Artykuły w czasopismach: „Large scale oscillations”

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Shen, Yuandeng. "Multi-wavelength observations of filament oscillations induced by shock waves". Proceedings of the International Astronomical Union 11, S320 (sierpień 2015): 106–8. http://dx.doi.org/10.1017/s1743921316000193.

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AbstractTwo cases of filament oscillations induced by large-scale coronal shock waves are presented. For the first case, a chain of transverse oscillating filaments are observed in a proper order after the passing of a shock wave, and it is found that the they were triggered by the surface component of the dome-shaped shock wave. For the second case, simultaneous transverse oscillation of a limb prominence and longitudinal oscillation in an on-disk filament are launched by a single shock wave. It is found that the interaction angle between the shock wave and the prominence axis is the key to launch transverse or longitudinal filament oscillations. In addition, filament magnetic fields are estimated, using the measured parameters.

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Garcia, Javier O., Emily D. Grossman i Ramesh Srinivasan. "Evoked potentials in large-scale cortical networks elicited by TMS of the visual cortex". Journal of Neurophysiology 106, nr 4 (październik 2011): 1734–46. http://dx.doi.org/10.1152/jn.00739.2010.

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Single pulses of transcranial magnetic stimulation (TMS) result in distal and long-lasting oscillations, a finding directly challenging the virtual lesion hypothesis. Previous research supporting this finding has primarily come from stimulation of the motor cortex. We have used single-pulse TMS with simultaneous EEG to target seven brain regions, six of which belong to the visual system [left and right primary visual area V1, motion-sensitive human middle temporal cortex, and a ventral temporal region], as determined with functional MRI-guided neuronavigation, and a vertex “control” site to measure the network effects of the TMS pulse. We found the TMS-evoked potential (TMS-EP) over visual cortex consists mostly of site-dependent theta- and alphaband oscillations. These site-dependent oscillations extended beyond the stimulation site to functionally connected cortical regions and correspond to time windows where the EEG responses maximally diverge (40, 200, and 385 ms). Correlations revealed two site-independent oscillations ∼350 ms after the TMS pulse: a theta-band oscillation carried by the frontal cortex, and an alpha-band oscillation over parietal and frontal cortical regions. A manipulation of stimulation intensity at one stimulation site (right hemisphere V1-V3) revealed sensitivity to the stimulation intensity at different regions of cortex, evidence of intensity tuning in regions distal to the site of stimulation. Together these results suggest that a TMS pulse applied to the visual cortex has a complex effect on brain function, engaging multiple brain networks functionally connected to the visual system with both invariant and site-specific spatiotemporal dynamics. With this characterization of TMS, we propose an alternative to the virtual lesion hypothesis. Rather than a technique that simulates lesions, we propose TMS generates natural brain signals and engages functional networks.

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FUNFSCHILLING, DENIS, ERIC BROWN i GUENTER AHLERS. "Torsional oscillations of the large-scale circulation in turbulent Rayleigh–Bénard convection". Journal of Fluid Mechanics 607 (30.06.2008): 119–39. http://dx.doi.org/10.1017/s0022112008001882.

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Measurements over the Rayleigh-number range 108 ≲ R ≲ 1011 and Prandtl-number range 4.4≲σ≲29 that determine the torsional nature and amplitude of the oscillatory mode of the large-scale circulation (LSC) of turbulent Rayleigh–Bénard convection are presented. For cylindrical samples of aspect ratio Γ=1 the mode consists of an azimuthal twist of the near-vertical LSC circulation plane, with the top and bottom halves of the plane oscillating out of phase by half a cycle. The data for Γ=1 and σ=4.4 showed that the oscillation amplitude varied irregularly in time, yielding a Gaussian probability distribution centred at zero for the displacement angle. This result can be described well by the equation of motion of a stochastically driven damped harmonic oscillator. It suggests that the existence of the oscillations is a consequence of the stochastic driving by the small-scale turbulent background fluctuations of the system, rather than a consequence of a Hopf bifurcation of the deterministic system. The power spectrum of the LSC orientation had a peak at finite frequency with a quality factor Q≃5, nearly independent of R. For samples with Γ≥2 we did not find this mode, but there remained a characteristic periodic signal that was detectable in the area density ρp of the plumes above the bottom-plate centre. Measurements of ρp revealed a strong dependence on the Rayleigh number R, and on the aspect ratio Γ that could be represented by ρp ~ Γ2.7±0.3. Movies are available with the online version of the paper.

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Haegeli, Pascal, Bret Shandro i Patrick Mair. "Using avalanche problems to examine the effect of large-scale atmosphere–ocean oscillations on avalanche hazard in western Canada". Cryosphere 15, nr 3 (29.03.2021): 1567–86. http://dx.doi.org/10.5194/tc-15-1567-2021.

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Abstract. Numerous large-scale atmosphere–ocean oscillations including the El Niño–Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), the Pacific North American Teleconnection Pattern (PNA), and the Arctic Oscillation (AO) are known to substantially affect winter weather patterns in western Canada. Several studies have examined the effect of these oscillations on avalanche hazard using long-term avalanche activity records from highway avalanche safety programmes. We present a new approach for gaining additional insight into these relationships that uses avalanche problem information published in public avalanche bulletins during the winters of 2010 to 2019. For each avalanche problem type, we calculate seasonal prevalence values for each forecast area, elevation band, and season, which are then included in a series of beta mixed-effects regression models to explore both the overall and regional effects of the Pacific-centered oscillations (POs; including ENSO, PDO, and PNA) and AO on the nature of avalanche hazard in the study area. We find significant negative effects of PO on the prevalence of storm slab avalanche problems, wind slab avalanche problems, and dry loose avalanche problems, which agree reasonably well with the known impacts of PO on winter weather in western Canada. The analysis also reveals a positive relationship between AO and the prevalence of deep persistent slab avalanche problems, particularly in the Rocky Mountains. In addition, we find several smaller-scale patterns that highlight that the avalanche hazard response to these oscillations varies regionally. Even though our study period is short, our study shows that the forecaster judgement included in avalanche problem assessments can add considerable value for these types of analyses. Since the predictability of the most important atmosphere–ocean oscillations is continuously improving, a better understanding of their effect on avalanche hazard can contribute to the development of informative seasonal avalanche forecasts in a relatively simple way.

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Restrepo, Juan Camilo, Aldemar Higgins, Jaime Escobar, Silvio Ospino i Natalia Hoyos. "Contribution of low-frequency climatic–oceanic oscillations to streamflow variability in small, coastal rivers of the Sierra Nevada de Santa Marta (Colombia)". Hydrology and Earth System Sciences 23, nr 5 (16.05.2019): 2379–400. http://dx.doi.org/10.5194/hess-23-2379-2019.

