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Artigos de revistas sobre o tema "Currents dynamics"

Autor: Grafiati

Publicado: 14 de março de 2023

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1

Luijendijk, Arjen, Johan Henrotte, Dirk Jan Walstra e Maarten Van Ormondt. "QUASI-3D MODELLING OF SURF ZONE DYNAMICS". Coastal Engineering Proceedings 1, n.º 32 (26 de janeiro de 2011): 52. http://dx.doi.org/10.9753/icce.v32.currents.52.

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A quasi-three-dimensional model (quasi-3D) has been developed through the implementation of an analytical 1DV flow model in existing depth-averaged shallow water equations. The model includes the effects of waves and wind on the vertical distribution of the horizontal velocities. Comparisons with data from both physical and field cases show that the quasi-3D approach is able to combine the effect of vertical structures with the efficiency of depth-averaged simulations. Inter-comparisons with three-dimensional simulations show that the quasi-3D approach can represent similar velocity profiles in the surf zone. Quasi-3D morphodynamic simulations show that the bed dynamics in the surf zone represent the relevant 3D effects in the surf zone much more than the depth-averaged computations. It was shown that the quasi-3D approach is computationally efficient as it only adds about 15-20% to the runtimes of a 2DH simulation which is minor compared to a run time increase of 250-800% when switching to a 3D simulation.

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Frank, Anna G., Sergey G. Bugrov e Vladimir S. Markov. "Hall currents in a current sheet: Structure and dynamics". Physics of Plasmas 15, n.º 9 (setembro de 2008): 092102. http://dx.doi.org/10.1063/1.2972158.

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Dujardin, Romain. "Laminar currents and birational dynamics". Duke Mathematical Journal 131, n.º 2 (fevereiro de 2006): 219–47. http://dx.doi.org/10.1215/s0012-7094-06-13122-8.

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4

Ozdemir, Celalettin Emre, e Sahar Haddadian. "SEDIMENT TRANSPORT DUE TO CURRENT-SUPPORTED TURBIDITY CURRENTS OVER AN ERODIBLE BED". Coastal Engineering Proceedings, n.º 36 (30 de dezembro de 2018): 33. http://dx.doi.org/10.9753/icce.v36.currents.33.

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Wave- and current-supported turbidity currents (WCSTCs), are one of the chief participants in shaping the marine geomorphology. What makes WCSTCs different from other turbidity currents is that boundary layer turbulence is required to suspend the sediments rather than the self-motion of the turbidity currents. In the presence of a mild slope, the gravitational acceleration drives the suspended sediments offshore (Sternberg et al., 1996; Wright et al., 2001). Depending on what dominates the boundary layer turbulence (BLT), we further define two major subclasses of WCSTCs: (i) wave-supported (WSTCs), and (ii) current-supported turbidity currents (CSTCs). Although significant advances have been made on the details of WSTCs (Ozdemir et al., 2011; Yu et al., 2014; Cheng et al., 2015), less is known about CSTCs. The objective of present study is to investigate the role of alongshore currents on CSTC dynamics over an erodible bottom boundary. The focus here is to identify the possible role of erosion on CSTC dynamics, and assess the coupling between current-induced BLT and suspended sediments for various bed erodibility parameters, i.e. critical shear stress, erosion coefficient, and settling velocity.

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Nasrollahpour, Reza, Mohamad Hidayat Jamal, Mehdi Ghomesi, Zulhilmi Ismail e Peiman Roushenas. "Density Currents Dynamics over Rough Beds". Applied Mechanics and Materials 735 (fevereiro de 2015): 159–62. http://dx.doi.org/10.4028/www.scientific.net/amm.735.159.

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Density currents are flows driven by density differences caused by suspended fine solid material, dissolved contents, temperature gradient or a combination of them. Reservoir sedimentation is often related to sediment transport by density currents. This sedimentation can block bottom outlets, reduce the capacity of reservoir and harms the dam power plants. The head is the leading edge of density currents. In this paper, the influences of artificially roughened beds on dynamics of the frontal region of density currents are investigated experimentally. Three rough beds using conic roughness elements and a smooth bed were tested. The observed trend is that as the surface roughness increases the head concentration and velocity decreases.

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6

Diller, Jeffrey. "Birational maps, positive currents, and dynamics." Michigan Mathematical Journal 46, n.º 2 (setembro de 1999): 361–75. http://dx.doi.org/10.1307/mmj/1030132416.

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da Silveira, Ilson C. A., Glenn R. Flierl e Wendell S. Brown. "Dynamics of Separating Western Boundary Currents". Journal of Physical Oceanography 29, n.º 2 (fevereiro de 1999): 119–44. http://dx.doi.org/10.1175/1520-0485(1999)029<0119:doswbc>2.0.co;2.

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8

Cessi, Paola, R. Vance Condie e W. R. Young. "Dissipative dynamics of western boundary currents". Journal of Marine Research 48, n.º 4 (1 de novembro de 1990): 677–700. http://dx.doi.org/10.1357/002224090784988719.

