate that depth-averaged velocities from the two methods agree over the scales of resolution of the techniques. While the passive- and active-source techniques both quantify Vs, each method has distinct advantages and disadvantages during data acquisition and analysis. The passive-source method has the advantage of generating a three dimensional distribution of subsurface Vs structure across a broad area. Because this method relies on the ambient seismic field as a source, which varies unpredictably across space and time, data quality and depth of investigation are outside the control of the user. Meanwhile, traditional active-source surveys can be designed around a desired depth of investigation. However, they only generate a two dimensional image of Vs structure. Whereas traditional active-source surveys can be inverted quickly on a personal computer in the field, passive source surveys require significantly more computations, and are best conducted in a high-performance computing environment. We use data from our study sites to compare these methods across different scales and to explore how these methods can be used to better understand subsurface CZ architecture.

  14. Blood pressure estimation from pulse wave velocity measured on the chest.

    Science.gov (United States)

    Puke, Sawa; Suzuki, Takuji; Nakayama, Kanako; Tanaka, Hirokazu; Minami, Shigenobu

    2013-01-01

    Recently, monitoring of blood pressure fluctuation in the daily life is focused on in the hypertension care area to predict the risk of cardiovascular and cerebrovascular disease events. In this paper, in order to propose an alternative system to the existed ambulatory blood pressure monitoring (ABPM) sphygmomanometer, we have developed a prototype of small wearable device consisting of electrocardiogram (ECG) and photopelthysmograph (PPG) sensors. In addition, it was examined whether blood pressure can be estimated based on pulse wave transit time (PWTT) only by attaching that device on the surface of the chest. We indicated that our system could also sense tendency of time-dependent change of blood pressure by measuring pulse of vessel over the sternum while its propagation distance is short.

  15. Factors associated with high brachial–ankle pulse wave velocity in non-hypertensive and appropriately treated hypertensive patients with atherosclerotic risk factors

    Directory of Open Access Journals (Sweden)

    Ato D

    2017-10-01

    Full Text Available Dai Ato,1 Toshitami Sawayama2 1Gakujutsu Shien (Academic Support Co., Ltd. Tokyo, 2Sawayama Clinic, Okayama, Japan Abstract: While pulse wave velocity (PWV correlates with blood pressure (BP, its extent differs between patients, and some cases of high PWV in normotensives are present. Moreover, PWV frequently remains high in hypertensive patients despite adequate BP control. The factors associated with such phenomena are yet to be elucidated. Here, we investigated the factors associated with brachial–ankle PWV (baPWV in 107 patients whose systolic BP was under 140 mmHg at their latest baPWV measurement. There were 64 controlled hypertensives and 43 normotensives. Multivariate regression analysis identified age, hypertension, body mass index (BMI, systolic BP, and heart rate (HR as independent factors for baPWV. Next, we divided the subjects into groups according to their age (in 5-year increments and calculated the mean and standard deviation (SD of the baPWV for each group. For each age group, we defined patients with a baPWV above the mean + SD baPWV for the group as the high-baPWV cohort. Multivariate logistic regression analysis revealed that BMI, hypertension, and smoking were independent determinants of a high-baPWV subject. This represents the first study to report the existence of the hypertensive state itself as one of the independent predictors of high baPWV in normotensive and well-treated hypertensive patients. This finding implies that the hypertensive state itself possibly worsens arterial stiffness independently from aging in spite of adequate BP maintenance. To prevent the early progression of arterial stiffness, the application of an appropriate intervention during the early stages of hypertension is important and the continuation of an appropriate BP treatment is suggested. Keywords: arterial stiffness, brachial–ankle pulse wave velocity, heart failure, hypertension, peripheral arterial disease

  16. The story of a craton from heart to margins: illuminating cratonic lithosphere with Rayleigh wave phase velocities in Eastern Canada

    Science.gov (United States)

    Petrescu, L.; Darbyshire, F. A.; Gilligan, A.; Bastow, I. D.; Totten, E. J.

    2015-12-01

    Cratons are Precambrian continental nuclei that are geologically distinct from modern continental regions and are typically underlain by seismically fast lithospheric roots (keels) to at least 200 km depth. Both plate and non-plate tectonic origin theories such as stacking of subducted slabs or multiple mantle plume underplating have been proposed to explain keel growth.Eastern Canada is an ideal continental region to investigate cratonization processes and the onset of plate tectonics. It comprises part of the largest Archean craton in the world, the Superior Province, flanked by a ~1.1 Ga Himalayan-scale orogenic belt, the Grenville Province, and the 500-300 Ma old Appalachian orogenic province, following the same general SW-NE axial trend. The region is also cross-cut by the Great Meteor Hotspot track, providing an excellent opportunity to study the interaction of hotspot tectonism with progressively younger lithospheric domains.We investigate the lithospheric structure of Precambrian Eastern Canada using teleseismic earthquake data recorded at permanent and temporary networks. We measure interstation dispersion curves of Rayleigh wave phase velocities between ~15 and 220 s, and compare the results to standard continental and cratonic reference models. We combine the dispersion curves via a tomographic inversion which solves for isotropic phase velocity heterogeneity and azimuthal anisotropy across the region at a range of periods. The phase velocity maps indicate variations in lithospheric properties from the heart of the Superior craton to the SE Canadian coast.The new regional-scale models will help to understand the processes that generated, stabilized and reworked the cratonic roots through their billion-year tectonic history. We investigate how surface tectonic boundaries relate to deeper lithospheric structural changes, and consider the effects of the multiple Wilson cycles that affected Laurentia.

  17. Effect of particle size distribution on the correlation between liquefaction resistance and shear wave velocity of granular soils

    Science.gov (United States)

    Zhou, Changtao; Xu, Xiao Min; Cheng, Yi Pik

    2017-06-01

    Shear wave method has been increasingly popular in assessing the liquefaction potential of granular soils. Two particle-scale parameters, the inter-particle friction and the shear modulus of grains, play vital roles in correlation between Cyclic Resistance Ratio (CRR) and shear wave velocity corrected by overburden stress (Vs1). Series of drained one-dimensional compression tests were simulated on samples of different inter-particle friction angles assigned during preparation stage. Uniformity coefficients of these Particle Size Distribution (PSD) curves are 2 and 4 whose average particle size d50 are identical. The shearing results, as well as their assigned inter-particle friction angles form calibration curves for real sands. Dissimilar PSD curves result in different calibration outcomes. For Silica sand no.8, these curves give divergent inter-particle friction angles. This study calibrates particle shear modulus for Silica sand no.8 as well. Different PSD curves give divergent values of particle shear modulus. PSDs show impacts on calibrations of both vital parameters, which have converse effects on CRR-Vs1 curves. This study suggests that the CRR-Vs1 correlation should be independent of PSDs.

  18. Application of Refraction Microtremor (ReMi) technique for determination of 1-D shear wave velocity in a landslide area

    Science.gov (United States)

    Coccia, S.; Del Gaudio, V.; Venisti, N.; Wasowski, J.

    2010-06-01

    The application of the Refraction Microtremor (ReMi) method on slopes affected by or prone to landsliding is complicated by the presence of lateral lithological heterogeneities and irregular topography, which may hinder the extension of the geophone array to the minimum lengths (100-200 m) usually adopted in standard applications of this technique. We focus on deriving one-dimensional shear-wave velocity (Vs) vertical profiles from the analysis of microtremor recordings carried out in the municipality of Caramanico Terme (central Italy) where the seismic response has been monitored with a local accelerometer network since 2002. The stability of the ReMi data acquisitions and the reliability of the results in irregular landslide terrain were tested by using ReMi campaigns in three different periods and different acquisition parameters (seismograph channel number, geophone frequency and spacing). We also investigated the possible presence of directional variations in soil properties by carrying out noise recordings along L-shaped arrays. The influence of changing environmental conditions and of different acquisition parameters was tested by comparing the data obtained from different campaigns, using the same acquisition parameters, with the data from simultaneous acquisitions using different parameters. The tests showed that stable results can be obtained under different acquisition conditions provided that i) the ratio between the coherent and incoherent part of ambient noise is sufficiently high and ii) spatial aliasing does not contaminate the signal in the p (slowness)- f (frequency) matrix near the picking area: the latter condition can be satisfied by selecting geophone frequency and spacing appropriate for the site characteristics and for the investigation purpose. The differences in Vs measured in two orthogonal directions did not exceed 10-20 % and their analysis suggests that these directional variations are most likely due to anisotropy in noise source

  19. Low-velocity impact-induced delamination detection by use of the S{sub 0} guided wave mode in cross-ply composite plates: a numerical study

    Energy Technology Data Exchange (ETDEWEB)

    Hayat, Khazar; Ha, Sung Kyu [Hanyang University, Ansan (Korea, Republic of)

    2014-02-15

    Finite element method based numerical simulations are performed to identify low-velocity impact-induced asymmetrically-located delamination in the [0/90{sub 3}]{sub S} and [0/90]{sub 2S} composite plates, respectively, using a fundamental symmetric guided wave mode (S{sub 0}). The wave attenuation effect due to the viscoelasticity of the composite material is modeled by calculating the Lamb wave attenuation constants and using the Rayleigh proportional damping model. The estimated sizes and locations of the delamination in both plates were in good agreement with the experimental measurements. Moreover, the analysis of wave structure of the impacted plates shows that when the S{sub 0} mode propagates through the damaged region, the delamination mouth opens up due to the presence of standing waves, which are generated as a consequence of multiple reflections of trapped waves with the delamination boundaries.

  20. Analysis of the effects of curvature and thickness on elastic wave velocity in cornea-like structures by finite element modeling and optical coherence elastography

    Science.gov (United States)

    Han, Zhaolong; Li, Jiasong; Singh, Manmohan; Aglyamov, Salavat R.; Wu, Chen; Liu, Chih-hao; Larin, Kirill V.

    2015-06-01

    Wave models that have been used to extract the biomechanical properties of the cornea from the propagation of an elastic wave are based on an assumption of thin-plate geometry. However, this assumption does not account for the effects of corneal curvature and thickness. This study conducts finite element (FE) simulations on four types of cornea-like structures as well as optical coherence elastography (OCE) experiments on contact lenses and tissue-mimicking phantoms to investigate the effects of curvature and thickness on the group velocity of an elastic wave. The elastic wave velocity as determined by FE simulations and OCE of a spherical shell section decreased from ˜2.8 m/s to ˜2.2 m/s as the radius of curvature increased from 19.1 mm to 47.7 mm and increased from ˜3.0 m/s to ˜4.1 m/s as the thickness of the agar phantom increased from 1.9 mm to 5.6 mm. Both the FE simulation and OCE results confirm that the group velocity of the elastic wave decreases with radius of curvature but increases with thickness. These results demonstrate that the effects of the curvature and thickness must be considered in the further development of accurate wave models for reconstructing biomechanical properties of the cornea.

  1. A Comparison Between Compounding Techniques Using Large Beam-Steered Plane Wave Imaging for Blood Vector Velocity Imaging in a Carotid Artery Model.

    Science.gov (United States)

    Saris, Anne E C M; Hansen, Hendrik H G; Fekkes, Stein; Nillesen, Maartje M; Rutten, Marcel C M; de Korte, Chris L

    2016-11-01

    Conventional color Doppler imaging is limited, since it only provides velocity estimates along the ultrasound beam direction for a restricted field of view at a limited frame rate. High-frame-rate speckle tracking, using plane wave transmits, has shown potential for 2-D blood velocity estimation. However, due to the lack of focusing in transmit, image quality gets reduced, which hampers speckle tracking. Although ultrafast imaging facilitates improved clutter filtering, it still remains a major challenge in blood velocity estimation. Signal dropouts and poor velocity estimates are still present for high beam-to-flow angles and low blood flow velocities. In this paper, ultrafast plane wave imaging was combined with multiscale speckle tracking to assess the 2-D blood velocity vector in a common carotid artery (CCA) flow field. A multiangled plane wave imaging sequence was used to compare the performance of displacement compounding, coherent compounding, and compound speckle tracking. Zero-degree plane wave imaging was also evaluated. The performance of the methods was evaluated before and after clutter filtering for the large range of velocities (0-1.5 m/s) that are normally present in a healthy CCA during the cardiac cycle. An extensive simulation study was performed, based on a sophisticated model of the CCA, to investigate and evaluate the performance of the methods at different pulse repetition frequencies and signal-to-noise levels. In vivo data were acquired of a healthy carotid artery bifurcation to support the simulation results. In general, methods utilizing compounding after speckle tracking, i.e., displacement compounding and compound speckle tracking, were least affected by clutter filtering and provided the most robust and accurate estimates for the entire velocity range. Displacement compounding, which uses solely axial information to estimate the velocity vector, provided most accurate velocity estimates, although it required sufficiently high pulse

  2. Convenient method for estimating underground s-wave velocity structure utilizing horizontal and vertical components microtremor spectral ratio; Bido no suiheido/jogedo supekutoru hi wo riyoshita kan`i chika s ha sokudo kozo suiteiho

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, H.; Yoshioka, M.; Saito, T. [Iwate University, Iwate (Japan). Faculty of Engineering

    1996-05-01

    Studies were conducted about the method of estimating the underground S-wave velocity structure by inversion making use of the horizontal/vertical motion spectral ratio of microtremors. For this purpose, a dynamo-electric velocity type seismograph was used, capable of processing the east-west, north-south, and vertical components integratedly. For the purpose of sampling the Rayleigh wave spectral ratio, one out of all the azimuths was chosen, whose horizontal motion had a high Fourier frequency component coherency with the vertical motions. For the estimation of the underground S-wave velocity structure, parameters (P-wave velocity, S-wave velocity, density, and layer thickness) were determined from the minimum residual sum of squares involving the observed microtremor spectral ratio and the theoretical value calculated by use of a model structure. The known boring data was utilized for the study of the S-wave velocity in the top layer, and it was determined using an S-wave velocity estimation formula for the Morioka area constructed using the N-value, depth, and geological classification. It was found that the optimum S-wave velocity structure even below the top layer well reflects the S-wave velocity obtained by the estimation formula. 5 refs., 6 figs.

  3. Estimation of Shear Wave Velocity from MASW and H/V Joint Inversion in a Noisy Area of Sao Paulo City, Brazil

    Science.gov (United States)

    Ullah, I.; Luiz Prado, R.

