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Journal articles on the topic 'Frequency of oscillation'
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1
DANA, SYAMAL KUMAR, and SATYABRATA CHAKRABORTY. "GENERATION OF HOMOCLINIC OSCILLATION IN THE PHASE SYNCHRONIZATION REGIME IN COUPLED CHUA'S OSCILLATORS." International Journal of Bifurcation and Chaos 14, no. 04 (April 2004): 1375–83. http://dx.doi.org/10.1142/s0218127404009958.
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An experimental method for generating homoclinic oscillations using two nonidentical Chua's oscillators coupled in unidirectional mode is described here. A homoclinic oscillation is obtained at the response oscillator in the weaker coupling limit of phase synchronization. Different phase locking phenomena of homoclinic oscillations with external periodic pulse have been observed when the frequency of the pulse is close to the natural frequency of the homoclinic oscillation or its subharmonics.
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Mureşan, Raul C., Ovidiu F. Jurjuţ, Vasile V. Moca, Wolf Singer, and Danko Nikolić. "The Oscillation Score: An Efficient Method for Estimating Oscillation Strength in Neuronal Activity." Journal of Neurophysiology 99, no. 3 (March 2008): 1333–53. http://dx.doi.org/10.1152/jn.00772.2007.
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We present a method that estimates the strength of neuronal oscillations at the cellular level, relying on autocorrelation histograms computed on spike trains. The method delivers a number, termed oscillation score, that estimates the degree to which a neuron is oscillating in a given frequency band. Moreover, it can also reliably identify the oscillation frequency and strength in the given band, independently of the oscillation in other frequency bands, and thus it can handle superimposed oscillations on multiple scales ( theta, alpha, beta, gamma, etc.). The method is relatively simple and fast. It can cope with a low number of spikes, converging exponentially fast with the number of spikes, to a stable estimation of the oscillation strength. It thus lends itself to the analysis of spike-sorted single-unit activity from electrophysiological recordings. We show that the method performs well on experimental data recorded from cat visual cortex and also compares favorably to other methods. In addition, we provide a measure, termed confidence score, that determines the stability of the oscillation score estimate over trials.
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HIROKI, Fujio, Keijiro YAMAMOTO, and Taiji MASUDA. "Oscillation Frequency of Supersonic Fluidic Oscillator." Transactions of the Society of Instrument and Control Engineers 28, no. 3 (1992): 358–65. http://dx.doi.org/10.9746/sicetr1965.28.358.
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SHUTTLEWORTH, Trevor J., and Jill L. THOMPSON. "Ca2+ entry modulates oscillation frequency by triggering Ca2+ release." Biochemical Journal 313, no. 3 (February 1, 1996): 815–19. http://dx.doi.org/10.1042/bj3130815.
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As in many cells, the frequency of agonist-induced cytosolic Ca2+ concentration ([Ca2+]i) oscillations in exocrine avian nasal gland cells is dependent on the rate of Ca2+ entry. Experiments reveal that the initiation of each oscillatory spike is independent of the relative fullness of the stores and, furthermore, the oscillating pool is normally fully refilled by the end of each [Ca2+]i spike. Therefore, contrary to current models, the interspike interval (which essentially sets the frequency) does not reflect the time taken to recharge the oscillating stores. Instead, the data show that it is the previously demonstrated role that Ca2+ entry plays in triggering the repetitive release of Ca2+ from the oscillating stores, rather than the recharging of those stores, that provides the basis for the observed effects of Ca2+ entry rate on oscillation frequency.
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Bao, Weili, and Jian-Young Wu. "Propagating Wave and Irregular Dynamics: Spatiotemporal Patterns of Cholinergic Theta Oscillations in Neocortex In Vitro." Journal of Neurophysiology 90, no. 1 (July 2003): 333–41. http://dx.doi.org/10.1152/jn.00715.2002.
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Neocortical “theta” oscillation (5–12 Hz) has been observed in animals and human subjects but little is known about how the oscillation is organized in the cortical intrinsic networks. Here we use voltage-sensitive dye and optical imaging to study a carbachol/bicuculline induced theta (∼8 Hz) oscillation in rat neocortical slices. The imaging has large signal-to-noise ratio, allowing us to map the phase distribution over the neocortical tissue during the oscillation. The oscillation was organized as spontaneous epochs and each epoch was composed of a “first spike,” a “regular” period (with relatively stable frequency and amplitude), and an “irregular” period (with variable frequency and amplitude) of oscillations. During each cycle of the regular oscillation, one wave of activation propagated horizontally (parallel to the cortical lamina) across the cortical section at a velocity of ∼50 mm/s. Vertically the activity was synchronized through all cortical layers. This pattern of one propagating wave associated with one oscillation cycle was seen during all the regular cycles. The oscillation frequency varied noticeably at two neighboring horizontal locations (330 μm apart), suggesting that the oscillation is locally organized and each local oscillator is about ≤300 μm wide horizontally. During irregular oscillations, the spatiotemporal patterns were complex and sometimes the vertical synchronization decomposed, suggesting a de-coupling among local oscillators. Our data suggested that neocortical theta oscillation is sustained by multiple local oscillators. The coupling regime among the oscillators may determine the spatiotemporal pattern and switching between propagating waves and irregular patterns.
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Беляев, М. А., and А. А. Величко. "Исследование динамических пороговых характеристик VO-=SUB=-2-=/SUB=--переключателя в осцилляторном контуре." Письма в журнал технической физики 46, no. 3 (2020): 38. http://dx.doi.org/10.21883/pjtf.2020.03.48991.17890.
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This paper investigates the dependence of the dynamic threshold characteristics of a VO2-switch on the oscillation frequency of a self-oscillating circuit. A transitional oscillation regime related to the self-heating of the substrate is discovered. Proposed analytical formulas allow consider these regularities and having practical significance in designing oscillator neural networks based on VO2-switches.
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Potkonjak, N., Lj Kolar-Anić, T. Potkonjak, S. Nikola Blagojević, and S. Anić. "Oscillatory Phenomena during Anodic Copper Electrodissolution in Trifluoroacetic Acid Solution." Materials Science Forum 518 (July 2006): 301–6. http://dx.doi.org/10.4028/www.scientific.net/msf.518.301.
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This work presents the current oscillation phenomena observed in an electrochemical Cu/0.5 M CF3COOH system. The dynamical response of this new oscillator was followed by both current density-potential (j-E) and current density-time (j-t) curves. The current oscillation phenomena of the investigated system were monitored over various potential scan rates and constant applied potentials as control parameters. The increase of potential scan rate significantly decreases both the potential range of current oscillations and the frequency of oscillations. At the j-t curves both the simple and the complex (period adding) oscillations were found. Moreover, with the increase of applied potential, the increase of period of oscillations and current oscillation amplitudes were observed. It appears that the period of current oscillations exponentially grows with applied potential.
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Leontini, Justin S., David Lo Jacono, and Mark C. Thompson. "A numerical study of an inline oscillating cylinder in a free stream." Journal of Fluid Mechanics 688 (November 3, 2011): 551–68. http://dx.doi.org/10.1017/jfm.2011.403.