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Abstract. This study evaluated the influence of low-frequency oscillations, that are linked to large-scale oceanographic–atmospheric processes, on streamflow variability in small tropical coastal mountain rivers of the Sierra Nevada de Santa Marta, Colombia. We used data from six rivers that had > 32 years of complete, continuous monthly streamflow records. This investigation employed spectral analyses to (1) explore temporal characteristics of streamflow variability, (2) estimate the net contribution to the energy spectrum of low-frequency oscillations to streamflow anomalies, and (3) analyze the linkages between streamflow anomalies and large-scale, low-frequency oceanographic–atmospheric processes. Wavelet analyses indicate that the 8–12-year component exhibited a quasi-stationary state, with a peak of maximum power between 1985 and 2005. These oscillations were nearly in phase in all rivers. Maximum power peaks occurred for the Palomino and Rancheria rivers in 1985 and 1995, respectively. The wavelet spectrum highlights a change in river variability patterns between 1995 and 2015, characterized by a shift towards the low-frequency oscillations' domain (8–12 years). The net contribution of these oscillations to the energy spectrum was as high as 51 %, a value much larger than previously thought for rivers in northwestern South America. The simultaneous occurrence of hydrologic oscillations, as well as the increase in the amplitude of the 8–12-year band, defined periods of extremely anomalous wet seasons during 1989–1990, 1998–2002 and 2010–2011, reflecting the role of low-frequency oscillations in modulating streamflow variability in these rivers. Cross-wavelet transform and wavelet coherence revealed high common powers and significant coherences in low-frequency bands (>96 months) between streamflow anomalies and Atlantic Meridional Oscillation (AMO), Pacific Decadal Oscillation (PDO) and the Tropical North Atlantic Index (TNA). These results show the role of large-scale, low-frequency oceanographic–climate processes in modulating the long-term hydrological variability of these rivers.

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Švestka, Zdeněk. "Slow-mode oscillations of large-scale coronal loops". Solar Physics 152, nr 2 (lipiec 1994): 505–8. http://dx.doi.org/10.1007/bf00680454.

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Schwarze, Rüdiger, Antje Rückert, Ronny Leonhardt i Frank Obermeier. "Large Scale Oscillations in the Continuous Casting Process". PAMM 5, nr 1 (grudzień 2005): 479–80. http://dx.doi.org/10.1002/pamm.200510216.

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Yang, Dandan, Yanfeng Gao, Ming Yu, Xiaoping Wen i Ming-Xiang Zhao. "Analysis of drag reduction effects in turbulent Taylor–Couette flow controlled via axial oscillation of inner cylinder". Physics of Fluids 34, nr 4 (kwiecień 2022): 045111. http://dx.doi.org/10.1063/5.0087966.

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Analysis of drag reduction effects due to axial oscillation of an inner cylinder in a turbulent Taylor–Couette (TC) flow is performed in the present study. The frictional Reynolds number on the inner cylinder is 218, and the non-dimensional oscillating period is varied from 8 to 32. By examining turbulence statistics, we uncover different impacts of the long- and short-period oscillations on the circumferential ( θ) and radial ( r) velocity fluctuations in large ([Formula: see text]) and small ([Formula: see text]) scales. One of the most surprising findings is that the short-period oscillation increases the large-scale Reynolds shear stress [Formula: see text] by the strong intensification of [Formula: see text] exceeding the suppression of [Formula: see text]. To understand the phenomena, the spectra of each term in the transport equations of the Reynolds normal stresses [Formula: see text] and [Formula: see text] are analyzed. First, it is shown that the short-period oscillation weakens the productions of [Formula: see text], and [Formula: see text] while it enhances that of [Formula: see text]. In contrast, the long-period oscillation reduces the productions of [Formula: see text] and [Formula: see text] while it mainly intensifies that of [Formula: see text]. Second, the investigations of the pressure–strain terms indicate that the short-period oscillation mainly impedes the inter-component energy transfer originating from the small-scale background turbulence. However, the long-period oscillation benefits the small-scale inter-component energy communication while it hinders the large-scale one. In addition, the inverse energy transfer in the turbulent TC flow is confirmed by inspecting the inter-scale energy transfer terms. The hindrance of the inter-scale energy transfer by the inner-cylinder oscillation plays a non-negligible role in the reduction of the wall friction drag.

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Shao, Jun, Jun Wang, Sunyun Lv i Jianping Bing. "Spatial and temporal variability of seasonal precipitation in Poyang Lake basin and possible links with climate indices". Hydrology Research 47, S1 (3.05.2016): 51–68. http://dx.doi.org/10.2166/nh.2016.249.

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Based on the precipitation data of 21 meteorological stations in Poyang Lake basin, the temporal and spatial variability of seasonal precipitation was analyzed by wavelet analysis method. This study adopted the cross wavelet transform to analyze the correlation between the seasonal precipitation and climate indices in time and frequency scales, discussed the possible links between its precipitation variations and climate indices, and preliminarily analyzed its mechanism and regular pattern of variation. The results showed that the oscillations in 2–4 years' and 4–8 years' bands were the main variation periods of seasonal precipitation in Poyang Lake basin. In the 2–4 years' band, the years of rainfall peaks appearing in Poyang Lake were basically consistent with the years when El Niño appeared, and the precipitation oscillations in summer appeared more dramatic in space. According to analysis on the cross wavelet power spectra between different seasonal rainfalls and climate indices, certain correlations between climate factors and seasonal precipitation had existed in specific time periods. Large-scale climate oscillations like the El Niño/Southern Oscillation, North Atlantic Oscillation, Indian Ocean Dipole, and Pacific Decadal Oscillation caused the variability of large-scale circulations through their respective independent or inter-coupled climate systems, and affected the precipitation distribution in Poyang Lake basin by changing local climate conditions like the East Asian Monsoon.

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Jiang, Peng, Zhongbo Yu i Kumud Acharya. "Drought in the Western United States: Its Connections with Large-Scale Oceanic Oscillations". Atmosphere 10, nr 2 (16.02.2019): 82. http://dx.doi.org/10.3390/atmos10020082.

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In this paper, we applied the Empirical Orthogonal Function (EOF) analysis on a drought index expressed as consecutive dry days (CDD) to identify the drought variability in western United States. Based on the EOF analysis, correlation maps were generated between the leading principle component (PC) of seasonal CDD and sea surface temperature (SST) anomalies to explore the dynamic context of the leading modes in CDD. The EOF analysis indicates that the spatiotemporal pattern of winter CDD is related to an integrated impact from El Niño–Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and Atlantic Multi-decadal Oscillation (AMO), while summer CDD is mainly controlled by PDO phases. We also calculated seasonal CDD anomalies during selected climatic phases to further evaluate the impacts of large-scale oceanic oscillation on the spatial pattern of droughts. We found that AMO+/PDO− will contribute to a consistent drought condition during the winter in the western United States. El Niño will bring a dry winter to the northern part of western United States while La Niña will bring a dry winter to the southern part. During El Niño years, the drought center changes with the type of El Niño events. Considering the future states of the examined ocean oscillations, we suggest possible drier than normal conditions in the western United States for upcoming decades, and moreover, an intensified drought for the coast areas of the north Pacific region and upper Mississippi River Basin.

