During the two cruises in March and July of 2011, the tidal cycling of turbulent properties and the T/S profiles at the same location in seasonally stratified East China Sea （ECS） were measured synchronously by a bo...During the two cruises in March and July of 2011, the tidal cycling of turbulent properties and the T/S profiles at the same location in seasonally stratified East China Sea （ECS） were measured synchronously by a bottom-mounted fast sampling ADCP （acoustic Doppler current profiler） and a RBR CTD （RBR-620） profiler. While focusing on the tide-induced and stratification＇s impact on mixing, the Reynolds stress and the turbulent kinetic energy （TKE） production rate were calculated using the ‘variance method＇. In spring, the features of mixing mainly induced by tides were clear when the water column was well-mixed. Velocity shear and turbulent parameters intensified towards the seabed due to the bottom friction. The components of the velocity shear and the Reynolds stress displayed a dominant semi-diurnal variation related to velocity changes caused by the flood and ebb of M2 tide. Stratification occurred in summer, and the water column showed a strongly stratified pycnocline with a characteristic squared buoy- ancy frequency of N2~ （1-6）x 10 3 S-2 The components of the velocity shear and the Reynolds stress penetrated upwards very fast from the bottom boundary layer to the whole water column in spring, while in summer they only penetrated to the bottom of the pycnocline with a relatively slow propagation speed. In summer, the TKE production within the pycnocline was comparable with and sometimes larger than that in the well-mixed bottom layer under the pycnocline. Considering the associated high velocity shear, it is speculated that the mixing in the pycnocline is a result of the local velocity shear.展开更多
As the Smart city trend especially artificial intelligence,data science,and the internet of things has attracted lots of attention,many researchers have created various smart applications for improving people’s life ...As the Smart city trend especially artificial intelligence,data science,and the internet of things has attracted lots of attention,many researchers have created various smart applications for improving people’s life quality.As it is very essential to automatically collect and exploit information in the era of industry 4.0,a variety of models have been proposed for storage problem solving and efficient data mining.In this paper,we present our proposed system,Trendy Keyword Extraction System(TKES),which is designed for extracting trendy keywords from text streams.The system also supports storing,analyzing,and visualizing documents coming from text streams.The system first automatically collects daily articles,then it ranks the importance of keywords by calculating keywords’frequency of existence in order to find trendy keywords by using the Burst Detection Algorithm which is proposed in this paper based on the idea of Kleinberg.This method is used for detecting bursts.A burst is defined as a period of time when a keyword is continuously and unusually popular over the text stream and the identification of bursts is known as burst detection procedure.The results from user requests could be displayed visually.Furthermore,we create a method in order to find a trendy keyword set which is defined as a set of keywords that belong to the same burst.This work also describes the datasets used for our experiments,processing speed tests of our two proposed algorithms.展开更多
Due to the arid and sandy surface of the Taklimakan Desert(TD)in China,the turbulence structure and vertical distribution of ozone exhibit unique and complex characteristics.However,few studies have focused on these i...Due to the arid and sandy surface of the Taklimakan Desert(TD)in China,the turbulence structure and vertical distribution of ozone exhibit unique and complex characteristics.However,few studies have focused on these issues.To reveal the variation characteristics of summertime atmospheric turbulence and ozone concentration over the TD,we conducted joint detection experiments in July 2016 and July 2021 at Tazhong in the hinterland of the TD using an eddy covariance detection system,a GPS(Global Positioning System)sounding system,and a meteorological gradient tower.Using methods such as statistical analysis,nonlinear fitting,and Fast Fourier Transform,this study analyzed and processed parameters including temperature,relative humidity,wind speed,turbulence parameters,turbulence spectra,and ozone concentration.The high average temperature is accompanied by low relative humidity over the TD,showing a negative correlation between the two.The temperature of the 10.0-cm-deep sand layer lags the near-surface air temperature by nearly 4 h.From 09:30 to 21:00(Beijing Time),under conditions where the sensible heat flux is positive but stability parameter(z/L,where z is the height and L is the Obukhov length)is negative,the atmosphere is heated by the land surface,with the occurrence of unstable stratification;however,the conditions are the opposite(sensible heat flux is negative and z/L is positive)after 22:00,which are accompanied with the cooling of the surface radiation,occurrence of temperature inversion in the lower atmosphere,and stable stratification.A positive correlation is identified between the diurnal variation of turbulent kinetic energy(TKE)and the atmospheric boundary layer(ABL)height,with significant contributions from both the buoyancy and shear terms during the daytime.Under unstable stratification,the normalized standard deviations of the three-dimensional wind speed,temperature,and humidity conform to the Monin-Obukhov Similarity Theory(MOST).As the stability parameter z/L transitions from strongly unstable to strongly stable,the energy of the dimensionless turbulent velocity spectra gradually decreases and conforms to the -2/3 power law within the inertial subrange.In the hinterland of the TD,the summertime tropospheric ozone concentration remains below approximately 0.70×10^(-6)(volume concentration).Above the troposphere,within the range of 16,500.0-30,000.0 m,a significant increasing trend is identified in the ozone concentration with altitude.At an altitude of 30,000.0 m,the maximum ozone concentration can reach up to 7.50×10^(-6).The research findings provide both theoretical and data foundations for future in-depth studies of turbulent motion and ozone concentration distribution in the TD,as well as in the similar areas around the world.展开更多
