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The building-damper system designed by a seismic code is usually considered to be able to withstand the attack of strong earthquakes. However, near-fault earthquakes, especially those with the forward-directivity effect, might cause early and unexpected failure of code-designed dampers and consequent severe structural damage. In this paper, by taking into account near-fault earthquakes, seismic performance of the building-damper system and damper failure’s influence are evaluated systematically. A 9-storey steel building is designed by the Chinese seismic code as the benchmark model, and five typical dampers, including buckling-restrained brace damper (BRB), friction damper (FD), self-centering damper (SCD), viscous damper (VD), and viscoelastic damper (VED), are adopted. It was found that the building-damper systems show a large response and possible damper failure under the near-fault earthquake excitations. Then, the influence of damper failure is investigated, which reveals that damper failure would significantly affect seismic performance of the building-damper system, especially for the building-SCD system. Subsequently, by introducing the artificial near-fault earthquake excitation, the influences of different pulse parameters, such as pulse velocity amplitude, pulse period, and the number of significant pulses, are studied. It shows that the pulse velocity amplitude and pulse period obviously affect the seismic performance, while the number of significant pulses presents little influence.

This study measures the acoustic power loss that occurs when an acoustic wave passes through a tube with an abrupt change in area. It is determined that the power loss is proportional to the third power of the velocity amplitude, and that the proportionality coefficient depends upon the area change ratio of the tube. On the other hand, the proportionality coefficient is almost independent of the acoustic impedance and frequency in the 80-250 Hz range. Furthermore, the effect of a tapered tube in reducing the coefficient is experimentally investigated. Based on these experimental results, an empirical estimation method for the acoustic power loss is proposed and validated using a high-pressure-helium-filled tube.

Velocity and amplitude are two basic characteristics of any autowave, and their relationship reflects the internal regulation of the autowave system. This study proposes an approach to approximately estimate steady velocity–amplitude (VA) relation without deriving separate formulas for V and A. The approach presumes constructing an ansatz which represents the “petal” form of phase trajectory and contains V, A, and a free parameter (parameters). After substituting this ansatz, integration of model equations leads to a VA relation analytically. A free parameter (parameters) can be determined by comparing the analytical VA relation to the numerical data. As an example, we used the simplest autowave model possessing threshold, that is, the Gray–Scott model (cubic autocatalysis with linear inhibition) in isolated conditions with an immobilized precursor and a diffusible reactant. For all values of the inhibition rate constant allowing autowave solution (i.e., except approaching zero), the free parameter of ansatz belongs to a narrow interval has little effect on VA relation and can be regarded as fixed. Assumption of precursor immobilization does not influence the results qualitatively. This approach will be useful in investigations of more complex active media systems in biochemistry, combustion, and disease control.

Common features of the flow behavior over mountains within the hydraulic jump model are identified based on an analysis of 36 episodes of severe winds in the regions of Novorossiysk, Pevek, and Novaya Zemlya. In all these episodes, the incoming flow is characterized by a strong inversion layer at altitudes of 0.5–1.5 km and, in the case of bora, by a critical level in the wind profile in the middle troposphere, which creates conditions for a weakened dynamic interaction between the low-level air flowing over mountains and the upper layers of the atmosphere. The wind-speed increase on the lee slope is caused by the transition of the incoming flow from the subcritical to supercritical state. In this case, the velocity amplitude increases with increasing inversion intensity. Model estimates of wind-speed increase are in good agreement with observations at lee-side weather stations for episodes with a strong elevated inversion.

Microsaccades occur during gaze fixation to correct for miniscule foveal motor errors. The mechanisms governing such fine oculomotor control are still not fully understood. In this study, we explored microsaccade control by analyzing the impacts of transient visual stimuli on these movements’ kinematics. We found that such kinematics can be altered in systematic ways depending on the timing and spatial geometry of visual transients relative to the movement goals. In two male rhesus macaques, we presented peripheral or foveal visual transients during an otherwise stable period of fixation. Such transients resulted in well-known reductions in microsaccade frequency, and our goal was to investigate whether microsaccade kinematics would additionally be altered. We found that both microsaccade timing and amplitude were modulated by the visual transients, and in predictable manners by these transients’ timing and geometry. Interestingly, modulations in the peak velocity of the same movements were not proportional to the observed amplitude modulations, suggesting a violation of the well-known “main sequence” relationship between microsaccade amplitude and peak velocity. We hypothesize that visual stimulation during movement preparation affects not only the saccadic “Go” system driving eye movements but also a “Pause” system inhibiting them. If the Pause system happens to be already turned off despite the new visual input, movement kinematics can be altered by the readout of additional visually evoked spikes in the Go system coding for the flash location. Our results demonstrate precise control over individual microscopic saccades and provide testable hypotheses for mechanisms of saccade control in general. NEW & NOTEWORTHY Microsaccadic eye movements play an important role in several aspects of visual perception and cognition. However, the mechanisms for microsaccade control are still not fully understood. We found that microsaccade kinematics can be altered in a systematic manner by visual transients, revealing a previously unappreciated and exquisite level of control by the oculomotor system of even the smallest saccades. Our results suggest precise temporal interaction between visual, motor, and inhibitory signals in microsaccade control.

