Improvement in Bending Strength of Silicon Nitride through Laser Peening

This study aimed to improve the bending strength and reliability of ceramics using laser peening (LP). In the experiment, LP without coating (LPwC) and with coating (LPC) were applied to silicon nitride (Si₃N₄) under various conditions. The surface roughness, residual stress, and bending strength were then measured for the non-LP, LPwC, and LPC specimens. The results show that the LPwC specimen had a greater surface roughness but introduced larger and deeper compressive residual stress when compared with the non-LP and LPC specimens. In addition, the bending strength of the LPwC specimen was higher and scatter in bending strength was less compared with the non-LP and LPC specimens. This may be attributed to the transition of the fracture initiation point from the surface to the interior of the LPwC specimen because of the compressive residual stress introduced near the surface. Thus, it was demonstrated that the application of LP is effective in improving the strength and reliability of ceramics.

Relation between diet and protozoal population in the rumen

1. Four feeding trials were made to investigate relations between diet and protozoal population in the rumen.

2. When a ration containing no concentrate was used, the number of entodiniomorphs decreased rapidly. The number of entodiniomorphs increased with the amount of concentrate. Rice straw, which was used as a sole source of roughage, was not always necessary for protozoa to survive in the rumen.

3. The type of diet affected the holotrich population to a much smaller extent than the entodiniomorph population.