With a warming climate,temperature extremes have been a main global issue in recent decades due to their potential influence on the sustainable development of human life and natural ecosystems.In this study,12 indicat...With a warming climate,temperature extremes have been a main global issue in recent decades due to their potential influence on the sustainable development of human life and natural ecosystems.In this study,12 indicators of extreme temperature events are used to evaluate the spatiotemporal distribution,periodic structure and teleconnections with large-scale atmospheric circulation in Xinjiang,Northwest China by combining wavelet coherence(WTC) analysis based on continuous wavelet transform(CWT) analysis with the sequential Mann-Kendall test.We find that over the past six decades,the climate in Xinjiang has become warmer and has suffered from increases in the frequency of warm extremes and decreases in the frequency of cold extremes.Warm extremes have mainly occurred in the southern Tianshan Mountains surrounding the Tarim Basin and western part of the Taklamakan Desert,and cold extremes have primarily occurred in the southwestern Altai Mountains and northern foot of the Tianshan Mountains.Extreme temperature events,including warm extremes,cold extremes,and other temperature indices,have significant interannual variability,with the main oscillation periods at smaller(2–4-year band),intermediate(4–7-year band),and greater time scales in recent decades.Furthermore,cold-extreme indices,including frost days,cool days,and cool nights all show a clear changepoint during 1990–1997 at the 95% confidence level,and both ice days and cold spell duration indicator have a potential changepoint during 1981–1986.However,the changing points for warmextreme indices are detected during 1992–1998.The temperature variables are significantly correlated with the EI Ni?o-Southern Oscillation(ENSO) and Arctic Oscillation(AO),but less well correlated with the Pacific Decadal Oscillation(PDO).The phase difference in the WTC spectra is not uniform between temperature extremes and climatic oscillations.Our findings will have important implications for local governments in taking effective measures to mitigate the potential effects of regional climate warming due to human activities in Xinjiang.展开更多
The Centre for China and Globalisation(CCG)hosted a side event on February 17 titled"China,Europe,and the United States:Climate Cooperation in an Era of Great Power Politics"at the Munich Security Conference...The Centre for China and Globalisation(CCG)hosted a side event on February 17 titled"China,Europe,and the United States:Climate Cooperation in an Era of Great Power Politics"at the Munich Security Conference(MSC)2024,which was convened from February 16 to 18,2024 in Munich,Germany.展开更多
This study investigates the major patterns of large-scale tilted ridges(LSTRS)over the Eurasian continent and their connections with large-scale surface air temperature during boreal winter.A total number of 134 LSTR ...This study investigates the major patterns of large-scale tilted ridges(LSTRS)over the Eurasian continent and their connections with large-scale surface air temperature during boreal winter.A total number of 134 LSTR events with zonal extent exceeding 90°of longitude on the peak day are identified.Using self-organizing map(SOM),the LSTRs are classified into five clusters that are characterized by different spatial distributions and orientations.The leading two clusters are closely associated with extensive and persistent cold events over different places.Considering the first cluster,LSTRs extend from the Ural Mountains to Northeast Asia and are favorable for the amplification and southeastward extension of the Siberian high.Therefore,this cluster is closely associated with the occurrence of extensive and persistent cold events in china.In comparison with the first cluster,the LSTRs of second group are situated to the west,with starting points from the Kola Peninsula,and cause extensive and persistent cold events over Eastern Europe,central Asia,and central Siberia.The results suggest that the vertical coupling between LSTRs and the corresponding anomalous sea level pressure is crucial for the persistent cold temperature events associated with the leading two SOM clusters.展开更多
This article describes the design and implementation of Residents Life Event Management System (hereinafter called as RLEMS) with high level reliability and security by blockchain technology. The data access environme...This article describes the design and implementation of Residents Life Event Management System (hereinafter called as RLEMS) with high level reliability and security by blockchain technology. The data access environment provided by blockchain is highly secure and trustworthy. In Blockchain system, some data fragments are grouped into one piece called as <i>blocks</i>, and all blocks are connected to create a chain of blocks in database. When blocks are connected, hash value is used to connect blocks properly. Blockchain technology enables highly secure and reliable data management system under relatively poor ICT environment. For example, developing countries such as African countries do not have sufficient ICT environment. Therefore adopting blockchain technology is suitable for such countries. Based on this consideration, we have started to build RLEMS on the blockchain system. In previous work, we used the MultiChain as a blockchain platform. However, as MultiChain platform is mainly for private blockchain system, it is not suitable for government-level data management system. Therefore, we tried to use another blockchain framework. We selected Hyperledger Fabric which was developed by Linux Foundation. It enables to implement all styles of blockchain system. This article describes the design and implementation of RLEMS by using Hyperledger Fabric. Furthermore, to provide the best user experience, we also built the web application interface with Java web application framework named PrimeFace. The implementation of a prototype revealed that the Hyperledger Fabric blockchain technology is more suitable than MultiChain.展开更多