Breaking wave induced nearsurface turbulence has important consequences for many physical and biochemical processes including water column and nutrients mixing, heat and gases exchange across air-sea interface. The en...Breaking wave induced nearsurface turbulence has important consequences for many physical and biochemical processes including water column and nutrients mixing, heat and gases exchange across air-sea interface. The energy loss from wave breaking and the bubble plume penetration depth are estimated. As a consequence, the vertical distribution of the turbulent kinetic energy （TKE）, the TKE dissipation rate and the eddy viscosity induced by wave breaking are also provided. It is indicated that model results are found to be consistent with the observational evidence that most TKE generated by wave breaking is lost within a depth of a few meters near the sea surface. High turbulence level with intensities of eddy viscosity induced by breaking is nearly four orders larger than vw1（ = κu ＊wz）, the value predicted for the wall layer scaling close to the surface, where u ＊w is the friction velocity in water, κ with 0. 4 is the yon Kármán constant, and z is the water depth, and the strength of the eddy viscosity depends both on wind speed and sea state, and decays rapidly through the depth. This leads to the conclusion that the breaking wave induced vertical mixing is mainly limited to the near surface layer, well above the classical values expected from the similarity theory. Deeper down, however, the effects of wave breaking on the vertical mixing become less important.展开更多
基金supported by the National Basic Research Program of China (973 Program,2010CB428904)the National Science Foundation of China (No.41276016)+1 种基金the Program for New Century Excellent Talents in University (NCET-11-0475)the National Key Technology R&D Program of China (2011BAC03B02)
文摘During the two cruises in March and July of 2011, the tidal cycling of turbulent properties and the T/S profiles at the same location in seasonally stratified East China Sea （ECS） were measured synchronously by a bottom-mounted fast sampling ADCP （acoustic Doppler current profiler） and a RBR CTD （RBR-620） profiler. While focusing on the tide-induced and stratification＇s impact on mixing, the Reynolds stress and the turbulent kinetic energy （TKE） production rate were calculated using the ‘variance method＇. In spring, the features of mixing mainly induced by tides were clear when the water column was well-mixed. Velocity shear and turbulent parameters intensified towards the seabed due to the bottom friction. The components of the velocity shear and the Reynolds stress displayed a dominant semi-diurnal variation related to velocity changes caused by the flood and ebb of M2 tide. Stratification occurred in summer, and the water column showed a strongly stratified pycnocline with a characteristic squared buoy- ancy frequency of N2~ （1-6）x 10 3 S-2 The components of the velocity shear and the Reynolds stress penetrated upwards very fast from the bottom boundary layer to the whole water column in spring, while in summer they only penetrated to the bottom of the pycnocline with a relatively slow propagation speed. In summer, the TKE production within the pycnocline was comparable with and sometimes larger than that in the well-mixed bottom layer under the pycnocline. Considering the associated high velocity shear, it is speculated that the mixing in the pycnocline is a result of the local velocity shear.
基金The work of Tham Vo is supported by Lac Hong University,and funded by Thu Dau Mot University(No.DT.20-031)The work of Phuc Do is funded by Vietnam National University,Ho Chi Minh City(No.DS2020-26-01).
文摘As the Smart city trend especially artificial intelligence,data science,and the internet of things has attracted lots of attention,many researchers have created various smart applications for improving people’s life quality.As it is very essential to automatically collect and exploit information in the era of industry 4.0,a variety of models have been proposed for storage problem solving and efficient data mining.In this paper,we present our proposed system,Trendy Keyword Extraction System(TKES),which is designed for extracting trendy keywords from text streams.The system also supports storing,analyzing,and visualizing documents coming from text streams.The system first automatically collects daily articles,then it ranks the importance of keywords by calculating keywords’frequency of existence in order to find trendy keywords by using the Burst Detection Algorithm which is proposed in this paper based on the idea of Kleinberg.This method is used for detecting bursts.A burst is defined as a period of time when a keyword is continuously and unusually popular over the text stream and the identification of bursts is known as burst detection procedure.The results from user requests could be displayed visually.Furthermore,we create a method in order to find a trendy keyword set which is defined as a set of keywords that belong to the same burst.This work also describes the datasets used for our experiments,processing speed tests of our two proposed algorithms.
