Small and micro fractures are the most developed fractures in the buried hill reservoir, whose width and areal porosity are positively related.

There is a big difference in the percolation ability be-tween the microfracture and the matrix with that of former is 83 times as large as the latter.

Brazing quality and product reliability are both increased as using high frequency pulse microplasma arc heating process for assembly brazing of cathode and photoetching grid of electron tube.