Objective As a new type of gas hydrates,the natural gas hydrates in the perfost region of the Qilian Mountains are characterized by their shallow burial depth,welldeveloped coal seam,high content of heavy hydrocarbons...Objective As a new type of gas hydrates,the natural gas hydrates in the perfost region of the Qilian Mountains are characterized by their shallow burial depth,welldeveloped coal seam,high content of heavy hydrocarbons and multiple sets of mature and over-mature source rocks.Gas sources of these gas hydrates in the study area include coal-type gas and oil-type gas.展开更多
The formation of rice distribution is based on certain natural ecological conditions and social economic environments. In China, rice cropping is distributed in a vast area extending across 5 tempera ture belts, the n...The formation of rice distribution is based on certain natural ecological conditions and social economic environments. In China, rice cropping is distributed in a vast area extending across 5 tempera ture belts, the northernmost of rice growing area in the world being in China. Distribution of rice cropping is characterized by a gradual decrease from south to north, from large and concentrated regions in Southeast to small and separated areas in Northwest. Natural conditions in rice regions differ in China with a varied topography, high in the west and low in the east. Rice fields in the west are mostly distributed on flatlands on plains, valleys among mountains, tablelands in river valleys, yellow-soil plains and basins in low valleys, alluvial plains, plains in river valleys, while those in the east are mainly distributed on alluvial plains, hilly areas among low mountains, coastal plains, along rivers and lakes and in basins among mountains.展开更多
According to climatic, hydrological, soil and vegetation data from671 stations in China, 12 temperate zones contains 45 natural regions areidentified. In this paper, methods like migration of crop distribution ,...According to climatic, hydrological, soil and vegetation data from671 stations in China, 12 temperate zones contains 45 natural regions areidentified. In this paper, methods like migration of crop distribution , potentialproductivity, and dynamic modelling are used to research changs of naturalzones and natural regions of eco-envirotunent.展开更多
For structural parameters with uncertainties, interval mathematicscan , in the case where the probabilistic distribution density ofuncertain variables is unavailable, deal with the influ- ence ofuncertainties in struc...For structural parameters with uncertainties, interval mathematicscan , in the case where the probabilistic distribution density ofuncertain variables is unavailable, deal with the influ- ence ofuncertainties in structural parameters on the response of structures.In order to evaluate the re- gion containing natural frequencies ofstructures with interval parameters, the interval parameter per-turbation method is presented in this paper. The advantage of thepresent method is its computational efficiency in evaluating theregion containing natural frequencies. A numerical example is used toil- lustrate the efficiency of the method proposed.展开更多
基金financially supported by the National Science Foundation of china(Grant No.41273066)
文摘Objective As a new type of gas hydrates,the natural gas hydrates in the perfost region of the Qilian Mountains are characterized by their shallow burial depth,welldeveloped coal seam,high content of heavy hydrocarbons and multiple sets of mature and over-mature source rocks.Gas sources of these gas hydrates in the study area include coal-type gas and oil-type gas.
文摘The formation of rice distribution is based on certain natural ecological conditions and social economic environments. In China, rice cropping is distributed in a vast area extending across 5 tempera ture belts, the northernmost of rice growing area in the world being in China. Distribution of rice cropping is characterized by a gradual decrease from south to north, from large and concentrated regions in Southeast to small and separated areas in Northwest. Natural conditions in rice regions differ in China with a varied topography, high in the west and low in the east. Rice fields in the west are mostly distributed on flatlands on plains, valleys among mountains, tablelands in river valleys, yellow-soil plains and basins in low valleys, alluvial plains, plains in river valleys, while those in the east are mainly distributed on alluvial plains, hilly areas among low mountains, coastal plains, along rivers and lakes and in basins among mountains.
文摘According to climatic, hydrological, soil and vegetation data from671 stations in China, 12 temperate zones contains 45 natural regions areidentified. In this paper, methods like migration of crop distribution , potentialproductivity, and dynamic modelling are used to research changs of naturalzones and natural regions of eco-envirotunent.
基金The project is supported by National Youth Natural Science Foundation of ChinaNational Outstanding Youth Science Foundation of China
文摘For structural parameters with uncertainties, interval mathematicscan , in the case where the probabilistic distribution density ofuncertain variables is unavailable, deal with the influ- ence ofuncertainties in structural parameters on the response of structures.In order to evaluate the re- gion containing natural frequencies ofstructures with interval parameters, the interval parameter per-turbation method is presented in this paper. The advantage of thepresent method is its computational efficiency in evaluating theregion containing natural frequencies. A numerical example is used toil- lustrate the efficiency of the method proposed.
