Analytical Solution of the Perturbed Magnetic Fields of Plates Under Tensile Stress

2008 ◽  
Vol 75 (3) ◽  
Author(s):  
Fei Qin ◽  
Dongmei Yan
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Analytic Solutions ◽  
Round Hole ◽  
Governing Equations ◽  
Displacement Gradient ◽  
Weak Magnetic Fields ◽  
Testing Technology ◽  
Perturbed Magnetic Field ◽  
The Magnetic Field

Development of magnetism based nondestructive testing technology and the Microelectronic mechanical system require accurate computation of perturbed magnetic fields generated by mechanical stress. In this paper, based on the linearized magnetoelastic theory, the governing equations and continuity conditions to determine the perturbed magnetic fields were formulated for the case of weak external magnetic fields such as the earth’s magnetic field. Under those weak magnetic fields, the effect of the magnetic fields on mechanical deformation was neglected. As a result, the interaction between the deformation and the magnetic field was simplified. The effect of deformation on the perturbed magnetic field was taken into account by introducing the displacement gradient into the boundary conditions that the perturbed field should satisfy. As examples, analytic solutions of the perturbed magnetic field of infinite plates with and without a round hole, which are subjected to tensile stresses and weak external magnetic fields, were obtained by the approach presented. The results show that the perturbed magnetic fields induced by stress are three orders less in magnitude of intensity than that of magnetic fields without stress, and some prominent local features such as that has more peaks and decays more rapidly in the radial direction than the case of stress free that are predicted by the solutions.

scholarly journals Discovery of weak magnetic fields in four DZ white dwarfs in the local 20 pc volume

2019 ◽  
Vol 630 ◽  
pp. A65 ◽  
Author(s):  
S. Bagnulo ◽  
J. D. Landstreet
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
White Dwarfs ◽  
Field Measurements ◽  
Weak Magnetic Fields ◽  
Polluted Atmosphere ◽  
Highly Sensitive ◽  
Cool White Dwarfs ◽  
The Magnetic Field ◽  
Made In

We report the discovery of weak magnetic fields in three white dwarfs within the local 20 pc volume (WD 0816−310, WD 1009−184, and WD 1532+129), and we confirm the magnetic nature of a fourth star (WD 2138−332) in which we had previously detected a field at a 3σ level. The spectra of all these white dwarfs are characterised by the presence of metal lines and lack of H and He lines, that is, they belong to the spectral class DZ. The polarisation signal of the Ca II H+K lines of WD 1009−184 is particularly spectacular, with an amplitude of 20% that is due to the presence of a magnetic field with an average line-of-sight component of 40 kG. We have thus established that at least 40% of the known DZ white dwarfs with an He-rich atmosphere contained in the 20 pc volume have a magnetic field, while further observations are needed to establish whether the remaining DZ white dwarfs in the same volume are magnetic or not. Metal lines in the spectra of DZ white dwarfs are thought to have originated by accretion from rocky debris, and it might be argued that a link exists between metal accretion and higher occurrence of magnetism. However, we are not able to distinguish whether the magnetic field and the presence of a polluted atmosphere have a common origin, or if it is the presence of metal lines that allows us to detect a higher frequency of magnetic fields in cool white dwarfs, which would otherwise have featureless spectra. We argue that the new highly sensitive longitudinal field measurements that we have made in recent years are consistent with the idea that the magnetic field appears more frequently in older than in younger white dwarfs.

scholarly journals Evolution of quasi-bound states in the circular n–p junction of bilayer graphene under magnetic field

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Haijiao Ji ◽  
Yueting Pan ◽  
Haiwen Liu
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Bound States ◽  
Local Density ◽  
Energy Levels ◽  
Bilayer Graphene ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Weak Magnetic Fields ◽  
The Magnetic Field

Abstract Electron in gapless bilayer graphene can form quasi-bound states when a circular symmetric potential is created in bilayer graphene. These quasi-bound states can be adjusted by tuning the radius and strength of the potential barrier. We investigate the evolution of quasi-bound states spectra in the circular n–p junction of bilayer graphene under the magnetic field numerically. The energy levels of opposite angular momentum split and the splitting increases with the magnetic field. Moreover, weak magnetic fields can slightly shift the energy levels of quasi-bound states. While strong magnetic fields induce additional resonances in the local density states, which originates from Landau levels. We demonstrate that these numerical results are consistent with the semiclassical analysis based on Wentzel–Kramers–Brillouin approximation. Our results can be verified experimentally via scanning tunneling microscopy measurements.

