基于DAE和GRU组合的流量异常检测方法

流量异常检测能够有效识别网络流量数据中的攻击行为,是一种重要的网络安全防护手段。近年来,深度学习在流量异常检测领域得到了广泛应用,现有的深度学习模型进行流量异常检测存在两个问题:一是数据受噪声影响导致检测鲁棒性差、准确率低;二是数据特征维度高以及模型参数多导致训练和检测速度慢。为了在降低流量数据噪声影响的基础上提高检测速度和准确性,本文提出了一种基于去噪自编码器(Denoising Auto Encoder,DAE)和门控循环单元(Gated Recurrent Unit,GRU)组合的流量异常检测方法。首先设计了基于DAE的流量特征提取算法,采用小批量梯度下降算法对DAE进行训练,通过最小化含噪声数据的重构向量与原始输入向量间的差异,有效提取具有较强鲁棒性的流量特征,降低特征维度。然后设计了基于GRU的异常检测算法,利用提取的低维流量特征数据训练GRU,从而构建异常流量分类器,实现对攻击流量的准确检测。最后在NSL-KDD、UNSW-NB15、CICIDS2017数据集上的实验结果表明:与其他的机器学习、深度学习方法相比,本文所提方法的检测准确率最大提升了18.71%。同时,本文方法可以实现较高的精确率、召回率和检测效率,同时具有较低的误报率。在面对数据受到噪声破坏时,具有较强的检测鲁棒性。     

拟态路由器TCP代理设计实现与形式化验证研究

拟态路由器基于拟态防御的动态异构冗余架构进行设计,对于未知漏洞后门具有良好的防御能力。协议代理在拟态路由器中处于内外联络的枢纽位置,协议代理的安全性和功能正确性对于拟态路由器有着重要意义。本文设计实现了拟态路由器的TCP协议代理,并采用形式化方法,对其安全性和功能正确性进行了验证。TCP协议代理嗅探邻居和主执行体之间的TCP报文,模拟邻居和从执行体建立TCP连接,并向上层应用层协议代理提供程序接口。基于分离逻辑与组合思想,采用Verifast定理证明器,对TCP协议代理的低级属性,包括指针安全使用、无内存泄露、无死代码等,进行了验证;同时,还对TCP协议代理的各主要功能模块的部分高级属性进行了形式化验证。搭建了包含3个执行体的拟态路由器实验环境,对实现结果进行了实际测试,结果表明所实现的TCP代理实现了预期功能。TCP协议代理实现总计1611行C代码,其中形式化验证所需人工引导定理检查器书写的证明共计588行。实际开发过程中,书写代码实现与书写人工证明所需的时间约为1:1。本文对TCP协议代理的实现与形式化验证工作证明了将形式化验证引入拟态路由器的关键组件开发中是确实可行的,且证明代价可以接受。     

Accelerating approximate matrix multiplication for near-sparse matrices on GPUs

The Journal of Supercomputing - Although the matrix multiplication plays a vital role in computational linear algebra, there are few efficient solutions for matrix multiplication of the near-sparse...     

Structure and Magnetic Properties of Ce-Substituted Yttrium Iron Garnet Prepared by Conventional Sintering Techniques

Y_3?xCe _x Fe₅ O ₁₂ (CeYIG) ceramics, with x = 0, 0.15, 0.25, 0.35, 0.45, and 0.5, were fabricated by a conventional ceramic sintering technique. We studied the structures and magnetic fields of a series of CeYIG ceramics using X-ray powder diffraction, a scanning electron microscope, and a superconducting quantum interference device magnetometer. Findings showed that the substitution limit of the concentration of Ce³⁺ ions in the yttrium iron garnet structure was approximately x = 0.25. An extra CeO₂ phase was detected in the ceramic when the addition of CeO₂ content overtook the limit. The lattice constants and relative densities increased by increasing the Ce³⁺ contents in the ceramics. First, the saturation magnetization increased gradually with increases in the substitute concentration of Ce³⁺ ions and then decreased gradually when x = 0.35, 0.45, and 0.5. Overall, this study showed that the Y_3?xCe _x Fe₅ O ₁₂ material with x ≤ 0.15 exhibited excellent magnetic properties. Hence, the material show promise for magneto-optical and microwave communication applications.     

Self-reinforcing mechanisms for cellularisation: a longitudinal case study

Firms that adopt cellular manufacturing (CM) often need to restructure their products, personnel, equipment, factory management and organisation culture. Despite voluminous literature on CM, only a few case studies related to cellularisation exist. Therefore, to enhance understanding in this area, this paper presents a longitudinal case study on cellularisation in an electronic assembly plant. Six years of data were collected from the observations and discussions of an industrialist and an academician. Events instrumental to the persistence of CM were highlighted, with reference to path dependence analysis. Cellularisation is not entirely evolutionary or teleological but is an interplay of the two; it is significantly influenced by the positive feedback of self-reinforcing mechanisms after departing from critical junctures. The observed self-reinforcing mechanisms were expounded and divided into six categories.