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As the surface shape of a reflection mirror is different from the target shape at the end stage of the grinding process,and the profilometers and common interferometers can not measure the surface error exactly,this paper proposed a method to measure the large aperture aspheric surface by using a Shack-Hartmann Wavefront Sensor(SHWS) with a large dynamic range and high precision.The principle of the measuring system for SHWS was researched,its measuring errors were analyzed and a corresponding data processing software was compiled.Using a simulation reference file,a hyperboloid reflection mirror with a diameter of 350 mm was tested by the SHWS.Results indicate that the PV and RMS of the surface error are 0.388λ and 0.043λ,respectively(λ=632.8 nm).In order to testify the measurement result,the mirror is also measured by an interferometer with a null compensator.Comparing the two testing results,the PV and RMS of the deviation are 0.014λ and 0.001λ,respectively,which proves the feasibility of measuring large aperture aspheric surfaces by SHWSs.

In order to test large and off-axis aspheric surfaces without the aid of other null optics,a new method subaperture stitching interferometry(SSI) is introduced.The basic principle of the technique is analysed,and the synthetical optimization stitching model and effective stitching algorithm are established based on homogeneous coordinates transformation and simultaneous least-squares method.The stitching software and prototype for testing of large aspheres by SSI are devised and developed.An off-axis asphere with the aperture of 376×188 mm2 is tested by this method.For the comparison and validation,the asphere is also tested by null compensation,the synthesized surface map is consistent to the entire surface map from the null test,and the difference of PV and RMS error between them is 0.047λ and 0.006λ,respectively.So it provides another quantitive measurement for testing large aspheric surfaces and off-axis aspheres besides null-compensation.

Take an experimental middle school of rural-distance education projects in the west area of China as an example, The paper constructs and implements a rural-distance education model based on Moodle. Although the study found that the model does not significantly improve the achievement of students, it can reduce the gap anong the students and improve students' interest in learning, and it can also save expenses for school.

In this paper, based on the boundary element method, the cavitation shape of the three-dimensional slender at a small attack angle in a steady flow is simulated through the iterative method, while Dirichlet boundary conditions and Neumann boundary conditions are satisfied in cavitation and slender respectively. The linear triangular elements are adopted and the control points are arranged in grid nodes. The velocity potential for cavity surface is determined through an iterative method in a local orthogonal coordinate system, and then the distribution of cavitation thickness can be determined by the boundary integral equation. To prevent the remeshing operation in the iterative process, the Lagrange interpolation method is used to determine the thickness at the end of cavity. The numerical results are in good agreement with the experimental data. The influence of those on cavitation shape of the three-dimensional slender are investigated, such as cavitation number, attack angle and cone angle. Numerical results show that the cavitation shape of the three-dimensional slender is asymmetric at an attack angle and is analogous to the cavitation stacking in the lee side. While with the decrease in the cavity number or the increase in the cone angle, the asymmetry for the cavity shape will be more serious.