基于路网的不确定性轨迹预测

移动对象的轨迹预测研究已成为当前移动对象研究中关注的热点,移动对象的轨迹预测技术具有高度的研究价值及广阔的应用前景.目前移动对象的轨迹预测方法主要是针对历史轨迹确定的欧氏空间轨迹预测,但有相当一部分的应用要求预测历史轨迹存在不确定性的移动对象在受限路网中的轨迹.为了解决这一问题,首先提出了不确定性轨迹的生成方法及其表示形式,然后提出了一种基于路网的不确定性轨迹频繁模式挖掘算法,最后给出了利用索引快速查找轨迹模式并进行预测的方法.实验结果表明该方法具有较高的预测准确率、较好的查询效率以及较低的存储空间.

一种空间飞行器编队重组的轨道优化方法

现有的空间飞行器编队重组的轨道规划方法在求解能量最优策略时,都预先给定了变轨花费的时间,但没有说明给定的时间是怎么选择的。将空间飞行器主从编队重组的轨道规划视为一个多目标优化问题,提出了一种小生境进化算法。该方法通过使用特定的染色体表示方法和进化算子,能有效的搜索到飞行器编队重组轨道规划问题的时间-能量前沿,并引入等值分享法保证优秀个体具有较大的选中概率和前沿的多样性。该方法能同时提供多种变轨方案,编队飞行的任务制定者从而可以根据实际应用情况选择最合适的方案。仿真结果表明了该方法的正确性。

一种基于进化计算的空间飞行器编队重构轨道规划方法

基于进化算法提出了一种两层结构的空间飞行器编队重构的轨道规划算法,高层算法通过优化构型映射来优化编队的总燃耗,实现全局规划并确保飞行器之间保持一定的安全距离以避免相互碰撞;低层规划算法采用Chebyshev多项式逼近控制变量空间,为每颗飞行器规划满足约束条件的最优轨道。该方法充分利用了编队的分布式结构,由各飞行器并行实现各自的轨道规划,能有效解决大型编队的轨道规划问题。仿真结果表明了该方法的有效性。

带燃料均衡的空间多飞行器编队重构的轨道规划方法

航天任务需求的多样化对空间多飞行器编队重构的轨道规划问题不仅提出了燃料或时间最优的要求,还提出了燃料和时间最优以及燃料均衡的要求。将带燃料均衡的多飞行器编队重构的轨道规划建模为一个多目标优化问题,通过将进化计算与问题领域的知识相结合,提出了一种基于小生境进化算法的最优轨道规划方法。该方法能从变轨时间、燃料消耗和燃料消耗方差三方面分别评价一个变轨方案的最优性,并且一次规划能够提供多个Pareto最优变轨方案。仿真结果证明了该方法的正确性和有效性,还揭示了编队重构轨道规划问题的三个优化目标之间的关系,对于制定任务计划具有重要的参考价值.

Bending of jets in the QSO NRAO 530

We present radio images of NRAO 530 on scales ranging from pc to kpc. The observations include the EVN at 5 GHz, the VLBA at 1.6, 8.6 and 15 GHz, the MERLIN at 1.6 and 5 GHz, and the VLA at 5, 8.4, 15, 22, and 43 GHz. The VLBI images show a core-jet structure with an oscillating trajectory on a scale of about 30 mas north of the strongest compact component (core). Superluminal motions are detected in five of the jet components with apparent velocities in the range of 13.6 to 25.2c. A new component is detected at 15 GHz with the VLBA observations, which appears to be associated with the outburst in 2002. Significant polarized emission is detected around the core with the VLBA observations at 15 GHz. Rapid variations of the polarization intensity and angle are found between the epochs in 2002 and 2004. On the kpc-scale, a distant component (labelled as WL) located 11 aresec west (PA=-86 degrees) of the core is detected beyond the core-jet structure which extended to several hundreds of mas in the north-west direction (-50 degrees). A significant emission between the core-jet structure and the WL is revealed. A clump of diffuse emission (labelled EL, 12 arcsec long) at PA 70 degrees to the core, is also detected in the VLA observations, suggesting the presence of double lobes in the source. The core component shows a flat spectrum, while the distant components WL and EL have steep spectra. The steep spectra of the distant components and the detection of the arched emission suggest that the distant components are lobes or hot-spots powered by the core of NRAO 530. The morphologies from pc- to kpc-scales and the bending of jets are investigated. The observed radio morphology from pc to kcp appears to favor the model in which precession or wobbling of the nuclear disk drives the helical motion of the radio plasma and produces the S-shaped structure on kpc scale.

Period-doubling bifurcations of the thermocapillary convection in a floating half zone

This study experimentally explored the fine structures of the successive period-doubling bifurcations of the time-dependent thermocapillary convection in a floating half zone of 10 cSt silicone oil with the diameter d (0)=3.00 mm and the aspect ratio A=l/d (0)=0.72 in terrestrial conditions. The onset of time-dependent thermocapillary convection predominated in this experimental configuration and its subsequent evolution were experimentally detected through the local temperature measurements. The experimental results revealed a sequence of period-doubling bifurcations of the time-dependent thermocapillary convection, similar in some way to one of the routes to chaos for buoyant natural convection. The critical frequencies and the corresponding fractal frequencies were extracted through the real-time analysis of the frequency spectra by Fast-Fourier-Transformation (FFT). The projections of the trajectory onto the reconstructed phase-space were also provided. Furthermore, the experimentally predicted Feigenbaum constants were quite close to the theoretical asymptotic value of 4.669 [Feigenbaum M J. Phys Lett A, 1979, 74: 375-378].

