Lifelines are critical infrastructure systems characterized by a high level of interdependency that can lead to cascading failures after any disaster.Many approaches can be used to analyze infrastructural interdepende...Lifelines are critical infrastructure systems characterized by a high level of interdependency that can lead to cascading failures after any disaster.Many approaches can be used to analyze infrastructural interdependencies,but they are usually not able to describe the sequence of events during emergencies.Therefore,interdependencies need to be modeled also taking into account the time effects.The methodology proposed in this paper is based on a modified version of the Input-output Inoperability Model and returns the probabilities of failure for each node of the system.Lifelines are modeled using graph theory,while perturbations,representing a natural or man-made disaster,are applied to the elements of the network following predetermined rules.The cascading effects among interdependent networks have been simulated using a spatial multilayer approach,while the use of an adjacency tensor allows to consider the temporal dimension and its effects.The method has been tested on a case study based on the 2011 Fukushima Dai-ichi nuclear disaster.Different configurations of the system have been analyzed and their probability of occurrence evaluated.Two models of the nuclear power plant have been developed to evaluate how different spatial scales and levels of detail affect the results.展开更多
Integrated power-gas systems(IPGSs)make the power system and natural gas system(NGS)as a whole,and strengthen interdependence between the two systems.Due to bidirectional energy conversion in IPGS,a disturbance may tu...Integrated power-gas systems(IPGSs)make the power system and natural gas system(NGS)as a whole,and strengthen interdependence between the two systems.Due to bidirectional energy conversion in IPGS,a disturbance may turn into a catastrophic outage.Meanwhile,increasing proportion of renewable energy brings challenges to reliability of IPGS.Moreover,partial failure or degradation of system performance leads IPGS operate at multiple performance levels.Therefore,this paper proposes a reliability assessment model of IPGSs which represents multiple performance of components and considers cascading effects,as well as renewable energy uncertainty.First,a framework of IPGS reliability assessment is proposed:multistate models for main elements in the IPGS are represented.Especially a gas-power-generation calculation operator and a power-to-gas calculation operator are utilized to bi-directionally convert a multi-state model between NGS and power systems.Furthermore,nodal reliability indices for IPGS are given to display impacts of cascading effects and renewable energy uncertainty on reliabilities of IPGSs.Numerical results on IPGS test system demonstrate the proposed methods.展开更多
Enhanced terahertz wave generation via a Stokes cascade process has been demonstrated using picosecond pulse pumped terahertz parametric generation at 1 kHz repetition rate.Clear cascade saturation of terahertz output...Enhanced terahertz wave generation via a Stokes cascade process has been demonstrated using picosecond pulse pumped terahertz parametric generation at 1 kHz repetition rate.Clear cascade saturation of terahertz output was observed,and the corresponding cascade-Stokes spectra were analyzed.The maximum terahertz wave average power was 22μW under a pump power of 30 W,whereas the maximum power conversion efficiency was 8×10^(-7)under a pump power of 21 W.The THz power fluctuation was measured to be about 1%in 20 min.This THz parametric source with a relatively stable output is suitable for a variety of practical applications.展开更多
Modern critical infrastructure,such as a water treatment plant,water distribution system,and power grid,are representative of Cyber Physical Systems(CPSs)in which the physical processes are monitored and controlled in...Modern critical infrastructure,such as a water treatment plant,water distribution system,and power grid,are representative of Cyber Physical Systems(CPSs)in which the physical processes are monitored and controlled in real time.One source of complexity in such systems is due to the intra-system interactions and inter-dependencies.Consequently,these systems are a potential target for attackers.When one or more of these infrastructure are attacked,the connected systems may also be affected due to potential cascading effects.In this paper,we report a study to investigate the cascading effects of cyber-attacks on two interdependent critical infrastructure namely,a Secure water treatment plant(SWaT)and a Water Distribution System(WADI).展开更多
Plasmonic Ag nanowire homotrimer with asymmetrical radii and separations, which exhibits characteristics of multiple plamonic resonances and different electric field distributions, is systematically investigated by me...Plasmonic Ag nanowire homotrimer with asymmetrical radii and separations, which exhibits characteristics of multiple plamonic resonances and different electric field distributions, is systematically investigated by means of 2D finite element method. It was found that the dark and bright modes appear in asymmetrical nanowire homotrimer. In addition, when the dark modes appear between the smaller radii of the nanowires, the cascade effect results in enhanced electric field between the smaller radii nanowires. As a result of the appearance of the bright modes between the smaller radii of the nanowires, the restriction of the cascade effect generates enhanced electric field between the bigger nanowires.展开更多