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Fedotov, A. B. "LONG-PERIOD VARIABILITY OF LARGE-SCALE CIRCULATION SYSTEM AND MESOSCALE VORTICES AS SELF-ORGANIZATION PHENOMENON". DEDICATED TO THE 90TH ANNIVERSARY OF PROF. K.N. FEDOROV OCEAN PHYSICS 47, nr 3 (6.11.2019): 206–19. http://dx.doi.org/10.29006/1564-2291.jor-2019.47(3).16.

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Within the framework of the numerical model of a two-layer ocean with the depth of layers corresponding to the average ocean conditions, the evolution of large-scale circulation under the action of an external stationary vorticity flow under constant dissipation parameters is studied, the time scales of long-period oscillations of the energy of flows are analyzed. The temporal variability of the enstrophy spectrum of the system of flows is considered, the connection of oscillations of the total energy of large-scale circulation with oscillations of the position of the center of mass of the enstrophy spectrum of the system is revealed.

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Rouhinen, Santeri, Felix Siebenhühner, J. Matias Palva i Satu Palva. "Spectral and Anatomical Patterns of Large-Scale Synchronization Predict Human Attentional Capacity". Cerebral Cortex 30, nr 10 (2.06.2020): 5293–308. http://dx.doi.org/10.1093/cercor/bhaa110.

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Abstract The capacity of visual attention determines how many visual objects may be perceived at any moment. This capacity can be investigated with multiple object tracking (MOT) tasks, which have shown that it varies greatly between individuals. The neuronal mechanisms underlying capacity limits have remained poorly understood. Phase synchronization of cortical oscillations coordinates neuronal communication within the fronto-parietal attention network and between the visual regions during endogenous visual attention. We tested a hypothesis that attentional capacity is predicted by the strength of pretarget synchronization within attention-related cortical regions. We recorded cortical activity with magneto- and electroencephalography (M/EEG) while measuring attentional capacity with MOT tasks and identified large-scale synchronized networks from source-reconstructed M/EEG data. Individual attentional capacity was correlated with load-dependent strengthening of theta (3–8 Hz), alpha (8–10 Hz), and gamma-band (30–120 Hz) synchronization that connected the visual cortex with posterior parietal and prefrontal cortices. Individual memory capacity was also preceded by crossfrequency phase–phase and phase–amplitude coupling of alpha oscillation phase with beta and gamma oscillations. Our results show that good attentional capacity is preceded by efficient dynamic functional coupling and decoupling within brain regions and across frequencies, which may enable efficient communication and routing of information between sensory and attentional systems.

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Wu, Yanfei, i Yu Xu. "Assessing the Climate Tendency over the Yangtze River Delta, China: Properties, Dry/Wet Event Frequencies, and Causes". Water 12, nr 10 (30.09.2020): 2734. http://dx.doi.org/10.3390/w12102734.

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In view of the important role to in revealing climate wet/dry tendency, Standardized Precipitation Index (SPI) was applied to identify wetness/dryness trends and their relationship with large-scale climate oscillations in the Yangtze River Delta (YRD) from 1957 to 2016. The daily precipitation in 43 meteorological stations was used to calculate SPI time series for a time scale of 12 months. The results indicate that there are three dominant geographic sub-regions of SPI-12 modes. Increasing trends dominate, except for some of the northern regions. High frequencies of wet and dry events are mainly located in the southern regions and part of the northwestern and southeastern regions, respectively. Temporally, large-scale dry events mainly happened in the 1960s–1970s, and wet events in the 1990s and the 2010s. They show a tendency towards more wet conditions of the regional climate in the YRD. The climate variations are primarily controlled by large-scale atmospheric oscillations. The North Atlantic Oscillation (NAO) and Southern Oscillation Index (SOI) have much higher influence on the variation of SPI in the mid and east; whereas the Pacific Decadal Oscillation (PDO) and North Pacific Index (NP) show higher correlations with SPI in the northern regions of the YRD.

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BROWN, ERIC, i GUENTER AHLERS. "The origin of oscillations of the large-scale circulation of turbulent Rayleigh–Bénard convection". Journal of Fluid Mechanics 638 (1.10.2009): 383–400. http://dx.doi.org/10.1017/s0022112009991224.

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In agreement with a recent experimental discovery by Xi et al. (Phys. Rev. Lett., vol. 102, 2009, paper no. 044503), we also find a sloshing mode in experiments on the large-scale circulation (LSC) of turbulent Rayleigh–Bénard convection in a cylindrical sample of aspect ratio one. The sloshing mode has the same frequency as the torsional oscillation discovered by Funfschilling & Ahlers (Phys. Rev. Lett., vol. 92, 2004, paper no. 1945022004). We show that both modes can be described by an extension of a model developed previously Brown & Ahlers (Phys. Fluids, vol. 20, 2008, pp. 105105-1–105105-15; Phys. Fluids, vol. 20, 2008, pp. 075101-1–075101-16). The extension consists of permitting a lateral displacement of the LSC circulation plane away from the vertical centreline of the sample as well as a variation of the displacement with height (such displacements had been excluded in the original model). Pressure gradients produced by the sidewall of the container on average centre the plane of the LSC so that it prefers to reach its longest diameter. If the LSC is displaced away from this diameter, the walls provide a restoring force. Turbulent fluctuations drive the LSC away from the central alignment, and combined with the restoring force they lead to oscillations. These oscillations are advected along with the LSC. This model yields the correct wavenumber and phase of the oscillations, as well as estimates of the frequency, amplitude and probability distributions of the displacements.

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Rulkov, N. F., I. Timofeev i M. Bazhenov. "Oscillations in Large-Scale Cortical Networks: Map-Based Model". Journal of Computational Neuroscience 17, nr 2 (wrzesień 2004): 203–23. http://dx.doi.org/10.1023/b:jcns.0000037683.55688.7e.

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Rulkov, Nikolai F., i Maxim Bazhenov. "Oscillations and Synchrony in Large-scale Cortical Network Models". Journal of Biological Physics 34, nr 3-4 (17.06.2008): 279–99. http://dx.doi.org/10.1007/s10867-008-9079-y.

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Fedotov, A. B. "Long-period variability of ocean circulation at different intensity of wind impact". Monitoring systems of environment, nr 4 (24.12.2020): 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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Guervilly, Céline, David W. Hughes i Chris A. Jones. "Large-scale-vortex dynamos in planar rotating convection". Journal of Fluid Mechanics 815 (20.02.2017): 333–60. http://dx.doi.org/10.1017/jfm.2017.56.

