WorldWideScience

Sample records for stress wave velocity

  1. 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...

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

    Indian Academy of Sciences (India)

    Wave velocities in a pre-stressed anisotropic elastic medium. M D Sharma ... Modified Christoffel equations are derived for three-dimensional wave propagation in a general anisotropic medium under initial stress.The three roots of a ... Department of Mathematics, Kurukshetra University, Kurukshetra 136 119, India. UIET ...

  3. 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 ...

  4. 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–...

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

    Indian Academy of Sciences (India)

    of differential stress environment in the sediments. In the problems of foundation engineering, the influence of initial stress appears in a buoyancy effect which amounts to floating a building on its foundation. The theory of elastic wave propaga- tion in pre-stressed solids has a nearly two-century long history. In perhaps, the ...

  6. Determination of relationship between Rayleigh wave velocity and stress with laser Doppler velocimeter

    Science.gov (United States)

    He, Lingfeng; Kobayashi, Shoichi

    2002-05-01

    A non-contact measurement technique of Rayleigh wave velocity is proposed. In the non-contact measurement system, a laser Doppler velocimeter is used to determine wave motions. With above technique, the relationship between Rayleigh wave velocity and stress for an aluminum alloy 5052 and steel SS400 is determined, and the results are in good agreement with that obtained by contact measurement method.

  7. 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...

  8. Stress-wave velocity of wood-based panels: effect of moisture, product type, and material direction

    Science.gov (United States)

    Guangping Han; Qinglin Wu; Xiping Wang

    2006-01-01

    The effect of moisture on longitudinal stress-wave velocity (SWV), bending stiffness. and bending strength of commercial oriented strandboard, plywood. particleboard. and southern pine lumber was evaluated. It was shown that the stress-wave verocity decreased in general with increases in panel moisture content (MC). At a given MC level. SWV varied with panel type and...

  9. Potential applicability of stress wave velocity method on pavement base materials as a non-destructive testing technique

    Science.gov (United States)

    Mahedi, Masrur

    Aggregates derived from natural sources have been used traditionally as the pavement base materials. But in recent times, the extraction of these natural aggregates has become more labor intensive and costly due to resource depletion and environmental concerns. Thus, the uses of recycled aggregates as the supplementary of natural aggregates are increasing considerably in pavement construction. Use of recycled aggregates such as recycled crushed concrete (RCA) and recycled asphalt pavement (RAP) reduces the rate of natural resource depletion, construction debris and cost. Although recycled aggregates could be used as a viable alternative of conventional base materials, strength characteristics and product variability limit their utility to a great extent. Hence, their applicability is needed to be evaluated extensively based on strength, stiffness and cost factors. But for extensive evaluation, traditionally practiced test methods are proven to be unreasonable in terms of time, cost, reliability and applicability. On the other hand, rapid non-destructive methods have the potential to be less time consuming and inexpensive along with the low variability of test results; therefore improving the reliability of estimated performance of the pavement. In this research work, the experimental program was designed to assess the potential application of stress wave velocity method as a non-destructive test in evaluating recycled base materials. Different combinations of cement treated recycled concrete aggregate (RAP) and recycled crushed concrete (RCA) were used to evaluate the applicability of stress wave velocity method. It was found that, stress wave velocity method is excellent in characterizing the strength and stiffness properties of cement treated base materials. Statistical models, based on P-wave velocity were derived for predicting the modulus of elasticity and compressive strength of different combinations of cement treated RAP, Grade-1 and Grade-2 materials. Two

  10. 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

  11. 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.

  12. 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.

  13. Group Velocity for Leaky Waves

    Science.gov (United States)

    Rzeznik, Andrew; Chumakova, Lyubov; Rosales, Rodolfo

    2017-11-01

    In many linear dispersive/conservative wave problems one considers solutions in an infinite medium which is uniform everywhere except for a bounded region. In general, localized inhomogeneities of the medium cause partial internal reflection, and some waves leak out of the domain. Often one only desires the solution in the inhomogeneous region, with the exterior accounted for by radiation boundary conditions. Formulating such conditions requires definition of the direction of energy propagation for leaky waves in multiple dimensions. In uniform media such waves have the form exp (d . x + st) where d and s are complex and related by a dispersion relation. A complex s is required since these waves decay via radiation to infinity, even though the medium is conservative. We present a modified form of Whitham's Averaged Lagrangian Theory along with modulation theory to extend the classical idea of group velocity to leaky waves. This allows for solving on the bounded region by representing the waves as a linear combination of leaky modes, each exponentially decaying in time. This presentation is part of a joint project, and applications of these results to example GFD problems will be presented by L. Chumakova in the talk ``Leaky GFD Problems''. This work is partially supported by NSF Grants DMS-1614043, DMS-1719637, and 1122374, and by the Hertz Foundation.

  14. Wave Measurements Using GPS Velocity Signals

    Directory of Open Access Journals (Sweden)

    Chia Chuen Kao

    2011-01-01

    Full Text Available 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.

  15. Association between work-related psychological stress and arterial stiffness measured by brachial-ankle pulse-wave velocity in young Japanese males from an information service company.

    Science.gov (United States)

    Nomura, Kyoko; Nakao, Mutsuhiro; Karita, Kanae; Nishikitani, Mariko; Yano, Eiji

    2005-10-01

    This study examined the relationship between work-related psychological stress and arterial stiffness in young Japanese workers. A cross-sectional study was conducted on 396 Japanese male workers, aged 24 to 39 years, employed in a Japanese information service company. Work-related psychological stress was measured by the Job Content Questionnaire based on the job demand-control model. The job-strain index was defined as the ratio of job demand to job-control scores. The outcome of the study was the degree of arteriosclerosis as assessed by brachial pulse-wave velocity (baPWV). The cardiovascular risk factors analyzed were age, heart rate, blood pressure, body mass index, serum lipid, blood sugar levels, catecholamine levels, ethanol consumption, smoking, and overtime. In addition, psychological responses were assessed by tension-anxiety and anger-hostility scales in the Profile of Mood States (POMS). The baPWV was positively (P<0.05) associated with physiological variables including age, heart rate, body mass index, and serum levels of total cholesterol, fasting glucose, and noradrenaline, but negatively (P<0.01) associated with the job-strain index. Significant associations were not found on the POMS tension-anxiety and anger-hostility scale scores. The negative correlation between baPWV and the job-strain index was consistent even after control for the effects of significant physiological variables. The association between job stress and baPWV was found to be inconsistent with the results of previous western studies, and it may require further investigation while taking into account occupation, cardiovascular risk factors, and Japanese culture.

  16. Analysis of Wave Velocity Patterns in Black Cherry Trees and its Effect on Internal Decay Detection

    Science.gov (United States)

    Guanghui Li; Xiping Wang; Jan Wiedenbeck; Robert J. Ross

    2013-01-01

    In this study, we examined stress wave velocity patterns in the cross sections of black cherry trees, developed analytical models of stress wave velocity in sound healthy trees, and then tested the effectiveness of the models as a tool for tree decay diagnosis. Acoustic tomography data of the tree cross sections were collected from 12 black cherry trees at a production...

  17. Analysis of wave velocity patterns in black cherry trees and its effect on internal decay detection

    Science.gov (United States)

    Guanghui Li; Xiping Wang; Hailin Feng; Jan Wiedenbeck; Robert J. Ross

    2014-01-01

    In this study, we examined stress wave velocity patterns in the cross sections of black cherry trees, developed analytical models of stress wave velocity in sound healthy trees, and then tested the effectiveness of the models as a tool for tree decay diagnosis. Acoustic tomography data of the tree cross sections were collected from 12 black cherry trees at a production...

  18. Pulse Wave Velocity and Electroneurophysiological Evaluation in ...

    African Journals Online (AJOL)

    undetermined etiology involving the synovial membranes and articular structures of multiple joints and is also associated with carditis, pleuritis, hepatitis, peripheral neuropathy and vasculitis. The present study was undertaken to investigate arterial stiffness using carotid-radial and femoral-dorsalis pedis pulse wave velocity ...

  19. 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.

  20. Investigation into stress wave propagation in metal foams

    Directory of Open Access Journals (Sweden)

    Li Lang

    2015-01-01

    Full Text Available The aim of this study is to investigate stress wave propagation in metal foams under high-speed impact loading. Three-dimensional Voronoi model is established to represent real closed-cell foam. Based on the one-dimensional stress wave theory and Voronoi model, a numerical model is developed to calculate the velocity of elastic wave and shock wave in metal foam. The effects of impact velocity and relative density of metal foam on the stress wave propagation in metal foams are explored respectively. The results show that both elastic wave and shock wave propagate faster in metal foams with larger relative density; with increasing the impact velocity, the shock wave propagation velocity increase, but the elastic wave propagation is not sensitive to the impact velocity.

  1. Smoldering Wave-Front Velocity in Fiberboard.

    Science.gov (United States)

    1980-09-01

    upstream of phases. least 2 weeks or until moisture the plates. Then a Bunsen burner equilibrium had been reached. When flame (burning natural gas) was...important parameters of in- plates. If necessary, the burner flame terest is the propagation velocity of Experimental Wave- was reapplied until no more...decomposition process once smoldering continued in the Involved the process has been Initiated. The material. Flames were observed in the distinguishing

  2. Measurement of longitudinal and rayleigh wave velocities by advanced one-sided technique in concrete

    International Nuclear Information System (INIS)

    Lee, Joon Hyun; Song, Won Joon; Popovics, J. S.; Achenbach, J. D.

    1997-01-01

    A new procedure for the advanced one-sided measurement of longitudinal wave and surface wave velocities in concrete is presented in this paper. Stress waves are generated in a consistent fashion with a DC solenoid. Two piezoelectric accelerometers are mounted on the surface of a specimen as receivers. Stress waves propagate along the surface of the specimen and are detected by the receivers. In order to reduce the large incoherent noise levels of the signals, signals are collected and manipulated by a computer program for each velocity measurement. For a known distance between the two receivers and using the measured flight times, the velocities of the longitudinal wave and the surface wave are measured. The velocities of the longitudinal wave determined by this method are compared with those measured by conventional methods on concrete, PMMA and steel.

  3. Seismic Wave Velocity in Earth's Shallow Core

    Science.gov (United States)

    Alexandrakis, C.; Eaton, D. W.

    2008-12-01

    Studies of the outer core indicate that it is composed of liquid Fe and Ni alloyed with a ~10% fraction of light elements such as O, S or Si. Recently, unusual features, such as sediment accumulation, immiscible fluid layers or stagnant convection, have been predicted in the shallow core region. Secular cooling and compositional buoyancy drive vigorous convection that sustains the geodynamo, although critical details of light-element composition and thermal regime remain uncertain. Seismic velocity models can provide important constraints on the light element composition, however global reference models, such as Preliminary Reference Earth Model (PREM), IASP91 and AK135 vary significantly in the 200 km below the core-mantle boundary. Past studies of the outermost core velocity structure have been hampered by traveltime uncertainties due to lowermost mantle heterogeneities. The recently published Empirical Transfer Function (ETF) method has been shown to reduce the uncertainty using a waveform stacking approach to improve global observations of SmKS teleseismic waves. Here, we apply the ETF method to achieve a precise top-of-core velocity measurement of 8.05 ± 0.03 km/s. This new model accords well with PREM. Since PREM is based on the adiabatic form of the Adams-Williamson equation, it assumes a well mixed (i.e. homogeneous) composition. This result suggests a lack of heterogeneity in the outermost core due to layering or stagnant convection.

  4. Velocity of interplanetary shock waves according to radioastronomical data

    International Nuclear Information System (INIS)

    Vlasov, V.I.

    1988-01-01

    Velocities of 34 interplanetary shock waves are estimated by the method of radioastronomical cartography of scintillation indices of cosmic radiosources. The velocity of shock waves within the limits of approximately 0.2-1.2 a.e. is shown to decrease as far as they are far from the Sun at a distance equalling 1/r α , where 0.25 < or approx. α ≤ 1. In this case the degree of shock wave slowing-down dependences on their initial velocity; the velocity radial gradient is approximately proportional to the square of the shock wave initial velocity

  5. Dynamic Characterization of Cohesive Material Based on Wave Velocity Measurements

    Directory of Open Access Journals (Sweden)

    Wojciech Sas

    2016-02-01

    Full Text Available The paper presents a description of the dynamic properties of cohesive material, namely silty clays, obtained by using one of the applied seismology methods, the bender elements technique. The authors’ aim was to present the dynamics of a porous medium, in particular an extremely important passage of seismic waves that travel through the bulk of a medium. Nowadays, the application of the bender element (BE technique to measure, e.g., small strain shear stiffness of soils in the laboratory is well recognized, since it allows for reliable and relatively economical shear wave velocity measurements during various laboratory experiments. However, the accurate estimation of arrival time during BE tests is in many cases unclear. Two different interpretation procedures (from the time domain of BE tests in order to measure travel times of waves were examined. Those values were then used to calculate shear and compression wave velocities and elastic moduli. Results showed that the dynamic parameters obtained by the start-to-start method were always slightly larger (up to about 20% than those obtained using the peak-to-peak one. It was found that the peak-to-peak method led to more scattered results in comparison to the start-to-start method. Moreover, the influence of the excitation frequency, the mean effective stress and the unloading process on the dynamic properties of the tested material was studied. In addition, the obtained results highlighted the importance of initial signal frequency and the necessity to choose an appropriate range of frequencies to measure the shear wave velocity in clayey soils.

  6. Aortic pulse wave velocity improves cardiovascular event prediction

    DEFF Research Database (Denmark)

    Ben-Shlomo, Yoav; Spears, Melissa; Boustred, Chris

    2014-01-01

    To determine whether aortic pulse wave velocity (aPWV) improves prediction of cardiovascular (CVD) events beyond conventional risk factors.......To determine whether aortic pulse wave velocity (aPWV) improves prediction of cardiovascular (CVD) events beyond conventional risk factors....

  7. 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

  8. 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

    ) 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...

  9. Shear wave crustal velocity model of the Western Bohemian Massif from Love wave phase velocity dispersion

    Czech Academy of Sciences Publication Activity Database

    Kolínský, Petr; Málek, Jiří; Brokešová, J.

    2011-01-01

    Roč. 15, č. 1 (2011), s. 81-104 ISSN 1383-4649 R&D Projects: GA AV ČR IAA300460602; GA AV ČR IAA300460705; GA ČR(CZ) GA205/06/1780 Institutional research plan: CEZ:AV0Z30460519 Keywords : love waves * phase velocity dispersion * frequency-time analysis Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.326, year: 2011 www.springerlink.com/content/w3149233l60111t1/

  10. Response of Velocity Anisotropy of Shale Under Isotropic and Anisotropic Stress Fields

    Science.gov (United States)

    Li, Xiaying; Lei, Xinglin; Li, Qi

    2018-03-01

    We investigated the responses of P-wave velocity and associated anisotropy in terms of Thomsen's parameters to isotropic and anisotropic stress fields on Longmaxi shales cored along different directions. An array of piezoelectric ceramic transducers allows us to measure P-wave velocities along numerous different propagation directions. Anisotropic parameters, including the P-wave velocity α along a symmetry axis, Thomsen's parameters ɛ and δ, and the orientation of the symmetry axis, could then be extracted by fitting Thomsen's weak anisotropy model to the experimental data. The results indicate that Longmaxi shale displays weakly intrinsic velocity anisotropy with Thomsen's parameters ɛ and δ being approximately 0.05 and 0.15, respectively. The isotropic stress field has only a slight effect on velocity and associated anisotropy in terms of Thomsen's parameters. In contrast, both the magnitude and orientation of the anisotropic stress field with respect to the shale fabric are important in controlling the evolution of velocity and associated anisotropy in a changing stress field. For shale with bedding-parallel loading, velocity anisotropy is enhanced because velocities with smaller angles relative to the maximum stress increase significantly during the entire loading process, whereas those with larger angles increase slightly before the yield stress and afterwards decrease with the increasing differential stress. For shale with bedding-normal loading, anisotropy reversal is observed, and the anisotropy is progressively modified by the applied differential stress. Before reaching the yield stress, velocities with smaller angles relative to the maximum stress increase more significantly and even exceed the level of those with larger angles. After reaching the yield stress, velocities with larger angles decrease more significantly. Microstructural features such as the closure and generation of microcracks can explain the modification of the velocity anisotropy

  11. Gas Transfer Velocity in the Presence of Wave Breaking

    Science.gov (United States)

    Li, S.

    2016-02-01

    Wave breaking is known to intensify the gas exchange across the air-sea interface through air entrainment and enhancement of the near-surface turbulence. We proposed a composite model for the gas transfer velocity by examining the near-surface turbulence induced by wave breaking, which was determined based on the combination of the vertical distribution of the turbulence in the wave-affected layer and the breaking wave energy dissipation rate in the wave-breaking layer. The gas transfer velocity was calculated as a function of the air frictional velocity, wave age, and whitecap coverage. The model was validated for both the wind and wave-age dependence against field and laboratory measurements. The results supported the hypothesis that the large uncertainties in the traditional wind speed-based gas transfer velocities at moderate to high wind speeds can be ascribed to the neglect of the wind-wave effect, which is mainly attributed to the whitecap coverage as a function of the wind-wave Reynolds number.

  12. Estimating propagation velocity through a surface acoustic wave sensor

    Science.gov (United States)

    Xu, Wenyuan; Huizinga, John S.

    2010-03-16

    Techniques are described for estimating the propagation velocity through a surface acoustic wave sensor. In particular, techniques which measure and exploit a proper segment of phase frequency response of the surface acoustic wave sensor are described for use as a basis of bacterial detection by the sensor. As described, use of velocity estimation based on a proper segment of phase frequency response has advantages over conventional techniques that use phase shift as the basis for detection.

  13. Relationship between ultrasonic Rayleigh waves and surface residual stress

    International Nuclear Information System (INIS)

    Adler, L.; Cook, K.V.; Dewey, B.R.; King, R.T.

    1977-01-01

    Local variations of Rayleigh (surface) circumferential ultrasonic wave velocity near a pipe-girth weld in large-diameter thin-wall type 316H stainless steel pipe were measured. The weldment was similar to those anticipated for the Liquid Metal Fast Breeder Reactor (LMFBR) piping systems. The residual stress distribution was estimated independently from shell theory for an elastic, infinite, thin shell with circumferential line loading. An upper bound on the magnitude of the residual stresses was estimated assuming the deformation of the shell was entirely elastic. The pattern of surface wave velocity variations matches the theoretical residual stress pattern closely. It is suggested that the monitoring of surface wave velocity variations might be used for characterizing residual stress patterns near critical welds in piping, aiding in design calculations, and for in-service monitoring of the state of stress of weldments

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

    African Journals Online (AJOL)

    Phase velocity and attenuation of plane waves in dissipative elastic media: Solving complex transcendental equation using functional iteration method. ... a solution at all. Then the absence of solution implies that the mathematical model used does not represent the propagation of defined wave in the medium considered.

  15. Lithology and shear-wave velocity in Memphis, Tennessee

    Science.gov (United States)

    Gomberg, J.; Waldron, B.; Schweig, E.; Hwang, H.; Webbers, A.; Van Arsdale, R.; Tucker, K.; Williams, R.; Street, R.; Mayne, P.; Stephenson, W.; Odum, J.; Cramer, C.; Updike, R.; Hutson, S.; Bradley, M.

    2003-01-01

    We have derived a new three-dimensional model of the lithologic structure beneath the city of Memphis, Tennessee, and examined its correlation with measured shear-wave velocity profiles. The correlation is sufficiently high that the better-constrained lithologic model may be used as a proxy for shear-wave velocities, which are required to calculate site-amplification for new seismic hazard maps for Memphis. The lithologic model and its uncertainties are derived from over 1200 newly compiled well and boring logs, some sampling to 500 m depth, and a moving-least-squares algorithm. Seventy-six new shear-wave velocity profiles have been measured and used for this study, most sampling to 30 m depth or less. All log and velocity observations are publicly available via new web sites.

  16. Reflection of plane waves in an initially stressed perfectly ...

    Indian Academy of Sciences (India)

    Reflection of plane waves is studied at a free surface of a perfectly conducting transversely isotropic elastic solid half-space with initial stress. The governing equations are solved to obtain the velocity equation which indicates the existence of two quasi planar waves in the medium. Reflection coefficients and energy.

  17. Reflection of plane waves in an initially stressed perfectly ...

    Indian Academy of Sciences (India)

    Reflection of plane waves is studied at a free surface of a perfectly conducting transversely isotropic elastic solid half-space with initial stress. The governing equations are solved to obtain the velocity equation which indicates the existence of two quasi planar waves in the medium. Reflection coefficients and energy ratios ...

  18. 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.

  19. Surface wave phase velocities between Bulgaria and the Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Gaždová, Renata; Kolínský, Petr; Popova, I.; Dimitrova, L.

    2011-01-01

    Roč. 18, č. 2 (2011), s. 16-23 ISSN 1803-1447. [OVA´11 – New Knowledge and Measurements in Seismology, Engineering Geophysics and Geotechnics. Ostrava, 12.04.2011-14.04.2011] R&D Projects: GA ČR GA205/09/1244 Institutional research plan: CEZ:AV0Z30460519 Keywords : surface waves * phase velocity * shear wave velocity Subject RIV: DC - Siesmology, Volcanology, Earth Structure http://www.caag.cz/egrse/2011-2/03%20gazdova_ova.pdf

  20. 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...

  1. Study on Rayleigh Wave Inversion for Estimating Shear-wave Velocity Profile

    Directory of Open Access Journals (Sweden)

    T.A. Sanny

    2003-05-01

    Full Text Available Rayleigh wave or ground roll is a noise in seismic body waves. However, how to use this noise for soil characterization is very interesting since Rayleigh wave phase velocity is a function of compression-wave velocity, shear-wave velocity, density and layer thickness. In layered-medium Rayleigh wave velocity also depends on wavelength or frequency, and this phenomenon is called dispersion. Inversion procedure to get shear-wave velocity profile needs a priori information about the solution of the problem to limit the unknown parameters. The Lagrange multiplier method was used to solve the constrained optimization problems or well known as a smoothing parameter in inversion problems. The advantage of our inversion procedure is that it can guarantee the convergence of solution even though the field data is incomplete, insufficient, and inconsistent. The addition of smoothing parameter can reduce the time to converge. Beside numerical stability, the statistical stability is also involved in inversion procedure. In field experiment we extracted ground roll data from seismic refraction record. The dispersion curves had been constructed by applying f-k analysis and f-k dip filtering. The dispersion curves show the dependence of Rayleigh wave phase velocities in layered media to frequency. The synthetic models also demonstrate the stability and the speed of inversion procedure.

  2. Analysis of sediment particle velocity in wave motion based on wave flume experiments

    Science.gov (United States)

    Krupiński, Adam

    2012-10-01

    The experiment described was one of the elements of research into sediment transport conducted by the Division of Geotechnics of West-Pomeranian University of Technology. The experimental analyses were performed within the framework of the project "Building a knowledge transfer network on the directions and perspectives of developing wave laboratory and in situ research using innovative research equipment" launched by the Institute of Hydroengineering of the Polish Academy of Sciences in Gdańsk. The objective of the experiment was to determine relations between sediment transport and wave motion parameters and then use the obtained results to modify formulas defining sediment transport in rivers, like Ackers-White formula, by introducing basic parameters of wave motion as the force generating bed material transport. The article presents selected results of the experiment concerning sediment velocity field analysis conducted for different parameters of wave motion. The velocity vectors of particles suspended in water were measured with a Particle Image Velocimetry (PIV) apparatus registering suspended particles in a measurement flume by producing a series of laser pulses and analysing their displacement with a high-sensitivity camera connected to a computer. The article presents velocity fields of suspended bed material particles measured in the longitudinal section of the wave flume and their comparison with water velocity profiles calculated for the definite wave parameters. The results presented will be used in further research for relating parameters essential for the description of monochromatic wave motion to basic sediment transport parameters and "transforming" mean velocity and dynamic velocity in steady motion to mean wave front velocity and dynamic velocity in wave motion for a single wave.

  3. 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.

  4. Model basin, measurement of particle velocities in wave crests

    Energy Technology Data Exchange (ETDEWEB)

    1989-11-15

    A model set-up, which makes it possible to measure water particle velocities in wave crests, has been developed and tested. The technique includes a tri-axial ultrasonic current probe mounted on a movable frame which is moved vertically by a hydraulic piston thus following the oscillating water surface. Recording is hereby done at a constant depth beneath the water surface and the velocity profiles are found by interpolation/extrapolation between the recordings taken in different levels at a given time during the wave time series. The set-up has been successfully used for measurements indeep-water regular and irregular seastates. Detailed analysis and comparison with various theoretical descriptions of wave kinematics has been performed. Furthermore, the set-up has been used for measurements in freak waves reproduced at a limited waterdepth. The analysis and comparisons with theoretical predictions have shed new light on the freak wave phenomenon. Some disturbance into the area of measurements is introduced by the ultrasonic proble. For the maximum values of particle velocities (under a crest or a trough), this disturbance is minimal as the particles move in practically horizontal directons. (BN).

  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. 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.

  7. 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.

  8. 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.

  9. Wave-equation migration velocity inversion using passive seismic sources

    Science.gov (United States)

    Witten, B.; Shragge, J. C.

    2015-12-01

    Seismic monitoring at injection sites (e.g., CO2 sequestration, waste water disposal, hydraulic fracturing) has become an increasingly important tool for hazard identification and avoidance. The information obtained from this data is often limited to seismic event properties (e.g., location, approximate time, moment tensor), the accuracy of which greatly depends on the estimated elastic velocity models. However, creating accurate velocity models from passive array data remains a challenging problem. Common techniques rely on picking arrivals or matching waveforms requiring high signal-to-noise data that is often not available for the magnitude earthquakes observed over injection sites. We present a new method for obtaining elastic velocity information from earthquakes though full-wavefield wave-equation imaging and adjoint-state tomography. The technique exploits the fact that the P- and S-wave arrivals originate at the same time and location in the subsurface. We generate image volumes by back-propagating P- and S-wave data through initial Earth models and then applying a correlation-based extended-imaging condition. Energy focusing away from zero lag in the extended image volume is used as a (penalized) residual in an adjoint-state tomography scheme to update the P- and S-wave velocity models. We use an acousto-elastic approximation to greatly reduce the computational cost. Because the method requires neither an initial source location or origin time estimate nor picking of arrivals, it is suitable for low signal-to-noise datasets, such as microseismic data. Synthetic results show that with a realistic distribution of microseismic sources, P- and S-velocity perturbations can be recovered. Although demonstrated at an oil and gas reservoir scale, the technique can be applied to problems of all scales from geologic core samples to global seismology.

  10. 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...

  11. Ionization waves of arbitrary velocity driven by a flying focus

    Science.gov (United States)

    Palastro, J. P.; Turnbull, D.; Bahk, S.-W.; Follett, R. K.; Shaw, J. L.; Haberberger, D.; Bromage, J.; Froula, D. H.

    2018-03-01

    A chirped laser pulse focused by a chromatic lens exhibits a dynamic, or flying, focus in which the trajectory of the peak intensity decouples from the group velocity. In a medium, the flying focus can trigger an ionization front that follows this trajectory. By adjusting the chirp, the ionization front can be made to travel at an arbitrary velocity along the optical axis. We present analytical calculations and simulations describing the propagation of the flying focus pulse, the self-similar form of its intensity profile, and ionization wave formation. The ability to control the speed of the ionization wave and, in conjunction, mitigate plasma refraction has the potential to advance several laser-based applications, including Raman amplification, photon acceleration, high-order-harmonic generation, and THz generation.

  12. 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.

  13. Allowable Pressure In Soils and Rocks by Seismic Wave Velocities

    International Nuclear Information System (INIS)

    Tezcan, S.; Keceli, A.; Oezdemir, Z.

    2007-01-01

    Firstly, the historical background is presented for the determination of ultimate bearing capacity of shallow foundations. The principles of plastic equilibrium used in the classical formulation of the ultimate bearing capacity are reviewed, followed by a discussion about the sources of approximations inherent in the classical theory. Secondly, based on a variety of case histories of site investigations, including extensive bore hole data, laboratory testing and geophysical prospecting, an empirical formulation is proposed for the determination of allowable bearing capacity of shallow foundations. The proposed expression corroborates consistently with the results of the classical theory and is proven to be reliable and safe, also from the view point of maximum allowable settlements. It consists of only two soil parameters, namely, the Institut measured shear wave velocity, and the unit weight. The unit weight may be also determined with sufficient accuracy, by means of another empirical expression, using the P-wave velocity. It is indicated that once the shear and P-wave velocities are measured Institut by an appropriate geophysical survey, the allowable bearing capacity is determined reliably through a single step operation. Such an approach, is considerably cost and time-saving, in practice

  14. Velocity profiles and surface roughness under breaking waves

    Science.gov (United States)

    Craig, Peter D.

    1996-01-01

    Recent measurements under wave-breaking conditions in the ocean, lakes, and tanks reveal a layer immediately below the surface in which dissipation decays as depth to the power -2 to -4 and downwind velocities are approximately linear with depth. This behavior is consistent with predictions of a conventional, one-dimensional, level 2.5 turbulence closure model, in which the influence of breaking waves is parameterized as a surface source of turbulent kinetic energy. The model provides an analytic solution which describes the near-surface power law behavior and the deeper transition to the "law of the wall." The mixing length imposed in the model increases linearly away from a minimum value, the roughness length, at the surface. The surface roughness emerges as an important scaling factor in the wave-enhanced layer but is the major unknown in the formulation. Measurements in the wave-affected layer are still rare, but one exceptional set, both in terms of its accuracy and proximity to the surface, is that collected by Cheung and Street [1988] in the Stanford wind tunnel. Their velocity profiles first confirm the accuracy of the model, and, second, allow estimation, via a best fit procedure, of roughness lengths at five different wind speeds. Conclusions are tentative but indicate that the roughness length increases with wind speed and appears to take a value of approximately one sixth the dominant surface wavelength. A more traditional wall-layer model, which ignores the flux of turbulent kinetic energy, will also accurately reproduce the measured velocity profiles. In this case, enhanced surface turbulence is forced on the model by the assumption of a large surface roughness, three times that required by the full model. However, the wall-layer model cannot predict the enhanced dissipation near the surface.

  15. Feasibility of Residual Stress Nondestructive Estimation Using the Nonlinear Property of Critical Refraction Longitudinal Wave

    Directory of Open Access Journals (Sweden)

    Yu-Hua Zhang

    2017-01-01

    Full Text Available Residual stress has significant influence on the performance of mechanical components, and the nondestructive estimation of residual stress is always a difficult problem. This study applies the relative nonlinear coefficient of critical refraction longitudinal (LCR wave to nondestructively characterize the stress state of materials; the feasibility of residual stress estimation using the nonlinear property of LCR wave is verified. The nonlinear ultrasonic measurements based on LCR wave are conducted on components with known stress state to calculate the relative nonlinear coefficient. Experimental results indicate that the relative nonlinear coefficient monotonically increases with prestress and the increment of relative nonlinear coefficient is about 80%, while the wave velocity only decreases about 0.2%. The sensitivity of the relative nonlinear coefficient for stress is much higher than wave velocity. Furthermore, the dependence between the relative nonlinear coefficient and deformation state of components is found. The stress detection resolution based on the nonlinear property of LCR wave is 10 MPa, which has higher resolution than wave velocity. These results demonstrate that the nonlinear property of LCR wave is more suitable for stress characterization than wave velocity, and this quantitative information could be used for residual stress estimation.

  16. 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

  17. 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

  18. 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

  19. High resolution 3-D shear wave velocity structure in South China from surface wave tomography

    Science.gov (United States)

    Ning, S.; Guo, Z.; Chen, Y. J.

    2017-12-01

    Using continuous data from a total of 638 seismic stations, including 484 from CEArray between 2008 and 2013 and 154 from SINOPROBE between 2014 and 2015, we perform both ambient noise and earthquake Rayleigh wave tomography across South China. Combining Rayleigh wave phase velocity between 6and 40s periods from ambient noise tomography and Rayleigh wave phase velocity between 20and 140s from teleseismic two-plane-wave tomography, we obtain phase velocity maps between 6 and140 s periods. We then invert Rayleigh wave phase velocity to construct a 3-D shear wave velocity structure of South China by Markov Chain Monte Carlo method. Similar to other inversion results, our results correspond topography well. Moreover, our results also reveal that velocity structure of the eastern South China in mantle depth is similar to eastern North China, the core of the western South China, Sichuan Block (SB),still exists thick lithosphere. However, owing to much more data employed and some data quality control techniques in this research, our results reveal more detailed structures. Along Qinling-Dabie Orogenic Belt (QDOB), North-South Gravity Lineament (NSGL) and the Sichuan-Yunnan Rhombic Block (SYRB), there are obvious high speed anomalies in depths of 10-20 km, which possibly imply ancient intrusions. Moreover, it seems that Tancheng-Lujiang Fault Zone (TLFZ) has already cut through QDOB, forming a deep fracture cutting through the crust of the whole China continent. Although SB still exists thick lithosphere, there are indications for thermal erosion. At the same time, the lithosphere of the central SYRB seems to be experiencing delamination process, obviously forming a barrier to prevent the hot Tibetan Plateau (TP) mantle material from flowing further southeast. Upwelling hot mantle material possibly triggered by this delamination process might be the cause of the Emeishan Large Igneous Province. There exists an intercontinental low velocity layer in the crust of the TP

  20. Determinants of brachial-ankle pulse wave velocity and carotid-femoral pulse wave velocity in healthy Koreans.

    Science.gov (United States)

    Jang, Shin Yi; Ju, Eun Young; Huh, Eun Hee; Kim, Jung Hyun; Kim, Duk-Kyung

    2014-06-01

    The aim of this study was to determine the normal value of brachial-ankle pulse wave velocity (baPWV) and carotid-femoral pulse wave velocity (cfPWV) according to age group, gender, and the presence of cardiovascular risk factors in healthy Koreans, and to investigate the association between PWV and risk factors such as prehypertension, dyslipidemia, smoking, and obesity. We measured an arterial stiffness in 110 normal subjects who were 20 to 69 yr-old with no evidence of cardiovascular disease, cerebrovascular accident or diabetes mellitus. The mean values of baPWV and cfPWV were 12.6 (± 2.27) m/sec (13.1 ± 1.85 in men, 12.1 ± 2.51 in women; P=0.019) and 8.70 (± 1.99) m/sec (9.34 ± 2.13 in men, 8.15 ± 1.69 in women; P=0.001), respectively. The distribution of baPWV (Pgender showed an increase in the mean value with age. Men had higher baPWV and cfPWV than women (Pdifference in baPWV and cfPWV by age group on prehypertension, dyslipidemia, current smoking, or obesity (Pgender, and prehypertension in healthy Koreans.

  1. Estimated carotid-femoral pulse wave velocity has similar predictive value as measured carotid-femoral pulse wave velocity

    DEFF Research Database (Denmark)

    Greve, Sara V; Blicher, Marie K; Kruger, Ruan

    2016-01-01

    BACKGROUND: Carotid-femoral pulse wave velocity (cfPWV) adds significantly to traditional cardiovascular risk prediction, but is not widely available. Therefore, it would be helpful if cfPWV could be replaced by an estimated carotid-femoral pulse wave velocity (ePWV) using age and mean blood...... pressure, and previously published equations. The aim of this study was to investigate whether ePWV could predict cardiovascular events independently of traditional cardiovascular risk factors and/or cfPWV. METHOD: cfPWV was measured and ePWV was calculated in 2366 patients from four age groups...... healthy patients, ePWV and cfPWV (per SD) added independently to SCORE in prediction of combined endpoint [hazard ratio (95%CI) = 1.38(1.09-1.76) and hazard ratio (95%CI) = 1.18(1.01-1.38)] and to FRS [hazard ratio (95%CI) = 1.33(1.06-1.66) and hazard ratio (95%CI) = 1.16(0.99-1.37)]. If healthy patients...

  2. Estimated carotid-femoral pulse wave velocity has similar predictive value as measured carotid-femoral pulse wave velocity

    DEFF Research Database (Denmark)

    Olsen, Michael; Greve, Sara; Blicher, Marie

    2016-01-01

    OBJECTIVE: Carotid-femoral pulse wave velocity (cfPWV) adds significantly to traditional cardiovascular (CV) risk prediction, but is not widely available. Therefore, it would be helpful if cfPWV could be replaced by an estimated carotid-femoral pulse wave velocity (ePWV) using age and mean blood...... pressure and previously published equations. The aim of this study was to investigate whether ePWV could predict CV events independently of traditional cardiovascular risk factors and/or cfPWV. DESIGN AND METHOD: cfPWV was measured and ePWV calculated in 2366 apparently healthy subjects from four age......, ePVW and cfPWV (per standard deviation) added independently to SCORE in prediction of CEP (HR [95% CI] = 1.38[1.09-1.76] and HR [95% CI] = 1.18[1.01-1.38]) and to FRS (HR [95% CI] = 1.33[1.06-1.66] and HR [95% CI] = 1.16[0.99-1.37]). If healthy subjects with ePWV and/or cfPWV ≥ 10 m/s were...

  3. Recovery of Stokes waves from velocity measurements on an axis of symmetry

    International Nuclear Information System (INIS)

    Matioc, Bogdan-Vasile

    2015-01-01

    We provide a new method to recover the profile of Stokes waves, and more generally of waves with smooth vorticity, from measurements of the horizontal velocity component on a vertical axis of symmetry of the wave surface. Although we consider periodic waves only, the extension to solitary waves is straightforward. (paper)

  4. 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.

  5. 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.

  6. 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 levels were measured using capacitive waves gauges, while the instantaneous velocity flow fields were measured using video techniques together with digital correlation techniques. The instantaneous velocity flow fields were further analyzed to yield...

  7. The Western Bohemia Uppermost Crust Shear Wave Velocities from Love Wave Dispersion

    Czech Academy of Sciences Publication Activity Database

    Kolínský, Petr; Brokešová, Johana

    -, č. 11 (2007), s. 101-120 ISSN 1383-4649 R&D Projects: GA AV ČR IAA300460602; GA ČR(CZ) GA205/06/1780 Institutional research plan: CEZ:AV0Z30460519 Keywords : frequency–time analysis * group velocity * Love wave dispersion Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.769, year: 2007

  8. 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

  9. Friction velocity estimation using Reynolds shear stress profile data

    Science.gov (United States)

    Volino, Ralph; Schultz, Michael

    2017-11-01

    A method for using profiles of the mean streamwise velocity and the Reynolds shear stress to estimate the friction velocity, uτ, is presented. The Reynolds averaged two-dimensional streamwise momentum equation is solved for the Reynolds shear stress term. The remaining terms in the equation are separated into those which depend on the local gradient of the mean streamwise velocity profile and those which do not. Using only the terms retained with the Couette flow assumption, the Reynolds shear stress profile can be matched in the inner 10 percent of the boundary layer with the appropriate choice of uτ. Including the other terms which do not depend on the streamwise velocity profile gradient, the fit can be extended to the inner 30 percent of the boundary layer. Using all terms the full Reynolds shear stress profile can be fit. The method is verified using laminar solutions for zero and non-zero pressure gradient boundary layers, and with ZPG turbulent DNS results. It is then applied to zero, favorable and adverse pressure gradient experimental data from smooth and rough walls. Results obtained for local friction velocities agree well with those obtained by other techniques. The method may prove useful when other methods are not practical or fully appropriate. Sponsored by the Office of Naval Research.

  10. 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

    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...

  11. 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.

  12. Hammering Yucca Flat, Part One: P-Wave Velocity

    Science.gov (United States)

    Tang, D. G.; Abbott, R. E.; Preston, L. A.; Hampshire, J. B., II

    2015-12-01

    Explosion-source phenomenology is best studied when competing signals (such as instrument, site, and propagation effects), are well understood. The second phase of the Source Physics Experiments (SPE), is moving from granite geology to alluvium geology at Yucca Flat, Nevada National Security Site. To improve subsurface characterization of Yucca Flat (and therefore better understand propagation and site effects), an active-source seismic survey was conducted using a novel 13,000-kg impulsive hammer source. The source points, spaced 200 m apart, covered a N-S transect spanning 18 km. Three component, 2-Hz geophones were used to record useable signals out to 10 km. We inverted for P-wave velocity by computing travel times using a finite-difference 3D eikonal solver, and then compared that to the picked travel times using a linearized iterative inversion scheme. Preliminary results from traditional reflection processing methods are also presented. 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.

  13. Upper-Mantle Shear Velocities beneath Southern California Determined from Long-Period Surface Waves

    OpenAIRE

    Polet, J.; Kanamori, H.

    1997-01-01

    We used long-period surface waves from teleseismic earthquakes recorded by the TERRAscope network to determine phase velocity dispersion of Rayleigh waves up to periods of about 170 sec and of Love waves up to about 150 sec. This enabled us to investigate the upper-mantle velocity structure beneath southern California to a depth of about 250 km. Ten and five earthquakes were used for Rayleigh and Love waves, respectively. The observed surface-wave dispersion shows a clear Love/Rayleigh-wave d...

  14. 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, predict...

  15. Stress wave propagation on standing trees. Part 2, Formation of 3D stress wave contour maps.

    Science.gov (United States)

    Juan Su; Houjiang Zhang; Xiping Wang

    2009-01-01

    Nondestructive evaluation (NDE) of wood quality in standing trees is an important procedure in the forest operational value chain worldwide. The goal of this paper is to investigate how a stress wave travel in a tree stem as it is introduced into the tree through a mechanical impact. Experimental stress wave data was obtained on freshly cut red pine logs in the...

  16. S-wave velocity structures of the Taipei Basin, Taiwan, using microtremor array measurements

    Science.gov (United States)

    Huang, Huey-Chu; Wu, Cheng-Feng; Lee, Feng-Mei; Hwang, Ruey-Der

    2015-04-01

    The S-wave velocity structures of the Taipei Basin in Taiwan are investigated using the array records of microtremors at 15 sites. Dispersion curves at these sites are calculated using the frequency-wavenumber (F-K) spectrum method. The S-wave velocity structures in the Taipei Basin are then estimated by employing surface wave inversion technique. Harder strata sites have higher phase velocities than softer sites. If the S-wave velocity of the Tertiary Basement is assumed to be 1000 m/s, then the Quaternary alluvial thicknesses in the Taipei Basin are between about 100 m and 650 m. The thickness of the alluvium gradually increases from the southeast to the northwest. The inversion results are also in good agreement with well-logging data and seismic reflection studies of the Taipei Basin. The study concludes that microtremor array measurement is a useful tool for estimating S-wave velocity structure.

  17. Magneto-thermo-visco-elastic waves in an initially stressed conducting layer

    International Nuclear Information System (INIS)

    Rakshit, Amit Kumar; Sengupta, P.R.

    1998-01-01

    The aim of this paper is to investigate magneto-thermo-visco-elastic surface waves in electrically and thermally conducting layers involving time rates of strain and stress of order n, the media being under an initial stress in the nature of hydrostatic tension or compression. The theory of magneto-thermo-visco-elastic surface waves in the conducting medium involving strain rate and stress rate of nth order is derived under initial stress. This theory is then employed to obtain wave velocity equations in specific cases. Results obtained in the above cases reduce to well-known classical results when additional fields are absent. (author)

  18. S-wave velocity measurements along levees in New Orleans using passive surface wave methods

    Science.gov (United States)

    Hayashi, K.; Lorenzo, J. M.; Craig, M. S.; Gostic, A.

    2017-12-01

    In order to develop non-invasive methods for levee inspection, geophysical investigations were carried out at four sites along levees in the New Orleans area: 17th Street Canal, London Avenue Canal, Marrero Levee, and Industrial Canal. Three of the four sites sustained damage from Hurricane Katrina in 2005 and have since been rebuilt. The geophysical methods used include active and passive surface wave methods, and capacitively coupled resistivity. This paper summarizes the acquisition and analysis of the 1D and 2D passive surface wave data. Twelve wireless seismic data acquisition units with 2 Hz vertical component geophones were used to record data. Each unit includes a GPS receiver so that all units can be synchronized over any distance without cables. The 1D passive method used L shaped arrays of three different sizes with geophone spacing ranging from 5 to 340 m. Ten minutes to one hour of ambient noise was recorded with each array, and total data acquisition took approximately two hours at each site. The 2D method used a linear array with a geophone spacing of 5m. Four geophones were moved forward every 10 minutes along 400 1000 m length lines. Data acquisition took several hours for each line. Recorded ambient noise was processed using the spatial autocorrelation method and clear dispersion curves were obtained at all sites (Figure 1a). Minimum frequencies ranged from 0.4 to 0.7 Hz and maximum frequencies ranged from 10 to 30 Hz depending on the site. Non-linear inversion was performed and 1D and 2D S-wave velocity models were obtained. The 1D method penetrated to depths ranging from 200 to 500 m depending on the site (Figure 1b). The 2D method penetrated to a depth of 40 60 m and provided 400 1000 m cross sections along the levees (Figure 2). The interpretation focused on identifying zones beneath the levees or canal walls having low S-wave velocities corresponding to saturated, unconsolidated sands, or low-rigidity clays. Resultant S-wave velocity profiles

  19. Velocity dispersion of guided waves propagating in a free gradient elastic plate: application to cortical bone.

    Science.gov (United States)

    Vavva, Maria G; Protopappas, Vasilios C; Gergidis, Leonidas N; Charalambopoulos, Antonios; Fotiadis, Dimitrios I; Polyzos, Demosthenes

    2009-05-01

    The classical linear theory of elasticity has been largely used for the ultrasonic characterization of bone. However, linear elasticity cannot adequately describe the mechanical behavior of materials with microstructure in which the stress state has to be defined in a non-local manner. In this study, the simplest form of gradient theory (Mindlin Form-II) is used to theoretically determine the velocity dispersion curves of guided modes propagating in isotropic bone-mimicking plates. Two additional terms are included in the constitutive equations representing the characteristic length in bone: (a) the gradient coefficient g, introduced in the strain energy, and (b) the micro-inertia term h, in the kinetic energy. The plate was assumed free of stresses and of double stresses. Two cases were studied for the characteristic length: h=10(-4) m and h=10(-5) m. For each case, three subcases for g were assumed, namely, g>h, gguided waves were numerically obtained and compared with the Lamb modes. The results indicate that when g was not equal to h (i.e., g not equal h), microstructure affects mode dispersion by inducing both material and geometrical dispersion. In conclusion, gradient elasticity can provide supplementary information to better understand guided waves in bones.

