BulkTree: an overlay network architecture for live media streaming

Peer-to-peer (P2P) systems are now very popular. Current P2P systems are broadly of two kinds, structured and unstructured. The tree structured P2P systems used technologies such as distributed hash tables (DHT) and hierarchical clustering can search the required target quickly, however, in a tree, the internal node has a higher load and its leave or crash often causes a large population of its offspring's problems, so that in the highly dynamic Internet environment the tree structure may still suffer frequent breaks. On the other hand, most widely used unstructured P2P networks rely on central directory servers or massive message flooding, clearly not scalable. So, we consider both of the above systems' advantages and disadvantages and realize that in the P2P systems one node may fail easily, but that when a number of nodes organized as a set, which we call super node, the set is robust. Super nodes can be created and updated aware of topology-aware, and used with simple protocol such as flooding or servers to exchange information. Furthermore the entire robust super node can be organized into exquisite tree structure. By using this overlay network architecture, P2P systems are robust, efficient, scalable and secure. The simulation results demonstrated that our architecture greatly reduces the alteration time of the structure while decreasing the average delay time, compared to the common tree structure.     

Control DHT maintenance costs with session heterogeneity

The maintaining overheads of Distributed Hash Table (DHT) topology have recently received considerable attention.This paper presents a novel SHT (Session Heterogeneity Topology) model, in which DHT is reconstructed with session heterogeneity. SHT clusters nodes by means of session heterogeneity among nodes and selects the stable nodes as the participants of DHT. With an evolving process, this model gradually makes DHT stable and reliable. Therefore the high maintaining overheads for DHT are effectively controlled. Simulation with real traces of session distribution showed that the maintaining overheads are reduced dramatically and that the data availability is greatly improved.     

Rate-distortion optimized bitstream switching for peer-to-peer live streaming

Peer-to-peer （P2P） technology provides a cost-effective and scalable way to distribute video data. However, high heterogeneity of the P2P network, which rises not only from heterogeneous link capacity between peers but also from dynamic variation of available bandwidth, brings forward great challenge to video streaming. To attack this problem, an adaptive scheme based on rate-distortion optimization （RDO） is proposed in this paper. While low complexity RDO based frame dropping is exploited to shape bitrate into available bandwidth in peers, the streamed bitstream is dynamically switched among multiple available versions in an RDO way by the streaming server. Simulation results show that the proposed scheme based on RDO achieves great gain in overall perceived quality over simple heuristic schemes.     

Study on semantic-oriented hybrid indexing strategy of resource metadata in peer-to-peer network

INTRODUCTION In some large scale corporations and virtual or-ganization environment (education system, military organizations, etc.), much electronics information resources are distributed physically and diverse in types. Each unit of an organization manages some resources respectively, according to the domain knowledge or the particular mission. In technical aspect, each unit is a node working independently in the information network. These nodes can join or leave the network at any tim…     

基于P2P网络的反垃圾邮件系统的设计

垃圾邮件已成为当今邮件系统的主要问题,垃圾邮件发送者通过伪装邮件来逃避反垃圾邮件系统的检测.针对目前的垃圾邮件过滤器大多数单机运行,所能获得的数据和信息较少,效率较低的问题,本文提出了一个点对点(P2P)的无服务器的E-mail系统的体系结构,系统测试结果表明,该系统结构有效地实现了相似邮件的聚集,从而达到了过滤垃圾邮件的目的.     

Improving network service performance and reliability via links trunking technologies

INTRODUCTION Because of the critical role that computing sys-tems and networks play in today’s business envi-ronment, it is not surprising that business success often goes to the company with the best information and the most efficient process for delivering that in-formation. As the principal tool for business col-laboration, corporate LANs are a vital resource in enabling today’s enterprises to adopt competitive strategies. The number of users wanting to share and access data across…     

Using scaffolded rubrics to improve peer assessment in a MOOC writing course

This study explored the value of using a guided rubric to enable students participating in a massive open online course in writing to produce more reliable assessments of their fellow students’ writing. To test the assumption that training students to assess will improve their ability to provide quality feedback, a multivariate factorial analysis was used to determine differences in assessments made by students who received guidance on using a rating rubric and those who did not. Although results were mixed, on average students who were provided no guidance in scoring writing samples were less likely to successfully differentiate between novice, intermediate, and advanced writing samples than students who received rubric guidance. Rubric guidance was most beneficial for items that were subjective, technically complex, and likely to be unfamiliar to the student. Items addressing relatively simple and objective constructs were less likely to be improved by rubric guidance.     