We present results of theoretical modeling of macroscopic circulating flow induced in a drop of ferrofluid by oscillating running magnetic field. The drop is placed in a narrow flat channel filled by a nonmagnetic liquid. The aim of this work is development of a scientific basis for a progressive method of address drug delivery to thrombus clots in blood vessels with the help of the magnetically induced circulation flow. Our results show that the oscillating running field allows inducing the carrier fluid flow with velocity amplitude 1–10 cm/s. This is the range of values, presenting interest from the point of view of the drug delivery. © 2020, EDP Sciences, Springer-Verlag GmbH Germany, part of Springer Nature.

The effect of vertically imposed, low frequency oscillations on the rheology of shear-thinning non- Newtonian fluids are studied numerically by computational fluid dynamics (CFD). Both Newtonian (water) and inelastic time-independent fluids of power-law (Poly-Anionic Cellulose (PAC)) are used as test fluids. Unsteady state simulations were performed using ANSYS Fluent version 18.0 for a vertical 2-D pipe geometry (ID = 50 mm and H = 850 mm) and sinusoidal, vertical oscillations to the liquid body itself were imposed with a user-defined function (UDF). The multiphase volume of fluid (VOF) method with realizable k-å method was used to impose the turbulence nature of the flow for the cases with water while the cases with non-Newtonian fluids were simulated under the laminar condition. Oscillations of different low frequency values (0.25–5 Hz) and different velocity amplitudes (0.1–0.3 m/s) were tested numerically. The dynamic variation of velocity and shear rate within the oscillated, bulk liquid medium is demonstrated. The flow inside the vertical pipe acts plug like at higher frequencies for both Newtonian and non-Newtonian fluids. The air–liquid interface becomes unstable with small disruptive peaks for the cases with water at higher velocity amplitudes while that is very calm for the laminar cases with non-Newtonian fluids. The achieved velocity gradients and the resultant shear rate variation are low with the increased PAC concentration due to the viscous resistance. However, the instantaneous velocity profiles display a progressively more complex structure with increased frequency and velocity amplitude, revealing the presence of alternating upward/downward motion. These alternating velocity profiles confirm the varying shear field present within a drilling pipe at different frequencies and velocity amplitudes while the variation of the shear field is more dependent on the velocity amplitude.

A finite Stokes layer with a large half-width over three-dimensional wall roughness is numerically simulated by solving the perturbation equations. Simulations are conducted for different parameters that affect the shape of the wall roughness, e.g., streamwise wave number, spanwise wave number and the amplitude of the roughness. The calculations are performed at a Reynolds number of R δ = 600 , which represents the transitional Reynolds number observed in experimental cases. The onset of the transition is shown to be highly correlated with the amplitude of pre-existing two-dimensional waves. It is found that the critical amplitude of the two-dimensional wave is approximately 1% of the velocity amplitude of the external flows. Moreover, the results indicate that the appearance of the transition is also affected by the fundamental wave numbers.

The interactive influences of oscillation frequency and velocity amplitude ratio on onset of transition in pulsatile pipe flow are investigated experimentally in the ranges of time-averaged and oscillating Reynolds numbers of 1019 ± 35 ⩽ Re ta ⩽ 4817 ± 164 and 107 ± 4 ⩽ Re os ⩽ 4261 ± 145 with velocity amplitude ratio of 0.05 ± 0.0017 ⩽ A 1 ⩽ 0.96 ± 0.03 for 227 runs. Oscillation frequency is in the range of 0.1 Hz ⩽ f ⩽ 14 Hz corresponding to Womersley number range of 2.72 ⩽ ω ′ ⩽ 32.21 covering quasi-steady, intermediate and beginning of inertia dominant regimes of pulsatile laminar flow. The onset of transition in laminar pulsatile pipe flow can be retarded up to Re ta , crit = 4817 at ω ′ = 3.85 in the covered experimental range. No more effect of A 1 on Re ta , crit is seen for ω ′ > 8.61 although there is a considerable effect of A 1 on Re os , crit . The effect of ω ′ on Re ta , crit and Re os , crit is not observed for A 1 ω ′ and A 1 are also investigated on Re ta , crit as functions of Re ta , crit = Re ta , crit ( A 1 ω ′ ) and Re ta , crit = Re ta , crit ( ω ′ / A 1 ). The interactive influences of ω ′ and A 1 are not seen on Re ta , crit for ω ′ > 8.61. This shows that the time-periodicity ( ω ′ , A 1 ) does not affect significantly the onset of transition at the beginning of inertia dominant region of pulsatile laminar flow ( ω ′ > 8.61) when compared with their interactive effects in the quasi-steady and intermediate regions ( ω ′ ⩽ 8.61). For flow classification of pulsatile flow at the onset of transition, a new non-dimensional interactive oscillation number, I os = ω ′ / A 1 is proposed. According to this non-dimensional number, the pulsatile flow at the onset of transition can be subclassified such as quasi-steady for I os I os ⩽ 30 and inertia dominant regions of pulsatile pipe flows for I os > 30 considering the effects of both ω ′ and A 1 on contrary to the classifications available in the literature.

