分布式多媒体系统服务质量管理实现支持机制

近年来，分布式多媒体系统中的服务质量QoS(quality of service)管理及其实现支持机制取得了很大进展.本文从接纳控制与资源预约、基于速率的流控、差错控制、调度与同步几个方面出发，讨论QoS管理实现支持机制，并展望今后的研究工作.     

Android开发中利用反射获取存储路径的研究

Android应用的开发中对存储的访问非常频繁,但是Android各个版本对存储的支持比较混乱,部分版本甚至没有公开的API支持对扩展存储访问.对Android的内置、外置存储设备进行研究后,提出将存储分为内部存储、外部存储及扩展存储三个类型.分析了各个存储的类型的特点及访问方式,重点讨论了扩展存储的访问方式,提出利用JAVA的反射机制来获取Android平台的扩展存储目录,解决了Android不同版本对存储进行访问的兼容性问题.通过分析工具分析了反射机制在此应用中的效率问题,并在不同Android版本的设备上进行了测试.     

二维网格片上网络中的新型自适应路由算法

本文针对二维网格的片上网络设计了一种称为维度气泡流控(DBFC)的新型流控策略。利用虚跨步切换技术中消息的依存关系只与相邻缓冲区队列相关的特点,设计实现了维度气泡流控。该流控策略建立在虚跨步(VCT)切换和信约流控机制之上,通过分析端口信约值和路由信息实现点点间的流控。在二维网格的片上网络中采用DBFC流控策略,即使网络中存在环相关,本文设计的自适应维度气泡路由(ADBR)算法仍可实现无死锁、最短距离的路由。对于以上结论,本文提供了详细证明。最后,通过修改通用的片上网络模拟工具-NOXIM的代码,实现了DBFC流控策略和ADBR算法。在NOXIM上分析了ADBR算法的性能,结果显示ADBR算法拥有较好的性能。     

基于Flash的高速大容量固态存储系统设计

介绍一个高速大容量固态存储系统的组成机制和实现技术.特点是使用固态存储芯片Flash(闪存)阵列作为存储介质,采用多级流水线和并行总线技术存储高速数据.通过FPGA(现场可编程门阵列)产生控制时序和进行数据缓冲,成功实现了4×4片Flash阵列对30 MB/s高速数据的实时存储,并可通过扩展Flash阵列满足更高速度和更大容量的存储要求.系统通过USB2.0与计算机进行数据通信.     

PostgreSQL存储过程移植方法

在对PostgreSQL存储过程处理机制进行研究的基础上,分析了Oracle存储过程移植到PostgreSQL时的语法、参数默认值、out参数、事务回滚、游标和内置函数等问题,并从成本、收益和技术难度的角度比较了两种存储过程移植方法--改写存储过程方法和扩展PostgreSQL的存储过程功能方法.深入研究了通过扩展PL/pgSQL源码来调整PostgreSQL存储过程功能的PLSE方法.     

星载同步NAND FLASH存储控制器设计

为满足海量空间科学数据对高速存储的需求,设计一种星载同步NAND FLASH存储控制器.通过对星载存储系统吞吐率影响因素的分析,提出采用具有同步数据接口的NAND FLASH存储器件、在存储阵列之间引入八级流水操作、对NAND FLASH数据总线进行并行扩展的设计方案,对存储控制器的软硬件进行设计.实验结果表明,该设计能够有效提升星载存储系统的吞吐率,设计中的功能模块化及接口标准化有利于系统进一步灵活扩展.     

MiroSot大场地足球机器人系统的软件体系结构研究

为提高MiroSot大场地(11vs11)足球机器人系统的实时性,在分析集控式足球机器人系统的原理以及大场地项目特点的基础上,建立了大场地足球机器人系统的客户机/服务器(C/S)模式体系结构。该体系结构通过采用内核同步机制、消息映射等多线程技术和基于Socket的网络通讯技术实现了双摄像头的采集结构和客服模式的双机通信。其次,提出多级缓冲区的数据管理方式,保证了系统处理数据以及客户机与服务器之间传递数据的实时性和一致性。     

扩展时间流Petri网多媒体同步模型

多媒体同步的一个主要问题是多媒体同步时间要求的描述与建模。文中基于时间流Ｐｅｔｒｉ网模型（ＴＳＰＮ）,通过分析ＴＳＰＮ模型的不足之处,提出了一种新的多媒体同步模型－－扩展时间流Ｐｅｔｒｉ网模型（ＳＴＳＰＮ）,ＳＴＳＰＮ不但可以完全、准确地描述媒体流内和流间的时间行为,而且通过引入容许阻塞时间、问题算法等对ＴＳＰＮ进行扩展,可以有铲地克服网络随机延迟、阻塞和丢包等因素的不良影响,提高了模型的建模能力     

