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Journal articles on the topic 'Oscillation period'
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1
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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Dinh, Nguyen Van. "A note on the method of harmonic balance." Vietnam Journal of Mechanics 23, no. 1 (April 1, 2001): 34–38. http://dx.doi.org/10.15625/0866-7136/9938.
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Free oscillation period of the Duffing oscillator with cubic non-linearity was examined. A comparison between the exact period and those obtained by the asymptotic and the harmonic balance methods was done. It was shown that the remits given by the harmonic balance are acceptable even for large oscillations whereas the asymptotic method can only be applied for small oscillations.
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Kaur, Manpreet, Amy Ng, Pyonghwa Kim, Casey Diekman, and Yong-Ick Kim. "CikA Modulates the Effect of KaiA on the Period of the Circadian Oscillation in KaiC Phosphorylation." Journal of Biological Rhythms 34, no. 2 (February 13, 2019): 218–23. http://dx.doi.org/10.1177/0748730419828068.
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Cyanobacteria contain a circadian oscillator that can be reconstituted in vitro. In the reconstituted circadian oscillator, the phosphorylation state of KaiC oscillates with a circadian period, spending about 12 h in the phosphorylation phase and another 12 h in the dephosphorylation phase. Although some entrainment studies have been performed using the reconstituted oscillator, they were insufficient to fully explain entrainment mechanisms of the cyanobacterial circadian clock due to the lack of input pathway components in the in vitro oscillator reaction mixture. Here, we investigate how an input pathway component, CikA, affects the phosphorylation state of KaiC in vitro. In general, CikA affects the amplitude and period of the circadian oscillation of KaiC phosphorylation by competing with KaiA for the same binding site on KaiB. In the presence of CikA, KaiC switches from its dephosphorylation phase to its phosphorylation phase prematurely, due to an early release of KaiA from KaiB as a result of competitive binding between CikA and KaiA. This causes hyperphosphorylation of KaiC and lowers the amplitude of the circadian oscillation. The period of the KaiC phosphorylation oscillation is shortened by adding increased amounts of CikA. A constant period can be maintained as CikA is increased by proportionally decreasing the amount of KaiA. Our findings give insight into how to reconstitute the cyanobacterial circadian clock in vitro by the addition of an input pathway component, and explain how this affects circadian oscillations by directly interacting with the oscillator components.
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Olshanskii, Vasiliy, and Stanislav Olshanskii. "Modeling the motion of an oscillator with a soft elastic characteristic." Physico-mathematical modelling and informational technologies, no. 25 (May 25, 2017): 113–24. http://dx.doi.org/10.15407/fmmit2017.25.113.
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The free oscillations of a system with one degree of freedom are considered under the assumption that the elasticity of a spring is proportional to the cubic root of its deformation. Two forms of the analytical solution of the nonlinear differential equation of motion of the oscillator are obtained. In the first displacement of the oscillator in time is expressed in terms of incomplete elliptic integrals of the first and second kind. In the second form, the solution is expressed in terms of periodic Ateb-functions. The tables of the involved functions are made, which simplify the calculation. Formulas are also derived for calculating the oscillation periods when the oscillator is signaled or the initial deviation from the equilibrium position or the initial velocity (instantaneous pulse) in this position. The dependence of the oscillation period on the parameters of the oscillator and the initial conditions is established. Examples of calculations of oscillations are presented with the use of compiled tables of special functions and using the proposed approximations of the Ateb-functions. Comparison of numerical results obtained by different methods is made.
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Hocke, K., S. Studer, O. Martius, D. Scheiben, and N. Kämpfer. "A 20-day period standing oscillation in the northern winter stratosphere." Annales Geophysicae 31, no. 4 (April 25, 2013): 755–64. http://dx.doi.org/10.5194/angeo-31-755-2013.
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Abstract. Observations of the ozone profile by a ground-based microwave radiometer in Switzerland indicate a dominant 20-day oscillation in stratospheric ozone, possibly related to oscillations of the polar vortex edge during winter. For further understanding of the nature of the 20-day oscillation, the ozone data set of ERA Interim meteorological reanalysis is analyzed at the latitude belt of 47.5° N and in the time from 1979 to 2010. Spectral analysis of ozone time series at 7 hPa indicates that the 20-day oscillation is maximal at two locations: 7.5° E, 47.5° N and 60° E, 47.5° N. Composites of the stream function are derived for different phases of the 20-day oscillation of stratospheric ozone at 7 hPa in the Northern Hemisphere. The streamline at Ψ = −2 × 107 m2 s−1 is in the vicinity of the polar vortex edge. The other streamline at Ψ = 4 × 107 m2 s1 surrounds the Aleutian anticyclone and goes to the subtropics. The composites show 20-day period standing oscillations at the polar vortex edge and in the subtropics above Northern Africa, India, and China. The 20-day period standing oscillation above Aral Sea and India is correlated to the strength of the Aleutian anticyclone.
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Ševčík, Peter, and Ľubica Adamčíková. "Bromine and period of Belousov-Zhabotinskii type oscillation reaction." Collection of Czechoslovak Chemical Communications 50, no. 4 (1985): 799–805. http://dx.doi.org/10.1135/cccc19850799.
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Belousov-Zhabotinskii type oscillation reaction with oxalic acid proceeds in a closed system, in a flow-through open system, as well as under intermediate conditions. Oscillations are started in either of the following three ways: 1) Increasing the removal of bromine from solution by bubbling inert gases, 2) chemically, and 3) in a flow-through reactor. The oscillation period is largely dependent on the removal rate of bromine, other reactant concentrations being constant.
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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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Sneyd, James, Jung Min Han, Liwei Wang, Jun Chen, Xueshan Yang, Akihiko Tanimura, Michael J. Sanderson, Vivien Kirk, and David I. Yule. "On the dynamical structure of calcium oscillations." Proceedings of the National Academy of Sciences 114, no. 7 (February 1, 2017): 1456–61. http://dx.doi.org/10.1073/pnas.1614613114.
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Oscillations in the concentration of free cytosolic Ca2+ are an important and ubiquitous control mechanism in many cell types. It is thus correspondingly important to understand the mechanisms that underlie the control of these oscillations and how their period is determined. We show that Class I Ca2+ oscillations (i.e., oscillations that can occur at a constant concentration of inositol trisphosphate) have a common dynamical structure, irrespective of the oscillation period. This commonality allows the construction of a simple canonical model that incorporates this underlying dynamical behavior. Predictions from the model are tested, and confirmed, in three different cell types, with oscillation periods ranging over an order of magnitude. The model also predicts that Ca2+ oscillation period can be controlled by modulation of the rate of activation by Ca2+ of the inositol trisphosphate receptor. Preliminary experimental evidence consistent with this hypothesis is presented. Our canonical model has a structure similar to, but not identical to, the classic FitzHugh–Nagumo model. The characterization of variables by speed of evolution, as either fast or slow variables, changes over the course of a typical oscillation, leading to a model without globally defined fast and slow variables.
