Compacting process of fine powder is greatly affected by the aggregate structure of particles. According to the experiment in which several kinds of silicon nitrides in different partical shape and size were compacted...Compacting process of fine powder is greatly affected by the aggregate structure of particles. According to the experiment in which several kinds of silicon nitrides in different partical shape and size were compacted in uniaxialorientation, it is found that the volume compacting rate offorming body differs with the pressure. The aggregatestructure of each sample A, B or C was estimated by applying Cooper's equation to the analysis of the compacting process of each sample展开更多
The fresh snow density was observed with snow analyzer (Snow Fork) at Tianshan Station for Snowcover and Avalanche Research, Chinese Academy of Sciences from February 21 to March 5, 2009. Results show that fresh snow ...The fresh snow density was observed with snow analyzer (Snow Fork) at Tianshan Station for Snowcover and Avalanche Research, Chinese Academy of Sciences from February 21 to March 5, 2009. Results show that fresh snow density increases from the 5th h to the 291st h after the snowfall, with an average rate of increase of 4.0×10-4 g/(cm3·h) (R2 = 0.943). Analysis shows that fresh snow density is negatively correlated with the compac-tion rate of fresh snow (R2 = -0.960). Inversely, it is positively correlated with fresh snow viscosity (R2 = 0.896). In relation to meteorological factors, ground temperature rising at a depth of 40 cm is the major driving factor of snow density increase. The temperature increase in fresh snow layer and the decrease in depth hoar layer have the most prominent impacts on the snow density increase in the afternoon. Principal component analysis shows that the de-terminant factors of fresh snow density change can be grouped into 3 types as follows: 1) dynamic factor contributes about 69.71% to fresh snow density change, with a significant effect from the 5th h to the 106th h after the snowfall; 2) exogenous energy factor contributes about 20.91% to it, with a significant effect at the 130th h; and c) endoge-nous energy factor contributes about 9.38% to it, with a significant effect at the 130th h and the 195th h.展开更多
We report a simple approach to amplify Ti:sapphire femtosecond pulses to moderate energy levels by a chirped regenerative amplifier. The seed pulses are broaden naturally because of the material dispersion of system c...We report a simple approach to amplify Ti:sapphire femtosecond pulses to moderate energy levels by a chirped regenerative amplifier. The seed pulses are broaden naturally because of the material dispersion of system components in regenerative cavity. The off-focusing Ti:sapphire crystal avoids effectively the optical damage. It sustains amplification over a wavelength range from 775 nm to more than 810 nm with a birefringent filter and an oscillation bandwidth of 7.7 nm, and produces 2.1 ps chirped output pulse energy of 100 uJ at 1.1-mJ pumping energy. This system shows good performances in stability and efficiency with the benefits of two thin-film polarizers and TEMoo mode pumping laser.展开更多
文摘Compacting process of fine powder is greatly affected by the aggregate structure of particles. According to the experiment in which several kinds of silicon nitrides in different partical shape and size were compacted in uniaxialorientation, it is found that the volume compacting rate offorming body differs with the pressure. The aggregatestructure of each sample A, B or C was estimated by applying Cooper's equation to the analysis of the compacting process of each sample
基金Under the auspices of National R & D Project of Social Welfare, Ministry of Science and Technology Development, China (No. GYHY200706008, GYHY200806011)West Light Foundation of Chinese Academy of Sciences (No. RCPY200902)
文摘The fresh snow density was observed with snow analyzer (Snow Fork) at Tianshan Station for Snowcover and Avalanche Research, Chinese Academy of Sciences from February 21 to March 5, 2009. Results show that fresh snow density increases from the 5th h to the 291st h after the snowfall, with an average rate of increase of 4.0×10-4 g/(cm3·h) (R2 = 0.943). Analysis shows that fresh snow density is negatively correlated with the compac-tion rate of fresh snow (R2 = -0.960). Inversely, it is positively correlated with fresh snow viscosity (R2 = 0.896). In relation to meteorological factors, ground temperature rising at a depth of 40 cm is the major driving factor of snow density increase. The temperature increase in fresh snow layer and the decrease in depth hoar layer have the most prominent impacts on the snow density increase in the afternoon. Principal component analysis shows that the de-terminant factors of fresh snow density change can be grouped into 3 types as follows: 1) dynamic factor contributes about 69.71% to fresh snow density change, with a significant effect from the 5th h to the 106th h after the snowfall; 2) exogenous energy factor contributes about 20.91% to it, with a significant effect at the 130th h; and c) endoge-nous energy factor contributes about 9.38% to it, with a significant effect at the 130th h and the 195th h.
基金This work was supported by innovation foundation of Chinese Academy of Sciences and the National Natural Science Foundation of China under Grant No. 60078004. G. Cheng's e-mail address is guanghuacheng@163.com.
文摘We report a simple approach to amplify Ti:sapphire femtosecond pulses to moderate energy levels by a chirped regenerative amplifier. The seed pulses are broaden naturally because of the material dispersion of system components in regenerative cavity. The off-focusing Ti:sapphire crystal avoids effectively the optical damage. It sustains amplification over a wavelength range from 775 nm to more than 810 nm with a birefringent filter and an oscillation bandwidth of 7.7 nm, and produces 2.1 ps chirped output pulse energy of 100 uJ at 1.1-mJ pumping energy. This system shows good performances in stability and efficiency with the benefits of two thin-film polarizers and TEMoo mode pumping laser.