In this study, differences of signal characteristics between mine shocks and coal and gas outbursts in coal mines were examined with the micro-seismic monitoring technique and time–frequency analysis. The duration of the mine shock is short while the coal and gas outburst lasts longer. The outburst consists of three stages: the pre-shock, secondary shock and main shock stage, respectively. The velocity amplitude of the mine shock is between 10−5 and 10−3 m/s, which is higher than that of the outburst with the same energy level. In addition, in both cases, the correlation between the velocity amplitude and energy is positive while the correlation between the signal frequency band distribution and energy is negative. The signal frequency band of the high energy mine shock is distributed between 0 and 50 Hz, and the low energy mine shock is between 50 and 100 Hz. The fractal characteristics of mine shocks were studied based on a fractal theory. The box dimensions of high energy mine shocks are lower than the low energy ones, however, the box dimensions of outbursts are higher than that of mine shocks with the same energy level. The higher box dimensions indicate more dangerous dynamic events. Keywords: Mine shock, Coal and gas outburst, Micro-seismic signal, Spectrum characteristics, Fractal characteristics

Wind-velocity data obtained from in situ measurements at the Golitsyno-4 marine stationary platform have been compared with QuikSCAT scatterometer data; NCEP, MERRA, and ERA-Interim global reanalyses and MM5 regional atmospheric reanalysis. In order to adjust wind velocity measured at a height of 37 m above the sea surface to a standard height of 10 m with stratification taken into account, the Monin–Obukhov theory and regional atmospheric reanalysis data are used. Data obtained with the QuikSCAT scatterometer most adequately describe the real variability of wind over the Black Sea. Errors in reanalysis data are not high either: the regression coefficient varies from 0.98 to 1.06, the rms deviation of the velocity amplitude varies from 1.90 to 2.24 m/s, and the rms deviation of the direction angle varies from 26° to 36°. Errors in determining the velocity and direction of wind depend on its amplitude: under weak winds ( 12 m/s), its velocity is underestimated. The influence of these errors on both spatial and temporal estimates of the characteristics of wind over the Black Sea is briefly considered.

Global recurrence plots (GRPs) and windowed recurrence quantification analysis (WRQA) are two recurrence paradigms which find wide applications to detect the onset of instability in a dynamic system. The present work reports the attempt to employ these recurrence paradigms to assess the effect of frontal gust on the force patterns of an insect-sized flapping wing in the inclined-stroke plane. Horizontal and vertical forces generated by the flapping wing in the presence of gusts of the form $$ \frac{{{\text{u}}_{\text{G}} }}{{{\text{u}}_{\text{w}} }} = \frac{{{\text{u}}_{\infty } }}{{{\text{u}}_{\text{w}} }} + \left( {\frac{{{\text{u}}_{\text{g}} }}{{{\text{u}}_{\text{w}} }}} \right)\sin \left( {2\uppi\frac{{{\text{f}}_{\text{g}} }}{{{\text{f}}_{\text{w}} }}{\text{t}}} \right) $$ were numerically estimated in the 2D reference frame for Re = 150. Nine gusts with combinations of the ratio of gust frequency to wing’s flapping frequency, fg/fw = 0.1, 0.5 and 1 and ratio of gust velocity amplitude to root mean square averaged flapping velocity, ug/uw = 0.1, 0.5 and 1 were considered. Recurrence studies of the forces were carried out to find out the gusty condition, which would trigger an onset of unstable behaviour. Studies indicated a possible onset of instability in the force patterns for gust with fg/fw = 0.1 and ug/uw = 1. The onset of unstable behaviour was prominently captured by WRQA of the vertical force coefficient based on determinism (DET) and laminarity (LAM) series.

