二维谱估计算法的空间探测性能分析及验证

针对二维谱估计算法的空间探测性能分析的需求,从计算速度、计算量、顽健性、计算精度以及实际工程应用的角度出发,对基于L型阵列的二维MUSIC、二维干涉仪、二维增广矩阵束的谱估计算法进行了简要介绍,并对上述二维谱估计算法的性能进行了仿真分析,得到了3种算法的角度RMSE的对比分析,可知在同样仿真条件下,二维增广矩阵束算法最优,二维MUSIC算法次之,二维干涉算法最差。同时,构建了相应的试验场景,通过试验分析上述二维谱估计算法的空间探测性能,得到的试验结论与仿真结论一致。在此基础上,提出了二维增广矩阵束算法可扩展应用到雷达测控一体化系统的思路。     

铋烯材料生长控制及光电子器件应用研究进展

石墨烯和其他二维材料凭借其自身独特的物理和化学性能,引起了科学和工程领域的广泛关注。探索新型二维材料体系并扩展其应用范围是研究人员的热点研究内容。其中,第五主族单元素二维烯(二维磷烯、二维砷烯、二维锑烯、二维铋烯)具有较窄的且可调节的能带宽度、高的载流子迁移率、良好的透光性和优异的光电子学性能,成为二维材料及其在光电子应用领域的新的研究对象。鉴于此方面,从基本物理结构、材料的制备方法和在光电子方面的应用深入分析二维铋烯的相关理论以及实验研究的工作进展。在材料的可控制备方面,重点围绕二维铋烯的电化学剥离法展开相应论述。最后讨论了二维铋烯在光电子学应用领域的现状,包括在超快光电子学器件的应用,并且对二维铋烯未来的发展进行了展望。     

倾斜放置二维数字阵列雷达天线参数优化

介绍了二维相控阵或二维数字阵列天线锥形扫描与俯仰、方位扫描时的坐标变换,重点阐述了倾斜放置二维相控阵或二维数字阵列天线按俯仰、方位扫描时的坐标变换关系,基于该坐标变换,得出倾斜放置二维平面相控阵或二维平面数字阵列天线扫描区域边界在变换域上呈椭圆形的结论。基于这样的结论,可以实现对阵面倾斜角度、几何参数的优化。     

多维地址码对OCDMA系统性能的影响

讨论了一维/二维二次素数码、光正交码的构造过程、相关性、容量等特性,分析了它们对光码分多址(OCDMA)系统误码性能和用户容量的影响.为得到不同码字与不同维数码字对OCDMA系统的误码率影响程度,仿真比较了一维、二维二次素数码和一维、二维光正交码之间的误码率与同步用户数的关系以及二维素数码与二维光正交码的误码率与同步用...     

PAL信号二维频域分析及应用

本文较系统地论述了PAL电视信号的二维频谱、二维自相关系数及二维功率谱密度,讨论了PAL二维频率响应的CZP测量法,分析了以往PAL视频处理的二维响应,并给出了一种PAL二维自适应视频综合处理器的方案分析。     

一种构造最佳四元二维互补阵列的新方法

该文利用最佳四元二维互补阵列和准最佳四元二维互补阵列的性质,给出了一种构造最佳四元二维互补阵列的新方法。使用这种方法,可以将一个二维的st 阶的最佳四元二维互补阵列和一个2st 阶的准最佳四元二维互补阵列,构造成新的一类二维4st 阶和2s2t 阶的最佳四元二维互补阵列。     

基于二维循环统计量的二维谐波信号参数估计

本文利用二维循环统计量方法对二维平稳乘性噪声与二维平稳加性噪声共存情况下的二维谐波信号参数估计问题进行了讨论.利用二维循环统计量能够有效地抑制二维平稳乘性噪声和二维平稳加性噪声的特点,有效地从噪声中提取出信号参数.仿真实验对算法作了说明.     

二维地址码对OCDMA系统误码率性能的研究

介绍了二维二次素数码、二维光正交码及二维Rs地址码的构造,讨论了它们对OCDMA系统误码性能和用户容量的影响.通过仿真分析了二维地址码的用户容量与码长、码重的关系,以及误码率随同步用户数、判决门限的变化曲线.结果表明,对于二维OCDMA系统,在判决门限一定的条件下,同步用户数越大,系统的误码率越低;系统同步用户容量随着...     

