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Relative variation of the particle volume fraction of the electronanofluidized bed as a function of the peak field strength E0 for different humidity conditions of the fluidizing air. Electric field oscillation frequency and superficial gas velocity are fixed to 20Hz and vg=2.7cm/s, respectively. In the case of the humidified air, the bed was previously subjected to a fixed superficial gas velocity vg=0.7cm/s for periods of time of 30min and 55min, respectively (indicated). ... Relative variation of the particle volume fraction of the electronanofluidized bed as a function of the field strength for three different waveform types. Top: Data is shown as a function of the peak field strength E0. Bottom: Data is shown as a function of the root-mean-squared field strength Erms (Erms=E0 for square wave, Erms=E0/2 for sine wave, Erms=E0/3 for triangular wave). Electric field oscillation frequency and superficial gas velocity are fixed to 20Hz and vg=2.7cm/s, respectively. The inset is a log–log plot of the data, where the solid line shows E2 behavior. ... Relative variation of the particle volume fraction of the electronanofluidized bed as a function of the superficial gas velocity. Electric field oscillation frequency and strength are fixed to 500Hz and E0=1.25kV/m (square wave), respectively. The lines are predicted curves by the model. Solid line: complex-agglomerate charge Q∗∗0=1.9×10−14C. Dotted line: Q∗∗0=1×10−14C. Dashed line: Q∗∗0=3×10−14C. ... Relative variation of the particle volume fraction of the electronanofluidized bed as a function of the oscillation frequency of the alternating electric field. Peak field strength is fixed to 1.25kV/cm. Data is shown for three different values of the superficial gas velocity vg (indicated). Inset: Photographs of the electronanofluidized bed at 1Hz (left) and 20Hz (right).
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Natural vibration frequency... The analysis of the quality of fluidization of the potato starch powder appears somewhat different from the FCC powder. Two examples of picture of the bed surface and the corresponding time series of the bed surface position and of the column displacement are reported in Figs. 6 and 7, for a fluidized bed of 1.155kg and vibration acceleration a/g=2.0. Also in this case air rate was kept constant close to the minimum for fluidization. At 20Hz (Video 3, Fig. 6a and b) the bed surface motion appears regular and smooth, and also in this case the amplitude of the bed surface oscillation appears always larger than the amplitude imparted to the bed. Time series reported in Fig. 7a with a significant phase lag are well described by a sinusoidal curve of the same frequency of that representing the column displacement. In this case the amplitude ratio is about 2.25. The phase lag between the bed surface and the column is significant and close to be in perfect opposition. At 18.5Hz the bed surface presents very large bed surface oscillations and visible corrugations as shown in Video 4, Fig. 6c and d. Differently from FCC, for potato starch these corrugations appear to move with the column and probably are the result of material sticking on the column wall. The presence of such corrugations makes the surface tracking more difficult. Local evaluation of surface motion produces bed height time series as those reported in Fig. 7b which show a non sinusoidal oscillatory motion. The average amplitude ratio increases up to about 5.5. The phase lag is close to half a cycle also at this frequency.... The quality of the effect of vibration on the surface oscillation of fluidized bed of FCC aeratable powder appears to be strongly affected by the frequency of the applied vibration. For example at 15Hz the surface of a 0.800kg FCC bed is always well defined and qualitatively appears as in Video 1, Figs. 3 and 4a, with changing surface height both with respect to the image (a fixed reference) and with respect to the column (displayed by the mark). The amplitude of the bed surface appears comparable with the column oscillation but with a different phase. Instead, the appearance of the same bed at 20Hz (Video 2, Fig. 4b, c and d) is completely different. At this frequency the amplitude of the surface is much larger than the column oscillation and the bed, close to the surface, does not appear any more a compact continuum. The material instead is thrown up at the highest surface level concentrated in sort of solid jets and then rains down apparently at a smaller velocity than that of the column (Fig. 4b). At this point a new rising surface within the bed starts to be visible. As it appears in the sequence of Fig. 4c and d, this surface becomes more and more evident as it meets the falling solids. It corresponds to the formation of a solid concentration front probably determined by a difference between the faster rising velocity of the particulate