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Magnetic turbulence suppression by a helical mode in a cylindrical geometry

J.-H. Kim, P. W. Terry
2012 Physics of Plasmas  
In case of the sub-Alfv enic flow ðV A =V 0 ( 1Þ and the similar shear lengths of flow and magnetic field, L J $ L X , a coherent structure is likely to be bounded by the magnetic field shear X 0 w ¼ r  ...  One approach is to apply a statistical closure to Eqs. (4a) and (4b), consider the nonlinear interactions as nonlinear diffusion, and compare shearing rates with nonlinear diffusion rates.  ... 
doi:10.1063/1.4769369 fatcat:mjf4unmpabc43ozpfspxzi3s7e

Page 6120 of Mathematical Reviews Vol. , Issue 2002H [page]

2002 Mathematical Reviews  
The presence of this term, though small, can produce totally different linear and nonlinear stability behavior for the flow at subcritical Reynolds numbers.  ...  In the linear stability case, with the presence of this mean flow perturbation term, the instabilities are obtained well below the critical value of 5772.  ... 

Page 1107 of Mathematical Reviews Vol. 57, Issue 3 [page]

1979 Mathematical Reviews  
The present paper discusses the case of nonlinear modulation for strongly dispersive systems in which a coherent wave and a turbulent wave coexist.  ...  The two other cases are concerned with the symmetric and asymmetric flows arising from velocity profiles which have zero shear and consequently are relevant to almost separating flows.  ... 

Transport properties of energetic particles in a turbulent electrostatic field

G. Manfredi, R. O. Dendy
1997 Physics of Plasmas  
It is shown that nonlinear coupling significantly reduces the level of transport compared to the linear regime, and the physical mechanisms leading to this effect are analyzed in detail.  ...  The scaling of the diffusion coefficient with Larmor radius is derived from a closure theory, and the predictions are compared to results from computer experiments.  ...  Connor and Dr. M. Ottaviani. This work was partially funded by the Commission of the European Communities ͑Contract No. ERBCH-BICT941009͒, the UK Department of Trade and Industry and Euratom.  ... 
doi:10.1063/1.872159 fatcat:miijscvjhnhhzoztkyy7pphcmy

Adaptive Structure Tensors and their Applications [chapter]

Thomas Brox, Rein van den Boomgaard, François Lauze, Joost van de Weijer, Joachim Weickert, Pavel Mrázek, Pierre Kornprobst
2006 Mathematics and Visualization  
This article wants to give an overview of the different approaches, whereas the focus lies on the methods based on robust statistics and nonlinear diffusion.  ...  Here the main focus lies on optic flow estimation, but also texture analysis and corner detection are considered.  ...  Acknowledgements Our research was partly funded by the DFG project WE 2602/1-1 and the project Relations between Nonlinear Filters in Digital Image Processing within the DFG Priority Program 1114.  ... 
doi:10.1007/3-540-31272-2_2 fatcat:x2uckts37ffu7bbrjsc3suvnq4

Diffraction from an edge in a self-focusing medium

Wenjie Wan, Dmitry V. Dylov, Christopher Barsi, Jason W. Fleischer
2010 Optics Letters  
Diffraction into the shadow region is suppressed with increasing nonlinearity, but mode coupling leads to excitations and traveling waves on the high-intensity side.  ...  We experimentally demonstrate diffraction from a straight edge in a medium with self-focusing nonlinearity.  ...  For fixed coherence, the shock width scales linearly for both weak and strong nonlinearity [Figs. 4(c) and 4(d) ].  ... 
doi:10.1364/ol.35.002819 pmid:20717468 fatcat:5t6ukgel6bf6jjovhstej5ry5y

Nonlinear structure tensors

Thomas Brox, Joachim Weickert, Bernhard Burgeth, Pavel Mrázek
2006 Image and Vision Computing  
In all these cases, the nonlinear structure tensors demonstrate their superiority over the classical linear one.  ...  Two types of nonlinear diffusion processes for tensor data are studied: an isotropic one with a scalar-valued diffusivity, and its anisotropic counterpart with a diffusion tensor.  ...  Acknowledgements Our research has partly been funded by the projects WE 2602/1-1 and WE 2602/2-1 of the Deutsche Forschungsgemeinschaft (DFG). This is gratefully acknowledged.  ... 
doi:10.1016/j.imavis.2005.09.010 fatcat:aexnkgsxavasbcz2ubgzvreoua

Effects of parallel dynamics on vortex structures in electron temperature gradient driven turbulence

M. Nakata, T.-H. Watanabe, H. Sugama, W. Horton
2011 Physics of Plasmas  
In particular, the formation of coherent vortex streets is correlated with the strong generation of zonal flows for the cases with weak parallel compression, even though the maximum growth rate of linear  ...  Numerical results show three different types of vortex structures, i.e., coherent vortex streets accompanied with the transport reduction, turbulent vortices with steady transport, and a zonal-flow-dominated  ...  I Time-averaged heat diffusivity in the early and late nonlinear phases. FIG. 3. ͑  ... 
doi:10.1063/1.3535584 fatcat:wplkcy33qzgpnfqngkzdktedza

