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缝合泡沫夹芯结构复合材料VARTM工艺树脂充填模拟及验证 被引量:11
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作者 王科 赖家美 +2 位作者 鄢冬冬 黄志超 柳和生 《高分子材料科学与工程》 EI CAS CSCD 北大核心 2015年第11期124-129,共6页
采用"长条"模型代替泡沫中沿缝线方向树脂流动模型并对其等效渗透率及孔隙率进行计算;然后用PAM-RTM软件对缝合泡沫夹芯结构真空辅助树脂传递模塑成型(VARTM)工艺树脂充填过程进行数值模拟,最后建立了流动可视化实验装置对模... 采用"长条"模型代替泡沫中沿缝线方向树脂流动模型并对其等效渗透率及孔隙率进行计算;然后用PAM-RTM软件对缝合泡沫夹芯结构真空辅助树脂传递模塑成型(VARTM)工艺树脂充填过程进行数值模拟,最后建立了流动可视化实验装置对模拟结果进行实验验证。对比模拟与实验结果表明,模拟与实验完成整个充填过程的时间非常接近,并且树脂在预成型体中流动方式及在预成型体上、下面板流动状态的数值模拟与实验结果也非常地一致。故建立的"长条"模型及其相关参数的计算是合理的,可以用来准确地预测缝合泡沫夹芯结构VARTM工艺树脂充填过程。另外,树脂在上面板流动前沿在沿宽度方向较为统一,而树脂在下面板流动前沿呈现锯齿状,容易产生空隙及干斑等缺陷,影响制品的质量。 展开更多
关键词 缝合泡沫夹芯结构 真空辅助树脂传递模塑成型 复合材料 “长条”模型 PAM-RTM
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Comparison of stand structure and growth between artificial and natural forests of Pinus sylvestiris var. mongolica on sandy land 被引量:25
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作者 朱教君 范志平 +2 位作者 曾德慧 姜凤岐 MATSUZAKI Takeshi 《Journal of Forestry Research》 SCIE CAS CSCD 2003年第2期103-111,共9页
Mongolian pine (Pinus sylvestiris Linnaeus var. mongolica Litvinov) as a valuable conifer tree species has been broadly introduced to the sandy land areas in 揟hree North?regions (North, northwest and northeast of Chi... Mongolian pine (Pinus sylvestiris Linnaeus var. mongolica Litvinov) as a valuable conifer tree species has been broadly introduced to the sandy land areas in 揟hree North?regions (North, northwest and northeast of China), but many problems occurred in the earliest Mongolian pine plantations in Zhanggutai, Zhangwu County, Liaoning Province (ZZL). In order to clarify the reason, comprehensive investigations were carried out on differences in structure characteristics, growth processes and ecological factors between artificial stands (the first plantation established in ZZL in 1950s) and natural stands (the origin forests of the tree species in Honghuaerji, Inner Mongolia) on sandy land. The results showed that variation of diameter-class distributions in artificial stands and natural stands could be described by Weibull and Normal distribution models, respectively. Chapman-Richards growth model was employed to reconstruct the growth process of Mongolian pine based on the data from field investigation and stem analysis. The ages of maximum of relative growth rate and average growth rate of DBH, height, and volume of planted trees were 11, 22 years, 8, 15 years and 35, 59 years earlier than those of natural stand trees, respectively. In respect of the incremental acceleration of volume, the artificial and natural stands reached their maximum values at 14 years and 33 years respectively. The quantitative maturity ages of artificial stands and natural stands were 43 years and 102 years respectively. It was concluded that the life span of the Mongolian pine trees in natural stands was about 60 years longer than those in artificial stands. The differences mentioned above between artificial and natural Mongolian pine forests on sandy land were partially attributed to the drastic variations of ecological conditions such as latitude, temperature, precipitation, evaporation and height above sea level. Human beings' disturbances and higher density in plantation forest may be ascribed as additional reasons. Those results may be potentially useful for the management and afforestation of Mongolian pine plantations on sandy land in arid and semi-arid areas. 展开更多
关键词 Pinus sylvestiris var. mongolica Mongolian pine Sandy land COMPARISON Growth model
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