Flash Joule heating(FJH),as a high-efficiency and low-energy consumption technology for advanced materials synthesis,has shown significant potential in the synthesis of graphene and other functional carbon materials.B...Flash Joule heating(FJH),as a high-efficiency and low-energy consumption technology for advanced materials synthesis,has shown significant potential in the synthesis of graphene and other functional carbon materials.Based on the Joule effect,the solid carbon sources can be rapidly heated to ultra-high temperatures(>3000 K)through instantaneous high-energy current pulses during FJH,thus driving the rapid rearrangement and graphitization of carbon atoms.This technology demonstrates numerous advantages,such as solvent-and catalyst-free features,high energy conversion efficiency,and a short process cycle.In this review,we have systematically summarized the technology principle and equipment design for FJH,as well as its raw materials selection and pretreatment strategies.The research progress in the FJH synthesis of flash graphene,carbon nanotubes,graphene fibers,and anode hard carbon,as well as its by-products,is also presented.FJH can precisely optimize the microstructures of carbon materials(e.g.,interlayer spacing of turbostratic graphene,defect concentration,and heteroatom doping)by regulating its operation parameters like flash voltage and flash time,thereby enhancing their performances in various applications,such as composite reinforcement,metal-ion battery electrodes,supercapacitors,and electrocatalysts.However,this technology is still challenged by low process yield,macroscopic material uniformity,and green power supply system construction.More research efforts are also required to promote the transition of FJH from laboratory to industrial-scale applications,thus providing innovative solutions for advanced carbon materials manufacturing and waste management toward carbon neutrality.展开更多
研究聚焦于闪存转换层(FTL)中间件的性能差异,在256 MB Nor Flash硬件平台上,对FlashFX和TrueFFS两种闪存转换层进行了系统性对比评估,通过测量包括扇区擦除、文件打开、文件删除、单文件写入及文件连续写入等关键操作的耗时,量化分析...研究聚焦于闪存转换层(FTL)中间件的性能差异,在256 MB Nor Flash硬件平台上,对FlashFX和TrueFFS两种闪存转换层进行了系统性对比评估,通过测量包括扇区擦除、文件打开、文件删除、单文件写入及文件连续写入等关键操作的耗时,量化分析两者性能表现。结果表明FlashFX与TrueFFS在不同操作场景下(如擦除粒度处理、写入调度策略)存在显著性能差异,TrueFFS适用于高可靠性、长寿命需求的系统,FlashFX更适合对操作速度敏感的应用,二者选择需基于具体场景的性能与寿命进行权衡。展开更多
We investigate high-frequency traders’behavior in the context of the fastest and most extreme price movements(EPMs)that can be observed in the market,specifically ultrafast flash events,challenging the methodologies ...We investigate high-frequency traders’behavior in the context of the fastest and most extreme price movements(EPMs)that can be observed in the market,specifically ultrafast flash events,challenging the methodologies employed in the academic and practitioner literature for identifying sudden liquidity black holes.To refine the price-shock identification methodology,we introduce a new approach called sequence-based flash events(SFEs),which relies on tick sequences instead of predetermined fixed-time intervals within which all flash events in the sample are assumed to occur.This alternative methodology offers the advantage of pinpointing the exact time and duration of a crash,which,in turn,provides a way to more accurately define the observation windows around it.We compare our sample of SFEs with both the so-called“mini flash crashes”,as identified by the Nanex detection algorithm,and the so-called EPMs,as identified by Brogaard et al.(2018).We use close and open prices,as well as high and low prices.Based on our sample of SFEs,we find no evidence that HFTs trigger extreme price shocks.However,we find that HFTs exacerbate SFEs by increasing the net imbalance in the direction of these shocks as they occur.Finally,we show that the choice of the price-shock identification methodology is critical.Thus,we urge regulators to exercise caution and avoid hasty conclusions regarding HFTs’contribution to price stability in stressful market conditions.展开更多
Among natural disasters,flash floods are the most destructive events,causing signif-icant damage to the economy and posing a serious threat to human life and property.Comprehensive risk assessment of these sudden floo...Among natural disasters,flash floods are the most destructive events,causing signif-icant damage to the economy and posing a serious threat to human life and property.Comprehensive risk assessment of these sudden floods is a key strategy to mitigate their impact.Accurate analysis of flash flood hazards can greatly enhance prevention efforts and inform critical decision-making processes,ultimately improving our ability to protect communities from these fast-onset disasters.This study analyzed the driving forces of flash flood disaster-causing factors in Heilongjiang Province.Meanwhile,nine different categories of variables affecting the occurrence of flash floods were selected,and the degree of influence of each driving factor on flash floods was quantitatively analyzed,and the driving force analysis of the driving factors of flash floods in Hei-longjiang