phase, caused by the column movement, and the falling velocity of the particulate phase, limited by the raining velocity of the particles. The corresponding time series of the bed height and of the column displacement are reported in Fig. 5, for a fluidized bed of 0.800kg recorded at conditions close to the minimum for fluidization and vibration acceleration a/g=1.0. At 15Hz (Fig. 5a) the time series confirm the direct observation of the bed surface. In fact, the bed surface motion appears regular and well described by a sinusoidal curve of the same frequency of that representing the column displacement. In this case the amplitude ratio is about 2.3. At 20Hz (Fig. 5b) instead the maximum amplitude ratio increases up to about 3.5 and, furthermore, the curve representing the bed surface time series is not a sinusoidal curve. As it appears in Fig. 4c and d, during the descending phase a secondary edge appears below the bed surface describing the formation of the second solid front described above. Correspondingly the curve of Fig. 5b representing the bed height shows multiple branching corresponding to the coexistence of two concentration fronts: an ascending front starting from inside the bed and a descending front stopping when it meets the other. In this and similar situations two values of the amplitude ratio were derived. One was evaluated as the difference between the maximum peak value and the minimum value of the descending branch curve and will be referred to as AR′. The other was evaluated as the difference between the maximum peak value and the minimum value of the ascending branch curve and will be referred to as AR″. The first of these amplitude ratios does not account for the overall surface oscillation but it can be evaluated more precisely than the other which, instead, is subject to higher uncertainty in the visualization of the initial phase of the rising concentration front. At all frequencies tested the bed and column oscillations do not appear to be in phase. Time series confirm this observation and indicate a larger phase difference at 20Hz (Fig. 5b) than at 15Hz (Fig. 5a).
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The experimental results of response frequency as a function of different velocities and for different plates fluttering motion. ... Response frequency of flow induced rotation versus vortex shedding frequency. ... Natural frequency... (a)Time series for the rotation of the hinged flat plate about the vertical axis submitted to a uniform current (Re=1.26×105), and (b) the respective frequency domain response.
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ECoG frequency alteration induced by a seizure and subsequent administration of midazolam in patient 1. Forty subdural electrodes on the left frontal lobe (33 on the lateral surface and 7 on the medial surface), 17 electrodes on the left parietal lobe (14 on the lateral surface and 3 on the medial surface), and 16 electrodes on the left temporal lobe (12 on the temporal neocortex and 4 on the medial temporal region) were included in further analyses. An electrographic seizure occurred in the epilepsy monitoring unit, when the patient had verbal communication with a physician. The seizure discharges (red arrows in [C] and [D]) were characterized by paroxysmal rhythmic discharges at alpha and sigma range, followed by rhythmic spike-and-wave discharges arising from the left superior frontal cortex overlying the tumor; the seizure discharge was slowly propagated to the adjacent left frontal neocortex. During this seizure event, the patient continued to communicate with the physician appropriately and denied having an epileptic seizure. Neither tremor nor clonic movement of the body was noted. Intravenous boluses of midazolam (0.1mg/kg) were given twice to abort the ongoing electrographic seizure and to reduce the risk of generalized tonic–clonic seizure. The seizure discharge lasted 10min. Quantitative assessment of ECoG amplitude spectra showed that the seizure discharge was initially characterized by focal augmentation of alpha and sigma amplitudes in the seizure focus followed by amplitude augmentation of widespread frequency bands as the seizure progressed. The seizure offset was characterized by sweep subsidence of amplitudes of all eight frequency bands but delta band in the seizure focus. The non-epileptic brain region distant from the seizure focus (i.e.: the inferior-frontal region, parietal lobe, temporal neocortex as well as the medial temporal lobe structure) showed gradual augmentation of sigma-oscillations (best shown by a blue arrowhead in [E]) with a waxing and waning pattern. [F–I] show z-score maps (standard deviation score maps) of ECoG spectral amplitudes. