永磁同步电机弱磁性能参数的有限元分析

本文针对永磁同步电动机转子磁路,在功率容量有限的情况下,限制电动机的调速范围这一问题。根据永磁同步电机的矢量控制方法,在分析永磁同步电动机的交、直轴电感参数对弱磁性能的影响基础上,提出了利用Ansoft有限元分析软件,得出交、直轴电感随交轴电流逐渐增大时的变化规律,并分析不同转子磁路结构对交、直轴电感参数的影响。仿真结果表明,在相同的气隙长度和永磁体磁化方向长度下,内置式转子结构永磁同步电动机比表贴式电机直轴电感大,有利于恒功率的弱磁扩速运行。     

浅探汉代陶瓷艺术的文化内涵

汉代陶瓷艺术在我国漫长的陶瓷史上极具特色和个性张力,异彩纷呈,是中国陶瓷艺术继原始彩陶繁荣之后的又一个兴盛期.本文谨希望浅探在两汉陶瓷艺术背后所折射的其时代之文化内涵.     

基于光谱共焦测量原理的波形弹簧自由高度检测技术分析

为解决波形弹簧人工检测效率低、检测精度差等问题,提出了一种基于光谱共焦测量原理的波形弹簧自由高度检测方法。该方法利用光谱共焦位移传感器与精密机械转台组成旋转扫描测量系统,在自由状态下实现对波形弹簧表面轮廓扫描测量,并针对其轮廓特征提出一种等步距窗口移动的峰值提取算法,完成了波形弹簧所有波峰峰值点的精确提取,最终实现对波形弹簧自由高度的精确评定。与传统人工测量方法相比,本方法的测量效率提高200%以上,测量精度由0.01mm提高到0.003mm,对波形弹簧工艺参数的优化以及制造性能的提升具有重要意义。     

组织机构数字证书在电子政务中的应用

本文从组织机构数字证书的技术原理,组织机构数字证书在组织机构代程中的重要作用,组织机构数字证书的社会效益及经济效益,组织机构数字证书在电子政务中的应用市场以及应用前景等方面进行详细的阐述。     

基于多级分类的网络流量在线识别方法(英文)

Internet traffic classification plays an important role in network management. Many approaches have been proposed to classify different categories of Internet traffic. However, these approaches have specific usage contexts that restrict their ability when they are applied in the current network environment. For example, the port based approach cannot identify network applications with dynamic ports; the deep packet inspection approach is invalid for encrypted network applications; and the statistical based approach is time-consuming. In this paper, a novel technique is proposed to classify different categories of network applications. The port based, deep packet inspection based and statistical based approaches are integrated as a multistage classifier. The experimental results demonstrate that this approach has high recognition rate which is up to 98% and good performance of real-time for traffic identification.     

基于特征加权与最近邻法的P2P协议识别算法

针对新的P2P协议以及加密P2P协议无法使用传统方法进行识别的问题,提出一种新的基于流量统计特征的识别方法。首先定义了网络协议特征矢量的概念,并在此基础上使用类内、类间距离与遗传算法定量地对特征子集进行选择,同时由于不同属性所起的作用不同,提出了网络协议特征加权的概念,并使用粒子群优化算法计算特征权值。为了提高识别率,针对TCP协议与UDP协议分别建立了相应的特征空间。实验结果表明该方法能够有效地从多种属性特征中选择出最能够体现P2P协议之间以及P2P协议与非P2P协议之间区别的特征子集,且通过粒子群优化算法计算出的特征权值使识别率得到提高。实验证明通过该算法,对常见的P2P协议平均识别率达到了96%。     

基于DASP系统的某型号数控车床模态测试与分析

基于"计算模态分析+试验模态分析"的方法,以ANSYS计算模态分析结果为参考依据确定机床导纳原点,并应用DASP振动测试系统对自主研发的桌面数控车床进行了试验模态分析。分析确定了车床的前18阶模态振型、固有频率及阻尼等动力学特征和参数,为数控车床的结构优化设计、加工工艺优化提供参考依据,同时也为建立车床实际结构的动力学模型、指导修正有限元分析结果提供依据和支持。     

内置式减振镗杆的试制和减振性能分析

介绍了一款内置阻尼减振器的减振镗杆,阐述其基本设计原理及设计过程。试制减振镗杆并与普通镗杆进行安装状态下的振动试验,采集力锤激励下的镗杆振动信号并求出对应的传递函数图像,得出两种镗杆安装状态的一阶、二阶固有频率,比较减振镗杆相对于普通镗杆的固有频率差异。进行两种镗杆的切削试验,采集镗杆径向的振动信号,比较两种镗杆在相同切削参数下的径向振动波形图,评价该款减振镗杆的减振性能,为该款减振镗杆的设计及仿真结果提供试验数据支撑。     

基于优化SVM的P2P协议识别*

针对P2P应用提出了一种采用DFI深度流分析的方法,通过还原会话流,提取P2P数据流的各种属性特征,采用Grid Search、遗传算法、粒子群算法三种不同算法优化的支持向量机对网络数据流进行分类。通过实验测试,在P2P与非P2P的多种应用中,使用支持向量机进行设计的分类器分类准确率较高,均在90%以上,最高能达到97%。     

Accurate P2P traffic identification based on data transfer behavior

Peer-to-Peer (P2P) technology is one of the most popular techniques nowadays, and accurate identification of P2P traffic is important for many network activities. The classification of network traffic by using port-based or payload-based analysis is becoming increasingly difficult when many applications use dynamic port numbers, masquerading techniques, and encryption to avoid detection. A novel method for P2P traffic identification is proposed in this work, and the methodology relies only on the statistics of end-point, which is a pair of destination IP address and destination port. Features of end-point behaviors are extracted and with which the Support Vector Machine classification model is built. The experimental results demonstrate that this method can classify network applications by using TCP or UDP protocol effectively. A large set of experiments has been carried over to assess the performance of this approach, and the results prove that the proposed approach has good performance both at accuracy and robustness.