An approach of DVL-aided SDINS alignment for in-motion vessel

An in-motion alignment algorithm of strapdown inertial navigation system (SDINS) aided by Doppler velocity log (DVL) is described. As the bias and scale factor errors of DVL cannot be estimated by using conventional algorithm, error model of DVL along axes on local level navigation frame is developed while the ship is sailing at a constant speed. Analysis shows that by using this error model in Kalman filter, the observability of state variable can be improved by the angular motion of the ship. Simulation results show that the DVL measurement error can be estimated precisely and the accuracy of the DVL-aided in-sail alignment can be enhanced greatly by using the proposed approach.     

基于叠栅条纹的光刻对准理论分析及标定方法

在线光栅用于纳米光刻对准理论的基础上,为实现光栅方向的标定和掩模硅片对准,提出一种利用相位斜率消除角位移的新方法,并给出线光栅标记及其对准原理。在对准前,掩模对准标记和硅片对准标记存在角位移,重点讨论了此种情况下叠栅条纹的特性以及与光栅物理参数的关系,并给出了相应的计算公式。基于傅里叶频域分析法,对叠栅条纹频率成分与条纹的关系做了简要分析。利用提取叠栅条纹行列方向的一维相位,通过数据拟合,得出了相位斜率与角位移的内在关系,实现了条纹方向的标定。模拟实验结果表明,该方法简单可靠,可分辨的最小角位移低于0.02°。     

Single cell analysis using a glass microchamber for studying movement fluctuations of Navicula pavillardii and Seminavis robusta diatom cells

We propose a new technique for quantitative trajectory analysis of gliding phenomenon of Navicula pavillardii (NP) and Seminavis robusta (SR) diatom cells by single cell observation using a glass microchamber in this short technical note. Two-dimensional trajectory analysis of cell movements was used to determine the angular velocity, velocity, and migration distances of the diatom movement. Based on the trajectory analysis, we found that asymmetrically shaped SR had a larger angular velocity with large fluctuations compared to symmetrically shaped NP, although the velocity of SR was less than that of NP. It suggests that lateral frictional force in a culture medium is an important factor for diatom movements. Our results revealed that the single cell observation using a glass microchamber is effective on quantitative analysis of angular velocity of diatom gliding.     

Product polarization distribution: Stereodynamics of the reaction of atom H and radical NH

The product angular momentum polarization of the reaction of H+NH is calculated via the quasiclassical trajectory method (QCT) based on the extended London-Eyring-Polanyi-Sato (LEPS) potential energy surface (PES) at a collision energy of 5.1 kcal/mol. The calculated results of the vector correlations are denoted by using the angular distribution functions. The polarization-dependent differential cross sections (PDDCSs) demonstrate that the rotational angular momentum of the product H₂ is aligned and oriented along the direction perpendicular to the scattering plane. Vector correlation shows that the angular momentum of the product H₂ is aligned in the plane perpendicular to the velocity vector. It suggests that the reaction proceeds preferentially when the reactant velocity vector lies in a plane containing all three atoms. The orientation and alignment of the product angular momentum affects the scattering direction of the product molecules. The polarization-dependent differential cross sections (PDD-CSs) reveal that scattering is predominantly in the backward hemisphere.     

A high-precision angular control system for HIFU calibration

A design of high-precision angular position control system for calibrating high intensity focused ultrasound (HIFU) is presented with alignment procedures. Two independent angular controls are achieved by combining a worm gear and a belt gear system. The proposed system verifies alignment by comparing simulation data and experimental data with three different transducers and two different types of hydrophones. The performance of the proposed system is compared to that of a commercial system. The results indicate that the proposed system provides high precision angular alignment (e.g., <0.01 radians) with robust reproducibility regardless of the hydrophone type.     

Product polarization distribution: Stereodynamics of the reaction of atom H and radical NH

The product angular momentum polarization of the reaction of H+NH is calculated via the quasiclassical trajectory method (QCT) based on the extended London-Eyring-Polanyi-Sato (LEPS) potential energy surface (PES) at a collision energy of 5.1 kcal/mol. The calculated results of the vector correlations are denoted by using the angular distribution functions. The polarization-dependent differential cross sections (PDDCSs) demonstrate that the rotational angular momentum of the product H2 is aligned and oriented along the direction perpendicular to the scattering plane. Vector correlation shows that the angular momentum of the product H₂ is aligned in the plane perpendicular to the velocity vector. It suggests that the reaction proceeds preferentially when the reactant velocity vector lies in a plane containing all three atoms. The orientation and alignment of the product angular momentum affects the scattering direction of the product molecules. The polarization-dependent differential cross sections (PDDCSs) reveal that scattering is predominantly in the backward hemisphere.      

Laser beam alignment by fast feedback control of both linear and angular drifts

A new way to enhance the directional stability of laser beams with alternating intensity by fast feedback control of both linear and angular drifts has been proposed for alignment of laser beams at higher accuracy. Both linear and angular drifts of laser beams, processed through light intensity modulation and primary alignment using single-mode optical fiber (SMOF), are separated using light path arrangement and detected using phase-lock technique, and are controlled using fast feedback control mechanisms according to their detected magnitudes, so that both linear and angular drifts are suppressed to enhance the directional stability of the emitting laser beams. Theoretical analyses and preliminary experimental results indicate that the approach proposed can be used to achieve an alignment accuracy of more than 10⁻⁸ rad.     