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Several recent studies have demonstrated how large-scale vortices may arise spontaneously in rotating planar convection. Here, we examine the dynamo properties of such flows in rotating Boussinesq convection. For moderate values of the magnetic Reynolds number ($100\lesssim Rm\lesssim 550$, with $Rm$ based on the box depth and the convective velocity), a large-scale (i.e. system-size) magnetic field is generated. The amplitude of the magnetic energy oscillates in time, nearly out of phase with the oscillating amplitude of the large-scale vortex. The large-scale vortex is disrupted once the magnetic field reaches a critical strength, showing that these oscillations are of magnetic origin. The dynamo mechanism relies on those components of the flow that have length scales lying between that of the large-scale vortex and the typical convective cell size; smaller-scale flows are not required. The large-scale vortex plays a crucial role in the magnetic induction despite being essentially two-dimensional; we thus refer to this dynamo as a large-scale-vortex dynamo. For larger magnetic Reynolds numbers, the dynamo is small scale, with a magnetic energy spectrum that peaks at the scale of the convective cells. In this case, the small-scale magnetic field continuously suppresses the large-scale vortex by disrupting the correlations between the convective velocities that allow it to form. The suppression of the large-scale vortex at high $Rm$ therefore probably limits the relevance of the large-scale-vortex dynamo to astrophysical objects with moderate values of $Rm$, such as planets. In this context, the ability of the large-scale-vortex dynamo to operate at low magnetic Prandtl numbers is of great interest.

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Liu, Ju, Wei Yao, Jinyu Wen, Haibo He i Xueyang Zheng. "Active Power Oscillation Property Classification of Electric Power Systems Based on SVM". Journal of Applied Mathematics 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/218647.

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Nowadays, low frequency oscillation has become a major problem threatening the security of large-scale interconnected power systems. According to generation mechanism, active power oscillation of electric power systems can be classified into two categories: free oscillation and forced oscillation. The former results from poor or negative damping ratio of power system and external periodic disturbance may lead to the latter. Thus control strategies to suppress the oscillations are totally different. Distinction from each other of those two different kinds of power oscillations becomes a precondition for suppressing the oscillations with proper measures. This paper proposes a practical approach for power oscillation classification by identifying real-time power oscillation curves. Hilbert transform is employed to obtain envelope curves of the power oscillation curves. Twenty sampling points of the envelope curve are selected as the feature matrices to train and test the supporting vector machine (SVM). The tests on the 16-machine 68-bus benchmark power system and a real power system in China indicate that the proposed oscillation classification method is of high precision.

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Alavash, Mohsen, Christoph Daube, Malte Wöstmann, Alex Brandmeyer i Jonas Obleser. "Large-scale network dynamics of beta-band oscillations underlie auditory perceptual decision-making". Network Neuroscience 1, nr 2 (czerwiec 2017): 166–91. http://dx.doi.org/10.1162/netn_a_00009.

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Perceptual decisions vary in the speed at which we make them. Evidence suggests that translating sensory information into perceptual decisions relies on distributed interacting neural populations, with decision speed hinging on power modulations of the neural oscillations. Yet the dependence of perceptual decisions on the large-scale network organization of coupled neural oscillations has remained elusive. We measured magnetoencephalographic signals in human listeners who judged acoustic stimuli composed of carefully titrated clouds of tone sweeps. These stimuli were used in two task contexts, in which the participants judged the overall pitch or direction of the tone sweeps. We traced the large-scale network dynamics of the source-projected neural oscillations on a trial-by-trial basis using power-envelope correlations and graph-theoretical network discovery. In both tasks, faster decisions were predicted by higher segregation and lower integration of coupled beta-band (∼16–28 Hz) oscillations. We also uncovered the brain network states that promoted faster decisions in either lower-order auditory or higher-order control brain areas. Specifically, decision speed in judging the tone sweep direction critically relied on the nodal network configurations of anterior temporal, cingulate, and middle frontal cortices. Our findings suggest that global network communication during perceptual decision-making is implemented in the human brain by large-scale couplings between beta-band neural oscillations.

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Brandenburg, Axel. "Gravity wave generation by large scale bubbles". Symposium - International Astronomical Union 123 (1988): 383–86. http://dx.doi.org/10.1017/s0074180900158401.

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The response of an isothermal atmosphere to small disturbances in entropy is studied taking compressible effects fully into account. The method of Green's functions is applied to solve the linearized hydrodynamic equations by Fourier transformation. A bubble may be created by perturbing the entropy within a finite volume. At first Lamb waves will be then emitted radially and the bubble undergoes a series of Brunt-Väisälä oscillations. We find that horizontally propagating waves are generated only by large bubbles “exceeding a radius of about ten pressure scale heights, whereas smaller bubbles lead to motions propagating principally in the vertical direction.

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Resagk, Christian, Ronald du Puits, André Thess, Felix V. Dolzhansky, Siegfried Grossmann, Francisco Fontenele Araujo i Detlef Lohse. "Oscillations of the large scale wind in turbulent thermal convection". Physics of Fluids 18, nr 9 (wrzesień 2006): 095105. http://dx.doi.org/10.1063/1.2353400.

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Gao, Xin Hai, i John L. Stanford. "Low-Frequency Oscillations of the Large-Scale Stratospheric Temperature Field". Journal of the Atmospheric Sciences 44, nr 15 (sierpień 1987): 1991–2000. http://dx.doi.org/10.1175/1520-0469(1987)044<1991:lfootl>2.0.co;2.

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Kay, Leslie M., i Philip Lazzara. "How Global Are Olfactory Bulb Oscillations?" Journal of Neurophysiology 104, nr 3 (wrzesień 2010): 1768–73. http://dx.doi.org/10.1152/jn.00478.2010.

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Previous studies in waking animals have shown that the frequency structure of olfactory bulb (OB) local field potential oscillations is very similar across the OB, but large low-impedance surface electrodes may have favored highly coherent events, averaging out local inhomogeneities. We tested the hypothesis that OB oscillations represent spatially homogeneous phenomena at all scales. We used pairs of concentric electrodes (200 μm outer shaft surrounding an inner 2–3 μm recording site) beginning on the dorsal OB at anterior and medial locations in urethane-anesthetized rats and measured local field potential responses at successive 200 μm depths before and during odor stimulation. Within locations (outer vs. inner lead on a single probe), on the time scale of 0.5 s, coherence in all frequency bands was significant, but on larger time scales (10 s), only respiratory (1–4 Hz) and beta (15–30 Hz) oscillations showed prominent peaks. Across locations, coherence in all frequency bands was significantly lower for both sizes of electrodes at all depths but the most superficial 600 μm. Near the pial surface, coherence across outer (larger) electrodes at different sites was equal to coherence across outer and inner (small) electrodes within a single site and larger than coherence across inner electrodes at different sites. Overall, the beta band showed the largest coherence across bulbar sites and electrodes. Therefore larger electrodes at the surface of the OB favor globally coherent events, and at all depths, coherence depends on the type of oscillation (beta or gamma) and duration of the analysis window.

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Mitra, Dhrubaditya, Reza Tavakol, Axel Brandenburg i Petri J. Käpylä. "Oscillatory migratory large-scale fields in mean-field and direct simulations". Proceedings of the International Astronomical Union 5, S264 (sierpień 2009): 197–201. http://dx.doi.org/10.1017/s1743921309992626.