    2015-12-01

    The parameters shear wave velocity and soft sediment thickness are very important for the site investigation. Shear wave velocities are usually obtained from the dispersion curve analysis of surface wave (MASW), which are obtained by active or passive seismic array. Dispersion curve provides a reliable velocity estimate at frequencies above the fundamental resonant frequency of the site (Hobiger et al, 2009), however dispersion curve analysis does not provide information about the deeper layers,. The information of deeper layer can be included from H/V spectral ratio analysis, which provides a very good estimate of fundamental frequency of site. A joint inversion analysis of dispersion and H/V curves have been made, the dispersion curve has been obtained by active source (MASW) while H/V ratios are obtained from seismic ambient noise recording through single 3 component broadband seismometer. H/V curve inversion are linked with Rayleigh wave ellipticty curve, however Bonnefoy-Claudet (2008) have shown that both Rayleigh and Love waves contribute to the H/V spectrum, so it is necessary to accurately extract Rayleigh wave ellipticity from single station recording. We have utilized two techniques to retrieve Rayliegh wave ellipticty from our noise recording. One is random decrement technique, RayDec (Hobiger et al, 2009) and second, time frequency analysis (Neries project, 2010). This Rayleigh wave ellipticty from H/V recording and dispersion curve from MASW have been jointly inverted. The inversion has been carried out using neighborhood algorithm introduced to geophysics by Sambridge (1999). Shear wave velocity profile have been compared with borehole result (at same location), which showed a very promising correlation, especially within zone of high velocity contrast and depth of bedrock.References 1. Bonnefoy-Claudet, (2008), Effects of Love waves on microtremor H/V ratio, Bull. Seismol.Soc 2. Hobiger, (2009), Single station determination of Rayleigh wave

  4. A Fast Multimodal Ectopic Beat Detection Method Applied for Blood Pressure Estimation Based on Pulse Wave Velocity Measurements in Wearable Sensors

    OpenAIRE

    Maik Pflugradt; Kai Geissdoerfer; Matthias Goernig; Reinhold Orglmeister

    2017-01-01

    Automatic detection of ectopic beats has become a thoroughly researched topic, with literature providing manifold proposals typically incorporating morphological analysis of the electrocardiogram (ECG). Although being well understood, its utilization is often neglected, especially in practical monitoring situations like online evaluation of signals acquired in wearable sensors. Continuous blood pressure estimation based on pulse wave velocity considerations is a prominent example, which depen...

  5. A fast multimodal ectopic beat detection method applied for blood pressure estimation based on pulse wave velocity measurements in wearable sensors

    OpenAIRE

    Pflugradt, Maik; Geißdörfer, Kai; Görnig, Matthias; Orglmeister, Reinhold

    2017-01-01

    Automatic detection of ectopic beats has become a thoroughly researched topic, with literature providing manifold proposals typically incorporating morphological analysis of the electrocardiogram (ECG). Although being well understood, its utilization is often neglected, especially in practical monitoring situations like online evaluation of signals acquired in wearable sensors. Continuous blood pressure estimation based on pulse wave velocity considerations is a prominent example, which depen...

  6. Determinants of pulse wave velocity in healthy people and in the presence of cardiovascular risk factors: 'establishing normal and reference values'

    DEFF Research Database (Denmark)

    Hansen, Tine Willum

    2010-01-01

    Carotid-femoral pulse wave velocity (PWV), a direct measure of aortic stiffness, has become increasingly important for total cardiovascular (CV) risk estimation. Its application as a routine tool for clinical patient evaluation has been hampered by the absence of reference values. The aim of the ...

  7. Compressional wave velocity and index properties of the gabbroic rocks drilled at hole 1105A of the Atlantis Bank, southwest Indian Ridge

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, D.G.; Krishna, K.S.

    Compressional wave velocities (Vp) and index properties of 70 mini- gabbroic rock- core samples of 2.5 cm diameter x 2.1 cm long from 157.1 m below seafloor in Hole 1105Aof the Atlantis Bank, Southwest Indian Ridge, were measured in the laboratory...

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

    Science.gov (United States)

    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.

  9. Evaluation of arterial stiffness by finger-toe pulse wave velocity: optimization of signal processing and clinical validation.

    Science.gov (United States)

    Obeid, Hasan; Khettab, Hakim; Marais, Louise; Hallab, Magid; Laurent, Stéphane; Boutouyrie, Pierre

    2017-08-01

    Carotid-femoral pulse wave velocity (PWV) (cf-PWV) is the gold standard for measuring aortic stiffness. Finger-toe PWV (ft-PWV) is a simpler noninvasive method for measuring arterial stiffness. Although the validity of the method has been previously assessed, its accuracy can be improved. ft-PWV is determined on the basis of a patented height chart for the distance and the pulse transit time (PTT) between the finger and the toe pulpar arteries signals (ft-PTT). The objective of the first study, performed in 66 patients, was to compare different algorithms (intersecting tangents, maximum of the second derivative, 10% threshold and cross-correlation) for determining the foot of the arterial pulse wave, thus the ft-PTT. The objective of the second study, performed in 101 patients, was to investigate different signal processing chains to improve the concordance of ft-PWV with the gold-standard cf-PWV. Finger-toe PWV (ft-PWV) was calculated using the four algorithms. The best correlations relating ft-PWV and cf-PWV, and relating ft-PTT and carotid-femoral PTT were obtained with the maximum of the second derivative algorithm [PWV: r = 0.56, P signal processing chain. Selecting the maximum of the second derivative algorithm for detecting the foot of the pressure waveform, and combining it with an optimized signal processing chain, improved the accuracy of ft-PWV measurement in the current population sample. Thus, it makes ft-PWV very promising for the simple noninvasive determination of aortic stiffness in clinical practice.

  10. Four criteria to find an optimal location in Colombia for a millimeter wave astronomical observatory

    Science.gov (United States)

    Ramírez Suárez, O. L.; Martínez Mercado, A. M.; Restrepo Gaitán, O. A.; Chaparro Molano, G.

    2017-07-01

    To find an optimal location for a mm-wave astronomical observatory, all factors that directly or indirectly affect the water vapor column density should be considered. After estimating a weighted classification of these factors to obtain a range of acceptable values, places satisfying as many of these suitability conditions can be proposed as candidates. Here we analyze data from NASA and IDEAM to find places satisfying the best conditions to build a mm-wave astronomical observatory in Colombia, according to seven variables grouped into four classes. From NASA, we analyze the satellite data of: (i) relative humidity and (ii) cloud coverage/direct normal radiation, averaged monthly from 1983 to 2005. From IDEAM, we analyze data of relative humidity, sunshine, and (iii) precipitation/number of days with rain, averaged yearly over each month from 1981 to 2010. The data has been obtained in-situ by 2046 weather monitoring stations across Colombia, for which their (iv) altitude is known. For each quantity, we do a Principal Component Analysis, reducing the dimensionality of the yearly-averaged data to 2 components covering >90% of the variance. After this, we make a classification of the reduced-dimension data using a 4 cluster Gaussian Mixture Model (GMM), identifying similar geographic and climatological patterns. After selecting clusters of stations sharing optimal conditions (i.e. high altitude, low rain, etc.), we group and look for geographical clusters by applying a GMM on a Monte Carlo sampling of latitude, longitude, and altitude data in order to correct for biases. This method allows us to find regions of interest where further in-situ measurements of atmospheric absorption of mm-wave should be carried out in the future.

  11. Correlates of Segmental Pulse Wave Velocity in Older Adults: The Atherosclerosis Risk in Communities (ARIC) Study.

    Science.gov (United States)

    Meyer, Michelle L; Tanaka, Hirofumi; Palta, Priya; Cheng, Susan; Gouskova, Natalia; Aguilar, David; Heiss, Gerardo

    2016-01-01

    Carotid-femoral PWV (cfPWV) is a well-established measure of central arterial stiffness, while brachial-ankle PWV (baPWV) is being used more frequently in East Asian countries. Few studies have simultaneously characterized the distributions and correlates of segment-specific PWV measures and their associations with cardiovascular risk factors. We evaluated segment-specific PWV (cfPWV, baPWV, and femoral-ankle (faPWV)) in 4,974 older-aged African American and Caucasian adults in the community-based Atherosclerosis Risk in Communities (ARIC) Study using a standardized protocol and the OMRON VP-1000 Plus system. We examined the distribution and multivariable-adjusted correlates of PWV measures by race and sex. Mean age ranged from 74 ± 5 to 76 ± 5 years across race-sex groups. In all race-sex groups, cfPWV correlated with baPWV but not with faPWV, and cfPWV and baPWV were higher with age, whereas faPWV was not. Heart rate and systolic blood pressure (SBP) were positively associated and weight was negatively associated with all PWV measures; however, the associations with age, glycated hemoglobin, triglycerides, and high-density lipoprotein (HDL) cholesterol varied by segment and race-sex group. Our findings indicate that cfPWV and faPWV reflect distinct aspects of segment-specific vascular stiffness and their associated profile of cardiovascular risk factors. Even among older adults, age is associated with higher cfPWV and baPWV, but not with faPWV. Understanding factors that ostensibly play a role in increasing arterial stiffness in different arterial territories can inform opportunities for cardiovascular disease (CVD) prevention and risk management. © American Journal of Hypertension, Ltd 2015. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  12. A new scheme for joint surface wave and earthquake travel-time inversion and resulting 3-D velocity model for the western North Island, New Zealand

    Science.gov (United States)

    Eberhart-Phillips, Donna; Fry, Bill

    2017-08-01

    We have developed a joint inversion of surface wave group velocity (U) and local earthquake travel-time (LET) data and applied it to the North Island, New Zealand, to improve the existing New Zealand wide 3-D seismic velocity model. This approach takes full advantage of the differing sensitivities of surface and body waves. The data are complementary, particularly at shallow depths where LET tomography suffers from vertical smearing and surface wave tomography is susceptible to horizontal smearing. The employed U observations are 2-D models at discrete periods which were developed for Rayleigh wave dispersion curves measured from the 1744 interstation Green's Functions obtained by stacked cross-correlations of broadband ambient noise data. In the volume surrounding each U observation, we distribute numerous points for relating the U observation to the gridded 3-D tomography model, analogous to points along a raypath. The partial derivatives at the points are computed using the U sensitivity kernels for Vp and Vs, with Vs related to Vp and Vp/Vs perturbations. Thus, the U observations are included along with the travel-time observations in a joint inversion to best fit the data and the existing tomography model. The resulting model favors the U where there is little travel-time resolution. The combined inversion used 2949 U observations at 6-16 s period and LET from 1509 earthquakes that extend to 370 km depth, and improved the model fit by reducing the U residual data variance by 62% and the LET by 9%. The resulting model generally has better constrained depth of shallow anomalies, with decreased velocity in the upper 2 km in the western North Island, and slight focusing of crustal high velocity features at 8 km depth. Significantly, the increased resolution in the shallowest 5 km of the model improves the utility of the 3-D model for use in seismic hazard assessment, wave propagation studies, and studies comparing seismic velocities to geological mapping.

  13. Pulse Wave Velocity as Marker of Preclinical Arterial Disease: Reference Levels in a Uruguayan Population Considering Wave Detection Algorithms, Path Lengths, Aging, and Blood Pressure

    Directory of Open Access Journals (Sweden)

    Ignacio Farro

    2012-01-01

    Full Text Available Carotid-femoral pulse wave velocity (PWV has emerged as the gold standard for non-invasive evaluation of aortic stiffness; absence of standardized methodologies of study and lack of normal and reference values have limited a wider clinical implementation. This work was carried out in a Uruguayan (South American population in order to characterize normal, reference, and threshold levels of PWV considering normal age-related changes in PWV and the prevailing blood pressure level during the study. A conservative approach was used, and we excluded symptomatic subjects; subjects with history of cardiovascular (CV disease, diabetes mellitus or renal failure; subjects with traditional CV risk factors (other than age and gender; asymptomatic subjects with atherosclerotic plaques in carotid arteries; patients taking anti-hypertensives or lipid-lowering medications. The included subjects (n=429 were categorized according to the age decade and the blood pressure levels (at study time. All subjects represented the “reference population”; the group of subjects with optimal/normal blood pressures levels at study time represented the “normal population.” Results. Normal and reference PWV levels were obtained. Differences in PWV levels and aging-associated changes were obtained. The obtained data could be used to define vascular aging and abnormal or disease-related arterial changes.

  14. The Accountability Turn in Third Wave Human Rights Fact-Finding

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    Federica D'Alessandra

    2017-04-01

    Full Text Available Whereas the characteristics of human rights fact-finding largely vary depending on the typology and scope of the entity that carries it out, consensus seems to be developing that a common set of challenges to human rights fact-finding exists. This is especially so when carried out under United Nations auspices. For example, it has long been acknowledged that the very nature of the institution, sitting as it does at the crossroads of international politics, as well as the seemingly irresolvable tension between calls for human rights protection on the one hand, and State sovereignty on the other, present some structural challenges to human rights fact-finding. Furthermore, issues of coordination between the United Nations and other institutions (such as international governmental and non-governmental organisations, or international tribunals, as well as what some have called a ‘lack of institutional memory’ arguably often feature as regular traits among fact-finding mechanisms. In recent years, a further set of challenges has been added to the mix by additional requirements, featuring increasingly often in mandates, that instruct fact-finding mechanisms to make further determinations of facts (concerning, 'e.g.', the identity of those most responsible for the violations being documented, or the existence of an armed conflict and even consider questions of law ('e.g.' the qualification of the violations as crimes under international law. Building on an expanding body of scholarship on the subject, as well as the author’s own experience with fact-finding efforts sitting at the intersection between traditional international human rights law and international criminal justice, this article argues: (i that human rights fact-finding has evolved in three waves; (ii that the third wave of human rights fact-finding is characterised by an “accountability turn”; and that (iii this turn has brought about an additional set of challenges to the

  15. Impact of brachial-ankle pulse wave velocity and ankle-brachial blood pressure index on mortality in hemodialysis patients.

    Science.gov (United States)

    Kitahara, Tokuyuki; Ono, Kumeo; Tsuchida, Akiyasu; Kawai, Hironobu; Shinohara, Masahiko; Ishii, Yoshitaka; Koyanagi, Hikaru; Noguchi, Toshiharu; Matsumoto, Takayuki; Sekihara, Tetsuo; Watanabe, Yukiyasu; Kanai, Hideo; Ishida, Hideki; Nojima, Yoshihisa

    2005-10-01

    Pulse wave velocity (PWV) and ankle-brachial blood pressure index (ABPI) are markers for atherosclerosis, and each predicts mortality in patients undergoing hemodialysis. However, there have been no studies in the past that compared head-to-head the clinical validity of these 2 parameters. Compared with conventional aortic PWV, brachial-ankle PWV (baPWV) is considered simple and thereby easily applicable to clinical use. To clarify the relationship between baPWV and ABPI and assess their prognostic values, we analyzed 785 hemodialysis patients with a mean age of 60.2 +/- 12.5 (SD) years for whom ABPI and baPWV at baseline had been measured simultaneously and who were followed up for 33.8 +/- 10.8 months. Of 785 patients, 131 deaths were recorded. In Kaplan-Meier analysis, all-cause mortality was progressively and significantly greater from the lowest quartile of baPWV onward (log-rank test, 41.8; P hemodialysis patients. However, baPWV was useful to pick a high-risk population in patients with ABPI greater than 0.9. Thus, screening hemodialysis patients by means of baPWV and ABPI provides complementary information in identifying a high-risk population.

  16. Fibrin glue: an alternative technique for nerve coaptation--Part I. Wave amplitude, conduction velocity, and plantar-length factors.