激光陀螺捷联惯导垂向通道测量研究

在参考国外相关垂向通道测量方法的基础上,提出了垂向速度和升沉位移的测量方法。分析了舰船在海平面上的运动特性,设计了关于高度通道的三阶阻尼网络。假设航行在海平面上舰船的高度为零,对阻尼网络引入外部零高度进行阻尼,得到舰船运动的垂向速度,对速度进行高通滤波,积分高通滤波后的高频速度,得到舰船的垂向位移。在此基础上,利用杆臂效应原理,设计了基于双轴摇摆台的升沉测量检测方法,对激光陀螺捷联惯导做了检测实验,结果表明此设计方法已达到国外相关技术先进水平。     

Electronic-polarization investigations of the electron velocity distribution function in an anisotropic plasma

The electron velocity distribution function (EVDF) in an anisotropic plasma is investigated using both the probe method and the magnetic-polarization Hanle techniques. In a helium beam-plasma discharge, the moments of the anisotropic EVDF are measured and the rate constant is determined for the disalignment of helium atoms in the 4¹ D ₂ state due to collisions with charged particles. A new method for investigating anisotropic properties of distant plasma objects unavailable for contact diagnostics is tested experimentally. The EVDF, the cross sections for the alignment of the total angular moments of the excited helium atoms by electron impact, and the degree of the electron pressure anisotropy are measured. An advantage of the method proposed is the possibility of directly measuring the EVDF anisotropy in distant plasma objects, which until now has been estimated only theoretically.     

Dynamic analysis and design of air spring mounting system for marine propulsion system

Marine propulsion unit (MPU) is one of the dominant vibration and noise sources onboard ship. Its vibration can be attenuated effectively by isolating MPU with low-frequency mounting system. But this is difficult to implement due to the stringent requirement of MPU alignment with the propulsion shafting. In this paper a novel air spring mounting system (ASMS) for propulsion system is proposed consisting of air spring subsystem, alignment control subsystem and safety protection subsystem. The load distribution optimization method and dynamic model of ASMS are presented. The factors that affect system stability and natural frequencies are analyzed, as well as the design measures to enhance system performance. A theoretical model is presented to estimate the isolation effect of ASMS. The monitoring model of alignment between MPU and propulsion shafting is established, followed by the alignment control algorithm and converge rule which assures the fast and uniform convergence of both air springs? load distribution and alignment control process. Safety protection mechanism is designed to ensure that the MPU can operate safely in case of ASMS failure or other extreme circumstances. A scaled ASMS prototype is manufactured and tested on a special experimental setup. Experimental results validate the effectiveness of theoretical models and show that the performance of ASMS satisfies the operation requirements of MPU.     

基于互相关的气泡速度的测量方法研究

通过对比互相关技术和多普勒技术的差别，从一个新的角度把互相关技术应用于尾流测速的研究中.实验中利用高速CCD相机拍摄模拟尾流图像.利用快速傅里叶变换实现互相关算法，为提高计算准确度采用高斯曲线拟合互相关函数的峰值并给出拟合公式，得到了亚像素级的运动速度.为标定互相关算法的准确度，文中采用图像平移的方法验证算法的可行性和可靠性.最后把算法应用于模拟尾流的实验中.该方法有望在舰船尾流速度信息的实时获取上起到重要的应用价值.     

Dynamic and geometric alignment of molecules induced by intense laser fields

We present a method to discuss simultaneously the relative importance of molecular dynamic and geometric alignment induced by intense laser fields in theoretical view. This method divides the process of molecular alignment into three steps, which are tightly correlated with that of molecular multielectron dissociative ionization and Coulomb explosion. A fourth-order Runge-Kutta algorithm and a developed counting approach are used to calculate the angular distribution of molecules in the first and second steps of molecular alignment. The last step is described by a field-ionization, Coulomb explosion model. The angular distribution of molecules at the critical distance originated from geometric alignment is obtained by calculating the volume of shells associated with a series of particular angle. The final angular distributions of molecules are obtained by properly weighting the results of three steps. The numerical results of distinguishing between dynamic and geometric alignment for certain conditions are presented and discussed. Our computational results show that the alignment mechanism, which dominates the observed anisotropy of angular distributions of ionic fragments for a given condition, is determined by the dependences of the extent of dynamic and geometric alignment on laser parameters and molecular parameters.     

Direct observation of dynamics of single spinning dust grains in weakly magnetized complex plasma

The rotational dynamics of single dust grains in a weak magnetic field is investigated on a kinetic level. Experiments reveal spin-up of spherical dust grains and alignment of their magnetic moments parallel to the magnetic induction vector. The angular velocity of spinning prolate grains varies as magnetic induction increases to 250 G. Spinning dust grains are found to flip over only when the magnetic field magnitude is changing. The results demonstrate that dusty plasma has paramagnetic properties. Qualitative interpretations are proposed to explain newly discovered phenomena.     

