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Cross-frequency coupling... Simulation results. Coupling portraits for simulated data for (A) clean (SNR=20dB) and (B) noisy cases (SNR=−10dB). PAC was generated to be at 60–80Hz (amplitude frequency) and 15Hz (phase frequency). The simulated signal contained also oscillations (at 20, 25, 30, 40 and 100Hz) having no coupling relation. These portraits show the mean PAC estimates over 100 repetitions for each method. Only methods robust enough were presented: direct PAC estimate, GLM with spurious term removed, MI with statistics and raw MI without statistics (ordered from left to right). Notice that the first two methods yield very similar outputs identifying PAC correctly and they are robust to both non-coupled oscillations and noise. ... Oscillations
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Conduction block and ventricular fibrillation vulnerability. A: Percentage of trials (a) initiating and (b) terminating ventricular fibrillation (VF) as a function of field frequency and strength. (c) Mean defibrillation threshold (DFT; red line) and upper limit of vulnerability (ULV; black line) as functions of frequency. Lines at the bottom of the plot indicate pairwise statistical significance. B: (a) Average loss of conduction power (LCP) values and (b) average conduction block (CB) size as a function of field strength and frequency. LCP standard errors are given in Table S2. Correlation between (C) average LCP or (D) average CB size and (a) the percentage of trials initiating VF or (b) the percentage of trials terminating VF. ... Surface and subsurface conduction block and ventricular fibrillation termination. (A) Percentage of simulations terminating ventricular fibrillation (VF), (B) average (a) surface and (b) subsurface loss of conduction power (LCP) values, and (C) average (a) surface and (b) subsurface conduction block (CB) size as a function of field frequency and strength. Correlation between (D) average LCP or (E) CB size on the surface (red) or the subsurface (blue) myocardium and the percentage of simulations terminating ventricular fibrillation (VF). ... Conduction block on the surface and subsurface myocardium during high frequency alternating current (HFAC) fields. (A) Successful and (B) failed termination of ventricular fibrillation (VF), following 15-V/cm and 10-V/cm HFAC fields, respectively. Spatial maps of loss of conduction power (LCP) on (left) the epicardial surface and (middle) a short-axis slice. (Right) Transmembrane potential (Vm) traces at sites a–e, shown in the spatial maps in image A, with the corresponding LCP values. Gray bar indicates time of the HFAC field. The time windows used for LCP analysis before and during the HFAC field are shown in red and blue, respectively. ... Successful and failed defibrillation following partial conduction block. (A) Successful and (B) failed defibrillation, following 10.7-V/cm and 9.2-V/cm high frequency alternating current (HFAC) fields, respectively. Top: Time-space plot, along the dashed line in the first panel of Figure 1B. Red regions in the plots indicate fully depolarized cells; deep blue indicates fully repolarized cells at rest. Propagating activations are denoted by white arrows. Bottom: Spatial map of loss of conduction power (LCP). ... Defibrillation by high frequency alternating current (HFAC) field. A: Anterior surface of the heart: left ventricle (LV), right ventricle (RV), and left anterior descending (LAD) artery. The optical mapped field of view is shown in the white box. B: Normalized transmembrane potential (Vm) maps before, during (gray backing), and after 200-Hz 300-ms HFAC field application. Red regions in the maps indicate fully depolarized cells; deep blue indicates fully repolarized cells at rest. C: Vm before, during, and after partial conduction block during the HFAC field. The time windows used for loss of conduction power (LCP) analysis before and during the HFAC field are shown in red and blue, respectively. Gray bar indicates the time of the HFAC field. D: Vm power spectrum before and during partial conduction block during the HFAC field. Sites a and c are close to the left and right field of view edges, respectively; site b is at the center of the field of the view, shown in image A. LCP values for each site are shown.
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3D representation of the frequencies of the active oscillation modes for all phases of the recorded collisions. Top view represents the dependence of the frequencies of the transverse mode, while front view the dependence of the horizontal mode frequencies on the frequency of the axisymmetric mode. ... Temporal variation of the axis ratio: (a) the virtual canting angle, and (b) the projected drop size (c) of the largest drop during collision. The collision process is divided in four phases: I: pre-collision phase; IIa: transverse oscillation and/or rotation phase including also the very short transient phase instantaneously after collision; IIb: damping phase; and IIc: phase with quiescent drop characteristics. (Details about the definitions of the phases are given in Section 4 Results and Discussion.) ... Raindrop oscillation
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Flow forces acting on an oscillating cylinder. ... Dimensionless (a) amplitude (A*=A/D) and (b) frequency (f*=fos/fna) of the crossflow oscillations versus the reduced velocity for a curved cylinder in the convex configuration (■) and a vertical cylinder (○). ... Flow visualizations in the wake of a curved cylinder for the fixed (a) convex and (b) concave configurations, and free-to-oscillate (c) convex and (d) concave configurations. Flow is from left to right. ... Dimensionless (a) amplitude (A*=A/D) and (b) frequency (f*=fos/fna) of the crossflow oscillations versus the reduced velocity for a curved cylinder in the concave configuration (▲) and a vertical cylinder (○).