    Science.gov (United States)

    Ornelas, Lorraine; Padilla, Luis; Di Silvio, Mauricio; Schalch, Paul; Esperante, Sandro; Infante, Paul López; Bustamante, Juan Carlos; Avalos, Pablo; Varela, Deborah; López, Manuel

    2006-02-01

    The search for better surgical repair of nerve injuries should be aimed at uncovering alternatives that not only are efficient, but also enhance nerve growth. The purpose of this study was to compare functional nerve responses following repair with either a traditional microsuture technique or Quixil human fibrin sealant. Thirty female Lewis rats received transection of the right sciatic nerve. Nerve repair was achieved with either epineurial microsuture (n = 15) or Quixil fibrin glue (n = 15). Functional results were assessed at 2, 6, and 12 weeks postoperatively with walking-track analysis. Electrophysiologic nerve recordings were also performed 12 weeks postoperatively. Rats receiving Quixil nerve repair returned to baseline performance on the walking-track analysis significantly faster than those with microsuture repairs (6 and 12 weeks postoperatively; p < 0.0001). Recovery of nerve conduction velocities and wave amplitudes was also significantly better in the nerves repaired with Quixil than in those repaired with microsuture (p's < 0.0001). Quixil human fibrin sealant is a good alternative to traditional microsuture nerve repair techniques.

  17. Determination of the elastic and stiffness characteristics of cross-laminated timber plates from flexural wave velocity measurements

    Science.gov (United States)

    Santoni, Andrea; Schoenwald, Stefan; Van Damme, Bart; Fausti, Patrizio

    2017-07-01

    Cross-laminated timber (CLT) is an engineered wood with good structural properties and it is also economically competitive with the traditional building construction materials. However, due to its low volume density combined with its high stiffness, it does not provide sufficient sound insulation, thus it is necessary to develop specific acoustic treatments in order to increase the noise reduction performance. The material's mechanical properties are required as input data to perform the vibro-acoustic analyses necessary during the design process. In this paper the elastic constants of a CLT plate are derived by fitting the real component of the experimental flexural wave velocity with Mindlin's dispersion relation for thick plates, neglecting the influence of the plate's size and boundary conditions. Furthermore, its apparent elastic and stiffness properties are derived from the same set of experimental data, for the plate considered to be thin. Under this latter assumption the orthotropic behaviour of an equivalent thin CLT plate is described by using an elliptic model and verified with experimental results.

  18. Development of site class and site coefficient maps of Semarang, Indonesia using field shear wave velocity data

    Directory of Open Access Journals (Sweden)

    Partono Windu

    2017-01-01

    Full Text Available The new Indonesian National Code for seismic resistance design (SNI-03-1726-2012 issued recently utilizes seismic response spectra for the whole area of the country. Site class and site coefficient are two parameters needed for designing response spectra. Site class can be estimated using average standard penetration test (N-SPT, average shear wave velocity (Vs and average un-drained shear strength (Su of top 30 meter soil deposit. Site coefficients can be predicted using probabilistic seismic hazard analysis (PSHA by implementing total probability theorem. To perform PSHA, Vs30 is a parameter needed for calculating ground motion at bedrock elevation. This paper presents the results of PSHA and site class analysis using Vs30 values estimated based on N-SPT results collected from 265 boring locations in Semarang. Seismic data in a radius of 500 km from Semarang were collected for PSHA. Site class and site coefficient maps are then developed for the whole study area.

  19. A prospective study on pulse wave velocity (PWV) and response to anti-hypertensive treatments: PWV determines BP control.

    Science.gov (United States)

    Zheng, Meili; Huo, Yong; Wang, Xiaobin; Xu, Xin; Qin, Xianhui; Tang, Genfu; Xing, Houxun; Fan, Fangfang; Li, Jianping; Zhang, Yan; Wang, Binyan; Xu, Xiping; Yang, Xinchun; Chen, Yundai; Qian, Geng

    2015-01-15

    Recent data indicate that hypertension is not well controlled in many populations throughout the world. The factors that influence individual response to anti-hypertensive treatment need to be clarified. Pulse wave velocity (PWV), as a marker of arterial stiffness, has been demonstrated to have important relationships with BP progression; however, little information is available on the role of PWV in blood pressure (BP) control. We aimed to assess BP control during the run-in treatment period in the China Stroke Primary Prevention Trial (CSPPT). These analyses included a total of 3056 treated hypertensive subjects (age: 59.6±7.5years, male/female 1339/1717) with PWV measured at baseline. The average BP at enrollment was 166/95mmHg, and declined to 141/85mmHg after short-term antihypertensive treatment (a median follow-up of 20days). There was an inverse relationship between PWV level and BP reduction during the treatment, most notably for systolic BP (with estimated coefficients of -9.01 (Panti-hypertensive treatment. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  20. Comparison of echotracking and magnetic resonance assessment of abdominal aorta distensibility and relationships with pulse wave velocity.

    Science.gov (United States)

    Giannattasio, Cristina; Cesana, Francesca; Maestroni, Silvia; Salvioni, Alessandra; Maloberti, Alessandro; Nava, Stefano; Cairo, Matteo; Madotto, Fabiana; Zerboni, Filippo; Sironi, Sandro; Grassi, Guido; Mancia, Giuseppe

    2011-12-01

    Arterial distensibility can be measured either by echotracking or by nuclear magnetic resonance (MRI). Little information, however, is available on the comparison between the two methods and on the relationships between the results obtained with the two approaches and the arterial stiffness gold standard measurement, i.e., pulse wave velocity (PWV). In 28 normotensive subjects (age 33.0 ± 10.4 years, mean ± SD) we measured aortic diameter 1 cm above iliac bifurcation, aortic pulse pressure by tonometry and calculated arterial distensibility via the Reneman formulae for both methods. Aortic diameter and aortic distensibility were not superimposable and higher values were systematically detected with the MRI approach than with the ultrasound one. However, PWV showed a significant correlation with aortic distensibility values obtained by both methods (r = 0.50 and r = 0.49, p < 0.05). These data provide evidence that MRI-measured distensibility value is higher than that obtained via echotracking. The significant correlation with PWV, however, suggests that both methods can be regarded as valuable approaches. Considering the greater economic cost and the lower availability in daily clinical and research practice of MRI, echotracking ultrasonography can be regarded as a reliable and feasible method to assess aortic distensibility. Copyright © 2011. Published by Elsevier Inc.

  1. Effect of the specimen length on ultrasonic P-wave velocity in some volcanic rocks and limestones

    Science.gov (United States)

    Karaman, Kadir; Kaya, Ayberk; Kesimal, Ayhan

    2015-12-01

    Ultrasonic P-wave velocity (UPV) is commonly used in different fields such as civil, mining, geotechnical, and rock engineering. One of the significant parameters which affect the UPV of rock materials is likely to be the length of test cores although it is not mentioned in the literature. In this study, in order to explore the influence of the specimen length on the UPV, rock samples were collected from eight different locations in Turkey. The NX-sized core specimens having different length of 50, 75, 100, 125, and 150 mm were prepared. Before the analyses, rocks were divided into two groups in terms of their geological origins such as volcanic and chemical sedimentary (limestone) rocks. The UPV tests were carried out under dry and saturated conditions for each 200 core specimens. By evaluating the test results, it was shown that the length of the specimens significantly affects the UPV values. Based on the regression analyses, a method was developed to determine the threshold specimen length of studied rocks. Fluctuations in UPVdry and UPVsat values were generally observed for cores smaller than the threshold specimen length. In this study, the threshold specimen length was determined as 79 mm for volcanic rocks and 109 mm for limestones.

  2. The effect of workplace smoking bans on heart rate variability and pulse wave velocity of non-smoking hospitality workers.

    Science.gov (United States)

    Rajkumar, Sarah; Schmidt-Trucksäss, Arno; Wellenius, Gregory A; Bauer, Georg F; Huynh, Cong Khanh; Moeller, Alexander; Röösli, Martin

    2014-08-01

    To investigate the effect of a change in second-hand smoke (SHS) exposure on heart rate variability (HRV) and pulse wave velocity (PWV), this study utilized a quasi-experimental setting when a smoking ban was introduced. HRV, a quantitative marker of autonomic activity of the nervous system, and PWV, a marker of arterial stiffness, were measured in 55 non-smoking hospitality workers before and 3-12 months after a smoking ban and compared to a control group that did not experience an exposure change. SHS exposure was determined with a nicotine-specific badge and expressed as inhaled cigarette equivalents per day (CE/d). PWV and HRV parameters significantly changed in a dose-dependent manner in the intervention group as compared to the control group. A one CE/d decrease was associated with a 2.3% (95% CI 0.2-4.4; p = 0.031) higher root mean square of successive differences (RMSSD), a 5.7% (95% CI 0.9-10.2; p = 0.02) higher high-frequency component and a 0.72% (95% CI 0.40-1.05; p < 0.001) lower PWV. PWV and HRV significantly improved after introducing smoke-free workplaces indicating a decreased cardiovascular risk.

  3. Brachial-Ankle Pulse Wave Velocity and the Risk Prediction of Cardiovascular Disease: An Individual Participant Data Meta-Analysis.

    Science.gov (United States)

    Ohkuma, Toshiaki; Ninomiya, Toshiharu; Tomiyama, Hirofumi; Kario, Kazuomi; Hoshide, Satoshi; Kita, Yoshikuni; Inoguchi, Toyoshi; Maeda, Yasutaka; Kohara, Katsuhiko; Tabara, Yasuharu; Nakamura, Motoyuki; Ohkubo, Takayoshi; Watada, Hirotaka; Munakata, Masanori; Ohishi, Mitsuru; Ito, Norihisa; Nakamura, Michinari; Shoji, Tetsuo; Vlachopoulos, Charalambos; Yamashina, Akira

    2017-06-01

    An individual participant data meta-analysis was conducted in the data of 14 673 Japanese participants without a history of cardiovascular disease (CVD) to examine the association of the brachial-ankle pulse wave velocity (baPWV) with the risk of development of CVD. During the average 6.4-year follow-up period, 687 participants died and 735 developed cardiovascular events. A higher baPWV was significantly associated with a higher risk of CVD, even after adjustments for conventional risk factors ( P for trend risk of CVD. Moreover, addition of baPWV to a model incorporating the Framingham risk score significantly increased the C statistics from 0.8026 to 0.8131 ( P analysis clearly established baPWV as an independent predictor of the risk of development of CVD in Japanese subjects without preexisting CVD. Thus, measurement of the baPWV could enhance the efficacy of prediction of the risk of development of CVD over that of the Framingham risk score, which is based on the traditional cardiovascular risk factors. © 2017 American Heart Association, Inc.

  4. Genetically elevated levels of circulating triglycerides and brachial-ankle pulse wave velocity in a Chinese population.

    Science.gov (United States)

    Yao, W-M; Zhang, H-F; Zhu, Z-Y; Zhou, Y-L; Liang, N-X; Xu, D-J; Zhou, F; Sheng, Y-H; Yang, R; Gong, L; Yin, Z-J; Chen, F-K; Cao, K-J; Li, X-L

    2013-04-01

    Elevated levels of circulating triglycerides and increased arterial stiffness are associated with cardiovascular disease. Numerous studies have reported an association between levels of circulating triglycerides and arterial stiffness. We used Mendelian randomization to test whether this association is causal. We investigated the association between circulating triglyceride levels, the apolipoprotein A-V (ApoA5) -1131T>C single nucleotide polymorphism and brachial-ankle pulse wave velocity (baPWV) by examining data from 4421 subjects aged 18-74 years who were recruited from the Chinese population. baPWV was significantly associated with the levels of circulating triglycerides after adjusting for age, sex, body mass index (BMI), systolic blood pressure, heart rate, waist-to-hip ratio, antihypertensive treatment and diabetes mellitus status. The -1131C allele was associated with a 5% (95% confidence interval 3-8%) increase in circulating triglycerides (adjusted for age, sex, BMI, waist-to-hip ratio, diabetes mellitus and antihypertensive treatment). Instrumental variable analysis showed that genetically elevated levels of circulating triglycerides were not associated with increased baPWV. These results do not support the hypothesis that levels of circulating triglycerides have a causal role in the development of arterial stiffness.

  5. Surface stress, initial stress and Knudsen-dependent flow velocity effects on the electro-thermo nonlocal wave propagation of SWBNNTs

    Energy Technology Data Exchange (ETDEWEB)

    Ghorbanpour Arani, A., E-mail: aghorban@kashanu.ac.ir [Faculty of Mechanical Engineering, University of Kashan, Kashan, Islamic Republic of Iran. (Iran, Islamic Republic of); Institute of Nanoscience and Nanotechnology, University of Kashan, Kashan, Islamic Republic of Iran (Iran, Islamic Republic of); Roudbari, M.A. [Faculty of Mechanical Engineering, University of Kashan, Kashan, Islamic Republic of Iran. (Iran, Islamic Republic of)

    2014-11-01

    This paper investigates the electro-thermal nonlocal wave propagation of fluid-conveying single-walled Boron Nitride nanotubes (SWBNNTs) using nonlocal piezoelasticity with surface stress, initial stress and Knudsen-dependent flow velocity effect. SWBNNT is embedded in a vicsoelastic medium which is simulated as visco-Pasternak foundation. Using Euler–Bernoulli beam (EBB) model, Hamilton's principle and nonlocal piezoelasticity theory, the higher order governing equation is derived. A detailed parametric study is conducted, focusing on the combined effects of the electric parameters, viscoelastic medium, initial stress, surface stress, Knudsen number (Kn) and small scale on the wave propagation behaviour of the fluid-conveying SWBNNT. The results show that for smaller values of wave number the dispersion relation for different fluid viscosities seems to be similar. At the higher values of wave numbers, increase in the wave frequency values is remarkable due to increase in fluid viscosity. The electric field as a smart controller, surface effect, initial stress, temperature change and slip velocity effect have significant role on the wave frequency. The results of this work is hoped to be of use in design and manufacturing of smart MEMS/NEMS in advanced medical applications such as drug delivery systems with great applications in biomechanics.

  6. Seismicity and S-wave velocity structure of the crust and the upper mantle in the Baikal rift and adjacent regions

    Science.gov (United States)

    Seredkina, Alena; Kozhevnikov, Vladimir; Melnikova, Valentina; Solovey, Oksana

    2016-12-01

    Correlations between seismicity, seismotectonic deformation (STD) field and velocity structure of the crust and the upper mantle in the Baikal rift and the adjacent areas of the Siberian platform and the Mongol-Okhotsk fold belt have been investigated. The 3D S-wave velocity structure up to the depths of 500 km has been modeled using a representative sample of Rayleigh wave group velocity dispersion curves (about 3200 paths) at periods from 10 to 250 s. The STD pattern has been reconstructed from mechanisms of large earthquakes, and is in good agreement with GPS and structural data. Analysis of the results has shown that most of large shallow earthquakes fall in regions of low S-wave velocities in the uppermost mantle (western Mongolia and areas of recent mountain building in southern Siberia) and in zones of their relatively high lateral variations (northeastern flank of the Baikal rift). In the first case the dominant STD regime is compression manifested in a mixture of thrust and strike-slip deformations. In the second case we observe a general predominance of extension.

