The void defect in intermetallic compounds(IMCs)layer at the joints caused by inhomogeneous atomic diffusion is one of the most important factors limiting the further development of Sn-based solders.In this work,the t...The void defect in intermetallic compounds(IMCs)layer at the joints caused by inhomogeneous atomic diffusion is one of the most important factors limiting the further development of Sn-based solders.In this work,the thermodynamic stability of IMCs(high-temperatureη-Cu_(6)Sn_(5)and o-Cu_(3)Sn phases)was improved by adding small amounts of indium(In),and the IMCs layers with moderate thickness,low defect concentrations and stable interface bonding were successfully obtained.The formation order of compounds and the interfacial orientation relationships in IMCs layers,the atomic diffusion mechanism,and the growth tuning mechanism of In onη-Cu_(6)Sn_(5)and Cu_(3)Sn,after In adding,were discussed com-prehensively by combining calculations and experiments.It is the first time that the classic heteroge-neous nucleation theory and CALPHAD data were used to obtain the critical nucleus radius ofη-Cu_(6)Sn_(5)and Cu_(3)Sn,and to explain in detail the main factors affecting the formation order and location of IMCs at joints during the welding process.A novel and systematic growth model about IMCs layers in the case of doping with alloying elements was proposed.The growth tuning mechanism of In doping onη-Cu_(6)Sn_(5)and Cu_(3)Sn was further clarified based on the proposed model using first-principles calculations.The growth model used in this study can provide insights into the development and design of multiele-ment Sn-based solders.展开更多
In this work,Mg(0001)/AlB_(2)(0001)interfaces with various terminations and stacking orders were constructed,and the atomic and electronic structures and adhesion work(Wad)of the interface were investigated using the ...In this work,Mg(0001)/AlB_(2)(0001)interfaces with various terminations and stacking orders were constructed,and the atomic and electronic structures and adhesion work(Wad)of the interface were investigated using the first-principles calculations.Notably,during the geometry optimization process,the B-mid-top(B-MT)Mg(0001)/AlB_(2)(0001)interface exhibits the most significant interface changes and manifests the least stability.Horizontal movement of Mg atoms in the first layer of the Mg surface slab,along the normal direction,results in a structure akin to the structurally optimized hexagonal close-packed(HCP)interface.The B-HCP interface demonstrates the highest stability,the largest ideal Wad,and the smallest interface distance.The interface enhances the binding strength of the Mg-side sub-interface,but diminishes the binding strength of the AlB_(2)-side sub-interface.Furthermore,Mg atoms can form metallic/covalent mixed bonds with Al atoms on the Al-terminal AlB_(2) surface and form ionic bonds with B atoms on the B-terminal AlB_(2) surface.Mg(0001)/AlB_(2)(0001)interface has good bonding properties.This research provides strong theoretical support for an in-depth understanding of Mg/AlB_(2) interface characteristics.展开更多
Information on the population distribution at the building scale can help governments make supplemental decisions to address complex urban management issues.However,the discontinuity and strong spatial heterogeneity o...Information on the population distribution at the building scale can help governments make supplemental decisions to address complex urban management issues.However,the discontinuity and strong spatial heterogeneity of research units at the building scale make it challenging to fuse multi-source geographic data,which causes significant errors in population estimation.To address this problem,this study proposes a method for population estimation at the building scale based on Dual-Environment Feature Fusion(DEFF).The dual environments of buildings were constructed by splitting the physical boundaries and extracting features suitable for the dual-environment scale from multi-source geographic data to describe the complex environmental features of buildings.Meanwhile,Data Quality Weighting based Technique for Order of Preference by Similarity to Ideal Solution(DQW-TOPSIS)method was proposed to assign appropriate weights to the features of the external environment for better feature