[Objective] This paper aimed to understand the area change and distribu- tion of medium-low yield farmland, and offered basis to the improvement of mediumlow farmland and its increase of grain production in Tianjin. [...[Objective] This paper aimed to understand the area change and distribu- tion of medium-low yield farmland, and offered basis to the improvement of mediumlow farmland and its increase of grain production in Tianjin. [Method] Based on the statistical date of Tianjin and its relevant counties and districts, the yield standard was set up to classify high-yield, medium-yield and low-yield farmland in Tianjin. The author analyzed area change of medium-low yield farmland in six agricultural counties and districts （including Jixian County, Wuqing District, Baodi District, Ninghe County, Jinghai County and Dagang district of Binghai New Area） from 1980 to 2010. [Result] The results showed that the average yield of grain rose from 2 445 kg/hm^2 in 1980 to 5 130 kg/hm^2 in 2010, increasing 109.82%. The area of mediumlow yield farmland was reduced from 291 250.13 hm^2 in 1985 to 76 489.87 hm^2 in 2010, coming down 74%. In Tianjin, the area of medium-low yield farmland of 2010 accounted for 19% of the total farmland, of which the ratios of medium-low yield farmland of Jinghai County, Jixian County, Dagang district of Binghai New Area, Wuqing District, Baodi District and Ninghe County were 43.12%, 18.59%, 17.23%, 14.01%, 7.05% and 0, respectively. Low soil nutrient content, drought and water shortage, as well as soil salinization were the main yield limiting factors to mediumlow yield farmland in Tianjin in 2010. [Conclusion] The countermeasures to improve the medium-low yield farmland were proposed, involving enhancing the investment of the government, strengthening the construction of water conservancy infrastructure, further improving the soil fertility, as well as saline and alkaline land, optimizing the farming system and planting drought and salt tolerance crops, etc.展开更多
The variation of the atmospheric Carbon Dioxide （CO2） concentration plays an important role in global cli- mate and agriculture. We analyzed the spatial-temporal characteristics of CO2 in the China region and around...The variation of the atmospheric Carbon Dioxide （CO2） concentration plays an important role in global cli- mate and agriculture. We analyzed the spatial-temporal characteristics of CO2 in the China region and around the globe with the CO2 column mixing ratios observed by the Japanese GOSAT satellite （Greenhouse Gases Observing Satellite）. In order to make sure that the accuracy of the CO2 data retrieved by the satellite meets the needs of the climate charac- teristics analyses, we ran a validation on the CO2 column mixing ratios retrieved by the satellite against the ground-based TCCON （Total Carbon Column Observing Network） observation data. The result shows that the two sets of data have a correlation coefficient of higher than 0.7, and a bias of within 2.2 ppmv. Therefore, the GOSAT CO2 da- ta can be used for the climate characteristics analysis of global CO2. Our analysis on the spatial-temporal characteristics of the CO2 column mixing ratios observed during the period of June 2009 through January 2014 proved that, with the impact of the natural emission of near ground CO2 and human activities, the global CO2 concentration has a significant latitudinal characteristics with its highest level averaging 390 oomv in the 0-40？N latitudinal zone in the Northern Hemisphere, and 387 ppmv in the Southern Hemisphere. China has a relatively higher CO2 concentration with the highest level exceeding 398 ppmv, and the eastern area higher than the western area. The variation of global CO2 concentration shows a seasonal pattern, i.e. the CO2 concen- tration reaches its highest in spring in the Northern Hemisphere averaging more than 392 ppmv, second highest in win- ter, and lowest in summer averaging less than 387 ppmv. It fluctuates the most in the Northern Hemisphere with an av- erage concentration of 392.5 ppmv in April, and 385.5 ppmv in July. While in the Southern Hemisphere, the seasonal fluctuation is smaller with the highest concentration occurring in July. Over the recent years, the global CO2 concentra- tion has shown an elevating trend with an average annual increase rate of 1.58 ppmv per year. It is a challenge that the human kind has to face to slow down the increase of the CO2 concentration.展开更多
This study examined non-uniform loading in goaf cantilever rock masses via testing,modeling,and mechanical analysis to solve instantaneous fracture and section buckling from mining abutment pressure.The study investig...This study examined non-uniform loading in goaf cantilever rock masses via testing,modeling,and mechanical analysis to solve instantaneous fracture and section buckling from mining abutment pressure.The study investigates the non-uniform load gradient effect on fracture characteristics,including load characteristics,fracture location,fracture distribution,and section roughness.A digital model for fracture interface buckling analysis was developed,elucidating the influence of non-uniform load gradients on Fracture Interface Curvature(FIC),Buckling Rate of Change(BRC),and Buckling Domain Field(BDF).The findings reveal that nonlinear tensile stress concentration and abrupt tensile-compressive-shear strain mutations under non-uniform loading are fundamental mechanisms driving fracture path buckling in cantilever rock mass structures.The buckling process of rock mass under non-uniform load can be divided into two stages:low load gradient and high gradient load.In the stage of low gradient load,the buckling behavior is mainly reflected in the compression-shear fracture of the edge.In the stage of high gradient load,a buckling band along the loading direction is gradually formed in the rock mass.These buckling principles establish a theoretical basis for accurately characterizing bearing fractures,fracture interface instability,and vibration sources within overlying cantilever rock masses in goaf.展开更多
As a significant city in the Yangtze River Delta regions,Hefei has experienced rapid changes in the sources of air pollution due to its high-speed economic development and urban expansion.However,there has been limite...As a significant city in the Yangtze River Delta regions,Hefei has experienced rapid changes in the sources of air pollution due to its high-speed economic development and urban expansion.However,there has been limited research in recent years on the spatial-temporal distribution and emission of its atmospheric pollutants.To address this,this study conducted mobile observations of urban roads using the Mobile-DOAS instrument from June 2021 to May 2022.The monitoring results exhibit a favourable consistent with TROPOMI satellite data and ground monitoring station data.Temporally,there were pronounced seasonal variations in air pollutants.Spatially,high concentration of HCHO and NO_(2)were closely associated with traffic congestion on roadways,while heightened SO_(2)levels were attributed to winter heating and industrial emissions.The study also revealed that with the implementation of road policies,the average vehicle speed increased by 95.4%,while the NO concentration decreased by 54.4%.In the estimation of urban NO_(x)emission flux,it was observed that in temporal terms,compared with inventory data,the emissions calculated viamobile measurements exhibitedmore distinct seasonal patterns,with the highest emission rate of 349 g/sec in winter and the lowest of 142 g/sec in summer.In spatial terms,the significant difference in emissions between the inner and outer ring roads also suggests the presence of the city’s primary NO_(x)emission sources in the area between these two rings.This study offers data support for formulating the next phase of air pollution control measures in urban areas.展开更多
Microplastic contamination is considered a major threat to the marine environment.Although microplastic pollution in the Pacific Ocean has been studied,its abundance,distribution,composition,and origin in the western ...Microplastic contamination is considered a major threat to the marine environment.Although microplastic pollution in the Pacific Ocean has been studied,its abundance,distribution,composition,and origin in the western Pacific Ocean remain unclear.Here,we investigated the abundance and distribution characteristics of microplastics in surface waters of the western Pacific Ocean and analyzed their potential sources.Results show that microplastics were widespread in the western Pacific Ocean,with abundance ranging from 0.03 to 2.36 particles/m^(3)(average 0.37±0.47 particles/m^(3)).Fibers/filaments and fragments were the main shapes of microplastics(71.6%)and the most abundant microplastic size class was<1.0 mm(42.4%).Significant differences in microplastic abundance were observed in different regions,with the lowest abundance in the South China Sea(0.03 particles/m^(3))and highest abundance in the seamount area in the western Pacific Ocean(0.58 particles/m^(3)).This study provides baseline data and insights into the fate and transportation of microplastics in the western Pacific region.展开更多