Application of data envelopment analysis on the indicators contributing to learning and teaching performance

This paper applies data envelopment analysis (DEA) to explore the quantitative relative efficiency of 18 classes of freshmen students studying a course of English conversation in a university of Taiwan from the academic year 2004-2006. A diagram of teaching performance improvement mechanism is designed to identify key performance indicators for evaluation in order to help teachers concentrate their efforts on the formulated teaching suggestions. The sensitivity study highlights the priority of the richness of course contents over the other evaluated indicators. The performance improvement mechanism can help decision-makers to design educational policies.     

基于PCA-CMAC的设备性能退化评估

提出了一种用于设备性能退化评估的PCA-CMAC(主成分分析-小脑模型节点控制器)模型.该模型利用PCA进行特征提取,去除多个传感器信号特征的冗余信息,并且减少CMAC的输入维数;利用CMAC的局部泛化能力定量地评估设备的性能退化.给出了模型的实现过程,并将模型应用于钻削过程刀具状态的评估,试验结果证明该模型能基于刀具的正常状态,对刀具的磨损状态进行定量的评估.分析了CMAC中泛化参数g和量化参数r对评估结果的影响,g越大,CMAC的泛化能力越好,但各退化状态之间的区别越不明显;r越小,各退化状态之间越容易区分,但所需的权存储空间越大.2个参数的基本选择原则是CMAC的权存储空间应尽量小,与此同时,各退化状态之间应容易区分.     

Using FEM to predict tree motion in a wind field

In this paper we propose a finite element （FE） simulation method to predict tree motion in a wind field, Two FE tree models were investigated： One model was generated based on a realistic nature-looking geometric tree model, and the other was a symmetric model to investigate the influence of asymmetric material properties on tree motion. The vortex-induced vibration （VIV） theory is introduced to estimate the fluctuating wind force being exerted on tree stems and the fluid-structure interaction （FSI） analysis is also included in the simulation. The results indicate that asymmetric material properties result in the crosswind displacement of the investigated node and the main swaying direction deviation. The simulation reveals that under wind loading, a tree with leaves has much larger swaying amplitude along the wind direction and longer swaying period than a tree without leaves. However, the crosswind swaying amplitude is mainly due to branch interaction. The numerical simulation proved that the interaction of tree branches can prevent dangerous swaying motion developing.     

Connectionism and learning to read: Steps towards a psychologically plausible model

We consider the prospects and need for a psychologically plausible connectionist model of the development of word recognition skills. We present an outline of the Seidenberg and McClelland (1989) distributed, developmental model of word recognition and naming. We emphasize certain incompatibilities between this model and the assumptions underlying it and psychological evidence from studies of children learning to read. In particular, we emphasize the importance of phonological skills as precursors and facilitators of learning to read. We argue that it may be possible to develop a connectionist model of the development of word recognition skills which, by having a built in knowledge of phonology, will be more consistent with evidence from studies of both normal and dyslexic children.     

Expectation-perceived performance of urban dwellers in ReBAM:an empirical research on Wuhan city

To comprehend the practical apperception of urban dwellers in ReBAM (recreational belt around metropolis) and to adjust and optimize the strategy, using a questionnaire administered to Wuhan citizens, the satisfaction of urban dwellers in ReBAM is measured based on an expectation-disconfirmation model. The differences between expectation and perceived performance of satisfaction of urban dwellers are compared, and then Pearson correlate to total satisfaction and disconfirmation of urban dwellers is carried out. The research findings are as follows. First, expectation and perceived performance values are significantly higher than three, which are beyond the normal level. Second, perceived performances are lower than expectations, which indicates negative disconfirmations. Third, disconfirmations are negative while total satisfaction is relatively high, and there is a low correlation between the two. The conclusion is that urban dwellers are interested in ReBAM but they have more expectation and obtain lower experience. Managers should advance their perceived performance through improving travel infrastructure, strengthening product innovation and service innovation.     

