This paper defines the hazards that can cause direct localized damage or interruption as Spatially Localized Attacks (SLAs). The SLAs-induced impact on a critical infrastructure system (CIS) is ...modeled as the failure of system components that exist within some localized area while those outside this area remain operating. Instead of identifying and analyzing each type of the SLAs-related hazards, this paper makes a worst-case analysis and proposes a mathematical framework to support resilience optimization of interdependent CISs under the worst SLA. For illustrative purposes, this paper mainly considers two types of strategies to enhance CIS resilience, including protecting weak components, and building new components to increase redundancy. The problem is mathematically formulated as a tri-level defender–attacker–defender model, which is exactly solved by a proposed decomposition algorithm. The case study on interdependent power and water systems demonstrates how the proposed approach can not only identify the optimum resilience enhancement strategy as well as the worst-case SLA, but also analyze the importance of considering interdependencies from both the attacker's and the defender's perspectives.
•We model the worst-case of spatially localized attacks.•We model interdependent critical infrastructure systems under disruptions.•We propose a method to optimize interdependent infrastructure resilience.•A tri-level defender-attacker-defender model is formulated for the problem.•A decomposition algorithm is proposed to exactly solve the model.
Modern societies are becoming increasingly dependent on critical infrastructure systems (CISs) to provide essential services that support economic prosperity, governance, and quality of life. These ...systems are not alone but interdependent at multiple levels to enhance their overall performance. However, recent worldwide events such as the 9/11 terrorist attack, Gulf Coast hurricanes, the Chile and Japanese earthquakes, and even heat waves have highlighted that interdependencies among CISs increase the potential for cascading failures and amplify the impact of both large and small scale initial failures into events of catastrophic proportions. To better understand CISs to support planning, maintenance and emergency decision making, modeling and simulation of interdependencies across CISs has recently become a key field of study. This paper reviews the studies in the field and broadly groups the existing modeling and simulation approaches into six types: empirical approaches, agent based approaches, system dynamics based approaches, economic theory based approaches, network based approaches, and others. Different studies for each type of the approaches are categorized and reviewed in terms of fundamental principles, such as research focus, modeling rationale, and the analysis method, while different types of approaches are further compared according to several criteria, such as the notion of resilience. Finally, this paper offers future research directions and identifies critical challenges in the field.
•Modeling approaches on interdependent critical infrastructure systems are reviewed.•I mainly review empirical, agent-based, system-dynamics, economic, network approaches.•Studies by each approach are sorted out in terms of fundamental principles.•Different approaches are further compared with resilience as the main criterion.
•We develop a probabilistic method to assess hurricane resilience of power systems.•We consider multi-dimensional technical, social, organizational, economic resilience.•The organizational resilience ...chiefly affects the Harris County system restoration.•The social resilience is rather infective for the case study system restoration.•Departing from ideal resilience causes losses of tens of millions of dollars per year.
Electric power systems are critical to economic prosperity, national security, public health and safety. However, in hurricane-prone areas, a severe storm may simultaneously cause extensive component failures in a power system and lead to cascading failures within it and across other power-dependent utility systems. Hence, the hurricane resilience of power systems is crucial to ensure their rapid recovery and support the needs of the population in disaster areas. This paper introduces a probabilistic modeling approach for quantifying the hurricane resilience of contemporary electric power systems. This approach includes a hurricane hazard model, component fragility models, a power system performance model, and a system restoration model. These coupled four models enable quantifying hurricane resilience and estimating economic losses. Taking as an example the power system in Harris County, Texas, USA, along with real outage and restoration data after Hurricane Ike in 2008, the proposed resilience assessment model is calibrated and verified. In addition, several dimensions of resilience as well as the effectiveness of alternative strategies for resilience improvement are simulated and analyzed. Results show that among technical, organizational and social dimensions of resilience, the organizational resilience is the highest with a value of 99.964% (3.445 in a proposed logarithmic scale) while the social resilience is the lowest with a value of 99.760% (2.620 in the logarithmic scale). Although these values seem high in absolute terms due to the reliability of engineered systems, the consequences of departing from ideal resilience are still high as economic losses can add up to $83 million per year.
This article establishes a tri‐level decision‐making model supporting critical infrastructure (CI) resilience optimization against intentional attacks. A novel decomposition algorithm is proposed to ...exactly identify the best pre‐event defense strategy (protecting vulnerable components and building new lines), the worst‐case attack scenario, and the optimal postevent repair sequence of damaged components. As different types of CIs have different flow models, this article mainly considers the direct current power flow model and the maximal flow model for illustrative purposes. The proposed framework is illustrated by a simple but representative case system with nine nodes, and main results include: (1) the marginal value of extra defense investment under low defense budget is more considerable for mitigating system resilience loss, especially under large intentional attacks; (2) no defense strategy is always the best under different attack budgets; (3) increasing amount of repair resources can dramatically enhance CI resilience, but makes the pre‐event defense strategy less effective; (4) the use of maximal flow model can provide a lower bound estimation of the resilience loss from the power flow model; (5) the optimum defense strategy and the worst‐case attack identified by minimizing CI resilience loss largely differ from those by minimizing CI vulnerability, where the latter does not consider the recovery actions. Finally, the algorithm complexity is analyzed by comparing with the enumeration method and by testing two larger electric power systems.