This study discussed the water sector as a critical infrastructural element in Jordan where the sector is exposed to the extreme events. The exposure of the country to extreme events has initiated this study. Such eve...This study discussed the water sector as a critical infrastructural element in Jordan where the sector is exposed to the extreme events. The exposure of the country to extreme events has initiated this study. Such events are Pollution accidents, flooding, draughts, overexploitation, failure in electricity supply, climate changes, earthquakes, landslides, failure of dams, failure of wastewater treatment plants, failure of desalination plants, sabotage, fire, water theft, migration and demographic changes (immigration and urban migration), relations to neighboring countries, epidemics, and others. These extreme events are discussed in this article and the results show that failures in the water infrastructure and water supply, in Jordan, with its water sector situation have rigorous percussions on the country’s health, food supply, economy, societal stability, the built environment, and on other water-related issues. The study concludes that developing national programs to protect the water infrastructure in the water-fragile country has become very crucial to reach a robust and resilient water sector which not only means providing the inhabitants with quantitatively sufficient and qualitatively healthy water but also aims to incorporate guaranteeing social, economic and political stability.展开更多
Floods caused by extreme weather events and climate change have increased in occurrence and severity all over the world,resulting in devastation and disruption of activities.Researchers and policy practitioners have i...Floods caused by extreme weather events and climate change have increased in occurrence and severity all over the world,resulting in devastation and disruption of activities.Researchers and policy practitioners have increasingly paid attention to the role of critical infrastructure(CI)in disaster risk reduction,flood resilience and climate change adaptation in terms of its backbone functions in maintaining societal services in hazard attacks.The analysed city in this study,Xinxiang(Henan province,China),was affected by an extreme flood event that occurred on 17–23 July 2021,which caused great socio-economic losses.However,few studies have focused on medium-sized cities and the flood cascading effects on CI during this event.Therefore,this study explores the damages caused by this flooding event with links to CI,such as health services,energy supply stations,shelters and transport facilities(HEST infrastructure).To achieve this,the study first combines RGB(red,green blue)composition and supervised classification for flood detection to monitor and map flood inundation areas.Second,it manages a multiscenario simulation and evaluates the cascading effects on HEST infrastructure.Diverse open-source data are employed,including Sentinel-1 synthetic aperture radar(SAR)data and Landsat-8 OIL data,point-of-interest(POI)and OpenStreetMap(OSM)data.The study reveals that this extreme flood event has profoundly affected croplands and villagers.Due to the revisiting period of Sentinel-1 SAR data,four scenarios are simulated to portray the retreated but‘omitted’floodwater:Scenario 0 is the flood inundation area on 27 July,and Scenarios 1,2 and 3 are built based on this information with a buffer of 50,100 and 150 m outwards,respectively.In the four scenarios,as the inundation areas expand,the affected HEST infrastructure becomes more clustered at the centre of the core study area,indicating that those located in the urban centre are more susceptible to flooding.Furthermore,the affected transport facilities assemble in the north and east of the core study area,implying that transport facilities located in the north and east of the core study area are more susceptible to flooding.The verification of the flood inundation maps and affected HEST infrastructure in the scenario simulation support the series method adopted in this study.The findings of this study can be used by flood managers,urban planners and other decision makers to better understand extreme historic weather events in China,improve flood resilience and decrease the negative impacts of such events on HEST infrastructure.展开更多
