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Journal articles on the topic 'Magnetic anomalies Mathematical models'

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Published: 10 December 2022
Last updated: 28 January 2023

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1

Gay, S. Parker, and Bronson W. Hawley. "Syngenetic magnetic anomaly sources: Three examples." GEOPHYSICS 56, no. 7 (July 1991): 902–13. http://dx.doi.org/10.1190/1.1443124.

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Aeromagnetic anomalies encountered in three areas, two in the western United States and one in Central America, are shown to arise from magnetic sedimentary formations. These examples are selected from a larger number of similar areas surveyed by Applied Geophysics, Inc. in various places in the U.S. Midcontinent and Rocky Mountain regions. The first area discussed is the northwest corner of Nebraska where the Miocene Arikaree formation, comprised of magnetic airfall and windblown tuffs, causes anomalies in areas of incised topography. The second area is located in south central Utah, where the Upper Cretaceous Kaiparowits sandstones contain detrital magnetite that causes large anomalies in tilted structures and over incised topography. The third area treated covers over half of southern Belize in Central America, including much of the offshore portion. Here, the Toledo formation of Paleocene‐Eocene age contains a thick section of clastic detritus rich in lithic grains of volcanic rocks that produce magnetic highs over thrusted and folded anticlinal axes. These three examples of magnetic anomalies due to syngenetic magnetite in widely scattered areas and from different types of source materials bring into question the assumption of so‐called “diagenetic magnetite” (or other magnetic minerals) as a cause of magnetic anomalies in other petroleum basins. It is necessary in all cases to determine the magnetic source from surface or subsurface geology, as was done here, rather than making assumptions strictly from magnetic profiles or mathematical models.
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2

Barraclough, D. R. "International Geomagnetic Reference Field Revision 1987." GEOPHYSICS 53, no. 4 (April 1988): 576–78. http://dx.doi.org/10.1190/1.1442493.

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The International Geomagnetic Reference Field (IGRF) is a series of mathematical models of the main geomagnetic field and its secular variation, the models consisting of sets of spherical harmonic (or Gauss) coefficients. The IGRF has become a widely used means of deriving values of geomagnetic field components in, for example, studies of magnetic anomalies and investigations of charged particle motions in the ionosphere and the magnetosphere.
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3

Garca‐Abdeslem, Juan, and Gordon E. Ness. "Inversion of the power spectrum from magnetic anomalies." GEOPHYSICS 59, no. 3 (March 1994): 391–401. http://dx.doi.org/10.1190/1.1443601.

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We develop methods for the modeling and inversion of the power‐density spectrum from magnetic anomaly data assuming that the crustal magnetic field is caused by an ensemble of vertical‐sided and uniformly magnetized prisms. The solution of the forward problem is achieved in the wavenumber domain, where a synthetic spectrum is given by the product of the mathematical expectations of single‐valued functions that describe depth, thickness, and horizontal dimensions of prisms in the ensemble. We use Gaussian and uniform distributions to describe the ensemble and provide a variety of functions from which different statistical models can be obtained. The solution of the inverse problem is achieved iteratively, starting from an initial set of model parameters. It is based on the ridge‐regression algorithm, and its usefulness is assessed in a number of examples with numeric, synthetic and real data spectra. The methods are first tested on the spectrum obtained from a simple artificial magnetic anomaly and on the artificial spectrum caused by an ensemble of source bodies and are found to be capable of recovering the source parameters. Next, the methods are applied to marine magnetic data from a survey offshore of the Yucatán Peninsula, Mexico. The results of this last application are consistent with the crustal structure observed at Chicxulub hole.
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4

Савин, Михаил, Mihail Savin, Юрий Израильский, and Yuriy Izrailsky. "New capabilities of Chetaev´s model." Solnechno-Zemnaya Fizika 2, no. 2 (June 17, 2016): 86–92. http://dx.doi.org/10.12737/13465.

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This paper considers anomalies in the magnetotelluric field in the Pc3 range of geomagnetic pulsations. We present experimental data on Pc3 field recording which show negative (from Earth’s surface to air) energy fluxes Sz<0 and reflection coefficients |Q|>1. Using the model of inhomogeneous plane wave (Chetaev’s model), we try to analytically interpret anomalies of energy fluxes. According to a mathematical experiment there are two three-layer models with both electrical and magnetic modes satisfying the condition |Qh|>1. Here we discuss a possibility of explaining observable effects within the framework of the resonance model inhomogeneous plane wave — layered medium.
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5

Journal, Baghdad Science. "Land Magnetic survey along a profile from Akaz to Rutba town and its applications." Baghdad Science Journal 9, no. 1 (March 4, 2012): 63–71. http://dx.doi.org/10.21123/bsj.9.1.63-71.

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A land magnetic survey was carried out along regional profile, which is located at the north part of the Iraqi western desert. It starts from al –Qaam City (at north) toward Rutba City (at south) with a total length of 238km. The survey was carried out along the paved road between the two cities, About 113 measuring points were done with inter-station distance of 2 km (for 198 km) and 2 to 5km (for 40km). Two proton magnetometers were used in this survey. One of them is used for base station monitoring, which was fixed as of Salah Aldin field (Akkas). Its readings were used for diurnal corrections. All magnetic measurements were corrected for normal and topographic corrections. The readings were reduced to a certain base level. The resulted magnetic anomalies show a good correlation with those of Arial - magnetic survey anomalies conducted by (C.G.G, 1974). This is true for those anomalies with wavelength more than 50km. While the land magnetic survey has shown more small anomalies which may reflect near surface sources. In addition, there is a considerable difference between the magnetic intensity values of both surveys. The downward continuation method was used in this study for detecting the depth of magnetic anomaly source. But before applying this method the total magnetic field was converted to its vertical component using computer program packages. The 2.5 mathematical modeling techniques were used for interpreting magnetic anomaly. Several models were suggested according to the geological and geophysical surface and subsurface data. These models clearly suggest that the tectonic of the studied area may be completely affected by deep faults that could reach the basements or even cut it. These faults resulted in tectonic blocks with relative movements that could happen through the geological time, and they may be responsible for the tectonic features of the western desert. These faults could also responsible for the lateral and vertical variations that are noticed in subsurface rocks of the studied area. The subsurface lateral susceptibility variation between the different blocks could result from the variation in physical parameter of the rocks (like porosity, fracture density…) and there is a possibility that rocks beneath 18km (lower crust) still possess some magnetic properties.
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6

Balk, P. I., and A. S. Dolgal. "HISTORY OF DEVELOPMENT AND CURRENT STATUS OF THE FINITE ELEMENT APPROACH IN THE THEORY OF INTERPRETATION OF GRAVITATIONAL AND MAGNETIC ANOMALIES." Bulletin of Kamchatka Regional Association «Educational-Scientific Center». Earth Sciences, no. 5(56) (December 26, 2022): 19–40. http://dx.doi.org/10.31431/1816-5524-2022-4-56-19-40.

