There are a few fundamental pointing-based user interface techniques for performing selections in 3D environments. One of these techniques is ray pointing, which makes selections by determining intersections of object...
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The detection of failures is a fundamental issue for fault tolerance in distributed systems. Recently, many people have come to realize that failure detection ought to be provided as some form of generic service, simi...
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The detection of failures is a fundamental issue for fault tolerance in distributed systems. Recently, many people have come to realize that failure detection ought to be provided as some form of generic service, similar to IP address lookup. However, this has not been successful so far; one of the reasons being the fact that classical failure detectors were not designed to satisfy several application requirements simultaneously. More specifically, traditional implementations of failure detectors are often tuned for running over local networks and fail to address some important problems found in wide-area distributed systems with a large number of monitored components. In this paper, we study the quality of service (QoS) of failure detectors. We first present a novel failure detector scheme combined with control theory that can help in solving or optimizing some problems. Furthermore, this paper discusses the design and analysis of implementing a scalable failure detection service for such large wide-area distributed systems considering dynamically adjusting the heartbeat streams, so that it satisfies the bottleneck router requirements. We further show how the online failure detector control algorithm can be used to design a controller, analyze the theoretical aspects of the proposed algorithm and verify its agreement. Simulation results show the efficiency of our scheme in terms of high utilization of the bottleneck link, fast response and good stability of the bottleneck router buffer occupancy as well as of the controlled sending rates. In conclusion, the new failure detector algorithm provides a better QoS.
In this paper, we propose a cooperative control strategy for a group of robotic vehicles to achieve the specified task issued from a high-level astronaut command. The problem is mathematically formulated as designing ...
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In this paper, we propose a cooperative control strategy for a group of robotic vehicles to achieve the specified task issued from a high-level astronaut command. The problem is mathematically formulated as designing the cooperative control for a general class of multiple-input-multiple-output (MIMO) dynamical systems in canonical form with arbitrary but finite relative degrees such that the outputs of the overall system converge to the explicitly given steady state. The proposed cooperative control for individual vehicle only need to use the sensed and communicated outputs information from its local neighboring vehicles. No fixed leader and time-invariant communication networks are assumed among vehicles. Particularly, a set of less-restrictive conditions on the connectivity of the sensor/communication networks are established, under which it is rigorously proven by using the newly found nice properties of the convergence of sequences of row stochastic matrices that the cooperative objective of the overall system can be achieved. Simulation results for a group of vehicles achieving a target and surrounding a specified object in formation are provided to support the proposed approach in this paper.
Current and future space-based processing applications are requiring, and will require, increasing amounts of onboard processing capability. One way to achieve a high level of processing capability is through the use ...
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Current and future space-based processing applications are requiring, and will require, increasing amounts of onboard processing capability. One way to achieve a high level of processing capability is through the use of COTS (commercial-off-the-shelf) high-performance processors. While state-of-the-art COTS processors are exhibiting adequate total integrated dose (TID) performance to meet the requirements of the natural space radiation environment, single event upsets (SEUs) caused by galactic cosmic rays and solar protons remain a problem. Traditional approaches to mitigate the SEU problem involve fixed redundancy schemes such as self checking pairs (SCP) or triple modular redundancy (TMR). While effective in mitigating the effects of SEUs, use of these techniques comes at a high price, 100% overhead for SCP, and 200% overhead for TMR, particularly when such a level of protection is not needed. In such cases, it would be beneficial to be able to convert that overhead into useful mission processing capability or power reduction. The idea behind Dependable Multiprocessor is to sense the environment and configure the processing system appropriately to maximize the computational performance density, i.e., the computational performance to power ratio, available to the mission. The goal of the Dependable Multiprocessor Project is to provide spacecraft/payload processing capability 10times - 100times what is available today, enabling heretofore unrealizable levels of science and autonomy. To date, Dependable Multiprocessor (DM) technology has been developed as part of NASA's New Millennium Program (NMP) ST8 (Space Technology 8) project. The objective of this NMP ST8 effort is to combine high-performance, fault tolerant, COTS-based cluster processing and fault tolerant middleware in an architecture and software framework capable of supporting a wide variety of mission applications. Dependable Multiprocessor development is continuing as one of the four selected ST8 flight e
We propose an efficient placement algorithm and per-disk prefetching method to effectively support interactive operations in the media server. Our placement policy is incorporated with an encoder having a special bitc...
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We propose an efficient placement algorithm and per-disk prefetching method to effectively support interactive operations in the media server. Our placement policy is incorporated with an encoder having a special bitcount control scheme that repeatedly tunes quantization parameters to adjust the bitcounts of video frames. This encoder can generate coded frames whose sizes are synchronized with the RAID stripe size, so that when various fast-forward levels are accessed we can reduce the seek and rotational latency and enhance the disk throughput of each disk in the RAID system. In the experimental results, the proposed placement policy and bitrate control scheme can significantly improve the average service time, which can enlarge the capacity of the interactive media server. Copyright 2005 ACM.
Service providing as an important activity in service-oriented architecture, which is the most popular architecture for applications of distributed environments needs a change to obtain better efficiency, so in this p...
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ISBN:
(纸本)0780392701
Service providing as an important activity in service-oriented architecture, which is the most popular architecture for applications of distributed environments needs a change to obtain better efficiency, so in this paper we will present neighbor providing and Extended Neighbor Providing (ENP) methods, which are apply the neighborhood computing in traditional methods. As evaluation of these methods we will use the efficiency, scalability, and reliability metrics obtained from the results of omnet++ simulation and we measured the users' satisfactions with their opinions about the quality of implemented ENP system.
A scheme is proposed to provide multiple QoS guarantees for survivable generalised multiprotocol label switching (GMPLS) networks. The shared risk link group (SRLG) information is considered to provide failure-indepen...
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In this paper, we propose a new technique, called a delayed locking technique, to improve the real-time performance of embedded Linux. The proposed technique employs the rule that entering a critical section is allowe...
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We propose a new random beamforming technique in forward link multiuser MIMO systems that exploits efficient multiuser diversity and spatial multiplexing gain. The common channels are allocated to more than one user s...
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