The microstructure evolution and its effects on the mechanical performance of 2000 MPa bridge cable steel wires were investigated by transmission electron microscope(TEM),electron backscatter diffraction(EBSD),X-ray d...The microstructure evolution and its effects on the mechanical performance of 2000 MPa bridge cable steel wires were investigated by transmission electron microscope(TEM),electron backscatter diffraction(EBSD),X-ray diffractometer(XRD)and mechanical tests.Experimental results reveal that,with the increasing strain from 0 to 1.42,a fiber structure and a<110>fiber texture aligned with the wire axis are gradually developed accompanied by cementite decomposition and the formation of sub-grains;the tensile strength increases linearly from 1510 to 2025 MPa,and the reduction of the area is stable with a slight decline from 44%to 36%.After annealing at 450℃for different times,pronounced changes in the microstructure occur.Cementite lamella fragment into coarser globules corresponding to a remarkable spheroidization process,while ferrite domains recover and recrystallize,and this process is associated to modifications in the mechanical properties.Furthermore,based on the observations on dislocation lines crossing through cementite lamellae,a possible mechanism of cementite decomposition is discussed.展开更多
The characteristic of near-surface microstructure and its effects on the torsion performance of cold-drawn pearlitic steel wires for bridge cables were investigated by focused ion beam-scanning electron microscope,tra...The characteristic of near-surface microstructure and its effects on the torsion performance of cold-drawn pearlitic steel wires for bridge cables were investigated by focused ion beam-scanning electron microscope,transmission electron microscopy and differential scanning calorimetry.The samples with similar tensile strength before and after hot-dip galvanizing process are,respectively,characterized as delaminated and non-delaminated in torsion test which indicates that the tensile strength is independent of the toughness value(i e,reduction area and torsion ability).It is interesting to find that there exists submicron granular ferrite on near-surface of the wires,which can be attributed to dislocation rearrangement and sub-grains rotation during cold drawing and hot-dip galvanizing process.And their distribution can suggest homogeneousness of deformation degree to a certain extent:the closer to the surface of their distribution,the more homogeneous deformation of the wires.There is a close relationship between the thermal stability of the cementite layer and distribution of granular ferrite:differential scanning calorimetry(DSC)analysis shows that the sample is accompanied by submicron granular ferrite which is located closer to the surface has higher thermal stability under galvanizing temperature(450°C).A new mechanism of the torsion delamination of pearlitic steel wires is discussed in terms of the thermal stability of the cementite layer and distribution of granular ferrite.展开更多
One new triterpcnoid saponin, quinquenoside L17 （1）, was isolated from the leaves and stems of Panax quinquefolium L., and its structure was elucidated as 20-O-[（β-D-xylopyranosyl-（1-6）-O-β-D-glucopyranosy）]-6...One new triterpcnoid saponin, quinquenoside L17 （1）, was isolated from the leaves and stems of Panax quinquefolium L., and its structure was elucidated as 20-O-[（β-D-xylopyranosyl-（1-6）-O-β-D-glucopyranosy）]-6-O-β-D-glucopyranosy1-dammar-24-ene- 3,6,12,20-tetraol, by the combination analysis of one-dimensional NMR and two-dimensional NMR, mass spectrometry, CD spectrum and chemical evidences.展开更多
A new compound, kudinoside LZ2 （1）, was isolated from the leaves of llex kudincha. Its structure was elucidated by the combination of one- and two-dimensional NMR analysis, HR-ESI-MS, CD spectrum measurement and che...A new compound, kudinoside LZ2 （1）, was isolated from the leaves of llex kudincha. Its structure was elucidated by the combination of one- and two-dimensional NMR analysis, HR-ESI-MS, CD spectrum measurement and chemical evidences.展开更多
China’s urbanization level has reached a new stage.Urban development has changed from incremental expansion to inventory renewal.The demand of residents for a good living environment and compact living space is incre...China’s urbanization level has reached a new stage.Urban development has changed from incremental expansion to inventory renewal.The demand of residents for a good living environment and compact living space is increasing.How to realize the intensive development of land based on human needs has become an urgent problem to be solved in urban development.Based on the planning concepts of inventory planning and life circle,this study made the renewal and transformation of old urban area of Medical Saint Temple in Nanyang City and analyzed the current spatial characteristic elements.Optimize the layout of public space in combination with residents’living needs,improve the functions and quality of urban areas,and build a healthy and sustainable development model to improve the living environment of the community and provide reference for the future urban renewal and transformation.展开更多
战斗部破片群运动参数对弹药毁伤威力评估具有重要的意义。针对破片尺寸较小、背景信息复杂以及破片数据样本少导致的破片检测精度较低的问题,本文提出一种YOLOv5-FD的战斗部破片群目标检测方法。首先,在网络输出端增加微小目标检测层,...战斗部破片群运动参数对弹药毁伤威力评估具有重要的意义。针对破片尺寸较小、背景信息复杂以及破片数据样本少导致的破片检测精度较低的问题,本文提出一种YOLOv5-FD的战斗部破片群目标检测方法。首先,在网络输出端增加微小目标检测层,将原始的三尺度改为四尺度,并在特征融合网络中引入内容感知特征重组(Content Aware ReAssembly of Features,CARAFE)上采样模块替换原有的最近邻插值上采样,减少小目标特征信息损失,提高弱小破片的提取能力。其次,在特征提取网络引入坐标注意力模块(Coordinate Attention,CA),加强对破片特征的提取,弱化背景信息,抑制复杂背景的干扰。最后,在模型训练过程中引入模型不可知元学习方法(Model Agnostic Meta Learning,MAML),达到仅用小样本破片数据集实现较高的检测性能。实验结果表明,YOLOv5-FD破片检测算法在自制破片数据集中,精确率达到了90.5%,召回率达到了85.4%,平均精度mAP_0.5达到了88.2%,与原始YOLOv5s算法相比分别提高了7.1%,7.9%和7.5%,有效提高了破片目标检测准确性。展开更多
基金Funded by the National Key R&D Program of China(No.2017YFB0304801)
文摘The microstructure evolution and its effects on the mechanical performance of 2000 MPa bridge cable steel wires were investigated by transmission electron microscope(TEM),electron backscatter diffraction(EBSD),X-ray diffractometer(XRD)and mechanical tests.Experimental results reveal that,with the increasing strain from 0 to 1.42,a fiber structure and a<110>fiber texture aligned with the wire axis are gradually developed accompanied by cementite decomposition and the formation of sub-grains;the tensile strength increases linearly from 1510 to 2025 MPa,and the reduction of the area is stable with a slight decline from 44%to 36%.After annealing at 450℃for different times,pronounced changes in the microstructure occur.Cementite lamella fragment into coarser globules corresponding to a remarkable spheroidization process,while ferrite domains recover and recrystallize,and this process is associated to modifications in the mechanical properties.Furthermore,based on the observations on dislocation lines crossing through cementite lamellae,a possible mechanism of cementite decomposition is discussed.