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) ... In-vivo animation of spectral amplitudes altered by a seizure and subsequent administration of midazolam in patient 2. An electrographic seizure was associated with augmentation of widespread frequency bands in the left medial temporal lobe region. The seizure offset was associated with subsidence of such amplitude augmentation in the left medial temporal lobe region. Following administration of midazolam, gradual sigma-augmentation was noted in the widespread region (including both medial temporal lobe structures) with a waxing and waning pattern. SD: standard deviation score also known as z-score. ... Gamma-oscillations... ECoG frequency alteration induced by a seizure and subsequent administration of midazolam in patient 2. Twenty-six subdural electrodes on the right frontal lobe, 15 electrodes on the right parietal lobe, 46 electrodes on the right temporal lobe (39 on the temporal neocortex and 7 on the medial temporal region), 8 electrodes on the right occipital lobe, and 10 electrodes on the left temporal lobe (4 on the temporal neocortex and 6 on the medial temporal region) were included in further analyses. An electrographic seizure occurred in the epilepsy monitoring unit, when the patient was asleep. The seizure discharges (denoted by a red arrow in [C]) were characterized by paroxysmal rhythmic discharges involving alpha and sigma bands, followed by rhythmic spike-and-wave discharges arising from the left medial temporal region; the seizure discharge was slowly propagated to the adjacent left temporal lobe region. During this seizure event, the patient did not show clinical changes. Neither tremor nor clonic movement of the body was noted. This seizure was considered as simple partial seizure, since no alteration of consciousness was noted when another electrographic seizure event showing a similar ECoG finding occurred during awake state. An intravenous bolus of midazolam (0.1mg/kg) was given in order to abort the ongoing electrographic seizure. The seizure discharge lasted 40s. Quantitative assessment of ECoG amplitude spectra showed that the seizure discharge was initially characterized by focal augmentation of alpha and sigma amplitudes in the seizure focus followed by amplitude augmentation of widespread frequency bands as the seizure progressed. Following the seizure offset, the non-epileptic brain region distant from the seizure focus showed gradual augmentation of sigma-oscillations (denoted by blue arrowheads in [D]) with a waxing and waning pattern. [E–G] show z-score maps (standard deviation score maps) of ECoG spectral amplitudes. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) ... ECoG frequency alteration induced by sedation using midazolam and subsequent general anesthesia induction in patient 3. Thirty-seven subdural electrodes on the left frontal lobe (31 on the lateral surface and 6 on the medial surface), 33 electrodes on the left parietal lobe (27 on the lateral surface and 6 on the medial surface), 26 electrodes on the left temporal lobe (20 on the temporal neocortex and 6 on the medial temporal region), 4 electrodes on the left medial occipital region, 7 electrodes on the right medial frontal region, 3 electrodes on the right medial parietal region, and 2 electrodes on the right medial occipital region were included in further analyses. An intravenous bolus of midazolam (0.03mg/kg) was given in order to provide sedation prior to induction of general anesthesia. Prior to the administration of propofol, significant augmentation of sigma amplitudes was noted in the left medial temporal region (denoted by blue arrowheads in [C]). Two and a half minutes after administration of midazolam, general anesthesia was induced using an intravenous bolus of propofol (2.5mg/kg); sweep reduction in the amplitudes of all eight frequency bands was noted in the entire electrode sites. Visual assessment of ECoG recording showed electrical silence lasting for 60s [D]. Subsequently, ECoG recording showed a burst-suppression pattern characterized by waxing and waning of ECoG amplitudes of all frequency bands (see Video S3). [E–G] show z-score maps (standard deviation score maps) of ECoG spectral amplitudes. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) ... In-vivo animation of spectral amplitudes altered by a seizure and subsequent administration of midazolam in patient 1. An electrographic seizure was associated with augmentation of widespread frequency bands (including the sigma band) in the left superior frontal region. Augmentation of low-frequency (32–64Hz), high-frequency (64–100Hz) and very high-frequency gamma-oscillations (100–200Hz) was noted in the presumed seizure focus in the left superior frontal gyrus. The seizure offset was associated with subsidence of such amplitude augmentation in the left superior frontal region. Following administration of midazolam, gradual sigma-augmentation was noted in the widespread region (including the medial temporal lobe structures) with a waxing and waning pattern. SD: standard deviation score also known as z-score.