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Due to the discreteness of gravitational and magnetic fields measurements in the mathematical theory of interpretation, finite element models of the environment, which have universal capabilities to deploy various a priori information, are of paramount importance. Known methods for solving inverse problems for finite element models of field sources can be divided into two classes. The first, where the interpretation result is traditionally a single solution that is optimal according to some criterion, and the second, where the interpretation results reflect a representative subset of feasible solutions of the inverse problem, which increases their authenticity. The developments of the article authors for second class methods took shape in a guaranteed approach and additive technologies for interpreting geopotential fields. The proposed review aims to promote the second class methods in the practice of interpreting gravity and magnetic anomalies, which should contribute to a more complete extraction of information from geophysical data.
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7

Wang, Benlong, and Hua Liu. "Space–time behaviour of magnetic anomalies induced by tsunami waves in open ocean." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 469, no. 2157 (September 8, 2013): 20130038. http://dx.doi.org/10.1098/rspa.2013.0038.

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The magnetic anomaly induced by an inhomogeneous velocity field under tsunami waves in open ocean is investigated. With asymptotical analysis, an explicit series solution of the kinematic dynamo problem is established for weak dispersive water waves. The magnetic field induced by typical tsunami models, including single wave and -wave, can be directly obtained using the proposed series solution. The characteristics of the magnetic field induced by two realistic tsunami events are investigated. By analysis, the magnetic magnitude induced by a 1 m high tsunami is estimated as of the order of 10 nT at the sea surface, which depends on the wave parameters as well as the Earth's magnetic field. The space and time behaviour of the magnetic field shows fair similarity with the field data at Easter Island during the 2010 Chile tsunami.
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8

Ben Abdallah, Naoufel, Pierre Degond, and Florian Méhats. "Mathematical models of magnetic insulation." Physics of Plasmas 5, no. 5 (May 1998): 1522–34. http://dx.doi.org/10.1063/1.872810.

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9

Zhelnorovich, V. A. "On mathematical models of magnetic fluids." Journal of Applied Mathematics and Mechanics 51, no. 4 (January 1987): 539–48. http://dx.doi.org/10.1016/0021-8928(87)90097-9.

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10

Kluth, Tobias. "Mathematical models for magnetic particle imaging." Inverse Problems 34, no. 8 (June 12, 2018): 083001. http://dx.doi.org/10.1088/1361-6420/aac535.

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11

Gawȩdzki, Krzysztof, Rafał R. Suszek, and Konrad Waldorf. "Global Gauge Anomalies in Two-Dimensional Bosonic Sigma Models." Communications in Mathematical Physics 302, no. 2 (November 21, 2010): 513–80. http://dx.doi.org/10.1007/s00220-010-1162-0.

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12

Keating, Pierre B., and Mark Pilkington. "An automated method for the interpretation of magnetic vertical‐gradient anomalies." GEOPHYSICS 55, no. 3 (March 1990): 336–43. http://dx.doi.org/10.1190/1.1442841.

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The use of airborne magnetic vertical‐gradient surveys is increasing. Interpretation, however, is mostly used qualitatively as an aid to geologic mapping. Presently, quantitative interpretation techniques are based on the analysis of isolated anomalies. In this paper, we develop a numerical method for interpreting the magnetic vertical‐gradient anomalies of dipping dikes and planar geologic contacts. The method is based on a linearization of the equations describing these anomalies. The solution can be used to interpret isolated anomalies or whole profiles in a Werner‐style deconvolution. Using data from the Val d’Or mining area (Canada), we have calculated magnetic models to test the interpretation technique. Magnetic vertical‐gradient profiles calculated from the interpreted models closely match the observed data.
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13

Wołoszyn, Mirosław. "Detection of ferromagnetic objects in local magnetic anomaly of the Baltic Sea." Polish Maritime Research 15, no. 2 (April 1, 2008): 77–82. http://dx.doi.org/10.2478/v10012-007-0068-z.

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Detection of ferromagnetic objects in local magnetic anomaly of the Baltic Sea In geological researches several kinds of methods are applied to discovering the natural resources. Planes, helicopters and UAVs (UnmAnned Vehicle) are used in researches in large areas. The gravity, electromagnetic and magnetic methods, which are used in geological researches, are presented in this paper. The special attention was paid to magnetic systems installed on mobile platforms. The magnetic field of the Earth obtained from mathematical model was compared to the real magnetic field in the selected part of the Baltic Sea. The results of the calculations showed that the mathematical model of the Earth's magnetic field does not consider local magnetic anomalies. The strong local magnetic anomalies cause serious problems with detection of underwater objects. Special problems appear in the magnetic system on a helicopter, which are presented in this paper.
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14

Reynolds, R. L., M. Webring, V. J. S. Grauch, and M. Tuttle. "Magnetic forward models of Cement oil field, Oklahoma, based on rock magnetic, geochemical, and petrologic constraints." GEOPHYSICS 55, no. 3 (March 1990): 344–53. http://dx.doi.org/10.1190/1.1442842.