Summary Over the last decade the acoustic 3-D full-waveform inversion technique has become almost a common tool for imaging geologically complex structures in marine, as well as in land settings. However, it has been speculated that excluding the elastic effect from the waveform modeling in some cases could have a big impact and potentially result in an erroneous image of the subsurface. To examine the contribution of the elastic effect, we conduct acoustic and elastic 3-D FWI on the 3-D seismic data, collected at the East Pacific Rise (EPR) 9°50’N, deep-water environment (minimum depth ~2500 m) with high compression velocity contrast at the seafloor. We first establish a strategy for inversion within the EPR setting, which suggest simultaneous multi-parameter inversion for the frequencies

A staggered impulse turbine is proposed for asymmetric air flows in Oscillating Water Column wave energy plants, which is expected to enhance the pneumatic power output in a wave cycle. The setting angle of rotor blades is set as 5°. The 3D numerical simulations were conducted under steady conditions using MRF and Mixing Plane model based on CFD software Fluent 12.0. Its mean efficiencies under different velocity amplitude ratios are studied using quasi-steady analysis, which derive corresponding data from the numerical simulation. It is found that the staggered turbine shows better performance than the conventional one under the asymmetrical air flows. Furthermore, its mean efficiency and output-work in a wave period are compared with another unsymmetrical twin impulse turbine system. The results show that the staggered turbine shows better output-work performance than the twin turbine system over the high flow coefficient domain (φ>0.7), which provides more choices to future research on turbine’s optimization.

Non-thermal motions in the intra-cluster medium (ICM) are believed to play a non-negligible role in the pressure support to the total gravitating mass of galaxy clusters. Future high-precision X-ray missions will allow us to directly detect the signature of these motions from highly resolved spectra of the ICM. With this perspective, we will present here a study on a set of clusters extracted from a cosmological hydrodynamical simulation, for which we simulated X-ray observations and characterized them via the non-thermal velocity amplitude of the ICM. We have applied the X-ray virtual telescope PHOX to generate mock observations of the simulated clusters and estimated in an observational fashion global X-ray properties. We included ICM non-thermal motions as additional parameter to further identify non-regular clusters. In particular, the influence of internal gas motions on the location of clusters in the LX-T plane was investigated and was found that objects with the largest amount of non-thermal velocity have on average higher X-ray luminosities. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The author firstly summarized the principles, performance and theoretical resilience model of the new type electromagnetic damper. The theoretical resilience model is further improved on this basis—normalizing the impact of vibrant frequency and vibrant amplitude on resilience as the impact of single parameter velocity amplitude. The results show that improved model can give a better effect as shown in experiment. This lays a sound foundation for simulation calculation in developing products using for practical engineering and installing the structural vibration reduction system of electromagnetic damper.

The transition criterion in the improved eN method is that transition would occur whenever the velocity amplitude of disturbance reaches 1%–2% of the free stream velocity, while in the conventional eN method, the N factor is an empirical factor. In this paper the reliability of this key assumption in the improved eN method is checked by results of transition prediction by using the Parabolized Stability Equations (PSE). Transition locations of an incompressible boundary layer and a hypersonic boundary layer at Mach number 6 on a flat plate are predicted by both the improved eN method and the PSE method. Results from both methods agree fairly well with each other, implying that the transition criterion proposed in the improved eN method is reliable.

About 25 years ago, in Paper 12 of this series, the author presented a spectroscopic orbit for 6 Boo. The velocity amplitude of little more than 1 km s−1 was much smaller than for any star whose orbit had been determined up till that time. Although it was objectively demonstrated that the orbit was very secure, a few years ago subjective misgivings prompted the author to restore the star to his observing programme. New observations of much higher precision confirm not only the spectroscopic-binary nature of 6 Boo but also, with almost astonishing fidelity, the elements already given for it.

Context. Investigations of the behavior of small-scale threads can provide an alternative approach to studying prominence dynamics and understanding its origin and nature. Aims. The behavior of threads are analyzed in a quiescent prominence, including drifting and both the horizontally and vertically oscillating motions. These indicate waves in the solar prominence. Methods. We used the Ha images at a setting wavelength of +0.076 angstrom. A quiescent prominence was observed by HINODE/SOT on 2008 January 15 for about 3 h in total. Results. Consistent with previous findings, prominences show numerous thread-like structures. Some threads clearly exhibit both vertically and horizontally oscillatory motions, while others are only drifting. Complicated cases show both drifting and oscillatory motions simultaneously. In the upper part of the prominence, the threads are oscillating independently of each other. We find that three threads oscillate with the same phase for at least two periods. The oscillations seem to be strongly damped since they disappear after a few periods. The maximum number of observed periods is 8 in our observations. In the lower part of the prominence, however, the different threads have a mixed character with the individual oscillatory motions unstable for one entire period. Most oscillatory motions will disappear after a half period or less, while the new oscillatory motions are excited nearby. A 5-min period is predominant, and the oscillating amplitudes show an average value of +/- 3.5 km s(-1). We find some upflows in the spicule layer, and they appear to transport the mass from photosphere ( or spicules themselves) to the prominence. These upflows have an average velocity amplitude of 0.8 km s(-1). Conclusions. The threads exhibit three distinct behaviors. The first is only drifting, the second is typically oscillating, and the third shows both characteristics. There are no substantial differences between the periods of horizontally and vertically oscillating threads in this prominence.