Microplastics(MPs)pollution has emerged as a critical global environmental issue,for which rivers serve as key conduits for the transport of MPs from land to ocean.There remained a lack of clarity regarding the charac...Microplastics(MPs)pollution has emerged as a critical global environmental issue,for which rivers serve as key conduits for the transport of MPs from land to ocean.There remained a lack of clarity regarding the characteristics and transport patterns of MPs pollution in diverse environmental media and seasons within a river basin.The Jiulong River basin in Fujian,southeast China was studied as case,whose spatial-temporal distribution,pollution characteristics,and transport dynamics of MPs in both surface water and groundwater were analyzed.Additionally,the features of MPs in different land use types during the dry season were examined.Results show that in wet season,the abundance of MPs in river water varied from 840 to 12300 p/m^(3),with an average of 3920 p/m^(3);in groundwater,the range was 740-1820 p/m^(3),averaging 1107 p/m^(3);and from 68 to 951 p/kg,with an average value of 265 p/kg in the soil(dry weight).In dry season,levels of MPs in river water ranged from 580 to 8880 p/m^(3),with an average of 4034 p/m^(3);groundwater exhibited a range of 860-14980 p/m^(3),averaging 3453 p/m^(3).Fibers consistently dominated the morphology of MPs,of which polyethylene terephthalate was identified as the predominant composition in each environmental medium.Our findings underscore the spatial and temporal variability in distribution and contamination characteristics of MPs across different media.Notably,MPs abundance in river water and groundwater exhibited a seasonal pattern,being higher in levels in dry season than in wet season.The downstream transport of MPs was facilitated by surface runoff,in which MPs in groundwater and surface water could complement to each other.Furthermore,population density and human activities were identified as influential factors on the distribution and abundance of MPs.This study revealed the order of magnitude of difference in annual estimates of MPs entering the sea among different models.Additionally,the interception volume by mangrove forest in the Jiulong River estuary was estimated approximately 1.51×10^(10)MPs particles per year.Ecological interception shall be considered when estimating the fluxes of MPs into the sea.展开更多
Taking 138 key rural tourism villages in Beijing for example,this paper applied GIS analysis to analyze the spatial distribution characteristics of these villages,selected the influence factors of the villages conside...Taking 138 key rural tourism villages in Beijing for example,this paper applied GIS analysis to analyze the spatial distribution characteristics of these villages,selected the influence factors of the villages considering the classification characteristics,so as to explore the impact of different influence factors on its spatial distribution.The results showed(i)Key rural tourism villages in Beijing manifested an aggregated distribution on the whole,they were unevenly distributed and mostly located in the fringe area of northern mountainous areas and plains,such as Huairou District and Miyun District.Such a“multi-center distribution”pattern was significantly influenced by terrains and natural resources.(ii)Depending on local natural and cultural resources,tourism resources,development characteristics and functional differences,key rural tourism villages in Beijing could be devided into natural scenery type,scenic area-dependent type and agriculture experiencing type.(iii)Key factors influencing the distribution of these villages included mean temperature,annual precipitation,quantity of scenic area,road network density,agricultural land and so on,and the interaction of dual factors exerted more significant impact on single factors.展开更多
Thornthwaite Memorial model and other statistic methods were used to calculate the climate-productivity of plants with the meteorological data from 1961 to 2007 at 9 stations distributed on Inner Mongolia desert stepp...Thornthwaite Memorial model and other statistic methods were used to calculate the climate-productivity of plants with the meteorological data from 1961 to 2007 at 9 stations distributed on Inner Mongolia desert steppe.The spatial and temporal variation characteristics of climate-productivity were analyzed by using the methods of the tendency rate of the climate trend,accumulative anomaly,and spatial difference and so on.The results showed that the climate-productivity kept linear increased trend over Inner Mongolia desert steppe in recent 47 years,but not significant.In spatial distribution,the climate-productivity reduced with the increased latitude.The climate-productivity in southwest part of Inner Mongolia desert steppe was growing while that in the southeast was reducing.The variation rate of the climate-productivity increased from the northwest part to the southeast part of Inner Mongolia desert steppe.In recent 47 years,the climate-productivity in southeast Jurh underwent the greatest decreasing extent,and the region was the sensitive area of the climate-productivity variation.展开更多
[Objective] The aim of this study was to reveal the mechanism of Cu2+ hyper-accumulator in Setcreasea purpurea Boom from the angle of distribution characteristics and binding form of Cu2+ in tissue cells.[Method]The d...[Objective] The aim of this study was to reveal the mechanism of Cu2+ hyper-accumulator in Setcreasea purpurea Boom from the angle of distribution characteristics and binding form of Cu2+ in tissue cells.[Method]The distribution characteristics of Cu2+ in subcells of Setcreasea purpurea Boom was studied by the technique of differential centrifugation,and the binding form of Cu2+ in roots and leaves of Setcreasea purpurea Boom was also investigated by the sequential chemical extraction method and the enzymolysis method.[Result]Cu2+ in roots mainly distributed in the cell wall which is accounting for one third of the Total Cu2+ in roots,while Cu2+ in leaves mainly distributed in the chloroplast which is accounting for a quarter to the Total Cu2+ in leaves.Under the high concentration of Cu2+ or the extended treatment duration,the translocation of Cu2+ in root cells into the cell wall increased but the translocation of Cu2+ in root cells into the plastid decreased,while the translocation of Cu2+ in leaf cells into the chloroplast increased but the translocation of Cu2+ in leaf cells into the cell wall decreased.Cu2+ in leaves was mainly combined with amino acid,small molecular polymeric pigments,protein and polysaccharide,while Cu2+ in roots was mainly combined with cell wall substances such as cellulose and membrane-bound protein.[Conclusion]The distribution characteristics and binding form of Cu2+ in cells is possibly one of the dominant mechanisms for Cu2+ hyper-accumulator in Setcreasea purpurea Boom.展开更多
Based on the special landscape and regional characteristics,the lightning location information from 1999 to 2008 and conventional observation data from 1971 to 2000 provided by electricity departments in Hebei Provinc...Based on the special landscape and regional characteristics,the lightning location information from 1999 to 2008 and conventional observation data from 1971 to 2000 provided by electricity departments in Hebei Province were applied to analyze spatial and temporal distribution of lightning.With lighting disaster data since 2000 provided by meteorological department,and records from civil affair,statistics,insurance,and other departments,the lighting disaster distribution of Hebei Province was studied from aspects of economic and people losses,and some countermeasures for several lightning disasters industries were put forward.展开更多
The surveys on the COD in the Lingdingyang waters of Pearl River estuary were carried out in May and August of 2002. The results showed that the concentrations of COD in the waters ranged from 0,41 to 2.72 mg·L^-...The surveys on the COD in the Lingdingyang waters of Pearl River estuary were carried out in May and August of 2002. The results showed that the concentrations of COD in the waters ranged from 0,41 to 2.72 mg·L^-1 with an average of 1.21 mg·L^-1.The spatial distributions showed that COD concentration decreased gradually from the north to south of Pearl River estuary, and the concentration near coastal waters was higher than that in offshore waters. The concentration of COD in summer was higher than in spring. Evaluated by the first class （COD ≤ 2 mg·L^-1） of sea water quality standard （Chinese standard）, there were about 15 % of COD concentrations over the standard. The concentration of COD showed a positive correlation with the concentration of suspend substances in spring and summer, but in summer it showed a negative correlation with the concentrations of inorganic nitrate and phosphate.展开更多