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AbstractSimulations of a cylinder undergoing externally controlled sinusoidal oscillations in the free stream direction have been performed. The frequency of oscillation was kept equal to the vortex shedding frequency from a fixed cylinder, while the amplitude of oscillation was varied, and the response of the flow measured. With varying amplitude, a rich series of dynamic responses was recorded. With increasing amplitude, these states included wakes similar to the Kármán vortex street, quasiperiodic oscillations interleaved with regions of synchronized periodicity (periodic on multiple oscillation cycles), a period-doubled state and chaotic oscillations. It is hypothesized that, for low to moderate amplitudes, the wake dynamics are controlled by vortex shedding at a global frequency, modified by the oscillation. This vortex shedding is frequency modulated by the driven oscillation and amplitude modulated by vortex interaction. Data are presented to support this hypothesis.
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Hehner, Marc T., Davide Gatti, Marios Kotsonis, and Jochen Kriegseis. "Effects of actuation mode on plasma-induced spanwise flow oscillations." Journal of Physics D: Applied Physics 55, no. 20 (February 22, 2022): 205203. http://dx.doi.org/10.1088/1361-6463/ac526b.
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Abstract Two different plasma actuation strategies for producing near-wall flow oscillations, namely the burst-modulation and beat-frequency mode, are characterized with planar particle image velocimetry in quiescent air. Both concepts are anticipated to work as non-mechanical surrogates of oscillating walls aimed at turbulent flow drag reduction, with the added benefit of no moving parts, as the fluid is purely manipulated by plasma-generated body forces. The current work builds upon established flow-control and proof-of-concept demonstrators, as such, delivering an in-depth characterization of cause and impact of the plasma-induced flow oscillations. Various operational parameter combinations (oscillation frequency, duty cycle and input body force) are investigated. A universal performance diagram that is valid for plasma-based oscillations, independent of the actuation concept is derived. Results show that selected combinations of body force application methods suffice to reproduce oscillating wall dynamics from experimental data. Accordingly, the outcomes of this work can be exploited to create enhanced actuation models for numerical simulations of plasma-induced flow oscillations, by considering the body force as a function of the oscillation phase. Furthermore, as an advantage over physically displaced walls, the exerted body force appears not to be hampered by resonances and therefore remains constant independent of the oscillation frequency. Hence, the effects of individual parameter changes on the plasma actuator performance and fluid response as well as strategies to avoid undesired effects can be determined.
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Bergadà, Josep M., Masoud Baghaei, Bhanu Prakash, and Fernando Mellibovsky. "Fluidic Oscillators, Feedback Channel Effect under Compressible Flow Conditions." Sensors 21, no. 17 (August 27, 2021): 5768. http://dx.doi.org/10.3390/s21175768.
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Fluidic oscillators are often used to modify the forces fluid generates on any given bluff body; they can also be used as flow, pressure or acoustic sensors, with each application requiring a particular oscillator configuration. Regarding the fluidic oscillators’ main performance, a problem which is not yet clarified is the understanding of the feedback channel effect on the oscillator outlet mass flow frequency and amplitude, especially under compressible flow conditions. In order to bring light to this point, a set of three-dimensional Direct Numerical Simulations under compressible flow conditions are introduced in the present paper; four different feedback channel lengths and two inlet Reynolds numbers Re = 12,410 and Re = 18,617 are considered. From the results obtained, it is observed that as the inlet velocity increases, the fluidic oscillator outlet mass flow frequency and amplitude increase. An increase of the feedback channel length decreases the outlet mass flow oscillating frequency. At large feedback channel lengths, the former main oscillation tends to disappear, the jet inside the mixing chamber simply fluctuates at high frequencies. Once the Feedback Channel (FC) length exceeds a certain threshold, the oscillation stops. Under all conditions studied, pressure waves are observed to be traveling along the feedback channels, their origin and interaction with the jet entering the mixing chamber are thoroughly evaluated. The paper proves that jet oscillations are pressure-driven.
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Liang, Yan, Zeng Fu Zhang, Wen Liang Chen, and Ke Xin Xu. "Study of the Composite Oscillator of Particulate Monitoring Instrument Based on TEOM." Applied Mechanics and Materials 678 (October 2014): 274–80. http://dx.doi.org/10.4028/www.scientific.net/amm.678.274.
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The effects of atmospheric particulates were more prominent in recent years, so accurate monitoring of particulate matter was a problem needed to resolve. In the existing particulate monitoring instrument based on the principle of Tapered Element Oscillating Microbalance method (TEOM),the particle concentration detection system was tapered quartz tube simple harmonic oscillator. Due to the oscillator relying mainly on analog circuit closed-loop self-excitation oscillator to drive, loop resonance frequency, oscillation stability and Q value was greatly influenced by the oscillator physical characteristics and the interference of mechanical structure and circuit design parameters. And oscillation frequency must be read by the digital circuit frequency detection system, then figured out the corresponding quality. In this paper, we studied a kind of composite oscillator tube which can overcome the lack of stability in the existing technology and reduce the impact of coexistence at the same time of digital circuit and analog circuit. And oscillator frequency step precision raised almost an order of magnitude compared with the national standard detection accuracy of 10ug.
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Fisher, C. E., and K. S. Ball. "Plume Dynamics in Natural Convection in a Horizontal Cylindrical Annulus." Journal of Heat Transfer 121, no. 3 (August 1, 1999): 598–602. http://dx.doi.org/10.1115/1.2826021.
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Measurements of the unsteady temperature fluctuations in the plume region between differentially heated horizontal concentric cylinders are reported. In particular, power spectral density estimates of the temperature fluctuations within the plume show the development and breakdown of the oscillatory plume structure at high Rayleigh number, Rad, by two relatively independent processes: (1) the development of harmonic oscillations related to the dominant plume oscillation frequency, and (2) interactions between the oscillating plume and the adjacent relatively stagnant core flow (shear and entrainment). The harmonic oscillations are shown to be the dominant energy transfer mode at moderate Rad (up to Rad = 108), acting to disperse the plume energy without generating a broadband spectrum. The spectral density estimates show that while a distinct plume oscillation is still present near the inner cylinder at Rad = 109, the plume becomes increasingly turbulent as the outer cylinder is approached. A new correlation for the plume oscillation frequency, which is found to be proportional to Rad0.5, is also presented.
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Tu, Lian, Di Chen Liu, Qing Fen Liao, Fei Fei Dong, Xing Pei Ji, Chun Li Song, and Zhen Shan Zhu. "Distinction of the Property of Low Frequency Oscillation Based on ARMA Mode Identification." Applied Mechanics and Materials 336-338 (July 2013): 1086–91. http://dx.doi.org/10.4028/www.scientific.net/amm.336-338.1086.
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Aiming at how to solve the question of quantitatively distinguish negative damping low frequency oscillation and forced power oscillation, the difference in frequency and damping ratio between the two kinds of oscillations have been discovered through mechanism analysis, and a new quantitative distinction criterion for the property of the low frequency is proposed. The oscillation data is windowing identified by ARMA model based on weighted recursive least squares algorithm dynamically, and low frequency type can be distinguished according to the changes of oscillation frequency and damping ratio during the oscillation. The simulative results have shown that the method is feasible and effective.