scholarly journals Magnetic fields in astrophysical objects

2008 ◽  
Vol 366 (1884) ◽  
pp. 4453-4464 ◽  
Author(s):  
L.J Silvers
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Large Scale ◽  
Accretion Discs ◽  
Weak Magnetic Fields ◽  
Large Scale Magnetic Field ◽  
Astrophysical Objects ◽  
Recent Developments ◽  
The Magnetic Field

Magnetic fields are known to reside in many astrophysical objects and are now believed to be crucially important for the creation of phenomena on a wide variety of scales. However, the role of the magnetic field in the bodies that we observe has not always been clear. In certain situations, the importance of a magnetic field has been overlooked on the grounds that the large-scale magnetic field was believed to be too weak to play an important role in the dynamics. In this article I discuss some of the recent developments concerning magnetic fields in stars, planets and accretion discs. I choose to emphasize some of the situations where it has been suggested that weak magnetic fields may play a more significant role than previously thought. At the end of the article, I list some of the questions to be answered in the future.

Application of Magnetovision Scanning System for Detection of Dangerous Objects

2015 ◽  
Vol 220-221 ◽  
pp. 355-360
Author(s):  
Michał Nowicki ◽  
Roman Szewczyk
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Measurement System ◽  
Field Vector ◽  
Magnetic Field Vector ◽  
Scanning System ◽  
Passive Detection ◽  
Weak Magnetic Fields ◽  
The Magnetic Field

This paper presents application of magnetovision scanning system for detection of dangerous objects in weak magnetic fields. Measurement system was developed to study the magnetic field vector distributions. The measurements of the Earth’s field disturbances caused by dangerous ferromagnetic objects were carried out. The ability for passive detection of hidden dangerous objects and determine their location was demonstrated.

scholarly journals Line Formation in Inhomogeneous Magnetic Fields

1971 ◽  
Vol 43 ◽  
pp. 162-164 ◽  
Author(s):  
R. Göhring
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Differential Equations ◽  
Faraday Rotation ◽  
Atmospheric Model ◽  
Analytic Solutions ◽  
Line Formation ◽  
System Of Differential Equations ◽  
The Magnetic Field

Until now, analytic solutions for the problem of line formation in magnetic fields have been given only under special assumptions concerning either the magnetic field or the atmospheric model. Conditions are given for which the system of differential equations can be solved analytically. For the general case a method is given to solve the system in approximation and analytically. LTE is generally assumed which means that we use the system given by Unno (1956) or that given by Beckers (1969) including the Faraday rotation.

Wave propagation in a moving plasma. Part 2. Wave propagation along, and plasma motion normal to, the magnetic field

1974 ◽  
Vol 12 (2) ◽  
pp. 271-278
Author(s):  
D. N. Srivastava
Keyword(s):  
Magnetic Field ◽  
Wave Propagation ◽  
Magnetic Fields ◽  
Low Frequency ◽  
Wave Band ◽  
Weak Magnetic Fields ◽  
Moving Plasma ◽  
The One ◽  
The Right ◽  
The Magnetic Field

This paper analyses the dispersion relation for a collisionless moving electron plasma, when the direction of motion is normal to the magnetic field and that of the wave propagation along the magnetic field. It is shown that, in strong magnetic fields, the one continuous allowed band of the left-handed wave (of the stationary plasma) splits into two, and the right-handed wave shows a second resonance besides the cyclotron resonance. In weak magnetic fields, the lefthanded wave develops a backward wave band, which shows resonance at its low frequency edge, and the right-handed wave also develops an extra band of propagation. The effect of the motion of the plasma, on waves of frequency much lower than the plasma frequency, is identical to a doppler shift, but, on those of frequency much higher than that, is negligible.

