Linux进程管理体系的研究与分析

Using an opened source system, Linux, as the supported OS is more and more appealing to many developers. So it is attractive to many developers to understand the designing philosophy of Linux and more importantly, improve its performance to satisfy the specific requirements. This paper analyzes process management of Linux ,and the schedule algorithm of Linux is alsopresented.     

Modeling Distributed Multimedia Synchronization with DSPN

Multimedia synchronization is the essential technology for the integration of multimedia in distributed multimedia systems.The multimedia synchronization model has been recognized by many researchers as a premise of the implementation of multimedia synchronization.In distributed multimedia systems,the characteristic of multimedia synchronization is dynamic,and the key medium has the priority in multimedia synchronization.The previously proposed multimedia synchronization models cannot meet these requirements.So a new multimedia dynamic synchronization model-DSPN,based on the timed Petri-net has been designed in this paper.This model can not only let the distributed multimedia system keep multimedia synchronization in a more precise and effective manner according to the runtime situation of the system,but also allow the user to interact with the presentation of multimedia.     

Design of Objects Tracking System Based on ARM Embedded Platform

In recent years, according to the need of intelligent video surveillance system increasing rapidly in metropolitan cities ,a design based on $3C2440 microprocessor and embedded Linux operating system is adopted for real-time video target tracking. However, it is very challenging as embedded systems usually afford limited processing power and limited resources. Therefore, to address this problem, a real-time tracking algorithm using multi-features based on compressive sensing is proposed and implemented The algorithm uses multiple matrix as the projection matrix of the compressive sensing and the compressed date as the multiple features to extract useful information needed by tracking process. Functions and libraries in OpenCV which were developed by Intel Corporation are utilized for building the tracking algorithms. It is tested with variant video sequences and the results show that the algorithm achieves stable tracking for the target moved of the light changed.     

Real-time Design Constraints in Implementing Active Vibration Control Algorithms

Although computer architectures incorporate fast processing hardware resources, high performance real-time implementation of a complex control algorithm requires an efficient design and software coding of the algorithm so as to exploit special features of the hardware and avoid associated architecture shortcomings. This paper presents an investigation into the analysis and design mechanisms that will lead to reduction in the execution time in implementing real-time control algorithms. The proposed mechanisms are exemplified by means of one algorithm, which demonstrates their applicability to real-time applications. An active vibration control (AVC) algorithm for a flexible beam system simulated using the finite difference (FD) method is considered to demonstrate the effectiveness of the proposed methods. A comparative performance evaluation of the proposed design mechanisms is presented and discussed through a set of experiments.     

3D Modelling,Simulation and Prediction of Facial Wrinkles

The FA （facial ageing） process has been of a great interest to many researchers and some finns like airports and police departments, this is due to the fact that the face appearance changes as people age resulting in difficulties identifying certain individuals. In this paper, 2D wrinkle maps will be used in the design of a 3D system for the purpose of facial wrinkles simulation and prediction. Our findings will challenge many commercial soffwares in the innovation of the techniques in setting solid grounds to generate real-time 3D wrinkles that can be used later for various reasons. The 2D binary wrinkles will be mapped on the corresponding 3D face models using the generated outlined images. NURBS curves will then be projected on those wrinkles to form a 3D wrinkle map. The coloured wrinkle map, as well as some parameters, will be combined together in an algorithm to predict the appearance of the individual wrinkles in every age group that are divided into decades, starting from the age of 20. The novelty of the adopted procedure in comparison to the previous works is the new elements that have been integrated and collaborated to boost accuracy and generate a more realistic outcome.     

