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1.
The problem of stability of the trivial equilibrium position in the Sitnikov problem is considered in the first approximation.
The first approximation is shown to have the form of a linear second-order equation with time-periodic coefficient (the Hill-type
equation). The equilibrium stability was studied on the basis of equation regularization in the vicinity of a singular point
with subsequent calculation of the trace a of the monodromy matrix. The equilibrium stability is shown to be stable for almost all values of eccentricity e from the [0, 1] interval. The instability takes place on the discrete set of e values, when the mutipliers are multiple (with non-simple elementary divisors), e = 1 being a point of crowding of this set. 相似文献
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A simple diffusion model of Saturn's radiation belts with a constant internal source and particle losses at the boundaries is considered. The radial diffusion coefficient is supposed to be D
LL L
4. The analytical solution to the stationary diffusion equation describes well the observed radial profiles of the distribution function of energetic protons in Saturn's magnetosphere. 相似文献
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We investigated the dependence of the geomagnetic activity index K
p on the velocity and density of the solar wind and the intensity of the interplanetary magnetic field (IMF). A three-layer neural network was used to create the model. The degree of the influence of input parameters on K
p was determined by the value of the mean and root-mean square deviations of the model index values from the real indices. It was found that the largest contribution to the K
p index is provided by the Z component of the IMF, the velocity and density of the solar wind measured with a delay from 0 to 3 h relative to the studied value of K
p, and the previous value of the index itself. For the model with such a set of input parameters, the correlation coefficient between model and real series is ±0.89. The analysis of deviations from the real values of K
p showed that high indices are simulated worse than low indices. In order to solve this problem the data distribution was reduced to a uniform distribution over K
p, and this considerably decreased the standard deviations for large values of K
p. 相似文献
4.
V. L. Levtov V. V. Romanov A. A. Boguslavsky V. V. Sazonov S. M. Sokolov Yu. N. Glotov 《Cosmic Research》2009,47(6):513-524
A space experiment aimed at determination of quasi-static microaccelerations onboard an artificial satellite of the Earth
using video images of the objects executing free motion is considered. The experiment was carried out onboard the Foton M-3 satellite. Several pellets moved in a cubic box fixed on the satellite’s mainframe and having two transparent adjacent walls.
Their motion was photographed by a digital video camera. The camera was installed facing one of the transparent walls; a mirror
was placed at an angle to another transparent wall. Such an optical system allowed us to have in a single frame two images
of the pellets from differing viewpoints. The motion of the pellets was photographed on time intervals lasting 96 s. Pauses
between these intervals were also equal to 96 s. A special processing of a separate image allowed us to determine coordinates
of the pellet centers in the camera’s coordinate system. The sequence of frames belonging to a continuous interval of photography
was processed in the following way. The time dependence of each coordinate of every pellet was approximated by a second degree
polynomial using the least squares method. The coefficient of squared time is equal to a half of the corresponding microacceleration
component. As has been shown by processing made, the described method of determination of quasi-static microaccelerations
turned out to be sufficiently sensitive and accurate. 相似文献
5.
D. Sh. Shirapov 《Cosmic Research》2012,50(1):32-38
The relations between electric fields in the daytime and nighttime sectors of the polar ionosphere and magnetic activity indices
of auroral region (AL) and northern polar cap (PCN) are studied. It is found that the above relations do exist and are described
by: a) equations U
pc(1) (kV) = 27.62 + 21.43PCN with a correlation coefficient R = 0.87 and U
pc(1) (kV) = 4.06 + 49.21PCN - 6.24 PCN2 between the difference in the electric potentials across the polar cap in the daytime sector U
pc(1) and PCN and b) regression equation U
pc(2) (kV) = 23.33 + 0.08|AL| with R = 0.86 between the difference in the electric potentials across the polar cap in the nighttime sector U
pc(2) and |AL|. It is shown that: a) it is possible to use the AL and PCN indices for real-time diagnostics of instantaneous values of the electric fields in the daytime and nighttime sectors of the polar ionosphere in the process of a substorm development;
b) at the expansion phase of a substorm, due to calibration of PCN values by the values of the solar wind electric field E
sw, the PCN index does not feel the contribution of the western electrojet and, accordingly, the contribution of the nighttime
ionospheric electric field U
pc(2), governed by the reconnection in the magnetospheric tail. 相似文献
6.