  7. The Use of GPR in Delineating an Iron Sand Boundary and the Determination of Its Electromagnetic Wave Velocity: A Case Study in Jepara, Central Java

    Directory of Open Access Journals (Sweden)

    S. Bijaksana

    2005-11-01

    Full Text Available Exploring the vertical extent of iron sand deposit is challenging as conventional geophysical methods (electrical resistivity, geomagnetic, and seismic refraction are inappropriate and unsuccessful in delineating the iron sand deposit from the bedrock. Ground-penetrating radar (GPR offers a solution to the above problem as radar is not affected negatively by the physical properties of iron sand. In the year 2003, a RAMAC’s GPR survey was carried out in the coast of Bayuran in the Regency of Jepara, Central Java to map the distribution of sub-bottom iron sand. The sand is highly magnetic. The survey used 100 MHz antennas. The survey is also complimented by a novel method in determining the electromagnetic (EM wave velocity of iron sand. Combination of reflection profiling and CMP sounding was deployed. Results of CMP sounding were processed using CMP-semblance analysis that produces the RMS velocity in velocity-time spectra. The RMS velocity is then converted to interval velocity using Dix’s formula and is found to be about 135 mm/ns. Meanwhile, combination of magnetic susceptibility, relative permittivity, and dissipation factors produces radiowaves velocity of iron sand as a function of frequency. The velocities of radiowaves estimated from laboratory match that estimated from CMP analysis.

  8. Application of a simplified calculation for full-wave microtremor H/ V spectral ratio based on the diffuse field approximation to identify underground velocity structures

    Science.gov (United States)

    Wu, Hao; Masaki, Kazuaki; Irikura, Kojiro; Sánchez-Sesma, Francisco José

    2017-12-01

    Under the diffuse field approximation, the full-wave (FW) microtremor H/ V spectral ratio ( H/ V) is modeled as the square root of the ratio of the sum of imaginary parts of the Green's function of the horizontal components to that of the vertical one. For a given layered medium, the FW H/ V can be well approximated with only surface waves (SW) H/ V of the "cap-layered" medium which consists of the given layered medium and a new larger velocity half-space (cap layer) at large depth. Because the contribution of surface waves can be simply obtained by the residue theorem, the computation of SW H/ V of cap-layered medium is faster than that of FW H/ V evaluated by discrete wavenumber method and contour integration method. The simplified computation of SW H/ V was then applied to identify the underground velocity structures at six KiK-net strong-motion stations. The inverted underground velocity structures were used to evaluate FW H/ Vs which were consistent with the SW H/ Vs of corresponding cap-layered media. The previous study on surface waves H/ Vs proposed with the distributed surface sources assumption and a fixed Rayleigh-to-Love waves amplitude ratio for horizontal motions showed a good agreement with the SW H/ Vs of our study. The consistency between observed and theoretical spectral ratios, such as the earthquake motions of H/ V spectral ratio and spectral ratio of horizontal motions between surface and bottom of borehole, indicated that the underground velocity structures identified from SW H/ V of cap-layered medium were well resolved by the new method.[Figure not available: see fulltext.

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

    Science.gov (United States)

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

    2016-04-01

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

  10. Ten kilometer vertical Moho offset and shallow velocity contrast along the Denali fault zone from double-difference tomography, receiver functions, and fault zone head waves

    Science.gov (United States)

    Allam, A. A.; Schulte-Pelkum, V.; Ben-Zion, Y.; Tape, C.; Ruppert, N.; Ross, Z. E.

    2017-11-01

    We examine the structure of the Denali fault system in the crust and upper mantle using double-difference tomography, P-wave receiver functions, and analysis (spatial distribution and moveout) of fault zone head waves. The three methods have complementary sensitivity; tomography is sensitive to 3D seismic velocity structure but smooths sharp boundaries, receiver functions are sensitive to (quasi) horizontal interfaces, and fault zone head waves are sensitive to (quasi) vertical interfaces. The results indicate that the Mohorovičić discontinuity is vertically offset by 10 to 15 km along the central 600 km of the Denali fault in the imaged region, with the northern side having shallower Moho depths around 30 km. An automated phase picker algorithm is used to identify 1400 events that generate fault zone head waves only at near-fault stations. At shorter hypocentral distances head waves are observed at stations on the northern side of the fault, while longer propagation distances and deeper events produce head waves on the southern side. These results suggest a reversal of the velocity contrast polarity with depth, which we confirm by computing average 1D velocity models separately north and south of the fault. Using teleseismic events with M ≥ 5.1, we obtain 31,400 P receiver functions and apply common-conversion-point stacking. The results are migrated to depth using the derived 3D tomography model. The imaged interfaces agree with the tomography model, showing a Moho offset along the central Denali fault and also the sub-parallel Hines Creek fault, a suture zone boundary 30 km to the north. To the east, this offset follows the Totschunda fault, which ruptured during the M7.9 2002 earthquake, rather than the Denali fault itself. The combined results suggest that the Denali fault zone separates two distinct crustal blocks, and that the Totschunda and Hines Creeks segments are important components of the fault and Cretaceous-aged suture zone structure.

  11. Combined estimation of thickness and velocities using ultrasound guided waves: a pioneering study on in vitro cortical bone samples.

    Science.gov (United States)

    Foiret, Josquin; Minonzio, Jean-Gabriel; Chappard, Christine; Talmant, Maryline; Laugier, Pascal

    2014-09-01

    This paper reports for the first time on inverse estimation of several bone properties from guided-wave measurements in human bone samples. Previously, related approaches have focused on ultrasonic estimation of a single bone property at a time. The method is based on two steps: the multi-Lamb mode response is analyzed using the singular value decomposition signal processing method recently introduced in the field, then an identification procedure is run to find thickness and anisotropic elastic properties of the considered specimen. Prior to the measurements on bone, the method is validated on cortical bone-mimicking phantoms. The repeatability and the trueness of the estimated parameters on bone-mimicking phantoms were found around a few percent. Estimation of cortical thickness on bone samples was in good agreement with cortical thickness derived from high-resolution peripheral quantitative computed tomography data analysis of the samples.

  12. Association of Brachial-Ankle Pulse Wave Velocity and Cardiomegaly With Aortic Arch Calcification in Patients on Hemodialysis.

    Science.gov (United States)

    Shin, Ming-Chen Paul; Lee, Mei-Yueh; Huang, Jiun-Chi; Tsai, Yi-Chun; Chen, Jui-Hsin; Chen, Szu-Chia; Chang, Jer-Ming; Chen, Hung-Chun

    2016-05-01

    Aortic arch calcification (AoAC) is associated with cardiovascular and all-cause mortality in end-stage renal disease population. AoAC can be simply estimated with an AoAC score using plain chest radiography. The objective of this study is to evaluate the association of AoAC with brachial-ankle pulse wave velocity (baPWV) and cardiomegaly in patients who have undergoing hemodialysis (HD).We retrospectively determined AoAC and cardiothoracic ratio (CTR) by chest x-ray in 220 HD patients who underwent the measurement of baPWV. The values of baPWV were measured by an ankle-brachial index-form device. Multiple stepwise logistic regression analysis was used to identify the factors associated with AoAC score >4.Compared patients with AoAC score ≦4, patients with AoAC score >4 had older age, higher prevalence of diabetes and cerebrovascular disease, lower diastolic blood pressure, higher baPWV, higher CTR, higher prevalence of CTR ≧50%, lower total cholesterol, and lower creatinine level. After the multivariate stepwise logistic analysis, old age, cerebrovascular disease, high baPWV (per 100 cm/s, odds ratio [OR] 1.065, 95% confidence interval [CI] 1.003-1.129, P = 0.038), CTR (per 1%, OR 1.116, 95% CI 1.046-1.191, P = 0.001), and low total cholesterol level were independently associated with AoAC score >4.Our study demonstrated AoAC severity was associated with high baPWV and high CTR in patients with HD. Therefore, we suggest that evaluating AoAC on plain chest radiography may be a simple and inexpensive method for detecting arterial stiffness in HD patients.

  13. Identifying Coronary Artery Disease in Asymptomatic Middle-Aged Sportsmen: The Additional Value of Pulse Wave Velocity.

    Directory of Open Access Journals (Sweden)

    Thijs L Braber

    Full Text Available Cardiovascular screening may benefit middle-aged sportsmen, as coronary artery disease (CAD is the main cause of exercise-related sudden cardiac death. Arterial stiffness, as measured by pulse wave velocity (PWV, may help identify sportsmen with subclinical CAD. We examined the additional value of PWV measurements to traditional CAD risk factors for identifying CAD.From the Measuring Athlete's Risk of Cardiovascular events (MARC cohort of asymptomatic, middle-aged sportsmen who underwent low-dose Cardiac CT (CCT after routine sports medical examination (SME, 193 consecutive sportsmen (aged 55 ± 6.6 years were included with additional PWV measurements before CCT. Sensitivity, specificity and predictive values of PWV values (>8.3 and >7.5 m/s assessed by Arteriograph were used to identify CAD (coronary artery calcium scoring ≥ 100 Agatston Units or coronary CT angiography luminal stenosis ≥ 50% and to assess the additional diagnostic value of PWV to established cardiovascular risk factors.Forty-seven sportsmen (24% had CAD on CCT. They were older (58.9 vs. 53.8 years, p8.3m/s respectively >7.5 m/s sensitivity to detect CAD on CT was 43% and 74%, specificity 69% and 45%, positive predictive value 31% and 30%, and negative predictive value 79% and 84%. Adding PWV to traditional risk factor models did not change the area under the curve (from 0.78 (95% CI = 0.709-0.848 to AUC 0.78 (95% CI 0.710-0.848, p = 0.99 for prediction of CAD on CCT.Limited additional value was found for PWV on top of established risk factors to identify CAD. PWV might still have a role to identify CAD in middle-aged sportsmen if risk factors such as cholesterol are unknown.

  14. REFERENCE VALUES OF AORTIC PULSE WAVE VELOCITY IN A LARGE HEALTHY POPULATION AGED BETWEEN 3 AND18 YEARS

    Directory of Open Access Journals (Sweden)

    Erzsebet Valeria Hidvegi

    2013-01-01

    Full Text Available Objective: The measurement of aortic pulse wave velocity (PWVao is an accepted marker in stratifying individual cardiovascular risk in adults. There is an increasing volume of evidence concerning impaired vascular function in different diseases in paediatric populations, but, unfortunately, only a few studies are available on the measurement of normal PWVao values in children. The aim of our study was to determine the reference values of PWVao in a large healthy population using a newly developed technique. Methods: Three thousand, three hundred and seventyfour healthy individuals (1802 boys aged 3–18 years were examined by an invasively validated, occlusive, oscillometric device. Results: The mean PWVao values increased from 5.5_0.3 to 6.5_0.3 m/s (P<0.05 in boys and from 5.6_0.3 to 6.4_0.3 m/s (P<0.05 in girls. The increase, however, was not constant, and the values exhibited a flat period between the ages of 3 and 8 years in both sexes. The first pronounced increase occurred at the age of 12.1 years in boys and 10.4 years in girls. Moreover, between the ages of 3 and 8 years, the brachial SBP and mean blood pressures increased continuously and gradually, whereas the PWVao remained unchanged. By contrast, beyond the age of 9 years, blood pressure and aortic stiffness trends basically moved together. Conclusion: Our study provides the largest database to date concerning arterial stiffness in healthy children and adolescents between the ages of 3 and 18 years, and the technology adopted proved easy to use in large paediatric populations, even at a very young age.  

  15. Liver shear-wave velocity and serum fibrosis markers to diagnose hepatic fibrosis in patients with chronic viral hepatitis B

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jian Xue; Ji, Yong Hao; Zhao Junzhi; Zhang, Yao Ren; Dun, Guo Liang; Ning, Bo [Dept. of Ultrasonography, Baoji Central Hospital, Baoji (China); Ai, Hong [Dept. of Ultrasonography, The First Affiliated Hospital of Medical College, Xi' an Jiaotong University, Xi' an (China)

    2016-06-15

    To compare several noninvasive indices of fibrosis in chronic viral hepatitis B, including liver shear-wave velocity (SWV), hyaluronic acid (HA), collagen type IV (CIV), procollagen type III (PCIII), and laminin (LN). Acoustic radiation force impulse (ARFI) was performed in 157 patients with chronic viral hepatitis B and in 30 healthy volunteers to measure hepatic SWV (m/s) in a prospective study. Serum markers were acquired on the morning of the same day of the ARFI evaluation. Receiver operating characteristic (ROC) analysis was performed to evaluate and compare the accuracies of SWV and serum markers using METAVIR scoring from liver biopsy as a reference standard. The most accurate test for diagnosing fibrosis F ≥ 1 was SWV with the area under the ROC curve (AUC) of 0.913, followed by LN (0.744), HA (0.701), CIV (0.690), and PCIII (0.524). The best test for diagnosing F ≥ 2 was SWV (AUC of 0.851), followed by CIV (0.671), HA (0.668), LN (0.562), and PCIII (0.550). The best test for diagnosing F ≥ 3 was SWV (0.854), followed by CIV (0.693), HA (0.675), PCIII (0.591), and LN (0.548). The best test for diagnosing F = 4 was SWV (0.965), followed by CIV (0.804), PCIII (0.752), HA (0.744), and LN (0.662). SWV combined with HA and CIV did not improve diagnostic accuracy (AUC = 0.931 for F ≥ 1, 0.863 for F ≥ 2, 0.855 for F ≥ 3, 0.960 for F = 4). The performance of SWV in diagnosing liver fibrosis is superior to that of serum markers. However, the combination of SWV, HA, and CIV does not increase the accuracy of diagnosing liver fibrosis and cirrhosis.

  16. Shear wave velocity measurements using acoustic radiation force impulse in young children with normal kidneys versus hydronephrotic kidneys

    Energy Technology Data Exchange (ETDEWEB)

    Shon, Beom Seok; Kim, Myung Joon; Han, Sang Won; Im, Young Jae; Lee, Mi Jung [Severance Children' s Hospital, Yonsei University College of Medicine, Seoul (Korea, Republic of)

    2014-04-15

    To measure shear wave velocities (SWVs) by acoustic radiation force impulse (ARFI) ultrasound elastography in normal kidneys and in hydronephrotic kidneys in young children and to compare SWVs between the hydronephrosis grades. This study was approved by an institutional review board, and informed consent was obtained from the parents of all the children included. Children under the age of 24 months were prospectively enrolled. Hydronephrosis grade was evaluated on ultrasonography, and three valid ARFI measurements were attempted using a high-frequency transducer for both kidneys. Hydronephrosis was graded from 0 to 4, and high-grade hydronephrosis was defined as grades 3 and 4. Fifty-one children underwent ARFI measurements, and three valid measurements for both kidneys were obtained in 96% (49/51) of the patients. Nineteen children (38.8%) had no hydronephrosis. Twenty-three children (46.9%) had unilateral hydronephrosis, and seven children (14.3%) had bilateral hydronephrosis. Seven children had ureteropelvic junction obstruction (UPJO). Median SWVs in kidneys with high-grade hydronephrosis (2.02 m/sec) were higher than those in normal kidneys (1.75 m/sec; P=0.027). However, the presence of UPJO did not influence the median SWVs in hydronephrotic kidneys (P=0.362). Obtaining ARFI measurements of the kidney is feasible in young children with median SWVs of 1.75 m/sec in normal kidneys. Median SWVs increased in high-grade hydronephrotic kidneys but were not different between hydronephrotic kidneys with and without UPJO.

