多投影系统D-vision中双手6自由度力觉交互

D-vision系统(这里"D"有"Divide Screen"和"Duplex-Vision"双重含义)是一类基于PC机群的多投影虚拟现实系统(或简称多投影系统).给出D-vision系统中双手6自由度力觉交互的实现过程:在客户端协同控制两个力觉交互设备Spidar-G(Space Interface for Artificial Reality withGrip)实现双手协作交互,其次构造一个基于UDP的Socket类完成客户端和绘制服务器节点之间的通讯,传递跟踪球的位置、方向等信息;然后,通过分布绘制实现在大屏幕上无缝显示.最后实验结果表明:在D-vision系统中双手6自由度力觉交互是一种自然直观的人机交互方式.

船载综合信息显示系统设计与实现

船载综合信息显示系统是以船用计算机网络为平台，将卫星导航、数据采集、重点部位监控等功能集成为一个综合的船舶计算机网络信息显示系统，用来提高整个船舶的动态信息实时获取与显示能力和现代化管理水平。在船载综合信息显示系统的开发过程中，存在着软硬件相兼容的问题；同时，由于船载设备种类多、数据量大，对信息系统的性能和可靠性都具有较高的要求。 本文以“科学三号”海洋科学考察船的综合信息显示系统的设计和开发过程为例，从体系结构、信息流程和实现方法三个方面对船载综合信息显示系统的实现过程进行了详细描述。 本文结合“科学三号”考察船的实际信息网络环境，设计船载综合信息显示系统的实际架构。采用C/S三层架构，将船载综合信息显示系统分为服务器端软件和客户端软件二部分。对于服务器端软件，介绍了船载设备的信息流程和信息技术。通过利用XML标准化数据格式，提高了数据存储、传输的性能和灵活性；通过利用UDP实现高性能传输，并对传输的可靠性加以扩展。对于客户端软件，可以实时显示服务器端转发的各种传感器数据，并对符合国际标准的电子海图的显示进行了研究。 在文章的最后，给出了已经实现的原型系统，证明上述的技术方案是具有可行的，并且能够达到预想的目标。

含硒抗体酶及酶法合成~（13）C尿苷二磷酸葡萄糖

胞质谷胱甘肽过氧化物酶（cGPX）是生物体内重要的抗氧化含硒酶，在保护机体免受活性氧损伤方面起着重要作用，因此利用抗体酶技术进行cGPX的人工模拟具有重要意义。本文在疏水腔修饰法指导下，设计合成了两种新的具有GSH特征的半抗原Hp4和Hp5。通过单克隆抗体及化学诱变技术制备得到三种针对半抗原Hp4的含硒抗体酶和两种针对Hp5 特异的含硒抗体酶。其中SeHB5(1867 U/μmol)和SeIA7（3567U/μmol）活力达到和天然酶同一数量级，进一步验证了疏水腔修饰法。本文还对含硒抗体酶SeHB5和SeIA7的酶学性质进行了系统的研究。生物活性实验表明含硒抗体酶对不同浓度H_2O_2损伤的小鼠心肌细胞均有一定程度的保护作用。本文同时报道了三种硒代β-环糊精作为cGPX模拟物的活力，其中6,6'-(O-亚苯基）二硒基桥联-β-环糊精二聚体的活力超过目前被认为最理想的补硒试剂Ebselen。~（13）C标记UDPG在利用核磁手段发现新的UDPG依赖糖基转移酶和检测新的糖基化合物，确定糖基间连接方式，合成同位素标记寡糖和多糖等方面具有广阔的应用前景。本文首次从植物培养细胞Rauvolfia serpentina经四步纯化得到具有一定纯度的UDPG焦磷酸化酶，并应用该酶建立了经济，简便，高产率的从葡萄糖出发，酶法大量合成UDPG的方法。利用该方法首次合成得到0.5克级的UDP-[4-~（13）C]-glucose，产率高达～70%。在NMR谱学方面确定了UDPG中葡萄糖基上4位C的归属，从而纠正了文献中关于UDPG核磁谱归属中的部分错误。

一种基于排队论的DoS攻防绩效评估方法

提出了一种新的基于排队论的DoS攻防绩效评估方法.针对不同种类DoS攻防手段建立了统一的指标体系和绩效计算方法,基于排队论方法分别建立评估模型,对UDP Flood和SYN Flood攻击的绩效进行不包含主观因素的定量评估,分析不同攻击手段和强度的有效性.针对典型DoS攻防场景,利用网络仿真工具进行模拟,通过实验与模型推导结果对比验证了排队论模型的合理性,并阐述了此方法在不同类型DoS攻防手段中的应用.

