The typical regions of the Taihu Lake Basin,China,were selected to analyze the variation characteristics of river-lake networks under intensive human activities.The characteristics of the fractal dimension of river ne...The typical regions of the Taihu Lake Basin,China,were selected to analyze the variation characteristics of river-lake networks under intensive human activities.The characteristics of the fractal dimension of river networks and lakes for different periods were investigated and the influences of river system evolution on water level changes were further explored through the comparison of their fractal characters.The results are as follows:1) River network development of the study area is becoming more monotonous and more simple;the number of lakes is reducing significantly,and the water surface ratio has dropped significantly since the 1980s.2) The box dimension of the river networks in all the cities of the study area decreased slowly from the 1960s to the 1980s,while the decrease was significant from the 1980s to the 2000s.The variations of lake correlation dimension are similar to those of the river network box dimensions.This is unfavorable for the storage capacity of the river networks and lakes.3) The Hurst exponents of water levels were all between 0.5 and 1.0 from the 1960s to the 1980s,while decreased in the 2000s,indicating the decline in persistence and increase in the complexity of water level series.The paper draws a conclusion that the relationship between the fractal dimension of river-lake networks and the Hurst exponents of the water level series can reveal the impacts of river system changes on flood disasters to some extent:the disappearance of river networks and lakes will increase the possibility of flood occurrence.展开更多
Let F q be a finite field with qelements where q=p~α. In the present paper, the authors study the existence and structure of Carter subgroups of singular symplectic group Sp (n+t,n)(F q), singular unitary group U (n+...Let F q be a finite field with qelements where q=p~α. In the present paper, the authors study the existence and structure of Carter subgroups of singular symplectic group Sp (n+t,n)(F q), singular unitary group U (n+t,n)(F (q^2)) and singular orthogonal group O (n+t,n)(F q)(n is even) over finite fields F q.展开更多
Water level is an important index for studying hydrologic processes. Water level rise processes were studied in three catchments(catchment I, II, III in Chen Jiagou watershed in the Three Gorge Reservoir Area) with di...Water level is an important index for studying hydrologic processes. Water level rise processes were studied in three catchments(catchment I, II, III in Chen Jiagou watershed in the Three Gorge Reservoir Area) with different areas to provide useful information to inform data extension from a gauged-catchment to an ungauged catchment. The results showed that there are seasonal changes in the dominant driving mode of the rise of the water level. The rise of the water level in March is likely mainly driven by the mode of stored-full runoff, and in September or October, it is mainly driven by Horton-flow. The correlation coefficients of all indexes were significant among the three catchments, suggesting that these catchments have similarities and that water level data extension is likely to be completed successfully between the large catchment(III-Catchment) and the small catchment(ICatchment). It was confirmed that there is good similarity between the 0.6 km^2 and 6 km^2 catchments, and the data correlation is good between the catchments with the area differences in the Three Gorges Reservoir Area. In addition, the rise processes of the water level in the catchments were not only different under the same rain conditions, but this difference could also change with the rain condition.展开更多
Diatoms are widely used to study past and present changes in the marine environment. Unimodal models are appropriate for exploring the relationship between environmental properties in Chinese inshore waters and fossil...Diatoms are widely used to study past and present changes in the marine environment. Unimodal models are appropriate for exploring the relationship between environmental properties in Chinese inshore waters and fossil diatom species derived from modem surface sediments. The best-fit relationships between two multivariate datasets (diatom species and environmental variables) were identified using canonical correspondence analysis (CCA), which is a constrained ordination technique. The absolute abundance of diatoms in the Chinese inshore waters ranged from 500 to 48 000 valves/g, and the average absolute abundance of all the 29 sites was l l 300 valves/g. 153 species