scholarly journals On the magnetic shielding of large spaces, and its experimental measurement

1916 ◽  
Vol 92 (644) ◽  
pp. 529-549 ◽  
Keyword(s):  
Magnetic Field ◽  
Experimental Determination ◽  
Recent Work ◽  
Experimental Measurement ◽  
Magnetic Shielding ◽  
Small Space ◽  
The Earth ◽  
Order Of Magnitude ◽  
The Subject

It is not a matter of difficulty to annul almost completely the field of the earth throughout a small space by a suitable choice of an iron shield. If, however, the region over which the field must be reduced is large, the problem becomes more difficult unless considerable masses of iron are used. For it is evident that the absolute dimensions of the shield are not important to the degree of shielding produced, that is to say, that a given shield magnified in all its parts in the same ratio continues to give the same degree of shielding. The object of the present investigation is to show that the shielding of large spaces can nevertheless be achieved by the employment of properly designed multiple or concentric shields, without the necessity for a prohibitive amount of iron. In connection with some recent work, moreover, the necessity has arisen for maintaining a magnetic field at least as small as 5·10 -3 within a region of comparatively large dimensions. It is evident that the most suitable means is to reduce the field of the earth to this extent, but calculations soon show that the usual arrangements of soft iron shields involve a prohibitive amount of material. The necessity in fact arises for the determination of the most economical arrangement capable of giving a specified high shielding ratio. Since, in view of applications of the work, the actual magnitude of the field must be known, corrected for every variety of magnetic leakage which can invalidate the theory, some experimental device is also required for the measurement of such fields. There is apparently no record of the experimental determination directly of fields even of this order of magnitude, and since a method has been found which is capable of considerable accuracy and is in fact suitable for the measurement of fields only 10 -4 times that of the earth, a description of this and of other methods with their practical limitations appears to be of value. It must be emphasised that the difficulties which are encountered, and the methods necessary to overcome them, are to a great extent peculiar and inevitable to work which must be carried on with large quantities of material. The investigation which originally led to the necessity for known fields of such a small order—it has since been supplemented by others which cannot at present be described—was the subject of earlier communications by one of us.

scholarly journals 42. Solar cosmic radiation and the interstellar magnetic field

1958 ◽  
Vol 6 ◽  
pp. 404-419 ◽  
Author(s):  
A. Ehmert
Keyword(s):  
Magnetic Field ◽  
Solar Radiation ◽  
Cosmic Radiation ◽  
The Sun ◽  
High Latitudes ◽  
Narrow Angle ◽  
The Earth ◽  
Order Of Magnitude ◽  
The Impact ◽  
Impact Zones

The increase of cosmic radiation on 23 February 1956 by solar radiation exhibited in the first minutes a high peak at European stations that were lying in direct impact zones for particles coming from a narrow angle near the sun, whilst other stations received no radiation for a further time of 10 minutes and more. An hour later all stations in intermediate and high latitudes recorded solar radiation in a distribution as would be expected if this radiation fell into the geomagnetic field in a fairly isotropic distribution. The intensity of the solar component decreased at this time at all stations according to the same hyperbolic law (~t–2).It is shown, that this decreasing law, as well as the increase of the impact zones on the earth, can be understood as the consequence of an interstellar magnetic field in which the particles were running and bent after their ejection from the sun.Considering the bending in the earth's magnetic field, one can estimate the direction of this field from the times of the very beginning of the increase in Japan and at high latitudes. The lines of magnetic force come to the earth from a point with astronomical co-ordinates near 12·00, 30° N. This implies that within the low accuracy they have the direction of the galactic spiral arm in which we live. The field strength comes out to be about 0·7 × 10–6gauss. There is a close agreement with the field, that Fermi and Chandrasekhar have derived from Hiltner's measurements of the polarization of starlight and the strength of which they had estimated to the same order of magnitude.

scholarly journals On residual magnetism in relation to magnetic shielding

1917 ◽  
Vol 93 (653) ◽  
pp. 393-412
Keyword(s):  
Internal Field ◽  
Magnetic Shielding ◽  
Careful Study ◽  
Present Communication ◽  
Magnetic Shield ◽  
Spherical Shells ◽  
The Earth ◽  
Order Of Magnitude ◽  
Usual Process ◽  
Residual Magnetism

The present communication records the final stages of an investigation, of a somewhat exhaustive character, into the various problems which were presented by the necessity for constructing a magnetic shield suitable for large spaces, and capable of giving such a degree of shielding that the internal field caused by the earth should not exceed the order of magnitude 10 -3 C. G. S. unit. The theoretical calculation of the best form of shield, and the details of its construction, were given, together with an examination of the various methods of testing the efficiencies of large shields, in the first paper. A study of the effect of leakage through small air spaces was made at the same time, and it became apparent that not only this problem, but several others which are vital to the production of the theoretical efficiency of a shield, needed a more careful study than they had received hitherto. The usual process adopted for removing permanent magnetism from a shell or set of shells, by the reversals of a slowly decreasing current, ceases to be efficient when the magnetisation is very small, unless special methods are introduced, and there was previously no definite indication of the degree of accuracy with which the magnetic induction at any point due to a coil, wound in a helix on one member of a set of spherical shells, could be either predicted or measured. A study of these problems was made, and the results described in a second paper.

