Vehicular ad hoc networks (VANETs) are envisaged to become a flexible platform for monitoring road traffic, which will gradually replace more cumbersome fixed sensor deployments. The efficacy of vehicle-assisted traff...
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ISBN:
(纸本)9781605581668
Vehicular ad hoc networks (VANETs) are envisaged to become a flexible platform for monitoring road traffic, which will gradually replace more cumbersome fixed sensor deployments. The efficacy of vehicle-assisted traffic monitoring systems depends on the freshness of traffic data that they can deliver to users, and the bandwidth used to do so. Clearly, high data freshness will allow users to estimate trip times accurately, and to select the fastest route to a destination. Low bandwidth utilization will allow the traffic monitoring application to coexist symbiotically with a wide variety of vehicle-based applications, ranging from road safety to advertising and entertainment. In this paper, we investigate the problem of minimizing the bandwidth utilization of a vehicle-assisted traffic monitoring system, whilst adhering to user-defined requirements for data freshness. The novelty of our approach is that we jointly optimize two intertwined aspects of traffic monitoring: data acquisition and data forwarding. We investigate how their combined operation trades data freshness for bandwidth utilization, and we propose a novel mechanism that fine-tunes their parameters to optimize the overall system performance. Our mechanism is evaluated using realistic vehicular traces on a real city map. Copyright 2009 acm.
This paper proposes a novel method of achieving fast networking in hosted virtual machine (VM) environments. This method, called socket-outsourcing, replaces the socket layer in a guest operating system (OS) with the ...
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ISBN:
(纸本)9781605581668
This paper proposes a novel method of achieving fast networking in hosted virtual machine (VM) environments. This method, called socket-outsourcing, replaces the socket layer in a guest operating system (OS) with the socket layer of the host OS. Socket-outsourcing increases network performance by eliminating duplicate message copying in both the host OS and the guest OS. Furthermore, socket-outsourcing significantly enhances inter-VM communication within the same host OS since it enables network packets to bypass the protocol stack in guest OSes. Socket-outsourcing was implemented in two representative operating systems (Linux and NetBSD) and on two virtual machine monitors (Linux KVM and PansyVM). These virtual machine monitors provided support for socket-outsourcing through shard memory, event queues, and VM-specific Remote Procedure Call between a guest OS and a host OS. The experimental results revealed that a guest OS outsourcing the socket layer achieved the same network throughput as a native OS using up to four Gigabit Ethernet links. Moreover, the benchmark results obtained from an N-tier Web application that generated a significant amount of inter-VM communication indicated that socket-outsourcing improved performance by up to 45 percent compared with conventional hosted VM environments. Copyright 2009 acm.
The prediction of the correct secondary structures of large RNAs is one of the unsolved challenges of computational molecular biology. Among the major obstacles is the fact that accurate calculations scale as O(n4), s...
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ISBN:
(纸本)9781605581668
The prediction of the correct secondary structures of large RNAs is one of the unsolved challenges of computational molecular biology. Among the major obstacles is the fact that accurate calculations scale as O(n4), so the computational requirements become prohibitive as the length increases. Existing folding programs implement heuristics and approximations to overcome these limitations. We present a new parallel multicore and scalable program called GTfold, which is one to two orders of magnitude faster than the de facto standard programs and achieves comparable accuracy of prediction. Development of GTfold opens up a new path for the algorithmic improvements and application of an improved thermodynamic model to increase the prediction accuracy. In this paper we analyze the algorithm's concurrency and describe the parallelism for a shared memory environment such as a symmetric multiprocessor or multicore chip. In a remarkable demonstration, GTfold now optimally folds 11 picornaviral RNA sequences ranging from 7100 to 8200 nucleotides in 8 minutes, compared with the two months it took in a previous study. We are seeing a paradigm shift to multicore chips and parallelism must be explicitly addressed to continue gaining performance with each new generation of systems. We also show that the exact algorithms like internal loop speedup can be implemented with our method in an affordable amount of time. GTfold is freely available as open source from our website. Copyright 2009 acm.
Self-assembly is an autonomous process by which small simple parts assemble into larger and more complex objects. Self-assembly occurs in nature, for example, when atoms combine to form molecules, and molecules combin...
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ISBN:
(纸本)9781605581668
Self-assembly is an autonomous process by which small simple parts assemble into larger and more complex objects. Self-assembly occurs in nature, for example, when atoms combine to form molecules, and molecules combine to form crystals. It has been suggested that intricate self-assembly schemes will ultimately be useful for circuit fabrication, nanorobotics, DNA computing, and amorphous computing [2, 7]. To study the process of self-assembly we use the Tile Assembly Model proposed by Rothemund and Winfree [5]. This model considers the assembly of square blocks called "tiles" and a set of glues called "binding domains". Each binding domain has a strength. Each of the four sides of a tile can have a glue on it that determines interactions with neighbouring tiles. The two neighbouring tiles form a bond if the binding domains on the touching sides are the same. The strength of this bond is the strength of the matching binding domain. The process of self-assembly is initiated by a single seed tile and proceeds by attaching tiles one by one. A tile can only attach to the growing complex if it binds strongly enough, i.e., if the sum of the strengths of its bonds to the existing complex is at least the temperature τ. It is assumed that there is an infinite supply of tiles of each tile type. When this growing process stops, i.e., no tile can be attached to the existing complex, we say that the tile system has assembled this shape. A tile system is specified by the seed tile, the set of tile types, the strengths of glues and the temperature. The physical plausibility and relevance of this abstraction was demonstrated by simple self-assembling systems of tiles built out of certain types of DNA molecules [3, 4]. In this paper we only consider self-assembly at temperature τ = 1. Self-assemblies at temperature τ > 1 have been considered in [5, 6, 1]. A measure of complexity of self-assembly is the minimum number of distinct tile types needed to uniquely assemble a certain shape (
In this paper we present our efforts to measure different quality aspects of large-scale, binary software. We apply four well established metrics to binary versions of Windows and Debian Linux, analyze our results and...
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This paper describes a software architecture approach which leads to a simplified solution for information retrieval in multiple backend systems. It is mainly based on the core ideas of service oriented and pattern or...
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Peerless Technologies Corporation and team members Clear Creek applied Technologies (CCAT) and Science Applications International Corporation (SAIC) propose our exclusive uniform, yet extensible, virtual platform, nam...
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Many Universities and Colleges are building interdisciplinary programs between engineering and fine arts that focus on games, special effects, animation and other areas that require interdisciplinary efforts. This is ...
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