scholarly journals LARGE-SCALE FLUCTUATIONS AND PARTICLE DIFFUSION ACROSS EXTERNAL MAGNETIC FIELD IN TURBULENT PLASMAS

2000 ◽  
Vol 3 (2) ◽  
pp. 295 ◽  
Author(s):  
Zagorodny ◽  
Holod
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Large Scale ◽  
Particle Diffusion ◽  
Turbulent Plasmas

Exploration of the Structures of the Magnetically Induced Self-Assembly Photonic Crystals in a Solidified Polymer Matrix

2013 ◽  
Vol 634-638 ◽  
pp. 2324-2331
Author(s):  
Hai Bo Hu ◽  
Qian Wang Chen ◽  
Ran Li ◽  
Xiang Kai Kong ◽  
Jian Chen
Keyword(s):  
Magnetic Field ◽  
Photonic Crystal ◽  
External Magnetic Field ◽  
Crystal Structures ◽  
Polymer Matrix ◽  
Self Assembly ◽  
Large Scale ◽  
Solid Polymer ◽  
One Dimension ◽  
Polyacrylamide Hydrogel

The carbon-encapsulated superparamagnetic colloidal nanoparticles (SCNps) were rigidized into soft solids by embedding the SCNps into polyacrylamide hydrogel matrixes under the induction of an external magnetic field. Stabilized by the balance of attractive (magnetic) and repulsive (electrostatic) forces, the SCNps form one-dimension photonic crystal structures along the direction of the external magnetic field and further the structures are frozen into the solidified polymer matrix. The polymer matrix embedded one-dimension photonic crystal structures can strongly diffract visible light and present brilliant color in the light. This novel and soft solid polymer matrix that could be shaped and sliced not only paves a new avenue for develop novel magnetic-responsive photonic crystal materials and devices, but also provides a method to observe the magnetic-induced self-assembly structures of the SCNps in media such as polyacrylamide hydrogel matrixs as a result of the ordered structures frozen into the polyacrylamide hydrogel matrixs. So we can reveal the relationship between their structure and color, and furthermore permit a systematic exploration on magnetically induced self-assembling dynamics, colloidal crystallography which have important significance in the large-scale industrial production in the future.

scholarly journals Quadrature Photonic Spatial Ising Machine

2021 ◽  
Author(s):  
Wenjia Zhang ◽  
Wencheng Sun ◽  
Yuanyuan Liu ◽  
Qingwen Liu ◽  
Jiangbing Du ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Large Scale ◽  
Spin Interaction ◽  
Problem Solution ◽  
Np Hard ◽  
Combinatorial Optimization Problems ◽  
Max Cut Problem ◽  
Hard Problems ◽  
Np Hard Problems

Abstract The mining in physics and biology for accelerating the hardcore algorithm to solve non-deterministic polynomial (NP) hard problems has inspired a great amount of special-purpose ma-chine models. Ising machine has become an efficient solver for various combinatorial optimization problems. As a computing accelerator, large-scale photonic spatial Ising machine have great advantages and potentials due to excellent scalability and compact system. However, current fundamental limitation of photonic spatial Ising machine is the configuration flexibility of problem implementation in the accelerator model. Arbitrary spin interaction is highly desired for solving various NP hard problems. Moreover, the absence of external magnetic field in the proposed photonic Ising machine will further narrow the freedom to map the optimization applications. In this paper, we propose a novel quadrature photonic spatial Ising machine to break through the limitation of photonic Ising accelerator by synchronous phase manipulation in two and three sections. Max-cut problem solution with graph order of 100 and density from 0.5 to 1 is experimentally demonstrated after almost 100 iterations. We derive and verify using simulation the solution for Max-cut problem with more than 1600 nodes and the system tolerance for light misalignment. Moreover, vertex cover problem, modeled as an Ising model with external magnetic field, has been successfully implemented to achieve the optimal solution. Our work suggests flexible problem solution by large-scale photonic spatial Ising machine.

scholarly journals Nonlinear Dynamo in Obliquely Rotating Stratified Electroconductive Fluid in an Uniformly Magnetic Field

2020 ◽  
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
External Magnetic Field ◽  
Uniform Magnetic Field ◽  
Large Scale ◽  
Conducting Fluid ◽  
Magnetic Vortex ◽  
Small Scale ◽  
Large Scale Vortex ◽  
External Uniform Magnetic Field