Security in Ad Hoc network is an important issue under the opening circumstance of application service. Some protocols and models of security auditing have been proposed to ensure rationality of contracting strategy a...Security in Ad Hoc network is an important issue under the opening circumstance of application service. Some protocols and models of security auditing have been proposed to ensure rationality of contracting strategy and operating regulation and used to identify abnormal operation. Model of security auditing based on access control of devices will be advanced to register sign of devices and property of event of access control and to audit those actions. In the end, the model is analyzed and simulated.展开更多
The paper conducts analysis on the causes of dangerous goods road transportation accidents by applying analytic technique of security system science - Event Tree Analysis （ETA）. By computing minimum cut and minimal ...The paper conducts analysis on the causes of dangerous goods road transportation accidents by applying analytic technique of security system science - Event Tree Analysis （ETA）. By computing minimum cut and minimal path set of event tree and the important level of elementary event, the paper elicits the results that the factors of causing road transportation accident are multiple and its hazard is great while the paper also elicits the sorting of structural important level of elementary event. The paper offers the security countermeasures for dangerous goods road transportation which plays a vital role in safeguarding dangerous goods road transportation security.展开更多
Aiming at the industry cyber-physical system(ICPS)where Denial-of-Service(DoS)attacks and actuator failure coexist,the integrated security control problem of ICPS under multi-objective constraints was studied.First,fr...Aiming at the industry cyber-physical system(ICPS)where Denial-of-Service(DoS)attacks and actuator failure coexist,the integrated security control problem of ICPS under multi-objective constraints was studied.First,from the perspective of the defender,according to the differential impact of the system under DoS attacks of different energies,the DoS attacks energy grading detection standard was formulated,and the ICPS comprehensive security control framework was constructed.Secondly,a security transmission strategy based on event triggering was designed.Under the DoS attack energy classification detection mechanism,for large-energy attacks,the method based on time series analysis was considered to predict and compensate for lost data.Therefore,on the basis of passive and elastic response to small energy attacks,the active defense capability against DoS attacks was increased.Then by introducing the conecomplement linearization algorithm,the calculation methods of the state and fault estimation observer and the integrated safety controller were deduced,the goal of DoS attack active and passive hybrid intrusion tolerance and actuator failure active fault tolerance were realized.Finally,a simulation example of a four-capacity water tank system was given to verify the validity of the obtained conclusions.展开更多
Power system optimal dispatch with transient security constraints is commonly represented as transient securityconstrained optimal power flow(TSC-OPF).Deep reinforcement learning(DRL)-based TSC-OPF trains efficient de...Power system optimal dispatch with transient security constraints is commonly represented as transient securityconstrained optimal power flow(TSC-OPF).Deep reinforcement learning(DRL)-based TSC-OPF trains efficient decisionmaking agents that are adaptable to various scenarios and provide solution results quickly.However,due to the high dimensionality of the state space and action spaces,as well as the nonsmoothness of dynamic constraints,existing DRL-based TSCOPF solution methods face a significant challenge of the sparse reward problem.To address this issue,a fast-converging DRL method for optimal dispatch of large-scale power systems under transient security constraints is proposed in this paper.The Markov decision process(MDP)modeling of TSC-OPF is improved by reducing the observation space and smoothing the reward design,thus facilitating agent training.An improved deep deterministic policy gradient algorithm with curriculum learning,parallel exploration,and ensemble decision-making(DDPGCL-PE-ED)is introduced to drastically enhance the efficiency of agent training and the accuracy of decision-making.The effectiveness,efficiency,and accuracy of the proposed method are demonstrated through experiments in the IEEE 39-bus system and a practical 710-bus regional power grid.The source code of the proposed method is made public on GitHub.展开更多
The increasing frequency of compound extreme events under ongoing climate change threatens global food security.Compared to individual extreme events,the simultaneous occurrence of multiple extreme events can exacerba...The increasing frequency of compound extreme events under ongoing climate change threatens global food security.Compared to individual extreme events,the simultaneous occurrence of multiple extreme events can exacerbate crop yield reductions,yet comprehensive assessments of these compound effects remain limited.To bridge this gap,we applied a linear mixed-effects model to quantify the impacts of individual extreme events(cold days(CD)and killing degree days(KDD))and triple compound extreme events(heatwave and low precipitation(HWLP)and hot-dry-windy(HDW))on the global yields of winter wheat,soybeans,and maize from 1982 to 2016.Our analysis indicated that regions severely impacted by extreme events(exceeding the 95%threshold)experienced total crop yield losses of more than 9.16,24.89,26.69,and 7.12%due to CD,KDD,HWLP,and HDW,respectively.The adverse effects of compound events were particularly pronounced during critical growth stages.HWLP results in yield losses of 9.4%for winter wheat and 6.8%for maize per 10 hours of exposure during the heading to harvesting stages,while soybean yields declined by 8.8%per 10 hours during the planting to three-true-leaf stage.Similarly,KDD caused a 7.4%yield reduction in winter wheat per 10°C day during the heading to harvesting stages,a 9.5%reduction in maize per 10°C day during the planting to jointing stages,and a 3.8%reduction in soybean per 10°C day during the planting to three-true-leaf stages.These findings underscore the substantial contribution of compound extreme events,which are often overlooked in existing risk assessments,in determining the global yields of major staple crops.展开更多