We report a synthetic route to achieving nanoscale heterostructures consisting of a metal core and monocrystalline semiconductor shell with substantial lattice mismatches between them, which cannot ...be obtained by conventional epitaxial techniques. By controlling soft acid-base coordination reactions between molecular complexes and colloidal nanostructures, we show that chemical thermodynamics can drive nanoscale monocrystalline growth of the semiconductor shell with a lattice structure incommensurate with that of the core. More complex hybrid core-shell structures with azimuthal and radial nanotailoring of structures and compositions of the monocrystalline semiconductor shell are also demonstrated.
Abstract
Tropical cyclones (TCs) have caused extensive power outages. The impacts of TC-caused blackouts may worsen in the future as TCs and heatwaves intensify. Here we couple TC and heatwave ...projections and power outage and recovery process analysis to investigate how TC-blackout-heatwave compound hazard risk may vary in a changing climate, with Harris County, Texas as an example. We find that, under the high-emissions scenario RCP8.5, long-duration heatwaves following strong TCs may increase sharply. The expected percentage of Harris residents experiencing at least one longer-than-5-day TC-blackout-heatwave compound hazard in a 20-year period could increase dramatically by a factor of 23 (from 0.8% to 18.2%) over the 21
st
century. We also reveal that a moderate enhancement of the power distribution network can significantly mitigate the compound hazard risk. Thus, climate adaptation actions, such as strategically undergrounding distribution network and developing distributed energy sources, are urgently needed to improve coastal power system resilience.
Researchers often face the challenge of estimating the counterfactuals to evaluate the treatment effects. Hsiao et al. (2012) propose a method that offers more flexibilities by allowing the influence ...of the unobservable latent factors to vary cross-section. This paper relaxes the linear conditional mean assumption in their method by extending it to a semi-parametric setting. The asymptotic distribution properties of the average treatment effect estimator is derived and studied. The semi-parametric model and the Hsiao et al. (2012) are both applied to study the macroeconomic effect of the 2008 Chinese Economic Stimulus Program. The estimation results show the fiscal stimulus plan had raised the annual real GDP growth in China by about 3.2%, but only temporarily. These results are robust to linear setting, semiparametric setting, and various control group selections. The temporary boost in economic activities of the stimulus plan is also evident in the estimation of other economic indicators such as real investment, real consumption, real export, and real import.
The human body absorbs and loses heat largely through infrared radiation centering around a wavelength of 10 micrometers. However, neither our skin nor the textiles that make up clothing are capable ...of dynamically controlling this optical channel for thermal management. By coating triacetate-cellulose bimorph fibers with a thin layer of carbon nanotubes, we effectively modulated the infrared radiation by more than 35% as the relative humidity of the underlying skin changed. Both experiments and modeling suggest that this dynamic infrared gating effect mainly arises from distance-dependent electromagnetic coupling between neighboring coated fibers in the textile yarns. This effect opens a pathway for developing wearable localized thermal management systems that are autonomous and self-powered, as well as expanding our ability to adapt to demanding environments.
•We model the metro and the high-speed rail systems as an integrated rail system.•We propose three types of accessibility metrics to analyze the integrated system.•Departure time makes the travel ...time based accessibility time-varied.•We analyze system vulnerability under worst-case single high-speed station failure.•We analyze system vulnerability under two real extreme weather events.
Intra-city metro rail systems together with the inter-city high-speed rail system can provide very punctual transportation services for those trips with origins and destinations both served by metro stations. The travel time by metro and the transfer time between metro and high-speed rail stations averagely accounts for 26.5% of the shortest travel time of a typical trip in China. This paper considers these two types of rail systems as a whole, called integrated metro and high-speed rail systems. Different operation frequencies of these two types of rail systems make the accessibility via an integrated rail system time-varied, not only depending on the travel time, but also depending on the departure time from the origin station. In this context, this paper proposes three types of accessibility metrics: (a) the travel time based accessibility, which provides the minimum travel time from one city's metro station i departed at a given time to another city's metro station j; (b) the best departure based accessibility, which quantifies the length of the periods during which the departure time makes the travel time acceptable; (c) the round trip based accessibility, which measures the maximum time duration that a passenger can stay at the destination station for a round trip in a typical day. Based on these accessibility metrics, this paper also investigates the vulnerability of the integrated rail system in China under single high-speed train station failure and two real severe weather events. The findings provide insightful suggestions to plan the two types of rail systems as a whole.