MRE Damping Characteristics Evaluation

2016 ◽  
Vol 699 ◽  
pp. 31-36 ◽  
Author(s):  
Eduard Chirila ◽  
Ionel Chirica ◽  
Doina Boazu ◽  
Elena Felicia Beznea
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Smart Materials ◽  
Magnetorheological Elastomers ◽  
Damping Characteristics ◽  
The Subject ◽  
Energy Absorbing ◽  
The Magnetic Field ◽  
Material Form

The paper addresses the study of the damping characteristics estimation and behaviour of the magnetorheological elastomers (MREs) in the absence of magnetic field. This type of material actively changes the size, internal structure and viscoelastic characteristics under the external influences. These particular composite materials whose characteristics can vary in the presence of a magnetic fields are known as smart materials. The feature which causes the variation of properties in magnetic fields is explained by the existence of polarized particles which change the material form by energy absorbing. Damping is a special characteristic that influences the vibratory of the mechanical system. As an effect of this property is the reducing of the vibration amplitudes by dissipating the energy stored during the vibratory moving. The main characteristic that is based on the determination of the damping coefficient is the energy loss, which is the subject of the present paper. Before to start the characteristics determination in the presence of the magnetic field, it is necessary to study these characteristics in the absence of magnetic field. The MRE specimens have been manufactured and tested under the light conditions (non magnetic field). A special experimental test rig was built to investigate the response of the MRE specimens under the charging force. The experimental results show that the loss energy of the MRE specimen can be determined from the charging-discharging curves versus displacement. The results of the MRE specimen are presented in this paper: MRE with feromagnetic particles not exposed in magnetic field during fabrication.

scholarly journals I. On the theory of lubrication and its application to Mr. Beauchamp tower’s experiments, including an experimental determination of the viscosity of olive oil

1886 ◽  
Vol 40 (242-245) ◽  
pp. 191-203 ◽  
Keyword(s):  
Olive Oil ◽  
Experimental Determination ◽  
Friction And Wear ◽  
Viscous Fluids ◽  
Solid Surfaces ◽  
Fundamental Importance ◽  
Theoretical Treatment ◽  
The Subject

Lubrication, or the action of oils and other viscous fluids to diminish friction and wear between solid surfaces, does not appear to have hitherto formed a subject for theoretical treatment. Such treatment may have been prevented by the obscurity of the physical actions involved, which belong to a class as yet but little known, namely, the boundary or surface actions of fluids; but the absence of such treatment has also been owing to the want of any general laws revealed by experiment. The subject is of such fundamental importance in practical mechanics, and the opportunities of observation so frequent, that it may well be a matter of surprise that any general laws should have for so long escaped detection.

IV. On the theory of lubrication and its application to Mr. Beauchamp tower’s experiments, including an experimental determination of the viscosity of olive oil

1886 ◽  
Vol 177 ◽  
pp. 157-234 ◽  
Keyword(s):  
Olive Oil ◽  
Experimental Determination ◽  
Friction And Wear ◽  
Viscous Fluids ◽  
Solid Surfaces ◽  
Fundamental Importance ◽  
Theoretical Treatment ◽  
The Subject

1. Lubrication, or the action of oils and other viscous fluids to diminish friction and wear between solid surfaces, does not appear to have hitherto formed a subject for theoretical treatment. Such treatment may have been prevented by the obscurity of the physical actions involved, which belong to a class as yet but little known, namely, the boundary or surface actions of fluids; but the absence of such treatment has also been owing to the want of any general laws discovered by experiment. The subject is of such fundamental importance in practical mechanics, and the opportunities for observation are so frequent, that it may well be a matter of surprise that any general laws should have for so long escaped detection.

scholarly journals Measurability of D-concurrence

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
N. Karimi ◽  
A. Heshmati ◽  
M. Yahyavi ◽  
M. A. Jafarizadeh ◽  
A. Mohammadzadeh
Keyword(s):  
Quantum Information ◽  
Experimental Determination ◽  
Pure State ◽  
Information Science ◽  
Direct Method ◽  
Entanglement Measure ◽  
Quantum Information Science ◽  
The Subject ◽  
A Direct Method

AbstractAn effective approach to quantify entanglement of any bipartite systems is D-concurrence, which is important in quantum information science. In this paper, we present a direct method for experimental determination of the D-concurrence of an arbitrary bipartite pure state. To do this, we show that measurement of the D-concurrence of bipartite pure state can be conversed into the measurement performed on some observables so called generalized Gell-Mann operators. We first introduce the concept of D-concurrence for a bipartite system. Then we explain the method of measuring this entanglement measure for the pure state. Finally, for clarify of the subject, we give an example consisting of two parties A and B with dimensions 3.

Experimental determination of the magnetic field spectrum in the Helically Symmetric Experiment using passing particle orbits

2001 ◽  
Vol 8 (12) ◽  
pp. 5165-5170 ◽  
Author(s):  
J. N. Talmadge ◽  
V. Sakaguchi ◽  
F. S. B. Anderson ◽  
D. T. Anderson ◽  
A. F. Almagri
Keyword(s):  
Magnetic Field ◽  
Experimental Determination ◽  
Field Spectrum ◽  
Particle Orbits ◽  
The Magnetic Field
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