小行星的奇特动力学1）

小行星数以百万计,有着千奇百怪的外形.无论是小行星自身长期演化、还是它们附近的绕飞物体,都有着奇特的动力学现象.介绍小行星研究现状和发展趋势,阐明影响小行星姿态轨道长期演化的重要作用--雅科夫斯基效应和YORP效应.概述小行星不规则引力场描述方法与其中复杂的周期轨道,尝试提炼其中的科学问题和研究方向.     

周期法测G实验中磁场对扭秤周期的影响

磁场波动是周期法测G实验中的一个误差来源,作用到扭秤上的周期性变化磁场力矩会影响扭秤的运动周期.把磁场作用力矩当作噪声来处理,并利用非线性最小方差拟合法来提取扭秤周期.根据实验给出的相关参数值,利用数值模拟得到了周期性变化磁场力矩所引起扭秤周期的变化δT约为3.8×10-6s.     

Improving the accuracy of GRACE Earth's gravitational field using the combination of different inclinations

In this paper,the GRACE Earth's gravitational field complete up to degree and order 120 is recovered based on the combination of different inclinations using the energy conservation principle.The results show that because different inclinations of satellite are sensitive to the geopotential coefficients with different degrees/and orders m.the design of GRACE exploiting 89° inclination can effectively improve the accuracy of geopotential zonal harmonic coefficients.However,it is less sensitive to the geopotential tesseral harmonic coefficients.Accordingly.the second group of GRACE exploiting lower inclination is required to determine high-accurately the geopotential tesseral harmonic coefficients and cover the shortage of the single group of GRACE exploiting 89° inclination.Two groups of GRACE individually exploiting 89° (82°-84°)inclinations are the optimal combination of the Earth'S gravitational field recovery complete up to degree and order 120.In the degree 120,the joint accuracy of cumulative geoid height based on two groups of GRACE individually exploiting 89° and 83° inclinations is averagely two times higher than the accuracy of a group of GRACE exploiting 89° inclination.     

TRANSCAD在交通量分配中的应用

公路交通需求预测是公路交通规划的关键,它能否符合未来的发展,将直接影响所规划的交通系统的效益。以务川县为例,介绍了TransCAD中几种交通预测模型标定流程和操作方法。     

Current-induced modification of spin wave mode interference

We have studied the effect of adiabatic spin-transfer torque on mode interference of spin waves. The mode interference generates amplitude-localized spots at special positions which do not move with time. When applying current, the wavevector of spin wave is modified, resulting in current-dependent displacement of amplitude-localized spots. This current-dependent change in the mode interference may allow to probe current-induced spin wave Doppler shift in space-domain. In favorable situations, it can be used to estimate the intrinsic properties of magnetic materials such as spin polarization.     

Maxwell: A new vision of the world

The paper outlines the crucial contributions of James Clerk Maxwell to Physics and more generally to our vision of the world. He achieved 150 years ago a synthesis of the pioneering works in magnetostatics, electrostatics, induction and, by introducing the notion of displacement current, gave birth to Electromagnetics. Then, he deduced the existence of electromagnetic waves and identified light as one of them.Maxwell equations deeply changed a Newtonian conception of the world based on particle interactions by pointing out the vital role of waves in physics. This new conception had a strong influence on the development of quantum physics. Finally, the invariance of light velocity in Galilean frames led to Lorentz transformations, a key step toward the theory of relativity.     

Fusion,fission, and annihilation of complex waves for the(2+1)-dimensional generalized Calogero–Bogoyavlenskii–Schiff system

With the help of the symbolic computation system, Maple and Riccati equation( ξ= a0+ a1ξ+ a22ξ), expansion method, and a linear variable separation approach, a new family of exact solutions with q = lx + my + nt + Γ(x, y,t) for the(2+1)-dimensional generalized Calogero–Bogoyavlenskii–Schiff system(GCBS) are derived. Based on the derived solitary wave solution, some novel localized excitations such as fusion, fission, and annihilation of complex waves are investigated.     

Space time fractional KdV Burgers equation for dust acoustic shock waves in dusty plasma with non-thermal ions

The KdV–Burgers equation for dust acoustic waves in unmagnetized plasma having electrons, singly charged nonthermal ions, and hot and cold dust species is derived using the reductive perturbation method. The Boltzmann distribution is used for electrons in the presence of the cold(hot) dust viscosity coefficients. The semi-inverse method and Agrawal variational technique are applied to formulate the space–time fractional KdV–Burgers equation which is solved using the fractional sub-equation method. The effect of the fractional parameter on the behavior of the dust acoustic shock waves in the dusty plasma is investigated.     

Test particle simulations of resonant interactions between energetic electrons and discrete,multi-frequency artificial whistler waves in the plasmasphere

Modulated high frequency(HF) heating of the ionosphere provides a feasible means of artificially generating extremely low frequency(ELF)/very low frequency(VLF) whistler waves, which can leak into the inner magnetosphere and contribute to resonant interactions with high energy electrons. Combining the ray tracing method and test particle simulations, we evaluate the effects of energetic electron resonant scattering driven by the discrete, multi-frequency artificially generated ELF/VLF waves. The simulation results indicate a stochastic behavior of electrons and a linear profile of pitch angle and kinetic energy variations averaged over all test electrons. These features are similar to those associated with single-frequency waves. The computed local diffusion coefficients show that, although the momentum diffusion of relativistic electrons due to artificial ELF/VLF whistlers with a nominal amplitude of ～ 1 pT is minor, the pitch angle scattering can be notably efficient at low pitch angles near the loss cone, which supports the feasibility of artificial triggering of multi-frequency ELF/VLF whistler waves for the removal of high energy electrons from the magnetosphere. We also investigate the dependences of diffusion coefficients on the frequency interval(△f) of the discrete, multi-frequency waves.We find that there is a threshold value of △f for which the net diffusion coefficient of multi-frequency whistlers is inversely proportional to △f(proportional to the frequency components Nw) when △f is below the threshold value but it remains unchanged with increasing △f when △f is larger than the threshold value. This is explained as being due to the fact that the resonant scattering effect of broadband waves is the sum of the effects of each frequency in the ‘effective frequency band’. Our results suggest that the modulation frequency of HF heating of the ionosphere can be appropriately selected with reasonable frequency intervals so that better performance of controlled precipitation of high energy electrons in the plasmasphere by artificial ELF/VLF whistler waves can be achieved.     

Fusion,fission, and annihilation of complex waves for the （2＋l）-dimensional generalized Calogero-Bogoyavlenskii-Schiff system

With the help of the symbolic computation system, Maple and Riccati equation （ξ＇ = ao ＋ a1ξ＋ a2ξ2）, expansion method, and a linear variable separation approach, a new family of exact solutions with q = lx ＋ my ＋ nt ＋ Г（x,y, t） for the （2＋1）-dimensional generalized Calogero-Bogoyavlenskii-Schiff system （GCBS） are derived. Based on the derived solitary wave solution, some novel localized excitations such as fusion, fission, and annihilation of complex waves are investigated.