云同步系统中采用增量存储的版本控制技术研究

用户在使用云同步系统时,常常需要对文件执行版本恢复等操作.涉及到文件的版本问题,需要在云同步系统中引入版本控制功能对用户文件进行版本管理,这将不可避免地给系统带来版本冲突、版本存储冗余等诸多问题,这些问题可以通过建立一个良好的版本模型,制定完善的策略予以解决.首先对云同步系统以及其版本特点进行了分析和描述,并根据这些特点对版本以及版本存储进行建模,提出了增量存储以及版本恢复的具体实现,并通过对与全量存储方式以及现有增量存储方式的对比实验进行分析,论证了方案的合理性、可用性以及优越性.     

基于Linux流控机制的QoS网络

对Linux内核中的流控机制进行剖析，以区分服务(DiffServ)模型为侧重点，根据区分服务模型的体系结构，提出了利用Linux流控机制实现加速转发逐跳行为的应用方案。实验表明，该方案适合于QoS网络的构建。     

基于子字并行的串行图像处理算法表示方法

多媒体应用程序的一个最突出的特点就是其内在的并行性,要求同时对多个数据单元进行相同的规则操作,这种并行性被称为子字并行。如何让编译器产生有效的并行代码,如何从普通的串行C程序中识别出子字并行指令,是一个前沿性的研究课题。提出了一种用于实现对串行源代码进行显式表示的方法,该方法对数字信号处理领域常用的同步数据流图方法进行改进,结合模式匹配技术,着眼于内层循环,通过扩展规范的模式库,对带模式识别的数据流、控制流进行分析,能够从串行应用程序中自动地提取其固有的子字并行,得到显式的并行化中间表示,基于这种数据流图表示,采用改进的树模式匹配实现子字并行指令选择和代码生成。实验测试表明了该方法的有效性。     

Real-Time Camera Tracking for Mobile Devices: The VisiTrack System

This paper presents VisiTrack, a novel approach for video based incremental tracking in real-time. The major objectives in the development of VisiTrack was to design or select algorithms that are well suited for embedded real-time computation. We had a special focus on latency reduction and storage minimization since the algorithms should run on mobile devices like PDAs with the appropriate extension, i.e. mainly a camera, in real-time. The image analysis, camera localization and feature position approximation of VisiTrack are explained in detail. The CV-SDF model, an extension of Synchronous Dataflow graphs (SDF), supporting the principles of linear processing and fine-grained pipelining was defined and applied for the design of all VisiTrack modules in order to fulfill real-time constraints and reduce system latency. Furthermore the camera localization and position approximation include mechanisms for minimization of errors that may arise for instance due to measurement inaccuracies. Current applications of VisiTrack in the augmented reality domain and robotic self localization show its good performance. However VisiTrack is not limited to these application domains.     

HSP传输协议的设计与实现

首先对传输层协议进行了介绍,并给出了协议设计时的一些考虑,然后对HSP协议进行了详细描述。HSP协议针对局域网存储系统进行优化,通过精简层次和高效的流控方式来提高系统的吞吐率。同时给出了HSP在Linux下的实现,最后对协议进行了初步的性能测试,结果表明,HSP在局域网存储系统环境中比TCP／IP具有更好的性能。     

采用2D-SMPC码的S-OCDMA系统性能分析

在同步修正素数码（SMPC）基础上,通过给每个不同的种子分配一个不同的波长片,构造了二维正交地址码（2D-SMPC）;分析了码字的相关特性,确定了地址码选取原则;通过Optisystem仿真,研究了该码的多址干扰（MAI）和系统容量等性能。与一维SMPC码性能相比较,验证了其用于S-OCDMA系统时的性能改善。     

I/O-aware bandwidth allocation for petascale computing systems

In the Big Data era, the gap between the storage performance and an application’s I/O requirement is increasing. I/O congestion caused by concurrent storage accesses from multiple applications is inevitable and severely harms the performance. Conventional approaches either focus on optimizing an application’s access pattern individually or handle I/O requests on a low-level storage layer without any knowledge from the upper-level applications. In this paper, we present a novel I/O-aware bandwidth allocation framework to coordinate ongoing I/O requests on petascale computing systems. The motivation behind this innovation is that the resource management system has a holistic view of both the system state and jobs’ activities and can dynamically control the jobs’ status or allocate resource on the fly during their execution. We treat a job’s I/O requests as periodical sub-jobs within its lifecycle and transform the I/O congestion issue into a classical scheduling problem. Based on this model, we propose a bandwidth management mechanism as an extension to the existing scheduling system. We design several bandwidth allocation policies with different optimization objectives either on user-oriented metrics or system performance. We conduct extensive trace-based simulations using real job traces and I/O traces from a production IBM Blue Gene/Q system at Argonne National Laboratory. Experimental results demonstrate that our new design can improve job performance by more than 30%, as well as increasing system performance.     

