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Heterogeneous Networks (heterogeneous + network)
Selected AbstractsAn evaluation of European air pollution regulations for particulate matter monitored from a heterogeneous networkENVIRONMETRICS, Issue 8 2009Sujit K. Sahu Abstract Statistical methods are needed for evaluating many aspects of air pollution regulations increasingly adopted by many different governments in the European Union. The atmospheric particulate matter (PM) is an important air pollutant for which regulations have been issued recently. A challenging task here is to evaluate the regulations based on data monitored on a heterogeneous network where PM has been observed at a number of sites and a surrogate has been observed at some other sites. This paper develops a hierarchical Bayesian joint space,time model for the PM measurements and its surrogate between which the exact relationship is unknown, and applies the methods to analyse spatio -temporal data obtained from a number of sites in Northern Italy. The model is implemented using MCMC techniques and methods are developed to meet the regulatory demands. These enablefull inference with regard to process unknowns, calibration, validation, predictions in time and space and evaluation of regulatory standards. Copyright © 2008 John Wiley & Sons, Ltd. [source] Mobile locations: construction of home in a group of mobile transnational professionalsGLOBAL NETWORKS, Issue 1 2007MAGDALENA NOWICKA Abstract How do professionals constitute their homes under conditions of extensive mobility? The study is based on interviews with professionals working for an international organization who are chronically mobile. Despite their high mobility, they describe little difficulty constructing homes. Home can best be understood here not as a fixed location, but as a set of relationships, to both humans and non-humans. There are elements of spatial proximity, but also of distance, and homes may be defined by both objects present and excluded. They may be a focal point, but at the same time part of a heterogeneous network that spans localities as well as binds past and present. Home is therefore territorially defined, but only as an extended network rather than as a bounded location. [source] Parallel heterogeneous CBIR system for efficient hyperspectral image retrieval using spectral mixture analysisCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 9 2010Antonio J. Plaza Abstract The purpose of content-based image retrieval (CBIR) is to retrieve, from real data stored in a database, information that is relevant to a query. In remote sensing applications, the wealth of spectral information provided by latest-generation (hyperspectral) instruments has quickly introduced the need for parallel CBIR systems able to effectively retrieve features of interest from ever-growing data archives. To address this need, this paper develops a new parallel CBIR system that has been specifically designed to be run on heterogeneous networks of computers (HNOCs). These platforms have soon become a standard computing architecture in remote sensing missions due to the distributed nature of data repositories. The proposed heterogeneous system first extracts an image feature vector able to characterize image content with sub-pixel precision using spectral mixture analysis concepts, and then uses the obtained feature as a search reference. The system is validated using a complex hyperspectral image database, and implemented on several networks of workstations and a Beowulf cluster at NASA's Goddard Space Flight Center. Our experimental results indicate that the proposed parallel system can efficiently retrieve hyperspectral images from complex image databases by efficiently adapting to the underlying parallel platform on which it is run, regardless of the heterogeneity in the compute nodes and communication links that form such parallel platform. Copyright © 2009 John Wiley & Sons, Ltd. [source] Pipelines on heterogeneous systems: models and toolsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 9 2005F. Almeida Abstract We study the performance of pipeline algorithms in heterogeneous networks. The concept of heterogeneity is not only restricted to the differences in computational power of the nodes, but also refers to the network capabilities. We develop a skeleton tool that allows us an efficient block-cyclic mapping of pipelines on heterogeneous systems. The tool supports pipelines with a number of stages much larger than the number of physical processors available. We derive an analytical formula that allows us to predict the performance of pipelines in heterogeneous systems. According to the analytical complexity formula, numerical strategies to solve the optimal mapping problem are proposed. The computational results prove the accuracy of the predictions and effectiveness of the approach. Copyright © 2005 John Wiley & Sons, Ltd. [source] The heterogeneous distribution of functional synaptic connections in rat