Wind erosion is a major contributor to land degradation and desertification. Ac- cording to the Global Assessment of Human Induced Soil Degradation, the dryland territories of Mongolia are significantly affected by wi...Wind erosion is a major contributor to land degradation and desertification. Ac- cording to the Global Assessment of Human Induced Soil Degradation, the dryland territories of Mongolia are significantly affected by wind erosion. We used the wind erosion equation model in an ArcGIS environment to evaluate wind erosion across Mongolia. The individual factors of the wind erosion equation were parameterized using the following datasets： （a） monthly climatic data from 45 meteorological stations; （b） 16-day composites of MODIS Normalized Difference Vegetation Index data; （c） a SRTM DEM with a 90 m spatial resolution; and （d） the soil map of Mongolia. The results revealed the significant influence of aridity on wind erosion. The desert and semi-desert ecosystems were more vulnerable to wind erosion, hence more affected. The map of wind erosion revealed three major wind erosion regions where the maximum soil loss of 15-27 t/（hm2.a） was observed. In general, the wind erosion potentials for the entire country of Mongolia are 15-27 t/（hm2.a） in the deserts and semi-deserts, 10-15 t/（hm2.a） in the dry steppes and 5-10 t/（hm2.a） in the steppe regions.展开更多
The e-N method is widely used in transition prediction. The amplitude growth rate used in the e-N method is usually provided by the linear stability theory （LST） based on the local parallel hypothesis. Considering t...The e-N method is widely used in transition prediction. The amplitude growth rate used in the e-N method is usually provided by the linear stability theory （LST） based on the local parallel hypothesis. Considering the non-parallelism effect, the parabolized stability equation （PSE） method lacks local characteristic of stability analysis. In this paper, a local stability analysis method considering non-parallelism is proposed, termed as EPSE since it may be considered as an expansion of the PSE method. The EPSE considers variation of the shape function in the streamwise direction. Its local characteristic is convenient for stability analysis. This paper uses the EPSE in a strong non-parallel flow and mode exchange problem. The results agree well with the PSE and the direct numerical simulation （DNS）. In addition, it is found that the growth rate is related to the normalized method in the non-parallel flow. Different results can be obtained using different normalized methods. Therefore, the normalized method must be consistent.展开更多
The present study aims to estimate the annual soil loss in the Soummam watershed in the northeast of Algeria,using the Revised Universal Soil Loss Equation(RUSLE),geographic information system(GIS),and remote sensing(...The present study aims to estimate the annual soil loss in the Soummam watershed in the northeast of Algeria,using the Revised Universal Soil Loss Equation(RUSLE),geographic information system(GIS),and remote sensing(RS).RUSLE model has been used for modelling the main factors involved in erosive phenomena.The Soummam watershed covers a surface area of 9108.45 km^2 of irregular shape,northeast–southwest towards southeast.It is characterized by an altitude varying between 2 m in the northeast and 2308 m in the northwest.Results showed that the average erosivity factor(R)is 70.64(MJ·mm)/(ha·h·year)and the maximum value reaches 140(MJ·mm)/(ha·h·year),the average soil erodibility factor(K)is 0.016(t·h·ha)/(MJ·ha·mm)and maximum values reach 0.0204(t·h·ha)/(MJ·ha·mm)in the southeast regions of the watershed,the average slope length and steepness factor(LS)is 9.79 and the mean C factor is estimated to be 0.62.Thematic maps integration of different factors of RUSLE in GIS with their database,allowed with a rapid and efficient manner to highlight complexity and factors interdependence in the erosion risk analyses.The resulting map for soils losses,with an average erosion rate of 6.81 t/(ha·year)shows a low erosion(<7.41 t/(ha·year))which covers 73.46%of the total area of the basin,and a medium erosion(7.42 to 19.77 t/(ha·year)),which represents 17.66%of the area.Areas with extreme erosion risk exceeding 32.18 t/(ha·year)cover more than 3.54%of the basin area.The results can certainly aid in implementation of soil management and conservation practices to reduce the soil erosion in the Soummam watershed.展开更多
Single soliton and compound solitons are described by coupled-mode equation. It is noted that three parameters, which are dimensionless group velocity, normalized frequency, and grating strength, influence formed soli...Single soliton and compound solitons are described by coupled-mode equation. It is noted that three parameters, which are dimensionless group velocity, normalized frequency, and grating strength, influence formed solitons by emulation. The novel designs of parallel and serial multi-grating are advanced, and the compound solitons formed from parallel multi-grating are linear superposition; the compound solitons formed from serial multi-grating are nonlinear superposition, and finally two general formulae are obtained. Furthermore, it is theoretically shown that the compound grating solitons are prominent and flexible signals in optical communication.展开更多
In this article, we prove that viscosity solutions of the parabolic inhomogeneous equationsn＋p/put-△p^Nu=f（x,t）can be characterized using asymptotic mean value properties for all p ≥ 1, including p = 1 and p = ∞...In this article, we prove that viscosity solutions of the parabolic inhomogeneous equationsn＋p/put-△p^Nu=f（x,t）can be characterized using asymptotic mean value properties for all p ≥ 1, including p = 1 and p = ∞. We also obtain a comparison principle for the non-negative or non-positive inhomogeneous term f for the corresponding initial-boundary value problem and this in turn implies the uniqueness of solutions to such a problem.展开更多
基金Swiss Agency for Development and Cooperation(SDC),No.81013651
文摘Wind erosion is a major contributor to land degradation and desertification. Ac- cording to the Global Assessment of Human Induced Soil Degradation, the dryland territories of Mongolia are significantly affected by wind erosion. We used the wind erosion equation model in an ArcGIS environment to evaluate wind erosion across Mongolia. The individual factors of the wind erosion equation were parameterized using the following datasets： （a） monthly climatic data from 45 meteorological stations; （b） 16-day composites of MODIS Normalized Difference Vegetation Index data; （c） a SRTM DEM with a 90 m spatial resolution; and （d） the soil map of Mongolia. The results revealed the significant influence of aridity on wind erosion. The desert and semi-desert ecosystems were more vulnerable to wind erosion, hence more affected. The map of wind erosion revealed three major wind erosion regions where the maximum soil loss of 15-27 t/（hm2.a） was observed. In general, the wind erosion potentials for the entire country of Mongolia are 15-27 t/（hm2.a） in the deserts and semi-deserts, 10-15 t/（hm2.a） in the dry steppes and 5-10 t/（hm2.a） in the steppe regions.
