O(3P)+H2→OH+H反应的立体动力学研究

利用BMS1势能面[Brandao等,J.Chem.Phys.121,8861(2004)],选取碰撞能为34.6 kcal/mol,用准经典轨线方法研究了O(3P)+H2反应的立体动力学性质.计算并讨论了k与j'的夹角的分布关系P(θr)以及描述k-k'-j'三者关系的二面角分布P((ρ)r).(k)为反应物速度方向,k'为产物的速度方向,j'为产物的角动量方向)P(θr)的峰值在90°附近并且关于90°呈对称性分布,这表明产物角动量的方向与初速度的方向垂直.二面角分布P((ρ)r)关于散射平面呈反对称性分布,这一结果表明产物的角动量具有强烈的极化效应.另外,我们还研究了振动激发对产物角动量的影响,结果表明产物的矢量性质对反应物的初始振动态非常敏感.     

固体火箭发动机内弹道性能的仿真研究

研究发动机燃烧室内压强随时间变化的规律,是固体火箭发动机工作过程分析的主要方面,一般采用实验法可以获得直观可靠的数据,但实验法耗资大、周期长,不易操作。本文根据零维内弹道数学模型,运用龙格库塔法及MATLAB语言对某型固体导弹发动机内弹道工作过程进行数值仿真,画出燃烧室内压强随时间变化的曲线,并进一步分析得出影响发动机内弹道性能的因素,仿真结果与发动机燃烧室内工作情况相符,影响因素分析与实验相一致,为固体火箭发动机内弹道性能研究提供了参考。     

散粒噪声用于纳米电子器件与结构的量子效应表征

论述了纳米电子器件与结构中散粒噪声的产生机理和影响因素,表明散粒噪声与输运过程密切相关,按照噪声功率谱的幅值大小将散粒噪声分为泊松散粒噪声、亚泊松散粒噪声和超泊松散粒噪声四类。将散粒噪声的这些规律应用于纳米电子器件和结构,可表征不同器件与结构中的量子效应。利用散粒噪声已经成功检测到无序导线中的开放通道与量子点混沌腔中的波动性,测量出超导体与分数量子霍尔效应中的准粒子电荷。将散粒噪声用于检测纠缠态对量子计算具有重要的意义,自旋相干输运的检测是自旋电子学的重要研究课题。     

光学雷达大气折射误差修正方法研究

光学雷达是靶场试验外弹道测量系统中的主要设备之一.由于大气对光波传播引起的折射效应,使得光学雷达测量中产生折射误差.针对靶场常用的光学雷达系统,根据光波射线在大气中的运行轨迹,利用逐次逼近法得到了实用的光学雷达大气折射误差修正方法.通过对某靶场的实际测量数据检验,证实了该方法的适用性和有效性.目前,该方法已成功地应用于试验靶场,满足了靶场试验的精度要求.     

High resolution dynamic cardiac MRI using partial separability of spatiotemporal signals with a novel sampling scheme

The partial separability (PS) of spatiotemporal signals has been exploited to accelerate dynamic cardiac MRI by sampling two datasets (training and imaging datasets) without breath-holding or ECG triggering. According to the theory of partially separable functions, the wider the range of spatial frequency components covered by the training dataset, the more accurate the temporal constraint imposed by the PS model. Therefore, it is necessary to develop a new sampling scheme for the PS model in order to cover a wider range of spatial frequency components. In this paper, we propose the use of radial sampling trajectories for collecting the training dataset and Cartesian sampling trajectories for collecting the imaging dataset. In vivo high resolution cardiac MRI experiments demonstrate that the proposed data sampling scheme can significantly improve the image quality. The image quality using the PS model with the proposed sampling scheme is comparable to that of a commercial method using retrospective cardiac gating and breath-holding. The success of this study demonstrates great potential for high-quality, high resolution dynamic cardiac MRI without ECG gating or breath-holding through use of the PS model and the novel data sampling scheme.     

The limit set of trajectory in quasi-homogeneous system in ℝ3

In this article, we study the limit set of trajectory in three-dimensional quasi-homogeneous system. For the trajectory which is close to a singular curve, we show that either it approaches a fixed point or infinity, or it oscillates. Moreover, an oscillating example is given. The behaviour of trajectory which is near a closed orbit is also studied. At the end, we classify the integral manifolds of the system with isolated singularities.     

The effect of the rotational excitation of NO on the stereodynamics for the reaction C(~3P)+NO(X~2Π)→CN(X~2Σ~+)+O(~3P)

The stereodynamic properties of the reaction C(3P)+NO(X2Π)→CN(X2Σ+)+O(3P) in different rotational states of reactant NO are studied theoretically by using the quasiclassical trajectory method on 2A' and 2A' potential energy surfaces(PESs) at a collision energy of 0.06 eV.The vector properties in different rotational states on the two surfaces are discussed in detail.The results indicate that the rotational excitation of NO has considerable influence on the stereodynamic property of the reaction occurring on the two surfaces.At the same time,the calculated polarization-dependent differential cross sections(PDDCSs) in different initial rotational states manifest that products are strongly polarized at three scattering angles.     

Extension of high-order harmonic cutoff frequency by synthesizing the waveform of a laser field via the optimization of classical electron trajectory in the laser field

We theoretically investigate high-order harmonic generation by employing strong-field approximation （SFA） and present a new approach to the extension of the high-order harmonic cutoff frequency via an exploration of the dependence of high-order harmonic generation on the waveform of laser fields. The dependence is investigated via detailed analysis of the classical trajectories of the ionized electron moving in the continuum in the velocity-position plane. The classical trajectory consists of three sections （Acceleration Away, Deceleration Away, and Acceleration Back）, and their relationship with the electron recollision energy is investigated. The analysis of classical trajectories indicates that, besides the final （Acceleration Back） section, the electron recollision energy also relies on the previous two sections. We simultaneously optimize the waveform in all three sections to increase the electron recollision energy, and an extension of the cutoff frequency up to Ip ＋ 20.26Up is presented with a theoretically synthesized waveform of the laser field.     

Quasiclassical trajectory theoretical study on the chemical stereodynamics of the O(~1D)+H_2→OH+H reaction and its isotopic variants (HD,D_2)

The quasiclassical trajectory (QCT) method is used to study stereodynamic information about the reaction O ( 1 D) + H 2 →OH + H on the DK (Dobbyn and Knowles) (1 1 A' ) ab initio potential energy surface (PES). A wide scale of collision energy (E c ) from 0.05 eV to 0.5 eV is considered in the dynamic calculations. To reveal the rovibrational excitation effect, calculations at a collision energy of 0.52 eV are carried out for the v = 0 ～ 5, j = 0 and v = 0, j = 0 ～ 15 initial states. The two popularly used polarization-dependent differential cross sections (PDDCSs), dσ 00 /dω t (0, 0) and dσ 20 /dω t (2, 0), and two angular distributions, P(θ r ) and P( r ) are calculated to obtain an insight into the alignment and the orientation of the product molecules. From the calculations, we can obtain that the alignment of the OH product is weaker at high collision energy and becomes stronger with the increase of initial vibrational level, and it is almost insensitive to the initially rotational excitation. Influences of the mass values of isotopes (HD, D 2 ) on the stereodynamics are also shown and discussed. Comparisons between available theoretical results and experimental results are made and discussed.