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Numerical Calculation of Time-Domain Airborne Electromagnetic Response about Conductive Sphere Model

Author: GongYuanFeng
Tutor: ZuoYanJu
School: Jilin University
Course: Theory and New
Keywords: Conducting Sphere Dipole Source Electromagnetic Response Bessel Function Mixed Programming
CLC: P631.325
Type: Master's thesis
Year: 2010
Downloads: 148
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Abstract

AEM basic principle is the same with ground electromagnetic method,The only difference is that generally the airborne electromagnetic method launchers (without having to receive natural field emission device) and receiver on the aircraft, the pod or in the airplane’s nose, the two wing tips and tail cone . So many of the basic ground electromagnetic methods are applicable to AEM . AEM basic principle of measurement is based on the physics of electromagnetic induction。Its work can be divided into emission, electromagnetic induction and receive three parts. In the transmitter loop in the stability of the current suddenly cut off when transmitter loop current in a sudden change in the magnetic field will produce around,by the theory of electromagnetic induction。The magnetic field called the primary field. If it is a good conductor encountered deep underground, they will be generated in its internal excitation induced current. We call it the eddy current. As the secondary current of change over time, this resulted in around a new field, called the secondary magnetic field. Since the induced current good conductor of heat loss, the secondly magnetic field decay exponentially with time, forming a transient magnetic field. Secondary magnetic field comes mainly from good conductive ore body changes induced current; it contains a relationship with the ore geological information.China’s vast territory and natural resources and rich, but there are the more mountainous areas and terrain. These issues to the surface electromagnetic detection equipment brought great difficulties. Moreover, the current situation of China’s mineral resources and water resources is critical, how to effectively carry out the investigation is imminent. Airborne electromagnetic exploration methods can be in the forest, deserts, swamps, lakes, and residential areas and other areas of exploration work. In this study, the entire space under the sphere of air time domain electromagnetic response of conductive. Provide a theoretical basis for the actual investigation. Specific contents are as follows:1. By deriving from the classical electromagnetic theory as Maxwell’s equations, wave equation, we obtained the corresponding response of the magnetic dipole. And then we derived dipole field in the spherical conductor of the electromagnetic anomaly expression with numerical methods.2. Firstly, deriving from the spherical conductor. Airborne Time-domain electromagnetic anomaly expression Secondly, using Fourier analysis to the frequency domain expression means to transform the time domain expressions. Using the Bessel function of the continued fraction we can obtained the sphere response function. Not only the method is simple and fast, but also we can control the accurate easily.3. Using the above function , we calculated and discussed in different emission wave, pulse width of the emission parameters, different altitudes, flight distance and ball parameters such as the radius of the sphere conductivity .In particular, we are focused on the ramp down step pulse, triangle pulse, half-sine pulse waveform on the spherical conductor launch incentive which was exceptional. We introduced the airborne electromagnetic background field briefly. A showed the formula method and draw the two models of the background field curve. Transient electromagnetic response of the physical mechanism from a sphere to explain the sphere radius, the conductivity of the electromagnetic sphere and the corresponding impact of the law.4. A brief introduction that is C programming language and MATLAB mixed ,the idea is to speed up operations primarily speed, improve the algorithm efficient in order to reduce manpower and time. Also you can use some c language which has a much efficient algorithm in MATLAB.5. Using MATLAB GUI interface written procedures, so the calculation of different parameters of the electromagnetic corresponding relatively easy, the final will be prepared using MATLAB DEPLOYTOOL toolbox released from the MATLAB environment to run the program independently.This thesis completed conductive sphere model in time domain airborne electromagnetic response of numerical calculation, on the conductive sphere model of time domain airborne electromagnetic response of the study, as the outdoor field-testing provides a theoretical basis, for time domain airborne electromagnetic measurement system reference design.

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