  20. Daily dialysis reduces pulse wave velocity in chronic hemodialysis patients.

    Science.gov (United States)

    Di Micco, Lucia; Torraca, Serena; Sirico, Maria Luisa; Tartaglia, Domenico; Di Iorio, Biagio

    2012-05-01

    Pulse wave velocity (PWV) is a predictor of morbidity and mortality in patients with end-stage renal disease (ESRD). Dialysis patients show cyclic changes in PWV related to their hydration status and blood pressure. Our aim is to assess the impact of daily dialysis on PWV. We performed a randomized crossover study of 60 patients who underwent standard hemodialysis (HD) three times per week for at least 6 months. Patients were classified into three groups according to their PWV values before (pre-) and after (post-) HD, with a cutoff value of 12 m s(-1), as follows: the low-low (LL) group had normal pre-HD and post-HD PWV; the high-low (HL) group had high pre-HD PWV and normal post-HD PWV; and the high-high (HH) group had high pre- and post-HD PWV. All patients continued standard HD for 2 weeks. A total of 10 patients from each group were randomly assigned to continue standard HD for 1 week and then underwent daily dialysis for 1 week. The remaining 10 patients underwent daily dialysis for 1 week and then underwent standard HD for 1 week. PWV values were measured before and 1 h after each dialysis session. With daily dialysis treatment, 2 of 20 patients (10%) moved from the PWV-HH group to the PWV-HL group, whereas 18 of 20 patients (90%) moved from the PWV-HL group to the PWV-LL group (P = 0.030). Daily dialysis reduces PWV in the ESRD patients. As PWV is a strong predictor of mortality in ESRD and has cyclic variations in patients who are on standard HD, we believe that daily dialysis may be used in patients with high PWV levels to reduce their mortality risk.

  1. Mass sensitivity of acoustic wave devices from group and phase velocity measurements

    Science.gov (United States)

    McHale, G.; Martin, F.; Newton, M. I.

    2002-09-01

    The effect of dispersion on acoustic wave sensors is considered. The discussion is focused upon layer guided surface acoustic waves (Love waves), which obtain their high mass sensitivity for the first Love wave mode by optimizing the guiding layer thickness, d, such that dapprox][lambdal/4; the wavelength in the layer is given by lambdal=f/vl where f is the operating frequency and vl is the shear acoustic speed of the guiding layer. We show that this optimization of guiding layer thickness corresponds to strong dispersion so that the phase and group velocities can be quite different. From the definition of the phase velocity mass sensitivity, we show that it can be determined from either the slope of the curve of phase velocity with normalized guiding layer thickness, z=d/lambdal, or from the phase and group velocities measured for a given guiding layer thickness. Experimental data for a poly(methylmethacrylate) polymer guiding layer on 36deg XY Lithium Tantalate is presented. Measurements of phase velocity and group velocity determined by a network analyzer were obtained for systematically increasing guiding layer thicknesses; a pulse transit experiment was also used to provide independent confirmation of the group velocity data. Two independent estimates of the mass sensitivity are obtained for z=d/lambdal<0.22 from (i) the slope of the phase velocity curve and (ii) the measurements of the group and phase velocity. These two estimates are shown to be consistent and we, therefore, conclude that it is possible to determine the mass sensitivity for a Love wave device with a given guiding layer thickness from measurements of the phase and group velocities. Moreover, we argue that the formula using group velocity to determine phase velocity mass sensitivity can be extended to a wide range of other acoustic wave sensors. In addition, we suggest that variations in the group velocity due to deposited mass may be a more sensitive parameter than variations in the phase

  2. Characterization of Residual Stress in Shot Peened Al 7075 Alloy Using Surface Acoustic Wave

    International Nuclear Information System (INIS)

    Kim, Chung Seok; Kwun, Sook In; Kim, Yong Kwon; Park, Ik Keun

    2006-01-01

    The residual stress in shot-peened Al 7075 alloy was evaluated using surface acoustic wave (SAW). Shot peening was conducted to produce a variation in the residual stress with the depth below the surface under a shot velocity of 30 m/s. The SAW velocity was measured from the V(z) curve using a scanning acoustic microscopy (SAM). The Vickers hardness profile from the surface showed a significant work hardening near the surface layer with a thickness of about 0.25 mm. As the residual stress became more compressive, the SAW velocity increased, whereas as the residual stress became more tensile, the SAW velocity decreased. The variation in the SAW velocity through the shot peened surface layer was in good agreement with the distribution of the residual stress measured by X-ray diffraction technique

  3. Stress wave analysis: applied to rotating machines; Stress wave analysis: aplicado a maquinas rotativas

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Paulo Garcia de [Invensys Brasil Ltda., Sao Paulo, SP (Brazil)

    2009-11-01

    Stress wave analysis is the technology of data analysis (stress profile - ultrasound spectrum) collected by high-frequency acoustic sensors. Monitoring and analysis of rotating equipment, is a crucial element in predictive maintenance and condition based maintenance projects and, in a broader context, of performance management and optimization of assets. This article discusses the application of stress wave analysis to rotating machines in the context of assets optimization and CBM. (author)

  4. Wave-induced stress and breaking of sea ice in a coupled hydrodynamic discrete-element wave-ice model

    Science.gov (United States)

    Herman, Agnieszka

    2017-11-01

    In this paper, a coupled sea ice-wave model is developed and used to analyze wave-induced stress and breaking in sea ice for a range of wave and ice conditions. The sea ice module is a discrete-element bonded-particle model, in which ice is represented as cuboid grains floating on the water surface that can be connected to their neighbors by elastic joints. The joints may break if instantaneous stresses acting on them exceed their strength. The wave module is based on an open-source version of the Non-Hydrostatic WAVE model (NHWAVE). The two modules are coupled with proper boundary conditions for pressure and velocity, exchanged at every wave model time step. In the present version, the model operates in two dimensions (one vertical and one horizontal) and is suitable for simulating compact ice in which heave and pitch motion dominates over surge. In a series of simulations with varying sea ice properties and incoming wavelength it is shown that wave-induced stress reaches maximum values at a certain distance from the ice edge. The value of maximum stress depends on both ice properties and characteristics of incoming waves, but, crucially for ice breaking, the location at which the maximum occurs does not change with the incoming wavelength. Consequently, both regular and random (Jonswap spectrum) waves break the ice into floes with almost identical sizes. The width of the zone of broken ice depends on ice strength and wave attenuation rates in the ice.

  5. Disturbance of SH-type waves due to moving stress discontinuity in ...

    Indian Academy of Sciences (India)

    The disturbance and propagation of SH-type waves in an anisotropic soil layer overlying an inhomogeneous elastic half-space by a moving stress discontinuity is considered. Stress discontinuity moves with non-uniform velocity and is impulsive in nature. The displacements are obtained in exact form by themethod due to ...

  6. Disturbance of SH-type waves due to moving stress discontinuity in ...

    Indian Academy of Sciences (India)

    Abstract. The disturbance and propagation of SH-type waves in an anisotropic soil layer overlying an inhomogeneous elastic half-space by a moving stress discontinuity is considered. Stress discontinuity moves with non-uniform velocity and is impulsive in nature. The displacements are obtained in exact form by the method ...

  7. 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.

  8. 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

  9. Numerical simulation of stress wave propagation from underground nuclear explosions

    International Nuclear Information System (INIS)

    Cherry, J.T.; Petersen, F.L.

    1970-01-01

    This paper presents a numerical model of stress wave propagation (SOC) which uses material properties data from a preshot testing program to predict the stress-induced effects on the rock mass involved in a Plowshare application. SOC calculates stress and particle velocity history, cavity radius, extent of brittle failure, and the rock's efficiency for transmitting stress. The calculations are based on an equation of state for the rock, which is developed from preshot field and laboratory measurements of the rock properties. The field measurements, made by hole logging, determine in situ values of the rock's density, water content, and propagation velocity for elastic waves. These logs also are useful in judging the layering of the rock and in choosing which core samples to test in the laboratory. The laboratory analysis of rock cores includes determination of hydrostatic compressibility to 40 kb, triaxial strength data, tensile strength, Hugoniot elastic limit, and, for the rock near the point of detonation, high-pressure Hugoniot data. Equation-of-state data are presented for rock from three sites subjected to high explosive or underground nuclear shots, including the Hardhat and Gasbuggy sites. SOC calculations of the effects of these two shots on the surrounding rock are compared with the observed effects. In both cases SOC predicts the size of the cavity quite closely. Results of the Gasbuggy calculations indicate that useful predictions of cavity size and chimney height can be made when an adequate preshot testing program is run to determine the rock's equation of state. Seismic coupling is very sensitive to the low-pressure part of the equation of state, and its successful prediction depends on agreement between the logging data and the static compressibility data. In general, it appears that enough progress has been made in calculating stress wave propagation to begin looking at derived numbers, such as number of cracks per zone, for some insight into the

  10. 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.

  11. 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.

  12. The effect of austenitizing conditions in the ductile iron hardening process on longitudinal ultrasonic wave velocity

    Directory of Open Access Journals (Sweden)

    A. W. Orłowicz

    2014-04-01

    Full Text Available The paper presents results of a research on the effect of austenitizing temperature and time adopted in the hardening operation on the ultrasonic wave velocity in ductile iron. It has been found that with increasing austenitizing temperature and with the passage of the austenitizing time, a monotonic decrease of the ultrasonic longitudinal wave velocity value occurred. Implementation of ultrasonic testing of results obtained in the course of the cast iron hardening process both in production and as-cast conditions, requires development of a test methodology that must take into account the influence of base material structure (degree of nodularization, graphite precipitation count on the ultrasound wave velocity.

  13. 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.

  14. 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.

  15. 3D shear wave velocity structure revealed with ambient noise tomography on a DAS array

    Science.gov (United States)

    Zeng, X.; Thurber, C. H.; Wang, H. F.; Fratta, D.

    2017-12-01

    An 8700-m Distributed Acoustic Sensing (DAS) cable was deployed at Brady's Hot Springs, Nevada in March 2016 in a 1.5 by 0.5 km study area. The layout of the DAS array was designed with a zig-zag geometry to obtain relatively uniform areal and varied angular coverage, providing very dense coverage with a one-meter channel spacing. This array continuously recorded signals of a vibroseis truck, earthquakes, and traffic noise during the 15-day deployment. As shown in a previous study (Zeng et al., 2017), ambient noise tomography can be applied to DAS continuous records to image shear wave velocity structure in the near surface. To avoid effects of the vibroseis truck operation, only continuous data recorded during the nighttime was used to compute noise cross-correlation functions for channel pairs within a given linear segment. The frequency band of whitening was set at 5 to 15 Hz and the length of the cross-correlation time window was set to 60 second. The phase velocities were determined using the multichannel analysis of surface waves (MASW) methodology. The phase velocity dispersion curve was then used to invert for shear wave velocity profiles. A preliminarily velocity model at Brady's Hot Springs (Lawrence Livermore National Laboratory, 2015) was used as the starting model and the sensitivity kernels of Rayleigh wave group and phase velocities were computed with this model. As the sensitivity kernel shows, shear wave velocity in the top 200 m can be constrained with Rayleigh wave group and phase velocities in our frequency band. With the picked phase velocity data, the shear wave velocity structure can be obtained via Occam's inversion (Constable et al., 1987; Lai 1998). Shear wave velocity gradually increases with depth and it is generally faster than the Lawrence Livermore National Laboratory (2015) model. Furthermore, that model has limiting constraints at shallow depth. The strong spatial variation is interpreted to reflect the different sediments and

  16. 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

  17. Rayleigh and Love Wave Phase Velocities in the Northern Gulf Coast of the United States

    Science.gov (United States)

    Li, A.; Yao, Y.

    2017-12-01

    The last major tectonic event in the northern Gulf Coast of the United States is Mesozoic continental rifting that formed the Gulf of Mexico. This area also experienced igneous activity and local uplifts during Cretaceous. To investigate lithosphere evolution associated with the rifting and igneous activity, we construct Rayleigh and Love wave phase velocity models at the periods of 6 s to 125 s in the northern Gulf Coast from Louisiana to Alabama including the eastern Ouachita and southern Appalachian orogeny. The phase velocities are derived from ambient noise and earthquake data recorded at the 120 USArray Transportable Array stations. At periods below 20 s, phase velocity maps are characterized by significant low velocities in the Interior Salt Basin and Gulf Coast Basin, reflecting the effects of thick sediments. The northern Louisiana and southern Arkansas are imaged as a low velocity anomaly in Rayleigh wave models but a high velocity anomaly of Love wave at the periods of 14 s to 30 s, indicating strong lower crust extension to the Ouachita front. High velocity is present in the Mississippi Valley Graben from period 20 s to 35 s, probably reflecting a thin crust or high-velocity lower crust. At longer periods, low velocities are along the Mississippi River to the Gulf Coast Basin, and high velocity anomaly mainly locates in the Black Warrior Basin between the Ouachita Belt and Appalachian Orogeny. The magnitude of anomalies in Love wave images is much smaller than that in Rayleigh wave models, which is probably due to radial anisotropy in the upper mantle. A 3-D anisotropic shear velocity model will be developed from the phase velocities and will provide more details for the crust and upper mantle structure beneath the northern Gulf of Mexico continental margin.

  18. 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...... wave and ±2 s for S wave, with early arrivals in shield areas of southern Sweden and later arrivals in the Danish and North German Basins, as well as in most of southern Norway. In good accordance with previous, mainly P-velocity models, a marked upper-mantle velocity boundary (UMVB) is accurately...... pronounced in our new S-velocity model, with velocity contrasts of up to ±2–3 per cent. It is also clearly reflected in the VP/VS ratio. Differences in this ratio of up to about ±2 per cent are observed across the boundary, with generally low values in shield areas to the east and relatively higher values...

  19. 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.

  20. 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.

  1. Renal shear wave velocity by acoustic radiation force impulse did not reflect advanced renal impairment.

    Science.gov (United States)

    Takata, Tomoaki; Koda, Masahiko; Sugihara, Takaaki; Sugihara, Shinobu; Okamoto, Toshiaki; Miyoshi, Kenichi; Matono, Tomomitsu; Hosho, Keiko; Mae, Yukari; Iyama, Takuji; Fukui, Takeaki; Fukuda, Satoko; Munemura, Chishio; Isomoto, Hajime

    2016-12-01

    Acoustic radiation force impulse is a noninvasive method for evaluating tissue elasticity on ultrasound. Renal shear wave velocity measured by this technique has not been fully investigated in patients with renal disease. The aim of the present study was to compare renal shear wave velocity in end-stage renal disease patients and that in patients without chronic kidney disease and to investigate influencing factors. Renal shear wave velocities were measured in 59 healthy young subjects (control group), 31 subjects without chronic kidney disease (non-CKD group), and 39 end-stage renal disease patients (ESRD group). Each measurement was performed 10 times at both kidneys, and the mean value of eight of 10 measurements, excluding the maximum and minimum values, was compared. Renal shear wave velocity could be measured in all subjects. Renal shear wave velocity in the control group was higher than in the non-CKD group and in the ESRD group, and no difference was found between the non-CKD group and the ESRD group. Age and depth were negatively correlated to the renal shear wave velocity. In multiple regression analysis, age and depth were independent factors for renal shear wave velocity, while renal impairment was not. There was no difference between the non-CKD group and the ESRD group, even when ages were matched and depth was adjusted. Renal shear wave velocity was not associated with advanced renal impairment. However, it reflected alteration of renal aging, and this technique may be useful to detect renal impairment in the earlier stages. © 2015 Asian Pacific Society of Nephrology.

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

    Science.gov (United States)

    2017-09-05

    crystal symmetries and directions of propagation, and the advantages and disadvantages are dis- cussed. An alternative method of finding the RSW velocity...efficient in calculating RSW velocity curves in all cases. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license ...http://creativecommons.org/ licenses /by-nc-nd/4.0/). 1. Introduction Surface acoustic waves (SAW) such as Rayleigh surface waves (RSW) are important in

  3. Single Tracking Location Methods Suppress Speckle Noise in Shear Wave Velocity Estimation

    OpenAIRE

    Elegbe, Etana C.; McAleavey, Stephen A.

    2013-01-01

    In ultrasound-based elastography methods, the estimation of shear wave velocity typically involves the tracking of speckle motion due to an applied force. The errors in the estimates of tissue displacement, and thus shear wave velocity, are generally attributed to electronic noise and decorrelation due to physical processes. We present our preliminary findings on another source of error, namely, speckle-induced bias in phase estimation. We find that methods that involve tracking in a single l...

  4. 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.

  5. Flow under standing waves Part 1. Shear stress distribution, energy flux and steady streaming

    DEFF Research Database (Denmark)

    Gislason, Kjartan; Fredsøe, Jørgen; Deigaard, Rolf

    2009-01-01

    The conditions for energy flux, momentum flux and the resulting streaming velocity are analysed for standing waves formed in front of a fully reflecting wall. The exchange of energy between the outer wave motion and the near bed oscillatory boundary layer is considered, determining the horizontal...... energy flux inside and outside the boundary layer. The momentum balance, the mean shear stress and the resulting time averaged streaming velocities are determined. For a laminar bed boundary layer the analysis of the wave drift gives results similar to the original work of Longuet-Higgins from 1953...

  6. Video imaging measurement of interfacial wave velocity in air-water flow through a horizontal elbow

    Science.gov (United States)

    Al-Wazzan, Amir; Than, Cheok F.; Moghavvemi, Mahmoud; Yew, Chia W.

    2001-10-01

    Two-phase flow in pipelines containing elbows represents a common situation in the oil and gas industries. This study deals with the stratified flow regime between the gas and liquid phase through an elbow. It is of interest to study the change in wave characteristics by measuring the wave velocity and wavelength at the inlet and outlet of the elbow. The experiments were performed under concurrent air-water stratified flow in a horizontal transparent polycarbonate pipe of 0.05m diameter and superficial air and water velocities up to 8.97 and 0.0778 m/s respectively. A non-intrusive video imaging technique was applied to capture the waves. For image analysis, a frame by frame direct overlapping method was used to detect for pulsating flow and a pixel shifting method based on the detection of minimum values in the overlap function was used to determine wave velocity and wavelength. Under superficial gas velocity of less than 4.44 m/s, the results suggest a regular pulsating outflow produced by the elbow. At higher gas velocities, more random pulsation was found and the emergence of localized interfacial waves was detected. Wave velocities measured by this technique were found to produce satisfactory agreement with direct measurements.

  7. Experimental Study of Damage Development in Salt Rock under Uniaxial Stress Using Ultrasonic Velocity and Acoustic Emissions

    Directory of Open Access Journals (Sweden)

    Haoran Li

    2018-04-01

    Full Text Available Ultrasonic waves and acoustic emissions (AE are important technologies to reveal rock damage. However, few studies have simultaneously monitored both types of data in the same experiment because of limitations on the experimental apparatus. In this study, an integrated ultrasonic wave and AE testing device was developed to investigate the deformation characteristics and damage development of salt rock. Fracture experiments under uniaxial compression were carried out on three samples from the Jintan Salt Mine, Jiangsu Province, China. The deformation process can be divided into five stages. In the compression fissure and linear deformation stages, P- and S-waves rose slightly to stability, and acoustic emission activity was weak (0.04% and 2.66%, respectively. Subsequently, S-wave velocity slowly declined and AE events become more active, with about 13.8% of the total in the stabilized-growth cracks stage. When the salt rock entered the accelerated-growth cracks stage, AE events increased to 75.27%; with features of an earthquake swarm, the velocities of P- and S-waves began to fall significantly. After the peak stress, salt rock produced only a small number of AE events. The beginning stress of rock damage and dilatancy were about 42–50% and 62–67% of the uniaxial compressive strength, respectively. The ultrasonic wave velocity ratio, Ib-value, and r-value effectively predicted rock failure, but the r-value was superior owing to its sensitivity and ease of measurement.

  8. 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.

  9. Site-effect estimations for Taipei Basin based on shallow S-wave velocity structures

    Science.gov (United States)

    Chen, Ying-Chi; Huang, Huey-Chu; Wu, Cheng-Feng

    2016-03-01

    Shallow S-wave velocities have been widely used for earthquake ground-motion site characterization. Thus, the S-wave velocity structures of Taipei Basin, Taiwan were investigated using array records of microtremors at 15 sites (Huang et al., 2015). In this study, seven velocity structures are added to the database describing Taipei Basin. Validity of S-wave velocity structures are first examined using the 1D Haskell method and well-logging data at the Wuku Sewage Disposal Plant (WK) borehole site. Basically, the synthetic results match well with the observed data at different depths. Based on S-wave velocity structures at 22 sites, theoretical transfer functions at five different formations of the sedimentary basin are calculated. According to these results, predominant frequencies for these formations are estimated. If the S-wave velocity of the Tertiary basement is assumed to be 1000 m/s, the predominant frequencies of the Quaternary sediments are between 0.3 Hz (WUK) and 1.4 Hz (LEL) in Taipei Basin while the depths of sediments between 0 m (i.e. at the edge of the basin) and 616 m (i.e. site WUK) gradually increase from southeast to northwest. Our results show good agreement with available geological and geophysical information.

  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

    resistance (qc1Ncs), the overburden corrected shear wave velocity (V S1), and the magnitude and effective stress corrected cyclic stress ratio (CSRM=7.5,σv'=1atm) were considered as input variables. In this case the graphical representation of the cyclic resistance ratio curve for a given probability has been replaced by a surface that separates the liquefaction and non-liquefaction cases.

  11. 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.

  12. Ultra-low velocity zone heterogeneities at the core-mantle boundary from diffracted PKKPab waves

    Science.gov (United States)

    Ma, Xiaolong; Sun, Xinlei

    2017-08-01

    Diffracted waves around Earth's core could provide important information of the lowermost mantle that other seismic waves may not. We examined PKKPab diffraction waves from 52 earthquakes occurring at the western Pacific region and recorded by USArray to probe the velocity structure along the core-mantle boundary (CMB). These diffracted waves emerge at distances up to 10° past the theoretical cutoff epicentral distance and show comparable amplitudes. We measured the ray parameters of PKKPab diffraction waves by Radon transform analysis that is suitable for large-aperture arrays. These ray parameters show a wide range of values from 4.250 to 4.840 s/deg, suggesting strong lateral heterogeneities in sampling regions at the base of the mantle. We further estimated the P-wave velocity variations by converting these ray parameters and found the CMB regions beneath the northwestern edge of African Anomaly (Ritsma et al. in Science 286:1925-1928, 1999) and southern Sumatra Islands exhibit velocity reductions up to 8.5% relative to PREM. We suggest that these low velocity regions are Ultra-low velocity zones, which may be related to partial melt or iron-enriched solids.[Figure not available: see fulltext.

  13. Negative group velocity Lamb waves on plates and applications to the scattering of sound by shells.

    Science.gov (United States)

    Marston, Philip L

    2003-05-01

    Symmetric Lamb waves on plates exhibit anomalies for certain regions of frequency. The phase velocity appears to be double-valued [M. F. Werby and H. Uberall, J. Acoust. Soc. Am. 111, 2686-2691 (2002)] with one of the branches having a negative group velocity relative to the corresponding phase velocity. The classification of the symmetric plate modes for frequencies appearing to have a double-valued phase velocity is reviewed here. The complication of a double-valued velocity is avoided by examining mode orthogonality and the complex wave-number spectra. Various authors have noted an enhancement in the backscattering of sound by elastic shells in water that occurs for frequencies where symmetric leaky Lamb waves (generalized to case of a shell) have contra-directed group and phase velocities. The ray diagram for negative group velocity contributions to the scattering by shells [G. Kaduchak, D. H. Hughes, and P. L. Marston, J. Acoust. Soc. Am. 96, 3704-3714 (1994)] is unusual since for this type of mode the energy on the shell flows in the opposite direction of the wave vector. Circumnavigation of the shell is not required for the leaky ray to be backward directed.

  14. Shear wave velocity structure of northern and North-Eastern Ethiopia

    International Nuclear Information System (INIS)

    Kebede, F.; Mammo, T.; Panza, G.F.; Vuan, A.; Costa, G.

    1995-10-01

    The non-linear inversion technique known as hedgehog is utilized to define the average crustal structure of North and North-Eastern Ethiopia. To accomplish the task a two dimensional frequency-time analysis is performed to obtain Rayleigh wave group velocity dispersion curves. Six earthquakes recorded by the broad-band digital seismograph installed at the Geophysical Observatory of Addis Ababa University are utilized. The crustal structure between the Gulf of Tadjura (western Gulf of Aden) and Addis Ababa crossing southern Afar (path I) can be approximated by a total thickness of about 22 km with average S-wave velocity in the range 2.3 - 3.9 km/s. The crust-mantle transition is poorly developed at greater depths and the shear wave velocity ranges from 4.0 km/s to 4.3 km/s. If the effect of the plateau part is taken into account the average total crustal thickness is found to be less than 18 km and the average S-wave velocity varies in the range 2.4 - 3.9 km/s. The low shear wave velocity under the Afar crust is consistent with the result of other geophysical studies. For path II, which passes through the border of the Western Ethiopian plateau, the average crustal structure is found to be approximated by a thickness of about 40 km and average S-wave velocity between 3.0 km/s and 3.9 km/s. The crust overlies a lithospheric mantle with a shear wave velocity in the range 4.1-4.4 km/s. (author). 37 refs, 11 figs, 4 tabs

  15. Towards a new technique to construct a 3D shear-wave velocity model based on converted waves

    Science.gov (United States)

    Hetényi, G.; Colavitti, L.

    2017-12-01

    A 3D model is essential in all branches of solid Earth sciences because geological structures can be heterogeneous and change significantly in their lateral dimension. The main target of this research is to build a crustal S-wave velocity structure in 3D. The currently popular methodologies to construct 3D shear-wave velocity models are Ambient Noise Tomography (ANT) and Local Earthquake Tomography (LET). Here we propose a new technique to map Earth discontinuities and velocities at depth based on the analysis of receiver functions. The 3D model is obtained by simultaneously inverting P-to-S converted waveforms recorded at a dense array. The individual velocity models corresponding to each trace are extracted from the 3D initial model along ray paths that are calculated using the shooting method, and the velocity model is updated during the inversion. We consider a spherical approximation of ray propagation using a global velocity model (iasp91, Kennett and Engdahl, 1991) for the teleseismic part, while we adopt Cartesian coordinates and a local velocity model for the crust. During the inversion process we work with a multi-layer crustal model for shear-wave velocity, with a flexible mesh for the depth of the interfaces. 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, 1999), whose goal is to find an ensemble of models that sample the good data-fitting regions of a multidimensional parameter space. Depending on the studied area, this method can accommodate possible independent and complementary geophysical data (gravity, active seismics, LET, ANT, etc.), helping to reduce the non-linearity of the inversion. Our first focus of application is the Central Alps, where a 20-year long dataset of

  16. Research on definition of hard rock shear wave velocity of site for nuclear power plant

    International Nuclear Information System (INIS)

    Ding Zhenkun; Xia Zufeng

    2013-01-01

    Background: The definition of hard rock shear wave velocity is one of the most critical issues in the work of site selection. Purpose: To make a definition of hard rock site on which the model can be assumed as fixed-base condition, a series of research had been done. Several possible hard rock site soil models were developed. Methods: Shear wave velocity of hard rock had been assumed from 1100 m/s to 3200 m/s. For each case, free field analysis and soil structure analysis had been performed. And responses in soil and key nodes of structure were compared. Results: In free field analysis, responses of models that shear wave velocity below 2400 m/s decreased a lot. In SSI analysis, structure responses didn't change much when shear wave velocity was above 2400 m/s. Conclusions: 2400 m/s was the lowest shear wave velocity for hard rock site for fixed-base assumption. (authors)

  17. S-Wave Velocity Structure of the Puli Basin, Taiwan, Using the Array Records of Microtremors

    Science.gov (United States)

    Wu, C.; Huang, H.

    2009-12-01

    The September 21, 1999 Chi-Chi earthquake induced strong shaking, resulting in severe damage in the Puli area. According to Huang and Tarng (2005), the collapse of many structures during the earthquake was very closely related to the site effects. The Shallow Shear-wave velocities have widely been used for earthquake ground-motion site characterization. Thus, the S-wave velocity structures of the Puli area are investigated using the array records of microtremors at 16 sites. The dispersion curves at these sites are calculated using the F-K method (Capon, 1969); then, the S-wave velocity structures at the Puli area are estimated by employing the surface wave inversion technique (Herrmann, 1991). If the S-wave velocity of bedrock is assumed to be 2000m/sec, the depths of the alluvium at the Puli area are between 360m (ZHO) and 810m (AIL, DAH). Besides, there are 3~4 distinct interfaces in the shallow velocity structure (0~1000m). The depth of the alluvium gradually increases from east to west and the deepest one appears at stations AIL and DAH. The results in this study are similar to those using the seismic exploration method (Wang et al., 2003; Huang, 2008) in the Puli area and the well-logging method at LAC.

  18. Classification and assessment of rock mass parameters in Choghart iron mine using P-wave velocity

    Directory of Open Access Journals (Sweden)

    Mohammadreza Hemmati Nourani

    2017-04-01

    Full Text Available Engineering rock mass classification, based on empirical relations between rock mass parameters and engineering applications, is commonly used in rock engineering and forms the basis for designing rock structures. The basic data required may be obtained from visual observation and laboratory or field tests. However, owing to the discontinuous and variable nature of rock masses, it is difficult for rock engineers to directly obtain the specific design parameters needed. As an alternative, the use of geophysical methods in geomechanics such as seismography may largely address this problem. In this study, 25 seismic profiles with the total length of 543 m have been scanned to determine the geomechanical properties of the rock mass in blocks I, III and IV-2 of the Choghart iron mine. Moreover, rock joint measurements and sampling for laboratory tests were conducted. The results show that the rock mass rating (RMR and Q values have a close relation with P-wave velocity parameters, including P-wave velocity in field (VPF, P-wave velocity in the laboratory (VPL and the ratio of VPF to VPL (i.e. KP = VPF/VPL. However, Q value, totally, has greater correlation coefficient and less error than the RMR. In addition, rock mass parameters including rock quality designation (RQD, uniaxial compressive strength (UCS, joint roughness coefficient (JRC and Schmidt number (RN show close relationship with P-wave velocity. An equation based on these parameters was obtained to estimate the P-wave velocity in the rock mass with a correlation coefficient of 91%. The velocities in two orthogonal directions and the results of joint study show that the wave velocity anisotropy in rock mass may be used as an efficient tool to assess the strong and weak directions in rock mass.

  19. High resolution Rayleigh wave group velocity tomography in North-China from ambient seismic noise

    International Nuclear Information System (INIS)

    Fang Lihua; Wu Jianping; Ding Zhifeng; Panza, G.F.

    2009-03-01

    This study presents the results of the Rayleigh wave group velocity tomography in North-China performed using ambient seismic noise observed at 190 broadband and 10 very broadband stations of the North-China Seismic Array. All available vertical component time-series for the 14 months span between January, 2007 and February, 2008 are cross-correlated to obtain empirical Rayleigh wave Green functions that are subsequently processed, with the multiple filter method, to isolate the group velocity dispersion curves of the fundamental mode of Rayleigh wave. Tomographic maps, with a grid spacing of 0.25 deg. x 0.25 deg., are computed at the periods of 4.5s, 12s, 20s, 28s. The maps at short periods reveal an evident lateral heterogeneity in the crust of North-China, quite well in agreement with known geological and tectonic features. The North China Basin is imaged as a broad low velocity area, while the Taihangshan and Yanshan uplifts and Ordos block are imaged as high velocity zones, and the Quaternary intermountain basins show up as small low-velocity anomalies. The group velocity contours at 4.5s, 12s and 20s are consistent with the Bouguer gravity anomalies measured in the area of the Taihangshan fault, that cuts through the lower crust at least. Most of the historical strong earthquakes (M≥6.0) are located where the tomographic maps show zones with moderate velocity gradient. (author)

  20. Waves in nonlinear pre-stressed materials

    CERN Document Server

    Schneider, Wilhelm; Saccomandi, G

    2007-01-01

    The papers in this book provide a unique state-of-the-art multidisciplinary overview on the subject of waves in pre-stressed materials through the interaction of several topics, ranging from the mathematical modelling of incremental material response (elastic and inelastic), to the analysis of the governing differential equations and boundary-value problems, and to computational methods for the solution to these problems, with particular reference to industrial, geophysical, and biomechanical applications. A complete view on the title subject is proposed, including: The basic and fundamental theoretical issues (mechanical modelling, exact solutions, asymptotic methods, numerical treatment); A unified introduction to wave propagation (small on large and large on large); A look toward classical (such as geophysics and the mechanics of rubber-like solids) and emergent (such as biomechanics) applications.

  1. Existence of longitudinal waves in pre-stressed anisotropic elastic ...

    Indian Academy of Sciences (India)

    In a pre-stressed anisotropic elastic medium, three types of quasi-waves propagate along an arbi- trary direction. In general, none of the waves is truly longitudinal. The present study finds the specific directions in a pre-stressed anisotropic elastic medium along which longitudinal waves may propagate. This paper ...

  2. Seafloor age dependence of Rayleigh wave phase velocities in the Indian Ocean

    Science.gov (United States)

    Godfrey, Karen E.; Dalton, Colleen A.; Ritsema, Jeroen

    2017-05-01

    Variations in the phase velocity of fundamental-mode Rayleigh waves across the Indian Ocean are determined using two inversion approaches. First, variations in phase velocity as a function of seafloor age are estimated using a pure-path age-dependent inversion method. Second, a two-dimensional parameterization is used to solve for phase velocity within 1.25° × 1.25° grid cells. Rayleigh wave travel time delays have been measured between periods of 38 and 200 s. The number of measurements in the study area ranges between 4139 paths at a period of 200 s and 22,272 paths at a period of 40 s. At periods Rodriguez Triple Junction and the Australian-Antarctic Discordance and anomalously low velocities immediately to the west of the Central Indian Ridge.

  3. 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.

  4. 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.

  5. 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

  6. Energy density and velocity of electromagnetic waves in lossy chiral medium

    International Nuclear Information System (INIS)

    Vorobyev, O B

    2014-01-01

    The average energy density of the macroscopic quasimonochromatic electromagnetic field U ts (t,r) in a linear passive chiral lossy medium described by the constitutive E–H relations is determined using a microscopic model. According to the model, U ts (t,r) is equal to the sum of the average energy densities of the electromagnetic field in free space U t0 (t,r) and electromagnetic oscillations in structural elements U s (t,r) induced by the electromagnetic wave. Making use of the Poynting theorem, the energy density U ts (t,r)≥U t0 (t,r) and power density of losses are derived as functions of the Poynting vector, polarization of the electromagnetic waves, phase shift between the field vectors and refractive index of a chiral medium. The exact energy velocity of the quasimonochromatic electromagnetic waves satisfying relativistic causality is determined using U ts (t,r). The approximate energy velocities of the quasimonochromatic electromagnetic wave are determined using energy density components approximating U ts (t,r) (e.g., the sum of the positive energy densities of the macroscopic electric and magnetic fields as well as the energy density of magnetoelectric cross-coupling). Comparison of the exact and approximate energy velocities with the group velocity in the case of a chiral lossy medium with a single-resonant frequency clarifies the concept of the electromagnetic energy and demonstrates the fundamental significance of the exact energy velocity. (paper)

  7. Single tracking location methods suppress speckle noise in shear wave velocity estimation.

    Science.gov (United States)

    Elegbe, Etana C; McAleavey, Stephen A

    2013-04-01

    In ultrasound-based elastography methods, the estimation of shear wave velocity typically involves the tracking of speckle motion due to an applied force. The errors in the estimates of tissue displacement, and thus shear wave velocity, are generally attributed to electronic noise and decorrelation due to physical processes. We present our preliminary findings on another source of error, namely, speckle-induced bias in phase estimation. We find that methods that involve tracking in a single location, as opposed to multiple locations, are less sensitive to this source of error since the measurement is differential in nature and cancels out speckle-induced phase errors.

  8. The effect of gradational velocities and anisotropy on fault-zone trapped waves

    Science.gov (United States)

    Gulley, A. K.; Eccles, J. D.; Kaipio, J. P.; Malin, P. E.

    2017-08-01

    Synthetic fault-zone trapped wave (FZTW) dispersion curves and amplitude responses for FL (Love) and FR (Rayleigh) type phases are analysed in transversely isotropic 1-D elastic models. We explore the effects of velocity gradients, anisotropy, source location and mechanism. These experiments suggest: (i) A smooth exponentially decaying velocity model produces a significantly different dispersion curve to that of a three-layer model, with the main difference being that Airy phases are not produced. (ii) The FZTW dispersion and amplitude information of a waveguide with transverse-isotropy depends mostly on the Shear wave velocities in the direction parallel with the fault, particularly if the fault zone to country-rock velocity contrast is small. In this low velocity contrast situation, fully isotropic approximations to a transversely isotropic velocity model can be made. (iii) Fault-aligned fractures and/or bedding in the fault zone that cause transverse-isotropy enhance the amplitude and wave-train length of the FR type FZTW. (iv) Moving the source and/or receiver away from the fault zone removes the higher frequencies first, similar to attenuation. (v) In most physically realistic cases, the radial component of the FR type FZTW is significantly smaller in amplitude than the transverse.

  9. 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.

  10. A physics based approach to the pulse wave velocity prediction in compliant arterial segments.

    Science.gov (United States)

    Liberson, Alexander S; Lillie, Jeffrey S; Day, Steven W; Borkholder, David A

    2016-10-03

    Pulse wave velocity (PWV) quantification commonly serves as a highly robust prognostic parameter being used in a preventative cardiovascular therapy. Being dependent on arterial elastance, it can serve as a marker of cardiovascular risk. Since it is influenced by a blood pressure (BP), the pertaining theory can lay the foundation in developing a technique for noninvasive blood pressure measurement. Previous studies have reported application of PWV, measured noninvasively, for both the estimation of arterial compliance and blood pressure, based on simplified physical or statistical models. A new theoretical model for pulse wave propagation in a compliant arterial segment is presented within the framework of pseudo-elastic deformation of biological tissue undergoing finite deformation. An essential ingredient is the dependence of results on nonlinear aspects of the model: convective fluid phenomena, hyperelastic constitutive relation, large deformation and a longitudinal pre-stress load. An exact analytical solution for PWV is presented as a function of pressure, flow and pseudo-elastic orthotropic parameters. Results from our model are compared with published in-vivo PWV measurements under diverse physiological conditions. Contributions of each of the nonlinearities are analyzed. It was found that the totally nonlinear model achieves the best match with the experimental data. To retrieve individual vascular information of a patient, the inverse problem of hemodynamics is presented, calculating local orthotropic hyperelastic properties of the arterial wall. The proposed technique can be used for non-invasive assessment of arterial elastance, and blood pressure using direct measurement of PWV, with account of hyperelastic orthotropic properties. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Prediction of building limestone physical and mechanical properties by means of ultrasonic P-wave velocity.

    Science.gov (United States)

    Concu, Giovanna; De Nicolo, Barbara; Valdes, Monica

    2014-01-01

    The aim of this study was to evaluate ultrasonic P-wave velocity as a feature for predicting some physical and mechanical properties that describe the behavior of local building limestone. To this end, both ultrasonic testing and compressive tests were carried out on several limestone specimens and statistical correlation between ultrasonic velocity and density, compressive strength, and modulus of elasticity was studied. The effectiveness of ultrasonic velocity was evaluated by regression, with the aim of observing the coefficient of determination r(2) between ultrasonic velocity and the aforementioned parameters, and the mathematical expressions of the correlations were found and discussed. The strong relations that were established between ultrasonic velocity and limestone properties indicate that these parameters can be reasonably estimated by means of this nondestructive parameter. This may be of great value in a preliminary phase of the diagnosis and inspection of stone masonry conditions, especially when the possibility of sampling material cores is reduced.

  12. Three-dimensional P-wave velocity structure of Mt. Etna, Italy

    Science.gov (United States)

    Villasenor, A.; Benz, H.M.; Filippi, L.; De Luca, G.; Scarpa, R.; Patane, G.; Vinciguerra, S.

    1998-01-01

    The three-dimensional P-wave velocity structure of Mt. Etna is determined to depths of 15 km by tomographic inversion of first arrival times from local earthquakes recorded by a network of 29 permanent and temporary seismographs. Results show a near-vertical low-velocity zone that extends from beneath the central craters to a depth of 10 km. This low-velocity region is coincident with a band of steeply-dipping seismicity, suggesting a magmatic conduit that feeds the summit eruptions. The most prominent structure is an approximately 8-km-diameter high-velocity body located between 2 and 12 km depth below the southeast flank of the volcano. This high-velocity body is interpreted as a remnant mafic intrusion that is an important structural feature influencing both volcanism and east flank slope stability and faulting.

  13. Regional P wave velocity structure of the Northern Cascadia Subduction Zone

    Science.gov (United States)

    Ramachandran, K.; Hyndman, R.D.; Brocher, T.M.

    2006-01-01

    This paper presents the first regional three-dimensional, P wave velocity model for the Northern Cascadia Subduction. Zone (SW British Columbia and NW Washington State) constructed through tomographic inversion of first-arrival traveltime data from active source experiments together with earthquake traveltime data recorded at permanent stations. The velocity model images the structure of the subducting Juan de Fuca plate, megathrust, and the fore-arc crust and upper mantle. Beneath southern Vancouver Island the megathrust above the Juan de Fuca plate is characterized by a broad zone (25-35 km depth) having relatively low velocities of 6.4-6.6 km/s. This relative low velocity zone coincides with the location of most of the episodic tremors recently mapped beneath Vancouver Island, and its low velocity may also partially reflect the presence of trapped fluids and sheared lower crustal rocks. The rocks of the Olympic Subduction Complex are inferred to deform aseismically as evidenced by the lack of earthquakes withi the low-velocity rocks. The fore-arc upper mantle beneath the Strait of Georgia and Puget Sound is characterized by velocities of 7.2-7.6 km/s. Such low velocities represent regional serpentinization of the upper fore-arc mantle and provide evidence for slab dewatering and densification. Tertiary sedimentary basins in the Strait of Georgia and Puget Lowland imaged by the velocity model lie above the inferred region of slab dewatering and densification and may therefore partly result from a higher rate of slab sinking. In contrast, sedimentary basins in the Strait of Juan de Fuca lie in a synclinal depression in the Crescent Terrane. The correlation of in-slab earthquake hypocenters M>4 with P wave velocities greater than 7.8 km/s at the hypocenters suggests that they originate near the oceanic Moho of the subducting Juan de Fuca plate. Copyright 2006 by the American Geophysical Union.

  14. Nonlinear Wave-Particle Interaction: Implications for Newborn Planetary and Backstreaming Proton Velocity Distribution Functions

    Science.gov (United States)

    Romanelli, N.; Mazelle, C.; Meziane, K.

    2018-02-01

    Seen from the solar wind (SW) reference frame, the presence of newborn planetary protons upstream from the Martian and Venusian bow shocks and SW protons reflected from each of them constitutes two sources of nonthermal proton populations. In both cases, the resulting proton velocity distribution function is highly unstable and capable of giving rise to ultralow frequency quasi-monochromatic electromagnetic plasma waves. When these instabilities take place, the resulting nonlinear waves are convected by the SW and interact with nonthermal protons located downstream from the wave generation region (upstream from the bow shock), playing a predominant role in their dynamics. To improve our understanding of these phenomena, we study the interaction between a charged particle and a large-amplitude monochromatic circularly polarized electromagnetic wave propagating parallel to a background magnetic field, from first principles. We determine the number of fix points in velocity space, their stability, and their dependence on different wave-particle parameters. Particularly, we determine the temporal evolution of a charged particle in the pitch angle-gyrophase velocity plane under nominal conditions expected for backstreaming protons in planetary foreshocks and for newborn planetary protons in the upstream regions of Venus and Mars. In addition, the inclusion of wave ellipticity effects provides an explanation for pitch angle distributions of suprathermal protons observed at the Earth's foreshock, reported in previous studies. These analyses constitute a mean to evaluate if nonthermal proton velocity distribution functions observed at these plasma environments present signatures that can be understood in terms of nonlinear wave-particle processes.

  15. Effect of roughness on the phase velocity of Rayleigh waves in GaAs

    Czech Academy of Sciences Publication Activity Database

    Tarasenko A., Nataliya; Boháč, Petr; Jastrabík, Lubomír; Chvostová, Dagmar; Tarasenko, Alexander

    2005-01-01

    Roč. 491, 1-2 (2005), s. 184-189 ISSN 0040-6090 Institutional research plan: CEZ:AV0Z10100522 Keywords : gallium arsenide * surface roughness * surface acoustic waves * phase velocity Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.569, year: 2005

  16. 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 ...

  17. 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 stiffnes...

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

    Indian Academy of Sciences (India)

    Administrator

    Abstract. P-wave velocity test, a non-destructive and easy method to apply in both field and laboratory con- ditions, 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,.

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

    Indian Academy of Sciences (India)

    The aim of this study is to predict the rock properties including the uniaxial compressive strength, Schmidt hardness, modulus of elasticity, water absorption and effective porosity, slake durability index, saturated and dry density of rock using -wave velocity (p). For this purpose geotechnical properties of nine different rock ...

  20. An Undersea Mining Microseism Source Location Algorithm Considering Wave Velocity Probability Distribution

    Directory of Open Access Journals (Sweden)

    Furui Du

    2014-01-01

    Full Text Available The traditional mine microseism locating methods are mainly based on the assumption that the wave velocity is uniform through the space, which leads to some errors for the assumption goes against the laws of nature. In this paper, the wave velocity is regarded as a random variable, and the probability distribution information of the wave velocity is fused into the traditional locating method. This paper puts forwards the microseism source location method for the undersea mining on condition of the probability distribution of the wave velocity and comes up with the solving process of Monte Carlo. In addition, based on the simulated results of the Monte Carlo method, the space is divided into three areas: the most possible area (area I, the possible area (area II, and the small probability area (area III. Attached to corresponding mathematical formulations, spherical models and cylindrical models in different areas are, respectively, built according to whether the source is in the sensor arrays. Both the examples and the actual applications show that (1 the method of microseism source location in this paper can highly improve the accuracy of the microseism monitoring, especially for the source beyond the sensor arrays, and (2 the space-dividing method based on occurrence possibilities of the source can recognize and sweep the hidden dangers for it predicts the probable location range of the source efficiently, while the traditional method cannot.

  1. 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.

  2. 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.

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

    Indian Academy of Sciences (India)

    Administrator

    947. P-wave velocity test for assessment of geotechnical properties of some rock materials. SAFFET YAGIZ. Faculty of Engineering, Department of Geological ... ditions, has increasingly been conducted to determine the geotechnical properties of rock materials. ... ing method used in civil, geotechnical and mining pro-.

  4. Heating and current-drive with high phase velocity compressional Alfven waves

    International Nuclear Information System (INIS)

    Li, Y.M.; Mahajan, S.M.; Ross, D.W.

    1986-12-01

    It is shown that high phase velocity compressional Alfven waves have the desirable features needed for efficient current drive in fusion-reactor-like conditions; the energy deposition is low on the α-particles, and high on the hot electrons in the plasma interior

  5. The frequency dispersion of velocity and sound waves absorption coefficient in the electrolyte solutions

    International Nuclear Information System (INIS)

    Odinaev, S.; Dodarbekov, A.

    2001-01-01

    Present article is devoted to frequency dispersion of velocity and sound waves absorption coefficient in the electrolyte solutions. The analytical expressions for acoustic parameters in a wide range of thermodynamic parameters and frequencies change were obtained. The system of equations of generalized hydrodynamics for electrolyte solutions was constructed.

  6. 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 met...

