Snort入侵检测系统中数据包捕获模块的分析与设计

随着网络的高速发展,网络带宽得到了极大的提升。高速网络环境下对入侵检测系统提出了更高的要求,其中入侵检测系统的数据包捕获能力成为其发展的瓶颈。目前大多数系统使用传统的Libpcap库来实现数据包捕获功能,文章对一个基于Snort入侵检测系统中数据包捕获模块进行了分析设计,给出了设计架构,详细说明了工作流程,并对系统的性能进行了对比分析。     

基于自由摆的平板精确控制与激光追踪系统

以TI公司的MSP430F5438单片机为控制核心,结合步进电机和精密电位器WDD35D-4,实现了基于自由摆的平板控制与激光追踪系统。当摆杆摆角为45°～60°时,平板可以承载8枚一元硬币,并在5个摆动周期内维持稳定;当摆杆摆角为30°～60°时,固定在摆杆平板上的激光笔可以在15s内找到并跟踪1.5m远处的靶心。     

gbase: an efficient analysis platform for large graphs

Graphs appear in numerous applications including cyber security, the Internet, social networks, protein networks, recommendation systems, citation networks, and many more. Graphs with millions or even billions of nodes and edges are common-place. How to store such large graphs efficiently? What are the core operations/queries on those graph? How to answer the graph queries quickly? We propose Gbase, an efficient analysis platform for large graphs. The key novelties lie in (1) our storage and compression scheme for a parallel, distributed settings and (2) the carefully chosen graph operations and their efficient implementations. We designed and implemented an instance of Gbase using Mapreduce/Hadoop. Gbase provides a parallel indexing mechanism for graph operations that both saves storage space, as well as accelerates query responses. We run numerous experiments on real and synthetic graphs, spanning billions of nodes and edges, and we show that our proposed Gbase is indeed fast, scalable, and nimble, with significant savings in space and time.     

Power- and time-aware buffer cache management for real-time embedded databases

Due to the explosive increases of data from both the cyber and physical worlds, the demand for database support in embedded systems is increasing. Databases for embedded systems, or embedded databases, are expected to provide timely in situ data services under various resource constraints, such as limited energy. However, traditional buffer cache management schemes, in which the primary goal is to minimize the number of I/O operations, is problematic since they do not consider the constraints of modern embedded devices such as limited energy and distinctive underlying storage. In particular, due to asymmetric read/write characteristics of flash memory-based storage of modern embedded devices, minimum buffer cache misses neither coincide with minimum power consumption nor minimum I/O deadline misses. In this paper we propose a novel power- and time-aware buffer cache management scheme for embedded databases. A novel multi-dimensional feedback control architecture is proposed and the characteristics of underlying storage of modern embedded devices is exploited for the simultaneous support of the desired I/O power consumption and the I/O deadline miss ratio. We have shown through an extensive simulation that our approach satisfies both power and timing requirements in I/O operations under a variety of workloads while consuming significantly smaller buffer space than baseline approaches.     

Birman–Wenzl–Murakami algebra, topological parameter and Berry phase

In this paper, a 3?×?3-matrix representation of Birman?CWenzl?CMurakami (BWM) algebra has been presented. Based on which, unitary matrices A(??, ?? ₁, ?? ₂) and B(??, ?? ₁, ?? ₂) are generated via Yang?CBaxterization approach. A Hamiltonian is constructed from the unitary B(??, ??) matrix. Then we study Berry phase of the Yang?CBaxter system, and obtain the relationship between topological parameter and Berry phase.     

Signal tracking method of GNSS receivers for spinning vehicles

A signal tracking method of GNSS receivers for spinning vehicles is proposed in order to eliminate the influence of spinning to the GNSS signal of a vehicle. In the proposed method, a rotation tracking loop is added into the carrier tracking loop of a conventional GNSS receiver. The proposed method was verified through computer simulations and an experiment for live GPS signals. The results show that the proposed method gives an accurate tracking performance.     

Parameter identification and design of a robust attitude controller using <Emphasis Type="Italic">H</Emphasis><Subscript>∞</Subscript> methodology for the raptor E620 small-scale helicopter

Rigorous control synthesis for an unmanned aerial vehicle necessitates the availability of a good, reasonable model for such a vehicle. The work reported in this paper focuses on the modeling of a rotary unmanned aerial vehicle (RUAV) and the development of a robust controller that can handle parameter uncertainties and disturbances. The parameters of the plant model are obtained through the use of the prediction error method with real flight data. The response of the identified linear model shows a good match with the measured flight data. The H _∞ control scheme is applied to obtain a robustly stable controller using the identified model. The proposed controller is analyzed using frequency-domain analysis and time-domain simulations. The performance of the proposed H _∞ controller is better than that of the conventional proportional derivative controller in that the proposed controller has a shorter settling time and less overshoot. Furthermore, the degradation of the proposed controller performance is negligible and stability is maintained when the input gains to the plant are doubled, which demonstrates the good performance and robustness of the controller.     

Stability of a class of switched stochastic nonlinear systems under asynchronous switching

The stability of a class of switched stochastic nonlinear retarded systems with asynchronous switching controller is investigated. By constructing a virtual switching signal and using the average dwell time approach incorporated with Razumikhin-type theorem, the sufficient criteria for pth moment exponential stability and global asymptotic stability in probability are given. It is shown that the stability of the asynchronous stochastic systems can be guaranteed provided that the average dwell time is sufficiently large and the mismatched time between the controller and the systems is sufficiently small. This result is then applied to a class of switched stochastic nonlinear delay systems where the controller is designed with both state and switching delays. A numerical example illustrates the effectiveness of the obtained results.     

面向S3C2440的U-Boot分析与改进

针对目前U - Boot引导程序无法从大页Nandflash启动,以及不能同时支持从Nandflash和Norflash启动的问题,在不改变代码通用性的前提下对U- Boot进行了改进.首先分析U - Boot阶段l的启动原理和U- Boot通用性的实现方法;然后依据S3C2440处理器提供的Nandflash存储启动机制以及大页Nandflash数据操作原理,修改阶段l实现代码,添加从大页Nandflash启动;最后利用大页Nandflash和Norflash存储器读写数据的差异性以及两种存储启动方式实现的不同机理,添加S3C2440处理器自动判断从何种存储器启动的代码,实现U-Boot兼容Nandflash和Norflash启动的改进.通过在基于S3C2440处理器的目标板上运行,结果证明对U - Boot所做的改进具有有效性,扩展了U-Boot的适用范围,增强了代码兼容性.     

涡扇发动机最优加速控制规律

关于涡扇发动机最优加速控问题,由于状态系统存在较强的非线性,控制性能差,改善发动机加速性,传统非线性规划算法求解过程中因采用罚函数处理约束条件而无法充分搜索控制参数的可行域。为提高系统性能,并充分挖掘发动机的加速特性,采用Sigma方法的多目标粒子群算法求解。可以在带限制因子的粒子群算法的基础上,利用粒子群算法的快速寻优能力和Sigma方法沿约束边界的充分搜索方法,求解发动机加速过程中控制参数,并进行仿真。结果证明,采用多目标粒子群算法优化后,加速时间缩短了约2.01s,结果表明改进方法是可行的,能在确保发动机安全工作的前提下,进一步提升了发动机的加速性能。