Simulation and optimization of SOFC-BCHP system

As the prime motor of dispersed energy system, the high-temperature solid oxide fuel cells (SOFC) are high efficient with large heat recovery. This study presents a simulation of SOFC building-based cooling, heat and power (BCHP) system, which can meet basic requirements in power and heating (cooling) of the designated customers. The peak power load can be met by power grid, while the peak heating (cooling) load requirement can be met by backup equipments. In order to solve the economic dispatch problem of the energy system, a restricted nonlinear optimization model has been developed. The production costs can be minimized via both the equality constraints of customer’s heat and power demands, and other inequality constrains of equipments’ capacities. The sequential quadratic programming method has been used to search the solution. The study indicates that the model can be used to optimize the system’s capacities and run strategy. An office building case has been computed, and it is indicated that the model can be served in design and optimization of SOFC-BCHP system.     

Research on the friction and wear mechanism of Poly(vinyl alcohol)/hydroxylapatite composite hydrogel

Poly(vinyl alcohol)/Hydroxylapatite (PVA/HA) composite hydrogel was prepared with poly(vinyl alcohol) and hydroxylapatite as raw materials, using the method of repeated freezing and thawing. The morphologies of PVA/HA composite hydrogel were observed by means of high-accuracy 3D profiler and scanning electron microscope (SEM). The compressive elastic modulus and the stress relaxation characteristics of PVA/HA composite hydrogel were measured using the flat-head cylinder indenter. The friction and wear tests between PVA/HA composite hydrogel and bovine knee articular cartilage were performed on the micro-tribometer. The worn morphologies of PVA/HA composite hydrogel were observed with environmental scanning electron microscope (ESEM). The results showed that PVA/HA composite hydrogel has the cross-link network microstructure which is similar to that of the natural bovine knee articular cartilages. With the increase of freezing-thawing cycles and the HA content, the degree of cross-link and the crystallization of PVA/HA composite hydrogel both increase, the elastic modulus increases evidently, the rate of stress relaxation is improved and the value of balance stress decreases. The friction coefficient decreases with the increase of the freezing-thawing cycles and the HA content. The more the freezing-thawing cycles are, the earlier the friction coefficient reaches the stable balance value. The friction deformation depth between PVA/HA composite hydrogel and bovine knee articular cartilage is inversely proportional to freezing-thawing cycles and the HA content. The main wear mechanisms of PVA/HA composite hydrogel are plastic flowing and adhesive flaking. The wear severity degree decreases with the increase of freezing-thawing cycles and the HA content. Supported by Key Program of the National Natural Science Foundation of China (Grant No. 50535050), Program for New Century Excellent Talents in University (Grant No. NCET-06-0479) and Natural Science Foundation of Jiangsu Province (Grant No. BK2005403)     

基于倒排列表的网流索引检索与压缩方法

随着计算机的广泛应用以及互联网的飞速发展,互联网流量呈现爆炸式增长的态势。为了应对日益严重的网络滥用以及网络安全事件,出于安全取证的需要,必须对互联网流量进行收集、存储和分析。互联网流量的监控需要及时统计网络流量的源地址、目的地址、源端口、目的端口、协议、时间戳等信息,以便进行流量统计和综合分析。但是网络流量信息是海量的,如何快速检索相关流量是一个挑战性问题。在搜索引擎中,为了处理海量数据检索,倒排索引是快速搜索技术的关键方法。文章把搜索引擎中的倒排索引方法和索引压缩算法应用到互联网网流信息检索中。通过实验测试和验证,在网流信息检索中,倒排索引以及索引压缩算法能够有效提高检索速度。     

一种适用于智能设备的多重操作系统架构

针对智能设备,为避免引入虚拟化技术而产生的性能开销,提出并实现了MuxOS。MuxOS是一种多重操作系统架构,使得智能设备可以在非虚拟化条件下运行多个操作系统。介绍了MuxOS工作原理,描述了MuxOS运行流程。测试结果表明, MuxOS性能优于Xen等虚拟化产品,可以实现操作系统间亚秒级的快速切换。     

PAIDD: a hybrid P2P-based architecture for improving data distribution in social networks

Rapid growth in social networks(SNs)presents a unique scalability challenge for SN operators because of the massive amounts of data distribution among large number of concurrent online users.A request from any user may trigger hundreds of server activities to generate a customized page and which has already become a huge burden.Based on the theoretical model and analytical study considering realistic network scenarios,this article proposes a hybrid P2P-based architecture called PAIDD.PAIDD fulfills effective data distribution primarily through P2P connectivity and social graph among users but with the help of central servers.To increase system efficiency,PAIDD performs optimized content prefetching based on social interactions among users.PAIDD chooses interaction as the criteria because user’s interaction graph is measured to be much smaller than the social graph.Our experiments confirm that PAIDD ensures satisfactory user experience without incurring extensive overhead on clients’network.More importantly,PAIDD can effectively achieve one order of magnitude of load reduction at central servers.     