Energy security planning is fundamental to safeguarding the traffic operation in large-scale events.To guarantee the promo-tion of green,zero-carbon,and environmental-friendly hydrogen fuel cell vehicles(HFCVs)in larg...Energy security planning is fundamental to safeguarding the traffic operation in large-scale events.To guarantee the promo-tion of green,zero-carbon,and environmental-friendly hydrogen fuel cell vehicles(HFCVs)in large-scale events,a five-stage planning method is proposed considering the demand and supply potential of hydrogen energy.Specifically,to meet the requirements of the large-scale events’demand,a new calculation approach is proposed to calculate the hydrogen amount and the distribution of hydrogen stations.In addition,energy supply is guaranteed from four aspects,namely hydrogen produc-tion,hydrogen storage,hydrogen delivery,and hydrogen refueling.The emergency plan is established based on the overall support plan,which can realize multi-dimensional energy security.Furthermore,the planning method is demonstrative as it powers the Beijing 2022 Winter Olympics as the first“green”Olympic,providing both theoretical and practical evidence for the energy security planning of large-scale events.This study provides suggestions about ensuring the energy demand after the race,broadening the application scenarios,and accelerating the application of HFCVs.展开更多
With the load growth and the power grid expansion,the problem of short-circuit current(SCC)exceeding the secure limit in large-scale power grids has become more serious,which poses great challenge to the optimal secur...With the load growth and the power grid expansion,the problem of short-circuit current(SCC)exceeding the secure limit in large-scale power grids has become more serious,which poses great challenge to the optimal secure operation.Aiming at the SCC limitations,we use multiple back-toback voltage source converter based(B2B VSC)systems to separate a large-scale AC power grid into two asynchronous power grids.A multi-objective robust optimal secure operation model of large-scale power grid with multiple B2B VSC systems considering the SCC limitation is established based on the AC power flow equations.The decision variables include the on/off states of synchronous generators,power output,terminal voltage,transmission switching,bus sectionalization,and modulation ratios of B2B VSC systems.The influence of inner current sources of renewable energy generators on the system SCC is also considered.To improve the computational efficiency,a mixedinteger convex programming(MICP)framework based on convex relaxation methods including the inscribed N-sided approximation for the nonlinear SCC limitation constraints is proposed.Moreover,combined with the column-and-constraint generation(C&CG)algorithm,a method to directly solve the compromise optimal solution(COS)of the multi-objective robust optimal secure operation model is proposed.Finally,the effectiveness and computational efficiency of the proposed solution method is demonstrated by an actual 4407-bus provincial power grid and the modified IEEE 39-bus power grid,which can reduce the consumed CPU time of solving the COS by more than 90%and obtain a better COS.展开更多
Two types of persistent heavy rainfall events （PHREs） over the Yangtze River-Huaihe River Basin were determined in a recent statistical study： type A, whose precipitation is mainly located to the south of the Yangt...Two types of persistent heavy rainfall events （PHREs） over the Yangtze River-Huaihe River Basin were determined in a recent statistical study： type A, whose precipitation is mainly located to the south of the Yangtze River; and type B, whose precipitation is mainly located to the north of the river. The present study investigated these two PHRE types using a newly derived set of energy equations to show the scale interaction and main energy paths contributing to the persistence of the precipitation. The main results were as follows. The available potential energy （APE） and kinetic energy （KE） associated with both PHRE types generally increased upward in the troposphere, with the energy of the type-A PHREs stronger than that of the type-B PHREs （except for in the middle troposphere）. There were two main common and universal energy paths of the two PHRE types： （1） the baroclinic energy conversion from APE to KE was the dominant energy source for the evolution of large-scale background circulations; and （2） the downscaled energy cascade processes of KE and APE were vital for sustaining the eddy flow, which directly caused the PHREs. The significant differences between the two PHRE types mainly appeared in the lower troposphere, where the baroclinic energy conversion associated with the eddy flow in type-A PHREs was from KE to APE, which reduced the intensity of the precipitation-related eddy flow; whereas, the conversion in type-B PHREs was from APE to KE, which enhanced the eddy flow.展开更多
Concurrence of low temperature,precipitation and freezing weather in an extensive area would cause devastating impacts on local economy and society.We call such a combination of concurrent disastrous weather“extensiv...Concurrence of low temperature,precipitation and freezing weather in an extensive area would cause devastating impacts on local economy and society.We call such a combination of concurrent disastrous weather“extensive coldprecipitation-freezing”events(ECPFEs).In this study,the ECPFEs in southern China(15°−35°N,102°−123°E)are objectively defined by using daily surface observational data for the period 1951−2013.An ECPFE in southern China is defined if the low temperature area,precipitation area and freezing area concurrently exceed their respective thresholds for at least three consecutive days.The identified ECPFEs are shown to be reasonable and reliable,compared with those in previous studies.The circulation anomalies in ECPFEs are characterized by a large-scale tilted ridge and trough pairing over mid-and high-latitude Eurasia,and the intensified subtropical westerlies along the southern foot of the Tibetan Plateau and the anomalous anticyclonic circulation over the subtropical western Pacific.Comparative analysis reveals that the stable cold air from the north and the warm and moist air from the south converge,facilitating a favorable environment for the concurrence of extensive low-temperature,precipitation and freezing weather.展开更多