  7. Evaluation of arterial propagation velocity based on the automated analysis of the Pulse Wave Shape

    International Nuclear Information System (INIS)

    Clara, F M; Scandurra, A G; Meschino, G J; Passoni, L I

    2011-01-01

    This paper proposes the automatic estimation of the arterial propagation velocity from the pulse wave raw records measured in the region of the radial artery. A fully automatic process is proposed to select and analyze typical pulse cycles from the raw data. An adaptive neuro-fuzzy inference system, together with a heuristic search is used to find a functional approximation of the pulse wave. The estimation of the propagation velocity is carried out via the analysis of the functional approximation obtained with the fuzzy model. The analysis of the pulse wave records with the proposed methodology showed small differences compared with the method used so far, based on a strong interaction with the user. To evaluate the proposed methodology, we estimated the propagation velocity in a population of healthy men from a wide range of ages. It has been found in these studies that propagation velocity increases linearly with age and it presents a considerable dispersion of values in healthy individuals. We conclude that this process could be used to evaluate indirectly the propagation velocity of the aorta, which is related to physiological age in healthy individuals and with the expectation of life in cardiovascular patients.

  8. On elastic waves in an thinly-layered laminated medium with stress couples under initial stress

    Directory of Open Access Journals (Sweden)

    P. Pal Roy

    1988-01-01

    Full Text Available The present work is concerned with a simple transformation rule in finding out the composite elastic coefficients of a thinly layered laminated medium whose bulk properties are strongly anisotropic with a microelastic bending rigidity. These elastic coefficients which were not known completely for a layered laminated structure, are obtained suitably in terms of initial stress components and Lame's constants λi, μi of initially isotropic solids. The explicit solutions of the dynamical equations for a prestressed thinly layered laminated medium under horizontal compression in a gravity field are derived. The results are discussed specifying the effects of hydrostatic, deviatoric and couple stresses upon the characteristic propagation velocities of shear and compression wave modes.

  9. Shear-wave velocity compilation for Northridge strong-motion recording sites

    Science.gov (United States)

    Borcherdt, Roger D.; Fumal, Thomas E.

    2002-01-01

    Borehole and other geotechnical information collected at the strong-motion recording sites of the Northridge earthquake of January 17, 1994 provide an important new basis for the characterization of local site conditions. These geotechnical data, when combined with analysis of strong-motion recordings, provide an empirical basis to evaluate site coefficients used in current versions of US building codes. Shear-wave-velocity estimates to a depth of 30 meters are derived for 176 strong-motion recording sites. The estimates are based on borehole shear-velocity logs, physical property logs, correlations with physical properties and digital geologic maps. Surface-wave velocity measurements and standard penetration data are compiled as additional constraints. These data as compiled from a variety of databases are presented via GIS maps and corresponding tables to facilitate use by other investigators.

  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. 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.

  12. Simultaneous measurement of acoustic and streaming velocities in a standing wave using laser Doppler anemometry

    Science.gov (United States)

    Thompson, Michael W.; Atchley, Anthony A.

    2005-04-01

    Laser Doppler anemometry (LDA) with burst spectrum analysis (BSA) is used to study the acoustic streaming generated in a cylindrical standing-wave resonator filled with air. The air column is driven sinusoidally at a frequency of approximately 310 Hz and the resultant acoustic-velocity amplitudes are less than 1.3 m/s at the velocity antinodes. The axial component of fluid velocity is measured along the resonator axis, across the diameter, and as a function of acoustic amplitude. The velocity signals are postprocessed using the Fourier averaging method [Sonnenberger et al., Exp. Fluids 28, 217-224 (2000)]. Equations are derived for determining the uncertainties in the resultant Fourier coefficients. The time-averaged velocity-signal components are seen to be contaminated by significant errors due to the LDA/BSA system. In order to avoid these errors, the Lagrangian streaming velocities are determined using the time-harmonic signal components and the arrival times of the velocity samples. The observed Lagrangian streaming velocities are consistent with Rott's theory [N. Rott, Z. Angew. Math. Phys. 25, 417-421 (1974)], indicating that the dependence of viscosity on temperature is important. The onset of streaming is observed to occur within approximately 5 s after switching on the acoustic field. .

  13. Inversion of Surface Wave Phase Velocities for Radial Anisotropy to an Depth of 1200 km

    Science.gov (United States)

    Xing, Z.; Beghein, C.; Yuan, K.

    2012-12-01

    This study aims to evaluate three dimensional radial anisotropy to an depth of 1200 km. Radial anisotropy describes the difference in velocity between horizontally polarized Rayleigh waves and vertically polarized Love waves. Its presence in the uppermost 200 km mantle has well been documented by different groups, and has been regarded as an indicator of mantle convection which aligns the intrinsically anisotropic minerals, largely olivine, to form large scale anisotropy. However, there is no global agreement on whether anisotropy exists in the region below 200 km. Recent models also associate a fast vertically polarized shear wave with vertical upwelling mantle flow. The data used in this study is the globally isotropic phase velocity models of fundamental and higher mode Love and Rayleigh waves (Visser, 2008). The inclusion of higher mode surface wave phase velocity provides sensitivities to structure at depth that extends to below the transition zone. While the data is the same as used by Visser (2008), a quite different parameterization is applied. All the six parameters - five elastic parameters A, C, F, L, N and density - are now regarded as independent, which rules out possible biased conclusions induced by scaling relation method used in several previous studies to reduce the number of parameters partly due to limited computing resources. The data need to be modified by crustal corrections (Crust2.0) as we want to look at the mantle structure only. We do this by eliminating the perturbation in surface wave phase velocity caused by the difference in crustal structure with respect to the referent model PREM. Sambridge's Neighborhood Algorithm is used to search the parameter space. The introduction of such a direct search technique pales the traditional inversion method, which requires regularization or some unnecessary priori restriction on the model space. On the contrary, the new method will search the full model space, providing probability density

  14. 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...

  15. Reflection of plane waves in an initially stressed perfectly ...

    Indian Academy of Sciences (India)

    stress and magnetic field on the reflection coef- ficients and energy ratios of reflected waves in a perfectly conducting initially stressed transversely isotropic elastic solid half-space. The present work is supposed to be useful in further studies of wave propagation in the more realistic models which have been extensively ...

  16. Nondestructive evaluation of standing trees with a stress wave method.

    Science.gov (United States)

    Xiping Wang; Robert J. Ross; Michael McClellan; R. James Barbour; John R. Erickson; John W. Forsman; Gary D. McGinnis

    2001-01-01

    The primary objective of this study was to investigate the usefulness of a stress wave technique for evaluating wood strength and stiffness of young-growth western hemlock and Sitka spruce in standing trees. A secondary objective was to determine if the effects of silvicultural practices on wood quality can be identified using this technique. Stress wave measurements...

  17. 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

  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. Determination of elastic anisotropy of rocks from P- and S-wave velocities: numerical modelling and lab measurements

    Science.gov (United States)

    Svitek, Tomáš; Vavryčuk, Václav; Lokajíček, Tomáš; Petružálek, Matěj

    2014-12-01

    The most common type of waves used for probing anisotropy of rocks in laboratory is the direct P wave. Information potential of the measured P-wave velocity, however, is limited. In rocks displaying weak triclinic anisotropy, the P-wave velocity depends just on 15 linear combinations of 21 elastic parameters, called the weak-anisotropy parameters. In strong triclinic anisotropy, the P-wave velocity depends on the whole set of 21 elastic parameters, but inversion for six of them is ill-conditioned and these parameters are retrieved with a low accuracy. Therefore, in order to retrieve the complete elastic tensor accurately, velocities of S waves must also be measured and inverted. For this purpose, we developed a lab facility which allows the P- and S-wave ultrasonic sounding of spherical rock samples in 132 directions distributed regularly over the sphere. The velocities are measured using a pair of P-wave sensors with the transmitter and receiver polarized along the radial direction and using two pairs of S-wave sensors with the transmitter and receiver polarized tangentially to the spherical sample in mutually perpendicular directions. We present inversion methods of phase and ray velocities for elastic parameters describing general triclinic anisotropy. We demonstrate on synthetic tests that the inversion becomes more robust and stable if the S-wave velocities are included. This applies even to the case when the velocity of the S waves is measured in a limited number of directions and with a significantly lower accuracy than that of the P wave. Finally, we analyse velocities measured on a rock sample from the Outokumpu deep drill hole, Finland. We present complete sets of elastic parameters of the sample including the error analysis for several levels of confining pressure ranging from 0.1 to 70 MPa.

  20. Crust and upper mantle velocity structure of the northwestern Indian Peninsular Shield from inter-station phase velocities of Rayleigh and Love waves

    Directory of Open Access Journals (Sweden)

    Gaddale Suresh

    2015-06-01

    Full Text Available We measure the inter-station Rayleigh and Love wave phase velocities across the northwestern Indian Peninsular shield (NW-IP through cross-correlation and invert these velocities to evaluate the underneath crust and upper mantle velocity structure down to 400 km. We consider a cluster of three stations in the northern tip of the Peninsula and another cluster of eight stations in the south. We measure phase velocities along 28 paths for Rayleigh waves and 17 paths for Love waves joining two stations with one from each cluster and using broadband records of earthquakes which lie nearly on the great circle joining the pair of stations. The phase velocities are in the period range of 10 to 275 s for Rayleigh waves and of 10 to 120 s for Love waves. The isotropic model obtained through inversion of the phase velocities indicates 199.1 km thick lithosphere with 3-layered crust of thickness 36.3 km; the top two layers have nearly same velocities and both constitute the upper crust with thickness of 12.6 km. The upper crust is mafic, whereas the lower crust is felsic. In the mantle lid, velocities increase with depth. The velocities of mantle lid beneath NW-IP is lower than those beneath south Indian Peninsula showing the former is hotter than the later perhaps due to large Phanerozoic impact on NW-IP. The significant upper mantle low velocity zone beneath NW-IP indicates high temperature which could be attributed to the past existence of a broad plume head at the west-central part of the Peninsula.

  1. 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

  2. Crustal P-wave velocity model for the central-western region of Mexico

    Science.gov (United States)

    Ochoa, J.; Escudero, C. R.; Perez, O. G.; Nunez-Cornu, F. J.

    2012-12-01

    Several studies require a p-wave velocity model to obtain accurate results moreover such models could provide an insight of the tectonic structure of the study area. Accordingly, in this study we estimate the crustal 3D p-wave velocity model for the Jalisco Block located at the central-western region of Mexico. The Jalisco Block is limited on its eastern side by the Colima and Tepic-Zacoalcos Rifts, and the Trans-Mexican Volcanic Belt; while on its western side it is limited by the Mesoamerican Trench. Cocos and Rivera plates are subducting beneath the Jalisco Block conforming a tectonically complex region. We used earthquakes occurring within the limits of lithosphere volume from which we want to estimate the velocity model. Such events were registered by the Mapping the Rivera Subduction Zone experiment (MARS) and the Seismic and Acelerometric Network of Jalisco (RESAJ). During MARS experiment 51broadband stations active from January 2006 to June 2007 were deployed while RESAJ by July of 2012consists of nine active stations however more stations will be deployed until reach 30 stations. The velocity model is estimated using the Fast Marching Tomography (FMTOMO) software. FMTOMO uses the Fast Marching Method (FMM) in order to solve the forward problem; the FMM is a numerical algorithm that tracks the interfaces evolution along a nodes narrow band, and travel times are updated solving the eikonal equation. Finally , the inverse problem is about adjusting the model parameters (interface depth, velocity, hypocenter location) in order to try to satisfy the observed data (travel times). We perform a resolution test using several events that show good resolution results up to a 60 km depth. We present a 3D p-wave velocity model, we compare our results within the MARS data with previous results for greater depths, approximately the upper mantle, finally we also present studies towards the northern portion of the Jalisco Block using the RESAJ data.

  3. Torsional Wave Propagation in a Pre-Stressed Structure with Corrugated and Loosely Bonded Surfaces

    Directory of Open Access Journals (Sweden)

    Singh Manoj K.

    2017-12-01

    Full Text Available An analytical model is presented to study the behaviour of propagation of torsional surface waves in initially stressed porous layer, sandwiched between an orthotropic half-space with initial stress and pre-stressed inhomogeneous anisotropic half-space. The boundary surfaces of the layer and halfspaces are taken as corrugated, as well as loosely bonded. The heterogeneity of the lower half-space is due to trigonometric variation in elastic parameters of the pre-stressed inhomogeneous anisotropic medium. Expression for dispersion relation has been obtained in closed form for the present analytical model to observe the effect of undulation parameter, flatness parameter and porosity on the propagation of torsional surface waves. The obtained dispersion relation is found to be in well agreement with classical Love wave equation for a particular case. The cases of ideally smooth interface and welded interface have also been analysed. Numerical example and graphical illustrations are made to demonstrate notable effect of initial stress, wave number, heterogeneity parameter and initial stress on the phase velocity of torsional surface waves.

  4. Stresses in a submarine topography under ocean waves

    Energy Technology Data Exchange (ETDEWEB)

    Mei, C.C.; McTigue, D.F.

    1984-01-01

    The problem of submarine slope stability is of interest to both offshore engineering and geology. In an uneven topography, the weight above a horizontal plane induces two-dimensional variation in the static stress field. The action of wave pressure, which changes with depth, further introduces excess pore pressure and dynamic stresses in the sea bottom. In the present paper, we combine a simple analytical theory for the static stress by the present authors, and the recent solution by Mei and Foda for wave-induced stresses in a plane poro-elastic sea bed to account for mild bottom slope and wave shoaling, to obtain the effective stress field in a submarine topography under sea waves. Sample results are given for a ridge and a canyon. In particular the dynamic pore pressure and the combined static and dynamic effective stresses are presented. 10 references, 11 figures.

  5. Stresses in a submarine topography under ocean waves

    Energy Technology Data Exchange (ETDEWEB)

    Mei, C.C.; McTigue, D.F.

    1984-09-01

    The problem of submarine slope stability is of interest to both offshore engineering and geology. In an uneven topography, the weight above a horizontal plane induces two-dimensional variation in the static stress field. The action of wave pressure, which changes with depth, further introduces excess pore pressure and dynamic stresses in the sea bottom. In the present paper, we combine a simple analytical theory for the static stress by the present authors, and the recent solution by Mei and Foda for wave-induced stresses in a plane poro-elastic sea bed to account for mild bottom slope and wave shoaling, and obtain the effective stress field in a submarine topography under sea waves. Sample results are given for a ridge and a canyon. In particular, the dynamic pore pressure and the combined static and dynamic effective stresses are presented.

  6. Surface wave waveform inversions for local shear-wave velocities under eastern Australia

    NARCIS (Netherlands)

    Passier, M.L.; Hilst, R.D. van der; Snieder, R.K.

    1997-01-01

    The waveform inversion method developed by Kushnir et al. [1989] and expanded by Passier and Snieder [1995b] yields estimates of structure along short interstation paths and of average velocity gradients. In contrast, 3D tomographic inversions yield local estimates of the earth structure by

  7. 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).

  8. 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

  9. 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.

  10. 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

    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...... in a flow rig phantom is scanned at beam-to-flow angles of 90, 75, and 60◦ . The relative bias is between -1.4 % and -5.8 % and the relative std. between 5 % and 8.2 % for the lateral velocity component at the measured beam-to-flow angles. The estimated flow angle is 73.4◦± 3.6◦ for the measurement at 75...

  11. Full Waveform Inversion of Diving & Reflected Waves based on Scale Separation for Velocity and Impedance Imaging

    Science.gov (United States)

    Brossier, Romain; Zhou, Wei; Operto, Stéphane; Virieux, Jean

    2015-04-01

    Full Waveform Inversion (FWI) is an appealing method for quantitative high-resolution subsurface imaging (Virieux et al., 2009). For crustal-scales exploration from surface seismic, FWI generally succeeds in recovering a broadband of wavenumbers in the shallow part of the targeted medium taking advantage of the broad scattering-angle provided by both reflected and diving waves. In contrast, deeper targets are often only illuminated by short-spread reflections, which favor the reconstruction of the short wavelengths at the expense of the longer ones, leading to a possible notch in the intermediate part of the wavenumber spectrum. To update the velocity macromodel from reflection data, image-domain strategies (e.g., Symes & Carazzone, 1991) aim to maximize a semblance criterion in the migrated domain. Alternatively, recent data-domain strategies (e.g., Xu et al., 2012, Ma & Hale, 2013, Brossier et al., 2014), called Reflection FWI (RFWI), inspired by Chavent et al. (1994), rely on a scale separation between the velocity macromodel and prior knowledge of the reflectivity to emphasize the transmission regime in the sensitivity kernel of the inversion. However, all these strategies focus on reflected waves only, discarding the low-wavenumber information carried out by diving waves. With the current development of very long-offset and wide-azimuth acquisitions, a significant part of the recorded energy is provided by diving waves and subcritical reflections, and high-resolution tomographic methods should take advantage of all types of waves. In this presentation, we will first review the issues of classical FWI when applied to reflected waves and how RFWI is able to retrieve the long wavelength of the model. We then propose a unified formulation of FWI (Zhou et al., 2014) to update the low wavenumbers of the velocity model by the joint inversion of diving and reflected arrivals, while the impedance model is updated thanks to reflected wave only. An alternate inversion of

  12. Short-period surface-wave phase velocities across the conterminous United States

    Science.gov (United States)

    Ekström, G.

    2017-09-01

    Surface-wave phase-velocity maps for the full footprint of the USArray Transportable Array (TA) across the conterminous United States are developed and tested. Three-component, long-period continuous seismograms recorded on more than 1800 seismometers, most of which were deployed for 18 months or longer, are processed using a noise cross-correlation technique to derive inter-station Love and Rayleigh dispersion curves at periods between 5 and 40 s. The phase-velocity measurements are quality controlled using an automated algorithm and then used in inversions for Love and Rayleigh phase-velocity models at discrete periods on a 0.25°-by-0.25° pixel grid. The robustness of the results is examined using comparisons of maps derived from subsets of the data. A winter-summer division of the cross-correlation data results in small model differences, indicating relatively minor sensitivity of the results to seasonal variations in the distribution of noise sources. Division of the dispersion data based on inter-station azimuth does not result in geographically coherent model differences, suggesting that azimuthal anisotropy at the regional scale is weak compared with variations in isotropic velocities and does not substantially influence the results for isotropic velocities. The phase-velocity maps and dispersion measurements are documented and made available as data products of the 10-year-long USArray TA deployment.

  13. Waves with negative group velocity. Conditions of their existence in a isotropic medium

    International Nuclear Information System (INIS)

    Makarov, V.P.; Rukhadze, A.A.; Samokhin, A.A.

    2005-01-01

    The analysis of the frequency and spatial dispersions of the dielectric permittivity and magnetic permeability of an isotropic medium are carried out in the (E-vector, B-vector, D-vector) and (E-vector, B-vector, D-vector, H-vector) approaches of electrodynamics. The conditions under which the phase and group velocities of transverse electromagnetic waves have opposite directions are clarified, and the consequences arised are discussed

  14. Regional velocity structure in northern California from inversion of scattered seismic surface waves

    Science.gov (United States)

    Pollitz, Fred F.

    1999-07-01

    Seismic surface waves recorded by the Berkeley Digital Seismic Network have been analyzed in order to constrain three-dimensional lateral heterogeneity of the upper mantle under northern California. A total of 2164 seismograms from 173 teleseismic events were windowed for the fundamental mode Rayleigh wave, followed by estimation of complex amplitude spectra over the period range 16 to 100 s using a multiple-taper method. Since Rayleigh waves at shorter periods, particularly below 35 s, suffer from serious multipathing or "non-plane" wave arrivals, these amplitude spectra have been interpreted as the product of wavefront distortion along the teleseismic propagation path and seismic structure beneath the network. The amplitude spectra are first modeled in terms of non-plane incoming wavefields and structural phase velocity perturbations period by period. After corrections for Moho and surface topography, the phase velocity maps are inverted for three-dimensional shear velocity perturbations δνs down to a depth of 200 km. The δνs maps are in good agreement with the results of body studies over a broad spatial scale. The dominant signals are associated with the thermal effects of the active Gorda and fossil Farallon subducted slab stretching from Mount Shasta through the western Sierran foothills to the southern Great Valley and asthenospheric upwelling beneath the northern Coast Ranges. The southern Sierra Nevada Range is characterized by fast δνs down to ˜50 km and slow velocities between ˜60 and 120 km depth, in agreement with independent inferences of a cold crust and warm upper mantle, which may provide the buoyancy forces necessary to support the elevation of the range.

  15. A seismic waves velocity model for Gran Canaria Island from ambient noise correlations

    Science.gov (United States)

    García-Jerez, Antonio; Almendros, Javier; Martínez-Arévalo, Carmen; de Lis Mancilla, Flor; Luzón, Francisco; Carmona, Enrique; Martín, Rosa; Sánchez, Nieves

    2014-05-01

    We have analysed continuous ambient seismic noise recorded by a temporary array in Gran Canaria (Canary Islands, Spain) in order to find a velocity model for the top few kilometers. The SISTEVOTENCAN-IGN seismic array consisted of five broadband stations surrounding a sixth central one placed close to Pico de las Nieves, at the center of the island. The array had a radius of 12-14 km, with interstation distances ranging from 10 to 27 km. This network was operative from December 2009 to November 2011. The Green's functions between the 15 pairs of stations have been estimated in the time domain by stacking cross-correlations of 60-s time windows for the whole recording period (~2 years). The effects of several processing adjustments such as 1-bit normalization and spectral whitening are discussed. We observe significant differences (mainly in amplitude) between causal and acausal parts of the estimated Green's functions, which can be associated to an uneven distribution of the seismic noise sources. The application of a phase-matched filter based on an average dispersion curve allowed the effective reduction of some spurious early arrivals and the selection of fundamental-mode Rayleigh wave pulses, making possible an automatic extraction of their group velocities. Then, Rayleigh-wave dispersion curves were retrieved for the set of paths by using frequency-time analysis (FTAN) as well as by following the procedure described by Herrin and Goforth (1977, BSSA) based on the iterative fitting of a phase-matched filter which optimally undisperses the signal. Reliable curves were obtained from 1 s to 6-7 s with group velocities ranging between 1.5 and 2.2 km/s. Some lateral variations in velocity have been detected in spite of the limited spatial coverage and path density, which substantially restricted the resolution. A mean S-wave velocity model has been inverted for this area down to ~3 km.

  16. 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.

  17. AE source localization on the material with unknown elastic wave propagation velocity

    International Nuclear Information System (INIS)

    Lee, Weom Heum; Kim, Dal Jung; Jhang, Kyung Young

    1996-01-01

    The ability to locate defects in materials is one of the major attractions of the acoustic emission technique. The standard method of planar source location is to place three or more transducers on the surface of a specimen and to triangulate the source position by using the differences in arrival times of the acoustic emission wave at the sensors. But the standard method have limited applications if the propagation velocity in the medium is riot known. In this paper, we propose a method for AE source localization on the material with unknown elastic wave propagation velocity. In this method, it is not needed to know the propagation velocity previously, that is, we can apply this method to arbitrary materials of which properties is not known exactly. We discuss the robustness of detecting AE source location algorithm according to the errors, and signal processing for measurement of the differences in arrival times of acoustic emission wave at the sensors. For performance evaluation of this algorithm, experiments performed using a lead break as the AE source on the surface of an aluminum plate.

  18. 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

  19. 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.

  20. Standard practice for measuring the ultrasonic velocity in polyethylene tank walls using lateral longitudinal (LCR) waves

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2011-01-01

    1.1 This practice covers a procedure for measuring the ultrasonic velocities in the outer wall of polyethylene storage tanks. An angle beam lateral longitudinal (LCR) wave is excited with wedges along a circumferential chord of the tank wall. A digital ultrasonic flaw detector is used with sending-receiving search units in through transmission mode. The observed velocity is temperature corrected and compared to the expected velocity for a new, unexposed sample of material which is the same as the material being evaluated. The difference between the observed and temperature corrected velocities determines the degree of UV exposure of the tank. 1.2 The practice is intended for application to the outer surfaces of the wall of polyethylene tanks. Degradation typically occurs in an outer layer approximately 3.2-mm (0.125-in.) thick. Since the technique does not interrogate the inside wall of the tank, wall thickness is not a consideration other than to be aware of possible guided (Lamb) wave effects or reflection...

  1. 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.

  2. Generation of lower hybrid and whistler waves by an ion velocity ring distribution

    International Nuclear Information System (INIS)

    Winske, D.; Daughton, W.

    2012-01-01

    Using fully kinetic simulations in two and three spatial dimensions, we consider the generation and nonlinear evolution of lower hybrid waves produced by a cold ion ring velocity distribution in a low beta plasma. We show that the initial development of the instability is very similar in two and three dimensions and not significantly modified by electromagnetic effects, consistent with linear theory. At saturation, the level of electric field fluctuations is a small fraction of the background thermal energy; the electric field and corresponding density fluctuations consist of long, field-aligned striations. Energy extracted from the ring goes primarily into heating the background ions and the electrons at comparable rates. The initial growth and saturation of the magnetic components of the lower hybrid waves are related to the electric field components, consistent with linear theory. As the growing electric field fluctuations saturate, parallel propagating whistler waves develop by the interaction of two lower hybrid waves. At later times, these whistlers are replaced by longer wavelength, parallel propagating whistlers that grow through the decay of the lower hybrid fluctuations. Wave matching conditions demonstrate these conversion processes of lower hybrid waves to whistler waves. The conversion efficiency (=ratio of the whistler wave energy to the energy in the saturated lower hybrid waves) is computed and found to be significant (∼15%) for the parameters of the three-dimensional simulation (and even larger in the two-dimensional simulation), although when normalized in terms of the initial kinetic energy in the ring ions the overall efficiency is very small ( −4 ). The results are compared with relevant linear and nonlinear theory.

  3. Near-surface wave velocity structure of Faial (Azores - Portugal) Island for site effect studies

    Science.gov (United States)

    Borges, José; Neves, Samuel; Caldeira, Bento; Bezzeghoud, Mourad; Carvalho, João; Carvalho, Alexandra

    2015-04-01

    Throughout history, the life of the Azorean people has been marked by earthquakes that have had different effects depending on their proximity and magnitude. This seismic activity, which may have volcanic or tectonic origins, has affected the population of these islands by destroying infrastructure and claiming lives. The social and economic impacts of these phenomena are enormous. The last significant event affecting the Azores (Portugal) was the July 1998 Mw=6.2 earthquake causing major destruction affecting more than 5000 people, causing 8 deaths, 150 persons injured and 1500 homeless. Ground motion simulations are mainly based on source characteristics and are heavily dependent on the medium, which is still poorly understood. Subsurface soil condition can amplify the seismic waves, so, for seismic response analysis, it is necessary to know the shallow soil properties and its spatial variability. For this purpose, we applied P and S-wave refraction, Multichannel Analysis of Surface Waves (MASW) to characterize shear wave velocity at different sites in the Faial Island, in particular, in sites where already occurred amplification. Ambient vibrations can also be used to estimate physical properties of the shallower geological formations. With this goal, the obtained velocity models were confirmed by comparison between real H/V curves with synthetic ones. We concluded that the anomalous intensities observed in some sites are strongly related to thick layers of soft sediments of pyroclastic deposits produced by old volcanic eruptions occurred in the Faial Island.

  4. 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.

  5. Effects of group velocity and multiplasmon resonances on the modulation of Langmuir waves in a degenerate plasma.

    Science.gov (United States)

    Misra, Amar P; Chatterjee, Debjani; Brodin, Gert

    2017-11-01

    We study the nonlinear wave modulation of Langmuir waves (LWs) in a fully degenerate plasma. Using the Wigner-Moyal equation coupled to the Poisson equation and the multiple scale expansion technique, a modified nonlocal nonlinear Schrödinger (NLS) equation is derived which governs the evolution of LW envelopes in degenerate plasmas. The nonlocal nonlinearity in the NLS equation appears due to the group velocity and multiplasmon resonances, i.e., resonances induced by the simultaneous particle absorption of multiple wave quanta. We focus on the regime where the resonant velocity of electrons is larger than the Fermi velocity and thereby the linear Landau damping is forbidden. As a result, the nonlinear wave-particle resonances due to the group velocity and multiplasmon processes are the dominant mechanisms for wave-particle interaction. It is found that in contrast to classical or semiclassical plasmas, the group velocity resonance does not necessarily give rise the wave damping in the strong quantum regime where ℏk∼mv_{F} with ℏ denoting the reduced Planck's constant, m the electron mass, and v_{F} the Fermi velocity; however, the three-plasmon process plays a dominant role in the nonlinear Landau damping of wave envelopes. In this regime, the decay rate of the wave amplitude is also found to be higher compared to that in the modest quantum regime where the multiplasmon effects are forbidden.

  6. 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.

  7. Effect of wind waves on air-sea gas exchange: proposal of an overall CO2 transfer velocity formula as a function of breaking-wave parameter

    International Nuclear Information System (INIS)

    Zhao, D.; Suzuki, Y.; Komori, S.

    2003-01-01

    A new formula for gas transfer velocity as a function of the breaking-wave parameter is proposed based on correlating gas transfer with whitecap coverage. The new formula for gas transfer across an air-sea interface depends not only on wind speed but also on wind-wave state. At the same wind speed, a higher gas transfer velocity will be obtained for a more developed wind-sea, which is represented by a smaller spectral peak frequency of wind waves. We suggest that the large uncertainties in the traditional relationship of gas transfer velocity with wind speed be ascribed to the neglect of the effect of wind waves. The breaking-wave parameter can be regarded as a Reynolds number that characterizes the intensity of turbulence associated with wind waves in the downward-bursting boundary layer (DBBL). DBBL provides an effective way to exchange gas across the air-sea interface, which might be related to the surface renewal

  8. Thermodynamic relations for shock waves in materials with a linear relation between shock-wave and particle velocities

    International Nuclear Information System (INIS)

    Rodean, H.C.

    1977-01-01

    The Rankine-Hugoniot relations for shock waves and the empirical linear relation between the shock-wave and particle velocities define an incomplete thermodynamic description of the states along the Hugoniot curve. This incomplete description defines the following along the Hugoniot: (1) internal energy and pressure as functions of specific volume, (2) the ratio of enthalpy to internal energy, (3) the ratio of the changes in enthalpy and internal energy across a shock wave, and (4) the relation between the Grueneisen coefficient and the effective isentropic exponent. We use the Dugdale-MacDonald relation for the Grueneisen coefficient at low pressure, an assumed constant value for the specific heat at constant volume, and reasonable physical assumptions for extremely strong shock waves together with the incomplete thermodynamic state description to define the following along the Hugoniot: (5) the Grueneisen coefficient, (6) the effective isentropic exponent, (7) the ratio of specific heats, and (8) thermal and elastic components of pressure, temperature, and entropy. We present representative numerical values of these parameters as functions of reduced volumetric compression. We show how the solutions for these parameters define tangent planes to the surfaces of the incomplete E,P, and V and P,V, and T equations of state at each point along the Hugoniot curve

  9. Multi-channel analysis of surface waves MASW of models with high shear-wave velocity contrast

    Science.gov (United States)

    Ivanov, J.; Miller, R.D.; Peterie, S.; Zeng, C.; Xia, J.; Schwenk, T.

    2011-01-01

    We use the multi-channel analysis of surface waves MASW method to analyze synthetic seismic data calculated using models with high shear-wave velocity Vs contrast. The MASW dispersion-curve images of the Rayleigh wave are obtained using various sets of source-offset and spread-size configurations from the synthetic seismic data and compared with the theoretically calculated fundamental- and higher-mode dispersion-curves. Such tests showed that most of the dispersion-curve images are dominated by higher-mode energy at the low frequencies, especially when analyzing data from long receiver offsets and thus significantly divert from numerically expected dispersion-curve trends, which can lead to significant Vs overestimation. Further analysis showed that using data with relatively short spread lengths and source offsets can image the desired fundamental-mode of the Rayleigh wave that matches the numerically expected dispersion-curve pattern. As a result, it was concluded that it might be possible to avoid higher-mode contamination at low frequencies at sites with high Vs contrast by appropriate selection of spread size and seismic source offset. ?? 2011 Society of Exploration Geophysicists.

  10. 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

  11. Frictional response of simulated faults to normal stresses perturbations probed with ultrasonic waves

    Science.gov (United States)

    Shreedharan, S.; Riviere, J.; Marone, C.

    2017-12-01

    We report on a suite of laboratory friction experiments conducted on saw-cut Westerly Granite surfaces to probe frictional response to step changes in normal stress and loading rate. The experiments are conducted to illuminate the fundamental processes that yield friction rate and state dependence. We quantify the microphysical frictional response of the simulated fault surfaces to normal stress steps, in the range of 1% - 600% step increases and decreases from a nominal baseline normal stress. We measure directly the fault slip rate and account for changes in slip rate with changes in normal stress and complement mechanical data acquisition by continuously probing the faults with ultrasonic pulses. We conduct the experiments at room temperature and humidity conditions in a servo controlled biaxial testing apparatus in the double direct shear configuration. The samples are sheared over a range of velocities, from 0.02 - 100 μm/s. We report observations of a transient shear stress and friction evolution with step increases and decreases in normal stress. Specifically, we show that, at low shear velocities and small increases in normal stress ( 5% increases), the shear stress evolves immediately with normal stress. We show that the excursions in slip rate resulting from the changes in normal stress must be accounted for in order to predict fault strength evolution. Ultrasonic wave amplitudes which first increase immediately in response to normal stress steps, then decrease approximately linearly to a new steady state value, in part due to changes in fault slip rate. Previous descriptions of frictional state evolution during normal stress perturbations have not adequately accounted for the effect of large slip velocity excursions. Here, we attempt to do so by using the measured ultrasonic amplitudes as a proxy for frictional state during transient shear stress evolution. Our work aims to improve understanding of induced and triggered seismicity with focus on

  12. 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.

  13. Joint inversion of high resolution S-wave velocity structure underneath North China Basin

    Science.gov (United States)

    Yang, C.; Li, G.; Niu, F.

    2017-12-01

    North China basin is one of earthquake prone areas in China. Many devastating earthquakes occurred in the last century and before, such as the 1937 M7.0 Heze Earthquake in Shandong province, the 1966 M7.2 Xingtai Earthquake and 1976 Tangshan Earthquake in Hebei province. Knowing the structure of the sediment cover is of great importance to predict strong ground motion caused by earthquakes. Unconsolidated sediments are loose materials, ranging from clay to sand to gravel. Earthquakes can liquefy unconsolidated sediments, thus knowing the distribution and thickness of the unconsolidated sediments has significant implication in seismic hazard analysis of the area. Quantitative estimates of the amount of extension of the North China basin is important to understand the thinning and evolution of the eastern North China craton and the underlying mechanism. In principle, the amount of lithospheric stretching can be estimated from sediment and crustal thickness. Therefore an accurate estimate of the sediment and crustal thickness of the area is also important in understanding regional tectonics. In this study, we jointly invert the Rayleigh wave phase-velocity dispersion and Z/H ratio data to construct a 3-D S-wave velocity model beneath North China area. We use 4-year ambient noise data recorded from 249 temporary stations, and 139 earthquake events to extract Rayleigh wave Z/H ratios. The Z/H ratios obtained from ambient noise data and earthquake data show a good agreement within the overlapped periods. The phase velocity dispersion curve was estimated from the same ambient noise data. The preliminary result shows a relatively low Z/H ratio and low velocity anomaly at the shallow part of sediment basins.

  14. Theoretical Studies of Stress Wave Propagation in Laterally Confined Soils

    National Research Council Canada - National Science Library

    Rohani, Behzad

    1999-01-01

    .... A considerable body of scientific literature on one-dimensional stress wave propagation for such models has been published in recent years by various researchers, both in the United States and abroad...

  15. Seismic Wave Propagation from Underground Chemical Explosions: Sensitivity to Velocity and Thickness of a Weathered Layer

    Science.gov (United States)

    Hirakawa, E. T.; Ezzedine, S. M.

    2017-12-01

    Recorded motions from underground chemical explosions are complicated by long duration seismic coda as well as motion in the tangential direction. The inability to distinguish the origins of these complexities as either source or path effects comprises a limitation to effective monitoring of underground chemical explosions. With numerical models, it is possible to conduct rigorous sensitivity analyses for chemical explosive sources and their resulting ground motions under the influence of many attributes, including but not limited to complex velocity structure, topography, and non-linear source characteristics. Previously we found that topography can cause significant scattering in the direct wave but leads to relatively little motion in the coda. Here, we aim to investigate the contribution from the low-velocity weathered layer that exists in the shallow subsurface apart from and in combination with surface topography. We use SW4, an anelastic anisotropic fourth order finite difference code to simulate chemical explosive source in a 1D velocity structure consisting of a single weathered layer over a half space. A range of velocity magnitudes are used for the upper weathered layer with the velocities always being lower than that of the granitic underlaying layer. We find that for lower weathered layer velocities, the wave train is highly dispersed and causes a large percentage of energy to be contained in the coda in relation to the entire time series. The percentage of energy contained in the coda grows with distance from the source but saturates at a certain distance that depends on weathered layer velocity and thickness. The saturation onset distance increases with decreasing layer thickness and increasing velocity of the upper layer. Measurements of relative coda energy and coda saturation onset distance from real recordings can provide an additional constraint on the properties of the weathered layer in remote sites as well as test sites like the Nevada

  16. 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.

  17. Porosity and sonic velocity depth trends of Eocene chalk in Atlantic Ocean: Influence of effective stress and temperature

    DEFF Research Database (Denmark)

    Awedalkarim, Ahmed; Fabricius, Ida Lykke

    2014-01-01

    data were correlated to vertical effective stresses and to TTI.Our porosity data showed a broader porosity trend in the mechanical compaction zone, and the onset of the formation of limestone at a shallower burial depth than the porosity data of the Ontong Java Plateau chalk show. Our porosity data do...... of geological age on chalk compaction trends. For each depth, vertical effective stresses as defined by Terzaghi and by Biot were calculated. We used bottom-hole temperature data to calculate the time–temperature index of thermal maturity (TTI) as defined by Lopatin. Porosity and compressional wave velocity...... not show or at least it is difficult to define a clear pore-stiffening contact cementation trend as the Ontong Java Plateau chalk. Mechanical compaction is the principal cause of porosity reduction (at shallow depths) in the studied Eocene chalk, at least down to about 5MPa Terzaghi׳s effective stress...

  18. The effect of inhomogeneous initial stress on Love wave propagation in layered magneto-electro-elastic structures

    International Nuclear Information System (INIS)

    Zhang, J; Shen, Y P; Du, J K

    2008-01-01

    The effect of inhomogeneous initial stress on Love wave propagation in layered magneto-electro-elastic structures is investigated in this paper. The coupled magneto-electro-elastic field equations are solved by adopting the Wentzel–Kramers–Brillouin (WKB) approximate approach. Then the phase velocity can be calculated by applying boundary and continuity conditions. A specific example of a structure consisting of a CoFe 2 O 4 layer and a BaTiO 3 substrate is used to illustrate the influence of inhomogeneous initial stress on the phase velocity, corresponding coupled magneto-electric factor and stress fields. The different influence between constant initial stress and inhomogeneous initial stress is discussed and the results are expected to be helpful for the preparation and application of Love wave sensors

  19. Stress Wave Propagation in Larch Plantation Trees-Numerical Simulation

    Science.gov (United States)

    Fenglu Liu; Fang Jiang; Xiping Wang; Houjiang Zhang; Wenhua Yu

    2015-01-01

    In this paper, we attempted to simulate stress wave propagation in virtual tree trunks and construct two dimensional (2D) wave-front maps in the longitudinal-radial section of the trunk. A tree trunk was modeled as an orthotropic cylinder in which wood properties along the fiber and in each of the two perpendicular directions were different. We used the COMSOL...

  20. Improved Blood Pressure Prediction Using Systolic Flow Correction of Pulse Wave Velocity.

    Science.gov (United States)

    Lillie, Jeffrey S; Liberson, Alexander S; Borkholder, David A

    2016-12-01

    Hypertension is a significant worldwide health issue. Continuous blood pressure monitoring is important for early detection of hypertension, and for improving treatment efficacy and compliance. Pulse wave velocity (PWV) has the potential to allow for a continuous blood pressure monitoring device; however published studies demonstrate significant variability in this correlation. In a recently presented physics-based mathematical model of PWV, flow velocity is additive to the classic pressure wave as estimated by arterial material properties, suggesting flow velocity correction may be important for cuff-less non-invasive blood pressure measures. The present study examined the impact of systolic flow correction of a measured PWV on blood pressure prediction accuracy using data from two published in vivo studies. Both studies examined the relationship between PWV and blood pressure under pharmacological manipulation, one in mongrel dogs and the other in healthy adult males. Systolic flow correction of the measured PWV improves the R 2 correlation to blood pressure from 0.51 to 0.75 for the mongrel dog study, and 0.05 to 0.70 for the human subjects study. The results support the hypothesis that systolic flow correction is an essential element of non-invasive, cuff-less blood pressure estimation based on PWV measures.

  1. 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.

  2. Evolution of microstructure and elastic wave velocities in dehydrated gypsum samples

    Science.gov (United States)

    Milsch, Harald; Priegnitz, Mike

    2012-12-01

    We report on changes in P and S-wave velocities and rock microstructure induced by devolatilization reactions using gypsum as a reference analog material. Cylindrical samples of natural alabaster were dehydrated in air, at ambient pressure, and temperatures between 378 and 423 K. Dehydration did not proceed homogeneously but via a reaction front moving sample inwards separating an outer highly porous rim from the remaining gypsum which, above approximately 393 (±5) K, concurrently decomposed into hemihydrate. Overall porosity was observed to continuously increase with reaction progress from approximately 2% for fully hydrated samples to 30% for completely dehydrated ones. Concurrently, P and S-wave velocities linearly decreased with porosity from 5.2 and 2.7 km/s to 1.0 and 0.7 km/s, respectively. It is concluded that a linearized empirical Raymer-type model extended by a critical porosity term and based on the respective time dependent mineral and pore volumes reasonably replicates the P and S-wave data in relation to reaction progress and porosity.

  3. 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.

  4. Eulerian-Lagrangian analysis for particle velocities and trajectories in a pure wave motion using particle image velocimetry.

    Science.gov (United States)

    Umeyama, Motohiko

    2012-04-13

    This paper investigates the velocity and the trajectory of water particles under surface waves, which propagate at a constant water depth, using particle image velocimetry (PIV). The vector fields and vertical distributions of velocities are presented at several phases in one wave cycle. The third-order Stokes wave theory was employed to express the physical quantities. The PIV technique's ability to measure both temporal and spatial variations of the velocity was proved after a series of attempts. This technique was applied to the prediction of particle trajectory in an Eulerian scheme. Furthermore, the measured particle path was compared with the positions found theoretically by integrating the Eulerian velocity to the higher order of a Taylor series expansion. The profile of average travelling distance is also presented with a solution of zero net mass flux in a closed wave flume.

  5. Crustal structure of northern Egypt from joint inversion of receiver functions and surface wave dispersion velocities

    Science.gov (United States)

    Badawy, Ahmed; Hegazi, Mona; Gaber, Hanan; Korrat, Ibrahim

    2018-01-01

    In this study, we used a combined inversion of body wave receiver functions and surface wave dispersion measurements to provide constraints on the crustal structure of northern Egypt. The two techniques are complementary to each other: receiver functions (RFs) are sensitive to shear-wave velocity contrasts, while surface wave dispersion (SWD) measurements are sensitive to finite variations of shear-wave velocity with depth. A database of 122 teleseismic events digitally recorded by the Egyptian National Seismological Network (ENSN) stations has been used as well. To enhance the resulting RFs at each ENSN station, the H-k stacking method was applied. A joint inversion process between the resulting receiver functions and the surface wave dispersion curves was applied as well. We have produced three averaged velocity structure models for distinct geographic and tectonic provinces namely Sinai, eastern desert, and western desert from east to the west respectively. These models will deeply help in estimation the epicenter distance of earthquake, focal mechanism solutions, and earthquake hazard analysis in northern Egypt. An obvious image of the subsurface structure has been determined which shows that generally the crustal structure of northern Egypt consists of three layers covered with a sequence of sediments that differs in thickness from across the region except in the Sharm area where the sedimentary cover is absent. The obtained results indicate that crustal thickness differs from east to west and reaches its maximum value of about 36 km at Siwa station (SWA) in the western desert and its minimum value of about 28 km at Sharm station (SHR) of the southern tip of the Sinai Peninsula. The Vp/Vs ratio varies between 1.71 and 2.07 in northern Egypt. Generally, the high values (1.93) of (Vp/Vs) at SWA station may reflect the well-known rich aquifer with fully saturated sediments of the Swia Oasis in the Western Desert. Moreover, the highest value (2.07) of (Vp/Vs) at

  6. 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.

  7. 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.

  8. Shallow S-Wave Velocity Structures in the Western Coastal Plain of Taiwan

    Directory of Open Access Journals (Sweden)

    Che-Min Lin

    2009-01-01

    Full Text Available The western coastal plain of Taiwan borders the Western Foot hills, which is a fold-and-thrust zone and one of Taiwan's major seismic zones. Earth quakes from the Western Foot hills are a frequent cause of disaster in the western coastal plain. In this study, array measurements of microtremors were conducted at seven sites through out the western coastal plain. At each site, four arrays (S, M, L, and XL arrays of different sizes were considered. The largest radius of each array ranged from 32 m to 1 km. The Maximum Likelihood Method of Frequency-Wavenumber (F-K analyses was used to obtain phase velocity dispersion curves. After the inversion of the dispersion curves with the initial models decided by Genetic Algorithm (GA searching, shallow S-wave velocity structures for the western coastal plain were estimated.

  9. A Novel Dynamic Model for Predicting Pressure Wave Velocity in Four-Phase Fluid Flowing along the Drilling Annulus

    Directory of Open Access Journals (Sweden)

    Xiangwei Kong

    2015-01-01

    Full Text Available A dynamic pressure wave velocity model is presented based on momentum equation, mass-balance equation, equation of state, and small perturbation theory. Simultaneously, the drift model was used to analyze the flow characteristics of oil, gas, water, and drilling fluid multiphase flow. In addition, the dynamic model considers the gas dissolution, virtual mass force, drag force, and relative motion of the interphase as well. Finite difference and Newton-Raphson iterative are introduced to the numerical simulation of the dynamic model. The calculation results indicate that the wave velocity is more sensitive to the increase of gas influx rate than the increase of oil/water influx rate. Wave velocity decreases significantly with the increase of gas influx. Influenced by the pressure drop of four-phase fluid flowing along the annulus, wave velocity tends to increase with respect to well depth, contrary to the gradual reduction of gas void fraction at different depths with the increase of backpressure (BP. Analysis also found that the growth of angular frequency will lead to an increase of wave velocity at low range. Comparison with the calculation results without considering virtual mass force demonstrates that the calculated wave velocity is relatively bigger by using the presented model.

  10. Electromagnetic energy density and stress tensor in a warm plasma with finite flow velocity

    International Nuclear Information System (INIS)

    Choi, Cheong R.; Lee, Nam C.

    2004-01-01

    The expressions of the average of energy density and the average stress tensor of the electromagnetic field in a warm collisionless plasma moving with a finite velocity are obtained by using a microscopic method that uses the fluid description of plasma. The result contains terms involved with derivatives of the dielectric tensor with respect to the velocity, which explicitly represent the effects of the finite velocity of the medium. In the zero-velocity limit, the results reduce to the well-known expressions for a plasma at rest with temporal and spatial dispersion

  11. 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.

  12. 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...

  13. Effect of pore pressure on the velocity of compressional waves in low-porosity rocks.

    Science.gov (United States)

    Todd, T.; Simmons, G.