基于改进二维分形海面模型的分层海面电磁散射分析 总被引:5,自引:0,他引:5
用微扰法研究了平面波入射分层介质粗糙面的电磁散射。由改进的二维分形海面模型模拟实际的分层海面,导出了平面波入射时的散射系数计算公式。通过数值计算获得了不同散射角的HH极化双站散射系数,并讨论了中间介质介电常数与厚度、摩擦风速和入射波频率对双站散射系数的影响,得到改进的二维分形分层海面散射系数的基本特征、分区特征和随频率变化的特征。结果表明:散射系数近似具有"量子化"特征。 相似文献
7.
Using the new technology of global GPS detection of ionospheric disturbances (GLOBDET), it is found that a sharp increase of the time derivative of the magnetic field strength during magnetic storms is accompanied by a simultaneous decrease of the mid-latitude total electron content (TEC) over the entire dayside of the globe. The corresponding negative correlation coefficient is no less than 0.8, and the delay relative to the sudden commencement of magnetic storm is about 3–10 min. The effect is especially clearly pronounced for magnetic storms with sudden commencements (SSC). The analysis is carried out for a set of 90 to 300 GPS stations for 10 days (January 6 and April 23, 1998; April 6, June 8, July 13, 14, and 15, 2000; March 31, April 4 and 11, 2001) with various levels of geomagnetic activity (D
st and K
p varied from –6 to –295 nT and from 0 to 9, respectively). The amplitude of the response in the total electron content for the events considered was 0.1–0.4 × 1016 m–2 (which is a deviation of 0.2–2.6% from the TEC background value). The velocity of the disturbance motion from the dayside to the nightside was about 10–20 km/s. The results obtained agree with the data of ionospheric parameter measurements conducted earlier by methods with high temporal resolution. 相似文献
8.
针对火星探测任务中降落伞开伞环境为低密度大气的特点,本文由降落伞气动力系数与透气量关系,提出了通过降落伞有效透气量预测降落伞气动力系数的方法,该方法先由织物透气量试验获取伞衣透气量拟合曲线和透气量常数,再根据风洞试验得到两种有效透气量下的气动力系数,然后由有效透气量插值获取了盘缝带(DGB)伞火星大气条件下气动力系数,并且通过空投试验数据对该方法进行验证。计算结果表明,在火星条件下,降落伞气动力系数与风洞条件下变化趋势基本一致。Ma 0.4工况阻力系数的变化范围为0.583~0.622,Ma 0.8工况阻力系数的变化范围为0.438~0.494。 相似文献
9.
为了解决大空域、宽速域水平起降可重复使用飞行器的气动适应性问题,设计了一种满足高超声速巡航飞行性能的飞行器,为解决该种飞行器地面水平起飞和高速巡航飞行气动性能矛盾的问题,提出了两种变形布局方式——伸缩翼布局和翻转翼布局。通过数值手段比较分析了两种变形布局的低速气动特性,并通过风洞试验对其性能进行了验证。结果表明,在增加相同机翼面积时,伸缩翼在起飞状态增升效率为68%,同时阻力增加35%;翻转翼在起飞状态增升效率为42%,阻力增加15%;伸缩翼布局比翻转翼布局的起飞升力大16%,阻力大20%,伸缩翼布局具有明显的升力优势,说明亚声速状态增加机翼展弦比是增升的有效手段,但同时也带来阻力的增加;鸭翼具有显著的增升效果,起飞状态增升12.8%,同时阻力降低1.4%,纵向压心系数绝对值前移0.48%,有效缓解了起飞状态升力和纵向稳定性的问题。 相似文献
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皮卫星能源有限、姿控能力差等特点决定其对星箭分离初始姿态要求较高。在采用自主研发的皮卫星星箭分离机构的基础上,以多体动力学理论为基础,采用ADAMS软件建立了皮卫星及其星箭分离机构虚拟样机模型,分别就皮卫星质心偏离量、分离弹簧与舱门扭簧弹性系数对入轨初始姿态影响展开了分析。分析结果表明:质心偏心量对分离姿态影响最明显,分离弹簧与舱门扭簧弹性系数对其影响次之,合理配置分离弹簧与舱门扭簧弹性系数有利于卫星保持良好的姿态分离。在轨分离试验显示:分离时刻皮卫星滚动角速度、俯仰角速度、偏航角速度分别为-0.18(°)/s,-1.6(°)/s,0.95(°)/s,与在轨环境下仿真结果基本相符;入轨初始姿态能满足皮卫星的姿控要求,为其后续工作提供了保障。 相似文献
14.
