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
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
Defense systems are needed to prevent catastrophic failures of a power grid due to cascaded events.Cascaded events can be attributed to improper operations of protective relays.The most challenging problem for the des...Defense systems are needed to prevent catastrophic failures of a power grid due to cascaded events.Cascaded events can be attributed to improper operations of protective relays.The most challenging problem for the design and implementation of a defense system is the perform- ance in accuracy and speed in a real time environment.Protective devices are normally designed to operate fast in order to isolate the fault(s).This paper proposes a new methodology to distin- guish line overloads from actual faults for distance relays.In order to distinguish between line flow transfers from a line outage and an actual fault,the line outage distribution factor(LODF)and gen- eration shift factor(GSF)based power flow estimation method,and a secure peer to peer(P2P) communication structure are adopted.Computer simulations of cascaded events for a 6-bus system and the Korean power grid have been performed to establish the feasibility of the proposed scheme.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
This paper offers preliminary work on system dynamics and Data mining tools. It tries to understand the dynamics of carrying out large-scale events, such as Hajj. The study looks at a large, recurring problem as a var...This paper offers preliminary work on system dynamics and Data mining tools. It tries to understand the dynamics of carrying out large-scale events, such as Hajj. The study looks at a large, recurring problem as a variable to consider, such as how the flow of people changes over time as well as how location interacts with placement. The predicted data is analyzed using Vensim PLE 32 modeling software, GIS Arc Map 10.2.1, and AnyLogic 7.3.1 software regarding the potential placement of temporal service points, taking into consideration the three dynamic constraints and behavioral aspects: a large population, limitation in time, and space. This research proposes appropriate data analyses to ensure the optimal positioning of the service points with limited time and space for large-scale events. The conceptual framework would be the output of this study. Knowledge may be added to the insights based on the technique.展开更多
Large-scale urban events like the Olympic Games,the World Expo,etc.,have brought about an "approach" leading to renewed conservation measures for old city areas.While they make many heritages receive better ...Large-scale urban events like the Olympic Games,the World Expo,etc.,have brought about an "approach" leading to renewed conservation measures for old city areas.While they make many heritages receive better protection,they also create new problem of "threshold" to heritage conservation;thus,ideas about the effects of large-scale urban events on cultural heritage preservation are polarized into two opposite directions.Using cultural anthropology as the basis of analysis,this article interprets how these conflicting concepts came to be.As large-scale urban events accelerate and strengthen urban development,they also often cause the abandonment of specific cultural elements during the process of heritage conservation for the oldest city areas.This leads to a general loss of direction in cultural protection efforts.A potential solution is to unearth the cultural spirit of the old cities and preserve it through practical technologies,in considering the specific function of large-scale urban events.In so doing,it is possible to explore new directions and approaches to conserve the heritages of the old city under the guide of urban cultural development strategies.展开更多
Power system restoration has attracted more attention and made great progress recently. Research progress of the power system restoration from 2006 to 2016 is reviewed in this paper, including black-start, network rec...Power system restoration has attracted more attention and made great progress recently. Research progress of the power system restoration from 2006 to 2016 is reviewed in this paper, including black-start, network reconfiguration and load restoration. Some emerging methods and key techniques are also discussed in the context of the integration of variable renewable energy and development of the smart grid. There is a long way to go to achieve automatic self-healing in bulk power systems because of its extreme complexity. However, rapidly developing artificial intelligence technology will eventually enable the step-by-step dynamic decision-making based on the situation awareness of supervisory control and data acquisition systems(SCADA) and wide area measurement systems(WAMS) in the near future.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.
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Ministry of Science&Technology of Korea and Korea Science&Engineering Foundation Through ERC(Engineering Research Center)Program.
文摘Defense systems are needed to prevent catastrophic failures of a power grid due to cascaded events.Cascaded events can be attributed to improper operations of protective relays.The most challenging problem for the design and implementation of a defense system is the perform- ance in accuracy and speed in a real time environment.Protective devices are normally designed to operate fast in order to isolate the fault(s).This paper proposes a new methodology to distin- guish line overloads from actual faults for distance relays.In order to distinguish between line flow transfers from a line outage and an actual fault,the line outage distribution factor(LODF)and gen- eration shift factor(GSF)based power flow estimation method,and a secure peer to peer(P2P) communication structure are adopted.Computer simulations of cascaded events for a 6-bus system and the Korean power grid have been performed to establish the feasibility of the proposed scheme.
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.
文摘This paper offers preliminary work on system dynamics and Data mining tools. It tries to understand the dynamics of carrying out large-scale events, such as Hajj. The study looks at a large, recurring problem as a variable to consider, such as how the flow of people changes over time as well as how location interacts with placement. The predicted data is analyzed using Vensim PLE 32 modeling software, GIS Arc Map 10.2.1, and AnyLogic 7.3.1 software regarding the potential placement of temporal service points, taking into consideration the three dynamic constraints and behavioral aspects: a large population, limitation in time, and space. This research proposes appropriate data analyses to ensure the optimal positioning of the service points with limited time and space for large-scale events. The conceptual framework would be the output of this study. Knowledge may be added to the insights based on the technique.
文摘Large-scale urban events like the Olympic Games,the World Expo,etc.,have brought about an "approach" leading to renewed conservation measures for old city areas.While they make many heritages receive better protection,they also create new problem of "threshold" to heritage conservation;thus,ideas about the effects of large-scale urban events on cultural heritage preservation are polarized into two opposite directions.Using cultural anthropology as the basis of analysis,this article interprets how these conflicting concepts came to be.As large-scale urban events accelerate and strengthen urban development,they also often cause the abandonment of specific cultural elements during the process of heritage conservation for the oldest city areas.This leads to a general loss of direction in cultural protection efforts.A potential solution is to unearth the cultural spirit of the old cities and preserve it through practical technologies,in considering the specific function of large-scale urban events.In so doing,it is possible to explore new directions and approaches to conserve the heritages of the old city under the guide of urban cultural development strategies.
基金supported by National Basic Research Program of China(973 Program)(No.2012CB215101)
文摘Power system restoration has attracted more attention and made great progress recently. Research progress of the power system restoration from 2006 to 2016 is reviewed in this paper, including black-start, network reconfiguration and load restoration. Some emerging methods and key techniques are also discussed in the context of the integration of variable renewable energy and development of the smart grid. There is a long way to go to achieve automatic self-healing in bulk power systems because of its extreme complexity. However, rapidly developing artificial intelligence technology will eventually enable the step-by-step dynamic decision-making based on the situation awareness of supervisory control and data acquisition systems(SCADA) and wide area measurement systems(WAMS) in the near future.