and varieties of diatoms belonging to 42 genera in all were identified in the Chinese inshore waters. There were 28 dominant diatom species in all. According to the absolute abundance of the dominant species and the spatial distribution of the currents from the Chinese inshore waters, 12 diatom assemblages were distinguished from north to south, which reflected the different oceanographic conditions at the regional scale. Of the eight environmental variables considered, the most important environmental variable is winter sea surface salinity (WSS), which was also the only environmental variable with statistical significance. Therefore, it may be used to establish a transfer functions for the Chinese inshore waters in future paleoclimate studies.展开更多
The important role of Three Gorges Project (TGP) in the flood management of the Yangtze River Basin is summarized.The Optimal Regulation Schemes of the Three Gorge Reservoir is briefly described.The flood regulation e...The important role of Three Gorges Project (TGP) in the flood management of the Yangtze River Basin is summarized.The Optimal Regulation Schemes of the Three Gorge Reservoir is briefly described.The flood regulation effect of TGP is analyzed.Typical issues related to reservoir operation for flood regulation are discussed and suggestions are put forward for the future work.展开更多
While over two thousand years apart, Western postmodernism and ancient Chinese philosophy share some extraordinary similarities, especially epistemology wise. For example, they both recognize the role of language in c...While over two thousand years apart, Western postmodernism and ancient Chinese philosophy share some extraordinary similarities, especially epistemology wise. For example, they both recognize the role of language in constructing, and limiting, knowledge and reality. This is because thinkers of different cultures and geographical regions, and of different historical periods, can possibly come up with similar philosophical conclusions when addressing what is commonly known as the "human condition". The paper will discuss, in general terms, some of the philosophical similarities between postmodemism and classical Chinese philosophy; it will also take a close look at three concepts in Chinese philosophy that register strong affinity with Western postmodernism: namely, change, dialectic, and relativism.展开更多
Ten runoff plots with different planting patterns were established for experimental observation in Yangjichong small watershed of Longli County in Karst region of Guizhou Province. Results show that under the same rai...Ten runoff plots with different planting patterns were established for experimental observation in Yangjichong small watershed of Longli County in Karst region of Guizhou Province. Results show that under the same rainfall condition, shrub land, natural grassland and abandoned land presented the best function of soil and water conservation. The function of soil and water conservation was poor for arbor planting pattern, because the shrub layer, herb layer and forest floor were not formed. Because of no-tillage, surface crust and other effects, the function of soil and water conservation in slope farmland was better than that in runoffplots with arbor planting pattern.展开更多
Parameter estimation of the attributed scattering center(ASC) model is significant for automatic target recognition(ATR). Sparse representation based parameter estimation methods have developed rapidly. Construction o...Parameter estimation of the attributed scattering center(ASC) model is significant for automatic target recognition(ATR). Sparse representation based parameter estimation methods have developed rapidly. Construction of the separable dictionary is a key issue for sparse representation technology. A compressive time-domain dictionary(TD) for ASC model is presented. Two-dimensional frequency domain responses of the ASC are produced and transformed into the time domain. Then these time domain responses are cutoff and stacked into vectors. These vectored time-domain responses are amalgamated to form the TD. Compared with the traditional frequency-domain dictionary(FD), the TD is a matrix that is quite spare and can markedly reduce the data size of the dictionary. Based on the basic TD construction method, we present four extended TD construction methods, which are available for different applications. In the experiments, the performance of the TD, including the basic model and the extended models, has been firstly analyzed in comparison with the FD. Secondly, an example of parameter estimation from SAR synthetic aperture radar(SAR) measurements of a target collected in an anechoic room is exhibited. Finally, a sparse image reconstruction example is from two apart apertures. Experimental results demonstrate the effectiveness and efficiency of the proposed TD.展开更多