推导了基尔霍夫驻留相位近似法理论的计算公式.基于基尔霍夫驻留相位近似法研究了平面波入射深粗糙度高斯型粗糙面的光散射,综合高斯型粗糙面的自相关函数给出了不同极化状态下散射系数的数学表达式.由数值计算获得了不同散射角、散射方位角及入射波波长的双站和单站散射系数,讨论了粗糙面高度起伏均方根、相关长度、介质介电常数和入射波波长... 相似文献
15.
基于飞行轨迹及质量分析数学模型,对以RBCC为动力的巡航飞行器有效载荷的敏感性进行了分析,主要考虑了发动机比冲、发射马赫数、发射高度、模态转换点(转换马赫数)及惰性质量系数等对有效载荷质量的影响。分析结果表明,提高发射马赫数和发射高度、增加发动机比冲、降低模态转换马赫数及飞行器惰性质量系数有利于提高巡航飞行器的有效载荷质量。其中有效载荷质量对惰性质量系数最敏感,当惰性质量系数分别减小7.3%和增大7.3%时,有效载荷质量的增大量和减小量将分别达到58%和103.7%。 相似文献
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用矩量法(MOM)导出求解X波段波导端头裂缝单元间互耦等效磁流的模型。在此基础上给出了等效磁流在激励和未激励单元内部产生的场、反射系数、驻波系数和两单元间耦合系数等的计算公式。分别在共E、H面条件下分析了两X波段波导端头裂缝互耦的影响,并对单元间不同相对距离和工作频率时的互耦影响规律进行了讨论。研究结果表明,该算法简单,计算值与测试结果吻合较好。 相似文献
18.
HTPB推进剂中增塑剂扩散系数计算 总被引:3,自引:0,他引:3
针对丁羟推进剂/衬层界面增塑剂的迁移问题,研究增塑剂的扩散特性。采用分子动力学方法模拟增塑剂在丁羟粘合剂体系中的运动,再通过爱因斯坦关系式求得扩散系数;采用对衬层加厚的粘接试件进行加速老化实验方法,再通过费克第二定律计算得到增塑剂的扩散系数;考察不同环境温度和不同增塑剂含量条件下癸二酸二辛酯的扩散系数的变化。分析认为,增塑剂在丁羟粘合体系高分子链段运动产生的间隙中,以"跳跃"方式发生空间位置迁移。结果表明,扩散系数模拟值和实验值基本一致,数量级为10-12m2/s;温度升高,增塑剂运动活性加强,有效活动空间增大,扩散系数增大;粘合体系与增塑剂的共容限量使得增塑剂含量大于3%时,模拟得到的扩散系数依次略有下降。分子动力学方法计算增塑剂扩散系数更具优势。 相似文献
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The tensile properties, the thermal expansion coefficient and the thermal conductivity of woven roving (WR) reinforced Kevlar fabrics were experimentally determined. Theoretical values for tensile Young's modulus were calculated by simulating a fabric as an equivalent cross-ply laminate. As thermal expansion coefficient concerns the fabrics have shown an isotropic behaviour. The thermal conductivity normal to fabric plane has also been determined. 相似文献