No abstract

There has been a decline in tree growth since the operation of factories at Pinus thunbergii forests around a petrochemical industrial complex in Korea. This study was carried out to investigate the effects of air pollution on tree ring width and ring density of Pinus thunbergii. Soft X-ray densitometrieal method was used. Decline of ring width was the highest during 3 years immediately after the operation of factories. The percentage of decrease was almost bigger immediately after operation as compared with before. Maximum density (MAXD), and the difference (DD) between maximum density and minimum density (MIND) generally decreased since operation of factories, while minimum density increased in the beginning of operation of factories. There was a significant correlation between ring width and high temperature, and precipitation in the beginning of growing season, respectively. There was also a negative correlation between annual mean concentration of SO2 and ring width at 5% level (r = --0.627*). It is suggested that the decline of ring width after operation of factories was due to compound factors of air pollution and climate. The effect of other factors should be still more studied.

No abstract

No abstract

Superplastic behavior of powder-metallurgy (PM) processed 7475 +0.7Zr AI alloy having a fine grain size of 2 I.tm was investigated. Strain-rate-change tests were conducted at elevated temperatures to examine the strain rate-stress relations. The deformation behavior was analyzed by assuming the presence of threshold stress for grain boundary sliding. After the threshold-stress compensation, the plastic flow was found to correlated well with lattice self-diffusion in pure aluminum. A maximum tensile elongation of up to 1000% was observed at a very high strain rate near 10Is 1 and 515~ A deformation map was constructed to identify the dominant deformation mechanism for the PM alloy. It was the grain boundary sliding controlled by lattice diffusion in aluminum. Evidence of short fiber or whisker-like formation were observed on the fractured samples over a wide range of temperature.