On the basis of the solution of the space-time characteristic system by the method of geometric optics using symbolic calculations,analytical and numerical simulation of the propagation of the ordinary and extraordina...On the basis of the solution of the space-time characteristic system by the method of geometric optics using symbolic calculations,analytical and numerical simulation of the propagation of the ordinary and extraordinary radio waves in the conducting equatorial ionospheric plasma was made considering the anisotropy of plasma irregularities and non-stationary nature of propagation medium.Broadening of the spectrum and the displacement of its maximum contain velocity of a turbulent plasma flow and parameters characterizing anisotropic plasmonic structures.Statistical moments of both radio waves do not depend on the absorption sign and are valid for both active and absorptive random media.Temporal pulsations and conductivity of a turbulent ionospheric plasma have an influence on the evaluation of the spectrum-varying propagation distances travelling by these waves.The new double-humped effect in the temporal spectrum has been revealed for the ordinary wave varying anisotropy coefficient and dip angle of stretched plasmonic structures.From a theoretical point of view,the algorithms developed in this work allow effective modelling of the propagation of both radio signals in the equatorial conductive ionospheric plasma,considering the external magnetic field,inhomogeneities of electron density in-homogeneities,as well as non-stationary.展开更多
The statistical characteristics of the Current fluctuations during metastable pitting of 316L stain- less steel in NaCI solution were studied using potentiostatic method. The growth rates and peak currents of metastab...The statistical characteristics of the Current fluctuations during metastable pitting of 316L stain- less steel in NaCI solution were studied using potentiostatic method. The growth rates and peak currents of metastable pits followed log-normal distributions. As potential and chloride concentration increased, both growth rate and peak current of metastable pits increased. The lifetime of metastable pits also followed log-normal distribution. and was almost not affected by potential. Higher growth rates did not definitely result in larger metastable pits. A certain propagation rate range was found beneficial for the micropit to remain growth. At constant potential, the maximum peak currents in different time intervals during a potentiostatic test followed extreme distribution. The statistical characteristics of metastable pitting may be used to predict the tendency of pitting corrosion.展开更多
In recent years, most of domestic and foreign researches about heavy metal pollutions of metal mine mainly focus on water, soil and plants on the surface. There is lack of researches about heavy metal pollution in gro...In recent years, most of domestic and foreign researches about heavy metal pollutions of metal mine mainly focus on water, soil and plants on the surface. There is lack of researches about heavy metal pollution in groundwater of metal mine. In this research, a certain antimony mine area is selected as a typical study area. Also, the study about statistical characteristics of heavy metals in groundwater has been carried out. Furthermore, the interrelationships have been preliminarily discussed through related analysis, such as relevant analysis, cluster analysis and principle component analysis. The results show that: the excessive elements in groundwater of study area are Sb, As, Pb, Se, and Ni. The average mass concentration of Sb, As, and Pb is higher than that of drinking water standards(GB5749-2006). The concentration of most heavy metals in dry season is lower than or equal to that in wet season for groundwater. Zn is the only metal in groundwater showing a different pattern, the concentration of which in dry season is higher than that in wet season. Under the impacts of stratum leaching and absorption effect, the concentration of heavy metals(except Pb and Ba) in groundwater are lower than or equal to that in surface water. As and Se, the two heavy metals have a significant positive correlation, which shows the two elements might have gone through similar environmental geochemical effect. Also, the connection among Zn, Hg, Pb, and Mn is not obvious; therefore, the sources of those elements are quite different. In addition, the elements of Se and As have obvious positive interrelationship with elements of CO_3^(2-) and F^-. Also, the Pb has significant positive correlation with PO_4^(3-), H_2SiO_3 and oxygen consumption. The results of cluster analysis show that 9 different heavy metals in the study area can be divided into 3 categories: Zn, Cd, Mn, Hg, Cu, and Cr belong to the first category, Se and As belong to the second one, and the last category is Pb. Also, the principle component analysis divides 6 heavy metals(Zn, As, Hg, Pb, Mn, and Se) into 4 different principle components, which can be utilized to assess heavy metals pollution situations in groundwater. The reliability of this method is higher than 91%. Moreover, the research provides theory basis and models for establishing evaluation index system and exploring the evaluation method of heavy mental pollution in groundwater.展开更多
A database called eukaryotic intron database(EID)was developed based on the data from GenBank.Studies on the statistical characteristics of EID show that there were 103,848 genes,478,484 introns,and 582,332 exons,with...A database called eukaryotic intron database(EID)was developed based on the data from GenBank.Studies on the statistical characteristics of EID show that there were 103,848 genes,478,484 introns,and 582,332 exons,with an average of 4.61 introns and 5.61 exons per gene.Introns of 40−120 nt in length were abundant in the database.Results of the statistical analysis on the data from nine model species showed that in eukaryotes,higher species do not necessarily have more introns or exons in a gene than lower species.Furthermore,characteristics of EID,such as intron phase,distribution of different splice sites,and the relationship between genome size and intron proportion or intron density,have been studied.展开更多