Based on the 1961-1990 observed daily precipitation in the Changjiang-Huaihe River Basin, the NCEP/NCAR reanalysis data, and the HadCM3 model data for IPCC SRES A1B climate projections, the simulation capabilities of ...Based on the 1961-1990 observed daily precipitation in the Changjiang-Huaihe River Basin, the NCEP/NCAR reanalysis data, and the HadCM3 model data for IPCC SRES A1B climate projections, the simulation capabilities of the BP-CCA downscaling approach for extreme precipitation indices of the current climate are assessed by applying canonical correlation analysis (CCA). In addition, future extreme precipitation indices in the middle and late 21st century are projected. The results show that simulation capability of the HadCM3 for regional climate characteristics can be effectively improved by the downscaling approach, with 30%-100% reduction of the relative errors of the climatological mean state of extreme precipitation indices. However, the downscaling results still show wetter winter and dryer summer than the observation. Under the SRES A1B emission scenario, frequency and intensity of extreme precipitation events are projected to increase, and the estimated increasing rate is higher for extreme precipitation indices than for mean precipitation index; and in summer than in winter. Extreme precipitations in the middle and late 21st century are expected to increase by 14% and 25% respectively in winter, and by 24% and 32% respectively in summer.展开更多
The National Road RN 91 has been threatened for about twenty-five years by a huge landslide, located 25 km south-east to the town of Grenoble (France). If several million cubic meters of rock fall down, the debris wil...The National Road RN 91 has been threatened for about twenty-five years by a huge landslide, located 25 km south-east to the town of Grenoble (France). If several million cubic meters of rock fall down, the debris will dam the valley. Then the failure of the dam by overtopping and rapid erosion might result in a catastrophic flood and dramatic consequences for human life, environment and economy throughout the valley. The paper presents the hazard assessment based on geological and hydrological surveys, including small scale hydraulic tests, as well as the risk evaluation that has been performed. The risk management relies first upon a high level monitoring and an emergency plan; various mitigation strategies have been considered.展开更多
In this paper, Schwarz-Pick estimates for high order FrSchet derivatives of holo- morphic self-mappings on classical domains are presented. Moreover, the obtained result can deduce the early work on Sc:hwarz-Pick est...In this paper, Schwarz-Pick estimates for high order FrSchet derivatives of holo- morphic self-mappings on classical domains are presented. Moreover, the obtained result can deduce the early work on Sc:hwarz-Pick estimates of higher-order partial derivatives for bounded holomorphic functions on classical domains.展开更多
Abstract homomorphisms between subgroups of algebraic groups were studied in detail by A.Borel, J.Tit.[1] and B.Wei.feile.[2] provided that the images of the homomorphisms are Zariski dense subsets and that the fields...Abstract homomorphisms between subgroups of algebraic groups were studied in detail by A.Borel, J.Tit.[1] and B.Wei.feile.[2] provided that the images of the homomorphisms are Zariski dense subsets and that the fields over which algebraic groups are defined are infinite. The purpose of this paper is to determine all embedding homomorphisms of SLn(k) into SLn(K) when k and K are any fields of the same characteristic, without assumption of Zariski density and infinitude of fields. The result in this paper generalizes a result of Chen Yu on homomorphisms of two dimensional linear groups[3].展开更多
Monthly discharge of four rivers with various permafrost coverage and little anthropogenic influence was used to identify effects of permafrost degradation during the last 50 years,which has occurred because of signif...Monthly discharge of four rivers with various permafrost coverage and little anthropogenic influence was used to identify effects of permafrost degradation during the last 50 years,which has occurred because of significant increases in air temperature in the river regions.The basins of the Shule,Heihe,Shiyang and upper Yellow Rivers in northwestern China have 73%,58%,33% and 43% permafrost coverage,respectively.There is snow cover in the basins and no rain to supply rivers during winter. The monthly recession coefficient(RC) in winter reflects