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AbstractWe summarise recent results form direct numerical simulations of both non-rotating helically forced and rotating convection driven MHD equations in spherical wedge-shape domains. In the former, using perfect-conductor boundary conditions along the latitudinal boundaries we observe oscillations, polarity reversals and equatorward migration of the large-scale magnetic fields. In the latter we obtain angular velocity with cylindrical contours and large-scale magnetic field which shows oscillations, polarity reversals but poleward migration. The occurrence of these behviours in direct numerical simulations is clearly of interest. However the present models as they stand are not directly applicable to the solar dynamo problem. Nevertheless, they provide general insights into the operation of turbulent dynamos.

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Le Van Quyen, Michel, Lyle E. Muller, Bartosz Telenczuk, Eric Halgren, Sydney Cash, Nicholas G. Hatsopoulos, Nima Dehghani i Alain Destexhe. "High-frequency oscillations in human and monkey neocortex during the wake–sleep cycle". Proceedings of the National Academy of Sciences 113, nr 33 (1.08.2016): 9363–68. http://dx.doi.org/10.1073/pnas.1523583113.

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Beta (β)- and gamma (γ)-oscillations are present in different cortical areas and are thought to be inhibition-driven, but it is not known if these properties also apply to γ-oscillations in humans. Here, we analyze such oscillations in high-density microelectrode array recordings in human and monkey during the wake–sleep cycle. In these recordings, units were classified as excitatory and inhibitory cells. We find that γ-oscillations in human and β-oscillations in monkey are characterized by a strong implication of inhibitory neurons, both in terms of their firing rate and their phasic firing with the oscillation cycle. The β- and γ-waves systematically propagate across the array, with similar velocities, during both wake and sleep. However, only in slow-wave sleep (SWS) β- and γ-oscillations are associated with highly coherent and functional interactions across several millimeters of the neocortex. This interaction is specifically pronounced between inhibitory cells. These results suggest that inhibitory cells are dominantly involved in the genesis of β- and γ-oscillations, as well as in the organization of their large-scale coherence in the awake and sleeping brain. The highest oscillation coherence found during SWS suggests that fast oscillations implement a highly coherent reactivation of wake patterns that may support memory consolidation during SWS.

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Huo, Xueli, Zhongfang Liu, Qingyun Duan, Pengmei Hao, Yanyan Zhang, Yonghong Hao i Hongbin Zhan. "Linkages between Large-Scale Climate Patterns and Karst Spring Discharge in Northern China". Journal of Hydrometeorology 17, nr 2 (1.02.2016): 713–24. http://dx.doi.org/10.1175/jhm-d-15-0085.1.

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Abstract The Niangziguan Springs (NS) discharge is used as a proxy indicator of the variability of the karst groundwater system in relation to major climate indices such as El Niño–Southern Oscillation (ENSO), Pacific decadal oscillation (PDO), Indian summer monsoon (ISM), and west North Pacific monsoon (WNPM). The relationships between spring discharge and these climate indices are determined using the multitaper method (MTM), continuous wavelet transform (CWT), and wavelet transform coherence (WTC). Significant periodic components of spring discharge in the 1-, 3.4-, and 26.8-yr periodicities are identified and reconstructed for further investigation of the correlation between spring discharge and large-scale climate patterns on these time scales. Correlation coefficients and WTC between spring discharge and the climate indices indicate that variability in spring discharge is significantly and positively correlated with monsoon indices in the 1-yr periodicity and negatively correlated with ENSO in the 3.4-yr periodicity and PDO in the 26.8-yr periodicity. This suggests that the oscillations of the spring discharge on annual, interannual, and interdecadal time scales are dominated by monsoon, ENSO, and PDO in the NS basin, respectively. Results show that monsoons modulate the spring discharge by affecting local meteorological parameters. ENSO and PDO impact the variability of the NS discharge by affecting the climate conditions in northern China.

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28

BARGER, V., D. MARFATIA i K. WHISNANT. "PROGRESS IN THE PHYSICS OF MASSIVE NEUTRINOS". International Journal of Modern Physics E 12, nr 05 (październik 2003): 569–647. http://dx.doi.org/10.1142/s0218301303001430.

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The current status of the physics of massive neutrinos is reviewed with a forward-looking emphasis. The article begins with the general phenomenology of neutrino oscillations in vacuum and matter and documents the experimental evidence for oscillations of solar, reactor, atmospheric and accelerator neutrinos. Both active and sterile oscillation possibilities are considered. The impact of cosmology (BBN, CMB, leptogenesis) and astrophysics (supernovae, highest energy cosmic rays) on neutrino observables and vice versa, is evaluated. The predictions of grand unified, radiative and other models of neutrino mass are discussed. Ways of determining the unknown parameters of three-neutrino oscillations are assessed, taking into account eight-fold degeneracies in parameters that yield the same oscillation probabilities, as well as ways to determine the absolute neutrino mass scale (from beta-decay, neutrinoless double-beta decay, large scale structure and Z-bursts). Critical unknowns at present are the amplitude of νμ→νe oscillations and the hierarchy of the neutrino mass spectrum; the detection of CP violation in the neutrino sector depends on these and on an unknown phase. The estimated neutrino parameter sensitivities at future facilities (reactors, superbeams, neutrino factories) are given. The overall agenda of a future neutrino physics program to construct a bottom-up understanding of the lepton sector is presented.

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29

Goldman, Samuel, Maximino Aldana i Philippe Cluzel. "Resonant learning in scale-free networks". PLOS Computational Biology 19, nr 2 (21.02.2023): e1010894. http://dx.doi.org/10.1371/journal.pcbi.1010894.

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Large networks of interconnected components, such as genes or machines, can coordinate complex behavioral dynamics. One outstanding question has been to identify the design principles that allow such networks to learn new behaviors. Here, we use Boolean networks as prototypes to demonstrate how periodic activation of network hubs provides a network-level advantage in evolutionary learning. Surprisingly, we find that a network can simultaneously learn distinct target functions upon distinct hub oscillations. We term this emergent property resonant learning, as the new selected dynamical behaviors depend on the choice of the period of the hub oscillations. Furthermore, this procedure accelerates the learning of new behaviors by an order of magnitude faster than without oscillations. While it is well-established that modular network architecture can be selected through evolutionary learning to produce different network behaviors, forced hub oscillations emerge as an alternative evolutionary learning strategy for which network modularity is not necessarily required.

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30

Ahmedov, Bobomurat J., Roustam M. Zalaletdinov, Zafar Ya Turakulov, Salakhutdin N. Nuritdinov i Karomat T. Mirtadjieva. "Relativistic astrophysics and cosmology in Uzbekistan". Proceedings of the International Astronomical Union 2, SPS5 (sierpień 2006): 159–66. http://dx.doi.org/10.1017/s174392130700693x.