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Out of phase oscillations... Detailed view of the mode amplitudes during the rotating oscillations for Model C. ... Initial growth of oscillations for Model C after an artificial perturbation was introduced at a simulation time of 1s. ... Detailed view of the mode amplitudes during the rotating oscillations for Model B. ... Progression of the radial power during the out-of-phase oscillations of the simulated turbine trip event for Model E. ... Parameters calculated for Model B during the stable limit cycle oscillations.
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A study of the plane Poiseuille flow of a micellar aqueous solution of cetylpyridinium chloride 100mM and sodium salicylate 60mM was performed in this work. The experiments were run at 27.5°C under controlled pressure using a transparent flow cell, where simultaneous measurements of transmitted light intensity, pressure drop and flow rate were performed in order to asses the flow stability. Particle image velocimetry (PIV) was also used to analyze the flow kinematics upstream of the contraction. Different regimes were observed in the flow curve, including shear banding and spurt. In the high shear rate branch the flow became unstable and was composed by asymmetric shear bands of structured and isotropic fluid, which oscillated with respect to the zero-shear stress plane. Symmetric lip vortices were observed to grow upstream of the contraction, and then to oscillate and decrease their average length under unstable flow. The shear bands downstream of the contraction oscillated in the same way as upstream vortices, with a frequency that increased along with the flow rate. Finally, the oscillating flow upstream of the contraction produced jets or spurts of highly oriented material followed by recoiling, akin to those reported in the melt fracture regime of polymers.
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(a) X and Y displacements of particle and the magnitude of the 3f current against the oscillation amplitude, with db=5.6μm and β=37.5°. (b) X and Y displacements of the particle and the phase of 3f current against oscillation amplitude, with db=5.6μm and β=37.5°. ... (a) 3f real and imaginary components of current with streptavidin-coated polystyrene microbeads show ‘wiggles’ resembling the oscillations in these components observed from modelling. (b) Magnitude of 3f current due to surface–particle interaction from model and experiment plotted as a functional of inferred QCM displacement. ... (a) Positions of minima of the potential before and after rotation by an angle β=37°. (b) Sliding of the particle on the oscillating surface (db=5μm and β=37°). ... (a) X and Y displacements for a single particle and the magnitude of 3f current against oscillation amplitude for 3000 particles with db=5.6μm (all averaged over various crystal orientations). (b) X and Y displacements for a single particle and the phase of 3f current against oscillation amplitude for 3000 particles with db=5.6μm (all averaged over various crystal orientations. ... (a) X and Y displacements of particle and the real component of the 3f current against the oscillation amplitude, with db=5.6μm and β=37.5°. (b) X and Y displacements of the particle and the imaginary component of 3f current against oscillation amplitude, with db=5.6μm and β=37.5°.
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Direct numerical simulation (DNS) of hydrogen–air turbulent swirling premixed flame in a cuboid combustor is conducted to investigate thermoacoustic instability and dynamic modes of turbulent swirling premixed flame in combustors. A detailed kinetic mechanism and temperature dependency of physical properties are considered in DNS. Two swirl number cases of 0.6 and 1.2 are investigated. Large-scale helical vortical structures are generated near the inlet of combustion chamber, and a lot of fine-scale vortices emerge downstream. Flame structure is engulfed by the vortical structures and depends largely on the swirl number. Spectral analysis of pressure oscillation on walls shows that quarter-wave mode of longitudinal acoustics has the largest energy, and that characteristic oscillations are found at higher frequencies. To investigate oscillation modes of pressure and heat release rate fields, dynamic mode decomposition (DMD) is applied to DNS results. It is shown that there are differences between dominant frequencies in spectral analysis of time-series pressure data at one point of walls and DMD of time-series pressure field data. DMD of pressure field reveals that the quarter-wave mode in longitudinal acoustics has the largest energy for the case of S=0.6. Furthermore, it is clarified that the transverse acoustic plane waves and pressure oscillations induced by large-scale vortical motions play important roles for the pressure oscillations in combustors. DMD of heat release rate field reveals that the DMD modes of pressure with high amplitude do not necessarily have coupling with fluctuations of heat release rate. Interactions between dynamic modes of pressure and heat release rate are also discussed.
