The intermediate phase of hydrothermal synthesis of the Na0.44MnO2(NMO)nanowires is systematically investigated by means of transmission electron microscopy(TEM).The coexistence of Na-birnessite and NMO is commonly ob...The intermediate phase of hydrothermal synthesis of the Na0.44MnO2(NMO)nanowires is systematically investigated by means of transmission electron microscopy(TEM).The coexistence of Na-birnessite and NMO is commonly observed in the nanosheets.The NMO nanobelts in general have the width of~15 nm embedded in the(001)oriented Na-birnessite nanosheet.It is also found that the nanosheets of this intermediate phase often split along the NMO and Na-birnessite interface.Our structural study also shows that the NMO nanobelts prefer to grow along the[001]direction and gives rise to the[001]elongated NMO nanowires.Based on our TEM observations,the visible lattice mismatch and the resultant strain at the NMO/Na-birnessite interface play a critical role for formation of notable splitting structures in this kind of nanomaterial.The mechanism for the formation of the[001]NMO nanobelt is briefly discussed.展开更多
目的使用卷积神经网络(convolutional neural network,CNN)从欠采样的磁共振成像K空间数据快速重建出无伪影的高质量图像。材料与方法实验数据包含60位自愿者矢状位、横断位、冠状位全采的T1加权脑部MR图像,使用旋转和拉伸等操作对训练...目的使用卷积神经网络(convolutional neural network,CNN)从欠采样的磁共振成像K空间数据快速重建出无伪影的高质量图像。材料与方法实验数据包含60位自愿者矢状位、横断位、冠状位全采的T1加权脑部MR图像,使用旋转和拉伸等操作对训练数据进行扩增。不同欠采模式的MR图像和金标准图像分别输入CNN进行训练,学习获得的网络可实现由欠采图像到全采集图像之间的非线性映射。重建时,将CNN重建图像的K空间与原始的K空间数据进行合并保真。实验中利用金标准图像,计算重建图像的峰值信噪比(peak signal to noise ratio,PSNR)、结构相似度(structural similarity,SSIM)和高频误差范数(high frequency error norm,HFEN),定量评价重建结果。结果 (1)CNN重建出的中央采样MR图像的PSNR、SSIM、HFEN分别为31.13、0.93、223.81,优于Tukey窗函数的25.69、0.86、482.75;(2)CNN重建出的伪随机采样MR图像的PSNR、SSIM、HFEN分别为32.78、0.95、195.51,优于压缩感知的31.01、0.93、184.69。结论卷积神经网络可以从欠采数据重建出高质量的磁共振图像,无论是主观的视觉效果还是客观的评价参数都优于传统的处理方法。与K空间中央连续采集相比,伪随机采样模式更有利于CNN重建出高质量的MR图像。展开更多
Considering the influence of reagent adjustment in different flotation bank on the final production index and the difficulty of establishing an effective mathematical model,a coordinated optimization method for dosage...Considering the influence of reagent adjustment in different flotation bank on the final production index and the difficulty of establishing an effective mathematical model,a coordinated optimization method for dosage reagent based on key characteristics variation tendency and case-based reasoning is proposed.On the basis of the expert reagent regulation method in antimony flotation process,the reagent dosage pre-setting model of the roughing–scavenging bank is constructed based on case-based reasoning.Then,the sensitivity index is used to calculate the key features of reagent dosage.The reagent dosage compensation model is constructed based on the variation tendency of the key features in the roughing and scavenging process.At last,the prediction model is used to finish the classification and discriminant analysis.The simulation results and industrial experiment in antimony flotation process show that the proposed method reduces fluctuation of the tailings indicators and the cost of reagent dosage.It can lay a foundation for optimizing the whole process of flotation.展开更多
Structural features of MgB2 superconductors prepared under different conditions have been analysed by means of transmission electron microscopy.The MgB_(2) crystal is identified to have a hexagonal structure with the ...Structural features of MgB2 superconductors prepared under different conditions have been analysed by means of transmission electron microscopy.The MgB_(2) crystal is identified to have a hexagonal structure with the space group of P6/mmm.Superconducting materials synthesized under a high pressure of 6 Gpa are made of regularly stacked grains as large as a few microns in sizes.Stacking faults and microstructure properties of grain boundaries either with or without impurities,appearing in a sample with the critical current density greater than 10^(5)A/cm^(2),have been systematically investigated.展开更多
Structural and thermal transitions in the materials with nominal compositions of NaxCoO2 （0.5≤x≤0.75） have been investigated from room temperature to 800 K. In-situ heating transmission electron microscopy observa...Structural and thermal transitions in the materials with nominal compositions of NaxCoO2 （0.5≤x≤0.75） have been investigated from room temperature to 800 K. In-situ heating transmission electron microscopy observations revealed certain distinctive structural phase transitions commonly existing in this system. A superstructure hexagonal phase, proposed arising from partial Na ordering, appears in this system in a high temperature range. The structural model for the superstructure phase has been given. Measurements of thermogravimetry （TG） and differential thermal analysis （DTA） demonstrated that certain structural phase transitions appear around 430 K. NaxCoO2 is decomposed at a temperature higher than 600 K.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 11004229 and 11190022the Chinese Academy of Sciences,and the National Basic Research Program of China under Grant Nos 2011CBA00101 and 2012CB821404.
