ON THE ELECTROMAGNETIC RESPONSE OF A CONDUCTING SPHERE TO A DIPOLE FIELD

Geophysics ◽  
1960 ◽  
Vol 25 (3) ◽  
pp. 649-658 ◽  
Author(s):  
James R. Wait
Keyword(s):  
Magnetic Dipole ◽  
Electromagnetic Coupling ◽  
Wave Length ◽  
Dipole Field ◽  
Electromagnetic Response ◽  
Geophysical Prospecting ◽  
End Points ◽  
Conducting Sphere ◽  
Ore Body ◽  
Set Up

The electromagnetic coupling between an electric and a magnetic dipole in the presence of a spherical ore body is discussed in the present paper. It is shown that both electric and magnetic modes must be considered even though all dimensions are small compared to the wave length. The results have application to a geophysical prospecting scheme where the exciting fields are set up by a straight insulating wire grounded at its end points and the secondary fields are detected by an ungrounded closed wire loop.

scholarly journals Calibration of Radiocarbon Dates for the Late Pleistocene Using U/Th Dates on Stalagmites

Radiocarbon ◽  
1997 ◽  
Vol 39 (1) ◽  
pp. 27-32 ◽  
Author(s):  
John C. Vogel ◽  
Joel Kronfeld
Keyword(s):  
South Africa ◽  
Magnetic Dipole ◽  
Satisfactory Agreement ◽  
Late Pleistocene ◽  
Calibration Curve ◽  
Dipole Field ◽  
Radiocarbon Dates ◽  
The Past ◽  
The Earth ◽  
Magnetic Dipole Field

Twenty paired 14C and U/Th dates covering most of the past 50,000 yr have been obtained on a stalagmite from the Cango Caves in South Africa as well as some additional age-pairs on two stalagmites from Tasmania that partially fill a gap between 7 ka and 17 ka ago. After allowance is made for the initial apparent 14C ages, the age-pairs between 7 ka and 20 ka show satisfactory agreement with the coral data of Bard et al. (1990, 1993). The results for the Cango stalagmite between 25 ka and 50 ka show the 14C dates to be substantially younger than the U/Th dates except at 49 ka and 29 ka, where near correspondence occurs. The discrepancies may be explained by variations in 14C production caused by changes in the magnetic dipole field of the Earth. A tentative calibration curve for this period is offered.

Electromagnetic response of a permeable inhomogeneous conducting sphere

1973 ◽  
Vol 11 (1-3) ◽  
pp. 1-20 ◽  
Author(s):  
Janardan G. Negi ◽  
Chandra P. Gupta ◽  
Upendra Raval
Keyword(s):  
Electromagnetic Response ◽  
Conducting Sphere

THE CYLINDRICAL ORE BODY IN THE PRESENCE OF A CABLE CARRYING AN OSCILLATING CURRENT

Geophysics ◽  
1952 ◽  
Vol 17 (2) ◽  
pp. 378-386 ◽  
Author(s):  
James R. Wait
Keyword(s):  
Electrical Properties ◽  
Massive Sulphide ◽  
Conducting Medium ◽  
Geophysical Prospecting ◽  
Conducting Cylinder ◽  
Sulphide Ore ◽  
Ore Body ◽  
The Media ◽  
Special Case ◽  
Ore Zones

The problem of an infinite cable carrying an oscillating current parallel to a conducting cylinder is solved. The homogeneous electrical properties of the media inside and outside the cylinder can be arbitrary. The special case is considered in detail where the exterior medium is a relatively poor conducting medium. The application to geophysical prospecting for massive sulphide ore zones is discussed.

scholarly journals Railway Ballast Monitoring by Gpr: A Test Site Investigation

2019 ◽  
Vol 11 (20) ◽  
pp. 2381 ◽  
Author(s):  
Bianchini Ciampoli ◽  
Calvi ◽  
D’Amico
Keyword(s):  
Asset Management ◽  
Construction Materials ◽  
Site Investigation ◽  
Horn Antenna ◽  
Test Site ◽  
Electromagnetic Response ◽  
Actual Condition ◽  
Railway Ballast ◽  
Set Up ◽  
Ground Penetrating