  17. Nuclear velocity perturbation theory for vibrational circular dichroism: An approach based on the exact factorization of the electron-nuclear wave function

    CERN Document Server

    Scherrer, Arne; Sebastiani, Daniel; Gross, E K U; Vuilleumier, Rodolphe

    2015-01-01

    The nuclear velocity perturbation current-density theory (NVPT) for vibrational circular dichroism (VCD) is derived from the exact factorization of the electron-nuclear wave function. This new formalism offers an exact starting point to include correction terms to the Born-Oppenheimer (BO) form of the molecular wave function, similarly to the complete-adiabatic approximation. The corrections depend on a small parameter that, in a classical treatment of the nuclei, is identified as the nuclear velocity. Apart from proposing a rigorous basis for the NVPT, we show that the rotational strength, related to the intensity of the VCD signal, contain a new contribution beyond-BO that can be evaluated with the NVPT and that only arises when the exact factorization approach is employed. Numerical results are presented for chiral and non-chiral systems to test the validity of the approach.

  18. Analysis of the effect of the fluid-structure interface on elastic wave velocity in cornea-like structures by OCE and FEM

    Science.gov (United States)

    Han, Zhaolong; Li, Jiasong; Singh, Manmohan; Vantipalli, Srilatha; Aglyamov, Salavat R.; Wu, Chen; Liu, Chih-hao; Raghunathan, Raksha; Twa, Michael D.; Larin, Kirill V.

    2016-03-01

    Air-pulse optical coherence elastography (OCE) is a promising technique for quantifying biomechanical properties of the cornea. This technique typically involves imaging and analysis of the propagation of the air-pulse induced elastic waves to reconstruct corneal biomechanical properties using an analytical model. However, the effect of the fluid-structure interface (FSI) at the corneal posterior surface on the elastic wave velocity is not accounted for in many models. In this study, we examined the effect of the FSI with OCE experiments on contact lenses with and without fluid in the posterior gap. Finite element models (FEM), also with and without the FSI, were constructed to simulate the elastic wave propagation based on the OCE measurements. The FEM and OCE results were in good agreement demonstrating the feasibility of the method. To further investigate the effect of the FSI, OCE experiments and subsequent FEM simulations were conducted on in situ rabbit corneas before and after rose bengal/green light corneal collagen cross-linking (RGX). Both the OCE experiments and the FE simulations demonstrated that the FSI significantly reduced the group velocity of the elastic wave, and thus, should be considered when determining corneal biomechanical properties from an appropriate mechanical model. By matching the FEM-calculated velocity to the OCE-measured velocity, the corneal elasticity was quantified. The Young’s modulus of the rabbit cornea before RGX was E  =  65  ±  10 kPa at a controlled intraocular pressure (IOP) of 15 mmHg. After RGX, the Young’s modulus increased to E  =  102  ±  7 kPa at the same IOP.

  19. MHD dissipative flow and heat transfer of Casson fluids due to metachronal wave propulsion of beating cilia with thermal and velocity slip effects under an oblique magnetic field

    Science.gov (United States)

    Akbar, Noreen Sher; Tripathi, D.; Bég, O. Anwar; Khan, Z. H.

    2016-11-01

    A theoretical investigation of magnetohydrodynamic (MHD) flow and heat transfer of electrically-conducting viscoplastic fluids through a channel is conducted. The robust Casson model is implemented to simulate viscoplastic behavior of fluids. The external magnetic field is oblique to the fluid flow direction. Viscous dissipation effects are included. The flow is controlled by the metachronal wave propagation generated by cilia beating on the inner walls of the channel. The mathematical formulation is based on deformation in longitudinal and transverse velocity components induced by the ciliary beating phenomenon with cilia assumed to follow elliptic trajectories. The model also features velocity and thermal slip boundary conditions. Closed-form solutions to the non-dimensional boundary value problem are obtained under physiological limitations of low Reynolds number and large wavelength. The influence of key hydrodynamic and thermo-physical parameters i.e. Hartmann (magnetic) number, Casson (viscoplastic) fluid parameter, thermal slip parameter and velocity slip parameter on flow characteristics are investigated. A comparative study is also made with Newtonian fluids (corresponding to massive values of plastic viscosity). Stream lines are plotted to visualize trapping phenomenon. The computations reveal that velocity increases with increasing the magnitude of Hartmann number near the channel walls whereas in the core flow region (center of the channel) significant deceleration is observed. Temperature is elevated with greater Casson parameter, Hartmann number, velocity slip, eccentricity parameter, thermal slip and also Brinkmann (dissipation) number. Furthermore greater Casson parameter is found to elevate the quantity and size of the trapped bolus. In the pumping region, the pressure rise is reduced with greater Hartmann number, velocity slip, and wave number whereas it is enhanced with greater cilia length.

  20. Self-action of propagating and standing Lamb waves in the plates exhibiting hysteretic nonlinearity: Nonlinear zero-group velocity modes.

    Science.gov (United States)

    Gusev, Vitalyi E; Lomonosov, Alexey M; Ni, Chenyin; Shen, Zhonghua

    2017-09-01

    An analytical theory accounting for the influence of hysteretic nonlinearity of micro-inhomogeneous plate material on the Lamb waves near the S 1 zero group velocity point is developed. The theory predicts that the main effect of the hysteretic quadratic nonlinearity consists in the modification of the frequency and the induced absorption of the Lamb modes. The effects of the nonlinear self-action in the propagating and standing Lamb waves are expected to be, respectively, nearly twice and three times stronger than those in the plane propagating acoustic waves. The theory is restricted to the simplest hysteretic nonlinearity, which is influencing only one of the Lamé moduli of the materials. However, possible extensions of the theory to the cases of more general hysteretic nonlinearities are discussed as well as the perspectives of its experimental testing. Applications include nondestructive evaluation of micro-inhomogeneous and cracked plates. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Fast retrospectively triggered local pulse-wave velocity measurements in mice with CMR-microscopy using a radial trajectory.

    Science.gov (United States)

    Winter, Patrick; Kampf, Thomas; Helluy, Xavier; Gutjahr, Fabian T; Meyer, Cord B; Rommel, Null; Bauer, Wolfgang R; Jakob, Peter M; Herold, Volker

    2013-10-01

    The aortic pulse-wave velocity (PWV) is an important indicator of cardiovascular risk. In recent studies MRI methods have been developed to measure this parameter noninvasively in mice. Present techniques require additional hardware for cardiac and respiratory gating. In this work a robust self-gated measurement of the local PWV in mice without the need of triggering probes is proposed. The local PWV of 6-months-old wild-type C57BL/6J mice (n=6) was measured in the abdominal aorta with a retrospectively triggered radial Phase Contrast (PC) MR sequence using the flow-area (QA) method. A navigator signal was extracted from the CMR data of highly asymmetric radial projections with short repetition time (TR=3 ms) and post-processed with high-pass and low-pass filters for retrospective cardiac and respiratory gating. The self-gating signal was used for a reconstruction of high-resolution Cine frames of the aortic motion. To assess the local PWV the volume flow Q and the cross-sectional area A of the aorta were determined. The results were compared with the values measured with a triggered Cartesian and an undersampled triggered radial PC-Cine sequence. In all examined animals a self-gating signal could be extracted and used for retrospective breath-gating and PC-Cine reconstruction. With the non-triggered measurement PWV values of 2.3±0.2 m/s were determined. These values are in agreement with those measured with the triggered Cartesian (2.4±0.2 m/s) and the triggered radial (2.3±0.2 m/s) measurement. Due to the strong robustness of the radial trajectory against undersampling an acceleration of more than two relative to the prospectively triggered Cartesian sampling could be achieved with the retrospective method. With the radial flow-encoding sequence the extraction of a self-gating signal is feasible. The retrospective method enables a robust and fast measurement of the local PWV without the need of additional trigger hardware.

  2. Differential effects of vitamin D receptor activators on aortic calcification and pulse wave velocity in uraemic rats.

    Science.gov (United States)

    Noonan, William; Koch, Kristin; Nakane, Masaki; Ma, Junli; Dixon, Doug; Bolin, Antoinette; Reinhart, Glenn

    2008-12-01

    Vascular calcification is associated with an increase in cardiovascular mortality in stage 5 chronic kidney disease. To determine if vitamin D receptor activators (VDRAs) have differential effects in the pathogenesis of aortic calcification, we assessed the effects of paricalcitol and doxercalciferol in vivo using 5/6 nephrectomized (NX) rats. To quantify the functional consequences of vascular calcification, pulse wave velocity (PWV), an aortic compliance index, was measured. NX rats were fed a diet containing 0.9% phosphorous and 0.6% calcium 4 weeks prior to and throughout the study. On Day 0, rats received vehicle or VDRA (0.083, 0.167 and 0.333 microg/kg, i.p.) three times per week for 6 weeks. At Day 0 and Weeks 2 and 6, blood was drawn and PWV was measured by Doppler ultrasound. VDRAs (0.167 and 0.333 microg/kg) consistently lowered PTH at Weeks 2 and 6. All doses of paricalcitol increased serum calcium at Week 6 but not at Week 2, while the two higher doses of doxercalciferol increased serum calcium at both Weeks 2 and 6. Treatment with paricalcitol (0.333 microg/kg) increased serum phosphorus at Weeks 2 and 6; these changes were not different from those observed in 5/6 NX rats. All doses of doxercalciferol increased serum phosphorus at Week 6. Paricalcitol had no effect on Ca x P; however, the two highest doses of doxercalciferol increased Ca x P at Weeks 2 and 6 above that observed in the 5/6 NX vehicle-treated group. There were no differences in aortic calcium and phosphorus contents at the end of 6 weeks among SHAM-, 5/6 NX- and paricalcitol-treated rats. However, treatment with the two higher doses of doxercalciferol caused a significant elevation in aortic calcium and phosphorus contents. Measurements of PWV demonstrated differential effects of VDRAs on vascular compliance. Paricalcitol produced no effects on PWV, while the two highest doses of doxercalciferol increased PWV at Week 6. In uraemic rats with established secondary hyperparathyroidism, we

  3. Percentiles for central blood pressure and pulse wave velocity in children and adolescents recorded with an oscillometric device.

    Science.gov (United States)

    Elmenhorst, Julia; Hulpke-Wette, Martin; Barta, Christiane; Dalla Pozza, Robert; Springer, Stephan; Oberhoffer, Renate

    2015-01-01

    In adults with arterial hypertension, measuring arterial stiffness by pulse wave velocity (PWV) can determine the extent of cardiovascular subclinical organ damage. PWV has independent predictive value for cardiovascular events, but there are currently no recommendations for measuring PWV in children. In addition, central systolic blood pressure (cSBP) strongly reflects vascular changes. The aim of this study was to establish percentiles for cSBP and PWV in children and adolescents to evaluate and classify altered vascular function in youths. We measured PWV and cSBP with an oscillometric device with inbuilt ARCSolver-algorithm (estimated by using the brachial waveform) and calculated smoothed reference percentiles for 1445 children and young adults (49.5% female; 13.41 ± 2.80 years, range 8-22 years; PWV 4.67 ± 0.34 m/s; cSBP 100.7 ± 8.9 mmHg) using the LMS-method based on age and height. PWV and cSBP increased with age and height, but slightly differently for girls and boys, possibly reflecting different growth patterns. Between 8 and 21 years, PWV increased from 4.29 ± 0.32 to 4.98 ± 0.33 m/s in girls and from 4.27 ± 0.18 to 5.22 ± 0.46 m/s in boys. While girls showed a minor increase in cSBP (91.2 ± 7.5 to 109.1 ± 8.6 mmHg), the cSBP in boys ranged from 90.0 ± 5.8 to 110.5 ± 9.6 mmHg with a more pronounced increase between 14 and 17 years. These percentiles for PWV and cSBP can help define arterial stiffness in youths and contribute to risk stratification for cardiovascular disease. For example, in children with prehypertension or isolated systolic hypertension, PWV and cSBP can provide additional information about the function of the vascular system, thereby strengthening intervention strategies. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  4. Seismic Wave Velocity Decrease near the Fault Zone Associated with the 2007 Noto Peninsula Earthquake, Japan, Detected by Using Ambient Noise

    Science.gov (United States)

    Ohmi, S.

    2012-12-01

    We preliminarily reported the temporal change of the crustal structure associated with the 2007 Noto peninsula earthquake (Mw6.6), Japan, using passive image interferometry (Ohmi et al., 2008, Earth Planets Space). In Ohmi et al. (2008), they computed the autocorrelation function (ACF) of band-pass filtered (1.5 Hz - 10 Hz or 2.0 Hz - 10 Hz) ambient seismic noise recorded with each short-period seismometer at several seismic stations. In some stations, comparison of each 1-day ACF shows temporal evolutions of the ACF, which are interpreted as the change of seismic velocity structure in the volume considered. Sudden changes of ACF are detected associated with the occurrence of the main shock in one station which is located just above the source region. In this paper, we re-analyzed the data around the source region to delineate the temporal change of the crustal structure more quantitatively. First, we calculated the seismic wave velocity change associated with the main shock near the seismic stations. We applied the 'stretch and compression method' to the newly obtained ACF's. Lag time range from 3s to 10s of the ACF's are analyzed, which sample the information of the upper crust portion if we assume the seismic wave in the ACF's is S-wave. At the seismic stations whose epicentral distance are around 20 km - 40 km, velocity decrease of about 1 %, which is the maximum case, is observed. We also calculated the velocity change using the lag time range from 2s to 7s, that generally exhibit larger velocity changes, which is 2 % at the maximum case, compared to those obtained from 3s to 10s range. It is probably because the velocity changes are localized in the shallower portion. On the other hand, lag time range from 2s to 7s of the ACF's at the seismic station just above the source fault exhibits the velocity decrease of more than 6 % and that from 2s to 5s range shows velocity decrease less than 6%, which indicates velocity change is localized in the deep portion in

  5. Normal values of liver shear wave velocity in healthy children assessed by acoustic radiation force impulse imaging using a convex probe and a linear probe.

    Science.gov (United States)

    Fontanilla, Teresa; Cañas, Teresa; Macia, Araceli; Alfageme, Marta; Gutierrez Junquera, Carolina; Malalana, Ana; Luz Cilleruelo, Maria; Roman, Enriqueta; Miralles, Maria

    2014-03-01

    Acoustic radiation force impulse (ARFI) is an image-guided ultrasound elastography method that allows quantification of liver stiffness by measurement of shear wave velocity. One purpose of the work described in this article was to determine the normal liver stiffness values of healthy children using ARFI with two different probes, 4 C1 and 9 L4. Another purpose was to evaluate the effects of site of measurement, age, gender and body mass index on liver stiffness values. This prospective study included 60 healthy children (newborn to 14 y) divided into four age groups. One thousand two hundred ARFI measurements were performed, that is, 20 measurements per patient (5 measurements in each lobe, with each probe). Means, standard deviations (SD) and confidence intervals for velocity were calculated for each hepatic lobe and each probe in each age group and for the whole group. Mean shear wave velocity measured in the right lobe was 1.19 ± 0.04 m/s (SD = 0.13) with the 4 C1 transducer and 1.15 ± 0.04 m/s (SD = 0.15) with the 9 L4 transducer. Age had a small effect on shear wave measurements. Body mass index and sex had no significant effects on ARFI values, whereas site of measurement had a significant effect, with lower ARFI values in the right hepatic lobe. ARFI is a non-invasive technique that is feasible to perform in children with both the 4 C1 and 9 L4 probes. The aforementioned velocity values obtained in the right lobe may be used as reference values for normal liver stiffness in children. Published by Elsevier Inc.