Relay selection with feedback beamforming information through designed sector sweep report frame for mmWave WPANs

This paper proposes a novel relay selection strategy based on the feedback beamforming （BF） information through designed sector sweep （SSW） report frame for millimeter-wave （mmWave） wireless personal networks （WPANs）. First, an SSW report frame compatible with IEEE 802.11ad standard is designed. Second, an approach collecting instantaneous channel state information （CSI） overheard during BF is devised. Third, with the aim of minimizing the outage probability and maximizing the overall network throughput capacity, the optimal relay selection issue for non-line-of-sight （NLoS） links is formulated as a bipartite graph, and Kuhn Munkres （KM） algorithm is provided to resolve it. Both theoretical analysis and simulation results show, with CSI considering NLoS conditions and selected relays according to the overall network throughput capacity maximization principle, the improvements achieved over opportunistic relay selection strategy in terms of overall network throughput capacity and outage probability with minimal modifications to IEEE 802.1lad.     

Requirements model driven adaption and evolution of Internetware

Today’s software systems need to support complex business operations and processes.The development of the web-based software systems has been pushing up the limits of traditional software engineering methodologies and technologies as they are required to be used and updated almost real-time,so that users can interact and share the same applications over the internet as needed.These applications have to adapt quickly to the diversified and dynamic changing requirements in the physical,technological,economical and social environments.As a consequence,we are expecting a major paradigm shift in software engineering to reflect such changes in computing environment in order to better address the fundamental needs of organisations in this new era.Existing software technologies,such as model driven development,business process engineering,online(re-)configuration,composition and adaptation of managerial functionalities are being repurposed to reduce the time taken for software development by reusing software codes.The ability to dynamically combine contents from numerous web sites and local resources,and the ability to instantly publish services worldwide have opened up entirely new possibilities for software development.In retrospect to the ten years applied research on Internetware,we have witnessed such a paradigm shift,which brings about many changes to the developmental experience of conventional web applications.Several related technologies,such as cloud computing,service computing,cyber-physical systems and social computing,have converged to address this emerging issue with emphasis on different aspects.In this paper,we first outline the requirements that the Internetware software paradigm should meet to excel at web application adaptation;we then propose a requirement model driven method for adaptive and evolutionary applications;and we report our experiences and case studies of applying it to an enterprise information system.Our goal is to provide high-level guidelines to researchers and practitioners to meet the challenges of building adaptive industrial-strength applications with the spectrum of processes,techniques and facilities provided within the Internetware paradigm.     

Towards evolvable Internet architecture-design constraints and models analysis

There is a general consensus about the success of Internet architecture in academia and industry. However, with the development of diversified application, the existing Internet architecture is facing more and more challenges in scalability, security, mobility and performance. A novel evolvable Internet architecture framework is proposed in this paper to meet the continuous changing application requirements. The basic idea of evolvability is relaxing the constraints that limit the development of the architecture while adhering to the core design principles of the Internet. Three important design constraints used to ensure the construction of the evolvable architecture, including the evolvability constraint, the economic adaptability constraint and the manageability constraint, are comprehensively described. We consider that the evolvable architecture can be developed from the network layer under these design constraints. What＇s more, we believe that the address system is the foundation of the Internet. Therefore, we propose a general address platform which provides a more open and efficient network environment for the research and development of the evolvable architecture.     

An integrated emotional and physiological assessment for VR-based active shooter incident experiments

Unfortunately, active shooter incidents are on the rise in the United States. With the recent technological advancements, virtual reality (VR) experiments could serve as an effective method to prepare civilians and law enforcement personnel for such scenarios. However, for VR experiments to be effective for active shooter training and research, such experiments must be able to evoke emotional and physiological responses as live active shooter drills and events do. The objective of this study is thus to test the effectiveness of an active shooter VR experiment on emotional and physiological responses. Additionally, we consider different locomotion techniques (i.e., walk-in-place and controller) and explore their impact on users’ sense of presence. The results suggest that the VR active shooter experiment in this study can induce emotional arousal and increase heart rate of the participants immersed in the virtual environment. Furthermore, compared to the controller, the walk-in-place technique resulted in a higher emotional arousal in terms of negative emotions and a stronger sense of presence. The study presents a foundation for future active shooter experiments as it supports the ecological validity using VR for active shooter incident related work for the purposes of training or research.