Integrated power-gas systems(IPGS)have developed critical infrastructure in integrated energy systems.Moreover,various extreme weather events with low probability and high risk have seriously affected the stable opera...Integrated power-gas systems(IPGS)have developed critical infrastructure in integrated energy systems.Moreover,various extreme weather events with low probability and high risk have seriously affected the stable operation of IPGSs.Due to close interconnectedness through coupling elements between the power system(PS)and natural gas system(NGS)when a disturbance happens in one system,a series of complicated sequences of dependent events may follow in another system.Especially under extreme conditions,this coupling can lead to a dramatic degradation of system performance,resulting in catastrophic failures.Therefore,there is an urgent need to model and evaluate resilience of IPGSs under extreme weather.Following this development trend,an integrated model for resilience evaluation of IPGS is proposed under extreme weather events focusing on windstorms.First,a framework of IPGS is proposed to describe states of the system at different stages under disaster conditions.Furthermore,an evaluation model considering cascading effects is used to quantify the impact of windstorms on NGS and PS.Meanwhile,a Monte Carlo simulation(MCS)technique is utilized to characterize chaotic fault of components.Moreover,time-dependent nodal and system resilience indices for IPGS are proposed to display impacts of windstorms.Numerical results on the IPGS test system demonstrate the proposed methods.展开更多
Climate change,habitat loss and fragmentation are major threats for populations and a challenge for individual behavior,interactions and survival.Predator-prey interactions are modified by climate processes.In the nor...Climate change,habitat loss and fragmentation are major threats for populations and a challenge for individual behavior,interactions and survival.Predator-prey interactions are modified by climate processes.In the northern latitudes,strong seasonality is changing and the main predicted feature is shortening and instability of winter.Vole populations in the boreal Fennoscandia exhibit multiannual cycles.High amplitude peak numbers of voles and dramatic population lows alternate in 3-5-year cycles shortening from North to South.One key factor,or driver,promoting the population crash and causing extreme extended lows,is suggested to be predation by the least weasel.We review the arms race between prey voles and weasels through the multiannual density fluctuation,affected by climate change,and especially the changes in the duration and stability of snow cover.For ground-dwelling small mammals,snow provides thermoregulation and shelter for nest sites,and helps them hide from predators.Predicted increases in the instability of winter forms a major challenge for species with coat color change between brown summer camouflage and white winter coat.One of these is the least weasel,Mustela nivalis nivalis.Increased vulnerability of wrong-colored weasels to predation affects vole populations and may have dramatic effects on vole dynamics.It may have cascading effects on other small rodent-predator interactions and even on plant-animal interactions and forest dynamics.展开更多
Femtosecond stimulated Raman spectroscopy （FSRS）, using an overlapping pair of narrow band Raman pump and broadband probe pulses with heterodyne detection along the probe pulse direction, is a new nonlinear spectros...Femtosecond stimulated Raman spectroscopy （FSRS）, using an overlapping pair of narrow band Raman pump and broadband probe pulses with heterodyne detection along the probe pulse direction, is a new nonlinear spectroscopic technique to record vibrational spectra of even highly fluorescent molecules and to study vibrational dynamics on excited electronic states of molecules, as in photoisomerization. FSRS is described by diagrammatic third-order perturbation theory with wave packet analysis. The phase matching condition gives rise to forty-eight terms for FSRS, but the resonant condition reduces it to just eight terms, which can be depicted by Feynman dual time-line diagrams, or closed time path loop diagrams, or the complementary four-wave mixing energy level diagrams. The eight terms fall into four sets-SRS（I）, SRS（Ⅱ）, IRS（I）, IRS（Ⅱ）-where SRS stands for stimulated Raman scattering and IRS stands for inverse Raman scattering. The SRS（I） set can also account for spontaneous Raman scattering, but the remaining SRS（Ⅱ）, IRS（I） and IRS（Ⅱ） terms are only present in stimulated scattering with the presence of a probe field. The SRS（I） set accounts for the Stokes Raman lines while the IRS（I） term accounts for the anti-Stokes lines, relative to the Raman pump frequency, in the FSRS spectrum. The remaining SRS（Ⅱ） and IRS（Ⅱ） terms give rise to broad baselines. Using a harmonic oscillator model, analytic results are obtained for the four-time correlation functions in the third-order polarizations. The issue of high time and high frequency resolution in time-resolved FSRS spectra is discussed. Calculations are made with the theory to compare with experimental results for： （a） resonance FSRS of fluorescent Rhodamine 6G and （b） 2D-FSRS from a coherent vibrational state that has been prepared by an impulsive, off-resonant pump pulse on CDCl3. The calculated results compared well with experimental results, and in the case of 2D-FSRS on CDCl3 there is a dominant cascade effect contributing to the FSRS spectra.展开更多
基金the European Research Council under the Grant agreement no.ERC_IDEAL RESCUE_637842 of the project IDEAL RESCUE_Integrated Design and Control of Sustainable Communities during Emergencies.