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The effects of an ultrasonic wave (20kHz) on the dendritic microstructure of Sn–13at%Bi alloys were studied using time-resolved in situ X-ray imaging. Sequential images clearly showed the secondary effects such as the ultrasonic streaming and the oscillation with much lower frequency comparing to the ultrasonic vibration frequency. The ultrasonic wave caused a circulating convection, whose domain size was almost the same as the specimen size, and simultaneously periodic convection (40Hz), which was identified from the longitudinal oscillation of the dendrites. The fragmentation of the primary and secondary dendrite arms in the columnar zone was significantly enhanced under the ultrasonic wave. The secondary effects of the ultrasonic wave play a significant role for modifying the solidification structure.
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The trajectories of the diameter oscillation during the free vibration study for different viscosities. Notice that the subsequent amplitudes of the free vibration oscillation decrease for higher viscosities until the oscillations present are negligible, as in μ=64μref. ... The oscillations of the diameter during the free vibration study as a function of time. The diameter is measured as the distance between two symmetric points at the widest cross-section of the bell. ... The inverted Strouhal number (St−1) vs. driving frequency for several choices of force magnitude. St−1 was calculated using the maximum amplitude and forward velocity information taken from the driving frequency simulations. Although the best performing frequency is the recorded frequency of free vibration for small applied forces, the frequency that produces the largest deformations is shifted to lower force magnitudes as the force magnitude is increased. The different values of P show how the swimming speeds change in time as steady state is approached. ... Comparing the maximum amplitude of diameter oscillation for each of the driving frequencies, f, at different force magnitudes, FMag, during the pulse cycle P=5,10,15,20,25. The recorded frequency of free vibration is highlighted with the dotted red line. Notice that the frequency with the largest maximum amplitude is found for the largest force magnitude when f=.75s−1, which is slightly below the measured frequency of vibration. The different values of P show how the maximum amplitudes change in time as steady state is approached. (For interpretation of the references to color in this figure caption, the reader is referred to the web version of this paper.) ... A comparison of the 5th, 10th, and 15th propulsive cycles of the maximum amplitude of diameter oscillation during a driving force study with differing levels of μ. Notice that the peak frequency shifts lower frequencies as more fluid damping is added. Also note how the maximum amplitudes stay relatively fixed in more damped fluid environments.
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High frequency... High frequency two-phase oscillations powered by bubble growth/collapse processes at a heat flux of 100W/cm2 for a mass flux of 400kg/m2s. ... Self-sustained two-phase oscillation
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In this figure we report as a function of optical depth the computed frequencies, center of mass (γ0), amplitudes and phases derived from the fit of velocities for each of the selected lines. Meaning of the symbols is: circles (red) carbon lines, stars (magenta) silicon lines, triangles (blues) oxygen lines and boxes (green) nitrogen lines. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) ... Pulsations, oscillations, and stellar seismology
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(a) Time history of non-dimensional flame stand-off distance for a single oscillation cycle for non-responsive (unpulsed and 200Hz), responsive (80Hz, 100Hz and 120Hz) and transition (125Hz) frequencies. Yellow bands indicate the amplitude of Rf fluctuations (b) frequency spectra of Rf fluctuations at unpulsed and 100Hz excitation. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) ... (a) Time-resolved dynamic flame behavior in a single oscillation cycle showing three distinct flame states at 100Hz pulsing and (b) 2D flame image sequences at the non-responsive 200Hz pulsing and 125Hz transition mode. ... Dimensionless RMS flame stand-off distance fluctuations as a function of forcing frequency (fP). Normalization parameter is the average Rf magnitude in unexcited case. ... Normalized rms velocity variation with forcing frequency at front stagnation point of the droplet under isothermal conditions. ... (a) Temporal variation of flame stand-off distance (Rf) (b) Time-dependent fluctuations in non-dimensional flame area (Af/Af avg, 0Hz) in a single 14Hz oscillation cycle.
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The same as Fig. 17, but for a monochromatic wave excitation of frequency f2=0.2Hz and amplitude A2=0.50m. ... Oscillating water column... The same as Fig. 18, but for a monochromatic wave excitation of frequency f2=0.2Hz and amplitude A2=0.50m. ... The same as Fig. 22, but for a monochromatic wave excitation of frequency f2=0.2Hz and amplitude A2=0.50m. ... The same as Fig. 3, but for different constant frequency, i.e., f2=0.05Hz. ... Frequency-amplitude domain... Maximum dynamic pressure, max(pD(t;Aexc,Texc)), against (mean wave elevation) oscillation's amplitude Aexc.
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