An analytical approximate approach for determining periodic solutions of non-linear jerk equations involving third-order time-derivative is presented. This approach incorporates salient features of both Newton's method and the method of harmonic balance. By appropriately imposing the method of harmonic balance to the linearized equation, the approach requires only one or two iterations to predict very accurate analytical approximate solutions for a large range of initial velocity amplitude. One typical example is used to verify and illustrate the usefulness and effectiveness of the proposed approach.

Laboratory experiments were conducted in a recirculating flow tank to evaluate the effects of waves on herbivory by the Rabbitfish Siganus fuscescens. rabbitfish (27 cm FL) increased feeding on the kelp Ecklonia cava or Eisenia bicyclis in a faster oscillating flow with a seasonally increased appetite. When feeding activity was highest, oscillating flow reduced feeding to 50% at the velocity amplitude of 1.1 m/s and to nil at ca 1.5 m/s. Swimming speeds observed in different fish sizes suggested that the upper velocity limit for feeding increased little for larger fish. The results and the wave-induced water velocity predictions indicate that destructive feeding by rabbitfish on kelp is very unlikely to be inhibited by waves on the Pacific coast of central Honshu.

An analytic solution of the flow of a third-grade fluid on a porous plate is constructed. The porous plate is executing oscillations in its own plane with superimposed injection or suction. An increasing or decreasing velocity amplitude of the oscillating porous plate is also examined. It is also shown that in case of third-grade fluid, a combination of suction/injection and decreasing/increasing velocity amplitude is possible as well. Several limiting situations with their implications are given and discussed.

With the aim of providing reliable benchmark values, we have measured the Soret, diffusion and thermal diffusion coefficients of the three binary mixtures of dodecane, isobutylbenzene and 1,2,3,4 tetrahydronaphthalene for a concentration of 50 wt% at a temperature of 25°C. The experimental techniques applied by the five participating laboratories are transient holographic gratings, annular and parallelepipedic thermogravitational columns, and vertical parallelepipedic columns with velocity amplitude determination by laser doppler velocimetry. The systems have also been studied in a annular thermogravitational column filled with a porous medium in the gap. There is a good agreement between the different experiments with deviations of the order of a few per cent in most cases (8.5% at most). The numerical values are tabulated in the paper.

This research work uses parameter variation techniques for calculating the set of vehicle parameters that result in the best ride comfort for the driver. Tractor semi-trailer vertical dynamic ride model is developed using 9 degrees-of-freedom. The simulation of the model is conducted using MATLAB. The input to the system is a velocity amplitude function of the vertical road irregularities. Other inputs include the load conditions, vehicle speed and road conditions. The RMS vertical weighted acceleration at the driver’s seat and at the centre of gravity of tractor and semi-trailer for different parameters of the vehicle are assessed for ride comfort analysis.

A vacuumed artificial mouth has been assembled and tested to measure reed velocity for a Bb clarinet along the width of the reed. Reed velocity measurements may be useful for better estimation of parameters in physical models, such as the relevant surface area of the vibrating reed. Use of a vacuum system instead of a pressurized mouth chamber allows straightforward observation and manipulation of the mouthpiece apparatus. Point measurements of reed velocity were obtained via a laser-Doppler vibrometer directed at the reed surface when artificially blown. Simultaneous high-speed exposures were recorded to visualize reed motion. Preliminary results indicate that the velocity amplitude of any torsional motion in the reed is negligible compared to an asymmetric reed velocity, likely caused by natural limitations of the clarinet ligature. Velocity measurements also indicate that the reed may sometimes rebound against the mouthpiece in its oscillatory period. High-speed exposures support this conclusion by vis...

An exact analytic solution of the unsteady Navier–Stokes equations is obtained for the flow caused by the non-coaxial rotations of a porous disk and a fluid at infinity. The porous disk is executing oscillations in its own plane with superimposed injection or suction. An increasing or decreasing velocity amplitude of the oscillating porous disk is also discussed. Further, it is shown that a combination of suction/injection and decreasing/increasing velocity amplitude is possible as well. In addition, the flow due to porous oscillating disk and a fluid at infinity rotating about an axis parallel to the z-axis is attempted as a second problem.

The influence of nonuniform transducer velocity distribution in the near-field echo formation scattered from a cavity in steel is analyzed. In the present study, the velocity amplitude on the transducer face was modeled using an offset error function. Using this distribution, the echo waveforms scattered from a cylinder cavity in steel were estimated and compared with the echo estimated using uniform distribution and echo observed experimentally. The estimation accuracy of the near-field echo waveforms were improved quantitatively.