文摘Lifelines are critical infrastructure systems characterized by a high level of interdependency that can lead to cascading failures after any disaster.Many approaches can be used to analyze infrastructural interdependencies,but they are usually not able to describe the sequence of events during emergencies.Therefore,interdependencies need to be modeled also taking into account the time effects.The methodology proposed in this paper is based on a modified version of the Input-output Inoperability Model and returns the probabilities of failure for each node of the system.Lifelines are modeled using graph theory,while perturbations,representing a natural or man-made disaster,are applied to the elements of the network following predetermined rules.The cascading effects among interdependent networks have been simulated using a spatial multilayer approach,while the use of an adjacency tensor allows to consider the temporal dimension and its effects.The method has been tested on a case study based on the 2011 Fukushima Dai-ichi nuclear disaster.Different configurations of the system have been analyzed and their probability of occurrence evaluated.Two models of the nuclear power plant have been developed to evaluate how different spatial scales and levels of detail affect the results.
基金supported in part by the Key Projects of National Natural Science Foundation of China under Grant 51936003。
文摘Integrated power-gas systems(IPGSs)make the power system and natural gas system(NGS)as a whole,and strengthen interdependence between the two systems.Due to bidirectional energy conversion in IPGS,a disturbance may turn into a catastrophic outage.Meanwhile,increasing proportion of renewable energy brings challenges to reliability of IPGS.Moreover,partial failure or degradation of system performance leads IPGS operate at multiple performance levels.Therefore,this paper proposes a reliability assessment model of IPGSs which represents multiple performance of components and considers cascading effects,as well as renewable energy uncertainty.First,a framework of IPGS reliability assessment is proposed:multistate models for main elements in the IPGS are represented.Especially a gas-power-generation calculation operator and a power-to-gas calculation operator are utilized to bi-directionally convert a multi-state model between NGS and power systems.Furthermore,nodal reliability indices for IPGS are given to display impacts of cascading effects and renewable energy uncertainty on reliabilities of IPGSs.Numerical results on IPGS test system demonstrate the proposed methods.
基金funded by the National Natural Science Foundation of China (Grant Nos.U22A20353,U22A20123,62175182,and 62275193)Daheng Atlas (Beijing)Laser Technology Co.Ltd.for their support。
文摘Enhanced terahertz wave generation via a Stokes cascade process has been demonstrated using picosecond pulse pumped terahertz parametric generation at 1 kHz repetition rate.Clear cascade saturation of terahertz output was observed,and the corresponding cascade-Stokes spectra were analyzed.The maximum terahertz wave average power was 22μW under a pump power of 30 W,whereas the maximum power conversion efficiency was 8×10^(-7)under a pump power of 21 W.The THz power fluctuation was measured to be about 1%in 20 min.This THz parametric source with a relatively stable output is suitable for a variety of practical applications.
基金the National Research Foundation(NRF),Prime Minister’s Office,Singapore,under its National Cybersecurity R&D Programme(Award No.NRF2015NCR-NCR003-001)and administered by the National Cybersecurity R&D Directorate.
文摘Modern critical infrastructure,such as a water treatment plant,water distribution system,and power grid,are representative of Cyber Physical Systems(CPSs)in which the physical processes are monitored and controlled in real time.One source of complexity in such systems is due to the intra-system interactions and inter-dependencies.Consequently,these systems are a potential target for attackers.When one or more of these infrastructure are attacked,the connected systems may also be affected due to potential cascading effects.In this paper,we report a study to investigate the cascading effects of cyber-attacks on two interdependent critical infrastructure namely,a Secure water treatment plant(SWaT)and a Water Distribution System(WADI).