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9

Fan, Shuangshuang, e Craig A. Woolsey. "Dynamics of underwater gliders in currents". Ocean Engineering 84 (julho de 2014): 249–58. http://dx.doi.org/10.1016/j.oceaneng.2014.03.024.

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Leonetti, Marc. "Dynamics of concentration-dependent ionic currents". Physical Review E 52, n.º 1 (1 de julho de 1995): R33—R35. http://dx.doi.org/10.1103/physreve.52.r33.

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Moreno, Javier, Mark Warren e José Jalife. "Ionic Currents and Ventricular Fibrillation Dynamics". Revista Española de Cardiología (English Edition) 57, n.º 1 (janeiro de 2004): 69–79. http://dx.doi.org/10.1016/s1885-5857(06)60089-3.

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12

Wargula, Anna, Britt Raubenheimer, Steve Elgar, Jia-Lin Chen e Fengyan Shi. "TIME-VARYING WAVE EFFECTS ON FLOWS AND DYNAMICS AT AN UNSTRATIFIED INLET". Coastal Engineering Proceedings, n.º 36 (30 de dezembro de 2018): 45. http://dx.doi.org/10.9753/icce.v36.currents.45.

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Surface gravity waves alter discharge and circulation near and within coastal inlets, affecting the exchange and transport of water masses, nutrients, sediments, and pollutants between inland waters and the ocean. Field observations and numerical simulations suggest that, during storms, wave forcing (radiation-stress gradients) owing to wave dissipation across the ebb shoal can enhance fluxes into the inlet (Bertin et al. 2009; Wargula et al. 2014). As a result, water levels may increase inside the bay (Olabarrieta et al. 2011; Dodet et al. 2013), creating an offshore-directed pressure gradient that may balance onshore fluxes during energetic waves, and may enhance offshore fluxes after the waves decrease. Spatial and tidal variability in water depths on the ebb shoal lead to complex wave breaking patterns that drive spatially and tidally asymmetric flows. Here, field observations and numerical simulations are used to evaluate the effects of waves on discharge and circulation, and the relative importance of wave radiation-stress and pressure gradients at an unstratified inlet during and following energetic waves.

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13

Kuruma, Akinori, e H. Criss Hartzell. "Dynamics of calcium regulation of chloride currents inXenopus oocytes". American Journal of Physiology-Cell Physiology 276, n.º 1 (1 de janeiro de 1999): C161—C175. http://dx.doi.org/10.1152/ajpcell.1999.276.1.c161.

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Ca-activated Cl currents are widely expressed in many cell types and play diverse and important physiological roles. The Xenopus oocyte is a good model system for studying the regulation of these currents. We previously showed that inositol 1,4,5-trisphosphate (IP3) injection into Xenopus oocytes rapidly elicits a noninactivating outward Cl current ( I Cl1-S) followed several minutes later by the development of slow inward ( I Cl2) and transient outward ( I Cl1-T) Cl currents. In this paper, we investigate whether these three currents are mediated by the same or different Cl channels. Outward Cl currents were more sensitive to Ca than inward Cl currents, as shown by injection of different amounts of Ca or by Ca influx through a heterologously expressed ligand-gated Ca channel, the ionotropic glutamate receptor iGluR3. These data could be explained by two channels with different Ca affinities or one channel with a higher Ca affinity at depolarized potentials. To distinguish between these possibilities, we determined the anion selectivity of the three currents. The anion selectivity sequences for the three currents were the same (I > Br > Cl), but I Cl1-Shad an I-to-Cl permeability ratio more than twofold smaller than the other two currents. The different anion selectivities and instantaneous current-voltage relationships were consistent with at least two different channels mediating these currents. However, after consideration of possible errors, the hypothesis that a single type of Cl channel underlies the complex waveforms of the three different macroscopic Ca-activated Cl currents in Xenopus oocytes remains a viable alternative.

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Cienfuegos, Rodrigo, L. Duarte, L. Suarez e P. A. Catalán. "NUMERICAL COMPUTATION OF INFRAGRAVITY WAVE DYNAMICS AND VELOCITY PROFILES USING A FULLY NONLINEAR BOUSSINESQ MODEL". Coastal Engineering Proceedings 1, n.º 32 (29 de janeiro de 2011): 48. http://dx.doi.org/10.9753/icce.v32.currents.48.

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We present experimental and numerical analysis of nonlinear processes responsible for generating infragravity waves in the nearshore. We provide new experimental data on random wave propagation and associated velocity profiles in the shoaling and surf zones of a very mild slope beach. We analyze low frequency wave generation mechanisms and dynamics along the beach and examine in detail the ability of the fully nonlinear Boussinesq- type model SERR1D (Cienfuegos et al., 2010) to reproduce the complex dynamics of high frequency wave propagation and energy transfer mechanisms that enhance infragravity wave generation in the laboratory.