  6. The interaction of a circularly orbiting electromagnetic harmonic wave with an electron having a constant time independent drift velocity

    NARCIS (Netherlands)

    Rashid, M.

    2011-01-01

    A circularly orbiting electromagnetic harmonic wave may appear when a 1S electron encounters a decelerating stopping positively charged hole inside a semiconductor. The circularly orbiting electromagnetic harmonic wave can have an interaction with a conducting electron which has a constant time

  7. Brachial-ankle pulse wave velocity and the cardio-ankle vascular index as a predictor of cardiovascular outcomes in patients on regular hemodialysis.

    Science.gov (United States)

    Kato, Akihiko; Takita, Takako; Furuhashi, Mitsuyoshi; Maruyama, Yukitaka; Miyajima, Hiroaki; Kumagai, Hiromichi

    2012-06-01

    Brachial-ankle pulse wave velocity (baPWV) and the cardio-ankle vascular index (CAVI) are both used to evaluate arterial stiffness. The aim of the present study is to determine whether baPWV or CAVI is superior as a marker of arterial stiffness in hemodialysis (HD) patients. Of 194 patients, 59 patients had been excluded from the study due to advanced age over 76 years old (n = 29), or abnormal ankle-brachial pressure index (ABI) (<0.90 or ≥1.30) (n = 30). We then followed the 135 patients (age: 60 ± 11 years, time on HD: 110 ± 93 months) for the 63 ± 4 (55-70) months. Thirty-two (23.7%) patients had expired, 22 of them of cardiovascular (CV) causes. There were 37 fatal and non-fatal CV events. Kaplan-Meier analysis revealed that the patients with the highest tertile of baPWV (≥16.6 m/s) had a significantly lower survival rate (P < 0.01) when compared with the second (13.4 ≤ baPWV < 16.6 m/s) and the lowest tertiles (<13.4 m/s). Cox hazards analysis after adjustment for comorbid risk factors revealed that the top tertile of baPWV was a determinant of CV death (hazards ratio [HR]: 16.9 [1.1-251.8], P < 0.05) In contrast, CAVI did not associate with CV mortality or events. These findings suggest that baPWV is superior to CAVI as a predictor of CV outcomes in patients on regular HD. © 2012 The Authors. Therapeutic Apheresis and Dialysis © 2012 International Society for Apheresis.

  8. Arterial stiffness in patients after Kawasaki disease without coronary artery involvement: Assessment by performing brachial ankle pulse wave velocity and cardio-ankle vascular index.

    Science.gov (United States)

    Nakagawa, Ryo; Kuwata, Seiko; Kurishima, Clara; Saiki, Hirofumi; Iwamoto, Yoichi; Sugimoto, Masaya; Ishido, Hirotaka; Masutani, Satoshi; Senzaki, Hideaki

    2015-08-01

    It remains unclear whether systemic arterial beds other than the coronary arteries are truly healthy in patients without coronary artery lesions (CAL) after Kawasaki disease (KD). We tested the hypothesis that patients with KD without echocardiographic evidence of CAL during the acute phase of the disease have abnormal mechanical properties in systemic arteries later. We studied 201 consecutive patients with KD (age 2-23 years, mean 10±4 years; 109 male, 92 female) without CAL during the acute phase. Data were compared with those in 129 control subjects (age 2-25 years, mean 10±4 years; 73 male, 56 female; control group). We examined arterial stiffness by using the brachial-ankle pulse wave velocity (baPWV) and the cardio-ankle vascular index (CAVI). The baPWV in the KD group was significantly higher than that in the control group (913±121cm/s vs. 886±135cm/s, p=0.04). In contrast, there was no significant difference in CAVI (4.0±1.0 vs. 4.2±1.0, p=0.9) between the two groups. Multivariate analysis indicated a highly significant difference in baPWV (higher baPWV in patients with KD than in controls, p=0.004), after controlling for age, gender, body height and weight, and systolic and diastolic blood pressure, but no difference in CAVI between the groups. Years after KD occurs in patients without apparent CAL during the acute phase, there is a small but significant change in systemic arterial properties, characterized by increased wall stiffness. The clinical importance of these findings must be clarified by performing long-term follow-up studies. Copyright © 2014 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.

  9. Ambulatory Pulse Wave Velocity Is a Stronger Predictor of Cardiovascular Events and All-Cause Mortality Than Office and Ambulatory Blood Pressure in Hemodialysis Patients.

    Science.gov (United States)

    Sarafidis, Pantelis A; Loutradis, Charalampos; Karpetas, Antonios; Tzanis, Georgios; Piperidou, Alexia; Koutroumpas, Georgios; Raptis, Vasilios; Syrgkanis, Christos; Liakopoulos, Vasilios; Efstratiadis, Georgios; London, Gérard; Zoccali, Carmine

    2017-07-01

    Arterial stiffness and augmentation of aortic blood pressure (BP) measured in office are known cardiovascular risk factors in hemodialysis patients. This study examines the prognostic significance of ambulatory brachial BP, central BP, pulse wave velocity (PWV), and heart rate-adjusted augmentation index [AIx(75)] in this population. A total of 170 hemodialysis patients underwent 48-hour ambulatory monitoring with Mobil-O-Graph-NG during a standard interdialytic interval and followed-up for 28.1±11.2 months. The primary end point was a combination of all-cause death, nonfatal myocardial infarction, and nonfatal stroke. Secondary end points included: (1) all-cause mortality; (2) cardiovascular mortality; and (3) a combination of cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, resuscitation after cardiac arrest, coronary revascularization, or hospitalization for heart failure. During follow-up, 37(21.8%) patients died and 46(27.1%) had cardiovascular events. Cumulative freedom from primary end point was similar for quartiles of predialysis-systolic BP (SBP), 48-hour peripheral-SBP, and central-SBP, but was progressively longer for increasing quartiles for 48-hour peripheral-diastolic BP and central-diastolic BP and shorter for increasing quartiles of 48-hour central pulse pressure (83.7%, 71.4%, 69.0%, 62.8% [log-rank P=0.024]), PWV (93.0%, 81.0%, 57.1%, 55.8% [log-rank Pambulatory PWV and AIx(75). In multivariate analysis, 48-hour PWV was the only vascular parameter independently associated with the primary end point (hazard ratios, 1.579; 95% confidence intervals, 1.187-2.102). Ambulatory PWV, AIx(75), and central pulse pressure are associated with increased risk of cardiovascular events and mortality, whereas office and ambulatory SBP are not. These findings further support that arterial stiffness is the prominent cardiovascular risk factor in hemodialysis. © 2017 American Heart Association, Inc.

  10. EEG slow waves in traumatic brain injury: Convergent findings in mouse and man

    Directory of Open Access Journals (Sweden)

    Mo H. Modarres

    2017-01-01

    Conclusion and implications: Taken together, our data from both mouse and human studies suggest that EEG slow wave quantity and the global coherence index of slow waves may represent a sensitive marker for the diagnosis and prognosis of mTBI and post-concussive symptoms.

  11. Use of Refraction Microtremor (ReMi) technique for the determination of 1-D shear wave velocity in a landslide area

    Science.gov (United States)

    Coccia, S.; Del Gaudio, V.; Venisti, N.; Wasowski, J.

    2009-04-01

    In the context of an ongoing study on seismic response of landslide-prone hill-slopes in Central Italy (area of Caramanico Terme), we tested the applicability of the Refraction Microtremor (ReMi) analysis technique (Louie, 2001) to obtain geometrical and physical parameters needed for numerical modelling. In particular, we used this technique to determine one-dimensional shear-wave velocity profiles (Vs) at sites located on and close to a recent landslide that mobilized 30-40 m thick Quaternary colluvium overlying Pliocene mudstones. The use of this technique in unstable slope areas presents difficulties related to rough topography and lateral lithological heterogeneities, which prevent the extension of geophone array up to the minimum lengths (100 - 200 m) commonly adopted in standard applications. Moreover, sites distant from anthropic sources of microtremors can have unfavourable noise conditions in comparison with other well established cases of application. To check the stability of the ReMi data in these operative conditions and the confidence level of the results, three ReMi campaigns were conducted at different times using different acquisition parameters (seismograph channel number, geophone frequency and spacing). We also tested simultaneous noise recording along orthogonal arrays to investigate a possible presence of directional variations of soil properties. The Rayleigh wave velocity dispersion data derived from picking carried out on p (slowness)-f (frequency) matrix showed the presence in noise recordings of different Rayleigh wave vibration modes (fundamental and first two higher modes), which prevail at different frequency intervals. This indicates that it is essential to correctly identify the different vibration modes to avoid erroneous data interpretation (e.g. fictitious identification of velocity decrease with depth). An analysis of the influence of changing environmental conditions and of different acquisition parameters was conducted through

  12. Exploiting the leaky-wave properties of transmission-line metamaterials for single-microphone direction finding.

    Science.gov (United States)

    Esfahlani, Hussein; Karkar, Sami; Lissek, Hervé; Mosig, Juan R

    2016-06-01

    A transmission-line acoustic metamaterial is an engineered, periodic arrangement of relatively small unit-cells, the acoustic properties of which can be manipulated to achieve anomalous physical behaviours. These exotic properties open the door to practical applications, such as an acoustic leaky-wave antenna, through the implementation of radiating channels along the metamaterial. In the transmitting mode, such a leaky-wave antenna is capable of steering sound waves in frequency-dependent directions. Used in reverse, the antenna presents a well defined direction-frequency behaviour. In this paper, an acoustic leaky-wave structure is presented in the receiving mode. It is shown that it behaves as a sound source direction-finding device using only one sensor. After a general introduction of the acoustic leaky-wave antenna concept, its radiation pattern and radiation efficiency are expressed in closed form. Then, numerical simulations and experimental assessments of the proposed transmission-line based structure, implementing only one sensor at one termination, are presented. It is shown that such a structure is capable of finding the direction of an incoming sound wave, from backward to forward, based on received sound power spectra. This introduces the concept of sound source localization without resorting to beam-steering techniques based on multiple sensors.

  13. EEG slow waves in traumatic brain injury: Convergent findings in mouse and man.

    Science.gov (United States)

    Modarres, Mo; Kuzma, Nicholas N; Kretzmer, Tracy; Pack, Allan I; Lim, Miranda M

    2016-07-01

    Evidence from previous studies suggests that greater sleep pressure, in the form of EEG-based slow waves, accumulates in specific brain regions that are more active during prior waking experience. We sought to quantify the number and coherence of EEG slow waves in subjects with mild traumatic brain injury (mTBI). We developed a method to automatically detect individual slow waves in each EEG channel, and validated this method using simulated EEG data. We then used this method to quantify EEG-based slow waves during sleep and wake states in both mouse and human subjects with mTBI. A modified coherence index that accounts for information from multiple channels was calculated as a measure of slow wave synchrony. Brain-injured mice showed significantly higher theta:alpha amplitude ratios and significantly more slow waves during spontaneous wakefulness and during prolonged sleep deprivation, compared to sham-injured control mice. Human subjects with mTBI showed significantly higher theta:beta amplitude ratios and significantly more EEG slow waves while awake compared to age-matched control subjects. We then quantified the global coherence index of slow waves across several EEG channels in human subjects. Individuals with mTBI showed significantly less EEG global coherence compared to control subjects while awake, but not during sleep. EEG global coherence was significantly correlated with severity of post-concussive symptoms (as assessed by the Neurobehavioral Symptom Inventory scale). Taken together, our data from both mouse and human studies suggest that EEG slow wave quantity and the global coherence index of slow waves may represent a sensitive marker for the diagnosis and prognosis of mTBI and post-concussive symptoms.

  14. Multi-Sensor Core Logger (MSCL) P-wave velocity, gamma-ray density, and magnetic susceptibility whole-core logs of sediment cores collected in 2009 offshore from Palos Verdes, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of the data release includes Multi-Sensor Core Logger (MSCL) P-wave velocity, gamma-ray density, and magnetic susceptibility whole-core logs of sediment...

  15. Findings

    Science.gov (United States)

    ... topic Print Magazine Subscribe & Order a Free Copy Classroom Poster Order a Free Poster Findings showcases diverse ... Genetics, Evolution, Stem Cells, Model Organisms, Diseases, Sleep Research Pharmacology Biochemical Actions of Drugs in the Body, Pharmacogenomics, Drug Design, ...

  16. Difference of horizontal-to-vertical spectral ratios of observed earthquakes and microtremors and its application to S-wave velocity inversion based on the diffuse field concept

    Science.gov (United States)

    Kawase, Hiroshi; Mori, Yuta; Nagashima, Fumiaki

    2018-01-01

    We have been discussing the validity of using the horizontal-to-vertical spectral ratios (HVRs) as a substitute for S-wave amplifications after Nakamura first proposed the idea in 1989. So far a formula for HVRs had not been derived that fully utilized their physical characteristics until a recent proposal based on the diffuse field concept. There is another source of confusion that comes from the mixed use of HVRs from earthquake and microtremors, although their wave fields are hardly the same. In this study, we compared HVRs from observed microtremors (MHVR) and those from observed earthquake motions (EHVR) at one hundred K-NET and KiK-net stations. We found that MHVR and EHVR share similarities, especially until their first peak frequency, but have significant differences in the higher frequency range. This is because microtremors mainly consist of surface waves so that peaks associated with higher modes would not be prominent, while seismic motions mainly consist of upwardly propagating plain body waves so that higher mode resonances can be seen in high frequency. We defined here the spectral amplitude ratio between them as EMR and calculated their average. We categorize all the sites into five bins by their fundamental peak frequencies in MHVR. Once we obtained EMRs for five categories, we back-calculated EHVRs from MHVRs, which we call pseudo-EHVRs (pEHVR). We found that pEHVR is much closer to EHVR than MHVR. Then we use our inversion code to invert the one-dimensional S-wave velocity structures from EHVRs based on the diffuse field concept. We also applied the same code to pEHVRs and MHVRs for comparison. We found that pEHVRs yield velocity structures much closer to those by EHVRs than those by MHVRs. This is natural since what we have done up to here is circular except for the average operation in EMRs. Finally, we showed independent examples of data not used in the EMR calculation, where better ground structures were successfully identified from p

  17. Comparison of shear wave velocity measurements assessed with two different ultrasound systems in an ex-vivo tendon strain phantom.

    Science.gov (United States)

    Rosskopf, Andrea B; Bachmann, Elias; Snedeker, Jess G; Pfirrmann, Christian W A; Buck, Florian M

    2016-11-01

    The purpose of this study is to compare the reliability of SW velocity measurements of two different ultrasound systems and their correlation with the tangent traction modulus in a non-static tendon strain model. A bovine tendon was fixed in a custom-made stretching device. Force was applied increasing from 0 up to 18 Newton. During each strain state the tangent traction modulus was determined by the stretcher device, and SW velocity (m/s) measurements using a Siemens S3000 and a Supersonic Aixplorer US machine were done for shear modulus (kPa) calculation. A strong significant positive correlation was found between SW velocity assessed by the two ultrasound systems and the tangent traction modulus (r = 0.827-0.954, p < 0.001), yet all SW velocity-based calculations underestimated the reference tissue tangent modulus. Mean difference of SW velocities with the S3000 was 0.44 ± 0.3 m/s (p = 0.002) and with the Aixplorer 0.25 ± 0.3 m/s (p = 0.034). Mean difference of SW velocity between the two US-systems was 0.37 ± 0.3 m/s (p = 0.012). In conclusion, SW velocities are highly dependent on mechanical forces in the tendon tissue, but for controlled mechanical loads appear to yield reproducible and comparable measurements using different US systems.