A statistical study of GMS low cloud winds in January,April,July and October,1983 shows that on an average,there exist 223.5 low cloud winds over western North Pacific each synoptic time.The low cloud winds have a diu...A statistical study of GMS low cloud winds in January,April,July and October,1983 shows that on an average,there exist 223.5 low cloud winds over western North Pacific each synoptic time.The low cloud winds have a diurnal change with more low cloud winds at 12 Z than at 00 Z. The wind fields at 850 hPa over western North Pacific,with and without application of low cloud winds, have been analyzed by a successive correction scheme.The results indicate that the flow patterns without low cloud winds are considerably distorted from short of wind data over the oceanic region.On the con- trary,with application of low cloud winds,the flow patterns get much more improved over the oceanic region.展开更多
Bridge failure, which is generally associated with serious economic and life losses, is defined as the incapacity of a constructed bridge or its components to perform as specified in the design and construction requir...Bridge failure, which is generally associated with serious economic and life losses, is defined as the incapacity of a constructed bridge or its components to perform as specified in the design and construction requirements. This paper presents an overview of current researches on the typical characteristics and causes of bridge failures based on 10 former investigations. Principal causes can be divided into internal causes and external causes or natural factors and human factors. Design error, construction mistakes, hydraulic, collision, and overload are the top 5 leading causes of bridge failures, resulting in more than70% of the bridge failures. Causes of bridge failures are closely related to regional economy,structural type, type of use, material type, and service age. The failure rate is very high for steel bridges, which is inseparable from excessive emphasis on structure strength but lack of consideration on structure stability and fatigue in early years. Researchers need to strengthen their research on the stability and fatigue of steel bridges, as well as inspection and maintenance. Extreme loads such as flood, collision, and overload contribute to a large number of bridge failures because of the lack of extreme loads data and design theory defects. It is critical for such bridges to have sufficient redundancy and capacity protection measures to reduce the probability of bridge failure due to extreme loads. Previous statistical methods and classification methods for the characteristics and causes of bridge failures lack unified standards, and a more scientific method needs to be established. A comprehensive electronic database on bridge damage and failures needs to be developed to establish damage models and conduct forensic studies to improve the design theory and specifications.展开更多
In order to clarify the statistical pattern by which landfalling strong tropical cyclones(LSTCs)influenced the catastrophic migrations of rice brown planthopper(BPH),Nilaparvata lugens(stl)in China,the data of the L...In order to clarify the statistical pattern by which landfalling strong tropical cyclones(LSTCs)influenced the catastrophic migrations of rice brown planthopper(BPH),Nilaparvata lugens(stl)in China,the data of the LSTCs in China and the lighting catches of BPH that covered the main Chinese rice-growing regions from 1979 to 2008 were collected and analyzed in this work with the assistance of ArcGIS9.3,a software of geographic information system.The results were as follows:(1)In China,there were 220 strong tropical cyclones that passed the main rice-growing regions and 466 great events of BPH’s immigration in the 30 years from 1979 to 2008.73 of them resulted in the occurrence of BPH’s catastrphic migration(CM)events directly and 147 of them produced indirect effect on the migrations.(2)The number of the LSTCs was variable in different years during 1979 to 2008 and their influence was not the same in the BPH’s northward and southward migrations in the years.In the 30 years,the LSTCs brought more obvious influence on the migrations in 1980,1981,2005,2006 and 2007.The influence was the most obvious in2007 and all of the 7 LSTCs produced remarkable impact on the CMs of BPH’s populations.The effect of the LSTCs on the northward immigration of BPH’s populations was the most serious in 2006 and the influence on the southward immigration was the most remarkable in 2005.(3)In these years,the most of LSTCs occurred in July,August and September and great events of BPH's immigration occurred most frequently in the same months.The LSTCs played a more important role on the CM of BPH’s populations in the three months than in other months.(4)The analysis on the spatial distribution of the LSTCs and BPH’s immigration events for the different provinces showed that the BPH’s migrations in the main rice-growing regions of the Southeastern China were influenced by the LSTCs and the impact was different with the change of their spatial probability distribution during their passages.The most serious influence of the LSTCs on the BPH’s migrations occurred in Guangdong and Fujian provinces.(5)The statistical results indicated that a suitable insect source is an indispensable condition of the CMs of BPH when a LSTC influenced a rice-growing region.展开更多
