It is sure that there are a lot of subgrains in some sections of the tube, which is the basic cause of bringing about that the tube colour turns into the black, through the investigation and the simulation test to the macrostructure characteristics of the tube, the fonnation mechanism about the subgrains and the methods to eliminate them are explained.

It was shown that the subgrains are well formed and the size decrease withincreasing of rolling pass.

GaN epilayer grown on single buffer layer has poor quality which were investigated by double-crystal X-ray diffraction (DCXRD) and transmission electron microscope (TEM), it can be seen that there are dislocations, inversion domains and sub-grains, while just low density dislocations can be seen in GaN epilayer.

At the same time, the subgrain size and microstrain were calculated using X-ray diffraction profile analysis method.

The cemented carbide inserts made of sub-micron grained carbides tungsten and 13% cobalt were used on 81/2XA537 three-roller bits.

Numerical simulation of scattering of electromagnetic waves from the subcylindrical particles;