Junhua Wang

Computer electromagnetic radiation carcinogenic doses based on Monte Carlo algorithm

With the popularity of computer, people currently use computers more and more frequently, and the human being surrounded by ubiquitous electromagnetic field. Therefore, people pay increasing attention to the harm of electromagnetic wave antennas to the health of human body. Computer electromagnetic radiation carcinogenic doses was studied through Monte Carlo algorithm. Simulation calculation was conducted on the electromagnetic dose absorbed by head in the near field of computer through Monte Carlo procedure Geant4 and simulation model of the human body, and from the aspects of radiation flux and the effective dose of human body. Besides, the SAR distribution of the human body exposed to far field of mobile communication base station antenna and human body head exposed to near field of mobile communication base station antenna was explored when radiation system launched at peak power. Besides, the calculated results were compared with existing international and domestic hygiene standards.

Optimization design of wireless charging system for autonomous robots based on magnetic resonance coupling

Wireless charging is the key technology to realize real autonomy of mobile robots. As the core part of wireless power transfer system, coupling mechanism including coupling coils and compensation topology is analyzed and optimized through simulations, to achieve stable and practical wireless charging suitable for ordinary robots. Multi-layer coil structure, especially double-layer coil is explored and selected to greatly enhance coupling performance, while shape of ferrite shielding goes through distributed optimization to guarantee coil fault tolerance and cost effectiveness. On the basis of optimized coils, primary compensation topology is analyzed to adopt composite LCL compensation, to stabilize operations of the primary side under variations of mutual inductance. Experimental results show the optimized system does make sense for wireless charging application for robots based on magnetic resonance coupling, to realize long-term autonomy of robots.

Improved FEM for distribution network cables rating using multiple forgetting factors least-square

Complicated surroundings of distribution network cables make it difficult to compute maximum ampacity according to actual operations. However, single numerical method for cable rating causes complex computation load which is not suitable for ampacity dynamic adjustment. This paper deals with the contradiction between simplicity and accuracy of the distribution network cables rating. A novel approach with the combination of an Improved Finite Elements Model (IFEM) and Multiple Forgetting Factors Least-Square (MFLS) for distribution network cables rating is proposed. One of key boundary conditions, heat dissipation coefficient is corrected dynamically in the IFEM to improve the accuracy of boundary calculations, which shows better performance compared with the classical FEM and the IEC Standard. In addition, the proposed method capitalizes on the power of MFLS method to attain the maximum ampacity with a lower computation load while the conductor temperature reaches prescribed value instead of iterations. M...

Magnetic shielding structure optimization design for wireless power transmission coil

In order to improve the performance of the wireless power transmission (WPT) system, a novel design scheme with magnetic shielding structure on the WPT coil is presented in this paper. This new type of shielding structure has great advantages on magnetic flux leakage reduction and magnetic field concentration. On the basis of theoretical calculation of coil magnetic flux linkage and characteristic analysis as well as practical application feasibility consideration, a complete magnetic shielding structure was designed and the whole design procedure was represented in detail. The simulation results show that the coil with the designed shielding structure has the maximum energy transmission efficiency. Compared with the traditional shielding structure, the weight of the new design is significantly decreased by about 41%. Finally, according to the designed shielding structure, the corresponding experiment platform is built to verify the correctness and superiority of the proposed scheme.

Research of acoustic vibration technique in online defects detection in porcelain post insulator

High voltage porcelain post insulator is one of the most important facilities in power plant and substation in the procedure of generating and transmitting electric energy which is used to hold up the electric transmission line as support bracket and insulate high voltage, when deteriorated or cracked it will pose a serious threat to the normal operation of power system.