GEOMAGNETIC EFFECTS OF SLOPING AND SHELVING DISCONTINUITIES OF EARTH CONDUCTIVITY

Geophysics ◽  
1971 ◽  
Vol 36 (1) ◽  
pp. 58-66 ◽  
Author(s):  
F. Walter Jones ◽  
Albert T. Price
Keyword(s):  
Apparent Resistivity ◽  
Surface Effects ◽  
Two Dimensional ◽  
Horizontal Extent ◽  
Earth Conductivity ◽  
Conductivity Models

The surface effects on electric and magnetic variations arising from interfaces in three two‐dimensional conductivity models are compared in detail for four frequencies. It is found that the horizontal extent of the surface effects greatly depends on the dimensions of the different structures relative to the skin depths at the frequencies used. Also, a fundamentally important difference is revealed between H‐polarization and E‐polarization problems in that the apparent resistivity computed on the surface near the contact is discontinuous and changes abruptly in the H‐polarization case, whereas for E‐polarization the apparent resistivity is continuous and changes gradually across the contact.

Apparent Resistivity Calculations for Three Two-dimensional Conductivity Models with Vertical Discontinuities

1971 ◽  
Vol 8 (8) ◽  
pp. 961-966 ◽  
Author(s):  
F. W. Jones
Keyword(s):  
Surface Charge ◽  
Numerical Method ◽  
Surface Structure ◽  
Electromagnetic Induction ◽  
Apparent Resistivity ◽  
Two Dimensional ◽  
Near Surface ◽  
A Value ◽  
Surface Contact ◽  
Conductivity Models

Electromagnetic induction in three two-dimensional models of conductors with two regions of different conductivity is considered. Solutions are obtained for both the H-polarization and E-polarization cases by a numerical method. Apparent resistivity as a function of period is plotted for various locations relative to the surface contact. For the H-polarization case, the apparent resistivity values calculated for points near the surface contact are affected by the varying surface charge on the interface between the regions, and a value different from the expected value is obtained. In the E-polarization case the apparent resistivity curves exhibit a "dip" characteristic when the apparent resistivity is calculated for surface points near a shelf or step structure. In both cases the value of apparent resistivity calculated at or near surface contacts between different conducting regions depends greatly on the sub-surface structure.

Intriguing electronic structures and carrier mobilities of two-dimensional GaN nanosheets: Thickness and surface effects

2020 ◽  
Vol 172 ◽  
pp. 109337 ◽  
Author(s):  
Jun Wang ◽  
Haibo Shu ◽  
Pei Liang ◽  
Xiangyu Zhou ◽  
Dan Cao ◽  
...  
Keyword(s):  
Electronic Structures ◽  
Surface Effects ◽  
Two Dimensional

Surface Effects on Bandgaps of Transverse Waves Propagating in Two Dimensional Phononic Crystals with Nanosized Holes

2011 ◽  
Vol 675-677 ◽  
pp. 611-614 ◽  
Author(s):  
Ni Zhen ◽  
Yue Sheng Wang
Keyword(s):  
Laplace Equation ◽  
Surface Effect ◽  
Phononic Crystal ◽  
Surface Effects ◽  
Phononic Crystals ◽  
Square Lattice ◽  
Two Dimensional ◽  
Transverse Waves ◽  
Circular Holes

In this paper, a method based on the displacement-traction map is developed to calculate the bandgaps of transverse waves propagating in a 2D phononic crystal composed of nanosized circular holes in a square lattice. The Young-Laplace equation is employed to take into account of the surface effects of the nanosized holes. Detailed calculations are performed for the system with nanosized circular holes in an aluminum host with or without the surface effect. The result shows that all bands descend with the first bandgap becoming wider due to the existence of the surface effects.

scholarly journals VLF surface-impedance measurements for ice-depth mapping — an assessment of some commonly encountered interference effects

1996 ◽  
Vol 42 (140) ◽  
pp. 33-36 ◽  
Author(s):  
David V. Thiel ◽  
Daniel James ◽  
Peter Johnson
Keyword(s):  
Surface Impedance ◽  
Apparent Resistivity ◽  
Low Frequency ◽  
Two Dimensional ◽  
Interference Effects ◽  
Impedance Measurements ◽  
Very Low Frequency ◽  
Dimensional Boundary ◽  
Lateral Variations ◽  
Made In

AbstractThe effects on very low-frequency surface-impedence measurements of lateral variations commonly found in ice environments have been measured and modelled numerically using die quasi-static two-dimensional boundary-element method. Results indicate that surface-impedance measurements made in the vicinity of crevasses oriented perpendicular to the plane Of incidence, and those made in the vicinity of moraines and melt streams, can all show significant changes to the measured apparent resistivity. It is, therefore, misleading to use such measurements in the interpretation of ice depth.

Towed Underwater SPIV Measurement of Flow Fields Around a Surface-Piercing Cylinder With Free Surface Effects

2015 ◽  
Author(s):  
Jeonghwa Seo ◽  
Bumwoo Han ◽  
Shin Hyung Rhee
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
Surface Wave ◽  
Flow Field ◽  
Cross Section ◽  
Surface Effects ◽  
Flow Fields ◽  
Two Dimensional ◽  
Two Dimensional Flow ◽  
Wave Induced

Effects of free surface on development of turbulent boundary layer and wake fields were investigated. By measuring flow field around a surface piercing cylinder in various advance speed conditions in a towing tank, free surface effects were identified. A towed underwater Stereoscopic Particle Image Velocimetry (SPIV) system was used to measure the flow field under free surface. The cross section of the test model was water plane shape of the Wigley hull, of which longitudinal length and width were 1.0 m and 100 mm, respectively. With sharp bow shape and slender cross section, flow separation was not expected in two-dimensional flow. Flow fields near the free-surface and in deep location that two-dimensional flow field was expected were measured and compared to identify free-surface effects. Some planes perpendicular to longitudinal direction near the model surface and behind the model were selected to track development of turbulent boundary layer. Froude numbers of the test conditions were from 0.126 to 0.40 and corresponding Reynolds numbers were from 395,000 to 1,250,000. In the lowest Froude number condition, free-surface wave was hardly observed and only free surface effects without surface wave could be identified while violent free-surface behavior due to wave-induced separation dominated the flow fields in the highest Froude number condition. From the instantaneous velocity fields, Time-mean velocity, turbulence kinetic energy, and flow structure derived by proper orthogonal decomposition (POD) were analyzed. As the free-surface effect, development of retarded wake, free-surface waves, and wave-induced separation were mainly observed.