    1972-01-01

    The velocity V sub p of compressional waves has been measured in rock samples of low porosity to confining pressures P sub c of 2 kb for a number of different constant pore pressures P sub p. An effective pressure defined by P sub e = P sub c-nP sub p, n less than or equal to 1, is found to be the determining factor in the behavior of V sub p rather than an effective pressure defined simply by the differential pressure Delta P = P sub c-P sub p. As pore pressure increases at constant effective pressure, the value of n increases and approaches 1, but as effective pressure increases at constant pore pressure, the value of n decreases. These observations are consistent with Biot's theory of the propagation of elastic waves in a fluid-saturated porous solid.

  14. Weak-anisotropy approximations of P-wave phase and ray velocities for anisotropy of arbitrary symmetry

    Czech Academy of Sciences Publication Activity Database

    Farra, V.; Pšenčík, Ivan

    2016-01-01

    Roč. 60, č. 3 (2016), s. 403-418 ISSN 0039-3169 Institutional support: RVO:67985530 Keywords : weak anisotropy * P-wave * phase velocity * ray velocity Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.764, year: 2016

  15. Shear wave velocity structure of the lower crust in southern Africa: evidence for compositional heterogeneity within Archaean and Proterozoic terrains

    CSIR Research Space (South Africa)

    Kgaswane, EM

    2009-12-01

    Full Text Available . For large parts of both Archaean and Proterozoic terrains, the velocity models obtained from the inversions show shear wave velocities =4.0 km/s below ~20–30 km depth, indicating a predominantly mafic lower crust. However, for much of the Kimberley terrain...

  16. Crack closure and healing studies in WIPP [Waste Isolation Pilot Plant] salt using compressional wave velocity and attenuation measurements: Test methods and results

    International Nuclear Information System (INIS)

    Brodsky, N.S.

    1990-11-01

    Compressional wave ultrasonic data were used to qualitatively assess the extent of crack closure during hydrostatic compression of damaged specimens of WIPP salt. Cracks were introduced during constant strain-rate triaxial tests at low confining pressure (0.5 MPa) as specimens were taken to either 0.5, 1.0, or 1.5 percent axial strain. For three specimens taken to 1.0 percent axial strain, the pressure was increased to 5, 10 or 15 MPa. For the remaining specimens, pressure was raised to 15 MPa. Waveforms for compressional waves traveling both parallel and perpendicular to the direction of maximum principal stress were measured in the undamaged state, during constant strain-rate tests, and then monitored as functions of time while the specimens were held at pressure. Both wave velocities and amplitudes increased over time at pressure, indicating that cracks closed and perhaps healed. The recovery of ultrasonic wave characteristics depended upon both pressure and damage level. The higher the pressure, the greater the velocity recovery; however, amplitude recovery showed no clear correlation with pressure. For both amplitudes and velocities, recoveries were greatest in the specimens with the least damage. 13 refs., 15 figs., 1 tab

  17. The thin section rock physics: Modeling and measurement of seismic wave velocity on the slice of carbonates

    Energy Technology Data Exchange (ETDEWEB)

    Wardaya, P. D., E-mail: pongga.wardaya@utp.edu.my; Noh, K. A. B. M., E-mail: pongga.wardaya@utp.edu.my; Yusoff, W. I. B. W., E-mail: pongga.wardaya@utp.edu.my [Petroleum Geosciences Department, Universiti Teknologi PETRONAS, Tronoh, Perak, 31750 (Malaysia); Ridha, S. [Petroleum Engineering Department, Universiti Teknologi PETRONAS, Tronoh, Perak, 31750 (Malaysia); Nurhandoko, B. E. B. [Wave Inversion and Subsurface Fluid Imaging Research Laboratory (WISFIR), Dept. of Physics, Institute of Technology Bandung, Bandung, Indonesia and Rock Fluid Imaging Lab, Bandung (Indonesia)

    2014-09-25

    This paper discusses a new approach for investigating the seismic wave velocity of rock, specifically carbonates, as affected by their pore structures. While the conventional routine of seismic velocity measurement highly depends on the extensive laboratory experiment, the proposed approach utilizes the digital rock physics view which lies on the numerical experiment. Thus, instead of using core sample, we use the thin section image of carbonate rock to measure the effective seismic wave velocity when travelling on it. In the numerical experiment, thin section images act as the medium on which wave propagation will be simulated. For the modeling, an advanced technique based on artificial neural network was employed for building the velocity and density profile, replacing image's RGB pixel value with the seismic velocity and density of each rock constituent. Then, ultrasonic wave was simulated to propagate in the thin section image by using finite difference time domain method, based on assumption of an acoustic-isotropic medium. Effective velocities were drawn from the recorded signal and being compared to the velocity modeling from Wyllie time average model and Kuster-Toksoz rock physics model. To perform the modeling, image analysis routines were undertaken for quantifying the pore aspect ratio that is assumed to represent the rocks pore structure. In addition, porosity and mineral fraction required for velocity modeling were also quantified by using integrated neural network and image analysis technique. It was found that the Kuster-Toksoz gives the closer prediction to the measured velocity as compared to the Wyllie time average model. We also conclude that Wyllie time average that does not incorporate the pore structure parameter deviates significantly for samples having more than 40% porosity. Utilizing this approach we found a good agreement between numerical experiment and theoretically derived rock physics model for estimating the effective seismic

  18. The thin section rock physics: Modeling and measurement of seismic wave velocity on the slice of carbonates

    International Nuclear Information System (INIS)

    Wardaya, P. D.; Noh, K. A. B. M.; Yusoff, W. I. B. W.; Ridha, S.; Nurhandoko, B. E. B.

    2014-01-01

    This paper discusses a new approach for investigating the seismic wave velocity of rock, specifically carbonates, as affected by their pore structures. While the conventional routine of seismic velocity measurement highly depends on the extensive laboratory experiment, the proposed approach utilizes the digital rock physics view which lies on the numerical experiment. Thus, instead of using core sample, we use the thin section image of carbonate rock to measure the effective seismic wave velocity when travelling on it. In the numerical experiment, thin section images act as the medium on which wave propagation will be simulated. For the modeling, an advanced technique based on artificial neural network was employed for building the velocity and density profile, replacing image's RGB pixel value with the seismic velocity and density of each rock constituent. Then, ultrasonic wave was simulated to propagate in the thin section image by using finite difference time domain method, based on assumption of an acoustic-isotropic medium. Effective velocities were drawn from the recorded signal and being compared to the velocity modeling from Wyllie time average model and Kuster-Toksoz rock physics model. To perform the modeling, image analysis routines were undertaken for quantifying the pore aspect ratio that is assumed to represent the rocks pore structure. In addition, porosity and mineral fraction required for velocity modeling were also quantified by using integrated neural network and image analysis technique. It was found that the Kuster-Toksoz gives the closer prediction to the measured velocity as compared to the Wyllie time average model. We also conclude that Wyllie time average that does not incorporate the pore structure parameter deviates significantly for samples having more than 40% porosity. Utilizing this approach we found a good agreement between numerical experiment and theoretically derived rock physics model for estimating the effective seismic wave

  19. 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.

  20. Animal models of surgically manipulated flow velocities to study shear stress-induced atherosclerosis.

    Science.gov (United States)

    Winkel, Leah C; Hoogendoorn, Ayla; Xing, Ruoyu; Wentzel, Jolanda J; Van der Heiden, Kim

    2015-07-01

    Atherosclerosis is a chronic inflammatory disease of the arterial tree that develops at predisposed sites, coinciding with locations that are exposed to low or oscillating shear stress. Manipulating flow velocity, and concomitantly shear stress, has proven adequate to promote endothelial activation and subsequent plaque formation in animals. In this article, we will give an overview of the animal models that have been designed to study the causal relationship between shear stress and atherosclerosis by surgically manipulating blood flow velocity profiles. These surgically manipulated models include arteriovenous fistulas, vascular grafts, arterial ligation, and perivascular devices. We review these models of manipulated blood flow velocity from an engineering and biological perspective, focusing on the shear stress profiles they induce and the vascular pathology that is observed. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  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. The role of stress waves and cavitation in stone comminution in shock wave lithotripsy.

    Science.gov (United States)

    Zhu, Songlin; Cocks, Franklin H; Preminger, Glenn M; Zhong, Pei

    2002-05-01

    Using an experimental system that mimics stone fragmentation in the renal pelvis, we have investigated the role of stress waves and cavitation in stone comminution in shock-wave lithotripsy (SWL). Spherical plaster-of-Paris stone phantoms (D = 10 mm) were exposed to 25, 50, 100, 200, 300 and 500 shocks at the beam focus of a Dornier HM-3 lithotripter operated at 20 kV and a pulse repetition rate of 1 Hz. The stone phantoms were immersed either in degassed water or in castor oil to delineate the contribution of stress waves and cavitation to stone comminution. It was found that, while in degassed water there is a progressive disintegration of the stone phantoms into small pieces, the fragments produced in castor oil are fairly sizable. From 25 to 500 shocks, clinically passable fragments (stones with a primary composition of calcium oxalate monohydrate. After 200 shocks, 89% of the fragments of the kidney stones treated in degassed water became passable, but only 22% of the fragments of the kidney stones treated in castor oil were less than 2 mm in size. This apparent size limitation of the stone fragments produced primarily by stress waves (in castor oil) is likely caused by the destructive superposition of the stress waves reverberating inside the fragments, when their sizes are less than half of the compressive wavelength in the stone material. On the other hand, if a stone is only exposed to cavitation bubbles induced in SWL, the resultant fragmentation is much less effective than that produced by the combination of stress waves and cavitation. It is concluded that, although stress wave-induced fracture is important for the initial disintegration of kidney stones, cavitation is necessary to produce fine passable fragments, which are most critical for the success of clinical SWL. Stress waves and cavitation work synergistically, rather than independently, to produce effective and successful disintegration of renal calculi in SWL

  4. Shear wave velocity model beneath CBJI station West Java, Indonesia from joint inversion of teleseismic receiver functions and surface wave dispersion

    Science.gov (United States)

    Simanungkalit, R. H.; Anggono, T.; Syuhada; Amran, A.; Supriyanto

    2018-03-01

    Earthquake signal observations around the world allow seismologists to obtain the information of internal structure of the Earth especially the Earth’s crust. In this study, we used joint inversion of receiver functions and surface wave group velocities to investigate crustal structure beneath CBJI station in West Java, Indonesia. Receiver function were calculated from earthquakes with magnitude more than 5 and at distance 30°-90°. Surface wave group velocities were calculated using frequency time analysis from earthquakes at distance of 30°- 40°. We inverted shear wave velocity model beneath the station by conducting joint inversion from receiver functions and surface wave dispersions. We suggest that the crustal thickness beneath CBJI station, West Java, Indonesia is about 35 km.

  5. Resonant pressure wave setup for simultaneous sensing of longitudinal viscosity and sound velocity of liquids

    International Nuclear Information System (INIS)

    Beigelbeck, Roman; Cerimovic, Samir; Keplinger, Franz; Jakoby, Bernhard; Antlinger, Hannes; Clara, Stefan

    2013-01-01

    Increasing demands for online monitoring of liquids have not only resuted in many new devices relying on well-established sensing parameters like shear viscosity but also initiated research on alternative parameters. Recently, the longitudinal viscosity has been evaluated as a promising candidate because the devices arising enable the bulk of the liquid to be probed rather than a thin surface layer. We report on a multi-purpose sensor which allows simultaneous measurement of the sound velocity and longitudinal viscosity of liquids. The device embodiment features a cube-shaped chamber containing the sample liquid, where one boundary surface carries a flush-mounted PZT transducer. In operation, the transducer induces standing, resonant pressure waves in the liquid under test. We studied the influences of sound velocity and longitudinal viscosity on the generated pressure waves by means of the Navier–Stokes equation for adiabatic compressible liquids and exploited both parameters as the basic sensing mechanism. Furthermore, a three-port network model describing the interaction of the transducer and sample liquid was developed in order to be applied for extracting the parameters of interest from the raw measurement data. Finally, we demonstrate the device and method by carrying out and discussing test measurements on glycerol–water solutions. (paper)

  6. Statistical correlations of shear wave velocity and penetration resistance for soils

    Science.gov (United States)

    Dikmen, Ünal

    2009-03-01

    In this paper, the correlation between shear wave velocity and standard penetration test blow counts (SPT-N) is investigated. The study focused primarily on the correlation of SPT-N and shear wave velocity (Vs) for several soil categories: all soils, sand, silt and clay-type soils. New empirical formulae are suggested to correlate SPT-N and Vs, based on a dataset collected in a part of Eskişehir settlement in the western central Anatolia region of Turkey. The formulae are based on geotechnical soundings and active and passive seismic experiments. The new and previously suggested formulae showing correlations between uncorrected SPT-N and Vs have been compared and evaluated by using the same dataset. The results suggest that better correlations in estimation of Vs are acquired when the uncorrected blow counts are used. The blow count is a major parameter and the soil type has no significant influence on the results. In cohesive soils, the plasticity contents and, in non-cohesive soils except for gravels, the graded contents have no significant effect on the estimation of Vs. The results support most of the conclusions of earlier studies. These practical relationships developed between SPT-N and Vs should be used with caution in geotechnical engineering and should be checked against measured Vs.

  7. 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.

  8. 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.

  9. Shear-wave velocity-based probabilistic and deterministic assessment of seismic soil liquefaction potential

    Science.gov (United States)

    Kayen, R.; Moss, R.E.S.; Thompson, E.M.; Seed, R.B.; Cetin, K.O.; Der Kiureghian, A.; Tanaka, Y.; Tokimatsu, K.

    2013-01-01

    Shear-wave velocity (Vs) offers a means to determine the seismic resistance of soil to liquefaction by a fundamental soil property. This paper presents the results of an 11-year international project to gather new Vs site data and develop probabilistic correlations for seismic soil liquefaction occurrence. Toward that objective, shear-wave velocity test sites were identified, and measurements made for 301 new liquefaction field case histories in China, Japan, Taiwan, Greece, and the United States over a decade. The majority of these new case histories reoccupy those previously investigated by penetration testing. These new data are combined with previously published case histories to build a global catalog of 422 case histories of Vs liquefaction performance. Bayesian regression and structural reliability methods facilitate a probabilistic treatment of the Vs catalog for performance-based engineering applications. Where possible, uncertainties of the variables comprising both the seismic demand and the soil capacity were estimated and included in the analysis, resulting in greatly reduced overall model uncertainty relative to previous studies. The presented data set and probabilistic analysis also help resolve the ancillary issues of adjustment for soil fines content and magnitude scaling factors.

  10. The effects of pressure, temperature, and pore water on velocities in Westerly granite. [for seismic wave propagation

    Science.gov (United States)

    Spencer, J. W., Jr.; Nur, A. M.

    1976-01-01

    A description is presented of an experimental assembly which has been developed to conduct concurrent measurements of compressional and shear wave velocities in rocks at high temperatures and confining pressures and with independent control of the pore pressure. The apparatus was used in studies of the joint effects of temperature, external confining pressure, and internal pore water on sonic velocities in Westerly granite. It was found that at a given temperature, confining pressure has a larger accelerating effect on compressional waves in dry rock, whereas at a given confining pressure, temperature has a larger retarding effect on shear waves.

  11. 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

  12. Arterial viscoelasticity: role in the dependency of pulse wave velocity on heart rate in conduit arteries.

    Science.gov (United States)

    Xiao, Hanguang; Tan, Isabella; Butlin, Mark; Li, Decai; Avolio, Alberto P

    2017-06-01

    Experimental investigations have established that the stiffness of large arteries has a dependency on acute heart rate (HR) changes. However, the possible underlying mechanisms inherent in this HR dependency have not been well established. This study aimed to explore a plausible viscoelastic mechanism by which HR exerts an influence on arterial stiffness. A multisegment transmission line model of the human arterial tree incorporating fractional viscoelastic components in each segment was used to investigate the effect of varying fractional order parameter (α) of viscoelasticity on the dependence of aortic arch to femoral artery pulse wave velocity (afPWV) on HR. HR was varied from 60 to 100 beats/min at a fixed mean flow of 100 ml/s. PWV was calculated by intersecting tangent method (afPWV Tan ) and by phase velocity from the transfer function (afPWV TF ) in the time and frequency domain, respectively. PWV was significantly and positively associated with HR for α ≥ 0.6; for α = 0.6, 0.8, and 1, HR-dependent changes in afPWV Tan were 0.01 ± 0.02, 0.07 ± 0.04, and 0.22 ± 0.09 m/s per 5 beats/min; HR-dependent changes in afPWV TF were 0.02 ± 0.01, 0.12 ± 0.00, and 0.34 ± 0.01 m/s per 5 beats/min, respectively. This crosses the range of previous physiological studies where the dependence of PWV on HR was found to be between 0.08 and 0.10 m/s per 5 beats/min. Therefore, viscoelasticity of the arterial wall could contribute to mechanisms through which large artery stiffness changes with changing HR. Physiological studies are required to confirm this mechanism. NEW & NOTEWORTHY This study used a transmission line model to elucidate the role of arterial viscoelasticity in the dependency of pulse wave velocity on heart rate. The model uses fractional viscoelasticity concepts, which provided novel insights into arterial hemodynamics. This study also provides a means of assessing the clinical manifestation of the association of pulse wave velocity and heart rate

  13. S-Wave's Velocities of the Lithosphere-Asthenosphere System in the Caribbean Region

    International Nuclear Information System (INIS)

    Gonzalez, O'Leary; Alvarez, Jose Leonardo; Moreno, Bladimir; Panza, Giuliano F.

    2010-06-01

    An overview of the S-wave velocity (Vs) structural model of the Caribbean is presented with a resolution of 2 o x2 o . As a result of the frequency time analysis (FTAN) of more than 400 trajectories epicenter-stations in this region, new tomographic maps of Rayleigh waves group velocity dispersion at periods ranging from 10 s to 40 s have been determined. For each 2 o x2 o cell, group velocity dispersion curves were determined and extended to 150 s adding data from a larger scale tomographic study (Vdovin et al., 1999). Using, as independent a priori information, the available geological and geophysical data of the region, each dispersion curve has been mapped, by non-linear inversion, into a set of Vs vs. depth models in the depth range from 0 km to 300 km. Due to the non-uniqueness of the solutions for each cell a Local Smoothness Optimization (LSO) has been applied to the whole region to identify a tridimensional model of Vs vs. depth in cells of 2 o x2 o , thus satisfying the Occam razor concept. Through these models some main features of the lithosphere and asthenosphere are evidenced, such as: the west directed subduction zone of the eastern Caribbean region with a clear mantle wedge between the Caribbean lithosphere and the subducted slab; the complex and asymmetric behavior of the crustal and lithospheric thickness in the Cayman ridge; the diffused presence of oceanic crust in the region; the presence of continental type crust in the South America, Central America and North America plates, as well as the bottom of the upper asthenosphere that gets shallower going from west to east. (author)

  14. Effects of beam steering in pulsed-wave ultrasound velocity estimation.

    Science.gov (United States)

    Steinman, Aaron H; Yu, Alfred C H; Johnston, K Wayne; Cobbold, Richard S C

    2005-08-01

    Experimental and computer simulation methods have been used to investigate the significance of beam steering as a potential source of error in pulsed-wave flow velocity estimation. By simulating a typical linear-array transducer system as used for spectral flow estimation, it is shown that beam steering can cause an angle offset resulting in a change in the effective beam-flow angle. This offset primarily depends on the F-number and the nominal steering angle. For example, at an F-number of 3 and a beam-flow angle of 70 degrees , the velocity error changed from -5% to + 5% when the steering angle changed from -20 degrees to + 20 degrees . Much higher errors can occur at higher beam-flow angles, with smaller F-numbers and greater steering. Our experimental study used a clinical ultrasound system, a tissue-mimicking phantom and a pulsatile waveform to determine peak flow velocity errors for various steering and beam-flow angles. These errors were found to be consistent with our simulation results.

  15. Precise seismic-wave velocity atop Earth's core: No evidence for outer-core stratification

    Science.gov (United States)

    Alexandrakis, Catherine; Eaton, David W.

    2010-05-01

    Earth's outer core is composed of liquid Fe and Ni alloyed with a ˜10% fraction of light elements such as O, S, or Si. Secular cooling and compositional buoyancy drive vigorous convection that sustains the geodynamo, but critical details of light-element composition and thermal regime remain uncertain. Seismic velocities can provide important observational constraints on these parameters, but global reference models such as Preliminary Reference Earth Model ( PREM), IASP91 and AK135 exhibit significant discrepancies in the outermost ˜200 km of the core. Here, we apply an Empirical Transfer Function method to obtain precise arrival times for SmKS waves, a whispering-gallery mode that propagates near the underside of the core-mantle boundary. Models that fit our data are all characterized by seismic velocities and depth gradients in the outermost 200 km of the core that correspond best with PREM. This similarity to PREM, which has a smooth velocity profile that satisfies the adiabatic Adams and Williamson equation, argues against the presence of an anomalous layer of light material near the top of the core as suggested in some previous studies. A new model, AE09, is proposed as a slight modification to PREM for use as a reference model of the outermost core.

  16. Determining the relationship of thermal conductivity and compressional wave velocity of common rock types as a basis for reservoir characterization

    Science.gov (United States)

    Mielke, P.; Bär, K.; Sass, I.

    2017-05-01

    A comprehensive dataset detailing thermal conductivity and acoustic (compressional) wave velocity of 1430 oven-dry rock samples from clastic sedimentary (sandstone, arkose, greywacke), carbonatic (limestone, marl, dolomite, marble, coquina), plutonic (gabbro, gabbrodiorite, diorite, granodiorite, granite) and volcanic (basalt, andesite, rhyolite) rock types is presented. Correlation of thermal conductivity, compressional wave velocity and porosity are discussed in detail for each tested rock type. The study confirms that thermal conductivity of dry rocks can be predicted from acoustic velocity for porous rock types such as volcanites and sandstones, while non- and low-porous rocks show no to minor trends. With a prediction accuracy ± 0.5 W m- 1 K- 1 and a confidence of > 80% for sediments and mafic volcanites the calculated data is far more comprehensive than data collected from literature, and is likely accurate enough for most first exploration approaches or geoscientific models before detailed site-scale investigation or modelling is conducted. To investigate the effect of water saturation on thermal conductivity and compressional wave velocity 118 sedimentary samples (arkose and fine-, medium- and coarse sandstones) were saturated in de-aired water and the heat conduction and acoustic velocity were remeasured. The obtained data shows that both thermal conductivity and compressional wave velocity of saturated samples markedly increase in contrast to dry samples. The extent of the thermal conductivity and compressional wave velocity gain is mainly controlled by porosity. Thermal conductivity of saturated samples increases twice as much for higher porous samples than for low porous fine and medium sandstones. In contrast, the gain of compressional wave velocity of saturated sandstones decreases with increasing porosity.

  17. Continental lithospheric subduction and intermediate-depth seismicity: Constraints from S-wave velocity structures in the Pamir and Hindu Kush

    Science.gov (United States)

    Li, Wei; Chen, Yun; Yuan, Xiaohui; Schurr, Bernd; Mechie, James; Oimahmadov, Ilhomjon; Fu, Bihong

    2018-01-01

    The Pamir has experienced more intense deformation and shortening than Tibet, although it has a similar history of terrane accretion. Subduction as a primary way to accommodate lithospheric shortening beneath the Pamir has induced the intermediate-depth seismicity, which is rare in Tibet. Here we construct a 3D S-wave velocity model of the lithosphere beneath the Pamir by surface wave tomography using data of the TIPAGE (Tien Shan-Pamir Geodynamic program) and other seismic networks in the area. We imaged a large-scale low velocity anomaly in the crust at 20-50 km depth in the Pamir overlain by a high velocity anomaly at a depth shallower than 15 km. The high velocity anomalies colocate with exposed gneiss domes, which may imply a similar history of crustal deformation, partial melting and exhumation in the hinterland, as has occurred in the Himalaya/Tibet system. At mantle depths, where the intermediate-depth earthquakes are located, a low velocity zone is clearly observed extending to about 180 km and 150 km depth in the Hindu Kush and eastern Pamir, respectively. Moreover, the geometry of the low-velocity anomaly suggests that lower crustal material has been pulled down into the mantle by the subducting Asian and Indian lithospheric mantle beneath the Pamir and Hindu Kush, respectively. Metamorphic processes in the subducting lower crust may cause the intermediate-depth seismicity down to 150-180 km depth beneath the Pamir and Hindu Kush. We inverted focal mechanisms in the seismic zone for the stress field. Differences in the stress field between the upper and lower parts of the Indian slab imply that subduction and detachment of the Indian lithosphere might cause intense seismicity associated with the thermal shear instability in the deep Hindu Kush.

  18. 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.

  19. Effect of initial stress on Love waves in a piezoelectric structure carrying a functionally graded material layer.

    Science.gov (United States)

    Qian, Zheng-Hua; Jin, Feng; Lu, Tianjian; Kishimoto, Kikuo; Hirose, Sohichi

    2010-01-01

    The effect of initial stress on the propagation behavior of Love waves in a piezoelectric half-space of polarized ceramics carrying a functionally graded material (FGM) layer is analytically investigated in this paper from the three-dimensional equations of linear piezoelectricity. The analytical solutions are obtained for the dispersion relations of Love wave propagating in this kind of structure with initial stress for both electrical open case and electrical short case, respectively. One numerical example is given to graphically illustrate the effect of initial stress on dispersive curve, phase velocity and electromechanical coupling factor of the Love wave propagation. The results reported here are meaningful for the design of surface acoustic wave (SAW) devices with high performance.

  20. Softening of stressed granular packings with resonant sound waves.

    Science.gov (United States)

    Reichhardt, C J Olson; Lopatina, L M; Jia, X; Johnson, P A

    2015-08-01

    We perform numerical simulations of a two-dimensional bidisperse granular packing subjected to both a static confining pressure and a sinusoidal dynamic forcing applied by a wall on one edge of the packing. We measure the response experienced by a wall on the opposite edge of the packing and obtain the resonant frequency of the packing as the static or dynamic pressures are varied. Under increasing static pressure, the resonant frequency increases, indicating a velocity increase of elastic waves propagating through the packing. In contrast, when the dynamic amplitude is increased for fixed static pressure, the resonant frequency decreases, indicating a decrease in the wave velocity. This occurs both for compressional and for shear dynamic forcing and is in agreement with experimental results. We find that the average contact number Zc at the resonant frequency decreases with increasing dynamic amplitude, indicating that the elastic softening of the packing is associated with a reduced number of grain-grain contacts through which the elastic waves can travel. We image the excitations created in the packing and show that there are localized disturbances or soft spots that become more prevalent with increasing dynamic amplitude. Our results are in agreement with experiments on glass bead packings and earth materials such as sandstone and granite and may be relevant to the decrease in elastic wave velocities that has been observed to occur near fault zones after strong earthquakes, in surficial sediments during strong ground motion, and in structures during earthquake excitation.

  1. A Gordeyev integral for electrostatic waves in a magnetized plasma with a kappa velocity distribution

    International Nuclear Information System (INIS)

    Mace, R.L.

    2003-01-01

    A Gordeyev-type integral for the investigation of electrostatic waves in magnetized plasma having a kappa or generalized Lorentzian velocity distribution is derived. The integral readily reduces, in the unmagnetized and parallel propagation limits, to simple expressions involving the Z κ function. For propagation perpendicular to the magnetic field, it is shown that the Gordeyev integral can be written in closed form as a sum of two generalized hypergeometric functions, which permits easy analysis of the dispersion relation for electrostatic waves. Employing the same analytical techniques used for the kappa distribution, it is further shown that the well-known Gordeyev integral for a Maxwellian distribution can be written very concisely as a generalized hypergeometric function in the limit of perpendicular propagation. This expression, in addition to its mathematical conciseness, has other advantages over the traditional sum over modified Bessel functions form. Examples of the utility of these generalized hypergeometric series, especially how they simplify analyses of electrostatic waves propagating perpendicular to the magnetic field, are given. The new expression for the Gordeyev integral for perpendicular propagation is solved numerically to obtain the dispersion relations for the electrostatic Bernstein modes in a plasma with a kappa distribution

  2. Rayleigh wave group-velocity across the Dominican Republic and Puerto Rico from ambient noise tomography

    Science.gov (United States)

    Quiros, D.; Pulliam, J.; Polanco Rivera, E.; Huerfano Moreno, V. A.

    2017-12-01

    The eastern North America-Caribbean (NA-CAR) plate boundary near the islands of Hispaniola (which is comprised of the Dominican Republic and Haiti) and Puerto Rico is a complex transition zone in which strain is accommodated by two transform fault systems and oblique subduction. In 2013, scientists from Baylor University, the Autonomous University of Santo Domingo, and the Puerto Rico Seismic Network deployed 16 broadband stations on the Dominican Republic to expand the local permanent network. The goal of the Greater Antilles Seismic Program (GrASP) is to combine its data with that from permanent networks in Puerto Rico, Haiti, Cuba, the Cayman Islands, and Jamaica to develop a better understanding of the crust and upper mantle structure in the Northeastern Caribbean (Greater Antilles). One important goal of GrASP is to develop robust velocity models that can be used to improve earthquake location and seismic hazard efforts. In this study, we focus on obtaining Rayleigh wave group velocity maps from ambient noise tomography. By cross-correlating ambient seismic noise recorded at 53 stations between 2010 to present, we obtain Green's functions between 1165 pairs of stations. From these, we obtain dispersion curves by the application of FTAN methods with phase-matched filtering. Selection criteria depend on the signal-to-noise ratio and seasonal variability, with further filtering done by rejecting velocities incompatible with maps produced from overdamped tomographic inversions. Preliminary dispersion maps show strong correlations with large-scale geological and tectonic features for periods between 5 - 20 s, such as the Cordillera Central in both the Dominican Republic and Puerto Rico, the Mona Passage, and the NA-CAR subduction zone. Ongoing efforts focus on including shorter periods in Puerto Rico as its denser station distribution could allow us to retrieve higher resolution group velocity maps.

  3. Solitary waves on inclined films: their characteristics and the effects on wall shear stress

    Energy Technology Data Exchange (ETDEWEB)

    Tihon, J. [Academy of Sciences of the Czech Republic, Institute of Chemical Process Fundamentals, Prague 6 (Czech Republic); Serifi, K.; Argyriadi, K.; Bontozoglou, V. [University of Thessaly, Department of Mechanical and Industrial Engineering, Volos (Greece)

    2006-07-15

    The properties of solitary waves, developing from inlet disturbances of controlled frequency along an inclined film flow, are systematically studied experimentally and computationally. Time-variations of film height and wall shear stress are measured, using respectively a capacitance probe and an electrodiffusion sensor. Computational data are provided from simulations performed by a Galerkin finite element scheme. The height and spacing of solitary humps, their phase velocity and the wavelength of the preceding capillary ripples are reported as functions of the Reynolds number (10stress modulation imposed by the passage of solitary waves is studied experimentally and computationally as a function of Re. Distinct nonlinear characteristics are noted, including a steep maximum and a negative minimum, with the effects intensifying at intermediate Re. All computer predictions are found to be in good quantitative agreement with the experimental data. (orig.)

  4. 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.

  5. 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

    and of guided waves through cortical bone could be used to estimate BMD. In two centres, Kiel and Odense, we measured time-of-flight (TOF) of waves through the trabecular greater trochanter and cortical intertrochanter as well as a wave through soft tissue only. TOF was adjusted for leg width using ultrasound......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...

  6. The effect of air velocity on heat stress at increased air temperature

    DEFF Research Database (Denmark)

    Bjerg, Bjarne Schmidt; Wang, Xiaoshuai; Zhang, Guoqiang

    Increased air velocity is a frequently used method to reduce heat stress of farm animals housed in warm conditions. The main reason why the method works is that higher air velocity increases the convective heat release from the animals. Convective heat release from the animals is strongly related...... to the temperature difference between the surfaces of animals and the surrounding air, and this temperature difference declines when the air temperature approaches the animal body temperature. Consequently it can it by expected that the effect of air velocity decreases at increased air temperature. The literature...... on farm animals in warm conditions includes several thermal indices which incorporate the effect of air velocities. But, surprisingly none of them predicts a decreased influence of air velocity when the air temperature approaches the animal body temperature. This study reviewed published investigations...

  7. Uncertainty Estimation of Shear-wave Velocity Structure from Bayesian Inversion of Microtremor Array Dispersion Data

    Science.gov (United States)

    Dosso, S. E.; Molnar, S.; Cassidy, J.

    2010-12-01

    Bayesian inversion of microtremor array dispersion data is applied, with evaluation of data errors and model parameterization, to produce the most-probable shear-wave velocity (VS) profile together with quantitative uncertainty estimates. Generally, the most important property characterizing earthquake site response is the subsurface VS structure. The microtremor array method determines phase velocity dispersion of Rayleigh surface waves from multi-instrument recordings of urban noise. Inversion of dispersion curves for VS structure is a non-unique and nonlinear problem such that meaningful evaluation of confidence intervals is required. Quantitative uncertainty estimation requires not only a nonlinear inversion approach that samples models proportional to their probability, but also rigorous estimation of the data error statistics and an appropriate model parameterization. A Bayesian formulation represents the solution of the inverse problem in terms of the posterior probability density (PPD) of the geophysical model parameters. Markov-chain Monte Carlo methods are used with an efficient implementation of Metropolis-Hastings sampling to provide an unbiased sample from the PPD to compute parameter uncertainties and inter-relationships. Nonparametric estimation of a data error covariance matrix from residual analysis is applied with rigorous a posteriori statistical tests to validate the covariance estimate and the assumption of a Gaussian error distribution. The most appropriate model parameterization is determined using the Bayesian information criterion (BIC), which provides the simplest model consistent with the resolving power of the data. Parameter uncertainties are found to be under-estimated when data error correlations are neglected and when compressional-wave velocity and/or density (nuisance) parameters are fixed in the inversion. Bayesian inversion of microtremor array data is applied at two sites in British Columbia, the area of highest seismic risk in

  8. Influence of local mechanical properties of high strength steel from large size forged ingot on ultrasonic wave velocities

    Science.gov (United States)

    Dupont-Marillia, Frederic; Jahazi, Mohamad; Lafreniere, Serge; Belanger, Pierre

    2017-02-01

    In the metallurgical industry, ultrasonic inspection is routinely used for the detection of defects. For the non-destructive inspection of small high strength steel parts, the material can be considered isotropic. However, when the size of the parts under inspection is large, the isotropic material hypothesis does not necessarily hold. The aim of this study is to investigate the effect of the variation in mechanical properties such as grain size, Young's modulus, Poissons ratio, chemical composition on longitudinal and transversal ultrasonic wave velocities. A 2 cm thick slice cut from a 40-ton bainitic steel ingot that was forged and heat treated was divided into 875 parallelepiped samples of 2x4x7 cm3. A metallurgical study has been performed to identify the phase and measure the grain size. Ultrasonic velocity measurements at 2.25 MHz for longitudinal and transversal waves were performed. The original location of the parallelepiped samples in the large forged ingot, and the measured velocities were used to produce an ultrasonic velocity map. Using a local isotropy assumption as well as the local density of the parallelepiped samples calculated from the chemical composition of the ingot provided by a previously published study, Youngs modulus and Poissons ratio were calculated from the longitudinal and transversal wave velocities. Micro-tensile test was used to validate Youngs modulus obtained by the ultrasonic wave velocity and an excellent agreement was observed.

  9. Determination of Stress-Acoustic Coefficients of Rayleigh Wave by Use of Laser Doppler Velocimetry

    Science.gov (United States)

    He, Lingfeng; Kobayashi, Shoichi

    In the present paper, 1) a new non-contact ultrasonic stress measurement technique is proposed based on acoustoelasticity, in which ultrasonic wave motion is detected by use of a laser Doppler velocimeter, and 2) the stress-acoustic coefficients of Rayleigh wave for aluminum alloy and structural steel are determined by the technique. In the measurement system, Rayleigh waves are emitted into the specimen by a wedge-type piezoelectric transducer and vertical velocities of the surface motions of the traveling Rayleigh waves are detected by the laser Doppler velocimeter at two points of 4 cm apart. In order to measure the traveling time of the wave between the two points, the converted voltage signals are supplied both to i) a sing-around unit and ii) to a digital oscilloscope. The time-of-flight over the distance between the two points is obtained either by subtracting the sing-around periods measured at the two points or by direct reading at zero-cross of the overlapped images of the two waves on the CR display of the oscilloscope. Both measurements are made at the same time under increasing or decreasing loads. The stress-acoustic coefficients obtained are -1.2×10-5/MPa and -0.21×10-5/MPa for aluminum alloy 5052 and structural steel SS400, respectively. These results are in good agreement with those determined using two knife-edge contact piezoelectric transducers. This study shows that the proposed non-contact measuring technique by use of laser velocimetry is applicable to determining the stress-acoustic coefficients.

  10. Flow velocities and bed shear stresses in a stone cover under an oscillatory flow

    DEFF Research Database (Denmark)

    Stenanato, F.; Nielsen, Anders Wedel; Sumer, B. Mutlu

    2010-01-01

    layers of stones. The flow velocities in the pores of the stones were measured using LDA (Laser Doppler Anemometer). In addition to the velocity measurements, the bed shear stresses were also measured using a hotfilm (Constant Temperature Anemometry). It is found that the boundary layer of the outer flow...... current boundary layer without any externally generated turbulence. The bd shear stress is found to be very low, more than ten times smaller than in the case of a smooth base bottom without stone cover....

  11. 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.

  12. Acute effects of different aerobic exercise duration on pulse wave velocity in healthy young men.

    Science.gov (United States)

    Kobayashi, Ryota; Hatakeyama, Hiroyuki; Hashimoto, Yuto; Okamoto, Takanobu

    2017-12-01

    The purpose of present study was to determine the acute effects of different aerobic exercise duration on pulse wave velocity (PWV) in healthy young men. One week after measuring peak oxygen uptake to determine the duration of each exercise trial, 11 healthy males (age: 23.4±0.6 years, height: 172.5±2.3 cm, weight: 64.1±2.4 kg) cycled on an ergometer for 15 (15 min-EX), 30 (30 min-EX) and 45 minutes (45 min-EX) at 65% peak oxygen uptake in random order. After supine rest for at least 15 minutes, aortic (carotid-femoral) and leg (femoral-ankle) PWV were measured before and at 30, 60 and 90 minutes after each exercise trial. Compared with before exercise trials, aortic PWV decreased at 30 minutes after 15, 30 and 45 min-EX (Pexercise.

  13. Artificial Intelligence Estimation of Carotid-Femoral Pulse Wave Velocity using Carotid Waveform.

    Science.gov (United States)

    Tavallali, Peyman; Razavi, Marianne; Pahlevan, Niema M

    2018-01-17

    In this article, we offer an artificial intelligence method to estimate the carotid-femoral Pulse Wave Velocity (PWV) non-invasively from one uncalibrated carotid waveform measured by tonometry and few routine clinical variables. Since the signal processing inputs to this machine learning algorithm are sensor agnostic, the presented method can accompany any medical instrument that provides a calibrated or uncalibrated carotid pressure waveform. Our results show that, for an unseen hold back test set population in the age range of 20 to 69, our model can estimate PWV with a Root-Mean-Square Error (RMSE) of 1.12 m/sec compared to the reference method. The results convey the fact that this model is a reliable surrogate of PWV. Our study also showed that estimated PWV was significantly associated with an increased risk of CVDs.

  14. Stress-wave experiments on selected crustal rocks and minerals

    Science.gov (United States)

    Grady, D. E.

    1983-09-01

    Large amplitude compressive stress wave experiments on selected crustal rocks and minerals was performed. The materials studied included Vermont marble, Blair dolomite, Oakhall limestone, z-cut calcite and oil shale. In each case specific constitutive features were studied. Features include interrelation of plastic yielding and phase transformation, rate dependent plastic flow, dilatency under dynamic loading conditions, and energy dissipation at stress amplitudes below measured Hugoniot elastic limits. A new experimental method using inmaterial mutual inductance magnetic gauges is also described.

  15. The focusing effect of P-wave in the Moon's and Earth's low-velocity core. Analytical solution

    Science.gov (United States)

    Fatyanov, A. G.; Burmin, V. Yu

    2018-04-01

    The important aspect in the study of the structure of the interiors of planets is the question of the presence and state of core inside them. While for the Earth this task was solved long ago, the question of whether the core of the Moon is in a liquid or solid state up to the present is debatable up to present. If the core of the Moon is liquid, then the velocity of longitudinal waves in it should be lower than in the surrounding mantle. If the core is solid, then most likely, the velocity of longitudinal waves in it is higher than in the mantle. Numerical calculations of the wave field allow us to identify the criteria for drawing conclusions about the state of the lunar core. In this paper we consider the problem of constructing an analytical solution for wave fields in a layered sphere of arbitrary radius. A stable analytic solution is obtained for the wave fields of longitudinal waves in a three-layer sphere. Calculations of the total wave fields and rays for simplified models of the Earth and the Moon with real parameters are presented. The analytical solution and the ray pattern showed that the low-velocity cores of the Earth and the Moon possess the properties of a collecting lens. This leads to the emergence of a wave field focusing area. As a result, focused waves of considerable amplitude appear on the surface of the Earth and the Moon. In the Earth case, they appear before the first PKP-wave arrival. These are so-called "precursors", which continue in the subsequent arrivals of waves. At the same time, for the simplified model of the Earth, the maximum amplitude growth is observed in the 147-degree region. For the Moon model, the maximum amplitude growth is around 180°.

  16. LITHOSTRATIGRAPHY AND SHEAR-WAVE VELOCITY IN THE CRYSTALLIZED TOPOPAH SPRING TUFF, YUCCA MOUNTAIN, NEVADA

    International Nuclear Information System (INIS)

    D. BUESCH; K.H. STOKOE; M. SCHUHEN

    2006-01-01

    Evaluation of the seismic response of the proposed spent nuclear fuel and high-level radioactive waste repository at Yucca Mountain, Nevada, is in part based on the seismic properties of the host rock, the 12.8-million-year-old Topopah Spring Tuff. Because of the processes that formed the tuff, the densely welded and crystallized part has three lithophysal and three nonlithophysal zones, and each zone has characteristic variations in lithostratigraphic features and structures of the rocks. Lithostratigraphic features include lithophysal cavities, rims on lithophysae and some fractures, spots (which are similar to rims but without an associated cavity or aperture), amounts of porosity resulting from welding, crystallization, and vapor-phase corrosion and mineralization, and fractures. Seismic properties, including shear-wave velocity (V s ), have been measured on 38 pieces of core, and there is a good ''first order'' correlation with the lithostratigraphic zones; for example, samples from nonlithophysal zones have larger V s values compared to samples from lithophysal zones. Some samples have V s values that are beyond the typical range for the lithostratigraphic zone; however, these samples typically have one or more fractures, ''large'' lithophysal cavities, or ''missing pieces'' relative to the sample size. Shear-wave velocity data measured in the tunnels have similar relations to lithophysal and nonlithophysal rocks; however, tunnel-based values are typically smaller than those measured in core resulting from increased lithophysae and fracturing effects. Variations in seismic properties such as V s data from small-scale samples (typical and ''flawed'' core) to larger scale traverses in the tunnels provide a basis for merging our understanding of the distributions of lithostratigraphic features (and zones) with a method to scale seismic properties

  17. LITHOSTRATIGRAPHY AND SHEAR-WAVE VELOCITY IN THE CRYSTALLIZED TOPOPAH SPRING TUFF, YUCCA MOUNTAIN, NEVADA

    Energy Technology Data Exchange (ETDEWEB)

    D. BUESCH; K.H. STOKOE; M. SCHUHEN

    2006-03-20

    Evaluation of the seismic response of the proposed spent nuclear fuel and high-level radioactive waste repository at Yucca Mountain, Nevada, is in part based on the seismic properties of the host rock, the 12.8-million-year-old Topopah Spring Tuff. Because of the processes that formed the tuff, the densely welded and crystallized part has three lithophysal and three nonlithophysal zones, and each zone has characteristic variations in lithostratigraphic features and structures of the rocks. Lithostratigraphic features include lithophysal cavities, rims on lithophysae and some fractures, spots (which are similar to rims but without an associated cavity or aperture), amounts of porosity resulting from welding, crystallization, and vapor-phase corrosion and mineralization, and fractures. Seismic properties, including shear-wave velocity (V{sub s}), have been measured on 38 pieces of core, and there is a good ''first order'' correlation with the lithostratigraphic zones; for example, samples from nonlithophysal zones have larger V{sub s} values compared to samples from lithophysal zones. Some samples have V{sub s} values that are beyond the typical range for the lithostratigraphic zone; however, these samples typically have one or more fractures, ''large'' lithophysal cavities, or ''missing pieces'' relative to the sample size. Shear-wave velocity data measured in the tunnels have similar relations to lithophysal and nonlithophysal rocks; however, tunnel-based values are typically smaller than those measured in core resulting from increased lithophysae and fracturing effects. Variations in seismic properties such as V{sub s} data from small-scale samples (typical and ''flawed'' core) to larger scale traverses in the tunnels provide a basis for merging our understanding of the distributions of lithostratigraphic features (and zones) with a method to scale seismic properties.

  18. 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

  19. 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.

  20. 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.

  1. MEASUREMENT OF COMPRESSIONAL-WAVE SEISMIC VELOCITIES IN 29 WELLS AT THE HANFORD SITE

    Energy Technology Data Exchange (ETDEWEB)

    PETERSON SW

    2010-10-08

    Check shot seismic velocity surveys were collected in 100 B/C, 200 East, 200-PO-1 Operational Unit (OU), and the Gable Gap areas in order to provide time-depth correlation information to aid the interpretation of existing seismic reflection data acquired at the Hanford Site (Figure 1). This report details results from 5 wells surveyed in fiscal year (FY) 2008, 7 wells in FY 2009, and 17 wells in FY 2010 and provides summary compressional-wave seismic velocity information to help guide future seismic survey design as well as improve current interpretations of the seismic data (SSC 1979/1980; SGW-39675; SGW-43746). Augmenting the check shot database are four surveys acquired in 2007 in support of the Bechtel National, Inc. Waste Treatment Plant construction design (PNNL-16559, PNNL-16652), and check shot surveys in three wells to support seismic testing in the 200 West Area (Waddell et al., 1999). Additional sonic logging was conducted during the late 1970s and early 1980s as part of the Basalt Waste Isolation Program (BWIP) (SSC 1979/1980) and check shot/sonic surveys as part of the safety report for the Skagit/Hanford Nuclear project (RDH/10-AMCP-0164). Check shot surveys are used to obtain an in situ measure of compressional-wave seismic velocity for sediment and rock in the vicinity of the well point, and provide the seismic-wave travel time to geologic horizons of interest. The check shot method deploys a downhole seismic receiver (geophone) to record the arrival of seismic waves generated by a source at the ground surface. The travel time of the first arriving seismic-wave is determined and used to create a time-depth function to correlate encountered geologic intervals with the seismic data. This critical tie with the underlying geology improves the interpretation of seismic reflection profile information. Fieldwork for this investigation was conducted by in house staff during the weeks of September 22, 2008 for 5 wells in the 200 East Area (Figure 2); June 1

  2. Impact of inhomogeneity on SH-type wave propagation in an initially stressed composite structure

    Science.gov (United States)

    Saha, S.; Chattopadhyay, A.; Singh, A. K.