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Inertial oscillations... Differential rotation rate of the sphere versus the amplitude of oscillations b (a) and the same dependency in the dimensionless form (b). The dashed line shows the dependence ΔΩ/Ωrot∼b2/R1δ obtained theoretically in the case of a cylindrical body in  [39]. ... The amplitude of the sphere oscillations with respect to the cavity shown on a photograph of the radially displaced sphere (a) and plotted versus rotation rate of the cavity for fluids of different viscosity (b).
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Dominant frequency... Computer modeling of ICl,vol effects on ventricular fibrillation (VF) dynamics. Wave dynamics in VF were simulated in two dimensions with the canine ventricular myocyte model plus insertion of ICl,vol. A: Snapshot of Vm. Note that a significantly larger spiral occupies most of the central region, where ICl,vol is higher. B: Typical examples of Vm oscillations in VF. Note that the trace from the dominant spiral shows high-frequency regular patterns of Vm oscillations (top trace). C: VF frequency map. Lines are drawn every 2 Hz. Darker colors indicate higher frequency. D: Frequency analysis of Vm. Note that the higher ICl,vol density in the center shows high VF frequencies substantially (6.2 ± 0.2 Hz vs 13.6 ± 0.1 Hz). A movie of transition from complex to stable rotor in the center is provided in the supplementary data (Simulation-VF-IClvol.mpg). ... Time-frequency distribution of ventricular fibrillation (VF) frequencies. Time-frequency domain (TFD) analysis was applied to the right ventricle (RV; left panels) and left ventricle (LV; right panels) to track the time-dependent changes in frequency distribution during iso-osmotic and hypo-osmotic conditions. Spectrograms (i.e., frequencies vs time) and power distributions are displayed as gray-scale maps, such that the darker the pixel, the higher the energy level. Under hypo-osmotic stress, VF frequencies increased gradually (∼20 minutes of hypo-osmotic perfusion) and then reached a stable level, especially in the LV (top and middle panels). Note that hypo-osmotic solution increased VF frequencies in both RV and LV, but LV had marked frequency changes compared with RV. Perfusion with 10 μM indanyloxyacetic acid-94 (IAA-94) first slowed VF frequencies (bottom panels), but then after 20 minutes VF terminated spontaneously (n = 7/9 hearts). ... Effect of hypo-osmotic solution on ventricular fibrillation (VF) frequencies. VF was induced by burst stimulation, and changes in VF frequencies were monitored under normal, hypo-osmotic, and ICl,vol inhibition using indanyloxyacetic acid-94 (IAA-94). Vm was recorded optically during a control VF (A), hypo-osmotic solution (B), and during VF after perfusion with 10 μM IAA-94 (C). In panel B, Vm oscillations were considerably more regular, and VF frequencies gradually shifted to a single high frequency. A movie file (experimental VF-Hypo-osmotic.mpg) in supplementary data depicts the high level of organization of VF in hypo-osmotic conditions. In panel C, inhibition of ICl,vol under hypo-osmotic conditions reversed the changes in VF dynamics. ... Spatial distribution of peak frequencies from TDF analysis. Distribution of ventricular fibrillation (VF) frequencies is represented as a three-dimensional volume plot. A: Orientation. B: Control perfusion. C: Hypo-osmotic perfusion. Here, VF frequencies are distributed in discrete regions with sharp boundary between left ventricle (LV) and right ventricle (RV). D: Perfusion with hypo-osmotic plus indanyloxyacetic acid-94 (IAA-94) resulted in substantially lower VF frequencies and reduced regional heterogeneities in frequency. ... Time-frequency domain analysis
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