EVA促进企业价值创造

为了正确评估于企业价值创造 ,在管理会计领域出现了许多绩效评估指标。但 90年代以后在欧美的许多著名的企业采用了EVA作为企业法定的业绩评估指标 ,并取得了良好的效果。EVA基于股东 (所有者 )立场 ,修正了传统的财务指标的缺陷 ,客观 ,不受会计操纵的影响 ,能正确评价经理人员绩效 ,如果将这个绩效评估指标引入我国国有企业绩效评估体系中 ,可能会大大促进国有企业价值最大化的实现     

用单片机制作可编程控制器实验

分析PLC的运行原理，系统程序的安排，以及用户程序的编译方法，并在此基础上说明如何用单片机制作可编程逻辑控制器。     

Application of system dynamics for assessment of sustainable performance of construction projects

INTRODUCTION Sustainable development is commonly definedas meeting the needs of the present without compro-mising the ability of future generations to meet theirown needs (WCED, 1987). All industries, includingthe construction industry should contribute to themission. Compared to other industries, constructionactivities are generally considered to have more im-pact on the environment, which provides the basicconditions for the sustainability and development oflife on the Earth. The…     

直接液相微萃取-高效液相色谱法测定水中速灭威残留

农药的使用对农业有重要的、不可替代的意义,然而很多农药的使用会给环境带来污染,影响人类健康.本文采用直接液相微萃取法（Dir-LPME）与高效液相色谱（HPLC）联用分析测定环境水样中的速灭威.对影响Dir-LPME的各种因素如萃取溶剂类型、萃取溶剂体积、萃取时间等条件进行了优化,并将其应用于江水、自来水和农田水中速灭威的分析检测.速灭威的萃取富集倍数为10,线性范围为0.2-2μg/mL,加标回收率在95%—105%之间,相对标准偏差低于7.4%.     

Predictive performance of'Diprifusor'TCI system in patients during upper abdominal surgery under propofol/fentanyl anesthesia

Objective: To evaluate the predictive performance of'Diprifusor' TCI (target-controlled infusion) system for its better application in clinical anesthesia. Methods: The predictive performance of a ‘Diprifusor’ TCI system was investigated in 27Chinese patients (16 males and 11 females) during upper abdominal surgery under total intravenous anesthesia (TIVA) with propofol/fentanyl. Measured arterial propofol concentrations were compared with the values predicted by the TCI infusion system.Performance was determined by the median performance error (MDPE), the median absolute performance error (MDAPE), the divergence (the percentage change of the absolute PE with time), and the wobble (the median absolute deviation of each PE from the MDPE). Results: The median (range) values of 14.9% (-21.6%～42.9%) for MDPE, 23.3% (6.9%～62.5%) for MDAPE, -1.9%h-1 (-32.7%～23.0% h-1) for divergence, and 18.9% (4.2%～59.6%) for wobble were obtained from 227 samples from all patients.For the studied population, the PE did not increase with time but with increasing target propofol concentration, particularly following induction. Conclusions: The control of depth of anaesthesia was good in all patients undergoing upper abdominal surgical operation and the predictive performance of the ‘Diprifusor’ target controlled infusion system was considered acceptable for clinical purposes. But the relatively bigger wobble showed that the pharmacokinetic model is not so suitable and requires improvement.     

Comparison of an SMS text messaging and phone reminder to improve attendance at a health promotion center： A randomized controlled trial

Objective To compare the efficacy of a short messaging service (SMS) text messaging and phone reminder to improve attendance rates at a health promotion center. Methods A total of 1 859 participants who had scheduled appointments in the health promotion center of our hospital from April 2007 to May 2007 were enrolled in the study and randomly assigned into 3 groups control (no reminder) group, SMS text messaging reminder group and telephone reminder group. Attendance rates and costs of interventions were collected. Results A total of 1848 participants were eligible for analysis. Attendance rates of control,SMS and telephone groups were 80.5%, 87.5% and 88.3%, respectively. The attendance rates were significantly higher in SMS and telephone groups than that in the control group, with odds ratio 1.698, 95% confidence interval 1.224 to 2.316, P=0.001 in the SMS group, and odds ratio 1.829, 95% confidence interval 1.333 to 2.509, P＜0.001 in the telephone group. However, there was no difference between the SMS group and the telephone group (P=0.670). The cost effectiveness analysis showed that the cost per attendance for the SMS group (0.31 Yuan) was significantly lower than that for the telephone group (0.48 Yuan). ConclusionSMS and telephone are effective reminders for improving attendance rate at a health promotion center. SMS reminder may be more cost-effective compared with the telephone reminder.     

勒让德多项式拟合IGS精密星历

在阐述勒让德多项式拟合算法的基础上,推导出ICS精密星历的勒让德拟合多项式,通过实例分析拟合的精度,并与经典的拉格朗日插值、切比雪夫拟合等其他算法进行比较.结果表明,在00:00:00至23:45:00时间段内8阶勒让德多项式拟合的精度高于其他任何一种同阶多项式插值或拟合方法,并且最大误差不超过1 cm.