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This paper made an overview and introduction of urban PM2.5 numerical forecast models in China, and mainly introduced air quality simulated forecast system of Beijing, Shanghai, and Nanjing. On this basis, it discussed development direction and existing problems of urban PM2.5 forecast models in China. Besides, it revealed significance of numerical models for air quality forecast. In a heavy air poUution of Beijing - Tianjin - Hebei in October 6 - 12 th of 2014, the forecast results indicated that poUutants was transported from south to north, so the regional transport exerts great influence on concentration of PM2.5. [ABSTRACT FROM AUTHOR]

In order to clarify the influence of different forest types on soil erosion resistance in water source area of Central Yunnan, with the soils under three different kinds of typical forest in Yizhe watershed as the research object, this paper uses field simulation method and principal component analysis to analyze the soil erosion resistance of three kinds of soils. The results show that there is a significant difference in the shear strength of soil among three types of typical forest, and the size of soil shear strength is in the order of Pinus yunnanensis forest land > mixed broadleaf-conifer forest land > eucalyptus forest land. The difference in the soil erosion coefficient among different forests is not significant, and the soil erosion resistance is highest in mixed broadleaf-conifer forest land (39. 0% ), followed by eucalyptus woodland (37. 0% ) and Pinus yunnanensis forest land (24. 0% ). Under heavy rain intensity and long duration of rainfall, the ability of soil under eucalyptus x Pinus yunnanensis mixed forests to resist disintegration is more obvious. Using principal component analysis to analyze soil erosion resistance of soils under three different forests, we get the comprehensive evaluation model for soil erosion resistance: F-0. 763 Y1 +0. 236Y2. The soil erosion resistance is in the order of mixed broadleaf-conifer forest land (0.150) > eucalyptus forest land (0.127) > Pinus yunnanensis forest land ( - 0. 079), indicating that the mixed forests have better water loss and soil erosion control effect than pure forests. [ABSTRACT FROM AUTHOR]

The integration of rural information resources is a key factor restricting rural informationization and effective operation of rural information services. To solve problems of separate rural information resources and departments acting willfully regardless of overall interest, this paper analyzed characteristics and distribution of rural information resources, built a basic framework for integration of rural information resources and a mathematic model of integration, and finally came up with specific solutions to integration of rural information resources. [ABSTRACT FROM AUTHOR]

The mathematical model is often used for fitting the trend of changes in cultivated land resources in the land use planning, but the fitting effect is different in different study areas. In this paper, we take two geographically adjacent cities with great differences in the economic development model, Xinghua City and Jingjiang City, as the research object. Using logarithmic model (M1), Kuznets model (M2), logistic model (M3) and multivariate linear model (M4), we fit the process of changes in cultivated land resources during the period 1980 - 2009, and compare the differences in the fitting effect between different models. In terms of the model fitting effect in Xinghua City, it is in the order of M3 > M4 > M1 > M2, which is related to the fact that the local areas lay great emphasis on agicultural development, and pay close attention to ensuring the cultivated land area; in terms of the model fitting effect in Jing'iang City, it is in the order of M1 > M3 > M4 > M2, and the deep-seated cause is that its development model is dominated by extended trade expansion, and the level of intensive land use is constantly improved. In addition, we discuss the multi-stage characteristics of changes in cultivated land resources, and propose a solution of using the same model to simulate in various phases. The research results in Jing'iang City show that the coefficient of determination in the first phase (R2=0.958) and the standard error (SE=0.261) are both better than those of the original model (R2=0.945, SE=0.312); the coefficient of determination in the second phase is slightly low (R2=0.851), but the standard error is greatly improved (SE=0.137). Compared with the research conclusions of other scholars, it can be believed that this method can better solve the problems that the scatter plot of logistic model presents wave-shape and the scatter plot of Kuznets model presents "M"-shape, in order to improve the applicability of mathematica models. [ABSTRACT FROM AUTHOR]