Based on hourly precipitation from national surface stations,persistent heavy rainfall events(PHREs)over the Sichuan Basin(SCB)are explored during the warm season(May to September)from 2000 to 2015 to compare synoptic...Based on hourly precipitation from national surface stations,persistent heavy rainfall events(PHREs)over the Sichuan Basin(SCB)are explored during the warm season(May to September)from 2000 to 2015 to compare synoptic circulations and maintenance mechanisms between different PHRE types.There are two main types of PHREs:one is characterized by a rain belt west of 106°E over the SCB(WSB-PHREs),and the other features a rain belt east of 106°E over the SCB(ESB-PHREs).In total,there are 18 ESB-PHREs and 10 WSB-PHREs during the study period.Overall,the rain belts of WSB-PHREs are along the terrain distribution east of the Tibetan Plateau,while the precipitation intensity of ESB-PHREs is stronger.For the two types of PHREs,the shortwave trough over the SCB and the western Pacific subtropical high act as their favorable background environments,particularly for ESB-PHREs.The water vapor of WSB-PHREs is mainly transported from the South China Sea,whereas for ESB-PHREs the South China Sea and Bay of Bengal are their main moisture sources.The composite vorticity budgets of southwest vortices during their mature stage indicate that the convergence effect is a dominant factor for maintaining the two types of PHREs,and the strong vertical vorticity advection is also favorable,but the relative contribution of vertical advection is larger for WSB-PHREs.展开更多
AIM To investigate the incidence of disadvantageous events by using the Global Trigger Tool in an intensive care unit(ICU).METHODS A retrospective descriptive study was performed in a 12-bed university ICU in the city...AIM To investigate the incidence of disadvantageous events by using the Global Trigger Tool in an intensive care unit(ICU).METHODS A retrospective descriptive study was performed in a 12-bed university ICU in the city of Medellin, Colombia. Clinical charts of hospitalized patients were reviewed, between January 1 and December 31, 2016, with the following inclusion criteria: subjects aged over 18 years, with at least 24 h of hospitalization and who had a complete medical history that could be accessed. Interventions: Trained reviewers conducted a retros pective examination of medical charts searching for clue events that elicit investigation, in order to detect an unfavorable event. Measurements: Information was processed through SPSS softwareversion 21; for numerical variables, the mean was reported with standard deviation(SD). Percentages were calculated for qualitative variables. RESULTS Two hundred and forty-four triggers occurred, with 82.4% of subjects having presented with at least one and an average of 3.37 (SD 3.47). A total of 178 adverse events (AEs) took place in 48 individuals, with an incidence of 52.1%. On average, four events per patient were recorded, and for each unfortunate event, 1.98 triggers were presented. The most frequent displeasing issues were: pressure ulcers(17.6%), followed by complications or reactions to medical devices(4.3%), and lacerations or skin defects(3.7%); the least frequent was delayed diagnosis or treatment (0.56%). Thirty-eight point four percent of mishap events caused temporary damage that required intervention, and 48.9% of AEs were preventable. Comparison between AEs and admission diagnoses found that hypertension and sepsis were the only diagnoses that had statistical significance (P = 0.042 and 0.022, respectively).CONCLUSION Almost half of the unfavorable issues were classified as avoidable, which leaves a very wide field of work in terms of preventative activities.展开更多
The analytical and monitoring capabilities of central event re-positories, such as log servers and intrusion detection sys-tems, are limited by the amount of structured information ex-tracted from the events they rece...The analytical and monitoring capabilities of central event re-positories, such as log servers and intrusion detection sys-tems, are limited by the amount of structured information ex-tracted from the events they receive. Diverse networks and ap-plications log their events in many different formats, and this makes it difficult to identify the type of logs being received by the central repository. The way events are logged by IT systems is problematic for developers of host-based intrusion-detection systems （specifically, host-based systems）, develop-ers of security-information systems, and developers of event-management systems. These problems preclude the develop-ment of more accurate, intrusive security solutions that obtain results from data included in the logs being processed. We propose a new method for dynamically normalizing events into a unified super-event that is loosely based on the Common Event Expression standard developed by Mitre Corporation. We explain how our solution can normalize seemingly unrelat-ed events into a single, unified format.展开更多
Advanced Persistent Threat(APT)is now the most common network assault.However,the existing threat analysis models cannot simultaneously predict the macro-development trend and micro-propagation path of APT attacks.The...Advanced Persistent Threat(APT)is now the most common network assault.However,the existing threat analysis models cannot simultaneously predict the macro-development trend and micro-propagation path of APT attacks.They cannot provide rapid and accurate early warning and decision responses to the present system state because they are inadequate at deducing the risk evolution rules of network threats.To address the above problems,firstly,this paper constructs the multi-source threat element analysis ontology(MTEAO)by integrating multi-source network security knowledge bases.Subsequently,based on MTEAO,we propose a two-layer threat prediction model(TL-TPM)that combines the knowledge graph and the event graph.The macro-layer of TL-TPM is based on the knowledge graph to derive the propagation path of threats among devices and to correlate threat elements for threat warning and decision-making;The micro-layer ingeniously maps the attack graph onto the event graph and derives the evolution path of attack techniques based on the event graph to improve the explainability of the evolution of threat events.The experiment’s results demonstrate that TL-TPM can completely depict the threat development trend,and the early warning results are more precise and scientific,offering knowledge and guidance for active defense.展开更多
