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放任柿树的修剪
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作者 李锋 《农村科技开发》 2002年第1期25-25,共1页
放任生长的柿树,树体高大,结构不合理,大枝多而密集,上强下弱,内膛光秃,结果部位严重外移,产量低而不稳,大小年结果比较严重。在修剪上应掌握以疏为主,短截为辅,适当回缩的原则,主要方法是: 1.对中干过高的要落头开心,打开天窗,改善内... 放任生长的柿树,树体高大,结构不合理,大枝多而密集,上强下弱,内膛光秃,结果部位严重外移,产量低而不稳,大小年结果比较严重。在修剪上应掌握以疏为主,短截为辅,适当回缩的原则,主要方法是: 1.对中干过高的要落头开心,打开天窗,改善内膛光照条件,促进中下部枝叶的生长。 展开更多
关键词 放任柿树 修剪 疏枝 短截 回宿
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Heteroclinic bifurcations in attitude maneuver of coupled slosh-spacecraft with flexible appendage 被引量:2
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作者 YUE BaoZeng SONG XiaoJuan 《Science China(Technological Sciences)》 SCIE EI CAS 2011年第8期2090-2099,共10页
In this paper, the chaotic dynamics in an attitude transition maneuver of a slosh-spacecraft coupled with flexible appendage in going from minor axis to major axis spin under the influence of dissipative effects due t... In this paper, the chaotic dynamics in an attitude transition maneuver of a slosh-spacecraft coupled with flexible appendage in going from minor axis to major axis spin under the influence of dissipative effects due to fuel slosh and a small flexible appendage constrained to only torsional vibration is investigated. The slosh-spacecraft coupled with flexible appendage in attitude maneuver carrying a sloshing liquid is considered as multi-body system with the sloshing motion modeled as a spherical pendulum. The focus in this paper is that the dynamics of the liquid and flexible appendage vibration are coupled. The equations of motion are derived and transformed into a form suitable for the application of Melnikov’s method. Melnikov’s integral is used to predict the transversal intersections of the stable and unstable manifolds for the perturbed system. An analytical criterion for chaotic motion is derived in terms of system parameters. This criterion is evaluated for its significance to the design of spacecraft. The dependence of the onset of chaos on quantities such as body shape and magnitude of damping values, fuel fraction and torsional vibration frequency of flexible appendage are investigated. In addition, we show that a spacecraft carrying a sloshing liquid, after passive reorientation maneuver, will end up with periodic limit motion other than a final major axis spin because of the intrinsic non-linearity of fuel slosh. Furthermore, an extensive numerical simulation is carried out to validate the Melnikov’s analytical result. 展开更多
关键词 CHAOTIC attitude maneuver liquid-filled spacecraft flexible appendage liquid slosh
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