Province was carried out by using the geographic probe model.This paper employs an uncertainty approach,utilizing a statistical-based interval weight deter-mination technique for evaluation indices and a two-dimensional information-based interval number sorting method.These methodologies are combined to construct a comprehensive flash flood risk assessment model.On this basis,the model was implemented in six regions within China's Heilongjiang province to evaluate and prioritize flash flood risks.The resulting risk ranking for these areas was as follows:Bayan≻Shuangcheng≻Boli≻Suibin≻Hailun≻Yian.The findings demonstrate that the interval number-based evaluation method effectively handles uncertainty,providing a more reliable risk grading system.This approach,by leveraging modern scientific advances and risk quantification techniques,is crucial for improving disaster management and mitigating flash flood impacts.展开更多
Flash drought is characterized by a period of rapid drought intensification with impacts on agriculture,water resources,ecosystems,and human environment.In the Qilian Mountains,northwestern China,flash droughts are be...Flash drought is characterized by a period of rapid drought intensification with impacts on agriculture,water resources,ecosystems,and human environment.In the Qilian Mountains,northwestern China,flash droughts are becoming more frequently due to the global climate warming.However,the spatiotemporal variations and their driving factors of flash droughts are not clear in this region.In this study,the European Centre for Medium-range Weather Forecasts(ECMWF)Reanalysis v5-Land(ERA5-Land)dataset was utilized to identify two types of flash drought events(heatwave-induced and water scarcity-induced flash drought events)that occurred in the growing season(April‒September)during 1981-2020 in this area.The results showed that the frequency of heatwave-induced flash droughts has decreased since 2010,while the frequency of water scarcity-induced flash droughts has declined markedly.Spatially,heatwave-induced flash droughts were predominantly concentrated in the western Qilian Mountains,whereas water scarcity-induced flash droughts were primarily concentrated in the central and eastern Qilian Mountains.A significantly increasing temporal trend in both types of flash droughts in the eastern Qilian Mountains was found.Meanwhile,there was a decreasing temporal trend of heatwave-induced flash droughts in the southwestern part of the region.Additionally,the influence of two major atmospheric modes,i.e.,the El Niño‒Southern Oscillation(ENSO)and North Atlantic Oscillation(NAO),on these two types of flash droughts was explored by the Superposed Epoch Analysis.The ENSO mainly influences flash droughts in the central and eastern parts of the Qilian Mountains by altering the strength of the East Asian monsoon,while the NAO mainly affects flash droughts in the entire parts of the Qilian Mountains by inducing anomalous westerlies activity.Our findings have important implications for predicting the evolution of flash drought events in the Qilian Mountains region under continued climate warming.展开更多
基金supported by the National Natural Science Foundation of China(52276196)the Foundation of State Key Laboratory of Coal Combustion(FSKLCCA2508)the High-level Talent Foundation of Anhui Agricultural University(rc412307).
文摘Flash Joule heating(FJH),as a high-efficiency and low-energy consumption technology for advanced materials synthesis,has shown significant potential in the synthesis of graphene and other functional carbon materials.Based on the Joule effect,the solid carbon sources can be rapidly heated to ultra-high temperatures(>3000 K)through instantaneous high-energy current pulses during FJH,thus driving the rapid rearrangement and graphitization of carbon atoms.This technology demonstrates numerous advantages,such as solvent-and catalyst-free features,high energy conversion efficiency,and a short process cycle.In this review,we have systematically summarized the technology principle and equipment design for FJH,as well as its raw materials selection and pretreatment strategies.The research progress in the FJH synthesis of flash graphene,carbon nanotubes,graphene fibers,and anode hard carbon,as well as its by-products,is also presented.FJH can precisely optimize the microstructures of carbon materials(e.g.,interlayer spacing of turbostratic graphene,defect concentration,and heteroatom doping)by regulating its operation parameters like flash voltage and flash time,thereby enhancing their performances in various applications,such as composite reinforcement,metal-ion battery electrodes,supercapacitors,and electrocatalysts.However,this technology is still challenged by low process yield,macroscopic material uniformity,and green power supply system construction.More research efforts are also required to promote the transition of FJH from laboratory to industrial-scale applications,thus providing innovative solutions for advanced carbon materials manufacturing and waste management toward carbon neutrality.