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Chang, Pao-Liang, Wei-Ting Fang, Pin-Fang Lin, and Yu-Shuang Tang. "Influence of Wind-Induced Antenna Oscillations on Radar Observations and Its Mitigation." Weather and Forecasting 35, no. 6 (December 2020): 2235–54. http://dx.doi.org/10.1175/waf-d-20-0064.1.
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AbstractAs Typhoon Goni (2015) passed over Ishigaki Island, a maximum gust speed of 71 m s−1 was observed by a surface weather station. During Typhoon Goni’s passage, mountaintop radar recorded antenna elevation angle oscillations, with a maximum amplitude of ~0.2° at an elevation angle of 0.2°. This oscillation phenomenon was reflected in the reflectivity and Doppler velocity fields as Typhoon Goni’s eyewall encompassed Ishigaki Island. The main antenna oscillation period was approximately 0.21–0.38 s under an antenna rotational speed of ~4 rpm. The estimated fundamental vibration period of the radar tower is approximately 0.25–0.44 s, which is comparable to the predominant antenna oscillation period and agrees with the expected wind-induced vibrations of buildings. The reflectivity field at the 0.2° elevation angle exhibited a phase shift signature and a negative correlation of −0.5 with the antenna oscillation, associated with the negative vertical gradient of reflectivity. FFT analysis revealed two antenna oscillation periods at 0955–1205 and 1335–1445 UTC 23 August 2015. The oscillation phenomenon ceased between these two periods because Typhoon Goni’s eye moved over the radar site. The VAD analysis-estimated wind speeds at a range of 1 km for these two antenna oscillation periods exceeded 45 m s−1, with a maximum value of approximately 70 m s−1. A bandpass filter QC procedure is proposed to filter out the predominant wavenumbers (between 40 and 70) for the reflectivity and Doppler velocity fields. The proposed QC procedure is indicated to be capable of mitigating the major signals resulting from antenna oscillations.
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Darelius, E., I. Fer, T. Rasmussen, C. Guo, and K. M. H. Larsen. "On the modulation of the periodicity of the Faroe Bank Channel overflow instabilities." Ocean Science Discussions 12, no. 3 (May 21, 2015): 823–61. http://dx.doi.org/10.5194/osd-12-823-2015.
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Abstract. The Faroe Bank Channel (FBC) is one of the major pathways where dense, cold water formed in the Nordic Seas flows southward towards the north Atlantic. The plume region downstream of the FBC sill is characterized by high mesoscale variability, quasi-regular oscillations and intense mixing. Here, one year-long time series of velocity and temperature from eight moorings deployed in May 2012 in the plume region is analyzed to describe variability in the strength and period of the oscillations. The eddy kinetic energy (EKE) associated with the oscillations is modulated with a factor of ten during the year and the dominant period of the oscillations changes between three to four and six days, where the shorter period oscillations are more energetic. The dense water is observed on a wider portion of the slope (both deeper and shallower) during periods with energetic, short period oscillations. The observations are complemented by results from a regional, high resolution model that shows a similar variability in EKE and a gradual change in oscillation period between three and four days. The observed variability in oscillation period is directly linked to changes in the volume transport across the sill: the oscillation period decreases with about six days Sv−1 both in the observations and in the model. This is in agreement with results from linear instability analysis which suggests that the period and growth rate decrease for decreased plume thickness. The changes in oscillation period can partly be explained by variability in the upper layer, background flow and advection of the oscillations past the stationary moorings, but the changes in the fraction of the EKE that is derived from the cross isobath motion suggests that the intrinsic period of the instability is modulated. It is further shown that about 50% of the transport variability across the sill is explained by changes in the local barotropic forcing, which is obtained from satellite altimetry.
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Cowley, S. W. H., and G. Provan. "Planetary period oscillations in Saturn's magnetosphere: comments on the relation between post-equinox periods determined from magnetic field and SKR emission data." Annales Geophysicae 33, no. 7 (July 24, 2015): 901–12. http://dx.doi.org/10.5194/angeo-33-901-2015.
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Abstract. We discuss the properties of Saturn planetary period oscillations (PPOs) deduced from analysis of Saturn kilometric radiation (SKR) modulations by Fischer et al. (2014), and from prior analysis of magnetic field oscillations data by Andrews et al. (2012) and Provan et al. (2013), with emphasis on the post-equinox interval from early 2010 to early 2013. Fischer et al. (2014) characterize this interval as showing single phase-locked periods in the northern and southern SKR modulations observed in polarization-separated data, while the magnetic data generally show the presence of separated dual periods, northern remaining shorter than southern. We show that the single SKR period corresponds to the southern magnetic period early in 2010, segues into the northern period in late 2010, and returns to the southern period in mid-2012, approximately in line with changes in the dominant magnetic oscillation. An exception occurs in mid-February to late August 2011 when two periods are again discerned in SKR data, in good agreement with the ongoing dual periods in the magnetic data. Fischer et al. (2014) discuss this change in terms of a large jump in the southern SKR period related to the Great White Spot storm, which the magnetic data show is primarily due instead to a reappearance in the SKR data of the ongoing southern modulation in a transitory interval of resumed southern dominance. In the earlier interval from early April 2010 to mid-February 2011 when Fischer et al. (2014) deduce single phase-locked periods, we show unequivocal evidence in the magnetic data for the presence of separated dual oscillations of approximately equal amplitude. We suggest that the apparent single SKR periods result from a previously reported phenomenon in which modulations associated with one hemisphere appear in polarization-separated data associated with the other. In the following interval, mid-August 2011 to early April 2012, when Fischer et al. (2014) again report phase-locked northern and southern oscillations, no ongoing southern oscillation of separate period is discerned in the magnetic data. However, the magnetic amplitude data show that if a phase-locked southern oscillation is indeed present, its amplitude must be less than ~ 5–10 % of the northern oscillation.
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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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Pattiaratchi, Charitha, and Sarath Wijeratne. "PROCESSES LEADING TO INFRA-GRAVITY PERIOD OSCILLATIONS AND CURRENTS IN PORTS AND MARINAS." Coastal Engineering Proceedings, no. 36 (December 30, 2018): 78. http://dx.doi.org/10.9753/icce.v36.currents.78.
