A new method for quantitative phase analysis is proposed by using X-ray diffraction multi-peak match intensity ratio. This method can obtain the multi-peak match intensity ratio among each phase in the mixture sample ...A new method for quantitative phase analysis is proposed by using X-ray diffraction multi-peak match intensity ratio. This method can obtain the multi-peak match intensity ratio among each phase in the mixture sample by using all diffraction peak data in the mixture sample X-ray diffraction spectrum and combining the relative intensity distribution data of each phase standard peak in JCPDS card to carry on the least square method regression analysis. It is benefit to improve the precision of quantitative phase analysis that the given single line ratio which is usually adopted is taken the place of the multi-peak match intensity ratio and is used in X-ray diffraction quantitative phase analysis of the mixture sample. By analyzing four-group mixture sample, adopting multi-peak match intensity ratio and X-ray diffraction quantitative phase analysis principle of combining the adiabatic and matrix flushing method, it is tested that the experimental results are identical with theory.展开更多
Beam splitting is one of the main approaches to achieving x-ray ghost imaging, and the intensity correlation between diffraction beam and transmission beam will directly affect the imaging quality. In this paper, we i...Beam splitting is one of the main approaches to achieving x-ray ghost imaging, and the intensity correlation between diffraction beam and transmission beam will directly affect the imaging quality. In this paper, we investigate the intensity correlation between the split x-ray beams by Laue diffraction of stress-free crystal. The analysis based on the dynamical theory of x-ray diffraction indicates that the spatial resolution of diffraction image and transmission image are reduced due to the position shift of the exit beam. In the experimental setup, a stress-free crystal with a thickness of hundredmicrometers-level is used for beam splitting. The crystal is in a non-dispersive configuration equipped with a double-crystal monochromator to ensure that the dimension of the diffraction beam and transmission beam are consistent. A correlation coefficient of 0.92 is achieved experimentally and the high signal-to-noise ratio of the x-ray ghost imaging is anticipated.Results of this paper demonstrate that the developed beam splitter of Laue crystal has the potential in the efficient data acquisition of x-ray ghost imaging.展开更多
Under the quadratic approximation of the Rytov＇s phase structure function, this paper derives the general closed-form expressions for the mean-squared width and the angular spread of partially coherent beams in turbu...Under the quadratic approximation of the Rytov＇s phase structure function, this paper derives the general closed-form expressions for the mean-squared width and the angular spread of partially coherent beams in turbulence. It finds that under a certain condition different types of partially coherent beams may have the same directionality as a fully coherent Gaussian beam in free space and also in atmospheric turbulence if the angular spread is chosen as the characteristic parameter of beam directionality. On the other hand, it shows that generally, the directionality of partially coherent beams expressed in terms of the angular spread is not consistent with that in terms of the normalized far-field average intensity distribution in free space, but the consistency can be achieved due to turbulence.展开更多
A set of absorption curves was priorly prepared on transparent films to fit the background and peak intensities in continuous scanning X-ray stress measurement.It may be better to correct both background and absorptio...A set of absorption curves was priorly prepared on transparent films to fit the background and peak intensities in continuous scanning X-ray stress measurement.It may be better to correct both background and absorption of pure diffraction intensity.Experimental results revealed this to be a reliable correction method.展开更多
