It was found that GaN layer was multicrystal with rough surface when low-temperature nucleation layer was not used.

In this paper, the source of the background carrier in GaN buffer layer, the mechanism of C-V measurement, correlation between the buffer leakage current and different nucleation layer of AlGaN/GaN heterostructure and inhibition carrier of the GaN buffer background by high-temperature AlN interlayer are studied.

The relations between the buffer leakage current and the characteristics of nucleation layer of AlGaN/GaN heterostructure have been obtained by comparative study of depletion capacitance of C-V characteristics in GaN-based heterostructure.

Study on Diagnosis and Assessment Technology of Stress Wave Tomography in Old and Famous Trees;

According to the projects, the three dimension images of internal structures were reconstructed by computed tomography technique.

X-ray tomographic imaging with a straight-line trajectory scan,which has advantages of high speed,no overlapping and relatively low cost,has a great future in potential applications for fast security inspection and large-object scanning.

X-ray tomographic imaging with a straight-line trajectory scan, which has advantages of high speed,no overlapping and relatively low cost,has a great future in potential applications for fast security inspec- tion and large-object scan.