    2018-02-01

    The present analysis has been made on the influence of distinct form of inhomogeneity in a composite structure comprised of double superficial layers lying over a half-space, on the phase velocity of SH-type wave propagating through it. Propagation of SH-type wave in the said structure has been examined in four distinct cases of inhomogeneity viz. when inhomogeneity in double superficial layer is due to exponential variation in density only (Case I); when inhomogeneity in double superficial layers is due to exponential variation in rigidity only (Case II); when inhomogeneity in double superficial layer is due to exponential variation in rigidity, density and initial stress (Case III) and when inhomogeneity in double superficial layer is due to linear variation in rigidity, density and initial stress (Case IV). Closed-form expression of dispersion relation has been accomplished for all four aforementioned cases through extensive application of Debye asymptotic analysis. Deduced dispersion relations for all the cases are found in well-agreement to the classical Love-wave equation. Numerical computation has been carried out to graphically demonstrate the effect of inhomogeneity parameters, initial stress parameters as well as width ratio associated with double superficial layers in the composite structure for each of the four aforesaid cases on dispersion curve. Meticulous examination of distinct cases of inhomogeneity and initial stress in context of considered problem has been carried out with detailed analysis in a comparative approach.

  3. THE BASIS OF MATHEMATICAL DESCRIPTION FOR WAVE MODEL OF STRESSES PROPAGATION IN RAILWAY TRACK

    Directory of Open Access Journals (Sweden)

    D. M. Kurhan

    2016-10-01

    Full Text Available Purpose. Modern scientific research has repeatedly cited practical examples of the dynamic effects of railway track operation that go beyond the static calculation schemes. For the track sections where the train speed is approaching to the velocity of wave propagation in the slab track layers such issues are of particular relevance. An adequate tool for the study of such issues can be the use of the wave theory of stress propagation. The purpose of the article is the creation of a mathematical description of the basic principles of the stress propagation wave model in the railway track, which can be used as a basis for the practical development of the relevant calculation system. Methodology. The model of stress-strain states of the railway track on the basis of the stress wave propagation theory is to bring together the equations of the geometry of the outline of the space systems that is involved in the interaction at a given time, and the dynamic equilibrium equations of deformation. The solution is based on the use of the laws of the theory of elasticity. The wave front is described by an ellipsoid equation. When determining the variation in time of the surface position of the ellipsoid a vector approach is used. Findings. The geometry equations of the wave motion determine the volumes of material layers of the slab track involved in the interaction at a given time. The dynamic equilibrium determination of the deformed condition of the space bounded by the wave front makes it possible to calculate both the stresses and strains, and their changes during the time of the load perception. Thus, mathematical descriptions of the processes that occur in the perception of the load by the elements of railway track at high speeds were obtained. Originality. The simulation tasks of the track and rolling stock interaction, in particular taking into account the dynamic deflection of slab track were further developed. For the first time the article

  4. Very Broadband Rayleigh-Wave Dispersion (0.06 - 60 Hz) and Shear-Wave Velocity Structure Under Yucca Flat, Nevada Test Site

    Science.gov (United States)

    Schramm, K. A.; Bilek, S. L.; Patton, H. J.; Abbott, R. E.; Stead, R.; Pancha, A.; White, R.

    2009-12-01

    Earth structure plays an important role in the generation of seismic waves for all sources. Nowhere is this more evident than at near-surface depths where man-made sources, such as explosions, are conducted. For example, short-period Rayleigh waves (Rg) are excited and propagate in the upper 2 km of Earth's crust. The importance of Rg in the generation of S waves from explosion sources through near-source scattering depends greatly on the shear-wave velocity structure at very shallow depths. Using three distinct datasets, we present a very broadband Rayleigh-wave phase velocity dispersion curve for the Yucca Flat (YF) region of the Nevada Test Site (NTS). The first dataset consists of waveforms of historic NTS explosions recorded on regional seismic networks and will provide information for the lowest frequencies (0.06-0.3 Hz). The second dataset is comprised of waveforms from a non-nuclear explosion on YF recorded at near-local distances and will be used for mid-range frequencies (0.2-1.5 Hz). The third dataset contains high-frequency waveforms recorded from refraction microtremor surveys on YF. This dataset provides information between 1.5 and 60 Hz. Initial results from the high frequency dataset indicate velocities range from 0.45-0.9 km/s at 1.5 Hz and 0.25-0.45 km/s at 60 Hz. The broadband nature of the dispersion curve will allow us to invert for the shear-wave velocity structure to 10 km depth, with focus on shallow depths where nuclear tests were conducted in the YF region. The velocity model will be used by researchers as a tool to aid the development of new explosion source models that incorporate shear wave generation. The new model can also be used to help improve regional distance yield estimation and source discrimination for small events.

  5. Comment on Group Velocity Measurement of Surfac Waves by Wavelet Transform

    Directory of Open Access Journals (Sweden)

    Taishi Okamoto

    2007-01-01

    Full Text Available Yamada and Yomogida (1997 applied the discrete wavelet transform (DWT to group velocity measurements for the first time. Although their study is one of the pioneering works in application of DWT to seismological analysis, their method gives an inaccurate value as a group velocity in some cases and requires modification. In this report, we point out the problem and propose a modified DWT method for overcoming the problem. In our method, DWT is carried out not for an analysed signal itself but for its complex envelope (Farnbach 1975. A computation algorithm for DWT coefficients for our method is given and shown to be almost the same as that by Yamada and Ohkitani (1991. The influence of the difference between the conventional method and our method on identification of group arrival times of a wave is also shown by a numerical experiment. If analysts want to identify group arrival times using DWT, our method must be adopted instead of the conventional method.

  6. Observations of intense velocity shear and associated electrostatic waves near an auroral arc

    International Nuclear Information System (INIS)

    Kelley, M.C.; Carlson, C.W.

    1977-01-01

    An intense shear in plasma flow velocity of magnitude 20 (m/s)m -1 has been detected at the edge of an auroral arc. The region of shear appears to display structure with two characteristic scale sizes. The larger structures were of the order of a few kilometers in size and were identified by a deviation of the direction of the charge sheets crossed by the rocket from a direction parallel to the visible arc. As is shown in the companion paper (Carlson and Kelley, 1977), the average (undisturbed) charge sheet was parallel to the arc. These observations are consistent with television studies which often display such structures propagating along the edges of auroral forms. Additional intense irregularities were detected with characteristic wavelengths smaller than the scale size of the shear. The irregularities are discussed in light of the branches of a velocity shear driven instability suggested by several workers: the Kelvin-Helmholtz instability operating at the longest wavelengths and the drift shear instability at the shorter. Neither mode has wavelengths as short as those observed however. A velocity shear mechanism operating at wavelengths short in comparison with the shear scale length, such as those observed here, would be of significant geophysical importance. For example, it could be responsible for production of high-latitude irregularities which exist throughout the polar cap and for the short-wavelength waves responsible for intense 3-m backscatter during equatorial spread F conditions. Since the wavelengths produced by the short-wavelength mode are in the range of typical auroral E region radars, such data must be carefully checked for F region contamination

  7. 4D Lorentz electron microscopy imaging: magnetic domain wall nucleation, reversal, and wave velocity.

    Science.gov (United States)

    Park, Hyun Soon; Baskin, J Spencer; Zewail, Ahmed H

    2010-09-08

    Magnetization reversal is an important topic of research in the fields of both basic and applied ferromagnetism. For the study of magnetization reversal dynamics and magnetic domain wall (DW) motion in ferromagnetic thin films, imaging techniques are indispensable. Here, we report 4D imaging of DWs by the out-of-focus Fresnel method in Lorentz ultrafast electron microscopy (UEM), with in situ spatial and temporal resolutions. The temporal change in magnetization, as revealed by changes in image contrast, is clocked using an impulsive optical field to produce structural deformation of the specimen, thus modulating magnetic field components in the specimen plane. Directly visualized are DW nucleation and subsequent annihilation and oscillatory reappearance (periods of 32 and 45 ns) in nickel films on two different substrates. For the case of Ni films on a Ti/Si(3)N(4) substrate, under conditions of minimum residual external magnetic field, the oscillation is associated with a unique traveling wave train of periodic magnetization reversal. The velocity of DW propagation in this wave train is measured to be 172 m/s with a wavelength of 7.8 microm. The success of this study demonstrates the promise of Lorentz UEM for real-space imaging of spin switching, ferromagnetic resonance, and laser-induced demagnetization in ferromagnetic nanostructures.

  8. Pulse Wave Velocity Prediction and Compliance Assessment in Elastic Arterial Segments.

    Science.gov (United States)

    Lillie, Jeffrey S; Liberson, Alexander S; Mix, Doran; Schwarz, Karl Q; Chandra, Ankur; Phillips, Daniel B; Day, Steven W; Borkholder, David A

    2015-03-01

    Pressure wave velocity (PWV) is commonly used as a clinical marker of vascular elasticity. Recent studies have increased clinical interest in also analyzing the impact of heart rate, blood pressure, and left ventricular ejection time on PWV. In this article we focus on the development of a theoretical one-dimensional model and validation via direct measurement of the impact of ejection time and peak pressure on PWV using an in vitro hemodynamic simulator. A simple nonlinear traveling wave model was developed for a compliant thin-walled elastic tube filled with an incompressible fluid. This model accounts for the convective fluid phenomena, elastic vessel deformation, radial motion, and inertia of the wall. An exact analytical solution for PWV is presented which incorporates peak pressure, ejection time, ejection volume, and modulus of elasticity. To assess arterial compliance, the solution is introduced in an alternative form, explicitly determining compliance of the wall as a function of the other variables. The model predicts PWV in good agreement with the measured values with a maximum difference of 3.0%. The results indicate an inverse quadratic relationship ([Formula: see text]) between ejection time and PWV, with ejection time dominating the PWV shifts (12%) over those observed with changes in peak pressure (2%). Our modeling and validation results both explain and support the emerging evidence that, both in clinical practice and clinical research, cardiac systolic function related variables should be regularly taken into account when interpreting arterial function indices, namely PWV.

  9. 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.

  10. Analysis of Rupture Directivity for the 2004 Sumatra Earthquake from the Rayleigh-Wave Phase Velocity

    Directory of Open Access Journals (Sweden)

    Jo-Pan Chang

    2010-01-01

    Full Text Available The rupture directivity for the 2004 Sumatra earthquake is analyzed by examining differences between the phase-de lay times of Rayleigh-waves (in the 140 - 160 sec period range arising from the main shock and reference earth quakes. A long source-process time (~463.0 sec and large rupture length (~1164.0 km are de rived from this analysis of rupture directivity. The source-process time for this earth quake is larger than for either the 1960 Chile or 1964 Alaska earth quakes. This might be due to the length of the rupture that occurred during earth quake faulting. The estimated rise time for the 2004 Sumatra earthquake, 92.0 sec, is approximately 20% of the whole source duration and also larger than those for the 1960 Chile and 1964 Alaska earth quakes. This likely reflects a fundamental difference between the frictional properties of these earth quakes. When the rise time is taken into ac count, an estimated rupture velocity of approximately 3.1 km sec-1 is obtained. This value is higher than that found in previous studies carried out on the basis of hydro acoustic data and regional seismic net works. In this study, we obtain additional evidence from analysis of the surface-wave phase-de lay time which con firms the basic features of the rupturing of the 2004 Sumatra earth quake. The results can also provide some constraints for the study of source rupturing for this earthquake.

  11. Stress wave emission: a bibliographical survey No 2

    International Nuclear Information System (INIS)

    Lucia, A.C.; Galli, M.

    1976-01-01

    This report gives an inventory of papers and publications which deal with stress wave emission (ultrasonic emission). This bibliography is up date until end of 1974. It contains also titles of papers published before 1973 but not contained in our first bibliographical report (EUR--5616e)

  12. Measurement and modeling of bed shear stress under solitary waves

    Digital Repository Service at National Institute of Oceanography (India)

    Jayakumar, S.; Guard, P.A.; Baldock, T.E.

    Direct measurements of bed shear stresses (using a shear cell apparatus) generated by non-breaking solitary waves are presented. The measurements were carried out over a smooth bed in laminar and transitional flow regimes (~ 10 sup (4) < R sub (e...

  13. 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.

  14. 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.

  15. 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.

  16. Hydraulic experiment on evaluation method of tsunami wave pressure using inundation depth and velocity in front of land structure

    International Nuclear Information System (INIS)

    Arimitsu, Tsuyoshi; Ooe, Kazuya; Kawasaki, Koji

    2012-01-01

    Hydraulic experiments were conducted to estimate tsunami wave pressure acting on several different types of land structures and examine the influence of a seawall in front of the structure on tsunami wave pressure. Wave pressures were measured at some points on the structure. The existing hydrostatic formula tended to underestimate tsunami wave pressure under the condition of inundation flow with large Froude number. Estimation method of tsunami wave pressure using inundation depth and horizontal velocity at the front of the structure was proposed based on the experimental results. It was confirmed from comparison with the experiments that the vertical distribution of the maximum tsunami wave pressure can be reproduced by employing the proposed method in this study. (author)

  17. Using shear wave velocity to monitor the curing process of self-consolidating concrete by bender element.

    Science.gov (United States)

    2014-08-01

    The evaluation of the curing process of a fresh concrete is critical to its construction process and monitoring. Traditionally stress : sensor and compressive wave sensor were often used to measure concrete properties. Bender element (BE) test, a non...

  18. Strength evolution of simulated carbonate-bearing faults: The role of normal stress and slip velocity

    Science.gov (United States)

    Mercuri, Marco; Scuderi, Marco Maria; Tesei, Telemaco; Carminati, Eugenio; Collettini, Cristiano

    2018-04-01

    A great number of earthquakes occur within thick carbonate sequences in the shallow crust. At the same time, carbonate fault rocks exhumed from a depth stresses (from 5 to 120 MPa) and slip velocities (from 0.3 to 100 μm/s). At high normal stresses (σn > 20 MPa) fault gouges undergo strain-weakening, that is more pronounced at slow slip velocities, and causes a significant reduction of frictional strength, from μ = 0.7 to μ = 0.47. Microstructural analysis show that fault gouge weakening is driven by deformation accommodated by cataclasis and pressure-insensitive deformation processes (pressure solution and granular plasticity) that become more efficient at slow slip velocity. The reduction in frictional strength caused by strain weakening behaviour promoted by the activation of pressure-insensitive deformation might play a significant role in carbonate-bearing faults mechanics.

  19. Alignment of stress, mean wind, and vertical gradient of the velocity vector

    DEFF Research Database (Denmark)

    Berg, Jacob; Mann, Jakob; Patton, E.G.

    2012-01-01

    In many applications in the atmospheric surface layer the turbulent-viscosity hypothesis is applied, i.e. the stress vector can be described through the vertical gradient of velocity. In the atmospheric surface layer, where the Coriolis force and baroclinic effects are considered negligible...

  20. Frictional melting of gabbro under extreme experimental conditions of normal stress, acceleration, and sliding velocity

    NARCIS (Netherlands)

    Niemeijer, A.; Di Toro, G.; Nielsen, S.; Di Felice, F.

    2011-01-01

    With the advent of high‐velocity shear apparatus, several experimental studies have been performed in recent years, improving our understanding of the evolution of fault strength during seismic slip. However, these experiments were conducted under relatively low normal stress (<20 MPa) and using

  1. Mountain Building in Central and Western Tien Shan Orogen: Insight from Joint Inversion of Surface Wave Phase Velocities and Body Wave Travel Times

    Science.gov (United States)

    Wu, S.; Yang, Y.; Wang, K.

    2017-12-01

    The Tien Shan orogeny, situated in central Asia about 2000 km away from the collision boundary between Indian plate and Eurasian plate, is one of the highest, youngest, and most active intracontinental mountain belts on the earth. It first formed during the Paleozoic times and became reactivated at about 20Ma. Although many studies on the dynamic processes of the Tien Shan orogeny have been carried out before, its tectonic rejuvenation and uplift mechanism are still being debated. A high-resolution model of crust and mantle beneath Tien Shan is critical to discern among competing models for the mountain building. In this study, we collect and process seismic data recorded by several seismic arrays in the central and western Tien Shan region to generate surface wave dispersion curves at 6-140 s period using ambient noise tomography (ANT) and two-plane surface wave tomography (TPWT) methods. Using these dispersion curves, we construct a high-resolution 3-D image of shear wave velocity (Vs) in the crust and upper mantle up to 300 km depth. Our current model constrained only by surface waves shows that, under the Tien Shan orogenic belt, a strong low S-wave velocity anomaly exists in the uppermost mantle down to the depth of 200km, supporting the model that the hot upper mantle is upwelling under the Tien Shan orogenic belt, which may be responsible for the mountain building. To the west of central Tien Shan across the Talas-Fergana fault, low S-wave velocity anomalies in the upper mantle become much weaker and finally disappear beneath the Fergana basin. Because surface waves are insensitive to the structures below 300 km, body wave arrival times will be included for a joint inversion with surface waves to generate S-wave velocity structure from the surface down to the mantle transition zone. The joint inversion of both body and surface waves provide complementary constraints on structures at different depths and helps to achieve a more realistic model compared with

  2. Gravity waves from quantum stress tensor fluctuations in inflation

    International Nuclear Information System (INIS)

    Wu, Chun-Hsien; Hsiang, Jen-Tsung; Ford, L. H.; Ng, Kin-Wang

    2011-01-01

    We consider the effects of the quantum stress tensor fluctuations of a conformal field in generating gravity waves in inflationary models. We find a nonscale invariant, non-Gaussian contribution which depends upon the total expansion factor between an initial time and the end of inflation. This spectrum of gravity wave perturbations is an illustration of a negative power spectrum, which is possible in quantum field theory. We discuss possible choices for the initial conditions. If the initial time is taken to be sufficiently early, the fluctuating gravity waves are potentially observable both in the CMB radiation and in gravity wave detectors, and could offer a probe of trans-Planckian physics. The fact that they have not yet been observed might be used to constrain the duration and energy scale of inflation. However, this conclusion is contingent upon including the contribution of modes which were trans-Planckian at the beginning of inflation.

  3. Gravity waves from quantum stress tensor fluctuations in inflation

    Science.gov (United States)

    Wu, Chun-Hsien; Hsiang, Jen-Tsung; Ford, L. H.; Ng, Kin-Wang

    2011-11-01

    We consider the effects of the quantum stress tensor fluctuations of a conformal field in generating gravity waves in inflationary models. We find a nonscale invariant, non-Gaussian contribution which depends upon the total expansion factor between an initial time and the end of inflation. This spectrum of gravity wave perturbations is an illustration of a negative power spectrum, which is possible in quantum field theory. We discuss possible choices for the initial conditions. If the initial time is taken to be sufficiently early, the fluctuating gravity waves are potentially observable both in the CMB radiation and in gravity wave detectors, and could offer a probe of trans-Planckian physics. The fact that they have not yet been observed might be used to constrain the duration and energy scale of inflation. However, this conclusion is contingent upon including the contribution of modes which were trans-Planckian at the beginning of inflation.

  4. 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.

  5. The Effect of Air Velocity on the Prevention of Heat Stress in Iranian Veiled Females

    Directory of Open Access Journals (Sweden)

    Habibi

    2016-09-01

    Full Text Available Background Some environmental factors such as the ambient temperature, radiant temperature, humidity and air velocity as well as clothing and activity level are effective to induce heat strain on the workers. Objectives The current study aimed to evaluate the effect of air velocity on Iranian veiled females at various exercise intensities and climatic conditions. Methods The current experimental study was conducted on 51 healthy veiled females with Islamic clothing (n = 30 in two hot-dry climatic chambers (wet-bulb globe temperature (WBGT = 32 ± 0.1°C and WBGT = 30 ± 0.1°C, 40% relative humidity (RH without air velocity and (n = 21 with air velocity 0.31 m/s in sitting and light workload conditions, respectively, for 60 minutes. The WBGT, oral temperature and heart rate were measured simultaneously every five minutes during the heat exposure and resting state. Data were analyzed using correlation and line regression by SPSS ver. 16. Results In both groups, oral temperature and heart rate increased during heat exposure. The increase of oral temperature and heart rate were larger in the group with air velocity (sitting position, 37.05 ± 0.20°C, 98.30 ± 7.79 bpm, light workload, 37.34 ± 0.24°C, 124.08 ± 6.09 bpm compared those of the group without air velocity (sitting position, 36.70 ± 0.36°C, 69.74 ± 0.98 bpm, light workload, 36.71 ± 0.27°C, 110.78 ± 17.9 bpm. The difference in physiological strain index (PSI between resting and low workload were higher in with air velocity group than those of the group without air velocity. Conclusions The results showed that the heat stress increased by increasing air velocity and humidity in both groups. The air velocity with high humidity can be considered as a positive factor in the occurrence of heat strain. Therefore, the incidence of heat stress decreases with the increase of humidity and reduction of air velocity or with increase of air velocity and reduction of humidity in Iranian veiled

  6. 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

  7. Exploration of deep S-wave velocity structure using microtremor array technique to estimate long-period ground motion

    International Nuclear Information System (INIS)

    Sato, Hiroaki; Higashi, Sadanori; Sato, Kiyotaka

    2007-01-01

    In this study, microtremor array measurements were conducted at 9 sites in the Niigata plain to explore deep S-wave velocity structures for estimation of long-period earthquake ground motion. The 1D S-wave velocity profiles in the Niigata plain are characterized by 5 layers with S-wave velocities of 0.4, 0.8, 1.5, 2.1 and 3.0 km/s, respectively. The depth to the basement layer is deeper in the Niigata port area located at the Japan sea side of the Niigata plain. In this area, the basement depth is about 4.8 km around the Seirou town and about 4.1 km around the Niigata city, respectively. These features about the basement depth in the Niigata plain are consistent with the previous surveys. In order to verify the profiles derived from microtremor array exploration, we estimate the group velocities of Love wave for four propagation paths of long-period earthquake ground motion during Niigata-ken tyuetsu earthquake by multiple filter technique, which were compared with the theoretical ones calculated from the derived profiles. As a result, it was confirmed that the group velocities from the derived profiles were in good agreement with the ones from long-period earthquake ground motion records during Niigata-ken tyuetsu earthquake. Furthermore, we applied the estimation method of design basis earthquake input for seismically isolated nuclear power facilities by using normal mode solution to estimate long-period earthquake ground motion during Niigata-ken tyuetsu earthquake. As a result, it was demonstrated that the applicability of the above method for the estimation of long-period earthquake ground motion were improved by using the derived 1D S-wave velocity profile. (author)

  8. Low Velocity Seismic Waves Produced by Stick-Slip Processes During the Drainage of Two Supraglacial Lakes in Greenland

    Science.gov (United States)

    Kenyon, P. M.; Orantes, E. J.; Grynewize, S.; Tedesco, M.

    2016-12-01

    The drainage of supraglacial lakes over the Greenland ice sheet has been shown to have a significant impact on ice dynamics and subglacial hydrology. As supraglacial lakes drain, they produce seismic waves that can be detected on both local and regional scales. Studying such waves and the originating phenomena has the potential to advance our understanding of the subglacial processes involved. Here we present the results of an analysis of high frequency seismic waves generated during the drainage of two supraglacial lakes in southwestern Greenland. The two lakes drained by contrasting mechanisms. One (Lake Half Moon) drained slowly by overflow into an existing moulin. Here GPS data, recorded during the drainage, show an increase in ice sheet velocity that begins well before the time of maximum lake depth. The other lake (Lake Ponting) drained suddenly by hydrofracture through the lake bed. In this case, the GPS data show an increase in velocity that is essentially simultaneous with the maximum lake depth. In both cases, vertical component seismograms were obtained from the Greenland Ice Sheet Monitoring Network (GLISN) for several hours before and after the lake drainage. Arrival times were picked manually, using the criterion that an arrival must have a minimum amplitude of twice the noise level. The arrivals were then plotted on graphs of time versus distance from the lake in question. Several linear trends are visible on each graph. The velocities calculated from the slopes of these trends are unexpectedly low. We suggest that one explanation for this might be that the waves are traveling in a layer of till at the base of the ice sheet, that forms a low velocity channel. When compared with GPS and lake depth data, the origin times of the waves coincide with the velocity increase in both cases. Therefore, we conclude that the waves are being generated by stick-slip processes involving the slippage of the ice sheet on an underlying layer of till.

  9. Anisotropic Velocity Structure near the Alpine Fault, New Zealand, from Shear Wave Splitting of Local Earthquakes

    Science.gov (United States)

    Savage, M. K.; Boese, C. M.; Townend, J.

    2015-12-01

    We use shear wave splitting of local earthquakes to characterize seismic anisotropy along the central portion of the transpressive, plate-bounding Alpine Fault and surrounding the Deep Fault Drilling Project (DFDP) boreholes. We combine data from the SAMBA network of 2 Hz borehole seismometers, the DFDP10 short-period surface network, and the GeoNet broadband network. Using the MFAST automatic shear wave splitting program applied to hand-picked S arrivals, 1.5 years of data yielded 15,902 measurements. Of these, 1291 measurements from 23 stations were of high quality (grades of A or B); their fast azimuths exhibit three predominant trends: one NE/SW, subparallel to the Alpine Fault, one perpendicular to it and the third E-W. The last of these, observed at the six stations closest to the fault, is roughly parallel to the maximum principal stress direction. Some stations show a single population of fast directions and others show two or more populations. We consider that the orientations are likely caused by a combination of stress-controlled, crack-induced anisotropy and structure-controlled anisotropy associated with the fault fabric and its interaction with the dominantly schistose rocks in the region. Delay times for the highest-quality measurements average 0.067±0.002 s, consistent with small splitting of the high-frequency phases (dominant frequencies 6.9±0.07 Hz) with short path lengths (4.5±0.09 s travel-time). If the anisotropy is present along the entire path, the percentage anisotropy is 1. 5%. However, delay times do not increase much with hypocentral distance, suggesting near-surface effects are dominant and hence that anisotropy is larger near the surface. To ensure the shear-wave splitting results do not depend on the particular algorithm used, a second semi-automated processing routine with different shear-wave splitting criteria is applied. A comparison of the results is anticipated to help to eliminate any possible artefacts.

  10. Shear wave velocities in the Pampean flat-slab region from Rayleigh wave tomography: Implications for slab and upper mantle hydration

    Science.gov (United States)

    Porter, Ryan; Gilbert, Hersh; Zandt, George; Beck, Susan; Warren, Linda; Calkins, Josh; Alvarado, Patricia; Anderson, Megan

    2012-11-01

    The Pampean flat-slab region, located in central Argentina and Chile between 29° and 34°S, is considered a modern analog for Laramide flat-slab subduction within western North America. Regionally, flat-slab subduction is characterized by the Nazca slab descending to ˜100 km depth, flattening out for ˜300 km laterally before resuming a more "normal" angle of subduction. Flat-slab subduction correlates spatially with the track of the Juan Fernandez Ridge, and is associated with the inboard migration of deformation and the cessation of volcanism within the region. To better understand flat-slab subduction we combine ambient-noise tomography and earthquake-generated surface wave measurements to calculate a regional 3D shear velocity model for the region. Shear wave velocity variations largely relate to changes in lithology within the crust, with basins and bedrock exposures clearly defined as low- and high-velocity regions, respectively. We argue that subduction-related hydration plays a significant role in controlling shear wave velocities within the upper mantle. In the southern part of the study area, where normal-angle subduction is occurring, the slab is visible as a high-velocity body with a low-velocity mantle wedge above it, extending eastward from the active arc. Where flat-slab subduction is occurring, slab velocities increase to the east while velocities in the overlying lithosphere decrease, consistent with the slab dewatering and gradually hydrating the overlying mantle. The hydration of the slab may be contributing to the excess buoyancy of the subducting oceanic lithosphere, helping to drive flat-slab subduction.

  11. Numerical Simulation of the Field Velocities and Local Disturbances of a Long Gravity Wave Passing above an Immersed Vertical Barrier

    Directory of Open Access Journals (Sweden)

    Laouar Abdelhamid

    2008-01-01

    Full Text Available This work is interested in the study of the passage of a long gravity wave above an immersed vertical barrier. The latter is placed at a right angle in the middle of the occupied fluid domain which is limited vertically by both a free surface and an impermeable horizontal bottom. We want to determine the field velocity and the local disturbances in the vicinity of the barrier. For this, we use the generalized theory of shallow water and complex variables method. For illustration, we consider a solitary wave as an emitted long wave.

  12. 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.

  13. Enhancing PIV image and fractal descriptor for velocity and shear stresses propagation around a circular pier

    Directory of Open Access Journals (Sweden)

    Alireza Keshavarzi

    2017-07-01

    Full Text Available In this study, the fractal dimensions of velocity fluctuations and the Reynolds shear stresses propagation for flow around a circular bridge pier are presented. In the study reported herein, the fractal dimension of velocity fluctuations (u′, v′, w′ and the Reynolds shear stresses (u′v′ and u′w′ of flow around a bridge pier were computed using a Fractal Interpolation Function (FIF algorithm. The velocity fluctuations of flow along a horizontal plane above the bed were measured using Acoustic Doppler Velocity meter (ADV and Particle Image Velocimetry (PIV. The PIV is a powerful technique which enables us to attain high resolution spatial and temporal information of turbulent flow using instantaneous time snapshots. In this study, PIV was used for detection of high resolution fractal scaling around a bridge pier. The results showed that the fractal dimension of flow fluctuated significantly in the longitudinal and transverse directions in the vicinity of the pier. It was also found that the fractal dimension of velocity fluctuations and shear stresses increased rapidly at vicinity of pier at downstream whereas it remained approximately unchanged far downstream of the pier. The higher value of fractal dimension was found at a distance equal to one times of the pier diameter in the back of the pier. Furthermore, the average fractal dimension for the streamwise and transverse velocity fluctuations decreased from the centreline to the side wall of the flume. Finally, the results from ADV measurement were consistent with the result from PIV, therefore, the ADV enables to detect turbulent characteristics of flow around a circular bridge pier.

  14. Hybrid ANFIS with ant colony optimization algorithm for prediction of shear wave velocity from a carbonate reservoir in Iran

    Directory of Open Access Journals (Sweden)

    Hadi Fattahi

    2016-12-01

    Full Text Available Shear wave velocity (Vs data are key information for petrophysical, geophysical and geomechanical studies. Although compressional wave velocity (Vp measurements exist in almost all wells, shear wave velocity is not recorded for most of elderly wells due to lack of technologic tools. Furthermore, measurement of shear wave velocity is to some extent costly. This study proposes a novel methodology to remove aforementioned problems by use of hybrid adaptive neuro fuzzy inference system (ANFIS with ant colony optimization algorithm (ACO based on fuzzy c–means clustering (FCM and subtractive clustering (SCM. The ACO is combined with two ANFIS models for determining the optimal value of its user–defined parameters. The optimization implementation by the ACO significantly improves the generalization ability of the ANFIS models. These models are used in this study to formulate conventional well log data into Vs in a quick, cheap, and accurate manner. A total of 3030 data points was used for model construction and 833 data points were employed for assessment of ANFIS models. Finally, a comparison among ANFIS models, and six well–known empirical correlations demonstrated ANFIS models outperformed other methods. This strategy was successfully applied in the Marun reservoir, Iran.

  15. Crustal shear wave velocity structure in the northeastern Tibet based on the Neighbourhood algorithm inversion of receiver functions

    Science.gov (United States)

    Wu, Zhenbo; Xu, Tao; Liang, Chuntao; Wu, Chenglong; Liu, Zhiqiang

    2018-03-01

    The northeastern (NE) Tibet records and represents the far-field deformation response of the collision between the Indian and Eurasian plates in the Cenozoic time. Over the past two decades, studies have revealed the existence of thickened crust in the NE Tibet, but the thickening mechanism is still in debate. We deployed a passive-source seismic profile with 22 temporary broad-band seismic stations in the NE Tibet to investigate the crustal shear wave velocity structure in this region. We selected 288 teleseismic events located in the west Pacific subduction zone near Japan with similar ray path to calculate P-wave receiver functions. Neighbourhood algorithm method is applied to invert the shear wave velocity beneath stations. The inversion result shows a low-velocity zone (LVZ) is roughly confined to the Songpan-Ganzi block and Kunlun mountains and extends to the southern margin of Gonghe basin. Considering the low P-wave velocity revealed by the wide-angle reflection-refraction seismic experiment and high ratio of Vp/Vs based on H-κ grid searching of the receiver functions in this profile, LVZ may be attributed to partial melting induced by temperature change. This observation appears to be consistent with the crustal ductile deformation in this region derived from other geophysical investigations.

  16. Velocity model of the Hronov-Poříčí Fault Zone from Rayleigh wave dispersion

    Czech Academy of Sciences Publication Activity Database

    Kolínský, Petr; Valenta, Jan; Málek, Jiří

    2014-01-01

    Roč. 18, č. 3 (2014), s. 617-635 ISSN 1383-4649 R&D Projects: GA ČR GA205/09/1244; GA MŠk LM2010008 Institutional support: RVO:67985891 Keywords : Bohemian Massif * surface waves * phase-velocity * dispersion curve Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.386, year: 2014

  17. 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.

  18. Relationship between serum albumin and pulse wave velocity in patients on continuous ambulatory peritoneal dialysis

    Directory of Open Access Journals (Sweden)

    Li-Tao Cheng

    2008-08-01

    Full Text Available Li-Tao Cheng1, Li-Jun Tang1,2, Hui-Min Chen1,3, Wen Tang1, Tao Wang11Division of Nephrology, Peking University Third Hospital, Beijing, China; 2Division of Nephrology, Qilu Hospital of Shandong University, Ji’nan, China; 3Division of Cardiology, Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou, ChinaBackground: Hypoalbuminemia is a risk factor for cardiovascular events and mortality in dialysis patients, but the underlying mechanism remains unclear. Meanwhile, increased pulse wave velocity (PWV, the marker of arterial stiffness, has been proved to be an independent predictor of cardiovascular disease. The relationship between serum albumin and PWV in continuous ambulatory peritoneal dialysis patients (CAPD was studied.Methods: Sixty-two CAPD patients were studied. The average age was 63 ± 12 years and dialysis duration was 23 ± 22 months. Serum albumin, C-reactive protein (CRP, and carotid-femoral PWV were measured.Results: Among these patients, 43.5% were men. The mean serum albumin concentration was 37 ± 4 g/L and PWV was 11.9 ± 2.3 m/s. PWV positively correlated with age (r = 0.35, P < 0.01, diabetes (yes = 1, no = 0; r = 0.292, P < 0.05, systolic blood pressure (SBP; r = 0.493, P < 0.001 and CRP (r = 0.295, P < 0.05, but negatively correlated with serum albumin (r = −0.357, P < 0.01. In multiple regression analysis, SBP (β = 0.615, P < 0.001, age (β = 0.414, P < 0.01, albumin (β = −0.315, P < 0.05 and total cholesterol (β = 0.275, P < 0.05 were independent determinants of PWV. In a non-inflamed subgroup (CRP < 3 mg/L, n = 30, albumin still negatively correlated with PWV (r = −0.66, P < 0.001.Conclusion: Serum albumin inversely correlated with increased PWV in CAPD patients, suggesting that increased arterial stiffness might be the link between hypoalbuminemia and increased cardiovascular mortality in dialysis patients.Keywords: hypoalbuminemia, cardiovascular events, pulse wave velocity, arterial

  19. Absence of P-wave Reflectivity Near the D" S-wave Velocity Discontinuity in the Lowermost Mantle beneath the Cocos Plate

    Science.gov (United States)

    Hutko, A.; Lay, T.; Revenaugh, J.; Garnero, E.

    2007-12-01

    An abrupt 1-2.5% S-wave velocity increase has been observed in the lowermost mantle beneath the Cocos plate in several studies. This is commonly attributed to the perovskite to post-perovskite phase transition. This phase transition is expected to have much weaker effects on P-wave velocities than on S-wave velocities and the depth range of the transition is expected to depend on Al and Fe content of the perovskite. We image lowermost mantle P-wave reflectivity beneath the Cocos plate using 1D stacking and 3D Kirchhoff migration. Our carefully processed data set comprises 8000 seismograms from deep South American earthquakes recorded by broadband and short-period seismic networks in western North America. Stacked P-wave source wavelets are deconvolved from the data for each event, allowing band-pass filtered signals to be combined for many events. Events are discarded if individual event-stacks do not show an impulsive PcP arrival with significant signal-to- noise ratio. Depth shifts are applied to each event to align PcP arrivals in the combined stacks. These shifts increase systematically from south to north. We observe a widespread weak P-wave reflector about 320 km above the CMB modeled well by a P-wave velocity (Vp) change of -0.2 to -0.4%, depending on the thickness of the velocity change. The depth of this relatively flat reflector is tightly constrained and is a few tens of km shallower than the local S-wave reflector, which may have regional topography of up to 100 km. We model a clear feature in the P-wave reflectivity with a change in dVp/dZ about 180 km above the CMB, accompanied by a sharp 0.2% increase in Vp. Different narrow band filters up to 2 Hz and forward modeling of double-array stacks show that this small velocity increase must occur over less than 10 km in depth. This also does not directly correspond to any significant feature in the S-wave velocity structure. The high signal-to-noise ratio of our locally binned data stacks allows us to

  20. Impulse excitation scanning acoustic microscopy for local quantification of Rayleigh surface wave velocity using B-scan analysis.

    Science.gov (United States)

    Cherry, M; Dierken, J; Boehnlein, T; Pilchak, A; Sathish, S; Grandhi, R

    2018-01-01

    A new technique for performing quantitative scanning acoustic microscopy imaging of Rayleigh surface wave (RSW) velocity was developed based on b-scan processing. In this technique, the focused acoustic beam is moved through many defocus distances over the sample and excited with an impulse excitation, and advanced algorithms based on frequency filtering and the Hilbert transform are used to post-process the b-scans to estimate the Rayleigh surface wave velocity. The new method was used to estimate the RSW velocity on an optically flat E6 glass sample, and the velocity was measured at ±2 m/s and the scanning time per point was on the order of 1.0 s, which are both improvement from the previous two-point defocus method. The new method was also applied to the analysis of two titanium samples, and the velocity was estimated with very low standard deviation in certain large grains on the sample. A new behavior was observed with the b-scan analysis technique where the amplitude of the surface wave decayed dramatically on certain crystallographic orientations. The new technique was also compared with previous results, and the new technique has been found to be much more reliable and to have higher contrast than previously possible with impulse excitation.

  1. Impulse excitation scanning acoustic microscopy for local quantification of Rayleigh surface wave velocity using B-scan analysis

    Science.gov (United States)

    Cherry, M.; Dierken, J.; Boehnlein, T.; Pilchak, A.; Sathish, S.; Grandhi, R.

    2018-01-01

    A new technique for performing quantitative scanning acoustic microscopy imaging of Rayleigh surface wave (RSW) velocity was developed based on b-scan processing. In this technique, the focused acoustic beam is moved through many defocus distances over the sample and excited with an impulse excitation, and advanced algorithms based on frequency filtering and the Hilbert transform are used to post-process the b-scans to estimate the Rayleigh surface wave velocity. The new method was used to estimate the RSW velocity on an optically flat E6 glass sample, and the velocity was measured at ±2 m/s and the scanning time per point was on the order of 1.0 s, which are both improvement from the previous two-point defocus method. The new method was also applied to the analysis of two titanium samples, and the velocity was estimated with very low standard deviation in certain large grains on the sample. A new behavior was observed with the b-scan analysis technique where the amplitude of the surface wave decayed dramatically on certain crystallographic orientations. The new technique was also compared with previous results, and the new technique has been found to be much more reliable and to have higher contrast than previously possible with impulse excitation.

  2. Development of Coronary Pulse Wave Velocity: New Pathophysiological Insight Into Coronary Artery Disease.

    Science.gov (United States)

    Harbaoui, Brahim; Courand, Pierre-Yves; Cividjian, Andrei; Lantelme, Pierre

    2017-02-02

    Although aortic stiffness assessed by pulse wave velocity (PWV) is a strong predictor of coronary artery disease, the significance of local coronary stiffness has never been tackled. The first objective of this study was to describe a method of measuring coronary PWV (CoPWV) invasively and to describe its determinants. The second objective was to assess both CoPWV and aortic PWV in patients presenting with acute coronary syndromes or stable coronary artery disease. In 53 patients, CoPWV was measured from the delay in pressure wave and distance traveled as a pressure wire was withdrawn from the distal to the proximal coronary segment. Similarly, aortic PWV was measured invasively when the wire was pulled across the ascending aorta; carotid-femoral PWV was also measured noninvasively using the SphygmoCor system (AtCor Medical). Mean CoPWV was 10.3±6.1 m/s. Determinants of increased CoPWV were fractional flow reserve, diastolic blood pressure, and previous stent implantation in the recorded artery. CoPWV was lower in patients with acute coronary syndromes versus stable coronary artery disease (7.6±3 versus 11.5±6.4 m/s; P=0.02), and this persisted after adjustment for confounders. In contrast, aortic stiffness, assessed by aortic and carotid-femoral PWV, did not differ significantly. CoPWV seems associated with acute coronary events more closely than aortic PWV. High coronary compliance, whether per se or because it leads to a distal shift in compliance mismatch, may expose vulnerable plaques to high cyclic stretch. CoPWV is a new tool to assess local compliance at the coronary level; it paves the way for a new field of research. © 2017 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

  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. Surface wave group velocity in the Osaka sedimentary basin, Japan, estimated using ambient noise cross-correlation functions

    Science.gov (United States)

    Asano, Kimiyuki; Iwata, Tomotaka; Sekiguchi, Haruko; Somei, Kazuhiro; Miyakoshi, Ken; Aoi, Shin; Kunugi, Takashi

    2017-08-01

    Inter-station cross-correlation functions estimated using continuous ambient noise or microtremor records were used to extract the seismic wave propagation characteristics of the Osaka sedimentary basin, Japan. Temporary continuous observations were conducted at 15 sites in the Osaka basin between 2011 and 2013. The data were analyzed using seismic interferometry. The target period range was 2-8 s. Cross-correlations between all of the possible station pairs were calculated and stacked to produce a year-long data set, and Rayleigh wave signals in the vertical and radial components and Love wave signals in the transverse component were identified from the results. Simulation of inter-station Green's functions using the finite difference method was conducted to check the performance of the current three-dimensional velocity structure model. The measured time lag between the observed and theoretical Green's functions was less than 2 s for most station pairs, which is less than the wave period of interest in the target frequency range. Group velocity tomography was applied to group delay times estimated by means of multiple filter analysis. The estimated group velocities for longer periods of 5-8 s exhibited spatial variation within the basin, which is consistent with the bedrock depth distribution; however, the group velocities for shorter periods of 2-3 s were almost constant over the studied area. The waveform and group velocity information obtained by seismic interferometry analysis can be useful for future reconstruction of a three-dimensional velocity structure model in the Osaka basin.[Figure not available: see fulltext.

  5. Prediction of coronary artery disease using pulse wave velocity and retinal artery lesions.

    Science.gov (United States)

    Wang, De-Zhao; Tang, Qing; Hua, Qi

    2011-09-01

    Coronary artery disease (CAD) is the leading cause of death worldwide. The prevention and early diagnosis of CAD is important for the treatment of this disease. Since the coronary angiographic examination is not available for every hospital, the convenient, quick and cheap prediction marker is needed for the screening of the suspected CAD patients. The aim of this study was to assess whether the combination of brachial-ankle pulse wave velocity (baPWV) and staging of retinal artery lesions could be a useful approach to predict CAD in symptomatic patients, including atypical chest pain. To prove this question, 472 Chinese patients with suspected CAD underwent coronary angiography, the eye fundus examination and measurement of baPWV. The results show that the frequency of baPWV of 1,400 cm/s or retinal artery atherosclerosis of ≥ Stage 2 is higher in patients with CAD (n = 312) than those without CAD (n = 160, p predict the presence of CAD even with atypical chest pain. The combination of the two non-invasive methods is also useful for predicting CAD in symptomatic Chinese patients.

  6. Prediction of all-cause death in hemodialysis patients using elevated postdialysis pulse wave velocity.

    Science.gov (United States)

    Fu, Xiaohong; Yang, Jihong; Fan, Zhaoxin; Chen, Xianguang; Wu, Jie; Li, Jie; Wu, Hua

    2016-02-01

    To identify the relationship between predialysis pulse wave velocity (PWV), postdialysis PWV during 1 hemodialysis (HD) session, and deaths in maintenance HD patients. 43 patients were recruited. PWV was measured before and after one HD session and dialysis- related data were recorded. Clinical data such as blood pressure, blood lipids, and blood glucose, were carefully observed and managed in a 5-year follow-up. The association between all-cause death, predialysis PWV, postdialysis PWV, change of PWV (ΔPWV), and other related variables were analyzed. After 5 years, 17 patients (39.5%) died. Univariate Cox regression analysis showed that all-cause death of the patients significantly correlated with age, postdialysis PWV, and ΔPWV. Multivariate Cox regression analysis revealed that postdialysis PWV was an independent predictor for all-cause death in these patients (HR: 1.377, 95% CI: 1.146 - 1.656, p = 0.001). Elevated postdialysis PWV significantly correlated with and was an independent predictor for all-cause death in maintenance HD patients.

  7. 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.

  8. 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.

  9. Brachial-ankle pulse wave velocity and metabolic syndrome in general population: the APAC study.

    Science.gov (United States)

    Wang, Anxin; Su, Zhaoping; Liu, Xiaoxue; Yang, Yuling; Chen, Shuohua; Wang, Suzhen; Luo, Yanxia; Guo, Xiuhua; Zhao, Xingquan; Wu, Shouling

    2016-11-18

    Metabolic syndrome (MetS) is correlated with arterial stiffness and can be evaluated by brachial-ankle pulse wave velocity (baPWV). We investigated potential associations between MetS and baPWV in a Chinese community population. The community-based Asymptomatic Polyvascular Abnormalities in Community study examined asymptomatic polyvascular abnormalities in a Chinese population aged ≥40 years. The relationship between MetS and its components and baPWV was analyzed by multivariate logistic and linear regression models. Out of 5181 study participants, 1271 subjects (24.53%) had MetS. Mean values of baPWV in subjects with 0, 1, 2,3, 4, and 5 components of MetS were 1430, 1526, 1647, 1676,1740, and 1860 cm/s, respectively (p < 0.001 for trend). After adjusting for confounding risk factors, MetS was significantly associated with baPWV (odds ratio [OR]: 2.74; 95% CI: 2.28, 3.30). Among the five components of MetS, elevated blood pressure was the most important factor for baPWV. All models of multivariate linear regression analysis showed a significant positive correlation between the increasing numbers of MetS components and baPWV (p < 0.0001). baPWV was associated with MetS and was greater with increasing numbers of MetS components. Elevated blood pressure was the most important factor for baPWV.

  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. Renal shear wave velocity and estimated glomerular filtration rate in children with chronic kidney disease.

