Periodic orbits and their bifurcations in a 3-D system     

G. Contopoulos  B. Barbanis 《Celestial Mechanics and Dynamical Astronomy》1994,59(3):279-300

We study some simple periodic orbits and their bifurcations in the Hamiltonian . We give the forms of the orbits, the characteristics of the main families, and some existence diagrams and stability diagrams. The existence diagram of the family 1a contains regions that are stable (S), simply unstable (U), doubly unstable (DU) and complex unstable (). In the regionsS andU there are lines of equal rotation numberm/n. Along these lines we have bifurcations of families of periodic orbits of multiplicityn. When these lines reach the boundary of the complex unstable region, they are tangent to it. Inside the region there are linesm/n, along which the orbits 1a, describedn-times, are doubly unstable; however, along these lines there are no bifurcations ofn-ple periodic orbits. The families bifurcating from 1a exist only in certain regions of the parameter space (, ). The limiting lines of these regions join at particular points representing collisions of bifurcations. These collisions of bifurcations produce a nonuniqueness of the various families of periodic orbits. The complicated structure of the various bifurcations can be understood by constructing appropriate stability diagrams.  相似文献   

Stability of outer planetary orbits around binary stars: A comparison of Hill's and Laplace's stability criteria     

A. Kubala  D. Black  V. Szebehely 《Celestial Mechanics and Dynamical Astronomy》1993,56(1-2):51-68

A comparison is made between the stability criteria of Hill and that of Laplace to determine the stability of outer planetary orbits encircling binary stars. The restricted, analytically determined results of Hill's method by Szebehely and co-workers and the general, numerically integrated results of Laplace's method by Graziani and Black are compared for varying values of the mass parameter =m ₂/(m ₁+m ₂). For 00.15, the closest orbit (lower limit of radius) an outer planet in a binary system can have and still remain stable is determined by Hill's stability criterion. For >0.15, the critical radius is determined by Laplace's stability criterion. It appears that the Graziani-Black stability criterion describes the critical orbit within a few percent for all values of .  相似文献   

The arrangement in mean elements space of the periodic orbits close to that of the Moon     

G. B. Valsecchi  E. Perozzi  A. E. Roy  B. A. Steves 《Celestial Mechanics and Dynamical Astronomy》1993,56(1-2):373-380

In a simplified model of the Earth-Moon-Sun system based on the restricted circular 3-dimensional 3-body problem, it is possible to find numerically a set of 8 periodic orbits whose time evolutions closely resemble that of the Moon's orbit. These orbits have a period of 223 synodic months (i.e. the period of the Saros cycle known for more than two millennia as a means of predicting eclipses), and are characterized by a secular rotation of the argument of perigee . Periodic orbits of longer durations exhibiting this last feature are very abundant in Earth-Moon-Sun dynamical models. Their arrangement in the space of the mean orbital elements- for various values of the lunar mean motion is presented.  相似文献   

Periodic orbits of an electric charge in a magnetic dipole field     

Lidia Jiménez-Lara  Eduardo Piña 《Celestial Mechanics and Dynamical Astronomy》1990,49(4):327-345

Periodic orbits in the Stormer problem are studied using the symmetry lines of the Poincaré map introduced by De Vogelaere. Many known facts are explained by mean of these lines. The dynamics of four special symmetry lines when the Stormer parameter ₁ changes is presented, and we obtain a clear global view of the structure of the simple periodic orbits and their bifurcations, including the asymmetrical ones. New asymmetrical multiple periodic orbits are obtained.  相似文献   

滇西水成铀矿勘探综合测井成果   总被引：2，自引：0，他引：2  

罗志明  张世涛 《云南地质》2005,24(4):386-394

滇西龙川江盆地发现水成铀矿。本文借助地球物理综合测井技术，对龙川江盆地水成铀矿的成矿规律作有益分析和探讨。重点论述滇西水成铀成矿的成矿（沉积）环境及其成矿物征。  相似文献   

航磁异常轴向特征提取算法研究及其应用   总被引：1，自引：4，他引：1  

刘艳  李桐林  黄旭钊  梁月明  韩英杰 《地球物理学进展》2002,17(1):141-144

通过分析航磁异常的空间分布特征，提出一种在平面等值线追踪基础上，根据封闭等值线之间的关系并应用离散卡洛变换，自动检测和绘制航磁异常轴向图的方法，将该方法用于新疆某地航磁异常分析，发现了断裂构造，有效地验证了算法的正确性。  相似文献   

