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Evaluation and Analysis of Ecosystem Services Value in Beijing-Tianjin-Hebei Region Based on Demand Zoning
TANG Xiumei, LIU Yu, REN Yanmin, ZHOU Yanbing
Acta Scientiarum Naturalium Universitatis Pekinensis    2021, 57 (1): 173-180.   DOI: 10.13209/j.0479-8023.2020.112
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Based on the analysis of the logical relationship between supply and demand of ecosystem services, this study evaluates the demand status of ecosystem services in Beijing-Tianjin-Hebei region, delimits the demand type areas, calculates the spatial and temporal changes of ecosystem services value (ESV) based on land use status maps in 2000 and 2015, and puts forward corresponding land use strategies. The result is as follows. 1) Human beings have material, environmental and cultural needs for ecosystem. The demand for ecosystem services can be evaluated from four aspects: population, economic level, industrial development and educational level, corresponding to the nine services of the four functions of ecosystem, including supply, regulation, support and culture; 2) There is a large gap in the demand for ecosystem services in Beijing-Tianjin-Hebei region, which can be divided into four types: extremely high demand area, high demand area, medium demand area and low demand area. 3) From 2000 to 2015, the total value of ecosystem services in Beijing-Tianjin-Hebei region decreased. At county level, the total value of ecosystem services and the average value of land decreased gradually from north to south in space; 4) The value distribution of ecosystem services in different demand areas was unbalanced. From 2000 to 2015, the value of all types of areas has decreased, and the land use strategies of different types of areas are different.
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Noether Symmetry and Conserved Quantity for Fractional Birkhoffian Systems in Terms of Riesz Derivatives
ZHANG Yi, ZHOU Yan
Acta Scientiarum Naturalium Universitatis Pekinensis    2016, 52 (4): 658-668.   DOI: 10.13209/j.0479-8023.2016.068
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The Noether symmetry and the conserved quantity for a fractional Birkhoffian system in terms of Riesz fractional derivatives are studied. The fractional Pfaff variational problems are presented and the fractional Birkhoff’s equations are established within Riesz-Riemann-Liouville fractional derivatives and Riesz-Caputo fractional derivatives, respectively. Based on the invariance of the Pfaff action under the infinitesimal transformations, the Noether theorems for the fractional Birkhoffian system are given. The proof of the Noether theorem is done in two steps: first, the Noether theorem under a special one-parameter group of infinitesimal transformations without transforming the time is proved; second, by using a technique of time-reparameterization, the Noether theorem in its general form is obtained. Two examples are given to illustrate the application of the results.

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Automatic Extraction of Coastline from TM Image Integrating Texture and Spatial Relationship
ZHOU Yanan,ZHU Zhiwen,SHEN Zhanfeng,CHENG Xi
Acta Scientiarum Naturalium Universitatis Pekinensis