The global solution of the N-body problem     

Wang Qiu-Dong 《Celestial Mechanics and Dynamical Astronomy》1990,50(1):73-88

The problem of finding a global solution for systems in celestial mechanics was proposed by Weierstrass during the last century. More precisely, the goal is to find a solution of the n-body problem in series expansion which is valid for all time. Sundman solved this problem for the case of n = 3 with non-zero angular momentum a long time ago. Unfortunately, it is impossible to directly generalize this beautiful theory to the case of n > 3 or to n = 3 with zero-angular momentum.A new blowing up transformation, which is a modification of McGehee's transformation, is introduced in this paper. By means of this transformation, a complete answer is given for the global solution problem in the case of n > 3 and n = 3 with zero angular momentum.The main result in this paper has appeared in Chinese in Acta Astro. Sinica. 26 (4), 313–322. In this version some mistakes have been rectified and the problems we solved are now expressed in a much clearer fashion.  相似文献   

A "radically new method": balloon buoy communications of the Baldwin–Ziegler Polar Expedition, Franz Josef Land, June 1902     

P.J. Capelotti 《Polar research》2008,27(1):52-72

  相似文献   

中国北方春季起沙活动时间序列及其与气候要素的关系   总被引：10，自引：5，他引：5  

周自江  章国材  艾婉秀  张洪政  牛若芸 《中国沙漠》2006,26(6):935-941

利用1961—2002年春季中国681个站沙尘天气的实测资料,将起沙机理相似的扬沙、沙尘暴通过并集运算进行复合,得到一个新的能体现完整起沙活动的时间序列。统计学检验表明,新序列较单一的沙尘暴序列具有诸多优点。进一步从681个站中筛选出代表性较好的中国北方175个站,探讨了春季起沙活动（DBS）时间序列与冷空气、大风、气温、降水等气候要素的关系。结果表明:①春季DBS与大风日数、冷空气次数的相关系数分别为0.946和0.406。②春季DBS与平均气温、最低气温、最高气温的相关系数分别为-0.494、-0.607和-0.269。③春季降水对DBS的影响主要取决于降水的强度和降水的时间分布,5 mm以上的降水才能有效地抑制DBS的发生。  相似文献   

一次冷锋过境时引发多种天气现象的成因分析          下载免费PDF全文

于雷.  丁和悦  熊秋芬  郭志强  韩英杰 《沙漠与绿洲气象(新疆气象)》2023,17(3):59-65

利用观测数据、雷达产品、ERA5再分析资料对2021年4月15日河北保定一次天气过程进行综合分析，结果表明：(1)天气背景高层干冷，低层有暖脊，整层大气较为干燥。冷锋过境引起地面风力加大，锋面触发干对流后，冷池出流进一步加大了地面风速，湍流加强并出现扬沙。(2)对流云内存在水平弱风区，其径向速度近于0 m/s，弱风区后侧的雷达回波强度呈增加趋势。雷达低仰角0径向速度区的上方有水凝物粒子迅速集中、生长，生长区内径向速度为5～10 m/s，降雹区域上空各仰角均为0径向速度。(3)下击暴流和动量下传引发了干对流大风，降水粒子的蒸发、拖曳作用进一步加剧了气流下沉，其中蒸发作用的贡献更显著。(4)干对流消亡后，锋面东移，锋后西北风减弱，扬沙天气结束，较小的近地层风通量有利于沙尘粒子缓慢下降，地面能见度好转但PM₁₀浓度依然较高。(5)夜间冷空气下沉，上游输送的沙尘粒子随之沉降，造成了浮尘天气。  相似文献