Aim To quantitatively study three characteristics of the Weibull distribution. Methods Theoritical analysis of the three characteristics of parameters of the Weibull distribution was done and mathematics software wa...Aim To quantitatively study three characteristics of the Weibull distribution. Methods Theoritical analysis of the three characteristics of parameters of the Weibull distribution was done and mathematics software was used to make some chart analysis. Results 17 equations and 7 figures were made. Conclusion Under the standard form, the class of the Weibull probable density founction(pdf) curves appear double peak shape. Under the standard form, the maximum value point curve of the Weibull pdf takes line t =0 and t=1 as asymptotes. When β = 3 30-3 40, the Weibull distribution is the most similar to the normal distribution.展开更多
According to the analysis on the characteristics of historic earthquakes in Jiangsu Province and South Huanghai Sea region, the historical earthquakes in the studied area are divided into two kinds of comparatively sa...According to the analysis on the characteristics of historic earthquakes in Jiangsu Province and South Huanghai Sea region, the historical earthquakes in the studied area are divided into two kinds of comparatively safe class and comparatively dangerous class. Then the statistical result of earthquake class, the characteristics of geo-graphical distribution and geological structures are studied. The study shows: a) In Jiangsu Province and South Huanghai Sea region, the majority of historical strong earthquakes belong to comparatively safe class, only 13.8% belong to comparatively dangerous class; b) Most historical earthquakes belong to comparatively safe class in the land area of Jiangsu, eastern sea area of Yangtze River mouth and northern depression of South Huanghai Sea region. However, along the coast of middle Jiangsu Province and in the sea area of South Huanghai Sea, the distribution of historical earthquake classes is complex and the earthquake series of comparatively dan-gerous class and comparatively safe class are equivalent in number; c) In the studied area, the statistical results of historical earthquake classes and the characteristics of spatial distribution accord very well with the real case of present-day earthquake series. It shows that the seismic activity in the region has the characteristic of succession, and the result from this study can be used as a reference for early postseismic judgment in the earthquake emer-gency work in Jiangsu Province.展开更多
Macroscopic grasp of agricultural carbon emissions status, spatial-temporal characteristics as well as driving factors are the basic premise in further research on China’s agricultural carbon emissions. Based on 23 k...Macroscopic grasp of agricultural carbon emissions status, spatial-temporal characteristics as well as driving factors are the basic premise in further research on China’s agricultural carbon emissions. Based on 23 kinds of major carbon emission sources including agricultural materials inputs, paddy ifeld, soil and livestock breeding, this paper ifrstly calculated agricultural carbon emissions from 1995 to 2010, as well as 31 provinces and cities in 2010 in China. We then made a decomposed analysis to the driving factors of carbon emissions with logarithmic mean Divisia index （LMDI） model. The results show：（1） The amount of agricultural carbon emissions is 291.1691 million t in 2010. Compared with 249.5239 million t in 1995, it increased by 16.69%, in which, agricultural materials inputs, paddy ifeld, soil, enteric fermentation, and manure management accounted for 33.59, 22.03, 7.46, 17.53 and 19.39%of total agricultural carbon emissions, respectively. Although the amount exist ups and downs, it shows an overall trend of cyclical rise; （2） There is an obvious difference among regions：the amount of agricultural carbon emissions from top ten zones account for 56.68%, while 9.84%from last 10 zones. The traditional agricultural provinces, especially the major crop production areas are the main source regions. Based on the differences of carbon emission rations, 31 provinces and cities are divided into ifve types, namely agricultural materials dominant type, paddy ifeld dominant type, enteric fermentation dominant type, composite factors dominant type and balanced type. The agricultural carbon emissions intensity in west of China is the highest, followed by the central region, and the east zone is the lowest; （3） Compared with 1995, efifciency, labor and structure factors cut down carbon emissions by 65.78, 27.51 and 3.19%, respectively;while economy factor increase carbon emissions by 113.16%.展开更多
Using the cultivars with high and low calcium in brown rice as tested ma- terials, the effects of calcium on photosynthetic characteristics and its subcellular dis- tribution in different rice cultivars at seedling st...Using the cultivars with high and low calcium in brown rice as tested ma- terials, the effects of calcium on photosynthetic characteristics and its subcellular dis- tribution in different rice cultivars at seedling stage were investigated with hydrocul- ture method. The results showed that the photosynthetic rate in leaves of high cal- cium cultivar was higher than that low calcium cultivar. The calcium content in leaves of rice was higher than that in roots. Among various tissues and organs, the calcium contents ranked as cell wall〉ribosome and intracellular soluble components〉 plastid （or chloroplasts）〉mitochondria〉nucleus. Cell wall is the most important distri- bution place for calcium, while calcium is rarely distributed in nuclei or mitochon- drias. In all the organelles, the calcium concentrations were all increased with the increased treatment concentration of calcium, especially in high calcium cultivar. The high calcium treatment showed more significant effects on calcium contents in im- portant organelles of high calcium cultivar, so it is speculated that the high calcium cultivar had higher calcium accumulation and tolerance capacities.展开更多
Haze pollution has become a severe environmental problem in the daily life of the people in China. PM2.s makes a significant contribution to poor air quality. The spatio-temporal features of China＇s PM2.s concentrati...Haze pollution has become a severe environmental problem in the daily life of the people in China. PM2.s makes a significant contribution to poor air quality. The spatio-temporal features of China＇s PM2.s concentrations should be investigated. This paper, based on ob- served data from 945 newly located monitoring sites in 2014 and industrial working population data obtained from International Standard Industrial Classification （ISIC）, reveals the spa- tio-temporal variations of PM2.5 concentrations in China and the correlations among different industries. We tested the spatial autocorrelation of PM2.5 concentrations in the cities of China with the spatial autocorrelation model. A correlation coefficient to examine the correlativity of PM2.5 concentrations and 23 characteristic variables for 190 cities in China in 2014, from which the most important ones were chosen, and then a regression model was built to further reveal the social and economic factors affecting PMg.g concentrations. Results： （1） The Hu Huanyong Line and the Yangtze River were the E-W divide and S-N divide between high and low values of China. （2） The PM2.5 concentrations shows great seasonal variation, which is high in autumn and winter but low in spring and summer. The monthly average shows a U-shaped pattern, and daily average presents a periodic and impulse-shaped change. （3） PM2.5 concentrations had a distinct characteristic of spatial agglomeration. The North China Plain was the predominant region of agglomeration, and the southeastern coastal area had stable good air quality.展开更多
Overwhelming evidence reveals that concentrations of dissolved organic carbon （DOC） have increased in streams which brings negative environmental impacts. DOC in stream flow is mainly originated from soil-water solu...Overwhelming evidence reveals that concentrations of dissolved organic carbon （DOC） have increased in streams which brings negative environmental impacts. DOC in stream flow is mainly originated from soil-water solutions of watershed. Wetlands prove to be the most sensitive areas as an important DOC reserve between terrestrial and fluvial biogeosystems. This reported study was focused on the distribution characteristics and the controlling factors of DOC in soil-water solutions of annular wetland, i.e., a dishing wetland and a forest wetland together, in the Sanjiang Plain, Northeast China. The results indicate that DOC concentrations in soilwater solutions decreased and then increased with increasing soil depth in the annular wetland. In the upper soil layers of 0-10 cm and 10-20 cm, DOC concentrations in soil-water solutions linearly increased from edge to center of the annular wetland （R^2 = 0.3122 and R^2 = 0.443）. The distribution variations were intimately linked to DOC production and utilization and DOC transport processes in annular wetland soil-water solutions. The concentrations of total organic carbon （TOC）, total carbon （TC） and Fe（II）, DOC mobility and continuous vertical and lateral flow affectext the distribution variations of DOC in soil-water solutions. The correlation coefficients between DOC concentrations and TOC, TC and Fe（II） were 0.974, 0.813 and 0.753 respectively. These distribution characteristics suggested a systematic response of the distribution variations of DOC in annular wetland soil-water solutions to the geometry of closed depressions on a scale of small catchments. However, the DOC in soil pore water of the annular wetland may be the potential source of DOC to stream flow on watershed scale. These observations also implied the fragmentation of wetland landscape could bring the spatial-temporal variations of DOC distribution and exports, which would bring negative environmental impacts in watersheds of the Sanjiang Plain.展开更多