Phase Dynamics Criterion for Fast Relaxation of High-Confinement-Mode Plasmas

P. W. Xi, X. Q. Xu, P. H. Diamond
2014 Physical Review Letters  
This phase coherence time is determined by both linear and nonlinear dynamics.  ...  We demonstrate that ELMs can be mitigated by reducing the phase coherence time without changing linear instability.  ...  In conclusion, we presented a new, nonlinear criterion for the ELM crash. The occurrence of the crash depends on both the linear MHD growth rate γðnÞ and the phase coherence time τ c ðnÞ.  ... 
doi:10.1103/physrevlett.112.085001 fatcat:i6n5iul6nnhxjkqdkyjfzwxjzu

Image Denoising Using Non Linear Diffusion Tensors

Faouzi Benzarti, Hamid Amiri
2012 Advances in Computing  
One allows diffusion along the orientation of greatest coherence while the other allows diffusion along orthogonal directions.  ...  In this paper, we propose a new approach for image denoising based on the combination of two non linear diffusion tensors.  ...  Non Linear Diffusion PDE: Overview In this section, we review some basic mathematical concepts of the nonlinear diffusion PDEs proposed by Perona and Malik [1] .  ... 
doi:10.5923/ fatcat:l37p7mzs3zd7xlqqarogbvjo3a

Nonlinear dynamics of forced baroclinic critical layers

Chen Wang, Neil J. Balmforth
2019 Journal of Fluid Mechanics  
to create a drifting coherent structure.  ...  By using matched asymptotic expansions, we construct a nonlinear baroclinic critical layer theory to study how the flow perturbation evolves once they enter the nonlinear regime.  ...  We thank Professors Philip Marcus, Richard Kerswell and Dr. Thomas Eaves for important discussions, and the referees for helpful comments. We also thank Dr. Timm Treskatis and Mr.  ... 
doi:10.1017/jfm.2019.829 fatcat:mffx6ebv2zfufi4t5fnjvqfroa

Interpretation of Four Unique Phenomena and the Mechanism in Unsteady Flow Separation Controls

Weiyu Lu, Guoping Huang, Jinchun Wang, Yuxuan Yang
2019 Energies  
First, numerical simulation and some experimental results of a separated curved diffuser using pulsed jet flow control are discussed to show the four unique phenomena.  ...  Second, the bases of unsteady flow control, flow instability, and free shear flow theories are introduced to elucidate the unique phenomena and mechanism in unsteady flow separation controls.  ...  of Aeronautics and Astronautics) for technical support.  ... 
doi:10.3390/en12040587 fatcat:7hdsqi44w5f5jalrjo5nrrzy6y

Nonlinear waves in stratified Taylor--Couette flow. Part 2. Buoyancy flux [article]

Colin Leclercq, Jamie L. Partridge, Colm-Cille P. Caulfield, Stuart B. Dalziel, Paul F. Linden
2016 arXiv   pre-print
In a first paper, we showed that the dynamics of the flow was dominated by coherent structures made of a superposition of nonlinear waves.  ...  This coupling is primarily caused by diffusion of density at low Schmidt number Sc, but can also be a nonlinear effect at larger Sc.  ...  Acknowledgements We are indebted to Liang Shi, Markus Rampp, José-Manuel Lopez, Björn Hof and Marc Avila for sharing with us their excellent DNS code (Shi et al. 2015) . C.  ... 
arXiv:1609.02886v1 fatcat:irs6ipi435d2vk3dhjnaaicuca

Probability distribution function for self-organization of shear flows

Eun-jin Kim, Han-Li Liu, Johan Anderson
2009 Physics of Plasmas  
diffusing by a nonlinear eddy diffusivity.  ...  The first prediction of the probability distribution function (PDF) of self-organized shear flows is presented in a nonlinear diffusion model where shear flows are generated by a stochastic forcing while  ...  The resulting PDFs are found to be Gaussian since the diffusion [Eq. (1)] in this case is essentially linear except at |u x | = u xc .  ... 
doi:10.1063/1.3132631 fatcat:e7hnj5sts5bxdisqmmyk5qht2q

Coherent vortex extraction and simulation of 2D isotropic turbulence

2006 Journal of turbulence  
We compare two ways of choosing the threshold and show how one can thus split each flow realization into coherent vortices and quasi-Gaussian white noise.  ...  For the second approach we derive an additional linear equation to compute the effect of the incoherent background flow whose coefficients have been discarded.  ...  Titi and financial support from the Center for Nonlinear Studies, Los Alamos.  ... 
doi:10.1080/14685240600601061 fatcat:hvpwi74zerh4lhvtng5yif556y
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