groundwater conditions.The RC has increased obviously for the Shule and Heihe rivers with 73% and 58% permafrost coverage,respectively,but did not increase for the Shiyang River,and decreased insignificantly for the upper Yellow River,which had less permafrost coverage.There is a distinct positive relationship between RC and annual negative degree-day temperature(NDDT) at the meteorological stations in the basins with high permafrost coverage.These results imply that permafrost degradation due to climate warming affects hydrological processes in winter.The effect is obvious in the basins with high permafrost coverage but negligible in those with low permafrost coverage. Permafrost degradation increases infiltration,enlarges the groundwater reservoir,and leads to slow discharge recession.The result means that hydrological processes are affected strongly by permafrost degradation in river basins with high permafrost coverage,but less in river basins with less permafrost coverage.展开更多
Basic facts for Gabor frame {Eu(m)bTu(n)ag}m, n∈P on local field are investigated. Accurately, that the canonical dual of frame {Eu(m)bTu(n)ag}m,n∈P also has the Gabor structure is showed; that the product a...Basic facts for Gabor frame {Eu(m)bTu(n)ag}m, n∈P on local field are investigated. Accurately, that the canonical dual of frame {Eu(m)bTu(n)ag}m,n∈P also has the Gabor structure is showed; that the product ab decides whether it is possible for {Eu(m)bTu(n)ag}m,n∈P to be a frame for L^2(K) is discussed; some necessary conditions and two sufficient conditions of Gabor frame for L^2 (K) are established. An example is finally given.展开更多
This study provides basis information for estimating the feasibility of the environmental and ecological forestry construction project in the area. Through the survey in Miyun watershed, the economical benefits of car...This study provides basis information for estimating the feasibility of the environmental and ecological forestry construction project in the area. Through the survey in Miyun watershed, the economical benefits of carbon sequestration in five typical forest types have been studied by calculating the biomass from the timber accumulation data and converting to the money value. The results show that: in the duration of 100 years, at a discount rate of 5%, and 197 RMB yuan/t as the price of the carbon sequestration, the present value (PV) of the carbon sequestration in different forests are: 6900-9300 yuan/ha in Chinese pine forest,6100-8200 yuan/ha in oak forest, 4500-6100 yuan/ha in other broadleaf forests, 2300-3200 yuan/ha in shrubs and 1300-1800 yuan/ha in cypress forest. The annual mean economic benefit of carbon sequestration is 770-1040 yuan/ha. The pine forest has the highest carbon sequestration benefit, followed by oak forest, other broadleaf forest, shrubs, and cypress forest. If the land is suitable for all forests, pine forest and oak forest should be planted in order to sequestrate more carbon.展开更多
For quadratic number ?elds F = Q(√2p1 ···pt?1 ) with primes pj ≡ 1 mod 8, the authors study the class number and the norm of the fundamental unit of F. The resultsgeneralize nicely what has been famil...For quadratic number ?elds F = Q(√2p1 ···pt?1 ) with primes pj ≡ 1 mod 8, the authors study the class number and the norm of the fundamental unit of F. The resultsgeneralize nicely what has been familiar for the ?elds Q(√2p) with a prime p ≡ 1 mod 8, including density statements. And the results are stated in terms of the quadratic form x2 + 32y2 and illustrated in terms of graphs.展开更多
Freshwater habitats and organisms are among the most threatened on Earth, and freshwater ecosystems have been subject to large biodiversity losses. We developed a Climate Change Sensitivity (CCS) indicator based on ...Freshwater habitats and organisms are among the most threatened on Earth, and freshwater ecosystems have been subject to large biodiversity losses. We developed a Climate Change Sensitivity (CCS) indicator based on trait information for a selection of stream- and lake-dwelling Ephemeroptera, Plecoptera and Trichoptera taxa. We calculated the CCS scores based on ten species traits identified as sensitive to global climate change. We then assessed climate change sensitivity between the six main ecoregions of Sweden as well as the three Swedish regions based on lilies. This was done using biological data from 1,382 stream and lake sites where we compared large-scale (ecoregional) patterns in climate change sensitivity with potential future exposure of these ecosystems to increased temperatures using ensemble-modelled future changes in air temperature. Current (1961-1990) measured temperature and ensemble-modelled future (2100) temperature showed an increase from the northernmost towards the southern ecoregions, whereas the predicted temperature change increased from south to north. The CCS indicator scores were highest in the two northernmost boreal ecoregions where we also can expect the largest global climate change-induced increase in temperature, indicating an unfortunate congruence of exposure and sensitivity to climate change. These results are of vital importance when planning and implementing management and conservation strategies in freshwater ecosystems, e.g., to mitigate increased temperatures using riparian buffer strips. We conclude that traits information on taxa specialization, e.g., in terms of feeding specialism or taxa having a preference for high altitudes as well as sensitivity to changes in temperature are important when assessing the risk from future global climate change to freshwater ecosystems [Current Zoology 60 (2): 221-232, 2014].展开更多
基金Under the auspices of Special Fund for Scientific Research in the Public Interestgranted by Ministry of Water Resources(No.2012010072,200701024)+3 种基金Key Program of National Natural Science Foundation of China(No.40730635)Open Foundation of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering(No.2011491111)Research Foundation of Nanjing University of Information Science and Technology(No.20100406)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘The typical regions of the Taihu Lake Basin,China,were selected to analyze the variation characteristics of river-lake networks under intensive human activities.The characteristics of the fractal dimension of river networks and lakes for different periods were investigated and the influences of river system evolution on water level changes were further explored through the comparison of their fractal characters.The results are as follows:1) River network development of the study area is becoming more monotonous and more simple;the number of lakes is reducing significantly,and the water surface ratio has dropped significantly since the 1980s.2) The box dimension of the river networks in all the cities of the study area decreased slowly from the 1960s to the 1980s,while the decrease was significant from the 1980s to the 2000s.The variations of lake correlation dimension are similar to those of the river network box dimensions.This is unfavorable for the storage capacity of the river networks and lakes.3) The Hurst exponents of water levels were all between 0.5 and 1.0 from the 1960s to the 1980s,while decreased in the 2000s,indicating the decline in persistence and increase in the complexity of water level series.The paper draws a conclusion that the relationship between the fractal dimension of river-lake networks and the Hurst exponents of the water level series can reveal the impacts of river system changes on flood disasters to some extent:the disappearance of river networks and lakes will increase the possibility of flood occurrence.
文摘Let F q be a finite field with qelements where q=p~α. In the present paper, the authors study the existence and structure of Carter subgroups of singular symplectic group Sp (n+t,n)(F q), singular unitary group U (n+t,n)(F (q^2)) and singular orthogonal group O (n+t,n)(F q)(n is even) over finite fields F q.
基金funded by West Light Foundation of The Chinese Academy of Sciences,CASthe State Council Three Gorges Construction Committee Project of China
文摘Water level is an important index for studying hydrologic processes. Water level rise processes were studied in three catchments(catchment I, II, III in Chen Jiagou watershed in the Three Gorge Reservoir Area) with different areas to provide useful information to inform data extension from a gauged-catchment to an ungauged catchment. The results showed that there are seasonal changes in the dominant driving mode of the rise of the water level. The rise of the water level in March is likely mainly driven by the mode of stored-full runoff, and in September or October, it is mainly driven by Horton-flow. The correlation coefficients of all indexes were significant among the three catchments, suggesting that these catchments have similarities and that water level data extension is likely to be completed successfully between the large catchment(III-Catchment) and the small catchment(ICatchment). It was confirmed that there is good similarity between the 0.6 km^2 and 6 km^2 catchments, and the data correlation is good between the catchments with the area differences in the Three Gorges Reservoir Area. In addition, the rise processes of the water level in the catchments were not only different under the same rain conditions, but this difference could also change with the rain condition.