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Magnetic forward models of the Cement oil field, Oklahoma, were generated to assess the possibility that ferrimagnetic pyrrhotite related to hydrocarbon seepage in the upper 1 km of Permian strata contributes to aeromagnetic anomalies at Cement. Six bodies having different magnetizations were constructed for the magnetic models, based on geology and on petrologic and geochemical results, supplemented by rock magnetic measurements of shallow‐core and outcrop samples. The column of rock through which hydrocarbons have passed is divided into three sulfide zones on the basis of pyrrhotite content, and the column is capped by a 30 m thick zone that contains ferric oxide minerals formed mainly from oxidized pyrite. Red beds unaffected by sulfidization, as well as a zone of rock depleted in hematite but lacking sulfide, surround sulfidic zones. The synthetic magnetic profiles are controlled mainly by pyrrhotite‐bearing strata at depths of 200–500 m. The magnetizations of these bodies are calculated from: (1) petrographic estimates of pyrrhotite content relative to pyrite; (2) content of sulfide sulfur determined from chemical analysis; and (3) values for the magnetic susceptibility of monoclinic pyrrhotite. Total magnetizations of the bodies of highest pyrrhotite content range from about [Formula: see text] to [Formula: see text] in the present field direction and yield magnetic anomalies (at 120 m altitude) having amplitudes of less than 1 nT to ∼6 to 7 nT, respectively. Such amplitudes are much lower than those (as high as 60 nT) reported from the original total‐field survey over the Cement field. Numerous assumptions were made in the generation of the models, and thus the results neither prove nor disprove the existence of aeromagnetic anomalies related to hydrocarbon seepage at Cement. Nevertheless, the results suggest that pyrrhotite, formed via hydrocarbon reactions and within a range of concentrations estimated at Cement, is capable of causing magnetic anomalies.
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15

Semerak, Mykhailo, and Hanna Lyantse. "Mathematical modeling and investigation of anomalies of the temperature field of the earth′s crust over oil and gas reservoirs." Physico-mathematical modelling and informational technologies, no. 28, 29 (December 27, 2019): 92–101. http://dx.doi.org/10.15407/fmmit2020.28.092.

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In geothermal studies of oil and gas fields, temperature anomalies were found in the surface layers of the crust. In the paper, mathematical models of temperature fields of the Earth's crust over the oil and gas reservoirs have been constructed. The anomalies of the temperature field in the neutral layer depending on the depth of deposits, the capacity of the reservoir have been investigated using experimental data. A mathematical model of the Earth's crust has been also constructed taking into account its lithological structure. The influence of lithological heterogeneity of the layer on the temperature fields in the neutral layer has been investigated.
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16

Dasgupta, S. P. "On: “Computing the gravitational and magnetic anomalies due to a polygon: Algorithms and Fortran subroutines” by I. J. Won and Michael Bevis (GEOPHYSICS, 52, 232–238, February 1987)." GEOPHYSICS 53, no. 8 (August 1988): 1129–30. http://dx.doi.org/10.1190/1.1442552.

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I thank the authors of this article for their nice investigation. In addition, I would like to add a few observations on the comlex representation for gravity and magnetic anomalies of a 2-D polygonal body. These observations lead to considerable simplication in the mathematical forms of the anomalies, providing a straightforward computing procedure.
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17

Hijab, Basim. "NEW INTERPRETATION OF THE EARTH’S MAGNETIC FIELD EFFECTS’ ON LIFE." Iraqi Geological Journal 53, no. 2C (September 30, 2020): 13–25. http://dx.doi.org/10.46717/igj.53.2c.2rs-2020-09-02.

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The relationships of the Earth’s magnetic field intensity and time (the past 320 years) for many locations around the world are obtained, based on the IGRF-13 mathematical model. The results showed that each location on the earth surface has its magnetic intensity relation with time that reflects local variations. The sudden changes (magnetic anomalies) in the Earth’s magnetic field with time are natural phenomena, which are different from place to another. These magnetic anomalies are investigated for possible relationship to the historical records of the influenza pandemic outbreaks. The results showed clear congruences between the Earth’s magnetic anomalies and influenza outbreaks times. The congruences become clearer when comparing the highest magnetic anomaly intensity and the first outbreak location of the influenza pandemic. This is true for the recorded historical data since 1890 AD. It is not known how the changes in Earth’s magnetic field affect the virus’s outbreaks or evolution, but there is a clear relation that needs detailed studies.
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18

Williams, J. P., and V. J. S. Grauch. "Comparison of magnetic and gravity terrain models." Exploration Geophysics 20, no. 2 (1989): 201. http://dx.doi.org/10.1071/eg989201.

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Modelling of magnetic terrain and comparison with actual data is an efficient method for assessing large sets when residual anomalies are important. The technique of Blakely (1981) which utilises a rapidly converging series of Fast Fourier Transforms is an efficient and sufficiently accurate method for this assessment.The technique has been applied to a data set at Kilkivan, south eastern Queensland. Here the magnetic sources are near horizontal Triassic volcanic flows unconformably overlying a non- magnetic Palaeozoic basement.Geological control is good so that it is possible to model the bottom of the flow. It is postulated that the difference between the calculated and actual data represents paleochannels in the basement. Similar techniques applied to gravity data have not been as successful.
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19

Wu, Kai, Liang Tu, Diqing Su, and Jian-Ping Wang. "Magnetic dynamics of ferrofluids: mathematical models and experimental investigations." Journal of Physics D: Applied Physics 50, no. 8 (February 1, 2017): 085005. http://dx.doi.org/10.1088/1361-6463/aa590b.

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20

Apeh, O. I., E. C. Moka, and V. N. Uzodinma. "Evaluation of Gravity Data Derived from Global Gravity Field Models Using Terrestrial Gravity Data in Enugu State, Nigeria." Journal of Geodetic Science 8, no. 1 (December 1, 2018): 145–53. http://dx.doi.org/10.1515/jogs-2018-0015.

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Abstract Spherical harmonic expansion is a commonly applied mathematical representation of the earth’s gravity field. This representation is implied by the potential coeffcients determined by using elements/parameters of the field observed on the surface of the earth and/or in space outside the earth in the spherical harmonic expansion of the field. International Centre for Gravity Earth Models (ICGEM) publishes, from time to time, Global Gravity Field Models (GGMs) that have been developed. These GGMs need evaluation with terrestrial data of different locations to ascertain their accuracy for application in those locations. In this study, Bouguer gravity anomalies derived from a total of eleven (11) recent GGMs, using sixty sample points, were evaluated by means of Root-Mean-Square difference and correlation coeficient. The Root-Mean-Square differences of the computed Bouguer anomalies from ICGEMwebsite compared to their positionally corresponding terrestrial Bouguer anomalies range from 9.530mgal to 37.113mgal. Additionally, the correlation coe_cients of the structure of the signal of the terrestrial and GGM-derived Bouguer anomalies range from 0.480 to 0.879. It was observed that GECO derived Bouguer gravity anomalies have the best signal structure relationship with the terrestrial data than the other ten GGMs. We also discovered that EIGEN-6C4 and GECO derived Bouguer anomalies have enormous potential to be used as supplements to the terrestrial Bouguer anomalies for Enugu State, Nigeria.
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21

Thalabard, Simon, Sergey Medvedev, Vladimir Grebenev, and Sergey Nazarenko. "Inverse cascade anomalies in fourth-order Leith models." Journal of Physics A: Mathematical and Theoretical 55, no. 1 (December 15, 2021): 015702. http://dx.doi.org/10.1088/1751-8121/ac3858.

