Mountain area accounts for a high proportion of the land area in China,and it is the focal area to solve the contradiction of imbalanced regional development,as well as an important source of ecosystem services.Theref...Mountain area accounts for a high proportion of the land area in China,and it is the focal area to solve the contradiction of imbalanced regional development,as well as an important source of ecosystem services.Therefore,this area has been facing long-term pressure and challenges in economic development and ecological protection.In this paper,we selected a rocky desertification mountain area,an active mountain area of new tectonic movement and a typical northern earth-rock mountain area,as Qian-Gui karst Mountain area,Hengduan Mountain area and Taihang Mountain area,as examples to represent three main types of mountain areas.Three representative types of ecosystem services,including NPP(Net Primary Productivity)as a support service,water conservation as a regulation service,and agricultural produce as a supply service,were incorporated into this study.Linear regression,correlation analysis and other methods were then used to investigate the spatial-temporal characteristics of the trade-offs and synergies in each of the three kinds of mountain areas during 1990-2015 in China.The analysis yielded three main conclusions for the three mountainous areas.(1)The agricultural produce supply service decreased relatively,while the support and regulation services of NPP and hydrological regulation increased significantly.(2)There was a synergistic relationship between NPP and the hydrological regulation services in the three mountainous areas.The synergistic relation in Qian-Gui karst Mountain area became enhanced,while those in Hengduan and Taihang Mountain areas became weakened,and the former was weakened to a greater extent.There was a trade-off between NPP,the hydrological regulation service and the agricultural produce supply service among the three mountainous areas.In particular,the trade-off between NPP and the agricultural produce supply service in Qian-Gui karst Mountain area became weaker,while those in Hengduan and Taihang Mountain areas were enhanced,and the latter was enhanced to a greater degree.(3)Significan展开更多
The differences in the microstructure and elevated temperature tensile properties of gravity die cast,squeeze cast,and semi-solid thixoformed Al-Si-Cu-Mn-Fe alloys after thermal exposure at 300℃were discussed.The res...The differences in the microstructure and elevated temperature tensile properties of gravity die cast,squeeze cast,and semi-solid thixoformed Al-Si-Cu-Mn-Fe alloys after thermal exposure at 300℃were discussed.The results demonstrate that the elevated temperature tensile properties of semi-solid thixoformed alloys were significantly higher than those of gravity die cast and squeeze cast alloys,especially after thermal exposure for 100 h.The ultimate tensile strength(UTS)of semi-solid thixoformed alloys after thermal exposure at 300℃for 0.5,10 and 100 h were 181,122 and 110 MPa,respectively.The UTS values of semi-solid thixoformed alloys were higher than those of heat resistant aluminum alloys used in commercial applications.The enhanced elevated temperature tensile properties of semi-solid thixoformed experimental alloys after thermal exposure can be attributed to the combined reinforcement of precipitation strengthening and grain boundary strengthening due to thermally stable intermetallic phases as well as suitable grain size.展开更多
This exploratory study examines whether genre has an impact on syntactic complexity and holistic rating in EFL writing. Over 300 sample texts produced by intermediate learners were collected from a test and some regul...This exploratory study examines whether genre has an impact on syntactic complexity and holistic rating in EFL writing. Over 300 sample texts produced by intermediate learners were collected from a test and some regular after-class assignments for English writing courses. Each participant completed two writing tasks, one argumentative and the other narrative. Results show that genre type has a significant impact on L2 syntactic complexity. Genre effect is found stronger with timed writing tasks. L2 holistic ratings show correlation with syntactic complexity on the different measure(s) depending on genre type and planning conditions. Regression analyses reveal that for timed writing tasks, clausal density(clauses per sentence) is a reliable predictor for holistic assessment on intermediate EFL learners’ writing quality. It is found to account for 6% of the score variance for timed writing and 10% for timed argumentative writing. Genre is evidenced to be related to EFL writing holistic ratings. Closer examination indicates that while syntactic complexity is predictive of holistic writing scores for argumentative writing, it does not correlate with holistic scores for narrative writing. Other linguistic features rather than syntactic complexity may be accountable. Overall, the study lends support to genre effect in the relationship between syntactic complexity and L2 writing quality holistic rating.展开更多
