Fabrication of ZnO nanorod-based hydrogen gas nanosensor

We report a first work on nanofabrication of hydrogen nanosensor from single ZnO branched nanorods (tripod) using in-situ lift-out technique and performed in the chamber of focused ion beam (FIB) system. Self-assembled ZnO branched nanorod has been grown by a cost-effective and fast synthesis route using an aqueous solution method and rapid thermal processing. Their properties were analyzed by X-ray diffraction, scanning electron microscopy, energy dispersion X-ray spectroscopy, transmission electron microscopy, and micro-Raman spectroscopy. These analyses indicate high quality ZnO nanorods. Furthermore, our synthesis technique permits branched nanorods to be easily transferred to other substrates. This flexibility of substrate choice opens the possibility of using FIB system for handling.

The main advantage of the proposed in-situ approach is a controllable lift-out procedure which permitted us to obtain a 90% success rate for building nanodevices. The fabricated nanosensor uses only single self-assembled ZnO branched nanorod (tripod) to gauge the 150 ppm H₂ in the air at room temperature. The hydrogen sensitivity is in the range of 0.6–2% depending on which two branches to use. The nanosensor has selectivity against other gases such as O₂, CH₄, CO and LPG, which shows sensitivity of <0.02%. The single ZnO branched nanorod sensor can operate at low power of <5 μW.     

一种高精密集成运算放大器的研制

基于运算放大器的基本原理和一些关键技术(基流自举补偿、偏置微调等)的运用,成功地研制出一种双极型高精度低失调集成运算放大器.测试结果显示,该运算放大器失调电压仅为10 μV,失调电流小于1 nA,开环增益为120 dB,单位增益带宽680 kHz.     

高速客运通信系统中的动态资源预留

针对高速客运系统中用户频繁切换产生的大量资源开销,引入了组移动性概念,通过设置列车中继站,实现了车内用户的单用户切换方式.同时,针对大量用户同时切换至目标基站导致的基站拥塞,提出了基于基站协作的动态资源预留方案.即当前基站根据列车运行状态信息提前获知切换目标基站,并通告其资源需求,使其为车内用户预留资源.仿真结果表明列车业务量对系统性能产生了严重影响,采用动态资源预留方案,可以有效地提高列车用户的通信性能.     

雷达的杂波特性及杂波抑制技术

针对脉冲多普勒体制雷达,从杂波特性入手,就雷达的动目标检测和杂波抑制技术进行了讨论,并举例说明有关指标的计算。经过工程实践验证,采用大动态范围的线性接收机和FFT数字信号处理技术相结合的方案,能获得更高的改善因子和杂波抑制能力。     

基于光谱控制与色散优化的飞秒啁啾脉冲放大系统

飞秒激光在工业加工、精密测量、军事国防、科学研究等领域具有广阔的应用前景。报道了基于光谱控制与色散优化的高功率、高脉冲质量飞秒啁啾脉冲放大系统。利用与压缩器色散量相匹配的色散可调啁啾布拉格光纤光栅(CFBG)作为展宽器,通过微调CFBG色散量补偿系统的残余色散使整个系统的净色散趋于零;同时引入光谱滤波等手段,保证入射到主放大器之前的脉冲光谱形状不发生畸变,避免了放大过程中脉冲质量的劣化。最终获得了重复频率为50 MHz、平均功率为24 W、脉冲宽度为198 fs的高脉冲质量飞秒激光输出。     

一种Alpha稳定分布噪声下的体积目标长度估计方法

为了解决Alpha稳定分布噪声环境下运动舰船目标的长度估计问题,该文借鉴非线性变换抑制脉冲噪声以及多普勒目标运动特性估计思想,提出基于广义时频分析(G-TFA)和最小二乘估计的运动目标长度估计方法。该方法首先利用G-TFA获取Alpha稳定分布噪声环境下运动目标的多普勒频率,然后利用最小二乘方法估计出目标航速和不同位置的横正时刻,最后利用上述估计结果计算目标长度。以广义Winger-Ville分布(G-WVD)为例,从理论上推导了G-TFA在Alpha稳定分布噪声环境下具有提取目标多普勒特征的能力,并通过仿真实验验证了该算法在中低混合信噪比下的稳健性。与现有算法相比,该文所提算法不需要估计噪声特征指数,算法性能优于基于传统时频分析的估计方法。     

准连续均匀光栅的接头对其光谱特性的影响

本文研究了以准连续均匀光栅代替线性啁啾光栅时的接头影响,利用耦合模理论和傅立叶频谱分析对接头的数目,大小及其影响进行了理论研究和数值模拟计算,并给出了接头和对其光谱特性影响的分析,计算结果。     

Nonuniform sampling theorems for random signals in the linear canonical transform domain

Nonuniform sampling can be encountered in various practical processes because of random events or poor timebase. The analysis and applications of the nonuniform sampling for deterministic signals related to the linear canonical transform (LCT) have been well considered and researched, but up to now no papers have been published regarding the various nonuniform sampling theorems for random signals related to the LCT. The aim of this article is to explore the nonuniform sampling and reconstruction of random signals associated with the LCT. First, some special nonuniform sampling models are briefly introduced. Second, based on these models, some reconstruction theorems for random signals from various nonuniform samples associated with the LCT have been derived. Finally, the simulation results are made to prove the accuracy of the sampling theorems. In addition, the latent real practices of the nonuniform sampling for random signals have been also discussed.     

一种基于最优控制的网络管理整体策略

随着当前运营商所运营接入网络制式的不断发展,网络管理的负担大大增加,网络管理变得更加频繁。在这种情况下,网络管理不能只保证网络系统处于良好状态,需要同时保证网络状态调整的过程最优。从控制论的角度研究了这一问题,基于最优控制理论提出了最优化网络管理方法。本文的研究成果已经在天津联通的接入网络中得到了证实,相关研究对自动控制理论与网络管理的相关研究有着十分重要的意义。     

基于协方差分析描述函数技术的弹道导弹落点预报

针对采用Monte-Carlo方法对非线性系统进行统计分析效率低下的问题,将协方差分析描述函数法(CADET)应用于弹道导弹落点预报与精度分析.介绍CADET方法的统计线性化思想,提出一种针对一阶可微随机变量函数的统计线性化方法,建立弹道导弹被动段的均值和方差计算的CADET模型.该方法通过一次计算就可得到随机变量数字...