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15

Khajetoorians, Alexander Ako, Benjamin Baxevanis, Christoph Hübner, Tobias Schlenk, Stefan Krause, Tim Oliver Wehling, Samir Lounis et al. "Current-Driven Spin Dynamics of Artificially Constructed Quantum Magnets". Science 339, n.º 6115 (3 de janeiro de 2013): 55–59. http://dx.doi.org/10.1126/science.1228519.

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The future of nanoscale spin-based technologies hinges on a fundamental understanding and dynamic control of atomic-scale magnets. The role of the substrate conduction electrons on the dynamics of supported atomic magnets is still a question of interest lacking experimental insight. We characterized the temperature-dependent dynamical response of artificially constructed magnets, composed of a few exchange-coupled atomic spins adsorbed on a metallic substrate, to spin-polarized currents driven and read out by a magnetic scanning tunneling microscope tip. The dynamics, reflected by two-state spin noise, is quantified by a model that considers the interplay between quantum tunneling and sequential spin transitions driven by electron spin-flip processes and accounts for an observed spin-transfer torque effect.

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Zorndt, Anna C., Torsten Schlurmann e Iris Grabemann. "THE INFLUENCE OF EXTREME EVENTS ON HYDRODYNAMICS AND SALINITIES IN THE WESER ESTUARY IN THE CONTEXT OF CLIMATE IMPACT RESEARCH". Coastal Engineering Proceedings 1, n.º 33 (15 de dezembro de 2012): 50. http://dx.doi.org/10.9753/icce.v33.currents.50.

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The salinity and its longitudinal distribution in the Weser estuary, Germany, has implications for water management as the estuarine water is needed, e.g., for irrigation of the agricultural used hinterlands and as industrial water and because of its intrusion into groundwater. Generally, the salinity distribution is determined by tidal dynamics, river runoff from the catchment area, amount of intruding seawater from the German Bight (North Sea) as well as by the salinities of both river and seawater. Anthropogenic climate change may have an impact on the estuarine dynamics and, thus, on the salinity distribution. This study focuses on the impact of storm surges. A semi-implicit Eulerian-Lagrangian finite element model was used to simulate hydrodynamics and salinities in the estuary. By comparing simulated and observed data of two past storm surges it is shown that the model is well capable of reproducing estuarine dynamics. Possible future changes due to climate change are investigated for three scenario- based storm surges; two of them represent future storm conditions and one specifies reference (today's) conditions for comparison. These storm surges were simulated using boundary conditions from water level simulations with a hydrodynamic model for the North Sea together with the respective meteorological forcing. It can be shown that during storm tides, isohalines penetrate more than 30 km further upstream than during normal conditions. For the most severe scenario-based storm surge, this leads to a salinity increase of up to 30 psu within the mixing zone during the highest storm tide.

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17

Yang, Xiufeng, Dale Kerper, Shubhra Misra, James Stear, Tao Shen e Knut LisÃ¦ter. "THE DYNAMICS OF STORM SURGE AND MEAN SEA LEVEL VARIABILITY IN THE NORTHEASTERN CASPIAN SEA". Coastal Engineering Proceedings, n.º 36 (30 de dezembro de 2018): 60. http://dx.doi.org/10.9753/icce.v36.currents.60.

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Storm surge is a major natural hazard to the construction and operation of infrastructure projects in shallow and gently sloping coastal areas such as the northeastern part of the Caspian Sea. Up-surge events cause significant coastal flooding, while down-surge events disrupt marine transportation by constraining safe navigable water depths. Coastal developments therefore have to achieve a judicious balance of these conflicting constraints. Further, the unpredictability of long-term and intra-annual Mean Sea Level (MSL) variability as well as periodic freeze-up and break-up due to ice formation in this part of the Caspian Sea complicate a robust and unequivocal basis for defining storm surge hazards.

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Larsen, Bjarke Eltard, e David R. Fuhrman. "RUN-UP, BOUNDARY LAYERS AND SHEAR STRESSES BENEATH SHOALING TSUNAMIS". Coastal Engineering Proceedings, n.º 36 (30 de dezembro de 2018): 24. http://dx.doi.org/10.9753/icce.v36.currents.24.

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While the tsunami propagation, run-up and inundation has received considerable attention in literature, the associated boundary layer dynamics and induced sediment transport have received relatively little attention. Recently, Williams and Fuhrman (2016) simulated a series of tsunami scale boundary layers, emphasizing that they are simultaneously both current- and wave-like due to their long duration yet unsteady nature. They viewed the tsunami as a time varying current, something that has also been done by Larsen et al. (2017) and Larsen et al. (2018) in studies of tsunami-induced scour around monopile foundations. This approach is valid sufficiently far off-shore, but nearshore, the effects of the free-surface will inevitably become important. While difficult due to the large scales involved, the run-up and inundation can likewise be studied experimentally (Sriram et al. 2016). In this work the run-up process of full-scale tsunamis will be simulated in detail using CFD, which can naturally resolve shorter dispersive waves, wave breaking and boundary layer dynamics.