We generalize the fluid flow problem of an oscillating flat plate (II. Stokes problem) in two directions. We discuss first the oscillating porous flat plate with superimposed blowing or suction. The second generalization is concerned with an increasing or decreasing velocity amplitude of the oscillating flat plate. Finally we show that a combination of both effects is possible as well.

We present photometry of 11 and spectroscopy of 35 potential cataclysmic variables from the Sloan Digital Sky Survey, the Catalina Real-Time Transient Survey and vsnet-alerts. The photometry results include quasi-periodic oscillations during the decline of V1363 Cyg, nightly accretion changes in the likely Polar (AM Herculis binary) SDSS J1344+20, eclipses in SDSS J2141+05 with an orbital period of 76+/-2 min, and possible eclipses in SDSS J2158+09 at an orbital period near 100 min. Time-resolved spectra reveal short orbital periods near 80 min for SDSS J0206+20, 85 min for SDSS J1502+33, and near 100 min for CSS J0015+26, RXS J0150+37, SDSS J1132+62, SDSS J2154+15 and SDSS J2158+09. The prominent HeII line and velocity amplitude of SDSS J2154+15 are consistent with a Polar nature for this object, while the lack of this line and a low velocity amplitude argue against this classification for RXS J0150+37. Single spectra of 10 objects were obtained near outburst and the rest near quiescence, confirming the dwarf novae nature of these objects., Comment: 34 pages, 14 figures, in press at AJ

Relations have been demonstrated between the preejection period (PEP) and indexes of left ventricular (LV) systolic function. Doppler tissue M-mode imaging has the capability to measure wall velocities and to display as colored strips within the walls velocity reversals representing changes in direction of wall motion. To document LV preejectional wall motions, this procedure was performed on 16 normal subjects with a twofold purpose: to measure septal and posterior preejectional intramyocardial velocities and durations and to correlate preejectional parameters with LV ejection fraction (LVEF). Parasternal M-mode images of simultaneously recorded walls were digitized. Subendocardial wall velocities were measured every 3.8 ms from the Q wave to the onset of ejection. Total duration measured from Doppler tissue and flow traces was compared in 10 subjects. PEP total duration did not differ between both walls or techniques. Several adjacent velocity reversals with mirror signs in opposite walls were substantiated by 2 to 5 colored strips. Colored strips corresponding to the same sign in each wall had a progressively damped velocity amplitude (septum 19 +/- 8, -21 +/- 10, 15 +/- 7, -8 +/- 5, 4 +/- 2 mm/s; posterior wall -13 +/- 16, 11 +/- 7, -8 +/- 5, 9 +/- 6, -2 mm/s). Peak velocity values of opposite signs significantly differed between both walls (p0.0001). Absolute values differed only for colored strips 2 and 3 (p0.009). Strip 2 featured a simultaneous early inward motion of both walls toward the LV cavity with significantly prolonged duration (p0.0001). The only positive correlation with LVEF was found for peak velocities of strip 2 in the posterior wall (r = 0.71, p0.006). Thus, the posterior wall and its inward motion velocities have potential for future clinical implications.

We investigate the influence of the solar atmospheric temperature stratification on the amplitude of waves at different heights and its dependence on frequency and wave number. Special interest is taken in the influence of atmospheric layers on the appearence of the recently observed p-mode crossing features and their location in the Fourier domain. We consider four stratification models. One of them is the standard model with convection-zone, VAL-atmosphere and corona. The others are modifications of this model in order to discuss the influence of specific layers of the atmosphere. The changes in the temperature structure significantly influence the velocity amplitude at certain frequency-wave number combinations at certain heights.

During cochlear implantation, hearing preservation is a concern. Minimizing disturbances to the cochlea and protection of the underlying endosteal membrane during the formation of a cochleostomy are considered important factors. The robotic micro-drill system tested in this article is the first example of an autonomous surgical drill successfully producing a cochleostomy, which keeps the underlying endosteal membrane intact. This study compares induced disturbances within the cochlea during formation of cochleostomy using the robotic micro-drill with that of conventional manual drilling. The disturbance of the endosteal membrane is measured using a Microscope Scanning Vibrometer at a third window, produced in the cochlea. Results show that the highest velocity amplitude measured was associated with manual drilling technique. The robotic micro-drill technique produced only about 1% of the peak velocity amplitude seen in manual drilling and exhibited much more uniform behaviour, while keeping the underlying membrane intact. The technique applied when using the robotic drill could be a major step in reducing the trauma to the cochlea, by reducing disturbance levels.

