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2 2020

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Effects of Increased Precipitation and Nitrogen Deposition on Methane Uptake of Alpine Meadow in Qinghai-Tibet Plateau : in situ Experiments

Guo Xiaowei, Dail Licong, Zhang Fawei, Li Yikang, Lin Li, Li Qian, Dawen Qian, Fan Bo, Ke Xun, Cao Guangmin, Zhou Huakun, Du Yangong

Polish Journal of Ecology

2020

Vol. 68, nr 2

109--120

The methane (CH4) fluxes in grasslands are sensitive to changes in precipitation and soil nitrogen concentrations, which was poorly understood, especially on the Tibetan Plateau. Therefore, an experiment was conducted from May 2012 to October 2013, by using the static chamber technique and gas chromatography method. We set up five treatments: an increased 2 g m-2 NH4NO3 treatment (2gN); an increased 4 g m-2 NH4NO3 treatment (4gN); and treatment with precipitation increased by 20% (Pre), and added 2 g m-2 NH4NO3 and precipitation (20%) treatment (N+Pre), and a control treatment (CK). The five treatments showed decreasing CH4 uptake rates in the following order: CK (71.66 ± 6.6 µg m-2 h-1) > N+Pre (58.57 ± 3.7 µg m-2 h-1) > Pre (52.66 ± 2.3 µg m-2 h-1) > 2gN (47.63 ± 3.1 µg m-2 h-1) > 4gN (39.12 ± 3.3 µg m-2 h-1). The 2gN and 4gN treatment resulted in 33.5% and 45.4% lower CH4 uptake than the CK treatment, respectively. The path analysis indicated that the above-ground biomass and litter fall were the most important factor promoting and limiting the CH4 uptake rate of alpine meadow, respectively.

A dynamic model for the heat transfer behavior of a cooling system

Liu Wen, Zhang Chi, Hu Xiao-Xiong, Cao Jian-Bo, Liu Li-Jiao, Ye Xin-Y, Lin Li, Qi Xun-Ji

Control and Cybernetics

2020

Vol. 49, No. 3

315--332

For purposes of studying the heat transfer behavior of various fluids in a refrigeration system, a dynamic model is established, obtained on the basis of analysis concerning the effects of adsorption velocity, adsorbent bed temperature, condensing temperature, and heat transfer fluids, as well as changes of external conditions. It is demonstrated that adsorption velocity increases sharply in the initial phase of adsorption process and gradually declines after reaching a peak value, whereas condensing temperature increases sharply in the initial phase of desorption process and decreases after reaching a peak value with the desorption quantity decreasing. Furthermore, the increase of heat source temperature and the decrease of cooling water temperature can advance the adsorption process. The present study therefore suggests some ways of improving the performance of such a refrigeration system by increasing heat source temperature, decreasing ambient air temperature, increasing return air temperature and decreasing cooling water temperature.