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In this paper, we take the broad definition of tsunami (‘harbour wave’) to describe oscillations in the infragravity (IG) periods (between 30 and 300s) in ports and marinas that often lead to interruption in harbour operations due to excessive vessel movements. The main processes that lead to these oscillations (also called seiches) are examined through the analysis of field measurements of water levels and currents from Western Australia. In a port or marina with lengths of the order of 500m and depths of the order of 10m, the natural oscillation periods are of the order of a few minutes. Changes in water levels in the coastal ocean adjacent to the port can setup oscillations within the port at its natural frequency. This results in water level fluctuations and strong horizontal currents within the port. If the incoming forcing is close to the natural frequency of oscillation resonance conditions may arise resulting in increased agitation inside the port. In addition if the harbour oscillation periods coincide with natural period of moored vessels, harbour operations can be severely interrupted due to strong vessel movements damaging to mooring lines and fenders.
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BELÉNDEZ, A., D. I. MÉNDEZ, M. L. ALVAREZ, C. PASCUAL, and T. BELÉNDEZ. "APPROXIMATE ANALYTICAL SOLUTIONS FOR THE RELATIVISTIC OSCILLATOR USING A LINEARIZED HARMONIC BALANCE METHOD." International Journal of Modern Physics B 23, no. 04 (February 10, 2009): 521–36. http://dx.doi.org/10.1142/s0217979209049954.
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The analytical approximate technique developed by Wu et al. for conservative oscillators with odd nonlinearity is used to construct approximate frequency-amplitude relations and periodic solutions to the relativistic oscillator. By combining Newton's method with the method of harmonic balance, analytical approximations to the oscillation period and periodic solutions are constructed for this oscillator. The approximate periods obtained are valid for the complete range of oscillation amplitudes, A, and the discrepancy between the second approximate period and the exact one never exceeds 1.24%, and it tends to 1.09% when A tends to infinity. Excellent agreement of the approximate periods and periodic solutions with the exact ones are demonstrated and discussed.
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Darelius, E., I. Fer, T. Rasmussen, C. Guo, and K. M. H. Larsen. "On the modulation of the periodicity of the Faroe Bank Channel overflow instabilities." Ocean Science 11, no. 5 (October 26, 2015): 855–71. http://dx.doi.org/10.5194/os-11-855-2015.
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Abstract. The Faroe Bank Channel (FBC) is one of the major pathways where dense, cold water formed in the Nordic Seas flows southward as a bottom-attached energetic plume towards the North Atlantic. The plume region downstream of the FBC sill is characterized by high mesoscale variability, quasi-regular oscillations and intense mixing. Here, 1 year long time series of velocity and temperature from ten moorings deployed in May 2012 in the plume region are analysed to describe variability in the strength and period of the oscillations. The eddy kinetic energy (EKE) associated with the oscillations changes by a factor of 10 during the year and the dominant period of the oscillations is modulated and varies between 3 to 4 and 6 days, where the shorter-period oscillations are more energetic. The dense water is observed on a wider portion of the slope (both deeper and shallower) during periods with energetic, short-period oscillations. The observations are complemented by results from a regional, high-resolution model that shows a similar variability in EKE and a gradual change in oscillation period of between 3 and 4 days. The observed variability in oscillation period is directly linked to changes in the volume transport across the sill: the oscillation period increases from approximately 3 days to about 6 days when the transport decreases from 2.4 to 1.9 Sv. A similar relation is obtained from the model. This is in agreement with results from a linear baroclinic instability analysis, which suggests that the period increases while the growth rate decreases for decreased plume thickness. Advective effects, caused by the variable background current, further modulate the observed periodicity by up to 1 day. In addition, it is shown that about 50 % of the transport variability across the sill is explained by changes in the local sea surface height gradient.
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Asano, Toshiyuki, Toru Yamashiro, and Taro Kakinuma. "FIELD OBSERVATIONS OF SEICHE EVENTS IN A T-SHAPE BAY." Coastal Engineering Proceedings 1, no. 32 (January 17, 2011): 38. http://dx.doi.org/10.9753/icce.v32.currents.38.
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Field observations on secondary oscillations (seiche) in Urauchi Bay of Kami-koshiki Island, Japan were conducted during October 7-21, 2008. The seiches prone bay has a unique configuration as T-shape, which may cause the inherent characteristics of the eigen oscillations. The analyzed data show that the oscillations of the bay have at least two distinct modes; mode-1 oscillation of the period around 25 minutes with forming anti-nodes at the both inward inlets and possessing a node at the bay mouth, mode-2 oscillation of the period around 12 minutes which oscillates between the both inward inlets having the node at the branching point. Next, numerical simulations were conducted to reproduce the secondary oscillations in the bay by providing input sinusoidal waves with the eigen periods of oscillations to the calculating bay geometry. The numerical results are found to show basically consistent characteristics with the field observations.
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Knizhnik, Kalman, Manuel Luna, Karin Muglach, Holly Gilbert, Therese Kucera, and Judith Karpen. "Observational Study of Large Amplitude Longitudinal Oscillations in a Solar Filament." Proceedings of the International Astronomical Union 8, S300 (June 2013): 428–29. http://dx.doi.org/10.1017/s174392131301140x.
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AbstractOn 20 August 2010 an energetic disturbance triggered damped large-amplitude longitudinal (LAL) oscillations in almost an entire filament. In the present work we analyze this periodic motion in the filament to characterize the damping and restoring mechanism of the oscillation. Our method involves placing slits along the axis of the filament at different angles with respect to the spine of the filament, finding the angle at which the oscillation is clearest, and fitting the resulting oscillation pattern to decaying sinusoidal and Bessel functions. These functions represent the equations of motion of a pendulum damped by mass accretion. With this method we determine the period and the decaying time of the oscillation. Our preliminary results support the theory presented by Luna and Karpen (2012) that the restoring force of LAL oscillations is solar gravity in the tubes where the threads oscillate, and the damping mechanism is the ongoing accumulation of mass onto the oscillating threads. Following an earlier paper, we have determined the magnitude and radius of curvature of the dipped magnetic flux tubes hosting a thread along the filament, as well as the mass accretion rate of the filament threads, via the fitted parameters.
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Tozzi, J. T., and C. H. von Kerczek. "The Stability of Oscillatory Hagen-Poiseuille Flow." Journal of Applied Mechanics 53, no. 1 (March 1, 1986): 187–92. http://dx.doi.org/10.1115/1.3171709.
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The linear stability theory of the nonzero mean, sinusoidally oscillating flow in a tube of circular cross section is examined. It is found that the relevant axisymmetric disturbances in the oscillatory flow are more stable (i.e., have larger decay rates) than the axisymmetric disturbances of the mean flow alone. This result holds for values of the cross-sectional average oscillation velocity amplitude at least as large as seven-tenths the average mean-flow velocity amplitude. Although the instantaneous velocity profile contains generalized inflection rings for a substantial portion of the oscillation period, the disturbances do not become instantaneously unstable at any time, even for very low frequency oscillations.
