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层状半空间中凹陷地形对斜入射平面P波的2.5维散射 总被引:1,自引:0,他引:1
采用间接边界元法研究了层状半空间中凹陷地形对斜入射平面P波的2.5维散射问题。取无限长凹陷地形任一横截面,将边界以斜线单元离散,通过自由场反应分析,求得假想边界上各单元的应力响应。施加虚拟移动均布斜线荷载,求得应力格林函数。根据凹陷边界上的零应力边界条件确定虚拟移动均布斜线荷载密度,将自由场响应和虚拟移动均布斜线荷载产生的响应叠加起来,即得到问题的解答。通过与已有结果的对比,验证了本文方法的正确性。最后,以均匀弹性半空间和基岩上单一土层中凹陷地形对斜入射平面P波的2.5维散射为例,进行了数值计算分析,结果表明:凹陷地形的2.5维散射和二维散射之间存在明显差异;层状半空间中凹陷地形和均匀半空间中凹陷地形对波的散射作用存在显著差别。分析了造成差别的原因,并深入讨论了入射角度、覆盖层厚度和刚度对散射作用的影响。 相似文献
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本文研究了强碱性条件下,以乙二胺为络合剂,用水合肼把二价镍离子还原为单质镍的方法。经过大量实验,镍粉的产率在99%以上,其纯度也在99%以上。通过这种方法,既回收了镍,又降低了对环境的污染,结果令人满意。 相似文献
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荒漠植物红砂研究进展 总被引:2,自引:0,他引:2
主要综述了荒漠植物红砂的分布区及其生境、解剖学特征、种子萌发及幼苗生长影响因素、组织培养、生理生态特征、繁殖及育苗、分子生物学特性等方面的研究。简要阐述了修复和重建红砂植被的必要性,并着重研究了红砂种子萌发的影响因素及育苗技术的发展现状,在此基础上指出红砂研究中的不足之处,并对今后的研究方向提出了建议。 相似文献
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Penny A. Spiering Michael J. Somers Jesús E. Maldonado David E. Wildt Micaela Szykman Gunther 《Behavioral ecology and sociobiology》2010,64(4):583-592
Although dominant African wild dogs (Lycaon pictus) are generally believed to be the sole breeders within a pack, earlier behavioral and endocrine data suggest that reproduction
could be shared with subordinates. We performed an extensive behavioral, demographic, and genetic evaluation of a wild dog
population in South Africa to examine the level of such sharing and the proximate mechanisms influencing reproductive contributions
of each sex. While a majority of pups were born to dominants because of a lack of subordinate potential breeders, we discovered
a substantial portion of reproductive sharing between dominants and subordinates. Compared with alpha females that mated annually,
subordinate beta females bred in 54.5% of years whereas thetas never bred. The three top-ranking males all sired pups (56.0%,
32.0%, and 12.0%, respectively) when three or more adult males were present. With only two pack males, alpha and beta individuals
shared reproduction nearly equally (55.2% and 44.8%, respectively), and litters of mixed paternity were discovered on eight
of 15 (53.3%) occasions. A skewed adult sex-ratio and frequent alpha mortalities for females and behavioral aggression in
males allowed most individuals to attain dominant status in their lifetime, creating a constantly shifting social hierarchy.
Genetic parentage results corresponded to reported hormone profiles, suggesting physiological suppression in some lower-ranked
individuals of both sexes. Thus, a combination of demographic, behavioral, and hormonal proximate factors mediates reproductive
partitioning in wild dogs. We conclude that reproductive sharing can be significant in this species, especially for males
that have less robust suppressive mechanisms than females. 相似文献
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