Papers by Author: Hui Zhou

Abstract: A new quadrature signal generator based on Direct Digital Synthesis (DDS) algorithm for digital demodulation of MEMS gyroscope was proposed in this paper. To avoid quantization error, the dual-accumulator with signal-ROM structure was adopted. This signal generator was realized in FPGA chip, which could be quit compact to realize all digital demodulation in one chip. Simulations and tests of the generator were carried out. The test results demonstrate that the signal generator achieves high stability. The standard deviation of the frequency is 0.075Hz and the standard deviation of the amplitude is 0.037mV.

Abstract: Praseodymium doped KNbO₃ (KNbO₃:Pr) phosphors were synthesized by a facile solgel combustion method. Phase evolution, particle size and luminescent properties of the powders synthesized at various temperatures were investigated. Single-phase KNbO₃:Pr nanoscale particles were obtained at 600°C by directly crystallizing from amorphous precursors. The particle size of KNbO₃:Pr powders can be well controlled by varying the heat treatment temperature. Under the excitation of 450 nm, KNbO₃:Pr phosphors showed the well-known Pr³⁺ emissions associated with the 4f inter-level electronic transitions in Pr³⁺ ions.

Abstract: Based on the cellular automata of the plane truss structure, a 2D cellular automata model is presented to simulate the fracture of rock at meso-level. Cellular automata are made up of cell, states, lattice, neighbor and rule. Rock is divided into lattice in which each lattice point presents a cell. Each cell is assumed to connect with several cells, which are called as its neighbors, in virtue of truss elements. The truss elements can adopt some different simple local laws, i.e. constitutive law, which may be elastic or elastic-plastic and the simple fracture rule. It also can adopt different mechanical properties, which present their heterogeneity and anisotropy. This model can make full use of the advantages of cellular automata such as its intrinsic parallelism, localization and so on. In the meantime, as a powerful tool to analyze the nonlinear, complex system, cellular automata can be used to study the nonlinear, complex fracture process. The model is used to simulate the direct tensile of the rock plates, the complete fracture process and the stress-strain curves are attained which are accordance with the experiment.