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AbstractThe theoretical results obtained in Uzbekistan in the field of relativistic astrophysics and cosmology are presented. In particular electrostatic plasma modes along the open field lines of a rotating neutron star and Goldreich-Julian charge density in general relativity are analyzed for the rotating and oscillating magnetized neutron stars. The impact that stellar oscillations of different type (radial, toroidal and spheroidal ones) have on electric and magnetic fields external to a relativistic magnetized star has been investigated. A study of the dynamical evolution and the number of stellar encounters in globular clusters with a central black hole is presented. Perturbation features and instabilities of the large-scale oscillations on the background of the non-linearly pulsating isotropic and isotropic Ω-models are studied. The non-stationary dispersion equation of the sectorial perturbations for the general case and the results of certain oscillation mode analysis are given. The model composed as the linear superposition of two other models was constructed and the stability of this model is studied. In a cosmological setting the theory of macroscopic gravity as a large-distance scale generalization of general relativity has been developed. Exact cosmological solutions to the equations of macroscopic gravity for a flat spatially homogeneous, isotropic space-time are found. The gravitational correlation terms in the averaged Einstein equations have the form of spatial curvature, dark matter and dark energy (cosmological constant) with particular equations of state for each correlation regime. Interpretation of these cosmological models to explain the observed large-scale structure of the accelerating Universe with a significant amount of the nonluminous (dark) matter is discussed.

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31

Goodwin, Bradley P., Ellen Mosley-Thompson, Aaron B. Wilson, Stacy E. Porter i M. Roxana Sierra-Hernandez. "Accumulation Variability in the Antarctic Peninsula: The Role of Large-Scale Atmospheric Oscillations and Their Interactions*". Journal of Climate 29, nr 7 (29.03.2016): 2579–96. http://dx.doi.org/10.1175/jcli-d-15-0354.1.

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Abstract A new ice core drilled in 2010 to bedrock from the Bruce Plateau (BP) on the Antarctic Peninsula (AP) provides a high temporal resolution record of environmental conditions in this region. The extremely high annual accumulation rate at this site facilitates analysis of the relationships between annual net accumulation An on the BP and large-scale atmospheric oscillations. Over the last ~45 years, An on the BP has been positively correlated with both the southern annular mode (SAM) and Southern Oscillation index (SOI). Extending this analysis back to 1900 reveals that these relationships are not temporally stable, and they exhibit major shifts in the late-1940s and the mid-1970s that are contemporaneous with phase changes in the Pacific decadal oscillation (PDO). These varying multidecadal characteristics of the An–oscillation relationships are not apparent when only data from the post-1970s era are employed. Analysis of the longer ice core record reveals that the influence of the SAM on An depends not only on the phase of the SAM and SOI but also on the phase of the PDO. When the SAM’s influence on BP An is reduced, such as under negative PDO conditions, BP An is modulated by variability in the tropical and subtropical atmosphere through its impacts on the strength and position of the circumpolar westerlies in the AP region. These results demonstrate the importance of using longer-term ice core–derived proxy records to test conventional views of atmospheric circulation variability in the AP region.

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32

Chakraborty, Madhurima. "Dense neutrino oscillations : beyond two flavor". Journal of Physics: Conference Series 2156, nr 1 (1.12.2021): 012106. http://dx.doi.org/10.1088/1742-6596/2156/1/012106.

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Abstract In a dense supernova environment, neutrinos can undergo flavor conversions known as the collective oscillations. These self induced neutrino flavor conversions (collective oscillations) are almost exclusively studied in the standard two flavor scenario. We study these oscillations in the complete three flavor scenario. The ‘fast’ conversions are fascinating distinctions of the dense neutrino systems. In the fast modes the collective oscillation dynamics are independent of the neutrino mass, growing at the scale of the large neutrino-neutrino interaction strength (105 km−1 ) of the dense core. This is extremely fast, as compared to the usual ‘slow’ collective modes driven by much smaller vacuum oscillation frequencies (100 km−1). We perform the first non-linear simulations of fast conversions in the presence of three neutrino flavors which is motivated from the recent supernova simulations with muon production. We relax the standard ν μ , τ = ν ¯ μ , τ (two-flavor) assumption. Our results show the significance of muon and tau lepton number angular distributions, together with the traditional electron lepton number ones and thus explain the need for a complete three flavor analysis.

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33

Callebaut, Dirk K., Valentine I. Makarov i Ksenia S. Tavastsherna. "Large-Scale Patterns of Prominences in the Global Solar Cycles During 1880–1995". International Astronomical Union Colloquium 167 (1998): 442–45. http://dx.doi.org/10.1017/s0252921100048077.

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AbstractThe zonal distribution of prominences, their poleward migration from the sunspot zone to the poles, the polar magnetic field reversals and a correlation of the mean latitude of filament bands at minimum activity with the maximum of Wolf number in the next cycle are briefly discussed for the period 1880–1995. The need for research on the longterm latitude distribution of the prominences is emphasized. New results concerning long-term variations of the torsional oscillations of the Sun and quasi-periodic oscillations of the latitude zonal boundaries from an analysis of Hα charts (1915–1990) are given.

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34

Zhang, Jing, Kristina Safar, Zahra Emami, George M. Ibrahim, Shannon E. Scratch, Leodante da Costa i Benjamin T. Dunkley. "Local and large-scale beta oscillatory dysfunction in males with mild traumatic brain injury". Journal of Neurophysiology 124, nr 6 (1.12.2020): 1948–58. http://dx.doi.org/10.1152/jn.00333.2020.

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Mild traumatic brain injury (mTBI) disrupts the dynamic repertoire of neural oscillations, but so far beta activity has not been studied. In mTBI, we found reductions in frontal beta and large-scale beta networks, indicative of thalamocortical dysconnectivity and disrupted information flow through cortico-basal ganglia-thalamic circuits. Relatively, connectivity more accurately classifies individual mTBI cases compared with regional power. We show the relevance of beta oscillations in mTBI and the reliability of these markers in classification.

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35

Sands, J. D. "Fast large-scale current oscillations in SOFCs with intermediate fuel utilisation". IOP Conference Series: Materials Science and Engineering 639 (28.10.2019): 012018. http://dx.doi.org/10.1088/1757-899x/639/1/012018.

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Glover, J., A. C. Lazer i P. J. McKenna. "Existence and stability of large scale nonlinear oscillations in suspension bridges". ZAMP Zeitschrift f�r angewandte Mathematik und Physik 40, nr 2 (marzec 1989): 172–200. http://dx.doi.org/10.1007/bf00944997.

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Dominici, P., B. Zolesi i Lj R. Cander. "Preliminary results concerning atmospheric gravity waves deduced fromf0F2 large-scale oscillations". Physica Scripta 37, nr 3 (1.03.1988): 516–22. http://dx.doi.org/10.1088/0031-8949/37/3/041.