基于半监督学习的P2P协议识别

协议识别是进行有效的网络管理与控制的重要条件，由于新的P2P软件（以Skype,Emule，BitComet，迅雷为代表）开始使用加密协议和协议伪装等技术手段来防止被网管探测、识别、封堵，传统的根据协议特征码来识别的方式已经难以识别这些软件产生的流量。基于流量特征的P2P协议识别的方法是目前研究的主要方向，将机器学习的理论与模型运用到协议识别领域是发展的一个趋势。通过对传输层数据包(包括TCP和UDP数据包)进行分析，并结合P2P系统所表现出来的流量特征，来识别某个网络流是否属于P2P。这类方法包括：TCP/UDP端口识别技术、网络直径分析技术、节点角色分析技术、协议对分析技术和地址端口对分析技术等，但是其准确性和识别率不如特征码识别。本文就基于半监督聚类的模型运用到识别具体P2P应用的可能性进行了分析与实验，提出了一种基于Newton-Raphson方法学习特征权值矩阵的训练的办法，在依据P2P应用特征选取连接特征的基础上进一步提高系统识别准确率和召回率。在本文的实验环境下，针对具体的BitComet和Emule应用的识别器的识别率和召回率均达到了85%左右，在加密协议的识别上取得了不错的效果。如何优化系统的识别准确率和召回率，提高系统效率是本文重点研究并试图解决的问题，主要包括以下三个方面的成果：一、实验并分析了基于半监督学习的聚类模型在加密P2P应用识别上的效果，同时总结了一套分析P2P协议特征的办法。二、将Newton-Raphson方法引入到连接特征的选取上，将特征权值矩阵用于距离的计算，进一步提高了训练和识别的效果。三、基于KD-Tree的识别器的实现使得整个在线识别过程能在内核的协议层高效实现，有效的控制了系统的计算复杂度。

Purification and characterisation of a natural lectin from the serum of the shrimp Litopenaeus vannamei

A natural lectin from the serum of the shrimp Litopenaeus vannamei was purified to homogeneity by a single-step affinity chromatography using fetuin-coupled agarose. The purified serum lectin (named LVL) showed a strong affinity for human A/B/O erythrocytes (RBC), mouse RBC, chicken RBC and its haemagglutinating (HA) activity was specifically dependent on Ca2+ and reversibly sensitive to EDTA. LVL inactive form had a molecular mass estimate of 172 kDa and was composed of two non-identical subunits (32 and 38 kDa) cross-linked by interchain disulphide bonds. Significant LVL activity was observed between pH 7 and 11. In HA-inhibition assays performed with several carbohydrates and glycoproteins, LVL showed a distinct and unique specificity for GalNAc/GluNAc/NeuAc which had an acetyl group, while glycoproteins fetuin and bovine submaxillary mucin (BSM) had sialic acid. Moreover, this agglutinin appeared to recognise the terminal N- and O-acetyl groups in the oligosaccharide chain of glycoconjugates. The HA activity of L. vannamei lectin was also susceptible to inhibition by lipopolysaccharides from diverse Gram-negative bacteria, which might indicate a significant in vivo role of this humoral agglutinin in the host immune response against bacterial infections. (C) 2006 Elsevier Ltd. All rights reserved.

基于Internet的遥操作机器人足球系统设计

针对目前基于Internet的遥操作机器人系统普遍完成任务简单,复杂度低,影响力有限的状况,本文将遥操作技术和Internet技术应用于具有高动态性、高协作性和高对抗性的机器人足球系统中,建立了基于Internet的遥操作机器人足球系统的体系结构,提供了该系统的软件设计方法,并针对网络通信设计了应用UDP协议进行连接和数据传输的方法.实际建立的基于Internet的3对3遥操作机器人足球系统验证了系统设计方法的可行性和有效性.通过实验验证了应用UDP协议进行连接和数据传输相对于应用TCP协议的优越性.