基金financially supported by"Tianshan Talent"Training Program-Science and Technology Innovation Team(Tianshan Innovation Team)Project(2022TSYCTD0007)the Youth Innovation Team of China Meteorological Administration(CMA2024QN13)+2 种基金the Central Government Guidance Funds for Local Science and Technology Development Program(ZYYD2025ZY21)the S&T Development Fund of Chinese Academy of Meteorological Sciences(2021KJ034)the Xinjiang Science Fund for Distinguished Young Scholars(2022D01E07).
文摘Due to the arid and sandy surface of the Taklimakan Desert(TD)in China,the turbulence structure and vertical distribution of ozone exhibit unique and complex characteristics.However,few studies have focused on these issues.To reveal the variation characteristics of summertime atmospheric turbulence and ozone concentration over the TD,we conducted joint detection experiments in July 2016 and July 2021 at Tazhong in the hinterland of the TD using an eddy covariance detection system,a GPS(Global Positioning System)sounding system,and a meteorological gradient tower.Using methods such as statistical analysis,nonlinear fitting,and Fast Fourier Transform,this study analyzed and processed parameters including temperature,relative humidity,wind speed,turbulence parameters,turbulence spectra,and ozone concentration.The high average temperature is accompanied by low relative humidity over the TD,showing a negative correlation between the two.The temperature of the 10.0-cm-deep sand layer lags the near-surface air temperature by nearly 4 h.From 09:30 to 21:00(Beijing Time),under conditions where the sensible heat flux is positive but stability parameter(z/L,where z is the height and L is the Obukhov length)is negative,the atmosphere is heated by the land surface,with the occurrence of unstable stratification;however,the conditions are the opposite(sensible heat flux is negative and z/L is positive)after 22:00,which are accompanied with the cooling of the surface radiation,occurrence of temperature inversion in the lower atmosphere,and stable stratification.A positive correlation is identified between the diurnal variation of turbulent kinetic energy(TKE)and the atmospheric boundary layer(ABL)height,with significant contributions from both the buoyancy and shear terms during the daytime.Under unstable stratification,the normalized standard deviations of the three-dimensional wind speed,temperature,and humidity conform to the Monin-Obukhov Similarity Theory(MOST).As the stability parameter z/L transitions from strongly unstable to strongly stable,the energy of the dimensionless turbulent velocity spectra gradually decreases and conforms to the -2/3 power law within the inertial subrange.In the hinterland of the TD,the summertime tropospheric ozone concentration remains below approximately 0.70×10^(-6)(volume concentration).Above the troposphere,within the range of 16,500.0-30,000.0 m,a significant increasing trend is identified in the ozone concentration with altitude.At an altitude of 30,000.0 m,the maximum ozone concentration can reach up to 7.50×10^(-6).The research findings provide both theoretical and data foundations for future in-depth studies of turbulent motion and ozone concentration distribution in the TD,as well as in the similar areas around the world.
基金This research was supported by the National Natural Science Foundation of China under contract Nos 40576021 and 40531005.
文摘Breaking wave induced nearsurface turbulence has important consequences for many physical and biochemical processes including water column and nutrients mixing, heat and gases exchange across air-sea interface. The energy loss from wave breaking and the bubble plume penetration depth are estimated. As a consequence, the vertical distribution of the turbulent kinetic energy （TKE）, the TKE dissipation rate and the eddy viscosity induced by wave breaking are also provided. It is indicated that model results are found to be consistent with the observational evidence that most TKE generated by wave breaking is lost within a depth of a few meters near the sea surface. High turbulence level with intensities of eddy viscosity induced by breaking is nearly four orders larger than vw1（ = κu ＊wz）, the value predicted for the wall layer scaling close to the surface, where u ＊w is the friction velocity in water, κ with 0. 4 is the yon Kármán constant, and z is the water depth, and the strength of the eddy viscosity depends both on wind speed and sea state, and decays rapidly through the depth. This leads to the conclusion that the breaking wave induced vertical mixing is mainly limited to the near surface layer, well above the classical values expected from the similarity theory. Deeper down, however, the effects of wave breaking on the vertical mixing become less important.
