36,552 research outputs found
Reducing Cascading Failure Risk by Increasing Infrastructure Network Interdependency
Increased coupling between critical infrastructure networks, such as power
and communication systems, will have important implications for the reliability
and security of these systems. To understand the effects of power-communication
coupling, several have studied interdependent network models and reported that
increased coupling can increase system vulnerability. However, these results
come from models that have substantially different mechanisms of cascading,
relative to those found in actual power and communication networks. This paper
reports on two sets of experiments that compare the network vulnerability
implications resulting from simple topological models and models that more
accurately capture the dynamics of cascading in power systems. First, we
compare a simple model of topological contagion to a model of cascading in
power systems and find that the power grid shows a much higher level of
vulnerability, relative to the contagion model. Second, we compare a model of
topological cascades in coupled networks to three different physics-based
models of power grids coupled to communication networks. Again, the more
accurate models suggest very different conclusions. In all but the most extreme
case, the physics-based power grid models indicate that increased
power-communication coupling decreases vulnerability. This is opposite from
what one would conclude from the coupled topological model, in which zero
coupling is optimal. Finally, an extreme case in which communication failures
immediately cause grid failures, suggests that if systems are poorly designed,
increased coupling can be harmful. Together these results suggest design
strategies for reducing the risk of cascades in interdependent infrastructure
systems
Cascading Failures in Power Grids - Analysis and Algorithms
This paper focuses on cascading line failures in the transmission system of
the power grid. Recent large-scale power outages demonstrated the limitations
of percolation- and epid- emic-based tools in modeling cascades. Hence, we
study cascades by using computational tools and a linearized power flow model.
We first obtain results regarding the Moore-Penrose pseudo-inverse of the power
grid admittance matrix. Based on these results, we study the impact of a single
line failure on the flows on other lines. We also illustrate via simulation the
impact of the distance and resistance distance on the flow increase following a
failure, and discuss the difference from the epidemic models. We then study the
cascade properties, considering metrics such as the distance between failures
and the fraction of demand (load) satisfied after the cascade (yield). We use
the pseudo-inverse of admittance matrix to develop an efficient algorithm to
identify the cascading failure evolution, which can be a building block for
cascade mitigation. Finally, we show that finding the set of lines whose
removal has the most significant impact (under various metrics) is NP-Hard and
introduce a simple heuristic for the minimum yield problem. Overall, the
results demonstrate that using the resistance distance and the pseudo-inverse
of admittance matrix provides important insights and can support the
development of efficient algorithms
Governing Cascade Failures in Complex Social-Ecological-Technological Systems: Framing Context, Strategies, and Challenges
Cascade failures are events in networked systems with interconnected components in which failure of one or a few parts triggers the failure of other parts, which triggers the failure of more parts, and so on. Cascade failures occur in a wide variety of familiar systems, such as electric power distribution grids, transportation systems, financial systems, and ecosystems. Cascade failures have plagued society for centuries. However, modern social-ecological-technological systems (SETS) have become vast, fast moving, and highly interconnected, exposing these systems to cascade failures of potentially global proportions, spreading at breathtaking speed, and imposing catastrophic harms. The increasing potential for cascade failures of the magnitude of the 2008 financial system collapse, which had a truly global reach and affected systems well beyond finance, screams out for clear thinking about governing vulnerability to cascade failures in SETS. Yet, legal scholarship on the theme is essentially nil, and a more comprehensive, generalizable governance theory leveraging knowledge from scientific research on cascade failures has not emerged. Research initiatives are needed to forge ground on three fronts: (1) system modeling and monitoring; (2) event prediction; and (3) event prevention, response, and recovery. This Article is a first step in that direction. Part I outlines the cascade failures problem. Part II summarizes the scientific research on cascade failures. Part III identifies strategies for controlling cascade failures. Part IV explores the governance challenges of deploying those various strategies in large-scale SETS. Part Vextends the analysis to the special case of cascade failures within ecological systems and the difficulties of managing them through the strategies coming out of cascade failures science. Lastly, Part VI suggests directions of future research on governance of cascade failures
