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We consider the problem of finding the worst case packet transit delay in networks using deflection routing. Several classes of networks are studied, including many topologies for which deflection routing has been proposed or implemented (e.g., hypercube, Manhattan Street Network, shuffle-exchange network). We derive new upper bounds on the evacuation time of batch admissions, and present simple proofs for several existing bounds. Also derived are bounds on worst case transit delay for certain networks admitting packets continuously. To demonstrate the practical utility of our results, we compare a new delay bound to the maximum delay observed in simulations. The results have application in both protocol design and the determination of the required capacity of packet resequencing buffers  相似文献   
2.
We introduce a new two-phase technique to solve highly asymmetric assignment problems. In the first phase, the assignment problem is decomposed into subproblems which are solved in parallel. The first phase is used to exclude certain suboptimal assignments from consideration in the second phase. In the second phase, the optimal assignment is finalized. We show that the two-phase algorithm can reduce the theoretical time bound for solving an n×k assignment problem (nk/n  相似文献   
3.
Copyright protection for the electronic distribution of textdocuments   总被引:1,自引:0,他引:1  
Each copy of a text document can be made different in a nearly invisible way by repositioning or modifying the appearance of different elements of text, i.e., lines, words, or characters. A unique copy can be registered with its recipient, so that subsequent unauthorized copies that are retrieved can be traced back to the original owner. In this paper we describe and compare several mechanisms for marking documents and several other mechanisms for decoding the marks after documents have been subjected to common types of distortion. The marks are intended to protect documents of limited value that are owned by individuals who would rather possess a legal than an illegal copy if they can be distinguished. We describe attacks that remove the marks and countermeasures to those attacks. An architecture is described for distributing a large number of copies without burdening the publisher with creating and transmitting the unique documents. The architecture also allows the publisher to determine the identity of a recipient who has illegally redistributed the document, without compromising the privacy of individuals who are not operating illegally. Two experimental systems are described. One was used to distribute an issue of the IEEE Journal on Selected Areas in Communications, and the second was used to mark copies of company private memoranda  相似文献   
4.
Multihomed, mobile wireless computing and communication devices can spontaneously form communities to logically combine and share the bandwidth of each other's wide-area communication links using inverse multiplexing. But, membership in such a community can be highly dynamic, as devices and their associated WWAN links randomly join and leave the community. We identify the issues and trade-offs faced in designing a decentralized inverse multiplexing system in this challenging setting and determine precisely how heterogeneous WWAN links should be characterized and when they should be added to, or deleted from, the shared pool. We then propose methods of choosing the appropriate channels on which to assign newly arriving application flows. Using video traffic as a motivating example, we demonstrate how significant performance gains can be realized by adapting allocation of the shared WWAN channels to specific application requirements. Our simulation and experimentation results show that collaborative bandwidth aggregation systems are, indeed, a practical and compelling means of achieving high-speed Internet access for groups of wireless computing devices beyond the reach of public or private access points  相似文献   
5.
We propose a new, media-independent protocol for including program timing, structure and identity information in Internet media streams. The protocol uses signaling messages called cues to indicate events whose timing is significant to receivers, such as the start or stop time of a media program. We describe the implementation and operation of a prototype Internet radio station which transmits program cues in audio broadcasts using a real-time transport protocol (RTP). A collection of simple yet powerful stream processing applications we implemented demonstrate how application creation is greatly eased when media streams are enriched with program cues.  相似文献   
6.
The authors report on the Secure Electronic Publishing Trial (SEPTEMBER), a Communications Society initiative to determine how best to disseminate technical information over the Global Internet. SEPTEMBER uses World Wide Web (WWW) technology to distribute society publications. This article reports on the implementation and results of the trial. We believe that the results are of wide interest, from those interested in developing electronic publications to those who simply enjoy and learn by reading Communications Society publications  相似文献   
7.
Increasingly intelligent Internet overlay networks promise to deliver streaming media and value-added media services in ways that cannot be achieved easily with conventional broadcast networks. Such an overlay would allow an individual viewer or groups of viewers to receive unique programming content (e.g., commercial advertisements, entertainment) that matches their previously specified preferences. Toward this end, we introduce a scalable overlay network architecture and signaling mechanism that permits dynamic program insertions in live high-quality video streams transmitted over IP networks. We describe the implementation of an application proxy that dynamically inserts prerecorded video programs into NTSC Dl quality motion-JPEG streams with no visible artifacts. We argue that on-demand program switching is merely a first step toward a new generation of media services; increases in computing power ultimately permits network-based proxies to manipulate and augment multimedia content as it flows through the network.  相似文献   
8.
Retrieval of relevant unstructured information from the ever-increasing textual communications of individuals and businesses has become a major barrier to effective litigation/defense, mergers/acquisitions, and regulatory compliance. Such e-discovery requires simultaneously high precision with high recall (high-P/R) and is therefore a prototype for many legal reasoning tasks. The requisite exhaustive information retrieval (IR) system must employ very different techniques than those applicable in the hyper-precise, consumer search task where insignificant recall is the accepted norm. We apply Russell, et al.’s cognitive task analysis of sensemaking by intelligence analysts to develop a semi-autonomous system that achieves high IR accuracy of F1 ≥ 0.8 compared to F1 < 0.4 typical of computer-assisted human-assessment (CAHA) or alternative approaches such as Roitblat, et al.’s. By understanding the ‘Learning Loop Complexes’ of lawyers engaged in successful small-scale document review, we have used socio-technical design principles to create roles, processes, and technologies for scalable human-assisted computer-assessment (HACA). Results from the NIST-TREC Legal Track’s interactive task from both 2008 and 2009 validate the efficacy of this sensemaking approach to the high-P/R IR task.  相似文献   
9.
Modern computer networks make it possible to distribute documents quickly and economically by electronic means rather than by conventional paper means. However, the widespread adoption of electronic distribution of copyrighted material is currently impeded by the ease of unauthorized copying and dissemination. In this paper we propose techniques that discourage unauthorized distribution by embedding each document with a unique codeword. Our encoding techniques are indiscernible by readers, yet enable us to identify the sanctioned recipient of a document by examination of a recovered document. We propose three coding methods, describe one in detail, and present experimental results showing that our identification techniques are highly reliable, even after documents have been photocopied  相似文献   
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