FeAs^- single layer is tested as a simple model for LaFeAsO and BaFe2As2 based on firstprinciples calculations using generalized gradient approximation （GGA） and GGA＋U. The calculated single-layer geometric and ele...FeAs^- single layer is tested as a simple model for LaFeAsO and BaFe2As2 based on firstprinciples calculations using generalized gradient approximation （GGA） and GGA＋U. The calculated single-layer geometric and electronic structures are inconsistent with that of bulk materials. The bulk collinear antiferromagnetic ground state failed to be obtained in the FeAs^- single layer. The monotonous behavior of the Fe-As distance in z direction upon electron or hole doping is also in contrast with bulk materials. The results indicate that, in LaFeAsO and BaFe2As2, interactions between FeAs layer and other layers beyond simple charge doping are important, and a single FeAs layer may not represent a good model for Fe based superconducting materials.展开更多
During 2021 Chinese New Year,Headquarters of China Cultural Centers and Tourism Offices(under preparation)and the National Center for Public Cultural Development of the Ministry of Culture and Tourism jointly designed...During 2021 Chinese New Year,Headquarters of China Cultural Centers and Tourism Offices(under preparation)and the National Center for Public Cultural Development of the Ministry of Culture and Tourism jointly designed and released a series of short videos"Beautiful China":A Feast of Folk Spring Festival Galas.展开更多
Atomic characterization on tetragonal FeAs layer and engineering FeAs superlattices is highly desirable to get deep insight into the multi-band superconductivity in iron-pnictides.We fabricate the tetragonal FeAs laye...Atomic characterization on tetragonal FeAs layer and engineering FeAs superlattices is highly desirable to get deep insight into the multi-band superconductivity in iron-pnictides.We fabricate the tetragonal FeAs layer by topotactic reaction of FeTe films with arsenic and then obtain KxFe_(2)As_(2)upon potassium intercalation using molecular beam epitaxy.The in-situ low-temperature√2×√2scanning tunneling microscopy/spectroscopy investigations demonstrate characteristic reconstruction of the FeAs layer and stripe pattern of KxFe_(2)As_(2),accompanied by the development of a superconducting-like gap.The ex-situ transport measurement with FeTe capping layers shows a superconducting transition with an onset temperature of 10 K.This work provides a promising way to characterize the FeAs layer directly and explore rich emergent physics with epitaxial superlattice design.展开更多
The hyperloop idea,which is one of the most ecofriendly,low-carbon emissions,and fossil fuel-efficient modes of transportation,has recently become quite popular.In this study,a double-sided linear induction motor(LIM)...The hyperloop idea,which is one of the most ecofriendly,low-carbon emissions,and fossil fuel-efficient modes of transportation,has recently become quite popular.In this study,a double-sided linear induction motor(LIM)with 500 W of output power,60 N of thrust force and 200 V/38.58 Hz of supply voltage was designed to be used in hyperloop development competition hosted by the scientific and technological research council of turkey(TüB?TAK)rail transportation technologies institute(RUTE).In contrast to the studies in the literature,concentrated winding is preferred instead of distributed winding due to mechanical constraints.The electromagnetic design of LIM,whose mechanical and electrical requirements were determined considering the hyperloop development competition,was carried out by following certain steps.Then,the designed model was simulated and analyzed by finite element method(FEM),and the necessary optimizations have been performed to improve the motor characteristics.By examining the final model,the applicability of the concentrated winding type LIM for hyperloop technology has been investigated.Besides,the effects of primary material,railway material,and mechanical air-gap length on LIM performance were also investigated.In the practical phase of the study,the designed LIM has been prototyped and tested.The validation of the experimental results was achieved through good agreement with the finite element analysis results.展开更多
针对塔筒在复杂荷载作用以及不同工况下的结构响应问题,采用建筑信息模型(Building Information Modeling, BIM)+有限元分析(Finite Element Analysis, FEA)的方法,对某2 MW大型水平轴风力发电机组塔筒进行结构性能分析。首先参数化建...针对塔筒在复杂荷载作用以及不同工况下的结构响应问题,采用建筑信息模型(Building Information Modeling, BIM)+有限元分析(Finite Element Analysis, FEA)的方法,对某2 MW大型水平轴风力发电机组塔筒进行结构性能分析。首先参数化建立风力发电机组的BIM模型并对塔筒荷载进行分析计算,然后将塔筒BIM模型转换为有限元模型,最后在有限元软件ANSYS中对塔筒进行仿真分析。结果显示:塔筒最大应力出现在底部,塔筒顶部的位移最大。塔筒前六阶固有频率均不会与塔筒产生共振,且塔筒的固有频率随塔筒高度的增加而减小。随着塔筒顶部质量增加,塔筒的固有频率减小,塔筒顶部质量变化对塔筒的应力和顶部位移影响较小,对塔筒的固有频率影响较大。研究表明BIM+FEA方法能够为风力发电机组塔筒结构安全分析提供新思路,在风力发电机组塔筒的设计和运维中进行安全预警,为管理者决策提供有效数据信息。展开更多
基金Ⅴ. ACKNOWLEDGMENTS This work was partially supported by the National Natural Science Foundation of China （No.50721091, No.20533030, No.50731160010, No.20873129, and No.20803071）, the National Key Basic Research Program （No.2006CB922004）, the USTC-HP HPC Project, and by the SCCAS and Shanghai Supercomputer Center.