Reference implementation of scalable I/O low-level API on Intel Paragon

The Scalable I/O(SIO)Initiative‘s Low-Level Application Programming Interface(SIO LLAP)provides file system implementers with a simple low-Level interface to support high-level parallel /O interfaces efficiently and effectively.This paper describes a reference implementation and the evaluation of the SIO LLAPI on the Intel Paragon multicomputer.The implementation provides the file system structure and striping algorithm compatible with the Parallel File System(PFS)of Intel Paragon ,and runs either inside the kernel or as a user level library.The scatter-gather addressing read/write,asynchronous I/O,client caching and prefetching mechanism,file access hint mechanism,collective I/O and highly efficient file copy have been implemented.The preliminary experience shows that the SIO LLAPI provides opportunities of significant performance improvement and is easy to implement.Some high level file system interfaces and applications such as PFS,ADIO and Hartree-Fock application,are also implemented on top of SIO.The performance of PFS is at least the same as that of Intel‘s native pfs,and in many cases,such as small sequential file access,huge I/O requests and collective I/O,it is stable and much better,The SIO features help to support high level interfaces easily,quickly and more efficiently,and the cache,prefetching,hints are useful to get better performance based on different access models.The scalability and performance of SIO are limited by the network latency,network scalable bandwidth,memory copy bandwidth,memory size and pattern of I/O requests.The tadeoff between generality and efficienc should be considered in implementation.     

开放系统中实时中间件关键技术研究

The Real-Time Middleware is the best way to deal with open and real-time in the same time in open system. In this paper, the characteristic of open system, the policy of real-time implement in open system and the real-time CORBA specification and development are introduced, then the key technology of real-time CORBA in open system is discussed in detail according to the model of real-time CORBA including the technology of the real-time POA, real-time ORB, thread pool, pluggable network protocol, multiplexing and demultiplexing and presentation layer optimizations etc, which provides a viable method and research for open system real-time extension.     

WNN-Based Network Security Situation Quantitative Prediction Method and Its Optimization

The accurate and real-time prediction of network security situation is the premise and basis of preventing intrusions and attacks in a large-scale network. In order to predict the security situation more accurately, a quantitative prediction method of network security situation based on Wavelet Neural Network with Genetic Algorithm （GAWNN） is proposed. After analyzing the past and the current network security situation in detail, we build a network security situation prediction model based on wavelet neural network that is optimized by the improved genetic algorithm and then adopt GAWNN to predict the non-linear time series of network security situation. Simulation experiments prove that the proposed method has advantages over Wavelet Neural Network （WNN） method and Back Propagation Neural Network （BPNN） method with the same architecture in convergence speed, functional approximation and prediction accuracy. What is more, system security tendency and laws by which security analyzers and administrators can adjust security policies in near real-time are revealed from the prediction results as early as possible.     

Organizing Projects Around the Mitigation of Risks Arising from System Dynamic Behavior

Many of the key products and services used by modern societies are the result of large-scale engineering projects. Despite decades of theoretical and practical work in the art of systems engineering and project management, project execution results remain somewhat inconsistent, in the sense that many projects fail to produce a product that meets the original specifications, and many more projects achieve some measure of technical success only after taking significantly more time and/or money than originally expected. One source of such failures is the occurrence of unplanned and adverse dynamic behavior in the resulting system. This paper summarizes research being conducted to look at the potential of design-phase actions that centralize control of the eventual system''s dynamic behavior as a potential solution to some instances of this problem. This approach could lead to increased chances of success on future major system development projects, through a new method for instituting better control of the dynamic behavior of such a system.     

Editorial

It is our great pleasure and honor to organize this special issue “System Identification and Estimation”. System identification has been a surprisingly lively and resilient area of research in the control community for many years. It grew out of statisticians’ interest in time series analysis beginning in the 1940s and became a “regular control topic” in the 1960s, as indicated by the first IFAC Symposium on System Identification held in Prague, Czech Republic, in 1967. Sixty years later, it is still an important area of research in the field of control. It is relevant to ask why the interest in system identification has remained so intense. One answer might be that more and more applications in engineering require mathematical models and the combined use of system identification and physical modeling is the basic way to obtain reliable models. This special issue is focusing on the latest development, trends, and novel methods for system identification and estimation and these contributions will give interesting and inspiring insights into the current status of the area. There are 16 papers collected in this special issue....     

