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 analogies to improve the teaching performance of preservice teachers

Prior research in both education and cognitive science has identified analogy making as a powerful tool for explanation as well as a fundamental mechanism for facilitating an individual's construction of knowledge. While a considerable body of research exists focusing on the role analogy plays in learning science concepts, relatively little is known about how instruction in the use of analogies might influence the teaching performance of preservice teachers. The primary objective of this study was to investigate the relationship between pedagogical analogy use and pedagogical reasoning ability in a sample of preservice elementary teachers (PTs), a group that has been identified for their particular difficulties in teaching science. The study utilized a treatment/contrast group design in which the treatment group was provided instruction that guided them in the generation of analogies to aid in the explanation phase of learning cycle lessons. A relationship between analogy use and positive indicants of teaching performance was observed and a case study of a low performing preservice teacher who drastically improved teaching performance using analogy‐based pedagogy is presented. A notable effect on conceptual understanding of Newton's Third Law as a result of two brief analogy‐based demonstration lessons was also observed. © 2007 Wiley Periodicals, Inc. J Res Sci Teach 44: 565–585, 2007.     

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.     

Using multi-class queuing network to solve performance models of e-business sites

Due to e-business's variety of customers with different navigational patterns and demands, multi-class queuing network is a natural performance model for it. The open multi-class queuing network(QN) models are based on the assumption that no service center is saturated as a result of the combined loads of all the classes. Several formulas are used to calculate performance measures, including throughput, residence time, queue length, response time and the average number of requests. The solution technique of closed multi-class QN models is an approximate mean value analysis algorithm (MVA) based on three key equations, because the exact algorithm needs huge time and space requirement. As mixed multi-class QN models, include some open and some closed classes, the open classes should be eliminated to create a closed multi-class QN so that the closed model algorithm can be applied. Some corresponding examples are given to show how to apply the algorithms mentioned in this article. These examples indicate that multi-class QN is a reasonably accurate model of e-business and can be solved efficiently.     

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.     

Using LSA and text segmentation to improve automatic Chinese dialogue text summarization

Automatic Chinese text summarization for dialogue style is a relatively new research area. In this paper, Latent Semantic Analysis （LSA） is first used to extract semantic knowledge from a given document, all question paragraphs are identified, an automatic text segmentation approach analogous to Text＇filing is exploited to improve the precision of correlating question paragraphs and answer paragraphs, and finally some ＂important＂ sentences are extracted from the generic content and the question-answer pairs to generate a complete summary. Experimental results showed that our approach is highly efficient and improves significantly the coherence of the summary while not compromising informativeness.     

巧用美术材料 拓展表现空间

美术的发展伴随着对材料的探寻和研究,当今创作者更加需要突破思维定势,变革、创新美术材料在作品中的应用方式和效果,尝试用复杂而又丰富的材料表现求新求异的艺术作品。初中美术课堂中,教师应及早开展巧用材料,拓展艺术表现空间的教育活动,传输创新使用材料也是创作的观念,引导学生开发利用身边可用资源,探究寻常美术材料的"特别"用法,在体验尝试中感受美术创作的乐趣。     

Using argumentation as a learning strategy to improve student performance in engineering Statics

ABSTRACT

Research suggests that a significant reason that a large number of students earn low grades in the fundamental engineering science course Statics is that they may be entering the course with incorrect conceptual knowledge of mathematics and physics. The self-explanation learning approach called collective argumentation helps k-12 students to understand their misconceptions of mathematical principles that often appear abstract to them. This study investigated collective argumentation as an instructional approach that helps engineering students identify and correct their misconceptions of topics taught in Statics. Results suggest that argumentation improves student performance as measured by grades earned on semester exams. Survey and focus group results suggest that students did not understand the argumentation process. Therefore, the students did not like using it as a learning approach.     

Understanding research strategies to improve ERA performance in Australian universities: circumventing secrecy to achieve success

ABSTRACT

Many Australian universities have prioritised improving discipline performance on the national research assessment – Excellence for Research in Australia. However, a culture of secrecy pervades Excellence in Research for Australia (ERA). There are no specified criteria for the assignment of ratings on a 5-point scale ranging from ‘well above world standard’ (5) to ‘well below world standard’ (1). No rationale is provided to institutions for their discipline ratings and university staff on the ERA panels sign confidentiality agreements. However, what is available to universities are the research strategies that each university documents to improve its ERA performance in its Mission-based Compact, a government funding agreement. Thus, the purpose of this paper is to investigate the similarities and differences in the research strategies that universities with different performance profiles employ. Following an analysis of the strategies, substantial commonality was identified in strategy use. However, what was different was how universities employed these strategies and the associated contexts.     

固相微萃取-液相色谱联用在生物分析中的新策略

集萃取、浓缩、解吸、进样于一体的固相微萃取(solid-phase microextraction,SPME)样品预处理技术可与高效液相色谱(HPLC)联用,非常适合复杂生物样本中的痕量非挥发性目标化合物的定性与定量分析,但存在自动化程度不高、涂层种类少、涂层稳定性差等问题。为此,整理并总结了近年改进策略的研究进展,介绍了不同的SPME萃取形式与HPLC的联用接口设计、新型涂层的制作方法和研究思路,指出了SPME-HPLC未来的发展方向是全自动化、快速、高通量、高灵敏度。     

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.