Spatial-temporal traffic prediction technology is crucial for network planning,resource allocation optimizing,and user experience improving.With the development of virtual network operators,multi-operator collaboratio...Spatial-temporal traffic prediction technology is crucial for network planning,resource allocation optimizing,and user experience improving.With the development of virtual network operators,multi-operator collaborations,and edge computing,spatial-temporal traffic data has taken on a distributed nature.Consequently,noncentralized spatial-temporal traffic prediction solutions have emerged as a recent research focus.Currently,the majority of research typically adopts federated learning methods to train traffic prediction models distributed on each base station.This method reduces additional burden on communication systems.However,this method has a drawback:it cannot handle irregular traffic data.Due to unstable wireless network environments,device failures,insufficient storage resources,etc.,data missing inevitably occurs during the process of collecting traffic data.This results in the irregular nature of distributed traffic data.Yet,commonly used traffic prediction models such as Recurrent Neural Networks(RNN)and Long Short-Term Memory(LSTM)typically assume that the data is complete and regular.To address the challenge of handling irregular traffic data,this paper transforms irregular traffic prediction into problems of estimating latent variables and generating future traffic.To solve the aforementioned problems,this paper introduces split learning to design a structured distributed learning framework.The framework comprises a Global-level Spatial structure mining Model(GSM)and several Nodelevel Generative Models(NGMs).NGM and GSM represent Seq2Seq models deployed on the base station and graph neural network models deployed on the cloud or central controller.Firstly,the time embedding layer in NGM establishes the mapping relationship between irregular traffic data and regular latent temporal feature variables.Secondly,GSM collects statistical feature parameters of latent temporal feature variables from various nodes and executes graph embedding for spatial-temporal traffic data.Finally,NGM generates future traffic based on latent temporal and spatial feature variables.The introduction of the time attention mechanism enhances the framework’s capability to handle irregular traffic data.Graph attention network introduces spatially correlated base station traffic feature information into local traffic prediction,which compensates for missing information in local irregular traffic data.The proposed framework effectively addresses the distributed prediction issues of irregular traffic data.By testing on real world datasets,the proposed framework improves traffic prediction accuracy by 35%compared to other commonly used distributed traffic prediction methods.展开更多
In this paper,two typical stealth aircraft concepts（wing fuselage blended and flyingwing） were designed.Then three gradually changed surface distribution models with the same planform for each concept were created.B...In this paper,two typical stealth aircraft concepts（wing fuselage blended and flyingwing） were designed.Then three gradually changed surface distribution models with the same planform for each concept were created.Based on the multilevel fast multipole algorithm（MLFMA）,the vertical polarization transmitting/vertical polarization receiving（VV） and horizontal polarization transmitting/horizontal polarization receiving（HH） radar cross section（RCS） characteristics were simulated with five frequencies between 0.1 and 1.0 GHz.The influences and mechanisms of aircraft surface distribution on electromagnetic scattering characteristics were investigated.The results show that for the wing fuselage blended concept,the W RCS of this frequency range is higher than the HH RCS in most cases,while it is just the opposite for the flying-wing concept.As for the two aircraft concepts,the RCS levels of HH and W both decrease with the frequency increasing,but the HH RCS has a faster downward trend.The surface distribution has little influence on HH RCS characteristics.On the contrary,it has a significant impact on W RCS characteristics,and the amplitude of the VV RCS increases with the surface thickness.展开更多
Based on the survey data of five submarine seamount provinces （chains） in the Western Pacific, the distribution characteristics of cobalt-rich ferromanganese crust resources have been researched in this paper by usi...Based on the survey data of five submarine seamount provinces （chains） in the Western Pacific, the distribution characteristics of cobalt-rich ferromanganese crust resources have been researched in this paper by using the relative reference data and applying the theories of hotspot and seafloor spreading. The main research results obtained are as follows： The Co-rich crust thickness in the study area is gradually increasing from east to west and from south to north having a negative correlation （r = -0.59） with longitude and a positive correlation （r = 0.48） with latitude. The crust thickness varying along longitude and latitude is influenced by the hotspot and seafloor spreading. The oceanic crusts and seamounts in the northwest part of the study area are older, and the crust resources are superior to those in the southeast part. In the depth of 〈1500 m, 1500-2000 m, 2000-2500 m in the study area, the cobalt crust thickness is respectively 5.45 cm, 4.34 cm and 3.55 cm, and in the depth of 2500-3000 m and 3000-3500 m, it drops respectively to 2.84 cm and 3.37 cm. The Co-rich crust resources are mainly concentrated in the seamount summit margins and the upper flanks in the depth of 〈2500 m. There is a strong negative correlation （r = -0.67） between the cobalt crust abundance and the slope of the seamount, 75 kg/m^2 and 50 kg/mz at the slopes of 0°-20° and 20°-34° respectively. Cobalt crusts are mainly distributed in the parts whose slopes are less than 20°. It is consistent with the fractal result that the slope threshold of cobalt crust distribution is 19°, and slopes over 20° are not conducive to the crust growth. The cobalt crusts of high grade are mainly enriched in the region within 150°E-140°W and 30°S-30°N in the Pacific, where there are about 587 seamounts at the depth of 3500- 6000 m and over 30 Ma of the oceanic crusts. The perspective area rich in cobalt crust resources is about 41×104 km^2 and the resource quantity is approximately 27 billion tons.展开更多
文摘[Objective] This paper aimed to understand the area change and distribu- tion of medium-low yield farmland, and offered basis to the improvement of mediumlow farmland and its increase of grain production in Tianjin. [Method] Based on the statistical date of Tianjin and its relevant counties and districts, the yield standard was set up to classify high-yield, medium-yield and low-yield farmland in Tianjin. The author analyzed area change of medium-low yield farmland in six agricultural counties and districts （including Jixian County, Wuqing District, Baodi District, Ninghe County, Jinghai County and Dagang district of Binghai New Area） from 1980 to 2010. [Result] The results showed that the average yield of grain rose from 2 445 kg/hm^2 in 1980 to 5 130 kg/hm^2 in 2010, increasing 109.82%. The area of mediumlow yield farmland was reduced from 291 250.13 hm^2 in 1985 to 76 489.87 hm^2 in 2010, coming down 74%. In Tianjin, the area of medium-low yield farmland of 2010 accounted for 19% of the total farmland, of which the ratios of medium-low yield farmland of Jinghai County, Jixian County, Dagang district of Binghai New Area, Wuqing District, Baodi District and Ninghe County were 43.12%, 18.59%, 17.23%, 14.01%, 7.05% and 0, respectively. Low soil nutrient content, drought and water shortage, as well as soil salinization were the main yield limiting factors to mediumlow yield farmland in Tianjin in 2010. [Conclusion] The countermeasures to improve the medium-low yield farmland were proposed, involving enhancing the investment of the government, strengthening the construction of water conservancy infrastructure, further improving the soil fertility, as well as saline and alkaline land, optimizing the farming system and planting drought and salt tolerance crops, etc.