  18. Cracked rocks with positive and negative Poisson's ratio: real-crack properties extracted from pressure dependence of elastic-wave velocities

    Science.gov (United States)

    Zaitsev, Vladimir Y.; Radostin, Andrey V.; Dyskin, Arcady V.; Pasternak, Elena

    2017-04-01

    We report results of analysis of literature data on P- and S-wave velocities of rocks subjected to variable hydrostatic pressure. Out of about 90 examined samples, in more than 40% of the samples the reconstructed Poisson's ratios are negative for lowest confining pressure with gradual transition to the conventional positive values at higher pressure. The portion of rocks exhibiting negative Poisson's ratio appeared to be unexpectedly high. To understand the mechanism of negative Poisson's ratio, pressure dependences of P- and S-wave velocities were analyzed using the effective medium model in which the reduction in the elastic moduli due to cracks is described in terms of compliances with respect to shear and normal loading that are imparted to the rock by the presence of cracks. This is in contrast to widely used descriptions of effective cracked medium based on a specific crack model (e.g., penny-shape crack) in which the ratio between normal and shear compliances of such a crack is strictly predetermined. The analysis of pressure-dependences of the elastic wave velocities makes it possible to reveal the ratio between pure normal and shear compliances (called q-ratio below) for real defects and quantify their integral content in the rock. The examination performed demonstrates that a significant portion (over 50%) of cracks exhibit q-ratio several times higher than that assumed for the conventional penny-shape cracks. This leads to faster reduction of the Poisson's ratio with increasing the crack concentration. Samples with negative Poisson's ratio are characterized by elevated q-ratio and simultaneously crack concentration. Our results clearly indicate that the traditional crack model is not adequate for a significant portion of rocks and that the interaction between the opposite crack faces leading to domination of the normal compliance and reduced shear displacement discontinuity can play an important role in the mechanical behavior of rocks.

  19. Constructing 3D isotropic and azimuthally anisotropic crustal models across USArray using Rayleigh wave phase velocity and ellipticity: inferring continental stress field

    Science.gov (United States)

    Lin, F. C.; Schmandt, B.; Tsai, V. C.

    2014-12-01

    The EarthScope USArray Transportable Array (TA) has provided a great opportunity for imaging the detailed lithospheric structure beneath the continental US. In this presentation, we will report our recent progress on constructing detailed 3D isotropic and anisotropic crustal models of the contiguous US using Rayleigh wave phase velocity and ellipticity measurements across TA. In particular, we will discuss our recent methodology development of extracting short period Rayleigh wave ellipticity, or Rayleigh-wave H/V (horizontal to vertical) amplitude ratios, using multicomponent noise cross-correlations. To retain the amplitude ratio information between vertical and horizontal components, for each station, we perform daily noise pre-processing (temporal normalization and spectrum whitening) simultaneously for all three components. For each station pair, amplitude measurements between cross-correlations of different components (radial-radial, radial-vertical, vertical-radial and vertical-vertical) are then used to determine the Rayleigh-wave H/V ratios at the two station locations. Measurements from all available station pairs are used to determine isotropic and directionally dependent Rayleigh-wave H/V ratios at each location between 8- and 24-second period. The isotropic H/V ratio maps, combined with previous longer period Rayleigh-wave H/V ratio maps from earthquakes and Rayleigh-wave phase velocity maps from both ambient noise and earthquakes, are used to invert for a new 3-D isotropic crustal and upper-mantle model in the western United States. The new model has an outstanding vertical resolution in the upper crust and tradeoffs between different parameters are mitigated. A clear 180-degree periodicity is observed in the directionally dependent H/V ratio measurements for many locations where upper crustal anisotropy is likely strong. Across the US, good correlation is observed between the inferred fast directions in the upper crust and documented maximum

  20. Comparison between multi-channel LDV and PWI for measurement of pulse wave velocity in distensible tubes: Towards a new diagnostic technique for detection of arteriosclerosis

    Science.gov (United States)

    Campo, Adriaan; Dudzik, Grzegorz; Apostolakis, Jason; Waz, Adam; Nauleau, Pierre; Abramski, Krzysztof; Dirckx, Joris; Konofagou, Elisa

    2017-10-01

    The aim of this work, was to compare pulse wave velocity (PWV) measurements using Laser Doppler vibrometry (LDV) and the more established ultrasound-based pulse wave imaging (PWI) in smooth vessels. Additionally, it was tested whether changes in phantom structure can be detected using LDV in vessels containing a local hardening of the vessel wall. Results from both methods showed good agreement illustrated by the non-parametric Spearman correlation analysis (Spearman-ρ = 1 and pmarkers and larger distances between beams. In further studies, more LDV beams will be used to allow detection of local changes in arterial wall dynamics due to e.g. small inclusions or local hardenings of the vessel wall.

  1. Application of the H/V and SPAC Method to Estimate a 3D Shear Wave Velocity Model, in the City of Coatzacoalcos, Veracruz.

    Science.gov (United States)

    Morales, L. E. A. P.; Aguirre, J.; Vazquez Rosas, R.; Suarez, G.; Contreras Ruiz-Esparza, M. G.; Farraz, I.

    2014-12-01

    Methods that use seismic noise or microtremors have become very useful tools worldwide due to its low costs, the relative simplicity in collecting data, the fact that these are non-invasive methods hence there is no need to alter or even perforate the study site, and also these methods require a relatively simple analysis procedure. Nevertheless the geological structures estimated by this methods are assumed to be parallel, isotropic and homogeneous layers. Consequently precision of the estimated structure is lower than that from conventional seismic methods. In the light of these facts this study aimed towards searching a new way to interpret the results obtained from seismic noise methods. In this study, seven triangular SPAC (Aki, 1957) arrays were performed in the city of Coatzacoalcos, Veracruz, varying in sizes from 10 to 100 meters. From the autocorrelation between the stations of each array, a Rayleigh wave phase velocity dispersion curve was calculated. Such dispersion curve was used to obtain a S wave parallel layers velocity (VS) structure for the study site. Subsequently the horizontal to vertical ratio of the spectrum of microtremors H/V (Nogoshi and Igarashi, 1971; Nakamura, 1989, 2000) was calculated for each vertex of the SPAC triangular arrays, and from the H/V spectrum the fundamental frequency was estimated for each vertex. By using the H/V spectral ratio curves interpreted as a proxy to the Rayleigh wave ellipticity curve, a series of VS structures were inverted for each vertex of the SPAC array. Lastly each VS structure was employed to calculate a 3D velocity model, in which the exploration depth was approximately 100 meters, and had a velocity range in between 206 (m/s) to 920 (m/s). The 3D model revealed a thinning of the low velocity layers. This proved to be in good agreement with the variation of the fundamental frequencies observed at each vertex. With the previous kind of analysis a preliminary model can be obtained as a first

  2. Multichannel Analysis of Surface Waves and Down-Hole Tests in the Archeological "Palatine Hill" Area (Rome, Italy): Evaluation and Influence of 2D Effects on the Shear Wave Velocity

    Science.gov (United States)

    Di Fiore, V.; Cavuoto, G.; Tarallo, D.; Punzo, M.; Evangelista, L.

    2016-05-01

    A joint analysis of down-hole (DH) and multichannel analysis of surface waves (MASW) measurements offers a complete evaluation of shear wave velocity profiles, especially for sites where a strong lateral variability is expected, such as archeological sites. In this complex stratigraphic setting, the high "subsoil anisotropy" (i.e., sharp lithological changes due to the presence of anthropogenic backfill deposits and/or buried man-made structures) implies a different role for DH and MASW tests. This paper discusses some results of a broad experimental program conducted on the Palatine Hill, one of the most ancient areas of the city of Rome (Italy). The experiments were part of a project on seismic microzoning and consisted of 20 MASW and 11 DH tests. The main objective of this study was to examine the difficulties related to the interpretation of the DH and MASW tests and the reliability limits inherent in the application of the noninvasive method in complex stratigraphic settings. As is well known, DH tests provide good determinations of shear wave velocities (Vs) for different lithologies and man-made materials, whereas MASW tests provide average values for the subsoil volume investigated. The data obtained from each method with blind tests were compared and were correlated to site-specific subsurface conditions, including lateral variability. Differences between punctual (DH) and global (MASW) Vs measurements are discussed, quantifying the errors by synthetic comparison and by site response analyses. This study demonstrates that, for archeological sites, VS profiles obtained from the DH and MASW methods differ by more than 15 %. However, the local site effect showed comparable results in terms of natural frequencies, whereas the resolution of the inverted shear wave velocity was influenced by the fundamental mode of propagation.

  3. Two-slope ascending arm of the early trans-mitral flow velocity Doppler wave in patients with heart failure and preserved ejection fraction.

    Science.gov (United States)

    Dori, Guy; Egbaria, Muhammad A; Jabaren, Mohamed

    2014-12-01

    Trans-mitral flow velocity (TMFV) examination is a standard echocardiographic measure for assessing diastolic function of the heart. Typically, the Doppler signal representing the early rapid filling phase of the left ventricle (LV), termed: E wave, is triangular. The ascending arm of the E wave (EWAA) represents blood accelerating into the LV from the left atrium (LA), whereas the descending arm reflects blood decelerating as the LV fills and resists further filling. The slope of EWAA is linear, starting at TMFV of zero cm/s (prior to mitral valve opening) and building to peak E wave value. The physical meaning of a single slope is that blood acceleration is constant with time. Little data exist regarding the significance of the shape of EWAA. It is hypothesized that in heart failure with preserved ejection fraction (HFPEF) the EWAA displays 2 slopes. A first steeper slope followed by a second less steep slope reaching peak E wave. The different slopes represent a change in the composition of driving forces propelling blood from LA to LV. It is hypothesized that the first steeper slope of EWAA represents a set of driving force including a force termed: diastolic suction, whereas in the second slope diastolic suction has already dissipated. This 2-slope phenomenon is not expected in healthy subjects because the assumed underlying mechanism is not operative. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Correlation of microfractures with P-wave velocities and strain in cored rock samples from the Yutsubo geothermal well deformed under confining pressures; Fuatsuka no P ha sokudo henka to hizumi henka kara suiteisareta Yutsubo chinetsusei core shiryo no wareme no seijo

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Z. [Kiso-Jiban Consultants Co. Ltd., Tokyo (Japan); Nishizawa, O.; Kuwahara, Y. [Geological Survey of Japan, Tsukuba (Japan); Suzuki, S. [Okayama University, Okayama (Japan). Faculty of Science

    1996-12-27

    With an objective to identify underground rock properties, measurements were made on strains and elastic wave velocities of boring cores under hydrostatic pressure in a geothermal experimental field. Microstructures of rock samples were also observed by using a microscope. Four samples were collected from two test wells each at two locations of different depths. The following findings were obtained: a phenomenon exists that ratio of increase in the strain changes at certain pressure as a border in a high- pressure region (strain inflection point). Pressure at the strain inflection point was as relatively low as 40 MPa, no marks of void fracture were observed, and elastic deformation of particles was verified. This phenomenon varies with rock types. Samples taken from great depths presented cracks. Although hysteresis appears in mineral particles plastically deformed, cracks are filled with calcite, hence no variation corresponding to non-uniformity appears in the P-wave velocity. The reason for the P-wave velocity to become lower in a load removing process is because cracks have developed from cracks that have existed previously. Difference may be seen in anisotropy patterns of strains and P-wave velocities among samples, whose cause may be other than the cracks. 15 refs., 24 figs.

  5. Calibration of a micromachined particle velocity microphone in a standing wave tube using a LDA photon-correlation technique

    NARCIS (Netherlands)

    Raangs, R.; Schlicke, Ted; Barham, Richard

    2005-01-01

    In this paper, a new method of calibrating an acoustic particle velocity sensor using laser Doppler anemometry (LDA) is discussed. The results were compared and were in good agreement with the results obtained by conventional methods, where the sensitivity of the microflown is obtained with the use

  6. A regional view of urban sedimentary basins in Northern California based on oil industry compressional-wave velocity and density logs

    Science.gov (United States)

    Brocher, T.M.

    2005-01-01

    Compressional-wave (sonic) and density logs from 119 oil test wells provide knowledge of the physical properties and impedance contrasts within urban sedimentary basins in northern California, which is needed to better understand basin amplification. These wire-line logs provide estimates of sonic velocities and densities for primarily Upper Cretaceous to Pliocene clastic rocks between 0.1 - and 5.6-km depth to an average depth of 1.8 km. Regional differences in the sonic velocities and densities in these basins largely 1reflect variations in the lithology, depth of burial, porosity, and grain size of the strata, but not necessarily formation age. For example, Miocene basin filling strata west of the Calaveras Fault exhibit higher sonic velocities and densities than older but finer-grained and/or higher-porosity rocks of the Upper Cretaceous Great Valley Sequence. As another example, hard Eocene sandstones west of the San Andreas Fault have much higher impedances than Eocene strata, mainly higher-porosity sandstones and shales, located to the east of this fault, and approach those expected for Franciscan Complex basement rocks. Basement penetrations define large impedence contrasts at the sediment/basement contact along the margins of several basins, where Quaternary, Pliocene, and even Miocene deposits directly overlie Franciscan or Salinian basement rocks at depths as much as 1.7 km. In contrast, in the deepest, geographic centers of the basins, such logs exhibit only a modest impedance contrast at the sediment/basement contact at depths exceeding 2 km. Prominent (up to 1 km/sec) and thick (up to several hundred meters) velocity and density reversals in the logs refute the common assumption that velocities and densities increase monotonically with depth.

  7. High coupling and high velocity surface acoustic waves using a c-axis oriented ZnO film on translucent Al2O3 ceramics

    Science.gov (United States)

    Takeda, Fumio; Shiosaki, Tadashi; Kawabata, Akira

    1983-07-01

    The layered structure comprising a c-axis normally oriented ZnO piezoelectric film and a translucent Al2O3 ceramic substrate which has a high surface-acoustic-wave velocity and a small surface roughness has given both a high phase velocity Vp and a high coupling k2 for the 0th (Rayleigh) mode, 1st (Sezawa) mode, and leaky mode surface acoustic waves. The measured maximum values of k2 are 3.6% for the 0th mode at h/λ=0.45 where Vp is 3.2 km/s, 5.7% for the 1st mode at h/λ=0.21 where Vp is 5.6 km/s, and 6.7% for the leaky mode at h/λ=0.16 where Vp is 6.2 km/s, where the interdigital transducers are located at the interface in measuring the above values, and also electrically floating plane metals are on top of the ZnO film for the last two values.

