基于随机矩阵非渐近谱理论的协作频谱感知算法研究

将随机矩阵的非渐近谱理论应用到协作频谱感知中,对接收信号样本协方差矩阵的最大特征值和最小特征值进行分析,该文提出一种精确的最大最小特征值差(Exact Maximum Minimum Eigenvalue Difference, EMMED)的协作感知算法。对于任意给定的协作用户个数K和采样点数N,首先推导了最大最小特征值之差的精确概率密度函数(Probability Density Function, PDF)和累积分布函数(Cumulative Distribution Function, CDF),然后利用该分布函数设计了所提算法的判决阈值。理论分析表明,EMMED算法的判决阈值较已有的渐进最大最小特征值差(Asymptotic Maximum Minimum Eigenvalue Difference, AMMED)检测更为精确,算法无需主用户信号特征并且能够对抗噪声不确定度影响。仿真结果表明,存在噪声不确定度的感知环境下,EMMED算法较已有的精确最大特征值(Exact Maximum Eigenvalue, EME)和EMMER等频谱感知算法具有更好的检测性能。     

多通道光纤可燃气体监测系统的研究

采用可调谐激光吸收光谱(TDLAS)技术和光分路技术,实现了多通道光纤可燃气体监测系统 的 研制。系统中,监测仪部分采用分离式设计,无源传感探头和有源仪表之间通过光纤连接, 含有浓度信息的光信号通过光纤传输到仪表进行处理。传感探头仅由气室和光纤组成,不带 有任何电路,可以保证探头的本质安全性和抗电磁干扰能力。设计了乘法解调电路,以解决 光纤传输产生的相位延时,而导致测量结果偏差的问题。测试结果表明,本文系统能够实现 现场非电、远程、长期在线和分布式气体浓度监测预警预报,且检测结果不受光纤 长度变化的影响,在工业标准的100最低爆炸极限(LEL)测量范围内能 够正确检测CH₄气体浓度值,检测灵敏度为0.1LEL。     

Nonparametric Bayesian dictionary learning algorithm based on structural similarity

Though nonparametric Bayesian methods possesses significant superiority with respect to traditional comprehensive dictionary learning methods,there is room for improvement of this method as it needs more consideration over the structural similarity and variability of images.To solve this problem,a nonparametric Bayesian dictionary learning algorithm based on structural similarity was proposed.The algorithm improved the structural representing ability of dictionaries by clustering images according to their non-local structural similarity and introducing block structure into sparse representing of images.Denoising and compressed sensing experiments showed that the proposed algorithm performs better than several current popular unsupervised dictionary learning algorithms.     

Ultra-Stable and Sensitive Ultraviolet Photodetectors Based on Monocrystalline Perovskite Thin Films

The detection of ultraviolet (UV) radiation with effective performance and robust stability is essential to practical applications. Metal halide single-crystal perovskites (ABX₃) are promising next-generation materials for UV detection. The device performance of all-inorganic CsPbCl₃ photodetectors (PDs) is still limited by inner imperfection of crystals grown in solution. Here wafer-scale single-crystal CsPbCl₃ thin films are successfully grown by vapor-phase epitaxy method, and the as-constructed PDs under UV light illumination exhibit an ultralow dark current of 7.18 pA, ultrahigh ON/OFF ratio of ≈5.22 × 10⁵, competitive responsivity of 32.8 A W⁻¹, external quantum efficiency of 10867% and specific detectivity of 4.22 × 10¹² Jones. More importantly, they feature superb long-term stability toward moisture and oxygen within twenty-one months, good temperature tolerances at low and high temperatures. The ability of the photodetector arrays for excellent UV light imaging is further demonstrated.     

双面镜多元并扫遥感图像的几何校正方法

双面镜多元并扫成像方式在星载仪器中已得到越来越广泛的应用,但相应的遥感图像的预处理工作的重要性也日渐突出.文中从成像方式和仪器结构方面考虑,针对双面镜多元并扫成像方式提出了一套0级数据的几何方法,并对处理前后的图像质量进行了比较.结果表明,该校正方法可有效地改善图像的几何质量,校正效果良好.     

立体视频图像编码的研究进展

从编码方案、关键技术和评价准则3个方面综述了立体视频图像编码研究的发展.阐明了各种编码方案的特点及适用范围.详细分析了立体视频图像编码中视差估计、运动估计、遮挡检测、残差图像编码和码率控制5大关键技术,总结了各项技术的发展现状.最后指出了立体视频图像编码研究中存在的问题,并对未来的研究方向进行了展望.     

基于小波树模型的改进SP算法

针对传统的子空间追踪算法(SP)只利用了信号在某个字典下是稀疏的或者可压缩的这个简单的先验知识,没有将信号的内在模型考虑进去,因此重构效率较低的问题。根据一般信号的小波树系数的特点,提出了一种基于小波树模型的改进子空间追踪算法。由于引入了信号的小波树内在模型,使得改进后算法中得到的最佳K项小波树结构稀疏逼近比子空间追踪算法中的最佳K项稀疏逼近更加接近于原信号,实验仿真证明基于小波树模型的SP算法的重构性更好。     

基于Android的智能轮椅设计与实现

结合Android平台和操纵杆按钮式智能轮椅,本文设计实现了一款基于Android的智能轮椅。对操纵杆按钮式智能轮椅进行了电气化改造,安装了单片机、Wi-Fi模块、继电器等部件以使能用Android终端无线控制轮椅。在Android终端上设计实现了重力感应控制、语音识别控制等多种控制方式,使用户更加方便及多样化地控制轮椅;设计实现了GPS定位、短信报警、指南针等辅助功能,确保用户出行安全。此款智能轮椅具有多功能、廉价、使用方便、操作简单等特点,应用前景广阔。     

机载扫描成象系统的技术发展

叙述了机载扫描成象系统的发展,基本结构,特点及其应用.     

Advances in composition control for 16 µm LPE P-on-n HgCdTe heterojunction photodiodes for remote sensing applications at 60K

With good composition control in both p-type cap and n-type base LPE layers, it is possible to make barrier-free two-layer P-on-n HgCdTe heterojunction photodiodes with very long cutoff wavelengths. Diode arrays with good R_oA operability, good quantum efficiency, and low 1/f noise at 60K have been demonstrated at cutoff wavelengths to 16.3μm. The diode performance continues to improve at lower temperatures, following a diffusion-current trend to at least 35K. Measured R_oA values of 2×10⁵ ohm-cm² for an 18 μm cutoff at 35K are the highest reported at this very long wavelength. A simple defect model applied to the area dependence of R_oA at 40K implied a defect areal density of 3×10⁴ cm⁻² and a defect impedance of 3×10⁶ ohm.