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Wang, Wei, Kaiming Yang, and Yu Zhu. "Optimal Frequency and Amplitude of Vertical Viewpoint Oscillation for Improving Vection Strength and Reducing Neural Constrains on Gait." Entropy 23, no. 5 (April 28, 2021): 541. http://dx.doi.org/10.3390/e23050541.
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Inducing self-motion illusions referred as vection are critical for improving the sensation of walking in virtual environments (VE). Adding viewpoint oscillations to a constant forward velocity in VE is effective for improving vection strength under static conditions. However, the effects of oscillation frequency and amplitude on vection strength under treadmill walking conditions are still unclear. Besides, due to the visuomotor entrainment mechanism, these visual oscillations would affect gait patterns and be detrimental for achieving natural walking if not properly designed. This study was aimed at determining the optimal frequency and amplitude of vertical viewpoint oscillations for improving vection strength and reducing gait constraints. Seven subjects walked on a treadmill while watching a visual scene. The visual scene presented a constant forward velocity equal to the treadmill velocity with different vertical viewpoint oscillations added. Five oscillation patterns with different combinations of frequency and amplitude were tested. Subjects gave verbal ratings of vection strength. The mediolateral (M-L) center of pressure (CoP) complexity was calculated to indicate gait constraints. After the experiment, subjects were asked to give the best and the worst oscillation pattern based on their walking experience. The oscillation frequency and amplitude had strong positive correlations with vection strength. The M-L CoP complexity was reduced under oscillations with low frequency. The medium oscillation amplitude had greater M-L CoP complexity than the small and large amplitude. Besides, subjects preferred those oscillation patterns with large gait complexity. We suggested that the oscillation amplitude with largest M-L CoP complexity should first be chosen to reduce gait constraints. Then, increasing the oscillation frequency to improve vection strength until individual preference or the boundary of motion sickness. These findings provide important guidelines to promote the sensation of natural walking in VE.
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Shibahashi, Hiromoto, and Masao Takata. "Theory of The Oblique Pulsator Model For The Rapidly Oscillating Ap Stars." International Astronomical Union Colloquium 137 (1993): 563–65. http://dx.doi.org/10.1017/s0252921100018455.
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AbstractRecently, one of the rapidly oscillating Ap stars, HR 3831, has been found to have an equally split frequency septuplet, though its oscillation seems to be essentially an axisymmetric dipole mode with respect to the magnetic axis which is oblique to the rotation axis (Kurtz et al. 1992; Kurtz 1992). In order to explain this fine structure, we investigate oscillations of rotating magnetic stars by taking account of the perturbations due to the magnetic fields and the rotation. We show that the magnetic field on axisymmetric dipole modes distorts the dipole oscillation pattern to have axisymmetric octapole components so that the frequency pattern becomes a septuplet rather than a triplet, and that the additional effect of the rotation leads the frequency pattern to be asymmetric. The formula allows us to get information about the magnetic fields, the rotation, and the geometrical configuration of the star from the oscillation data.
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Szakáll, Miklós, Karoline Diehl, Subir K. Mitra, and Stephan Borrmann. "A Wind Tunnel Study on the Shape, Oscillation, and Internal Circulation of Large Raindrops with Sizes between 2.5 and 7.5 mm." Journal of the Atmospheric Sciences 66, no. 3 (March 1, 2009): 755–65. http://dx.doi.org/10.1175/2008jas2777.1.
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Abstract Precipitation prediction using weather radars requires detailed knowledge of the shape parameters of raindrops falling at their terminal velocities in air. Because the raindrops undergo oscillation, the most important shape parameters from the radar prediction point of view are the equilibrium drop shape, the time-averaged axis ratio, and the oscillation frequency. These parameters for individual water drops with equivalent diameter from 2.5 to 7.5 mm were investigated in a vertical wind tunnel using high-speed video imaging. A very good agreement was found between the measured and the theoretically determined raindrop shape calculated by a force balance model. A new method was developed to determine the equivalent drop diameter with the help of the oscillation frequency. The drop size determination by means of the frequency method was found to be three times more precise than by volumetric methods. The time-averaged axis ratio was found to be equal to the equilibrium axis ratio in the investigated raindrop size range. The analysis of the oscillation frequency of the raindrops revealed that the drops undergo multimode oscillations and are oscillating in a transverse mode in addition to an axisymmetric oblate–prolate mode. Experiments are included in which the internal circulation associated with drop oscillation was investigated and compared to theory.
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Capogrossi, M. C., and E. G. Lakatta. "Frequency modulation and synchronization of spontaneous oscillations in cardiac cells." American Journal of Physiology-Heart and Circulatory Physiology 248, no. 3 (March 1, 1985): H412—H418. http://dx.doi.org/10.1152/ajpheart.1985.248.3.h412.
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Both intact mammalian cardiac muscle and single adult Ca2+-tolerant myocytes, under appropriate experimental conditions, exhibit periodic, spontaneous myofilament oscillations that originate locally within a cell and propagate longitudinally as contractile waves. We have used microscopic imaging techniques to study the effect of electrical stimulation on the oscillation characteristics in single rat and rabbit myocytes. Unstimulated rat cells bathed in Cao of 1-3 mM exhibited these oscillations. During stimulation at rates between 6 and 120 min-1, oscillations did not occur in the interval between stimulated contractions, and following termination of stimulation a transient suppression of the spontaneous oscillation frequency occurred. Conversely, with higher cell Ca2+ loading, achieved by increasing the [Ca2+]o or by addition of isoproterenol or ouabain, stimulation caused de novo oscillations in rabbit cells and increased the spontaneous oscillation frequency in rat cells to levels that resulted in their appearance between stimulated contractions. The tendency for myofilament motion to occur simultaneously at multiple foci was also increased by stimulation at high frequencies, and partial synchronization of these foci resulted in oscillations of an increased amplitude. The modulation of the spontaneous oscillation characteristics in single cells by stimulation may explain, in part, some effects of stimulation on Ca2+-dependent oscillatory phenomena in intact cardiac tissues.
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Kornyushin, Y. "Plasma oscillations in porous samples." Science of Sintering 36, no. 1 (2004): 43–50. http://dx.doi.org/10.2298/sos0401043k.
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The influence of the shape of a sample on the type of uniform dipole collective electrons oscillations is discussed. In samples of a bulk shape uniform bulk dipole oscillations cannot exist. They exist in samples of a thin slab shape only. However in essentially porous materials the electrostatic energy of the oscillation in a sample is considerably larger thus leading to stronger restoring force and higher frequency of the oscillation. When this frequency exceeds the Langmuir frequency, the oscillation becomes of a bulk type. .
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Chu, Zhaobi, Yan Wang, Min Zhu, Xueping Dong, and Hua Li. "A Robust Online Identification of Sustained Low Frequency Oscillation in Steady-State Power Systems." Mathematical Problems in Engineering 2019 (June 10, 2019): 1–9. http://dx.doi.org/10.1155/2019/8435838.
