This paper comprehensively studies the spatio-temporal characteristics of the frequency of extremely heavy precipitation events over South China by using the daily precipitation data of 110 stations during 1961 to 200...This paper comprehensively studies the spatio-temporal characteristics of the frequency of extremely heavy precipitation events over South China by using the daily precipitation data of 110 stations during 1961 to 2008 and the extremely heavy precipitation thresholds determined for different stations by REOF, trend coefficients, linear trend, Mann-Kendall test and variance analysis. The results are shown as follows. The frequency distribution of extremely heavy precipitation is high in the middle of South China and low in the Guangdong coast and western Guangxi. There are three spatial distribution types of extremely heavy precipitation in South China. The consistent anomaly distribution is the main type. Distribution reversed between the east and the west and between the south and the north is also an important type. Extremely heavy precipitation events in South China mainly occurred in the summer-half of the year. Their frequency during this time accounts for 83.7% of the total frequency. In the 1960 s and 1980 s, extremely heavy precipitation events were less frequent while having an increasing trend from the late 1980 s. Their climatological tendency rates decrease in the central and rise in the other areas of South China, and on average the mean series also shows an upward but insignificant trend at all of the stations. South China's frequency of extremely heavy precipitation events can be divided into six major areas and each of them shows a different inter-annual trend and three of the representative stations experience abrupt changes by showing remarkable increases in terms of Mann-Kendall tests.展开更多
Spatial distribution and abundance of small fishes were studied in autumn 2007 in the Xiaosihai Lake, a shallow lake along the middle reach of the Changjiang （Yangtze） River. Based on the plant cover, the lake was d...Spatial distribution and abundance of small fishes were studied in autumn 2007 in the Xiaosihai Lake, a shallow lake along the middle reach of the Changjiang （Yangtze） River. Based on the plant cover, the lake was divided into three major habitats： Myriophyllum spicaturn habitat （MS habitat）, Trapa bispinosa habitat （TB habitat）, and non-vegetation habitat （NV habitat）. A modified pop-net was used for quantitative sampling of small fishes in the three habitats, and the Zippin＇s removal method was used for estimating densities of the small fishes. A total of 13 species belonging to 5 families were collected, with 11 species in MS habitat, 7 species in TB habitat, and 5 species in NV habitat. Habitat type had significant effect on the spatial distribution of small fishes. The Shannon-Wiener diversity index in the MS, TB and NV habitats were 1.28, 0.56 and 0.54, respectively. The total density and biomass of small fishes were significantly higher in the MS habitat （13.68 ind/m^2 and 4.44 g/m^2） than in the TB habitat （1.41 ind/m^2 and 0.54 g/m^2） and the NV habitat （1.08 ind/m^2 and 0.40 g/m^2）, and were not significantly different between the TB habitat and the NV habitat. Water depth had no significant effect on spatial distribution of the small fishes. It was suggested that vegetation type played an important role in habitat selectivity of small fishes, and the presence of submersed vegetation should be of significance in the conservation of small fish diversity.展开更多
A considerable number of in situ permeability tests in flysch are processed to a depth of 120m with a good spatial distribution. The distribution of permeability values for the different litho-types of this formation,...A considerable number of in situ permeability tests in flysch are processed to a depth of 120m with a good spatial distribution. The distribution of permeability values for the different litho-types of this formation, their comparison and their decrease with depth is discussed. The depth where a permeability of 3 to 5×10-7m/sec can be retained (the limit of a reasonable grouting under a high dam) may be twofold if the geological history of the formation could not contain a compressional tectonic process. This depth may reach 100m in some cases. The differences in the mean values of permeability among the various litho-types are minor, while the presence of siltstones, always present although with varied participation, dramatically controls the global permeability.展开更多
