Modeling complexly magnetized two‐dimensional bodies of arbitrary shape

Geophysics ◽  
1993 ◽  
Vol 58 (5) ◽  
pp. 637-644 ◽  
Author(s):  
John Mariano ◽  
William J. Hinze
Keyword(s):  
Arbitrary Shape ◽  
Lake Superior ◽  
Volcanic Rocks ◽  
Three Dimensional ◽  
Magnetic Anomalies ◽  
Two Dimensional ◽  
Discrete Elements ◽  
Convenient Means ◽  
Equivalent Dipole ◽  
Forward Computation

A method has been devised for the forward computation of magnetic anomalies due to two‐dimensional (2-D) polygonal bodies with heterogeneously directed magnetization. The calculations are based on the equivalent line source approach wherein the source is subdivided into discrete elements that vary spatially in their magnetic properties. This equivalent dipole line method provides a fast and convenient means of representing and computing magnetic anomalies for bodies possessing complexly varying magnitude and direction of magnetization. The algorithm has been tested and applied to several generalized cases to verify the accuracy of the computation. The technique has also been used to model observed aeromagnetic anomalies associated with the structurally deformed, remanently magnetized Keweenawan volcanic rocks in eastern Lake Superior. This method is also easily adapted to the calculation of anomalies due to two and one‐half‐dimensional (2.5-D) and three‐dimensional (3-D) heterogeneously magnetized sources.

Stability of flow in a channel with longitudinal grooves

2014 ◽  
Vol 757 ◽  
pp. 613-648 ◽  
Author(s):  
H. V. Moradi ◽  
J. M. Floryan
Keyword(s):  
Reynolds Number ◽  
Small Amplitude ◽  
Arbitrary Shape ◽  
Critical Reynolds Number ◽  
Critical Role ◽  
Three Dimensional ◽  
Travelling Wave ◽  
Two Dimensional ◽  
Wave Instability ◽  
Long Wavelength

AbstractThe travelling wave instability in a channel with small-amplitude longitudinal grooves of arbitrary shape has been studied. The disturbance velocity field is always three-dimensional with disturbances which connect to the two-dimensional waves in the limit of zero groove amplitude playing the critical role. The presence of grooves destabilizes the flow if the groove wavenumber $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\beta $ is larger than $\beta _{tran}\approx 4.22$, but stabilizes the flow for smaller $\beta $. It has been found that $\beta _{tran}$ does not depend on the groove amplitude. The dependence of the critical Reynolds number on the groove amplitude and wavenumber has been determined. Special attention has been paid to the drag-reducing long-wavelength grooves, including the optimal grooves. It has been demonstrated that such grooves slightly increase the critical Reynolds number, i.e. such grooves do not cause an early breakdown into turbulence.

A geophysical interpretation of the geology of Conception Bay, Newfoundland

1983 ◽  
Vol 20 (9) ◽  
pp. 1421-1433 ◽  
Author(s):  
H. G. Miller
Keyword(s):  
Magnetic Susceptibility ◽  
Volcanic Rocks ◽  
Magnetic Anomalies ◽  
Vertical Movement ◽  
Geophysical Data ◽  
Two Dimensional ◽  
Geophysical Interpretation ◽  
Gravity And Magnetic ◽  
Conception Bay ◽  
Avalon Peninsula

Geophysical data from Conception Bay and the adjacent peninsulas of the Avalon Peninsula, Newfoundland are presented and quantitatively interpreted using two-dimensional models to interpret the geology beneath the bay. The portion of the bay underlain by mafic volcanic rocks is determined and the maximum extent of the Cambro-Ordovician rocks containing the Wabana hematite deposit is delineated. All gravity and magnetic anomalies in the area are explained in terms of density and magnetic susceptibility variations confined to the upper 12 km of the crust. The geophysical models indicate that mafic volcanics underlie a significant portion of the study area and are more extensive than indicated by the surface outcrop on land. The models also indicate significant vertical movement on the Topsail Fault and on the extension of a fault passing out into the bay near Holyrood. The Cambro-Ordovician sediments are confined to the southern portion of the block bounded by these faults. The geophysical data are unable to detect the presence of the mafic volcanics east of the Topsail Fault in the study area.

Transfer properties of the reduction of magnetic anomalies to the pole and to the equator

Geophysics ◽  
1990 ◽  
Vol 55 (9) ◽  
pp. 1141-1147 ◽  
Author(s):  
Károly I. Kis
Keyword(s):  
Transfer Function ◽  
Frequency Band ◽  
Three Dimensional ◽  
Magnetic Anomalies ◽  
Two Dimensional ◽  
Magnetic Pole ◽  
Band Pass ◽  
Transfer Properties ◽  
Gaussian Band ◽  
Zero Frequency

Reduction of magnetic anomalies to the magnetic pole and magnetic equator can be regarded as a linear transformation. The Hermitian transfer function characteristics of these transformations are discussed and improved using the Gaussian band‐pass window. This procedure is of use in one‐ and two‐dimensional cases. The application of the Gaussian band‐pass window eliminates the finite discontinuity of the transfer function of reductions at zero frequency in all cases. The frequency band passed by the Gaussian window can be controlled by its parameters. Reduction to the equator can be used at low magnetic latitudes where reduction of two‐dimensional anomalies to the pole has some instabilities caused by the infinite discontinuities of its transfer function. The windowed reductions are illustrated by their application to magnetic anomalies produced by two‐dimensional and three‐dimensional prisms.

