The abundance distributions of more than 40 elements in the No. 502 Ordovician-Silurian (O/S) bounda-ry section at Fenxiang, Yichang have been studied by RNAA and INAA. The results show that in the bounda-ry bed, ther...The abundance distributions of more than 40 elements in the No. 502 Ordovician-Silurian (O/S) bounda-ry section at Fenxiang, Yichang have been studied by RNAA and INAA. The results show that in the bounda-ry bed, there is a distinctive Ir anomaly because the Ir concentration abruptly increases to 0.64 ppb.Furthermore, the Ir is positively correlated in abundance variation with some siderophile and sulphophile ele-ments. In the same bed of the O/S boundary section at Huanghuachang, Yichang, there is also a δ^(13)C excur-sion. These geochemical signs support the hypothesis that the terminal Ordovician mass extinction was proba-bly related to extraterrestrial event, and provide new evidence for defining the O/S boundary between theHirnantia-Kinnella and G. persculptus Zones.展开更多
The grain boundary microstructures of a heat-treated Ni-based cast superalloy IN792 were investigated. The results show that M5B3 boride precipitates at the grain boundary. A special orientation relationship between M...The grain boundary microstructures of a heat-treated Ni-based cast superalloy IN792 were investigated. The results show that M5B3 boride precipitates at the grain boundary. A special orientation relationship between M5B3 phase and the matrix at one side of the grain boundary is found. At the same time, two M5B3 borides with different orientations could co-exist in a single M5B3 particle as an intergrowth besides existing alone, thus forming orientation relationship between the two M5B3 phases and matrix. This phenomenon could be attributed to the special orientation relationship between M5B3 phase and the matrix.展开更多
The identification of factors that may be forcing ecological observations to approach the upper boundary provides insight into potential mechanisms affecting driver-response relationships,and can help inform ecosystem...The identification of factors that may be forcing ecological observations to approach the upper boundary provides insight into potential mechanisms affecting driver-response relationships,and can help inform ecosystem management,but has rarely been explored.In this study,we propose a novel framework integrating quantile regression with interpretable machine learning.In the first stage of the framework,we estimate the upper boundary of a driver-response relationship using quantile regression.Next,we calculate“potentials”of the response variable depending on the driver,which are defined as vertical distances from the estimated upper boundary of the relationship to observations in the driver-response variable scatter plot.Finally,we identify key factors impacting the potential using a machine learning model.We illustrate the necessary steps to implement the framework using the total phosphorus(TP)-Chlorophyll a(CHL)relationship in lakes across the continental US.We found that the nitrogen to phosphorus ratio(N:P),annual average precipitation,total nitrogen(TN),and summer average air temperature were key factors impacting the potential of CHL depending on TP.We further revealed important implications of our findings for lake eutrophication management.The important role of N:P and TN on the potential highlights the co-limitation of phosphorus and nitrogen and indicates the need for dual nutrient criteria.Future wetter and/or warmer climate scenarios can decrease the potential which may reduce the efficacy of lake eutrophication management.The novel framework advances the application of quantile regression to identify factors driving observations to approach the upper boundary of driver-response relationships.展开更多
文摘The abundance distributions of more than 40 elements in the No. 502 Ordovician-Silurian (O/S) bounda-ry section at Fenxiang, Yichang have been studied by RNAA and INAA. The results show that in the bounda-ry bed, there is a distinctive Ir anomaly because the Ir concentration abruptly increases to 0.64 ppb.Furthermore, the Ir is positively correlated in abundance variation with some siderophile and sulphophile ele-ments. In the same bed of the O/S boundary section at Huanghuachang, Yichang, there is also a δ^(13)C excur-sion. These geochemical signs support the hypothesis that the terminal Ordovician mass extinction was proba-bly related to extraterrestrial event, and provide new evidence for defining the O/S boundary between theHirnantia-Kinnella and G. persculptus Zones.
基金partly supported by the High Technology Research and Development Program of China (No. 2014AA041701)the National Natural Science Foundation of China (Nos. 51171179, 51271174, 51331005, and 11332010)China Postdoctoral Science Foundation under Grant No. 2015M580923
文摘The grain boundary microstructures of a heat-treated Ni-based cast superalloy IN792 were investigated. The results show that M5B3 boride precipitates at the grain boundary. A special orientation relationship between M5B3 phase and the matrix at one side of the grain boundary is found. At the same time, two M5B3 borides with different orientations could co-exist in a single M5B3 particle as an intergrowth besides existing alone, thus forming orientation relationship between the two M5B3 phases and matrix. This phenomenon could be attributed to the special orientation relationship between M5B3 phase and the matrix.
基金This research was funded by the National Natural Science Foundation of China(Nos.71761147001 and 42030707)the International Partnership Program by the Chinese Academy of Sciences(No.121311KYSB20190029)+2 种基金the Fundamental Research Fund for the Central Universities(No.20720210083)the National Science Foundation(Nos.EF-1638679,EF-1638554,EF-1638539,and EF-1638550)Any use of trade,firm,or product names is for descriptive purposes only and does not imply endorsement by the US Government.
文摘The identification of factors that may be forcing ecological observations to approach the upper boundary provides insight into potential mechanisms affecting driver-response relationships,and can help inform ecosystem management,but has rarely been explored.In this study,we propose a novel framework integrating quantile regression with interpretable machine learning.In the first stage of the framework,we estimate the upper boundary of a driver-response relationship using quantile regression.Next,we calculate“potentials”of the response variable depending on the driver,which are defined as vertical distances from the estimated upper boundary of the relationship to observations in the driver-response variable scatter plot.Finally,we identify key factors impacting the potential using a machine learning model.We illustrate the necessary steps to implement the framework using the total phosphorus(TP)-Chlorophyll a(CHL)relationship in lakes across the continental US.We found that the nitrogen to phosphorus ratio(N:P),annual average precipitation,total nitrogen(TN),and summer average air temperature were key factors impacting the potential of CHL depending on TP.We further revealed important implications of our findings for lake eutrophication management.The important role of N:P and TN on the potential highlights the co-limitation of phosphorus and nitrogen and indicates the need for dual nutrient criteria.Future wetter and/or warmer climate scenarios can decrease the potential which may reduce the efficacy of lake eutrophication management.The novel framework advances the application of quantile regression to identify factors driving observations to approach the upper boundary of driver-response relationships.