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ZHANG, JIANXIN, XIAODONG CHEN, and ANTHONY C. DAVIES. "LOOP GAIN AND ITS RELATION TO NONLINEAR BEHAVIOR AND CHAOS IN A TRANSFORMER-COUPLED OSCILLATOR." International Journal of Bifurcation and Chaos 14, no. 07 (July 2004): 2503–12. http://dx.doi.org/10.1142/s0218127404010783.
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A relationship between the loop gain and nonlinear behavior of a transformer-coupled oscillator is established in this paper. With increase of the loop gain, the system undergoes a series of changes in its dynamical behavior, i.e. no oscillation, near-sinusoidal, period-doubling, chaotic and squegging oscillations. It is expected that the approach of loop gain analysis can be universally applied to investigating the nonlinear behavior, especially chaos, in other oscillators.
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Tagliazucchi, M., and I. Szleifer. "Dynamics of dissipative self-assembly of particles interacting through oscillatory forces." Faraday Discussions 186 (2016): 399–418. http://dx.doi.org/10.1039/c5fd00115c.
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Dissipative self-assembly is the formation of ordered structures far from equilibrium, which continuously uptake energy and dissipate it into the environment. Due to its dynamical nature, dissipative self-assembly can lead to new phenomena and possibilities of self-organization that are unavailable to equilibrium systems. Understanding the dynamics of dissipative self-assembly is required in order to direct the assembly to structures of interest. In the present work, Brownian dynamics simulations and analytical theory were used to study the dynamics of self-assembly of a mixture of particles coated with weak acids and bases under continuous oscillations of the pH. The pH of the system modulates the charge of the particles and, therefore, the interparticle forces oscillate in time. This system produces a variety of self-assembled structures, including colloidal molecules, fibers and different types of crystalline lattices. The most important conclusions of our study are: (i) in the limit of fast oscillations, the whole dynamics (and not only those at the non-equilibrium steady state) of a system of particles interacting through time-oscillating interparticle forces can be described by an effective potential that is the time average of the time-dependent potential over one oscillation period; (ii) the oscillation period is critical to determine the order of the system. In some cases the order is favored by very fast oscillations while in others small oscillation frequencies increase the order. In the latter case, it is shown that slow oscillations remove kinetic traps and, thus, allow the system to evolve towards the most stable non-equilibrium steady state.
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Qian, S. B., L. Liu, and L. Y. Zhu. "Complex Period Variations of the Neglected W UMa-type Binary System NY Lyrae." Publications of the Astronomical Society of Australia 26, no. 1 (2009): 7–10. http://dx.doi.org/10.1071/as08009.
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AbstractOrbital-period variations of the neglected W UMa-type binary star, NY Lyr, were analyzed based on two newly determined eclipse times together with the others compiled from the literature. A cyclic oscillation with a period of 82.1 yr and an amplitude of 0.0247 d was discovered to be superimposed on a continuous period increase (dP/dt = +1.33 × 10−7 d yr−1). After the long-term period increase and the large-amplitude cyclic oscillation were removed from the O–C diagram, the residuals suggest that there is another small-amplitude period oscillation (A4 = 0.0053 d, P4 = 19.4 years) in the orbital period changes. As in the cases of AH Cnc and AD Cnc, both the continuous period increase and the two cyclic period oscillations make NY Lyr an interesting system to study in the future. In order to understand the evolutionary state of the binary system, new photometric and spectroscopic observations and a careful investigation on those data are needed.
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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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Jacobi, Ch, N. Samtleben, and G. Stober. "Meteor radar observations of mesopause region long-period temperature oscillations." Advances in Radio Science 14 (September 28, 2016): 169–74. http://dx.doi.org/10.5194/ars-14-169-2016.
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Abstract. Meteor radar observations of mesosphere/lower thermosphere (MLT) daily temperatures have been performed at Collm, Germany since August 2004. The data have been analyzed with respect to long-period oscillations at time scales of 2–30 days. The results reveal that oscillations with periods of up to 6 days are more frequently observed during summer, while those with longer periods have larger amplitudes during winter. The oscillations may be considered as the signature of planetary waves. The results are compared with analyses from radar wind measurements. Moreover, the temperature oscillations show considerable year-to-year variability. In particular, amplitudes of the quasi 5-day oscillation have increased during the last decade, and the quasi 10-day oscillations are larger if the equatorial stratospheric winds are eastward.
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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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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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Karpova, N. V., L. N. Petrova, and G. M. Shved. "Statistical study of seismic and ground pressure oscillations with steady frequencies in the 0.7–5 h period range." Annales Geophysicae 20, no. 6 (June 30, 2002): 823–33. http://dx.doi.org/10.5194/angeo-20-823-2002.
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Abstract. Product spectra of ground pressure variation and seismic oscillations have been calculated in the period sub-ranges of 42–90 min and 2.5–5 h, based on synchronous, co-located microbarograph and seismograph measurements at St. Petersburg (60° N, 30° E). The 200 records of 2–3.5 days in length and a combined duration of 525 days have been used. The product spectra have been computed for winter, spring, summer, and autumn, both individually and in combination. The spectra of different seasons are distinct from each other for both microbarograph and seismograph measurements; this can be caused by a seasonal variation in both frequency and amplitude of free oscillations of the atmosphere. There are pressure and seismic oscillations with close frequencies in the spectra for both, for each season and when all seasons are combined. At present, suggestions may only be made regarding the origin of most of these common oscillations. Once again, the penetration of the Earth’s free oscillation 0S2 with a period of about 54 min into the atmosphere has been confirmed. A common pressure and seismic oscillation with the 206 min period has been detected and has attracted considerable interest. The 159-min periodicity revealed in pressure variations may be associated with the well-known solar oscillation of the 160.01 min period.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)
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Nakariakov, Valery M., and Dmitrii Y. Kolotkov. "Magnetohydrodynamic Waves in the Solar Corona." Annual Review of Astronomy and Astrophysics 58, no. 1 (August 18, 2020): 441–81. http://dx.doi.org/10.1146/annurev-astro-032320-042940.