Line broadening in a diffraction intensity profile of powdered crystalline materials due to stacking fault has been characterized in terms of the zeroth, first, second, third, and fourth moments and the fourth cumulan...Line broadening in a diffraction intensity profile of powdered crystalline materials due to stacking fault has been characterized in terms of the zeroth, first, second, third, and fourth moments and the fourth cumulant. Calculations have been derived showing that the first moment causes a shift in the peak position of the profile while the third moment affects its shape. The intensity expression has been derived on the basis of usual Cartesian coordinates and also of polar coordinates indicated by the probability of the fault and the reciprocal lattice parameter as the two axes. The expressions for the fourth cumulant have also been so derived. Here we have used three different approaches to determine methods for calculating the fourth cumulant due to stacking faults. The three forms of the equations derived here are for different coordinate systems, but will arrive at the same answers.展开更多
Laue method is classical in X-ray analysis of crystals. Its diffraction spots are produced by the continuous spectrum of incident X-rays, in which the changeable wavelength can fit in with the different hkl diffractio...Laue method is classical in X-ray analysis of crystals. Its diffraction spots are produced by the continuous spectrum of incident X-rays, in which the changeable wavelength can fit in with the different hkl diffraction conditions.展开更多
Calculating interacting stress intensity factors(SIFs)of multiple ellipticalholes and cracks is very important for safety assessment,stop-hole optimization design and resource exploitation production in underground ro...Calculating interacting stress intensity factors(SIFs)of multiple ellipticalholes and cracks is very important for safety assessment,stop-hole optimization design and resource exploitation production in underground rock engineering,e.g.,buried tunnels,deep mining,geothermal and shale oil/gas exploitation by hydraulic fracturing technology,where both geo-stresses and surface stresses are applied on buried tunnels,horizontal wells and natural cracks.However,current literatures are focused mainly on study of interacting SIFs of multiple elliptical-holes(or circularholes)and cracks only under far-field stresses without consideration of arbitrary surface stresses.Recently,our group has proposed a new integral method to calculate interacting SIFs of multiple circular-holes and cracks subjected to far-filed and surface stresses.This new method will be developed to study the problem of multiple elliptical-hole and cracks subjected to both far-field and surface stresses.In this study,based on Cauchy integral theorem,the exact fundamental stress solutions of single elliptical-hole under arbitrarily concentrated surface normal and shear forces are derived to establish new integral equation formulations for calculating interacting SIFs of multiple elliptical-holes and cracks under both far-field and arbitrary surface stresses.The new method is proved to be valid by comparing our results of interacting SIFs with those obtained by Green’s function method,displacement discontinuity method,singular integral equation method,pseudo-dislocations method and finite element method.Computational examples of one elliptical-hole and one crack in an infinite elastic body are given to analyze influence of loads and geometries on interacting SIFs.Research results show that whenσ_(xx)^(∞)≥σ^(yy′)^(∞),there appears a neutral crack orientation angle b0(without elliptical-hole’s effect).Increasing s¥xx/s¥yy and b/a(close to circularhole)usually decreases b0 of KI and benefits to the layout of stop-holes.The surface compressive stresses applied onto elliptical-hole(n)and crack(p)have significant influence on interacting SIFs but almost no on b0.Increasing n and p usually results in increase of interacting SIFs and facilitates crack propagation and fracture networks.The elliptical-hole orientation angle(a)and holed-cracked distance(t)have great influence on the interacting SIFs while have little effect on b0.The present method is not only simple(without any singular parts),high-accurate(due to exact fundamental stress solutions)and wider applicable(under far-field stresses and arbitrarily distributed surface stress)than the common methods,but also has the potential for the anisotropic problem involving multiple holes and cracks.展开更多