文摘Plasmonic Ag nanowire homotrimer with asymmetrical radii and separations, which exhibits characteristics of multiple plamonic resonances and different electric field distributions, is systematically investigated by means of 2D finite element method. It was found that the dark and bright modes appear in asymmetrical nanowire homotrimer. In addition, when the dark modes appear between the smaller radii of the nanowires, the cascade effect results in enhanced electric field between the smaller radii nanowires. As a result of the appearance of the bright modes between the smaller radii of the nanowires, the restriction of the cascade effect generates enhanced electric field between the bigger nanowires.
文摘This study discussed the water sector as a critical infrastructural element in Jordan where the sector is exposed to the extreme events. The exposure of the country to extreme events has initiated this study. Such events are Pollution accidents, flooding, draughts, overexploitation, failure in electricity supply, climate changes, earthquakes, landslides, failure of dams, failure of wastewater treatment plants, failure of desalination plants, sabotage, fire, water theft, migration and demographic changes (immigration and urban migration), relations to neighboring countries, epidemics, and others. These extreme events are discussed in this article and the results show that failures in the water infrastructure and water supply, in Jordan, with its water sector situation have rigorous percussions on the country’s health, food supply, economy, societal stability, the built environment, and on other water-related issues. The study concludes that developing national programs to protect the water infrastructure in the water-fragile country has become very crucial to reach a robust and resilient water sector which not only means providing the inhabitants with quantitatively sufficient and qualitatively healthy water but also aims to incorporate guaranteeing social, economic and political stability.
基金This research is co-funded by the National Youth Science Fund Project of the National Natural Science Foundation of China(52108050)the Guangdong Basic and Applied Basic Research Foundation(2023A1515011653)+2 种基金the Guangzhou Science and Technology Program(202201010503)the State Key Laboratory of Subtropical Building Science at South China University of Technology(2022ZB08)the China Postdoctoral Science Foundation(2021M701238).
文摘Floods caused by extreme weather events and climate change have increased in occurrence and severity all over the world,resulting in devastation and disruption of activities.Researchers and policy practitioners have increasingly paid attention to the role of critical infrastructure(CI)in disaster risk reduction,flood resilience and climate change adaptation in terms of its backbone functions in maintaining societal services in hazard attacks.The analysed city in this study,Xinxiang(Henan province,China),was affected by an extreme flood event that occurred on 17–23 July 2021,which caused great socio-economic losses.However,few studies have focused on medium-sized cities and the flood cascading effects on CI during this event.Therefore,this study explores the damages caused by this flooding event with links to CI,such as health services,energy supply stations,shelters and transport facilities(HEST infrastructure).To achieve this,the study first combines RGB(red,green blue)composition and supervised classification for flood detection to monitor and map flood inundation areas.Second,it manages a multiscenario simulation and evaluates the cascading effects on HEST infrastructure.Diverse open-source data are employed,including Sentinel-1 synthetic aperture radar(SAR)data and Landsat-8 OIL data,point-of-interest(POI)and OpenStreetMap(OSM)data.The study reveals that this extreme flood event has profoundly affected croplands and villagers.Due to the revisiting period of Sentinel-1 SAR data,four scenarios are simulated to portray the retreated but‘omitted’floodwater:Scenario 0 is the flood inundation area on 27 July,and Scenarios 1,2 and 3 are built based on this information with a buffer of 50,100 and 150 m outwards,respectively.In the four scenarios,as the inundation areas expand,the affected HEST infrastructure becomes more clustered at the centre of the core study area,indicating that those located in the urban centre are more susceptible to flooding.Furthermore,the affected transport facilities assemble in the north and east of the core study area,implying that transport facilities located in the north and east of the core study area are more susceptible to flooding.The verification of the flood inundation maps and affected HEST infrastructure in the scenario simulation support the series method adopted in this study.The findings of this study can be used by flood managers,urban planners and other decision makers to better understand extreme historic weather events in China,improve flood resilience and decrease the negative impacts of such events on HEST infrastructure.