scholarly journals Pseudo 3D Imaging of Dielectric and Magnetic Anomalies from GPR Data

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Raffaele Persico ◽  
Sergio Negri ◽  
Francesco Soldovieri ◽  
Elena Pettinelli
Keyword(s):  
Experimental Data ◽  
Born Approximation ◽  
3D Imaging ◽  
Three Dimensional ◽  
Magnetic Anomalies ◽  
Magnetic Characteristics ◽  
Two Dimensional ◽  
Linear Inversion

This paper deals with the reconstruction of buried targets exhibiting both dielectric and magnetic characteristics, starting from GPR data collected at the interface air/soil. The problem is tackled under the Born approximation. In particular, two-dimensional migration and linear inversion results will be compared versus experimental data and three-dimensional representations of the reconstructions achieved from both methods will be shown.

Computation of Magnetic Anomalies Caused by Two‐Dimensional Structures of Arbitrary Shape: Derivation and Matlab Implementation

2019 ◽  
Vol 46 (13) ◽  
pp. 7345-7351 ◽  
Author(s):  
Vadim A. Kravchinsky ◽  
Danny Hnatyshin ◽  
Benjamin Lysak ◽  
Wubshet Alemie
Keyword(s):  
Arbitrary Shape ◽  
Magnetic Anomalies ◽  
Two Dimensional ◽  
Matlab Implementation

High Resolution Microscopy of Multi-Layered Biological Crystals

1982 ◽  
Vol 40 ◽  
pp. 80-83
Author(s):  
H.A. Cohen ◽  
T.W. Jeng ◽  
W. Chiu
Keyword(s):  
High Resolution ◽  
Low Dose ◽  
Three Dimensional ◽  
Data Interpretation ◽  
Two Dimensional ◽  
Biological Objects ◽  
Density Maps ◽  
Density Map ◽  
Complex Crystal ◽  
High Resolution Microscopy

This tutorial will discuss the methodology of low dose electron diffraction and imaging of crystalline biological objects, the problems of data interpretation for two-dimensional projected density maps of glucose embedded protein crystals, the factors to be considered in combining tilt data from three-dimensional crystals, and finally, the prospects of achieving a high resolution three-dimensional density map of a biological crystal. This methodology will be illustrated using two proteins under investigation in our laboratory, the T4 DNA helix destabilizing protein gp32*I and the crotoxin complex crystal.

Instrumentation For Quantitative Microscopy

1977 ◽  
Vol 35 ◽  
pp. 206-209
Author(s):  
B. Ralph ◽  
A.R. Jones
Keyword(s):  
Volume Fraction ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Automatic Data ◽  
Phase Volume Fraction ◽  
Statistical Confidence ◽  
Resultant Data ◽  
Automatic Data Collection ◽  
Third Dimension ◽  
Evolution Of Microstructure

In all fields of microscopy there is an increasing interest in the quantification of microstructure. This interest may stem from a desire to establish quality control parameters or may have a more fundamental requirement involving the derivation of parameters which partially or completely define the three dimensional nature of the microstructure. This latter categorey of study may arise from an interest in the evolution of microstructure or from a desire to generate detailed property/microstructure relationships. In the more fundamental studies some convolution of two-dimensional data into the third dimension (stereological analysis) will be necessary.In some cases the two-dimensional data may be acquired relatively easily without recourse to automatic data collection and further, it may prove possible to perform the data reduction and analysis relatively easily. In such cases the only recourse to machines may well be in establishing the statistical confidence of the resultant data. Such relatively straightforward studies tend to result from acquiring data on the whole assemblage of features making up the microstructure. In this field data mode, when parameters such as phase volume fraction, mean size etc. are sought, the main case for resorting to automation is in order to perform repetitive analyses since each analysis is relatively easily performed.

A linearity test for thick specimens imaged by HVEM over a 180° angular range

1991 ◽  
Vol 49 ◽  
pp. 552-553
Author(s):  
Yu Liu
Keyword(s):  
Phase Contrast ◽  
Three Dimensional ◽  
Angular Range ◽  
Two Dimensional ◽  
Back Projection ◽  
Line Integral ◽  
Exponential Law ◽  
Transmission Electron ◽  
Absorption Law ◽  
Linearity Test

The image obtained in a transmission electron microscope is the two-dimensional projection of a three-dimensional (3D) object. The 3D reconstruction of the object can be calculated from a series of projections by back-projection, but this algorithm assumes that the image is linearly related to a line integral of the object function. However, there are two kinds of contrast in electron microscopy, scattering and phase contrast, of which only the latter is linear with the optical density (OD) in the micrograph. Therefore the OD can be used as a measure of the projection only for thin specimens where phase contrast dominates the image. For thick specimens, where scattering contrast predominates, an exponential absorption law holds, and a logarithm of OD must be used. However, for large thicknesses, the simple exponential law might break down due to multiple and inelastic scattering.

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