性能虚拟化存储系统的设计与实现

针对集中共享存储环境中不同应用间的性能隔离和性能保证问题,在容量虚拟化管理的基础上提出一种性能虚拟化管理机制,实现同时支持容量和性能虚拟化管理的虚拟存储系统。该系统采用扩展了接纳管理和空闲资源公平分配机制的比例带宽资源分配算法,实现虚拟磁盘间的性能虚拟化,避免多个虚拟磁盘间的性能干扰。     

Operational predictive optimal control of Barcelona water transport network

This paper describes the application of model-based predictive control (MPC) techniques to the supervisory flow management in large-scale drinking water networks including a telemetry/telecontrol system. MPC is used to generate flow control strategies (set-points for the regulatory controllers) from the sources to the consumer areas to meet future demands, optimizing performance indexes associated to operational goals such as economic cost, safety storage volumes in the network and smoothness of the flow control actions. The designed management strategies are applied to a model of a real case study: the drinking water transport network of Barcelona (Spain).     

PMSM有效磁链滑模观测器及转矩精确控制

为了改善轨道交通永磁同步电动机转矩控制的性能,提出了一种改进的有效磁链滑模观测器,实现了永磁同步电动机的精确转矩闭环控制。采用有效磁链的概念,建立了基于有效磁链的内置式永磁同步电机数学模型;在[α-β]静止坐标系建立了有效磁链的滑模观测器,并基于滑模等值控制方法实现了有效磁链的观测,进而进行转矩的实时估算,以此和转矩给定值形成精确转矩闭环控制。通过仿真验证该方法的可行性和有效性。结果表明提高永磁同步电动机的转矩控制精度,改善了轨道永磁同步电动机控制系统的性能。该方法不仅适用于内置式永磁同步电机,而且适用于表贴式永磁同步电机。     

Massive Storage Systems

To accommodate the explosively increasing amount of data in many areas such as scientific computing and e-Business, physical storage devices and control components have been separated from traditional computing systems to become a scalable, intelligent storage subsystem that, when appropriately designed, should provide transparent storage interface, effective data allocation, flexible and efficient storage management, and other impressive features. The design goals and desirable features of such a storage subsystem include high performance, high scalability, high availability, high reliability and high security. Extensive research has been conducted in this field by researchers all over the world, yet many issues still remain open and challenging. This paper studies five different online massive storage systems and one offline storage system that we have developed with the research grant support from China. The storage pool with multiple network-attached RAIDs avoids expensive store-and-forward data copying between the server and storage system, improving data transfer rate by a factor of 2-3 over a traditional disk array. Two types of high performance distributed storage systems for local-area network storage are introduced in the paper. One of them is the Virtual Interface Storage Architecture (VISA) where VI as a communication protocol replaces the TCP/IP protocol in the system. VISA's performance is shown to achieve better than that of IP SAN by designing and implementing the vSCSI (Vl-attached SCSI) protocol to support SCSI commands in the VI network. The other is a fault-tolerant parallel virtual file system that is designed and implemented to provide high I/O performance and high reliability. A global distributed storage system for wide-area network storage is discussed in detail in the paper, where a Storage Service Provider is added to provide storage service and plays the role of user agent for the storage system. Object based Storage Systems not only store data but also adopt the attributes and methods of objects that encapsulate the data. The adaptive policy triggering mechanism (APTM), which borrows proven machine learning techniques to improve the scalability of object storage systems, is the embodiment of the idea about smart storage device and facilitates the self-management of massive storage systems. A typical offline massive storage system is used to backup data or store documents, for which the tape virtualization technology is discussed. Finally, a domain-based storage management framework for different types of storage systems is presented in the paper.     

云控制系统及其面临的挑战

本文提出的云控制系统(Cloud control systems, CCSs)是对之前的网络化控制系统(Networked control systems, NCSs)的进一步扩展.目前,物联网(Internet of things, IOT)已经成功应用于实际中,网络化控制技术在其中发挥了关键作用.与此同时,云计算的迅速发展为大数据存储与处理、控制器设计和控制系统性能优化提供了一个完美的平台.可以预见,虽然当前云控制技术的研究和应用还存在许多挑战,但在不久的将来,云控制系统的深入研究将对控制理论的发展和各种实际应用起到积极推动作用.