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The corona of the Sun is a unique environment in which magnetohydrodynamic (MHD) waves, one of the fundamental processes of plasma astrophysics, are open to a direct study. There is striking progress in both observational and theoretical research of MHD wave processes in the corona, with the main recent achievements summarized as follows: ▪ Both periods and wavelengths of the principal MHD modes of coronal plasma structures, such as kink, slow and sausage modes, are confidently resolved. ▪ Scalings of various parameters of detected waves and waveguiding plasma structures allow for the validation of theoretical models. In particular, kink oscillation period scales linearly with the length of the oscillating coronal loop, clearly indicating that they are eigenmodes of the loop. Damping of decaying kink and standing slow oscillations depends on the oscillation amplitudes, demonstrating the importance of nonlinear damping. ▪ The dominant excitation mechanism for decaying kink oscillations is associated with magnetized plasma eruptions. Propagating slow waves are caused by the leakage of chromospheric oscillations. Fast wave trains could be formed by waveguide dispersion. ▪ The knowledge gained in the study of coronal MHD waves provides ground for seismological probing of coronal plasma parameters, such as the Alfvén speed, the magnetic field and its topology, stratification, temperature, fine structuring, polytropic index, and transport coefficients.
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Hampson, John, and Peter Haynes. "Phase Alignment of the Tropical Stratospheric QBO in the Annual Cycle." Journal of the Atmospheric Sciences 61, no. 21 (November 1, 2004): 2627–37. http://dx.doi.org/10.1175/jas3276.1.
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Abstract This paper investigates the occurrence of phase alignment of the tropical stratospheric quasi-biennial oscillation (QBO) with the annual cycle. First, updating previous studies, observational results are shown for NCEP reanalysis data and Singapore radiosondes: both datasets show strong phase alignment of the QBO at 24.5 km. Phase alignment is investigated in a 3D mechanistic stratospheric model including explicit large-scale planetary waves, forced by a lower boundary geopotential anomaly, and a simple equatorial wave parameterization. The model simulates a QBO-like oscillation, with the period depending on the lower boundary momentum flux of the parameterized waves. Phase alignment is manifested in two different ways. First, simulated oscillations of both integer and noninteger year periods are shown to lock on to a certain phase of the annual cycle. Second, when the magnitude of the lower boundary momentum flux is varied about a range implying oscillation period close to 2 yr, the period of the resulting oscillation is exactly 2 yr for a finite range of such magnitude. Analysis of the 3D model results suggest that the the phase alignment is due largely to the annual cycle in tropical upwelling. This hypothesis is supported by simulations with a 1D equatorial model including both parameterized waves and seasonally varying upwelling. The oscillations in this model show significant phase alignment when the upwelling parameters are tuned to correspond to the 3D model, although the phase alignment is weaker than that seen in the 3D model.
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Wright, Peter B. "Homogenized long-period Southern Oscillation indices." International Journal of Climatology 9, no. 1 (January 1989): 33–54. http://dx.doi.org/10.1002/joc.3370090104.
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Mashnich, G. P., and V. S. Bashkirtsev. "Latitudinal Variations of Line-of-Sight Velocity Oscillations in the Photosphere, Chromosphere and Prominences." International Astronomical Union Colloquium 167 (1998): 131–34. http://dx.doi.org/10.1017/s0252921100047448.
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AbstractBy studying line-of-sight velocity time variations in prominences, we found that velocity oscillations with a period over 40 min have a reasonably well-marked dependence of the period length with heliolatitude. Simultaneous observations of line-of-sight velocities in the photosphere and chromosphere showed that quasi-hourly oscillation periods at these levels in the solar atmosphere and in prominences have a similar latitudinal behavior.
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REN, XIU-BIN, and XIANG-YUN GUO. "INFLUENCE OF THE REACTION TEMPERATURE ON THE OSCILLATORY BEHAVIOR DURING PARTIAL OXIDATION OF METHANE." Surface Review and Letters 15, no. 06 (December 2008): 769–74. http://dx.doi.org/10.1142/s0218625x0801213x.
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The oscillatory behavior during partial oxidation of methane was studied by the Monte Carlo simulation with Langmuir–Hinshelwood mechanism and oxide formation and removal. The well-developed reaction rate oscillations can be observed when the CH 4 adsorption probability varies in a small window. The oscillation window is very sensitive to the variation of reaction temperature. When the temperature increases, the window for sustained oscillation becomes narrow and has an obvious shift. In the meantime, the oscillation period tends to become small and the amplitude decreases. When the temperature increases to a certain value, the oscillations will disappear.
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Chou, H. F., N. Berman, and E. Ipp. "Oscillations of lactate released from islets of Langerhans: evidence for oscillatory glycolysis in beta-cells." American Journal of Physiology-Endocrinology and Metabolism 262, no. 6 (June 1, 1992): E800—E805. http://dx.doi.org/10.1152/ajpendo.1992.262.6.e800.
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Oscillations in the glycolytic process have been demonstrated in a number of different biological systems. However, their presence has never been demonstrated in insulin-secreting beta-cells. We used lactate as a marker for glycolysis and measured lactate and insulin concentrations in the effluent of isolated perifused rat islets of Langerhans. Sustained regular oscillations in lactate concentrations with an average period of 16-20 min were observed in islets that were perifused with medium containing 5.5 or 16.7 mM glucose. Sustained oscillations of insulin concentrations secreted by the islets were also observed in these experiments, and the average period of oscillation was 14.6 +/- 2.3 min at 16.7 mM glucose. Mean insulin concentrations at 5.5 mM glucose were too low to permit analysis of oscillations. Spectral analysis confirmed the regularity of the lactate and insulin oscillations and showed peaks that were consistent with the average periods obtained using the Clifton program. Moreover, spectral analysis demonstrated marked similarity between the patterns of lactate and insulin oscillation during perifusion with 16.7 mM glucose. Cross-correlation analysis found these oscillations not to be consistently in phase. In conclusion, sustained oscillations in lactate released from islets of Langerhans suggest that the glycolytic process in beta-cells also oscillates. The similarity of the periods of lactate and insulin raises the possibility that oscillations in glycolysis may provide a mechanism for pulsatile insulin secretion.
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Bianchini, A., M. Friedjung, and W. Brinkmann. "New Results About Post Optical Maximum Oscillations of Novae." International Astronomical Union Colloquium 122 (1990): 155–56. http://dx.doi.org/10.1017/s0252921100068482.
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AbstractNew results presented include the oscillations of intervals between maxima of light oscillations, while in the case of GK Per the Orion system velocities oscillated with twice the light oscillation period.
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Mitura, Z., S. L. Dudarev, and M. J. Whelan. "Theoretical Investigations of RHEED Oscillations." Microscopy and Microanalysis 5, S2 (August 1999): 710–11. http://dx.doi.org/10.1017/s1431927600016871.