hippocampal dissociated neuron culturesELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 6 2009Suguru N. Kudoh Abstract The dynamics of functional synaptic connections are critical for information processing systems in the brain, such as perception and learning. Using rat hippocampal cells cultured on multielectrode arrays, we investigated the spatiotemporal pattern of spontaneous action potentials. The neurons developed connections and a characteristic high-frequency bursting (HFB) activity was observed transiently. After the period of HFB activity, the distribution of spontaneous activity changed drastically with the appearance of neurons with frequent electrical activity and neurons with little activity in the network. The functional connections of all the combinations of recorded spike trains were estimated and depicted simultaneously in a Connection Map. This map revealed that each culture contained hublike neurons with many functional connections, suggesting that the cultures of dissociated rat hippocampal neurons on multielectrode arrays formed heterogeneous networks of functional connections. In addition, the functional connections were drastically reorganized after the induction of synaptic potentiation, and novel hub neurons emerged. These results indicate that spontaneous activity is enough to construct dynamic assemblies of neurons connected to each other by functional synaptic connections, and that synaptic potentiation can induce reorganization of such assemblies of neurons. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(6): 41,49, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10063 [source] A fuzzy approach to active usage parameter control in IEEE 802.11b wireless networksEXPERT SYSTEMS, Issue 5 2004David Soud Abstract: Usage parameter control (UPC) provides support for quality of service across heterogeneous networks. For the network operator UPC assists in limiting network usage through traffic shaping, to prevent unacceptable delay. Traditional methods to apply UPC involve the generic cell rate algorithm or ,leaky bucket' algorithm, now commonly implemented in asynchronous transmission mode networks. This paper proposes a novel form of UPC for 802.11b wireless networks. The method proposed measures the rate of individual network flows to actively manage link utilization using a fuzzy logic controller (FLC). The FLC monitors the flow rate and adjusts the sending transmissions to stabilize flows as close to the optimum desired rate as possible. Imposing UPC and using the FLC within a packet switched TCP network enforces cooperation between competing streams of traffic. After carrying out experiments within a wireless network, the results obtained significantly improve upon a ,best effort' service. [source] A terminal-controlled vertical handover decision scheme in IEEE 802.21-enabled heterogeneous wireless networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 7 2009Jung-Shyr Wu Abstract The seamless internetworking among heterogeneous networks is in great demand to provide ,always-on' connectivity services with quality of service (QoS) provision, anywhere at anytime. The integration of wireless-fidelity (Wi-Fi) and wireless metropolitan area networks (WiMAX) networks can combine their best features to provide ubiquitous access, while mediating the weakness of both networks. While it is challenging to obtain optimized handover decision-based dynamic QoS information, users can improve their perceived QoS by using the terminal-controlled handover decision in a single device equipped with multiple radio interfaces. The IEEE 802.21 aims at providing a framework that defines media-independent handover (MIH) mechanism that supports seamless handover across heterogeneous networks. In this paper, an multiple attributes decision making-based terminal-controlled vertical handover decision scheme using MIH services is proposed in the integrated Wi-Fi and WiMAX networks to provide ,always-on' connectivity QoS services. The simulation results show that the proposed scheme provides smaller handover times and lower dropping rate than the RSS-based and cost function-based vertical handover schemes. Copyright © 2009 John Wiley & Sons, Ltd. [source] Effort/gains dynamics in heterogeneous networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 4 2008L. Mamatas Abstract We investigate the behaviour of TCP(,, ,) protocols in the presence of wireless networks. We seek an answer to strategic issues of maximizing energy and bandwidth exploitation, without damaging the dynamics of multiple-flow equilibrium. We take a fresh perspective on protocol design: What is the return of the effort that a protocol expends? Can we achieve more gains with less effort? We study first the design assumptions of TCP(,, ,) protocols and discuss the impact of equation-based modulation of , and , on protocol efficiency. We introduce two new measures to capture protocol behaviour: the ,Extra Energy Expenditure' and the ,Unexploited Available Resource Index'. We