fusion.Finally,a regression model was established using dual-environment features for building-scale population estimation.The experimental areas chosen for this study were Jianghan and Wuchang Districts,both located in Wuhan City,China.The estimated results of the DEFF were compared with those of the ablation experiments,as well as three publicly accessible population datasets,specifically LandScan,WorldPop,and GHS-POP,at the community scale.The evaluation results showed that DEFF had an R2 of approximately 0.8,Mean Absolute Error(MAE)of approximately 1200,Root Mean Square Error(RMSE)of approximately 1700,and both Mean Absolute Percentage Error(MAPE)and Symmetric Mean Absolute Percentage Error(SMAPE)of approximately 26%,indicating an improved performance and verifying the validity of the proposed method for fine-scale population estimation.展开更多
Semantic segmentation for remote sensing images faces challenges of unbalanced category weight,rich context causing difficulties of recognition,blurred boundaries of multi-scale objects,and so on.To address these prob...Semantic segmentation for remote sensing images faces challenges of unbalanced category weight,rich context causing difficulties of recognition,blurred boundaries of multi-scale objects,and so on.To address these problems,we propose a new model by combining HRNet with attention mechanisms and dilated convolution,denoted as:AD-HRNet for the semantic segmentation of remote sensing images.In the framework of AD-HRNet,we obtained the weight value of each category based on an improved weighted cross-entropy function by introducing the median frequency balance method to solve the issue of class weight imbalance.The Shuffle-CBAM module with channel attention and spatial attention in AD-HRNet framework was applied to extract more global context information of images through slightly increasing the amount of computation.To address the problem of blurred boundaries caused by multi-scale object segmentation and edge segmentation,we developed an MDC-DUC module in AD-HRNet framework to capture the context information of multi-scale objects and the edge information of many irregular objects.Taking Postdam,Vaihingen,and SAMA-VTOL datasets as materials,we verified the performance of AD-HRNet by comparing with eight typical semantic segmentation models.Experimental results shown that AD-HRNet increases the mIoUs to 75.59%and 71.58%based on the Postdam and Vaihingen datasets,respectively.展开更多
基金supported by the Innovation Team Cultivation Project of Yunnan Province(No.202005AE160016)Key Research&Development Program of Yunnan Province(No.202103AA080017)Yunnan Ten Thousand Talents Plan Young&Elite Talents Project(No.YNWR-QNBJ-2018-044).
文摘The void defect in intermetallic compounds(IMCs)layer at the joints caused by inhomogeneous atomic diffusion is one of the most important factors limiting the further development of Sn-based solders.In this work,the thermodynamic stability of IMCs(high-temperatureη-Cu_(6)Sn_(5)and o-Cu_(3)Sn phases)was improved by adding small amounts of indium(In),and the IMCs layers with moderate thickness,low defect concentrations and stable interface bonding were successfully obtained.The formation order of compounds and the interfacial orientation relationships in IMCs layers,the atomic diffusion mechanism,and the growth tuning mechanism of In onη-Cu_(6)Sn_(5)and Cu_(3)Sn,after In adding,were discussed com-prehensively by combining calculations and experiments.It is the first time that the classic heteroge-neous nucleation theory and CALPHAD data were used to obtain the critical nucleus radius ofη-Cu_(6)Sn_(5)and Cu_(3)Sn,and to explain in detail the main factors affecting the formation order and location of IMCs at joints during the welding process.A novel and systematic growth model about IMCs layers in the case of doping with alloying elements was proposed.The growth tuning mechanism of In doping onη-Cu_(6)Sn_(5)and Cu_(3)Sn was further clarified based on the proposed model using first-principles calculations.The growth model used in this study can provide insights into the development and design of multiele-ment Sn-based solders.
基金supported by the Innovation Team Cultivation Project of Yunnan Province under Grant No.202005AE160016the Key Research&Development Program of Yunnan Province under Grant No.202103AA080017.