基金supported by the National Natural Science Foundation of China (No.41672246)the Fundamental Research Funds for the Central Universities,China University of Geosciences (Wuhan)(No.1910491T05)。
文摘With a warming climate,temperature extremes have been a main global issue in recent decades due to their potential influence on the sustainable development of human life and natural ecosystems.In this study,12 indicators of extreme temperature events are used to evaluate the spatiotemporal distribution,periodic structure and teleconnections with large-scale atmospheric circulation in Xinjiang,Northwest China by combining wavelet coherence(WTC) analysis based on continuous wavelet transform(CWT) analysis with the sequential Mann-Kendall test.We find that over the past six decades,the climate in Xinjiang has become warmer and has suffered from increases in the frequency of warm extremes and decreases in the frequency of cold extremes.Warm extremes have mainly occurred in the southern Tianshan Mountains surrounding the Tarim Basin and western part of the Taklamakan Desert,and cold extremes have primarily occurred in the southwestern Altai Mountains and northern foot of the Tianshan Mountains.Extreme temperature events,including warm extremes,cold extremes,and other temperature indices,have significant interannual variability,with the main oscillation periods at smaller(2–4-year band),intermediate(4–7-year band),and greater time scales in recent decades.Furthermore,cold-extreme indices,including frost days,cool days,and cool nights all show a clear changepoint during 1990–1997 at the 95% confidence level,and both ice days and cold spell duration indicator have a potential changepoint during 1981–1986.However,the changing points for warmextreme indices are detected during 1992–1998.The temperature variables are significantly correlated with the EI Ni?o-Southern Oscillation(ENSO) and Arctic Oscillation(AO),but less well correlated with the Pacific Decadal Oscillation(PDO).The phase difference in the WTC spectra is not uniform between temperature extremes and climatic oscillations.Our findings will have important implications for local governments in taking effective measures to mitigate the potential effects of regional climate warming due to human activities in Xinjiang.
文摘The Centre for China and Globalisation(CCG)hosted a side event on February 17 titled"China,Europe,and the United States:Climate Cooperation in an Era of Great Power Politics"at the Munich Security Conference(MSC)2024,which was convened from February 16 to 18,2024 in Munich,Germany.
基金jointly supported by the National Natural Science Foundation of China [grant number 41375064 and41675086]the National Key Technology Research and Development Program of the Ministry of Science and Technology of China [grant number 2015BAC03B03]
文摘This study investigates the major patterns of large-scale tilted ridges(LSTRS)over the Eurasian continent and their connections with large-scale surface air temperature during boreal winter.A total number of 134 LSTR events with zonal extent exceeding 90°of longitude on the peak day are identified.Using self-organizing map(SOM),the LSTRs are classified into five clusters that are characterized by different spatial distributions and orientations.The leading two clusters are closely associated with extensive and persistent cold events over different places.Considering the first cluster,LSTRs extend from the Ural Mountains to Northeast Asia and are favorable for the amplification and southeastward extension of the Siberian high.Therefore,this cluster is closely associated with the occurrence of extensive and persistent cold events in china.In comparison with the first cluster,the LSTRs of second group are situated to the west,with starting points from the Kola Peninsula,and cause extensive and persistent cold events over Eastern Europe,central Asia,and central Siberia.The results suggest that the vertical coupling between LSTRs and the corresponding anomalous sea level pressure is crucial for the persistent cold temperature events associated with the leading two SOM clusters.
文摘This article describes the design and implementation of Residents Life Event Management System (hereinafter called as RLEMS) with high level reliability and security by blockchain technology. The data access environment provided by blockchain is highly secure and trustworthy. In Blockchain system, some data fragments are grouped into one piece called as <i>blocks</i>, and all blocks are connected to create a chain of blocks in database. When blocks are connected, hash value is used to connect blocks properly. Blockchain technology enables highly secure and reliable data management system under relatively poor ICT environment. For example, developing countries such as African countries do not have sufficient ICT environment. Therefore adopting blockchain technology is suitable for such countries. Based on this consideration, we have started to build RLEMS on the blockchain system. In previous work, we used the MultiChain as a blockchain platform. However, as MultiChain platform is mainly for private blockchain system, it is not suitable for government-level data management system. Therefore, we tried to use another blockchain framework. We selected Hyperledger Fabric which was developed by Linux Foundation. It enables to implement all styles of blockchain system. This article describes the design and implementation of RLEMS by using Hyperledger Fabric. Furthermore, to provide the best user experience, we also built the web application interface with Java web application framework named PrimeFace. The implementation of a prototype revealed that the Hyperledger Fabric blockchain technology is more suitable than MultiChain.