基金National Natural Science Foundation of China(41375025)863 Program(2012AA120903,2011AA12A104-3)+2 种基金Public Welfare Research Foundation of China Meteorological Administration(GYHY201106044,GYHY201106045)Meteorological Application Demonstration Project(E310/1112)4th and 5th GOSAT/TANSO joint research Project 2013-2015
文摘The variation of the atmospheric Carbon Dioxide （CO2） concentration plays an important role in global cli- mate and agriculture. We analyzed the spatial-temporal characteristics of CO2 in the China region and around the globe with the CO2 column mixing ratios observed by the Japanese GOSAT satellite （Greenhouse Gases Observing Satellite）. In order to make sure that the accuracy of the CO2 data retrieved by the satellite meets the needs of the climate charac- teristics analyses, we ran a validation on the CO2 column mixing ratios retrieved by the satellite against the ground-based TCCON （Total Carbon Column Observing Network） observation data. The result shows that the two sets of data have a correlation coefficient of higher than 0.7, and a bias of within 2.2 ppmv. Therefore, the GOSAT CO2 da- ta can be used for the climate characteristics analysis of global CO2. Our analysis on the spatial-temporal characteristics of the CO2 column mixing ratios observed during the period of June 2009 through January 2014 proved that, with the impact of the natural emission of near ground CO2 and human activities, the global CO2 concentration has a significant latitudinal characteristics with its highest level averaging 390 oomv in the 0-40？N latitudinal zone in the Northern Hemisphere, and 387 ppmv in the Southern Hemisphere. China has a relatively higher CO2 concentration with the highest level exceeding 398 ppmv, and the eastern area higher than the western area. The variation of global CO2 concentration shows a seasonal pattern, i.e. the CO2 concen- tration reaches its highest in spring in the Northern Hemisphere averaging more than 392 ppmv, second highest in win- ter, and lowest in summer averaging less than 387 ppmv. It fluctuates the most in the Northern Hemisphere with an av- erage concentration of 392.5 ppmv in April, and 385.5 ppmv in July. While in the Southern Hemisphere, the seasonal fluctuation is smaller with the highest concentration occurring in July. Over the recent years, the global CO2 concentra- tion has shown an elevating trend with an average annual increase rate of 1.58 ppmv per year. It is a challenge that the human kind has to face to slow down the increase of the CO2 concentration.
基金support provided by the National Natural Science Foundation of China(No.52274077)the Natural Science Foundation of Henan(No.242300421072)+2 种基金the Youth Elite Teachers Cultivation Program for Higher Education Institutions in Henan Province(No.2024GGJS036)the Funds for Distinguished Young Scholars of Henan Polytechnic University(No.J2023-3)the Young Core Teacher Funding Scheme of Henan Polytechnic University(No.2023XQG-09).
文摘This study examined non-uniform loading in goaf cantilever rock masses via testing,modeling,and mechanical analysis to solve instantaneous fracture and section buckling from mining abutment pressure.The study investigates the non-uniform load gradient effect on fracture characteristics,including load characteristics,fracture location,fracture distribution,and section roughness.A digital model for fracture interface buckling analysis was developed,elucidating the influence of non-uniform load gradients on Fracture Interface Curvature(FIC),Buckling Rate of Change(BRC),and Buckling Domain Field(BDF).The findings reveal that nonlinear tensile stress concentration and abrupt tensile-compressive-shear strain mutations under non-uniform loading are fundamental mechanisms driving fracture path buckling in cantilever rock mass structures.The buckling process of rock mass under non-uniform load can be divided into two stages:low load gradient and high gradient load.In the stage of low gradient load,the buckling behavior is mainly reflected in the compression-shear fracture of the edge.In the stage of high gradient load,a buckling band along the loading direction is gradually formed in the rock mass.These buckling principles establish a theoretical basis for accurately characterizing bearing fractures,fracture interface instability,and vibration sources within overlying cantilever rock masses in goaf.
基金supported by the National Natural Science Foundation of China(Nos.U19A2044,42105132,42030609,41975037,and 42105133)the National Key Research and Development Program of China(No.2022YFC3703502)+1 种基金the Plan for Anhui Major Provincial Science&Technology Project(No.202203a07020003)Hefei Ecological Environment Bureau Project(No.2020BFFFD01804).
文摘As a significant city in the Yangtze River Delta regions,Hefei has experienced rapid changes in the sources of air pollution due to its high-speed economic development and urban expansion.However,there has been limited research in recent years on the spatial-temporal distribution and emission of its atmospheric pollutants.To address this,this study conducted mobile observations of urban roads using the Mobile-DOAS instrument from June 2021 to May 2022.The monitoring results exhibit a favourable consistent with TROPOMI satellite data and ground monitoring station data.Temporally,there were pronounced seasonal variations in air pollutants.Spatially,high concentration of HCHO and NO_(2)were closely associated with traffic congestion on roadways,while heightened SO_(2)levels were attributed to winter heating and industrial emissions.The study also revealed that with the implementation of road policies,the average vehicle speed increased by 95.4%,while the NO concentration decreased by 54.4%.In the estimation of urban NO_(x)emission flux,it was observed that in temporal terms,compared with inventory data,the emissions calculated viamobile measurements exhibitedmore distinct seasonal patterns,with the highest emission rate of 349 g/sec in winter and the lowest of 142 g/sec in summer.In spatial terms,the significant difference in emissions between the inner and outer ring roads also suggests the presence of the city’s primary NO_(x)emission sources in the area between these two rings.This study offers data support for formulating the next phase of air pollution control measures in urban areas.