具有实时性保障的INTERNET机器人控制系统设计方法

本文提出了一种具有实时性、可靠性保障的INTERNET网络机器人控制系统的设计方法。基于该方法设计的网络实时控制系统能够满足机器人实时、高效、灵活的技术特点。该方法的核心为基于UDP传输协议的网络数据补偿算法,通过对网络传输过程中丢失的数据进行实时在线补偿预测,降低了网络数据的丢失对系统的影响。实验结果证明该方法的有效性、合理性。

Efficiently and Fairly Allocating Bandwidth at a Highly Congested Link

We consider the problem of efficiently and fairly allocating bandwidth at a highly congested link to a diverse set of flows, including TCP flows with various Round Trip Times (RTT), non-TCP-friendly flows such as Constant-Bit-Rate (CBR) applications using UDP, misbehaving, or malicious flows. Though simple, a FIFO queue management is vulnerable. Fair Queueing (FQ) can guarantee max-min fairness but fails at efficiency. RED-PD exploits the history of RED's actions in preferentially dropping packets from higher-rate flows. Thus, RED-PD attempts to achieve fairness at low cost. By relying on RED's actions, RED-PD turns out not to be effective in dealing with non-adaptive flows in settings with a highly heterogeneous mix of flows. In this paper, we propose a new approach we call RED-NB (RED with No Bias). RED-NB does not rely on RED's actions. Rather it explicitly maintains its own history for the few high-rate flows. RED-NB then adaptively adjusts flow dropping probabilities to achieve max-min fairness. In addition, RED-NB helps RED itself at very high loads by tuning RED's dropping behavior to the flow characteristics (restricted in this paper to RTTs) to eliminate its bias against long-RTT TCP flows while still taking advantage of RED's features at low loads. Through extensive simulations, we confirm the fairness of RED-NB and show that it outperforms RED, RED-PD, and CHOKe in all scenarios.

On the Relationship Between File Sizes, Transport Protocols, and Self-Similar Network Traffic

Recent measurements of local-area and wide-area traffic have shown that network traffic exhibits variability at a wide range of scales self-similarity. In this paper, we examine a mechanism that gives rise to self-similar network traffic and present some of its performance implications. The mechanism we study is the transfer of files or messages whose size is drawn from a heavy-tailed distribution. We examine its effects through detailed transport-level simulations of multiple TCP streams in an internetwork. First, we show that in a "realistic" client/server network environment i.e., one with bounded resources and coupling among traffic sources competing for resources the degree to which file sizes are heavy-tailed can directly determine the degree of traffic self-similarity at the link level. We show that this causal relationship is not significantly affected by changes in network resources (bottleneck bandwidth and buffer capacity), network topology, the influence of cross-traffic, or the distribution of interarrival times. Second, we show that properties of the transport layer play an important role in preserving and modulating this relationship. In particular, the reliable transmission and flow control mechanisms of TCP (Reno, Tahoe, or Vegas) serve to maintain the long-range dependency structure induced by heavy-tailed file size distributions. In contrast, if a non-flow-controlled and unreliable (UDP-based) transport protocol is used, the resulting traffic shows little self-similar characteristics: although still bursty at short time scales, it has little long-range dependence. If flow-controlled, unreliable transport is employed, the degree of traffic self-similarity is positively correlated with the degree of throttling at the source. Third, in exploring the relationship between file sizes, transport protocols, and self-similarity, we are also able to show some of the performance implications of self-similarity. We present data on the relationship between traffic self-similarity and network performance as captured by performance measures including packet loss rate, retransmission rate, and queueing delay. Increased self-similarity, as expected, results in degradation of performance. Queueing delay, in particular, exhibits a drastic increase with increasing self-similarity. Throughput-related measures such as packet loss and retransmission rate, however, increase only gradually with increasing traffic self-similarity as long as reliable, flow-controlled transport protocol is used.

