TWO METHODS FOR COMPUTER INTERPRETATION OF MAGNETIC ANOMALIES OF DIKES

Geophysics ◽  
1973 ◽  
Vol 38 (4) ◽  
pp. 710-718 ◽  
Author(s):  
B. S. R. Rao ◽  
I. V. Radhakrishna Murthy ◽  
C. Visweswara Rao

Two computer‐oriented methods are presented in this paper for interpreting the magnetic anomalies of a dipping dike. In the first method, horizontal derivatives of the observed magnetic anomalies are calculated which define a single linear equation of the type [Formula: see text], where G is the horizontal gradient of the anomaly, and X is the distance of the gradient measured from any convenient point in the profile. Seven normal equations are derived and the coefficients [Formula: see text] to [Formula: see text] are solved from which the various parameters (Figure 1 of the body are obtained as [Formula: see text] [Formula: see text] [Formula: see text] and [Formula: see text]. In the second method, the method of iteration, the magnitudes and positions of the maximum and minimum anomaly points are located in the profile, and the approximate parameters of the dike are computed from these shape characteristics. The resulting anomalies are then calculated and compared with the observed data. The errors at each point of observation are solved for the changes to be given to the initial values. The process is repeated until the sum of the squares of the errors is less than a specified allowable error. Important features of the methods developed here are that all the observed data are utilized in the course of interpretation, and no input to the computer is required except the anomalies and their distances measured from a convenient point of observation in the profile.

Geophysics ◽  
2013 ◽  
Vol 78 (3) ◽  
pp. J33-J41 ◽  
Author(s):  
Francisco J. F. Ferreira ◽  
Jeferson de Souza ◽  
Alessandra de B. e S. Bongiolo ◽  
Luís G. de Castro

Magnetic anomaly maps reflect the spatial distribution of magnetic sources, which may be located at different depths and have significantly different physical and geometrical properties, complicating the identification of the corresponding geologic structures. Filtering techniques are frequently used to balance anomalies from shallow and deep sources, and to enhance certain features of interest, such as the edges of the causative bodies. Most methods used for enhancing magnetic data are based on vertical or horizontal derivatives of the magnetic anomalies or combinations of them, and the edges or centers of the sources are identified by maxima, minima, or null values in the transformed data. Normalized derivatives methods are used to equalize signals from sources buried at different depths. We present an edge detector method for the enhancement of magnetic anomalies, which is based on the tilt angle of the total horizontal gradient. The notable features of this method are that it produces amplitude maxima over the source edges and that it equalizes signals from shallow and deep sources. The method is applied to synthetic and real data. The effectiveness of the method is evaluated by comparing it with other edge detection methods that have been previously reported in the literature and that make use of derivatives. The results show that our method is less sensitive to variations in the depth of the sources and that it indicates the position of the edges of causative bodies in a more accurate fashion, when compared with previous methods, even for anomalies due to multiple interfering sources. These results demonstrate that the proposed method is a useful tool for the qualitative interpretation of magnetic data.


Geophysics ◽  
1977 ◽  
Vol 42 (3) ◽  
pp. 610-622 ◽  
Author(s):  
Chao C. Ku

A computational method, which combines the Gaussian quadrature formula for numerical integration and a cubic spline for interpolation in evaluating the limits of integration, is employed to compute directly the gravity and magnetic anomalies caused by 2-dimensional and 3-dimensional bodies of arbitrary shape and arbitrary magnetic polarization. The mathematics involved in this method is indeed old and well known. Furthermore, the physical concept of the Gaussian quadrature integration leads us back to the old concept of equivalent point masses or equivalent magnetic point dipoles: namely, the gravity or magnetic anomaly due to a body can be evaluated simply by a number of equivalent points which are distributed in the “Gaussian way” within the body. As an illustration, explicit formulas are given for dikes and prisms using 2 × 2 and 2 × 2 × 2 point Gaussian quadrature formulas. The basic limitation in the equivalent‐point method is that the distance between the point of observation and the equivalent points must be larger than the distance between the equivalent points within the body. By using a reasonable number of equivalent points or dividing the body into a number of smaller subbodies, the method might provide a useful alternative for computing in gravity and magnetic methods. The use of a simplified cubic spline enables us to compute the gravity and magnetic anomalies due to bodies of arbitrary shape and arbitrary magnetic polarization with ease and a certain degree of accuracy. This method also appears to be quite attractive for terrain corrections in gravity and possibly in magnetic surveys.


