MEMS加速度传感器计量检测技术的研究进展

MEMS加速度传感器在计量检测中有着广泛的应用。本文综述了MEMS加速度传感器的发展概况,总结了其分类方法、工作原理及特点,并提出发展趋势。     

LDPC码对无源互调干扰下通信性能改善研究

针对无源互调干扰信号的时变性和间断性特点,提出了利用低密度奇偶校验（LowDensityParityCheck,LDPC）码抗突发差错的特性来减弱无源互调干扰影响的方法。文章设计了LDPC编译码方案,采用了基于准循环矩阵的编码方案,并着重分析了译码环节,译码算法最终选定具有低迭代时延特点的基于行信息传递（RowMessagePassing,RMP）调度的最小和译码算法。译码仿真结果显示,用占空比为10%的脉冲模拟无源互调干扰,信噪比为3.1dB时,编码增益约为8.2dB。实测结果显示,信干比为2dB时,带有LDPC编码的系统误码率为0.00269,信干比增益超过10dB。     

端到端虚拟组网系统设计

端到端虚拟组网系统解决企业内部网内信息终端用户之间的网络安全通信问题,实现了IPSec VPN系统及基于用户的工作组级安全策略管理系统。首先介绍了IPSec VPN协议与安全策略管理标准;然后对系统的总体框架进行了讨论与设计;在方案设计的基础上,详细论述了系统内的安全策略管理子系统与W indows端虚拟网子系统的实现,并对所使用的技术进行了说明;最后,介绍了系统的应用情况,并对系统下一步的工作目标进行了展望。     

防火墙的安全机制研究

防火墙安全机制是Internet推广和应用关键技术之一.本文通过对防火墙实现技术的分析,论述了防火墙的安全机制,描述防火墙实现的典型结构,以及采用的安全保护实现方法,并对防火墙的安全策略和设计要求进行了深入的探索.     

Testability evaluation using prior information of multiple sources

Testability plays an important role in improving the readiness and decreasing the lifecycle cost of equipment. Testability demonstration and evaluation is of significance in measuring such testability indexes as fault detection rate（FDR） and fault isolation rate（FIR）, which is useful to the producer in mastering the testability level and improving the testability design, and helpful to the consumer in making purchase decisions. Aiming at the problems with a small sample of testability demonstration test data（TDTD） such as low evaluation confidence and inaccurate result, a testability evaluation method is proposed based on the prior information of multiple sources and Bayes theory. Firstly, the types of prior information are analyzed. The maximum entropy method is applied to the prior information with the mean and interval estimate forms on the testability index to obtain the parameters of prior probability density function（PDF）, and the empirical Bayesian method is used to get the parameters for the prior information with a success-fail form. Then, a parametrical data consistency check method is used to check the compatibility between all the sources of prior information and TDTD. For the prior information to pass the check, the prior credibility is calculated. A mixed prior distribution is formed based on the prior PDFs and the corresponding credibility. The Bayesian posterior distribution model is acquired with the mixed prior distribution and TDTD, based on which the point and interval estimates are calculated.Finally, examples of a flying control system are used to verify the proposed method. The results show that the proposed method is feasible and effective.     

A novel method for solving shortest tool length based on compressing 3D check surfaces relative to tool postures

Solving the shortest tool length quickly under a known tool trajectory in multi-axis machining of complex channel parts is an urgent problem in industrial production. To solve this problem, a novel and efficient method is proposed which is featured by extracting only a few necessary curves from the check surface instead of sampling the entire surface. By rotating and compressing the 3D check surface relative to all tool postures, the boundaries of the area occupied by the 2D compressed surfaces are the essential elements for determining the shortest tool length. A tracking-based numerical algorithm is introduced to efficiently solve the silhouette curves which are formed in compressing. To define the multi-taper shaped tool holding system (THS) which is commonly used in production, a characterization model for THS profile is established. A model for solving the shortest tool length is finally constructed based on the critical interference relationship between the THS profile and all compressed boundary curves. For acceleration, the boundary splines are segmented according to their knot vectors. Then a new concept called the axis-aligned tool length box (AATB) is introduced, which can provide a conservative range of tool length for a spline segment. By scanning the AATBs of all spline segments, the very few effective spline segments that may ultimately determine the shortest tool length are filtered out. This acceleration method makes the solution for the shortest tool length more focused and efficient. The results of experimental examples are also reported to validate the efficiency and accuracy of the proposed algorithm.     

基于5G的通导融合位置认证系统性能分析

随着无人化智能移动装备在工业、交通等安全敏感领域的普及应用，民用导航定位系统中的定位安全问题日益突出。位置认证是对终端的物理位置声明进行认证的过程，是导航定位安全技术的重要组成部分。基于第五代(5G)移动通信网络的通导融合位置认证系统具有覆盖范围广、认证精度高、用户容量大、建设运维成本低等多重优势。本文首先介绍了多基站位置认证系统的检测判决原理，提出了漏检平均距离的定义作为位置认证系统精度的量化评价指标。在此基础上，通过数值仿真分析了信号带宽、基站同步误差、信噪比对位置认证系统精度的影响，并利用5G信道模型评估了典型场景下的位置认证系统的性能。结果表明，在具备3个以上的视距基站时，基于5G的通导融合位置认证系统可以实现米级的位置认证精度。     

基于航天信息系统云平台的可授权数据安全共享研究

本文提出一种基于航天信息系统云平台的可授权数据安全共享方法。通过设计支持多     

一类基于可监管区块链的公共安全信息共享平台方案设计

公共安全涉及到应急管理、供应链管理和医疗健康等领域,其数据共享平台对提供全方位、全过程的公共安全服务具有重要意义,尤其在当前的疫情背景下.但目前,由于涉及敏感数据的隐私保护,公共安全数据共享平台的架构设计一直面临着严峻的挑战.基于通过智能合约实现工作流协调和访问控制机制的设计思路,给出了一类基于可监管区块链的新型公共安...