In this thesis, the principles of optical pickup signal detecting and process system are analyzed in detail with emphases on the actuator magnetic circuit design and the computation of the magnetic induction intensity in working gap of the actuator.
The operating principle of single degree of freedom Permanent and Electronic Hybrid Magnetic System is introduced. A method of calculating PEHMS by using alternately permanent and electronic magnetic flux is put forward, and gain theory formula of magnetic induction intensity and magnetic suspension force of PEHMS, based on the principle of the mechanics, electromagnetism, electronics and dynamics.
The best impelled current of the electromagnetic iron was determined by experiments, and magnetic induction intensity in electromagnetic acoustic transducer(EMAT) testing steel pipe's defaults was calculated by ANSYS finite element software.
The experimental results indicate that its dynamic range is better than 70 dB with the nonlinearity less than ±5% and its noise equivalent magnetic flux density is 1.5μT. The sensor can be used to measure pulsed magnetic field.
The magnetic field of high speed maglev train mainly distributes in the small air gap between the train and the rail. The air gap magnetic field is composed by the steady magnetic field and alternationg magnetic field. The magnetic flux density is very great even to 1.2 T.
The magnetic induction of the perturbed field is proportional to the applied force.
However, it is shown that not all corrections to the magnetic induction of the EMF of the same order of magnitude are taken into account in the course of transformation from the model of aligned dipole to the model of inclined dipole.
For example, for a typical MHD device  with characteristic length 0.1 m of the working region, velocity 1 m/sec of the medium, and magnetic induction 1 T (the medium is molten sodium at temperature 330°C) the Alfvén number is A ～- 900.
It was found that the velocity and inclination of the Mach shock depend significantly on the vector of the magnetic induction in the initial state.
The system of MHD equations (the Euler equations with volume MHD momentumand energy sources and the magnetic induction equation) was solved using the stabilization method.
It has been shown that the quantum yield of the photochemical reaction of bromine replacement by the sulfo group in 1-bromo-2-hydroxynaphthalene decreases with an increase in the magnetic flux density.
(iii) The relative magnetic-field sensitivity of collector current is dependent on the applied magnetic flux density; moreover, the former grows in magnitude with decreasing flux density if this is sufficiently low.
This device is composed of a detector array with 32 pipe wall thickness sensors that employ a Hall element as the element for sensing the magnetic flux density, and it can be adapted to pipe diameters from ?400mm to ?650 mm.
The density of the line number is assumed to be proportional to the magnetic flux density.
The model involves the magnetic Schr?dinger equation with spatially variable magnetic flux density.