<正>采用动态热机械分析对-130～130℃范围内不同含水率的竹材动态力学性能进行了研究。结果表明：在-130～130℃的范围内，湿热作用下的竹材动态力学性能表现为负效应，湿热作用使储能模量降低，玻璃态转变点也随着含水率的增加而降低。竹材在含水率为10%和34%时的玻璃化转变点及损耗因子分别为30.5℃、0.02和10.61℃、0.04。

The impact of precommercial thinning (PCT) on tree growth and stem quality in jack pine was examined. The study was based on a PCT trial established in 1966 in New Brunswick, Canada. Three thinning intensities, 1.22 m×1. 22 m (A), 1. 52 m×1.52 m (B), 2.13 m×2.13 m (C), and a control stand were studied and a total of 154 sample trees were collected from the trial. Mortality in jack pine stands decreased from 67.6% to 32.7% with increasing PCT intensity from A to C. With increasing thinning intensity, tree diameter, merchantable stem heights and volumes, stem taper, branch diameter, and total lumber volume recovery per tree increased. Yet, only the most intensive thinning intensity (C) showed a significant effect on total tree height and crown development. PCT increased clear stem length, yet had no significant effect on wood density.