  8. Impact of layer and substrate properties on the surface acoustic wave velocity in scandium doped aluminum nitride based SAW devices on sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Gillinger, M., E-mail: manuel.gillinger@tuwien.ac.at; Knobloch, T.; Schneider, M.; Schmid, U. [Institute of Sensor and Actuator Systems, TU Wien, 1040 Vienna (Austria); Shaposhnikov, K.; Kaltenbacher, M. [Institute of Mechanics and Mechatronics, TU Wien, 1040 Vienna (Austria)

    2016-06-06

    This paper investigates the performance of surface acoustic wave (SAW) devices consisting of reactively sputter deposited scandium doped aluminum nitride (Sc{sub x}Al{sub 1-x}N) thin films as piezoelectric layers on sapphire substrates for wireless sensor or for RF-MEMS applications. To investigate the influence of piezoelectric film thickness on the device properties, samples with thickness ranging from 500 nm up to 3000 nm are fabricated. S{sub 21} measurements and simulations demonstrate that the phase velocity is predominantly influenced by the mass density of the electrode material rather than by the thickness of the piezoelectric film. Additionally, the wave propagation direction is varied by rotating the interdigital transducer structures with respect to the crystal orientation of the substrate. The phase velocity is about 2.5% higher for a-direction compared to m-direction of the sapphire substrate, which is in excellent agreement with the difference in the anisotropic Young's modulus of the substrate corresponding to these directions.

  9. Review article "Remarks on factors influencing shear wave velocities and their role in evaluating susceptibilities to earthquake-triggered slope instability: case study for the Campania area (Italy"

    Directory of Open Access Journals (Sweden)

    V. Paoletti

    2012-07-01

    Full Text Available Shear wave velocities have a fundamental role in connection with the mitigation of seismic hazards, as their low values are the main causes of site amplification phenomena and can significantly influence the susceptibility of a territory to seismic-induced landslides. The shear wave velocity (Vs and modulus (G of each lithological unit are influenced by factors such as the degree of fracturing and faulting, the porosity, the clay amount and the precipitation, with the latter two influencing the unit water content. In this paper we discuss how these factors can affect the Vs values and report the results of different analyses that quantify the reduction in the rock Vs and shear modulus values connected to the presence of clay and water. We also show that significant results in assessing seismic-induced slope failure susceptibility for land planning targets could be achieved through a careful evaluation, based only on literature studies, of the geo-lithological and geo-seismic features of the study area.

  10. The thermo-chemical and physical structure beneath the North American continent from Bayesian inversion of surface-wave phase velocities

    DEFF Research Database (Denmark)

    Khan, A.; Zunino, A.; Deschamps, F.

    2011-01-01

    -consistent thermodynamic method whereby phase equilibria and physical properties (P-, S-wave velocity and density) are computed as functions of composition (in the Na2O-CaO-FeO-MgO-Al2O 3-SiO2 model system), pressure and temperature. We employ a sampling-based strategy to solve the non-linear inverse problem relying......We jointly invert local fundamental-mode and higher-order surface-wave phase-velocities for radial models of the thermo-chemical and anisotropic physical structure of the Earth's mantle to ∼1000 km depth beneath the North American continent. Inversion for thermo-chemical state relies on a self...... and oceans). In the transition zone the thermo-chemical structure decouples from that of the upper mantle, with a relatively hot thermal anomaly appearing beneath the cratonic area that likely extends into the lower mantle. In the lower mantle no consistent large-scale thermo-chemical heterogeneities...

  11. Calculations of Temperature, Conductive Heat Flux, and Heat Wave Velocities Due to Radiant Heating of Opaque Materials

    Science.gov (United States)

    2011-11-01

    presentation and the help of Dr. Anthony Kotlar with the Mathcad calculations are greatly appreciated. vi INTENTIONALLY LEFT BLANK. 1 1. Introduction...Corporation. Mathcad 2001; Needham, MA, 2001. 4. Joseph, D. D.; Preziosi, L. Heat Waves. Rev. Modern Physics 1989, 61 (1), 41–73. 5. Cao, B-Y; Guo, Z-Y

  12. Shear-wave velocity profile and seismic input derived from ambient vibration array measurements: the case study of downtown L'Aquila

    Science.gov (United States)

    Di Giulio, Giuseppe; Gaudiosi, Iolanda; Cara, Fabrizio; Milana, Giuliano; Tallini, Marco

    2014-08-01

    Downtown L'Aquila suffered severe damage (VIII-IX EMS98 intensity) during the 2009 April 6 Mw 6.3 earthquake. The city is settled on a top flat hill, with a shear-wave velocity profile characterized by a reversal of velocity at a depth of the order of 50-100 m, corresponding to the contact between calcareous breccia and lacustrine deposits. In the southern sector of downtown, a thin unit of superficial red soils causes a further shallow impedance contrast that may have influenced the damage distribution during the 2009 earthquake. In this paper, the main features of ambient seismic vibrations have been studied in the entire city centre by using array measurements. We deployed six 2-D arrays of seismic stations and 1-D array of vertical geophones. The 2-D arrays recorded ambient noise, whereas the 1-D array recorded signals produced by active sources. Surface-wave dispersion curves have been measured by array methods and have been inverted through a neighbourhood algorithm, jointly with the H/V ambient noise spectral ratios related to Rayleigh waves ellipticity. We obtained shear-wave velocity (Vs) profiles representative of the southern and northern sectors of downtown L'Aquila. The theoretical 1-D transfer functions for the estimated Vs profiles have been compared to the available empirical transfer functions computed from aftershock data analysis, revealing a general good agreement. Then, the Vs profiles have been used as input for a deconvolution analysis aimed at deriving the ground motion at bedrock level. The deconvolution has been performed by means of EERA and STRATA codes, two tools commonly employed in the geotechnical engineering community to perform equivalent-linear site response studies. The waveform at the bedrock level has been obtained deconvolving the 2009 main shock recorded at a strong motion station installed in downtown. Finally, this deconvolved waveform has been used as seismic input for evaluating synthetic time-histories in a strong

  13. Sixteen year variation of horizontal phase velocity and propagation direction of mesospheric and thermospheric waves in airglow images at Shigaraki, Japan

    Science.gov (United States)

    Takeo, D.; Shiokawa, K.; Fujinami, H.; Otsuka, Y.; Matsuda, T. S.; Ejiri, M. K.; Nakamura, T.; Yamamoto, M.

    2017-08-01

    We analyzed the horizontal phase velocity of gravity waves and medium-scale traveling ionospheric disturbances (MSTIDs) by using the three-dimensional fast Fourier transform method developed by Matsuda et al. (2014) for 557.7 nm (altitude: 90-100 km) and 630.0 nm (altitude: 200-300 km) airglow images obtained at Shigaraki MU Observatory (34.8°N, 136.1°E, dip angle: 49°) over ˜16 years from 16 March 1999 to 20 February 2015. The analysis of 557.7 nm airglow images shows clear seasonal variation of the propagation direction of gravity waves in the mesopause region. In spring, summer, fall, and winter, the peak directions are northeastward, northeastward, northwestward, and southwestward, respectively. The difference in east-west propagation direction between summer and winter is probably caused by the wind filtering effect due to the zonal mesospheric jet. Comparison with tropospheric reanalysis data shows that the difference in north-south propagation direction between summer and winter is caused by differences in the latitudinal location of wave sources due to convective activity in the troposphere relative to Shigaraki. The analysis of 630.0 nm airglow images shows that the propagation direction of MSTIDs is mainly southwestward with a minor northeastward component throughout the 16 years. A clear negative correlation is seen between the yearly power spectral density of MSTIDs and F10.7 solar flux. This negative correlation with solar activity may be explained by the linear growth rate of the Perkins instability and secondary wave generation of gravity waves in the thermosphere.

  14. In-plane ultrasonic velocity measurement of longitudinal and shear waves in the machine direction with transducers in rotating wheels

    Science.gov (United States)

    Hall, Maclin S.; Jackson, Theodore G.; Knerr, Christopher

    1998-02-17

    An improved system for measuring the velocity of ultrasonic signals within the plane of moving web-like materials, such as paper, paperboard and the like. In addition to velocity measurements of ultrasonic signals in the plane of the web in the MD and CD, one embodiment of the system in accordance with the present invention is also adapted to provide on-line indication of the polar specific stiffness of the moving web. In another embodiment of the invention, the velocity of ultrasonic signals in the plane of the web are measured by way of a plurality of ultrasonic transducers carried by synchronously driven wheels or cylinders, thus eliminating undue transducer wear due to any speed differences between the transducers and the web. In order to provide relatively constant contact force between the transducers and the webs, the transducers are mounted in a sensor housings which include a spring for biasing the transducer radially outwardly. The sensor housings are adapted to be easily and conveniently mounted to the carrier to provide a relatively constant contact force between the transducers and the moving web.

  15. Three-dimensional imaging of the S-velocity structure for the crust and the upper mantle beneath the Arabian Sea from Rayleigh wave analysis

    Science.gov (United States)

    Corchete, V.

    2017-04-01

    A 3D imaging of S-velocity for the Arabian Sea crust and upper mantle structure is presented in this paper, determined by means of Rayleigh wave analysis, for depths ranging from zero to 300 km. The crust and upper mantle structure of this region of the earth never has been the subject of a surface wave tomography survey. The Moho map performed in the present study is a new result, in which a crustal thickening beneath the Arabian Fan sediments can be observed. This crustal thickening can be interpreted as a quasi-continental oceanic transitional structure. A crustal thickness of up to 20 km also can be observed for the Murray Ridge system in this Moho map. This crustal thickening can be due to that the Murray Ridge System consists of Indian continental crust. This continental crust is extremely thinned to the southwest of this region, as shown in this Moho map. This area can be interpreted as oceanic in origin. In the depth range from 30 to 60 km, the S-velocity presents its lower values at the Carlsberg Ridge region, because it is the younger region of the study area. In the depth range from 60 to 105 km of depth, the S-velocity pattern is very similar to that shown for the previous depth range, except for the regions in which the asthenosphere is reached, for these regions appear a low S-velocity pattern. The lithosphere-asthenosphere boundary (LAB), or equivalently the lithosphere thickness, determined in the present study is also a new result, in which the lithosphere thickness for the Arabian Fan can be estimated in 60-70 km. The lower lithospheric thickness observed in the LAB map, for the Arabian Fan, shows that this region may be in the transition zone between continental and oceanic structure. Finally, a low-velocity zone (LVZ) has been determined, for the whole study area, located between the LAB and the boundary of the asthenosphere base (or equivalently the lithosphere-asthenosphere system thickness). The asthenosphere-base map calculated in the

  16. A compendium of P- and S-wave velocities from surface-to-borehole logging; summary and reanalysis of previously published data and analysis of unpublished data

    Science.gov (United States)

    Boore, David M.

    2003-01-01

    For over 28 years, the U.S. Geological Survey (USGS) has been acquiring seismic velocity and geologic data at a number of locations in California, many of which were chosen because strong ground motions from earthquakes were recorded at the sites. The method for all measurements involves picking first arrivals of P- and S-waves from a surface source recorded at various depths in a borehole (as opposed to noninvasive methods, such as the SASW method [e.g., Brown et al., 2002]). The results from most of the sites are contained in a series of U.S. Geological Survey Open-File Reports (see References). Until now, none of the results have been available as computer files, and before 1992 the interpretation of the arrival times was in terms of piecemeal interval velocities, with no attempt to derive a layered model that would fit the travel times in an overall sense (the one exception is Porcella, 1984). In this report I reanalyze all of the arrival times in terms of layered models for P- and for S-wave velocities at each site, and I provide the results as computer files. In addition to the measurements reported in the open-file reports, I also include some borehole results from other reports, as well as some results never before published. I include data for 277 boreholes (at the time of this writing; more will be added to the web site as they are obtained), all in California (I have data from boreholes in Washington and Utah, but these will be published separately). I am also in the process of interpreting travel time data obtained using a seismic cone penetrometer at hundreds of sites; these data can be interpreted in the same way of those obtained from surface-to-borehole logging. When available, the data will be added to the web site (see below for information on obtaining data from the World Wide Web (WWW)). In addition to the basic borehole data and results, I provide information concerning strong-motion stations that I judge to be close enough to the boreholes

  17. New tomographic images of P- , S- wave velocity and Q on the Philippine Sea Slab beneath Tokyo: Implication to seismotectonics and seismic hazard in the Tokyo metropolitan region

    Science.gov (United States)

    Hirata, Naoshi; Sakai, Shin'ichi; Nakagawa, Shigeki; Panayotopoulos, Yannis; Ishikawa, Masahiro; Sato, Hiroshi; Kasahara, Keiji; Kimura, Hisanor; Honda, Ryou

    2013-04-01

    The Central Disaster Management Council of Japan estimates the next great M7+ earthquake in the Tokyo metropolitan region will cause 11,000 fatalities and 112 trillion yen (1 trillion US) economic loss at worst case if it occur beneath northern Tokyo bay with M7.3. However, the estimate is based on a source fault model by conventional studies about the PSP geometry. To evaluate seismic hazard due to the great quake we need to clarify the geometry of PSP and also the Pacific palate (PAP) that subducs beneath PSP. We identify those plates with use of seismic tomography and available deep seismic reflection profiling and borehole data in southern Kanto area. We deployed about 300 seismic stations in the greater Tokyo urban region under the Special Project for Earthquake Disaster Mitigation in Tokyo Metropolitan Area. We obtain clear P- and S- wave velocity (Vp and Vs) and Q tomograms which show a clear image of PSP and PAP. A depth to the top of PSP, 20 to 30 kilometer beneath northern part of Tokyo bay, is about 10 km shallower than previous estimates based on the distribution of seismicity (Ishida, 1992). This shallower plate geometry changes estimations of strong ground motion for seismic hazards analysis within the Tokyo region. Based on elastic wave velocities of rocks and minerals, we interpreted the tomographic images as petrologic images. Tomographic images revealed the presence of two stepwise velocity increase of the top layer of the subducting PSP slab. Rock velocity data reveals that subducting PSP crust transforms from blueschists to amphibolites at depth of 30km and amphibolites to eclogites at depth of 50km, which suggest that dehydration reactions occurs in subducting crust of basaltic compositions during prograde metamorphism and water is released from the subducting PSP crust. Tomograms show evidence for a low-velocity zone (LVZ) beneath the area just north of Tokyo bay. A Q tomogram show a low Q zone in PSP slab. We interpret the LVZ as a

  18. Time-Synchronized Continuous Wave Laser-Induced Fluorescence Velocity Measurements of a Diverging Cusped Field Thruster

    Science.gov (United States)

    2012-10-01

    comparator signal and raw emission plus fluorescence signal from the PMT are then fed into an SRS SR-250 Boxcar Averager Time-Sync CW-LIF Velocity...the comparator signal, the boxcar averager samples the PMT signal for a period of time defined by the gate width. The last sampled value of the PMT...signal is held until the next comparator trigger, at which point the boxcar averager re-samples and holds the PMT signal. Fig. 5 provides an example of

  19. Deformation characteristics and wave velocities of hard rock block with cracks at low strain levels; Wareme wo yusuru koshitsu ganban no bisho hizumi ryoiki deno henkeisei to hado denpa sokudo

    Energy Technology Data Exchange (ETDEWEB)

    Sato, M.; Ueda, M.; Kondo, H. [Chubu Electric Power Co. Inc., Nagoya (Japan); Hasebe, N. [Nagoya Institute of Technology, Nagoya (Japan). Faculty of Engineering

    1997-03-21

    A dynamic compression test in which the loading velocity is changed was conducted for specimens of hard rock blocks with cracks to perform the measurement in a low strain level. Moreover, resonance method and ultrasonic method tests were made for comparison of