基金Supported by the National Natural Science Foundation of China(No.41306083)the Special Fund for Basic Work of Science and Technology from the Ministry of Science and Technology of China(No.2009FY210400)the Special Fund of the Third Institute of Oceanography,State Oceanic Administration for Basic Scientific Research Operations(No.HSK 2011028)
文摘Diatoms are widely used to study past and present changes in the marine environment. Unimodal models are appropriate for exploring the relationship between environmental properties in Chinese inshore waters and fossil diatom species derived from modem surface sediments. The best-fit relationships between two multivariate datasets (diatom species and environmental variables) were identified using canonical correspondence analysis (CCA), which is a constrained ordination technique. The absolute abundance of diatoms in the Chinese inshore waters ranged from 500 to 48 000 valves/g, and the average absolute abundance of all the 29 sites was l l 300 valves/g. 153 species and varieties of diatoms belonging to 42 genera in all were identified in the Chinese inshore waters. There were 28 dominant diatom species in all. According to the absolute abundance of the dominant species and the spatial distribution of the currents from the Chinese inshore waters, 12 diatom assemblages were distinguished from north to south, which reflected the different oceanographic conditions at the regional scale. Of the eight environmental variables considered, the most important environmental variable is winter sea surface salinity (WSS), which was also the only environmental variable with statistical significance. Therefore, it may be used to establish a transfer functions for the Chinese inshore waters in future paleoclimate studies.
文摘The important role of Three Gorges Project (TGP) in the flood management of the Yangtze River Basin is summarized.The Optimal Regulation Schemes of the Three Gorge Reservoir is briefly described.The flood regulation effect of TGP is analyzed.Typical issues related to reservoir operation for flood regulation are discussed and suggestions are put forward for the future work.
文摘While over two thousand years apart, Western postmodernism and ancient Chinese philosophy share some extraordinary similarities, especially epistemology wise. For example, they both recognize the role of language in constructing, and limiting, knowledge and reality. This is because thinkers of different cultures and geographical regions, and of different historical periods, can possibly come up with similar philosophical conclusions when addressing what is commonly known as the "human condition". The paper will discuss, in general terms, some of the philosophical similarities between postmodemism and classical Chinese philosophy; it will also take a close look at three concepts in Chinese philosophy that register strong affinity with Western postmodernism: namely, change, dialectic, and relativism.
文摘Ten runoff plots with different planting patterns were established for experimental observation in Yangjichong small watershed of Longli County in Karst region of Guizhou Province. Results show that under the same rainfall condition, shrub land, natural grassland and abandoned land presented the best function of soil and water conservation. The function of soil and water conservation was poor for arbor planting pattern, because the shrub layer, herb layer and forest floor were not formed. Because of no-tillage, surface crust and other effects, the function of soil and water conservation in slope farmland was better than that in runoffplots with arbor planting pattern.
基金Project(NCET-11-0866)supported by Education Ministry's new Century Excellent Talents Supporting Plan,China
文摘Parameter estimation of the attributed scattering center(ASC) model is significant for automatic target recognition(ATR). Sparse representation based parameter estimation methods have developed rapidly. Construction of the separable dictionary is a key issue for sparse representation technology. A compressive time-domain dictionary(TD) for ASC model is presented. Two-dimensional frequency domain responses of the ASC are produced and transformed into the time domain. Then these time domain responses are cutoff and stacked into vectors. These vectored time-domain responses are amalgamated to form the TD. Compared with the traditional frequency-domain dictionary(FD), the TD is a matrix that is quite spare and can markedly reduce the data size of the dictionary. Based on the basic TD construction method, we present four extended TD construction methods, which are available for different applications. In the experiments, the performance of the TD, including the basic model and the extended models, has been firstly analyzed in comparison with the FD. Secondly, an example of parameter estimation from SAR synthetic aperture radar(SAR) measurements of a target collected in an anechoic room is exhibited. Finally, a sparse image reconstruction example is from two apart apertures. Experimental results demonstrate the effectiveness and efficiency of the proposed TD.
