9180158
Protocol Design of MPEG-4 Media Delivery with Active Networks
Traditionally, the Internet supports best effort service. The quality of service available to real time applications such as the delivery of video and audio is therefore difficult to predict and control. Two new technologies have emerged recently, namely the MPEG-4 standard and active network, for media data compression and data networking, respectively. MPEG-4 uses a content or object-based representation. It supports object-based scalability and, in particular, it allows the modification or editing of objects without having to first decode them. Active network allows program code to be loaded dynamically into network nodes. In this paper, we describe a system for real-time media delivery that exploits the strengths of MPEG-4 media encoding and active networks. It is based on a best-effort transport service. Our system performs congestion avoidance, error concealment, and media scalability.
6719824
Performance modeling of multicast groups for multiplayer games in peer-to-peer networks
A computer game is usually considered as a finite state machine. For a distributed multiplayer game, state information has to be exchanged among its players when they move and interact in a virtual space. If the number of players is very large, only a small subset of the game entities, controlled by their players, is interested and forms a multicast group so as to reduce the information dissemination over the network. In this paper, analytical models are proposed for evaluating the performance of multicast groups with multiplayer games in peer-to-peer networks. The system modeling is based on two stochastic processes and their possible solutions in terms of game type, player activity, and entity vision size, mode of user input processing, and grouping strategy. The cost of game operations on consumed resources is introduced to characterize the performance measure. Numerical examples are demonstrated, which provide useful insights of the behaviors of such systems.
957553
A highly scalable and effective method for metasearch
A metasearch engine is a system that supports unified access to multiple local search engines. Database selection is one of the main challenges in building a large-scale metasearch engine. The problem is to efficiently and accurately determine a small number of potentially useful local search engines to invoke for each user query. In order to enable accurate selection, metadata that reflect the contents of each search engine need to be collected and used. This article proposes a highly scalable and accurate database selection method. This method has several novel features. First, the metadata for representing the contents of all search engines are organized into a single integrated representative. Such a representative yields both computational efficiency and storage efficiency. Second, the new selection method is based on a theory for ranking search engines optimally. Experimental results indicate that this new method is very effective. An operational prototype system has been built based on the proposed approach.
33661341
Cycles of each length in tournaments
Let G = (V,A) be a digraph of order n. Digraph G is said to be arc-k-cyclic if each arc of G is contained in a cycle of length k (3 ≤ k ≤ n). An arc e of G is said to be pancyclic if e is contained in cycles of all lengths m, 3 ≤ m ≤ n. Digraph G is said to be arc-pancyclic if each arc of G is pancyclic. The main results of this paper are that (1) except for a certain family of counterexamples, every arc-3-cyclic tournament is arc-pancyclic; (2) at most one arc of an arc-3-cyclic tournament is not pancyclic.
16923777
Identifying redundant search engines in a very large scale metasearch engine context
For a given set of search engines, a search engine is redundant if its searchable contents can be found from other search engines in this set. In this paper, we propose a method to identify redundant search engines in a very large-scale metasearch engine context. The general problem is equivalent to an NP hard problem -- the set-covering problem. Due to the large number of search engines that need to be considered and the large sizes of these search engines, approximate solutions must be developed. In this paper, we propose a general methodology to tackle this problem and within the context of this methodology, we propose several new heuristic algorithms for solving the set-covering problem.
6001645
Towards a highly-scalable and effective metasearch engine
A metasearch engine is a system that supports uni ed access to multiple local search engines. Database selection is one of the main challenges in building a large-scale metasearch engine. The problem is to eAEciently and accurately determine a small number of potentially useful local search engines to invoke for each user query. In order to enable accurate selection, metadata that re ect the contents of each search engine need to be collected and used. In this paper, we propose a highly scalable and accurate database selection method. This method has several novel features. First, the metadata for representing the contents of all search engines are organized into a single integrated representative. Such a representative yields both computation eAEciency and storage eAEciency. Second, our selection method is based on a theory for ranking search engines optimally. Experimental results indicate that this new method is very e ective. An operational prototype system has been built based on the proposed approach.
7810391
Refinement of Nmr-determined Protein Structures with Database Derived Distance Constraints
The protein structures determined by NMR (Nuclear Magnetic Resonance Spectroscopy) are not as detailed and accurate as those by X-ray crystallography and are often underdetermined due to the inadequate distance data available from NMR experiments. The uses of NMR-determined structures in such important applications as homology modeling and rational drug design have thus been severely limited. Here we show that with the increasing numbers of high quality protein structures being determined, a computational approach to enhancing the accuracy of the NMR-determined structures becomes possible by deriving additional distance constraints from the distributions of the distances in databases of known protein structures. We show through a survey on 462 NMR structures that, in fact, many inter-atomic distances in these structures deviate considerably from their database distributions and based on the refinement results on 10 selected NMR structures that these structures can actually be improved significantly when a selected set of distances are constrained within their high probability ranges in their database distributions.