A social network-based system for supporting interactive collaboration in knowledge sharing over peer-to-peer network

Knowledge sharing enables people in virtual communities to access relevant knowledge (explicit or tacit) from broader scope of resources. The performance in such environments is fundamentally based on how effectively the explicit and tacit knowledge can be shared across people, and how efficiently the created knowledge can be organized and disseminated to enrich digital content. This study will address how to apply social network-based system to support interactive collaboration in knowledge sharing over peer-to-peer networks. Results of this study demonstrate that applying such social network-based collaboration support to knowledge sharing helps people find relevant content and knowledgeable collaborators who are willing to share their knowledge.     

基于语义覆盖网的P2P信息共享系统研究

现有P2P信息共享系统存在仅支持粗粒度、弱语义共享以及系统效率低等局限性,限制了其更大规模、更高层次的应用。基于资源相似节点通过信息聚类聚集在同一主题域,实现节点资源有序组织的思想,提出了一种基于语义覆盖网的P2P信息共享系统,建立由资源层、信息服务中心层、语义覆盖网络层和应用层四个层次组成的系统框架结构,并阐述了系统流程。分析表明,该系统有效优化了网络性能,可扩展性好,可以胜任不同的网络规模。     

A facile on-demand droplet microfluidic system for lab-on-a-chip applications

We present a facile microfluidic droplet-on-demand (DOD) system in which a pulsed pressure generated by a high-speed solenoid valve is used to control the formation and movement of water-in-oil emulsion droplets in a T-junction microchannel. We investigated the working principle of the DOD system and established a scaling model for the droplet volume in terms of the amplitude and duration of the pulse and the hydraulic resistance of the injection channel. The droplet formation was characterized in three designs at various pressure pulses. The experimental results support our scaling model very well. In the DOD system we developed, nanoliter-volume droplets with a throughput of a few droplets per second were on-demand generated. Moreover, we examined the applicable scope of the DOD system. As examples of practical applications of the DOD system, we demonstrated a digital display module to show droplets formed at a prescribed time and a droplet array with a concentration gradient to show droplets formed with a precise volume. We expect our work can provide design guidelines for a robust DOD system and improve the capabilities of droplet-based microfluidics in ‘lab-on-a-chip’ systems.     

P2P文件共享系统中面向协商的激励机制

借鉴经济活动中的协商机制提出一种面向协商的P2 P激励机制。文件供求节点通过订立协议对双方的行为进行制约,新节点和信誉度较低的节点也可以通过订立协议参与文件交易,达到提高节点的文件交易成功率的目的。仿真结果表明,该机制有效抑制了搭便车行为,明显提高了网络文件资源的利用率。     

一种P2P文件共享系统中的激励机制*

提出了一种用于文件共享系统的激励机制,将节点享受服务的能力和提供服务的能力进行区分,贡献节点享有更高的服务优先级,而搭便车节点受到惩罚。仿真实验表明,该激励机制充分体现了公平性原则,同时大大提高了下载成功率。     

一种P2P文件共享系统中的激励机制*

提出了一种用于文件共享系统的激励机制,将节点享受服务的能力和提供服务的能力进行区分,贡献节点享有更高的服务优先级,而搭便车节点受到惩罚。仿真实验表明,该激励机制充分体现了公平性原则,同时大大提高了下载成功率。     

Distributed recommender for peer-to-peer knowledge sharing

A novel model of distributed knowledge recommender system is proposed to facilitate knowledge sharing among collaborative team members. Different from traditional recommender systems in the client-server architecture, our model is oriented to the peer-to-peer (P2P) environment without the centralized control. Among the P2P network of collaborative team members, each peer is deployed with one distributed knowledge recommender, which can supply proper knowledge resources to peers who may need them. This paper investigates the key techniques for implementing the distributed knowledge recommender model. Moreover, a series of simulation-based experiments are conducted by using the data from a real-world collaborative team in an enterprise. The experimental results validate the efficiency of the proposed model. This research paves the way for developing platforms that can share and manage large-scale distributed knowledge resources. This study also provides a new framework for simulating and studying individual or organizational behaviors of knowledge sharing in a collaborative team.     

