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In order to study the characteristics of the wake magnetic anomaly when multiple ships are sailing at the same time, based on the basic theoretical knowledge of ship wake, the waveform, velocity, and distribution of the induced magnetic field of the ship wake were studied, and the variation characteristics and distribution patterns of the induced magnetic field of the multi-ship wake were obtained. By taking the formation of three ships as an example, the distribution of the induced magnetic field and the distribution of the magnetic field in the directions of x and y during the movement of the ships were analyzed. The magnetic field distribution characteristics of the wake formed when the three ships sail at the same time were solved, and the abnormal induced magnetic field generated during various ship combination operations was analyzed. The experimental results obtained from the simulation were consistent with the existing measurement results. APP Design tools were used for magnetic anomaly simulation system software development of multi-ship wake. The system not only could accurately, intuitively, and quickly simulate and set the magnetic induction intensity and variation patterns of the wake of three ships in any direction but also had the advantages of simple operation and cost saving, which provided a theoretical reference and a more effective simulation platform for ship wake experiment.

Aiming at the difficulty in detecting concealed geological isomers using conventional geophysical method in ultra-wide coal working face, the electromagnetic response mechanism of mine transient electromagnetic (TEM) perspective detection with opposite side emission and reception is revealed in this study. The electromagnetic field diffusion characteristics, data influence mechanism and detection capability of transient electromagnetic perspective detection technology are studied in detail by means of theoretical research, numerical simulation and analysis of measured data. The results show that the transient electromagnetic field diffusion of the full-space elongated emission loop is different from that of the half-space electromagnetic field diffusion due to the boundary between ground and air. In the full-space state, the extreme value of the induced electromotive force (EMF) is located in the center of the emission coil for a long time, which cannot be interpreted directly by using the ground ‘smoke ring effect’. The early transient electromagnetic perspective data transmitted and received on the opposite side are mainly affected by the primary magnetic field and have high resolution and detection ability of left and right low resistance anomalies. The late data and the same-side transmitting and receiving data have the same generation mechanism, both them are formed by mutual induction and diffusion of secondary fields generated near the transmitting loop, and their resolution and detection ability are relatively weak. Compared with the transient electromagnetic method, this technology can distinguish the spatial position of the low-resistance anomaly relative to the transmitting loop and the receiving point by combining early and late data. The closer the low resistivity anomaly body is to the transmitter loop, the greater the impact on the early data received at the opposite side, and the impact time period of the late data increases, but the degree of influence is smaller. On the contrary, the closer it is to the receiving point in the roadway, the opposite the impact characteristics are. Therefore, the approximate position of the low-resistance anomaly body along the working face can be roughly determined. The transient electromagnetic perspective detection technology, which combines early and late data, can more accurately interpret the spatial information of hidden water inrush geological isomers which are inside and near the working face.

Magnetic nanoparticles can enhance the electrical and thermal conductivity of polymers, which are widely used in fields such as machinery, biomedicine, and energy storage. When a non-uniform magnetic field is imposed externally, the induced magnetic field cannot be ignored in the case of high Reynolds numbers. To explore the effects of magnetic nanoparticles on the unsteady flow and magnetic diffusion of viscoelastic fluid over the stretching sheet within the laminar boundary layer, the time distributed-order Maxwell constitutive equation was coupled with the momentum equation to establish partial differential equations for the velocity and magnetic diffusion of a 2D incompressible Maxwell magnetic nanofluid. Numerical analysis was performed with the finite difference method, and the velocity and the induced magnetic field distribution of the fluid within the boundary layer were analyzed by control of the magnetic nanoparticle type, the volume fraction and the magnetic parameter magnitude. The results show that, the velocity and induced magnetic field of the fluid are the largest in the case of Fe2O3 nanoparticles added to molten polymers, besides, the velocity and magnetic boundary layer thickness is the largest. With the increase of the Maxwell nanofluid relaxation time parameter, both the velocity and the magnetic diffusion will decrease. In addition, the velocity boundary layer thickness and the magnetic boundary layer thickness of the fluid decrease with the magnetic parameter. The larger the volume fraction of Fe3O4 nanoparticles is, the faster the fluid flow and the smaller the induced magnetic field will be. Therefore, the study of the addition of magnetic nanoparticles to polymers in non-uniform magnetic fields gives referential data for improving material properties. [ABSTRACT FROM AUTHOR]