量子点场效应单光子探测器二维电子气电子迁移率分析

设计了一种基于场效应晶体管的量子点场效应单光子探测器,利用二维弛豫时间的近似理论建立了二维电子气电子迁移率的散射模型,通过求解量子点场效应单光子探测器GaAs/AlxGa1-xAs二维电子气系统电子和声子相互作用的Hamiltonian函数,得到了不同温度、不同Al组分以及不同二维电子气电子面密度条件下晶格振动散射对探测器二维电子气电子迁移率的影响.仿真结果显示,提高二维电子气的电子面密度浓度和适当增大Al组分,并降低工作温度,有助于探测器获得更高的二维电子气电子迁移率.     

新型激光扫描仪RF620及其应用

RIFFEK公司的RF620系列二维激光位移传感器（二维轮廓扫描仪）问世以来,以其极高的性价比久负盛名。该激光轮廓扫描仪主要应用于物体轮廓、二维尺寸、二维位移的非接触测量与检验,以及目标物体的分拣。本文介绍了此系列扫描仪的原理、接口、配置及软件开发工具。     

A Calibration Technique for a Two‐Axis Magnetic Compass in Telematics Devices

This paper presents an efficient algorithm for using the two‐axis magnetic compass in portable devices. The general magnetic compass module consists of a three‐axis magnetic compass and a two‐axis inclinometer to calculate tilt‐compensated azimuth information. In this paper, the tilt error is compensated using just a two‐axis magnetic compass and two‐axis accelerometer. The third‐axis data of the magnetic compass is estimated using coordinate information that includes the extended dip angle and tilt information. The extended dip angle is estimated during the normalization process. This algorithm can be used to provide the tilt‐compensated heading information to small portable devices such as navigation systems, PDAs, cell phones, and so on.     

Reflection and transmission of a dielectric waveguide mirror

A numerical analysis of a generalized dielectric waveguide mirror of arbitrary structure angle is presented. A plane wave expansion technique is used to calculate output angle, power transmission, inter-waveguide and intra-waveguide coupling, far-field emission profile and losses of the waveguide mirror. In order to evaluate the effect of divergence, two methods are used and the result indicate that the effect is minimal. Furthermore, the introduction of a tilt in the mirror surface is examined and reveals a reduction in the inter-waveguide coupling as the tilt is increased. However, this coupling remains symmetric in tilt despite the asymmetry of the geometry due to the tilt. Results of the output angle and the FWHM (full-width half-maximum) of the emission profile are compared to experimental values obtained for a semiconductor triangular ring laser     

Gain tilt of erbium-doped fiber amplifiers due to signal-inducedinversion locking

A theoretical analysis describing an interpretation of the fundamental processes, responsible for the second-order distortion of AM signals in erbium-doped fiber amplifiers (EDFAs) is presented. It is shown that the locked-inversion gain tilt rather than the widely used continuous wave gain tilt is responsible for the distortion. The theoretical analysis is confirmed by experiments showing that the two types of gain tilt may differ by factors of up to 60. In particular, it is demonstrated that the locked-inversion gain-tilt may be significant even at the CW gain peak. Experimental results indicate that the relevant gain tilt can be reduced to acceptable levels by proper design of the EDFA     

TMT 三镜系统tilt 轴轴承方案研究

30 m口径望远镜(TMT)的三镜跟踪系统(M3PA)的运动性能和指向精度指标均高于已建成的各大望远镜,且工况复杂多变,给设计人员带来了巨大的挑战。三镜跟踪系统包括Rotator 轴和Tilt轴两部分。重点研究了Tilt 轴轴承布置方案以及相应分析。提出了两种轴承方案,经过分析,使用一对双列角接触转盘轴承的方案更适合于Tilt 轴的工作需要,此时结构第一阶谐振频率可达到15.1Hz,满足Tilt 轴的设计要求。选定方案后,针对所选择的轴承,使用ANSYS 进行了仿真。仿真结果显示,所选轴承中滚动体的最大承载达到5 000 N,最大应力大约为2 300 MPa,承载曲线满足经典余弦分布,从而证明仿真数据可靠,模拟方法可信;另外四列滚动体上都有明显的承载,从而说明所选择的轴系能够很好地将载荷分散到两侧结构架上。分析结果表明,这种结构形式能够满足TMT 三镜系统对刚度要求。     