Development of a peer-to-peer information sharing system using ontologies

Most existing agent-oriented methodologies ignore system extensibility, interoperability and reusability issues. Ontologies have been found to play a significant role in facilitating interoperability, reusability, MAS development activities (including MAS analysis and agent knowledge modeling) and MAS run-time operation (including agent communication and reasoning). However, most of the existing AOSE methodologies do not provide support for ontology-based MAS development. We present software engineering requirements for ontology-based development for MAS and examine an existing methodology, MOBMAS – a “Methodology for Ontology-Based MASs”, which makes use of ontologies as a modeling tool. In this examination, we highlight how MOBMAS can be extended to utilizing ontology roles in facilitating interoperability, reusability and verification. This will be based on using MOBMAS to develop peer-to-peer (P2P) community-based information sharing application which lead us to identify ontology related steps that can be added to enhance MOBMAS. MOBMAS is used by two experienced software developers who were not authors of the methodology, to guide the development of the P2P application.     

一种适用于移动对等网络的分簇算法

通过分簇算法减小网络振动效应,延长网络的寿命是移动对等网络的研究重点之一。在研究Kautz图及其特性的基础上,提出一种基于Kautz图的移动对等网络分簇算法。在算法中,定义地址空间树,使用Kautz串作为节点标识,并运用后根序和宽度优先算法遍历地址空间树等一系列技术生成簇。同时设计了相关机制管理和维护簇结构,保证结构一致性。理论证明和实验评估表明,该分簇算法能有效减小振动效应,延长网络寿命。     

Trust-based privacy preservation for peer-to-peer data sharing

Privacy preservation in a peer-to-peer (P2P) system tries to hide the association between the identity of a participant and the data that it is interested in. This paper proposes a trust-based privacy-preservation method for P2P data sharing. It adopts the trust relation between a peer and its collaborators (buddies). The buddy works as a proxy to send the request and acquire the data. This provides a shield under which the identity of the requester and the accessed data cannot be linked. A privacy measuring method is presented to evaluate the proposed mechanism. Dynamic trust assessment and the enhancement to supplier's privacy are discussed.     

Flexible security in peer-to-peer applications: Enabling new opportunities beyond file sharing

The widespread adoption of P2P applications in environments beyond ordinary file sharing demands the fulfillment of several security requirements. Important steps have been taken towards security in P2P systems, with relevant mechanisms being proposed in the past to address specific vulnerabilities. However, existing approaches lack flexibility, since they do not (include enough mechanisms to) tackle a wide range of requirements in an integrated fashion. In addition, they oblige the user/application to manipulate a complex programming interface, as well as going through a cumbersome configuration process. To address these issues, we present P2PSL (P2P Security Layer), a software architecture that allows gradual and flexible integration of security functionality into P2P applications. To show concept and technical feasibility, we have implemented P2PSL, assessed the overhead it induces, and estimated the feasibility of incorporating the layer into two categories of real world P2P applications.     

语义P2P系统上的知识分享研究*

由于语义P2P系统的知识分散部署于各个peer节点上,而每个peer节点都拥有其自身异构的知识模式和本体表示,这就给语义P2P节点间的知识分享带来了困难。对语义P2P系统进行了深入分析,着重对P2P节点之间的知识分享问题进行了论述,并进一步提出自己的设计思路来解决这一问题。     

Buffer-assisted on-demand multicast for VOD applications

Multicast communications is widely used by streaming video applications to reduce both server load and network bandwidth. However, receivers in a multicast group must access the multicast stream simultaneously, and this restriction on synchronous access diminishes the benefit of multicast because users in a video-on-demand service usually issue requests asynchronously, i.e., at anytime. In this paper, we not only formulate this streaming problem but also propose a new multicast infrastructure, called buffer-assisted on-demand multicast, to allow receivers accessing a multicast stream asynchronously. A timing control mechanism is integrated on intermediate routing nodes (e.g., routers, proxies, or peer nodes in a peer-to-peer network) to branch time-variant multicast sub-streams to corresponding receivers. Besides, an optimal routing path and the corresponding buffer allocations for each request must be carefully determined to maximize the throughput of the multicast stream. We prove that the time complexity to solve this routing problem over general graph networks is NP-complete, and then propose a routing algorithm for overlay networks to minimize server load. Simulation results demonstrate that buffer-assisted on-demand multicast outperforms many popular streaming methods.     