The scale and characteristics of rock mass are important indexes of the rock mass structural plane classification. This paper firstly analyzes the spatial distribution characteristics, the structural plane types （ori...The scale and characteristics of rock mass are important indexes of the rock mass structural plane classification. This paper firstly analyzes the spatial distribution characteristics, the structural plane types （original structural plane, tectonic structural plane and hypergenic structural plane） and the associated features of the Emeishan basalts and then studies the classification schemes of the built hydropower structure planes of different rock areas （the east district, the central district and the west district） in the Emeishan basalt distribution area, Southwest China. Based on the analysis and comparison of the scale and the engineering geological characteristics of the typical structure planes in the basalt hydroelectric Stations, the types of structural planes are used in the first order classification. The secondary order classification is made by considering the impact factors of rock mass quality, e.g., the state of the structural planes, infilling, joint opening, extending length, the grade of weathering and strength. The engineering geological classification for Emeishan basalt is proposed. Because there are no evidences of a large structure presenting in study area, the first-order （Ⅰ） controlling structural planes do not appear in the classification, there only appear Ⅱ, Ⅲ, Ⅳ and Ⅴ grade structural planes influencing the rock-mass quality. According to the different rock-block types in bedding fault zone, the second-grade （Ⅱ） structural planes consisted of bedding fault zone is further classified into Ⅱ1, Ⅱ2 and Ⅱ3. The third-grade （Ⅲ） structural planes constructed by intraformational faulted zones are not subdivided. According to the different characteristics of intrusion, alteration and weathering unloading structural planes, the Ⅳ grade structure plane is divided into Ⅳ1, Ⅳ2 and Ⅳ3. According to the development characteristics of joints and fractures, the V grade structure plane is divided into fracture Ⅴ1 and columnar joint Ⅴ2. In all, the structural planes are classified into four groups with nine subsets. The research proposes the engineering geological classification of the structural plane for the hydropower project in the Emishan basalts, and the result of the study has a potential application in similar regions.展开更多
The electromagnetic field relations are demonstrated on impulse radiating surface and point type sources, which are characterized by first and second order singularities at rest in a Schwartz-Sobolev space setting. Th...The electromagnetic field relations are demonstrated on impulse radiating surface and point type sources, which are characterized by first and second order singularities at rest in a Schwartz-Sobolev space setting. The investigation starts with a general introduction to Schwartz-Sobolev distributions, the electromagnetic field equations and various modes of impulsive radiation. This is followed by an outline of temporal distributional relations in arbitrary media and distributional derivative operations on an arbitrary regular surface, all of which are employed in an investigation of impulse radiation mechanism on single and double layer sources. Similar steps are followed in a description of point distributions and investigation of impulse radiation mechanism on electric and magnetic point dipoles.展开更多
基金"Variations of Extremely Heavy Precipitation and Their Response to Global Climate Change",a project in Research Fund for the Science of Tropical Marine and Meteorology(200804)"On the Regional Extremely Heavy Rain in South China Under the Background of Climate Warming,a project in Special China Meteorological Administration Program for Climate Change(CCSF-09-03)Assessment Report on the Climate Change in the South China Region(CCSF-09-11)
文摘This paper comprehensively studies the spatio-temporal characteristics of the frequency of extremely heavy precipitation events over South China by using the daily precipitation data of 110 stations during 1961 to 2008 and the extremely heavy precipitation thresholds determined for different stations by REOF, trend coefficients, linear trend, Mann-Kendall test and variance analysis. The results are shown as follows. The frequency distribution of extremely heavy precipitation is high in the middle of South China and low in the Guangdong coast and western Guangxi. There are three spatial distribution types of extremely heavy precipitation in South China. The consistent anomaly distribution is the main type. Distribution reversed between the east and the west and between the south and the north is also an important type. Extremely heavy precipitation events in South China mainly occurred in the summer-half of the year. Their frequency during this time accounts for 83.7% of the total frequency. In the 1960 s and 1980 s, extremely heavy precipitation events were less frequent while having an increasing trend from the late 1980 s. Their climatological tendency rates decrease in the central and rise in the other areas of South China, and on average the mean series also shows an upward but insignificant trend at all of the stations. South China's frequency of extremely heavy precipitation events can be divided into six major areas and each of them shows a different inter-annual trend and three of the representative stations experience abrupt changes by showing remarkable increases in terms of Mann-Kendall tests.