一种符合视觉规律的,基于地图数据的虚拟地景仿真   总被引：5，自引：1，他引：5  

陈刚 《测绘学报》1997,26(3):241-246

本文分析和解决了两个关键性问题，使计算机所生成的虚拟地景符合人的“越近看得越清”视觉规律，并通过实例对该方法的实现过程给予了详细的描述。  相似文献   

Biodegradability of the Anti-tumour Agents 5-Fluorouracil,Cytarabine, and Gemcitabine: Impact of the Chemical Structure and Synergistic Toxicity with Hospital Effluent     

K. Kümmerer  A. Al-Ahmad 《洁净——土壤、空气、水》1997,25(4):166-172

Most anti-tumour agents are known to be carcinogenic, mutagenic, teratogenic, embryotoxic or fetotoxic. Only little is known about the environmental impact of pharmaceuticals. Unmetabolized active substances are excreted and will show up in municipal wastewater. Therefore, we examined the biodegradability of the widely used anti-tumour agent 5-fluorouracil (5-FU), also as an example for assessing the impact of hospital effluent on the biodegradation of a test compound. The biodegradability of the structurally similar anti-tumour agents cytarabine and gemcitabine was also examined. Test systems used were the closed bottle test (OECD 301 D) and the modified Zahn-Wellens test (OECD 302 B). 5-FU was not biodegradable in the closed bottle test (CBT) nor in the Zahn-Wellens test (ZWT). At the highest concentration of 5-FU, with hospital effluent an inhibition of the degradation of substances present in hospital effluent was observed, probably as a result of a synergistic effect by 5-FU with antibiotics present in hospital sewage. Gemcitabine was biodegraded 42% in the CBT. The prolongation of the test period to 40 days only improved the result to 45%. In the ZWT, the biodegradation of gemcitabine was 50%. Cytarabine was partially biodegraded in the CBT (50%), but only after an adaptation period of 20 days. After a test prolongation to 40 days, the degree of biodegradation was 80%. In the ZWT, the biodegradability was > 95% after only a few days.  相似文献   

地史上巨量蒸发岩省的成因及其地质意义          下载免费PDF全文

李江海  马丽亚  王洪浩  许丽 《地质科学》2016,(2):619-632

全球蒸发岩从震旦纪到新近纪均有发育, 其最发育时期为震旦纪-寒武纪、二叠纪-三叠纪以及侏罗纪-白垩纪, 且具有幕式分布特点.它们在一定区域(低纬区)常大规模集中发育, 跨越不同的沉积盆地类型, 面积和厚度巨大, 时代跨度较短且连续, 笔者称之为巨量蒸发岩省.本文基于全球蒸发岩层系古板块再造、沉积岩相恢复、地层柱状对比、盆地构造分析等方法, 对巨量蒸发岩省的发育、分布、成因及其地质意义进行了探讨.巨量蒸发岩省形成、分布与地史中的造山带演化、超大陆的聚合与裂解、干旱气候带(南北纬30°之间)、海平面变化等因素有着密切联系; 其主要形成于干旱环境下相对封闭、靠海水潜流补给的台地和盆地中; 所处的构造单元主要为泛大陆板块内部狭长的裂谷带、特提斯造山带的残余洋盆、海-陆过渡带、陆表海或孤立板块的台地中心.  相似文献   

低轨卫星初始状态误差对反演地球重力场的影响     

张兴福  沈云中 《测绘科学》2009,34(3)

基于动力学法反演地球重力场的基本理论,研究了卫星初始状态向量误差对应用低轨卫星精密轨道数据反演地球重力场的影响。在仅考虑低轨卫星初始状态误差的情况下进行了模拟计算,结果表明:在利用低轨卫星精密轨道数据反演地球重力场时,卫星初始状态向量误差需要重新进行估计;在目前的轨道精度水平下,若不顾及误差方程二次项的影响,反演弧长不宜过长;卫星初始状态速度误差(约1.5mm/s)的影响要大于位置误差(约10 cm)的影响。  相似文献