Based on the routine observation data,the satellite cloud images and so on,the synoptics analysis and the diagnostic analysis of physical quantity field were used to analyze the heavy snowstorm process which happened ...Based on the routine observation data,the satellite cloud images and so on,the synoptics analysis and the diagnostic analysis of physical quantity field were used to analyze the heavy snowstorm process which happened in Northeast China during March 3-5 in 2007.The results showed that the main influence systems in the process were the eastward shift and up north of southern cyclone,the combination of south and north branches upper troughs in 500 hPa.The dynamic mechanisms of heavy snowstorm formation were the strong ascending movement which was caused by the configuration of high-layer divergence and low-layer convergence,the generation and maintenance of deep and thick positive vorticity in the middle and low layers.The sufficient water vapor in the East China Sea and the South China Sea which was brought by 700 hPa by south low-level jet stream reached Northeast China.The falling zones of strong precipitation were consistent with the big value zones of 850 hPa positive vorticity and 200 hPa positive divergence.Meanwhile,the intensity of temperature advection and the position of cold warm transition zone could reflect well the intensity and falling zone of precipitation.展开更多
Resource description framework(RDF)stream is useful to model spatio-temporal data.In this paper,we propose a framework for large-scale RDF stream processing,LRSP,to process general continuous queries over large-scale ...Resource description framework(RDF)stream is useful to model spatio-temporal data.In this paper,we propose a framework for large-scale RDF stream processing,LRSP,to process general continuous queries over large-scale RDF streams.Firstly,we propose a formalization(named CT-SPARQL)to represent the general continuous queries in a unified,unambiguous way.Secondly,based on our formalization we propose LRSP to process continuous queries in a common white-box way by separating RDF stream processing,query parsing,and query execution.Finally,we implement and evaluate LRSP with those popular continuous query engines on some benchmark datasets and real-world datasets.Due to the architecture of LRSP,many efficient query engines(including centralized and distributed engines)for RDF can be directly employed to process continuous queries.The experimental results show that LRSP has a higher performance,specially,in processing large-scale real-world data.展开更多
The production of high quality single-walled carbon nanotubes(SWCNTs)on a bulk scale has been an issue of considerable interest.Recently,it has been demonstrated that high quality SWCNTs can be continuously synthesize...The production of high quality single-walled carbon nanotubes(SWCNTs)on a bulk scale has been an issue of considerable interest.Recently,it has been demonstrated that high quality SWCNTs can be continuously synthesized on large scale by using induction thermal plasma technology.In this process,the high energy density of the thermal plasma is employed to generate dense vapor-phase precursors for the synthesis of SWCNTs.With the current reactor system,a carbon soot product which contains approximately 40 wt%of SWCNTs can be continuously synthesized at the high production rate of~100 g/h.In this article,our recent research efforts to achieve major advances in this technology are presented.Firstly,the processing parameters involved are examined systematically in order to evaluate their individual inuences on the SWCNT synthesis.Based on these results,the appropriate operating conditions of the induction thermal plasma process for an effective synthesis of SWCNTs are discussed.A characterization study has also been performed on the SWCNTs produced under the optimum processing conditions.Finally,a mathematical model of the process currently under development is described.The model will help us to better understand the synthesis of SWCNTs in the induction plasma process.展开更多
This paper proposes a new method for control of continuous large-scale systems where the measures and control functions are distributed on calculating members which can be shared with other applications and connected ...This paper proposes a new method for control of continuous large-scale systems where the measures and control functions are distributed on calculating members which can be shared with other applications and connected to digital network communications.At first, the nonlinear large-scale system is described by a Takagi-Sugeno(TS) fuzzy model. After that, by using a fuzzy LyapunovKrasovskii functional, sufficient conditions of asymptotic stability of the behavior of the decentralized networked control system(DNCS),are developed in terms of linear matrix inequalities(LMIs). Finally, to illustrate the proposed approach, a numerical example and simulation results are presented.展开更多
This observational study investigates the variation of PM2.5 concentration and its ratio against PM10 concentration under different weather systems and pollution types. The study was conducted in Hangzhou on east Chin...This observational study investigates the variation of PM2.5 concentration and its ratio against PM10 concentration under different weather systems and pollution types. The study was conducted in Hangzhou on east China＇s Yangtze River Delta using data collected at seven ambient air quality monitoring stations around the metropolitan area between 2006 and 2008 and using weather information in the same period. Nine predominant weather systems affecting the city were classified through careful analysis of the 11- year surface and upper air weather charts from 1996 to 2006. Each observational day was then assigned to one of the nine weather systems. It was found that the PM2.5 concentration varied greatly for different weather systems, with the highest PM2.5 concentration associated with the post-cold-frontal system at 0.091 mg/m^3 and the lowest PM2.5 concentration with the easterlies system at 0.038 mg/m^3, although the PM2.5/PM10 ratio remained consistently above 0.5 for all systems. The post-cold-frontal system typically occurs in autumn and winter while the easterlies system is more a summer phenomenon. Among all types of pollution, the highest PM2.5 concentration of 0.117 mg/m^3 coincided with the large-scale continuous pollution events, suggesting that this type of pollution was more conducive to the formation of secondary particulate matters. The ratio of PM2.5/PM10 was above 0.5 in non-pollution days and all pollution types but one under the influence of dust storms when the ratio decreased to 0.3 or less. The outcomes of this study could be used to develop a rudimental predictive model of PM2.5 concentration based on weather system and pollution type.展开更多
文摘Based on the routine observation data,the satellite cloud images and so on,the synoptics analysis and the diagnostic analysis of physical quantity field were used to analyze the heavy snowstorm process which happened in Northeast China during March 3-5 in 2007.The results showed that the main influence systems in the process were the eastward shift and up north of southern cyclone,the combination of south and north branches upper troughs in 500 hPa.The dynamic mechanisms of heavy snowstorm formation were the strong ascending movement which was caused by the configuration of high-layer divergence and low-layer convergence,the generation and maintenance of deep and thick positive vorticity in the middle and low layers.The sufficient water vapor in the East China Sea and the South China Sea which was brought by 700 hPa by south low-level jet stream reached Northeast China.The falling zones of strong precipitation were consistent with the big value zones of 850 hPa positive vorticity and 200 hPa positive divergence.Meanwhile,the intensity of temperature advection and the position of cold warm transition zone could reflect well the intensity and falling zone of precipitation.