文摘Security in Ad Hoc network is an important issue under the opening circumstance of application service. Some protocols and models of security auditing have been proposed to ensure rationality of contracting strategy and operating regulation and used to identify abnormal operation. Model of security auditing based on access control of devices will be advanced to register sign of devices and property of event of access control and to audit those actions. In the end, the model is analyzed and simulated.
文摘The paper conducts analysis on the causes of dangerous goods road transportation accidents by applying analytic technique of security system science - Event Tree Analysis （ETA）. By computing minimum cut and minimal path set of event tree and the important level of elementary event, the paper elicits the results that the factors of causing road transportation accident are multiple and its hazard is great while the paper also elicits the sorting of structural important level of elementary event. The paper offers the security countermeasures for dangerous goods road transportation which plays a vital role in safeguarding dangerous goods road transportation security.
基金supported by Gansu Higher Education Innovation Fund Project(No.2023B-439)。
文摘Aiming at the industry cyber-physical system(ICPS)where Denial-of-Service(DoS)attacks and actuator failure coexist,the integrated security control problem of ICPS under multi-objective constraints was studied.First,from the perspective of the defender,according to the differential impact of the system under DoS attacks of different energies,the DoS attacks energy grading detection standard was formulated,and the ICPS comprehensive security control framework was constructed.Secondly,a security transmission strategy based on event triggering was designed.Under the DoS attack energy classification detection mechanism,for large-energy attacks,the method based on time series analysis was considered to predict and compensate for lost data.Therefore,on the basis of passive and elastic response to small energy attacks,the active defense capability against DoS attacks was increased.Then by introducing the conecomplement linearization algorithm,the calculation methods of the state and fault estimation observer and the integrated safety controller were deduced,the goal of DoS attack active and passive hybrid intrusion tolerance and actuator failure active fault tolerance were realized.Finally,a simulation example of a four-capacity water tank system was given to verify the validity of the obtained conclusions.
基金supported in part by the National Natural Science Foundation of China(No.52107104)。
文摘Power system optimal dispatch with transient security constraints is commonly represented as transient securityconstrained optimal power flow(TSC-OPF).Deep reinforcement learning(DRL)-based TSC-OPF trains efficient decisionmaking agents that are adaptable to various scenarios and provide solution results quickly.However,due to the high dimensionality of the state space and action spaces,as well as the nonsmoothness of dynamic constraints,existing DRL-based TSCOPF solution methods face a significant challenge of the sparse reward problem.To address this issue,a fast-converging DRL method for optimal dispatch of large-scale power systems under transient security constraints is proposed in this paper.The Markov decision process(MDP)modeling of TSC-OPF is improved by reducing the observation space and smoothing the reward design,thus facilitating agent training.An improved deep deterministic policy gradient algorithm with curriculum learning,parallel exploration,and ensemble decision-making(DDPGCL-PE-ED)is introduced to drastically enhance the efficiency of agent training and the accuracy of decision-making.The effectiveness,efficiency,and accuracy of the proposed method are demonstrated through experiments in the IEEE 39-bus system and a practical 710-bus regional power grid.The source code of the proposed method is made public on GitHub.
基金supported by the National Natural Science Foundation of China(42371483,and 42401573)the Guangdong Basic and Applied Basic Research Foundation,China(2022B1515130001)+2 种基金the Natural Science Foundation of Guangdong Province,China(2024A1515012081 and 2025A1515010770)the Guangzhou Basic and Applied Basic Research Project,China(202201011666)the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation(GZB20240880).
文摘The increasing frequency of compound extreme events under ongoing climate change threatens global food security.Compared to individual extreme events,the simultaneous occurrence of multiple extreme events can exacerbate crop yield reductions,yet comprehensive assessments of these compound effects remain limited.To bridge this gap,we applied a linear mixed-effects model to quantify the impacts of individual extreme events(cold days(CD)and killing degree days(KDD))and triple compound extreme events(heatwave and low precipitation(HWLP)and hot-dry-windy(HDW))on the global yields of winter wheat,soybeans,and maize from 1982 to 2016.Our analysis indicated that regions severely impacted by extreme events(exceeding the 95%threshold)experienced total crop yield losses of more than 9.16,24.89,26.69,and 7.12%due to CD,KDD,HWLP,and HDW,respectively.The adverse effects of compound events were particularly pronounced during critical growth stages.HWLP results in yield losses of 9.4%for winter wheat and 6.8%for maize per 10 hours of exposure during the heading to harvesting stages,while soybean yields declined by 8.8%per 10 hours during the planting to three-true-leaf stage.Similarly,KDD caused a 7.4%yield reduction in winter wheat per 10°C day during the heading to harvesting stages,a 9.5%reduction in maize per 10°C day during the planting to jointing stages,and a 3.8%reduction in soybean per 10°C day during the planting to three-true-leaf stages.These findings underscore the substantial contribution of compound extreme events,which are often overlooked in existing risk assessments,in determining the global yields of major staple crops.