基金Funded by the National Key R&D Program of China(No.2017YFB0304801)。
文摘The characteristic of near-surface microstructure and its effects on the torsion performance of cold-drawn pearlitic steel wires for bridge cables were investigated by focused ion beam-scanning electron microscope,transmission electron microscopy and differential scanning calorimetry.The samples with similar tensile strength before and after hot-dip galvanizing process are,respectively,characterized as delaminated and non-delaminated in torsion test which indicates that the tensile strength is independent of the toughness value(i e,reduction area and torsion ability).It is interesting to find that there exists submicron granular ferrite on near-surface of the wires,which can be attributed to dislocation rearrangement and sub-grains rotation during cold drawing and hot-dip galvanizing process.And their distribution can suggest homogeneousness of deformation degree to a certain extent:the closer to the surface of their distribution,the more homogeneous deformation of the wires.There is a close relationship between the thermal stability of the cementite layer and distribution of granular ferrite:differential scanning calorimetry(DSC)analysis shows that the sample is accompanied by submicron granular ferrite which is located closer to the surface has higher thermal stability under galvanizing temperature(450°C).A new mechanism of the torsion delamination of pearlitic steel wires is discussed in terms of the thermal stability of the cementite layer and distribution of granular ferrite.
基金supported by 973 Program(No.2006CB708517)Program for New Century Excellent Talents in University of Peoples Republic of China(No.NCET-04-0289)
文摘One new triterpcnoid saponin, quinquenoside L17 （1）, was isolated from the leaves and stems of Panax quinquefolium L., and its structure was elucidated as 20-O-[（β-D-xylopyranosyl-（1-6）-O-β-D-glucopyranosy）]-6-O-β-D-glucopyranosy1-dammar-24-ene- 3,6,12,20-tetraol, by the combination analysis of one-dimensional NMR and two-dimensional NMR, mass spectrometry, CD spectrum and chemical evidences.
基金supported by Program for New Century Excellent Talents in University of People's Republic of China(No.NCET-04-0289)
文摘A new compound, kudinoside LZ2 （1）, was isolated from the leaves of llex kudincha. Its structure was elucidated by the combination of one- and two-dimensional NMR analysis, HR-ESI-MS, CD spectrum measurement and chemical evidences.
基金Sponsored by Social Science Fund Project of Hebei Province(HB19S039)Training Project of School of Architecture and Art,Hebei University of Engineering(2020-KJZD-001).
文摘China’s urbanization level has reached a new stage.Urban development has changed from incremental expansion to inventory renewal.The demand of residents for a good living environment and compact living space is increasing.How to realize the intensive development of land based on human needs has become an urgent problem to be solved in urban development.Based on the planning concepts of inventory planning and life circle,this study made the renewal and transformation of old urban area of Medical Saint Temple in Nanyang City and analyzed the current spatial characteristic elements.Optimize the layout of public space in combination with residents’living needs,improve the functions and quality of urban areas,and build a healthy and sustainable development model to improve the living environment of the community and provide reference for the future urban renewal and transformation.
文摘战斗部破片群运动参数对弹药毁伤威力评估具有重要的意义。针对破片尺寸较小、背景信息复杂以及破片数据样本少导致的破片检测精度较低的问题,本文提出一种YOLOv5-FD的战斗部破片群目标检测方法。首先,在网络输出端增加微小目标检测层,将原始的三尺度改为四尺度,并在特征融合网络中引入内容感知特征重组(Content Aware ReAssembly of Features,CARAFE)上采样模块替换原有的最近邻插值上采样,减少小目标特征信息损失,提高弱小破片的提取能力。其次,在特征提取网络引入坐标注意力模块(Coordinate Attention,CA),加强对破片特征的提取,弱化背景信息,抑制复杂背景的干扰。最后,在模型训练过程中引入模型不可知元学习方法(Model Agnostic Meta Learning,MAML),达到仅用小样本破片数据集实现较高的检测性能。实验结果表明,YOLOv5-FD破片检测算法在自制破片数据集中,精确率达到了90.5%,召回率达到了85.4%,平均精度mAP_0.5达到了88.2%,与原始YOLOv5s算法相比分别提高了7.1%,7.9%和7.5%,有效提高了破片目标检测准确性。