基金Supported by the National Key Research and Development Program(No.2016YFC1402201)the China Ocean Mineral Resources R&D Association Project(No.DY135-E2-2-04)。
文摘Microplastic contamination is considered a major threat to the marine environment.Although microplastic pollution in the Pacific Ocean has been studied,its abundance,distribution,composition,and origin in the western Pacific Ocean remain unclear.Here,we investigated the abundance and distribution characteristics of microplastics in surface waters of the western Pacific Ocean and analyzed their potential sources.Results show that microplastics were widespread in the western Pacific Ocean,with abundance ranging from 0.03 to 2.36 particles/m^(3)(average 0.37±0.47 particles/m^(3)).Fibers/filaments and fragments were the main shapes of microplastics(71.6%)and the most abundant microplastic size class was<1.0 mm(42.4%).Significant differences in microplastic abundance were observed in different regions,with the lowest abundance in the South China Sea(0.03 particles/m^(3))and highest abundance in the seamount area in the western Pacific Ocean(0.58 particles/m^(3)).This study provides baseline data and insights into the fate and transportation of microplastics in the western Pacific region.
基金Supported by the National Natural Science Foundation of China(No.41961144011)。
文摘Microplastics(MPs)pollution has emerged as a critical global environmental issue,for which rivers serve as key conduits for the transport of MPs from land to ocean.There remained a lack of clarity regarding the characteristics and transport patterns of MPs pollution in diverse environmental media and seasons within a river basin.The Jiulong River basin in Fujian,southeast China was studied as case,whose spatial-temporal distribution,pollution characteristics,and transport dynamics of MPs in both surface water and groundwater were analyzed.Additionally,the features of MPs in different land use types during the dry season were examined.Results show that in wet season,the abundance of MPs in river water varied from 840 to 12300 p/m^(3),with an average of 3920 p/m^(3);in groundwater,the range was 740-1820 p/m^(3),averaging 1107 p/m^(3);and from 68 to 951 p/kg,with an average value of 265 p/kg in the soil(dry weight).In dry season,levels of MPs in river water ranged from 580 to 8880 p/m^(3),with an average of 4034 p/m^(3);groundwater exhibited a range of 860-14980 p/m^(3),averaging 3453 p/m^(3).Fibers consistently dominated the morphology of MPs,of which polyethylene terephthalate was identified as the predominant composition in each environmental medium.Our findings underscore the spatial and temporal variability in distribution and contamination characteristics of MPs across different media.Notably,MPs abundance in river water and groundwater exhibited a seasonal pattern,being higher in levels in dry season than in wet season.The downstream transport of MPs was facilitated by surface runoff,in which MPs in groundwater and surface water could complement to each other.Furthermore,population density and human activities were identified as influential factors on the distribution and abundance of MPs.This study revealed the order of magnitude of difference in annual estimates of MPs entering the sea among different models.Additionally,the interception volume by mangrove forest in the Jiulong River estuary was estimated approximately 1.51×10^(10)MPs particles per year.Ecological interception shall be considered when estimating the fluxes of MPs into the sea.
文摘Taking 138 key rural tourism villages in Beijing for example,this paper applied GIS analysis to analyze the spatial distribution characteristics of these villages,selected the influence factors of the villages considering the classification characteristics,so as to explore the impact of different influence factors on its spatial distribution.The results showed(i)Key rural tourism villages in Beijing manifested an aggregated distribution on the whole,they were unevenly distributed and mostly located in the fringe area of northern mountainous areas and plains,such as Huairou District and Miyun District.Such a“multi-center distribution”pattern was significantly influenced by terrains and natural resources.(ii)Depending on local natural and cultural resources,tourism resources,development characteristics and functional differences,key rural tourism villages in Beijing could be devided into natural scenery type,scenic area-dependent type and agriculture experiencing type.(iii)Key factors influencing the distribution of these villages included mean temperature,annual precipitation,quantity of scenic area,road network density,agricultural land and so on,and the interaction of dual factors exerted more significant impact on single factors.
基金Supported by The Inner Mongolia Natural Science Foundation (2009ms0603)Inner Mongolia Scientific Innovation Program (nmqxkjcx200706)Special Fund for Scientific Research in Central Public Welfare Institution Fundamental(Grassland Research Institute of Chinese Academy of Agricultural Science)
文摘Thornthwaite Memorial model and other statistic methods were used to calculate the climate-productivity of plants with the meteorological data from 1961 to 2007 at 9 stations distributed on Inner Mongolia desert steppe.The spatial and temporal variation characteristics of climate-productivity were analyzed by using the methods of the tendency rate of the climate trend,accumulative anomaly,and spatial difference and so on.The results showed that the climate-productivity kept linear increased trend over Inner Mongolia desert steppe in recent 47 years,but not significant.In spatial distribution,the climate-productivity reduced with the increased latitude.The climate-productivity in southwest part of Inner Mongolia desert steppe was growing while that in the southeast was reducing.The variation rate of the climate-productivity increased from the northwest part to the southeast part of Inner Mongolia desert steppe.In recent 47 years,the climate-productivity in southeast Jurh underwent the greatest decreasing extent,and the region was the sensitive area of the climate-productivity variation.
基金Supported by the National Natural Science Foundation(30760021)Natural Science Foundation of Jiangxi Province(0530016)Project of the Education Department of Jiangxi Province(Jiangxi Education&Tech-nology No.[2007]151)~~
文摘[Objective] The aim of this study was to reveal the mechanism of Cu2+ hyper-accumulator in Setcreasea purpurea Boom from the angle of distribution characteristics and binding form of Cu2+ in tissue cells.[Method]The distribution characteristics of Cu2+ in subcells of Setcreasea purpurea Boom was studied by the technique of differential centrifugation,and the binding form of Cu2+ in roots and leaves of Setcreasea purpurea Boom was also investigated by the sequential chemical extraction method and the enzymolysis method.[Result]Cu2+ in roots mainly distributed in the cell wall which is accounting for one third of the Total Cu2+ in roots,while Cu2+ in leaves mainly distributed in the chloroplast which is accounting for a quarter to the Total Cu2+ in leaves.Under the high concentration of Cu2+ or the extended treatment duration,the translocation of Cu2+ in root cells into the cell wall increased but the translocation of Cu2+ in root cells into the plastid decreased,while the translocation of Cu2+ in leaf cells into the chloroplast increased but the translocation of Cu2+ in leaf cells into the cell wall decreased.Cu2+ in leaves was mainly combined with amino acid,small molecular polymeric pigments,protein and polysaccharide,while Cu2+ in roots was mainly combined with cell wall substances such as cellulose and membrane-bound protein.[Conclusion]The distribution characteristics and binding form of Cu2+ in cells is possibly one of the dominant mechanisms for Cu2+ hyper-accumulator in Setcreasea purpurea Boom.