Effective maintenance of railways requires a comprehensive assessment of the actual condition of the construction materials involved. In this regard, Ground-Penetrating Radar (GPR) stands as a viable alternative to the invasive and time-consuming traditional techniques for the inspection of these infrastructures. This work reports the experimental activities carried out on a test-site area within a railway depot in Rome, Italy. To this purpose, a 30 m-long railway section was divided into 10 sub-sections reproducing different various physical and structural conditions of the track-bed. In more detail, combinations of varying scenarios of fragmentation and fouling of the ballast were reproduced. The set-up was then investigated using different multi-frequency GPR horn antenna systems. The effects of the different physical conditions of ballast on the electromagnetic response of the material were analysed for each scenario using time- and frequency-domain signal processing techniques. Parallel to this, modelling was provided to estimate fouling content. Interpretation of results has proven the viability of the GPR method in detecting signs of decay at the network level, thereby proving this technique to be worthy of implementation in asset management systems.

scholarly journals Studies in the infra-red region of the spectrum. Part II.—Calibration of prism spectrometer; General procedure; and preparation of pure ammonia, phosphine and arsine

1928 ◽  
Vol 120 (784) ◽  
pp. 149-160 ◽  
Keyword(s):  
General Procedure ◽  
Wave Length ◽  
Refractive Indices ◽  
Screw Thread ◽  
Plane Mirror ◽  
Temperature Reading ◽  
Infra Red ◽  
Set Up ◽  
Centre Of Rotation ◽  
Angle Of Rotation

The instrument used was a No. 2 Hilger infra-red spectrometer fitted with a "wave-length drum." It soon became evident that the wave-length drum required calibration on account of the chance of periodic errors in the screw thread. If the screw remains constant, it would be better to have the drum marked in angles which could be referred to the refractive indices of the material of the respective prisms used. As any one prism varies in the refractive index with temperature, reading of wave-length on a wave-length drum can be accurate only for one temperature. A plane mirror was mounted vertically at the centre of rotation of the prism table and an illuminated scale set up parallel to it exactly 5 metres away. The image of the scale in the mirror was observed by means of a fixed telescope with cross wires in the eyepiece. Zero was taken as 0∙5893 on the drum, which was set successively on about 80 of its graduation marks and the scale image coinciding with the cross wires noted for each setting. The displacement of the image in millimetres in each case was thus observed, and as the distance from the scale of rotation and thence the angle itself was obtained within 2 seconds of arc. Three observers agreed closely in their observations, from which a curve was drawn connecting drum calibration marks with angle of rotation (first graph).

TIME‐DEPENDENT ELECTROMAGNETIC FIELDS OF AN INFINITE, CONDUCTING CYLINDER EXCITED BY A LONG CURRENT‐CARRYING CABLE

Geophysics ◽  
1973 ◽  
Vol 38 (2) ◽  
pp. 369-379 ◽  
Author(s):  
Saurabh K. Verma
Keyword(s):  
Time Domain ◽  
Horizontal Cylinder ◽  
The Body ◽  
Time Dependent ◽  
Electromagnetic Response ◽  
Secondary Field ◽  
Function Type ◽  
Ore Body ◽  
Induced Field ◽  
Time Domain Electromagnetic

Theoretical and numerical computations have been made for the quasi‐static, time‐domain electromagnetic response of an infinite, conducting horizontal cylinder stimulated by long cable‐carrying step and ramp‐function type pulses. The effect of higher‐order induced multipoles on the secondary electric and magnetic field components is analyzed in detail, and the “threshold distances” at which individual multipoles become effective (contributing more than 5 percent of the secondary field) are presented. Also, the field fall‐off directly above the body and the variations in different induced‐field components along a traverse perpendicular to the strike of the ore body are examined.

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