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The time-averaged shear-wave velocity of up to 30 m (V_(S30)), a vital parameter in building codes, is widely used in site classification and plays an important role in the analysis of site effects. Recently, the log-linear correl...
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The time-averaged shear-wave velocity of up to 30 m (V_(S30)), a vital parameter in building codes, is widely used in site classification and plays an important role in the analysis of site effects. Recently, the log-linear correlation (Boore, 2004) has become more prevalent to estimate V_(S30) of velocity profiles that do not extend to 30 m. In this study, we make a full analysis on the linear correlation with three publicly available data sets of shear-wave velocity profiles. A conditional independence property is derived from the partial correlation analysis of the data sets. Using this property, a new V_(S30) estimation model is proposed. Comparison of models based on the setup of training and testing data sets suggests that the new model achieves improved performance on the V_(S30) estimation. The impact of errors of estimation models on the prediction of ground-motion parameters is also evaluated, and the overall error of the predicted parameter by the new model is the least, especially at long periods.
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This paper presents our previous analyses of pickup gas velocity from a layer of particles in pipes and big wind tunnels, pickup liquid velocity, boundary saltation and minimum pressure velocities, and a new analysis of the minimu...
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This paper presents our previous analyses of pickup gas velocity from a layer of particles in pipes and big wind tunnels, pickup liquid velocity, boundary saltation and minimum pressure velocities, and a new analysis of the minimum fluidization velocity and the terminal velocity. All these threshold velocities are defined as simple relations between the Reynolds and Archimedes numbers as modified by various effects. The Reynolds number is modified by taking into account the pipe diameter while the Archimedes number is modified by taking into account various properties that affect each threshold mechanism. Since all threshold velocities could be defined successfully by the same non-dimensional groups it was possible, at the first time, to present a Generalized Master Curve, which provides an overview of all the threshold velocities. This overview enabled, for example, to find quantitatively the relationships between all the threshold velocities to the terminal velocity and to compare the pickup and saltation velocities.
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In-situ stress measurement for deep reservoir formation is difficult in terms of security, reliability and technique. Acoustic velocity anisotropy test is a basic method for stress measurement of rock cores, which is based on the ...
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In-situ stress measurement for deep reservoir formation is difficult in terms of security, reliability and technique. Acoustic velocity anisotropy test is a basic method for stress measurement of rock cores, which is based on the distribution of acoustic velocity in different directions around rock cores. The heterogeneity of core samples, such as fractures and gravel contained, can also lead to wave velocity anisotropy. Therefore, the corresponding reliability evaluation method is established to exclude some other anisotropy factors caused by non-tectonic stresses. In this paper, the reliability of testing results is evaluated from three aspects, i.e. phase difference, anisotropy index and waveform, to remove the factors caused by non-tectonic stresses.
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The article presents the results of a research work aimed at an effort to improve Carpathian basement structures imaging on a selected 2D seismic section from the Outer Carpathians region. This attempt represents the next step in ...
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The article presents the results of a research work aimed at an effort to improve Carpathian basement structures imaging on a selected 2D seismic section from the Outer Carpathians region. This attempt represents the next step in the research related to the development of a processing sequence designed to provide a more detailed seismic imaging of this complicated geological complex. The processing sequence developed at the Seismic Department of the Oil and Gas Institute - National Research Institute was used in this study. Velocity models were created based on vertical seismic measurements (VPS) in wells. In the current work, a velocity field was additionally generated in the processing sequence calculated from velocity analyses (stacking velocities). The most important part of the study was the modification of procedures and parameters in the processing sequence. That processing sequence included both changes in the way kinematic corrections and residual static corrections were introduced as well as modifications in the summation (stack) and post-summation (poststack) procedures. Poststack time migration was performed in two variants, i.e. Kirchoff migration and finite difference migration. Velocity percentages (20%, 40%, 60%, 80%, and 100%) were used for all analyzed velocity fields used for migration. The applied modifications to the stack and poststack procedures resulted in improvements of seismic images compared to versions developed in previous works. The best mapped zone characterized by higher resolution and more reliable dip angles is located mainly within the time interval for which the well average velocity measurements were made. However, within the time interval covering the Carpathian basement, for which there were no well measurements and the velocity field was generated by extrapolation from neighboring areas, no such improvement of seismic image was obtained using the interval velocity model. For that interval there was only a minor improvement in the reliability of the geological structure reflection in the seismic image that was achieved by using the velocity field calculated from velocity analyses (stacking velocities).
