scholarly journals Distortion of magnetotelluric sounding curves by three‐dimensional structures

Geophysics ◽  
1985 ◽  
Vol 50 (5) ◽  
pp. 785-797 ◽  
Author(s):  
Stephen K. Park
Keyword(s):  
Thin Sheet ◽  
Three Dimensional ◽  
Background Field ◽  
Upper Crust ◽  
Magnetotelluric Data ◽  
Dominant Mechanism ◽  
Frequency Effects ◽  
One Dimensional ◽  
Physical Mechanisms ◽  
Dimensional Modeling

Distortions of magnetotelluric fields caused by three‐dimensional (3‐D) structures can be severe and are not predictable using one‐dimensional or two‐dimensional modeling. I used a 3-D modeling algorithm based upon an extension of a generalized thin sheet analysis due to Ranganayaki and Madden (1980) to examine field distortions in crustal environments. Three major physical mechanisms cause these distortions. These mechanisms are resistive coupling between the electrical mantle and upper crust, resistive coupling between conductive features within the upper crust, and local induction of current loops within good conductors. Each mechanism produces different spatial and frequency effects upon the background field, so identification of the dominant mechanism can be used as an interpretational aid. I finally use this analysis to identify distortion mechanisms seen in magnetotelluric data from Beowawe, Nevada to aid in an interpretation of that area.

Reynolds Number Effects on the Performance Characteristic of a Small Regenerative Pump

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Shin-Hyoung Kang ◽  
Su-Hyun Ryu
Keyword(s):  
Reynolds Number ◽  
Three Dimensional ◽  
Internal Flow ◽  
Reynolds Numbers ◽  
Maximum Efficiency ◽  
Three Dimensional Flow ◽  
One Dimensional ◽  
Rotating Speed ◽  
Dimensional Modeling ◽  
Reynolds Number Effects

This paper studies the effect of the Reynolds number on the performance characteristics of a small regenerative pump. Since regenerative pumps have low specific speeds, they are usually applicable to small devices such as micropumps. As the operating Reynolds number decreases, nondimensional similarity parameters such as flow and head coefficients and efficiency become dependent on the Reynolds number. In this study, the Reynolds number based on the impeller diameter and rotating speed varied between 5.52×103 and 1.33×106. Complex three-dimensional flow structures of internal flow vary with the Reynolds numbers. The coefficients of the loss models are obtained by using the calculated through flows in the impeller. The estimated performances obtained by using one-dimensional modeling agreed reasonably well with the numerically calculated performances. The maximum values of flow and head coefficients depended on the Reynolds number when it is smaller than 2.65×105. The critical value of the Reynolds number for loss coefficient and maximum efficiency variations with Reynolds number was 1.0×105.

Computer Simulation of Composite Beams Dynamic Behavior

2019 ◽  
Vol 974 ◽  
pp. 687-692
Author(s):  
V.S. Fyodorov ◽  
Vladimir N. Sidorov ◽  
E.S. Shepitko
Keyword(s):  
Computer Simulation ◽  
Dynamic Behavior ◽  
Least Squares Method ◽  
Three Dimensional ◽  
Composite Beams ◽  
One Dimensional ◽  
Glass Fiber Reinforced Plastic ◽  
Finite Element Software ◽  
Dimensional Modeling ◽  
Damping Model

The paper is devoted to the computer simulation of polymer composite beams dynamic behavior. The use opportunity of one-dimensional beam models for the design of composite elements instead of three-dimensional ones is discussed. The tree-dimensional modeling is implemented using the finite-element software SIMULIA Abaqus considering the orthotropic properties of the composite material. For the one-dimensional modeling two hypothesis of the internal friction – local and nonlocal – are applied and compared. The Kelvin-Voigt hypothesis is used as a local damping model. The nonlocal model is based on the nonlocal mechanics principals and obtained using the Galerkin method. The example glass fiber reinforced plastic beam with the fixed ends is considered under an instantly applied load. The parameters of the nonlocal damping model are defined using the least squares method. The flexibility of the nonlocal damping model is shown and the use opportunity of one-dimensional beam models for the design of composite elements is justified.

The asymptotic response of three‐dimensional basin offsets to magnetotelluric fields at long periods: The effects of current channeling

Geophysics ◽  
1982 ◽  
Vol 47 (11) ◽  
pp. 1562-1573 ◽  
Author(s):  
John F. Hermance
Keyword(s):  
Thin Sheet ◽  
Three Dimensional ◽  
Sedimentary Basins ◽  
Transverse Magnetic ◽  
Clear Correlation ◽  
One Dimensional ◽  
Skewness Coefficient ◽  
Order Of Magnitude ◽  
D Model ◽  
Telluric Currents

