工程人员常通过对比设计软件与有限元软件的分析结果,以验算和校核结构设计的合理性。然而,由于软件分析内核的差异,设计软件与有限元软件之间的模型信息往往难以直接传递并转化。针对SAP2000结构设计分析软件向ANSYS有限元分析软件的...工程人员常通过对比设计软件与有限元软件的分析结果,以验算和校核结构设计的合理性。然而,由于软件分析内核的差异,设计软件与有限元软件之间的模型信息往往难以直接传递并转化。针对SAP2000结构设计分析软件向ANSYS有限元分析软件的模型转化问题,基于Python语言和APDL参数化设计语言,编译并开发了STAMT V1.0(SAP2000 To ANSYS Model Transformation V1.0)模型转化程序。相比已有转化程序,STAMT程序实现了更多单元类型、材料属性、截面类型、荷载形式的转化,提高了模型转化的通用性。其次,其涵盖了节点坐标系变换、梁单元坐标系变换、梁端自由度释放、创建刚性域等必备功能,进一步满足了模型转化过程中的功能性需求。然后,采用先建立几何模型后生成有限元模型的转化思路,实现了梁单元网格数量的自定义以及板壳荷载向梁的传递,软件操作界面简洁,便于工程人员的使用。最后,通过单层工业厂房和多层框架结构的两个算例分析,得到转化后模型的质量与原模型一致,前5阶周期的平均误差不超过3%,满足精度要求。研究分析验证了STAMT程序可实现SAP2000模型向ANSYS模型的准确、快速转化。展开更多
Lipids may play an important role in preventing gas embolisms by coating nanobubbles in xylem sap.Few studies on xylem sap lipids have been reported for temperate plants,and it remain unclear whether sap lipids have a...Lipids may play an important role in preventing gas embolisms by coating nanobubbles in xylem sap.Few studies on xylem sap lipids have been reported for temperate plants,and it remain unclear whether sap lipids have adaptational significance in tropical plants.In this study,we quantify the lipid composition of xylem sap for angiosperm species from a tropical savanna(seven species)and a seasonal rainforest(five species)using mass spectrometry.We found that all twelve species studied contained lipids in their xylem sap,including galactolipids,phospholipids and triacylglycerol,with a total lipid concentration ranging from 0.09 to 0.26 nmol/L.There was no difference in lipid concentration or composition between plants from the two sites,and the lipid concentration was negatively related to species’open vessel volume.Furthermore,savanna species showed little variation in lipid composition between the dry and the rainy season.These results support the hypothesis that xylem sap lipids are derived from the cytoplasm of individual conduit cells,remain trapped inside individual conduits,and undergo few changes in composition over consecutive seasons.A xylem sap lipidomic data set,which includes 12 tropical tree species from this study and 11 temperate tree species from literature,revealed no phylogenetic signals in lipid composition for these species.This study fills a knowledge gap in the lipid content of xylem sap in tropical trees and provides additional support for their common distribution in xylem sap of woody angiosperms.It appears that xylem sap lipids have no adaptive significance.展开更多
Lake is an important part of the natural ecosystem, and its morphological characteristics reflect the capacity of lake regulation and storage, the strength of material migration, and the characteristics of shoreline d...Lake is an important part of the natural ecosystem, and its morphological characteristics reflect the capacity of lake regulation and storage, the strength of material migration, and the characteristics of shoreline development. In most existing studies, remote sensing images are used to quantify the morphological characteristics of lakes. However, the extraction accuracy of lake water is greatly affected by cloud cover and vegetation cover, and the inversion accuracy of lake elevation data is poor, which cannot accurately describe the response relationship of lake landscape morphology with water level change. Therefore, this paper takes Tonle Sap Lake as the research object, which is the largest natural freshwater lake in Southeast Asia. DEM is constructed based on high-resolution measured topographic data, and morphological indicators such as lake area, lake shoreline length, perimeter area ratio, longest axis length, maximum width, shoreline development index, lake shape complexity, compactness ratio and form ratio are adopted to researching the evolution law of high water overflows and low water outbursts quantitatively, and clarifying the variation characteristics of landscape morphology with water level gradient in Tonle Sap Lake. The research results have important theoretical significance for the scientific utilization of Tonle Sap Lake water resources and the protection of the lake ecosystem.展开更多
