3,804 research outputs found
Spreading Processes over Socio-Technical Networks with Phase-Type Transmissions
Most theoretical tools available for the analysis of spreading processes over
networks assume exponentially distributed transmission and recovery times. In
practice, the empirical distribution of transmission times for many real
spreading processes, such as the spread of web content through the Internet,
are far from exponential. To bridge this gap between theory and practice, we
propose a methodology to model and analyze spreading processes with arbitrary
transmission times using phase-type distributions. Phase-type distributions are
a family of distributions that is dense in the set of positive-valued
distributions and can be used to approximate any given distributions. To
illustrate our methodology, we focus on a popular model of spreading over
networks: the susceptible-infected-susceptible (SIS) networked model. In the
standard version of this model, individuals informed about a piece of
information transmit this piece to its neighbors at an exponential rate. In
this paper, we extend this model to the case of transmission rates following a
phase-type distribution. Using this extended model, we analyze the dynamics of
the spread based on a vectorial representations of phase-type distributions. We
illustrate our results by analyzing spreading processes over networks with
transmission and recovery rates following a Weibull distribution
Dissemination of Health Information within Social Networks
In this paper, we investigate, how information about a common food born
health hazard, known as Campylobacter, spreads once it was delivered to a
random sample of individuals in France. The central question addressed here is
how individual characteristics and the various aspects of social network
influence the spread of information. A key claim of our paper is that
information diffusion processes occur in a patterned network of social ties of
heterogeneous actors. Our percolation models show that the characteristics of
the recipients of the information matter as much if not more than the
characteristics of the sender of the information in deciding whether the
information will be transmitted through a particular tie. We also found that at
least for this particular advisory, it is not the perceived need of the
recipients for the information that matters but their general interest in the
topic
Competing contagion processes: Complex contagion triggered by simple contagion
Empirical evidence reveals that contagion processes often occur with
competition of simple and complex contagion, meaning that while some agents
follow simple contagion, others follow complex contagion. Simple contagion
refers to spreading processes induced by a single exposure to a contagious
entity while complex contagion demands multiple exposures for transmission.
Inspired by this observation, we propose a model of contagion dynamics with a
transmission probability that initiates a process of complex contagion. With
this probability nodes subject to simple contagion get adopted and trigger a
process of complex contagion. We obtain a phase diagram in the parameter space
of the transmission probability and the fraction of nodes subject to complex
contagion. Our contagion model exhibits a rich variety of phase transitions
such as continuous, discontinuous, and hybrid phase transitions, criticality,
tricriticality, and double transitions. In particular, we find a double phase
transition showing a continuous transition and a following discontinuous
transition in the density of adopted nodes with respect to the transmission
probability. We show that the double transition occurs with an intermediate
phase in which nodes following simple contagion become adopted but nodes with
complex contagion remain susceptible.Comment: 9 pages, 4 figure
Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)
Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression
Epidemic spreading and information dissemination in technological and social systems
In dieser Arbeit betrachten wir Probleme aus dem Bereich der Nachrichten- und Krankheitsverbreitung in dynamischen als auch statischen Strukturen aus dem Gebiet der technologischen und der sozialen Netzwerke. Als erste Fragestellung untersuchen wir, ob ein verteiltes Protokoll zur Nachrichtenverbreitung in Netzwerken mit Power Law Knotengradverteilung existiert, so dass sich die Knotengradverteilung nicht negativ bemerkbar macht. Wir präsentieren ein Protokoll, welches mit hoher Wahrscheinlichkeit nur O(log n) viele Runden mit O(n loglog n) vielen Nachrichten benötigt um alle n Knoten zu informieren. Als nächstes untersuchen wir wie Strategien zur Eindämmung einer solchen Ausbreitung aussehen könnten. Sei V der für die Ausbreitung der schädlichen Nachricht verantwortliche Prozess. Wir lassen V sich von jedem infizierten Knoten über eine konstante Anzahl von Verbindungen verbreiten. Unsere Strategie zur Bekämpfung von V wird an jedem infizierten Knoten nach einer konstanten Anzahl von Schritten aktiviert. Ist der minimale Knotengrad loglog n, so zeigen wir, dass die Immunisierung der direkten Nachbarschaft ausreicht um die Infektion mit hoher Wahrscheinlichkeit zu eliminieren. Ist der minimale Knotengrad eine Konstante und immunisiert jeder infizierte Knoten v alle Knoten in seiner O(log(d(v)))-Nachbarschaft, wobei d(v) den Knotengrad von Knoten v bezeichnet, lassen sich ähnliche Abschätzungen zeigen. Zudem betrachten wir eine Epidemie in einer städtischen Umgebung mit mobilen Einwohnern. Werden keinerlei Gegenmaßnahmen getroffen, so bleibt dennoch mit hoher Wahrscheinlichkeit ein polynomieller Anteil der Population von der Epidemie unberührt. Werden jedoch Gegenmaßnahmen genutzt, so werden mit Wahrscheinlichkeit 1-o(1) nur polylogarithmisch viele Individuen infiziert.In this thesis we consider the problems of information dissemination and epidemic spreading in dynamic as well as static technological and social networks. We start by wondering if there might be a fast decentralized dissemination protocol, such that a power law degree distribution does not slow down the dissemination process in the network. We present a protocol that informs all n nodes within O(log n) many rounds using O(n loglog n) many transmissions with high probability. But how do we design a counteracting dissemination process to combat the malicious one denoted by V? Suppose V uses a constant number of randomly chosen connections of each infected node to infect others for one time only and suppose that the counteracting dissemination process is activated on each infected node after a constant delay. We show that it suffices to immunize the neighborhood of each infected node, provided the minimum degree of the network is loglog n. Otherwise, if the minimum degree of the network is constant, we propose to immunize every node within O(log(d(v))) many hops of each infected node v, where d(v) denotes the degree of node v. Executing these strategies we prove that V does not infect more than o(n) many nodes until it is eliminated with high probability. Finally, we take mobility into account and examine an epidemic outbreak in an urban environment inhabited by mobile individuals on a small and on a large scale. Amongst others, we show that at least a polynomial fraction of the individuals remains uninfected even if they do not respond to the epidemic outbreak in any way. However, if the epidemic outbreak does influence the individual's behavioral pattern and certain countermeasures are applied, then only a polylogarithmic amount of individuals is infected until the epidemic is embanked with probability 1-o(1).Tag der Verteidigung: 24.10.2014Paderborn, Univ., Diss., 201
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