Why does early childhood deprivation increase the risk for depression and anxiety in adulthood? A developmental cascade model
Abstract Background: Using data from the English & Romanian Adoptees (ERA) study we recently reported that early time-lmited exposure to severe institutional deprivation is
associated with early onset and persistent neurodevelopmental problems and later
onset emotional problems. Here we examine possible reasons for the late
emergence of emotional problems in this cohort. Our main focus is on testing a
developmental cascade mediated via the functional impact of early-appearing
neurodevelopmental problems on late adolescent functioning. We also explore a
second putative pathway via sensitization to stress. Methods: The ERA study includes 165 Romanian individuals who spent their early lives in grossly depriving institutions and were subsequently adopted into UK
families, along with 52 UK adoptees with no history of deprivation. Age six years
symptoms of neurodevelopmental problems and age 15 anxiety/depression
symptoms were assessed via parental reports. Young adult symptoms of depression
and anxiety were assessed by both parent and self-reports; young adults also
completed measures of stress reactivity , exposure to adverse life events and
functioning in work and interpersonal relationships. Results: The path between early institutional deprivation and adult emotional problems was mediated via the impact of early neurodevelopmental problems on
unemployment and poor friendship functioning during the transition to adulthood.
The findings with regard to early deprivation, later life stress reactivity and emotional
problems were inconclusive.
Conclusions: Our analysis suggests that the risk for adult depression and anxiety following extreme institutional deprivation is explained through the effects of early neurodevelopmental problems on later social and vocational functioning. Future research should more fully examine the role of stress susceptibility in this model
Dynamics of Tipping Cascades on Complex Networks
Tipping points occur in diverse systems in various disciplines such as
ecology, climate science, economy or engineering. Tipping points are critical
thresholds in system parameters or state variables at which a tiny perturbation
can lead to a qualitative change of the system. Many systems with tipping
points can be modeled as networks of coupled multistable subsystems, e.g.
coupled patches of vegetation, connected lakes, interacting climate tipping
elements or multiscale infrastructure systems. In such networks, tipping events
in one subsystem are able to induce tipping cascades via domino effects. Here,
we investigate the effects of network topology on the occurrence of such
cascades. Numerical cascade simulations with a conceptual dynamical model for
tipping points are conducted on Erd\H{o}s-R\'enyi, Watts-Strogatz and
Barab\'asi-Albert networks. Additionally, we generate more realistic networks
using data from moisture-recycling simulations of the Amazon rainforest and
compare the results to those obtained for the model networks. We furthermore
use a directed configuration model and a stochastic block model which preserve
certain topological properties of the Amazon network to understand which of
these properties are responsible for its increased vulnerability. We find that
clustering and spatial organization increase the vulnerability of networks and
can lead to tipping of the whole network. These results could be useful to
evaluate which systems are vulnerable or robust due to their network topology
and might help to design or manage systems accordingly.Comment: 22 pages, 12 figure
Priorities for EU-South Asia cooperation in research and innovation to address societal challenges
A briefing paper highlighting the priorities for EU-South Asia cooperation in research and innovation to address societal challenges has just been published as part of the CASCADE (Collaborative Action towards Societal Challenges through Awareness, Development, and Education ) project led by GDRC’s Professor Dilanthi Amaratunga.
This paper examines the policy and interests of seven countries in South Asia with respect to the seven thematic societal challenges identified under the EU’s Horizon 2020 research and innovation programme: Health, demographic change and wellbeing; Food security, sustainable agricultures, marine and maritime research and the bio-based economy; Clean and efficient energy; Smart, green and integrated transport; Climate action, resource efficiency and raw materials; A changing world - inclusive, innovative and reflective societies; and, Secure societies - protecting freedom and security of the country and its citizens.
Other key points include the need for EU linkages with Asian countries given the region’s rapidly growing research and innovation capacities; urgency to address major concerns shared by citizens in Europe, South Asia and elsewhere; and eleven priorities identified for cooperation in research and innovation to address societal challenges
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