Magnetic flux leakage (MFL) detection is one of the most popular methods of pipeline inspection. It is a nondestructive testing technique which uses magnetic sensitive sensors to detect the magnetic leakage field of defects on both the internal and external surfaces of pipelines. This paper introduces the main principles, measurement and processing of MFL data. As the key point of a quantitative analysis of MFL detection, the identification of the leakage magnetic signal is also discussed. In addition, the advantages and disadvantages of different identification methods are analyzed. Then the paper briefly introduces the expert systems used. At the end of this paper, future developments in pipeline MFL detection are predicted.
We present a new topological tensor current ofp-branes by making use of the φ-mapping theory. It is shown that the current is identically conserved and behave as δ( φ), and every isolated zero of the vector field φ(x) corresponds to a 'magnetic'p-brane. Using this topological current, the generalized Nambu action for multip-branes is given, and the field strength F corresponding to this topological tensor current is obtained. It is also shown that the 'magnetic' charges carried byp-branes are topologically quantized and labeled by Hopf index and Brouwer degree, the winding number of the φ-mapping.
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