A simple, inexpensive numerical algorithm is used to analyze the asymptotic long‐period behavior of magnetotelluric (MT) fields in the vicinity of lateral offsets in sedimentary basins. The model is based on the distortion or channeling of telluric currents in a horizontal thin sheet. Although a gross oversimplification of nature, the model represents a class of structures which, because of excessive computer costs, have been relatively unstudied previously. Within, and closely adjacent to, the region of the three‐dimensional (3-D) offset, significant distortion of the MT parameters occurs. Skewness coefficients vary from negligible values to over 0.7. Principal resistivities vary by an order of magnitude. On the other hand, there is not a clear correlation between the degree of distortion of the parameters usually evaluated during MT surveys and the magnitude of conventional 3-D indicators (e.g., the skewness coefficient). Calculations have simulated the technique of averaging resistivity parameters from a large number of field sites in order to arrive at a regionally representative one‐dimensional (1-D) model. The results indicate that unless care is taken in adapting the nature of the averaging algorithm to the class of distortions encountered, significant bias of the averaged parameters may result. Our results also suggest that for this class of structures grave problems may be associated with using the principal resistivity perpendicular to geologic strike, the so‐called transverse magnetic (TM) mode, to infer an equivalent two‐dimensional (2-D) model for the region. A 2-D model would likely show significant modulations in the physical character of the basement which are, in fact, an artifact of telluric distortion caused by current channeling in the surficial heterogeneity.

Inversion of infrared imaging bolometer based on one-dimensional and three-dimensional modeling in HL-2A

2014 ◽  
Vol 85 (4) ◽  
pp. 043505 ◽  
Author(s):  
J. M. Gao ◽  
Y. Liu ◽  
W. Li ◽  
Z. Y. Cui ◽  
Y. B. Dong ◽  
...  
Keyword(s):  
Infrared Imaging ◽  
Three Dimensional ◽  
One Dimensional ◽  
Three Dimensional Modeling ◽  
Dimensional Modeling

The electromagnetic response of thin sheets buried in a uniformly conducting half‐space

Geophysics ◽  
1987 ◽  
Vol 52 (1) ◽  
pp. 108-117 ◽  
Author(s):  
R. Clark Robertson
Keyword(s):  
Thin Layer ◽  
Half Space ◽  
Thin Sheet ◽  
Three Dimensional ◽  
Horizontal Layer ◽  
Thin Layers ◽  
Electromagnetic Response ◽  
Thin Sheets ◽  
Magnetotelluric Data ◽  
The Earth

The interpretation of magnetotelluric data is hampered by the effect of three‐dimensional (3-D) conductivity variations within the earth. In particular, the effects of deep structures are masked by heterogeneities near the surface. In order to understand the effects of 3-D anomalies on magnetotelluric investigations, the electromagnetic response of 3-D models of the earth must be investigated. One technique used to model a 3-D earth is the thin‐sheet approximation. This technique confines all lateral changes in conductivity to a horizontal layer in a laterally homogeneous earth; however, the thin‐sheet technique can be applied only to anomalies that are electrically thin at the frequency of investigation. The thin‐sheet technique can be extended to include a greater variety of models by stacking heterogeneous thin layers. As a first step, the thin‐sheet technique is extended to model a buried, heterogeneous thin layer. Extension of the method to account for buried thin sheets is theoretically and computationally more involved than for a surface thin sheet, but the buried thin sheet still has computational advantages over other 3-D models.

Thin-sheet EM modelling of the Tasman Sea

1989 ◽  
Vol 20 (2) ◽  
pp. 177 ◽  
Author(s):  
G.S. Heinson ◽  
F.E.M. Lilley
Keyword(s):  
Large Scale ◽  
Salt Water ◽  
Thin Sheet ◽  
Three Dimensional ◽  
One Dimensional ◽  
The Earth ◽  
Tasman Sea ◽  
Modelling Techniques ◽  
Tectonic Features ◽  
The University

The Tasman Project of Seafloor Magnetotelluric Exploration (TPSME) took place between December 1983 and April 1984 (Filloux et al., 1985; Ferguson et al., 1985; Lilley etal., 1989). Seven magnetotelluric and two (additional) magnetometer sites spanned a range of tectonic features across the Tasman Sea. Initial analysis by Ferguson (1988) indicated large-scale three-dimensional induction effects to be present in the data. It was concluded that the most probable causes were the continental margin effect and changes in bathymetry.In the present paper, a method is presented of modelling the salt water of the Tasman Sea and adjoining oceans as a thin sheet of variable lateral conductance, which overlies a series of uniform layers representing the solid Earth. The theory and a suitable computer algorithm were developed in a group led by J. T. Weaver at the University of Victoria, B.C., Canada. Many of the features present in the TPSME data are reproduced by this method, and with a greater understanding of induction processes in the ocean which is thus obtained, it is possible to remove three-dimensional effects from observed data. The TPSME data are then solely a measure of the response of the Earth directly beneath the observing sites, and one-dimensional modelling techniques may be used to determine the conductivity structures.

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