Papers by Author: Ying Xu

Abstract: The hole wall crushed and fractured zones length has been derived theoretically,and put forward the calculation formula of blasting crushing circle and radius of the corresponding fracture zone.Corresponding to the deep rock blasting parameters design on the basis of theoretical analysis,then lead to the reasonable parameters.These can provide certain reference design work for coal mine deep rock blasting parameters.

Abstract: In the absence of a three-phase power source, single-phase operation of three-phase induction motor used single-phase power source had a certain practical significance. In this paper, utilized symmetrical component method analysed the asymmetric circuit system of motor, will be voltage and current of the three-phase stator windings decomposed into positive, negative and zero sequence three groups symmetrical components. The theory is analyzed and the formula is deduced of capacitor phase shift method, solved the problem of starting torque, proposed to add starting capacitors and deduced the optimal value of starting capacitor. Finally, the single-phase operation of three-phase induction motor is simulated and verified by simulation software.

Abstract: Cadmium Selenide/Cadmium Sulfide (CdSe/CdS) core/shell quantum dots (QDs) in aqueous solution were prepared by solve-separate method using CdSe as core and mercapto-acetate acid as stabilizer and surfactants. The results of experiments indicate that the size of the CdSe/CdS QDs was about 5nm estimated by FE-TEM, which is accordant with that calculated from the XRD data by the Scherer equation after emendation. The QDs belong to the cubic structure (zinc blende) by XRD analysis. The intensity of luminescence of the quantum dots was greatly improved after the surface was coated with CdS shell. With increasing the time of refluence, the intensity of photoluminescence was promoted correspondingly. The excitation wavelength was 350nm, two emission peaks were clearly observed, the first high-energy peak was at 600nm and the second one located in 700nm. The first high-energy band was attributed to electron–hole recombination after relaxation and the second energy band was to deep traps in quantum-confined systems.

Abstract: Si₃N₄ based nanocomposites were prepared with nano-sized amorphous SiO₂ and Si₃N₄ powders by pressureless sintering method. The microstructures, phase composition, mechanical and dielectric properties of the nanocomposites were investigated. The scanning electrical microscope (SEM) photographs reveal that the grains are big and elongated. The X-ray diffraction (XRD) analysis shows that the main crystalline phase in the composites is Si₂N₂O formed during the sintering process. More β-Si₃N₄ phases were retained in the nanocomposites with the increase amount of the amorphous Si₃N₄ powders and no phase of SiO₂ were observed. The densities and the strength of the nanocomposites decreased with the increase of amorphous SiO₂ content. Despite low density, the flexural strengths of the composites reaches 220MPa and the ceramic has excellent dielectric properties with dielectric constant as low as 3.2-4.7 and dielectric loss in the range 2.6-3.9×10^-3.

Abstract: A new preparation method was developed to produce Si₃N₄-SiO₂-Si₂N₂O composites for broad band radome applications. The three-dimensional cross-linked polyphenylsiloxane (PPS) was used as an organic precursor. The composites obtained through react bonding between Si and the precursor powders in the stream of N₂ were examined. The conversion of the PPS polymer to the ceramic was examined by TG analysis and conventional X-ray diffraction (XRD) techniques. It was found that the ceramics contained a primary Si₂N₂O phase, some β-Si₃N₄ phase and a minor α-SiO₂ phase. Despite low density (1.7-2.0g•cm^-3), the flexural strengths of the composites reaches 195Mpa at room temperature. The ceramic has excellent dielectric properties with dielectric constants as low as 3.2-5.5.