基金supported by the Key Projects of National Natural Science Foundation of China(51936003)。
文摘Integrated power-gas systems(IPGS)have developed critical infrastructure in integrated energy systems.Moreover,various extreme weather events with low probability and high risk have seriously affected the stable operation of IPGSs.Due to close interconnectedness through coupling elements between the power system(PS)and natural gas system(NGS)when a disturbance happens in one system,a series of complicated sequences of dependent events may follow in another system.Especially under extreme conditions,this coupling can lead to a dramatic degradation of system performance,resulting in catastrophic failures.Therefore,there is an urgent need to model and evaluate resilience of IPGSs under extreme weather.Following this development trend,an integrated model for resilience evaluation of IPGS is proposed under extreme weather events focusing on windstorms.First,a framework of IPGS is proposed to describe states of the system at different stages under disaster conditions.Furthermore,an evaluation model considering cascading effects is used to quantify the impact of windstorms on NGS and PS.Meanwhile,a Monte Carlo simulation(MCS)technique is utilized to characterize chaotic fault of components.Moreover,time-dependent nodal and system resilience indices for IPGS are proposed to display impacts of windstorms.Numerical results on the IPGS test system demonstrate the proposed methods.
文摘Climate change,habitat loss and fragmentation are major threats for populations and a challenge for individual behavior,interactions and survival.Predator-prey interactions are modified by climate processes.In the northern latitudes,strong seasonality is changing and the main predicted feature is shortening and instability of winter.Vole populations in the boreal Fennoscandia exhibit multiannual cycles.High amplitude peak numbers of voles and dramatic population lows alternate in 3-5-year cycles shortening from North to South.One key factor,or driver,promoting the population crash and causing extreme extended lows,is suggested to be predation by the least weasel.We review the arms race between prey voles and weasels through the multiannual density fluctuation,affected by climate change,and especially the changes in the duration and stability of snow cover.For ground-dwelling small mammals,snow provides thermoregulation and shelter for nest sites,and helps them hide from predators.Predicted increases in the instability of winter forms a major challenge for species with coat color change between brown summer camouflage and white winter coat.One of these is the least weasel,Mustela nivalis nivalis.Increased vulnerability of wrong-colored weasels to predation affects vole populations and may have dramatic effects on vole dynamics.It may have cascading effects on other small rodent-predator interactions and even on plant-animal interactions and forest dynamics.
基金supported by the Ministry of Education,Singapore,and Nanyang Technological University Research Grants (T207B1222 &RG56/08)
文摘Femtosecond stimulated Raman spectroscopy （FSRS）, using an overlapping pair of narrow band Raman pump and broadband probe pulses with heterodyne detection along the probe pulse direction, is a new nonlinear spectroscopic technique to record vibrational spectra of even highly fluorescent molecules and to study vibrational dynamics on excited electronic states of molecules, as in photoisomerization. FSRS is described by diagrammatic third-order perturbation theory with wave packet analysis. The phase matching condition gives rise to forty-eight terms for FSRS, but the resonant condition reduces it to just eight terms, which can be depicted by Feynman dual time-line diagrams, or closed time path loop diagrams, or the complementary four-wave mixing energy level diagrams. The eight terms fall into four sets-SRS（I）, SRS（Ⅱ）, IRS（I）, IRS（Ⅱ）-where SRS stands for stimulated Raman scattering and IRS stands for inverse Raman scattering. The SRS（I） set can also account for spontaneous Raman scattering, but the remaining SRS（Ⅱ）, IRS（I） and IRS（Ⅱ） terms are only present in stimulated scattering with the presence of a probe field. The SRS（I） set accounts for the Stokes Raman lines while the IRS（I） term accounts for the anti-Stokes lines, relative to the Raman pump frequency, in the FSRS spectrum. The remaining SRS（Ⅱ） and IRS（Ⅱ） terms give rise to broad baselines. Using a harmonic oscillator model, analytic results are obtained for the four-time correlation functions in the third-order polarizations. The issue of high time and high frequency resolution in time-resolved FSRS spectra is discussed. Calculations are made with the theory to compare with experimental results for： （a） resonance FSRS of fluorescent Rhodamine 6G and （b） 2D-FSRS from a coherent vibrational state that has been prepared by an impulsive, off-resonant pump pulse on CDCl3. The calculated results compared well with experimental results, and in the case of 2D-FSRS on CDCl3 there is a dominant cascade effect contributing to the FSRS spectra.