A statistical comparative analysis of tropical cyclone activity over the Arabian Sea (AS) and Bay of Bengal(BoB) has been conducted using best-track data and wind radii information from 1977 to 2018 issued by the Join...A statistical comparative analysis of tropical cyclone activity over the Arabian Sea (AS) and Bay of Bengal(BoB) has been conducted using best-track data and wind radii information from 1977 to 2018 issued by the Joint Typhoon Warning Center. Results show that the annual variation in the frequency and duration of tropical cyclones has significantly increased over time over the AS and insignificantly decreased over the BoB. The monthly frequency of tropical cyclones over the AS and the BoB shows a notable bimodal character, with peaks occurring in May and OctoberNovember, respectively. The maximum frequency of tropical cyclones occurs in the second peak as a result of the higher moisture content at mid-levels in the autumn. However, the largest proportion of strong cyclones (H1-H5 grades) occurs in the first peak as a result of the higher sea surface temperatures in early summer. Tropical cyclones over the AS break out later during the first peak and activity ends earlier during the second peak, in contrast with those over the BoB. This is related to the onset and drawback times of the southwest monsoon in the two basins. Tropical cyclones over the AS are mainly generated in the eastern basin, whereas in the BoB the genesis locations are meridionally (zonally) distributed in May-June (October-November) as a result of the seasonal movement of the low-level positive vorticity belt. The Arabian Sea is dominated by tropical cyclones that track west and northwest, accounting for about 74.6%of all the tropical cyclones there, whereas the tropical cyclones with a NE track account for only 25.4%. The proportions of the three types of tracks are similar in the BoB, with each accounting for about 33%of the tropical cyclones. The mean intensity and size of tropical cyclones over the AS are stronger and larger, respectively, than those over the BoB and the size of tropical cyclones over the North Indian Ocean in early summer is larger than that in the autumn. The asymmetrical structure of tropical cyclones over the North Indian Ocean is affected by topography and the longest radius of the 34 kt surface wind often lies in the eastern quadrant of the tropical cyclone circulation in both sea areas.展开更多
[Objective] The aim was to study the characteristics of sunshine hour changes in Tacheng in recent 50 years.[Method] By dint of the measured data of annual,seasonal and monthly sunshine hour's changes in four mete...[Objective] The aim was to study the characteristics of sunshine hour changes in Tacheng in recent 50 years.[Method] By dint of the measured data of annual,seasonal and monthly sunshine hour's changes in four meteorological observatories from 1960 to 2009,using linear regression analysis method,the characteristics of sunshine hour changes in Tacheng in recent 50 years were studied.[Result] The results showed that the annual average sunshine hours in Tacheng Basin in recent 50 years were above 2 800.0 h,among which Tacheng,Yumin had the most,2 936.1,2 921.3 h respectively and Emin the least,2 814.2 h.The sunshine hours were the most in autumn and summer,followed by winter,and were least in spring;sunshine hours during growth season in Tacheng and Yumin were the most,followed by Emin and then Tuoli.The linear tendency rate of sunshine hours in four stations in February was negative.But only the value in Tacheng,Emin decreased at a rate of-4.7 and-6.0 respectively;the linear tendency rate of sunshine hours in four stations in May,June and October were positive,but only Yumin station mounted at a rate of 14.5,12.6,11.2 h/10 a.The linear tendency of seasonal sunshine hours during the year and the growth season increased in Yumin at a rate of 74.9 and 60.5 h/10 a.The linear tendency rate of sunshine hours in four stations in winter was negative,among which the rate of Tacheng,Emin and Tuoli decreased at a rate of-5.5,-6.7,-4.9 h/10 a;that in other three seasons,only in Yumin,it increased most rapidly at a rate of 9.7,7.7 and 7.0 h/10 a.[Conclusion] The study provides theoretical reference for the adjustment and perfection of husbandry industry structure and optimization,reasonable development and utilization of solar energy resources.展开更多
Hydrodynamic numerical simulations are used to conduct structural analyses and inform the design of engineered marine structures.In this paper,a hydrodynamic numerical model of“Nanhai Tiaozhan”(NHTZ)FPS platform was...Hydrodynamic numerical simulations are used to conduct structural analyses and inform the design of engineered marine structures.In this paper,a hydrodynamic numerical model of“Nanhai Tiaozhan”(NHTZ)FPS platform was established according to its design specifications.The model was assessed with two sets of field monitoring data representing harsh and conventional sea states.The motion responses of the platform according to the measured data and the hydrodynamic simulation were compared by reviewing their statistical characteristics,distributions,and spectrum characteristics.The comparison showed that the hydrodynamic model could correctly simulate the frequency domain characteristics of the motion responses of the platform.However,the simulation underestimated the reciprocating motions of the floating body and the influence of slow drift on the motion of the platform.Meanwhile,analysis of the monitoring data revealed that the translational degrees of freedom(DOF)and rotational DOF of the platform were coupled,but these coupled motion states were not apparent in the hydrodynamic simulation.展开更多