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Bittner, M., D. Offermann, I. V. Bugaeva, G. A. Kokin, J. P. Koshelkov, A. Krivolutsky, D. A. Tarasenko i in. "Long period/large scale oscillations of temperature during the DYANA campaign". Journal of Atmospheric and Terrestrial Physics 56, nr 13-14 (listopad 1994): 1675–700. http://dx.doi.org/10.1016/0021-9169(94)90004-3.

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39

Shi, Pengfei, Tao Yang, Chong-Yu Xu, Bin Yong, Quanxi Shao, Zhenya Li, Xiaoyan Wang, Xudong Zhou i Shu Li. "How do the multiple large-scale climate oscillations trigger extreme precipitation?" Global and Planetary Change 157 (październik 2017): 48–58. http://dx.doi.org/10.1016/j.gloplacha.2017.08.014.

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Verschuren, Iris L. M., Johan G. Wijers i Jos T. F. Keurentjes. "Large-scale oscillations of a feedstream inside a stirred tank reactor". AIChE Journal 48, nr 9 (wrzesień 2002): 1888–95. http://dx.doi.org/10.1002/aic.690480906.

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De los Santos, Hannah, Emily J. Collins, Catherine Mann, April W. Sagan, Meaghan S. Jankowski, Kristin P. Bennett i Jennifer M. Hurley. "ECHO: an application for detection and analysis of oscillators identifies metabolic regulation on genome-wide circadian output". Bioinformatics 36, nr 3 (6.08.2019): 773–81. http://dx.doi.org/10.1093/bioinformatics/btz617.

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Abstract Motivation Time courses utilizing genome scale data are a common approach to identifying the biological pathways that are controlled by the circadian clock, an important regulator of organismal fitness. However, the methods used to detect circadian oscillations in these datasets are not able to accommodate changes in the amplitude of the oscillations over time, leading to an underestimation of the impact of the clock on biological systems. Results We have created a program to efficaciously identify oscillations in large-scale datasets, called the Extended Circadian Harmonic Oscillator application, or ECHO. ECHO utilizes an extended solution of the fixed amplitude oscillator that incorporates the amplitude change coefficient. Employing synthetic datasets, we determined that ECHO outperforms existing methods in detecting rhythms with decreasing oscillation amplitudes and in recovering phase shift. Rhythms with changing amplitudes identified from published biological datasets revealed distinct functions from those oscillations that were harmonic, suggesting purposeful biologic regulation to create this subtype of circadian rhythms. Availability and implementation ECHO’s full interface is available at https://github.com/delosh653/ECHO. An R package for this functionality, echo.find, can be downloaded at https://CRAN.R-project.org/package=echo.find. Supplementary information Supplementary data are available at Bioinformatics online.

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42

OZGOREN, M., i D. ROCKWELL. "Interaction of a deep-water wave with a vertical cylinder: effect of self-excited vibrations on quantitative flow patterns". Journal of Fluid Mechanics 572 (23.01.2007): 189–217. http://dx.doi.org/10.1017/s0022112006003399.

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Interaction of a deep-water wave with a cylinder gives rise to ordered patterns of the flow structure, which are quantitatively characterized using a technique of high-image-density particle image velocimetry. When the cylinder is stationary, the patterns of instantaneous flow structure take on increasingly complex forms for increasing Keulegan--Carpenter number KC. These patterns involve stacking of small-scale vorticity concentrations, as well as large-scale vortex shedding. The time-averaged consequence of these patterns involves, at sufficiently high KC, an array of vorticity concentrations about the cylinder.When the lightly damped cylinder is allowed to undergo bidirectional oscillations, the trajectories can be classified according to ranges of KC. At low values of KC, the trajectory is elliptical, and further increases of KC allow, first of all, both elliptical and in-line trajectories as possibilities, followed by predominantly in-line and figure-of-eight oscillations at the largest value of KC.Representations of the quantitative flow structure, in relation to the instantaneous cylinder position on its oscillation trajectory, show basic classes of patterns. When the trajectory is elliptical, layers of vorticity rotate about the cylinder surface, in accordance with rotation of the relative velocity vector of the wave motion with respect to the oscillating cylinder. Simultaneously, the patterns of streamline topology take the form of large-scale bubbles, which also rotate about the cylinder. When the cylinder trajectory is predominantly in-line with the wave motion, generic classes of vortex formation and shedding can be identified; they include sweeping of previously shed vorticity concentrations past the cylinder to the opposite side. Certain of these patterns are directly analogous to those from the stationary cylinder.

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43

Dovgal, A. V., i A. M. Sorokin. "Interaction of Large-Scale and Small-Scale Oscillations During Separation of a Laminar Boundary Layer". Journal of Applied Mechanics and Technical Physics 45, nr 4 (lipiec 2004): 517–22. http://dx.doi.org/10.1023/b:jamt.0000030328.95959.1b.

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Braun, D., i W. Gujer. "Reactive tracers reveal hydraulic and control instabilities in full-scale activated sludge plant". Water Science and Technology 57, nr 7 (1.04.2008): 1001–7. http://dx.doi.org/10.2166/wst.2008.210.

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The hydraulic characteristics of aeration tanks in WWTPs have a major impact on the degradation of pollutants, as well as on the control of the aeration. In particular in long reactors, which are not separated by baffles, hydraulic shortcuts or large scale recirculation can lead to a loss of performance. This work demonstrates that reactive tracers such as ammonium and oxygen can be used to investigate the hydraulics of aeration tanks in detail. With the use of electrochemical sensors it is possible to investigate effects in a broad range of time scales. In the present case study a slow oscillation of the aeration control loop was investigated. Large scale recirculation in the aeration tank and fast fluctuations of the ammonium concentrations close to the oxygen sensor were identified as the cause of these oscillations. Both, the recirculation as well as the fluctuation of the ammonium have a substantial influence on the performance of the aeration tank and the aeration control loop.

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45

Chen, Ruidan, Zhiping Wen i Riyu Lu. "Large-Scale Circulation Anomalies and Intraseasonal Oscillations Associated with Long-Lived Extreme Heat Events in South China". Journal of Climate 31, nr 1 (11.12.2017): 213–32. http://dx.doi.org/10.1175/jcli-d-17-0232.1.

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Abstract South China experiences extreme heat (EH) most frequently in eastern China. This study specifically explores the large-scale circulation anomalies associated with long-lived EH events in south China. The results show that there is an anomalous cyclone (anticyclone) and active (inactive) convection over south China (the western Pacific) before the EH onset; then, an anticyclone develops and moves northwestward and dominates over south China on the onset day. The anomalous anticyclone maintains its strength over south China and then diminishes and is replaced by another cyclone migrating from the western Pacific after the final day of the EH event. Consequently, the temperature increases over south China around the onset day and is anomalously warm for approximately 10 days on average and then decreases shortly thereafter. The fluctuating anomalies over south China and the western Pacific are intimately related to two intraseasonal oscillation (ISO) modes, namely, the 5–25- and 30–90-day oscillations, which originate from the tropical western Pacific and propagate northwestward. The 5–25-day oscillation is vital to triggering and terminating EH, accounting for approximately half of the original temperature and circulation anomaly transitions. The 30–90-day oscillation favors the persistent warming during EH events, accounting for approximately one-third of the original prolonged warming and anticyclonic anomaly. This result suggests that different ISO modes play crucial roles at different stages of the events. Moreover, a higher annual frequency of long-lived EH days in south China is associated with the transition phase from El Niño to La Niña. It is suggested that both medium-range and interannual forecasting of long-lived EH in south China are possible.