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Abstract We analyze a family of fourth-order non-linear diffusion models corresponding to local approximations of four-wave kinetic equations of weak wave turbulence. We focus on a class of parameters for which a dual cascade behavior is expected with an infrared finite-time singularity associated to inverse transfer of waveaction. This case is relevant for wave turbulence arising in the nonlinear Schrödinger model and for the gravitational waves in the Einstein’s vacuum field model. We show that inverse transfer is not described by a scaling of the constant-flux solution but has an anomalous scaling. We compute the anomalous exponents and analyze their origin using the theory of dynamical systems.
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22

Shifman, M., A. Vainshtein, and R. Zwicky. "Central charge anomalies in 2D sigma models with twisted mass." Journal of Physics A: Mathematical and General 39, no. 41 (September 27, 2006): 13005–24. http://dx.doi.org/10.1088/0305-4470/39/41/s13.

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23

Lin, Dong, and Xin Chen. "Mathematical Models of 3D Magnetic Field and 3D Positioning System by Magnetic Field." Applied Mathematics & Information Sciences 8, no. 4 (July 1, 2014): 1647–54. http://dx.doi.org/10.12785/amis/080420.

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24

Yin, Jiang Ning, and Dun Hui Xiao. "3D Real-Time Modeling Issue in Gravity & Magnetic Anomalies Interpretation Tool." Advanced Materials Research 271-273 (July 2011): 495–500. http://dx.doi.org/10.4028/www.scientific.net/amr.271-273.495.

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We present a new approach for constructing the initial 3D geological models in the process of man-machine interactive interpretation for gravity and magnetic anomalies. Firstly, we introduced the steps of method. It includes some auxiliary vertexes and sections techniques. Then, the forward algorithm of the model is given. And the data structure of the model is devised, later the modifying method and visualization method is discussed. This method is realized in our 3D gravity & magnetic anomaly interpretation system based on VC++6.0 and OpenGL. Using this method, the geophysical interpreter can construct or modify the geological models easily under the three dimension environment. The tool can give them visual 3D models, so it enhances the efficiency of the interpretation.
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25

Ataullayev, N. O., D. F. Nizomova, and B. Q. Muxammadov. "Mathematical models of magnetic circuits of a magnetomodulation DC converter." Journal of Physics: Conference Series 2094, no. 5 (November 1, 2021): 052039. http://dx.doi.org/10.1088/1742-6596/2094/5/052039.

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Abstract Monitoring of the operation mode of autonomous power supplies with magnetically modulating DC converters and system control, differential sensitivity, improve accuracy and reliability and monitor its static characteristics in the form of a line graph.
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26

Bukhbinder, I. L., S. M. Kuzenko, and O. A. Solov'ev. "Effective action and superconformal anomalies of (p, p) ? models in (1, 1) superspace." Theoretical and Mathematical Physics 82, no. 1 (January 1990): 52–57. http://dx.doi.org/10.1007/bf01028252.

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27

Ravat, Dhananjay. "Magnetic properties of unrusted steel drums from laboratory and field‐magnetic measurements." GEOPHYSICS 61, no. 5 (September 1996): 1325–35. http://dx.doi.org/10.1190/1.1444056.

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Laboratory‐derived magnetic properties from samples of steel drums appear to be lower than bulk magnetic properties required to produce observed magnetic anomalies over the same drums. The origin of this discrepancy is perhaps in the shape demagnetization experienced by samples used in the laboratory study. Laboratory observations of magnetic susceptibility in different directions suggest that the demagnetization mechanism may have significantly attenuated the laboratory‐derived magnetization values from small samples of drums. Field observations and computer modeling indicate that even though the effect of demagnetization is important for drum‐shaped objects, demagnetization is less pronounced in the shape of the drum than in the samples cut for laboratory measurements. Therefore, laboratory‐derived magnetizations from samples of steel drums cannot be used to model magnetic anomalies of steel drums. If laboratory‐derived magnetizations were used to model steel drums, the models would underestimate the resulting magnetic anomalies considerably and, in turn, would overestimate the number of buried drums at an environmental investigation site. Apparent bulk magnetization values for unrusted vertically oriented 55 and 30 gallon drums have been calculated (i.e., the values corrected for the effect of shape demagnetization of the drums). These range from ∼90 to ∼125 SI units (∼7 to ∼10 cgs units) for volume susceptibility and from ∼325 to ∼2750 A/m (∼0.325 to [Formula: see text]) for remanent magnetization (based on eight 55 gallon and four 30 gallon drums). Further deviations in these values could arise from the type and thickness of the steel and variations in manufacturing conditions affecting magnetizations. From the point of view of modeling the drums, at most source‐to‐observation distances applicable to environmental investigations, the equivalent source method is able to approximate the observed anomalies of steel drums better than the 3-D modeling method. With two years of rusting, magnetic anomalies of some of the drums have reduced, while in other drums, they have slightly increased. The overall magnetic changes caused by rusting appear to be more complex than anticipated, at least in the initial phase of rusting.
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28

Fregoso, Emilia, Luis A. Gallardo, and Juan García-Abdeslem. "Structural joint inversion coupled with Euler deconvolution of isolated gravity and magnetic anomalies." GEOPHYSICS 80, no. 2 (March 1, 2015): G67—G79. http://dx.doi.org/10.1190/geo2014-0194.1.