The paper compares the correlations between individual factors of the cyclogenesis and the number of TCs formed in the western North Pacific in July to September(NTWNP). It also compares the characteristics of zonal a...The paper compares the correlations between individual factors of the cyclogenesis and the number of TCs formed in the western North Pacific in July to September(NTWNP). It also compares the characteristics of zonal anomaly distribution of the factors in the primary TC source areas of the Northern Hemisphere. Results show that the vorticity factor has the closest correlation with NTWNP. In TC genesis conditions, this feature is relatively rich but not enough, which determines that it is the sensitivity factor of NTWNP's annual variation. The paper also analyzes the source of annual variation of the vorticity factor in the key area of the western North Pacific as well as its advantage in showing NTWNP. Results show that the annual variation of the vorticity factor mentioned above is related to the annual variation of Southern Oscillation, Antarctica Oscillation and the geopotential height field of East Australia, which reflects the effect of two large-scale systems in the Southern Hemisphere and ENSO(El Ni?o–Southern Oscillation) on NTWNP. Since the area where the vorticity factor is significantly correlated with NTWNP is consistent with the area of dense TC genesis sources, the vorticity factor has an obvious advantage in showing annual variation of TCs. Those features are very significant for research on the influencing mechanism of NTWNP and simulation of climate models.展开更多
The characteristics of the atmospheric boundary layer height over the global ocean were studied based on the Constellation Observation System of Meteorology,Ionosphere and Climate(COSMIC) refractivity data from 2007 t...The characteristics of the atmospheric boundary layer height over the global ocean were studied based on the Constellation Observation System of Meteorology,Ionosphere and Climate(COSMIC) refractivity data from 2007 to2012.Results show that the height is much characteristic of seasonal,inter-annual and regional variation.Globally,the spatial distribution of the annual mean top height shows a symmetrical zonal structure,which is more zonal in the Southern Hemisphere than in the Northern Hemisphere.The boundary layer top is highest in the tropics and gradually decreases towards higher latitudes.The height is in a range of 3 to 3.5 km in the tropics,2 to 2.5 km in the subtropical regions,and 1 to 1.5 km or even lower in middle and high latitudes.The diurnal variation of the top height is not obvious,with the height varying from tens to hundreds of meters.Furthermore,it is different from region to region,some regions have the maximum height during 9:00 to 12:00,others at 15:00 to18:00.展开更多
In comparison with the number of studies into the impact on precipitation in China of tropical cyclones(TCs)over the western North Pacific,investigation of the effect of TCs in the Bay of Bengal(BoB)on precipitation i...In comparison with the number of studies into the impact on precipitation in China of tropical cyclones(TCs)over the western North Pacific,investigation of the effect of TCs in the Bay of Bengal(BoB)on precipitation in China is lacking.In this study,precipitation in China associated with TCs over the BoB was divided into direct rainfall induced by TC cloud clusters and indirect rainfall related to the long-distance transport of TC water vapor.We partitioned the BoB TC-related rainfall that occurred during 2000–2018 in China and analyzed its statistical features.It was found that 40 of the 67(60%)TCs that occurred over the BoB exerted influence on rainfall in China.Direct rainfall was mainly distributed over the southeastern Tibetan Plateau and Southwest China,while indirect rainfall was distributed widely with two high-value centers:one over Yunnan Province and the other over the area south of the middle–lower reaches of the Yangtze River.The highest mean daily rainfall amount of direct TC precipitation appeared in northern Yunnan Province and southeastern Tibet,while that of indirect TC precipitation occurred eastward of 110°E.During the bimodal period of peak occurrence of BoB TCs in May and October–November,the annual mean amount,intensity,and number of days of rainfall in China related to BoB TCs were generally greater in May,e.g.,the mean daily rainfall amount was twice that in October–November,except at stations in southeastern Tibet.In comparison with the BoB TCs that induced heavy rainfall in China in early summer,the TCs in autumn had a more southwestward mean position and a more asymmetric structure,with the long axis oriented in the northeast–southwest direction.Heavy rainfall induced by BoB TCs occurred mainly over southeastern Tibet and provinces south of the middle–lower reaches of the Yangtze River in early summer and over Yunnan and Sichuan provinces in autumn,mostly in response to circulation patterns of a“northern trough with a southern TC”and of“convergence of two high pressure systems,”respectively.展开更多
Particle swarm optimization(PSO)is one of the popular stochastic optimization based on swarm intelligence algorithm.This simple and promising algorithm has applications in many research fields.In PSO,each particle can...Particle swarm optimization(PSO)is one of the popular stochastic optimization based on swarm intelligence algorithm.This simple and promising algorithm has applications in many research fields.In PSO,each particle can adjust its‘flying’according to its own flying experience and its companions’flying experience.This paper proposes a new PSO variant,called the statistically tracked PSO,which uses group statistical characteristics to update the velocity of the particle after certain iterations,thus avoiding localminima and helping particles to explore global optimum with an improved convergence.The performance of the proposed algorithm is tested on a deregulated automatic generation control problem in power systems and encouraging results are obtained.展开更多
基金supported by Shota Rustaveli National Science Foundation of Georgia(SRNSFG),grant NFR-21-316“Investigation of the statistical characteristics of scattered electromagnetic waves in the terrestrial atmosphere and application”.
