A special perturbation method in orbital dynamics     

Jesús Peláez  José Manuel Hedo  Pedro Rodríguez de Andrés 《Celestial Mechanics and Dynamical Astronomy》2007,97(2):131-150

The special perturbation method considered in this paper combines simplicity of computer implementation, speed and precision, and can propagate the orbit of any material particle. The paper describes the evolution of some orbital elements based in Euler parameters, which are constants in the unperturbed problem, but which evolve in the time scale imposed by the perturbation. The variation of parameters technique is used to develop expressions for the derivatives of seven elements for the general case, which includes any type of perturbation. These basic differential equations are slightly modified by introducing one additional equation for the time, reaching a total order of eight. The method was developed in the Grupo de Dinámica de Tethers (GDT) of the UPM, as a tool for dynamic simulations of tethers. However, it can be used in any other field and with any kind of orbit and perturbation. It is free of singularities related to small inclination and/or eccentricity. The use of Euler parameters makes it robust. The perturbation forces are handled in a very simple way: the method requires their components in the orbital frame or in an inertial frame. A comparison with other schemes is performed in the paper to show the good performance of the method.  相似文献   

Non-diffusive propagation of ultra high energy cosmic rays     

G. A. Medina Tanco  E. M. de Gouveia Dal Pino  J. E. Horvath 《Astroparticle Physics》1997,6(3-4):337-342

We report the results of 3D simulations of non-diffusive propagation of Ultra High Energy Cosmic Rays (UHECR) (E > 10²⁰ eV) through the intergalactic and extended halo media. We quantify the expected angular and temporal correlations between the events and the sources, and the temporal delay between protons and gamma-ray counterparts with a common origin for both halo and extragalactic origins. It is shown that the proposed UHECR-supergalactic plane source associations require either extremely high values of the halo magnetic field over as much as 100 kpc length scale or a very large correlation length for the IGM, even for the largest possible values of the intergalactic magnetic field. It can be stated that the UHECR seem to point to the sources even more strongly than previously believed. The simulations also show that the calculated time delays between UHE protons and gamma-ray counterparts do not match the claimed GRB-UHECR associations for either cosmological or extended halo distance scales.  相似文献   

地下铁道的振动及其控制措施的研究     

关歆莹  刘超 《震灾防御技术》2011,6(1):77-84

150年来地下铁道得到了广泛的发展,近20年来我国的地下铁道更是得到了迅猛的发展.在地下铁道给城市居民的工作和生活带来方便的同时,其引发的振动与噪音也给城市建设和居民生活带来了危害.本文从振动产生、振动传播和振动作用三个阶段论述了地铁振源及其传播的规律;传播特性与振源频率、振源与轨道距离、振动频率,以及列车运行速度、隧道埋深、地质条件、建筑物结构等有关;振动传播影响因素包括:土壤类型、钢轨类型、轨道类型、建筑物质量类型、建筑物材料等;地铁振动的危害是多方面的,噪声干扰人们的日常生活,振动对建筑物的安全性、使用寿命造成影响,同时还影响精密仪表测量等.本文提出了在规划设计阶段、施工阶段的振动控制措施,以期减小其危害.  相似文献   

Development and propagation of equatorial waves     

Xiaofan Li  Han-Ru Cho 《大气科学进展》1997,14(3):323-338

Development and propagation of equatorial waves are investigated with the model which includes convection -wave convergence feedback and convection-frictional convergence feedback. Two experiments with an initial Kelvin wave (Exp. K) and with an initial Rossby wave (Exp. R) are carried out. The equatorial waves in Exp. R grow much faster than those in Exp. K. The equatorial waves in both experiments follow zonal (eastward / westward) and meridional (poleward) propagation. The equatorial waves can be partitioned into two meridional modes using Parabolic Cylinder Function. An equa?tor mode denotes a wave component with a positive precipitation center at the equator and an off-equator mode rep?resents a wave component with positive precipitation centers off the equator. The equator mode dominates in Exp. K whereeas the off-equator mode dominates in Exp. R. The rapid wave growth in Exp. R is interpreted by analyzing the eddy available potential energy (EAPE) generation. Stronger off-equator mode in Exp. R obtains more EAPE through convection-frictional convergence feedback which results in more rapid wave growth. The relative vorticity tendency is determined by interactions between Earth’s vorticity and lower-troposphere convergence (divergence effect) and between the meridional gradient and lower-troposphere circulation (beta effect). The eastward and poleward propagation of equatorial waves is a result of the divergence effect, and the westward movement is caused by the beta effect.  相似文献   

