On a Magnetic Damper Consisting of a Circular Magnetic Flux and a Conductor of Arbitrary Shape. Part II: Applications and Numerical Results

1984 ◽  
Vol 106 (1) ◽  
pp. 52-55 ◽  
Author(s):  
Kosuke Nagaya
Keyword(s):  
Numerical Calculation ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Arbitrary Shape ◽  
Companion Paper ◽  
Numerical Results ◽  
Typical Case ◽  
Potential Fields ◽  
Damping Coefficients ◽  
Theoretical Results

A method of numerical calculation for obtaining the damping coefficients and potential fields has been presented for magnetic dampers by utilizing the theoretical results given by the authors in a companion paper (Part I). The study developed in this paper is concerned with dampers consisting of the following conductors and magnetic fluxes: (a) a rectangular conductor and an eccentric circular flux, (b) a circular conductor and an eccentric circular flux, and (c) polygonal conductors of various shapes and a concentric circular flux. Numerical results for the damping coefficients, and potential lines of the magnetic fields have been obtained for these dampers. The results obtained are compared with those of the typical case of the conductor with a concentric circular flux.

On a Magnetic Damper Consisting of a Circular Magnetic Flux and a Conductor of Arbitrary Shape. Part I: Derivation of the Damping Coefficients

1984 ◽  
Vol 106 (1) ◽  
pp. 46-51 ◽  
Author(s):  
Kosuke Nagaya ◽  
Hiroyuki Kojima
Keyword(s):  
Boundary Condition ◽  
Exact Solution ◽  
Magnetic Flux ◽  
Electromagnetic Fields ◽  
Arbitrary Shape ◽  
Fourier Expansion ◽  
Polar Coordinates ◽  
Damping Coefficients ◽  
Theoretical Results ◽  
Good Agreement

Theoretical results for finding the damping coefficients of a magnetic damper consisting of a circular magnetic flux and an arbitrarily shaped conductor have been obtained. In the analysis the exact solution in polar coordinates for the governing equation of the electromagnetic fields is utilized. The boundary condition for arbitrarily shaped boundaries of the conductor is satisfied directly by means of the Fourier expansion collocation method. To discuss the accuracy of the present approximate results, the analysis also has been performed on damper consisting of a circular flux and a circular conductor. The comparison between the present results and the exact ones for the typical damper shows very good agreement.

Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

2000 ◽  
Vol 179 ◽  
pp. 263-264
Author(s):  
K. Sundara Raman ◽  
K. B. Ramesh ◽  
R. Selvendran ◽  
P. S. M. Aleem ◽  
K. M. Hiremath
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Ultra Violet ◽  
Active Regions ◽  
Morphological Properties ◽  
Energy Storage And Conversion ◽  
The Sun ◽  
X Rays ◽  
The Magnetic Field

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.

Solar Filaments as Tracers of Subsurface Processes

2000 ◽  
Vol 179 ◽  
pp. 177-183
Author(s):  
D. M. Rust
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Coronal Mass Ejections ◽  
Interplanetary Space ◽  
Intermediate Stage ◽  
Coronal Plasma ◽  
Magnetic Helicity ◽  
The Sun ◽  
New Paradigm ◽  
Solar Filaments

AbstractSolar filaments are discussed in terms of two contrasting paradigms. The standard paradigm is that filaments are formed by condensation of coronal plasma into magnetic fields that are twisted or dimpled as a consequence of motions of the fields’ sources in the photosphere. According to a new paradigm, filaments form in rising, twisted flux ropes and are a necessary intermediate stage in the transfer to interplanetary space of dynamo-generated magnetic flux. It is argued that the accumulation of magnetic helicity in filaments and their coronal surroundings leads to filament eruptions and coronal mass ejections. These ejections relieve the Sun of the flux generated by the dynamo and make way for the flux of the next cycle.

scholarly journals Hydrodynamic Forces Exerting on an Oscillating Cylinder under Translational Motion in Water Covered by Compressed Ice

Water ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 822
Author(s):  
Yury Stepanyants ◽  
Izolda Sturova
Keyword(s):  
Lift Force ◽  
Wave Motion ◽  
Translational Motion ◽  
Added Mass ◽  
Hydrodynamic Forces ◽  
Wave Resistance ◽  
Translational Velocity ◽  
Damping Coefficients ◽  
Incompressible Ideal Fluid ◽  
Theoretical Results

This paper presents the calculation of the hydrodynamic forces exerted on an oscillating circular cylinder when it moves perpendicular to its axis in infinitely deep water covered by compressed ice. The cylinder can oscillate both horizontally and vertically in the course of its translational motion. In the linear approximation, a solution is found for the steady wave motion generated by the cylinder within the hydrodynamic set of equations for the incompressible ideal fluid. It is shown that, depending on the rate of ice compression, both normal and anomalous dispersion can occur in the system. In the latter case, the group velocity can be opposite to the phase velocity in a certain range of wavenumbers. The dependences of the hydrodynamic loads exerted on the cylinder (the added mass, damping coefficients, wave resistance and lift force) on the translational velocity and frequency of oscillation were studied. It was shown that there is a possibility of the appearance of negative values for the damping coefficients at the relatively big cylinder velocity; then, the wave resistance decreases with the increase in cylinder velocity. The theoretical results were underpinned by the numerical calculations for the real parameters of ice and cylinder motion.

