Product polarization and mechanism of Li + HF(v=0, j=0) → LiF(v', j') + H collision reaction

A state-to-state dynamics analysis for the Li＋HF （v = 0, j = 0）→LiF （v’, j’）＋H collision reaction has been performed through quasiclassical trajectory （QCT） calculations. It is found that the differential cross section （DCS） of the LiF products from the title reaction is preferentially backward scattering for v’=0, yet forward scattering for v’=1 and 2. For v’=3, the DCS exhibits forward, backward, and sideways scatterings. The variation of the internuclear distances and angles along the propagation time reveals that more than 99.08% of reaction trajectories undergo the direct reaction mechanism. The values of the polarization parameters a1-{1} and a0{2} demonstrate that the product rotational angular moment j’ is not only aligned perpendicular to the reagent relative velocity vector k, but also oriented along the negative y axis. These product polarization results agree well with the recent quantum mechanical studies. The mechanism of these results was proposed and discussed in detail.

Trajectory analysis of few-cycle strong field ionization in two-color circularly polarized fields

Bichromatic circularly polarized fields provide a useful tool to probe the ionization dynamics.In this work, we compare the photoelectron momentum distribution in few-cycle bichromatic field of different helicities.The spectral features are analyzed with semiclassical trajectories derived from the strong field approximation.In particular, the interference fringes in momentum distribution are investigated by tracking the ionization time and tunneling exits of released photoelectrons.Different types of trajectories that contribute to the interference fringes are elucidated.

Influence of Isotope Effects on Product Polarizations of N(~2D)+D_2, N(~2D)+H_2 and N(~2D)+HD Reactive Systems

To figure out the influence of isotope effect on product polarizations of the N（2D）＋D2 reactive system and its isotope variants, quasi-classical trajectory（QCT） calculation was performed on Ho＇s potential energy surface（PES） of 2A″ state. Product polarizations such as product distributions of P（θr）, P（φr） and P（θr,φr）, as well as the generalized polarization-dependent differential cross sections（PDDCSs） were discussed and compared in detail among the four product channels of the title reactions. Both the intermolecular and intramolecular isotope effects were proved to be influential on product polarizations.

Intrinsic product polarization and branch ratio in the S（~1D,~3P）＋HD reaction on three electronic states

The intrinsic product polarization and intramolecular isotope effect of the S（~1D,~3P） ＋ HD reaction have been investigated on both the lowest singlet state（1A） and the triplet state（3A and 3A） potential energy surfaces by using quasi-classical trajectory and quantum mechanical methods.The calculations indicate that intramolecular isotope effects are different on the three electronic states.The stereodynamics study shows that the P（θr） distributions,P（φ r） distributions,and polarization-dependent differential cross sections（PDDCSs）（00） are sensitive to mass factor and the product angular momentum vectors are not only aligned but also oriented.

基于极化时变调控表面的有源欺骗干扰辨识方法

聚焦雷达对抗中极化信息获取与利用的应用需求,该文研究了基于极化时变调控表面的有源欺骗干扰辨识方法。首先,设计了一套在9.6~10.1 GHz频带内支持3 bit相位量化的各向异性相位调制表面,通过优化相位调制编码序列,实现了极化态按需调控。然后,将极化调控表面加装在单极化雷达天线上,使天线发射和接收电磁波的极化态沿特定极化轨道变化,通过提取目标与有源欺骗干扰的极化域差异,实现两者辨识。仿真分析表明,在3种不同的极化轨道约束下,干扰与目标均具有显著的聚类效应,可获得稳定的干扰辨识效果。相较于依赖双极化或全极化雷达体制的干扰辨识方法,该文所提方法兼具低成本与高效性,在雷达抗干扰中具有很大的应用潜力。

Trajectory Tracking Strategy for Gliding Hypersonic Vehicle with Aileron Stuck at an Unknown Angle

A nonlinear robust trajectory tracking strategy for a gliding hypersonic vehicle with an aileron stuck at an unknown position is presented in this paper. First, the components of translational motion dynamics perpendicular to the velocity are derived, and then a guidance law based on a time-varying sliding mode method is used to realize trajectory tracking. Furthermore, the rotational equations of motion are separated into an actuated subsystem and an unactuated subsystem. And an adaptive time-varying sliding mode attitude controller is proposed based on the actuated subsystem to track the command attitude and the tracking performance and robustness are therefore enhanced. The proposed guidance law and attitude controller make the hypersonic vehicle fly along the reference trajectory even when the aileron is stuck at an unknown angle. Finally, a hypersonic benchmark platform is used to demonstrate the effectiveness of the proposed strategy.

Quasi-classical trajectory study of the isotope effect on the stereodynamics in the reaction H(~2S) + CH(X^2Π;u= 0,j= 1) → C(~1D) + H_2(X^1Σ_g^+)

The isotope effect on the stereodynamic properties in the title reaction is investigated by a quasi-classical trajectory （QCT） method on the 11At potential energy surface at a collision energy of 23.06 kcal/mol. The angular distributions P（φr ）, P（θr）, P（θr, φr）, and the polarization-dependent generalized differential cross sections are calculated, which demonstrate the observable influences on the rotational polarization of the product by the isotopic substitution of H with D.