文摘On the basis of the solution of the space-time characteristic system by the method of geometric optics using symbolic calculations,analytical and numerical simulation of the propagation of the ordinary and extraordinary radio waves in the conducting equatorial ionospheric plasma was made considering the anisotropy of plasma irregularities and non-stationary nature of propagation medium.Broadening of the spectrum and the displacement of its maximum contain velocity of a turbulent plasma flow and parameters characterizing anisotropic plasmonic structures.Statistical moments of both radio waves do not depend on the absorption sign and are valid for both active and absorptive random media.Temporal pulsations and conductivity of a turbulent ionospheric plasma have an influence on the evaluation of the spectrum-varying propagation distances travelling by these waves.The new double-humped effect in the temporal spectrum has been revealed for the ordinary wave varying anisotropy coefficient and dip angle of stretched plasmonic structures.From a theoretical point of view,the algorithms developed in this work allow effective modelling of the propagation of both radio signals in the equatorial conductive ionospheric plasma,considering the external magnetic field,inhomogeneities of electron density in-homogeneities,as well as non-stationary.
文摘The statistical characteristics of the Current fluctuations during metastable pitting of 316L stain- less steel in NaCI solution were studied using potentiostatic method. The growth rates and peak currents of metastable pits followed log-normal distributions. As potential and chloride concentration increased, both growth rate and peak current of metastable pits increased. The lifetime of metastable pits also followed log-normal distribution. and was almost not affected by potential. Higher growth rates did not definitely result in larger metastable pits. A certain propagation rate range was found beneficial for the micropit to remain growth. At constant potential, the maximum peak currents in different time intervals during a potentiostatic test followed extreme distribution. The statistical characteristics of metastable pitting may be used to predict the tendency of pitting corrosion.
基金supported by Homeland Resource Non-Profit Research Special Funding Project(No.200911036)
文摘In recent years, most of domestic and foreign researches about heavy metal pollutions of metal mine mainly focus on water, soil and plants on the surface. There is lack of researches about heavy metal pollution in groundwater of metal mine. In this research, a certain antimony mine area is selected as a typical study area. Also, the study about statistical characteristics of heavy metals in groundwater has been carried out. Furthermore, the interrelationships have been preliminarily discussed through related analysis, such as relevant analysis, cluster analysis and principle component analysis. The results show that: the excessive elements in groundwater of study area are Sb, As, Pb, Se, and Ni. The average mass concentration of Sb, As, and Pb is higher than that of drinking water standards(GB5749-2006). The concentration of most heavy metals in dry season is lower than or equal to that in wet season for groundwater. Zn is the only metal in groundwater showing a different pattern, the concentration of which in dry season is higher than that in wet season. Under the impacts of stratum leaching and absorption effect, the concentration of heavy metals(except Pb and Ba) in groundwater are lower than or equal to that in surface water. As and Se, the two heavy metals have a significant positive correlation, which shows the two elements might have gone through similar environmental geochemical effect. Also, the connection among Zn, Hg, Pb, and Mn is not obvious; therefore, the sources of those elements are quite different. In addition, the elements of Se and As have obvious positive interrelationship with elements of CO_3^(2-) and F^-. Also, the Pb has significant positive correlation with PO_4^(3-), H_2SiO_3 and oxygen consumption. The results of cluster analysis show that 9 different heavy metals in the study area can be divided into 3 categories: Zn, Cd, Mn, Hg, Cu, and Cr belong to the first category, Se and As belong to the second one, and the last category is Pb. Also, the principle component analysis divides 6 heavy metals(Zn, As, Hg, Pb, Mn, and Se) into 4 different principle components, which can be utilized to assess heavy metals pollution situations in groundwater. The reliability of this method is higher than 91%. Moreover, the research provides theory basis and models for establishing evaluation index system and exploring the evaluation method of heavy mental pollution in groundwater.
基金This work was supported by the National Natural Science Foundation of China(No.30270752)the Guang-dong Natural Science Foundation(No.031616).