Research for HIRFL new improvement project

According to the newest matching mode between the two cyclotrons at HIRFL, the beam obit properties were researched, especially for the harm of existing ‘over-magnetic shim’ in SSC as well as the trajectory in the new mode. The results obtained are encouraging.

Guiding of 150 keV O6+ ions through nanocapillaries in an uncoated Al2O3 membrane: special time dependence of the transmission profile width

This paper reports that the transmission of O6+ ions with energy of 150keV through capillaries in an uncoated Al2O3 membrane was measured, and agreements with previously reported results in general angular distribution of the transmitted ions and the transmission fractions as a function of the tilt angle well fitted to Gaussian-like functions were observed. Due to using an uncoated capillary membrane, our c is larger than that using a gold-coated one with a smaller value of E-p/q, which suggests a larger equilibrium charge Q(infinity) in our experiment. The observed special width variation with time and a larger width than that using a smaller E-p/q were qualitatively explained by using mean-field classical transport theory based on a classical-trajectory Monte Carlo simulation.

Theoretical investigation on excitation, ionization and capture in H(1s, 2s)+H(1s, 2s) collisions

Cross sections of electron- loss in H( 1s)+ H( 1s) collisions and total collisional destruction of H( 2s) in H( 1s) + H( 2s) collisions are calculated by four- body classical- trajectory Monte Carlo ( CTMC) method and compared with previous theoretical and experimental data over the energy range of 4 - 100 keV. For the former a good agreement is obtained within di. erent four- body CTMC calculations, and for the incident energy Ep > 10 keV, comparison with the experimental data shows a better agreement than the results calculated by the impact parameter approximation. For the latter, our theory predicts the correct experimental behaviour, and the discrepancies between our results and experimental ones are less than 30%. Based on the successive comparison with experiments, the cross sections for excitation to H( 2p), single- and double- ionization and H- formation in H( 2s)+ H( 2s) collisions are calculated in the energy range of 4 - 100 keV for the. rst time, and compared with those in H( 1s)+ H( 1s) and H( 1s)+ H( 2s) collisions.

Entrance channel dependence of the correlation function of IMFs in Ar-36+Sn-112,Sn-124 at 35MeV/u

The reduced velocity correlation functions of the Intermediate Mass Fragments (IMFs) were measured in the reactions of Ar-36+ Sn-112,Sn-124 at 35MeV/u. The anti-correlation at small reduced velocities is more pronounced in Ar-36+ Sn-124 system than that in Ar-36+ Sn-112 system. The difference of the correlation functions between the two reactions is mainly contributed by the particle pairs with high momenta. A three-body Coulomb repulsive trajectory code (MENEKA) is employed to calculate the emission time scale of IMFs for-the both systems. The time scale is 150fm/c in the Ar-36+ Sn-112 system and 120fm/c in the Ar-36+ Sn-124 system, respectively. A calculation based on an Isospin dependence Quantum Molecular Dynamics code (IQMD) reveals that the emission time spectrum of IMFs is shifted slightly leftwards in Ar-36+ Sn-124 compared with that in the Ar-16+ Sn-112 system, indicating a shorter emission time scale. Correspondingly, the central density of the hot nuclei decreases faster in Ar-36+ Sn-124 than in Ar-36+ Sn-112

Retrieval of Electron Return Time from High-order Harmonics Generated in a Mixture of He and Ne Gases

In terms of single-atom induced dipole moment by Lewenstein model, we present the macroscopic high-order harmonic generation from mixed He and Ne gases with different mixture ratios by solving three-dimensional Maxwell's equation of harmonic field. And then we show the validity of mixture formulation by Wagner et al. [Phys. Rev. A 76 (2007) 061403(R)] in macroscopic response level. Finally, using least squares fitting we retrieve the electron return time of short trajectory by formulation in Kanai et al. [Phys. Rev. Lett. 98 (2007) 153904] when the gas jet is put after the laser focus.

Close-coupling time-dependent quantum dynamics study of the H+HCl reaction

The paper presents a theoretical study of the dynamics of the H + HCl system on the potential energy surface (PES) of Bian and Werner (Bian, W.; Werner, H. -J., J. Chem. Phys. 2000, 112, 220). A time-dependent wave packet approach was employed to calculate state-to-state reaction probabilities for the exchanged and abstraction channels. The most recent PES for the system has been used in the calculations. Reaction probabilities have also been calculated for several values of the total angular momentum J > 0. Those have then been used to estimate cross sections and rate constants for both channels. The calculated cross sections can be compared with the results of previous quasiclassical trajectory calculations and reaction dynamics experimental on the abstraction channel. In addition, the calculated rate constants are in the reasonably good agreement with experimental measurement.