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A review of the main instruments developed in Italy over more than two centuries to measure flow velocity of experience is presented, highlighting the relation with the development of hydraulics as a physical-mathematical science ...
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A review of the main instruments developed in Italy over more than two centuries to measure flow velocity of experience is presented, highlighting the relation with the development of hydraulics as a physical-mathematical science from the seventeenth century. The number and variety of Italian velocity meters partly reflect the vitality of a tradition, characterized by political polycentrism and rivalry among the individual cities and universities. In other aspects, the invention of ever-newer measuring instruments corresponds to the attitude of many of the early Italian hydraulicians, who interpreted hydraulics as a science of nature, based almost exclusively on observation and experience, which requires rather the gift of intuition than mathematical deduction. This work is part of a project of the BEIC Library and of the University of Milan, which will make available digital versions of hundreds of Italian historic texts of hydraulics on the portal .
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Sound is propagated as a wave. We can get some very interesting views by measuring the velocities of sound propagation, respectively, on the ground, in a fully enclosed car, and outside a car in movement. Light is also propagated ...
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Sound is propagated as a wave. We can get some very interesting views by measuring the velocities of sound propagation, respectively, on the ground, in a fully enclosed car, and outside a car in movement. Light is also propagated as a wave. By measuring the velocities of light propagation respectively on the ground, in a fully enclosed car, and outside a car in movement, and comparing the sound velocity with the light velocity, we can find out if their properties are the same.
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In previous research, a kalman tracker with a turning acceleration estimator is presented in order to track a maneuvering target. In turning acceleration estimator, the target trajectory is approximated by circle and turning accel...
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In previous research, a kalman tracker with a turning acceleration estimator is presented in order to track a maneuvering target. In turning acceleration estimator, the target trajectory is approximated by circle and turning acceleration is estimated from estimated radius, center of the circle and angular velocity. Then a change of velocity vector is expressed by turning acceleration. However, estimated radius and center of the circle include large errors. As the results, accurate turning acceleration cannot be estimated and tracking performance is degraded. In this paper, a Kalman estimator using two directions of angular velocity is presented. Proposed tracking filter calculate two directions of angular velocity from the difference of last three observation data. Furthermore, a change of velocity vector can be expressed without acceleration term. Then estimated error of radius and center of the circle can be eliminated and good tracking performance could be obtained. Simulation results show the effectiveness of our proposed tracking filter compared with conventional tracking filters.
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Known and previously unknown experimental observations of transfer, exchange, and combustion in vortex flames in high-velocity flows are analyzed. The evolution of our concepts of these processes with discoveries of new facts is t...
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Known and previously unknown experimental observations of transfer, exchange, and combustion in vortex flames in high-velocity flows are analyzed. The evolution of our concepts of these processes with discoveries of new facts is traced. It is demonstrated that four regimes of homogeneous combustion of the vortex ball in a high-velocity flow are possible: deterministic (coherent), resonant (vibrational), stochastic, and pseudo-detonation regimes. Pseudo-detonation combustion is understood as simultaneous homogeneous microturbulent frontal combustion of all layers of the vortex ball with the radius expansion rate several times greater than the entraining flow velocity. The intensity of injection of a homogeneous mixture or air into the burning vortex layer is found to be identical to the notion of intensity of homogeneous or diffusion combustion. It is demonstrated that the classical notions and the Shchelkin-Shchetinkov relations for burning surfaces and volumes are applicable, but only for certain phases and local zones of the burning vortex ball.
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The study was done to assess the tricuspid and mitral valve velocities in 45 fetuses between 18 and 28 weeks and to compare these findings with reported values from literature.
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It is shown that the delay time of a weak signal propagating in an amplifying medium on the wings of the spectral amplification line may be shorter than the time of propagation of the signal with the velocity of light in vacuum. I...
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It is shown that the delay time of a weak signal propagating in an amplifying medium on the wings of the spectral amplification line may be shorter than the time of propagation of the signal with the velocity of light in vacuum. It is found that in this case, the time dependence of the signal is exactly 'reconstructed' at the point of detection, and the detection of the signal continues even if it is abruptly terminated at the point of transmission. It is also shown that using the complex time of group delay of the signal, it is possible to improve the accuracy of the results in the first order of dispersion theory within this approximation.
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