Improved Reliability‐Based Iterative Decoding of LDPC Codes Based on Dynamic Threshold

A serial concatenated decoding algorithm with dynamic threshold is proposed for low‐density parity‐check codes with short and medium code lengths. The proposed approach uses a dynamic threshold to select a decoding result from belief propagation decoding and order statistic decoding, which improves the performance of the decoder at a negligible cost. Simulation results show that, under a high SNR region, the proposed concatenated decoder performs better than a serial concatenated decoder without threshold with an E_b/N₀ gain of above 0.1 dB.     

Blind Source Separation of Instantaneous Mixture of Delayed Sources Using High‐Order Taylor Approximation

This paper deals with the problem of blind source separation (BSS), where observed signals are a mixture of delayed sources. In reference to a previous work, when the delay time is small such that the first‐order Taylor approximation holds, delayed observations are transformed into an instantaneous mixture of original sources and their derivatives, for which an extended second‐order blind identification (SOBI) approach is used to recover sources. Inspired by the results of this previous work, we propose to generalize its first‐order Taylor approximation to suit higher‐order approximations in the case of a large delay time based on a similar version of its extended SOBI. Compared to SOBI and its extended version for a first‐order Taylor approximation, our method is more efficient in terms of separation quality when the delay time is large. Simulation results verify the performance of our approach under different time delays and signal‐to‐noise ratio conditions, respectively.     

A Graphene‐Based Vacuum Transistor with a High ON/OFF Current Ratio

A graphene‐based vacuum transistor (GVT) with a high ON/OFF current ratio is proposed and experimentally realized by employing electrically biased graphene as the electron emitter. The states of a GVT are switched by tuning the bias voltage applied to the graphene emitter with an ON/OFF current ratio up to 10⁶, a subthreshold slope of 120 mV dec^?1 and low working voltages of <10 V, exhibiting switching performances superior to those of previously reported graphene‐based solid‐state transistors. GVTs are fabricated and integrated using silicon microfabrication technology. A perfectly symmetric ambipolar device is achieved by integrating two GVTs, implying the potential of realizing vacuum integrated circuits based on GVTs. GVTs are expected to find applications in extreme environments such as high temperature and intense irradiation.     

三种宽色域视频信号兼容传输处理方案

宽色域数字电视标准ITU-R BT.1361限定伽马校正前的基色信号幅度范围为-0.25-+1.33,笔者用遍历法计算了其相应的最宽可感知色域,导出了对应的新三基色,证明其色域覆盖率达60.65%.为使该色域信号能在现行ITU-R BT.709常规色域视频系统兼容传输,依据IEC61966-2-4许用量化级范围,提出了...     

降低梳状谱信号PAPR的初相优化法

针对宽带梳状谱干扰信号存在峰均值功率比(PAPR)较高的问题,提出了一种新的包络优化法,采用了优化初相的快速搜索技术,不失真地降低了信号的PAPR。通过理论分析和仿真试验,验证了采用新方法而设计的梳状谱信号当N>20时可将PAPR降低到2.6 dB以下,方法简单,其适应性和可行性强,且子载波数目越多就越能显著提高搜索速度。     

一种用于角度传感器中的仪表放大器

主要设计了一种用于角度传感器系统中的仪表放大器。为了满足角度传感器系统中对信号频率的要求,需要仪表放大器的带宽足够宽能够达到3.3 MHz。该电路采用标准三运算放大器结构电路,以折叠共源共栅结构的放大器为基础,对共模信号进行抑制,对差分信号进行放大,提高了放大器的精度,增大了仪表放大器的带宽。采用Chartered 0.35μm CMOS双栅工艺对电路进行仿真和流片验证,测试结果表明:在0.8～2.85 V内,仪表放大器的共模抑制比达到了102 dB,带宽能够达到3.3 MHz,输出摆幅为1.7 V,电路功能良好,达到了设计要求,该电路可用于汽车电子以及医疗设备系统。     

非相干扩频捕获的匹配滤波器参数分析

在直接序列扩频传输系统中,接收端通常利用匹配滤波器实现扩频信号的初始捕获,扩频码同步时匹配滤波器的输出信噪比是决定捕获性能的一个重要因素。针对非相干直接序列扩频信号,通过理论推导和仿真验证得到了匹配滤波器输出信噪比与载波频差、扩频比以及匹配滤波器参数之间的关系,该结论可以为匹配滤波器的设计提供依据。     

单层SiO2和ZrO2薄膜激光辐照损伤的对比

分别采用物理气相沉积和溶胶-凝胶技术在K9基片上镀制了4块光学厚度相近的SiO2和ZrO2单层膜.分别采用椭偏仪、透射式光热透镜和原子力显微镜对两类薄膜的孔隙率、热吸收和微观表面形貌进行了表征;利用Nd:YAG激光器测试了样品的激光损伤阈值(LIDT;1064 nm/8.1 ns),并用光学显微镜观察了两类薄膜的损伤形...     

一种基于钩子链技术快速关闭所有窗口的方法

为了达到指战员在撤收转移或其他紧急情况下快速关闭所有打开的报文文档或军事信息系统的目的,通过分析Windows消息传递机制及钩子链技术的基本原理,在Windows平台下采取利用动态链接库装载全局鼠标钩子链来截获特定的鼠标消息,并自定义该消息触发的响应事件的方法,获得了任意处按下鼠标左键时双击右键即可快速关闭所有窗口且能够在窗口关闭时保存实时数据的结果。该方法简化了计算机操作,缩短了关闭所有窗口的时间,适应了现代作战快节奏的需求。     

A new biosynthetic tracer for the inline measurement of virus retention in membrane processes: part II. Biochemical and physicochemical characterizations of the new tracer

In a previous work, a reproducible procedure to produce a new biosynthetic tracer was developed. This new tracer is an MS2 bacteriophage with enzymatic probes grafted on its surface, which can induce enzymatic activity of the tracer. In this paper, the biochemical and physicochemical characteristics of this new tracer are determined. A protocol was developed to determine the specific enzymatic activity kcat_TRACER of the tracer, which was found to be 2.93 ± 0.78 × 10⁴ min⁻¹ on average. Physicochemical characterizations of this new tracer showed that it is representative of viruses and may thus be used as a virus surrogate to assess the virus retention of membrane systems inline. Notably, the mean diameter and molecular weight of the tracer were found to be respectively 64.1 ± 0.3 nm and 12140 ± 3654 kDa, which are within the size and molecular weight ranges of pathogenic viruses carried by water. The tracer surface was also studied and revealed the considerable porosity of the grafted probe layer, with a mean porosity of 88%, which could explain why the zeta potential of the tracers (−14.34 ± 1.66 mV) was nearly the same as that of the native MS2 phages. Finally, a comparison between filtration of the reference microorganism used for membrane performance assessment (the MS2 phage) and the tracer suspensions showed the same filtration behaviour.