基金The authors thank the support of colleagues from Beijing Transport Institute.
文摘Energy security planning is fundamental to safeguarding the traffic operation in large-scale events.To guarantee the promo-tion of green,zero-carbon,and environmental-friendly hydrogen fuel cell vehicles(HFCVs)in large-scale events,a five-stage planning method is proposed considering the demand and supply potential of hydrogen energy.Specifically,to meet the requirements of the large-scale events’demand,a new calculation approach is proposed to calculate the hydrogen amount and the distribution of hydrogen stations.In addition,energy supply is guaranteed from four aspects,namely hydrogen produc-tion,hydrogen storage,hydrogen delivery,and hydrogen refueling.The emergency plan is established based on the overall support plan,which can realize multi-dimensional energy security.Furthermore,the planning method is demonstrative as it powers the Beijing 2022 Winter Olympics as the first“green”Olympic,providing both theoretical and practical evidence for the energy security planning of large-scale events.This study provides suggestions about ensuring the energy demand after the race,broadening the application scenarios,and accelerating the application of HFCVs.
基金supported by the National Natural Science Foundation of China(No.51977080).
文摘With the load growth and the power grid expansion,the problem of short-circuit current(SCC)exceeding the secure limit in large-scale power grids has become more serious,which poses great challenge to the optimal secure operation.Aiming at the SCC limitations,we use multiple back-toback voltage source converter based(B2B VSC)systems to separate a large-scale AC power grid into two asynchronous power grids.A multi-objective robust optimal secure operation model of large-scale power grid with multiple B2B VSC systems considering the SCC limitation is established based on the AC power flow equations.The decision variables include the on/off states of synchronous generators,power output,terminal voltage,transmission switching,bus sectionalization,and modulation ratios of B2B VSC systems.The influence of inner current sources of renewable energy generators on the system SCC is also considered.To improve the computational efficiency,a mixedinteger convex programming(MICP)framework based on convex relaxation methods including the inscribed N-sided approximation for the nonlinear SCC limitation constraints is proposed.Moreover,combined with the column-and-constraint generation(C&CG)algorithm,a method to directly solve the compromise optimal solution(COS)of the multi-objective robust optimal secure operation model is proposed.Finally,the effectiveness and computational efficiency of the proposed solution method is demonstrated by an actual 4407-bus provincial power grid and the modified IEEE 39-bus power grid,which can reduce the consumed CPU time of solving the COS by more than 90%and obtain a better COS.
基金supported by the National Key Basic Research and Development Project of China(Grant No.2012CB417201)the National Natural Science Foundation of China(Grant Nos.41375053 and 41505038)
文摘Two types of persistent heavy rainfall events （PHREs） over the Yangtze River-Huaihe River Basin were determined in a recent statistical study： type A, whose precipitation is mainly located to the south of the Yangtze River; and type B, whose precipitation is mainly located to the north of the river. The present study investigated these two PHRE types using a newly derived set of energy equations to show the scale interaction and main energy paths contributing to the persistence of the precipitation. The main results were as follows. The available potential energy （APE） and kinetic energy （KE） associated with both PHRE types generally increased upward in the troposphere, with the energy of the type-A PHREs stronger than that of the type-B PHREs （except for in the middle troposphere）. There were two main common and universal energy paths of the two PHRE types： （1） the baroclinic energy conversion from APE to KE was the dominant energy source for the evolution of large-scale background circulations; and （2） the downscaled energy cascade processes of KE and APE were vital for sustaining the eddy flow, which directly caused the PHREs. The significant differences between the two PHRE types mainly appeared in the lower troposphere, where the baroclinic energy conversion associated with the eddy flow in type-A PHREs was from KE to APE, which reduced the intensity of the precipitation-related eddy flow; whereas, the conversion in type-B PHREs was from APE to KE, which enhanced the eddy flow.
基金This research was funded by the National Natural Science Foundation of China(Grant Nos.41975072 and 41675086)the National Science and Technology Support Program of China(Grant No.2015BAC03B03).
文摘Concurrence of low temperature,precipitation and freezing weather in an extensive area would cause devastating impacts on local economy and society.We call such a combination of concurrent disastrous weather“extensive coldprecipitation-freezing”events(ECPFEs).In this study,the ECPFEs in southern China(15°−35°N,102°−123°E)are objectively defined by using daily surface observational data for the period 1951−2013.An ECPFE in southern China is defined if the low temperature area,precipitation area and freezing area concurrently exceed their respective thresholds for at least three consecutive days.The identified ECPFEs are shown to be reasonable and reliable,compared with those in previous studies.The circulation anomalies in ECPFEs are characterized by a large-scale tilted ridge and trough pairing over mid-and high-latitude Eurasia,and the intensified subtropical westerlies along the southern foot of the Tibetan Plateau and the anomalous anticyclonic circulation over the subtropical western Pacific.Comparative analysis reveals that the stable cold air from the north and the warm and moist air from the south converge,facilitating a favorable environment for the concurrence of extensive low-temperature,precipitation and freezing weather.