文摘A database called eukaryotic intron database(EID)was developed based on the data from GenBank.Studies on the statistical characteristics of EID show that there were 103,848 genes,478,484 introns,and 582,332 exons,with an average of 4.61 introns and 5.61 exons per gene.Introns of 40−120 nt in length were abundant in the database.Results of the statistical analysis on the data from nine model species showed that in eukaryotes,higher species do not necessarily have more introns or exons in a gene than lower species.Furthermore,characteristics of EID,such as intron phase,distribution of different splice sites,and the relationship between genome size and intron proportion or intron density,have been studied.
基金supported by the National Natural Science Foundation of China
文摘A statistical study of GMS low cloud winds in January,April,July and October,1983 shows that on an average,there exist 223.5 low cloud winds over western North Pacific each synoptic time.The low cloud winds have a diurnal change with more low cloud winds at 12 Z than at 00 Z. The wind fields at 850 hPa over western North Pacific,with and without application of low cloud winds, have been analyzed by a successive correction scheme.The results indicate that the flow patterns without low cloud winds are considerably distorted from short of wind data over the oceanic region.On the con- trary,with application of low cloud winds,the flow patterns get much more improved over the oceanic region.
基金funded by the Communication Research Project of Department of Transport of Shaanxi Province(19-07K)the Special Fund for Basic Scientific Research of Central College of Chang’an University(300102219310)。
文摘Bridge failure, which is generally associated with serious economic and life losses, is defined as the incapacity of a constructed bridge or its components to perform as specified in the design and construction requirements. This paper presents an overview of current researches on the typical characteristics and causes of bridge failures based on 10 former investigations. Principal causes can be divided into internal causes and external causes or natural factors and human factors. Design error, construction mistakes, hydraulic, collision, and overload are the top 5 leading causes of bridge failures, resulting in more than70% of the bridge failures. Causes of bridge failures are closely related to regional economy,structural type, type of use, material type, and service age. The failure rate is very high for steel bridges, which is inseparable from excessive emphasis on structure strength but lack of consideration on structure stability and fatigue in early years. Researchers need to strengthen their research on the stability and fatigue of steel bridges, as well as inspection and maintenance. Extreme loads such as flood, collision, and overload contribute to a large number of bridge failures because of the lack of extreme loads data and design theory defects. It is critical for such bridges to have sufficient redundancy and capacity protection measures to reduce the probability of bridge failure due to extreme loads. Previous statistical methods and classification methods for the characteristics and causes of bridge failures lack unified standards, and a more scientific method needs to be established. A comprehensive electronic database on bridge damage and failures needs to be developed to establish damage models and conduct forensic studies to improve the design theory and specifications.
基金National Natural Science Foundation of China(41075086,30671340)National Meteorological Public Professional Science and Technology Program of China(GYHY201006026)+1 种基金Agricultural Science and Technology Independent Innovation Foundation in Jiangsu Province(CX(12)3056)Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘In order to clarify the statistical pattern by which landfalling strong tropical cyclones(LSTCs)influenced the catastrophic migrations of rice brown planthopper(BPH),Nilaparvata lugens(stl)in China,the data of the LSTCs in China and the lighting catches of BPH that covered the main Chinese rice-growing regions from 1979 to 2008 were collected and analyzed in this work with the assistance of ArcGIS9.3,a software of geographic information system.The results were as follows:(1)In China,there were 220 strong tropical cyclones that passed the main rice-growing regions and 466 great events of BPH’s immigration in the 30 years from 1979 to 2008.73 of them resulted in the occurrence of BPH’s catastrphic migration(CM)events directly and 147 of them produced indirect effect on the migrations.(2)The number of the LSTCs was variable in different years during 1979 to 2008 and their influence was not the same in the BPH’s northward and southward migrations in the years.In the 30 years,the LSTCs brought more obvious influence on the migrations in 1980,1981,2005,2006 and 2007.The influence was the most obvious in2007 and all of the 7 LSTCs produced remarkable impact on the CMs of BPH’s populations.The effect of the LSTCs on the northward immigration of BPH’s populations was the most serious in 2006 and the influence on the southward immigration was the most remarkable in 2005.(3)In these years,the most of LSTCs occurred in July,August and September and great events of BPH's immigration occurred most frequently in the same months.The LSTCs played a more important role on the CM of BPH’s populations in the three months than in other months.(4)The analysis on the spatial distribution of the LSTCs and BPH’s immigration events for the different provinces showed that the BPH’s migrations in the main rice-growing regions of the Southeastern China were influenced by the LSTCs and the impact was different with the change of their spatial probability distribution during their passages.The most serious influence of the LSTCs on the BPH’s migrations occurred in Guangdong and Fujian provinces.(5)The statistical results indicated that a suitable insect source is an indispensable condition of the CMs of BPH when a LSTC influenced a rice-growing region.