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19

Temgoua, Loannis Pavel Gauss, Jimmi Hervé Talla Mbé, Bernard Essimbi Zobo e Paul Woafo. "Dynamics of vertical-cavity surface-emitting lasers under AM and FM current modulations". Physica Scripta 96, n.º 12 (15 de novembro de 2021): 125523. http://dx.doi.org/10.1088/1402-4896/ac35bf.

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Abstract We numerically investigate the dynamics of Vertical-Cavity Surface-Emitting Lasers (VCSELs) described by the current-dependent gain model and subjected to current in the form of amplitude modulation (AM) and frequency modulation (FM). Since VCSELs have two polarization modes (PMs), the competition between them offers more complex dynamical behaviors. It is found that when operating close to the threshold current, the laser converts the AM and FM currents into a series of pulse packages (PPs) that are globally irregular and modulated either in amplitude or frequency. In the particular case of FM current, both modulations occur in a unique signal. Besides, chaotic light is recovered even at low frequencies (few MHz) where it is not usually expected when sinusoidal current modulation is used. But, if the AM and the FM currents evolve over the threshold value, the laser does not alter the form of the current. Therefore, those currents are linearly converted into light signals.

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Xu, R. L. "Particle dynamics and currents in the magnetotail". Astrophysics and Space Science 144, n.º 1-2 (maio de 1988): 257–77. http://dx.doi.org/10.1007/bf00793184.

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Gerasimov, Sergey. "Dynamics of Nonsymmetric Conductor with Foucault’s Currents". Известия высших учебных заведений. Электромеханика 65, n.º 1 (2022): 25–28. http://dx.doi.org/10.17213/0136-3360-2022-1-25-28.

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The purpose of this work is to measure the force acting on an asymmetric conductor in an alternating magnetic field. Since Foucault currents are inductive, the force acting on the conductor, averaged over the period of oscil-lations of the alternating magnetic field, must be equal to zero. This became the basis for making detailed meas-urements of the change in the weight of a conductor when a magnetic field is turned on. The nature of the magnet-ic field created by the source has been studied. This made it possible to determine the region where the magnetic field is uniform. Even when an unbalanced conductor is located in a region where the field is uniform, the aver-age force acting on the conductor is not zero. Particular attention is paid to the dependence of the change in the weight of the conductor in the form of a half ring on the angle of inclination with respect to the horizontal. This made it possible to separate the background component from the Abraham force, which is the force of the radia-tion reaction to the conductor. The maximum value of the measured Abraham force is significantly higher than the known experimental values and is observed with a horizontal conductor with a cylindrical surface located below

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Sharifuzzaman, M. D., Charles J. Lemckert e Amir Etemad-Shahidi. "Dynamics of lock-release crystalline gravity currents". Geology, Ecology, and Landscapes 1, n.º 4 (2 de outubro de 2017): 213–18. http://dx.doi.org/10.1080/24749508.2017.1389446.

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Patchkovskii, Serguei. "Electronic currents and Born-Oppenheimer molecular dynamics". Journal of Chemical Physics 137, n.º 8 (28 de agosto de 2012): 084109. http://dx.doi.org/10.1063/1.4747540.

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Yuan, Kai-Jun, Chuan-Cun Shu, Daoyi Dong e André D. Bandrauk. "Attosecond Dynamics of Molecular Electronic Ring Currents". Journal of Physical Chemistry Letters 8, n.º 10 (5 de maio de 2017): 2229–35. http://dx.doi.org/10.1021/acs.jpclett.7b00877.

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Kudtarkar, Santosh Kumar. "Dynamics of helimagnets with spin polarised currents". Physics Letters A 374, n.º 2 (dezembro de 2009): 366–75. http://dx.doi.org/10.1016/j.physleta.2009.11.006.

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MAXWORTHY, T. "The dynamics of sedimenting surface gravity currents". Journal of Fluid Mechanics 392 (10 de agosto de 1999): 27–44. http://dx.doi.org/10.1017/s002211209900556x.

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We have performed a series of experiments on the dynamics of sedimenting, surface gravity currents. The physical situation concerns a current, with total density ρC, evolving at the surface of a fluid of greater density, ρA. In turn ρC is made up of interstitial fluid of density ρI and heavy particles with a concentration by weight c and a density ρP. Only the case of the release of a constant volume of particles and interstitial fluid has been considered in detail. It has been found that the sedimentation of the particles, plus some of the interstitial fluid, through the interface between the two fluids has a profound effect upon the motion of the current. When the rejected mixture of particles and upper- and lower-layer fluids reaches the bottom of the experimental tank it generates a secondary gravity current which in turn interacts with the primary current to further modify its behaviour. Using simple models we have been able to rationalize the observations and reveal the dynamical balances which appear to be important. A subsidiary experiment and analysis on the flux characteristics of the interface have been performed in order to further clarify the important effects of the particle motion through that region.