confirm experimentally that, in general, smoothness and responsiveness constitute a tradeoff; however, we show that this tradeoff does not graft its dynamics into a conservative/aggressive behaviour, as it is traditionally believed. We uncover patterns of unjustified tactics; our results suggest that an adaptive congestion control algorithm is needed to integrate the dynamics of heterogeneous networks into protocol behaviour. Copyright © 2007 John Wiley & Sons, Ltd. [source] Multimedia transmission with adaptive QoS based on real-time protocolsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 3 2003Ch. Bouras Abstract In this paper, we describe a mechanism for adaptive transmission of multimedia data, which is based on real-time protocols. The proposed mechanism can be used for unicast or multicast transmission of multimedia data over heterogeneous networks, like the Internet, and has the capability to adapt the transmission of the multimedia data to network changes. In addition, the implemented mechanism uses an inter-receiver fairness function in order to treat the group of clients with fairness during the multicast transmission in a heterogeneous environment. The proposed mechanism uses a ,friendly' to the network users congestion control policy to control the transmission of the multimedia data. We implement a prototype application based on the proposed mechanism and we evaluate the proposed mechanism both in unicast and multicast transmission through a number of experiment and a number of simulations in order to examine its fairness to a group of clients and its behaviour against transport protocols (TCP) and UDP data streams. Copyright © 2003 John Wiley & Sons, Ltd. [source] A heterogeneous-network aided public-key management scheme for mobile ad hoc networksINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 1 2007Yuh-Min Tseng A mobile ad hoc network does not require fixed infrastructure to construct connections among nodes. Due to the particular characteristics of mobile ad hoc networks, most existing secure protocols in wired networks do not meet the security requirements for mobile ad hoc networks. Most secure protocols in mobile ad hoc networks, such as secure routing, key agreement and secure group communication protocols, assume that all nodes must have pre-shared a secret, or pre-obtained public-key certificates before joining the network. However, this assumption has a practical weakness for some emergency applications, because some nodes without pre-obtained certificates will be unable to join the network. In this paper, a heterogeneous-network aided public-key management scheme for mobile ad hoc networks is proposed to remedy this weakness. Several heterogeneous networks (such as satellite, unmanned aerial vehicle, or cellular networks) provide wider service areas and ubiquitous connectivity. We adopt these wide-covered heterogeneous networks to design a secure certificate distribution scheme that allows a mobile node without a pre-obtained certificate to instantly get a certificate using the communication channel constructed by these wide-covered heterogeneous networks. Therefore, this scheme enhances the security infrastructure of public key management for mobile ad hoc networks. Copyright © 2006 John Wiley & Sons, Ltd. [source] An architecture for Internet service via broadband satellite networksINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 1 2001Vijay G. Bharadwaj Abstract High bandwidth satellites offer the promise of a rapidly deployable communications infrastructure with a natural support for mobility. However, many widely used versions of the Transmission Control Protocol perform poorly over satellite links, and this presents an obstacle to the deployment of such systems. We present an architecture that overcomes these problems and allows easy integration of heterogeneous networks into the larger Internet. We also present some results from our initial implementation, which uses TCP connection splitting to improve TCP performance over satellite links. Copyright © 2001 John Wiley & Sons, Ltd. [source] Digital diasporas and governance in semi-authoritarian states: the case of the Egyptian Copts,PUBLIC ADMINISTRATION & DEVELOPMENT, Issue 3 2005Jennifer M. Brinkerhoff Abstract This article explores the potential role of diasporas and information technology (IT) in fostering good governance in semi-authoritarian states. Following a review of the literature on good governance and information technology, the case of the Egyptian Copt community and its diaspora is explored, focusing on the activities of the U.S. Copt Association. It is argued that, whether or not it is an explicit objective, the U.S. Copt Association is supporting improved and more democratic governance in Egypt. The case confirms that heterogeneous networks of communication and people can promote good governance, even for the socially excluded and disempowered in a weakly penetrated state. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||||||||