General packet induced queueing schemes for reducing packet delays in ADSL routers with peer-to-peer file sharing applications

This paper proposes a class of queueing schemes named general packet induced queueing schemes (GPIQS) in ADSL routers to reduce the queueing delays of non-P2P packets. The objective of the proposed queueing schemes is to send out the general packets first as well as P2P packets are able to be sent in a bounded queueing delay. The proposed queueing schemes use the general packet to induce the transmission of P2P packets which are from the same client and arrived at the ADSL router before the general packet. The outbound order of the packets transmitted from a specific client is not altered in the proposed schemes. Two queueing schemes named general packet induced queueing scheme with single P2P queue (GPIQS-SQ) and general packet induced queueing scheme with multiple P2P queues (GPIQS-MQ) are proposed. The two proposed queueing schemes differ in the number of P2P queues. In order to prevent the unlimited waiting time of P2P packets, we introduced a variable called the largest number of preempting packets to send out the P2P packets in a bounded time. Simulation results show that the proposed queueing schemes may send out the packets from ADSL router efficiently and the average queueing delay is smaller than the common used first-come first-served algorithm. Specifically, the GPIQS-MQ performs better than the GPIQS-SQ method in terms of average queueing delay of non-P2P packets. We also found that the increased average queueing delay of P2P packets is small. Finally, the values of the largest number of preempting packets are discussed.     

Using peer-to-peer technology for knowledge sharing in communities of practices

Communities of Practices (CoPs) are informal structures within organizations that bind people together through informal relationships and the sharing of expertise and experience. As such, they are effective tools for the creation and sharing of organizational knowledge, and an increasing number of organizations are adopting them as part of their knowledge management strategies. In this paper, we examine the knowledge sharing characteristics and roles of CoPs and develop a peer-to-peer knowledge sharing architecture that matches the behavioral characteristics of the members of the CoPs. We also propose a peer-to-peer knowledge sharing tool called KTella that enables a community's members to voluntarily share and retrieve knowledge more effectively.     

一种综合的P2P网络信任模型

安全有效的信任模型是保证P2P 系统高效、稳定的关键技术之一。介绍一种适用于P2P 网络的综合信任模型,它参考了社会网络中信任关系的建立方法,从两个角度来计算节点的综合可信度。该模型中引入了非对称加密等安全机制,通过分析与仿真证明该模型能有效地抑制冒名和诋毁等非法行为,具有较强的安全性。     

A benefit-aware on-demand provisioning approach for multi-tier applications in cloud computing

Dynamic resource provisioning is a challenging technique to meet the service level agreement (SLA) requirements of multi-tier applications in virtualization-based cloud computing. Prior efforts have addressed this challenge based on either a cost-oblivious approach or a cost-aware approach. However, both approaches may suffer frequent SLA violations under flash crowd conditions. Because they ignore the benefit gained that a multi-tier application continuously guarantees the SLA in the new configuration. In this paper, we propose a benefit-aware approach with feedback control theory to solve this problem. Experimental results based on live workload traces show that our approach can reduce resource provisioning cost by as much as 30% compared with a costoblivious approach, and can effectively reduce SLA violations compared with a cost-aware approach.     

A user-space file system for on-demand legacy desktop software

Some user-level virtualization technologies have been used to convert legacy software (like the existing Windows desktop applications) into the on-demand software without any modification. To give the client a friendly and compatible method to access on-demand legacy software across the Internet, this paper presents a clientend file system for this usage case. It is a Windows user-space file system based on the cloud storage (where the on-demand software is stored), which converts the local file system acce...     

A token-based incentive mechanism for video streaming applications in peer-to-peer networks

Free-riding is one of the main challenges of Peer-to-Peer (P2P) streaming systems which results in reduction in video streaming quality. Therefore, providing an incentive mechanism for stimulating cooperation is one of the essential requirements to maintain video Quality of Experience (QoE) in such systems. Among the existing mechanisms, payment-based schemes are most suitable for streaming applications due to their low overhead. However, to date, no dynamic payment mechanism has been proposed which can take the stochastic dynamics of the video streaming ecosystem (e.g., the request arrival, demand submission, bandwidth availability, etc.) into account. In this paper, we propose a dynamic token-based payment mechanism in which each peer earns tokens by admitting other peers’ requests and spends tokens for submitting its demands to the others. This system allows the peers to dynamically adjust their income level in adaptation to changes in the system state. We propose a Constrained Markov Decision Process (CMDP) formulation in which the goal of each peer is to obtain a request admission policy which minimizes the expected cumulative cost of consumed bandwidth, while satisfying a long-term constraint on the Mean Opinion Score (MOS) of the users as the measure of QoE. The proposed admission policy is adaptive to the request arrival process, bandwidth state and the token bucket length of each peer. To make up for the lack of design-time knowledge of the system’s statistics, each individual peer is equipped with a model-free algorithm to learn its optimal admission policy over the course of real-time interaction with the system. Simulation results are presented to compare the performance of the proposed algorithm against baseline schemes such as: random, token-threshold, bandwidth-threshold and myopic algorithms.