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For sustained low frequency oscillations in steady-state power systems, an algorithm is proposed for precise online identification of oscillation frequency, oscillation amplitude, and fundamental amplitude. The algorithm consists of a robust low frequency estimator and a notch filter in parallel. The asymptotical convergence property is analyzed by slow integral manifold, averaging method, and Lyapunov stability theorem sequentially. The steady-state antinoise property is investigated by perturbed system theorem. The robust advantages of the proposed algorithm are embodied in the following aspects: the fundamental amplitude identification is little influenced by oscillation frequency and oscillation amplitude, both oscillation frequency identification and oscillation amplitude identification have small steady-state errors under high order harmonics or bounded noises, the ramp variations of both fundamental amplitude and oscillation amplitude are also significantly tracked, and three design parameters have different effects on identification performance of oscillation frequency, oscillation amplitude, and fundamental amplitude, respectively. Simulation results verify the validity.
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Wang, JianGang, YaLi Wang, FangLi Guo, ZhiBo Feng, XiangFang Wang, and ChengBiao Lu. "Nicotinic modulation of Ca2+ oscillations in rat cortical neurons in vitro." American Journal of Physiology-Cell Physiology 310, no. 9 (May 1, 2016): C748—C754. http://dx.doi.org/10.1152/ajpcell.00197.2015.
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The roles of nicotine on Ca2+ oscillations [intracellular Ca2+ ([Ca2+]i) oscillation] in rat primary cultured cortical neurons were studied. The spontaneous [Ca2+]i oscillations (SCO) were recorded in a portion of the neurons (65%) cultured for 7–10 days in vitro. Application of nicotine enhanced [Ca2+]i oscillation frequency and amplitude, which were reduced by the selective α4β2-nicotinic acetylcholine receptors (nAChRs) antagonist dihydro-β-erythroidine (DHβE) hydrobromide, and the selective α7-nAChRs antagonist methyllycaconitine citrate (MLA, 20 nM). DHβE reduced SCO frequency and prevented the nicotinic increase in the frequency. DHβE somewhat enhanced SCO amplitude and prevented nicotinic increase in the amplitude. MLA (20 nM) itself reduced SCO frequency without affecting the amplitude but blocked nicotinic increase in [Ca2+]i oscillation frequency and amplitude. Furthermore, coadministration of both α4β2- and α7-nAChRs antagonists completely prevented nicotinic increment in [Ca2+]i oscillation frequency and amplitude. Thus, our results indicate that both α4β2- and α7-nAChRs mediated nicotine-induced [Ca2+]i oscillations, and two nAChR subtypes differentially regulated SCO.
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Eliseev, V. І., S. А. Shevchenko, A. P. Tolstopyat, L. A. Fleer, and А. Р. Shevchenko. "Dynamics of oscillations of the "liquid bath - lance" system during injection processing of the melt in the ledle." Fundamental and applied problems of ferrous metallurgy, no. 34 (2020): 90–100. http://dx.doi.org/10.52150/2522-9117-2020-34-90-100.
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The aim of the study was to evaluate the influence of key waveform factors on the dynamics of the process during injection molding of cast iron with granular magnesium in ladles, their significance and relationship between them. Based on the theories of wave motion of liquid layers, a mathematical model has been developed that allows to investigate the oscillatory processes in the ladle during the processing of cast iron melt with granular magnesium. The model involved the processing of cast iron by injection of granular magnesium through the tuyeres of devices that are immersed in the melt. The oscillating system "Liquid bath - lance" is considered on the example of the bath of a heavy - duty filling bucket with its own frequency - 0.47 Hz. The influence of the most probable oscillation sources (natural frequency of the lance oscillation and the frequency of the conditional source) on the amplitude-frequency oscillations of the system elements is calculated. It is established that in addition to the natural frequencies of these elements, the system has two more natural oscillations. Given that the mass of the melt is much greater than the mass of the lance, it practically determines the behavior of the system during its excitation. That is, the system responds only to those excitations in which the frequency is close to the natural frequency of the liquid bath. In turn, it is shown that the natural frequency of the bath is largely determined by its diameter at the top. In practice, it is necessary to know the resonant frequencies of the liquid bath, the tuyere device, as well as all other sources of oscillations (gas jet decay, and oscillations of pop-up bubbles). Accordingly, it is necessary to try to dampen the amplitude with this dangerous resonant frequency. To reduce the oscillation amplitude of the bath surface when treating cast iron with granular magnesium, it is recommended to first estimate the natural resonant frequency of the liquid bath, and then select design solutions and processing parameters, avoiding dangerous frequencies close to the natural frequency of the bath. However, it should be noted that the spectrum of oscillation frequencies in the purl zone is quite wide and, of course, contains dangerous low frequencies.
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Shao, Zhu Lei. "Design of CMOS Sawtooth Wave Oscillator for Switching Power Supply." Advanced Materials Research 960-961 (June 2014): 1268–71. http://dx.doi.org/10.4028/www.scientific.net/amr.960-961.1268.
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Based on the CMOS technology, the sawtooth wave oscillator used in switching power supply is designed. In the condition of 27 °C and 4 V power supply voltage, the oscillation frequency of sawtooth wave oscillator is 246.61 KHz. The oscillation frequency of sawtooth wave oscillator changes between 245.94 KHz and 247.89 KHz when the power supply voltage changes between 3V and 6V. The maximum deviation is ±0.52%. From the experimental results, the sawtooth wave oscillator has good linearity, the effect of temperature and power supply to the oscillation frequency of sawtooth wave oscillator is very little. The CMOS sawtooth wave oscillator is suitable for switching power supply.
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Iudin, Arkadii V., and Viktor S. Shestakov. "Analysis of connections and restrictions occurring due to the oscillations of vibrating screen working member and cantilevered screen deck." Izvestiya vysshikh uchebnykh zavedenii Gornyi zhurnal, no. 1 (February 17, 2020): 97–104. http://dx.doi.org/10.21440/0536-1028-2020-1-97-104.
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Research relevance is due to the need of mining companies in a more complete extraction of mineral resources, reduction of crude minerals losses, and extension of deposits’ life. Some enterprises face the problem of complicated high-quality separation of hard-to-screen rock mass. Screen which are common in the industry often become clogged causing decline in the effectiveness of screening. Research aim is to determine the links, build resonant curves and analyze the amplitude oscillations of the working member and cantilevered bars of the screen deck using numerical simulation. Methodology includes the theoretical study of the dual mass oscillatory system with the use of numerical simulation. Results. The motion of the vibrating screen with circular oscillations of the working member, which includes the screen deck of a cascade type with cantilevered bars, is regarded as oscillation of a dual mass system. The amplitudes of oscillations of both masses make in-phase and anti-phase movements relative to the driving force of the drive. The analysis showed that the amplitudes of the working member are practically independent of the screen deck parameters, and bars oscillation amplitudes vary over a wide range. The expressions are given calculating the parameters of cantilevered bars and the values of the initial data of the GIT-51 screen. Resonance curves of amplitude and frequency relations are constructed. The conditions are established under which the oscillation amplitudes of the cantilevered bars take on hyperadmissible values; it is shown that for a particular oscillating system there is a transitional resonance value. Summary. The natural oscillation frequency ratio ranges are established of the entire system with the frequency of forced oscillations in which the oscillation amplitudes of cantilevered bars reach the specified parameters. It is shown that by changing the screen deck parameters at the design stage, it is possible to adjust the inter-frequency range and establish the operating mode of the screen.