基金Supported by Scientific Research Special Fund for Public Welfare Industry(Meteorology)[GYHY200806014]
文摘Based on the special landscape and regional characteristics,the lightning location information from 1999 to 2008 and conventional observation data from 1971 to 2000 provided by electricity departments in Hebei Province were applied to analyze spatial and temporal distribution of lightning.With lighting disaster data since 2000 provided by meteorological department,and records from civil affair,statistics,insurance,and other departments,the lighting disaster distribution of Hebei Province was studied from aspects of economic and people losses,and some countermeasures for several lightning disasters industries were put forward.
文摘The surveys on the COD in the Lingdingyang waters of Pearl River estuary were carried out in May and August of 2002. The results showed that the concentrations of COD in the waters ranged from 0,41 to 2.72 mg·L^-1 with an average of 1.21 mg·L^-1.The spatial distributions showed that COD concentration decreased gradually from the north to south of Pearl River estuary, and the concentration near coastal waters was higher than that in offshore waters. The concentration of COD in summer was higher than in spring. Evaluated by the first class （COD ≤ 2 mg·L^-1） of sea water quality standard （Chinese standard）, there were about 15 % of COD concentrations over the standard. The concentration of COD showed a positive correlation with the concentration of suspend substances in spring and summer, but in summer it showed a negative correlation with the concentrations of inorganic nitrate and phosphate.
文摘Aim To quantitatively study three characteristics of the Weibull distribution. Methods Theoritical analysis of the three characteristics of parameters of the Weibull distribution was done and mathematics software was used to make some chart analysis. Results 17 equations and 7 figures were made. Conclusion Under the standard form, the class of the Weibull probable density founction(pdf) curves appear double peak shape. Under the standard form, the maximum value point curve of the Weibull pdf takes line t =0 and t=1 as asymptotes. When β = 3 30-3 40, the Weibull distribution is the most similar to the normal distribution.
基金Scientific and Technological Project of Social Development of Jiangsu Province (BS2002068).
文摘According to the analysis on the characteristics of historic earthquakes in Jiangsu Province and South Huanghai Sea region, the historical earthquakes in the studied area are divided into two kinds of comparatively safe class and comparatively dangerous class. Then the statistical result of earthquake class, the characteristics of geo-graphical distribution and geological structures are studied. The study shows: a) In Jiangsu Province and South Huanghai Sea region, the majority of historical strong earthquakes belong to comparatively safe class, only 13.8% belong to comparatively dangerous class; b) Most historical earthquakes belong to comparatively safe class in the land area of Jiangsu, eastern sea area of Yangtze River mouth and northern depression of South Huanghai Sea region. However, along the coast of middle Jiangsu Province and in the sea area of South Huanghai Sea, the distribution of historical earthquake classes is complex and the earthquake series of comparatively dan-gerous class and comparatively safe class are equivalent in number; c) In the studied area, the statistical results of historical earthquake classes and the characteristics of spatial distribution accord very well with the real case of present-day earthquake series. It shows that the seismic activity in the region has the characteristic of succession, and the result from this study can be used as a reference for early postseismic judgment in the earthquake emer-gency work in Jiangsu Province.
基金supported by the National Natural Science Foundation of China (71273105)the Fundamental Research Funds for the Central Universities,China (2013YB12)
文摘Macroscopic grasp of agricultural carbon emissions status, spatial-temporal characteristics as well as driving factors are the basic premise in further research on China’s agricultural carbon emissions. Based on 23 kinds of major carbon emission sources including agricultural materials inputs, paddy ifeld, soil and livestock breeding, this paper ifrstly calculated agricultural carbon emissions from 1995 to 2010, as well as 31 provinces and cities in 2010 in China. We then made a decomposed analysis to the driving factors of carbon emissions with logarithmic mean Divisia index （LMDI） model. The results show：（1） The amount of agricultural carbon emissions is 291.1691 million t in 2010. Compared with 249.5239 million t in 1995, it increased by 16.69%, in which, agricultural materials inputs, paddy ifeld, soil, enteric fermentation, and manure management accounted for 33.59, 22.03, 7.46, 17.53 and 19.39%of total agricultural carbon emissions, respectively. Although the amount exist ups and downs, it shows an overall trend of cyclical rise; （2） There is an obvious difference among regions：the amount of agricultural carbon emissions from top ten zones account for 56.68%, while 9.84%from last 10 zones. The traditional agricultural provinces, especially the major crop production areas are the main source regions. Based on the differences of carbon emission rations, 31 provinces and cities are divided into ifve types, namely agricultural materials dominant type, paddy ifeld dominant type, enteric fermentation dominant type, composite factors dominant type and balanced type. The agricultural carbon emissions intensity in west of China is the highest, followed by the central region, and the east zone is the lowest; （3） Compared with 1995, efifciency, labor and structure factors cut down carbon emissions by 65.78, 27.51 and 3.19%, respectively;while economy factor increase carbon emissions by 113.16%.
基金Supported by National Key Technology Research and Development Program of China during the"12th Five-Year Plan"(2011BAD16B01,2012BAD04B10)Key Project of the National Twelfth-Five Year Research Program of China(2013BAD07B11)~~
文摘Using the cultivars with high and low calcium in brown rice as tested ma- terials, the effects of calcium on photosynthetic characteristics and its subcellular dis- tribution in different rice cultivars at seedling stage were investigated with hydrocul- ture method. The results showed that the photosynthetic rate in leaves of high cal- cium cultivar was higher than that low calcium cultivar. The calcium content in leaves of rice was higher than that in roots. Among various tissues and organs, the calcium contents ranked as cell wall〉ribosome and intracellular soluble components〉 plastid （or chloroplasts）〉mitochondria〉nucleus. Cell wall is the most important distri- bution place for calcium, while calcium is rarely distributed in nuclei or mitochon- drias. In all the organelles, the calcium concentrations were all increased with the increased treatment concentration of calcium, especially in high calcium cultivar. The high calcium treatment showed more significant effects on calcium contents in im- portant organelles of high calcium cultivar, so it is speculated that the high calcium cultivar had higher calcium accumulation and tolerance capacities.
基金Major Program of the Natural Science Foundation of China,No.41590842
文摘Haze pollution has become a severe environmental problem in the daily life of the people in China. PM2.s makes a significant contribution to poor air quality. The spatio-temporal features of China＇s PM2.s concentrations should be investigated. This paper, based on ob- served data from 945 newly located monitoring sites in 2014 and industrial working population data obtained from International Standard Industrial Classification （ISIC）, reveals the spa- tio-temporal variations of PM2.5 concentrations in China and the correlations among different industries. We tested the spatial autocorrelation of PM2.5 concentrations in the cities of China with the spatial autocorrelation model. A correlation coefficient to examine the correlativity of PM2.5 concentrations and 23 characteristic variables for 190 cities in China in 2014, from which the most important ones were chosen, and then a regression model was built to further reveal the social and economic factors affecting PMg.g concentrations. Results： （1） The Hu Huanyong Line and the Yangtze River were the E-W divide and S-N divide between high and low values of China. （2） The PM2.5 concentrations shows great seasonal variation, which is high in autumn and winter but low in spring and summer. The monthly average shows a U-shaped pattern, and daily average presents a periodic and impulse-shaped change. （3） PM2.5 concentrations had a distinct characteristic of spatial agglomeration. The North China Plain was the predominant region of agglomeration, and the southeastern coastal area had stable good air quality.