Effective Thermal Conductivity of Ordered Mesoporous Carbon CMK-3

2013 ◽  
Author(s):  
Daili Feng ◽  
Yanhui Feng ◽  
Xinxin Zhang ◽  
Ge Wang
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Mesoporous Carbon ◽  
Two Dimensional ◽  
Hexagonal Array ◽  
Coupled Heat Transfer ◽  
Ordered Mesoporous ◽  
Carbon Rods ◽  
Conductivity Models

CMK-3 is a typical of carbon rods which are arranged in relatively regular two-dimensional hexagonal array. In our study, the effective thermal conductivity of CMK-3 composite is investigated. For the thermal conductivity of carbon rods, the equilibrium molecular dynamics (EMD) is performed with Tersoff potential. The influences of porosity and temperature are also considered. For the thermal conductivity of air confined in mesoporous can be estimated by the frequently used Kaganer model. Then, the effective thermal conductivity models developed for coupled heat transfer of air and solid are obtained by the unit cell method. ETCs along the X and Y directions are extremely poor, due to the overwhelming effect of air thermal resistance. However, in the Z direction, the ETC improves almost linearly as the porosity decreases, and the value is much higher than those of X and Y directions. This study is in attempts to explore the possibility of CMK-3 being a proper substrate for thermal usage.

scholarly journals VLF surface-impedance measurements for ice-depth mapping — an assessment of some commonly encountered interference effects

1996 ◽  
Vol 42 (140) ◽  
pp. 33-36
Author(s):  
David V. Thiel ◽  
Daniel James ◽  
Peter Johnson
Keyword(s):  
Surface Impedance ◽  
Apparent Resistivity ◽  
Low Frequency ◽  
Two Dimensional ◽  
Interference Effects ◽  
Impedance Measurements ◽  
Very Low Frequency ◽  
Dimensional Boundary ◽  
Lateral Variations ◽  
Made In

AbstractThe effects on very low-frequency surface-impedence measurements of lateral variations commonly found in ice environments have been measured and modelled numerically using die quasi-static two-dimensional boundary-element method. Results indicate that surface-impedance measurements made in the vicinity of crevasses oriented perpendicular to the plane Of incidence, and those made in the vicinity of moraines and melt streams, can all show significant changes to the measured apparent resistivity. It is, therefore, misleading to use such measurements in the interpretation of ice depth.

scholarly journals STRUCTURE OF FREEZING TALIK UNDER LAKE AT THE PARISENTO FIELD STATION (GYDAN PENINSULA) ACCORDING TO ELECTRICAL RESISTIVITY TOMOGRAPHY

2019 ◽  
Vol 2 (2) ◽  
pp. 103-110
Author(s):  
Alexandr Shein ◽  
Vladimir Olenchenko ◽  
Yaroslav Kamnev ◽  
Anton Sinitskiy
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Electrical Resistivity Tomography ◽  
Two Dimensional ◽  
Resistivity Tomography ◽  
Field Station ◽  
Approximate Rate

The article presents the results of studies of freezing talik under lake with using of electrical resistivity tomography. The research was conducted on one of paleolake – khasyrey. The measurements performed in two perpendicular profiles by pole-dipole array with a maximum spacing of 435 m. According to results of two-dimensional inversion, an area of low electrical resistivity of rocks at a depth of 25-30 m associated with a freezing talik under lake was identified. It was determined that the depth of freezing within drained lake for the period from 1996 to 2018 is 17-22 m. The approximate rate of freezing is 1 m/year. Formation of talik have a resistance of 5-15 Ω·m. Frozen formations in the contours of young paleolake have apparent resistivity hundreds Ω·m. Within the boundaries of the more ancient khasyrey apparent resistivity of the frozen rocks up to several thousand Ω·m.

On: “Geomagnetic Effects of Sloping. and Shelving Discontinuities of Earth Conductivity,” by F. Walter Jones and Albert T. Price (GEOPHYSICS, February 1971 p. 58–66)

Geophysics ◽  
1972 ◽  
Vol 37 (3) ◽  
pp. 540-541 ◽  
Author(s):  
John F. Hermance
Keyword(s):  
Finite Difference ◽  
Electromagnetic Fields ◽  
Apparent Resistivity ◽  
Finite Difference Methods ◽  
Analytical Calculation ◽  
Surface Charges ◽  
Difference Methods ◽  
Earth Conductivity ◽  
Effect Of Surface

In this recent paper, Jones and Price describe the application of finite difference methods to determining the electromagnetic fields near a vertical or inclined contact between materials having different resistivities. In the case of H polarization (the only case discussed in the following comments) they observed that as one approaches the contact from its conductive side the apparent resistivity decreases, which is to say that E horizontal decreases since H horizontal is constant. This behavior has previously been pointed out by d’Erceville and Kunetz (1962) for an analytical calculation. Jones and Price interpret this phenomenon as the effect of surface charges concentrating at the interface due to the impinging current.

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