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We generalized the Euler deconvolution method to a joint scheme, which consists of locating the horizontal and vertical positions of the top of potential-field 3D sources. These results were then used to constrain the depth to the top of the models obtained by cross-gradient joint 3D inversions, imposing fixed known values in the a priori models. The coupling of both methods produced more realistic density and magnetization models for separate and joint inversions, relative to those obtained by applying cross-gradient joint inversion only. This strategy was tested on a 3D synthetic experiment, and on a real field data set from the northwest region of the Baja California Peninsula, Mexico. After locating the vertical position of the source, the algorithm uses this information to obtain density and magnetization models that enhanced their structural compatibility and reduces the ambiguity on the interpretation of their structural characteristics laterally and at surface.
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29

Burazer, Milenko, Milinko Grbović, and Vicko Žitko. "Magnetic data processing for hydrocarbon exploration in the Pannonian Basin, Yugoslavia." GEOPHYSICS 66, no. 6 (November 2001): 1669–79. http://dx.doi.org/10.1190/1.1486769.

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Because magnetic minerals may directly indicate the presence of oil and gas deposits, magnetic methods are applied to hydrocarbon exploration in oil‐bearing sedimentary basins. The basic problem in applying these methods is the isolation of weak magnetic anomalies sourced by low concentrations of the magnetic minerals present. These weak anomalies are often masked by much stronger magnetic anomalies caused by underlying magnetic rocks and/or by rocks in the basin sediments. Weak local anomalies can efficiently be isolated by applying selective 1‐D digital frequency filters. The method of filtering has been checked by data obtained using simple models of magnetic sources and using a model representative of the local geology in our study area in the southern Pannonian basin, Yugoslavia, The magnetic field frequency content was analyzed by applying the power spectral density estimation, using the maximum entropy method. The digital filters were designed using the window function method. The best results were obtained by the Kaiser window function for the chosen range of the band‐pass filter. In our study area, me isolated local magnetic anomalies have amplitudes of ±10 nT and trend in an east‐west direction parallel to the predominant structural grain. These anomalies correlate very well with the known oil and gas fields. As an example, filter processing of magnetic anomaly data, combined with the 3‐D seismic data gained in the filtered magnetic field, correlate well with one of the oil fields. The next phase of the project will concentrate on the anomalies occurring outside the established gas and oil fields.
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30

Ermokhin, K. M., and V. A. Soldatov. "On the determination of sources and internal structure of the Earth's magnetic field based on analytical continetion by continued frations." Geoinformatika, no. 3 (2020): 20–28. http://dx.doi.org/10.47148/1609-364x-2020-3-20-28.

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A method is proposed for determining the real sources of the Earth’s internal magnetic field based on the conversion of the coefficients of the stationary earth field according to the IGRF model using the mathematical apparatus for transforming a power series into a continued fraction. Keywords: IGRF model, analytical continuation, continued fractions, spherical analysis, regional anomalies.
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31

Andronov, I. L. "Multiple Time Scales in Cataclysmic Variables: Observations Vs. Mathematical Models." Highlights of Astronomy 11, no. 1 (1998): 375. http://dx.doi.org/10.1017/s1539299600021250.

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Theoretical models and observational evidence for various processes in magnetic cataclysmic variables are briefly reviewed. Among them: modulation of the accretion rate by the magnetic field of the white dwarf; excitation of the orientation change of the magnetic axis of the white dwarf with respect to the secondary; structure of the accretion column and its instability; mass and angular momentum transfer; magnetic activity of the secondary; high/low luminosity state transitions; QPO’s, ”shot noise” and ”red noise” in polars, intermediate polars and nova-like objects.
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32

Choe, Hanjin, and Jerome Dyment. "Fading magnetic anomalies, thermal structure and earthquakes in the Japan Trench." Geology 48, no. 3 (January 17, 2020): 278–82. http://dx.doi.org/10.1130/g46842.1.

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Abstract Early magnetic studies of the Japan Trench showed that seafloor spreading magnetic anomalies progressively fade away and disappear during subduction, reflecting the increasing distance to magnetized sources and the removal of their remanent magnetization with alteration and increasing temperature. An improved magnetic anomaly map derived from both scalar and vector magnetic anomaly data, coupled with a better knowledge of the slab geometry in one hand, of the magnetic structure of the oceanic crust on the other hand, allow us to constrain the thermal structure of the subducting slab. We, for the first time, identify two steps in the anomaly disappearance: first the magnetization of extrusive basalt is rapidly erased between 9 and 12 km, where titanomagnetite reaches its blocking temperature between 150 °C and 350 °C, then the magnetization of deeper crustal layers slowly decreases down to ∼20 km, reflecting the progressive slab heating toward the Curie temperature of magnetite, 580 °C. The resulting slab temperatures are higher than predicted by most thermal models. Recent observations and models suggest rejuvenated hydrothermal activity triggered by lithospheric flexure before subduction that may significantly heat up the subducting oceanic crust through thermal blanketing and possibly serpentinization, with consequences on the depth of the seismogenic zone.
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Yüksel, Yusuf, and Erol Vatansever. "Dynamic phase transition in classical Ising models." Journal of Physics D: Applied Physics 55, no. 7 (October 27, 2021): 073002. http://dx.doi.org/10.1088/1361-6463/ac2f6c.

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Abstract When a ferromagnetic system is driven by an oscillating magnetic field, the system shows various intriguing magnetic properties. The two most common features are dynamic phase transition and dynamic hysteresis resulting from the competition between the period of the external field and the metastable lifetime of the system. In this article, we mainly review the similarities and dissimilarities between ferromagnetic systems in thermal equilibrium and those exposed to a driving time-dependent magnetic field. Extensive studies performed over two decades have shown that dynamic and thermodynamic phase transitions correspond to the same universality class and have similar phase diagrams, among other similarities. Remarkably, recent experimental studies have revealed that both fluctuations in dynamic order parameter and susceptibility can demonstrate anomalously sharp sidebands, which are known as metamagnetic anomalies, in the dynamically paramagnetic phase close to the critical point. This behavior is one of the most interesting behaviors observed in the magnetic systems driven by a time-dependent field which does not have an analog in the corresponding equilibrium counterparts. We discuss the general picture regarding the effects of the applied field components on the metamagnetic anomalies. As a main conclusion, we remark that a comprehensive literature overview reveals that the similarities between conventional thermodynamic phase transitions and corresponding dynamic counterpart are only limited to the vicinity of critical period regime with zero bias field, and they should be treated very carefully in the presence of surfaces. Finally, some of the main questions waiting to be answered and potential future research directions are underlined.
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34

Pirolo, John S., Lawrence L. Creswell, Stephen J. Bresina, William H. Perman, Barna A. Szabo, Kent W. Myers, Michael W. Vannier, and Michael K. Pasque. "Regional myocardial stress distribution from magnetic resonance image-based mathematical models." Annals of Thoracic Surgery 52, no. 2 (August 1991): 276–84. http://dx.doi.org/10.1016/0003-4975(91)91352-v.