基金supported by the National Natural Science Foundation (No. 40875058)the National Key Basic Research Program (No. 2012CB955200) of Chinafunded by the Priority Academic Program Development (PAPD) of Jiangsu Higher Edusation Institutions
文摘Based on the 1961-1990 observed daily precipitation in the Changjiang-Huaihe River Basin, the NCEP/NCAR reanalysis data, and the HadCM3 model data for IPCC SRES A1B climate projections, the simulation capabilities of the BP-CCA downscaling approach for extreme precipitation indices of the current climate are assessed by applying canonical correlation analysis (CCA). In addition, future extreme precipitation indices in the middle and late 21st century are projected. The results show that simulation capability of the HadCM3 for regional climate characteristics can be effectively improved by the downscaling approach, with 30%-100% reduction of the relative errors of the climatological mean state of extreme precipitation indices. However, the downscaling results still show wetter winter and dryer summer than the observation. Under the SRES A1B emission scenario, frequency and intensity of extreme precipitation events are projected to increase, and the estimated increasing rate is higher for extreme precipitation indices than for mean precipitation index; and in summer than in winter. Extreme precipitations in the middle and late 21st century are expected to increase by 14% and 25% respectively in winter, and by 24% and 32% respectively in summer.
文摘The National Road RN 91 has been threatened for about twenty-five years by a huge landslide, located 25 km south-east to the town of Grenoble (France). If several million cubic meters of rock fall down, the debris will dam the valley. Then the failure of the dam by overtopping and rapid erosion might result in a catastrophic flood and dramatic consequences for human life, environment and economy throughout the valley. The paper presents the hazard assessment based on geological and hydrological surveys, including small scale hydraulic tests, as well as the risk evaluation that has been performed. The risk management relies first upon a high level monitoring and an emergency plan; various mitigation strategies have been considered.
基金supported by the National Natural Science Foundation of China (Nos. 11171255, 11101373)the Doctoral Program Foundation of the Ministry of Education of China (No. 20090072110053)+1 种基金the Zhejiang Provincial Natural Science Foundation of China (No. Y6100007)the Zhejiang Innovation Project (No. T200905)
文摘In this paper, Schwarz-Pick estimates for high order FrSchet derivatives of holo- morphic self-mappings on classical domains are presented. Moreover, the obtained result can deduce the early work on Sc:hwarz-Pick estimates of higher-order partial derivatives for bounded holomorphic functions on classical domains.
文摘Abstract homomorphisms between subgroups of algebraic groups were studied in detail by A.Borel, J.Tit.[1] and B.Wei.feile.[2] provided that the images of the homomorphisms are Zariski dense subsets and that the fields over which algebraic groups are defined are infinite. The purpose of this paper is to determine all embedding homomorphisms of SLn(k) into SLn(K) when k and K are any fields of the same characteristic, without assumption of Zariski density and infinitude of fields. The result in this paper generalizes a result of Chen Yu on homomorphisms of two dimensional linear groups[3].
基金supported by National Basic Research Program of China(Grant No.2007CB411502)Key Research Project of the Knowledge Innovation Project of Chinese Academy of Sciences(Grant No.KZCX2-YW-301)+1 种基金Special Trade Project for Commonweal of Water Resource(Grant No.200701046)Hundred Talents Program of Chinese Academy of Sciences
文摘Monthly discharge of four rivers with various permafrost coverage and little anthropogenic influence was used to identify effects of permafrost degradation during the last 50 years,which has occurred because of significant increases in air temperature in the river regions.The basins of the Shule,Heihe,Shiyang and upper Yellow Rivers in northwestern China have 73%,58%,33% and 43% permafrost coverage,respectively.There is snow cover in the basins and no rain to supply rivers during winter. The monthly recession coefficient(RC) in winter reflects groundwater conditions.The RC has increased obviously for the Shule and Heihe rivers with 73% and 58% permafrost coverage,respectively,but did not increase for the Shiyang River,and decreased insignificantly for the upper Yellow River,which had less permafrost coverage.There is a distinct positive relationship between RC and annual negative degree-day temperature(NDDT) at the meteorological stations in the basins with high permafrost coverage.These results imply that permafrost degradation due to climate warming affects hydrological processes in winter.The effect is obvious in the basins with high permafrost coverage but negligible in those with low permafrost coverage. Permafrost degradation increases infiltration,enlarges the groundwater reservoir,and leads to slow discharge recession.The result means that hydrological processes are affected strongly by permafrost degradation in river basins with high permafrost coverage,but less in river basins with less permafrost coverage.