基金Supported by the National Natural Science Foundation of China (Nos. 30571440, 30830025)The National Key Technology R&D Program (No. 2007BAD37B03)the National Basic Research Program of China (973 Program) (No. 2007CB109205)
文摘Spatial distribution and abundance of small fishes were studied in autumn 2007 in the Xiaosihai Lake, a shallow lake along the middle reach of the Changjiang （Yangtze） River. Based on the plant cover, the lake was divided into three major habitats： Myriophyllum spicaturn habitat （MS habitat）, Trapa bispinosa habitat （TB habitat）, and non-vegetation habitat （NV habitat）. A modified pop-net was used for quantitative sampling of small fishes in the three habitats, and the Zippin＇s removal method was used for estimating densities of the small fishes. A total of 13 species belonging to 5 families were collected, with 11 species in MS habitat, 7 species in TB habitat, and 5 species in NV habitat. Habitat type had significant effect on the spatial distribution of small fishes. The Shannon-Wiener diversity index in the MS, TB and NV habitats were 1.28, 0.56 and 0.54, respectively. The total density and biomass of small fishes were significantly higher in the MS habitat （13.68 ind/m^2 and 4.44 g/m^2） than in the TB habitat （1.41 ind/m^2 and 0.54 g/m^2） and the NV habitat （1.08 ind/m^2 and 0.40 g/m^2）, and were not significantly different between the TB habitat and the NV habitat. Water depth had no significant effect on spatial distribution of the small fishes. It was suggested that vegetation type played an important role in habitat selectivity of small fishes, and the presence of submersed vegetation should be of significance in the conservation of small fish diversity.
文摘A considerable number of in situ permeability tests in flysch are processed to a depth of 120m with a good spatial distribution. The distribution of permeability values for the different litho-types of this formation, their comparison and their decrease with depth is discussed. The depth where a permeability of 3 to 5×10-7m/sec can be retained (the limit of a reasonable grouting under a high dam) may be twofold if the geological history of the formation could not contain a compressional tectonic process. This depth may reach 100m in some cases. The differences in the mean values of permeability among the various litho-types are minor, while the presence of siltstones, always present although with varied participation, dramatically controls the global permeability.
基金funded by the National Natural Science Foundation of China (Grant No.41072228)
文摘The scale and characteristics of rock mass are important indexes of the rock mass structural plane classification. This paper firstly analyzes the spatial distribution characteristics, the structural plane types （original structural plane, tectonic structural plane and hypergenic structural plane） and the associated features of the Emeishan basalts and then studies the classification schemes of the built hydropower structure planes of different rock areas （the east district, the central district and the west district） in the Emeishan basalt distribution area, Southwest China. Based on the analysis and comparison of the scale and the engineering geological characteristics of the typical structure planes in the basalt hydroelectric Stations, the types of structural planes are used in the first order classification. The secondary order classification is made by considering the impact factors of rock mass quality, e.g., the state of the structural planes, infilling, joint opening, extending length, the grade of weathering and strength. The engineering geological classification for Emeishan basalt is proposed. Because there are no evidences of a large structure presenting in study area, the first-order （Ⅰ） controlling structural planes do not appear in the classification, there only appear Ⅱ, Ⅲ, Ⅳ and Ⅴ grade structural planes influencing the rock-mass quality. According to the different rock-block types in bedding fault zone, the second-grade （Ⅱ） structural planes consisted of bedding fault zone is further classified into Ⅱ1, Ⅱ2 and Ⅱ3. The third-grade （Ⅲ） structural planes constructed by intraformational faulted zones are not subdivided. According to the different characteristics of intrusion, alteration and weathering unloading structural planes, the Ⅳ grade structure plane is divided into Ⅳ1, Ⅳ2 and Ⅳ3. According to the development characteristics of joints and fractures, the V grade structure plane is divided into fracture Ⅴ1 and columnar joint Ⅴ2. In all, the structural planes are classified into four groups with nine subsets. The research proposes the engineering geological classification of the structural plane for the hydropower project in the Emishan basalts, and the result of the study has a potential application in similar regions.
文摘The electromagnetic field relations are demonstrated on impulse radiating surface and point type sources, which are characterized by first and second order singularities at rest in a Schwartz-Sobolev space setting. The investigation starts with a general introduction to Schwartz-Sobolev distributions, the electromagnetic field equations and various modes of impulsive radiation. This is followed by an outline of temporal distributional relations in arbitrary media and distributional derivative operations on an arbitrary regular surface, all of which are employed in an investigation of impulse radiation mechanism on single and double layer sources. Similar steps are followed in a description of point distributions and investigation of impulse radiation mechanism on electric and magnetic point dipoles.
