Exponential stability for uncertain neutral systems with Markov jumps

This paper deals with the global exponential stability problems for stochastic neutral Markov jump systems （MJSs） with uncertain parameters and multiple time-delays. The delays are respectively considered as constant and time varying cases, and the uncertainties are assumed to be norm bounded. By selecting appropriate Lyapunov-Krasovskii functions, it gives the sufficient condition such that the uncertain neutral MJSs are globally exponentially stochastically stable for all admissible uncertainties. The stability criteria are formulated in the form of linear matrix inequalities （LMIs）, which can be easily checked in practice. Finally, two numerical examples are exploited to illustrate the effectiveness of the developed techniques.     

基于间歇控制的不确定主从Lur’e系统的指数同步

研究了不确定主从Lur’e系统的问歇控制同步问题．运用Lyapunov稳定性理论和S-过程,首先推导出保证标称主从Lur’e系统指数同步的一个充分条件．在此基础上进一步得到了具有范数有界不确定性主从Lur’e系统鲁棒指数同步的结果．这些同步判据以矩阵不等式的形式给出．另外我们还提出了一种最小化性能指标的优化策略．最后,通过两个数值例子验证了结果的有效性．     

采用改进型IHS变换的遥感图像融合算法

在分析亮度一色度-饱和度(IHS)变换影像融合方法的基础上,针对IHS变换存在光谱特征扭曲的局限性,提出了一种采用分辨率退化模型的基于IHS变换的局部回归分析融合方法.采用SPOT的全色影像和TM的多光谱影像为实验数据,经多个统计参数的定量分析以及Matlab仿真实验的验证表明,该方法在空间分辨率和光谱分辨率上都达到了较好的效果.     

闪烁噪声的自相关函数及其表征

闪烁噪声是一种非平稳随机过程,其功率谱密度函数在频率低端（ｆ＝０）发散,无法直接利用Ｗｉｅｎｅｒ－Ｋｈｉｎｔｃｈｉｎｅ关系得到它的自相关函数,本文采用“降阶－积分”方法,得到了频率源中闪烁调频噪声的自相关函数的解析表达式。根据这一结果,分析了频率稳定度的表征原理,指出了频率稳定度表征的实质是将非平稳过程转化为平稳过程并求取时间平均。最后,通过时域分析得到了闪烁噪声的Ａｌｌａｎ方差表达式。     

On structure and stability of (Hg, Mo)-1212 superconductors based on SAED and EDS analysis

A superconductor with nominal composition Hg_0.8Mo_0.2Sr₂Y_0.5Ca_0.5Cu₆₊ withT _c up to 96 K has been isolated and carefully examined by electron diffraction and X-ray energy dispersive spectrum analyses. Its structure can be attributed to space groupP4/mmm and lattice constantsa=3.82 å andc=11.91 å. Inhomogeneous distribution of the cations was observed, which is considered to be the key to the broadening ofT _c in theR-T curve. The effect of humid atmosphere on the stability of the sample has also been investigated.     

Event-triggered control for stochastic systems with multiple delays

This paper investigates the stabilization problem for continuous-time stochastic systems with multiple delays under continuous event-triggered mechanisms, of which both static case and dynamic case are considered individually. In order to avoid zeno phenomenon in every sample path, a suspension time after each successful execution is forced for our event-triggered mechanisms, resulting in intermittent detection of system states. Under such control strategy, we deduce mean square exponential stability of stochastic systems with multiple delays by means of Hanalay-type inequality and obtain a delay-dependent-based and less-conservative stabilization criterion without involving the upper bound of time delays. Besides, a co-design procedure is proposed for linear controller and event-triggered mechanisms. In the end, an illustrative example is presented to show effectiveness of the proposed co-design procedure and contrasts the system performance under static and dynamic event-triggered mechanisms.     

Ultraviolet photodetectors and readout based on a-IGZO semiconductor technology

In this work, real-time ultraviolet photodetectors are realized through metal–semiconductor–metal (MSM) structures. Amorphous indium gallium zinc oxide (a-IGZO) is used as semiconductor material and gold as metal electrodes. The readout of an individual sensor is implemented by a transimpedance amplifier (TIA) consisting of an all-enhancement a-IGZO thin-film transistor (TFT) operational amplifier and a switched capacitor (SC) as feedback resistance. The photosensor and the transimpedance amplifier are both manufactured on glass substrates. The measured photosensor possesses a high responsivity R , a low response time t _{R E S} , and a good noise equivalent power value NEP .     

Least squares decoding in binomial frequency division multiplexing

This paper proposes a method that can reduce the complexity of a system matrix by analyzing the characteristics of a pseudoinverse matrix to receive a binomial frequency division multiplexing (BFDM) signal and decode it using the least squares (LS) method. The system matrix of BFDM can be expressed as a band matrix, and as this matrix contains many zeros, its amount of calculation when generating a transmission signal is quite small. The LS solution can be obtained by multiplying the received signal by the pseudoinverse matrix of the system matrix. The singular value decomposition of the system matrix indicates that the pseudoinverse matrix is a band matrix. The signal-to-interference ratio is obtained from their eigenvalues. Meanwhile, entries that do not contribute to signal generation are erased to enhance calculation efficiency. We decode the received signal using the pseudoinverse matrix and the removed pseudoinverse matrix to obtain the bit error rate performance and to analyze the difference.     

扩频体制低轨卫星通信信号捕获与跟踪系统设计

针对扩频体制下低轨卫星信号的捕获及跟踪等系统设计实现问题,根据卫星信号模型进行了捕获及跟踪算法设计,重点对基于快速傅里叶变换的快速捕获算法、锁频环、锁相环和码跟踪环路进行了设计,并进行了工程系统实现。试验验证表明,该系统可以实现码分多址体制低轨卫星信号捕获、跟踪处理,工作性能参数满足系统需求。     

面向鲁棒频谱感知的模糊K-means++算法

恶意用户通过向数据融合中心发送伪造的频谱感知数据,解决自身频谱资源短缺问题,但会极大地降低频谱感知系统的检测概率。为了解决此问题,提出了基于模糊K means++的数据融合算法。该算法首先引入模糊处理机制处理样本的数据特征值,以此来增加样本间的差异性;然后将模糊处理后的数据发送到融合中心,融合中心采用离群点挖掘的方法排除恶意用户,并对保留下来的用户进行融合,使样本向量具有鲁棒性;最后运用K means++算法对样本向量进行聚类。该算法利用轮盘法选择聚类中心,可有效抵御恶意用户的攻击,提高系统感知性能;无需知晓信号与噪声的分布等一些先验信息,也避免了繁杂的门限推导。从仿真结果可以看出,该算法对抵御恶意用户攻击具有突出的效果,有效提升了协同频谱感知系统的稳定性和鲁棒性。