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81.
In this paper we explore the interest of computational intelligence tools in the management of heterogeneous communication networks, specifically to predict congestion, failures and other anomalies in the network that may eventually lead to degradation of the quality of offered services. We show two different applications based on neural and neuro-fuzzy systems for quality of service (QoS) management in next generation networks for voice and video service over heterogeneous Internet protocol (V2oIP) services. The two examples explained in this paper attempt to predict the communication network resources for new incoming calls, and visualizing the QoS of a communication network by means of self-organizing maps. 相似文献
82.
Rafael Antonello Stênio Fernandes Josilene Moreira Paulo Cunha Carlos Kamienski Djamel Sadok 《Multimedia Systems》2009,15(1):33-47
Virtual Worlds (VW), such as Massive Multiplayer Online Social Games, have been gaining increasing attention in the last few
years, mainly due to the new way users interact with them. However, little effort has been devoted to understand their traffic
profile and the implications to the traffic management area. With the current growing rate of VWs’ usage, their traffic demand
could eventually impose a significant burden on the operation of a typical Internet Service Provider (ISP) network. In this
paper, we seek to understand the traffic behavior of an increasingly popular VW application, namely Second Life (SL), from
both the connection and network level perspectives. We also show results of a traffic analysis of a SL client, when an avatar
performs different actions in the VW, at different places and under different network conditions. Our results show that SL
makes intensive use of network resources (mostly bandwidth), since the capacity needed for having a full SL experience (listening
to live music) may reach 500 kbps. We then extend the traffic analysis work on SL by providing analytical models for its traffic
profile. We aim at helping the network management and planning area to estimate the impact of an intense use of such VW on
access links or core networks. Such synthetic models are also useful to the networking research community for the use in network
simulations. 相似文献
83.
Israel Becerra Rafael Murrieta-Cid Raul Monroy Seth Hutchinson Jean-Paul Laumond 《Autonomous Robots》2016,40(2):395-423
In this paper, we address the problem of determining whether a mobile robot, called the pursuer, is able to maintain strong mutual visibility (a visibility notion between regions over a convex partition of the environment) of an antagonist agent, called the evader. We frame the problem as a non cooperative game. We consider the case in which the pursuer and the evader move at bounded speed, traveling in a known polygonal environment with or without holes, and in which there are no restrictions as to the distance that might separate the agents. Unlike our previous efforts (Murrieta-Cid et al. in Int J Robot Res 26:233–253, 2007), we give special attention to the combinatorial problem that arises when searching for a solution through visiting several locations in an environment with obstacles. In this paper we take a step further, namely, we assume an antagonistic evader who moves continuously and unpredictably, but with a constraint over its set of admissible motion policies, as the evader moves in the shortest-path roadmap, also called the reduced visibility graph (RVG). The pursuer does not know which among the possible paths over the RVG the evader will choose, but the pursuer is free to move within all the environment. We provide a constructive method to solve the decision problem of determining whether or not the pursuer is able to maintain strong mutual visibility of the evader. This method is based on an algorithm that computes the safe areas (areas that keep evader surveillance) at all times. We prove decidability of this problem, and provide a complexity measure to this evader surveillance game; both contributions hold for any general polygonal environment that might or not contain holes. All our algorithms have been implemented and we show simulation results. 相似文献
84.
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
85.
Simultaneous aligning and smoothing of surface triangulations 总被引:1,自引:0,他引:1
Jos�� M. Escobar Rafael Montenegro Eduardo Rodr��guez Gustavo Montero 《Engineering with Computers》2011,27(1):17-29
In this work we develop a procedure to deform a given surface triangulation to obtain its alignment with interior curves.
These curves are defined by splines in a parametric space and, subsequently, mapped to the surface triangulation. We have
restricted our study to orthogonal mapping, so we require the curves to be included in a patch of the surface that can be
orthogonally projected onto a plane (our parametric space). For example, the curves can represent interfaces between different
materials or boundary conditions, internal boundaries or feature lines. Another setting in which this procedure can be used
is the adaption of a reference mesh to changing curves in the course of an evolutionary process. Specifically, we propose
a new method that moves the nodes of the mesh, maintaining its topology, in order to achieve two objectives simultaneously:
the piecewise approximation of the curves by edges of the surface triangulation and the optimization of the resulting mesh.
We will designate this procedure as projecting/smoothing method and it is based on the smoothing technique that we have introduced for surface triangulations in previous works. The
mesh quality improvement is obtained by an iterative process where each free node is moved to a new position that minimizes a certain objective function. The minimization process is done on the parametric
plane attending to the surface piece-wise approximation and to an algebraic quality measure (mean ratio) of the set of triangles that are connected to the free node. So, the 3-D local projecting/smoothing problem is reduced to a 2-D optimization problem. Several applications of this method
are presented. 相似文献
86.