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Sherman, E. Ya, R. M. Abrarov e J. E. Sipe. "Dynamics of optically injected two-dimensional currents". Journal of Applied Physics 104, n.º 10 (15 de novembro de 2008): 103701. http://dx.doi.org/10.1063/1.3020519.

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Nogueira, Helena I. S., Claudia Adduce, Elsa Alves e Mário J. Franca. "Dynamics of the head of gravity currents". Environmental Fluid Mechanics 14, n.º 2 (10 de outubro de 2013): 519–40. http://dx.doi.org/10.1007/s10652-013-9315-2.

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Constantin, A., e G. Haller. "Preface: Dynamics of ocean waves and currents". Deep Sea Research Part II: Topical Studies in Oceanography 160 (fevereiro de 2019): 1–2. http://dx.doi.org/10.1016/j.dsr2.2019.01.004.

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ROBISON, ROSALYN A. V., HERBERT E. HUPPERT e M. GRAE WORSTER. "Dynamics of viscous grounding lines". Journal of Fluid Mechanics 648 (7 de abril de 2010): 363–80. http://dx.doi.org/10.1017/s0022112009993119.

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We have used viscous fluids in simple laboratory experiments to explore the dynamics of grounding lines between marine ice sheets and the freely floating ice shelves into which they develop. We model the ice sheets as shear-dominated gravity currents, and the ice shelves as extensional gravity currents having zero shear to leading order. We consider the flow of viscous fluid down an inclined plane into a dense inviscid ‘ocean’. A fixed flux of fluid is supplied at the top of the plane, which is at ‘sea level’. The fluid forms a gravity current flowing down and attached to the plane for some distance before detaching to form a freely floating extensional current. We have derived a mathematical model of the flow that incorporates a new dynamic boundary condition for the position of the grounding line, where the gravity current loses contact with the solid base. The grounding line initially advances and eventually reaches a steady position. Good agreement between our theoretical predictions and experimental measurements and observations gives confidence in the fundamental assumptions of our model.

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Barth, Alexander, Charles Troupin, Emma Reyes, Aida Alvera-Azcárate, Jean-Marie Beckers e Joaquín Tintoré. "Variational interpolation of high-frequency radar surface currents using DIVAnd". Ocean Dynamics 71, n.º 3 (23 de janeiro de 2021): 293–308. http://dx.doi.org/10.1007/s10236-020-01432-x.

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AbstractDIVAnd (Data-Interpolating Variational Analysis, in n-dimensions) is a tool to interpolate observations on a regular grid using the variational inverse method. We have extended DIVAnd to include additional dynamic constraints relevant to surface currents, including imposing a zero normal velocity at the coastline, imposing a low horizontal divergence of the surface currents, temporal coherence and simplified dynamics based on the Coriolis force, and the possibility of including a surface pressure gradient. The impact of these constraints is evaluated by cross-validation using the HF (high-frequency) radar surface current observations in the Ibiza Channel from the Balearic Islands Coastal Ocean Observing and Forecasting System (SOCIB). A small fraction of the radial current observations are set aside to validate the velocity reconstruction. The remaining radial currents from the two radar sites are combined to derive total surface currents using DIVAnd and then compared to the cross-validation dataset and to drifter observations. The benefit of the dynamic constraints is shown relative to a variational interpolation without these dynamical constraints. The best results were obtained using the Coriolis force and the surface pressure gradient as a constraint which are able to improve the reconstruction from the Open-boundary Modal Analysis, a quite commonly used method to interpolate HF radar observations, once multiple time instances are considered together.

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Rotstein, Horacio G., Motolani Olarinre e Jorge Golowasch. "Dynamic compensation mechanism gives rise to period and duty-cycle level sets in oscillatory neuronal models". Journal of Neurophysiology 116, n.º 5 (1 de novembro de 2016): 2431–52. http://dx.doi.org/10.1152/jn.00357.2016.

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Rhythmic oscillation in neurons can be characterized by various attributes, such as the oscillation period and duty cycle. The values of these features depend on the amplitudes of the participating ionic currents, which can be characterized by their maximum conductance values. Recent experimental and theoretical work has shown that the values of these attributes can be maintained constant for different combinations of two or more ionic currents of varying conductances, defining what is known as level sets in conductance space. In two-dimensional conductance spaces, a level set is a curve, often a line, along which a particular oscillation attribute value is conserved. In this work, we use modeling, dynamical systems tools (phase-space analysis), and numerical simulations to investigate the possible dynamic mechanisms responsible for the generation of period and duty-cycle levels sets in simplified (linearized and FitzHugh-Nagumo) and conductance-based (Morris-Lecar) models of neuronal oscillations. A simplistic hypothesis would be that the tonic balance between ionic currents with the same or opposite effective signs is sufficient to create level sets. According to this hypothesis, the dynamics of each ionic current during a given cycle are well captured by some constant quantity (e.g., maximal conductances), and the phase-plane diagrams are identical or are almost identical (e.g., cubic-like nullclines with the same maxima and minima) for different combinations of these maximal conductances. In contrast, we show that these mechanisms are dynamic and involve the complex interaction between the nonlinear voltage dependencies and the effective time scales at which the ionic current's dynamical variables operate.

