F206钢的热处理工艺及其力学性能研究

研究了Ｆ２０６钢的时效处理工艺及其显微组织与性能。试验结果表明，经８３０－８６０℃加热空冷后，在５１０℃时效５小时，产生明显的二次硬化效应，含碳从０．１４％增至０．１８％，钢的抗张强度１６３５和１８３０ＭＰａ，当晶粒尺雨粗化到３４μｍ时，钢的强度和韧性均有明显的降低。     

电磁成形中的测量

本文简要介绍了电磁成形中放电电流、管坯与线圈间隙中的磁场测量 ,以及管坯动态变形过程测量的各种方法。通过各种方法的比较分析 ,得出分流器法测放电电流、探测线圈法测感生磁场是切实可行的方法。金属坯料在电磁力作用下的变形过程可用撞针法和高速摄影的办法进行测量 ,每种方法各有其优势和适用范围 ,测量时 ,根据实际情况进行选用。     

A genetic tango attack against the David–Prasad RFID ultra‐lightweight authentication protocol

Radio frequency identification (RFID) is a powerful technology that enables wireless information storage and control in an economical way. These properties have generated a wide range of applications in different areas. Due to economic and technological constrains, RFID devices are seriously limited, having small or even tiny computational capabilities. This issue is particularly challenging from the security point of view. Security protocols in RFID environments have to deal with strong computational limitations, and classical protocols cannot be used in this context. There have been several attempts to overcome these limitations in the form of new lightweight security protocols designed to be used in very constrained (sometimes called ultra‐lightweight) RFID environments. One of these proposals is the David–Prasad ultra‐lightweight authentication protocol. This protocol was successfully attacked using a cryptanalysis technique named Tango attack. The capacity of the attack depends on a set of boolean approximations. In this paper, we present an enhanced version of the Tango attack, named Genetic Tango attack, that uses Genetic Programming to design those approximations, easing the generation of automatic cryptanalysis and improving its power compared to a manually designed attack. Experimental results are given to illustrate the effectiveness of this new attack.     

高速混合法在共混地膜生产中的应用

介绍了在原有吹制LDPE地膜设备上(挤出机长径比为20:1)吹制LDPE、LLDPE和HDPE共混微膜和超薄微膜,采用高速混合法的混料工艺达到了良好的预热效果,弥补了挤出机长径比小的不足。     

Dynamic compensation by fusing a high-speed actuator and high-speed visual feedback with its application to fast peg-and-hole alignment

This paper presents a dynamic compensation concept to grapple with the dynamic defects of a traditional robot arm, especially while performing high-speed endpoint regulations. The proposed high-speed dynamic compensation concept offers a new point of view for cooperating with a traditional manipulator to realize highly dexterous performance of manipulations. The concept is realized through adoption of a high-speed light-weight actuator as well as endpoint closed loop configured high-speed cameras. The dynamic compensation is analyzed experimentally with 1000 Hz visual feedback and a high-speed finger for a robot arm in the case of one degree of freedom. The advantage of the proposed approach is that the modeling for the robot system’s dynamics is not needed, whereas it is necessary and trivial in order to realize high-speed regulations by traditional approaches. Thus, the control issue becomes easier with the proposed approach. As an application for this concept, fast peg-and-hole alignment with large position and attitude uncertainty is studied. The alignment algorithm is based on a visual compliance strategy. Alignment experiments show that with the proposed concept of dynamic compensation as well as visual compliant motion control, robust and fast convergence was realized for most cases.     

Harnessing the Melting Peculiarities of Ultra‐High Molecular Weight Polyethylene Fibers for the Processing of Compacted Fiber Composites

Summary: Compacted fiber composites offer unique properties due to their lack of an extraneous matrix. The conditions of processing ultra‐high molecular weight polyethylene (UHMWPE) fibers were simulated in a heated pressure cell. In situ X‐ray diffraction measurements were used to follow the relevant transitions and the changes in the degree of crystallinity during melting and crystallization. The results strongly support the suggestion that the hexagonal crystal phase, in which the chain conformation is extremely mobile on the segmental level, constitutes the physical basis of compaction technologies for processing UHMWPE fibers into a single‐polymer composite. This report suggests that using a pseudo‐phase diagram outlining the occurrence of different phases during slow heating and the degree of crystallinity can provide valuable insight into the technological parameters relevant for optimal processing conditions.

Degree of crystallinity as a function of pressure and temperature in a region relevant to compaction processes.     

基于排列组合熵的高速列车走行部故障分析

针对列车走行部的多种故障模式,提出了基于排列组合熵的高速列车走行部故障诊断方法.对原车和抗蛇行减振器失效、空气弹簧失气、横向减振器失效四种工况进行仿真实验,得到列车不同位置的振动信号.计算列车振动信号的排列组合熵,首先实现了同一速度下不同故障的分离,然后以排列组合熵作为故障特征向量,对特征向量进行多级SVM分类识别.实验结果表明,该方法可以有效识别列车同一速度下的不同故障,高速时对四种工况的平均识别率达97％以上.     

高速以太网中实时相似性匹配算法的研究

在高速以太网中, 针对用户行为的特殊性及数据流五元组的特点, 提出了一种自适应相似性匹配算法(ASMA-HN)。该算法充分考虑了数据流五元组的随机性分布特点, 通过一种改进的XOR-SHIFT算法将数据流分类索引, 并提出了同类数据库(SD)及异类数据库(HD)的概念, 基于距离测度分别设计了加权相似性比较函数, 使得特征值能更精准地匹配到符合要求的数据文件, 提高了整体的匹配效率。通过对校园网实际流量的现场测试, 证明该算法具有较高的精准性及可适用性, 且匹配时间较低, 能很好地满足高速网络中相似性匹配业务的需求。     

高速列车振动监测数据的广义维数特征提取

为监测高速列车的运行状态,采用多重分形分析列车振动监测数据,提取一种基于多重分形理论的广义维数谱参数(谱最大值Dmax、谱最大值与最小值之差△D和谱均值-D),以3种广义维数谱参数作为特征量,实现对列车正常状态、空气弹簧失效、抗蛇行减振器失效和横向减振器失效状态的表征.实验结果表明,Dmax、△D和-D均能够表征高速列车的运行状态且具有一定稳定性,为高速列车运行状态的识别提供了一种有效的方法.     

HiSLIP协议的研究与应用

为解决无LAN口仪器仪表网络接入问题,仪器的网络代理应运而生。当前网络代理的仪器控制机制主要基于TCP/UDP协议,仪器控制及网络传输数据效率较低,为此,IVI联盟制定了标准的仪器控制协议HiSLIP。通过对该协议的功能和交互过程的详细分析,根据协议规范实现协议的运行代码,并基于此协议设计出仪器网络代理,可以实现对支持VXI仪器的便捷网络接入和高效控制,降低通信时延和网络带宽对仪器测量的影响,满足网络化测控系统中对仪器实时性的要求。