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Botros, K. K., G. H. Dunn, and J. A. Hrycyk. "Riser-Relief Valve Dynamic Interactions (Extension to a Previous Model)." Journal of Pressure Vessel Technology 120, no. 2 (May 1, 1998): 207–12. http://dx.doi.org/10.1115/1.2842242.
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Further investigation of the dynamic stability behavior of a typical pilot-operated relief valve is reported. The present study is an extension to Botros et al. (1997) model, which includes mapping of the oscillating frequencies and amplitudes with riser dimensionless length L/D; inclusion of the effects of a wedge-O-ring seal in the model; detailed analyses of the field tests revealing unknown values for model parameters. These model refinements resulted in a better agreement between simulation results and field measurements. Analysis of piston oscillation frequencies and amplitudes indicates that the piston oscillation frequency mirrors the riser’s one-quarter-wave resonance frequency for lower values of L/D. At L/D = 20 and higher, two modes of oscillations started to emerge with two distinct frequencies. Maximum oscillation amplitudes occurred at L/D corresponding to one-quarter wave. Wedge-O-ring seal mechanism helps in suppressing piston oscillations; but it must be used in conjunction with a proper lubricant, otherwise the piston may jam partway during the upward stroke.
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Kawano, Toshio. "High Frequency Oscillation." Pediatrics International 34, no. 6 (December 1992): 631–35. http://dx.doi.org/10.1111/j.1442-200x.1992.tb01022.x.
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BOHN, D. "HIGH FREQUENCY OSCILLATION." British Journal of Anaesthesia 63, no. 7 (1989): 16S—23S. http://dx.doi.org/10.1093/bja/63.7.16.
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Elsner, J. B., and A. A. Tsonis. "Low-frequency oscillation." Nature 372, no. 6506 (December 1994): 507–8. http://dx.doi.org/10.1038/372507b0.
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Schlesinger, Michael E., and Navin Ramankutty. "Low-frequency oscillation." Nature 372, no. 6506 (December 1994): 508–9. http://dx.doi.org/10.1038/372508a0.
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Greenough, Anne. "High frequency oscillation." European Journal of Pediatrics 153, S2 (February 1994): S2—S6. http://dx.doi.org/10.1007/bf02179665.
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Zhang, Mingsheng, Tiejun Zhou, and Zhimin Yuan. "Analysis of Switchable Spin Torque Oscillator for Microwave Assisted Magnetic Recording." Advances in Condensed Matter Physics 2015 (2015): 1–6. http://dx.doi.org/10.1155/2015/457456.
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A switchable spin torque oscillator (STO) with a negative magnetic anisotropy oscillation layer for microwave assisted magnetic recording is analyzed theoretically and numerically. The equations for finding the STO frequency and oscillation angle are derived from Landau-Lifshitz-Gilbert (LLG) equation with the spin torque term in spherical coordinates. The theoretical analysis shows that the STO oscillating frequency remains the same and oscillation direction reverses after the switching of the magnetization of the spin polarization layer under applied alternative magnetic field. Numerical analysis based on the derived equations shows that the oscillation angle increases with the increase of the negative anisotropy energy density (absolute value) but decreases with the increase of spin current, the polarization of conduction electrons, the saturation magnetization, and the total applied magnetic field in thezdirection. The STO frequency increases with the increase of spin current, the polarization of conduction electrons, and the negative anisotropy energy density (absolute value) but decreases with the increase of the saturation magnetization and the total applied magnetic field in thezdirection.
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SCHUSTER, STEFAN, and MARKO MARHL. "BIFURCATION ANALYSIS OF CALCIUM OSCILLATIONS: TIME-SCALE SEPARATION, CANARDS, AND FREQUENCY LOWERING." Journal of Biological Systems 09, no. 04 (December 2001): 291–314. http://dx.doi.org/10.1142/s021833900100044x.
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The behavior of calcium oscillations near bifurcations is analyzed for three different models. For the model developed by Somogyi and Stucki [42], it is shown that the range of oscillations is bounded by supercritical and subcritical Hopf bifurcations. Near the latter, canard orbits arise, that is, quasi-harmonic oscillations with a very small amplitude grow very fast to become pulsed oscillations. The potential biological significance of this behavior is discussed. A time-scale analysis of this model is performed and an approximation formula for the oscillation period is derived. For two models that we presented earlier [30, 31], it is shown that a homoclinic bifurcation and an infinite period bifurcation, respectively, occur. These imply that the oscillation period can reach arbitrarily high values. This behavior is discussed in the light of frequency encoding, and the scaling laws of the oscillation period are given.
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Kazimierczuk, Marian, and Dakshina Murthy-Bellur. "Loop Gain of the Common-Drain Colpitts Oscillator." International Journal of Electronics and Telecommunications 56, no. 4 (November 1, 2010): 423–26. http://dx.doi.org/10.2478/v10177-010-0057-5.
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Loop Gain of the Common-Drain Colpitts OscillatorThis paper presents the derivations of the voltage transfer functions of the amplifier A, the feedback network β, and the loop gainTof the common-drain (CD) Colpitts oscillator, using the small-signal model of the CD Colpitts oscillator. The derivation of the characteristic equation of the CD Colpitts oscillator is presented. Using the characteristic equation, the equation for the oscillation frequency of the sinusoidal output voltage and the condition for steady-state oscillation are derived. The characteristic equation is used to obtain a plot of trajectories of the poles of the CD Colpitts oscillator by varying the MOSFET small-signal transconductancegm. The locations of the complex conjugate poles depicting starting and steady-state conditions for oscillations are also presented.
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Bathellier, Brice, Alan Carleton, and Wulfram Gerstner. "Gamma Oscillations in a Nonlinear Regime: A Minimal Model Approach Using Heterogeneous Integrate-and-Fire Networks." Neural Computation 20, no. 12 (December 2008): 2973–3002. http://dx.doi.org/10.1162/neco.2008.11-07-636.
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Fast oscillations and in particular gamma-band oscillation (20–80 Hz) are commonly observed during brain function and are at the center of several neural processing theories. In many cases, mathematical analysis of fast oscillations in neural networks has been focused on the transition between irregular and oscillatory firing viewed as an instability of the asynchronous activity. But in fact, brain slice experiments as well as detailed simulations of biological neural networks have produced a large corpus of results concerning the properties of fully developed oscillations that are far from this transition point. We propose here a mathematical approach to deal with nonlinear oscillations in a network of heterogeneous or noisy integrate-and-fire neurons connected by strong inhibition. This approach involves limited mathematical complexity and gives a good sense of the oscillation mechanism, making it an interesting tool to understand fast rhythmic activity in simulated or biological neural networks. A surprising result of our approach is that under some conditions, a change of the strength of inhibition only weakly influences the period of the oscillation. This is in contrast to standard theoretical and experimental models of interneuron network gamma oscillations (ING), where frequency tightly depends on inhibition strength, but it is similar to observations made in some in vitro preparations in the hippocampus and the olfactory bulb and in some detailed network models. This result is explained by the phenomenon of suppression that is known to occur in strongly coupled oscillating inhibitory networks but had not yet been related to the behavior of oscillation frequency.
