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Using gray theory established entropy weight and gray association model in analyzing the mostly infection factors of coal and gas outburst, entropy theory was used to calculate the weights of contamination. Analysis of sample data, in accordance with the order of gray correlative degree, it is found out the closest relations with the outstanding master factors to identify the most likely sensitive indicators to improve the accuracy of coal and gas outburst forecast prominently.

The eletrodeposition nano-TiO2/Ni composite coating on AZ91PH Mg alloy was prepared using the nano-TiO2 as the second phase particles. The corrosion resistance of the composite coating was measured by the static immerging corrosion test and the polarization curve test. The result shows that the corrosion resistance of the composite coating was better than that of Mg alloy. The corrosion resistance of the composite coating was optimal when the content of nano-TiO2 in the plating solution was 10g/l-15g/l.

The Ni-SiO 2 nano-composite coatings were fabricated by electrodeposition on the AZ91HP magnesium alloy surface, in which nano-SiO 2 was chosen as the second-phase particulates. The microstructure was observed by SEM, the microhardness was measured by micro-density tester and the wear resistance was estimated by M-200 type block-on-wheel dry sliding frication and wear tester. The results indicate that the Ni-SiO 2 nano-composite coatings with uniform crystalline, dense structure can be obtained on AZ91HP magnesium alloy. The interface morphology shows that the combination between the nano-composite coatings and magnesium alloy is fine. The maximum value of microhardness reaches HV367 when the content of nanoparticles is 10 g/L, however, the microhardness of the pure nickel coatings is HV274 and the hardness of magnesium alloy only is HV82.7. The frication and wear experiments reveal that the wear resistance of nano-composite coatings are improved obviously compared to magnesium alloys and pure nickel coatings, which are induced by dispersive strengthening effect and grain refining effect. The main wear mechanism of nano-composite coating is abrasive wear, the wear mechanism of magnesium alloys is adhesion wear, and that of pure nickel coating is exfoliation wear, respectively.

Phase-shifting reactor (PSR) can be used to solve the harmonic problems caused by rectifiers. In this paper, according to the active power balance principle, the relationships among the DC current of the loads, the currents of power supply side, and the capacity of core limb are built, the product specification of winding and core are obtained. Meanwhile, the coupled field-circuit method based on Simplorer and Maxwell, and the circuit method based on MATLAB/Simulink are discussed by the simulation of the 6-phase rectifier system. The results show that the designed PSR meets the requirement well, and suppresses the harmonic of power supply side effectively.

A 3-dimensional electromagnetic-thermal numerical simulation of cold crucible levitation melting method considering surface-to-surface heat radiation is performed by adopting finite element method. Direct area integration method and hemi-cube method are adopted to calculate the surface-to-surface heat radiation separately. Results of considering surface-to-surface heat radiation are compared with those considering surface-to-ambient heat radiation, and neglecting heat radiation. The temperature difference between surface-to-ambient and surface-to-surface is relatively small, hence it is accurate enough to take surface-to-ambient heat radiation into consideration only for the calculation of temperature distribution of EMCC melting method.

Rectifier transformer is typical ac-dc converter for improving power quality by reducing the harmonic in ac mains and ripples in dc output. The design of rectifier transformer is difficult because it originates from the experience of designers. So a designer who is lack of experience would result in a waste of material and cost. In order to reduce the manufacturing cost of rectifier transformer, this paper employs the Genetic algorithm (GA) to optimize the size of iron core which is a main component of rectifier transformer. Three parameters are selected as optimization variables and the target of the optimization is to minimize the weight of iron core. The result shows that the weight of the iron core drops down greatly compared with a rectifier transformer which is designed by the traditional empirical formula. Finally, the simulation of optimization shows that the function of rectifier transformer is also achieved.

The short-circuit impedance calculation of CRT is especially important to the establishment of equivalent circuit and analysis of operating characteristics. The paper reveals the intrinsic link between short-circuit impedance and equivalent circuit inductance by mathematical formula, and it elaborates three different methods to calculate short-circuit impedance, respectively the formula method, which calculates short-circuit impedance directly and easily; self and mutual impedance analytical method and ANSYS finite-element method, which calculate short-circuit impedance through the self and mutual inductance indirectly and have no geometric space restrictions to the windings. Then, an example is given to show that the results of these three methods are consistent, so these methods can be rationally chosen according to their own characteristics and the actual situation.