Fe—Cr—Ni—Mo—C阀座材料的时效硬化及时效过程中的相转变

Fe-18.2Cr-6.9Ni-2.5Mo-1.5C材料铸态组成相为奥氏体和M7C_3型碳化物,在随后加热时可产生时效硬化现象,最佳时效温度为650℃。时效过程中可产生α-铁索体和M_23C_6型碳化物两个新相。     

金刚石修整滚轮CAD/CAPP集成技术研究

金刚石修整滚轮是目前最为有效的高效、高精砂轮成形修整工具，迎合了磨削技术高精、高速和高效发展趋势，内电镀高精度修整滚轮制造工艺复杂、工序多，影响制造精度因素较多，修整参数选择、滚轮图纸设计和工艺编制是生产中的关键环节。本文从分析金刚石修整滚轮设计制造的特点人手，应用CAD／CAPP集成技术实现了金刚石修整滚轮设计、工艺规程编制和技术文件管理的自动化，提高了滚轮制造工艺水平和对产品质量的控制能力，较好地解决了一些设计和工艺过程相对简单、变化较小的定型产品的CAD／CAPP集成化的问题。     

用胶粘代替点焊工艺

采用点焊工艺生产拖拉机机罩，点焊压痕影响了外观质量，通过对几种方案的探讨和大量的胶粘试验，确定了一种用结构胶粘结代替点焊的工艺，该工艺使制件的外观质量得以大幅度提高，而生产成本则明显降低。     

酚酞示波极谱及其在痕量钌催化分析中的应用

在稀盐酸介质中酚酞于－０．５５Ｖ处产生一灵敏的单扫描示波极谱波。基于在稀盐酸介质中及１００℃下，痕量Ｒｕ（Ⅲ）对高碘酸盐氧化酚酞这一缓慢反应的强烈催化作用，用自来水冷却中止反应，采用单扫描示波极谱波研究Ｒｕ这一新的指示反应，建立检出限和测定范围分别为０．０５ｎｇ／ｍｌＲｕ的催化反应－示波极谱分析新方法，并用于实际试样分析，结果较好。     

面向新型非易失存储器的文件级磨损均衡机制

自旋转移力矩磁存储器（spin transfer torque random access memory ,ST TRAM ）和磁阻式随机存储器（magnetic random access memory ,MRAM ）等新型存储器具有接近于 DRAM 的访问速度,是构建高性能外存系统和提高计算机系统性能的重要手段,但有限的写次数是其重要局限之一．设计了文件系统级磨损均衡机制,使用 Hash 函数分散文件在外存中的存储,避免在创建和删除文件时反复分配某些存储块,通过分配文件空间时选择写次数较低的存储块,避免写操作的集中;使用主动迁移策略,在外存系统 I/O 负载较低时主动迁移写次数较高的数据块,减少磨损均衡机制对 I/O 性能的影响．最后在开源的基于对象存储设备 Open‐osd 上实现了面向新型存储器文件系统级磨损均衡机制的原型,使用存储系统通用测试工具 filebench 和 postmark 的多个通用数据集进行了测试与分析,验证了基于新型存储器的文件系统级磨损均衡机制能稳定地将存储块写次数差减少到原来的1/20左右,同时最高仅损失了6％的 I/O 性能和增加了0．5％的额外写操作,具有高效和稳定的特性．     

融合信息熵与信任机制的防攻击推荐算法研究

由于对用户偏好信息的过分依赖,致使推荐系统易受到恶意攻击,从而影响系统的推荐质量。提出一个融合信息熵与信任机制的防攻击推荐算法。在考虑了托攻击与正常用户之间的评分变化幅度差异基础上,提出融合信息熵的相似性改进算法,同时引入信任更新机制,在推荐过程中将用户间信任度与相似度有机相结合,通过筛选推荐权重较高的邻居用户方法获得可靠推荐,从而降低恶意攻击对系统的影响。通过在真实数据集上实验表明该算法在提高推荐系统的准确性和脆弱性上有较好的表现。     

交叉口入口路段车流量及车辆换道率检测研究

针对交叉口入口路段交通视频中存在车辆遮挡严重、频繁走停以及频繁换道插队等特点,提出了一种获取交叉口停车线后大视野范围内车流量以及车辆换道率的检测方法.首先采用多级虚拟特征线生成多级时空图,对车辆进行快速检测和分割,获得车辆候选区域;然后对车辆候选区域内局部特征点进行初步分组和跟踪,并根据相同组内特征点运动趋势相似性来修正分组,解决车辆遮挡问题,用于检测车辆换道率;最后将多级时空图与特征点跟踪相结合,进行相互反馈,实现对车辆准确分割和鲁棒跟踪,避免车辆行驶中走停的影响.实验结果表明,通过该方法能实时准确地获取大视野范围内交叉口入口路段车流量和车辆换道率的交通参数.     

基于B/S架构的嵌入式网络视频监控系统

根据目前视频监控需求,采用ARM11处理器与Linux操作系统相结合的方式,提出了一种基于B/S架构的远程网络视频监控方案。使用V4L2进行视频图像采集,选择H.264压缩标准,通过硬件多格式编码器MFC完成视频硬件压缩。运用RTP流媒体传输技术实现视频数据的打包传输,客户端通过安装Active X控件完成视频图像的显示,最终实现网络视频监控功能。     

PCET based copy-move forgery detection in images under geometric transforms

With the advent of the powerful editing software and sophisticated digital cameras, it is now possible to manipulate images. Copy-move is one of the most common methods for image manipulation. Several methods have been proposed to detect and locate the tampered regions, while many methods failed when the copied region undergone some geometric transformations before being pasted, because of the de-synchronization in the searching procedure. This paper presents an efficient technique for detecting the copy-move forgery under geometric transforms. Firstly, the forged image is divided into overlapping circular blocks, and Polar Complex Exponential Transform (PCET) is employed to each block to extract the invariant features, thus, the PCET kernels represent each block. Secondly, the Approximate Nearest Neighbor (ANN) Searching Problem is used for identifying the potential similar blocks by means of locality sensitive hashing (LSH). In order to make the algorithm more robust, morphological operations are applied to remove the wrong similar blocks. Experimental results show that our proposed technique is robust to geometric transformations with low computational complexity.     

Study on the security of the authentication scheme with key recycling in QKD

In quantum key distribution (QKD), the information theoretically secure authentication is necessary to guarantee the integrity and authenticity of the exchanged information over the classical channel. In order to reduce the key consumption, the authentication scheme with key recycling (KR), in which a secret but fixed hash function is used for multiple messages while each tag is encrypted with a one-time pad (OTP), is preferred in QKD. Based on the assumption that the OTP key is perfect, the security of the authentication scheme has be proved. However, the OTP key of authentication in a practical QKD system is not perfect. How the imperfect OTP affects the security of authentication scheme with KR is analyzed thoroughly in this paper. In a practical QKD, the information of the OTP key resulting from QKD is partially leaked to the adversary. Although the information leakage is usually so little to be neglected, it will lead to the increasing degraded security of the authentication scheme as the system runs continuously. Both our theoretical analysis and simulation results demonstrate that the security level of authentication scheme with KR, mainly indicated by its substitution probability, degrades exponentially in the number of rounds and gradually diminishes to zero.