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Kravchuk, V. A. "Free oscillations of steel beams prestressed by wall stretching." Вестник гражданских инженеров 17, no. 6 (2020): 97–103. http://dx.doi.org/10.23968/1999-5571-2020-17-6-97-103.
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The article presents the study results of the impact of steel beam prestressing by wall stretching on changes in the circular frequency, frequency, period, and number of oscillations per minute for free oscillation, and for oscillation taking into account the resistance forces. The forced oscillations of the beam under impulse loading are investigated. There has been carried out a comparative analysis of the dynamic parameters of prestressed beams and conventional beams of equal cross-section with the same load-bearing capacity parameters. The analysis results of the influence of resistance forces on the oscillation process in prestressed beams and conventional beams are submitted. There has been established the time of oscillations damping in the compared beams at free oscillation, taking into account the resistance forces.
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Viriyopase, Atthaphon, Raoul-Martin Memmesheimer, and Stan Gielen. "Cooperation and competition of gamma oscillation mechanisms." Journal of Neurophysiology 116, no. 2 (August 1, 2016): 232–51. http://dx.doi.org/10.1152/jn.00493.2015.
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Oscillations of neuronal activity in different frequency ranges are thought to reflect important aspects of cortical network dynamics. Here we investigate how various mechanisms that contribute to oscillations in neuronal networks may interact. We focus on networks with inhibitory, excitatory, and electrical synapses, where the subnetwork of inhibitory interneurons alone can generate interneuron gamma (ING) oscillations and the interactions between interneurons and pyramidal cells allow for pyramidal-interneuron gamma (PING) oscillations. What type of oscillation will such a network generate? We find that ING and PING oscillations compete: The mechanism generating the higher oscillation frequency “wins”; it determines the frequency of the network oscillation and suppresses the other mechanism. For type I interneurons, the network oscillation frequency is equal to or slightly above the higher of the ING and PING frequencies in corresponding reduced networks that can generate only either of them; if the interneurons belong to the type II class, it is in between. In contrast to ING and PING, oscillations mediated by gap junctions and oscillations mediated by inhibitory synapses may cooperate or compete, depending on the type (I or II) of interneurons and the strengths of the electrical and chemical synapses. We support our computer simulations by a theoretical model that allows a full theoretical analysis of the main results. Our study suggests experimental approaches to deciding to what extent oscillatory activity in networks of interacting excitatory and inhibitory neurons is dominated by ING or PING oscillations and of which class the participating interneurons are.
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Kim, Ji Hyun, Seong Jun Park, Jin-Woo Han, and Jae-Hyuk Ahn. "Surface Potential-Controlled Oscillation in FET-Based Biosensors." Sensors 21, no. 6 (March 10, 2021): 1939. http://dx.doi.org/10.3390/s21061939.
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Field-effect transistor (FET)-based biosensors have garnered significant attention for their label-free electrical detection of charged biomolecules. Whereas conventional output parameters such as threshold voltage and channel current have been widely used for the detection and quantitation of analytes of interest, they require bulky instruments and specialized readout circuits, which often limit point-of-care testing applications. In this study, we demonstrate a simple conversion method that transforms the surface potential into an oscillating signal as an output of the FET-based biosensor. The oscillation frequency is proposed as a parameter for FET-based biosensors owing to its intrinsic advantages of simple and compact implementation of readout circuits as well as high compatibility with neuromorphic applications. An extended-gate biosensor comprising an Al2O3-deposited sensing electrode and a readout transistor is connected to a ring oscillator that generates surface potential-controlled oscillation for pH sensing. Electrical measurement of the oscillation frequency as a function of pH reveals that the oscillation frequency can be used as a sensitive and reliable output parameter in FET-based biosensors for the detection of chemical and biological species. We confirmed that the oscillation frequency is directly correlated with the threshold voltage. For signal amplification, the effects of circuit parameters on pH sensitivity are investigated using different methods, including electrical measurements, analytical calculations, and circuit simulations. An Arduino board to measure the oscillation frequency is integrated with the proposed sensor to enable portable and real-time pH measurement for point-of-care testing applications.
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Wang, Yunling, Fang Liu, Xinwei Du, Bo Li, Yang Liu, and Libo Jiang. "Low-frequency oscillation suppression strategy considering dynamic power characteristics of energy storage system." IOP Conference Series: Earth and Environmental Science 983, no. 1 (February 1, 2022): 012028. http://dx.doi.org/10.1088/1755-1315/983/1/012028.
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Abstract Aiming at the problem of low-frequency oscillation in the weak power grid, a low-frequency oscillation suppression strategy considering the dynamic power characteristics of the energy storage system (ESS) is proposed in this paper. Firstly, the principle of low-frequency oscillation in the power system is analyzed by using a single machine infinite bus system. Secondly, considering the dynamic characteristics of the ESS output active power, a controller for the ESS to suppress low-frequency oscillation is designed, which can provide positive damping for frequency oscillation of the power grid. Finally, the simulation analysis and experimental results of an actual weak grid are carried out to verify the effectiveness and feasibility of the proposed method. The results show that the suppression effect of the low-frequency oscillations is related to the ESS location in the weak power grid.
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Sebe, Joy Y., Johannes F. van Brederode, and Albert J. Berger. "Inhibitory Synaptic Transmission Governs Inspiratory Motoneuron Synchronization." Journal of Neurophysiology 96, no. 1 (July 2006): 391–403. http://dx.doi.org/10.1152/jn.00086.2006.
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Neurons within the intact respiratory network produce bursts of action potentials that cause inspiration or expiration. Within inspiratory bursts, activity is synchronized on a shorter timescale to generate clusters of action potentials that occur in a set frequency range and are called synchronous oscillations. We investigated how GABA and glycine modulate synchronous oscillations and respiratory rhythm during postnatal development. We recorded inspiratory activity from hypoglossal nerves using the in vitro rhythmically active mouse medullary slice preparation from P0–P11 mice. Average oscillation frequency increased with postnatal development, from 17 ± 12 Hz in P0–P6 mice ( n = 15) to 38 ± 7 Hz in P7–P11 mice ( n = 37) ( P < 0.0001). Bath application of GABAA and GlyR antagonists significantly reduced oscillation power in neonates (P0–P6) and juveniles (P7–P10) and increased peak integrated activity in both age groups. To test whether elevating slice excitability is sufficient to reduce oscillation power, Substance P was bath applied alone. Substance P, although increasing peak integrated activity, had no significant effect on oscillation power. Prolonging the time course of GABAergic synaptic currents with zolpidem decreased the median oscillation frequency in P9–P10 mouse slices. These data demonstrate that oscillation frequency increases with postnatal development and that both GABAergic and glycinergic transmission contribute to synchronization of activity. Further, the time course of synaptic GABAergic currents is a determinant of oscillation frequency.