Geophysics ◽  
1952 ◽  
Vol 17 (2) ◽  
pp. 344-364 ◽  
Author(s):  
Fraser S. Grant

A method is developed for determining the approximate size and shape of the three‐dimensional mass distribution that is required to produce a given gravitational field. The first few reduced multipole moments of the distribution are calculated from the derivatives of the surface field, and the approximative structure is determined from the values of these moments and a knowledge of the density contrast between the body and its surroundings. A system of classification of problems by symmetry is introduced and its practical usage discussed. A relaxation method is described which may be used to adjust the initial solution systematically to give agreement over the whole field. A descriptive discussion is appended.


2004 ◽  
pp. 147-176
Author(s):  
Stanimir Rakic

In this paper I examine compound names of plants, animals, human beings and other things in which at least one nominal component designates a part of the body or clothes, or some basic elements of houshold in Serbian and English. The object of my analysis are complex derivatives of the type (adjective noun) + suffix in Serbian and componds of the type noun's + noun, noun + noun and adjective + noun in English. I try to show that there is a difference in metaphorical designation of human beings and other living creatures and things by such compound nouns. My thesis is that the metathorical designation of human beings by such compounds is based on the symbolic meaning of some words and expressions while the designation of other things and beings relies on noticed similarity. In Serbian language such designation is provided by comples derivatives praznoglavac 'empty-headed person', tupoglavac 'dullard' debolokoiac 'callos person', golobradac 'young, inexperienced person' zutokljunac 'tledling' (fig), in English chicken liver, beetle brain birdbrain, bonehead, butterfingers, bigwig, blackleg, blue blood bluestocking, eat's paw, deadhead,fat-guts,fathead, goldbrick (kol) hardhat, hardhead, greenhorn, redcoat (ist), redneck (sl), thickhead, etc. Polisemous compounds like eat's paw lend support for this thesis because their designation of human beings is based on symbolic meaning of some words or expressions. I hypothesize that the direction and extend of the possible metaphorization of names may be accounted for by the following hierarchy (11) people - animals - plants - meterial things. Such hierarchy is well supported by the observations of Lakoff (1987) and Taylor (1995) about the role of human body in early experience and perception ofthe reality. Different restrictions which may be imposed in the hierarchy (11) should be the matter of further study, some of which have been noted on this paper. The compounds of this type denoting people have metaphorically meaning conected with some pejorative uses. These compounds refer to some psychological or characteral features, and show that for the classification of people such features are much more important than physical properties. While the animals and plants are classified according to some charecteristics of their body parts, people are usually classified according to psychollogical characteristics or their social functions. I have also noted a difference in structure between compounds designation animals and those designating plants and other things. The designation of animals relies more on metonymy, and that of plants and other things on metaphor based on comparision of noticed similarities. In the compounds designating animals, the nominal component relatively seldom refers to the parts of plants or other things. I guess that the cause may be the fact that the anatomy of plants is very different from the anatomy of animals. As a consequence the structure adjective + noun is much more characteristic of the compounds designating animals in English than the structure noun's + noun, and the same holds, although in a lesser degree for the compounds designating humans. It is also noticeable that in English compounds whose second component a part of body or clothes the first component rarely designates animals. On the other hand the compounds (9), in which the nominal head refers to some superordinate species, the first component often designates animal species, but usually of a very different kind. These data seem to lend support for Goldvarg & Gluksberg's thesis (1998) that metaforical interpretation is favoured if the nominal constituents denote quite different entities.