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46

Cox, Roy, Anna C. Schapiro i Robert Stickgold. "Variability and stability of large-scale cortical oscillation patterns". Network Neuroscience 2, nr 4 (październik 2018): 481–512. http://dx.doi.org/10.1162/netn_a_00046.

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Individual differences in brain organization exist at many spatiotemporal scales and underlie the diversity of human thought and behavior. Oscillatory neural activity is crucial for these processes, but how such rhythms are expressed across the cortex within and across individuals is poorly understood. We conducted a systematic characterization of brain-wide activity across frequency bands and oscillatory features during rest and task execution. We found that oscillatory profiles exhibit sizable group-level similarities, indicating the presence of common templates of oscillatory organization. Nonetheless, well-defined subject-specific network profiles were discernible beyond the structure shared across individuals. These individualized patterns were sufficiently stable to recognize individuals several months later. Moreover, network structure of rhythmic activity varied considerably across distinct oscillatory frequencies and features, indicating the existence of several parallel information processing streams embedded in distributed electrophysiological activity. These findings suggest that network similarity analyses may be useful for understanding the role of large-scale brain oscillations in physiology and behavior.

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47

Tai, Chang-Kou, i Lee-Lueng Fu. "The 25-Day-Period Large-Scale Oscillations in the Argentine Basin Revisited". Journal of Physical Oceanography 35, nr 8 (1.08.2005): 1473–79. http://dx.doi.org/10.1175/jpo2766.1.

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Abstract From sea surface height measurements made by the Ocean Topography Experiment (TOPEX)/Poseidon satellite, Fu et al. found and described large-scale oscillations at the period of 25 days in the Argentine Basin of the South Atlantic Ocean. These oscillations were previously hinted at by in situ observations. Only the extensive space–time sampling capability of TOPEX/Poseidon, however, was able to give a complete description of the phenomenon as a counterclockwise-rotating dipole centered at 45°S, 317°E over the Zapiola Rise. Fu et al. also undertook theoretical and numerical studies to suggest that the phenomenon is a resonantly excited barotropic normal mode of the locally closed f/H contour. In a simulation study, however, they also found that the space–time smoothing scheme employed would probably lower the amplitude of the estimated phenomenon by 30%–40%. By reprocessing the data using a different method and showing the amplitude to be almost 2 times as large, in this note it is confirmed that this is indeed the case. The original 5-yr study has also been extended to nearly 10 yr, demonstrating that the same phenomenon has persisted for almost 10 yr.

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48

Umirbekov, Atabek, Mayra Daniela Peña-Guerrero i Daniel Müller. "Regionalization of climate teleconnections across Central Asian mountains improves the predictability of seasonal precipitation". Environmental Research Letters 17, nr 5 (19.04.2022): 055002. http://dx.doi.org/10.1088/1748-9326/ac6229.

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Abstract Mountains play a critical role in water cycles in semiarid regions by providing for the majority of the total runoff. However, hydroclimatic conditions in mountainous regions vary considerably in space and time, with high interannual fluctuations driven by large-scale climate oscillations. Here, we investigated teleconnections between global climate oscillations and the peak precipitation season from February to June in the Tian-Shan and Pamir Mountains of Central Asia. Using hierarchical climate regionalization, we identified seven subregions with distinct precipitation patterns, and assessed correlations with selected climate oscillations at different time lags. We then simulated the seasonal precipitation in each subregion from 1979 to 2020 using the most prevalent teleconnections as predictors with support vector regression (SVR). Our findings indicate that the El Niño–Southern Oscillation, the Pacific Decadal Oscillation, and the Eastern Atlantic/West Russia pattern are among the major determinants of the seasonal precipitation. The dominant lead-lag times of these oscillations make them reliable predictors ahead of the season. We detected notable teleconnections with the North Atlantic Oscillation and Scandinavian Pattern, with their strongest associations emerging after onset of the season. While the SVR-based models exhibit robust prediction skills, they tend to underestimate precipitation in extremely wet seasons. Overall, our study highlights the value of appropriate spatial and temporal aggregations for exploring the impacts of climate teleconnections on precipitation in complex terrains.

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Alessio, S., C. Taricco, S. Rubinetti, G. Vivaldo i S. Mancuso. "Temperature and precipitation in Northeast China during the last 150 years: relationship to large-scale climatic variability". Annales Geophysicae 32, nr 7 (2.07.2014): 749–60. http://dx.doi.org/10.5194/angeo-32-749-2014.

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Abstract. The analysis of two historical time series of temperature and precipitation in Northeast China, spanning, respectively, 1870–2004 and 1841–2004, performed by continuous wavelet transform and other classical and advanced spectral methods, is presented here. Both variables show a particular trend and oscillations of about 85, 60, 35 and 20 years that are highly significant, with a phase opposition at the centennial scale and at the 20-year scale. The analysis of the four temperature series relative to single seasons shows that the 20-year cycle is typical of the summer monsoon season, while the 35-year cycle is most evident in winter. The cycles of ~ 60 years and longer are present in all seasons. The centennial variation of temperature and precipitation describes well the 1970–1980 transition between a period of relatively strong East Asian Summer Monsoon (EASM), corresponding to high precipitation and relatively cool temperatures in Northeast China, and a conditions of weak EASM (low precipitation and warm temperatures). The connection of the detected local variations with large-scale climatic variability is deduced from the comparison with different climatic records (Northern Hemisphere temperature, Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation indexes).

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Debono, Ivan. "Probing Inflation with Large-Scale Structure Data: The Contribution of Information at Small Scales". Physical Sciences Forum 2, nr 1 (1.03.2021): 45. http://dx.doi.org/10.3390/ecu2021-09371.

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Upcoming full-sky large-scale structure surveys such as Euclid can probe the primordial Universe. Using the specifications for the Euclid survey, we estimate the constraints on the inflation potential beyond slow-roll. We use mock Euclid and Planck data from fiducial cosmological models using the Wiggly Whipped Inflation (WWI) framework, which generates features in the primordial power spectrum. We include Euclid cosmic shear and galaxy clustering, with two setups (Conservative and Realistic) for the non-linear cut-off. We find that the addition of Euclid data gives an improvement in constraints in the WWI potential, with the Realistic setup providing marginal improvement over the Conservative for most models. This shows that Euclid may allow us to identify oscillations in the primordial spectrum present at intermediate to small scales.

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