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Stanger, Heather L., Rebekah Alford, David E. Jane, and Mark O. Cunningham. "The Role of -Containing Kainate Receptors in Entorhinal Cortex Gamma Frequency Oscillations." Neural Plasticity 2008 (2008): 1–12. http://dx.doi.org/10.1155/2008/401645.
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Using in vitro brain slices of hippocampus and cortex, neuronal oscillations in the frequency range of 30–80 Hz (gamma frequency oscillations) can be induced by a number of pharmacological manipulations. The most routinely used is the bath application of the broad-spectrum glutamate receptor agonist, kainic acid. In the hippocampus, work using transgenic kainate receptor knockout mice have revealed information about the specific subunit composition of the kainate receptor implicated in the generation and maintenance of the gamma frequency oscillation. However, there is a paucity of such detail regarding gamma frequency oscillation in the cortex. Using specific pharmacological agonists and antagonists for the kainate receptor, we have set out to examine the contribution of kainate receptor subtypes to gamma frequency oscillation in the entorhinal cortex. The findings presented demonstrate that in contrast to the hippocampus, kainate receptors containing the subunit are critically important for the generation and maintenance of gamma frequency oscillation in the entorhinal cortex. Future work will concentrate on determining the exact nature of the cellular expression of kainate receptors in the entorhinal cortex.
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Klimushkin, D. Yu, P. N. Mager, and K. H. Glassmeier. "Spatio-temporal structure of Alfvén waves excited by a sudden impulse localized on an L-shell." Annales Geophysicae 30, no. 7 (July 25, 2012): 1099–106. http://dx.doi.org/10.5194/angeo-30-1099-2012.
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Abstract. This paper is concerned with the spatial structure and temporal evolution of the azimuthally small scale Alfvén wave generated by a sudden impulse concentrated on a given magnetic shell. At the outset, both poloidal and toroidal components are present in the wave's magnetic field. The oscillation in the poloidal component on a given magnetic shell is a superposition of two monochromatic oscillations, one with the local resonance frequency on this shell, and the other with the frequency corresponding to the resonance frequency on the source surface. The superposition of these two oscillations leads to beating. Due to phase mixing, the poloidal component of the oscillation decreases with time down to zero, transferring its energy to the toroidal component. Beating in the toroidal component is less pronounced. As time elapses, energy concentration near the source magnetic shell occurs with the frequency of the oscillation corresponding to the Alfvénic resonance frequency on this surface. Outside this thin region wave amplitudes become rather small at oscillation frequencies corresponding to the local resonance frequency of the respective magnetic shell.
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Da, Hoang Van, and Nguyen Thac Sy. "Frequency entrainment in a self-oscillatory system under parametric excitation." Vietnam Journal of Mechanics 25, no. 3 (September 30, 2003): 137–44. http://dx.doi.org/10.15625/0866-7136/25/3/6586.
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In the present paper, the frequencies for appearing the entrained oscillations in a self-oscillatory system under the parametric excitation, have been determined. The almost periodic oscillation which develops from the entrained oscillation when the driving frequency is given just outside the region of entrainment also have been investigated by the method of the phase plane.
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Ward, H. E., J. Armengol, and R. L. Jones. "Ventilation by external high-frequency oscillation in cats." Journal of Applied Physiology 58, no. 4 (April 1, 1985): 1390–99. http://dx.doi.org/10.1152/jappl.1985.58.4.1390.
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Eight anesthetized tracheostomized cats were placed in an 8.2-liter airtight chamber with the trachea connected to the exterior. Thirty-two combinations of high-frequency oscillations (HFO) (0.5–30 Hz; 25–100 ml) were delivered for 10 min each in random order into the chamber. Arterial blood gas tensions during oscillation were compared with control measurements made after 10 min of spontaneous breathing without oscillation when the mean arterial PCO2 (PaCO2) was 30.1 Torr. Ventilation due to spontaneous breathing (Vs) and oscillation (Vo) were derived from the chamber pressure trace and a pneumotachograph, respectively. As the oscillation frequency increased, oscillated tidal volume (Vo) decreased from a mean of 39 (0.5 Hz) to 3.3 ml (30 Hz) when 100 ml was delivered to the chamber. From 6–25 Hz, apnea occurred with Vo less than estimated respiratory dead space (VD); the minimum effective Vo/VD ratio was 0.37 +/- 0.05. Although Vo was maximal at 10 Hz at each oscillation volume, the lowest PaCO2 occurred at 2–6 Hz, and arterial PO2 rose as expected during hypocapnia. Above 10 Hz, PaCO2 was determined by Vo and was independent of frequency, whereas at lower frequencies, PaCO2 was related to Vo; below 6 Hz, PaCO2 varied inversely with the calculated alveolar ventilation. As oscillations became more effective, both PaCO2 and Vs fell progressively and were highly correlated; apnea occurred when PaCO2 was reduced by a mean of 4.5 Torr. Mean chamber pressure remained near zero up to 15 Hz, indicating functional residual capacity did not change. We conclude that externally applied HFO can readily maintain gas exchange in vivo, with Vo less than VD at frequencies over 2 Hz.
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Adamatzky, Andrew, Claire Fullarton, Neil Phillips, Ben De Lacy Costello, and Thomas C. Draper. "Thermal switch of oscillation frequency in Belousov–Zhabotinsky liquid marbles." Royal Society Open Science 6, no. 4 (April 2019): 190078. http://dx.doi.org/10.1098/rsos.190078.
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External control of oscillation dynamics in the Belousov–Zhabotinsky (BZ) reaction is important for many applications including encoding computing schemes. When considering the BZ reaction, there are limited studies dealing with thermal cycling, particularly cooling, for external control. Recently, liquid marbles (LMs) have been demonstrated as a means of confining the BZ reaction in a system containing a solid–liquid interface. BZ LMs were prepared by rolling 50 μl droplets in polyethylene (PE) powder. Oscillations of electrical potential differences within the marble were recorded by inserting a pair of electrodes through the LM powder coating into the BZ solution core. Electrical potential differences of up to 100 mV were observed with an average period of oscillation ca 44 s. BZ LMs were subsequently frozen to −1°C to observe changes in the frequency of electrical potential oscillations. The frequency of oscillations reduced upon freezing to 11 mHz cf. 23 mHz at ambient temperature. The oscillation frequency of the frozen BZ LM returned to 23 mHz upon warming to ambient temperature. Several cycles of frequency fluctuations were able to be achieved.
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Marzabadi, F. Rasi, and Ramin Kamali Moghadam. "Effect of Reduced Frequency on Longitudinal Oscillatory Derivatives of an Airfoil Based on Wind Tunnel Data." Advanced Materials Research 1016 (August 2014): 465–70. http://dx.doi.org/10.4028/www.scientific.net/amr.1016.465.
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Longitudinal dynamic derivatives of an airfoil oscillating in pitching and plunging motions were calculated using variation of pitching moment coefficients with angle of attack in various conditions, based on wind tunnel data. The effect of reduced frequency on variation of longitudinal oscillatory derivatives was investigated, in three different regions of oscillation: before, over and post stall conditions. The results showed that reduced frequency has significant effects on longitudinal oscillatory coefficients in different conditions for both types of oscillations.
