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.

Accurate quantum mechanical calculation for the N+OH reaction

Accurate three-dimensional time-dependent quantum wave packet calculations for the N+OH reaction on the (3)A' potential energy surface [Guadagnini, Schatz, and Walch, J. Chem. Phys. 102, 774 (1995)] have been carried out. The calculations show for the first time that the initial state-selected reaction probabilities are dominated by resonance structures, and the lifetime of the resonance is generally in the subpicosecond time scale. The calculated reaction cross sections indicate that they are a decreasing function of the translational energy, which is in agreement qualitatively with the quasiclassical trajectory calculations. The rate constants obtained from the quantum mechanical calculations are consistent with the quasiclassical trajectory results and the experimental measurements. (C) 2003 American Institute of Physics.

基于神经网络的机器人视觉伺服控制

视觉伺服可以应用于机器人初始定位自动导引、自动避障、轨线跟踪和运动目标跟踪等控制系统中。传统的视觉伺服系统在运行时包括工作空间定位和动力学逆运算两个过程,需要实时计算视觉雅可比矩阵和机器人逆雅可比矩阵,计算量大,系统结构复杂。本文分析了基于图像的机器人视觉伺服的基本原理,使用BP神经网络来确定达到指定位姿所需要的关节角度,将视觉信息直接融入伺服过程,在保证伺服精度的情况下大大简化了控制算法。文中针对Puma560工业机器人的模型进行了仿真实验,结果验证了该方法的有效性。

虚拟现实水下机器人仿真系统

本文采用VR技术,模拟真实情况建立了一个水下机器人仿真系统。该系统使用与真实系统相同的控制器和输入设备,提供操作员训练、人—机智能控制仿真、机器人轨迹规划仿真等功能,仿真数据能够引导真实机器人运动。文中以仿真实例说明了系统的有效性。

Robust Guaranteed Cost Control for Yaw Control of Helicopter

针对具有时变不确定性且不确定性界为椭球的线性系统提出了一种新的具有自适应机制的鲁棒保性能控制器设计方法。首先,引入一个具有可由自适应律在线调整的可调参数的目标模型,通过该参数来保证由目标模型与被控模型所获得的误差系统渐近稳定。结合保证目标模型稳定性的设计,最终形成保证闭环系统稳定且控制器增益仿射依赖于可调参数的鲁棒保性能跟踪控制器。应用于安装在试验平台上的小型直升机航向控制中,仿真试验表明了该方法的有效性。

基于最小疼痛感的机器人操作臂轨迹规划方法

针对机器人操作臂跟踪运动目标的问题,从仿生学的角度提出一种新的轨迹规划方法。将关节加速度的增量进行编码,同时将疼痛感作为优化指标,利用遗传算法在操作臂的关节空间进行轨迹优化,得到操作臂在跟踪运动目标过程中的具有较小疼痛感的轨迹。仿真试验结果表明,所提出的方法是可行的,可以规划出正确的跟踪轨迹,同时有效的减小了操作臂运动过程中的疼痛感。

无人三体船试验平台的设计与实现

三体船特殊的构型使其非常适合用作水面无人平台(USV)的实验载体,本文介绍了一种自制的三体船型水面无人实验平台的系统设计、控制系统硬件以及实验结果,为以后开展三体船水动力建模、鲁棒控制方法的研究以及水面无人平台的开发提供依据。同时采用基于backstepping的控制方法对三体船进行了实验验证,实验结果表明控制方法的有效性以及平台的可靠性。

机器人操作臂跟踪动态目标的轨迹规划方法

针对机器人操作臂跟踪运动目标问题,提出一种基于遗传算法的轨迹规划方法。通过对关节加速度的增量进行编码,实现在操作臂的关节空间进行轨迹优化,得到操作臂在跟踪运动目标过程中所需要的轨迹。仿真计算的结果表明,所提出的方法是有效的。

基于二维位置敏感探测器的空间对接过程研究

为了准确地捕捉机器人空间对接的传感器信息,从对接机构的设计入手,研究了空间对接中传感器的选择、改制和基于传感器信息的空间对接问题.考虑到安装空间的限制和处理的信息量太多,提出了利用二维位置敏感探测器(PSD)配合红外发光器阵列的方法完成机器人的空间对接.通过对位置敏感探测器工作原理的分析和对传感器特性的试验,提出了在PSD光敏面上增加光学装置的方法以扩大它的探测范围和精度,同时大大减小了它对光信号的依赖程度.把该方法应用于可重构模块化探测机器人系统中,提出了基于传感器信息的轨迹规划方法,对子机器人空间对接过程的仿真试验验证了轨迹规划和空间对接的可行性.

机器人化纳米操作系统驱动器驱动与探针定位研究

对基于AFM的机器人化纳米操作系统而言,一个关键问题是如何实现纳米操作时探针的高精度驱动与定位。对此,本文基于对压电陶瓷驱动器的迟滞/非线性特性及现有驱动方法的详细分析,提出"基于复现扫描轨迹的驱动方法"来对操作时的驱动器进行驱动;另外,还对管式驱动器弯曲运动所产生的运动学耦合误差、探针悬臂变形所引起的针尖偏移误差进行了定量分析与补偿。采用上述驱动方法及进行误差补偿后,可以大大提高探针的定位精度,从而使纳米操作与装配得以高精度进行。纳米刻画实验验证了该新型驱动方法及误差补偿的有效性。

MWCNT操作的动力学运动学建模研究

为实现MWCNT操作运动过程的视觉显示,本文建立了MWCNT的动力学模型,据此可推导出推动MWCNT所需施加力的大小,并根据探针的实际受力判断其能否运动;同时还建立了MWCNT的运动学模型,根据探针的实际位置可获得探针操作下MWCNT的新位置与姿态,并借助虚拟现实技术对视觉界面进行实时更新,实现了MWCNT运动过程的实时视觉显示。基于上述视觉显示,操作者可在线控制探针的作用位置与运动轨迹、以及施加在探针上作用力的大小与方向,实现对MWCNT操作过程及结果的在线控制。MWCNT的操作实验初步验证了该模型的有效性。

基于循环抑制CPG模型的蛇形机器人控制器

依据生物利用中央模式发生器(Central pattern generator,CPG)的自激行为产生有节律的协调运动适应多种环境,基于循环抑制CPG建模理论设计了蛇形机器人CPG控制器模型,分析了单个神经元、循环抑制CPG以及该控制器模型的稳定性,并把该控制器应用到一个结合蛇形机器人“勘查者-Ⅰ”动力学特性的仿真模型,得到了实现蜿蜒运动的CPG控制器参数,进而研究了调节S波个数、身体构形曲率、蜿蜒运动速度以及运动轨迹曲率的CPG控制器参数设定策略。此外,“勘查者-Ⅰ”应用该CPG控制器的输出成功实现了蜿蜒运动。该研究结果为设计人工CPG控制器提供了一个可行的方法。