基金the National Key Research and Development Program of China under Grant No.2017YFC0908401the National Natural Science Foundation of China under Grant No.61672377the program of Peiyang Young Scholars of China under Grant No.2019XRX-0032.
文摘Resource description framework(RDF)stream is useful to model spatio-temporal data.In this paper,we propose a framework for large-scale RDF stream processing,LRSP,to process general continuous queries over large-scale RDF streams.Firstly,we propose a formalization(named CT-SPARQL)to represent the general continuous queries in a unified,unambiguous way.Secondly,based on our formalization we propose LRSP to process continuous queries in a common white-box way by separating RDF stream processing,query parsing,and query execution.Finally,we implement and evaluate LRSP with those popular continuous query engines on some benchmark datasets and real-world datasets.Due to the architecture of LRSP,many efficient query engines(including centralized and distributed engines)for RDF can be directly employed to process continuous queries.The experimental results show that LRSP has a higher performance,specially,in processing large-scale real-world data.
基金This work was supported by the Natural Science and Engineering Research Council(NSERC)of Canada.
文摘The production of high quality single-walled carbon nanotubes(SWCNTs)on a bulk scale has been an issue of considerable interest.Recently,it has been demonstrated that high quality SWCNTs can be continuously synthesized on large scale by using induction thermal plasma technology.In this process,the high energy density of the thermal plasma is employed to generate dense vapor-phase precursors for the synthesis of SWCNTs.With the current reactor system,a carbon soot product which contains approximately 40 wt%of SWCNTs can be continuously synthesized at the high production rate of~100 g/h.In this article,our recent research efforts to achieve major advances in this technology are presented.Firstly,the processing parameters involved are examined systematically in order to evaluate their individual inuences on the SWCNT synthesis.Based on these results,the appropriate operating conditions of the induction thermal plasma process for an effective synthesis of SWCNTs are discussed.A characterization study has also been performed on the SWCNTs produced under the optimum processing conditions.Finally,a mathematical model of the process currently under development is described.The model will help us to better understand the synthesis of SWCNTs in the induction plasma process.
文摘This paper proposes a new method for control of continuous large-scale systems where the measures and control functions are distributed on calculating members which can be shared with other applications and connected to digital network communications.At first, the nonlinear large-scale system is described by a Takagi-Sugeno(TS) fuzzy model. After that, by using a fuzzy LyapunovKrasovskii functional, sufficient conditions of asymptotic stability of the behavior of the decentralized networked control system(DNCS),are developed in terms of linear matrix inequalities(LMIs). Finally, to illustrate the proposed approach, a numerical example and simulation results are presented.
基金funded by the Hangzhou Key Sci_technology & Innovative Project(No.20092113A05)
文摘This observational study investigates the variation of PM2.5 concentration and its ratio against PM10 concentration under different weather systems and pollution types. The study was conducted in Hangzhou on east China＇s Yangtze River Delta using data collected at seven ambient air quality monitoring stations around the metropolitan area between 2006 and 2008 and using weather information in the same period. Nine predominant weather systems affecting the city were classified through careful analysis of the 11- year surface and upper air weather charts from 1996 to 2006. Each observational day was then assigned to one of the nine weather systems. It was found that the PM2.5 concentration varied greatly for different weather systems, with the highest PM2.5 concentration associated with the post-cold-frontal system at 0.091 mg/m^3 and the lowest PM2.5 concentration with the easterlies system at 0.038 mg/m^3, although the PM2.5/PM10 ratio remained consistently above 0.5 for all systems. The post-cold-frontal system typically occurs in autumn and winter while the easterlies system is more a summer phenomenon. Among all types of pollution, the highest PM2.5 concentration of 0.117 mg/m^3 coincided with the large-scale continuous pollution events, suggesting that this type of pollution was more conducive to the formation of secondary particulate matters. The ratio of PM2.5/PM10 was above 0.5 in non-pollution days and all pollution types but one under the influence of dust storms when the ratio decreased to 0.3 or less. The outcomes of this study could be used to develop a rudimental predictive model of PM2.5 concentration based on weather system and pollution type.