基金Project supported by the National Natural Science Foundation of China (No. 10571084, No. 10671062) the Postdoctoral Science Foundation of China (No. 2005037694)the Natural Science Foundation of the Education Department of Henan Province of China (No. 2006110001).
文摘Basic facts for Gabor frame {Eu(m)bTu(n)ag}m, n∈P on local field are investigated. Accurately, that the canonical dual of frame {Eu(m)bTu(n)ag}m,n∈P also has the Gabor structure is showed; that the product ab decides whether it is possible for {Eu(m)bTu(n)ag}m,n∈P to be a frame for L^2(K) is discussed; some necessary conditions and two sufficient conditions of Gabor frame for L^2 (K) are established. An example is finally given.
文摘This study provides basis information for estimating the feasibility of the environmental and ecological forestry construction project in the area. Through the survey in Miyun watershed, the economical benefits of carbon sequestration in five typical forest types have been studied by calculating the biomass from the timber accumulation data and converting to the money value. The results show that: in the duration of 100 years, at a discount rate of 5%, and 197 RMB yuan/t as the price of the carbon sequestration, the present value (PV) of the carbon sequestration in different forests are: 6900-9300 yuan/ha in Chinese pine forest,6100-8200 yuan/ha in oak forest, 4500-6100 yuan/ha in other broadleaf forests, 2300-3200 yuan/ha in shrubs and 1300-1800 yuan/ha in cypress forest. The annual mean economic benefit of carbon sequestration is 770-1040 yuan/ha. The pine forest has the highest carbon sequestration benefit, followed by oak forest, other broadleaf forest, shrubs, and cypress forest. If the land is suitable for all forests, pine forest and oak forest should be planted in order to sequestrate more carbon.
基金Project supported by the National Natural Science Foundation of China (No.10371054) and 02KJB11006.
文摘For quadratic number ?elds F = Q(√2p1 ···pt?1 ) with primes pj ≡ 1 mod 8, the authors study the class number and the norm of the fundamental unit of F. The resultsgeneralize nicely what has been familiar for the ?elds Q(√2p) with a prime p ≡ 1 mod 8, including density statements. And the results are stated in terms of the quadratic form x2 + 32y2 and illustrated in terms of graphs.
文摘Freshwater habitats and organisms are among the most threatened on Earth, and freshwater ecosystems have been subject to large biodiversity losses. We developed a Climate Change Sensitivity (CCS) indicator based on trait information for a selection of stream- and lake-dwelling Ephemeroptera, Plecoptera and Trichoptera taxa. We calculated the CCS scores based on ten species traits identified as sensitive to global climate change. We then assessed climate change sensitivity between the six main ecoregions of Sweden as well as the three Swedish regions based on lilies. This was done using biological data from 1,382 stream and lake sites where we compared large-scale (ecoregional) patterns in climate change sensitivity with potential future exposure of these ecosystems to increased temperatures using ensemble-modelled future changes in air temperature. Current (1961-1990) measured temperature and ensemble-modelled future (2100) temperature showed an increase from the northernmost towards the southern ecoregions, whereas the predicted temperature change increased from south to north. The CCS indicator scores were highest in the two northernmost boreal ecoregions where we also can expect the largest global climate change-induced increase in temperature, indicating an unfortunate congruence of exposure and sensitivity to climate change. These results are of vital importance when planning and implementing management and conservation strategies in freshwater ecosystems, e.g., to mitigate increased temperatures using riparian buffer strips. We conclude that traits information on taxa specialization, e.g., in terms of feeding specialism or taxa having a preference for high altitudes as well as sensitivity to changes in temperature are important when assessing the risk from future global climate change to freshwater ecosystems [Current Zoology 60 (2): 221-232, 2014].