    Science.gov (United States)

    Bruno, Costanza; Brugnara, Milena; Micciolo, Rocco; Cecchetto, Mariangela; Zuffante, Michele; Bucci, Alessandra; Zaffanello, Marco

    2016-01-01

    A shear wave velocity (SWV) value obtained by the acoustic radiation force impulse technique depends on tissue elasticity. We investigated the relationship between SWV values and the estimated glomerular filtration rate (eGFR) in children with chronic kidney disease. A total of 29 patients were enrolled in the study. There were 18 primary and 11 secondary cases of vesicoureteral reflux. eGFR was calculated using Schwartz's formulas (2012). Partial eGFR for each kidney was assessed by multiplying the eGFR by the percentage of renal function measured by means of renal (99m)Tc-dimercaptosuccinic acid scintigraphy. All ultrasound tests were done by a single qualified technician using a convex probe (frequency 4 MHz) on an S-2000 system. The mean SWV values of the two kidneys were significantly and negatively correlated with eGFR calculated with both univariate (cystatin C [Cys C] and multivariate (creatinine, Cys C, and nitrogen) equations. Of all the formulae, the strongest correlation was obtained with eGFR (Cys C). SWV of the renal cortex correlates with the eGFR of patients affected by malformative uropathies. Nevertheless, this technique needs standardization and validation.

  12. Velocity Models of the Upper Mantle Beneath the MER, Somali Platform, and Ethiopian Highlands from Body Wave Tomography

    Science.gov (United States)

    Hariharan, A.; Keranen, K. M.; Alemayehu, S.; Ayele, A.; Bastow, I. D.; Eilon, Z.

    2016-12-01

    The Main Ethiopian Rift (MER) presents a unique opportunity to improve our understanding of an active continental rift. Here we use body wave tomography to generate compressional and shear wave velocity models of the region beneath the rift. The models help us understand the rifting process over the broader region around the MER, extending the geographic region beyond that captured in past studies. We use differential arrival times of body waves from teleseismic earthquakes and multi-channel cross correlation to generate travel time residuals relative to the global IASP91 1-d velocity model. The events used for the tomographic velocity model include 200 teleseismic earthquakes with moment magnitudes greater than 5.5 from our recent 2014-2016 deployment in combination with 200 earthquakes from the earlier EBSE and EAGLE deployments (Bastow et al. 2008). We use the finite-frequency tomography analysis of Schmandt et al. (2010), which uses a first Fresnel zone paraxial approximation to the Born theoretical kernel with spatial smoothing and model norm damping in an iterative LSQR algorithm. Results show a broad, slow region beneath the rift with a distinct low-velocity anomaly beneath the northwest shoulder. This robust and well-resolved low-velocity anomaly is visible at a range of depths beneath the Ethiopian plateau, within the footprint of Oligocene flood basalts, and near surface expressions of diking. We interpret this anomaly as a possible plume conduit, or a low-velocity finger rising from a deeper, larger plume. Within the rift, results are consistent with previous work, exhibiting rift segmentation and low-velocities beneath the rift valley.

  13. Transient Stress Waves in Study of Coconut Physical Properties

    Czech Academy of Sciences Publication Activity Database

    Trnka, Jan; Dvořáková, Pavla

    2010-01-01

    Roč. 34, č. 1 (2010), s. 19-25 ISSN 0732-8818 R&D Projects: GA AV ČR IAA201990701 Institutional research plan: CEZ:AV0Z20760514 Keywords : stress waves * double-pulse holography * coconut * exploding wires Subject RIV: BI - Acoustics Impact factor: 0.505, year: 2010 http://www3.interscience.wiley.com/cgi-bin/fulltext/121567342/PDFSTART

  14. Slow waves moving near the openings in highly stressed conditions

    Science.gov (United States)

    Guzev, Michail; Makarov, Vladimir

    2017-04-01

    In situ experiments have shown the unusual deformation waves near the openings on high depth of the construction. Process of the wave spreading is beginning after the mining and has two stages of the zonal mesocracking structure formation and development [1]. Extending in a radial direction, the wave poorly fades with distance. For phenomenon modelling the theoretical decision for non-Eucledian models about opening of round cross-section in strongly compressed rock massif is used [2]. The decision qualitatively repeats behaviour of a wave in a rock mass, adjustment of phenomenological parametres is executed. References [1] Vladimir V. Makarov, Mikhail A. Guzev, Vladimir N. Odintsev, Lyudmila S. Ksendzenko (2016) Periodical zonal character of damage near the openings in highly-stressed rock mass conditions. Journal of Rock Mechanics and Geotechnical Engineering. Volume 8, Issue 2, pp. 164-169. [2] M.A. Guzev, V.V. Makarov, 2007. Deforming and failure of the high stressed rocks around the openings, RAS Edit., Vladivostok, 2007, P. 232 (in Russian).

  15. 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

    with permanent station data from the North Atlantic and Greenland, and a dense temporary profile, the East Greenland Caledonian Central Fjord Array (EGCFA). EGCFA resolves low upper-mantle velocities close to the east coast of Greenland and high mantle velocities below the high topography inland. High and low......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......-correlation and arrival-time picking, involving about 50% rewriting and 50% code extension, now also interfacing with the SAC-system and GMT. Ellipticity correction was built in, following the Kennett and Gudmundsson (1996). With these improved methods, I studied the upper-mantle velocity structure in three regions...

  16. Effect of velocity fluctuations length on the calculation accuracy of turbulent shearing stresses

    Directory of Open Access Journals (Sweden)

    Volgin Georgiy Valentinovich

    Full Text Available This article focuses on the method of improving shear stresses calculation accuracy based on the experimental data. It was proven that shear stresses value considerably changes (even up to change of sign from positive to negative depending on different velocity fluctuations amount (or length. Experimental database consists of velocity in turbulent flow at different times. Recommendations for practical use of methods of calculation depending on the type of engineering problems are presented. The method of finding optimal amount of the experimental database is proposed by the analysis of the values convergence of the standard deviations calculated for the whole sample and the standard deviation calculated by increasing interval. The calculation results for these intervals are at the points of the measuring system and the hypothesis about finding the optimal length of implementation is offered. The steps for further research are set out.

  17. Multiparameter full waveform inversion of multicomponent ocean-bottom-cable data from the Valhall field. Part 2: imaging compressive-wave and shear-wave velocities

    Science.gov (United States)

    Prieux, Vincent; Brossier, Romain; Operto, Stéphane; Virieux, Jean

    2013-09-01

    Multiparameter elastic full waveform inversion (FWI) is a promising technology that allows inferences to be made on rock and fluid properties, which thus narrows the gap between seismic imaging and reservoir characterization. Here, we assess the feasibility of 2-D vertical transverse isotropic visco-elastic FWI of wide-aperture multicomponent ocean-bottom-cable data from the Valhall oil field. A key issue is to design a suitable hierarchical data-driven and model-driven FWI workflow, the aim of which is to reduce the nonlinearity of the FWI. This nonlinearity partly arises because the shear (S) wavespeed can have a limited influence on seismic data in marine environments. In a preliminary stage, visco-acoustic FWI of the hydrophone component is performed to build a compressional (P)-wave velocity model, a density model and a quality-factor model, which provide the necessary background models for the subsequent elastic inversion. During the elastic FWI, the P and S wavespeeds are jointly updated in two steps. First, the hydrophone data are inverted to mainly update the long-to-intermediate wavelengths of the S wavespeeds from the amplitude-versus-offset variations of the P-P reflections. This S-wave velocity model is used as an improved starting model for the subsequent inversion of the better-resolving data recorded by the geophones. During these two steps, the P-wave velocity model is marginally updated, which supports the relevance of the visco-acoustic FWI results. Through seismic modelling, we show that the resulting visco-elastic model allows several P-to-S converted phases recorded on the horizontal-geophone component to be matched. Several elastic quantities, such as the Poisson ratio, and the ratio and product between the P and S wavespeeds, are inferred from the P-wave and S-wave velocity models. These attributes provide hints for the interpretation of an accumulation of gas below lithological barriers.

  18. Phase velocity estimation technique based on adaptive beamforming for ultrasonic guided waves propagating along cortical long bones

    Science.gov (United States)

    Okumura, Shigeaki; Nguyen, Vu-Hieu; Taki, Hirofumi; Haïat, Guillaume; Naili, Salah; Sato, Toru

    2017-07-01

    The axial transmission technique, which is used to estimate the phase velocity of an ultrasonic guided wave propagating along cortical bone is a promising tool for bone quality assessment. Lamb waves are ultrasonic guided waves that consist of multiple modes. The number of existing modes and the signal-to-noise ratio required for phase velocity estimation depend on the frequency of the signal. Hence, we employ an adaptive beamforming technique with spatial averaging to control signal-to-noise ratio and resolution by situating subarrays within the full array. Because the determination of the optimal size for spatial averaging is difficult, we propose a new algorithm that does not require a specific size with a new false-phase-velocity rejection technique. Using a 2.0-mm-thick copper plate, the proposed method accurately estimates phase velocity with fitting errors of 0.26 and 1.3%, as shown by simulation and experimental results, respectively. The measurement frequency ranges are more than twice wider than those measured by the conventional method.

  19. 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.

  20. Wave-induced stresses and pore pressures near a mudline

    Directory of Open Access Journals (Sweden)

    Andrzej Sawicki

    2008-12-01

    Full Text Available Conventional methods for the determination of water-wave induced stresses inseabeds composed of granular soils are based on Biot-type models, in which the soilskeleton is treated as an elastic medium. Such methods predict effective stressesin the soil that are unacceptable from the physical point of view, as they permittensile stresses to occur near the upper surface of the seabed. Therefore, in thispaper the granular soil is assumed to behave as an elastic-ideally plastic material,with the Coulomb-Mohr yield criterion adopted to bound admissible stress states inthe seabed. The governing equations are solved numerically by a~finite differencemethod. The results of simulations, carried out for the case of time-harmonicwater waves, illustrate the depth distributions of the excess pore pressures and theeffective stresses in the seabed, and show the shapes of zones of soil in the plastic state.~In particular, the effects on the seabed behaviour of suchparameters as the degree of pore water saturation, the soil permeability, and theearth pressure coefficient, are illustrated.

  1. 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. Mexico, and inverse modeling of regional drainage networks together suggest that this regional uplift occurred during Cenozoic time in at least two discrete phases. Earthquake tomographic models have imaged low velocity material beneath the bulk of western North America, including a ring-shaped anomaly encompassing the Colorado Plateau itself. Basaltic magmatism coincides with these low velocity zones and indicates an overall increase in melt volume at 40 Ma, as well as an abrupt change from lithospheric to asthenospheric signatures at 5 Ma. To investigate the quantitative relationship between seismic velocity anomalies and basaltic magmatism, we have analyzed >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

  2. 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.

  3. Plane-wave and common-translation-factor treatments of He2++H collisions at high velocities

    International Nuclear Information System (INIS)

    Errea, L.F.; Harel, C.; Jouin, H.; Maidagan, J.M.; Mendez, L.; Pons, B.; Riera, A.

    1992-01-01

    We complement previous work that showed that the molecular approach, modified with plane-wave translation factors, is able to reproduce the fall of charge-exchange cross sections in He 2+ +H collisions, by presenting the molecular data, and studying the corresponding mechanism. We test the accuracy of simplifications of the method that have been employed in the literature, and that lead to very simple calculations. We show that the common-translation-factor method is also successful at high nuclear velocities, provided that sufficiently excited states are included in the basis; moreover, it yields a simple picture of the mechanism and a description of ionization processes at high velocities

  4. 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

  5. Prediction of Coronary Artery Disease Extent and Severity Using Pulse Wave Velocity.

    Science.gov (United States)

    Chiha, Joseph; Mitchell, Paul; Gopinath, Bamini; Burlutsky, George; Plant, Adam; Kovoor, Pramesh; Thiagalingam, Aravinda

    2016-01-01

    Pulse-wave velocity (PWV) measures aortic stiffness. It is an independent predictor of cardiovascular events and mortality, yet there is paucity in the literature on its association with the severity and extent of coronary artery disease (CAD). To examine the utility of PWV in predicting CAD burden in men and women the PWV was determined in 344 patients (Men = 266, Women = 78) presenting for invasive coronary angiography for the assessment of suspected CAD. Pearson correlations and multivariate analysis were used to evaluate the relationship between these coronary scores, PWV and traditional cardiovascular risk factors. Compared to men, women with chest pain had lower mean Extent scores (19.2 vs. 35.6; p = 0.0001) and Gensini scores (23.6 vs. 41.9; p = 0.0001). PWV was similar between men and women (12.35 ± 3.74 vs. 12.43 ± 4.58; p = 0.88) and correlated with Extent score (r = 0.21, p = 0.0001) but not Gensini or vessel score (r = 0.03, p = 0.64 and r = 0.06, p = 0.26, respectively). PWV was associated with Extent score in men (B = 2.25 ± 0.78, p = 0.004 for men and B = 1.50 ± 0.88, p = 0.09 for women). It was not a predictor of Gensini score (B = -0.10, P = 0.90). PWV correlates with the extent of CAD, as measured by the 'Extent' score in men more than women. However, it does not correlate with the severity of obstructive CAD in either gender.

  6. Pulse wave velocity and cognitive decline in elders: the Health, Aging, and Body Composition study.

    Science.gov (United States)

    Zeki Al Hazzouri, Adina; Newman, Anne B; Simonsick, Eleanor; Sink, Kaycee M; Sutton Tyrrell, Kim; Watson, Nora; Satterfield, Suzanne; Harris, Tamara; Yaffe, Kristine

    2013-02-01

    Arterial stiffness is a measure of subclinical cardiovascular disease and increases with age. This study examines the association between arterial stiffness and cognitive decline in a cohort of older adults. A total of 2488 subjects with baseline measure of arterial stiffness (mean age, 74.2 years; 52.3% women) were prospectively followed over 9 years in the Health, Aging, and Body Composition Study. Arterial stiffness was measured as pulse wave velocity (PWV) and analyzed in tertiles. Cognitive function was assessed using the Modified Mini-Mental State examination at baseline and repeated at years 3, 5, 8, and 10. Lower Modified Mini-Mental State examination scores indicate worse function. We fit linear mixed models to examine longitudinal changes in cognitive function over the 9 years of follow-up and logistic regression models, restricted to 1331 participants, to examine cognitive impairment defined as a decrease of ≥5 points after 9 years. We adjusted for sociodemographics, Apoe4, and cardiovascular disease risk factors. The annual decrease in Modified Mini-Mental State examination scores was 0.30 points at low PWV (95% confidence interval [CI], -0.37 to -0.22), 0.46 points at middle PWV (95% CI, -0.54 to -0.39), and 0.45 points at high PWV (95% CI, -0.53 to -0.38), from fully adjusted linear mixed models. In fully adjusted models, the odds of cognitive impairment after 9 years of follow-up was 40% greater for subjects with middle PWV (odds ratio [OR], 1.40; 95% CI, 1.03-1.92) and 59% greater for subjects with high PWV (OR, 1.59; 95% CI, 1.16-2.18), compared with low PWV. High arterial stiffness was modestly associated with cognitive decline and impairment. Interventions to prevent arterial stiffness may be effective in delaying cognitive decline.

  7. 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/m 2 , 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.

  8. 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.

  9. Stress Wave Scattering: Friend or Enemy of Non Destructive Testing of Concrete?

    Science.gov (United States)

    Aggelis, Dimitrios G.; Shiotani, Tomoki; Philippidis, Theodore P.; Polyzos, Demosthenes

    Cementitious materials are by definition inhomogeneous containing cement paste, sand, aggregates as well as air voids. Wave propagation in such a material is characterized by scattering phenomena. Damage in the form of micro or macro cracks certainly enhances scattering influence. Its most obvious manifestation is the velocity variation with frequency and excessive attenuation. The influence becomes stronger with increased mis-match of elastic properties of constituent materials and higher crack content. Therefore, in many cases of large concrete structures, field application of stress waves is hindered since attenuation makes the acquisition of reliable signals troublesome. However, measured wave parameters, combined with investigation with scattering theory can reveal much about the internal condition and supply information that cannot be obtained in any other way. The size and properties of the scatterers leave their signature on the dispersion and attenuation curves making thus the characterization more accurate in case of damage assessment, repair evaluation as well as composition inspection. In this paper, three indicative cases of scattering influence are presented. Namely, the interaction of actual distributed damage, as well as the repair material injected in an old concrete structure with the wave parameters. Other cases are the influence of light plastic inclusions in hardened mortar and the influence of sand and water content in the examination of fresh concrete. In all the above cases, scattering seems to complicate the propagation behavior but also offers the way for a more accurate characterization of the quality of the material.

  10. Crust and uppermost-mantle structure of Greenland and the Northwest Atlantic from Rayleigh wave group velocity tomography

    Science.gov (United States)

    Darbyshire, Fiona A.; Dahl-Jensen, Trine; Larsen, Tine B.; Voss, Peter H.; Joyal, Guillaume

    2018-03-01

    The Greenland landmass preserves ˜4 billion years of tectonic history, but much of the continent is inaccessible to geological study due to the extensive inland ice cap. We map out, for the first time, the 3-D crustal structure of Greenland and the NW Atlantic ocean, using Rayleigh wave anisotropic group velocity tomography, in the period range 10-80 s, from regional earthquakes and the ongoing GLATIS/GLISN seismograph networks. 1-D inversion gives a pseudo-3-D model of shear wave velocity structure to depths of ˜100 km with a horizontal resolution of ˜200 km. Crustal thickness across mainland Greenland ranges from ˜25 km to over 50 km, and the velocity structure shows considerable heterogeneity. The large sedimentary basins on the continental shelf are clearly visible as low velocities in the upper ˜5-15 km. Within the upper continental basement, velocities are systematically lower in northern Greenland than in the south, and exhibit a broadly NW-SE trend. The thinning of the crust at the continental margins is also clearly imaged. Upper-mantle velocities show a clear distinction between typical fast cratonic lithosphere (Vs ≥4.6 km s-1) beneath Greenland and its NE margin and anomalously slow oceanic mantle (Vs ˜4.3-4.4 km s-1) beneath the NW Atlantic. We do not observe any sign of pervasive lithospheric modification across Greenland in the regions associated with the presumed Iceland hotspot track, though the average crustal velocity in this region is higher than that of areas to the north and south. Crustal anisotropy beneath Greenland is strong and complex, likely reflecting numerous episodes of tectonic deformation. Beneath the North Atlantic and Baffin Bay, the dominant anisotropy directions are perpendicular to the active and extinct spreading centres. Anisotropy in the subcontinental lithosphere is weaker than that of the crust, but still significant, consistent with cratonic lithosphere worldwide.

  11. TROTT computer program for two-dimensional stress wave propagation, volume 3

    Science.gov (United States)

    Seaman, L.; Curran, D. R.

    1980-04-01

    TROTT is a Lagrangian finite-difference computer program for calculating two dimensional stress wave propagation through solid, porous, and composite materials. The stress waves may be caused by impact, detonation of an explosive, or a prescribed velocity. The calculational procedure is the standard leapfrog method of von Neumann and Richtmyer, using artificial viscosity to smooth shock fronts. Quadrilateral or triangular cells are used. The momentum relations are derived by treating the cells as finite elements. Axisymmetric or planar flow can be handled. The constitutive relations include the standard Mie-Gruneisen equation-of-state and elastic-plastic, work-hardening deviator stress relations. A polytropic gas and detonating flow relations are provided for explosives. Ductile and brittle fracture and shear banding are provided by nucleation and growth models. Porous materials can be represented by a cap plasticity model. A model for layered composites is also present. The code is constructed for easy insertion of additional material models. The number of extra variables required for each cell for a material model can be specified on an input card. This manual includes many sample problems, a derivation of the flow equations, and a discussion of material models.

  12. Crack wave propagation along fracture with an induced low-velocity layer; Teisokudo no chika kiretsu zone wo denpasuru kiretsuha no bunsan tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Nagano, K. [Muroran Institute of Technology, Hokkaido (Japan)

    1997-10-22

    A study has been performed on underground cracks working as a geothermy reservoir layer, with respect to characteristics of elastic waves propagating with their energy concentrated on a boundary between rocks around the cracks and fluid in the underground cracks, or `crack waves`. The study has modeled a multi-crack reservoir layer according to the three-layer structure of the fluid layer and low-velocity solid layers around the former layer, whereas crack waves propagating therein were discussed for their dispersion characteristics. As a result of discussions, a guideline to the crack wave measurement at actual fields was put together as follows: because the low-velocity layer affects the dispersion characteristics of the crack waves, the structure and characteristics of the multi-crack reservoir layer may possibly be evaluated by measuring the velocity of the crack waves; evaluating the low-velocity layers requires proper selection of frequency of the crack wave to be measured; for example, at the Higashi Hachimantai field, a crack wave of several hundred hertz must be analyzed; and thickness of the low-velocity layers around main cracks, which can be estimated from the velocity of the crack wave is two meters at the greatest. 6 refs., 3 figs., 2 tabs.

  13. Crustal and upper mantle S-wave velocity structures across the Taiwan Strait from ambient seismic noise and teleseismic Rayleigh wave analyses

    Science.gov (United States)

    Huang, Y.; Yao, H.; Wu, F. T.; Liang, W.; Huang, B.; Lin, C.; Wen, K.

    2013-12-01

    Although orogeny seems to have stopped in western Taiwan large and small earthquakes do occur in the Taiwan Strait. Limited studies have focused on this region before and were barely within reach for comprehensive projects like TAICRUST and TAIGER for logistical reasons; thus, the overall crustal structures of the Taiwan Strait remain unknown. Time domain empirical Green's function (TDEGF) from ambient seismic noise to determine crustal velocity structure allows us to study an area using station pairs on its periphery. This research aims to resolve 1-D average crustal and upper mantle S-wave velocity (Vs) structures alone paths of several broadband station-pairs across the Taiwan Strait; 5-120 s Rayleigh wave phase velocity dispersion data derived by combining TDEGF and traditional surface wave two-station method (TS). The average Vs structures show significant differences in the upper 15 km as expected. In general, the highest Vs are observed in the coastal area of Mainland China and the lowest Vs appear along the southwest offshore of the Taiwan Island; they differ by about 0.6-1.1 km/s. For different parts of the Strait, the Vs are lower in the middle by about 0.1-0.2 km/s relative to those in the northern and southern parts. The overall crustal thickness is approximately 30 km, much thinner and less variable than under the Taiwan Island.

  14. A simplified method of evaluating the stress wave environment of internal equipment

    Science.gov (United States)

    Colton, J. D.; Desmond, T. P.

    1979-01-01

    A simplified method called the transfer function technique (TFT) was devised for evaluating the stress wave environment in a structure containing internal equipment. The TFT consists of following the initial in-plane stress wave that propagates through a structure subjected to a dynamic load and characterizing how the wave is altered as it is transmitted through intersections of structural members. As a basis for evaluating the TFT, impact experiments and detailed stress wave analyses were performed for structures with two or three, or more members. Transfer functions that relate the wave transmitted through an intersection to the incident wave were deduced from the predicted wave response. By sequentially applying these transfer functions to a structure with several intersections, it was found that the environment produced by the initial stress wave propagating through the structure can be approximated well. The TFT can be used as a design tool or as an analytical tool to determine whether a more detailed wave analysis is warranted.

  15. 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...

  16. Judgment value of brachial-ankle pulse wave velocity for lesion severity in hypertension patients with coronary arteriosclerosis

    Directory of Open Access Journals (Sweden)

    Zhong Zhao

    2016-07-01

    Full Text Available Objective: To analyze the judgment value of brachial-ankle pulse wave velocity for lesion severity in hypertension patients with coronary arteriosclerosis. Methods: A total of 100 cases of hypertension patients with coronary arteriosclerosis who received physical examination in Physical Examination Centre of our hospital were collected as research subjects of observation group, 100 cases patients with primary hypertension alone who received treatment in our hospital during the same period were selected as control group, brachial-ankle pulse wave velocity and ultrasound coronary area were detected, serum was collected to detect the levels of coronary arteriosclerosis illness-related indicators in it, and the judgment value of brachialankle pulse wave velocity for coronary arteriosclerosis severity was further analyzed. Results: PWV value of observation group was higher than that of control group while ABI value was lower than that of control group; intravascular ultrasound inspection showed that blood vessel volume, lumen volume and plaque volume of observation group were larger than those of control group; serum Hcy, Ox-LDL and ApoB/ApoA1 values of observation group were higher than those of control group while APN value was lower than that of control group; serum Lp-PLA2, sTWEAK, CML and bFGF values of observation group were higher than those of control group while secKlotho, Chrelin and MPO values were lower than those of control group; PWV and ABI values were directly correlated with disease severity-related factors. Conclusions: Brachial-ankle pulse wave velocity can effectively judge the lesion severity of hypertension patients with coronary arteriosclerosis, can be used as one of the accurate indicators to guide treatment and judge prognosis in clinical practice, and has important clinical value.

  17. 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

  18. Evaluation of stress and saturation effects on seismic velocity and electrical resistivity - laboratory testing of rock samples

    Science.gov (United States)

    Vilhelm, Jan; Jirků, Jaroslav; Slavík, Lubomír; Bárta, Jaroslav

    2016-04-01

    Repository, located in a deep geological formation, is today considered the most suitable solution for disposal of spent nuclear fuel and high-level waste. The geological formations, in combination with an engineered barrier system, should ensure isolation of the waste from the environment for thousands of years. For long-term monitoring of such underground excavations special monitoring systems are developed. In our research we developed and tested monitoring system based on repeated ultrasonic time of flight measurement and electrical resistivity tomography (ERT). As a test site Bedřichov gallery in the northern Bohemia was selected. This underground gallery in granitic rock was excavated using Tunnel Boring Machine (TBM). The seismic high-frequency measurements are performed by pulse-transmission technique directly on the rock wall using one seismic source and three receivers in the distances of 1, 2 and 3 m. The ERT measurement is performed also on the rock wall using 48 electrodes. The spacing between electrodes is 20 centimeters. An analysis of relation of seismic velocity and electrical resistivity on water saturation and stress state of the granitic rock is necessary for the interpretation of both seismic monitoring and ERT. Laboratory seismic and resistivity measurements were performed. One series of experiments was based on uniaxial loading of dry and saturated granitic samples. The relation between stress state and ultrasonic wave velocities was tested separately for dry and saturated rock samples. Other experiments were focused on the relation between electrical resistivity of the rock sample and its saturation level. Rock samples with different porosities were tested. Acknowledgments: This work was partially supported by the Technology Agency of the Czech Republic, project No. TA 0302408

  19. Structure of the crust beneath Cameroon, West Africa, from the joint inversion of Rayleigh wave group velocities and receiver functions

    Science.gov (United States)

    Tokam, Alain-Pierre K.; Tabod, Charles T.; Nyblade, Andrew A.; Julià, Jordi; Wiens, Douglas A.; Pasyanos, Michael E.

    2010-11-01

    The Cameroon Volcanic Line (CVL) consists of a linear chain of Tertiary to Recent, generally alkaline, volcanoes that do not exhibit an age progression. Here we study crustal structure beneath the CVL and adjacent regions in Cameroon using 1-D shear wave velocity models obtained from the joint inversion of Rayleigh wave group velocities and P-receiver functions for 32 broad-band seismic stations deployed between 2005 January and 2007 February. We find that (1) crustal thickness (35-39km) and velocity structure is similar beneath the CVL and the Pan African Oubanguides Belt to the south of the CVL, (2) crust is thicker (43-48km) under the northern margin of the Congo Craton and is characterized by shear wave velocities >=4.0kms-1 in its lower part and (3) crust is thinner (26-31km) under the Garoua rift and the coastal plain. In addition, a fast velocity layer (Vs of 3.6-3.8kms-1) in the upper crust is found beneath many of the seismic stations. Crustal structure beneath the CVL and the Oubanguides Belt is very similar to Pan African crustal structure in the Mozambique Belt, and therefore it appears not to have been modified significantly by the magmatic activity associated with the CVL. The crust beneath the coastal plain was probably thinned during the opening of the southern Atlantic Ocean, while the crust beneath the Garoua rift was likely thinned during the formation of the Benue Trough in the early Cretaceous. We suggest that the thickened crust and the thick mafic lower crustal layer beneath the northern margin of the Congo Craton may be relict features from a continent-continent collision along this margin during the formation of Gondwana.

  20. Non-invasive aortic systolic pressure and pulse wave velocity estimation in a primary care setting: An in silico study.

    Science.gov (United States)

    Guala, Andrea; Camporeale, Carlo; Ridolfi, Luca; Mesin, Luca

    2017-04-01

    Everyday clinical cardiovascular evaluation is still largely based on brachial systolic and diastolic pressures. However, several clinical studies have demonstrated the higher diagnostic capacities of the aortic pressure, as well as the need to assess the aortic mechanical properties (e.g., by measuring the aortic pulse wave velocity). In order to fill this gap, we propose to exploit a set of easy-to-obtain physical characteristics to estimate the aortic pressure and pulse wave velocity. To this aim, a large population of virtual subjects is created by a validated mathematical model of the cardiovascular system. Quadratic regressive models are then fitted and statistically selected in order to obtain reliable estimations of the aortic pressure and pulse wave velocity starting from the knowledge of the subject age, height, weight, brachial pressure, photoplethysmographic measures and either electrocardiogram or phonocardiogram. The results are very encouraging and foster clinical studies aiming to apply a similar technique to a real population. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

  1. 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.

  2. 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.

  3. Variable-Velocity Traveling-Wave Ion Mobility Separation Enhancing Peak Capacity for Data-Independent Acquisition Proteomics.

    Science.gov (United States)

    Haynes, Sarah E; Polasky, Daniel A; Dixit, Sugyan M; Majmudar, Jaimeen D; Neeson, Kieran; Ruotolo, Brandon T; Martin, Brent R

    2017-06-06

    High mass accuracy, data-dependent acquisition is the current standard method in mass spectrometry-based peptide annotation and quantification. In high complexity samples, limited instrument scan speeds often result in under-sampling. In contrast, all-ion data-independent acquisition methods bypass precursor selection, alternating high and low collision energies to analyze product and precursor ions across wide mass ranges. Despite capturing data for all events, peptide annotation is limited by inadequate alignment algorithms or overlapping ions. Ion mobility separation can add an orthogonal analytical dimension, reducing ion interference to improve reproducibility, peak capacity, and peptide identifications to rival modern hybrid quadrupole orbitrap systems. Despite the advantages of ion mobility separation in complex proteomics analyses, there has been no quantitative measure of ion mobility resolution in a complex proteomic sample. Here, we present TWIMExtract, a data extraction tool to export defined slices of liquid chromatography/ion mobility/mass spectrometry (LC-IM-MS) data, providing a route to quantify ion mobility resolution from a commercial traveling-wave ion mobility time-of-flight mass spectrometer. Using standard traveling-wave ion mobility parameters (600 m/s, 40 V), 90% of the annotated peptides occupied just 23% of the ion mobility drift space, yet inclusion of ion mobility nearly doubled the overall peak capacity. Relative to fixed velocity traveling-wave ion mobility settings, ramping the traveling-wave velocity increased drift space occupancy, amplifying resolution by 16%, peak capacity by nearly 50%, and peptide/protein identifications by 40%. Overall, variable-velocity traveling-wave ion mobility-mass spectrometry significantly enhances proteomics analysis in all-ion fragmentation acquisition.

  4. 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

  5. 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

  6. 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

    2018-03-01

    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

  7. Interaction of laser-induced stress waves with metals

    Science.gov (United States)

    Clauer, A. H.; Fairand, B. P.

    1979-01-01

    An investigation of the effect of high intensity laser induced stress waves on the hardness and tensile strength of 2024 and 7075 aluminum and on the fatigue properties of 7075 aluminum were investigated. Laser shocking increases the hardness of the underaged 2024-T351 but has little or no effect on the peak aged 2024-T351 and 7075-T651 or the overaged 7075-T73. The fretting fatigue life of fastener joints of 7075-T6 was increased by orders of magnitude by laser shocking the region around the fastener hole; the fatigue crack propagation rates were decreased by laser shocking.

  8. Measuring aortic pulse wave velocity using high-field cardiovascular magnetic resonance: comparison of techniques

    Directory of Open Access Journals (Sweden)

    Shaffer Jean M

    2010-05-01

    Full Text Available Abstract Background The assessment of arterial stiffness is increasingly used for evaluating patients with different cardiovascular diseases as the mechanical properties of major arteries are often altered. Aortic stiffness can be noninvasively estimated by measuring pulse wave velocity (PWV. Several methods have been proposed for measuring PWV using velocity-encoded cardiovascular magnetic resonance (CMR, including transit-time (TT, flow-area (QA, and cross-correlation (XC methods. However, assessment and comparison of these techniques at high field strength has not yet been performed. In this work, the TT, QA, and XC techniques were clinically tested at 3 Tesla and compared to each other. Methods Fifty cardiovascular patients and six volunteers were scanned to acquire the necessary images. The six volunteer scans were performed twice to test inter-scan reproducibility. Patient images were analyzed using the TT, XC, and QA methods to determine PWV. Two observers analyzed the images to determine inter-observer and intra-observer variabilities. The PWV measurements by the three methods were compared to each other to test inter-method variability. To illustrate the importance of PWV using CMR, the degree of aortic stiffness was assessed using PWV and related to LV dysfunction in five patients with diastolic heart failure patients and five matched volunteers. Results The inter-observer and intra-observer variability results showed no bias between the different techniques. The TT and XC results were more reproducible than the QA; the mean (SD inter-observer/intra-observer PWV differences were -0.12(1.3/-0.04(0.4 for TT, 0.2(1.3/0.09(0.9 for XC, and 0.6(1.6/0.2(1.4 m/s for QA methods, respectively. The correlation coefficients (r for the inter-observer/intra-observer comparisons were 0.94/0.99, 0.88/0.94, and 0.83/0.92 for the TT, XC, and QA methods, respectively. The inter-scan reproducibility results showed low variability between the repeated

  9. Transition from Slow to Fast Slip with Temperature, Forcing Velocity and Normal Stress: Experimental Evidence

    Science.gov (United States)

    Mitchell, E. K.; Brown, K. M.; Fialko, Y.

    2009-12-01

    We investigate frictional properties of K-feldspar bearing granite using a heated direct shear apparatus. We study the effects of temperature, applied forcing velocity and normal stress on the evolution of friction. We find that dramatic changes in slip rate and stress drop occur in response to changing experimental conditions. We perform two types of tests in this study: high sampling rate tests and hold tests. High sampling rate (10,000 Hz) tests reveal the effects of varying temperature, normal stress and forcing velocity on the amplitude, duration and velocity of individual slip events. Increasing temperature increases both slip amplitude and slip rate and decreases slip duration. Slip rates gradually increase as temperatures rise from 15 to 300 °C. However, we observe a dramatic jump in slip characteristics as temperatures rise from 300 to 400 °C; slip rates increase by two orders of magnitude from 0.17 to 10.46 mm/s. We speculate that the jump in slip velocities is related to the onset of substantial weakening of the quartz mineral phase and associated increases in contact area. The effect of increasing normal stress or decreasing forcing velocity is similar to but slightly different than temperature effects. We also tend to see increases in slip amplitude and velocity but slip time also increases. We also performed a series of hold tests to study the effect of temperature on the time dependent post slip healing of the frictional surface. We measure peak friction coefficient as a function of hold time at constant normal/shear load at 15, 300 and 500 °C. In rough agreement with results of Dieterich (1972), at 15°C the static coefficient of friction increases as a logarithm of hold time with a pre-multiplying coefficient. Raising temperature increases the value and rate of change of the static friction coefficient as a function of hold time. This suggests that post slip fault strengthening and the subsequent seismic stress drop are enhanced at higher

  10. [Relationship between brachial-ankle pulse wave velocity and metabolic syndrome].

    Science.gov (United States)

    Liu, Miao; He, Yao; Jiang, Bin; Wu, Lei; Wang, Jian-hua; Yang, Shan-shan; Wang, Yi-yan; Li, Xiao-ying

    2014-06-18

    To evaluate the association between brachial-ankle pulse wave velocity (ba-PWV) and metabolic syndrome (MetS) among the Chinese elderly and the gender difference. We conducted a population-based cross-sectional study in a representative urban area of Beijing, China. A sample of 2 102 community elderly (848 males, and 1 254 females) aged 60 to 95 years were included in the study. MetS was defined according to the 2009 harmonizing definition. The prevalence of MetS was 59.1% (50.1% in males and 65.2% in females, P<0.001). The baPWV value was between 8.2 to 45.6 (20.0 ± 4.4) m/s, and showed an increasing trend with age (P<0.001). The partial correlation showed baPWV was positively associated with BMI (r=0.076, P=0.037), systolic blood pressure (r=0.380, P<0.001), diastolic blood pressure (r=0.276, P<0.001), triglyceride (r=0.040, P=0.046), fasting blood glucose (r=0.140, P<0.001), 2-hour post-meal blood glucose (r=0.121, P<0.001), and negatively associated with HDL-C (r=-0.128, P=0.048). There was a strong association between baPWV and prevalence of MetS and its component number in females but not in males. Compared with the lowest quartile of baPWV, the adjusted ORs were 1.22 (95%CI 0.83-1.79), 1.32 (95%CI 0.90-1.93), 1.46(95%CI 1.00-2.14) in males and 1.28 (95%CI 0.93-1.77), 1.55 (95%CI 1.12-2.16), 1.86(95%CI 1.32-2.61) in females for the second, third and top quartiles. The prevalence of MetS increases substantially with increasing levels of baPWV among the Chinese elderly, especially in females.

  11. Group velocity dispersion measurement method using sinusoidally phase-modulated continuous wave light based on cyclic nature of optical waveform change by group velocity dispersion.

    Science.gov (United States)

    Yamamoto, Takashi; Mori, Takayoshi; Sakamoto, Taiji; Kurokawa, Kenji; Tomita, Shigeru; Tsubokawa, Makoto

    2010-09-20

    We show that any optical pulse train recovers its original waveform after passing through a group velocity dispersion (GVD) device when the total GVD value of the device is equal to an integral multiple of 1/(2πf(rep)(2)), where f(rep) is the repetition rate of the optical pulse train. In addition, we detail our proposed GVD measurement method, or optical phase-modulation (PM) method, which utilizes a sinusoidally PM continuous wave (CW) light as a probe light. The total GVD B(2) of a device under test (DUT) is derived by using a very simple equation, |B(2)|=1/(2πf(null)(2)), where f(null) is the smallest modulation frequency at which the sinusoidally PM light becomes CW light again after passing through the DUT.

  12. Surface shear stress dependence of gas transfer velocity parameterizations using DNS

    Science.gov (United States)

    Fredriksson, S. T.; Arneborg, L.; Nilsson, H.; Handler, R. A.

    2016-10-01

    Air-water gas-exchange is studied in direct numerical simulations (DNS) of free-surface flows driven by natural convection and weak winds. The wind is modeled as a constant surface-shear-stress and the gas-transfer is modeled via a passive scalar. The simulations are characterized via a Richardson number Ri=Bν/u*4 where B, ν, and u* are the buoyancy flux, kinematic viscosity, and friction velocity respectively. The simulations comprise 0water gas-exchange, (ii) determine, for a given buoyancy flux, the wind speed at which gas transfer becomes primarily shear driven, and (iii) find an expression for the gas-transfer velocity for flows driven by both convection and shear. The evaluated gas transfer-velocity parametrizations are based on either the rate of turbulent kinetic energy dissipation, the surface flow-divergence, the surface heat-flux, or the wind-speed. The parametrizations based on dissipation or divergence show an unfavorable Ri dependence for flows with combined forcing whereas the parametrization based on heat-flux only shows a limited Ri dependence. The two parametrizations based on wind speed give reasonable estimates for the transfer-velocity, depending however on the surface heat-flux. The transition from convection- to shear-dominated gas-transfer-velocity is shown to be at Ri≈0.004. Furthermore, the gas-transfer is shown to be well represented by two different approaches: (i) additive forcing expressed as kg,sum =AShearu*|Ri/Ric+1| 1/4Sc-n where Ric=|AShear/ABuoy|4, and (ii) either buoyancy or shear dominated expressed as, kg=ABuoy|Bν| 1/4Sc-n, Ri>Ric or kg=AShearu*Sc-n, Riwater surface-characteristics.

  13. Upper mantle structure of shear-waves velocities and stratification of anisotropy in the Afar Hotspot region

    Science.gov (United States)

    Sicilia, D.; Montagner, J.-P.; Cara, M.; Stutzmann, E.; Debayle, E.; Lépine, J.-C.; Lévêque, J.-J.; Beucler, E.; Sebai, A.; Roult, G.; Ayele, A.; Sholan, J. M.

    2008-12-01

    The Afar area is one of the biggest continental hotspots active since about 30 Ma. It may be the surface expression of a mantle "plume" related to the African Superswell. Central Africa is also characterized by extensive intraplate volcanism. Around the same time (30 Ma), volcanic activity re-started in several regions of the African plate and hotspots such as Darfur, Tibesti, Hoggar and Mount Cameroon, characterized by a significant though modest volcanic production. The interactions of mantle upwelling with asthenosphere, lithosphere and crust remain unclear and seismic anisotropy might help in investigating these complex interactions. We used data from the global seismological permanent FDSN networks (GEOSCOPE, IRIS, MedNet, GEO- FON, etc.), from the temporary PASSCAL experiments in Tanzania and Saudi Arabia and a French deployment of 5 portable broadband stations surrounding the Afar Hotspot. A classical two-step tomographic inversion from surface waves performed in the Horn of Africa with selected Rayleigh wave and Love wave seismograms leads to a 3D-model of both S V velocities and azimuthal anisotropy, as well as radial SH/ SV anisotropy, with a lateral resolution of 500 km. The region is characterized by low shear-wave velocities beneath the Afar Hotspot, the Red Sea, the Gulf of Aden and East of the Tanzania Craton to 400 km depth. High velocities are present in the Eastern Arabia and the Tanzania Craton. The results of this study enable us to rule out a possible feeding of the Central Africa hotspots from the "Afar plume" above 150-200 km. The azimuthal anisotropy displays a complex pattern near the Afar Hotspot. Radial anisotropy, although poorly resolved laterally, exhibits S H slower than S V waves down to about 150 km depth, and a reverse pattern below. Both azimuthal and radial anisotropies show a stratification of anisotropy at depth, corresponding to different physical processes. These results suggest that the Afar hotspot has a different and

  14. Mass sensitivity of acoustic wave devices from group and phase velocity measurements

    OpenAIRE

    McHale, G; Martin, F; Newton, MI

    2002-01-01

    The effect of dispersion on acoustic wave sensors is considered. The discussion is focused upon layer guided surface acoustic waves ~Love waves!, which obtain their high mass sensitivity for the first Love wave mode by optimizing the guiding layer thickness, d, such that d;ll/4; the wavelength in the layer is given by ll5f /vl where f is the operating frequency and vl is the shear acoustic speed of the guiding layer. We show that this optimization of guiding layer thickness corresponds to str...

  15. Determination of the Stress State From Transverse Wave Speeds in Isotropic Inelastic Solids

    National Research Council Canada - National Science Library

    Scheidler, Mike

    1997-01-01

    For a transverse acceleration wave propagating along a principal axis of strain in a nonlinear isotropic elastic solid, a simple formula due to Ericksen relates the wave speed to the stress and strain...

  16. Structure of the Crust Beneath Cameroon, West Africa, from the Joint Inversion of Rayleigh Wave Group Velocities and Receiver Functions

    International Nuclear Information System (INIS)

    Tokam, Alain-Pierre K.; Tabod, Charles T.; Nyblade, Andrew A.; Jordi Julia; Wiens, Douglas A.; Pasyanos, Michael E.

    2009-09-01

    The joint inversion of Rayleigh wave group velocities and receiver functions was carried out to investigate the crustal and uppermost mantle structures beneath Cameroon. This was achieved using data from 32 broadband seismic stations installed for 2 years across Cameroon. The Moho depth estimates reveal that the Precambrian crust is variable across the country and shows some significant differences compared to other similar geologic units in East and South Africa. These differences suggest that the setting of the Cameroon Volcanic Line (CVL) and the eastward extension of the Benue Trough have modified the crust of the Panafrican mobile belt in Cameroon by thinning beneath the Rift area and CVL. The velocity models obtained from the joint inversion show at most stations, a layer with shear wave velocities ≥ 4.0 km/s, indicating the presence of a mafic component in the lower crust, predominant beneath the Congo Craton. The lack of this layer at stations within the Panafrican mobile belt may partly explain the crustal thinning observed beneath the CVL and rift area. The significant presence of this layer beneath the Craton, results from the 2100 Ma magmatic events at the origin of the emplacement of swarms of mafic dykes in the region. The CVL stations are underlain by a crust of 35 km on average except near Mt-Cameroon where it is about 25 km. The crustal thinning observed beneath Mt. Cameroon supported by the observed positive gravity anomalies here, suggests the presence of dense astenospheric material within the lithosphere. Shear wave velocities are found to be slower in the crust and uppermost mantle beneath the CVL than the nearby tectonic terrains, suggesting that the origin of the line may be an entirely mantle process through the edge-flow convection process. (author)

  17. Correlation of pulse wave velocity with left ventricular mass in patients with hypertension once blood pressure has been normalized

    Directory of Open Access Journals (Sweden)

    Siu H. Chan

    2012-02-01

    Full Text Available Vascular stiffness has been proposed as a simple method to assess arterial loading conditions of the heart which induce left ventricular hypertrophy (LVH. There is some controversy as to whether the relationship of vascular stiffness to LVH is independent of blood pressure, and which measurement of arterial stiffness, augmentation index (AI or pulse wave velocity (PWV is best. Carotid pulse wave contor and pulse wave velocity of patients (n=20 with hypertension whose blood pressure (BP was under control (<140/90 mmHg with antihypertensive drug treatment medications, and without valvular heart disease, were measured. Left ventricular mass, calculated from 2D echocardiogram, was adjusted for body size using two different methods: body surface area and height. There was a significant (P<0.05 linear correlation between LV mass index and pulse wave velocity. This was not explained by BP level or lower LV mass in women, as there was no significant difference in PWV according to gender (1140.1+67.8 vs 1110.6+57.7 cm/s. In contrast to PWV, there was no significant correlation between LV mass and AI. In summary, these data suggest that aortic vascular stiffness is an indicator of LV mass even when blood pressure is controlled to less than 140/90 mmHg in hypertensive patients. The data further suggest that PWV is a better proxy or surrogate marker for LV mass than AI and the measurement of PWV may be useful as a rapid and less expensive assessment of the presence of LVH in this patient population.

  18. 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.

  19. 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

    -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...

  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...

  1. P-wave ray velocities and the inverse acoustic problem for anisotropic media

    Czech Academy of Sciences Publication Activity Database

    Zel, I. Yu.; Ivankina, T. I.; Levin, D.M.; Lokajíček, Tomáš

    2016-01-01

    Roč. 61, č. 4 (2016), s. 633-639 ISSN 1063-7745 Institutional support: RVO:67985831 Keywords : anisotropic media * P-Wawe velocities * elasticity Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.563, year: 2016

  2. 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...

