Yan Weili

Adaptive simulated annealing for the optimal design of electromagnetic devices

From the application of simulated annealing to the optimal design of electromagnetic devices, it is usually found that its convergence speed is low. Based on the analysis for the iterative procedure of simulated annealing, adaptive simulated annealing is put forward, which has a higher convergence speed. When used to solve the optimization problem that arises from the optimal design of a 6 kV fuse-contactor and involves a multimodal objective function, adaptive simulated annealing can not only obtain the global optimal solution but also save 30 percent of the computation time taken by simulated annealing.

Eddy current interaction with a thin-opening crack in a plate conductor

In eddy current testing (ECT), a thin-opening crack in a plate conductor is frequently encountered. The eddy current field perturbation due to the crack may be described as the effect produced by an equivalent current dipole layer located on its surface. The dipole density may be found by solving a boundary integral equation. In this paper, formulas of the electric dyadic Greens function for a limited thickness plate are derived. Following a moment method scheme, numerical predictions are made for benchmark models of ECT for steam generator. The eddy current perturbations due to the cracks are calculated. The probe impedance changes are also evaluated and are compared with experiments, and good agreement is found.

Using wavelet neural networks for the optimal design of electromagnetic devices

A feedforward neural network based on the wavelet transform which can be applied to the approximation of complex nonlinear functions is discussed. A wavelet neural network can establish an exact model through a self-adaptive procedure by learning input/output maps from the training sets which are generated by finite element analysis. The structure of the network can be definitely developed, and the learning speed is increased. We have applied it to the optimization design of an AC vacuum contactor with a DC exciting electrical circuit and obtained a satisfactory scheme.

Multi-frequency EIT Hardware System Based on DSP

Electrical impedance tomography (EIT) is a new functional imaging technique in the biomedical engineering. A multi-frequency hardware EIT system based on digital signal processor (DSP) has been developed, and the system also has been designed using modular structure. Some experiments in vitro tissue are done and their images are generated with the filtered back-projection algorithm using this system in real time. The results show that this system is feasible, stable, convenient and extended.

Finite element dynamic analysis for the electromagnet of AC contactor

The finite element analysis of the dynamic characteristics for the electromagnet of an AC contactor during its starting process is discussed. This is a coupled problem of electromagnetic fields, transient circuits, and mechanical movement. The parameter coupled method is adopted to resolve differential equations. This method is applied to design a typical 32 A AC contactor. >

Research and analysis on the effect of joint angle on EMG in thigh muscles

In this paper the effect of joint angle on EMG is analyzed qualitatively for finding the controlling mechanism of knee joint swing velocity and flexion angle. Wavelet transformation (WT) and wavelet packet transformation (WPT) are used to eliminate the noises of surface EMG sampled from the lower limb during the subjects of study walked normally on the flat. By comparing the denoise result, WPT wins an advantage of WP with the same threshold. And the result shows that if the suitable scale and the threshold are selected, the high-frequency noises can be eliminated effectively. According to the characteristic of WPT, the motion features are extracted during the stance phase and the swing phase using the WPT. The figures show the fine extraction result in this paper. While discrete Fourier transform (DFT) illustrates that the primary frequency band is from 20Hz to 200Hz whether flexion or extend.

DE2D interactive software package for 2D magnetostatic, electrostatic and Eddy current field computations

A 2D field computer software package DE2D has been developed. It can be used for magnetostatic, electrostatic and eddy current field computations. The package runs in mini or micro-computers. The data preparation is greatly simplified when configuration periodicity is fully used.

Event-Related Potential Studies of Attention to Shape Under Different Stimuli Tasks

Event-related potential (ERP) is a basic,non-invasive method of electrophysiological investigation. It can be used to assess aspects of human cognitive information processing. Recordings of ERPs from normal individuals have played an increasingly important role in our understanding of the mechanisms of attention. This paper focused on studies of specific cognitive subsystems such as visual pathway and attention with ERPs in different kinds of visual stimuli tasks using a 128-channel EEG system. The results have showed all potential amplitude of 19 electrodes varied largely with increasing stimuli task complexity and the P100, N200, P300 are elicited.

Modeling of electromagnetic environment of transmission lines for studying effect of ELF-EMF

By combining two groups of three-phase power lines, a modeling that can induce power frequency electromagnetic fields has been presented. Charge simulation method and Biot-Savart law have respectively been adopted to compute the three-dimensional electric and magnetic fields in exposed environment of the modeling. Simulations indicate that the intensity of electric field can reach up to 5 kil-volt per meter (kV/m) at ground level, and the magnetic flux density can amount to 15 microtesla (microT). A comparison has been conducted between the environments that mice and human bodies are exposed to. The paper concluded that the modeling can be utilized in studying white mice simultaneous exposure to power frequency electric field and magnetic field emitted from transmission lines.

Finite element analysis for eddy current in DC electromagnet during its closing process

A simplified eddy current model is used to analyze the effect of eddy current in a DC electromagnet core on the closing movement time of the armature. The dynamic characteristic of the DC electromagnet is then calculated by means of the finite-element method. The proposed eddy current model is shown to be simple and effective. >