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Nowadays there is great interest in the application of reflection high energy electron diffraction (RHEED) to monitor the growth of ultra thin films. This popularity of RHEED arose from the discovery of RHEED intensity oscillations in the early eighties. Namely, it was experimentally found that if the growth of a material follows a layer-by-layer mode then regular oscillating changes in the intensity of the specular beam occur, and the period of the oscillations corresponds to the deposition of one atomic layer of the material. These findings are of great practical importance and consequently RHEED is an important experimental technique used in nanoscale engineering. Nevertheless, the basic question of why RHEED oscillation are observed still remains open. In the past the Philips group suggested that intensity oscillations are a consequence of periodic changes in the roughness of the surface. About the same time, the University of Minnesota group claimed that during the growth the electron wave is reflected by two terraces (in an idealised case) and periodic changes of the interference conditions imply RHEED oscillation.
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Sharma, Vijay Kumar, Tom Kristian Bardal, and Anders Johnsson. "Light-Dependent Changes in the Leaflet Movement Rhythm of the Plant Desmodium gyrans." Zeitschrift für Naturforschung C 58, no. 1-2 (February 1, 2003): 81–86. http://dx.doi.org/10.1515/znc-2003-1-215.
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The movements of the lateral leaflets of the Indian telegraph plant Desmodium gyrans (L. F.) DC, have earlier been studied in detail with regards to the effects of chemicals, DC currents, and static magnetic fields. In the present paper we have discussed the oscillation of the lateral leaflets under the influence of white light of various light levels (0-75 μmol · m-2 · s-1), produced by an array of LEDs (light emitting diodes). LEDs were used in contrast to fluorescense tubes as in earlier studies in order to minimize changes of wavelength when light intensity was decreased or increased. Furthermore, care was taken to ensure that the temperature in the experimental chamber was constant. When the oscillations were first monitored in bright light, the oscillations were found to be very rapid and with decreasing light intensity the oscillations slowed down. For light levels lower than about 20 μmol · m-2 · s-1 the period of the oscillation of the lateral leaflets was almost constant (or even decreased slightly towards complete darkness). We also show that the oscillations could completely stop under prolonged darkness (for longer than about 6 h) and that such halted oscillations could be restarted in most of the leaflets when he light was turned back on. Such stopping of the oscillation of the lateral leaflets in prolonged darkness suggests that these short period oscillations of the lateral leaflets could have a daily component and in natural environment these oscillations could serve the purpose of optimising the amount of light falling on the leaflets or/and facilitating transpiration of water through stomata. Such a finding could have an implication for the answer to the long standing question of adaptive significance of short period oscillation of the Indian telegraph plant Desmodium gyrans (L.F.) DC
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Shi, Laishun, Xiaomei Wang, Na Li, Jie Liu, and Chunying Yan. "Chlorine Dioxide-Iodide-Methyl Acetoacetate Oscillation Reaction Investigated by UV-Vis and Online FTIR Spectrophotometric Method." Scientific World Journal 2012 (2012): 1–9. http://dx.doi.org/10.1100/2012/918620.
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In order to study the chemical oscillatory behavior and mechanism of a new chlorine dioxide-iodide ion-methyl acetoacetate reaction system, a series of experiments were done by using UV-Vis and online FTIR spectrophotometric method. The initial concentrations of methyl acetoacetate, chlorine dioxide, potassium iodide, and sulfuric acid and the pH value have great influence on the oscillation observed at wavelength of 289 nm. There is a preoscillatory or induction period, and the amplitude and the number of oscillations are associated with the initial concentration of reactants. The equations for the triiodide ion reaction rate changing with reaction time and the initial concentrations in the oscillation stage were obtained. Oscillation reaction can be accelerated by increasing temperature. The apparent activation energies in terms of the induction period and the oscillation period were 26.02 KJ/mol and 17.65 KJ/mol, respectively. The intermediates were detected by the online FTIR analysis. Based upon the experimental data in this work and in the literature, a plausible reaction mechanism was proposed for the oscillation reaction.
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Fabrikant, A. L. "Harbour oscillations generated by shear flow." Journal of Fluid Mechanics 282 (January 10, 1995): 203–17. http://dx.doi.org/10.1017/s0022112095000103.
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A new mechanism that could be responsible for excitation of long-period oscillations in partially enclosed harbours is discussed. This mechanism is based on the interaction between a shear flow and the harbour-basin natural mode and does not suppose any external exciting forces caused by wind waves, tsunami, etc. The growth rate of harbour oscillations is found in terms of a plane-wave reflection coefficient integrated on the wavenumber spectrum of the oscillating outflow field near the harbour entrance. Analytical considerations for simple shear flows (vortex sheet and jet) show that the growth rate changes its sign depending on the ratio of oscillation frequency to flow speed.
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Grančičová, Ol’ga, Anna Olexová, and Tomáš Zacher. "The Effect of Anionic, Cationic and Nonionic Surfactants on the Uncatalyzed Bromate Oscillator." Zeitschrift für Naturforschung A 63, no. 7-8 (August 1, 2008): 475–81. http://dx.doi.org/10.1515/zna-2008-7-815.
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The response of an uncatalyzed bromate oscillator with phenol as substrate to the increasing concentrations of cationic (CTAN), anionic (SDS) and nonionic surfactants (Brij-30 and Triton X-100) was monitored at (25±0.1) °C under stirred batch conditions. Addition of the surfactants influenced the oscillatory parameters: a slight increase of the induction period of the first series of oscillations, a significant increase of the induction period of the second series of oscillations and a gradual decrease of the oscillation numbers of both series until complete disappearance at a certain surfactant concentration. The changes in the oscillatory parameters have been ascribed to solubilization of phenol and of bromination products in the micelles, to inhibition of bromination of the aromatic substrate due to bromine solubilization, and to the catalytic effect of the charged micelle surface.
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Kravchenko, V. O., O. M. Evtushevsky, A. V. Grytsai, and G. P. Milinevsky. "Decadal variability of winter temperatures in the Antarctic Peninsula region." Antarctic Science 23, no. 6 (June 13, 2011): 614–22. http://dx.doi.org/10.1017/s0954102011000423.
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AbstractRapid climate warming has been observed in the region of the Antarctic Peninsula since the middle of the last century with the largest warming rate in the winter. Decadal variability of winter temperature on the regional scale was analysed using eight station datasets of the Antarctic Peninsula region. The Scientific Committee on Antarctic Research Reference Antarctic Data for Environmental Research from the period 1950–2009 were used. Fourier and wavelet transforms of the averaged temperature anomaly time series reveal a clear separation between the oscillations with three to eight year periods and a decadal oscillation with a period of around 16 years. On the Antarctic Peninsula region scale, 16 year periodicity in the winter temperature variability has not been described before. Both spectral components show similar spectral power and statistical significance (5–10%). This is evidence of their comparable importance for winter temperature changes in the Antarctic Peninsula region. The three to eight year periods are most probably related to the El Niño–Southern Oscillation and Antarctic Circumpolar Wave signals, but the 16 year oscillation has not been identified within the scope of this analysis. The possible effect of the decadal oscillation in the winter temperature trend estimate is discussed.