文摘研究聚焦于闪存转换层(FTL)中间件的性能差异,在256 MB Nor Flash硬件平台上,对FlashFX和TrueFFS两种闪存转换层进行了系统性对比评估,通过测量包括扇区擦除、文件打开、文件删除、单文件写入及文件连续写入等关键操作的耗时,量化分析两者性能表现。结果表明FlashFX与TrueFFS在不同操作场景下(如擦除粒度处理、写入调度策略)存在显著性能差异,TrueFFS适用于高可靠性、长寿命需求的系统,FlashFX更适合对操作速度敏感的应用,二者选择需基于具体场景的性能与寿命进行权衡。
文摘We investigate high-frequency traders’behavior in the context of the fastest and most extreme price movements(EPMs)that can be observed in the market,specifically ultrafast flash events,challenging the methodologies employed in the academic and practitioner literature for identifying sudden liquidity black holes.To refine the price-shock identification methodology,we introduce a new approach called sequence-based flash events(SFEs),which relies on tick sequences instead of predetermined fixed-time intervals within which all flash events in the sample are assumed to occur.This alternative methodology offers the advantage of pinpointing the exact time and duration of a crash,which,in turn,provides a way to more accurately define the observation windows around it.We compare our sample of SFEs with both the so-called“mini flash crashes”,as identified by the Nanex detection algorithm,and the so-called EPMs,as identified by Brogaard et al.(2018).We use close and open prices,as well as high and low prices.Based on our sample of SFEs,we find no evidence that HFTs trigger extreme price shocks.However,we find that HFTs exacerbate SFEs by increasing the net imbalance in the direction of these shocks as they occur.Finally,we show that the choice of the price-shock identification methodology is critical.Thus,we urge regulators to exercise caution and avoid hasty conclusions regarding HFTs’contribution to price stability in stressful market conditions.
基金Basic Scientific Research Expense Project of IWHR-Extreme rainstorm development trends and prediction techniques,Grant/Award Number:JZ0145B142024National Natural Science Foundation of China,Grant/Award Number:42271095。
文摘Among natural disasters,flash floods are the most destructive events,causing signif-icant damage to the economy and posing a serious threat to human life and property.Comprehensive risk assessment of these sudden floods is a key strategy to mitigate their impact.Accurate analysis of flash flood hazards can greatly enhance prevention efforts and inform critical decision-making processes,ultimately improving our ability to protect communities from these fast-onset disasters.This study analyzed the driving forces of flash flood disaster-causing factors in Heilongjiang Province.Meanwhile,nine different categories of variables affecting the occurrence of flash floods were selected,and the degree of influence of each driving factor on flash floods was quantitatively analyzed,and the driving force analysis of the driving factors of flash floods in Hei-longjiang Province was carried out by using the geographic probe model.This paper employs an uncertainty approach,utilizing a statistical-based interval weight deter-mination technique for evaluation indices and a two-dimensional information-based interval number sorting method.These methodologies are combined to construct a comprehensive flash flood risk assessment model.On this basis,the model was implemented in six regions within China's Heilongjiang province to evaluate and prioritize flash flood risks.The resulting risk ranking for these areas was as follows:Bayan≻Shuangcheng≻Boli≻Suibin≻Hailun≻Yian.The findings demonstrate that the interval number-based evaluation method effectively handles uncertainty,providing a more reliable risk grading system.This approach,by leveraging modern scientific advances and risk quantification techniques,is crucial for improving disaster management and mitigating flash flood impacts.
基金supported by the National Natural Science Foundation of China(42477481,42477483)the Science and Technology Program in Gansu Province(23JRRA599)the Chinese Academy of Sciences(CAS)"Light of West China"Program.
文摘Flash drought is characterized by a period of rapid drought intensification with impacts on agriculture,water resources,ecosystems,and human environment.In the Qilian Mountains,northwestern China,flash droughts are becoming more frequently due to the global climate warming.However,the spatiotemporal variations and their driving factors of flash droughts are not clear in this region.In this study,the European Centre for Medium-range Weather Forecasts(ECMWF)Reanalysis v5-Land(ERA5-Land)dataset was utilized to identify two types of flash drought events(heatwave-induced and water scarcity-induced flash drought events)that occurred in the growing season(April‒September)during 1981-2020 in this area.The results showed that the frequency of heatwave-induced flash droughts has decreased since 2010,while the frequency of water scarcity-induced flash droughts has declined markedly.Spatially,heatwave-induced flash droughts were predominantly concentrated in the western Qilian Mountains,whereas water scarcity-induced flash droughts were primarily concentrated in the central and eastern Qilian Mountains.A significantly increasing temporal trend in both types of flash droughts in the eastern Qilian Mountains was found.Meanwhile,there was a decreasing temporal trend of heatwave-induced flash droughts in the southwestern part of the region.Additionally,the influence of two major atmospheric modes,i.e.,the El Niño‒Southern Oscillation(ENSO)and North Atlantic Oscillation(NAO),on these two types of flash droughts was explored by the Superposed Epoch Analysis.The ENSO mainly influences flash droughts in the central and eastern parts of the Qilian Mountains by altering the strength of the East Asian monsoon,while the NAO mainly affects flash droughts in the entire parts of the Qilian Mountains by inducing anomalous westerlies activity.Our findings have important implications for predicting the evolution of flash drought events in the Qilian Mountains region under continued climate warming.