Why illuminant direction is fundamental to texture analysis

The author shows that directed illumination used in the image acquisition process can act as a directional filter of three-dimensional texture. An image model of texture is presented which, given the illuminant vector, may be used to predict the directional characteristics of image texture. Simulations and the results of laboratory experiments are presented that confirm the predicted directional filtering effects. The image model is used to predict the output of a directional texture measure: Laws' L5E5 operator (K.I. Laws, 1980), Empirical results using four samples of isotropic texture confirm that the operator's output is significantly affected by changes in the angle of tilt of the illuminant. They also show that the model provides a good basis for predicting the behaviour of such operators. Finally the effect of changes in illuminant tilt on the distributions of the operator for two isotropic textures are presented. These results show that considerable misclassification would result in using an L5E5-based classifier if the illuminant tilt angle were changed between training and classification sessions     

Coupled modes of anisotropic polarization maintaining fibers

Wave coupling between the fundamental vector modal fields of two identical, polarization-maintaining, weakly guiding fibers is analyzed. An improved coupled-mode theory is used that also applies to anisotropic materials. Coupling coefficients that are the elements of a coupling matrix are calculated and presented as functions of the relative tilt angle between the two fiber principal axes. Exact analytical expressions for the eigenvalues and their associated eigenvectors are given in terms of the elements of this coupling matrix, for any relative tilt angle. Symmetry relations that are found between elements of the coupling matrix much simplify the presentation of the eigenvectors. A weak-coupling approximation of the eigenvector expressions, which is also given, retains their qualitative properties     

气体摆式倾角传感器敏感机理的有限元分析

解释了气体摆式倾角传感器的敏感机理。采用有限元方法,利用ANSYS-FLOTRAN CFD软件,通过建模、划分网格、加载和求解等途径,计算了在不同倾斜状态下二维密闭腔中两点热源引起的对流场。计算结果表明:在水平状态时,两热源处的气流速度相等,两热电阻丝上的电流相等,电桥电路输出为零;在倾斜状态下时,两热源处的气流速度之差随着倾斜角度而变化,引起两热电阻丝上电流之差也随之变化,电桥输出一个对应于倾斜角度的电压。有限元计算方法为气体摆式倾角传感器的优化设计,开辟了一条有效的研究途径。     

The One-Wheel Cubli: A 3D inverted pendulum that can balance with a single reaction wheel

This article presents a novel 3D inverted pendulum that can balance on one of its corners using only a single reaction wheel. This is achieved by a careful design of the mass moment of inertia in such a way that the inertia along the two principal tilt axes is significantly different. The consequence is a time-scale separation of the underlying tilt dynamics, which renders the system controllable. We show that controllability is maximized when the ratio of the two principal inertia values amounts to the square of the silver ratio and discuss a sensor placement that minimizes variance in our tilt estimates. Both of these aspects lead to a principled design of the system. A model is derived from first-principles and used for delay compensation, state estimation, and to design a linear-quadratic regulator that stabilizes the highly underactuated system in its upright equilibrium. Thereby, the modeling and compensation of cantilever deflections, which arise from the lightweight design, is crucial. The article includes experimental results, which underline the efficacy of the system design and highlight an excellent balancing performance of the proposed feedback controller.     

Effect of tilt angle variations in a halo implant on V/sub th/ values for 0.14-/spl mu/m CMOS devices

Sensitivity of critical transistor parameters to halo implant tilt angle for 0.14-/spl mu/m CMOS devices was investigated. V/sub th/ sensitivity was found to be 3% per tilt degree. A tilt angle mismatch between two serial ion implanters used in manufacturing was detected by tracking V/sub th/ performance for 0.14-/spl mu/m production lots. Even though individual implanters may be within tool specifications for tilt angle control (/spl plusmn/0.5/spl deg/ for our specific tool type), the relative mismatch could be as large as 1/spl deg/, and therefore, result in a V/sub th/ mismatch of over 3% from nominal. The V/sub th/ mismatch results are in qualitative agreement with simulation results using SUPREM and MEDICI software.     

Three-dimensional finite-element method for solving electromagnetic problems

A 3-dimensional numerical method of determining the vector fields within a closed lossless electromagnetic system is described. The method is used to find the dominant-mode resonant frequencies for two cases of a rectangular cavity partially loaded with dielectric.