基金Project supported by the Knowledge Innovation Engineering Project of the Chinese Academy of Sciences(No. KSCX2-YW-N-46-06)the National Natural Science Foundation of China(No. 40501030).
文摘Overwhelming evidence reveals that concentrations of dissolved organic carbon （DOC） have increased in streams which brings negative environmental impacts. DOC in stream flow is mainly originated from soil-water solutions of watershed. Wetlands prove to be the most sensitive areas as an important DOC reserve between terrestrial and fluvial biogeosystems. This reported study was focused on the distribution characteristics and the controlling factors of DOC in soil-water solutions of annular wetland, i.e., a dishing wetland and a forest wetland together, in the Sanjiang Plain, Northeast China. The results indicate that DOC concentrations in soilwater solutions decreased and then increased with increasing soil depth in the annular wetland. In the upper soil layers of 0-10 cm and 10-20 cm, DOC concentrations in soil-water solutions linearly increased from edge to center of the annular wetland （R^2 = 0.3122 and R^2 = 0.443）. The distribution variations were intimately linked to DOC production and utilization and DOC transport processes in annular wetland soil-water solutions. The concentrations of total organic carbon （TOC）, total carbon （TC） and Fe（II）, DOC mobility and continuous vertical and lateral flow affectext the distribution variations of DOC in soil-water solutions. The correlation coefficients between DOC concentrations and TOC, TC and Fe（II） were 0.974, 0.813 and 0.753 respectively. These distribution characteristics suggested a systematic response of the distribution variations of DOC in annular wetland soil-water solutions to the geometry of closed depressions on a scale of small catchments. However, the DOC in soil pore water of the annular wetland may be the potential source of DOC to stream flow on watershed scale. These observations also implied the fragmentation of wetland landscape could bring the spatial-temporal variations of DOC distribution and exports, which would bring negative environmental impacts in watersheds of the Sanjiang Plain.
基金supported by the Beijing Natural Science Foundation(Certificate Number:L234025).
文摘Spatial-temporal traffic prediction technology is crucial for network planning,resource allocation optimizing,and user experience improving.With the development of virtual network operators,multi-operator collaborations,and edge computing,spatial-temporal traffic data has taken on a distributed nature.Consequently,noncentralized spatial-temporal traffic prediction solutions have emerged as a recent research focus.Currently,the majority of research typically adopts federated learning methods to train traffic prediction models distributed on each base station.This method reduces additional burden on communication systems.However,this method has a drawback:it cannot handle irregular traffic data.Due to unstable wireless network environments,device failures,insufficient storage resources,etc.,data missing inevitably occurs during the process of collecting traffic data.This results in the irregular nature of distributed traffic data.Yet,commonly used traffic prediction models such as Recurrent Neural Networks(RNN)and Long Short-Term Memory(LSTM)typically assume that the data is complete and regular.To address the challenge of handling irregular traffic data,this paper transforms irregular traffic prediction into problems of estimating latent variables and generating future traffic.To solve the aforementioned problems,this paper introduces split learning to design a structured distributed learning framework.The framework comprises a Global-level Spatial structure mining Model(GSM)and several Nodelevel Generative Models(NGMs).NGM and GSM represent Seq2Seq models deployed on the base station and graph neural network models deployed on the cloud or central controller.Firstly,the time embedding layer in NGM establishes the mapping relationship between irregular traffic data and regular latent temporal feature variables.Secondly,GSM collects statistical feature parameters of latent temporal feature variables from various nodes and executes graph embedding for spatial-temporal traffic data.Finally,NGM generates future traffic based on latent temporal and spatial feature variables.The introduction of the time attention mechanism enhances the framework’s capability to handle irregular traffic data.Graph attention network introduces spatially correlated base station traffic feature information into local traffic prediction,which compensates for missing information in local irregular traffic data.The proposed framework effectively addresses the distributed prediction issues of irregular traffic data.By testing on real world datasets,the proposed framework improves traffic prediction accuracy by 35%compared to other commonly used distributed traffic prediction methods.
文摘In this paper,two typical stealth aircraft concepts（wing fuselage blended and flyingwing） were designed.Then three gradually changed surface distribution models with the same planform for each concept were created.Based on the multilevel fast multipole algorithm（MLFMA）,the vertical polarization transmitting/vertical polarization receiving（VV） and horizontal polarization transmitting/horizontal polarization receiving（HH） radar cross section（RCS） characteristics were simulated with five frequencies between 0.1 and 1.0 GHz.The influences and mechanisms of aircraft surface distribution on electromagnetic scattering characteristics were investigated.The results show that for the wing fuselage blended concept,the W RCS of this frequency range is higher than the HH RCS in most cases,while it is just the opposite for the flying-wing concept.As for the two aircraft concepts,the RCS levels of HH and W both decrease with the frequency increasing,but the HH RCS has a faster downward trend.The surface distribution has little influence on HH RCS characteristics.On the contrary,it has a significant impact on W RCS characteristics,and the amplitude of the VV RCS increases with the surface thickness.
基金This work was supported by grant 2004DIB3J086 and 2006FY220400 from the State Ministry of Science and Technology； the National Natural Science Foundation of China （Grant 40676061） ； China Ocean Resource R＆D Association （Grant DYXM- 115-01-1-06）.
文摘Based on the survey data of five submarine seamount provinces （chains） in the Western Pacific, the distribution characteristics of cobalt-rich ferromanganese crust resources have been researched in this paper by using the relative reference data and applying the theories of hotspot and seafloor spreading. The main research results obtained are as follows： The Co-rich crust thickness in the study area is gradually increasing from east to west and from south to north having a negative correlation （r = -0.59） with longitude and a positive correlation （r = 0.48） with latitude. The crust thickness varying along longitude and latitude is influenced by the hotspot and seafloor spreading. The oceanic crusts and seamounts in the northwest part of the study area are older, and the crust resources are superior to those in the southeast part. In the depth of 〈1500 m, 1500-2000 m, 2000-2500 m in the study area, the cobalt crust thickness is respectively 5.45 cm, 4.34 cm and 3.55 cm, and in the depth of 2500-3000 m and 3000-3500 m, it drops respectively to 2.84 cm and 3.37 cm. The Co-rich crust resources are mainly concentrated in the seamount summit margins and the upper flanks in the depth of 〈2500 m. There is a strong negative correlation （r = -0.67） between the cobalt crust abundance and the slope of the seamount, 75 kg/m^2 and 50 kg/mz at the slopes of 0°-20° and 20°-34° respectively. Cobalt crusts are mainly distributed in the parts whose slopes are less than 20°. It is consistent with the fractal result that the slope threshold of cobalt crust distribution is 19°, and slopes over 20° are not conducive to the crust growth. The cobalt crusts of high grade are mainly enriched in the region within 150°E-140°W and 30°S-30°N in the Pacific, where there are about 587 seamounts at the depth of 3500- 6000 m and over 30 Ma of the oceanic crusts. The perspective area rich in cobalt crust resources is about 41×104 km^2 and the resource quantity is approximately 27 billion tons.