基金National Natural Science Foundation of China(41930972,51778617)S&T Development Fund of CAMS(2020KJ019)。
文摘A statistical comparative analysis of tropical cyclone activity over the Arabian Sea (AS) and Bay of Bengal(BoB) has been conducted using best-track data and wind radii information from 1977 to 2018 issued by the Joint Typhoon Warning Center. Results show that the annual variation in the frequency and duration of tropical cyclones has significantly increased over time over the AS and insignificantly decreased over the BoB. The monthly frequency of tropical cyclones over the AS and the BoB shows a notable bimodal character, with peaks occurring in May and OctoberNovember, respectively. The maximum frequency of tropical cyclones occurs in the second peak as a result of the higher moisture content at mid-levels in the autumn. However, the largest proportion of strong cyclones (H1-H5 grades) occurs in the first peak as a result of the higher sea surface temperatures in early summer. Tropical cyclones over the AS break out later during the first peak and activity ends earlier during the second peak, in contrast with those over the BoB. This is related to the onset and drawback times of the southwest monsoon in the two basins. Tropical cyclones over the AS are mainly generated in the eastern basin, whereas in the BoB the genesis locations are meridionally (zonally) distributed in May-June (October-November) as a result of the seasonal movement of the low-level positive vorticity belt. The Arabian Sea is dominated by tropical cyclones that track west and northwest, accounting for about 74.6%of all the tropical cyclones there, whereas the tropical cyclones with a NE track account for only 25.4%. The proportions of the three types of tracks are similar in the BoB, with each accounting for about 33%of the tropical cyclones. The mean intensity and size of tropical cyclones over the AS are stronger and larger, respectively, than those over the BoB and the size of tropical cyclones over the North Indian Ocean in early summer is larger than that in the autumn. The asymmetrical structure of tropical cyclones over the North Indian Ocean is affected by topography and the longest radius of the 34 kt surface wind often lies in the eastern quadrant of the tropical cyclone circulation in both sea areas.
文摘[Objective] The aim was to study the characteristics of sunshine hour changes in Tacheng in recent 50 years.[Method] By dint of the measured data of annual,seasonal and monthly sunshine hour's changes in four meteorological observatories from 1960 to 2009,using linear regression analysis method,the characteristics of sunshine hour changes in Tacheng in recent 50 years were studied.[Result] The results showed that the annual average sunshine hours in Tacheng Basin in recent 50 years were above 2 800.0 h,among which Tacheng,Yumin had the most,2 936.1,2 921.3 h respectively and Emin the least,2 814.2 h.The sunshine hours were the most in autumn and summer,followed by winter,and were least in spring;sunshine hours during growth season in Tacheng and Yumin were the most,followed by Emin and then Tuoli.The linear tendency rate of sunshine hours in four stations in February was negative.But only the value in Tacheng,Emin decreased at a rate of-4.7 and-6.0 respectively;the linear tendency rate of sunshine hours in four stations in May,June and October were positive,but only Yumin station mounted at a rate of 14.5,12.6,11.2 h/10 a.The linear tendency of seasonal sunshine hours during the year and the growth season increased in Yumin at a rate of 74.9 and 60.5 h/10 a.The linear tendency rate of sunshine hours in four stations in winter was negative,among which the rate of Tacheng,Emin and Tuoli decreased at a rate of-5.5,-6.7,-4.9 h/10 a;that in other three seasons,only in Yumin,it increased most rapidly at a rate of 9.7,7.7 and 7.0 h/10 a.[Conclusion] The study provides theoretical reference for the adjustment and perfection of husbandry industry structure and optimization,reasonable development and utilization of solar energy resources.
基金financially supported by the National Natural Science Foundation of China(Grant No.U1906233)the Central Guidance on Local Science and Technology Development Fund of Shenzhen(Grant No.2021Szvup021)。
文摘Hydrodynamic numerical simulations are used to conduct structural analyses and inform the design of engineered marine structures.In this paper,a hydrodynamic numerical model of“Nanhai Tiaozhan”(NHTZ)FPS platform was established according to its design specifications.The model was assessed with two sets of field monitoring data representing harsh and conventional sea states.The motion responses of the platform according to the measured data and the hydrodynamic simulation were compared by reviewing their statistical characteristics,distributions,and spectrum characteristics.The comparison showed that the hydrodynamic model could correctly simulate the frequency domain characteristics of the motion responses of the platform.However,the simulation underestimated the reciprocating motions of the floating body and the influence of slow drift on the motion of the platform.Meanwhile,analysis of the monitoring data revealed that the translational degrees of freedom(DOF)and rotational DOF of the platform were coupled,but these coupled motion states were not apparent in the hydrodynamic simulation.
