基于动态混沌映射的三维加密正交频分复用无源光网络

提出了一种基于混沌映射的三维加密正交频分复用无源光网络保密通信系统.该系统通过相关性检测锁定收发端混沌系统参数,实现收发双方混沌系统同步;并利用同步混沌系统生成密钥,实现符号扰动以及二重子载波加密.该加密方案的密钥空间超过10~(86),能够有效对抗穷举攻击.实验实现了13.3 Gb/s基于64进制正交幅度调制的加密正交频分复用信号在25 km标准单模光纤中的传输,并完成了信息的有效解密.     

Effective transport of passive particles induced by chiral-active particles in microchannel

Transport of passive particles induced by chiral-active particles in microchannel is investigated by using the overdamped Langevin dynamics simulation in a two-dimensional model system. Due to the chirality of active particles and special structure of microchannel, effective ratchet transport of passive particles is achieved. Effective transport of passive particles depends on the width of microchannel(d), the density(ρ), and the angular velocity(ω) of chiral-active particles.There exist optimal parameters for d and ω at which the transport efficiency for passive particles takes its maximal value.This investigation can help us understand the necessity of active motion for living systems to maintain a number of vital processes such as materials transport inside cells and the foraging dynamics of mobile organisms.     

MoEDAL – a new light on the high-energy frontier

In 2010, the MoEDAL (MOnopole and Exotics Detector at the LHC) experiment at the Large Hadron Collider (LHC) was unanimously approved by European Centre for Nuclear Research’s Research Board to start data taking in 2015. MoEDAL is a pioneering experiment designed to search for highly ionising manifestations of new physics such as magnetic monopoles or massive (pseudo-)stable charged particles. Its groundbreaking physics programme defines a number of scenarios that yield potentially revolutionary insights into such foundational questions as: are there extra dimensions or new symmetries; does magnetic charge exist; what is the nature of dark matter; and, how did the Big Bang develop. MoEDAL’s purpose is to meet such far-reaching challenges at the frontier of the field. The innovative MoEDAL detector employs unconventional methodologies tuned to the prospect of discovery physics. The largely passive MoEDAL detector, deployed at Point 8 on the LHC ring, has a dual nature. First, it acts like a giant camera, comprised of nuclear track detectors – analysed offline by ultra fast scanning microscopes – sensitive only to new physics. Second, it is uniquely able to trap the particle messengers of physics beyond the Standard Model for further study. MoEDAL’s radiation environment is monitored by a state-of-the-art real-time TimePix pixel detector array. A new MoEDAL sub-detector designed to extend MoEDAL reach to mini-charged, minimally ionising particles is under study.     

电子式互感器高频数据采集与传输方案

针对当前电力系统电子式互感器采样率偏低,难以满足行波测距装置准确定位电力故障的问题,提出了电子式互感器高频信号采集与传输方案;电子式互感器内部为Rogowski 线圈,电网电流信号被其微分作用转换为小电压信号并附加了90°超前相差,设计积分电路补偿该相差;设计采样率为2 MSps的高频信号采集电路,FPGA通过LVDS接口读取采样数据,并进行幅值处理,最后利用大容量FIFO(先入先出单元)进行缓存;由于百兆网数据传输速率有限,利用FPGA设计吉比特光纤以太网传输特定格式报文,把电流数据传输至电力行波测距装置;解决了积分电路由于运放输入偏置电压带来的积分饱和问题,以及高速ADC输入量程小于输入信号幅值等技术难点;试验结果表明,高频信号采集及传输方案能够满足行波测距装置百米级别的测距精度要求,具有一定工程应用价值。     