Quasi-classical trajectory approach to the O(~1D)+HBr→OH+Br reaction stereo-dynamics on X^1A'potential energy surface

The vector properties of reaction O（1D）＋HBr→OH＋Br on the potential energy surface （PES） of X1A＇ ground singlet state are studied by using the quasi-classical trajectory （QCT） theory. The polarization-dependent differential cross sections （PDDCSs）, the average rotational alignment factor （P 2 （j＇- k）〉, as well as the distributions reflecting vector correlations are also computed. The analysis of the results shows that the alignment and the orientation distribution of the rotation angular momentum vector of product molecule OH is influenced by both the effect of heavy-light heavy （HLH） type mass combination and the deep well of PES.

A Fuzzy Clustering Algorithm Based on Multipath Component Trajectory for Millimeter Wave Radio Channels

Time-varying channel modeling plays an important role for many applications in time-variant scenarios,while most clustering algorithms focus on static channels and cannot accurately model the channel time-evolution properties.In this paper,a fuzzy clustering algorithm based on multipath component(MPC)trajectory is proposed.Firstly,both the distance and velocity similarities of the MPCs in different snapshots are taken into account to track the MPC trajectory,in which the fuzzy scheme and a kernel function are used to calculate the distance and velocity similarities,respectively.Secondly,a fuzzy MPC trajectory clustering algorithm is proposed to cluster the MPCs in multiple snapshots.The MPCs in a snapshot are clustered according to the membership,which is defined as the probability that a MPC belongs to different clusters.Finally,time-varying channels at 28 GHz are simulated to validate the performance of our proposed algorithm.The results show that our proposed algorithm is able to accurately identify the clusters in time-varying channels compared with the existing clustering algorithms.

Role of potential on high-order harmonic generation from atoms irradiated by bichromatic counter-rotating circularly polarized laser fields

We investigate high-order harmonic generation from atoms irradiated by bichromatic counter-rotating circularly polarized laser pulses by numerically solving the time-dependent Schrödinger equation.It is found that the minimum energy position of the harmonic spectrum and the non-integer order optical radiation are greatly discrepant for different atomic potentials.By analyzing the quantum trajectory of the harmonic emission,discrepancies among the harmonic spectra from different potentials can be attributed to the action of the potential on the ionized electrons.In addition,based on the influence of the driving light intensity on the overall intensity and ellipticity of higher order harmonics,the physical conditions for generating a high-intensity circularly polarized harmonic can be obtained.

Quasi-classical trajectory study of collision energy effect on the stereodynamics of H + Br O → O + HBr reaction

Quasi-classical trajectory （QCT） studies on the stereodynamics of H ＋ BrO → O＋ HBr reaction have been performed on the X1A＇ state of ab initio potential energy surface by Peterson [Peterson K A 2000 J. Chem. Phys. 113 4598] in a collision energy range from 0 kcal/mol to 6 kcal/mol. Two of the polarization-dependent generalized differential cross sections （PDDCSs）, （2π/σ）（dσ 00/d ω） （PDDCSoo） and （2π/σ）（dσ20/doh） （PDDCS20） are considered. The rotational polarizations of these products show sensitive behaviors to the calculated collision energy range. Furthermore, in order to gain more knowledge about vector correlations, the product angular distribution, P（θr）, and the dihedral angle, P （Фr）, are calculated, and the results indicate that both the rotational alignment and orientation of the product are enhanced as collision energy increases.

Quasi-classical trajectory investigation on the stereodynamics of Li + DF(v=1-6,j=0)→LiF+D reaction

In this paper, the stereodynamics of Li ＋ DF → Li F ＋ D reaction is investigated by the quasi-classical trajectory（QCT）method on the ^2A＇ potential energy surface（PES） at a relatively low collision energy of 8.76 kcal/mol. The scalar properties of the title reaction such as reaction probability and cross section are studied with vibrational quantum number of v = 1–6. The product angular distributions P（θr） and P（φr） are presented in the same vibrational level range. Moreover, two polarization-dependent generalized differential cross sections（PDDCSs）, i.e., the PDDCS00 and PDDCS22＋are calculated as well. These stereodynamical results demonstrate sensitive behaviors to the vibrational quantum numbers.

基于多源信息紧耦合的四足机器人平面导航方法

四足机器人具有地形适应能力强,行动灵活的特点,适用于抢险救援以及星际探索等复杂环境。该文为了实现卫星拒止环境中四足机器人的自主导航,并提升系统的抗干扰性,提出了一种基于偏振定向原理的多源信息融合算法,并将该算法应用于四足机器人的平面导航规划中。首先,基于卡尔曼滤波方法,设计了“偏振光+惯性+地磁”的多传感器紧耦合导航算法,并通过主动干扰实验,验证融合航向角的鲁棒性,在光干扰下,航向角标准差较融合前减小64.8%,电磁干扰环境下基本不受影响;然后,基于该导航算法设计了四足机器人的平面循迹对比实验,结果表明该算法推算的路径绝对轨迹误差(ATE)两圈平均值为0.273 m,较传统磁航角参考算法减少了50.1%,较偏振角参考算法减少了35.2%。实验验证了该组合导航算法的航向鲁棒性得到有效提升,且适用于四足机器人在卫星拒止环境的自主导航。

