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81.
Rafael Xavier Lisandro Zambenedetti Granville Bruno Volckaert Filip De Turck 《Journal of Network and Systems Management》2017,25(4):699-734
Cloud technologies can provide elasticity to real-time audio and video (A/V) collaboration applications. However, cloud-based collaboration solutions generally operate on a best-effort basis, with neither delivery nor quality guarantees, and high-quality business focused solutions rely on dedicated infrastructure and hardware-based components. This article describes our 2-year of research in the EMD project, which targets to migrate a hardware-based and business focused A/V collaboration solution to a software-based platform hosted in the cloud, providing higher levels of elasticity and reliability. Our focus during this period was an educational collaboration scenario with teachers and students (locally present in the classroom or remotely following the classes). A model of collaboration streaming (e.g. network topology, codecs, stream, streaming workflow, software components) is defined as base for software deployment and preemptive VM allocation techniques. These heuristics are evaluated using a version of the CloudSim simulator extended to generate and simulate realistic collaboration scenarios, to manage network congestion and to monitor a.o. cost and session delay metrics. Our results show that the algorithms reduce costs when compared to previously designed approaches, having an effectiveness of 99% in meeting A/V collaboration setup deadlines, which is a stringent requirement for this collaboration application. 相似文献
82.
Sylvio BarbonJr Rodrigo Augusto Igawa Bruno Bogaz Zarpelão 《Multimedia Tools and Applications》2017,76(3):3213-3233
Compromising legitimate accounts has been the most used strategy to spread malicious content on OSN (Online Social Network). To address this problem, we propose a pure text mining approach to check if an account has been compromised based on its posts content. In the first step, the proposed approach extracts the writing style from the user account. The second step comprehends the k-Nearest Neighbors algorithm (k-NN) to evaluate the post content and identify the user. Finally, Baseline Updating (third step) consists of a continuous updating of the user baseline to support the current trends and seasonality issues of user’s posts. Experiments were carried out using a dataset from Twitter composed by tweets of 1000 users. All the three steps were individually evaluated, and the results show that the developed method is stable and can detect the compromised accounts. An important observation is the Baseline Updating contribution, which leads to an enhancement of accuracy superior of 60 %. Regarding average accuracy, the developed method achieved results over 93 %. 相似文献
83.
Stephen Wornom Hilde Ouvrard Maria Vittoria Salvetti Bruno Koobus Alain Dervieux 《Computers & Fluids》2011,47(1):44-50
Variational multiscale large-eddy simulations (VMS–LES) of the flow around a circular cylinder are carried out at different Reynolds numbers in the subcritical regime, viz. Re = 3900, 10,000 and 20,000, based on the cylinder diameter. A mixed finite-element/finite-volume discretization on unstructured grids is used. The separation between the largest and the smallest resolved scales is obtained through a variational projection operator and finite-volume cell agglomeration. The WALE subgrid scale model is used to account for the effects of the unresolved scales; in the VMS approach, it is only added to the smallest resolved ones. The capability of this methodology to accurately predict the aerodynamic forces acting on the cylinder and in capturing the flow features are evaluated for the different Reynolds numbers considered. The sensitivity of the results to different simulation parameters, viz. agglomeration level and numerical viscosity, is also investigated at Re = 20,000. 相似文献
84.
Bruno Salvy 《Theoretical computer science》2011,412(35):4469-4470
85.
Dynamic positioning of idle automated guided vehicles 总被引:2,自引:0,他引:2
Giuseppe Bruno Gianpaolo Ghiani Gennaro Improta 《Journal of Intelligent Manufacturing》2000,11(2):209-215
An automated guided vehicle (AGV) is a mobile robot commonly used to carry loads in material handling systems (MHS). Once a transfer is completed, an AGV stops at a home position, a point where it can park until it is assigned a new task. Determining the home positions is an important control problem with a direct influence on the overall performance of the MHS. The problem can be viewed as a location-allocation problem on a network. In this paper two fast and effective heuristics which dynamically determine the home positions are proposed. The methods were tested using two real-world instances. The obtained results are shown and discussed. 相似文献
86.
Modeling and visualizing molecular surfaces is an important and challenging task in bioinformatics. Such surfaces play an essential role in better understanding the chemical and physical properties of molecules. However, constructing and displaying molecular surfaces requires complex algorithms. In this article we introduce MetaMol, a new program that generates high-quality images in interactive time. In contrast with existing software that discretizes the surface with triangles or grids, our program is based on a GPU accelerated ray-casting algorithm that directly uses the piecewise-defined algebraic equation of the molecular skin surface. As a result, both better performances and higher quality are obtained. 相似文献
87.