文摘FeAs^- single layer is tested as a simple model for LaFeAsO and BaFe2As2 based on firstprinciples calculations using generalized gradient approximation （GGA） and GGA＋U. The calculated single-layer geometric and electronic structures are inconsistent with that of bulk materials. The bulk collinear antiferromagnetic ground state failed to be obtained in the FeAs^- single layer. The monotonous behavior of the Fe-As distance in z direction upon electron or hole doping is also in contrast with bulk materials. The results indicate that, in LaFeAsO and BaFe2As2, interactions between FeAs layer and other layers beyond simple charge doping are important, and a single FeAs layer may not represent a good model for Fe based superconducting materials.
文摘During 2021 Chinese New Year,Headquarters of China Cultural Centers and Tourism Offices(under preparation)and the National Center for Public Cultural Development of the Ministry of Culture and Tourism jointly designed and released a series of short videos"Beautiful China":A Feast of Folk Spring Festival Galas.
基金supported by the National Natural Science Foundation of China(Nos.12074210,51788104,11790311,and 12141403)the Basic and Applied Basic Research Major Programme of Guangdong Province of China(No.2021B0301030003)Jihua Laboratory(Project No.X210141TL210).
文摘Atomic characterization on tetragonal FeAs layer and engineering FeAs superlattices is highly desirable to get deep insight into the multi-band superconductivity in iron-pnictides.We fabricate the tetragonal FeAs layer by topotactic reaction of FeTe films with arsenic and then obtain KxFe_(2)As_(2)upon potassium intercalation using molecular beam epitaxy.The in-situ low-temperature√2×√2scanning tunneling microscopy/spectroscopy investigations demonstrate characteristic reconstruction of the FeAs layer and stripe pattern of KxFe_(2)As_(2),accompanied by the development of a superconducting-like gap.The ex-situ transport measurement with FeTe capping layers shows a superconducting transition with an onset temperature of 10 K.This work provides a promising way to characterize the FeAs layer directly and explore rich emergent physics with epitaxial superlattice design.
基金the Istanbul Technical University Scientific Research Projects Unit with grant number MGA-2022-43948。
文摘The hyperloop idea,which is one of the most ecofriendly,low-carbon emissions,and fossil fuel-efficient modes of transportation,has recently become quite popular.In this study,a double-sided linear induction motor(LIM)with 500 W of output power,60 N of thrust force and 200 V/38.58 Hz of supply voltage was designed to be used in hyperloop development competition hosted by the scientific and technological research council of turkey(TüB?TAK)rail transportation technologies institute(RUTE).In contrast to the studies in the literature,concentrated winding is preferred instead of distributed winding due to mechanical constraints.The electromagnetic design of LIM,whose mechanical and electrical requirements were determined considering the hyperloop development competition,was carried out by following certain steps.Then,the designed model was simulated and analyzed by finite element method(FEM),and the necessary optimizations have been performed to improve the motor characteristics.By examining the final model,the applicability of the concentrated winding type LIM for hyperloop technology has been investigated.Besides,the effects of primary material,railway material,and mechanical air-gap length on LIM performance were also investigated.In the practical phase of the study,the designed LIM has been prototyped and tested.The validation of the experimental results was achieved through good agreement with the finite element analysis results.
文摘针对塔筒在复杂荷载作用以及不同工况下的结构响应问题,采用建筑信息模型(Building Information Modeling, BIM)+有限元分析(Finite Element Analysis, FEA)的方法,对某2 MW大型水平轴风力发电机组塔筒进行结构性能分析。首先参数化建立风力发电机组的BIM模型并对塔筒荷载进行分析计算,然后将塔筒BIM模型转换为有限元模型,最后在有限元软件ANSYS中对塔筒进行仿真分析。结果显示:塔筒最大应力出现在底部,塔筒顶部的位移最大。塔筒前六阶固有频率均不会与塔筒产生共振,且塔筒的固有频率随塔筒高度的增加而减小。随着塔筒顶部质量增加,塔筒的固有频率减小,塔筒顶部质量变化对塔筒的应力和顶部位移影响较小,对塔筒的固有频率影响较大。研究表明BIM+FEA方法能够为风力发电机组塔筒结构安全分析提供新思路,在风力发电机组塔筒的设计和运维中进行安全预警,为管理者决策提供有效数据信息。
