| 1 | Comparison and Effects of Different Climate-Vegetation Models in Areas of Complex Terrain under Climate Change显示文摘Identifying the impacts of climate change is important for conservation of ecosystems under climate change, particularly in mountain regions. Holdridge life zone system and K?ppen classification provide two effective methods to assess impacts of climate change on ecosystems, as typical climate-vegetation models. Meanwhile, these previous studies are insufficient to assess the complex terrain as well as there are some uncertainties in results while using the given methods. Analysis of the impacts of the prevailing climate conditions in an area on shifts of ecosystems may reduce uncertainties in projecting climate change. In this study, we used different models to depict changes in ecosystems at 1 km × 1 km resolution in Sichuan Province, China during 1961–2010. The results indicate that changes in climate data during the past 50 years were sufficient to cause shifts in the spatial distribution of ecosystems. The trend of shift was from low temperature ecosystems to high temperature ecosystems. Compared with K?ppen classification, the Holdridge system has better adaptation to assess the impacts of climate change on ecosystems in low elevation(0–1000 m). Moreover, we found that changed areas in ecosystems were easily affected by climate change than unchanged areas by calculating current climate condition. | WANG Yukuan LU Yafeng LI Qinwen | 2016 | Chinese Geographical Science2016，26，2： | 3 |
| 2 | Optimization of a Lobed Mixer with BP Neural Network and Genetic Algorithm显示文摘A Sequential Approximate Optimization framework(SAO)for the multi-objective optimization of lobed mixer is established by using the BP neural network and Genetic Algorithm:the ratio of lobe wavelength to height(η)and the rise angle(α)are selected as the design parameters,and the mixing efficiency,thrust and total pressure loss are the optimization objectives.The CFX commercial solver coupled with the SST turbulence model is employed to simulate the flow field of lobed mixer.A tetrahedral unstructured grid with 5.6 million cells can achieve the similar global results.Based on the response surface approximation model of the lobed mixer,it is necessary to avoid increasing or decreasingαandηat the same time.Instead,theαshould be reduced while theηis appropriately increased,which is conducive to achieving the goal of increasing thrust and reducing losses at the expense of a small decrease in the mixing efficiency.Compared with the normalized method,the non-normalized method with better global optimization accuracy is more suitable for solving the multi-objective optimization problem of the lobed mixer,and its optimal solution(α=8.54°,η=1.165)is the optimal solution of the lobed mixer optimization problem studied in this paper.Compared with the reference lobed mixer,theα,β(the fall angle)and H(lobe height)of the optimal solution are reduced by 0.14°,1.34°and 3.97 mm,respectively,and theηis increased by 0.074;its mixing efficiency is decreased by 4.46%,but the thrust is increased by 2.29%and the total pressure loss is decreased by 0.64%.Downstream of the optimized lobed mixer,the radial scale and peak vorticity of the streamwise voritices decrease with the decreasing lobe height,thereby reducing the mixing efficiency.For the optimized lobed mixer,its low mixing efficiency is the main factor for the decrease of the total pressure loss,but the improvement of the geometric curvature is also conducive to reducing its profile loss.Within the scope of this study,the lobed mixer has an optimal mixing efficiency(ε=74.14%)that maximizes its thrust without excessively increasing the mixing loss. | SONG Yukuan LEI Zhijun LU Xin-Gen XU Gang ZHU Junqiang | 2023 | Journal of Thermal Science2023，32，1： | 1 |
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