In this paper, the effects of arterial length on pulse wave propagation are presented to validate our fluid-structure interaction model. Three models, called the original, lengthened and shortened artery models, were obtained by changing arterial length. The results show that there is an obvious time delay between the velocity waveforms at two different locations in the original artery model, the same as the lengthened artery model. Furthermore, the velocity amplitude increases greatly in the two models. However the time delay cannot be seen clearly and the increase of the velocity amplitude is very small in the shortened artery model. There is a highest increase in the velocity amplitude of the lengthened artery model. The results indicate that arterial length plays an important role and give our model effective.

The increase of current bottom shear stress in the presence of waves are studied. It is found that the increment is mainly due to the near-bed wave orbkal velocity amplitude Aw and may be practically considered to be independent of the relative bed roughness k{2} / A and the angle Θ between the wave propagation and the current A semi-empirical model is presented to calculate the current bottom shear stress in the presence of waves and gives reasonable agreements with a wide range of presently available experimental data.

A specially designed apparatus was set up to provide a known fluctuating velocity field for the purpose of quantifying both the frequency and the amplitude responses of a hot-wire anemometer operating in the near-wall regions. Results of the experiments indicated that the marginally elevated hot-wire anemometer can respond faithfully to a fluctuating velocity field of up to 1600 Hz and a velocity amplitude variation of at least 20%. This, together with the simplicity in design and compactness in the set-up, provides an indication that an easy and viable means is available for further study into the dynamic response characteristic of a hot-wire anemometer positioned closed to the wall.

A theory is presented for time-dependent two-layer hydraulic flows through straits. The theory is used to study exchange flows forced by a periodic barotropic (tidal) flow. For a given strait geometry the resulting flow is a function of two nondimensional parameters, γ = (g′H)1/2T/L and qb0 = ub0/(g′H)1/2. Here g′, H, L, T, and ub0 are, respectively, the reduced gravity, strait depth and length scales, the forcing period, and the barotropic velocity amplitude; γ is a measure of the dynamic length of the strait and qb0 a measure of the forcing strength. Numerical solutions for both a pure contraction and an offset sill-narrows combination show that the exchange flow, averaged over a tidal cycle, increases with qb0 for a fixed γ. For fixed qb0 the exchange increases with increasing γ. The maximum exchange is obtained in the quasi-steady limit γ→∞. The minimum exchange is found for γ→0 and is equal to the unforced steady exchange. The usual concept of hydraulic control occurs only in these two limit...

With the development and expansion of traffic systems, problems associated with ground vibrations have required increased attention. Increasing vehicle loads,traffic volumes, and aging roads and railways,vibrations induced by traffic are gradually becoming acrucialproblem.Traffic induced vibrations have much smaller amplitude than those considered in seismic design, but may nevertheless cause annoyance for humans, damage to building, disturb sensitive equipment such as measurements devices, automated manufacturing in factories, etc. It is the purposeto study the effects of the in-filled trench (cell foamis usedas in-filled material in the test)as a wave barrieron the ground vibrationunder excitation of amechanicalvibrator(with an electric motor) in small scale laboratory tests. Laboratory methods are utilized for investigating the influence of cell foam on vibrations in sand by conducting vertical vibration tests with different thickness of cell foam.It is concluded that cell foam used as a wave barriermaterialis significantly working forhighfrequency rangeand for low frequency range the effect is not so effective and obvious.

The detection and characterization of the first transiting super-Earth, CoRoT-7 b, has required an unprecedented effort in terms of telescope time and analysis. Although the star does display a radial velocity signal at the period of the planet, this has been difficult to disentangle from the intrinsic stellar variability, and pinning down the velocity amplitude has been very challenging. As a result, the precise value of the mass of the planet - and even the extent to which it can be considered to be confirmed - have been debated in the recent literature, with six mass measurements published so far based on the same spectroscopic observations, ranging from about 2 to 8 Earth masses. Here we report on an independent validation of the planet discovery, using one of the fundamental properties of a transit signal: its achromaticity. We observed four transits of CoRoT-7 b with Spitzer, in order to determine whether the depth of the transit signal in the near-infrared is consistent with that observed in the CoRoT bandpass, as expected for a planet. We detected the transit and found an average depth of 0.426 {\pm} 0.115 mmag at 4.5 {\mu}m, which is in good agreement with the depth of 0.350 {\pm} 0.011 mmag found by CoRoT. These observations place important constraints on the kinds of astrophysical false positives that could mimic the signal. Combining this with additional constraints reported earlier, we performed an exhaustive exploration of possible blends scenarios for CoRoT-7 b using the BLENDER technique. We are able to rule out the vast majority of false positives, and the remaining ones are found to be much less likely than a true transiting planet. We thus validate CoRoT-7 b as a bona-fide planet with a very high degree of confidence, independently of any radial-velocity information. Our Spitzer observations have additionally allowed us to significantly improve the ephemeris of the planet., Comment: Accepted by ApJ

One of the key problems in the nonlinear theory of the hydrodynamic stability is to determine the law of the evolution of the disturbance velocity amplitude. The methods, which have been obtained, can only be used for quasi-neutral flow and have some artificial factors. In this paper, a method is proposed for this problem.