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Shao, Xiao Yi, Ying Chang Wang, and Xi Chun Xing. "Detection of Earth’s Free Oscillations Stimulated by the Mw8.3 Okhotsk Sea Earthquake in 2013 Based on Observational Data of Water-Tube Tiltmeters in Shaanxi Province." Applied Mechanics and Materials 568-570 (June 2014): 198–202. http://dx.doi.org/10.4028/www.scientific.net/amm.568-570.198.
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Using power spectrum density estimation method, analyzed the digital observational data of water-tube tiltmeters of Shaanxi deformation monitoring network in 6 seismic stations as QL, HZ, HY, BJ, XA and NQ, which detected the earth’s free oscillations stimulated by the Mw8.3 Okhotsk Sea Earthquake in May 24th, 2013. The results show that radical shock of spherical oscillation (0S05~0S32), harmonic spherical oscillation (3S01, 1S04, 2S04, 1S06) and toroidal oscillations (0T05~0T09) are detected effectively. Comparing the period of the extracted oscillation with that the theoretical oscillation of the Preliminary Reference Earth Model (PREM), finding that they are accordant with each other and the relative error is less than 0.2%. And the result is consistent with the CDSN Urumqi observatory recorded in M8.1 Kunlun Mountains Earthquake in 2001.
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Svalov, A. M. "Effect of compact inclusion on the natural frequencies of vibrations of a pipe string in a well." SOCAR Proceedings, no. 1 (March 30, 2021): 73–77. http://dx.doi.org/10.5510/ogp20210100482.
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The influence of small-size inclusion of pipes in a well column on the natural frequency of its longitudinal vibrations is investigated. Using the asymptotic expansion in a small parameter, an analytical relation is obtained that describes the change in the period of the column oscillations in the form of some additional small term to the period of the homogeneous column oscillations. Numerical calculations show that the obtained analytical relations almost accurately describe the oscillation period of a column with a massive compact inclusion, while its difference from the oscillation period of a homogeneous column is within ~20%. The results obtained can be useful for preventing resonant phenomena in the drill string when drilling wells, as well as for optimal use of the longitudinal vibrations of the tubing string to influence the bottom-hole zones of producing wells.
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Fedotov, A. B. "Long-period variability of ocean circulation at different intensity of wind impact." Monitoring systems of environment, no. 4 (December 24, 2020): 29–34. http://dx.doi.org/10.33075/2220-5861-2020-4-29-34.
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Within the framework of a numerical model of a two-layer ocean with the depth of layers corresponding to average oceanic conditions, the evolution of large-scale circulation under the action of an external vorticity flow of different intensity with constant dissipation parameters is studied. The characteristic time scales of long-period oscillations of current energy at different values of wind impact, jet flow parameters, and the time-average level of total energy in the mode of long-period oscillations at different wind impact intensity are analyzed. The stability of the long-period oscillation regime under various initial conditions of the problem is discussed.
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Herrmann, Maximilian, Le Cao, Holger Sihler, Ulrich Platt, and Eva Gutheil. "On the contribution of chemical oscillations to ozone depletion events in the polar spring." Atmospheric Chemistry and Physics 19, no. 15 (August 13, 2019): 10161–90. http://dx.doi.org/10.5194/acp-19-10161-2019.
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Abstract. This paper presents a numerical study of the oscillations (or recurrences) of tropospheric ozone depletion events (ODEs) using the further-developed one-dimensional KInetic aNALysis of reaction mechanics with Transport (KINAL-T) chemistry transport model. Reactive bromine is the major contributor to the occurrence of ODEs. After the termination of an ODE, the reactive bromine in the air is deposited onto aerosols or on the snow surface, and the ozone may regenerate via NOx-catalyzed photochemistry or by turbulent transport from the free troposphere into the boundary layer. The replenished ozone then is available for the next cycle of autocatalytic bromine release (bromine explosion) leading to another ODE. The oscillation periods are found to be as short as 5 d for the purely chemically NOx-driven oscillation and 30 d for a diffusion-driven oscillation. An important requirement for oscillation of ODEs to occur is found to be a sufficiently strong inversion layer. In a parameter study, the dependence of the oscillation period on the nitrogen oxides' concentration, the inversion layer strength, the ambient temperature, the aerosol density, and the solar radiation is investigated. Parameters controlling the oscillation of ODEs are discussed.
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Saprykina, Yana, and Sergey Kuznetsov. "Analysis of the Variability of Wave Energy Due to Climate Changes on the Example of the Black Sea." Energies 11, no. 8 (August 3, 2018): 2020. http://dx.doi.org/10.3390/en11082020.
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An analysis of the variability of wave climate and energy within the Black Sea for the period 1960–2011 was made using field data from the Voluntary Observing Ship Program. Methods using wavelet analysis were applied. It was determined that the power flux of wave energy in the Black Sea fluctuates: the highest value is 4.2 kW/m, the lowest is 1.4 kW/m. Results indicate significant correlations among the fluctuations of the average annual wave heights, periods, the power flux of wave energy, and teleconnection patterns of the North Atlantic Oscillation (NAO), the Atlantic Multi-decadal Oscillation (AMO), the Pacific Decadal Oscillation (PDO) and the East Atlantic/West Russia (EA/WR). It was revealed that, in positive phases of long-term periods of AMO (50–60 years) as well as PDO, NAO, and AO (40 years), a decrease of wave energy was observed; however, an increase in wave energy was observed in the positive phase of a 15-year period of NAO and AO. The positive phase of changes of EA/WR for periods 50–60, 20–25, and 13 years led to an increase of wave energy. The approximation functions of the oscillations of the average annual wave heights, periods, and the power flux of wave energy for the Black Sea are proposed.
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Tian, Caixia, Xiong Hu, Yurong Liu, Xuan Cheng, Zhaoai Yan, and Bing Cai. "Seasonal Variations of High-Frequency Gravity Wave Momentum Fluxes and Their Forcing toward Zonal Winds in the Mesosphere and Lower Thermosphere over Langfang, China (39.4° N, 116.7° E)." Atmosphere 11, no. 11 (November 20, 2020): 1253. http://dx.doi.org/10.3390/atmos11111253.
