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油液激励转子不稳定性的计算机仿真
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作者 jiri tuma 《空军工程大学学报(自然科学版)》 CSCD 北大核心 2008年第5期80-85,共6页
基于Muszynska的理论,介绍了一种新的轴颈轴承转子振动的计算机仿真方法。转动过程中,轴颈轴承的转子依靠滑油油膜形成的油楔保持平衡,轴承受力可描述为旋转的弹簧阻尼系统。以轴心线为原点的复坐标系描述转子的运动,位置矢量的实部表... 基于Muszynska的理论,介绍了一种新的轴颈轴承转子振动的计算机仿真方法。转动过程中,轴颈轴承的转子依靠滑油油膜形成的油楔保持平衡,轴承受力可描述为旋转的弹簧阻尼系统。以轴心线为原点的复坐标系描述转子的运动,位置矢量的实部表示转子X方向的位移,虚部表示垂直方向的位移,即Y轴方向,运动方程为时间的复变量函数,方程参数亦为复数。描述了如何利用Simulink进行转子系统的计算机仿真,不同步干扰力的作用下转子运动的不稳定性及其振动模式。利用Simulink进行的转子系统的仿真进一步证实了Muszynska模型,仿真结果与具体的实验结果一致。 展开更多
关键词 轴颈轴承 非稳定性振动 系统仿真
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Unoccupied mounds of soil-feeding termites host diverse soil fauna both in primary and logged tropical forests
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作者 jiri tuma Kalsum M.Yusah Tom M.Fayle 《Soil Ecology Letters》 2025年第3期263-277,共15页
Many termite species create conspicuous,aboveground soil nest mounds.Once the resident termite colony disappears,the mound structure gradually disintegrates.The now empty mound,which is rich in nutrients,and stable in... Many termite species create conspicuous,aboveground soil nest mounds.Once the resident termite colony disappears,the mound structure gradually disintegrates.The now empty mound,which is rich in nutrients,and stable in microclimate,potentially provides an important microhabitat for a different range of species.However,the communities in unoccupied termite mounds remain poorly explored,and the relative importance of these mounds in anthropogenically modified habitats is completely unknown.Here we quantify the invertebrate communities in unoccupied mounds of the soil-feeding termites Dicuspiditermes spp.in primary and logged lowland tropical rain forest in Malaysian Borneo and compare them to communities found in control soil.We also quantify the introgression of plant roots into the mounds.We found the unoccupied mounds support a range of invertebrate groups,with ants(Formicidae)having the highest abundances of any group across both habitats.Mounds supported significantly higher abundances of invertebrates overall in both primary forest(nine times more)and logged forest(five times more).However,the number of invertebrate taxa did not differ between mounds and control soils.Plant root mass was higher in control soils than in unoccupied mounds,possibly due to dominance of fine roots in the latter microhabitat.Using previous estimates of mound densities,we estimate that unoccupied Dicuspiditermes spp.mounds support>340000 invertebrate individuals in primary forest and>17000 individuals in logged forest per hectare.Our results indicate that unoccupied mounds are an important,although ephemeral,microhabitat for a range of invertebrate groups,in both pristine and anthropogenically disturbed habitats. 展开更多
关键词 TERMITE Dicuspiditermes BORNEO TROPICS RAINFOREST
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