基金Program for Key Science and Technology Planning on Applied Research and Industrialization of Hainan Province,China(ZDXM20130081)
文摘The paper compares the correlations between individual factors of the cyclogenesis and the number of TCs formed in the western North Pacific in July to September(NTWNP). It also compares the characteristics of zonal anomaly distribution of the factors in the primary TC source areas of the Northern Hemisphere. Results show that the vorticity factor has the closest correlation with NTWNP. In TC genesis conditions, this feature is relatively rich but not enough, which determines that it is the sensitivity factor of NTWNP's annual variation. The paper also analyzes the source of annual variation of the vorticity factor in the key area of the western North Pacific as well as its advantage in showing NTWNP. Results show that the annual variation of the vorticity factor mentioned above is related to the annual variation of Southern Oscillation, Antarctica Oscillation and the geopotential height field of East Australia, which reflects the effect of two large-scale systems in the Southern Hemisphere and ENSO(El Ni?o–Southern Oscillation) on NTWNP. Since the area where the vorticity factor is significantly correlated with NTWNP is consistent with the area of dense TC genesis sources, the vorticity factor has an obvious advantage in showing annual variation of TCs. Those features are very significant for research on the influencing mechanism of NTWNP and simulation of climate models.
文摘The characteristics of the atmospheric boundary layer height over the global ocean were studied based on the Constellation Observation System of Meteorology,Ionosphere and Climate(COSMIC) refractivity data from 2007 to2012.Results show that the height is much characteristic of seasonal,inter-annual and regional variation.Globally,the spatial distribution of the annual mean top height shows a symmetrical zonal structure,which is more zonal in the Southern Hemisphere than in the Northern Hemisphere.The boundary layer top is highest in the tropics and gradually decreases towards higher latitudes.The height is in a range of 3 to 3.5 km in the tropics,2 to 2.5 km in the subtropical regions,and 1 to 1.5 km or even lower in middle and high latitudes.The diurnal variation of the top height is not obvious,with the height varying from tens to hundreds of meters.Furthermore,it is different from region to region,some regions have the maximum height during 9:00 to 12:00,others at 15:00 to18:00.
基金Supported by the National Natural Science Foundation of China(41930972 and 51778617)Advanced Program on Application of Fengyun Satellite Products in Numerical Forecast(2022).
文摘In comparison with the number of studies into the impact on precipitation in China of tropical cyclones(TCs)over the western North Pacific,investigation of the effect of TCs in the Bay of Bengal(BoB)on precipitation in China is lacking.In this study,precipitation in China associated with TCs over the BoB was divided into direct rainfall induced by TC cloud clusters and indirect rainfall related to the long-distance transport of TC water vapor.We partitioned the BoB TC-related rainfall that occurred during 2000–2018 in China and analyzed its statistical features.It was found that 40 of the 67(60%)TCs that occurred over the BoB exerted influence on rainfall in China.Direct rainfall was mainly distributed over the southeastern Tibetan Plateau and Southwest China,while indirect rainfall was distributed widely with two high-value centers:one over Yunnan Province and the other over the area south of the middle–lower reaches of the Yangtze River.The highest mean daily rainfall amount of direct TC precipitation appeared in northern Yunnan Province and southeastern Tibet,while that of indirect TC precipitation occurred eastward of 110°E.During the bimodal period of peak occurrence of BoB TCs in May and October–November,the annual mean amount,intensity,and number of days of rainfall in China related to BoB TCs were generally greater in May,e.g.,the mean daily rainfall amount was twice that in October–November,except at stations in southeastern Tibet.In comparison with the BoB TCs that induced heavy rainfall in China in early summer,the TCs in autumn had a more southwestward mean position and a more asymmetric structure,with the long axis oriented in the northeast–southwest direction.Heavy rainfall induced by BoB TCs occurred mainly over southeastern Tibet and provinces south of the middle–lower reaches of the Yangtze River in early summer and over Yunnan and Sichuan provinces in autumn,mostly in response to circulation patterns of a“northern trough with a southern TC”and of“convergence of two high pressure systems,”respectively.
文摘Particle swarm optimization(PSO)is one of the popular stochastic optimization based on swarm intelligence algorithm.This simple and promising algorithm has applications in many research fields.In PSO,each particle can adjust its‘flying’according to its own flying experience and its companions’flying experience.This paper proposes a new PSO variant,called the statistically tracked PSO,which uses group statistical characteristics to update the velocity of the particle after certain iterations,thus avoiding localminima and helping particles to explore global optimum with an improved convergence.The performance of the proposed algorithm is tested on a deregulated automatic generation control problem in power systems and encouraging results are obtained.