Angel Rivas Casado Rafael Martinez‐Tomás Antonio Fernández‐Caballero 《Expert Systems》2011,28(5):488-501
This work presents a multi‐agent system for knowledge‐based high‐level event composition, which interprets activities, behaviour and situations semantically in a scenario with multi‐sensory monitoring. A perception agent (plurisensory agent and visual agent)‐based structure is presented. The agents process the sensor information and identify (agent decision system) significant changes in the monitored signals, which they send as simple events to the composition agent that searches for and identifies pre‐defined patterns as higher‐level semantic composed events. The structure has a methodology and a set of tools that facilitate its development and application to different fields without having to start from scratch. This creates an environment to develop knowledge‐based systems generally for event composition. The application task of our work is surveillance, and event composition/inference examples are shown which characterize an alarming situation in the scene and resolve identification and tracking problems of people in the scenario being monitored. 相似文献
87.
Francisco García‐Sánchez Luís Álvarez Sabucedo Rodrigo Martínez‐Béjar Luís Anido Rifón Rafael Valencia‐García Juan Miguel Gómez 《Expert Systems》2011,28(5):416-436
The increasing volume of eGovernment‐related services is demanding new approaches for service integration and interoperability in this domain. Semantic web (SW) technologies and applications can leverage the potential of eGovernment service integration and discovery, thus tackling the problems of semantic heterogeneity characterizing eGovernment information sources and the different levels of interoperability. eGovernment services will therefore be semantically described in the foreseeable future. In an environment with semantically annotated services, software agents are essential as the entities responsible for exploiting the semantic content in order to automate some tasks, and so enhance the user's experience. In this paper, we present a framework that provides a seamless integration of semantic web services and intelligent agents technologies by making use of ontologies to facilitate their interoperation. The proposed framework can assist in the development of powerful and flexible distributed systems in complex, dynamic, heterogeneous, unpredictable and open environments. Our approach is backed up by a proof‐of‐concept implementation, where the breakthrough of integrating disparate eGovernment services has been tested. 相似文献
88.
Jorge Larrey-Ruiz Rafael Verdú-MonederoJuan Morales-Sánchez Jesús Angulo 《Image and vision computing》2011,29(9):620-630
The present work is intended to address two of the major difficulties that can be found when tackling the estimation of the local orientation of the data in a scene, a task which is usually accomplished by means of the computation of the structure tensor-based directional field. On one hand, the orientation information only exists in the non-homogeneous regions of the dataset, while it is zero in the areas where the gradient (i.e. the first-order intensity variation) remains constant. Due to this lack of information, there are many cases in which the overall shape of the represented objects cannot be precisely inferred from the directional field. On the other hand, the orientation estimation is highly dependent on the particular choice of the averaging window used for its computation (since a collection of neighboring gradient vectors is needed to obtain a dominant orientation), typically resulting in vector fields which vary from very irregular (thus yielding a noisy estimation) to very uniform (but at the expense of a loss of angular resolution). The proposed solution to both drawbacks is the regularization of the directional field; this process extends smoothly the previously computed vectors to the whole dataset while preserving the angular information of relevant structures. With this purpose, the paper introduces a suitable mathematical framework and deals with the d-dimensional variational formulation which is derived from it. The proposed formulation is finally translated into the frequency domain in order to obtain an increase of insight on the regularization problem, which can be understood as a low-pass filtering of the directional field. The frequency domain point of view also allows for an efficient implementation of the resulting iterative algorithm. Simulation experiments involving datasets of different dimensionality prove the validity of the theoretical approach. 相似文献
89.
The operation principle of the mass-controlled capillary viscometer is presented for a Newtonian liquid. The derived equation for the temporal changes of the mass in a liquid column draining under gravity through a discharge capillary tube accounts self-consistently for the inertial convective term associated with the acceleration effect. The viscosity of water measured at different temperatures using the new approach is in good agreement with literature data. 相似文献
90.
In a recent article, Prinz, Bucher, and Marder (2004) addressed the fundamental question of whether neural systems are built with a fixed blueprint of tightly controlled parameters or in a way in which properties can vary largely from one individual to another, using a database modeling approach. Here, we examine the main conclusion that neural circuits indeed are built with largely varying parameters in the light of our own experimental and modeling observations. We critically discuss the experimental and theoretical evidence, including the general adequacy of database approaches for questions of this kind, and come to the conclusion that the last word for this fundamental question has not yet been spoken. 相似文献