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Klemp, Joseph B., Richard Rotunno e William C. Skamarock. "On the dynamics of gravity currents in a channel". Journal of Fluid Mechanics 269 (25 de junho de 1994): 169–98. http://dx.doi.org/10.1017/s0022112094001527.

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We attempt to clarify the factors that regulate the propagation and structure of gravity currents through evaluation of idealized theoretical models along with two-dimensional numerical model simulations. In particular, we seek to reconcile research based on hydraulic theory for gravity currents evolving from a known initial state with analyses of gravity currents that are assumed to be at steady state, and to compare these approaches with both numerical simulations and laboratory experiments. The time-dependent shallow-water solution for a gravity current propagating in a channel of finite depth reveals that the flow must remain subcritical behind the leading edge of the current (in a framework relative to the head). This constraint requires that hf/d ≤ 0.347, where hf is the height of the front and d is the channel depth. Thus, in the lock-exchange problem, inviscid solutions corresponding to hf/d = 0.5 are unphysical, and the actual currents have depth ratios of less than one half near their leading edge and require dissipation or are not steady. We evaluate the relevance of Benjamin's (1968) well-known formula for the propagation of steady gravity currents and clarify discrepancies with other theoretical and observed results. From two-dimensional simulations with a frictionless lower surface, we find that Benjamin's idealized flow-force balance provides a good description of the gravity-current propagation. Including surface friction reduces the propagation speed because it produces dissipation within the cold pool. Although shallow-water theory over-estimates the propagation speed of the leading edge of cold fluid in the ‘dam-break’ problem, this discrepancy appears to arise from the lack of mixing across the current interface rather than from deficiencies in Benjamin's front condition. If an opposing flow restricts the propagation of a gravity current away from its source, we show that the propagation of the current relative to the free stream may be faster than predicted by Benjamin's formula. However, in these situations the front propagation remains dependent upon the specific source conditions and cannot be generalized.

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del Negro, Christopher A., Chie-Fang Hsiao e Scott H. Chandler. "Outward Currents Influencing Bursting Dynamics in Guinea Pig Trigeminal Motoneurons". Journal of Neurophysiology 81, n.º 4 (1 de abril de 1999): 1478–85. http://dx.doi.org/10.1152/jn.1999.81.4.1478.

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Outward currents influencing bursting dynamics in guinea pig trigeminal motoneurons. To initiate and maintain bursts (and plateau potentials) in the presence of serotonin, guinea pig trigeminal motoneurons utilize L-type Ca2+ and persistent Na+ inward currents. However, the intrinsic currents that contribute to burst termination and determine the duration of the interburst interval are unknown. Therefore we investigated the roles of outward currents, whose slow activation is coupled to cytosolic cation (Ca2+ and Na+) accumulation. First we examined a Ca2+-dependent K+ current ( I K-Ca) with apamin and Ba2+-substituted, low-Ca2+ solution. Blockade of I K-Ca lengthened burst duration and cycle time but did not abolish bursting. Next we studied the Na+/K+-ATPase pump current ( I p) with cardiac glycosides. In the presence of apamin or low-Ca2+/Ba2+ solution, blocking I p (with ouabain or strophanthidin) decreased both burst duration and cycle time and ultimately transformed bursting into tonic spiking. We conclude that I K-Ca and I p contribute to burst termination in trigeminal motoneurons. These currents influence temporal bursting properties such as burst duration and cycle time and may help determine the phasic activity of motoneurons during rhythmic oral-motor behaviors.

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Almar, Rafael, Rodrigo Cienfuegos, Eduardo Gonzalez, Patricio Catalán, Hervé Michallet, Philippe Bonneton, Bruno Castelle e Leandro Suarez. "BARRED-BEACH MORPHOLOGICAL CONTROL ON INFRAGRAVITY MOTION". Coastal Engineering Proceedings 1, n.º 33 (25 de outubro de 2012): 24. http://dx.doi.org/10.9753/icce.v33.currents.24.

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A conceptual analysis of the coupling between bars and infragravity waves is performed combining laboratory experiments and numerical modeling. Experiments are carried out in a wave flume with a barred profile. The Boussinesq fully-nonlinear model SERR1D is validated with the laboratory data and a sensitivity analysis is performed next to study the influence on the infragravity wave dynamics of bar amplitude and location, and swash zone slope. A novel technique of incident and reflected motions separation that conserves temporal characteristics is applied. We observe that changing bar characteristics induces substantial variations in trapped energy. Interestingly, a modification of swash zone slope has a large influence on the reflected component, controlling amplitude and phase time-lag, and consequently on the resonant pattern. Variations of trapped infragravity energy induced by changes of swash zone slope reach 25 %. These changes in infragravity pattern consequently affect short-wave dynamics by modifying the breakpoint location and the breaking intensity. Our conceptual investigation suggests the existence of a morphological feedback through the action of evolving morphology on infragravity structures which modulates the action of short-waves on the morphology itself.