Pinning features of the magnetic flux trapped by YBCO single crystals in weak constant magnetic fields

2013 ◽  
Vol 39 (2) ◽  
pp. 107-110 ◽  
Author(s):  
V. Yu. Monarkha ◽  
V. A. Paschenko ◽  
V. P. Timofeev
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Single Crystals

FINITE ENERGY ONE-HALF MONOPOLE SOLUTIONS

2012 ◽  
Vol 27 (40) ◽  
pp. 1250233 ◽  
Author(s):  
ROSY TEH ◽  
BAN-LOONG NG ◽  
KHAI-MING WONG
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Topological Charge ◽  
Magnetic Monopole ◽  
Magnetic Charge ◽  
Finite Energy ◽  
Spatial Infinity ◽  
Yang Mills ◽  
The Magnetic Field

We present finite energy SU(2) Yang–Mills–Higgs particles of one-half topological charge. The magnetic fields of these solutions at spatial infinity correspond to the magnetic field of a positive one-half magnetic monopole at the origin and a semi-infinite Dirac string on one-half of the z-axis carrying a magnetic flux of [Formula: see text] going into the origin. Hence the net magnetic charge is zero. The gauge potentials are singular along one-half of the z-axis, elsewhere they are regular.

scholarly journals Physical limitations on antennas of arbitrary shape

2007 ◽  
Vol 463 (2086) ◽  
pp. 2589-2607 ◽  
Author(s):  
Mats Gustafsson ◽  
Christian Sohl ◽  
Gerhard Kristensson
Keyword(s):  
Arbitrary Shape ◽  
Numerical Results ◽  
High Contrast ◽  
Arbitrary Geometry ◽  
Long Wavelength ◽  
Physical Limitations

In this paper, physical limitations on bandwidth, realized gain, Q -factor and directivity are derived for antennas of arbitrary shape. The product of bandwidth and realizable gain is shown to be bounded from above by the eigenvalues of the long-wavelength, high-contrast polarizability dyadics. These dyadics are proportional to the antenna volume and are easily determined for an arbitrary geometry. Ellipsoidal antenna volumes are analysed in detail, and numerical results for some generic geometries are presented. The theory is verified against the classical Chu limitations for spherical geometries and shown to yield sharper bounds for the ratio of the directivity and the Q -factor for non-spherical geometries.

A Case for Magneto Hydro Dynamics (MHD)

2001 ◽  
Author(s):  
Haim H. Bau
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Lorentz Force ◽  
Electric Fields ◽  
Biological Fluids ◽  
Fluid Volume ◽  
Chaotic Advection ◽  
Complex Flows ◽  
Electric Currents

Abstract In this paper, I review some of our work on the use of magneto hydrodynamics (MHD) for pumping, controlling, and stirring fluids in microdevices. In many applications, one operates with liquids that are at least slightly conductive such as biological fluids. By patterning electrodes inside flow conduits and subjecting these electrodes to potential differences, one can induce electric currents in the liquid. In the presence of a magnetic field, a Lorentz force is generated in a direction that is perpendicular to both the magnetic and electric fields. Since one has a great amount of freedom in patterning the electrodes, one can induce forces in various directions so as to generate complex flows including “guided” flows in virtual, wall-less channels. The magnetic flux generators can be either embedded in the device or be external. Despite their unfavorable scaling (the magnitude of the forces is proportional to the fluid volume), MHD offers many advantages such as the flexibility of applying forces in any desired direction and the ability to adjust the magnitude of the forces by adjusting either the electric and/or magnetic fields. We provide examples of (i) MHD pumps; (ii) controlled networks of conduits in which each conduit is equipped with a MHD actuator and by controlling the voltage applied to each actuator, one can direct the liquid to flow in any desired way without a need for valves; and (iii) MHD stirrers including stirrers that exhibit chaotic advection.

scholarly journals The number of lattice rules having given invariants

1992 ◽  
Vol 46 (3) ◽  
pp. 479-495 ◽  
Author(s):  
Stephen Joe ◽  
David C. Hunt
Keyword(s):  
Normal Form ◽  
Quadrature Rule ◽  
Unit Cube ◽  
Numerical Results ◽  
Smith Normal Form ◽  
Lattice Rules ◽  
Dimensional Unit ◽  
Lattice Rule ◽  
Positive Integers ◽  
Theoretical Results

A lattice rule is a quadrature rule used for the approximation of integrals over the s-dimensional unit cube. Every lattice rule may be characterised by an integer r called the rank of the rule and a set of r positive integers called the invariants. By exploiting the group-theoretic structure of lattice rules we determine the number of distinct lattice rules having given invariants. Some numerical results supporting the theoretical results are included. These numerical results are obtained by calculating the Smith normal form of certain integer matrices.

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