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Meteor radar data collected over Langfang, China (39.4° N, 116.7° E) were used to estimate the momentum flux of short-period (less than 2 h) gravity waves (GWs) in the mesosphere and lower thermosphere (MLT), using the Hocking (2005) analysis technique. Seasonal variations in GW momentum flux exhibited annual oscillation (AO), semiannual oscillation (SAO), and quasi-4-month oscillation. Quantitative estimations of GW forcing toward the mean zonal flow were provided using the determined GW momentum flux. The mean flow acceleration estimated from the divergence of this flux was compared with the observed acceleration of zonal winds displaying SAO and quasi-4-month oscillations. These comparisons were used to analyze the contribution of zonal momentum fluxes of SAO and quasi-4-month oscillations to zonal winds. The estimated acceleration from high-frequency GWs was in the same direction as the observed acceleration of zonal winds for quasi-4-month oscillation winds, with GWs contributing more than 69%. The estimated acceleration due to Coriolis forces to the zonal wind was studied; the findings were opposite to the estimated acceleration of high-frequency GWs for quasi-4-month oscillation winds. The significance of this study lies in estimating and quantifying the contribution of the GW momentum fluxes to zonal winds with quasi-4-month periods over mid-latitude regions for the first time.
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Shved, G. M., L. N. Petrova, and O. S. Polyakova. "Penetration of the Earth's free oscillations at 54 minute period into the atmosphere." Annales Geophysicae 18, no. 5 (May 31, 2000): 566–72. http://dx.doi.org/10.1007/s00585-000-0566-0.
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Abstract. It is known that the fundamental spheroidal mode 0S2 of the Earth free oscillation with a period of about 54 min forces atmospheric oscillations. We present a certain phase relationship for components of the 0S2 multiplet, which is based on synchronous collocated microbarograph and seismograph observations. This relationship is both the first observational manifestation of the Pekeris mode of global atmospheric oscillations with the 54 min period and a further proof of the Earth's 0S2 mode penetrating into the atmosphere. We show that the linear non-dissipative model of steady forced oscillations in isothermal atmosphere at rest does not describe the penetration of the 0S2 mode into the atmosphere adequately.Key words: Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)
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DI CICCA, GAETANO MARIA, GAETANO IUSO, PIER GIORGIO SPAZZINI, and MICHELE ONORATO. "Particle image velocimetry investigation of a turbulent boundary layer manipulated by spanwise wall oscillations." Journal of Fluid Mechanics 467 (September 24, 2002): 41–56. http://dx.doi.org/10.1017/s002211200200157x.
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Particle image velocimetry has been applied to the study of a canonical turbulent boundary layer and to a turbulent boundary layer forced by transversal wall oscillations. This work is part of the research programme at the Politecnico di Torino aerodynamic laboratory with the objective of investigating the response of near-wall turbulence to external perturbations. Results are presented for the optimum oscillation period of 100 viscous time units and for an oscillation amplitude of 320 viscous units. As expected, turbulent velocity fluctuations are considerably reduced by the wall oscillations. Particle image velocimetry has allowed comparisons between the canonical and forced flows in an attempt to find the physical mechanisms by which the wall oscillation influences the near-wall organized motions.
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Altadill, D. "On the 18-day quasi-periodic oscillation in the ionosphere." Annales Geophysicae 14, no. 7 (July 31, 1996): 716–24. http://dx.doi.org/10.1007/s00585-996-0716-0.
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Abstract. The presence and persistence of an 18-day quasi-periodic oscillation in the ionospheric electron density variations were studied. The data of lower ionosphere (radio-wave absorption at equivalent frequency near 1 MHz), middle and upper ionosphere (critical frequencies f0E and f0F2) for the period 1970–1990 have been used in the analysis. Also, solar and geomagnetic activity data (the sunspot numbers Rz and solar radio flux F10.7 cm, and aN index respectively) were used to compare the time variations of the ionospheric with the solar and geomagnetic activity data. Periodogram, complex demodulation, auto- and cross-correlation analysis have been used. It was found that 18-day quasi-periodic oscillation exists and persists in the temporal variations of the ionospheric parameters under study with high level of correlation and mean period of 18–19 days. The time variation of the amplitude of the 18-day quasi-periodic oscillation in the ionosphere seems to be modulated by the long-term solar cycle variations. Such oscillations exist in some solar and geomagnetic parameters and in the planetary wave activity of the middle atmosphere. The high similarities in the amplitude modulation, long-term amplitude variation, period range between the oscillation of investigated parameters and the global activity of oscillation suggests a possible solar influence on the 18-day quasi-periodic oscillation in the ionosphere.
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Hara, Yusuke, and Rumana A. Jahan. "Self-Oscillating Behaviors of Negatively Charged Polymer Chain Induced by the Belousov-Zhabotinsky Reaction." Advanced Materials Research 181-182 (January 2011): 206–11. http://dx.doi.org/10.4028/www.scientific.net/amr.181-182.206.
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In this paper, we studied the effect of the temperature and the initial concentration of sodium bromate (NaBrO3) on the aggregation-disaggregation self-oscillation for a polymer chain. The polymer chain consisted of N-isopropylacrylamide (NIPAAm), Ru catalyst of the BZ reaction and Acrylamide-2-methylpropanesulfonic acid (AMPS) as a solubility control site. The concentration of sodium bromate and the temperature significantly affected the self-oscillating behavior and the period of the aggregation-disaggregation self-oscillation. Moreover, the amplitude of the aggregation-disaggregation self-oscillation of the AMPS-containing polymer solution decreased with time. The damping behavior is originating from the increase in the size of the polymer chain. In addition, this study clarified that the period of the self-oscillation of the AMPS-containing polymer solution in the strongly acidic condition was significantly shorter than that in the acid-free condition.
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Offermann, Dirk, Christoph Kalicinsky, Ralf Koppmann, and Johannes Wintel. "Very long-period oscillations in the atmosphere (0–110 km)." Atmospheric Chemistry and Physics 21, no. 3 (February 5, 2021): 1593–611. http://dx.doi.org/10.5194/acp-21-1593-2021.
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Abstract. Multi-annual oscillations have been observed in measured atmospheric data. These oscillations are also present in general circulation models. This is the case even if the model boundary conditions with respect to solar cycle, sea surface temperature, and trace gas variability are kept constant. The present analysis contains temperature oscillations with periods from below 5 up to more than 200 years in an altitude range from the Earth's surface to the lower thermosphere (110 km). The periods are quite robust as they are found to be the same in different model calculations and in atmospheric measurements. The oscillations show vertical profiles with special structures of amplitudes and phases. They form layers of high or low amplitudes that are a few dozen kilometres wide. Within the layers the data are correlated. Adjacent layers are anticorrelated. A vertical displacement mechanism is indicated with displacement heights of a few 100 m. Vertical profiles of amplitudes and phases of the various oscillation periods as well as their displacement heights are surprisingly similar. The oscillations are related to the thermal and dynamical structure of the middle atmosphere. These results are from latitudes and longitudes in central Europe.