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Mishin, Vladimir, Vilen Mishin e Marina Kurikalova. "Dynamics of the field-aligned currents distribution asymmetry during substorms in the equinox season". Solar-Terrestrial Physics 7, n.º 1 (29 de março de 2021): 32–40. http://dx.doi.org/10.12737/stp-71202105.

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We continue to study the physical processes occurring during the August 17, 2001 magnetospheric storm by analyzing the dynamics of the intensity of field-aligned currents (FACs) in Iijima—Potemra Region 1 in the polar ionospheres of two hemispheres, using the modernized magnetogram inversion technique. The results obtained on the dynamics of the FAC asymmetry of two types (dawn–dusk and interhemispheric), as well as the previously obtained regularities in the behavior of Hall currents and polar cap boundaries depending on the large azimuthal component of the interplanetary magnetic field (IMF), observed during the storm, and the seasonal behavior of the conductivity are consistent with the open magnetosphere model and with satellite observations of auroras in two hemispheres. We have shown that the weakening of the asymmetry of two types in the FAC distribution during substorms in the storm under study occurs almost completely in the winter hemisphere and is much weaker in the summer one. We associate this phenomenon with the predominance of the effect of long-term exposure to the azimuthal IMF component in the sunlit polar ionosphere of the summer hemisphere over the substorm symmetrization effect of the night magnetosphere. A symmetrization effect of the polar cap and FACs, created by the solar wind pressure pulse at the end of the storm, is observed. We propose a qualitative explanation of this effect.

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Buongiorno Nardelli, Bruno, Davide Cavaliere, Elodie Charles e Daniele Ciani. "Super-Resolving Ocean Dynamics from Space with Computer Vision Algorithms". Remote Sensing 14, n.º 5 (26 de fevereiro de 2022): 1159. http://dx.doi.org/10.3390/rs14051159.

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Surface ocean dynamics play a key role in the Earth system, contributing to regulate its climate and affecting the marine ecosystem functioning. Dynamical processes occur and interact in the upper ocean at multiple scales, down to, or even less than, few kilometres. These scales are not adequately resolved by present observing systems, and, in the last decades, global monitoring of surface currents has been based on the application of geostrophic balance to absolute dynamic topography maps obtained through the statistical interpolation of along-track satellite altimeter data. Due to the cross-track distance and repetitiveness of satellite acquisitions, the effective resolution of interpolated data is limited to several tens of kilometres. At the kilometre scale, sea surface temperature pattern evolution is dominated by advection, providing indirect information on upper ocean currents. Computer vision techniques are perfect candidates to infer this dynamical information from the combination of altimeter data, surface temperature images and observing-system geometry. Here, we exploit one class of image processing techniques, super-resolution, to develop an original neural-network architecture specifically designed to improve absolute dynamic topography reconstruction. Our model is first trained on synthetic observations built from a numerical general-circulation model and then tested on real satellite products. Provided concurrent clear-sky thermal observations are available, it proves able to compensate for altimeter sampling/interpolation limitations by learning from primitive equation data. The algorithm can be adapted to learn directly from future surface topography, and eventual surface currents, high-resolution satellite observations.

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Fagotti, Maurizio. "Charges and currents in quantum spin chains: late-time dynamics and spontaneous currents". Journal of Physics A: Mathematical and Theoretical 50, n.º 3 (20 de dezembro de 2016): 034005. http://dx.doi.org/10.1088/1751-8121/50/3/034005.

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Spicer, D. S., e R. N. Sudan. "Beam-Return Current Systems in Solar Flares". Symposium - International Astronomical Union 107 (1985): 519–20. http://dx.doi.org/10.1017/s0074180900076051.

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The importance of electron beams in solar flare dynamics is well known. In order to understand the dynamics produced by beams it is essential to have a clear understanding of the role beam driven return currents play and whether electrostatic or inductive electric fields maintain the return current. We show that inductive electric fields are responsible for driving return currents under solar conditions.

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Yang, Xiaoting, Eli Tziperman e Kevin Speer. "Deep Eastern Boundary Currents: Idealized Models and Dynamics". Journal of Physical Oceanography 51, n.º 4 (abril de 2021): 989–1005. http://dx.doi.org/10.1175/jpo-d-20-0227.1.

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AbstractConcentrated poleward flows along eastern boundaries between 2- and 4-km depth in the southeast Pacific, Atlantic, and Indian Oceans have been observed, and appear in data assimilation products and regional model simulations at sufficiently high horizontal resolution, but their dynamics are still not well understood. We study the local dynamics of these deep eastern boundary currents (DEBCs) using idealized GCM simulations, and we use a conceptual vorticity model for the DEBCs to gain additional insights into the dynamics. Over most of the zonal width of the DEBCs, the vorticity balance is between meridional advection of planetary vorticity and vortex stretching, which is an interior-like vorticity balance. Over a thinner layer very close to the eastern boundary, a balance between vorticity tendencies due to friction and stretching that rapidly decay away from the boundary is found. Over the part of the DEBC that is governed by an interior-like vorticity balance, vertical stretching is driven by both the topography and temperature diffusion, while in the thinner boundary layer, it is driven instead by parameterized horizontal temperature mixing. The topographic driving acts via a cross-isobath flow that leads to stretching and thus to vorticity forcing for the concentrated DEBCs.