浅海运动目标波束域波导不变量测距方法研究

波导不变量是描述海洋波导环境声信号水平距离与频率干涉结构现象的特征参量。运动目标波导不变量测距方法需要已知目标速度值,运动目标速度一般是未知的。针对这一问题,本文提出了一种利用水平线阵估计目标运动速度的浅海波导不变量测距方法。该方法通过不同时刻波束域声信号互谱分析进行声源速度估计,结合HOUGH变换提取的LOFAR图斜率和波导不变量进行运动目标测距。仿真结果表明,该方法能够有效的进行运动目标的距离估计。利用2013年7月浅海实验数据,该方法估计出了发射船的距离,并与GPS测量的距离进行对比,相对误差小于10%。      

Parity splitting in nuclei involving octupole correlations and the alignment of the angular momentum

A rotational model based on a simultaneous analysis of parity splitting and the alignment of the angular momentum is developed to describe high-spin negative-parity states. A simple formula for the energy of these states is proposed. It is shown that negative-parity states exhibit alignment, provided that the ground-state band is aligned and that the two opposite-parity bands can be considered as a single alternating-parity band.     

In situ technique for measuring the orthogonality of a plane wave to a substrate

A new compact in situ method of measuring the perpendicularity of a plane wave to a substrate is proposed. Off-axis cylindrical Fresnel lenses are used to focus a portion of the incident plane wave onto target lines. The displacement of the focal line from the targets is determined by the degree of angular misalignment. The proposed design has been incorporated into a 10-mm-thick fused-silica module, which enables us to obtain an alignment precision of better than 0.0083 degrees. This method is designed for use in optical assembly procedures that require an incident collimated beam that is normal to the alignment features. Experimental results are presented.     

利用信号自相关函数warping变换的浅海水下移动观测平台机动优化方法

水下移动观测平台的机动航路对纯方位目标运动分析方法的使用性能具有重要的影响。针对此问题,提出了一种利用信号自相关函数warping变换的浅海水下移动观测平台机动优化方法。该方法利用warping变换从接收信号自相关函数中提取与目标距离相关的简正波相干项的特征频率,进而估计距离特征量,再根据预估的目标初始距离范围估计目标运动态势范围。针对观测平台机动方式为匀速转弯运动的情况,以目标方位变化率为评价指标得到了观测平台在所估计的目标运动态势范围下的最优转弯角速率。在浅海Pekeris波导环境下的数值仿真结果和实验数据处理结果表明:方位变化率与纯方位扩展卡尔曼滤波算法的性能密切相关;利用warping变换可以有效地估计距离特征量;观测平台根据以方位变化率为评价指标得到的最优转弯角速率进行机动可以获得较好的目标跟踪性能,收敛时间较短,目标位置估计误差较小。      

Use of nonlinear asymmetrical shock absorber to improve comfort on passenger vehicles

In this study the behaviour of two different types of shock absorbers, symmetrical (linear) and asymmetrical (nonlinear) is compared for use on passenger vehicles. The analyses use different standard road inputs and include variation of the severity parameter, the asymmetry ratio and the velocity of the vehicle. Performance indices and acceleration values are used to assess the efficacy of the asymmetrical systems. The comparisons show that the asymmetrical system, with nonlinear characteristics, tends to have a smoother and more progressive performance, both for vertical and angular movements. The half-car front asymmetrical system was introduced, and the simulation results show that the use of the asymmetrical system only at the front of the vehicle can further diminish the angular oscillations. As lower levels of acceleration are essential for improved ride comfort, the use of asymmetrical systems for vibrations and impact absorption can be a more advantageous choice for passenger vehicles.     

一种基于自适应滤波的高动态星敏感器在轨校正方法

为了提高高动态环境下星敏感器的质心提取精度,提出了一种基于自适应滤波的在轨校正方法.该方法能够适应角速度变化的星敏感器,自适应的调整校正矩阵.使用提出的基于时空相关性的噪声估计滤波器跟随星点窗口实时更新校正矩阵,对星点准确校正.与传统地面校正方法相比,本文方法不仅减少了成本,且实时更新校正矩阵,校正更加可靠.通过实验验...     

采用旋转涂膜法制备基底生长的定向碳纳米管阵列

 采用化学气相沉积技术,利用旋转涂膜法制备催化剂基底材料,通过对涂膜过程中的角速度、旋转时间以及基底还原过程中温度的控制改变催化剂颗粒的分布状态,获得了粒径均匀分布的催化剂基底,该基底上催化剂颗粒集中分布在47～62 nm区间,再利用该基底生长出定向碳纳米管阵列。运用扫描电镜、透射电镜、拉曼光谱仪对样品进行了表征。结果表明旋转涂膜法制备的基底平整性好于普通的滴膜法,且较其它基底制备方法具有简单易控、可使催化剂均匀分散等特点。利用该基底制备的碳纳米管阵列定向性良好。