一种基于改进时钟系统的Linux实时化方案

目前,实时领域的应用逐渐扩大,不仅传统的嵌入式系统需求日益紧迫,而且也渗透到桌面环境。而随着Linux操作系统的成功,改进Linux的设计和性能,使其应用于实时领域吸引了许多研究人员和开发人员的注意力。论文针对Linux时钟系统管理方面的研究,提出了一种针对时钟的改进算法,以此为基础,根据实时应用的特点,进一步给出一种调度算法的改进措施。试验证明,所做的改进有效地提高了Linux的调度精度,满足了软实时方面的需求。     

改善Linux核心可抢占性方法的研究与实现

随着开放源码的Linux应用逐渐普及，改进Linux的性能，使其适用于实时领域成为一个极具潜力的发展方向．在参考了与此相关的研究的基础上，该文对改善Linux核心可抢占性的方法提出了3个改进措施：中断管理进程化、改进互斥锁的机制和增加互斥锁协议支持，并在Linux2．2系列的核心上加以实现．试验证明，这些改进达到了减少系统的抢占粒度，提高调度精度的目的。     

一种改进的优先级继承协议及其算法研究

优先级反向是实时系统中由于任务间需要共享资源以及同步而引起的高优先级任务被低优先级任务阻塞的现象。优先级反向使得高优先级任务的执行时间无法预测,增加了实时系统的不确定性。早期的扩展协议较好地解决了优先级反转问题,但同时也存在着自身的不足。针对这些缺陷,在深入研究相关协议的基础上,该文提出了一种改进的优先级继承协议。该协议中信号量按预定义的非循环固定顺序获取,以防止死锁发生,设置超时保护机制,避免任务在获取信号量时长时间的阻塞,给出了关于该协议的分析,并在实时Linux上实现了基于该协议的算法。     

应用中的嵌入式Linux实时优化

以Linux2.6为对象,在分析了国内外有关提高Linux实时性的几种方法的基础上,对任务切换、优先级调度算法以及中断服务程序提出了改进方式。引入了“在实时系统中,只有当进程的临界区能在下一个实时任务开始之前结束才被允许进入”的任务切换机制,实现了优先级置顶的方法以避免发生优先级倒置的现象,并用内核线程代替中断服务程序。上述方法可用在嵌入式领域和对实时性有较高要求的Linux应用中。     

Linux抢占式内核的研究与实现

随着Linux操作系统的成功应用,尤其是在嵌入式实时应用领域,Linux实时性能的提高成为一个很重要的因素.系统核心的可抢占性是决定系统实时性能的一个重要条件,而Linux的核心是不可抢占的,通过将Linux的内核改造为可抢占式内核,可缩短系统的响应延时,提高Linux的实时性.分析了几种实现抢占式内核的方法,介绍了一种实现Linux可抢占式内核的方法,并对其实现细节进行了详细的说明.     

实时通告服务设计与实现

OMG通告服务为对策之间提供强有力的解耦通信支持,是CORBA提供的重要服务之一,目前很多应用需要之间的通信具有实时性,而现有的通告服务规范已不能满足这种需求,为此,设计并实现了具有实时功能的通告服务,提出了一种实时通告服务的体系结构,讨论了实时通告服务系统的实现技术。     

基于嵌入式Linux的实时优化方案

在分析了国外两种主流嵌入式Linux实时化的实现方法的基础上,根据实时操作系统和Linux的特点,就实时调度策略、细粒度定时器等几个方面提出了改善系统实时性的一种优化方案。     

基于RTAI-Linux的实时操作系统的分析与研究

本文讨论了实时操作系统的特性，分析了Linux作为实时操作系统的不足之处，深入剖析了RTAI增强Linux实时性的基本思想以及RTAI的设计与实现原理。     

嵌入式实时操作系统的内核抢占机制研究

随着嵌入式系统与理论技术的快速发展,越来越多的嵌入式设备被普及。改进其操作系统的实时性能,使其适用于实时领域已成为一个极具潜力的发展方向。该文基于自主开发的ARTs-Os嵌入式实时操作系统,提出了一种可抢占式内核的实现方案,并在ARTs-Os核心上实现。     

实时以太网研究与实现

以太网由于其低价、稳定等优点,在很多领域获得了广泛的应用,分析了以太网应用于实时系统的不足,并提出一套解决方案,最后描述了该方案在Linux系统中的实现方法.