Family of constrained signal detectors for hyperspectral imagery

Generalized likelihood ratio tests (GLRTs) are derived for the problem of detecting targets in hyperspectral images. These detectors are derived under the assumptions that the signals from the materials in the image mix linearly and that the noise in the system is Gaussian. It is also assumed that the abundances of the signals from the various materials in a pixel must sum to one. This constraint models the fact that the material abundances in a pixel are just the fraction of the pixel that they occupy. Under these assumptions, detectors are derived which outperform the detectors derived without the sum-to-one constraint.     

Practical stabilization in attitude thruster control

The attitude stabilization of a spacecraft using thrusters is considered from a practical point of view, i.e., when actuator constraints, uncertainties and failures, measurement noise, fuel consumption, and inertia matrix uncertainty are considered. A variable structure controller based on sliding modes is obtained first, which guarantees global exponential stability under actuator constraints, uncertainties, and failures. The design is based on a continuous average-proportional torque selection function and a set of feasible sliding surfaces, which may be adapted to improve performance. Exponential convergence towards ultimate bounds is guaranteed when all other practical issues arise.     

Track-before-detect procedures for early detection of moving target from airborne radars

In this paper we present a family of track-before-detect (TBD) procedures for early detection of moving targets from airborne radars. Upon a sectorization of the coverage area, the received echoes are jointly processed in the azimuth-range-Doppler domain and in the time domain through a Viterbi-like algorithm that exploits the physically admissible target transitions between successive illuminations, in order to collect all of the energy back-scattered during the time on target (TOT). A reduced-complexity implementation is derived assuming, at the design stage, that the target does not change resolution cell during the TOT in each scan. The constant false alarm rate (CFAR) constraint is also englobed in the proposed procedures as well as the possibility of working with quantized data. Simulation results show that the proposed algorithms have good detection and tracking capabilities even for high target velocities and low quantization rates.     

加油机加油过程视频监控需求分析

通过对一般加油过程的分析,提出了空中加油机加油过程视频监控需求。将加油过程分为会合、编队、对接、解散四个部分对监控区域进行讨论,并对监控区域进行整理及优化,从功能、分辨率及显示等方面进行分析,给出适应性的视频监控需求,为机外摄像头布局,摄像头和显示器选型,机外照明布置提供有效支持。     

基于Petri网的建模方法在叶片制造流程重组中的应用

采用基于Petri网的流程建模方法,结合数字化条件下叶片工艺流程设计与评估的相关理论,对叶片制造流程进行重组,并绘制流程框图.利用可达树对Petri网模型进行死锁分析,从而减少流程重组的盲目性和风险.最后通过工程事例说明Petri网模型的死锁分析过程.     

ARM嵌入式处理器在智能仪器中的应用

介绍了一种基于ARM嵌入式处理器系统的智能仪器的硬件和软件设计方案,并结合uc/os-II嵌入式实时操作系统,给出了一套完整的任务调度和管理的方法,最后给出实例说明.     

利用压电驱动器改善飞机横滚性能的试验验证

利用分布粘帖在矩形机翼上下两面的压电驱动器,探索使用该类结构提高飞行器横滚能力的可能性。通过风洞模型设计、材料性能测试、模型固有特性测试、压电柔度矩阵测试等试验项目,保证了有限元模型的计算精度,最终通过模型的风洞试验验证了利用气动弹性效应,获得了附加升力与横滚力矩的方案。该原理性试验说明利用分布式压电驱动器改善横滚性能是可行的。     

一种新型测距仪的研制

介绍了一种在中,小范围内,采用激光定位,超声测距的新型测量仪器,该仪器以单片微处理器为核心,对不同的测量距离,采用不同频率的超声波,结合信号处理方法,从而实现０．６～１４ｍ范围内高精度实时测量目标距离,其测量相对误差优于１％。     

LY12CZ 薄板拉伸过程中宏、细观损伤变量间的相关性分析

分别从宏观与细观的角度定义了D（E）、D（A）和D（Ra）3个损伤变量,对LY12CZ铝合金薄板同一损伤过程的D-ε曲线进行了分析与对比。结果表明：其D-ε曲线多呈幂函数变化;宏、细观损伤变量之间线性相关性良好,且表征损伤变量D（A）和D（Ra）较整征损伤变量D（E）的变化稍有滞后。     

The Low Metallicity Tail of the Halo Metallicity Distribution Function

Ongoing spectroscopy and photometry of stars selected in the HK objective-prism/interference-filter survey of Beers and colleagues has resulted in the identification of many hundreds of additional stars in the halo (and possibly the thick disk) of the Galaxy with abundances [Fe/H] -2.0. A new calibration of the technique for estimation of metal abundance based on a CaII K index as a function of broadband B - V color is applied to obtain metallicities for stars observed with the SSO 2.3m and INT 2.5m telescopes. This new data is combined with other samples of extremely metal-deficient stars (Ryan and Norris, 1991a; Beers et al., 1992; Carney et al., 1994) to form a large database of objects of low metallicity. The combined sample is examined and compared with expectations derived from a Simple Model of Galactic chemical evolution. There appears to be a statistically-significant deficit of stars more metal-weak than [Fe/H] = -3.0. An abundance of [Fe/H] -4.0 can be taken as the low-metallicity limit for presently-observable stars in the Galaxy.