To improve the agility,dynamics,composability,reusability,and development efficiency restricted by monolithic federation object model（FOM）,a modular FOM is proposed by high level architecture（HLA）evolved product development group.This paper reviews the state-of-the-art of HLA evolved modular FOM.In particular, related concepts,the overall impact on HLA standards,extension principles,and merging processes are discussed. Also permitted and restricted combinations,and merging rules are provided,and the influence on HLA interface specification is given.The comparison between modular FOM and base object model（BOM）is performed to illustrate the importance of their combination.The applications of modular FOM are summarized.Finally,the significance to facilitate compoable simulation both in academia and practice is presented and future directions are pointed out.

Effective caching in the Domain Name System (DNS) is critical to its performance and scalability. Existing DNS only supports weak cache consistency by using the Time-to-Live (TTL) mechanism, which functions reasonably well in normal situations. However, maintaining strong cache consistency in DNS as an indispensable exceptional handling mechanism has become more and more demanding for three important objectives: 1) to quickly respond and handle exceptions such as sudden and dramatic Internet failures caused by natural and human disasters, 2) to adapt increasingly frequent changes of Internet Protocol (IP) addresses due to the introduction of dynamic DNS techniques for various stationed and mobile devices on the Internet, and 3) to provide fine-grain controls for content delivery services to timely balance server load distributions. With agile adaptation to various exceptional Internet dynamics, strong DNS cache consistency improves the availability and reliability of Internet services. In this paper, we first conduct extensive Internet measurements to quantitatively characterize DNS dynamics. Then, we propose a proactive DNS cache update protocol (DNScup), running as middleware in DNS name servers, to provide strong cache consistency for DNS. The core of DNScup is an optimal lease scheme, called dynamic lease, to keep track of the local DNS name servers. We compare dynamic lease with other existing lease schemes through theoretical analysis and trace-driven simulations. Based on the DNS Dynamic Update protocol, we build a DNScup prototype with minor modifications to the current DNS implementation. Our system prototype demonstrates the effectiveness of DNScup and its easy and incremental deployment on the Internet.

Object detection quality and network lifetime are two conflicting aspects of a sensor network, but both are critical to many sensor applications such as military surveillance. Partial coverage, where a sensing field is partially sensed by active sensors at any time, is an appropriate approach to balancing the two conflicting design requirements of monitoring applications. Under partial coverage, we develop an analytical framework for object detection in sensor networks, and mathematically analyze average-case object detection quality in random and synchronized sensing scheduling protocols. Our analytical framework facilitates performance evaluation of a sensing schedule, network deployment, and sensing scheduling protocol design. Furthermore, we propose three wave sensing scheduling protocols to achieve bounded worst-case object detection quality. We justify the correctness of our analyses through rigorous proof, and validate the effectiveness of the proposed protocols through extensive simulation experiments

Effective caching in Domain Name System (DNS) is critical to its performance and scalability. Existing DNS only supports weak cache consistency by using the Time-To-Live (TTL) mechanism, which functions reasonably well in normal situations. However, maintaining strong cache consistency in DNS as an indispensable exceptional handling mechanismhas become more and more demanding for three important objectives: (1) to quickly respond and handle exceptional incidents, such as sudden and dramatic Internet failures caused by natural and human disasters, (2) to adapt increasingly frequent changes of IP addresses due to the introduction of dynamic DNS techniques for various stationed and mobile devices on the Internet, and (3) to provide finegrain controls for content delivery services to timely balance server load distributions. With agile adaptation to various exceptional Internet dynamics, strong DNS cache consistency improves the availability and reliability of Internet services. In this paper, we propose a proactive DNS cache update protocol, called DNScup, running as middleware in DNS nameservers, to provide strong cache consistency for DNS. The core of DNScup is a dynamic lease technique to keep track of the local DNS nameservers, whose clients need cache coherence to avoid losing service availability. Based on the DNS Dynamic Update protocol, we have built a DNScup prototype with minor modifications to the current DNS implementation. Our trace-driven simulation and system prototype demonstrate the effectiveness of DNScup and its easy and incremental deployment on the Internet.