煤层槽波的极化特征及其滤波

文章利用多分量数值模拟获得槽波信号及其极化轨迹图,结合槽波信号的本征方程,求取槽波的主极化方向和偏振系数;选取Poline滤波器,采用不同的滤波参数(p,q)对正演模拟信号进行滤波处理,并用极化轨迹图直观地显示出滤波前后差异。由于极化滤波实质是一种振幅加权滤波,滤波参数控制了信号对于其主极化方向的趋近程度,因此极化滤波会造成各分量的能量损失,需综合考虑选择合适的滤波参数。文中利用极化滤波法对实测信号进行了处理,取得了良好的应用效果。

反应物振动激发对反应He+H_2^+→HeH^++H影响的准经典轨线研究

基于PPA势能面(Palmieri,P.;Puzzarini,C.;Aquilanti,V.Mol.Phys.,2000,98:1835),运用准经典轨线(quasi-classical trajectory)方法,对反应He+H2+(v=0-2,j=0)→HeH++H的立体动力学性质进行了理论研究.结果表明,反应物振动激发对反应的k-j′两矢量相关和k-k′-j′三矢量相关分布都产生了较大影响.除此之外,极化微分反应截面对振动量子数v也非常敏感.

O+HCl→OH+Cl反应的立体动力学的准经典轨线研究

运用准经典轨线方法,基于Peterson从头计算势能面对O+HCl→OH+Cl反应的立体动力学性质进行了研究.讨论了在31.77和51.04 kJ/mol两种碰撞能情况下极化依赖的微分反应截面(2π/σ)(dσ00/dωt),(2π/σ)(dσ20/dωt),(2π/σ)(dσ22+/dωt)和(2π/σ)(dσ21-/dωt)以及描述k-j′两矢量相关和k-k′-j′三矢量相关的分布函数P(θr)和P(фr).计算得到的P(θr)分布表明,产物分子的转动角动量j′具有强烈的取向分布,并且产物转动角动量的取向效应对散射能的变化比较敏感.而P(фr)的分布表明,产物分子虽然具有沿着y轴的取向效应,但是没有明显的定向效应.

弹道扰动引力无奇异性计算模型的建立

利用地球重力场模型来计算飞行器轨道扰动引力,当飞行器飞越两极及其附近地区时,由于Legendre函数的一阶导数以及分母上所含余纬的正弦函数,将导致扰动引力的计算出现无穷大.本文推导了Legendre函数一阶导数以及球谐函数mP nm(cosθ)/sinθ无奇异性的计算公式,建立了飞行器轨道扰动引力各分量无奇异性的详细计算模型,并通过数值试验分析了扰动引力各分量在两极地区的变化趋势,从而彻底解决了利用地球重力场模型计算两极地区飞行器轨道扰动引力时存在的奇异性问题.

弹道导弹有源干扰的极化抑制

分析了弹道中段有源干扰机的章动特性,基于该特性对有源干扰信号的极化变化规律进行了研究,在上述研究的基础上,提出了弹道中段有源干扰的极化抑制方法:先根据接收极化估计干扰机章动特性,然后根据章动特性预测极化变化,最后利用雷达变极化接收抑制有源干扰。与以往的固定极化干扰抑制方法不同的是,该方法可有效预测干扰机章动产生的干扰信号极化变化,提高了干扰抑制性能。仿真实验验证了该方法的有效性。

基于伏安特性动态轨迹的谐振接地系统弧光高阻接地故障检测方法

在谐振接地系统中发生弧光高阻接地故障时,暂稳态故障电流均微弱,且电弧引发的非线性特征显著。现有检测方法多采用阈值设定的定量分析方法,其可靠性与灵敏性存在明显博弈,难以同时兼顾,正动率较低。针对上述问题,该文分析了弧光高阻接地故障时零模电压与零模电流间的伏安特性动态轨迹,并基于零模电压、零模电流间的初始极性特征和伏安特性动态轨迹设计了一种新的弧光高阻接地故障检测算法,可兼顾检测的灵敏性和可靠性;仿真和现场录波数据验证了所提算法的有效性。

基于极化不变量的谐波雷达导引头目标识别算法

为解决基于目标谐波散射系数的FFT识别算法无法有效识别目标全弹道谐波散射特性的问题,采用了基于极化不变量的目标识别算法.根据目标的半导体模型拟合出目标的谐波散射系数,用卡尔曼滤波器对谐波散射系数进行估计.将估计结果作为酉矩阵的对角元素,建立了目标谐波极化散射矩阵及与其对应的功率矩阵,通过就不同的目标进行谐波散射极化计算得到了仿真结果.结果表明,与基于目标谐波散射系数的FFT识别算法相比,目标谐波极化散射矩阵行列式的值及功率矩阵的迹能反映出目标的全弹道谐波散射特性,二者可以作为有效的目标识别特征量.