A MAGNETOTELLURIC STUDY OF RESISTIVITY ANISOTROPY

Geophysics ◽  
1969 ◽  
Vol 34 (3) ◽  
pp. 438-449 ◽  
Author(s):  
D. Rankin ◽  
I. K. Reddy
Keyword(s):  
Magnetic Field ◽  
Apparent Resistivity ◽  
Field Measurements ◽  
Impedance Analysis ◽  
Complete Agreement ◽  
Precambrian Basement ◽  
University Of Alberta ◽  
The North ◽  
Principal Axes ◽  
Linearly Polarized

The apparent resistivity curves obtained from the magnetotelluric field measurements at the University of Alberta Geophysical Observatory, near Leduc, Alberta, reveal a strong anisotropy. The significance of the direction of the incident magnetic field in interpreting the structure from the apparent resistivity curves is examined in detail for the case of a linearly polarized incident field. The tensor impedance analysis of the data indicates that the directions of the principal axes of anisotropy are aligned parallel to the north‐south and east‐west measuring axis. The high coherency between the orthogonal horizontal components of the incident magnetic field is in complete agreement with this interpretation. The two apparent resistivity curves are interpreted and an anisotropic layered model is derived. The anisotropy is found to lie in the Precambrian basement down to a depth of 14 km. The isotropic upper layer has a resistivity of 8 ohm‐m which is characteristic of the sedimentary section. The anisotropic resistivity structure proposed for the Precambrian basement may be attributed either to local lithological changes in the basement or to major but more distant structure.

Frequency‐ and time‐domain electromagnetic responses of layered earth—A multiseparation, multisystem approach

Geophysics ◽  
1995 ◽  
Vol 60 (1) ◽  
pp. 285-290 ◽  
Author(s):  
Umesh C. Das
Keyword(s):  
Magnetic Field ◽  
Direct Current ◽  
Apparent Resistivity ◽  
Field Measurements ◽  
Initial Guess ◽  
Dipole Source ◽  
Resistivity Sounding ◽  
Electromagnetic Methods ◽  
Time Domain Electromagnetic ◽  
Depth Sounding

EM depth soundings by controlled‐source electromagnetic methods (CSEM) are made to determine the vertical resistivity distribution of the earth. The two variations of soundings, namely frequency sounding and geometric sounding, are used for exploring the subsurface. Although in field applications electromagnetic (EM) sounding has relative advantages over direct current resistivity sounding, quantitative use of EM depth sounding has not been used as much as direct current resistivity sounding (Mundry and Bohlm, 1987). Mundry and Bohlm (1987) have pointed out that one of the problems in the application of frequency EM sounding is the lack of sophisticated interpretational tools. The interpretation of the mutual coupling ratio (MCR) from the EM field component measurements, [Formula: see text], invariably relies on numerical inversion routines. However, unlike the direct current (DC) or magnetotelluric (MT) apparent resistivity curves, MCR curves do not reflect the subsurface resistivity distributions, and an initial guess model from MCR required for its inversion is difficult. Conversion of single component EM measurements into apparent resistivity is ambiguous because for a single measurement, two apparent resistivity values are obtained. Combining the general expressions for MCR obtained from the quasi‐static tangential electric and vertical magnetic field components of a vertical magnetic dipole source on the surface of a half‐space, Das (1995) defined an apparent resistivity for the use of the CSEM. The CSEM apparent resistivity curves show features similar to DC and MT apparent resistivity curves and they greatly enhance the interpretation. I refer to this paper (Das, 1995, published in this issue) as Paper I. In the present paper, difficult measurements of the electric field have been avoided by combining [Formula: see text] and [Formula: see text] obtained from the magnetic field measurements of two different configurations, i.e., the horizontal coplanar loops (HCP) and vertical coplanar loops (VCP) systems, respectively. This combination of measurements provides operational simplicity in the field and gives the same CSEM apparent resistivity described in Paper I. However, complementary behavior of the two combinations would be realized.

Magnetic field measurements in space

1963 ◽  
Vol 1 (3) ◽  
pp. 399-414 ◽  
Author(s):  
Laurence J. Cahill
Keyword(s):  
Magnetic Field ◽  
Field Measurements ◽  
Magnetic Field Measurements

scholarly journals Laser Assisted Dirac Electron in a Magnetized Annulus

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 642
Author(s):  
Emilio Fiordilino
Keyword(s):  
Magnetic Field ◽  
Analytical Form ◽  
Relative Energy ◽  
Radial Force ◽  
Rate Of Change ◽  
Orthogonal Direction ◽  
Linearly Polarized ◽  
Dirac Electron ◽  
A Charge ◽  
Stretching Effect

We study the behaviour of a charge bound on a graphene annulus under the assumption that the particle can be treated as a massless Dirac electron. The eigenstates and relative energy are found in closed analytical form. Subsequently, we consider a large annulus with radius ρ∈[5000,10,000]a0 in the presence of a static magnetic field orthogonal to its plane and again the eigenstates and eigenenergies of the Dirac electron are found in both analytical and numerical form. The possibility of designing filiform currents by controlling the orbital angular momentum and the magnetic field is shown. The currents can be of interest in optoelectronic devices that are controlled by electromagnetic radiation. Moreover, a small radial force acts upon the annulus with a stretching effect. A linearly polarized electromagnetic field propagating in the orthogonal direction is added; the time evolution of the operators show that the acceleration of the electron is proportional to the rate of change of the spin of the particle.

scholarly journals Success factors in the realization of large ice projects in education

2021 ◽  
Vol 36 (1) ◽  
pp. 4-12
Author(s):  
Arno Pronk ◽  
Peng Luo ◽  
Qingpeng Li ◽  
Fred Sanders ◽  
Marjolein overtoom ◽  
...  
Keyword(s):  
Success Factors ◽  
Learning Experience ◽  
Learning By Doing ◽  
University Of Alberta ◽  
The North ◽  
3D Printed ◽  
Good Learning ◽  
The University ◽  
Ice Shell ◽  
Motivation And Learning

There has been a long tradition in making ice structures, but the development of technical improvements for making ice buildings is a new field with just a handful of researchers. Most of the projects were realized by professors in cooperation with their students as part of their education in architecture and civil engineering. The following professors have realized ice projects in this setting: Heinz Isler realized some experiments since the 1950s; Tsutomu Kokawa created in the past three decades several ice domes in the north of Japan with a span up to 25 m; Lancelot Coar realized a number of fabric formed ice shell structures including fiberglass bars and hanging fabric as a mold for an ice shell in 2011 and in 2015 he produced an fabric-formed ice origami structure in cooperation with MIT (Caitlin Mueller) and VUB (Lars de Laet). Arno Pronk realized several ice projects such as the 2004 artificially cooled igloo, in 2014 and 2015 dome structures with an inflatable mold in Finland and in 2016–2019, an ice dome, several ice towers and a 3D printed gridshell of ice in Harbin (China) as a cooperation between the Universities of Eindhoven & Leuven (Pronk) and Harbin (Wu and Luo). In cooperation between the University of Alberta and Eindhoven two ice beams were realized during a workshop in 2020. In this paper we will present the motivation and learning experiences of students involved in learning-by-doing by realizing one large project in ice. The 2014–2016 projects were evaluated by Sanders and Overtoom; using questionnaires among the participants by mixed cultural teams under extreme conditions. By comparing the results in different situations and cultures we have found common rules for the success of those kinds of educational projects. In this paper we suggest that the synergy among students participating in one main project without a clear individual goal can be very large. The paper will present the success factors for projects to be perceived as a good learning experience.

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