Design and Implementation of Embedded Network Image Acquisition System

随着多媒体技术和网络技术的发展，嵌入式网络图像采集系统的研究与实现越来越受到人们的重视。目前，图像的采集设备大都是以个人计算机为核心来进行处理的。利用计算机强大的处理能力和通用的接口，设计专用的图像采集卡来采集图像，应用非常广泛。但因其体积庞大、成本高、携带不便，因此许多户外场合下这类设备并不适合于图像的采集。在这种背景下，设计一种轻便小巧且性价比高的图像采集系统来采集、处理并传输所需的图像成为市场所需。 本文主要研究了以基于ARMv5TE体系结构的IntelXScaleIXP425处理器为核心的嵌入式网络图像采集系统的相关理论和可行性，并在此基础上给出了一种基于IntelXScaleIXP...With the rapid progress of multi mediate technology and computer networks, the research and realization of image acquisition have been highlighted in embedded systems. Currently, using its powerful processing capability and overall interface to design the image acquisition card, the equipments of image acquisition system are mostly based on personal computer, and the application is very extensiv...学位：工学硕士院系专业：软件学院_计算机软件与理论学号：2005130253

一种嵌入式 WLAN 安全系统的设计与实现

介绍无线局域网的概念。在分析无线局域网的安全机制原理的基础上，提出无线局域网存在的安全问题，给出一种嵌入式安全系 统的设计方案，该方案采用安全性更高的加密算法以及更完善的数据校验机制，对解决无线局域网中的安全问题具有一定的实用价值

Design and Implementation of Embedded WLAN Security System

介绍无线局域网的概念。在分析无线局域网的安全机制原理的基础上,提出无线局域网存在的安全问题,给出一种嵌入式安全系统的设计方案,该方案采用安全性更高的加密算法以及更完善的数据校验机制,对解决无线局域网中的安全问题具有一定的实用价值。The paper introduces the basic concept of WLAN,and on the base of analyzing the theory of security policy,discusses the security problem of WLAN.A design of security system that is based on embedded flat is proposed,which combines encryption algorithm with higher security and advance verification policy.It is of some value in solving the security problem in WLAN

Lactic acid extraction from kitchen wastes fermentation using aqueous two-phase systems

利用聚乙二醇(PEg)/葡聚糖(dEX)双水相体系分离餐厨垃圾发酵产物乳酸,分析了聚合物浓度和分子量的影响,以及餐厨垃圾多批次连续发酵时乳酸产率。实验结果表明,PEg/dEX双水相体系对乳酸菌生长影响不大,PEg和dEX浓度变化对乳酸产率、相体积比无显著影响;当dEX分子量由20 000升至40 000,乳酸生成速率由0.631 g/(l.H)降至0.518 g/(l.H),乳酸浓度由33 g/l降至22 g/l。多批次餐厨垃圾连续发酵可极大缩短发酵时间,在不投加缓冲剂的情况下,单批次乳酸产率仍大于0.30 g/g,累积产率大于0.45 g/g。Polyethylene glycol(PEG)/dextran(DEX) aqueous two-phase systems were used to extract lactic acid from kitchen wastes fermentation.Results showed that PEG/DEX system had insignificant effect on the growth of lactic acid bacteria.The variation of PEG and DEX concentrations influenced cells growth and lactic acid biosynthesis indistinctively.Volume ratio kept stable throughout the processes,despite the changes of raw material and product concentrations.Different from little influence of PEG molecular weight on fermentation,the increase of DEX molecular weight from 20 000 to 40 000 led to declines of lactate conversion rate from 0.631 g/(L·h) to 0.518 g/(L·h) and lactic acid concentration from 33 g/L To 22 g/L.A repeated extractive fermentation was carried out with four top-phase replacements.Results presented that when cell density reached the stationary phase in the first extractive fermentation,the lactate yield was maintained above 0.30 g/g per batch and 0.45 g/g in the total process.福建省自然科学基金资助项目(2009J05132);福建省科技计划项目(2010I004);厦门市科技计划项目(3502Z20111049

Monolithically Integrated Optical Receiver with Spatially Modulated Optical Detector in CMOS Technology

设计了与标准CMOS工艺兼容的850 nM空间调制(SPATIAlly MOdulATEd,SM)结构光电探测器,在分析器件物理模型的基础上,建立了SPECTrE环境中等效电路的新模型。提出标准CMOS工艺下SM探测器与前置放大电路单片集成的电路设计。仿真结果表明,在850 nM光照下,SM探测器带宽达到400 MHz,并提供62 MA/W的响应度。整个集成芯片的工作速率为400 Mb/S,增益为0.81 kV/W,功耗为91 MW。A monolithically integrated optical receiver(λ=850 nm) with spatially modulated(SM) optical detector is designed in standard 0.5 μm CMOS technology,the equivalent circuit model of the SM light detector is built in the SPECTRE environment.Simulation results show that the SM optical detector researches a bandwidth of 420 MHz and a responsibility of 78 mA/W.OEIC has a bandwidth of 400 Mb/s and gain of 0.81 kV/W with the power dissipation of 91 mW.厦门市科技计划项目(3502Z20063002