文摘The intermediate phase of hydrothermal synthesis of the Na0.44MnO2(NMO)nanowires is systematically investigated by means of transmission electron microscopy(TEM).The coexistence of Na-birnessite and NMO is commonly observed in the nanosheets.The NMO nanobelts in general have the width of~15 nm embedded in the(001)oriented Na-birnessite nanosheet.It is also found that the nanosheets of this intermediate phase often split along the NMO and Na-birnessite interface.Our structural study also shows that the NMO nanobelts prefer to grow along the[001]direction and gives rise to the[001]elongated NMO nanowires.Based on our TEM observations,the visible lattice mismatch and the resultant strain at the NMO/Na-birnessite interface play a critical role for formation of notable splitting structures in this kind of nanomaterial.The mechanism for the formation of the[001]NMO nanobelt is briefly discussed.
文摘目的使用卷积神经网络(convolutional neural network,CNN)从欠采样的磁共振成像K空间数据快速重建出无伪影的高质量图像。材料与方法实验数据包含60位自愿者矢状位、横断位、冠状位全采的T1加权脑部MR图像,使用旋转和拉伸等操作对训练数据进行扩增。不同欠采模式的MR图像和金标准图像分别输入CNN进行训练,学习获得的网络可实现由欠采图像到全采集图像之间的非线性映射。重建时,将CNN重建图像的K空间与原始的K空间数据进行合并保真。实验中利用金标准图像,计算重建图像的峰值信噪比(peak signal to noise ratio,PSNR)、结构相似度(structural similarity,SSIM)和高频误差范数(high frequency error norm,HFEN),定量评价重建结果。结果 (1)CNN重建出的中央采样MR图像的PSNR、SSIM、HFEN分别为31.13、0.93、223.81,优于Tukey窗函数的25.69、0.86、482.75;(2)CNN重建出的伪随机采样MR图像的PSNR、SSIM、HFEN分别为32.78、0.95、195.51,优于压缩感知的31.01、0.93、184.69。结论卷积神经网络可以从欠采数据重建出高质量的磁共振图像,无论是主观的视觉效果还是客观的评价参数都优于传统的处理方法。与K空间中央连续采集相比,伪随机采样模式更有利于CNN重建出高质量的MR图像。
基金Project(61725306)supported by the National Science Foundation for Distinguished Young Scholars of ChinaProjects(61473318,61403136,61703157,61751312)supported by the National Natural Science Foundation of ChinaProject(16C0940)supported by Foundation of Hunan Educational Committee,China
文摘Considering the influence of reagent adjustment in different flotation bank on the final production index and the difficulty of establishing an effective mathematical model,a coordinated optimization method for dosage reagent based on key characteristics variation tendency and case-based reasoning is proposed.On the basis of the expert reagent regulation method in antimony flotation process,the reagent dosage pre-setting model of the roughing–scavenging bank is constructed based on case-based reasoning.Then,the sensitivity index is used to calculate the key features of reagent dosage.The reagent dosage compensation model is constructed based on the variation tendency of the key features in the roughing and scavenging process.At last,the prediction model is used to finish the classification and discriminant analysis.The simulation results and industrial experiment in antimony flotation process show that the proposed method reduces fluctuation of the tailings indicators and the cost of reagent dosage.It can lay a foundation for optimizing the whole process of flotation.
基金Supported by the“Hundreds of Talents”Program of Chinese Academy of Sciences.
文摘Structural features of MgB2 superconductors prepared under different conditions have been analysed by means of transmission electron microscopy.The MgB_(2) crystal is identified to have a hexagonal structure with the space group of P6/mmm.Superconducting materials synthesized under a high pressure of 6 Gpa are made of regularly stacked grains as large as a few microns in sizes.Stacking faults and microstructure properties of grain boundaries either with or without impurities,appearing in a sample with the critical current density greater than 10^(5)A/cm^(2),have been systematically investigated.
基金This work was supported by the ‘Outstanding Youth Fund ’ (JQL) of China (No. 10225415)
文摘Structural and thermal transitions in the materials with nominal compositions of NaxCoO2 （0.5≤x≤0.75） have been investigated from room temperature to 800 K. In-situ heating transmission electron microscopy observations revealed certain distinctive structural phase transitions commonly existing in this system. A superstructure hexagonal phase, proposed arising from partial Na ordering, appears in this system in a high temperature range. The structural model for the superstructure phase has been given. Measurements of thermogravimetry （TG） and differential thermal analysis （DTA） demonstrated that certain structural phase transitions appear around 430 K. NaxCoO2 is decomposed at a temperature higher than 600 K.