With the development of active proxy, the functions of a proxy have been enhanced beyond simply storing Web contents. Web prefetching activity in proxy is such an example to reduce client-perceived latency. In this paper, we propose a coordinated proxy–server prefetching technique that adaptively utilizes the access information and coordinates prefetching activities at both proxy and Web servers. In our design, the access information stored in proxies will be the main source serving data prefetching for groups of clients sharing common surfing interests. The access information in the Web server will be used to serve data prefetching only for data objects that are not qualified for proxy-based prefetching. Conducting trace-driven simulations, we show that both hit ratios and byte hit ratios contributed from coordinated proxy–server prefetching are 30–75% higher than other prefetching schemes, and they are comparable to the ratios from a proxyless server-based prefetching that is able to observe every access to the server.

Object detection quality and network lifetime are two conflicting aspects of a sensor network, but both are critical to many sensor applications such as military surveillance. Probabilistic coverage is an appropriate approach to balancing the conflicting design requirements of monitoring applications. Under probabilistic coverage, we present an analytical model to analyze object detection quality with respect to different network conditions and sensor scheduling schemes. Our analytical model facilitates performance evaluation of a sensing schedule, network deployment, and sensing scheduling protocol design. Applying the model to real sensor networks, we design a set of sensing scheduling protocols to achieve targeted object detection quality while minimizing power consumption. The correctness of our model and the effectiveness of the proposed protocols are validated through extensive simulation experiments.

Sensor networks are used for a wide range of object tracking applications, such as vehicle tracking in military surveillance and wild animal tracking in habitat monitoring [1]. These applications, by their nature, enforce certain tracking quality and lifetime requirements. These two requirements, however, are two conflicting optimization goals due to the stringent energy constraints of sensor nodes.

While current Peer-to-Peer (P2P) systems facilitate static file sharing, newly-developed applications demand that P2P systems be able to manage dynamically-changing files. Maintaining consistency between frequently-updated files and their replicas is a fundamental reliability requirement for a P2P system. In this paper, we present SCOPE, a structured P2P system supporting consistency among a large number of replicas. By building a replica-partition-tree (RPT) for each key, SCOPE keeps track of the locations of replicas and then propagates update notifications. Our theoretical analyses and experimental results demonstrate that SCOPE can effectively maintain replica consistency while preventing hot-spot and node-failure problems. Its efficiency in maintenance and failure-recovery is particularly attractive to the deployment of large-scale P2P systems.

Internet has become a major infrastructure for information sharing in our daily life, and indispensable to critical and large applications in industry, government, business, and education. Internet bandwidth (or the network speed to transfer data) has been dramatically increased, however, the latency time (or the delay to physically access data) has been reduced in a much slower pace. The rich bandwidth and lagging latency can be effectively coped with in Internet systems by three data management techniques: caching, replication, and prefetching. The focus of this dissertation is to address the latency problem in Internet by utilizing the rich bandwidth and large storage capacity for efficiently prefetching data to significantly improve the Web content caching performance, by proposing and implementing scalable data consistency maintenance methods to handle Internet Web address caching in distributed name systems (DNS), and to handle massive data replications in peer-to-peer systems. While the DNS service is critical in Internet, peer-to-peer data sharing is being accepted as an important activity in Internet. We have made three contributions in developing prefetching techniques. First, we have proposed an efficient data structure for maintaining Web access information, called popularity-based Prediction by Partial Matching (PB-PPM), where data are placed and replaced guided by popularity information of Web accesses, thus only important and useful information is stored. PB-PPM greatly reduces the required storage space, and improves the prediction accuracy. Second, a major weakness in existing Web servers is that prefetching activities are scheduled independently of dynamically changing server workloads. Without a proper control and coordination between the two kinds of activities, prefetching can negatively affect the Web services and degrade the Web access performance. To address this problem, we have developed a queuing model to characterize the interactions. Guided by the model, we have designed a coordination scheme that dynamically adjusts the prefetching aggressiveness in Web Servers. This scheme not only prevents the Web servers from being overloaded, but it can also minimize the average server response time. Finally, we have proposed a scheme that effectively coordinates the sharing of access information for both proxy and Web servers. With the support of this scheme, the accuracy of prefetching decisions is significantly improved. Regarding data consistency support for Internet caching and data replications, we have conducted three significant studies. First, we have developed a consistency support technique to maintain the data consistency among the replicas in structured P2P networks. Based on Pastry, an existing and popular P2P system, we have implemented this scheme, and show that it can effectively maintain consistency while prevent hot-spot and node-failure problems. Second, we have designed and implemented a DNS cache update protocol, called DNScup, to provide strong consistency for domain/IP mappings. Finally, we have developed a dynamic lease scheme to timely update the replicas in Internet.

