Multi-EAP:Extended EAP for multi-estimate extraction for SMC-PHD filter

The ability to extract state-estimates for each target of a multi-target posterior, referred to as multi-estimate extraction (MEE), is an essential requirement for a multi-target filter, whose key performance assessments are based on accuracy, computational efficiency and reliability. The probability hypothesis density (PHD) filter, implemented by the sequential Monte Carlo approach, affords a computationally efficient solution to general multi-target filtering for a time-varying num-ber of targets, but leaves no clue for optimal MEE. In this paper, new data association techniques are proposed to distinguish real measurements of targets from clutter, as well as to associate par-ticles with measurements. The MEE problem is then formulated as a family of parallel single-estimate extraction problems, facilitating the use of the classic expected a posteriori (EAP) estima-tor, namely the multi-EAP (MEAP) estimator. The resulting MEAP estimator is free of iterative clustering computation, computes quickly and yields accurate and reliable estimates. Typical sim-ulation scenarios are employed to demonstrate the superiority of the MEAP estimator over existing methods in terms of faster processing speed and better estimation accuracy.     

Improved specular point prediction precision using gradient descent algorithm

Global Navigation Satellite Systems Reflectometry (GNSS-R) utilizes GNSS signals reflected off the Earth surface for remote sensing applications. Due to weak power of reflected signals, GNSS-R receiver needs to track reflected signals by open loop. The first step is to calculate the position of specular point. The specular point position error of the existing algorithm—Quasi-Spherical Earth (QSE) Approach—is about 3 km which may cause troubles in data post-processing. In this paper, gradient descent algorithm is applied to calculate position of specular point and the calculation is based on World Geodetic System 1984 (WGS 84) ellipsoid in geodetic coordinate. The benefit of this coordinate is that it is easy to investigate the effect of real surface’s altitude. Learning rate—the key parameter of the algorithm—is adaptively adjusted according to initial error, latitude and gradient descent rate. With self-adaptive learning rate strategy, the algorithm converges fast. Through simulation and test on Global Navigation Satellite System Occultation Sounder II (GNOS II), the performances of the algorithm are validated. The specular point position error of the proposed algorithm is about 10 m. The speed of the proposed algorithm is competitive compared with the existing algorithm. The test on GNOS II shows that the proposed algorithm has good real-time performance.     

Radial distribution of galactic cosmic rays at solar maximum

In this paper we analyze the spatial distribution of galactic cosmic rays during periods of maximum solar activity of the cycles 21, 22 and 23. We have used a two dimensional model to solve the cosmic ray transport equation. This model includes all relevant physical processes: diffusion, convection, drift and shock effects on cosmic ray propagation inside the heliosphere. We focused on the study of the radial distribution of galactic cosmic rays, and compare our results with the spacecraft observations for two energies (175 MeV H and 265 MeV/n He). Although the radial intensities of galactic cosmic rays can be explained qualitatively with all three local interstellar spectra (LISs) used in this work, we applied a reduced chi-squared analysis to investigate the best LIS that could fit the data.     

ALGORITHMS FOR TRACKING MANEUVERING TARGET WITH PHASED ARRAY RADAR

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功能梯度材料悬臂梁受复杂载荷作用的分层剪切理论

本文采用分层剪切变形理论对功能梯度材料层梁进行了分析，对立了功能梯度材料悬臂梁模型。取材料为非均质性，材料弹性系数随梯度变化，应用边界条件，层间连续条件，得出梁结构的变形与应力。结果表明，存在优化的梯度因子使得悬臂梁具有最佳的承载能力，载荷分布对结构应力场温度场有效大的影响。     

基于星敏感器四元数的卫星角速度预测滤波算法

为在无陀螺或陀螺故障时可用星敏感器估计姿态角速度，在扩展卡尔曼滤波（EKF）和非线性预测滤波的基础上提出了基于四元数的卫星角速度估计算法，并给出了相应的模型。该算法对角速度建模精度的要求较低，无需卫星动力学方程，方法简单且易于实现。仿真结果表明，算法的精度较高。虽然仍受噪声和步长的影响，但相对基于EKF和最小模型误差的角速度估计算法，其性能改善较大。     

用最小二乘法确定卫星间相对姿态

为确定多卫星编队飞行时卫星的相对姿态，采用坐标系的空间变换，用最小二乘法计算两卫星本体坐标系间的旋转参数。给出了方法的基本原理、步骤、方法和适用条件。     

梯度热障涂层的设计和性能与失效研究

介绍了梯度热障涂层的表层、底层及梯度过渡层材料的选用和设计原则,对梯度热障涂层的抗热震性能、抗氧化性能和力学性能的研究成果作了综述，探讨了梯度热障涂层的失效机理，并指出了需进一步研究的问题。     

基于机载实时模型的发动机执行机构 故障状态参数估计

为了对发动机的主燃烧室供油量控制器、喷管喉部面积控制器、风扇进口可调导叶角度控制器、压气机进口可调导叶角度控制器进行故障诊断,建立了基于简化n+1残量方法的非线性机载实时模型,并结合常增益扩展卡尔曼滤波器建立执行机构控制参数估计器,利用非线性部件级模型模拟飞行包线内发动机执行机构的软故障.仿真结果表明:执行机构控制参数估计器在飞行包线内能实现较高精度估计,且具有较好的稳定性.