Performance analysis of covert wireless communication based on beam forming with noise uncertainty

In order to establish covert wireless communication in Rayleigh fading environment with noise uncertainty,a scheme of downlink covert wireless communication based on complex Gaussian random coding and beam forming was adopted,and more importantly,the performance of covert wireless communication was analysed.Firstly,the covert probability of communication was analyzed by using the hypothesis test theory.Secondly,the optimal detection threshold of the illegal detection party was given and proved,and the closed expressions of the average covert probability,connection interruption probability and covert throughput of the system were further obtained.Finally,by jointly designing the transmission power and target covert rate,the optimal goal of the maximum covert throughput of the system was achieved,and the corresponding algorithm based on step search was given.The simulation results show that the beam forming technology could provide some gain for covert wireless communication.Compared with the ideal case in which the legitimate receiver is not affected by the noise uncertainty,the covert throughput in non-ideal case is significantly reduced and almost not affected by the basic noise level of the environment.     

信号发生器调频频偏测量结果的不确定度评定分析

信号发生器是科研和生产中应用非常广泛的一种仪器,频率调制是其最主要和基本的一种模拟调制功能。该文主要介绍在信号发生器计量中对调频频偏测量结果的不确定度评定的一种方法,希望对计量工作人员在计量信号发生器时提供一些参考。     

具有时滞和的非线性系统的鲁棒稳定性分析

针对具有时滞和及模有界参数不确定性的非线性系统,研究了鲁棒稳定性问题。通过构造新的Lyapunov泛函。其中考虑了时变时滞和时滞上界信息,并应用新的方法估计Lyapunov泛函导数的上界,以线性矩阵不等式形式给出了系统的时滞相关型稳定性判据。数值实例表明了结果的有效性和较小保守性。     

电源适配器能效检测实例分析

利用能效测试系统对不同的电源适配器样品进行检测,对检测的结果进行不确定度评估和分析。结果表明,在检测过程中要注意控制小功耗条件下的测量不确定度。     

基于滑模的运载器主动段俯仰通道姿控系统设计

与传统比例-积分-微分（PID）控制方法相比,滑模控制（SMC）方法可以比较容易地将不确定性纳入控制器设计中,从而增强系统的鲁棒性。探索了SMC技术在运载器主动段姿态控制中的工程应用,首先通过分析基于趋近律的SMC系统,提出了降低不连续切换项系数的需求,然后研究了基于干扰上界的SMC方法。三通道小偏差仿真结果验证了两种方法的控制效果,表明第2种控制器的鲁棒性更好,稳态误差小,同时发动机喷管摆角需求较小。     

Uncertainty of the spectral mismatch correction factor in STC measurements on photovoltaic devices

Valuation of photovoltaic devices depends strongly on the measured power output of the device. This quantity is usually determined under artificial sunlight in production line measurement systems or industrial or research test labs. A practical calibration chain is realized essentially with measurements at solar simulators. The measurement conditions are defined in the IEC 60904 series of standards. An important part of the standard testing conditions is the definition of a specific spectral distribution of the sunlight (AM1.5 global). The inevitable deviations of the spectrum of artificial light sources from the standard spectrum have to be taken into account by a spectral mismatch factor. The uncertainty of this crucial correction is spectrally dependent, in most cases unknown and complex and inconvenient to evaluate. In this article a randomizing method is proposed which allows one to calculate the uncertainty of the mismatch factor from the uncertainties of the input parameters determined with high spectral resolution. Based on a range of different spectral responses of solar cells on the one hand and variations of the solar simulator spectral distribution on the other, we are able to generalize the results to a broad set of measurement configurations. A sensitivity analysis reveals the crucial wavelength regions and thus allows the systematic optimization of simulator spectra and selection of reference cells. Copyright © 2010 John Wiley & Sons, Ltd.     

一类非线性不确定时滞系统的记忆与无记忆复合H∞状态反馈控制

针对一类具有状态非线性不确定性的线性时滞系统,基于Lyapunov稳定性理论,利用线性矩阵不等式（LMI）方法,讨论了该类时滞系统的记忆与无记忆复合H∞状态反馈控制器的设计问题。在非线性不确定性满足增益有界条件下,得到了该类时滞系统的满足鲁棒H∞性能的一个充分条件。通过求解一个线性矩阵不等式-LMI,即可获得鲁棒H∞控制器。     

医用注射泵和输液泵检测仪测量结果的不确定度分析

医用注射泵和输液泵检测仪主要由液体采样器、压力采样模块、计时器、信号处理单元、显示单元等构成。为确保检测仪测量数据的准确可靠和可溯源性,对医用注射泵和输液泵检测仪的测量结果进行不确定度分析。     

助燃条件下硼粉燃烧热测试不确定度分析

为提高硼粉燃烧热值测试的准确性,确定助燃条件下影响硼粉燃烧热值测量不确定度的主要因素,依据硼粉的点火、燃烧特性以及助燃条件下硼粉热值测试原理,采用直接评定法分析了影响硼粉燃烧热值测试的不确定度,进行了硼粉的燃烧热值测试。计算了各因素对硼粉燃烧热测试值不确定度的影响程度。结果表明:影响硼粉燃烧热测试不确定度的主要因素是量热体系的温升、助燃剂的热值、参与燃烧的硼粉的质量,降低系统热容量的不确定度可提高硼粉燃烧热值测量的准确度。助燃条件下测试硼粉燃烧热值的相对不确定度仅为0.95%。     

一种高精度爆速测量方法

为精确测量炸药拟定态爆速,设计了尖形探针和相应的实验测量方法,测量了有机玻璃、不锈钢、铝合金约束下片状TATB为基钝感炸药的拟定态爆速,结果为(7.527±0.017)km.s-1。表明:采用尖形电探针测量钝感炸药爆速的不确定度为19 m.s-1,相对不确定度为0.25%,与洛斯阿拉莫斯国家实验室(LANL)精密爆轰物理实验结果相当,为精密爆轰物理实验提供了一种新的爆速测量方法。