I. INTRODUCTION Object-tracking quality and network lifetime are two criti- cal and conicting objectives to object-tracking applications in a sensor network. Full sensing coverage (3) is too restricted and expensive to support long-time monitoring applications, and provides little leverage to tune the object-tracking quality and the battery power consumption. Recently, a relaxed sensing coverage ó probabilistic coverage where any point in a sens- ing eld is sensed with a certain probability at any time ó was proposed (1), (2), which is a more appropriate approach to bal- ancing the object-tracking quality and the battery power con- sumption. Under probabilistic coverage, we present an analytical model to investigate the object-tracking quality with respect to various network conditions and sensor scheduling schemes. The an- alytical model facilitates performance evaluation of a sensing schedule, network deployment, and sensing scheduling proto- col design. The contributions of our analytical model are three- fold. First, together with simulation to evaluate performances of different scheduling protocols, this analytical model can give more solid and thorough understanding about various protocols and provide insights into the pros and cons of each protocol. Secondly, the analytical model helps to plan a sensor net- work with certain object-tracking quality requirements and battery power budget. The analytical model is e xible enough to capture the interaction among the system pa- rameters, object-tracking quality requirements, and net- work energy limit. Thirdly, in sensing scheduling protocol design, aside from determining the parameters for sensing scheduling proto- cols, our analytical model can direct new protocol design. We validate the correctness of our model through extensive simulation experiments, and use this model to design schedul- ing algorithms.

Grid and P2P are both emerging technologies that aim at efficient resource sharing in recent years [1, 2]. Reference [3] named the coexist environment of Grid and P2P “Grid Society”. In the environment of Grid Society there exists a large pool of users as well as resource providers, just as in Human Society, whether all of them can be efficiently managed will greatly affect the performance of the whole system [4]. On the basis that Human Society and Grid Society are Similarity Systems, we use the methods of migration to explore the problem of accounting management and proposed a Society based Accounting Management model for Grid Society.

The demand of delivering streaming media content in the Internet has become increasingly high for scientific, educational, and commercial applications. Three representative technologies have been developed for this purpose, each of which has its merits and serious limitations. Infrastructure-based CDNs with dedicated network bandwidths and powerful media replicas can provide high quality streaming services but at a high cost. Server-based proxies are cost-effective but not scalable due to the limited proxy capacity and its centralized control. Client-based P2P networks are scalable but do not guarantee high quality streaming service due to the transient nature of peers. To address these limitations, we present a novel and efficient design of a scalable and reliable media proxy system supported by P2P networks. This system is called PROP abbreviated from our technical theme of "collaborating and coordinating PROxy and its P2P clients". Our objective is to address both scalability and reliability issues of streaming media delivery in a cost-effective way. In the PROP system, the clients' machines in an intranet are self-organized into a structured P2P system to provide a large media storage and to actively participate in the streaming media delivery, where the proxy is also embedded as an important member to ensure quality of streaming service. The coordination and collaboration in the system are efficiently conducted by our P2P management structure and replacement policies. We have comparatively evaluated our system by trace-driven simulations with synthetic workloads and with a real-life workload trace extracted from the media server logs in an enterprise network. The results show that our design significantly improves the quality of media streaming and the system scalability.

