Based on the assumption that solute transport in a semi-infinite soil columnor in a field soil profile can be described by the boundary-layer method, an analytical solution ispresented for the advance of a solute fron...Based on the assumption that solute transport in a semi-infinite soil columnor in a field soil profile can be described by the boundary-layer method, an analytical solution ispresented for the advance of a solute front with time. The traditional convection-dispersionequation (CDE) subjected to two boundary conditions: 1) at the soil surface (or inlet boundary) and2) at the solute front, was solved using a Laplace transformation. A comparison of residentconcentrations using a boundary-layer method and an exact solution (in a semi-infinite-domain)showed that both were in good agreement within the range between the two boundaries. This led to anew method for estimating solute transport parameters in soils, requiring only observation ofadvance of the solute front with time. This may be corroborated visually using a tracer solutionwith marking-dye or measured utilizing time domain reflectometry (TDR). This method is applicable toboth laboratory soil columns and field soils. Thus, it could be a step forward for modeling solutetransport in field soils and for better understanding of the transport processes in soils.展开更多
Based on the overall analysis of the floating population among big and medium-sized cities in China,this paper, by means of statistics and questionnaires, makes a systematical study on the migratory features of the fl...Based on the overall analysis of the floating population among big and medium-sized cities in China,this paper, by means of statistics and questionnaires, makes a systematical study on the migratory features of the floating population in Mianyang, its employment structure, migrating causes and channels. According to the findings, the author finds a fact that with the strategy of Western Development, and with the construction of science and technology city of Mianyang, the migrating in Mianyang conforms to the general patterns of the migration, which has happened in those big and medium-sized cities in China.In addition,the city has a new but unique feature — economic factor, as the driving force of population migration, is quite distinct from that of those citiesin eastern areas of China.展开更多
In this report, it is proven through stable iso-topic geochronological study that for the Jurassic sedimen-tary rocks in the Dushan area of Anhui Province, the source materials derived from high-pressure and ultrahigh...In this report, it is proven through stable iso-topic geochronological study that for the Jurassic sedimen-tary rocks in the Dushan area of Anhui Province, the source materials derived from high-pressure and ultrahigh-pressure metamorphic rocks are the products of subduction and ex-humation of the Yangtze plate under the North China plate during the Triassic period. The cobble of high-pressure or ultrahigh-pressure metamorphic rock in the Fenghuangtai Formation of Hefei Basin has Rb-Sr isotopic isochron age of phengite, apatite and whole rock, 232.1±2.1 Ma (MSWD = 0.59). Plateau ages of 40Ar/39Ar age spectra of detrital phengites in the Sanjianpu and Fenghuangtai formations are concordant, and they are 216.5±0.6 Ma and 217.4±1.3 Ma, respectively.展开更多
基金Project supported by the National Key Basic Research Support Foundation of China (No. 2000018605) the National Natural Science Foundation of China (Nos. 40025106 and 40371060).
文摘Based on the assumption that solute transport in a semi-infinite soil columnor in a field soil profile can be described by the boundary-layer method, an analytical solution ispresented for the advance of a solute front with time. The traditional convection-dispersionequation (CDE) subjected to two boundary conditions: 1) at the soil surface (or inlet boundary) and2) at the solute front, was solved using a Laplace transformation. A comparison of residentconcentrations using a boundary-layer method and an exact solution (in a semi-infinite-domain)showed that both were in good agreement within the range between the two boundaries. This led to anew method for estimating solute transport parameters in soils, requiring only observation ofadvance of the solute front with time. This may be corroborated visually using a tracer solutionwith marking-dye or measured utilizing time domain reflectometry (TDR). This method is applicable toboth laboratory soil columns and field soils. Thus, it could be a step forward for modeling solutetransport in field soils and for better understanding of the transport processes in soils.
文摘Based on the overall analysis of the floating population among big and medium-sized cities in China,this paper, by means of statistics and questionnaires, makes a systematical study on the migratory features of the floating population in Mianyang, its employment structure, migrating causes and channels. According to the findings, the author finds a fact that with the strategy of Western Development, and with the construction of science and technology city of Mianyang, the migrating in Mianyang conforms to the general patterns of the migration, which has happened in those big and medium-sized cities in China.In addition,the city has a new but unique feature — economic factor, as the driving force of population migration, is quite distinct from that of those citiesin eastern areas of China.
基金supported by the State Key Basic Research Development Program of China(Grant No.G1999075507)
文摘In this report, it is proven through stable iso-topic geochronological study that for the Jurassic sedimen-tary rocks in the Dushan area of Anhui Province, the source materials derived from high-pressure and ultrahigh-pressure metamorphic rocks are the products of subduction and ex-humation of the Yangtze plate under the North China plate during the Triassic period. The cobble of high-pressure or ultrahigh-pressure metamorphic rock in the Fenghuangtai Formation of Hefei Basin has Rb-Sr isotopic isochron age of phengite, apatite and whole rock, 232.1±2.1 Ma (MSWD = 0.59). Plateau ages of 40Ar/39Ar age spectra of detrital phengites in the Sanjianpu and Fenghuangtai formations are concordant, and they are 216.5±0.6 Ma and 217.4±1.3 Ma, respectively.
