基于累积和算法的域名系统缓存攻击检测

针对域名系统(DNS)缓存攻击,提出一种简单有效的检测机制。为增强对攻击行为的敏感性并减小计算复杂度,通过无参数累积和检测模型改进DNS的协议行为,利用变点检测的相关算法实现对攻击行为的检测。仿真结果表明,该机制能够有效检测DNS缓存攻击,并实现检测准确率和误警率间的平衡。     

基于单指令多数据技术的H.264编码优化

简要介绍了单指令多数据（Single-Istruction Multiple-Data，SIMD）指令系统，并用该技术对H.264中的整数离散余弦变换（Discrete Cosine Transform，DCT）、量化、插值和运动估计等模块进行了优化，实验结果表明优化后程序的编码速率可达到30fps左右，比未优化时速度提高了6～8倍。     

青岛市深基坑支护存在问题的分析

随着城市建设进度的加快,建筑密度越来越大,基坑近围环境越来越复杂,深基坑支护的难度也愈来愈大,所暴露的问题也愈来愈多.正确认识存在的问题,及时总结过去的经验教训,对今后深基坑支护工作将大有裨益.本文在简要介绍青岛市自然地理、工程地质特征及深基坑支护历史和现状的基础上,分析总结了深基坑支护方面所存在的主要问题,这对统一思...     

High-field versus high-pressure: Weakly adsorbed CO species on Pt(1 1 1)

Adsorption of carbon monoxide on a nanosized apex facet of a [1 1 1]-oriented Pt field emitter tip was studied under high electrostatic field conditions (15–20 V/nm) by field ion appearance energy spectroscopy (FIAES). Weakly bound highly mobile CO species have been detected and their possible role in surface reactions such as CO oxidation on Pt was elucidated.     

基于节点行为的主动P2P蠕虫检测

主动P2P蠕虫的传播会对P2P网络以及互联网的安全造成严重威胁。通过研究主动P2P蠕虫传播时节点行为,提出一种基于节点行为的主动P2P蠕虫检测方法PBD（Peer Behavior based Detection）。在此基础上设计和实现了一个主动P2P蠕虫检测系统PPWDS（Proactive P2P Worm Detection System）,该系统采用CUSUM算法对P2P节点出站短连接进行实时监控。实验表明,PBD是检测主动P2P蠕虫的一种有效方法。     

CDMA网络中基于粒子滤波的TSOA/AOA跟踪

阐述了CDMA网络中单台设备实现TSOA/AOA被动式定位的原理。采用非线性模型对移动台的运动状态进行了描述。利用粒子滤波对非线性系统和非高斯噪声环境的高度适应性,设计了一种基于粒子滤波的TSOA/AOA跟踪算法,实现了对移动台位置和速度的同时跟踪。仿真结果表明,与扩展卡尔曼滤波相比,采用粒子滤波有效提高了跟踪系统的性能。     

有限反馈SDMA中基于信干噪比的天线合并算法

多天线广播信道中基于信道量化的MISO-SDMA系统可通过增加用户端天线并采用相关的天线合并技术来有效降低反馈量的需求。该文提出了一种基于信干噪比SINR的天线合并准则,以寻求最优的合并矢量和等效信道量化值。由于综合考虑了接收信道等效功率、量化误差引起的用户间干扰和噪声等因素,改善已有合并算法中仅仅最大化接收端等效信噪比或最小化量化误差的不足。另外,该文从理论上推导分析了在信噪比趋于零和趋于无穷时该算法的极限情形,证明已有的最大比合并和基于量化的合并方法是该文所提算法在极限情况下的特例。计算机仿真表明在相同的反馈量下该文所提算法有着优于二者的性能。     

独立同指数分布随机变量和的高阶矩的计算

研究了独立同指数分布随机变量和的高阶矩。利用数学归纳法对指数分布随机变量的高阶矩进行了计算,并以此为基础,结合组合数学中的多项式定理和整数分拆的相关知识对独立同指数分布随机变量和的高阶矩进行计算,得到了其高阶矩的计算公式,并利用数值例子进行了说明。     

Operational optimization and real-time control of fuel-cell systems

Fuel cells is a rapidly evolving technology with applications in many industries including transportation, and both portable and stationary power generation. The viability, efficiency and robustness of fuel-cell systems depend strongly on optimization and control of their operation. This paper presents the development of an integrated optimization and control tool for Proton Exchange Membrane Fuel-Cell (PEMFC) systems. Using a detailed simulation model, a database is generated first, which contains steady-state values of the manipulated and controlled variables over the full operational range of the fuel-cell system. In a second step, the database is utilized for producing Radial Basis Function (RBF) neural network “meta-models”. In the third step, a Non-Linear Programming Problem (NLP) is formulated, that takes into account the constraints and limitations of the system and minimizes the consumption of hydrogen, for a given value of power demand. Based on the formulation and solution of the NLP problem, a look-up table is developed, containing the optimal values of the system variables for any possible value of power demand. In the last step, a Model Predictive Control (MPC) methodology is designed, for the optimal control of the system response to successive sep-point changes of power demand. The efficiency of the produced MPC system is illustrated through a number of simulations, which show that a successful dynamic closed-loop behaviour can be achieved, while at the same time the consumption of hydrogen is minimized.     

遗传算法在天线阵自适应算法中的应用

本文采用一种新的基于遗传算法的天线阵列的自适应算法。根据实际的硬件限制,不改变阵列的幅度加权,而通过遗传算法对相位加权作全局优化。为减小对天线方向图的破坏,并希望在干扰源来波方向实时置零,因而采用只优化搜索数字移相器的最后几位。计算机模拟结果证实了这种方法的有效性。