The diverse server, client, and unique file object types used today slow Web performance. Caching alone offers limited performance relief because it cannot handle many different file types easily.One solution combines caching with Web prefetching: obtaining the Web data a client might need from data about that client's past surfing activity. The prediction by partial match model, for example, makes prefetching decisions by reviewing URLs clients have accessed on a particular server, then structuring them in a Markov predictor tree. The authors propose a variation of this model that builds common surfing patterns and regularities into the tree.

Although Web prefetching is regarded as an effective method to improve client access performance, the associated overhead prevents it from being widely deployed. Specifically, a major weakness in existing Web servers is that prefetching activities are scheduled independently of dynamically changing server workloads. Without proper control and coordination between the two kinds of activities, prefetching can negatively affect the Web services and degrade Web access performance. We first develop an open queuing model to characterize detailed transactions in Web servers. Using this model, we analyze server resource utilization and average response time with different request arrival rates when prefetching is involved under different kinds of Web services. Guided by this model, we then design a responsive and adaptive prefetching scheme that dynamically adjusts the prefetching aggressiveness in Web servers. Our scheme not only prevents the Web servers from being overloaded, but it can also minimize the average server response time. We have effectively implemented this scheme on an Apache Web server. Our measurement-based performance evaluation shows our model can accurately predict the utilization of Web server resources and the correspondent average response time

To avoid or reduce the X-ray exposure in endoscopic examinations and therapy, as an alternative to the conventional two-dimensional X-ray fluoroscopy we are developing an intrabody navigation system that can directly measure and visualize the three-dimensional (3-D) position of the tip and the trace of an ultrasound endoscope. The proposed system can identify the 3-D location and direction of the endoscope probe inserted into the body to furnish endoscopic images. A marker transducer(s) placed on the surface of the body transmits ultrasound pulses, which are visualized as a marker synchronized to the scanning of the endoscope. The position (direction and distance of the marker transducer(s) outside the body relative to the scanning probe inside the body) of the marker is detected and measured in the scanned image of the ultrasound endoscope. Further, an optical localizer locates the marker transducer(s) with six degrees of freedom. Thus, the proposed method performs inside-body 3-D localization by utilizing the inherent image reconstruction function of the ultrasound endoscope, and is able to be used with currently available commercial ultrasound image scanners. The system may be envisaged as a kind of global positioning system for intrabody navigation.

Existing prefetching techniques rely on server-based, proxy-based, or client-based reference access information. Although Web servers may provide accurate access information, our studies show that significant communication overhead can be involved by sending unnecessary reference information to clients or/and proxy servers. Our study also shows that prediction accuracy of proxy-based prefetching can be significantly limited without input of Web servers. We propose a coordinated proxy-server prefetching technique that adaptively utilizes the reference information and coordinates prefetching activities at both proxy and web servers. In our design, the reference access information stored in proxy servers will be the main source serving data prefetching for groups of clients, each of whom shares the common surfing interests. The access information in the web server will be used to serve data prefetching only for data objects that are not qualified for proxy-based prefetching. Conducting trace-driven simulations, we show that both hit ratios and byte hit ratios contributed from coordinated proxy-server prefetching are are up to 88% higher than that from proxy-based prefetching, and they are comparable to the ratios from server-based prefetching with a difference of 5%.

Fusion welding of high-T/sub c/ superconducting ceramics via laser was explored. Superconducting BiSrCaCu/sub 2/O/sub y/ ceramics were welded by a CO/sub 2/ laser in air. During the welding process, oxygen flow was blown into the laser melting zone. The beads as welded exhibited semiconducting properties and were transformed into the superconducting state by subsequent annealing treatment with a zero resistance temperature of 80 K. The beads have a similar stoichiometry to that of the base material as revealed by EDAX investigation. Using this technique, butt welds and lap welds were obtained.< >

Fusion welding of high-Tc superconducting ceramics via laser was explored. Superconducting BiSrCaCu2O y ceramics were welded by a CO2 laser in air. During the welding process, oxygen flow was blown into the laser melting zone. The beads as welded exhibited semiconducting properties and were transformed into the superconducting state by subsequent annealing treatment with a zero resistance temperature of 80 K. The beads have a similar stoichiometry to that of the base material as revealed by EDAX investigation. Using this technique, butt welds and lap welds were obtained