TCP over CDMA2000 Networks: A Cross-Layer Measurement Study

Modern cellular channels in 3G networks incorporate sophisticated power control and dynamic rate adaptation which can have a significant impact on adaptive transport layer protocols, such as TCP. Though there exists studies that have evaluated the performance of TCP over such networks, they are based solely on observations at the transport layer and hence have no visibility into the impact of lower layer dynamics, which are a key characteristic of these networks. In this work, we present a detailed characterization of TCP behavior based on cross-layer measurement of transport, as well as RF and MAC layer parameters. In particular, through a series of active TCP/UDP experiments and measurement of the relevant variables at all three layers, we characterize both, the wireless scheduler in a commercial CDMA2000 network and its impact on TCP dynamics. Somewhat surprisingly, our findings indicate that the wireless scheduler is mostly insensitive to channel quality and sector load over short timescales and is mainly affected by the transport layer data rate. Furthermore, we empirically demonstrate the impact of the wireless scheduler on various TCP parameters such as the round trip time, throughput and packet loss rate.

On the Interaction between TCP and the Wireless Channel in CDMA2000 Networks

In this work, we conducted extensive active measurements on a large nationwide CDMA2000 1xRTT network in order to characterize the impact of both the Radio Link Protocol and more importantly, the wireless scheduler, on TCP. Our measurements include standard TCP/UDP logs, as well as detailed RF layer statistics that allow observability into RF dynamics. With the help of a robust correlation measure, normalized mutual information, we were able to quantify the impact of these two RF factors on TCP performance metrics such as the round trip time, packet loss rate, instantaneous throughput etc. We show that the variable channel rate has the larger impact on TCP behavior when compared to the Radio Link Protocol. Furthermore, we expose and rank the factors that influence the assigned channel rate itself and in particular, demonstrate the sensitivity of the wireless scheduler to the data sending rate. Thus, TCP is adapting its rate to match the available network capacity, while the rate allocated by the wireless scheduler is influenced by the sender's behavior. Such a system is best described as a closed loop system with two feedback controllers, the TCP controller and the wireless scheduler, each one affecting the other's decisions. In this work, we take the first steps in characterizing such a system in a realistic environment.

TCP over CDMA2000 Networks: A Cross-Layer Measurement Study

Modern cellular channels in 3G networks incorporate sophisticated power control and dynamic rate adaptation which can have significant impact on adaptive transport layer protocols, such as TCP. Though there exists studies that have evaluated the performance of TCP over such networks, they are based solely on observations at the transport layer and hence have no visibility into the impact of lower layer dynamics, which are a key characteristic of these networks. In this work, we present a detailed characterization of TCP behavior based on cross-layer measurement of transport layer, as well as RF and MAC layer parameters. In particular, through a series of active TCP/UDP experiments and measurement of the relevant variables at all three layers, we characterize both, the wireless scheduler and the radio link protocol in a commercial CDMA2000 network and assess their impact on TCP dynamics. Somewhat surprisingly, our findings indicate that the wireless scheduler is mostly insensitive to channel quality and sector load over short timescales and is mainly affected by the transport layer data rate. Furthermore, with the help of a robust correlation measure, Normalized Mutual Information, we were able to quantify the impact of the wireless scheduler and the radio link protocol on various TCP parameters such as the round trip time, throughput and packet loss rate.

Efficient building management with IP-based wireless sensor network

Existing Building/Energy Management Systems (BMS/EMS) fail to convey holistic performance to the building manager. A 20% reduction in energy consumption can be achieved by efficiently operated buildings compared with current practice. However, in the majority of buildings, occupant comfort and energy consumption analysis is primarily restricted by available sensor and meter data. Installation of a continuous monitoring process can significantly improve the building systems’ performance. We present WSN-BMDS, an IP-based wireless sensor network building monitoring and diagnostic system. The main focus of WSN-BMDS is to obtain much higher degree of information about the building operation then current BMSs are able to provide. Our system integrates a heterogeneous set of wireless sensor nodes with IEEE 802.11 backbone routers and the Global Sensor Network (GSN) web server. Sensing data is stored in a database at the back office via UDP protocol and can be access over the Internet using GSN. Through this demonstration, we show that WSN-BMDS provides accurate measurements of air-temperature, air-humidity, light, and energy consumption for particular rooms in our target building. Our interactive graphical user interface provides a user-friendly environment showing live network topology, monitor network statistics, and run-time management actions on the network. We also demonstrate actuation by changing the artificial light level in one of the rooms.