Transmission shielding technology for bistatic sonar

基线附近区域为双基地声呐的探测盲区,当目标位于基线区域时,目标回波与强直达波干扰同时同向到达,基于空域滤波等的传统直达波抑制方法失效。为实现双基地声呐对盲区内目标的探测,提出了一种适用于多发射阵元系统的发射声屏蔽技术。发射声屏蔽技术利用目标回波与直达波相异的多途信道结构特性,自动屏蔽在接收站位置处的直达波而不影响目标回波,且不需接收站进行任何后续处理。在已知回波信道信息时,发射声屏蔽技术可进一步实现对回波信号的聚焦,提高信干比。仿真结果表明,在不同信道条件下发射声屏蔽均能有效抑制直达波干扰。利用发射声屏蔽技术,双基地声呐能够实现对基线区内目标的检测。The area near the baseline is a dead zone for bistatic sonar.The echo and the strong direct wave will arrive in the same place simultaneously when the target is in the baseline area and the direct wave suppression method based on a spatial filter will fail.To detect targets in the dead zone,a transmission shielding method for a multi-element transmit system is proposed.The transmission shielding automatically suppresses the direct wave at the receiving station utilizing structural differences in multiple channels between the echo and the direct wave.The transmission shielding further focuses on the echo,so as to improve the Signal-Noise Ratio,using known echo channel information.The simulation results show the transmission shielding method can suppress direct wave interference for different multipath channels.Bistatic sonar can detect targets in the baseline area utilizing the transmission shielding method.国家自然科学基金资助项目(51179034); 海洋工程国家重点实验室(上海交通大学)资助项目(1211

电网中谐波的监督管理及限制谐波的标准

针对当前电网中谐波存在的问题 ,提出了对其进行监督管理及限制之标准

Network performance isolation for virtual machines

Cloud computing is a new computing paradigm that aims to transform computing services into a utility, just as providing electricity in a “pay-as-you-go” manner. Data centers are increasingly adopting virtualization technology for the purpose of server consolidation, flexible resource management and better fault tolerance. Virtualization-based cloud services host networked applications in virtual machines (VMs), with each VM provided the desired amount of resources using resource isolation mechanisms. Effective network performance isolation is fundamental to data centers, which offers significant benefit of performance predictability for applications. This research is application-driven. We study how network performance isolation can be achieved for latency-sensitive cloud applications. For media streaming applications, network performance isolation means both predicable network bandwidth and low-jittered network latency. The current resource sharing methods for VMs mainly focus on resource proportional share, whereas ignore the fact that I/O latency in VM-hosted platforms is mostly related to resource provisioning rate. The resource isolation with only quantitative promise does not sufficiently guarantee performance isolation. Even the VM is allocated with adequate resources such as CPU time and network bandwidth, problems such as network jitter (variation in packet delays) can still happen if the resources are provisioned at inappropriate moments. So in order to achieve performance isolation, the problem is not only how many/much resources each VM gets, but more importantly whether the resources are provisioned in a timely manner. How to guarantee both requirements to be achieved in resource allocation is challenging. This thesis systematically analyzes the causes of unpredictable network latency in VM-hosted platforms, with both technical discussion and experimental illustration. We identify that the varied network latency is jointly caused by VMM CPU scheduler and network traffic shaper, and then address the problem in these two parts. In our solutions, we consider the design goals of resource provisioning rate and resource proportionality as two orthogonal dimensions. In the hypervisor, a proportional share CPU scheduler with soft real-time support is proposed to guarantee predictable scheduling delay; in network traffic shaper, we introduce the concept of smooth window to smooth packet delay and apply closed-loop feedback control to maintain network bandwidth consumption. The solutions are implemented in Xen 4.1.0 and Linux 2.6.32.13, which are both the latest versions when this research was conducted. Extensive experiments have been carried out using both real-life applications and low-level benchmarks. Testing results show that the proposed solutions can effectively guarantee network performance isolation, by achieving both predefined network bandwidth and low-jittered network latency.published_or_final_versionComputer ScienceMasterMaster of Philosoph

Delay-aware network I/O virtualization for cloud computing

Cloud datacenters are largely adopting virtual machines (VMs) to provide elastic computing services. As many cloud applications are communication-intensive, such as distributed data processing and web services, satisfactory network performance is critical to guarantee the service quality. In virtualized environments, a major problem is that the end hosts are separated by a virtualization layer and subject to the intervention of the hypervisor’s scheduling. Since the scheduling delays due to CPU sharing are commonly from tens of milliseconds to over one hundred milliseconds, when they are added to packet processing, network performance can be seriously degraded. To tackle this problem, prior works focus dominantly on modifying the hypervisor scheduler to hide the virtualization reality by reducing the delays as much as possible. However, this type of approaches brings many other problems, such as increased VM context switches and more complicated CPU resource allocation. This thesis tries to look at the problem from a different but simpler angle: we let the guest operating system (OS) accept the reality that each virtual CPU (vCPU) can be suspended and resumed at any time, and then think about how to refactor the network I/O subsystem to automatically tolerate such scheduling delays. In general, network I/O processing in the kernel includes two layers: protocol layer and interrupt layer. Our study shows that both layers are very sensitive to VM scheduling delays, and therefore must be redesigned accordingly. First, in the protocol layer, we propose a paravirtualized approach to help TCP counteract the distortion of congestion control caused by the hypervisor scheduler. Second, in the interrupt layer, for SMP-VMs that have multiple vCPUs, we propose a method to dynamically migrate interrupts from a preempted vCPU to a running one whenever it is possible, so that the delays will not be propagated to the protocol layer. Experiments with our prototypes in Xen/Linux show that our approaches can significantly improve the network throughput and responsiveness.published_or_final_versionComputer ScienceDoctoralDoctor of Philosoph

开源交换机Asterisk的应用

Asterisk是由美国Digiun公司开发的开放源代码交换机系统。本文介绍了Asterisk的特点、功能、体系结 构, 并给出了Asterisk应用的一个具体实例