Xu D.,Institute of Science and Technical Information of China |
Li C.,Chinese Academy of Forest |
Song X.,Henan Agricultural University |
Ren H.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research
Catena | Year: 2014
The farming-pastoral region of North China is a region that has suffered from serious desertification, and the multiple transitional characteristics in this region make it very difficult to link the progress of desertification to the driving forces behind it. This paper mainly focuses on the dynamics of desertification over the past 10years and their relationship to climate change and human activity. According to the MODIS images in 2000 and 2010, the farming-pastoral region had experienced significant desertification dynamics over the past 10years. The area of regions that had undergone desertification reversion and expansion were 186,240km2 and 199,525km2 respectively, and the spatial distribution of these regions showed great heterogeneity. The relationship between desertification dynamics and their driving forces was investigated by comparing the change in the NPP that was induced by climate change and human activity for each pixel that experienced desertification reversion and expansion. From 2000 to 2010, the coupling of climate change and human activity was the dominant factor behind desertification reversion. However, the human activity was the dominant factor that controlled the desertification expansion process between 2000 and 2010. The driving processes of desertification also had considerable spatial heterogeneity, and the dominant factors behind desertification reversion and expansion in each sub-region were not completely the same. So, the scale effect must be considered when explaining the results from similar studies. © 2014 Elsevier B.V.
Xu D.Y.,Institute of Science and Technical Information of China |
Xu D.Y.,Nanjing Agricultural University |
Xu D.Y.,CAS Institute of Geographical Sciences and Natural Resources Research |
Kang X.W.,Institute of Science and Technical Information of China |
And 2 more authors.
Journal of Arid Environments | Year: 2010
Multi-scale quantitative assessment of the relative role that climate change and human activities play in desertification is an important approach to clarifying the causes of desertification. In this study, a quantitative method was developed to assess the relative roles of climate change and human activities in desertification by selecting NPP as an indicator. The potential NPP and the difference between the potential and actual NPP were used to represent the impacts of climate and human factors on desertification. Based on this method, the relative roles that climate change and human activities play in desertification reversion and expansion in the Ordos Plateau were assessed at different spatial-temporal scales. The results revealed that increasing the spatial scale resulted in the area of the primary desertification process and its dominated driving process becoming more predominant at coarser scales from 1980 to 20000. For assessment at multi-temporal scales, climate change was the dominant factor inducing the desertification reversion from 1980 to 1990; however, human activities controlled the desertification reversion from 1990 to 2000 and 1980 to 2000. Assessment at longer temporal scales may average the characteristics when it is assessed at shorter scales. Therefore, scale-dependent characteristics must be considered when evaluating the causes of desertification. © 2009 Elsevier Ltd. All rights reserved.
Yang G.-C.,Institute of Science and Technical Information of China |
Li G.,Hubei University |
Li C.-Y.,Hubei University |
Zhao Y.-H.,Institute of Science and Technical Information of China |
And 4 more authors.
Scientometrics | Year: 2015
Most approaches to patent citation network analysis are based on single-patent direct citation relation, which is an incomplete understanding of the nature of knowledge flow between patent pairs, which are incapable of objectively evaluating patent value. In this paper, four types of patent citation networks (direct citation, indirect citation, coupling and co-citation networks) are combined, filtered and recomposed based on relational algebra. Then, a method based on comprehensive patent citation (CPC) network for patent value evaluation is proposed, and empirical study of optical disk technology related patents has been conducted based on this method. The empirical study was carried out in two steps: observation of network characteristics over the entire process (citation time lag and topological and graphics characteristics), and measurement verification by independent proxies of patent value (patent family and patent duration). Our results show that the CPC network retains the advantages of patent direct citation, and performs better on topological structure, graphics features, centrality distribution, citation lag and sensitivity than a direct citation network; The verified results by the patent family and maintenance show that the proposed method covers more valuable patents than the traditional method. © 2015, Akadémiai Kiadó, Budapest, Hungary.