山东济阳坳陷岩层空隙比与应力传递速度的相关性研究          下载免费PDF全文

卜凡泉  王尤培 《地震地质》1997,19(1):25-30

统计了不同深度测层的群井降水附加应力从开始传递到水位响应的间隔时段，在此基础上建立了应力在地层中传递深度－时间相关模式，进行了有关参数反演，并结合相关地质、气象等资料，提出了岩层空隙比－应力传递速度的相关模型。该模型说明了应力传递速度与岩层结构、构造的内在联系，为不同类型应力在不同空隙比岩层中的单层传播速度、组合层段传播所需时间计算提供了简单、有效的方法，也为识别降水引起的附加应力对深井水位动态的干扰提供了依据  相似文献   

低纬纬向风年际振荡在太平洋地区的传播     

林永辉  林春育 《热带气象学报》1994,10(2):140-145

利用ＮＭＣ客观分析８５０ｈＰａ（１９７４．１２－１９８８．２）和２００ｈＰａ（１９６８．３－１９８８．２）平均纬向风资料，对其准两年振荡和准３－４年振荡进行了研究。结果发现：纬向风准两年、准３－４年振荡在热带地区上、下层均一致自西向东传播，但位相相反；在中纬度地区，纬向风准两年、准３－４年振荡上、下层均盛行自西向东传播，且位相一致；西太平洋地区低层纬向风准３－４年振荡均为从南、北半球中纬度地区向赤  相似文献   

Seasonal Variation of Stationary and Low-Frequency Rossby Wave Rays     

Lu Keli  Zhu Yongchun 《大气科学进展》1994,11(4):427-435

The wave rays and their seasonal variation of stationary and low－frequency Rossby waves are studied by using the Runge-Kutta scheme. The results show that for stationary waves the rays can reach lower latitudes in winter, and are limited in higher latitudes in summer. The main differences between the stationary and low-frequency wave rays are that low-frequency waves can propagate across the equator and the easterlies will not be an obstacle on their propagation. It explained to some extent the interaction of disturbances between the Northern and Southern Hemi-spheres. The lower wave frequencies and the stronger easterly flow are, the more difficult low-frequency waves will be to propagate across the equator. The waves with 20-day period are easier to propagate across the equator than that with 50-day period. The winter is the most favorable season for low-frequency waves to propagate into another hem-isphere.  相似文献   

GIS中矢量数据缓冲区操作的不确定性传播模型   总被引：6，自引：0，他引：6  

张保钢  朱凌  朱光 《测绘学报》1998,27(3):259-266,281

研究了矢量数据缓冲区操作点,线,面状地物的不确定性传播模型。研究结果表明：对点状地物做缓冲区操作,操作结果的绝对精度与缓冲区的宽度和点位中误差成反比,相对 精度与点位中误差和绘冲区宽度的比值成反比;对线状或面状地物做缓冲区域操作时,操作结果的绝对精度与缓冲区的宽度和“ε－带”或点位中误差成反比;相对精度与缓冲区的宽度成正比,与地物的“ε－带”或点位中误差成反比。  相似文献   

甘肃省秋季层状云冰雪晶粒子特征个例分析   总被引：3，自引：0，他引：3  

李照荣  李宝梓  庞朝云  杨增梓 《干旱气象》2002,20(3):21-23

利用安装有PMS探头、温湿仪和GPS的飞机 ,对 2 0 0 1年 10月 12日甘肃河西地区降水性层状云进行了探测。根据获取的资料分析了此次降水性层状云的冰雪晶特征 ,包括不同粒子的分布特性 ,给出不同温度下的冰雪晶粒子谱 ,还分析了粒子谱型随温度的变化及其包含的微物理机制。与我国其它地区的冰雪晶浓度比较认为 ,在一定的云水条件下 ,甘肃秋季层状云有较大的增雨催化潜力  相似文献   

垂直切变风场中声重波的谱传播          下载免费PDF全文

易帆  李钧  梁百先 《地球物理学报》1988,31(1):1-9

本文研究声重波在垂直切变风场中传播时谱结构的改变。根据可压缩情况下的流体力学方程组,导出垂直切变风场中大气声重波的谱方程。并指出,这个谱方程是Taylor-Goldstein方程在可压缩和任意垂直波长情况下的推广。由谱方程出发,考虑低边界上的声重波强迫为高斯谱型,采用差分方法,我们计算了ω-K_H二维空间中的高层谱响应。结果表明,在具有垂直切变的背景风场作用下,声重波的谱结构发生了改变:1.在原强迫谱所覆盖的谱区段内,一些谱成份被挖除,形成了尖锐的谱峰群;2.最大谱峰发生了偏移;3.波谱变得狭窄。这些变化是垂直切变风场对声重波谱滤波的结果。文中还将上述结论与电离层观测结果进行比较,解释了某些观测现象。  相似文献