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35

Durrant, CJ. "Linear Force-free Magnetic Fields and Coronal Models." Australian Journal of Physics 42, no. 3 (1989): 317. http://dx.doi.org/10.1071/ph890317.

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The mathematical properties of linear force-free fields generated by the Helmholtz equation are reviewed, and the solutions in terms of spherical, cartesian and cylindrical coordinate systems are discussed. When only the normal component of the field on a single (photospheric) surface is available as a boundary condition, the solutions are not niquely determined. If further conditions are imposed, solutions may be unique or multiple or may not exist. The
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36

Hartmann, Gelvam A., and Igor G. Pacca. "Time evolution of the South Atlantic Magnetic Anomaly." Anais da Academia Brasileira de Ciências 81, no. 2 (June 2009): 243–55. http://dx.doi.org/10.1590/s0001-37652009000200010.

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The South Atlantic Magnetic Anomaly (SAMA) is one of the most outstanding anomalies of the geomagnetic field. The SAMA secular variation was obtained and compared to the evolution of other anomalies using spherical harmonic field models for the 1590-2005 period. An analysis of data from four South American observatories shows how this large scale anomaly affected their measurements. Since SAMA is a low total field anomaly, the field was separated into its nondipolar, quadrupolar and octupolar parts. The time evolution of the non-dipole/total, quadrupolar/total and octupolar/total field ratios yielded increasingly high values for the South Atlantic since 1750. The SAMA evolution is compared to the evolution of other large scale surface geomagnetic features like the North and the South Pole and the Siberia High, and this comparison shows the intensity equilibrium between these anomalies in both hemispheres. The analysis of non-dipole fields in historical period suggests that SAMA is governed by (i) quadrupolar field for drift, and (ii) quadrupolar and octupolar fields for intensity and area of influence. Furthermore, our study reinforces the possibility that SAMA may be related to reverse fluxes in the outer core under the South Atlantic region.
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Menzhinski, A. B., A. N. Malashin, and P. B. Menzhinski. "Development of Refined Electromagnetic Models of Reciprocating Electric Generators with Permanent Magnets." ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 64, no. 4 (July 21, 2021): 291–302. http://dx.doi.org/10.21122/1029-7448-2021-64-4-291-302.

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The analysis of scientific papers devoted to the mathematical description of electric generators of reciprocating motion with permanent magnets demonstrated that the proposed mathematical models of this type of generators are based on the theory of magnetic circuits. Such mathematical models are based on a simplified representation of the magnetic system and the magnetic field in the form of a magnetic circuit with corresponding magnetic conductivities. However, unlike traditional rotary type electric machines, electric generators of reciprocating motion have a number of features, the omission of which in mathematical modeling causes the increase of the cost of their creation (due to the duration of the design and experimental refinement of the generators). Therefore, at the initial stages of electromagnetic calculation and solving optimization problems, it is necessary to use adequate mathematical models to improve the accuracy of calculations of the parameters of these generators. For this purpose, a mathematical model based on field theory can be used; however, its main drawback is the complexity of its application for solving optimization problems. In this regard, to improve the accuracy of calculations of the parameters of electric generators of reciprocating motion with permanent magnets, it is proposed to use refining coefficients (coefficients of scattering and buckling of the magnetic flux) in mathematical models based on the theory of magnetic circuits. The authors have developed refined electromagnetic models of electric generators of reciprocating motion with permanent magnets, which make it possible to obtain the main parameters of generators at the initial stages of electromagnetic calculation and when solving optimization problems with acceptable accuracy. A distinctive feature of the refined electromagnetic models of generators is the consideration of the scattering and buckling coefficients of the magnetic flux in the magnetic system that change during the simulation.
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Khlevna, Iuliia L., and Bohdan S. Koval. "Development of infrastructure for anomalies detectionin big data." Applied Aspects of Information Technology 5, no. 4 (December 28, 2022): 348–58. http://dx.doi.org/10.15276/aait.05.2022.23.

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The work describes the conducted analysis of models, methods, and technologies for detecting anomalies in data. It concludes that, based on the analysis, the solution to the problem of anomaly detection in data should be considered as a complex technology, which consists of the formation and application of mathematical models in combination with the research of data processing approaches. The article analyses the current state of big data stream processing technologies and reflects the peculiarities of the most commonly used and advanced of them, e.g. Apache Hadoop, Apache Spark, Apache Cassandra, Apache Kafka, Apache Storm, and Apache Beam. On top of these, it pays attention to the infrastructure, in which the created software models can be deployed and used, taking into account the high-load real-time nature of the data. The article proposes to form an infrastructure for anomaly detection in data as an applied example of big data processing cloud infrastructure. The paper demonstrates the developed infrastructure model for anomaly detection in real-time stream data, which is based on an expert method of forming requirements for a software component, choosing an algorithm for detecting anomalies, selecting tools, and improving the algorithm. The highlighted anomaly detection tools allow us to create a secure real-time anomaly detection solution using Dataflow, BigQuery ML, and Cloud DLP. The paper presents the applied implementation of anomaly detection in real-time using GCP and Apache Beam -data stream analysis of software logs in the information system and detection of fraudulent ones among them, which will help improve the cyber security of the system. In the end, the work demonstrates possible improvements to the basic model that could help to speed it up
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AMMARI, HABIB, YVES CAPDEBOSCQ, HYEONBAE KANG, and ANASTASIA KOZHEMYAK. "Mathematical models and reconstruction methods in magneto-acoustic imaging." European Journal of Applied Mathematics 20, no. 3 (June 2009): 303–17. http://dx.doi.org/10.1017/s0956792509007888.

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In this paper, we provide the mathematical basis for three different magneto-acoustic imaging approaches (vibration potential tomography, magneto-acoustic tomography with magnetic induction and magneto-acoustic current imaging) and propose new algorithms for solving the inverse problem for each of them.
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Portniaguine, Oleg, and Michael S. Zhdanov. "3‐D magnetic inversion with data compression and image focusing." GEOPHYSICS 67, no. 5 (September 2002): 1532–41. http://dx.doi.org/10.1190/1.1512749.