文摘工程人员常通过对比设计软件与有限元软件的分析结果,以验算和校核结构设计的合理性。然而,由于软件分析内核的差异,设计软件与有限元软件之间的模型信息往往难以直接传递并转化。针对SAP2000结构设计分析软件向ANSYS有限元分析软件的模型转化问题,基于Python语言和APDL参数化设计语言,编译并开发了STAMT V1.0(SAP2000 To ANSYS Model Transformation V1.0)模型转化程序。相比已有转化程序,STAMT程序实现了更多单元类型、材料属性、截面类型、荷载形式的转化,提高了模型转化的通用性。其次,其涵盖了节点坐标系变换、梁单元坐标系变换、梁端自由度释放、创建刚性域等必备功能,进一步满足了模型转化过程中的功能性需求。然后,采用先建立几何模型后生成有限元模型的转化思路,实现了梁单元网格数量的自定义以及板壳荷载向梁的传递,软件操作界面简洁,便于工程人员的使用。最后,通过单层工业厂房和多层框架结构的两个算例分析,得到转化后模型的质量与原模型一致,前5阶周期的平均误差不超过3%,满足精度要求。研究分析验证了STAMT程序可实现SAP2000模型向ANSYS模型的准确、快速转化。
基金supported by the Natural Science Foundation of China (project number 31861133008)financial support from the Deutsche Forschungsgemeinschaft (German Research Foundation, DFG, project number 410768178)
文摘Lipids may play an important role in preventing gas embolisms by coating nanobubbles in xylem sap.Few studies on xylem sap lipids have been reported for temperate plants,and it remain unclear whether sap lipids have adaptational significance in tropical plants.In this study,we quantify the lipid composition of xylem sap for angiosperm species from a tropical savanna(seven species)and a seasonal rainforest(five species)using mass spectrometry.We found that all twelve species studied contained lipids in their xylem sap,including galactolipids,phospholipids and triacylglycerol,with a total lipid concentration ranging from 0.09 to 0.26 nmol/L.There was no difference in lipid concentration or composition between plants from the two sites,and the lipid concentration was negatively related to species’open vessel volume.Furthermore,savanna species showed little variation in lipid composition between the dry and the rainy season.These results support the hypothesis that xylem sap lipids are derived from the cytoplasm of individual conduit cells,remain trapped inside individual conduits,and undergo few changes in composition over consecutive seasons.A xylem sap lipidomic data set,which includes 12 tropical tree species from this study and 11 temperate tree species from literature,revealed no phylogenetic signals in lipid composition for these species.This study fills a knowledge gap in the lipid content of xylem sap in tropical trees and provides additional support for their common distribution in xylem sap of woody angiosperms.It appears that xylem sap lipids have no adaptive significance.
文摘Lake is an important part of the natural ecosystem, and its morphological characteristics reflect the capacity of lake regulation and storage, the strength of material migration, and the characteristics of shoreline development. In most existing studies, remote sensing images are used to quantify the morphological characteristics of lakes. However, the extraction accuracy of lake water is greatly affected by cloud cover and vegetation cover, and the inversion accuracy of lake elevation data is poor, which cannot accurately describe the response relationship of lake landscape morphology with water level change. Therefore, this paper takes Tonle Sap Lake as the research object, which is the largest natural freshwater lake in Southeast Asia. DEM is constructed based on high-resolution measured topographic data, and morphological indicators such as lake area, lake shoreline length, perimeter area ratio, longest axis length, maximum width, shoreline development index, lake shape complexity, compactness ratio and form ratio are adopted to researching the evolution law of high water overflows and low water outbursts quantitatively, and clarifying the variation characteristics of landscape morphology with water level gradient in Tonle Sap Lake. The research results have important theoretical significance for the scientific utilization of Tonle Sap Lake water resources and the protection of the lake ecosystem.