POLAR GROWTH RESPONSE OF PISUM ARVENSE L. SEEDS TO WEAK MAGNETIC FIELDS

1979 ◽  
Vol 59 (3) ◽  
pp. 883-885 ◽  
Author(s):  
MASSIMO CERDONIO ◽  
SILVIA MORANTE-MAZZONCINI ◽  
MATILDE VICENTINI-MISSONI
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Plant Growth ◽  
Growth Response ◽  
Significant Inhibition ◽  
Polar Growth ◽  
Pisum Arvense ◽  
Weak Magnetic Fields ◽  
The Magnetic Field

The effect of exposure of seeds of Pisum arvense, before germination, to a weak artificial magnetic field has been investigated. The seeds, exposed in "parallel" and "antiparallel" orientation with respect to the magnetic field, showed a difference in plant growth with a significant inhibition for "antiparallel" seeds.

Magnetic flux transport in the photosphere of the Sun

2020 ◽  
Author(s):  
Dmitrii Baranov ◽  
Elena Vernova ◽  
Marta Tyasto ◽  
Olga Danilova
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Polar Field ◽  
The Sun ◽  
Time Diagram ◽  
Weak Magnetic Fields ◽  
The Magnetic Field

<p>On the basis of the synoptic maps of the photospheric magnetic field obtained by the National Solar Observatory Kitt Peak for 1978-2016, a latitude-time diagram of the magnetic field was built. When averaging intensity values over the heliolongitude, the magnetic field sign was taken into account. In order to consider the characteristics of the distribution of weak magnetic fields an upper limit of 5 G was set.</p><p>The latitude-time diagram clearly shows inclined bands corresponding to positive and negative polarity magnetic flows drifting towards the poles of the Sun. Two groups of flows are observed: 1. Relatively narrow bands, with alternating polarity, beginning near the equator and reaching almost the poles of the Sun. Along the time axis, the flow length of one polarity is on the order of 1-2 years; 2. short powerful flows, 3-4.5 years wide, propagating from the spot zone to the poles. These flows reach the poles simultaneously with the begin of the polar field reversal, apparently representing  the so-called “Rush to the Poles” phenomenon.</p><p>The pattern of magnetic field transport is significantly different for the northern and southern hemispheres. Alternating flows of positive and negative polarities most clearly appear in the southern hemisphere during periods of positive polarity of the southern polar field. For the northern hemisphere the picture is much less clear but for individual time intervals alternating flows of opposite polarities can be traced. The slopes of magnetic flux bands allow us to estimate the rate of meridional drift of magnetic fields, which was slightly different for the two hemispheres: V = (16±2) m/s for the southern hemisphere and V = (21±4) m/s for the northern hemisphere. The results obtained indicate that the distribution of weak magnetic fields over the surface of the Sun has a complex structure that is different for the two hemispheres and varies from cycle to cycle.</p>

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.

Tuning the Magnetic Alignment of Cellulose Nanocrystals from Perpendicular to Parallel Using Lepidocrocite Nanoparticles

2019 ◽  
Author(s):  
Valentina Guccini ◽  
Sugam Kumar ◽  
Yulia Trushkina ◽  
Gergely Nagy ◽  
Christina Schütz ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Cellulose Nanocrystals ◽  
Small Angle Neutron Scattering ◽  
Lower Amount ◽  
Magnetic Alignment ◽  
Polarized Optical Microscopy ◽  
Parallel Orientation ◽  
Weak Magnetic Fields

The magnetic alignment of cellulose nanocrystals (CNC) and lepidocrocite nanorods (LpN), pristine and in hybrid suspensions has been investigated using contrast-matched small-angle neutron scattering (SANS) under in situ magnetic fields (0 – 6.8 T) and polarized optical microscopy. The pristine CNC (diamagnetic) and pristine LpN (paramagnetic) align perpendicular and parallel to the direction of field, respectively. The alignment of both the nanoparticles in their hybrid suspensions depends on the relative amount of the two components (CNC and LpN) and strength of the applied magnetic field. In the presence of 10 wt% LpN and fields < 1.0 T, the CNC align parallel to the field. In the hybrid containing lower amount of LpN (1 wt%), the ordering of CNC is partially frustrated in all range of magnetic field. At the same time, the LpN shows both perpendicular and parallel orientation, in the presence of CNC. This study highlights that the natural perpendicular ordering of CNC can be switched to parallel by weak magnetic fields and the incorporation of paramagnetic nanoparticle as LpN, as well it gives a method to influence the orientation of LpN.<br>

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