Strong tidal flows are observed in Cook Strait which separates the North and South Islands of New Zealand. The high velocities within the 30 km wide Strait result from a 140° phase difference in the M 2 tide between the ends of the Strait. Extraordinarily 135° of this phase difference occurs over just 40 km in the narrowest section of the Strait. Measurements from a ship mounted Acoustic Doppler Current Profiler (ADCP) over a single tidal cycle are used to determine the horizontal and vertical variation of tidal phase and amplitude in the Strait. Results show that tidal velocity amplitude ranges from 70 cm s −1 on the west of the Strait to 140 cm s −1 on the east. There was little amplitude variation over most of the water column. The eastern side of the Strait led the west by 20°. Near bottom velocity led surface velocity by approximately 10° due to the effect of bottom friction on the oscillating flow. Results from a subsequent 1 month deployment of ADCPs on the same line as the ship track are used to hindcast the semi-diurnal tide on the day of the shipboard measurements. The shipboard measured semi-diurnal tidal amplitude and phase agree extremely well with the hindcast composite of the three largest tidal constituents. Thus shipboard measurements over a single tidal cycle were able to accurately determine the horizontal and vertical variation of phase and amplitude of the semi-diurnal tide in Cook Strait.

In this paper, we propose a sensor for measuring the three-dimensional (3D) velocity vector of airflows. The sensor, which was a 10 mm spherical figure, had a laminated structure with three channels fabricated inside. The components of the airflow velocity vector were measured respectively by three piezo-resistive cantilevers fabricated in each of the three channels. Experiments with a wind tunnel demonstrated that our sensor can measure not only the velocity amplitude but the 3D velocity direction as well.

The use of both shunted piezoelectric elements and periodic arrays have been investigated independently as well as used in conjunction to modify the vibration of a system. Piezoelectric patches bonded to a cantilever beam which is shunted with an active circuit, specifically a negative capacitance shunt, can control broadband flexural vibrations of a structure. Also, periodic arrays integrated into a structure allow for modification of propagating waves through the mechanical ‘‘stop-bands’’. The performance of a combined shunted periodic piezoelectric patch array will be analyzed in this study by investigating the velocity amplitude of the beam upstream and downstream of the array section and the number of control elements in the array. The negative capacitance shunts caused a global spatial average velocity reduction of 5 dB at the modal peaks from 500 to 5000 Hz. The reduction is shown to be greater in the downstream section of the beam. Also, by increasing the number of patches in the array, the attenuation of the resonances increased non-linearly. The results show that a negative capacitance periodic control array is an effective global vibration reduction system and has the ability to localize energy near the forcing of a structure.

Magnitude-frequency relations are investigated for the on-land area, covered by the Tohoku University seismic network, northeastern Japan. We combine the Japan Meteorological Agency (JMA) catalog with the Tohoku University catalog for the crustal events. The suite for the upper plane events of the double-planed Wadati-Benioff zone, from 60 km through 100 km deep, is based on the Tohoku University catalog only. Completeness analyses of the catalog reveal that the crustal events and the upper plane events suite is complete down to magnitude 2.0 and 2.1, respectively. Including events only with magnitude above the completeness threshold, the magnitude-frequency relations are found to be nonlinear both for the crustal events slightly and the upper plane events strongly. Consistency between total seismic wave duration magnitudes and velocity amplitude magnitudes suggests that the magnitude scale in the catalog is nonbiased. The completeness analyses and the non-biased magnitude scale suggest that the nonlinear magnitude-frequency relations are not artificial but substantial features of the earthquake occurrence.

Measurements of the ultrasonic vibrational potentials (UVP) were performed at 815 kHz in agar and agarose gels as well as in several biological tissues from frog, rat and pig. The results for gels show that the magnitude of the UVP depends on the charge of the solid components of the gel, its mechanical strength and particularly on the concentration of free electrolytes present in the gel. The UVP decreases to less than 10 μV for a velocity amplitude of 1 cm/s if the salt concentrations exceed 10 −2 mol/L. The measurements in biological tissue in vitro demonstrate that the UVP are of the order of magnitude of μV s cm −1 which is also explained by the presence of electrolytes of high concentrations in tissues. The measurements in biological tissue in vitro demonstrate that the UVP are of the order of magnitude of μV s cm −1 which is also explained by the presence of electrolytes of high concentrations in tissues. Based on these experiments, it can be concluded that the potential for harm to humans due to electrical effects of ultrasound as used in medical diagnostics is very low.