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We develop a method of 3‐D magnetic anomaly inversion based on traditional Tikhonov regularization theory. We use a minimum support stabilizing functional to generate a sharp, focused inverse image. An iterative inversion process is constructed in the space of weighted model parameters that accelerates the convergence and robustness of the method. The weighting functions are selected based on sensitivity analysis. To speed up the computations and to decrease the size of memory required, we use a compression technique based on cubic interpolation. Our method is designed for inversion of total magnetic anomalies, assuming the anomalous field is caused by induced magnetization only. The method is applied to synthetic data for typical models of magnetic anomalies and is tested on real airborne data provided by ExxonMobil Upstream Research Company.
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41

Konstantaras, A., G. N. Fouskitakis, J. P. Makris, and F. Vallianatos. "Stochastic analysis of geo-electric field singularities as seismically correlated candidates." Natural Hazards and Earth System Sciences 8, no. 6 (December 18, 2008): 1451–62. http://dx.doi.org/10.5194/nhess-8-1451-2008.

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Abstract. The study of the Earth's electromagnetic field prior to the occurrence of strong seismic events has repeatedly revealed cases where transient electric potential anomalies, often deemed as possible earthquake precursors, were observed on electromagnetic field recordings. In an attempt to understand the nature of such signals, several models have been proposed based upon the exhibited characteristics of the observed anomalies, often supported by different mathematical models simulating possible generation mechanisms. This paper discusses a candidate Electric Earthquake Precursor (EEP) signal, accompanying the Kythira Mw=6.9 earthquake in Greece (occurred on 8 January 2006). Neuro-Fuzzy along with stochastic models are currently incorporated for the modelling and analysis of the recorded Earth's electric field. The results of the study indicate that the Neuro-Fuzzy model treats the observed possible EEP signal as an external additive component to the recorded Earth's electric field, while the stochastic TARMA models accurately represent the recorded electric signals in both the time and the frequency domains. The complementary findings of both methodologies might potentially contribute to the future development of a more accurate and generalized framework for the efficient recognition and characterization of possible EEP's.
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42

Wac-Wlodarczyk, A., R. Goleman, D. Czerwinski, and T. Gizewski. "Mathematical models applied in inductive non-destructive testing." Journal of Magnetism and Magnetic Materials 320, no. 20 (October 2008): e1044-e1048. http://dx.doi.org/10.1016/j.jmmm.2008.04.179.

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43

Vikharev, D. Yu, and N. A. Rodin. "Model of implicit pole electric machine based on mathematical formulation of magnetic field in air gap." Vestnik IGEU, no. 6 (December 28, 2021): 27–37. http://dx.doi.org/10.17588/2072-2672.2021.6.027-037.

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When modeling transient processes in electric power systems, the issue of designing reliable models of electrical machines is of great interest. The most difficult task is to design the models of synchronous and asynchronous machines. The purpose of the project is to develop mathematical models of synchronous and asynchronous machines based on a generalized model of an implicit-pole machine that considers the change of rotor speed, geometric shapes, and the type of rotor and stator windings. Methods of mathematical modeling of electromagnetic fields in the air gap based on Maxwell equations and methods of the theory of electrical circuits are applied. A system of nonlinear differential equations is considered as a mathematical model of a generalized implicit-pole machine. The key assumption made is the high magnetic permeability of the stator and rotor cores. Technical data of real electric machines have been used for verification. Mathematical models of an implicit pole synchronous machine and an asynchronous machine with a phase rotor have been developed. These models can be used to analyze transient processes in the aggregate without dividing them into electromagnetic and electromechanical ones. The novelty of the models is the fact of non-sinusoidal distribution of the magnetic field in the air gap, various types of multiphase AC windings and rejecting the principle of constant rotation frequency at the time step of the simulation. The proposed mathematical models can be used to solve design problems, to analyze the modes of electric power systems, the operation of relay protection and automation of electric power facilities, and emergency automation. In the future, the equations that consider the influence of the damper circuits and the peculiarities of the windings will be added to the developed mathematical models. The purpose of further research is to develop models of salient-pole synchronous machines and asynchronous machines with a squirrel-cage rotor.
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44

Chang, Ya-Chiao, Richard Woollam, and Mark E. Orazem. "Mathematical Models for Under-Deposit Corrosion." Journal of The Electrochemical Society 161, no. 6 (2014): C321—C329. http://dx.doi.org/10.1149/2.034406jes.

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45

Jia, Zirui, and Chongxin Liu. "Fractional-Order Modeling and Simulation of Magnetic Coupled Boost Converter in Continuous Conduction Mode." International Journal of Bifurcation and Chaos 28, no. 05 (May 2018): 1850061. http://dx.doi.org/10.1142/s021812741850061x.

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By using fractional-order calculus theory and considering the condition that capacitor and inductor are naturally fractional, we construct the fractional mathematical model of the magnetic coupled boost converter with tapped-inductor in the operation of continuous conduction mode (CCM). The fractional state average model of the magnetic coupled boost converter in CCM operation is built by exploiting state average modeling method. In these models, the effects of coupling factor, which is viewed as one generally, are directly pointed out. The DC component, the AC component, the transfer functions and the requirements of the magnetic coupled boost converter in CCM operation are obtained and investigated on the basis of the state averaged model as well as its fractional mathematical model. Using the modified Oustaloup’s method for filter approximation algorithm, the derived models are simulated and compared using Matlab/Simulink. In order to further verify the fractional model, circuit simulation is implemented. Furthermore, the differences between the fractional-order mathematical models and the corresponding integer-order mathematical models are researched. Results of the model and circuit simulations validate the effectiveness of theoretical analysis.
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46

Korte, Monika, and Mioara Mandea. "Geopotential field anomalies and regional tectonic features – two case studies: southern Africa and Germany." Solid Earth 7, no. 3 (May 9, 2016): 751–68. http://dx.doi.org/10.5194/se-7-751-2016.