  3. Longitudinal-Type Leaky Surface Acoustic Wave on LiNbO3 with High-Velocity Thin Film

    Science.gov (United States)

    Matsukura, Fumiya; Uematsu, Masato; Hosaka, Keiko; Kakio, Shoji

    2013-07-01

    The loss reduction of a longitudinal-type leaky surface acoustic wave (LLSAW) by loading with a dielectric thin film with a higher velocity than the substrate is proposed. An aluminum nitride (AlN) thin film was adopted as a high-velocity thin film, and the propagation properties of an LLSAW on an X36°Y-LiNbO3 (LN) substrate were investigated. First, the elastic constants c11 and c44 of an amorphous AlN (a-AlN) thin film deposited by RF magnetron sputtering were determined from the measured phase velocities of two SAW modes with mutually perpendicular particle motion, and they were 78 and 96% of those of a single-crystal AlN thin film. Next, from the theoretical calculation for the LLSAW on X36°Y-LN using the determined constants, it was found that the LLSAW attenuation can be reduced to zero by loading with an a-AlN thin film. Then, the propagation properties of the LLSAW on X36°Y-LN were measured by using an interdigital transducer pair. It was found that the losses due to bulk wave radiation can be reduced by loading with an a-AlN thin film.

  4. IWA : an analysis program for isentropic wave measurements.

    Energy Technology Data Exchange (ETDEWEB)

    Ao, Tommy

    2009-02-01

    IWA (Isentropic Wave Analysis) is a program for analyzing velocity profiles of isentropic compression experiments. IWA applies incremental impedance matching correction to measured velocity profiles to obtain in-situ particle velocity profiles for Lagrangian wave analysis. From the in-situ velocity profiles, material properties such as wave velocities, stress, strain, strain rate, and strength are calculated. The program can be run in any current version of MATLAB (2008a or later) or as a Windows XP executable.

  5. Results of fatigue tests and prediction of fatigue life under superposed stress wave and combined superposed stress wave

    International Nuclear Information System (INIS)

    Takasugi, Shunji; Horikawa, Takeshi; Tsunenari, Toshiyasu; Nakamura, Hiroshi

    1983-01-01

    In order to examine fatigue life prediction methods at high temperatures where creep damage need not be taken into account, fatigue tests were carried out on plane bending specimens of alloy steels (SCM 435, 2 1/4Cr-1Mo) under superposed and combined superposed stress waves at room temperature and 500 0 C. The experimental data were compared with the fatigue lives predicted by using the cycle counting methods (range pair, range pair mean and zero-cross range pair mean methods), the modified Goodman's equation and the modified Miner's rule. The main results were as follows. (1) The fatigue life prediction method which is being used for the data at room temperature is also applicable to predict the life at high temperatures. The range pair mean method is especially better than other cycle counting methods. The zero-cross range pair mean method gives the estimated lives on the safe side of the experimental lives. (2) The scatter bands of N-bar/N-barsub(es) (experimental life/estimated life) becomes narrower when the following equation is used instead of the modified Goodman's equation for predicting the effect of mean stress on fatigue life. σ sub(t) = σ sub(a) / (1 - Sigma-s sub(m) / kσ sub(B)) σ sub(t); stress amplitude at zero mean stress (kg/mm 2 ) σ sub(B); tensile strength (kg/mm 2 ) σ sub(m); mean stress (kg/mm 2 ) σ sub(a); stress amplitude (kg/mm 2 ) k; modified coefficient of σ sub(B) (author)

  6. S-Wave Velocity Structure beneath Southwest North America from Seismogram Comparisons of the Mexico Earthquake on 22 June 1997

    Directory of Open Access Journals (Sweden)

    Bagus Jaya Santosa

    2008-09-01

    Full Text Available This research investigates earth structure beneath the Southwest North America landmass, especially between Mexico and California. Models based on S wave velocities for this area were obtained by carrying out seismogram fitting in time domain and three Cartesian components simultaneously. The data used is from an event, coded as C052297B that occurred in the state of Guerrero, Mexico and it was fitted to synthetic data computed with the GEMINI program at TS network stations. Earth model IASPEI91 and SPREM were used as input to create the synthetic data. Real and synthetic seismograms were subjected to a low-pass filter with a frequency corner of 20 mHz.Waveform analysis results show very unsystematic and strong deviations in the waveform, arrival times, amount of oscillation and the height of the wave amplitude. Discrepancies are met on S, Love, Rayleigh and ScS waves, where the stations epicentral distances are below 300. Deviation in analysis waveform because of the usage of model 1-D of SPREM and IASPEI91, because the 1-D was a kind of average value an elastic property at one particular depth of global earth. With the method of waveform analysis we can see how sensitive waveform is to structures within the layers of the Earth.To explain the discrepancies, a correction to the earth structure is essential. The corrections account for the thickness of the crust, speed gradient of bh, the coefficient for the bh and bv in the upper mantle for surface wave fitting, a small variation of the S speed structure at a layer under the upper mantle above 771 km for S wave fitting, and a small variation at the base the mantle layers for ScS wave fitting. At some stations, a correction for S speed structure have yielded P wave fitting. Results of this research indicate that the 1-D earth model obtained through seismogram fitting at every hypocenter-observation station pair is unique. The S-wave velocity on the upper mantle has strong negative anomalies. This

  7. 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 (volcanic fields in Iberia and Morocco, indicative of high temperatures at relatively shallow depths, and suggesting that the lithosphere has been removed beneath these areas.

  8. Horizontal velocities and propagation directions of gravity waves in the ionosphere over the Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Chum, Jaroslav; Šindelářová, Tereza; Laštovička, Jan; Hruška, František; Burešová, Dalia; Baše, Jiří

    2010-01-01

    Roč. 115, - (2010), A11322/1-A11322/13 ISSN 0148-0227 R&D Projects: GA ČR GA205/07/1367; GA ČR GA205/09/1253 Grant - others:AV ČR(CZ) M100420901 Institutional research plan: CEZ:AV0Z30420517 Keywords : Ionosphere * gravity waves * wave propagation * remote sensing Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.303, year: 2010

  9. Impaired resting myocardial annular velocities are independently associated with mental stress-induced ischemia in coronary heart disease.

    Science.gov (United States)

    Ersbøll, Mads; Al Enezi, Fawaz; Samad, Zainab; Sedberry, Brenda; Boyle, Stephen H; O'Connor, Christopher; Jiang, Wei; Velazquez, Eric J

    2014-04-01

    The aim of this study was to investigate the association between resting myocardial function as assessed by tissue Doppler myocardial velocities and the propensity to develop mental stress-induced ischemia (MSIMI). Tissue Doppler myocardial velocities detect preclinical cardiac dysfunction and clinical outcomes in a range of conditions. However, little is known about the interrelationship between myocardial velocities and the propensity to develop MSIMI compared with exercise stress-induced myocardial ischemia. Resting annular myocardial tissue Doppler velocities were obtained in 225 patients with known coronary heart disease who were subjected to both conventional exercise stress testing as well as a battery of 3 mental stress tests. Diastolic early (e') and late (a') as well as systolic (s') velocities were obtained, and the eas index, an integrated measure of myocardial velocities, was calculated as e'/(a' × s'). MSIMI was defined as: 1) the development or worsening of regional wall motion abnormality; 2) a reduction in left ventricular ejection fraction ≥ 8%; and/or 3) ischemic ST-segment changes during 1 or more of the 3 mental stress tests. A total of 98 of 225 patients (43.7%) exhibited MSIMI. Patients developing MSIMI had significantly lower s' (7.0 ± 1.7 vs. 7.5 ± 1.2, p = 0.016) and a' (8.9 ± 1.8 vs. 10.0 ± 1.9, p stress-induced myocardial ischemia. MSIMI but not exercise stress-induced myocardial ischemia is independently associated with resting abnormalities in myocardial systolic and late diastolic velocities as well as the integrated measure of the eas index in patients with known coronary artery disease. (Responses of Myocardial Ischemia to Escitalopram Treatment [REMIT]; NCT00574847). Copyright © 2014 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  10. Vector Flow Imaging Compared with Pulse Wave Doppler for Estimation of Peak Velocity in the Portal Vein

    DEFF Research Database (Denmark)

    Brandt, Andreas Hjelm; Moshavegh, Ramin; Hansen, Kristoffer Lindskov

    2018-01-01

    The study described here investigated whether angle-independent vector flow imaging (VFI) technique estimates peak velocities in the portal vein comparably to pulsed wave Doppler (PWD). Furthermore, intra- and inter-observer agreement was assessed in a substudy. VFI and PWD peak velocities were...... estimated with from intercostal and subcostal views for 32 healthy volunteers, and precision analyses were conducted. Blinded to estimates, three physicians rescanned 10 volunteers for intra- and inter-observer agreement analyses. The precision of VFI and PWD was 18% and 28% from an intercostal view and 23......% and 77% from a subcostal view, respectively. Bias between VFI and PWD was 0.57 cm/s (p = 0.38) with an intercostal view and 9.89 cm/s (p ...

  11. One dimensional P wave velocity structure of the crust beneath west Java and accurate hypocentre locations from local earthquake inversion

    International Nuclear Information System (INIS)

    Supardiyono; Santosa, Bagus Jaya

    2012-01-01

    A one-dimensional (1-D) velocity model and station corrections for the West Java zone were computed by inverting P-wave arrival times recorded on a local seismic network of 14 stations. A total of 61 local events with a minimum of 6 P-phases, rms 0.56 s and a maximum gap of 299° were selected. Comparison with previous earthquake locations shows an improvement for the relocated earthquakes. Tests were carried out to verify the robustness of inversion results in order to corroborate the conclusions drawn out from our reasearch. The obtained minimum 1-D velocity model can be used to improve routine earthquake locations and represents a further step toward more detailed seismotectonic studies in this area of West Java.

  12. One dimensional P wave velocity structure of the crust beneath west Java and accurate hypocentre locations from local earthquake inversion

    Energy Technology Data Exchange (ETDEWEB)

    Supardiyono; Santosa, Bagus Jaya [Physics Department, Faculty of Mathematics and Natural Sciences, State University of Surabaya, Surabaya (Indonesia) and Physics Department, Faculty of Mathematics and Natural Sciences, Sepuluh Nopember Institute of Technology, Surabaya (Indonesia); Physics Department, Faculty of Mathematics and Natural Sciences, Sepuluh Nopember Institute of Technology, Surabaya (Indonesia)

    2012-06-20

    A one-dimensional (1-D) velocity model and station corrections for the West Java zone were computed by inverting P-wave arrival times recorded on a local seismic network of 14 stations. A total of 61 local events with a minimum of 6 P-phases, rms 0.56 s and a maximum gap of 299 Degree-Sign were selected. Comparison with previous earthquake locations shows an improvement for the relocated earthquakes. Tests were carried out to verify the robustness of inversion results in order to corroborate the conclusions drawn out from our reasearch. The obtained minimum 1-D velocity model can be used to improve routine earthquake locations and represents a further step toward more detailed seismotectonic studies in this area of West Java.

  13. Final Report (1994 to 1996) Diagnostic of the Spatial and Velocity Distribution of Alpha Particles in Tokamak Fusion Reactor using Beat-wave Generated Lower Hybrid Wave

    International Nuclear Information System (INIS)

    Hwang, D.Q.; Horton, R.D.; Evans, R.W.

    1999-01-01

    The alpha particles in a fusion reactor play a key role in the sustaining the fusion reaction. It is the heating provided by the alpha particles that help a fusion reactor operating in the ignition regime. It is, therefore, essential to understand the behavior of the alpha population both in real space and velocity space in order to design the optimal confinement device for fusion application. Moreover, the alphas represent a strong source of free energy that may generate plasma instabilities. Theoretical studies has identified the Toroidal Alfven Eigenmode (TAE) as an instability that can be excited by the alpha population in a toroidal device. Since the alpha has an energy of 3.5 MeV, a good confinement device will retain it in the interior of the plasma. Therefore, alpha measurement system need to probe the interior of a high density plasma. Due to the conducting nature of a plasma, wave with frequencies below the plasma frequency can not penetrate into the interior of the plasma where the alphas reside. This project uses a wave that can interact with the perpendicular motion of the alphas to probe its characteristics. However, this wave (the lower hybrid wave) is below the plasma frequency and can not be directly launched from the plasma edge. This project was designed to non-linearly excite the lower hybrid in the interior of a magnetized plasma and measure its interaction with a fast ion population

  14. 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

    condition: High relative VP, even higher relative VS and hence low VP/VS, consistent with thick dry depleted lithosphere, similar to what is found in most of the Baltic Shield. This shows that upper-mantle velocity anomalies are very poor predictors of topography in this region. An important deviation from...... 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...... between Lofoten and the crest of the Northern Scandes Mountains and stays off the coast further north. Seismic velocities in the depth interval 100-300 km change across the UMVB from low relative VP and even lower relative VS on the western side to high relative VP and even higher relative VS to the east...

  15. Velocity evolution of electro-magnetically driven shock wave for beam-dissociated hydrogen interaction experiment

    International Nuclear Information System (INIS)

    Kondo, Kotaro; Oguri, Yoshiyuki

    2016-01-01

    We present the velocity measurements in electro-magnetic shock tube for beam interaction experiment by three methods; laser refraction, photodiode for self-emission, and high speed framing camera. The laser refraction showed that the average shock velocity was 6.7 km/s when the initial pressure was 1000 Pa and the initial charging voltage was 16 kV. The self-emissions from piston discharge plasma were measured by photodiodes and by high speed framing camera. The measurements showed that the duration between shock and piston was up to 8 microseconds with a 400-mm propagation in the shock tube, which is enough time as dissociation target for beam interaction experiment.The complementary velocity measurement is significant for understanding the electro-magnetically driven shock physics. (paper)

  16. 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.

  17. Analysis of stress wave propagation in an elasto-viscoplastic plate

    International Nuclear Information System (INIS)

    Nakagawa, Noritoshi; Kawai, Ryoji; Urushi, Norio.

    1986-01-01

    Stress waves which propagate in the body are reflected at the boundary, and due to the interaction of the reflected stress waves, the focussing of stress waves will take place and a high stress level can be caused. The focussing of stress waves due to the reflection from the boundary may bring about fracture of the body, so that this is an important problem from a viewpoint of dynamic strength of structures. In this paper the process of stress wave focussing and the strain-rate dependence of constitutive equation in elastic and plastic regions are investigated. In the case where an in-plane step load uniformly acts on the straight edge of the plate with a semi-circular boundary, the propagation of stress waves in the plate was numerically analyzed by the finite element method, applying viscoelastic, elasto-plastic and elasto-viscoplastic constitutive equations. As the result, the process of focussing of stress waves due to reflection from the semi-circular boundary was observed and the difference in propagation behaviour of stress waves was discussed in materials represented by some kinds of constitutive equations. (author)

  18. On the intermediate time behavior of the stress tensor and velocity autocorrelation functions for dense hard sphere systems

    NARCIS (Netherlands)

    Beijeren, H. van

    1984-01-01

    It is conjectured that the large values at intermediate times of the stress tensor autocorrelation function, found in computer simulations, may be caused by a coupling of the stress tensor to pairs of slowly decaying extended heat modes of large wave number. Approximate expressions, amenable to

  19. Time-resolved wave-profile measurements at impact velocities of 10 km/s

    Energy Technology Data Exchange (ETDEWEB)

    Chhabildas, L.C.; Furnish, M.D.; Reinhart, W.D.

    1998-06-01

    Development of well-controlled hypervelocity launch capabilities is the first step to understand material behavior at extreme pressures and temperatures not available using conventional gun technology. In this paper, techniques used to extend both the launch capabilities of a two-stage light-gas gun to 10 km/s and their use to determine material properties at pressures and temperature states higher than those ever obtained in the laboratory are summarized. Time-resolved interferometric techniques have been used to determine shock loading and release characteristics of materials impacted by titanium and aluminum fliers launched by the only developed three-stage light-gas gun at 10 km/s. In particular, the Sandia three stage light gas gun, also referred to as the hypervelocity launcher, HVL, which is capable of launching 0.5 mm to 1.0 mm thick by 6 mm to 19 mm diameter plates to velocities approaching 16 km/s has been used to obtain the necessary impact velocities. The VISAR, interferometric particle-velocity techniques has been used to determine shock loading and release profiles in aluminum and titanium at impact velocities of 10 km/s.

  20. 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

  1. 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.

  2. Lithospheric structure of the westernmost Mediterranean inferred from finite frequency Rayleigh wave tomography S-velocity model.

    Science.gov (United States)

    Palomeras, Imma; Villasenor, Antonio; Thurner, Sally; Levander, Alan; Gallart, Josep; Harnafi, Mimoun

    2016-04-01

    The Iberian Peninsula and Morocco, separated by the Alboran Sea and the Algerian Basin, constitute the westernmost Mediterranean. From north to south this region consists of the Pyrenees, the result of interaction between the Iberian and Eurasian plates; the Iberian Massif, a region that 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) and the Atlas Mountains, resulting from post-Oligocene subduction roll-back and Eurasian-Nubian plate convergence. In this study we analyze data from recent broad-band array deployments and permanent stations on the Iberian Peninsula and in Morocco (Spanish IberArray and Siberia arrays, the US 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, comparable to USArray. We have calculated the Rayleigh waves phase velocities from ambient noise for short periods (4 s to 40 s) and teleseismic events for longer periods (20 s to 167 s). We inverted the phase velocities to obtain a shear velocity model for the lithosphere to ~200 km depth. The model shows differences in the crust for the different areas, where the highest shear velocities are mapped in the Iberian Massif crust. The crustal thickness is highly variable ranging from ~25 km beneath the eastern Betics to ~55km beneath the Gibraltar Strait, Internal Betics and Internal Rif. Beneath this region a unique arc shaped anomaly with high upper mantle velocities (>4.6 km/s) at shallow depths (volcanic fields in Iberia and Morocco, indicative of high temperatures at relatively shallow depths, and suggesting that the lithosphere has been removed beneath these areas

  3. Stress Wave E-Rating of Structural Timber—Size and Moisture Content Effects

    Science.gov (United States)

    Xiping Wang

    2013-01-01

    The objectives of this study were to investigate the influence of cross sectional size and moisture content on stress wave properties of structural timber in various sizes and evaluate the feasibility of using stress wave method to E-rate timber in green conditions. Four different sizes of Douglas-fir (Pseudotsuga menziesii) square timbers were...

  4. 3D time-domain spectral elements for stress waves modelling

    International Nuclear Information System (INIS)

    Kudela, P; Ostachowicz, W

    2009-01-01

    Elastic stress waves induced by piezoelectric transducers are extensively used for damage detection purposes. Induced high frequency impulse signals cause that stress wave modelling by the finite element method is inefficient. Instead, numerical model based on the time-domain spectral element method has been developed to simulate stress wave propagation in metallic structures induced by the piezoelectric transducers. The model solves the coupled electromechanical field equations simultaneously in three-dimensional case. Visualisation of the propagating elastic waves generated by the actuator of different shapes and properties has been performed.

  5. Shear wave velocity investigation of soil liquefaction sites from the Tangshan, China M7.8 earthquake of 1976 using active and passive surface wave methods

    Science.gov (United States)

    Kayen, Robert E; Tao, Xiaxin; Shi, Lijing; Shi, Hailiang

    2008-01-01

    An initial investigation of soil liquefaction sites from the July, 28 1976 Tangshan M7.8 earthquake was conducted between 1976 and 1978 by the National Ministry of Railways, China. These data are the basis of the ‘Chinese Method’ for assessment of liquefaction potential of silty-sand deposits, and are an important component of the worldwide data set for modern probabilistic methods for assessment of soil liquefaction using Bayesian updating and system reliability tools. We revisited 26 sites identified in the maps and published 198 report of the Ministry of Railways in order to investigate these locations with a suite of active- and passive-array surface wave methods. These sites are clustered along the north coast of the Bo Hai Sea in three areas: Lutai, Tianjin; Tangshan City and outlying village, Hebei; and Luannan county, Hebei. First, we gathered and evaluated the Rayleigh wave dispersion characteristics of the ground by comparing dispersion curves from the active source harmonic wave-spectral analysis of surface waves (SASW) method and the passive array Spatial Auto-Correlation method (SPAC). The dispersive properties of the liquefied ground as measured by these two methods were found to be almost identical. These tests were hybridized and the data sets merged in order to invert of shear wave velocities for analysis of liquefaction potential using a probabilistic framework. The data from high-values of seismic intensity near Tangshan city to low-intensities distant of the event in Luannan County segregate out into clusters of liquefied and non liquefied points clearly separated by liquefaction boundary curves developed from a large global data set of 310 sites

  6. Effect of Stress on Energy Flux Deviation of Ultrasonic Waves in Ultrasonic Waves in GR/EP Composites

    Science.gov (United States)

    Prosser, William H.; Kriz, R. D.; Fitting, Dale W.

    1990-01-01

    Ultrasonic waves suffer energy flux deviation in graphite/epoxy because of the large anisotropy. The angle of deviation is a function of the elastic coefficients. For nonlinear solids, these coefficients and thus the angle of deviation is a function of stress. Acoustoelastic theory was used to model the effect of stress on flux deviation for unidirectional T300/5208 using previously measured elastic coefficients. Computations were made for uniaxial stress along the x3 axis fiber axis) and the x1 axis for waves propagating in the x1x3 plane. These results predict a shift as large as three degrees for the quasi-transverse wave. The shift in energy flux offers new nondestructive technique of evaluating stress in composites.

  7. Reciprocal Influence of Slow Waves Extracted in Intracranial Pressure, Arterial Pressure and Cerebral Blood Velocity Signals

    National Research Council Canada - National Science Library

    Cervenansky, F

    2001-01-01

    ...), and arterial blood pressure (ABP). To clarify the links, we compared two frequency methods based on coherence function to estimate the influence of ICP, ABP, and CBV on couples, respectively CBV-ABP, ICP-CBV and ICP-ABP, of slow waves...

  8. 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.

  9. 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

    Fractures are present in most geological formations and they tend to dominate not only their mechanical but also, and in particular, their hydraulic properties. For these reasons, the detection and characterization of fractures are of great interest in several fields of Earth sciences. Seismic attenuation has been recognized as a key attribute for this purpose, as both laboratory and field experiments indicate that the presence of fractures typically produces significant energy dissipation and that this attribute tends to increase with increasing fracture density. This energy loss is generally considered to be primarily due to wave-induced pressure diffusion between the fractures and the embedding porous matrix. That is, due to the strong compressibility contrast between these two domains, the propagation of seismic waves can generate a strong fluid pressure gradient and associated pressure diffusion, which leads to fluid flow and in turn results in frictional energy dissipation. Numerical simulations based on Biot's poroelastic wave equations are computationally very expensive. Alternative approaches consist in performing numerical relaxation or creep tests on representative elementary volumes (REV) of the considered medium. These tests are typically based on Biot's consolidation equations. Assuming that the heterogeneous poroelastic medium can be replaced by an effective, homogeneous viscoelastic solid, these numerical creep and relaxation tests allow for computing the equivalent seismic P-wave attenuation and phase velocity. From a practical point of view, an REV is typically characterized by the smallest volume for which rock physical properties are statistically stationary and representative of the probed medium in its entirety. A more general definition in the context of wavefield attributes is to consider an REV as the smallest volume over which the P-wave attenuation and phase velocity dispersion are independent of the applied boundary conditions. That is

  10. 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.

  11. 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.

  12. 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.

  13. Minimum 1D P wave velocity model for the Cordillera Volcanica de Guanacaste, Costa Rica

    International Nuclear Information System (INIS)

    Araya, Maria C.; Linkimer, Lepolt; Taylor, Waldo

    2016-01-01

    A minimum velocity model is derived from 475 local earthquakes registered by the Observatorio Vulcanologico y Sismologico Arenal Miravalles (OSIVAM) for the Cordillera Volcanica de Guanacaste, between January 2006 and July 2014. The model has consisted of six layers from the surface up to 80 km the depth. The model has presented speeds varying between 3,96 and 7,79 km/s. The corrections obtained from the seismic stations have varied between -0,28 to 0,45, and they have shown a trend of positive values on the volcanic arc and negative on the forearc, in concordance with the crustal thickness. The relocation of earthquakes have presented three main groups of epicenters that could be associated with activity in inferred failures. The minimum ID velocity model has provided a simplified idea of the crustal structure and aims to contribute with the improvement of the routine location of earthquakes performed by OSIVAM. (author) [es

  14. Sn-wave velocity structure of the uppermost mantle beneath the Australian continent

    Science.gov (United States)

    Wei, Zhi; Kennett, Brian L. N.; Sun, Weijia

    2018-03-01

    We have extracted a dataset of more than 5000 Sn traveltimes for source-station pairs within continental Australia, with 3-D source relocation using Pn arrivals to improve data consistency. We conduct tomographic inversion for S-wavespeed structure down to 100 km using the FMTOMO method for the whole Australian continent. We obtain a 3-D model with potential resolution of 3.0° 3.0°. The new S wavespeed model provides strong constraints on structure in a zone that was previously poorly characterised. The S velocities in the uppermost mantle are rather fast, with patterns of variation generally corresponding to those for Pn. We find strong heterogeneities of S wavespeed in the uppermost mantle across the entire continent of Australia with a close relation to crustal geological features. For instance, the cratons in the western Australia usually have high S velocities (> 4.70 km/s), while the volcanic regions on the eastern margin of Australia are characterised by low S velocities (continent. We find most of the uppermost mantle has Vp/Vs between 1.65 and 1.85, but with patches in central Australia and in the east with much higher Vp/Vs ratios. Distinctive local anomalies on the eastern margin may indicate the positions of remnants of mantle plumes.

  15. 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.

  16. 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.

  17. Lift-off compensation for improved accuracy in ultrasonic lamb wave velocity measurements using electromagnetic acoustic transducers (EMATs).

    Science.gov (United States)

    Morrison, J P; Dixon, S; Potter, M D G; Jian, X

    2006-12-22

    The crystalline texture of a sheet metal strongly affects its formability, so having knowledge of this texture is of great industrial relevance. The texture of rolled sheet metals, such as aluminium and steel, may be determined by ultrasonic measurement of the velocity of the zero order symmetric (S(0)) Lamb wave as a function of angle to the rolling direction. Electromagnetic acoustic transducers (EMATs) may perform this measurement without contacting the sample, therefore reducing perturbation to the plate wave system, as they are electromagnetically coupled to the sheet. The EMAT system measurements are non-destructive and may be made in real time, therefore offering advantages over the conventional techniques such as X-ray and neutron diffraction. It has been noticed that in the two EMAT pitch-catch system, the apparent arrival times of the ultrasonic waves change with variation in lift-off (distance between sample and transducer) due to impedance and aperture effects. For precise and accurate texture parameters to be obtained, accurate absolute ultrasonic velocity measurement is required and hence lift-off must be compensated for. This is of particular importance to online inspection systems where constant lift-off may be difficult to maintain. The impedance behaviour of various coil geometries has been investigated as a function of lift-off and frequency and compared to the received ultrasonic signal and the drive current pulse profile. Theoretical models have been used to explain the observed behaviour, and hence a scheme has been proposed for the compensation of lift-off effects in real time.

  18. Rayleigh wave group velocity model of the southeast flank of the Rio Grande Rift using Cross-Correlation

    Directory of Open Access Journals (Sweden)

    Luis M. Sandoval

    2018-03-01

    Full Text Available The southeast shoulder of the Rio Grande Rift is located in southeastern New Mexico and west Texas in US and northern Chihuahua in Mexico. Noted mineral resources in the region are enriched in rare earth elements increasing the interest of research. These resources are related to tertiary volcanism. The magmas of this volcanism have similar composition of that of the oceanic island basalts suggesting that they were created from asthenosphere derived magmas from the basement of the North American Craton. That basement, in the area of interest, constitutes the Mazatzal and Grenville Proterozoic provinces of the Proterozoic Laurentia plate. This study is intended to contribute to the general understanding of the basement features of the region. In order to understand the structure of the crust and upper mantle we create a Rayleigh surface wave group velocity model of the southeast flank (or shoulder of the Rio Grande Rift. Rayleigh wave group velocities were calculated using data from EarthScope’s TA and Flex arrays. The periods of the model range from 10 s to 160 s. The kernels of the model are taken from the joint inversions made for LA RISTRA, from where the depths corresponding to periods between 10 s to 160 s should be approximately between 10 km and 350 km of depth. The results show the anisotropy of the region and difficulties faced using the Rayleigh wave cross correlation. Some structures like the Delaware basin are complicated and sensitive to seismic radiation directions and patterns. In general, structures are better resolved when these radiation directions are perpendicular to the structure boundaries.

  19. Comparison of laboratory and field measurements of P and S wave velocities of a peridotite rock

    Czech Academy of Sciences Publication Activity Database

    Vilhelm, J.; Ivankina, T.; Lokajíček, Tomáš; Rudajev, V.

    2016-01-01

    Roč. 88, October (2016), s. 235-241 ISSN 1365-1609 R&D Projects: GA MŠk LH13102; GA ČR(CZ) GAP104/12/0915; GA ČR GA13-13967S Institutional support: RVO:67985831 Keywords : elastic waves * peridotite rocks * seismic anisotropy * neutron diffraction * pulse-transmission technique Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.268, year: 2016

  20. Velocity and attenuation of shear waves in the phantom of a muscle-soft tissue matrix with embedded stretched fibers

    Science.gov (United States)

    Rudenko, O. V.; Tsyuryupa, S. N.; Sarvazyan, A. P.

    2016-09-01

    We develop a theory of the elasticity moduli and dissipative properties of a composite material: a phantom simulating muscle tissue anisotropy. The model used in the experiments was made of a waterlike polymer with embedded elastic filaments imitating muscle fiber. In contrast to the earlier developed phenomenological theory of the anisotropic properties of muscle tissue, here we obtain the relationship of the moduli with characteristic sizes and moduli making up the composite. We introduce the effective elasticity moduli and viscosity tensor components, which depend on stretching of the fibers. We measure the propagation velocity of shear waves and the shear viscosity of the model for regulated tension. Waves were excited by pulsed radiation pressure generated by modulated focused ultrasound. We show that with increased stretching of fibers imitating muscle contraction, an increase in both elasticity and viscosity takes place, and this effect depends on the wave propagation direction. The results of theoretical and experimental studies support our hypothesis on the protective function of stretched skeletal muscle, which protects bones and joints from trauma.

  1. On the propagation velocity of a detonation-shock combined wave

    Science.gov (United States)

    Tsuge, S.; Fujiwara, T.

    1974-01-01

    A quasi-one-dimensional analysis and a generalized Chapman-Jouguet condition are developed for a gaseous free detonation in an inert environment. Two characteristic features derived from the results are that there exists a lower limit on the heat of combustion, the charge diameter, and the molecular weight of the ambient gas and that there are two propagation velocities for a parameter combination above a certain critical value. Therefore the detonation failure of a free gas column is a hydrodynamic rather than a chemical phenomenon.

  2. Continuous control of light group velocity from subluminal to superluminal propagation with a standing-wave coupling field in a Rb vapor cell

    International Nuclear Information System (INIS)

    Bae, In-Ho; Moon, Han Seb

    2011-01-01

    We present the continuous control of the light group velocity from subluminal to superluminal propagation with an on-resonant standing-wave coupling field in the 5S 1/2 -5P 1/2 transition of the Λ-type system of 87 Rb atoms. When a coupling field was changed from a traveling-wave to a standing-wave field by adjusting the power of a counterpropagating coupling field, the probe pulse propagation continuously transformed from subluminal propagation, due to electromagnetically induced transparency with the traveling-wave coupling field, to superluminal propagation, due to narrow enhanced absorption with the standing-wave coupling field. The group velocity of the probe pulse was measured to be approximately 0.004c to -0.002c as a function of the disparity between the powers of the copropagating and the counterpropagating coupling fields.

  3. Comparison of Approaches to the Prediction of Surface Wave Phase Velocity

    Science.gov (United States)

    Godfrey, K. E.; Dalton, C. A.; Hjorleifsdottir, V.; Ekstrom, G.

    2017-12-01

    Global seismic models provide crucial information about the state, composition, and dynamics of the Earth's interior, and in the shallow mantle these models are primarily constrained by observations of surface waves. Models developed by different groups have been constructed using different data sets and different techniques. While these models exhibit good agreement on the long-wavelength features, there is less consistency in the patterns and amplitude of smaller-scale heterogeneity. Here we investigate how approximations in the theoretical treatment of wave propagation and excitation influence the interpretation of measured phase delays and the tomographic images that result from inverting them. Synthetic seismograms were generated using SPECFEM3D_GLOBE for 42 earthquakes, 134 receiver locations, and two 3-D models of elastic Earth structure: S362ANI (Kustowski et al., 2008) and a rougher model constructed by adding realistic small-scale structure to S362ANI. Fundamental-mode Rayleigh and Love wave phase delays in the period range 35-250 seconds were measured using the approach of Ekström et al. (1997), for which PREM is the assumed reference Earth model. These measurements were compared to phase-delay predictions generated for the great-circle ray approximation, exact ray theory, and finite-frequency theory. We find that for both 3-D earth models exact ray theory provides the best fit to the measurements at short periods. At longer periods finite frequency theory provides the best fit. For the smooth earth model, the differences in fit for the various predictions are less significant at long periods than at shorter periods. The differences at long periods become more significant with increasing model roughness. In all cases, the agreement between predictions and measurements is best for paths located away from nodes in the source radiation pattern. The ability of the measured phase delays to recover the input Earth models is assessed through tests that explore

  4. 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.

  5. 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.

  6. P-wave velocity models of continental shelf of East Siberian Sea using the Laplace-domain full waveform inversion

    Science.gov (United States)

    Kang, S. G.; Hong, J. K.; Jin, Y. K.; Jang, U.; Niessen, F.; Baranov, B.

    2017-12-01

    2016 IBRV ARAON Arctic Cruise Leg-2, Expedition ARA07C was a multidisciplinary undertaking carried out in the East Siberian Sea (ESS) from August 25 to September 10, 2016. The program was conducted as a collaboration between the Korea Polar Research Institute (KOPRI), P.P. Shirshov Institute of Oceanology (IORAS), and Alfred Wegener Institute (AWI). During this expedition, the multi-channel seismic (MCS) data were acquired on the continental shelf and the upper slope of the ESS, totaling 3 lines with 660 line-kilometers. The continental shelf of ESS is one of the widest shelf seas in the world and it is believed to cover the largest area of sub-sea permafrost in the Arctic. According to the present knowledge of the glacial history of the western Arctic Ocean, it is likely that during the LGM with a sea level approximately 120 m below present, the entire shelf area of the ESS was exposed to very cold air temperatures so that thick permafrost should have formed. Indeed, in water depths shallower than 80 m, sub-bottom profiles in the ESS recorded from the shelf edge to a latitude of 74°30' N in 60 m water depth exhibited acoustic facies, suggesting that at least relicts of submarine permafrost are present. In order to identify the existence and/or non-existence of subsea permafrost in our study area, we analyze the MCS data using the Laplace domain full waveform inversion (FWI). In case of the Canadian continental shelf of the Beaufort Sea, subsea permafrost has high seismic velocity values (over 2.6 km/sec) and strong refraction events were found in the MCS shotgathers. However, in the EES our proposed P-wave velocity models derived from FWI have neither found high velocity structures (over 2.6 km/sec) nor indicate strong refraction events by subsea permafrost. Instead, in 300 m depth below sea floor higher P-wave velocity structures (1.8 2.2 km/s) than normal subsea sediment layers were found, which are interpreted as cemented strata by glaciation activities.

  7. 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.

  8. 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

  9. Reference values of brachial-ankle pulse wave velocity according to age and blood pressure in a central Asia population.

    Science.gov (United States)

    Yiming, Gulinuer; Zhou, Xianhui; Lv, Wenkui; Peng, Yi; Zhang, Wenhui; Cheng, Xinchun; Li, Yaodong; Xing, Qiang; Zhang, Jianghua; Zhou, Qina; Zhang, Ling; Lu, Yanmei; Wang, Hongli; Tang, Baopeng

    2017-01-01

    Brachial-ankle pulse wave velocity (baPWV), a direct measure of aortic stiffness, has increasingly become an important assessment for cardiovascular risk. The present study established the reference and normal values of baPWV in a Central Asia population in Xinjiang, China. We recruited participants from a central Asia population in Xinjiang, China. We performed multiple regression analysis to investigate the determinants of baPWV. The median and 10th-90th percentiles were calculated to establish the reference and normal values based on these categories. In total, 5,757 Han participants aged 15-88 years were included in the present study. Spearman correlation analysis showed that age (r = 0.587, p Central Asia population.

  10. 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.

  11. High-efficiency helical traveling-wave tube with dynamic velocity taper and advanced multistage depressed collector

    Science.gov (United States)

    Curren, Arthur N.; Palmer, Raymond W.; Force, Dale A.; Dombro, Louis; Long, James A.

    A NASA-sponsored research and development contract has been established with the Watkins-Johnson Company to fabricate high-efficiency 20-watt helical traveling wave tubes (TWTs) operating at 8.4 to 8.43 GHz. The TWTs employ dynamic velocity tapers (DVTs) and advanced multistage depressed collectors (MDCs) having electrodes with low secondary electron emission characteristics. The TWT designs include two different DVTs; one for maximum efficiency and the other for minimum distortion and phase shift. The MDC designs include electrodes of untreated and ion-textured graphite as well as copper which has been treated for secondary electron emission suppression. Objectives of the program include achieving at least 55 percent overall efficiency. Tests with the first TWTs (with undepressed collectors) indicate good agreement between predicted and measured RF efficiencies with as high as 30 percent improvement in RF efficiency over conventional helix designs.

  12. 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

    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...... 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...... the induction zone. The time-averaged mean wind speeds at different locations in the upstream induction zone are measured by scanning a horizontal plane at hub height and a vertical plane centered at the middle of the rotor extending roughly 1.5 rotor diameters (D) upstream of the rotor. Turbulence statistics...

  13. High-efficiency helical traveling-wave tube with dynamic velocity taper and advanced multistage depressed collector

    Science.gov (United States)

    Curren, Arthur N.; Palmer, Raymond W.; Force, Dale A.; Dombro, Louis; Long, James A.

    1987-01-01

    A NASA-sponsored research and development contract has been established with the Watkins-Johnson Company to fabricate high-efficiency 20-watt helical traveling wave tubes (TWTs) operating at 8.4 to 8.43 GHz. The TWTs employ dynamic velocity tapers (DVTs) and advanced multistage depressed collectors (MDCs) having electrodes with low secondary electron emission characteristics. The TWT designs include two different DVTs; one for maximum efficiency and the other for minimum distortion and phase shift. The MDC designs include electrodes of untreated and ion-textured graphite as well as copper which has been treated for secondary electron emission suppression. Objectives of the program include achieving at least 55 percent overall efficiency. Tests with the first TWTs (with undepressed collectors) indicate good agreement between predicted and measured RF efficiencies with as high as 30 percent improvement in RF efficiency over conventional helix designs.

  14. Acoustic velocity in rift basin mudstones: effects of in situ stress and sample lithology, and its relation to formation strength

    Science.gov (United States)

    Zakharova, N. V.; Goldberg, D.

    2017-12-01

    Acoustic/sonic velocity (Vp) provides one of the best proxies for formation strength, which is essential for geomechanical modeling and formation evaluation. Vp-strength relations need to be built empirically for specific basins and/or rock types. Since velocity is stress- and frequency-dependent, such relations can be very sensitive to experimental conditions; therefore, it is important to quantify their effect on velocity values. In this study, we present confined velocity and strength measurements for over 70 samples from the Newark Rift basin, a candidate site for carbon sequestration, and one of the largest in a series of the Mesozoic rift basins on the eastern North-American coast. Acoustic velocity measurements were obtained for a range of confining pressures from 0 to 6,000 psi, roughly corresponding to in situ confining pressure range. Although, overall, Vp values tend to increase with increasing pressure, the degree of Vp response to stress varies dramatically from sample to sample, and does not appear to correlate directly to lithology or porosity. Select samples exhibit near-zero change in Vp with increasing confining pressure, while others are characterized by up to 15% Vp change with 3,000 psi increase in confining pressure. Compared to sonic logs, the low-stress Vp values usually underestimate sonic velocities, while high-stress values tend to overestimate them. Therefore, a systematic frequency-dependent core-log difference is not observed in these rift basin formations, but accounting for Vp dependence on confining pressure is important. We quantify the Vp-pressure dependence using laboratory acoustic measurements, and develop depth-dependent Vp-strength relation, which could be used with sonic logs for geomechanical analysis in similar Mesozoic rift basin formations.

  15. 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.

  16. Increased Air Velocity Reduces Thermal and Cardiovascular Strain in Young and Older Males during Humid Exertional Heat Stress.

    Science.gov (United States)

    Wright Beatty, Heather E; Hardcastle, Stephen G; Boulay, Pierre; Flouris, Andreas D; Kenny, Glen P

    2015-01-01

    Older adults have been reported to have a lower evaporative heat loss capacity than younger adults during exercise when full sweat evaporation is permitted. However, it is unclear how conditions of restricted evaporative and convective heat loss (i.e., high humidity, clothing insulation) alter heat stress. to the purpose of this study was to examine the heat stress responses of young and older males during and following exercise in a warm/humid environment under two different levels of air velocity. Ten young (YOUNG: 24±2 yr) and 10 older (OLDER: 59±3 yr) males, matched for body surface area performed 4×15-min cycling bouts (15-min rest) at a fixed rate of heat production (400 W) in warm/humid conditions (35°C, 60% relative humidity) under 0.5 (Low) and 3.0 (High) m·s(-1) air velocity while wearing work coveralls. Rectal (Tre) and mean skin (MTsk) temperatures, heart rate (HR), local sweat rate, % max skin blood flow (SkBF) (recovery only), and blood pressure (recovery only) were measured. High air velocity reduced core and skin temperatures (p 0.05) but was more effective in reducing cardiovascular strain (absolute and % max HR; p velocity reduced the number of males surpassing the 38.0°C Tre threshold from 90% (Low) to 50% (High). Despite age-related local heat loss differences, YOUNG and OLDER males had similar levels of heat stress during intermittent exercise in warm and humid conditions while wearing work coveralls. Increased air velocity was effective in reducing heat stress equally, and cardiovascular strain to a greater extent, in YOUNG and OLDER males, and may be useful for mitigating heat stress in all workers.

  17. Imaging P- and S-wave velocity structures in hydrate bearing sediments along an OBS profile across the Yuan-An Ridge, off southwest Taiwan

    Directory of Open Access Journals (Sweden)

    Win-Bin Cheng

    2018-01-01

    Full Text Available In order to improve our understanding of the marine slope instability of hydrate-bearing sediments in the offshore southwestern Taiwan, P- and S-waves seismic data generated by P-S conversion on reflection from airgun shots recorded from a multi-component Ocean Bottom Seismometer (OBS survey were used to construct two-dimensional velocity model. The investigated profile lies above a structural high of the Yuan-An ridge, proposed as a high priority drilling site for gas hydrate investigations off southwest Taiwan. The locations of the OBSs were determined with high accuracy by an inversion based on the shot traveltimes. Traveltime inversion and forward modeling of seismic data result in general trends P- and S-wave velocities of sediments. Generally, P- and S-wave velocities are high beneath topographic ridges which might represent a series of thrust-cored anticlines develop in the accretionary wedge. P-wave velocities of the sea floor are about ~1.58 km s-1, increasing to the bottom simulating reflectors (BSR, reaching values of about ~2 km s-1. Below it, a low velocity layer (1.62 - 1.74 km s-1 is observed, which indicates the presence free gas in the sedimentary layer. S-wave velocities of the sediments over the entire section range from 0.3 to ~0.6 km s-1. Significant lateral velocity variations were found beneath the eastern flank of the Yuan-An ridge, probably represents thrust faults that extend from seafloor to hydrate-bearing layer. We suggest that the BSR has been disturbed by the thrust faults and further rupture of the fault could potentially trigger failures in the study area.

  18. Calculation of Phase Velocities of Traveling Waves in a Cylindrical Shell Based on the Solution Analysis of Boundary Problem of Forced Oscillations

    Directory of Open Access Journals (Sweden)

    V. O. Kaledin

    2014-01-01

    Full Text Available In this paper we consider a moving orthotropic cylindrical shell of rotation. The purpose is to assess the choice of kinematic hypothesis for calculating the phase velocities of cylindrical shells. The comparison was done for the two hypotheses, namely: those of Timoshenko and Kirchhoff-Love. The calculation was performed under the following assumptions: all Poisson's ratios of orthotropic material were taken to be zero; the principal axes of anisotropy coincide with the lines of curvature, the coefficients of mutual influence of forces per unit length and bending moments were taken to be zero, which is valid for sufficiently thin shells. Analysis of the phase velocity of the cylindrical shell has shown that at low frequencies of traveling wave Timoshenko’s hypothesis gives an infinite value of the phase velocity. However, with increasing frequency of the traveling wave phase velocities obtained with different kinematic hypotheses, in the limit approach each other. Additionally, this article presents a numerical calculation of the phase velocity of the traveling waves. Calculation technique developed by V.O. Kaledin is based on the assumption that the traveling (direct and reflected waves, forming a standing wave, are in superposition at sustained forced vibrations of a shell. Next, the analytical results, obtained for a cylindrical shell with the harmonic disturbing force acting at the front edge, have been compared with the numerical results obtained under the same assumptions. The difference between the numerical and analytical results is less than 1,5%.We note that many of the well-known works mention low accuracy when using the Kirchhoff-Love hypothesis to calculate phase velocities of the second and higher forms in thin cylindrical shells of rotation. This work is soundly refutes this claim and can form the basis of further studies of wave processes in shells of rotation of arbitrary Gaussian curvature using the Kirchhoff

  19. Scattering images from autocorrelation functions of P-wave seismic velocity images: the case of Tenerife Island (Canary Islands, Spain)

    Science.gov (United States)

    García-Yeguas, A.; Sánchez-Alzola, A.; De Siena, L.; Prudencio, J.; Díaz-Moreno, A.; Ibáñez, J. M.

    2018-03-01

    We present a P-wave scattering image of the volcanic structures under Tenerife Island using the autocorrelation functions of P-wave vertical velocity fluctuations. We have applied a cluster analysis to total quality factor attenuation ( {Q}_t^{-1} ) and scattering quality factor attenuation ( {Q}_{PSc}^{-1} ) images to interpret the structures in terms of intrinsic and scattering attenuation variations on a 2D plane, corresponding to a depth of 2000 m, and check the robustness of the scattering imaging. The results show that scattering patterns are similar to total attenuation patterns in the south of the island. There are two main areas where patterns differ: at Cañadas-Teide-Pico Viejo Complex, high total attenuation and average-to-low scattering values are observed. We interpret the difference as induced by intrinsic attenuation. In the Santiago Ridge Zone (SRZ) region, high scattering values correspond to average total attenuation. In our interpretation, the anomaly is induced by an extended scatterer, geometrically related to the surficial traces of Garachico and El Chinyero historical eruptions and the area of highest seismic activity during the 2004-2008 seismic crises.

  20. 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 ...... of the present study is to establish reference and normal values for PWV based on a large European population.......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...

  1. 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.