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Мясин, Е. А. "Генерация шума в одночастотном генераторе на лавинно-пролетном диоде миллиметрового диапазона длин волн под воздействием низкочастотного гармонического колебания." Письма в журнал технической физики 47, no. 22 (2021): 33. http://dx.doi.org/10.21883/pjtf.2021.22.51724.18937.
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The investigation of effect of the low-frequency harmonic oscillation on the nourishment circuit of the 7mm wave region IMPATT diode oscillator was continued. In first time it was shown, that excitement of noise and the maximum height-frequency noise spectrum extension at a low-frequency oscillation amplitude increasing are connected with a transitory decreasing of the diode current lower the start current of height-frequency generation in the IMPATT diode oscillator.
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Lestienne, Rémy. "Intrinsic and Extrinsic Neuronal Mechanisms in Temporal Coding: A Further Look at Neuronal Oscillations." Neural Plasticity 6, no. 4 (1999): 173–89. http://dx.doi.org/10.1155/np.1999.173.
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Many studies in recent years have been devoted to the detection of fast oscillations in the Central Nervous System (CNS), interpreting them as synchronizing devices. We should, however, refrain from associating too closely the two concepts of synchronization and oscillation. Whereas synchronization is a relatively well-defined concept, by contrast oscillation of a population of neurones in the CNS looks loosely defined, in the sense that both its frequency sharpness and the duration of the oscillatory episodes vary widely from case to case. Also, the functions of oscillations in the brain are multiple and are not confined to synchronization. The paradigmatic instantiation of oscillation in physics is given by the harmonic oscillator, a device particularly suited to tell the time, as in clocks. We will thus examine first the case of oscillations or cycling discharges of neurones, which provide a clock or impose a “tempo” for various kinds of information processing. Neuronal oscillators are rarely just clocks clicking at a fixed frequency. Instead, their frequency is often adjustable and controllable, as in the example of the “chattering cells” discovered in the superficial layers of the visual cortex. Moreover, adjustable frequency oscillators are suitable for use in “phase locked loops” (PLL) networks, a device that can convert time coding to frequency coding; such PLL units have been found in the somatosensory cortex of guinea pigs. Finally, are oscillations stricto sensu necessary to induce synchronization in the discharges of downstream neurones? We know that this is not the case, at least not for local populations of neurones. As a contribution to this question, we propose that repeating patterns in neuronal discharges production may be looked at as one such alternative solution in relation to the processing of information. We review here the case of precisely repeating triplets, detected in the discharges of olfactory mitral cells of a freely breathing rat under odor stimulation.
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Zhu, Ya Qing, Min Zhong, Feng Ping Pan, Jia Luo, Xi Zhang, and Wei Jian Huang. "Research of the Impact of Turbine Parameters on Low-Frequency Oscillation Based on Simulink." Applied Mechanics and Materials 607 (July 2014): 556–60. http://dx.doi.org/10.4028/www.scientific.net/amm.607.556.
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This paper analyzed the influence of various turbine parameters on the low-frequency oscillation using Simulink, including the oil motive slide valve time constant, the volume time constant, power grid damping factor, power grid power factor, self-balancing rotor coefficient etc. Meanwhile, comparing the influence of the pure speed regulator and power-frequency regulation on low-frequency oscillations, proven that power-frequency regulation will exacerbate the low frequency oscillation.
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Kumngern, Montree, and Kobchai Dejhan. "DDCC-Based Quadrature Oscillator with Grounded Capacitors and Resistors." Active and Passive Electronic Components 2009 (2009): 1–4. http://dx.doi.org/10.1155/2009/987304.
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A new voltage-mode quadrature oscillator using two differential difference current conveyors (DDCCs), two grounded capacitors, and three grounded resistors is presented. The proposed oscillator provides the following advantages: the oscillation condition and oscillation frequency are orthogonally controlled; the oscillation frequency is controlled through a single grounded resistor; the use of only grounded capacitors and resistors makes the proposed circuit ideal for IC implementation; low passive and active sensitivities. Simulation results verifying the theoretical analysis are also included.
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Ringermacher, H. I., and L. R. Mead. "Reaffirmation of cosmological oscillations in the scale factor from the Pantheon compilation of 1048 Type Ia supernovae." Monthly Notices of the Royal Astronomical Society 494, no. 2 (April 10, 2020): 2158–65. http://dx.doi.org/10.1093/mnras/staa872.
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ABSTRACT We observe damped temporal oscillations in the scale factor at a dominant frequency of ∼7 cycles/Hubble-time in the Pantheon compilation of 1048 Type Ia supernovae (SNe Ia). The residual oscillations observed in the Pantheon data closely match and reaffirm our initial observation of oscillations from earlier SNe data (primarily SNLS3 data of Conley 2011) at 2σ confidence. The nearly identical shapes in amplitude, frequency, phase, and damping constant makes it highly likely that the signal is real. Furthermore, two-thirds of the Pantheon SNe cover different portions of the sky compared with SNLS3 strengthening this conclusion. Our model describing the oscillation, presented in an earlier paper, is a simple scalar field harmonic oscillator coupled to the Lambda cold dark matter (ΛCDM) Friedmann equation, but carried into the present epoch. The scalar field energy density plays the role of the dark matter energy density in ΛCDM cosmology, fits well as an average, and closely matches the present dark matter density parameter, suggesting the oscillation plays a role in the dark matter sector. Temporal oscillations in the scale factor and its derivative, as described in this work, would also induce temporal oscillations of the Hubble parameter.
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Wang, Sijia, Xiangyu Wu, Gang Chen, and Yin Xu. "Small-Signal Stability Analysis of Photovoltaic-Hydro Integrated Systems on Ultra-Low Frequency Oscillation." Energies 13, no. 4 (February 24, 2020): 1012. http://dx.doi.org/10.3390/en13041012.
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In recent years, ultralow-frequency oscillation has repeatedly occurred in asynchronously connected regional power systems and brought serious threats to the operation of power grids. This phenomenon is mainly caused by hydropower units because of the water hammer effect of turbines and the inappropriate Proportional-Integral-Derivative (PID) parameters of governors. In practice, hydropower and solar power are often combined to form an integrated photovoltaic (PV)-hydro system to realize complementary renewable power generation. This paper studies ultralow-frequency oscillations in integrated PV-hydro systems and analyzes the impacts of PV generation on ultralow-frequency oscillation modes. Firstly, the negative damping problem of hydro turbines and governors in the ultralow-frequency band was analyzed through the damping torque analysis. Subsequently, in order to analyze the impact of PV generation, a small-signal dynamic model of the integrated PV-hydro system was established, considering a detailed dynamic model of PV generation. Based on the small-signal dynamic model, a two-zone and four-machine system and an actual integrated PV-hydro system were selected to analyze the influence of PV generation on ultralow-frequency oscillation modes under different scenarios of PV output powers and locations. The analysis results showed that PV dynamics do not participate in ultralow-frequency oscillation modes and the changes of PV generation to power flows do not cause obvious changes in ultralow-frequency oscillation mode. Ultra-low frequency oscillations are mainly affected by sources participating in the frequency adjustment of systems.