基金Project supported by the National Natural Science Foundation of China(Nos.11332007,11172203,and 91216111)
文摘The e-N method is widely used in transition prediction. The amplitude growth rate used in the e-N method is usually provided by the linear stability theory （LST） based on the local parallel hypothesis. Considering the non-parallelism effect, the parabolized stability equation （PSE） method lacks local characteristic of stability analysis. In this paper, a local stability analysis method considering non-parallelism is proposed, termed as EPSE since it may be considered as an expansion of the PSE method. The EPSE considers variation of the shape function in the streamwise direction. Its local characteristic is convenient for stability analysis. This paper uses the EPSE in a strong non-parallel flow and mode exchange problem. The results agree well with the PSE and the direct numerical simulation （DNS）. In addition, it is found that the growth rate is related to the normalized method in the non-parallel flow. Different results can be obtained using different normalized methods. Therefore, the normalized method must be consistent.
文摘The present study aims to estimate the annual soil loss in the Soummam watershed in the northeast of Algeria,using the Revised Universal Soil Loss Equation(RUSLE),geographic information system(GIS),and remote sensing(RS).RUSLE model has been used for modelling the main factors involved in erosive phenomena.The Soummam watershed covers a surface area of 9108.45 km^2 of irregular shape,northeast–southwest towards southeast.It is characterized by an altitude varying between 2 m in the northeast and 2308 m in the northwest.Results showed that the average erosivity factor(R)is 70.64(MJ·mm)/(ha·h·year)and the maximum value reaches 140(MJ·mm)/(ha·h·year),the average soil erodibility factor(K)is 0.016(t·h·ha)/(MJ·ha·mm)and maximum values reach 0.0204(t·h·ha)/(MJ·ha·mm)in the southeast regions of the watershed,the average slope length and steepness factor(LS)is 9.79 and the mean C factor is estimated to be 0.62.Thematic maps integration of different factors of RUSLE in GIS with their database,allowed with a rapid and efficient manner to highlight complexity and factors interdependence in the erosion risk analyses.The resulting map for soils losses,with an average erosion rate of 6.81 t/(ha·year)shows a low erosion(<7.41 t/(ha·year))which covers 73.46%of the total area of the basin,and a medium erosion(7.42 to 19.77 t/(ha·year)),which represents 17.66%of the area.Areas with extreme erosion risk exceeding 32.18 t/(ha·year)cover more than 3.54%of the basin area.The results can certainly aid in implementation of soil management and conservation practices to reduce the soil erosion in the Soummam watershed.
基金the National Natural Science Foundation of China(Grant No.40571097)Doctorial Innovative Foundation
文摘Single soliton and compound solitons are described by coupled-mode equation. It is noted that three parameters, which are dimensionless group velocity, normalized frequency, and grating strength, influence formed solitons by emulation. The novel designs of parallel and serial multi-grating are advanced, and the compound solitons formed from parallel multi-grating are linear superposition; the compound solitons formed from serial multi-grating are nonlinear superposition, and finally two general formulae are obtained. Furthermore, it is theoretically shown that the compound grating solitons are prominent and flexible signals in optical communication.
基金supported by the National Natural Science Foundation of China(11071119,11171153)
文摘In this article, we prove that viscosity solutions of the parabolic inhomogeneous equationsn＋p/put-△p^Nu=f（x,t）can be characterized using asymptotic mean value properties for all p ≥ 1, including p = 1 and p = ∞. We also obtain a comparison principle for the non-negative or non-positive inhomogeneous term f for the corresponding initial-boundary value problem and this in turn implies the uniqueness of solutions to such a problem.