基金supported by the National Key R&D Program of China[grant number 2018YFC0809400]the National Natural Science Foundation of China[grant number 41975057].
文摘Based on hourly precipitation from national surface stations,persistent heavy rainfall events(PHREs)over the Sichuan Basin(SCB)are explored during the warm season(May to September)from 2000 to 2015 to compare synoptic circulations and maintenance mechanisms between different PHRE types.There are two main types of PHREs:one is characterized by a rain belt west of 106°E over the SCB(WSB-PHREs),and the other features a rain belt east of 106°E over the SCB(ESB-PHREs).In total,there are 18 ESB-PHREs and 10 WSB-PHREs during the study period.Overall,the rain belts of WSB-PHREs are along the terrain distribution east of the Tibetan Plateau,while the precipitation intensity of ESB-PHREs is stronger.For the two types of PHREs,the shortwave trough over the SCB and the western Pacific subtropical high act as their favorable background environments,particularly for ESB-PHREs.The water vapor of WSB-PHREs is mainly transported from the South China Sea,whereas for ESB-PHREs the South China Sea and Bay of Bengal are their main moisture sources.The composite vorticity budgets of southwest vortices during their mature stage indicate that the convergence effect is a dominant factor for maintaining the two types of PHREs,and the strong vertical vorticity advection is also favorable,but the relative contribution of vertical advection is larger for WSB-PHREs.
文摘AIM To investigate the incidence of disadvantageous events by using the Global Trigger Tool in an intensive care unit(ICU).METHODS A retrospective descriptive study was performed in a 12-bed university ICU in the city of Medellin, Colombia. Clinical charts of hospitalized patients were reviewed, between January 1 and December 31, 2016, with the following inclusion criteria: subjects aged over 18 years, with at least 24 h of hospitalization and who had a complete medical history that could be accessed. Interventions: Trained reviewers conducted a retros pective examination of medical charts searching for clue events that elicit investigation, in order to detect an unfavorable event. Measurements: Information was processed through SPSS softwareversion 21; for numerical variables, the mean was reported with standard deviation(SD). Percentages were calculated for qualitative variables. RESULTS Two hundred and forty-four triggers occurred, with 82.4% of subjects having presented with at least one and an average of 3.37 (SD 3.47). A total of 178 adverse events (AEs) took place in 48 individuals, with an incidence of 52.1%. On average, four events per patient were recorded, and for each unfortunate event, 1.98 triggers were presented. The most frequent displeasing issues were: pressure ulcers(17.6%), followed by complications or reactions to medical devices(4.3%), and lacerations or skin defects(3.7%); the least frequent was delayed diagnosis or treatment (0.56%). Thirty-eight point four percent of mishap events caused temporary damage that required intervention, and 48.9% of AEs were preventable. Comparison between AEs and admission diagnoses found that hypertension and sepsis were the only diagnoses that had statistical significance (P = 0.042 and 0.022, respectively).CONCLUSION Almost half of the unfavorable issues were classified as avoidable, which leaves a very wide field of work in terms of preventative activities.
文摘The analytical and monitoring capabilities of central event re-positories, such as log servers and intrusion detection sys-tems, are limited by the amount of structured information ex-tracted from the events they receive. Diverse networks and ap-plications log their events in many different formats, and this makes it difficult to identify the type of logs being received by the central repository. The way events are logged by IT systems is problematic for developers of host-based intrusion-detection systems （specifically, host-based systems）, develop-ers of security-information systems, and developers of event-management systems. These problems preclude the develop-ment of more accurate, intrusive security solutions that obtain results from data included in the logs being processed. We propose a new method for dynamically normalizing events into a unified super-event that is loosely based on the Common Event Expression standard developed by Mitre Corporation. We explain how our solution can normalize seemingly unrelat-ed events into a single, unified format.
文摘Advanced Persistent Threat(APT)is now the most common network assault.However,the existing threat analysis models cannot simultaneously predict the macro-development trend and micro-propagation path of APT attacks.They cannot provide rapid and accurate early warning and decision responses to the present system state because they are inadequate at deducing the risk evolution rules of network threats.To address the above problems,firstly,this paper constructs the multi-source threat element analysis ontology(MTEAO)by integrating multi-source network security knowledge bases.Subsequently,based on MTEAO,we propose a two-layer threat prediction model(TL-TPM)that combines the knowledge graph and the event graph.The macro-layer of TL-TPM is based on the knowledge graph to derive the propagation path of threats among devices and to correlate threat elements for threat warning and decision-making;The micro-layer ingeniously maps the attack graph onto the event graph and derives the evolution path of attack techniques based on the event graph to improve the explainability of the evolution of threat events.The experiment’s results demonstrate that TL-TPM can completely depict the threat development trend,and the early warning results are more precise and scientific,offering knowledge and guidance for active defense.