In this paper, we investigated a new large-scale instability that arises in an obliquely rotating convective electrically conducting fluid in an external uniform magnetic field with a small-scale external force with zero helicity. This force excites small-scale velocity oscillations with a small Reynolds number. Using the method of multiscale asymptotic expansions, we obtain the nonlinear equations for vortex and magnetic disturbances in the third order of the Reynolds number. It is shown that the combined effects of the Coriolis force and the small external forces in a rotating conducting fluid possible large-scale instability. The linear stage of the magneto-vortex dynamo arising as a result of instabilities of -effect type is investigated. The mechanism of amplification of large-scale vortex disturbances due to the development of the hydrodynamic - effect taking into account the temperature stratification of the medium is studied. It was shown that a «weak» external magnetic field contributes to the generation of large-scale vortex and magnetic perturbations, while a «strong» external magnetic field suppresses the generation of magnetic-vortex perturbations. Numerical methods have been used to find stationary solutions of the equations of a nonlinear magneto-vortex dynamo in the form of localized chaotic structures in two cases when there is no external uniform magnetic field and when it is present.

Rapid distortion theory for homogeneous shear-driven MHD turbulence

2020 ◽  
Author(s):  
Sergei Safonov ◽  
Arakel Petrosyan
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Large Scale ◽  
Isotropic Turbulence ◽  
Basic Research ◽  
Small Time ◽  
Velocity Shear ◽  
Strong Nonlinearity ◽  
Mhd Turbulence ◽  
Rapid Distortion Theory

<p><span><span>In this report we study statistical properties of astrophysical turbulent plasma flows </span></span><span><span>subjected to large scale velocity shear and an external magnetic field</span></span><span><span> using Rapid Distortion Theory (RDT). </span></span><span><span>The problem of shear-driven turbulence arises in several important physical systems, such as</span></span> <span><span>the </span></span><span><span>solar wind </span></span><span><span>and ionized atmospheres of exoplanets</span></span><span><span>.</span></span> <span><span>Rapid distortion theory is a linearization method for Reynolds-averaged Navier-Stockes equations. Its</span></span> <span><span>main</span></span><span><span> assumption is that the turbulence responds to the external distortion </span></span><span><span>by velocity shear</span></span><span><span> so fast, that inertial </span></span><span><span>forces </span></span><span><span>result in a negligible change in velocity </span></span><span><span>field statistics at small time scales</span></span><span><span>. This allows to linearize equations and to derive equations for second moments of turbulence. We apply RDT </span></span><span><span>approach</span></span><span><span> to incompressible </span></span><span><span>homogeneous </span></span><span><span>MHD </span></span><span><span>turbulence</span></span><span><span> distorted with </span></span><span><span>an </span></span><span><span>external magnetic field and </span></span><span><span>a </span></span><span><span>linear velocity shear in cases of rotating and non-rotating plasma. It is shown that even with a strong nonlinearity many properties of turbulence can be qualitatively studied using a linear theory. A closed system of linear equations </span></span><span><span>is derived</span></span><span><span> for </span></span><span><span>e</span></span><span><span>nergy, helicity and polarization </span></span><span><span>of velocity and magnetic field correlations</span></span><span><span>. </span></span><span><span>Structural analysis is conducted showing the change of energy distribution between components of spectral tensor of turbulence. </span></span><span><span>Development of initially isotropic turbulence and transition to anisotropy are studied. </span></span><span><span>Model e</span></span><span><span>quations for fluid, current and cross helicity are derived. Differences in cases of rotating and non-rotating flows are discussed. This work was supported by the Russian Foundation for Basic Research (project no. 19-02-00016).</span></span></p>

An investigation on AC loss reduction for permanent-magnet wind power generator with superconducting windings

2021 ◽  
pp. 1-13
Author(s):  
Zhuo Chen ◽  
Ye Ma ◽  
Kaihe Zhang ◽  
Chenxi Zhou ◽  
Xiaoyan Huang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Wind Power ◽  
Large Scale ◽  
Ac Loss ◽  
Model Calculations ◽  
Power Generators ◽  
Wind Power Generator ◽  
Perpendicular Component ◽  
Wind Power Generators

High temperature superconducting (HTS) tapes could be introduced into large scale wind power generators in order to improve the power density. However, the alternating current (AC) loss of HTS tapes will cause the reduction of efficiency. On the basis of analytical and numerical model calculations, this paper presents an optimal design of the HTS armature winding aiming at lower AC loss. The main contribution of this work is that the relationship between the installation parameters and the AC loss of such HTS armature windings has been figured out based on the analysis of the shape feature of the HTS tape and the external magnetic field. When the tape is placed along a particular direction where the perpendicular component of external magnetic field has the lowest amplitude, the AC loss is the smallest. The modified installation location and angle are found based on the proposed generator. These results are verified using finite element method (FEM).

Evolution of Large-Scale Coronal Structures

1994 ◽  
Vol 144 ◽  
pp. 29-33
Author(s):  
P. Ambrož
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Solar Cycles ◽  
Characteristic Relationship ◽  
The Magnetic Field ◽  
Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

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