70,391 research outputs found
Self-describing and data propagation model for data distribution service
Abstract. To realize real-time information sharing in generic platforms, it is especially important to support dynamic message structure changes. For the case of IDL, it is necessary to rewrite applications to change data sample structures. In this paper, we propose a dynamic reconfiguration scheme of data sample structures for DDS. Instead of using IDL, which is the static data sample structure model of DDS, we use a self describing model using data sample schema, as a dynamic data sample structure model to support dynamic reconfiguration of data sample structures. We also propose a data propagation model to provide data persistency in distributed environments. We guarantee persistency by transferring data samples through relay nodes to the receiving nodes, which have not participated in the data distribution network at the data sample distribution time. The proposed schemes can be utilized to support data sample structure changes during operation time and to provide data persistency in various environments, such as real-time enterprise environments and connection-less internet environments
A review of wildland fire spread modelling, 1990-present 3: Mathematical analogues and simulation models
In recent years, advances in computational power and spatial data analysis
(GIS, remote sensing, etc) have led to an increase in attempts to model the
spread and behvaiour of wildland fires across the landscape. This series of
review papers endeavours to critically and comprehensively review all types of
surface fire spread models developed since 1990. This paper reviews models of a
simulation or mathematical analogue nature. Most simulation models are
implementations of existing empirical or quasi-empirical models and their
primary function is to convert these generally one dimensional models to two
dimensions and then propagate a fire perimeter across a modelled landscape.
Mathematical analogue models are those that are based on some mathematical
conceit (rather than a physical representation of fire spread) that
coincidentally simulates the spread of fire. Other papers in the series review
models of an physical or quasi-physical nature and empirical or quasi-empirical
nature. Many models are extensions or refinements of models developed before
1990. Where this is the case, these models are also discussed but much less
comprehensively.Comment: 20 pages + 9 pages references + 1 page figures. Submitted to the
International Journal of Wildland Fir
Simulation technique for available bandwidth estimation
The paper proposes a method for measuring available bandwidth, based on
testing network packets of various sizes (Variable Packet Size method, VPS).
The boundaries of applicability of the model have been found, which are based
on the accuracy of measurements of packet delays, also we have derived a
formula of measuring the upper limit of bandwidth. The computer simulation has
been performed and relationship between the measurement error of available
bandwidth and the number of measurements has been found. Experimental
verification with the use of RIPE Test Box measuring system has shown that the
suggested method has advantages over existing measurement techniques. Pathload
utility has been chosen as an alternative technique of measurement, and to
ensure reliable results statistics by SNMP agent has been withdrawn directly
from the router
Mitigating Epidemics through Mobile Micro-measures
Epidemics of infectious diseases are among the largest threats to the quality
of life and the economic and social well-being of developing countries. The
arsenal of measures against such epidemics is well-established, but costly and
insufficient to mitigate their impact. In this paper, we argue that mobile
technology adds a powerful weapon to this arsenal, because (a) mobile devices
endow us with the unprecedented ability to measure and model the detailed
behavioral patterns of the affected population, and (b) they enable the
delivery of personalized behavioral recommendations to individuals in real
time. We combine these two ideas and propose several strategies to generate
such recommendations from mobility patterns. The goal of each strategy is a
large reduction in infections, with a small impact on the normal course of
daily life. We evaluate these strategies over the Orange D4D dataset and show
the benefit of mobile micro-measures, even if only a fraction of the population
participates. These preliminary results demonstrate the potential of mobile
technology to complement other measures like vaccination and quarantines
against disease epidemics.Comment: Presented at NetMob 2013, Bosto
Performance analysis of downlink shared channels in a UMTS network
In light of the expected growth in wireless data communications and the commonly anticipated up/downlink asymmetry, we present a performance analysis of downlink data transfer over \textsc{d}ownlink \textsc{s}hared \textsc{ch}annels (\textsc{dsch}s), arguably the most efficient \textsc{umts} transport channel for medium-to-large data transfers. It is our objective to provide qualitative insight in the different aspects that influence the data \textsc{q}uality \textsc{o}f \textsc{s}ervice (\textsc{qos}). As a most principal factor, the data traffic load affects the data \textsc{qos} in two distinct manners: {\em (i)} a heavier data traffic load implies a greater competition for \textsc{dsch} resources and thus longer transfer delays; and {\em (ii)} since each data call served on a \textsc{dsch} must maintain an \textsc{a}ssociated \textsc{d}edicated \textsc{ch}annel (\textsc{a}-\textsc{dch}) for signalling purposes, a heavier data traffic load implies a higher interference level, a higher frame error rate and thus a lower effective aggregate \textsc{dsch} throughput: {\em the greater the demand for service, the smaller the aggregate service capacity.} The latter effect is further amplified in a multicellular scenario, where a \textsc{dsch} experiences additional interference from the \textsc{dsch}s and \textsc{a}-\textsc{dch}s in surrounding cells, causing a further degradation of its effective throughput. Following an insightful two-stage performance evaluation approach, which segregates the interference aspects from the traffic dynamics, a set of numerical experiments is executed in order to demonstrate these effects and obtain qualitative insight in the impact of various system aspects on the data \textsc{qos}
Estimating the Propagation of Interdependent Cascading Outages with Multi-Type Branching Processes
In this paper, the multi-type branching process is applied to describe the
statistics and interdependencies of line outages, the load shed, and isolated
buses. The offspring mean matrix of the multi-type branching process is
estimated by the Expectation Maximization (EM) algorithm and can quantify the
extent of outage propagation. The joint distribution of two types of outages is
estimated by the multi-type branching process via the Lagrange-Good inversion.
The proposed model is tested with data generated by the AC OPA cascading
simulations on the IEEE 118-bus system. The largest eigenvalues of the
offspring mean matrix indicate that the system is closer to criticality when
considering the interdependence of different types of outages. Compared with
empirically estimating the joint distribution of the total outages, good
estimate is obtained by using the multitype branching process with a much
smaller number of cascades, thus greatly improving the efficiency. It is shown
that the multitype branching process can effectively predict the distribution
of the load shed and isolated buses and their conditional largest possible
total outages even when there are no data of them.Comment: Accepted by IEEE Transactions on Power System
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