Geophysics ◽  
1979 ◽  
Vol 44 (4) ◽  
pp. 730-741 ◽  
Author(s):  
M. Okabe

Complete analytical expressions for the first and second derivatives of the gravitational potential in arbitrary directions due to a homogeneous polyhedral body composed of polygonal facets are developed, by applying the divergence theorem definitively. Not only finite but also infinite rectangular prisms then are treated. The gravity anomalies due to a uniform polygon are similarly described in two dimensions. The magnetic potential due to a uniformly magnetized body is directly derived from the first derivative of the gravitational potential in a given direction. The rule for translating the second derivative of the gravitational potential into the magnetic field component is also described. The necessary procedures for practical computer programming are discussed in detail, in order to avoid singularities and to save computing time.


Author(s):  
Etienne Grandjean ◽  
Wilhelm Hünting ◽  
Günter Wotzka ◽  
Richard Schärer

Twelve types of chairs were investigated using a sample of 50 men and women. Each chair was compared with every other chair for comfort. A questionnaire concerning comfort in different parts of the body was also administered. Analysis of the paired comparisons allowed a rank ordering of the 12 chairs. The questionnaire revealed advantages as well as disadvantages of specific parts of the chairs. Comparison of the judgments with the shape characteristics of the seats gave clues to the design of a chair for multiple uses.


Medicina ◽  
2018 ◽  
Vol 54 (4) ◽  
pp. 61 ◽  
Author(s):  
Agnieszka Chrustek ◽  
Iga Hołyńska-Iwan ◽  
Inga Dziembowska ◽  
Joanna Bogusiewicz ◽  
Marcin Wróblewski ◽  
...  

Pyrethroids are synthetic derivatives of natural pyrethrins extracted from Chrysanthemum cinerariaefolium. They are 2250 times more toxic to insects than to vertebrates due to insects’ smaller size, lower body temperature and more sensitive sodium channels. In particular, three pyrethroid compounds, namely deltamethrin, permethrin, and alpha-cypermethrin, are commonly used as insecticides and are recommended for in-home insect control because they are considered to be relatively non-toxic to humans in all stages of life. However, recent data show that they are not completely harmless to human health as they may enter the body through skin contact, by inhalation and food or water, and absorption level depending on the type of food. Permethrin seems to have an adverse effect on fertility, the immune system, cardiovascular and hepatic metabolism as well as enzymatic activity. Deltamethrin induces inflammation, nephro- and hepatotoxicity and influences the activity of antioxidant enzymes in tissues. Alpha-cypermethrin may impair immunity and act to increase glucose and lipid levels in blood. The aim of the review is to provide comprehensive information on potential hazards associated to human exposure to deltamethrin, permethrin and alpha-cypermethrin. The results of presented studies prove that the insecticides must be used with great caution.


Geophysics ◽  
1982 ◽  
Vol 47 (6) ◽  
pp. 926-931 ◽  
Author(s):  
H. V. Ram Babu ◽  
A. S. Subrahmanyam ◽  
D. Atchuta Rao

Magnetic anomalies in vertical and horizontal components, when plotted one against the other in polar form, result in a curve called the relation figure (Werner, 1953). In this paper, a comparative study of the relation figures of magnetic anomalies due to two‐dimensional (2-D) dike and vertical step models is made. The relation figures for these two models are found to be ellipses with different properties. The tangent at the origin to the ellipse is parallel to the major axis of the ellipse for the dike model, whereas it is perpendicular to the major axis for the vertical step. This property may be used to distinguish whether the source is a dike or a vertical step. For both of the models, the angle made by the axis of symmetry of the ellipse with the coordinate axis is equal to θ, the combined magnetic angle. The ratio between the lengths of the major and minor axes of the ellipse is directly related to the width‐to‐depth ratio of the dike or the bottom‐to‐top depth ratio of the vertical step. A few characteristic points defined on the ellipse are used to evaluate the body parameters. The major portion of the ellipse is obtained in the close vicinity of the source. Because of symmetry, the ellipse may be extrapolated easily outside the data length, and hence the effect of noise caused by adjacent objects is kept at a minimum.


1965 ◽  
Vol 19 (1) ◽  
pp. 78-83
Author(s):  
Peter Wilson

Several methods for solving normal equations in least squares solutions are explained and the variance-covariance matrix is developed from the law of error propagation.


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