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Energy security and sustainability are crucial factors for the development of China
. The creation of an evaluation theoretical system of the energy has theoretical and practical significance that is important for ensuring the safe and sustainable development of energy security that matches the national development phase and reflects the sustainable development of national energy. Sustainable energy security must not only take into account the security of energy supply–demand in the long-term and short-term, it must also focus on the coordinated development between energy, the environment, and the economy in China. This paper proposes five dimensions of energy security (availability, accessibility, affordability, acceptability, and develop-ability) to construct China’s Sustainable Energy Security (CSES) evaluation index model. Based on the model, an empirical study of China’s energy security is carried out with data from 2005 to 2015, and dynamic changing trends are analyzed accordingly. The results indicate that availability and develop-ability are the most important weights in China’s Sustainable Energy Security index system, where availability shows a general downward trend, and develop-ability presents an inverted U-type trend, with its lowest point in 2011. From 2008 to 2012, China’s sustainable energy security had been at risk. Taking the year 2010 as the demarcation, two phases were obtained: before and after 2010, during which the level of China’s sustainable energy security first dropped, and then rose. However, compared with 2005, CSES level decreased by 28% in 2015 due to the decline of availability and accessibility. During 2005–2015, China’s energy security system had relative high scores in acceptability and develop-ability, while the sustained downward trend of availability is in need of more regulation
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Seasonally variable thermal conductivity in active layers is one important factor that controls the thermal state of permafrost
. The common assumption is that this conductivity is considerably lower in the thawed than in the frozen state, ?t/?f??1.5?m) active layers with strong seasonal total water content changes in the regions with summer-monsoon-dominated precipitation pattern. The conductivity ratio can be further increased by typical soil architectures that may lead to a dry interlayer. The unique pattern of soil hydraulic and thermal dynamics in the active layer can be one important contributor for the rapid permafrost warming at the study site. These findings suggest that, given the increase in air temperature and precipitation, soil hydraulic properties, particularly soil architecture in those thick active layers must be properly taken into account in permafrost models
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