Operations on basic data structures such as queues, priority queues, stacks, and counters can dominate the execution time
of a parallel program due to both their frequency and their coordination and contention overheads. There are considerable
performance payoffs in developing highly optimized, asynchronous, distributed, cache-conscious, parallel implementations of
such data structures. Such implementations may employ a variety of tricks to reduce latencies and avoid serial bottlenecks,
as long as the semantics of the data structure are preserved. The complexity of the implementation and the difficulty in reasoning
about asynchronous systems increases concerns regarding possible bugs in the implementation.
In this paper we consider postmortem, black-box procedures for testing whether a parallel data structure behaved correctly. We present the first systematic study of algorithms
and hardness results for such testing procedures, focusing on queues, priority queues, stacks, and counters, under various
important scenarios. Our results demonstrate the importance of selecting test data such that distinct values are inserted
into the data structure (as appropriate). In such cases we present an O(n) time algorithm for testing linearizable queues, an O(n log n) time algorithm for testing linearizable priority queues, and an O( np
2
) time algorithm for testing sequentially consistent queues, where n is the number of data structure operations and p is the number of processors. In contrast, we show that testing such data structures for executions with arbitrary input
values is NP-complete. Our results also help clarify the thresholds between scenarios that admit polynomial time solutions
and those that are NP-complete. Our algorithms are the first nontrivial algorithms for these problems. 相似文献
88.
Multimodal support to group dynamics 总被引:1,自引:1,他引:0
Fabio Pianesi Massimo Zancanaro Elena Not Chiara Leonardi Vera Falcon Bruno Lepri 《Personal and Ubiquitous Computing》2008,12(3):181-195
The complexity of group dynamics occurring in small group interactions often hinders the performance of teams. The availability
of rich multimodal information about what is going on during the meeting makes it possible to explore the possibility of providing
support to dysfunctional teams from facilitation to training sessions addressing both the individuals and the group as a whole.
A necessary step in this direction is that of capturing and understanding group dynamics. In this paper, we discuss a particular
scenario, in which meeting participants receive multimedia feedback on their relational behaviour, as a first step towards
increasing self-awareness. We describe the background and the motivation for a coding scheme for annotating meeting recordings
partially inspired by the Bales’ Interaction Process Analysis. This coding scheme was aimed at identifying suitable observable
behavioural sequences. The study is complemented with an experimental investigation on the acceptability of such a service.
相似文献
Fabio Pianesi (Corresponding author)Email: |
Massimo ZancanaroEmail: |
Elena NotEmail: |
Chiara LeonardiEmail: |
Vera FalconEmail: |
Bruno LepriEmail: |
89.
Basic algorithms have been proposed in the field of low-power (Yao, F., et al. in Proceedings of lEEE annual foundations of
computer science, pp. 374–382, 1995) which compute the minimum energy-schedule for a set of non-recurrent tasks (or jobs) scheduled under EDF on a dynamically
variable voltage processor. In this study, we propose improvements upon existing algorithms with lower average and worst-case
complexities. They are based on a new EDF feasibility test that helps to identify the “critical intervals”. The complexity
of this feasibility test depends on structural characteristics of the set of jobs. More precisely, it depends on how tasks
are included one in the other. The first step of the algorithm is to construct the Hasse diagram of the set of tasks where
the partial order is defined by the inclusion relation on the tasks. Then, the algorithm constructs the shortest path in a
geometrical representation at each level of the Hasse diagram. The optimal processor speed is chosen according to the maximal
slope of each path.
相似文献
Nicolas NavetEmail: |
90.
Bruno Juliá-Díaz Joseph M. Burdis Frank Tabakin 《Computer Physics Communications》2006,174(11):914-934
This Mathematica 5.2 package1 is a simulation of a Quantum Computer. The program provides a modular, instructive approach for generating the basic elements that make up a quantum circuit. The main emphasis is on using the density matrix, although an approach using state vectors is also implemented in the package. The package commands are defined in Qdensity.m which contains the tools needed in quantum circuits, e.g., multiqubit kets, projectors, gates, etc. Selected examples of the basic commands are presented here and a tutorial notebook, Tutorial.nb is provided with the package (available on our website) that serves as a full guide to the package. Finally, application is made to a variety of relevant cases, including Teleportation, Quantum Fourier transform, Grover's search and Shor's algorithm, in separate notebooks: QFT.nb, Teleportation.nb, Grover.nb and Shor.nb where each algorithm is explained in detail. Finally, two examples of the construction and manipulation of cluster states, which are part of “one way computing” ideas, are included as an additional tool in the notebook Cluster.nb. A Mathematica palette containing most commands in QDENSITY is also included: QDENSpalette.nb.