文摘In this work,Mg(0001)/AlB_(2)(0001)interfaces with various terminations and stacking orders were constructed,and the atomic and electronic structures and adhesion work(Wad)of the interface were investigated using the first-principles calculations.Notably,during the geometry optimization process,the B-mid-top(B-MT)Mg(0001)/AlB_(2)(0001)interface exhibits the most significant interface changes and manifests the least stability.Horizontal movement of Mg atoms in the first layer of the Mg surface slab,along the normal direction,results in a structure akin to the structurally optimized hexagonal close-packed(HCP)interface.The B-HCP interface demonstrates the highest stability,the largest ideal Wad,and the smallest interface distance.The interface enhances the binding strength of the Mg-side sub-interface,but diminishes the binding strength of the AlB_(2)-side sub-interface.Furthermore,Mg atoms can form metallic/covalent mixed bonds with Al atoms on the Al-terminal AlB_(2) surface and form ionic bonds with B atoms on the B-terminal AlB_(2) surface.Mg(0001)/AlB_(2)(0001)interface has good bonding properties.This research provides strong theoretical support for an in-depth understanding of Mg/AlB_(2) interface characteristics.
基金supported by the National Natural Science Foundation of China[Grant numbers U20A2091,41930107]。
文摘Information on the population distribution at the building scale can help governments make supplemental decisions to address complex urban management issues.However,the discontinuity and strong spatial heterogeneity of research units at the building scale make it challenging to fuse multi-source geographic data,which causes significant errors in population estimation.To address this problem,this study proposes a method for population estimation at the building scale based on Dual-Environment Feature Fusion(DEFF).The dual environments of buildings were constructed by splitting the physical boundaries and extracting features suitable for the dual-environment scale from multi-source geographic data to describe the complex environmental features of buildings.Meanwhile,Data Quality Weighting based Technique for Order of Preference by Similarity to Ideal Solution(DQW-TOPSIS)method was proposed to assign appropriate weights to the features of the external environment for better feature fusion.Finally,a regression model was established using dual-environment features for building-scale population estimation.The experimental areas chosen for this study were Jianghan and Wuchang Districts,both located in Wuhan City,China.The estimated results of the DEFF were compared with those of the ablation experiments,as well as three publicly accessible population datasets,specifically LandScan,WorldPop,and GHS-POP,at the community scale.The evaluation results showed that DEFF had an R2 of approximately 0.8,Mean Absolute Error(MAE)of approximately 1200,Root Mean Square Error(RMSE)of approximately 1700,and both Mean Absolute Percentage Error(MAPE)and Symmetric Mean Absolute Percentage Error(SMAPE)of approximately 26%,indicating an improved performance and verifying the validity of the proposed method for fine-scale population estimation.
基金supported by the National Natural Science Foundation of China(No.42271449,41901394,41971405)open research fund program of Geomatics Technology and Application Key Laboratory of Qinghai Province.
文摘Semantic segmentation for remote sensing images faces challenges of unbalanced category weight,rich context causing difficulties of recognition,blurred boundaries of multi-scale objects,and so on.To address these problems,we propose a new model by combining HRNet with attention mechanisms and dilated convolution,denoted as:AD-HRNet for the semantic segmentation of remote sensing images.In the framework of AD-HRNet,we obtained the weight value of each category based on an improved weighted cross-entropy function by introducing the median frequency balance method to solve the issue of class weight imbalance.The Shuffle-CBAM module with channel attention and spatial attention in AD-HRNet framework was applied to extract more global context information of images through slightly increasing the amount of computation.To address the problem of blurred boundaries caused by multi-scale object segmentation and edge segmentation,we developed an MDC-DUC module in AD-HRNet framework to capture the context information of multi-scale objects and the edge information of many irregular objects.Taking Postdam,Vaihingen,and SAMA-VTOL datasets as materials,we verified the performance of AD-HRNet by comparing with eight typical semantic segmentation models.Experimental results shown that AD-HRNet increases the mIoUs to 75.59%and 71.58%based on the Postdam and Vaihingen datasets,respectively.