  2. Non-iterative determination of the stress-density relation from ramp wave data through a window

    Science.gov (United States)

    Dowling, Evan; Fratanduono, Dayne; Swift, Damian

    2017-06-01

    In the canonical ramp compression experiment, a smoothly-increasing load is applied the surface of the sample, and the particle velocity history is measured at interfaces two or more different distances into the sample. The velocity histories are used to deduce a stress-density relation by correcting for perturbations caused by reflected release waves, usually via the iterative Lagrangian analysis technique of Rothman and Maw. We previously described a non-iterative (recursive) method of analysis, which was more stable and orders of magnitude faster than iteration, but was subject to the limitation that the free surface velocity had to be sampled at uniform intervals. We have now developed more general recursive algorithms suitable for analyzing ramp data through a finite-impedance window. Free surfaces can be treated seamlessly, and the need for uniform velocity sampling has been removed. These calculations require interpolation of partially-released states using the partially-constructed isentrope, making them slower than the previous free-surface scheme, but they are still much faster than iterative analysis. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  3. Stress analysis applications to service failures of the traveling wave tubes

    Science.gov (United States)

    Yeh, H.-Y.

    By utilizing the mathematical analogy between the electrostatic fields and the elastic stress fields, the electrostatic stresses in high voltage electronic devices such as Traveling Wave Tubes (TWT) can be obtained from finite element technique. A new point of view about the vacuum electrical breakdown from the theory of elastic stress concentration has been proposed. The elastic stress concentration factors may be used as a good reference figure for TWT design works.

  4. Effect of membrane and through-wall bending stresses on fatigue crack growth behavior and coolant leakage velocity

    International Nuclear Information System (INIS)

    Yoo, Yeon-Sik

    2003-11-01

    This study clarified the effect of a membrane and a through-wall bending stresses on fatigue crack growth behavior and coolant leakage velocity due to irregularity of crack surface. Each stress component relates to fatigue crack growth behavior directly in general and thus the wild-used K I solutions are anticipated to give good evaluation results on it. Meanwhile, it is necessary to notify that surface irregularity for coolant leakage assessment is made by stress history in nature. Surface irregularity is known to be largely classified into the following two aspects: surface roughness due to continuous crack opening and closure behavior and surface turnover due to cyclic bending stress dominance. Therefore, the deterministic parameters on resistance of coolant leakage by surface irregularity are considered to be not only stress history but crack opening behavior. (author)

  5. Polyurea/Fused-silica interfacial decohesion induced by impinging tensile stress-waves

    Directory of Open Access Journals (Sweden)

    Mica Grujicic

    2016-04-01

    Full Text Available All-atom non-equilibrium molecular-dynamics simulations are used to investigate the problems of polyurea-borne tensile-stress waves interacting with a polyurea/fused-silica interface and fused-silica tensile-stress waves interacting with a fused-silica/polyurea interface, and the potential for the accompanying interfacial decohesion. To predict the outcome of the interactions of stress-waves with the material-interfaces in question, at the continuum level, previously determined material constitutive relations for polyurea and fused-silica are used within an acoustic-impedance-matching procedure. These continuum-level predictions pertain solely to the stress-wave/interface interaction aspects resulting in the formation of transmitted and reflected stress- or release-waves, but do not contain any information regarding potential interfacial decohesion. Present direct molecular-level simulations confirmed some of these continuum-level predictions, but also provided direct evidence of the nature and the extent of interfacial decohesion. In the molecular-level simulations, reactive force-field potentials are utilized to properly model the initial state of interfacial cohesion and its degradation during stress-wave-loading. Examination of the molecular-level interfacial structure before the stress-wave has interacted with the given interface, revealed local changes in the bonding structure, suggesting the formation of an “interphase.” This interphase was subsequently found to greatly affect the polyurea/fused-silica decohesion strength and the likelihood for interfacial decohesion during the interaction of the stress-wave with the interface.

  6. Estimation of Peak Wave Stresses in Slender Complex Concrete Armor Units

    DEFF Research Database (Denmark)

    Howell, G.L.; Burcharth, H. F.; Rhee, Joon R

    1991-01-01

    Recent methods for the structural design of concrete armor units divide the forces into static loads, impact loads, and wave or pulsating loads. Physical model technology is being developed at several laboratories to measure wave loads on model armor units. While this technology represents...... significant progress, structural designers require a maximum stress value to design armor units....

  7. 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.

  8. Stresses of PTT, Giesekus, and Oldroyd-B fluids in a Newtonian velocity field near the stick-slip singularity

    Science.gov (United States)

    Evans, J. D.; Palhares Junior, I. L.; Oishi, C. M.

    2017-12-01

    We characterise the stress singularity of the Oldroyd-B, Phan-Thien-Tanner (PTT), and Giesekus viscoelastic models in steady planar stick-slip flows. For both PTT and Giesekus models in the presence of a solvent viscosity, the asymptotics show that the velocity field is Newtonian dominated near to the singularity at the join of the stick and slip surfaces. Polymer stress boundary layers are present at both the stick and slip surfaces. By integrating along streamlines, we verify the polymer stress behavior of r-4/11 for PTT and r-5/16 for Giesekus, where r is the radial distance from the singularity. These asymptotic results for PTT and Giesekus do not hold in the limit of vanishing quadratic stress terms for Oldroyd-B. However, we can consider the Oldroyd-B model in the fixed kinematics of a prescribed Newtonian velocity field. In contrast to PTT and Giesekus, this is not the correct balance for the momentum equation but does allow insight into the behavior of the Oldroyd-B equations near the singularity. A three-region asymptotic structure is again apparent with now a polymer stress singularity of r-4/5. The high Weissenberg boundary layer equations are found to manifest themselves at the stick surface and are of thickness r3/2. At the slip surface, dominant balance between the upper convected stress and rate-of-strain terms gives a slip boundary layer of thickness r2. The solution of the slip boundary layer shows that the polymer stress is now singular along the slip surface. These results are supported through numerical integration along streamlines of the Oldroyd-B equations in a Newtonian velocity field. The Oldroyd-B model thus extends the point singularity at the join of the stick and slip surfaces to the whole of slip surface. As such, it does not have a physically meaningful solution in a Newtonian velocity field. We would expect a similar stress behavior for this model in the true viscoelastic velocity field.

  9. Accelerometer-based estimation and modal velocity feedback vibration control of a stress-ribbon bridge with pneumatic muscles

    International Nuclear Information System (INIS)

    Liu, Xiaohan; Goldack, Arndt; Schlaich, Mike; Schauer, Thomas; Bleicher, Achim

    2016-01-01

    Lightweight footbridges are very elegant but also prone to vibration. By employing active vibration control, smart footbridges could accomplish not only the architectural concept but also the required serviceability and comfort. Inertial sensors such as accelerometers allow the estimation of nodal velocities and displacements. A Kalman filter together with a band-limited multiple Fourier linear combiner (BMFLC) is applied to enable a drift-free estimation of these signals for the quasi-periodic motion under pedestrian excitation without extra information from other kinds of auxiliary sensors. The modal velocities of the structure are determined by using a second Kalman filter with the known applied actuator forces as inputs and the estimated nodal displacement and velocities as measurements. The obtained multi-modal velocities are then used for feedback control. An ultra-lightweight stress-ribbon footbridge built in the Peter-Behrens- Halle at the Technische Universitat Berlin served as the research object. Using two inertial sensors in optimal points we can estimate the dominant modal characteristics of this bridge. Real-time implementation and evaluation results of the proposed estimator will be presented in comparison to signals derived from classical displacement encoders. The real-time estimated modal velocities were applied in a multi-modal velocity feedback vibration control scheme with lightweight pneumatic muscle actuators. Experimental results demonstrate the feasibility of using inertial sensors for active vibration control of lightweight footbridges. (paper)

  10. Accelerometer-based estimation and modal velocity feedback vibration control of a stress-ribbon bridge with pneumatic muscles

    Science.gov (United States)

    Liu, Xiaohan; Schauer, Thomas; Goldack, Arndt; Bleicher, Achim; Schlaich, Mike

    2016-09-01

    Lightweight footbridges are very elegant but also prone to vibration. By employing active vibration control, smart footbridges could accomplish not only the architectural concept but also the required serviceability and comfort. Inertial sensors such as accelerometers allow the estimation of nodal velocities and displacements. A Kalman filter together with a band-limited multiple Fourier linear combiner (BMFLC) is applied to enable a drift-free estimation of these signals for the quasi-periodic motion under pedestrian excitation without extra information from other kinds of auxiliary sensors. The modal velocities of the structure are determined by using a second Kalman filter with the known applied actuator forces as inputs and the estimated nodal displacement and velocities as measurements. The obtained multi-modal velocities are then used for feedback control. An ultra-lightweight stress-ribbon footbridge built in the Peter-Behrens- Halle at the Technische Universitat Berlin served as the research object. Using two inertial sensors in optimal points we can estimate the dominant modal characteristics of this bridge. Real-time implementation and evaluation results of the proposed estimator will be presented in comparison to signals derived from classical displacement encoders. The real-time estimated modal velocities were applied in a multi-modal velocity feedback vibration control scheme with lightweight pneumatic muscle actuators. Experimental results demonstrate the feasibility of using inertial sensors for active vibration control of lightweight footbridges.

  11. Two-component laser Doppler anemometer for measurement of velocity and turbulent shear stress near prosthetic heart valves.

    Science.gov (United States)

    Woo, Y R; Yoganathan, A P

    1985-01-01

    The velocity and turbulent shear stress measured in the immediate vicinity of prosthetic heart valves play a vital role in the design and evaluation of these devices. In the past hot wire/film and one-component laser Doppler anemometer (LDA) systems were used extensively to obtain these measurements. Hot wire/film anemometers, however, have some serious disadvantages, including the inability to measure the direction of the flow, the disturbance of the flow field caused by the probe, and the need for frequent calibration. One-component LDA systems do not have these problems, but they cannot measure turbulent shear stresses directly. Since these measurements are essential and are not available in the open literature, a two-component LDA system for measuring velocity and turbulent shear stress fields under pulsatile flow conditions was assembled under an FDA contract. The experimental methods used to create an in vitro data base of velocity and turbulent shear stress fields in the immediate vicinity of prosthetic heart valves of various designs in current clinical use are also discussed.

  12. Local stimulation of cultured myocyte cells by femtosecond laser-induced stress wave

    Science.gov (United States)

    Kuo, Yung-En; Wu, Cheng-Chi; Hosokawa, Yoichiroh; Maezawa, Yasuyo; Okano, Kazunori; Masuhara, Hiroshi; Kao, Fu-Jen

    2010-12-01

    When an 800 nm femtosecond laser is tightly focused into cell culture medium a stress wave is generated at the laser focal point. Since the stress wave localizes in a few tens of μm, it is possible to locally stimulate single cells in vitro. In this work, several kinds of cultured mammalian cells, HeLa, PC12, P19CL6, and C2C12, were stimulated by the stress wave and the cell growth after the stress loading with the laser irradiation was investigated. In comparison with the control conditions, cell growth after the laser irradiation was enhanced for the cells of C2C12 and P19CL6, which can differentiate into myocytes, and suppressed for PC12 and HeLa cell lines. These results suggest a possibility of cell growth enhancement due to myogenic cells response to the femtosecond laser-induced stress.

  13. Measurement and modelling of bed shear induced by solitary waves

    Digital Repository Service at National Institute of Oceanography (India)

    JayaKumar, S.

    horizontal continental shelf. Measurements of bed shear stress, surface elevation and flow velocities were carried out. Periodic waves were also generated and the bed shear stresses measured over a horizontal bed were found to be comparable with the earlier...

  14. The association of 25(OH)D with blood pressure, pulse pressure and carotid-radial pulse wave velocity in African women.

    NARCIS (Netherlands)

    Kruger, I.M.; Kruger, M.C.; Doak, C.M.; Schutte, A.E.; Huisman, H.W.; van Rooyen, J.M.; Schutte, R.; Malan, L.; Malan, N.T.; Fourie, C.M.; Kruger, A.

    2013-01-01

    High susceptibility of the African population to develop cardiovascular disease obliges us to investigate possible contributing risk factors. Our aim was to determine whether low 25(OH)D status is associated with increased blood pressure and carotid-radial pulse wave velocity in black South African

  15. Monte Carlo search techniques applied to the measurement of higher mode phase velocities and anisotropic surface wave tomography. Geologica Ultraiectina (285)

    NARCIS (Netherlands)

    Visser, K.

    2008-01-01

    In this thesis we present all three stages of the inversion approach proposed by Kennett and Yoshizawa (2002). The three stage inversion approach consists of obtaining fundamental and higher mode Love and Rayleigh wave phase velocity measurements through waveform fitting in the first stage,

  16. Bayesian inversion of surface wave data for discontinuities and velocity structure in the upper mantle using Neural Networks. Geologica Ultraiectina (287)

    NARCIS (Netherlands)

    Meier, U.

    2008-01-01

    We present a neural network approach to invert surface wave data for discontinuities and velocity structure in the upper mantle. We show how such a neural network can be trained on a set of random samples to give a continuous approximation to the inverse relation in a compact and computationally

  17. Comparison of the measurement of changes of the ultrasonic wave velocity in the process of deformation for different types of equipment

    Czech Academy of Sciences Publication Activity Database

    Konečný, Pavel; Kanciruk, A.; Kožušníková, Alena; Nowakowski, A.

    2008-01-01

    Roč. 8, č. 2 (2008), s. 79-84 ISSN 1213-1962 R&D Projects: GA ČR GA105/06/0068 Institutional research plan: CEZ:AV0Z30860518 Keywords : ultrasonic wave velocity * physical rock properties Subject RIV: DH - Mining, incl. Coal Mining

  18. Compliance of the normal-sized aorta in adolescents with Marfan syndrome: comparison of MR measurements of aortic distensibility and pulse wave velocity

    International Nuclear Information System (INIS)

    Eichhorn, J.G.; Ruediger, H.J.; Gorenflo, M.; Khalil, M.; Ulmer, H.; Krissak, R.; Kauczor, H.U.; Ley, S.; Universitaetsklinik Heidelberg; Arnold, R.; Universitaetskinderklinik Freiburg; Boese, J.; Siemens AG, Medical Solutions, Forchheim; Krug, R.; Fink, C.

    2007-01-01

    Purpose: To compare the aortic compliance of the normal-sized aorta of adolescents with Marfan syndrome and healthy controls using MR measurements of the aortic distensibility and pulse wave velocity. Materials and Methods: Fourteen patients (median age: 15 [9-21] years) and 11 healthy subjects (23 [12-32] years) were examined at 1.5 T. The MR protocol included 2D steady-state free precession (SSFP)-CINE MRI of the aortic distensibility and PC-MRI of the pulse wave velocity. All measurements were positioned perpendicular to the descending aorta at the level of the diaphragm for assessing the changes in the aortic cross-sectional areas and additionally above and below this plane for assessing the pulse wave velocity. In addition contrast-enhanced 3D-MR angiography was performed in adolescents with Marfan syndrome to exclude morphologic changes and to prove normal-sized aorta. Results: Compared with control subjects, adolescents with Marfan syndrome had significantly decreased distensibility and significantly increased pulse wave velocity (χ 2 -test, p = 0.0002) using an age-related non-linear regression analysis. The related aortic compliance was significantly decreased (χ 2 -test, p = 0.0002). There was a good correlation between the two methods (r = 0.86). A low intraobserver variability was found for both methods (≤ 2 %). (orig.)

  19. 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...

  20. 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.

  1. Distributed Acoustic Sensing (DAS) Array near a Highway for Traffic Monitoring and Near-Surface Shear-Wave Velocity Profiles

    Science.gov (United States)

    Wang, H. F.; Fratta, D.; Lancelle, C.; Ak, E. Ms; Lord, N. E.

    2017-12-01

    Monitoring traffic is important for many technical reasons. It allows for better design of future roads and assessment of the state of current roads. The number, size, weight, and speed of vehicles control deterioration rate. Also, real-time information supplies data to intelligent information systems to help control traffic. Recently there have been studies looking at monitoring traffic seismically as vibrations from traffic are not sensitive to weather and poor visibility. Furthermore, traffic noise can be used to image S-wave velocity distribution in the near surface by capturing and interpreting Rayleigh and Love waves (Nakata, 2016; Zeng et al. 2016). The capability of DAS for high spatial sampling (1 m), temporal sampling (up to 10 kHz), and distributed nature (tens of kilometers) allows for a closer look at the traffic as it passes and how the speed of the vehicle may change over the length of the array. The potential and difficulties of using DAS for these objectives were studied using two DAS arrays. One at Garner Valley in Southern California (a 700-meter array adjacent to CA Highway 74) and another in Brady Hot Springs, Nevada (an 8700-meter array adjacent to Interstate 80). These studies experimentally evaluated the use of DAS data for monitoring traffic and assessing the use of traffic vibration as non-localized sources for seismic imaging. DAS arrays should also be resilient to issues with lighting conditions that are problematic for video monitoring and it may be sensitive to the weight of a vehicle. This study along a major interstate provides a basis for examining DAS' potential and limitations as a key component of intelligent highway systems.

  2. Lithosphere-asthenosphere interaction beneath the western United States from the joint inversion of body-wave traveltimes and surface-wave phase velocities

    Science.gov (United States)

    Obrebski, M.; Allen, R.M.; Pollitz, F.; Hung, S.-H.

    2011-01-01

    The relation between the complex geological history of the western margin of the North American plate and the processes in the mantle is still not fully documented and understood. Several pre-USArray local seismic studies showed how the characteristics of key geological features such as the Colorado Plateau and the Yellowstone Snake River Plains are linked to their deep mantle structure. Recent body-wave models based on the deployment of the high density, large aperture USArray have provided far more details on the mantle structure while surface-wave tomography (ballistic waves and noise correlations) informs us on the shallow structure. Here we combine constraints from these two data sets to image and study the link between the geology of the western United States, the shallow structure of the Earth and the convective processes in mantle. Our multiphase DNA10-S model provides new constraints on the extent of the Archean lithosphere imaged as a large, deeply rooted fast body that encompasses the stable Great Plains and a large portion of the Northern and Central Rocky Mountains. Widespread slow anomalies are found in the lower crust and upper mantle, suggesting that low-density rocks isostatically sustain part of the high topography of the western United States. The Yellowstone anomaly is imaged as a large slow body rising from the lower mantle, intruding the overlying lithosphere and controlling locally the seismicity and the topography. The large E-W extent of the USArray used in this study allows imaging the 'slab graveyard', a sequence of Farallon fragments aligned with the currently subducting Juan de Fuca Slab, north of the Mendocino Triple Junction. The lithospheric root of the Colorado Plateau has apparently been weakened and partly removed through dripping. The distribution of the slower regions around the Colorado Plateau and other rigid blocks follows closely the trend of Cenozoic volcanic fields and ancient lithospheric sutures, suggesting that the

  3. 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.

  4. Experimental Study of the Effect of Internal Defects on Stress Waves during Automated Fiber Placement

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    Zhenyu Han

    2018-04-01

    Full Text Available The detection technique of component defects is currently only realized to detect offline defects and online surface defects during automated fiber placement (AFP. The characteristics of stress waves can be effectively applied to identify and detect internal defects in material structure. However, the correlation mechanism between stress waves and internal defects remains unclear during the AFP process. This paper proposes a novel experimental method to test stress waves, where continuous loading induced by process itself is used as an excitation source without other external excitation. Twenty-seven groups of thermosetting prepreg laminates under different processing parameters are manufactured to obtain different void content. In order to quantitatively estimate the void content in the prepreg structure, the relation model between the void content and ultrasonic attenuation coefficient is revealed using an A-scan ultrasonic flaw detector and photographic methods by optical microscope. Furthermore, the high-frequency noises of stress waves are removed using Haar wavelet transform. The peaks, the Manhattan distance and mean stress during the laying process are analyzed and evaluated. Partial conclusions in this paper could provide theoretical support for online real-time detection of internal defects based on stress wave characteristics.

  5. Anisotropic stress as a signature of nonstandard propagation of gravitational waves.

    Science.gov (United States)

    Saltas, Ippocratis D; Sawicki, Ignacy; Amendola, Luca; Kunz, Martin

    2014-11-07

    We make precise the heretofore ambiguous statement that anisotropic stress is a sign of a modification of gravity. We show that in cosmological solutions of very general classes of models extending gravity-all scalar-tensor theories (Horndeski), Einstein-aether models, and bimetric massive gravity-a direct correspondence exists between perfect fluids apparently carrying anisotropic stress and a modification in the propagation of gravitational waves. Since the anisotropic stress can be measured in a model-independent manner, a comparison of the behavior of gravitational waves from cosmological sources with large-scale-structure formation could, in principle, lead to new constraints on the theory of gravity.

  6. Relationship between dietary patterns and brachial-ankle pulse wave velocity among middle-aged adults in Japan.

    Science.gov (United States)

    Moyama, Shota; Minami, Kazuhiro; Yano, Mihiro; Okumura, Masumi; Hayashi, Susumu; Takayama, Hiroshi; Yorimoto, Akira

    2017-05-01

    Arterial stiffness is a leading cause of cardiovascular disease (CVD), and it is considered to be affected by dietary intake. However, few studies have examined the relationship between major dietary patterns and brachial-ankle pulse wave velocity (baPWV) among Japanese middle-aged subjects. We studied whether major dietary patterns were associated with baPWV in this population. Between 2009 and 2012, 70 Japanese middle-aged subjects (39 men and 31 women) with no history of stroke, coronary heart disease, or cancer were studied. Dietary intake was documented using a validated food-frequency questionnaire, and dietary patterns were generated using factor analysis. Correlational analyses were performed between baPWV and identified dietary patterns and between baPWV and individual risk factors (total cholesterol, triglyceride, low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein cholesterol [HDL-C], non- HDL-C, LDL/HDL ratio, and augmentation index). Two dietary patterns were identified: a rice-rich pattern (high in rice, breads, oils and fats, meats, and confectionery) and a vegetable-rich pattern (high in vegetables, fruit, fish, and seaweed). The rice-rich pattern was not associated with baPWVor other risk factors. A significant inverse correlation was found between baPWV and the vegetable-rich dietary pattern (pvegetables, seafood, seaweed, fruit, and pulse is inversely associated with arterial stiffness measured by baPWV. This diet offers an additional nutritional approach to the prevention and treatment of arterial stiffness.

  7. Role of acoustic radiation force impulse and shear wave velocity in prediction of preterm birth: a prospective study.

    Science.gov (United States)

    Agarwal, Arjit; Agarwal, Shubhra; Chandak, Shruti

    2017-01-01

    Background Preterm birth is one of the important causes of neonatal morbidity where we rely on subjective criteria such as modified Bishop's scoring and contemporary sonographic measurement of cervical length. Acoustic radiation force impulse (ARFI) is a technological advancement in elastography that can be employed in prediction of cervical softening and preterm labor. Purpose To evaluate the role of ARFI technique and shear wave velocity (SWV) estimates as a predictor of preterm birth and its comparison with other clinical and sono-elastographic measures. Material and Methods Thirty-four pregnant women (gestation age = 28-37 weeks age) showing features suggestive of preterm labor were included and evaluated with modified Bishop's score, cervical length by ultrasound (US), ARFI to derive Elastography index (EI), and SWV of the cervix. The patients were later divided into two groups, using the clinical outcome of preterm or term delivery. Results Twenty patients delivered at term (gestational age > 37 weeks) and 14 were preterm. Receiver operating characteristics (ROC) curves showed SWV with highest sensitivity and specificity (93% and 90%, respectively) for the prediction of preterm birth at a cutoff value of 2.83 m/s. EI and modified Bishop's score were comparable to each other, but were less sensitive techniques. Conclusion Elastographic assessment of antenatal cervix is a novel technique of virtual palpation of internal os and can be utilized as an objective criterion for preterm birth prediction.

  8. Brachial-ankle pulse wave velocity for the prediction of the presence and severity of coronary artery disease.

    Science.gov (United States)

    Kim, Ji-Hyun; Rhee, Moo-Yong; Kim, Yong-Seok; Bae, Jun-Ho; Nah, Deuk-Young; Kim, Young-Kwon; Lee, Myoung-Mook; Lim, ChiYeon; Kim, Chan-Joo

    2014-01-01

    The predictability of brachial-ankle pulse wave velocity (baPWV) for the presence and severity of coronary artery disease (CAD) was investigated by measuring baPWV in 501 subjects scheduled for coronary angiography. Severity of CAD was measured using modified Gensini stenosis score (GSS) and classified as a vessel disease score (VDS) of 0-3. The presence of CAD was defined as diameter stenosis>50%. Subjects were grouped in tertile by level of baPWV (17 m/s). Subjects with CAD showed higher mean age, prevalence of men and diabetes, and systolic blood pressure. The prevalence of hypertension, use of antihypertensive medications and use of statin was not different. Subjects with CAD had higher baPWV than subjects without CAD (16.70 ± 3.46 versus 15.21 ± 3.19 m/s, ppredictive power of highest tertile of baPWV for the presence of CAD was 3.600 [95% confidence interval (CI) 1.884-6.881, p17 m/s may be a threshold value for the presence and severity of CAD.

  9. Data on the clinical usefulness of brachial-ankle pulse wave velocity in patients with suspected coronary artery disease

    Directory of Open Access Journals (Sweden)

    In-Chang Hwang

    2018-02-01

    Full Text Available Brachial-artery pulse wave velocity (baPWV is a simple and reliable tool for measurement of arterial stiffness. Our previous studies suggested that baPWV is associated with the presence and severity of coronary artery disease (CAD and the risk of cardiovascular events. In the present data article, we provided supplementary data supporting the independent prognostic value of arterial stiffness, assessed by baPWV, in patients with suspected CAD (Hwang et al., 2017 [1]. The data was obtained from 523 patients undergoing coronary CT angiography (CCTA, and baPWV was measured at the time of CCTA. Patients with vulnerable coronary plaque or obstructive CAD on CCTA had higher age, more cardiovascular risk factors, and higher baPWV values. Given the significant association between high baPWV and the presence of vulnerable plaque or obstructive CAD as shown in this data article, the prognostic value of baPWV was further assessed in subgroups divided according to the CCTA findings (vulnerable plaque or obstructive CAD. In each subgroup by CCTA findings, multivariable Cox proportional hazard model analysis showed that high baPWV was an independent risk factor for cardiovascular events even after adjusting for clinical risk factors.

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

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    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.

  11. 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.

  12. 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

  13. The relationship between microvascular endothelial function and carotid-radial pulse wave velocity in patients with mild hypertension.

    Science.gov (United States)

    McCall, Damian O; McGartland, Claire P; Woodside, Jayne V; Sharpe, Peter; McCance, David R; Young, Ian S

    2010-01-01

    Carotid-radial pulse wave velocity (CRPWV) can be measured rapidly using applanation tonometry and significantly higher values have been reported among patients with risk factors for vascular disease. Forearm blood flow responses to intrabrachial infusion of acetylcholine independently predict cardiovascular morbidity among hypertensive patients. We aimed to examine the relationship between CRPWV, a potentially informative, noninvasive measure and this more established parameter of arterial health. One hundred and fifteen mildly hypertensive individuals (67% men, mean (± SD) age 54 ± 8 years, mean (± SD) blood pressure (BP) 143 ± 16/83 ± 12 mmHg) were recruited from a weekly medical outpatient clinic. Each volunteer had CRPWV measured using sequential tonometry before forearm blood flow responses to intra-arterial, endothelium-dependent (acetylcholine) and independent (sodium nitroprusside) vasodilators were assessed. There was a significant negative correlation between CRPWV and maximum forearm blood flow response to acetylcholine (r = -0.225, p = 0.016). This association remained significant in a multiple regression analysis (β = -0.213, p = 0.034). Mean arterial pressure and weight were additional independent predictors of CRPWV in this model. There was no such relationship between CRPWV and response to sodium nitroprusside (r = 0.088, p = 0.349). In patients with mild hypertension, a poor forearm blood flow response to acetylcholine independently predicted faster CRPWV, thus linking an established measure of microvascular endothelial function with a noninvasive index of conduit vessel stiffness.

  14. 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.

  15. 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.

  16. Impact of Fibrotic Tissue on Shear Wave Velocity in Thyroid: An Ex Vivo Study with Fresh Thyroid Specimens

    Directory of Open Access Journals (Sweden)

    Takahiro Fukuhara

    2015-01-01

    Full Text Available We sought to elucidate the correlation between shear wave velocity (SWV and fibrosis in thyroid by precisely assessing pathological structures inside 5 × 5 mm2 regions of interest (ROIs of resected specimens, under conditions that excluded physical artifacts. The materials were unselected thyroid and lymph node specimens resected during thyroid surgery. Immediately after surgery, fresh unfixed thyroid and metastatic lymph node specimens were suspended in gel phantoms, and SWV was measured. Upon pathological examination of each specimen, the extent of fibrosis was graded as none, moderate, or severe. A total of 109 specimens were evaluated: 15 normal thyroid, 16 autoimmune thyroiditis, 40 malignant nodules, 19 benign thyroid nodules, and 19 metastatic lymph nodes. When all specimens were classified according to the degree of fibrosis determined by pathological imaging, the mean SWV was 1.49±0.39 m/s for no fibrosis, 2.13±0.66 m/s for moderate fibrosis, and 2.68±0.82 m/s for severe fibrosis. The SWVs of samples with moderate and severe fibrosis were significantly higher than those of samples without fibrosis. The results of this study demonstrate that fibrosis plays an important role in determining stiffness, as measured by SWV in thyroid.

  17. Swell impact on wind stress and atmospheric mixing in a regional coupled atmosphere-wave model

    DEFF Research Database (Denmark)

    Wu, Lichuan; Rutgersson, Anna; Sahlée, Erik

    2016-01-01

    Over the ocean, the atmospheric turbulence can be significantly affected by swell waves. Change in the atmospheric turbulence affects the wind stress and atmospheric mixing over swell waves. In this study, the influence of swell on atmospheric mixing and wind stress is introduced into an atmosphere......-neutral and unstable stratification conditions is introduced by changing the roughness length. Five year simulation results indicate that adding the swell influence on atmospheric mixing has limited influence, only slightly increasing the near-surface wind speed; in contrast, adding the swell influence on wind stress....... The influence varies with wave characteristics for different sea basins. Swell occurs infrequently in the studied area, and one could expect more influence in high-swell-frequency areas (i.e., low-latitude ocean). We conclude that the influence of swell on atmospheric mixing and wind stress should be considered...

  18. Effect of stress on energy flux deviation of ultrasonic waves in GR/EP composites

    Science.gov (United States)

    Prosser, William H.; Kriz, R. D.; Fitting, Dale W.

    1990-01-01

    Ultrasonic waves suffer energy flux deviation in graphite/epoxy because of the large anisotropy. The angle of deviation is a function of the elastic coefficients. For nonlinear solids, these coefficients and thus the angle of deviation is a function of stress. Acoustoelastic theory was used to model the effect of stress on flux deviation for unidirectional T300/5208 using previously measured elastic coefficients. Computations were made for uniaxial stress along the x3 axis (fiber axis) and the x1 for waves propagating in the x1x3 plane. These results predict a shift as large as three degrees for the quasi-transverse wave. The shift in energy flux offers a new nondestructive technique of evaluating stress in composites.

  19. THE GENERATION OF THERMOELASTIC STRESS WAVES BY IMPULSIVE ELECTROMAGNETIC RADIATION.

    Science.gov (United States)

    ELECTROMAGNETIC RADIATION , ABSORPTION), (*STRESSES, ELECTROMAGNETIC RADIATION ), SURFACE PROPERTIES, INTERACTIONS, HEAT TRANSFER, ELASTIC PROPERTIES, ELECTROMAGNETIC PULSES, LASERS, MATHEMATICAL ANALYSIS, BOUNDARY VALUE PROBLEMS, SOLIDS

  20. Numerical investigations of internal stresses on carbon steel based on ultrasonic LCR waves

    Science.gov (United States)

    Ramasamy, R.; Ibrahim, Z.; Chai, H. K.

    2017-10-01

    Internal stresses or residual stresses in the structural elements are very crucial in carrying out in-service evaluations and fitness-for-purpose assessments. The generation of these internal stresses can occur as result of the fabrication of the steel members, installation sequence or other ad-hoc events such as accidents or impact. The accurate prediction of the internal stresses will contribute towards estimating the integrity state of the structural elements, with respect to their material allowable stresses. This paper investigates the explicit FE based numerical modelling of the ultrasonic based non-destructive technique, utilising the measurable longitudinal critical refracted wave (LCR) and relating these to the internal stresses within the structural elements by the evaluation of the material dependent acoustoelastic factors. The subsurface travel path of the LCR wave inside the structural elements makes it a sub-surface stress measurement technique and the linearised relationship with corresponding internal stresses can be systematically applied repeatedly. The numerical results are compared against laboratory tests data to correlate the findings and to establish modelling feasibility for future proof-of-concepts. It can be concluded from this numerical investigation, that the subsurface ultrasonic LCR wave has great potential to be implemented for in-situ structural residual stress measurements, as compared to other available surface measurements such as strain gauges or x-ray diffraction.

  1. Stress Wave Propagation due to a Moving Force

    DEFF Research Database (Denmark)

    Rasmussen, K. M.; Nielsen, Søren R. K.; Kirkegaard, Poul Henning

    1999-01-01

    In this paper the performance of two numerical methods of solving the problem of a time dependent moving force on the surface of an elastic continuum will be evaluated. One method is the finite element method (FEM) formulated in convected coordinates coupled with an absorbing boundary condition...... of the impedance type. The other method to be considered is the boundary element method (BEM), where a new formulation using Green's functions transformed to a moving coordinate system is introduced. The methods are tested by the classic wave propagation problem of a Ricker Pulse propagating from the surface...... of an elastic halfspace. The time integral net impulse of the considered loading must be null for the considered FEM to work. Further, the FEM is unable to absorb Rayleigh waves, since the considered impedance condition has been tuned P- and S-waves. By contrast the BEM is able to handle also these cases...

  2. Viscous flux flow velocity and stress distribution in the Kim model of a long rectangular slab superconductor

    Science.gov (United States)

    Yang, Yong; Chai, Xueguang

    2018-05-01

    When a bulk superconductor endures the magnetization process, enormous mechanical stresses are imposed on the bulk, which often leads to cracking. In the present work, we aim to resolve the viscous flux flow velocity υ 0/w, i.e. υ 0 (because w is a constant) and the stress distribution in a long rectangular slab superconductor for the decreasing external magnetic field (B a ) after zero-field cooling (ZFC) and field cooling (FC) using the Kim model and viscous flux flow equation simultaneously. The viscous flux flow velocity υ 0/w and the magnetic field B* at which the body forces point away in all of the slab volumes during B a reduction, are determined by both B a and the decreasing rate (db a /dt) of the external magnetic field normalized by the full penetration field B p . In previous studies, υ 0/w obtained by the Bean model with viscous flux flow is only determined by db a /dt, and the field B* that is derived only from the Kim model is a positive constant when the maximum external magnetic field is chosen. This means that the findings in this paper have more physical contents than the previous results. The field B* stress changing with decreasing field B a after ZFC if B* ≤ 0. The effect of db a /dt on the stress is significant in the cases of both ZFC and FC.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. A comparative study of the effect of coronary atherosclerosis and age on aortic and pulmonary arterial pulse wave velocity

    International Nuclear Information System (INIS)

    Hanya, Shizuo

    2008-01-01

    The effect of coronary artery disease (CAD) and age on aortic (AO-PWV) and pulmonary arterial pulse wave velocity (PA-PWV) was studied. Aortic and pulmonary arterial pressure were measured at two sites (ascending and abdominal aorta, and the main pulmonary trunk and one of its principle branches, respectively) using a catheter-tip micromanometer in 24 patients divided in two groups. Control group (n=12) consisted of patients with normal coronaries, while the CAD group (n=12) consisted of patients with coronary artery disease estimated by coronary angiography. The interval between these two sites was determined by measuring the withdrawal distance of the microtip-catheter. AO-PWV was significantly higher (p<0.02) in the CAD group (12.0±4.1 m/sec) than in the control group (8.2±2.7 m/sec). There was no significant difference between the two groups in PA-PWV. AO-PWV was significantly (r=0.731, p<0.01) increased with age in the control group, while no significant correlation between the two was observed in the CAD group. There was no significant correlation between PA-PWV and age in control group. The results of this study indicate that only coronary atherosclerosis and age have significant predictive value regarding AO-PWV, but there was no significant correlation with PA-PWV for any of these parameters. The PA-PWV invasively measured in the 12 control subjects in this study was 2.3±0.7 m/sec, which is very close to values reported in the recent literatures using MRI. (author)

  8. Effects on carotid-femoral pulse wave velocity 24 h post exercise in young healthy adults.

    Science.gov (United States)

    Perdomo, Sophy J; Moody, Anne M; McCoy, Stephanie M; Barinas-Mitchell, Emma; Jakicic, John M; Gibbs, Bethany Barone

    2016-06-01

    Arterial stiffness, often measured by carotid-femoral pulse wave velocity (cfPWV), is a subclinical marker of cardiovascular disease that is known to be reduced by exercise training. Exercise is also known to have acute vascular effects, yet it is unclear whether exercise 24 h before cfPWV testing influences this outcome. Thirty healthy, young adults completed a supervised, 30-min bout of moderate-to-vigorous intensity treadmill running. cfPWV, systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) were measured both before (after 48 h of abstaining from exercise) and 24 h after (with no additional exercise) the exercise session. From pre-exercise to 24 h post exercise, cfPWV decreased from 6.05±0.82 to 5.84±0.87 m s(-1) (P=0.02), SBP from 119.7±13.8 to 116.8±11.4 mm Hg (P=0.03) and DBP from 65.1±5.7 to 63.2±5.4 mm Hg (P=0.02), with no significant changes in HR. cfPWV was positively correlated with SBP pre-exercise (r=0.54, Pexercise (r=0.53, Pexercise on cfPWV. Some evidence of gender differences was observed with higher cfPWV in males across assessments (Pexercise bout, suggesting that exercise completed in the past 24 h should be considered before cfPWV testing.

  9. 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.

  10. Effect of intradialytic resistance training on pulse wave velocity and associated cardiovascular disease biomarkers in end stage renal disease.

    Science.gov (United States)

    Chan, Danwin; Green, Simon; Fiatarone Singh, Maria A; Barnard, Robert; Bonder, Claudine S; Cheema, Birinder S

    2017-12-19

    Cardiovascular disease (CVD) is the leading cause of mortality in patients with end-stage renal disease (ESRD) receiving maintenance hemodialysis treatment. This study investigated the effect of a 12-week intradialytic progressive resistance training (PRT) intervention on pulse wave velocity (PWV) and associated hemodynamic, anthropometric, and hematologic outcomes in patients with ESRD. Twenty-two patients with ESRD (59% men, 71.3 ± 11.0 years) were recruited. Supervised PRT (3 sets of 11 exercises) was prescribed three times per week during routine dialysis. The primary outcome was brachial-ankle PWV via applanation tonometry. Secondary outcomes included augmentation index, brachial and aortic blood pressures, endothelial progenitor cells, C-reactive protein, blood lipids and anthropometrics. The intradialytic PRT regimen resulted in no significant change in PWV between control and intervention periods [mean difference = 0 (95% CI = -0.1 to 0.1); P=0.58]. Similarly, no significant change was noted in any secondary outcome measures between the control and intervention periods. Post-hoc analyses limited to high adherers (≥75% attendance; n=11) did not differ from the primary analysis, indicating no dose-response effect of our intervention. Our 12-week PRT intervention did not change PWV or any secondary outcomes. Future studies should determine if higher dosages of intradialytic PRT (i.e. longer duration and/or higher intensity) can be applied as a method improve arterial stiffness to potentially reduce cardiovascular disease and associated mortality this cohort. This article is protected by copyright. All rights reserved.

  11. 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.

  12. Seismogram Analysis of the Earthquakes in Sumatra on WRAB Observation Station: S Wave Velocity Structure on Subduction Zone of Sumatra-Java

    Directory of Open Access Journals (Sweden)

    Bagus Jaya Santosa

    2008-03-01

    Full Text Available The S wave velocity structure at subduction zone under Sumatra-Java was investigated through seismogram analysis in time domain and three Cartesian’s components simultaneously. The main data set was the comparison between the measured seismogram and the synthetic one, not the travel time data. The synthetic seismogram was calculated with the GEMINI method. The seismogram comparison shows that the global earth mantle of PREMAN gives deviating synthetic seismogram and has later arrival times than the measured one. The gradient bh in the upper mantle is altered to positive from its negative slope as in the PREMAN model, and positive corrections are added to the zero order of polynomial’s coefficients in all earth mantle layers. The excellent fitting, as well as travel time or waveform, were obtained on the surface waves of Love and Rayleigh, the S and SS mantle and repetitive depth waves. The additional positive corrections were also confirmed by a well fitting on the repetitive depth waves. This result expresses that part of the earth mantle that due to tectonic processes has positive anomaly on S wave velocity and vertical anisotropy in all of the earth mantle layers.

  13. Propagation behavior of the stress wave in a hollow Hopkinson transmission bar

    Science.gov (United States)

    Zou, G.; Shen, X.; Guo, C.; Vecchio, K. S.; Jiang, F.

    2018-03-01

    In order to investigate the stress wave propagation behavior through a hollow elastic bar that is used in a Hopkinson-bar-loaded fracture testing system, three-point bending fracture experiments were performed in such a system. The effects of sample span and diameter and wall thickness of the hollow elastic bar on the stress wave propagation behavior were studied numerically using the software of ANSYS/LS-DYNA. The experimental results demonstrated that the incident, reflected, and transmitted pulses calculated by the finite element method are coincident with those obtained from the Hopkinson-bar-loaded fracture tests. Compared to the solid transmission bar, the amplitude of the transmitted pulse is relatively larger in the hollow transmission bar under the same loading conditions and decreases with increasing wall thickness. On the other hand, when the inside diameter is fixed, the effect of the wall thickness on the stress wave characteristics is more obvious.

  14. Stress wave communication in concrete: I. Characterization of a smart aggregate based concrete channel

    Science.gov (United States)

    Siu, Sam; Ji, Qing; Wu, Wenhao; Song, Gangbing; Ding, Zhi

    2014-12-01

    In this paper, we explore the characteristics of a concrete block as a communication medium with piezoelectric transducers. Lead zirconate titanate (PZT) is a piezoceramic material used in smart materials intended for structural health monitoring (SHM). Additionally, a PZT based smart aggregate (SA) is capable of implementing stress wave communications which is utilized for investigating the properties of an SA based concrete channel. Our experiments characterize single-input single-output and multiple-input multiple-output (MIMO) concrete channels in order to determine the potential capacity limits of SAs for stress wave communication. We first provide estimates and validate the concrete channel response. Followed by a theoretical upper bound for data rate capacity of our two channels, demonstrating a near-twofold increase in channel capacity by utilizing multiple transceivers to form an MIMO system. Our channel modeling techniques and results are also helpful to researchers using SAs with regards to SHM, energy harvesting and stress wave communications.

  15. Wind stress, curl and vertical velocity in the Bay of Bengal during southwest monsoon, 1984

    Digital Repository Service at National Institute of Oceanography (India)

    Babu, M.T.; Heblekar, A.K.; Murty, C.S.

    Wind distribution observed during southwest monsoon of 1984 has used to derive the mean wind stress for the season at every 1 degree square grid and curl over the Bay of Bengal. Two regions of maximum wind stress are present over the Bay of Bengal...

  16. Stress Wave Propagation in Viscoelastic-Plastic Rock-Like Materials

    Directory of Open Access Journals (Sweden)

    Liu Lang

    2016-05-01

    Full Text Available Rock-like materials are composites that can be regarded as a mixture composed of elastic, plastic, and viscous components. They exhibit viscoelastic-plastic behavior under a high-strain-rate loading according to element model theory. This paper presents an analytical solution for stress wave propagation in viscoelastic-plastic rock-like materials under a high-strain-rate loading and verifies the solution through an experimental test. A constitutive equation of viscoelastic-plastic rock-like materials was first established, and then kinematic and kinetic equations were then solved to derive the analytic solution for stress wave propagation in viscoelastic-plastic rock-like materials. An experimental test using the SHPB (Split Hopkinson Pressure Bar for a concrete specimen was conducted to obtain a stress-strain curve under a high-strain-rate loading. Inverse analysis based on differential evolution was conducted to estimate undetermined variables for constitutive equations. Finally, the relationship between the attenuation factor and the strain rate in viscoelastic-plastic rock-like materials was investigated. According to the results, the frequency of the stress wave, viscosity coefficient, modulus of elasticity, and density play dominant roles in the attenuation of the stress wave. The attenuation decreases with increasing strain rate, demonstrating strongly strain-dependent attenuation in viscoelastic-plastic rock-like materials.

  17. Observation of the Near-seabed Velocity and Particles Resuspension During Nonlinear Internal Solitary Wave Events near the Dongsha Plateau at the Northern South China Sea

    Science.gov (United States)

    2015-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Observation of the Near-seabed Velocity and Particles...turbulence interaction and/or the dynamic pressure perturbation induced by ISWs cause the resuspension and redistribution of sediment particles and...likely form the continuous sediment waves on the seafloor [Ma et al., 2008 and Reeder et al., 2011]. To our knowledge, there are no direct observations

  18. Slow Replication Fork Velocity of Homologous Recombination-Defective Cells Results from Endogenous Oxidative Stress

    Science.gov (United States)

    Magdalou, Indiana; Machon, Christelle; Dardillac, Elodie; Técher, Hervé; Guitton, Jérôme; Debatisse, Michelle; Lopez, Bernard S.

    2016-01-01

    Replications forks are routinely hindered by different endogenous stresses. Because homologous recombination plays a pivotal role in the reactivation of arrested replication forks, defects in homologous recombination reveal the initial endogenous stress(es). Homologous recombination-defective cells consistently exhibit a spontaneously reduced replication speed, leading to mitotic extra centrosomes. Here, we identify oxidative stress as a major endogenous source of replication speed deceleration in homologous recombination-defective cells. The treatment of homologous recombination-defective cells with the antioxidant N-acetyl-cysteine or the maintenance of the cells at low O2 levels (3%) rescues both the replication fork speed, as monitored by single-molecule analysis (molecular combing), and the associated mitotic extra centrosome frequency. Reciprocally, the exposure of wild-type cells to H2O2 reduces the replication fork speed and generates mitotic extra centrosomes. Supplying deoxynucleotide precursors to H2O2-exposed cells rescued the replication speed. Remarkably, treatment with N-acetyl-cysteine strongly expanded the nucleotide pool, accounting for the replication speed rescue. Remarkably, homologous recombination-defective cells exhibit a high level of endogenous reactive oxygen species. Consistently, homologous recombination-defective cells accumulate spontaneous γH2AX or XRCC1 foci that are abolished by treatment with N-acetyl-cysteine or maintenance at 3% O2. Finally, oxidative stress stimulated homologous recombination, which is suppressed by supplying deoxynucleotide precursors. Therefore, the cellular redox status strongly impacts genome duplication and transmission. Oxidative stress should generate replication stress through different mechanisms, including DNA damage and nucleotide pool imbalance. These data highlight the intricacy of endogenous replication and oxidative stresses, which are both evoked during tumorigenesis and senescence initiation

  19. Wave Induced Stresses Measured at the Wave Dragon Nissum Bredning Prototype

    DEFF Research Database (Denmark)

    Corona, L.; Kofoed, Jens Peter

    2006-01-01

    for this paper, first to verify the FEM results obtained by Niras, Danish society in charge of the finite element modelling and structural design, and then to make a first experimental fatigue analysis of a particular part of the Wave Dragon. This last part shall be considered as an exercise for the further work...