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Lemmin, U., e D. M. Imboden. "Dynamics of bottom currents in a small lake1". Limnology and Oceanography 32, n.º 1 (janeiro de 1987): 62–75. http://dx.doi.org/10.4319/lo.1987.32.1.0062.

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Artemyev, Anton V., Vassilis Angelopoulos, Jasper S. Halekas, Alexander A. Vinogradov, Ivan Y. Vasko e Lev M. Zelenyi. "Dynamics of Intense Currents in the Solar Wind". Astrophysical Journal 859, n.º 2 (29 de maio de 2018): 95. http://dx.doi.org/10.3847/1538-4357/aabe89.

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Fredriksson, D. W., M. R. Swift, O. Eroshkin, I. Tsukrov, J. D. Irish e B. Celikkol. "Moored Fish Cage Dynamics in Waves and Currents". IEEE Journal of Oceanic Engineering 30, n.º 1 (janeiro de 2005): 28–36. http://dx.doi.org/10.1109/joe.2004.841412.

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Burch, J. L. "Energetic particles and currents: Results from Dynamics Explorer". Reviews of Geophysics 26, n.º 2 (1988): 215. http://dx.doi.org/10.1029/rg026i002p00215.

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Mayergoyz, I. D., C. Serpico e Y. Shimizu. "Coupling between eddy currents and Landau–Lifshitz dynamics". Journal of Applied Physics 87, n.º 9 (maio de 2000): 5529–31. http://dx.doi.org/10.1063/1.373394.

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Tansley, Claire E., e David P. Marshall. "On the Dynamics of Wind-Driven Circumpolar Currents". Journal of Physical Oceanography 31, n.º 11 (novembro de 2001): 3258–73. http://dx.doi.org/10.1175/1520-0485(2001)031<3258:otdowd>2.0.co;2.

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Özgökmen, Tamay M., e Eric P. Chassignet. "Dynamics of Two-Dimensional Turbulent Bottom Gravity Currents". Journal of Physical Oceanography 32, n.º 5 (maio de 2002): 1460–78. http://dx.doi.org/10.1175/1520-0485(2002)032<1460:dotdtb>2.0.co;2.

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Zgheib, N., T. Bonometti e S. Balachandar. "Dynamics of non-circular finite-release gravity currents". Journal of Fluid Mechanics 783 (22 de outubro de 2015): 344–78. http://dx.doi.org/10.1017/jfm.2015.580.

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The present work reports some new aspects of non-axisymmetric gravity currents obtained from laboratory experiments, fully resolved simulations and box models. Following the earlier work of Zgheib et al. (Theor. Comput. Fluid Dyn., vol. 28, 2014, pp. 521–529) which demonstrated that gravity currents initiating from non-axisymmetric cross-sectional geometries do not become axisymmetric, nor do they retain their initial shape during the slumping and inertial phases of spreading, we show that such non-axisymmetric currents eventually reach a self-similar regime during which (i) the local front propagation scales as $t^{1/2}$ as in circular releases and (ii) the non-axisymmetric front has a self-similar shape that primarily depends on the aspect ratio of the initial release. Complementary experiments of non-Boussinesq currents and top-spreading currents suggest that this self-similar dynamics is independent of the density ratio, vertical aspect ratio, wall friction and Reynolds number $\mathit{Re}$, provided the last is large, i.e. $\mathit{Re}\geqslant O(10^{4})$. The local instantaneous front Froude number obtained from the fully resolved simulations is compared to existing models of Froude functions. The recently reported extended box model is capable of capturing the dynamics of such non-axisymmetric flows. Here we use the extended box model to propose a relation for the self-similar horizontal aspect ratio ${\it\chi}_{\infty }$ of the propagating front as a function of the initial horizontal aspect ratio ${\it\chi}_{0}$, namely ${\it\chi}_{\infty }=1+(\ln {\it\chi}_{0})/3$. The experimental and numerical results are in good agreement with the proposed relation.

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Nakata, Kouki, Pascal Simon e Daniel Loss. "Spin currents and magnon dynamics in insulating magnets". Journal of Physics D: Applied Physics 50, n.º 11 (14 de fevereiro de 2017): 114004. http://dx.doi.org/10.1088/1361-6463/aa5b09.

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Marder, E., L. F. Abbott, G. G. Turrigiano, Z. Liu e J. Golowasch. "Memory from the dynamics of intrinsic membrane currents". Proceedings of the National Academy of Sciences 93, n.º 24 (26 de novembro de 1996): 13481–86. http://dx.doi.org/10.1073/pnas.93.24.13481.

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