采用3×3耦合器的分布反馈式光纤激光传感器解调技术

为了实现分布反馈式光纤激光传感器(DFB FL)大动态范围、稳定解调,建立了基于3×3耦合器的迈克尔逊干涉仪解调系统。对该系统所采用的对称解调算法(NPS)和反正切解调算法进行了深入研究。首先,介绍了基于3×3耦合器解调算法的原理及耦合器不对称时的调校方法。接着,对干涉仪所需最小非平衡路径长度的选取与系统强度噪声、激光器频率噪声的关系进行了分析。最后,针对NPS算法与反正切算法最大可解调信号幅度进行了分析对比,并研究了微分器对对称解调方法解调范围的影响。实验结果表明:NPS算法动态范围高于反正切算法,微分器的幅频特性不理想会减小解调动态范围。在采样频率为125 k Hz、信号频率为1 k Hz、干涉仪非平衡路径为100 m时,NPS算法与反正切算法的动态范围分别达到96 d B和90 d B。用解调前调校的方法,基于3×3耦合的解调方法动态范围大,能够实现稳定解调,满足工程应用要求。     

Passive Tracking of Multiple Underwater Targets in Incomplete Detection and Clutter Environment

A major advantage of the use of passive sonar in the tracking multiple underwater targets is that they can be kept covert, which reduces the risk of being attacked. However, the nonlinearity of the passive Doppler and bearing measurements, the range unobservability problem, and the complexity of data association between measurements and targets make the problem of underwater passive multiple target tracking challenging. To deal with these problems, the cardinalized probability hypothesis density (CPHD) recursion, which is based on Bayesian information theory, is developed to handle the data association uncertainty, and to acquire existing targets’ numbers and states (e.g., position and velocity). The key idea of the CPHD recursion is to simultaneously estimate the targets’ intensity and the probability distribution of the number of targets. The CPHD recursion is the first moment approximation of the Bayesian multiple targets filter, which avoids the data association procedure between the targets and measurements including clutter. The Bayesian-filter-based extended Kalman filter (EKF) is applied to deal with the nonlinear bearing and Doppler measurements. The experimental results show that the EKF-based CPHD recursion works well in the underwater passive multiple target tracking system in cluttered and noisy environments.     

基于LabVIEW的高分辨率光谱测试系统(英文)

提出了一种基于LabVIEW的无源器件光谱测试方案.通过LabVIEW编程控制可调谐激光器、可编程光滤波器、光功率计和数据采集平台,获得了具有不同传递函数的光谱特性.实验中激光器的扫描速度为10nm/s,扫描范围为10nm,数据采集卡的采样速率为1MS/s,结果表明:单个器件的光谱测试可以在1s内完成,光谱分辨率可达1pm;与利用宽带光源和光谱分析仪的传统光谱测试方法相比,所提方案的测试性能可达到传统方案水平,且能显示更精细的光谱细节.该方案能应用于有高分辨率、快速和高效要求的光谱测试中.     

Ultra-High-Capacity Passive Optical Network Systems with Free-Space Optical Communications

Abstract

This article experimentally demonstrates a hybrid fiber–free-space passive optical network that enables high spectral density, aggregated capacity, and total throughput through ultra-dense wavelength-division multiplexing baseband and radio-over-fiber channels. Ultra-dense wavelength-division multiplexing 10-Gb/s Nyquist-shaped 16-ary quadrature amplitude modulation, 10-Gb/s radio-over-fiber orthogonal frequency-division multiplexing, and 8.75-Gb/s baseband orthogonal frequency-division multiplexing signals per user were transmitted through a maximum 40-km passive optical network, which includes a 6-m free-space optics link with acceptable performance.     

温跃层及其变化对被动声纳检测概率的影响

根据被动声纳工作原理,构建被动声纳探测水下目标物概率数学模型。利用声学调查实测数据,综合考虑传播损失、环境噪声、和水文环境分布及季节变化,研究温跃层垂直分布及季节变化对声纳检测概率的影响。结果表明:温跃层对被动声纳影响巨大,逆温跃层环境中,声纳检测概率从海表向下逐渐减小;正温跃层对声纳总的影响与逆温跃层相反,在正温跃层上界,检测概率从表层向下先减小后增大;逆温跃层对被动声纳检测概率的影响随目标物与声纳距离的增大而增大,正温跃层影响相反。