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Abstract. Maps of magnetic and gravity field anomalies provide information about physical properties of the Earth's crust and upper mantle, helpful in understanding geological conditions and tectonic structures. Depending on data availability, whether from the ground, airborne, or from satellites, potential field anomaly maps contain information on different ranges of spatial wavelengths, roughly corresponding to sources at different depths. Focussing on magnetic data, we compare amplitudes and characteristics of anomalies from maps based on various available data and as measured at geomagnetic repeat stations. Two cases are investigated: southern Africa, characterized by geologically old cratons and strong magnetic anomalies, and the smaller region of Germany with much younger crust and weaker anomalies. Estimating lithospheric magnetic anomaly values from the ground stations' time series (repeat station crustal biases) reveals magnetospheric field contributions causing time-varying offsets of several nT in the results. Similar influences might be one source of discrepancy when merging anomaly maps from different epochs. Moreover, we take advantage of recently developed satellite potential field models and compare magnetic and gravity gradient anomalies of ∼ 200 km resolution. Density and magnetization represent independent rock properties and thus provide complementary information on compositional and structural changes. Comparing short- and long-wavelength anomalies and the correlation of rather large-scale magnetic and gravity anomalies, and relating them to known lithospheric structures, we generally find a better agreement in the southern African region than the German region. This probably indicates stronger concordance between near-surface (down to at most a few km) and deeper (several kilometres down to Curie depth) structures in the former area, which can be seen to agree with a thicker lithosphere and a lower heat flux reported in the literature for the southern African region.
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47

Scheglevatych, Roman, and Anton Sysoev. "STUDY ON NEURAL NETWORK MODEL TO DETECT ANOMALIES IN DATASETS." Applied Mathematics and Control Sciences, no. 1 (April 14, 2021): 23–40. http://dx.doi.org/10.15593/2499-9873/2021.1.02.

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Digitalization of various spheres of economic and social life is accompanied by the emergence of large amounts of data, processing of which is necessary to identify certain dependencies, build models of processes and systems. The study is devoted to the development and research of a mathematical model for the classification of data on medical care in the medical organization of Lipetsk region. As inputs there were used indicators of medical care, divided into five groups (data describing patient; data describing the medical organization in which the care was provided; indicators of the disease; data on health employee that assisted; indicators characterizing the specific features of the patient's visits to a particular specialist). The volume of records on which the study was conducted is more than one million records of the facts. The purpose of the study is to propose models and approaches for identifying erroneous records, as well as cases of falsification. The paper presents a statement of the binary classification problem. Anomaly detection refers to the problem of finding data that does not correspond to some expected process behavior or indicator that occurs in the system. When building systems for detecting anomalous observations, much attention must be paid to the model underlying the system. The study is devoted to the construction of a model for detecting anomalous values of a fixed indicator based on a combination of an isolation forest algorithm to estimatie the observation anomaly index and the subsequent application of a neural network classifier. The study contains the results of computational experiments to determine the threshold value for dividing records into classes of anomalous observations and data that do not have signs of abnormality. To evaluate which factors should be passed to the input of the neural network classifier (in order to increase the time efficiency of data processing), the approach to the reduction of the neural network model based on Sensitivity Analysis was proposed. The classical approach when considering the sensitivity of systems is to find the sensitivity by the parameter of the system under study, however, there is also a direction of Sensitivity Analysis that involves using its factors as the estimated parameters of the system. The proposed approach is based on applying Analysis of Finite Fluctuation. This analysis is based on replacing the mathematical model of the dependence of the system output on factors with a model of the dependence of the finite fluctuation in output on the finite fluctuations of factors. In Mathematical Analysis such a structure is known – this is Lagrange mean value theorem. The approach allows us to determine the values of the so-called factor loads. The paper presents a new approach to averaging the obtained values of factor loads and constructing interval characteristics for their estimation. A study of the stability of the proposed procedure for calculating the sensitivity coefficients of the model is presented.
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Yigui, Lionel Cedric, Theophile Ndougsa-Mbarga, Arsène Meying, and Olivier Ulrich-Igor Owono-Amougou. "Detection of sub-surface fractures based on filtering, modeling, and interpreting aeromagnetic data in the Deng Deng – Garga Sarali area, Eastern Cameroon." Open Geosciences 14, no. 1 (January 1, 2022): 646–62. http://dx.doi.org/10.1515/geo-2022-0357.

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Abstract The aeromagnetic anomalies existing in the Deng Deng – Garga Sarali region in Eastern Cameroon were filtered for a structural study of the region’s subsoil. This study presents the results of lineaments and fractures extracted by aeromagnetic image processing methods and compared with scientific data to obtain potential terrain models in the study area. The methodological approach used is based on the filtering of aeromagnetic image by using the analytical signal, the Euler deconvolution, and 2D3/4 modeling, to establish the maps of the lineaments and faults of the study area and their characteristics, and also to propose three models from three previously chosen profiles. Analytical signal and Euler deconvolution techniques have been applied to aeromagnetic anomalies to highlight the relationship between the depth and the source of magnetic anomalies, two parameters whose importance in geoexploration and modeling of the body is essential. We identified the potential contacts by interpretation of the deep Euler anomalies, these are highlighted on the basis of a certain similarity between the maps of the total magnetic field, the map of the analytical signal, the map of the maxima of the gradient horizontal, and geological map. Euler’s map of solutions correlates well with the edges of certain superficial and deep causative bodies.
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Eppelbaum, Lev V. "Quantitative interpretation of magnetic anomalies from bodies approximated by thick bed models in complex environments." Environmental Earth Sciences 74, no. 7 (June 23, 2015): 5971–88. http://dx.doi.org/10.1007/s12665-015-4622-1.

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Cooper, G. R. J. "An improved terracing algorithm for potential-field data." GEOPHYSICS 85, no. 5 (September 1, 2020): G109—G113. http://dx.doi.org/10.1190/geo2019-0129.1.

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Although the boundaries between geologic units with different physical properties are usually quite distinct, the potential-field anomalies associated with them are relatively smooth, particularly for deeper bodies. The terracing filter has been introduced to sharpen anomaly edges and to produce regions of constant amplitude between them, mimicking geologic units on a geologic map. The boundaries between the pseudogeologic units are defined by the zero contour of the Laplacian function. Unfortunately, this can result in the domains of terraced anomalies extending far from the original location of the causative body, producing an image that poorly represents the geology. I have determined that the use of the mathematical shape index of the anomalies, rather than their Laplacian, produces a much more geologically realistic result. The effect can be controlled as desired using a threshold parameter. I evaluate the benefits of the method on gravity and magnetic data from southern Africa.
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