4,866 research outputs found
Towards designing robust coupled networks
Natural and technological interdependent systems have been shown to be highly
vulnerable due to cascading failures and an abrupt collapse of global
connectivity under initial failure. Mitigating the risk by partial
disconnection endangers their functionality. Here we propose a systematic
strategy of selecting a minimum number of autonomous nodes that guarantee a
smooth transition in robustness. Our method which is based on betweenness is
tested on various examples including the famous 2003 electrical blackout of
Italy. We show that, with this strategy, the necessary number of autonomous
nodes can be reduced by a factor of five compared to a random choice. We also
find that the transition to abrupt collapse follows tricritical scaling
characterized by a set of exponents which is independent on the protection
strategy
Network robustness improvement via long-range links
Abstract Many systems are today modelled as complex networks, since this representation has been proven being an effective approach for understanding and controlling many real-world phenomena. A significant area of interest and research is that of networks robustness, which aims to explore to what extent a network keeps working when failures occur in its structure and how disruptions can be avoided. In this paper, we introduce the idea of exploiting long-range links to improve the robustness of Scale-Free (SF) networks. Several experiments are carried out by attacking the networks before and after the addition of links between the farthest nodes, and the results show that this approach effectively improves the SF network correct functionalities better than other commonly used strategies
Towards real-world complexity: an introduction to multiplex networks
Many real-world complex systems are best modeled by multiplex networks of
interacting network layers. The multiplex network study is one of the newest
and hottest themes in the statistical physics of complex networks. Pioneering
studies have proven that the multiplexity has broad impact on the system's
structure and function. In this Colloquium paper, we present an organized
review of the growing body of current literature on multiplex networks by
categorizing existing studies broadly according to the type of layer coupling
in the problem. Major recent advances in the field are surveyed and some
outstanding open challenges and future perspectives will be proposed.Comment: 20 pages, 10 figure
Symbiotic Cell Differentiation and Cooperative Growth in Multicellular Aggregates
As cells grow and divide under a given environment, they become crowded and
resources are limited, as seen in bacterial biofilms and multicellular
aggregates. These cells often show strong interactions through exchanging
chemicals, as in quorum sensing, to achieve mutualism. Here, to achieve stable
division of labor, three properties are required. First, isogenous cells
differentiate into several types. Second, this aggregate of distinct cell types
shows better growth than that of isolated cells, by achieving division of
labor. Third, this cell aggregate is robust in the number distribution of
differentiated cell types. We here address how cells acquire the ability of
cell differentiation and division of labor simultaneously, which is also
connected with the robustness of a cell society. For this purpose, we developed
a dynamical-systems model of cells consisting of chemical components with
intracellular catalytic reaction dynamics. The reactions convert external
nutrients into internal components for cellular growth, and the divided cells
interact via chemical diffusion. We found that cells sharing an identical
catalytic network spontaneously differentiate via induction from cell-cell
interactions, and then achieve division of labor, enabling a higher growth rate
than that in the unicellular case. This symbiotic differentiation emerged for a
class of reaction networks with limited resources and strong cell-cell
interactions. Then, robustness in the cell type distribution was achieved,
while instability of collective growth could emerge even among the cooperative
cells when the internal reserves of products were dominant. The present
mechanism is simple and general as a natural result of interacting cells with
resource limitation, and is consistent with the observed behaviors and forms of
several aggregates of unicellular organisms.Comment: 14 pages, 6 figure
Research needs towards a resilient community: Vulnerability reduction, infrastructural systems model, loss assessment, resilience-based design and emergency management
Most of the literature on resilience is devoted to its assessment. It seems time to move from analysis to design, to develop the tools needed to enhance resilience. Resilience enhancement, a close relative of the less fashionable risk mitigation, adds to the latter, at least in the general perception, a systemic dimension. Resilience is often paired with community, and the latter is a system. This chapter therefore discusses strategies to enhance resilience, endorses one of prevention rather than cure, and focuses in the remainder on the role played by systemic analysis, i.e. the analysis of the built environment modelled beyond a simple collection of physical assets, with due care to the associated interdependencies. Research needs are identified and include challenges in network modelling, the replacement of generic fragility curves for components, how to deal with evolving state of information
- …