基金The National Natural Science Foundation of China(41771115)National Key Basic Research and Development Program(2015CB452706)Guizhou Science and Technology Fund(Guizhou Technology Cooperation Basis 20181116)。
文摘Mountain area accounts for a high proportion of the land area in China,and it is the focal area to solve the contradiction of imbalanced regional development,as well as an important source of ecosystem services.Therefore,this area has been facing long-term pressure and challenges in economic development and ecological protection.In this paper,we selected a rocky desertification mountain area,an active mountain area of new tectonic movement and a typical northern earth-rock mountain area,as Qian-Gui karst Mountain area,Hengduan Mountain area and Taihang Mountain area,as examples to represent three main types of mountain areas.Three representative types of ecosystem services,including NPP(Net Primary Productivity)as a support service,water conservation as a regulation service,and agricultural produce as a supply service,were incorporated into this study.Linear regression,correlation analysis and other methods were then used to investigate the spatial-temporal characteristics of the trade-offs and synergies in each of the three kinds of mountain areas during 1990-2015 in China.The analysis yielded three main conclusions for the three mountainous areas.(1)The agricultural produce supply service decreased relatively,while the support and regulation services of NPP and hydrological regulation increased significantly.(2)There was a synergistic relationship between NPP and the hydrological regulation services in the three mountainous areas.The synergistic relation in Qian-Gui karst Mountain area became enhanced,while those in Hengduan and Taihang Mountain areas became weakened,and the former was weakened to a greater extent.There was a trade-off between NPP,the hydrological regulation service and the agricultural produce supply service among the three mountainous areas.In particular,the trade-off between NPP and the agricultural produce supply service in Qian-Gui karst Mountain area became weaker,while those in Hengduan and Taihang Mountain areas were enhanced,and the latter was enhanced to a greater degree.(3)Significan
基金financially supported by the National Natural Science Foundation of China(Nos.51704084,52074131)the Science and Technology Plan of Guizhou Province,China(Nos.ZK2021(267),ZK2021(067))the Cultivation Project of Guizhou University,China(No.2019(23))。
文摘The differences in the microstructure and elevated temperature tensile properties of gravity die cast,squeeze cast,and semi-solid thixoformed Al-Si-Cu-Mn-Fe alloys after thermal exposure at 300℃were discussed.The results demonstrate that the elevated temperature tensile properties of semi-solid thixoformed alloys were significantly higher than those of gravity die cast and squeeze cast alloys,especially after thermal exposure for 100 h.The ultimate tensile strength(UTS)of semi-solid thixoformed alloys after thermal exposure at 300℃for 0.5,10 and 100 h were 181,122 and 110 MPa,respectively.The UTS values of semi-solid thixoformed alloys were higher than those of heat resistant aluminum alloys used in commercial applications.The enhanced elevated temperature tensile properties of semi-solid thixoformed experimental alloys after thermal exposure can be attributed to the combined reinforcement of precipitation strengthening and grain boundary strengthening due to thermally stable intermetallic phases as well as suitable grain size.
文摘This exploratory study examines whether genre has an impact on syntactic complexity and holistic rating in EFL writing. Over 300 sample texts produced by intermediate learners were collected from a test and some regular after-class assignments for English writing courses. Each participant completed two writing tasks, one argumentative and the other narrative. Results show that genre type has a significant impact on L2 syntactic complexity. Genre effect is found stronger with timed writing tasks. L2 holistic ratings show correlation with syntactic complexity on the different measure(s) depending on genre type and planning conditions. Regression analyses reveal that for timed writing tasks, clausal density(clauses per sentence) is a reliable predictor for holistic assessment on intermediate EFL learners’ writing quality. It is found to account for 6% of the score variance for timed writing and 10% for timed argumentative writing. Genre is evidenced to be related to EFL writing holistic ratings. Closer examination indicates that while syntactic complexity is predictive of holistic writing scores for argumentative writing, it does not correlate with holistic scores for narrative writing. Other linguistic features rather than syntactic complexity may be accountable. Overall, the study lends support to genre effect in the relationship between syntactic complexity and L2 writing quality holistic rating.