本文基于衍射神经网络平台,探究经典修正线性单元(rectified linear unit, ReLU)及其衍生激活函数对光学神经网络(ONNs)推理能力的影响,阐明非线性函数与衍射神经网络结合方式与其学习能力的关联。结果显示,衍射网络训练适应性强,但不...本文基于衍射神经网络平台,探究经典修正线性单元(rectified linear unit, ReLU)及其衍生激活函数对光学神经网络(ONNs)推理能力的影响,阐明非线性函数与衍射神经网络结合方式与其学习能力的关联。结果显示,衍射网络训练适应性强,但不当的非线性函数可能降低其性能。例如,在5层网络中,在每层后添加RTReLU(rectified translational linear unit)因光强衰减导致在MNIST测试集上的分类准确率降至91.4%,低于纯线性网络的92.6%;而每层添加PReLU(parametric rectified linear unit)则保留阈值后信息,使准确率提升至95.8%。在3层网络中,因为较少的网络深度降低了光强的损耗,在每层后添加RTReLU后推理能力优于线性网络。进一步发现,在网络中适当位置添加单个ReLU激活函数可大幅提升性能,如5层网络仅最后一层添加RTReLU可达峰值准确率96.6%。展开更多
湖泊沉积物作为重要的环境演化记录载体,其矿物组合特征蕴含了丰富的古环境信息。然而,由于沉积物中晶质和非晶质组分的复杂共存关系,以及多相矿物体系的相互干扰效应,其精确定量分析一直是沉积学研究中的技术难点。该研究以西藏中部封...湖泊沉积物作为重要的环境演化记录载体,其矿物组合特征蕴含了丰富的古环境信息。然而,由于沉积物中晶质和非晶质组分的复杂共存关系,以及多相矿物体系的相互干扰效应,其精确定量分析一直是沉积学研究中的技术难点。该研究以西藏中部封闭咸水湖泊巴木错沉积物为研究对象,系统分析、评估了参比强度比(RIR)法和Rietveld全谱拟合法在复杂沉积物矿物定量分析中的可靠性和应用效果。文章采用高纯度刚玉作为内标物质,设计了1∶1、3∶7和1∶9三组不同配比的混合样品,通过X射线衍射(XRD)分析获取了完整的衍射数据。基于COD晶体结构数据库,分别采用RIR值法和Rietveld全谱拟合法进行定量计算,并结合非晶含量测定方法,构建了完整的矿物定量分析体系。研究结果表明,Rietveld全谱拟合法表现出优异的分析精度和稳定性:对于含量大于20%的主量相,相对标准偏差(RSD,Relative Standard Deviation)控制在3%以内;含量在5%~20%之间的次量相,RSD值保持在5%~10%范围内;即使对于含量低于5%的微量相,其定量结果也显著优于RIR值法。特别是在处理非均质样品时,Rietveld法表现出良好的适应性,各矿物相含量与混合比例呈现显著的线性相关性(R^(2)>0.95)。相比之下,RIR值法在高含量内标条件下(50%和30%)表现出显著的不稳定性,定量结果的相对偏差超出了SY/T5163-2018标准规定的允许范围。这种局限性主要源于其对单个衍射峰强度比值的过度依赖,易受样品基体效应和优势相干扰的影响。此外,通过非晶含量计算,获得了原始沉积物样品中约31%的非晶态物质含量,三组混合样品计算结果的高度一致性(RSD<3%)进一步验证了Rietveld法的可靠性。该研究不仅系统评估了两种定量方法的适用性,而且在复杂湖泊沉积物分析中首次实现了晶质矿物和非晶质组分的协同定量。研究结果对完善湖泊沉积物矿物定量分析方法,提高环境重建的准确性具有重要意义和应用价值。展开更多
Conventional periodic structures usually have nontunable refractive indices and thus lead to immutable photonic bandgaps. A periodic structure created in an ultracold atoms ensemble by externally controlled light can ...Conventional periodic structures usually have nontunable refractive indices and thus lead to immutable photonic bandgaps. A periodic structure created in an ultracold atoms ensemble by externally controlled light can overcome this disadvantage and enable lots of promising applications. Here, two novel types of optically induced square lattices, i.e., the amplitude and phase lattices, are proposed in an ultracold atoms ensemble by interfering four ordinary plane waves under different parameter conditions. We demonstrate that in the far-field regime, the atomic amplitude lattice with high transmissivity behaves similarly to an ideal pure sinusoidal amplitude lattice, whereas the atomic phase lattices capable of producing phase excursion across a weak probe beam along with high transmissivity remains equally ideal. Moreover, we identify that the quality of Talbot imaging about a phase lattice is greatly improved when compared with an amplitude lattice. Such an atomic lattice could find applications in alloptical switching at the few photons level and paves the way for imaging ultracold atoms or molecules both in the near-field and in the far-field with a nondestructive and lensless approach.展开更多
文摘A new method for quantitative phase analysis is proposed by using X-ray diffraction multi-peak match intensity ratio. This method can obtain the multi-peak match intensity ratio among each phase in the mixture sample by using all diffraction peak data in the mixture sample X-ray diffraction spectrum and combining the relative intensity distribution data of each phase standard peak in JCPDS card to carry on the least square method regression analysis. It is benefit to improve the precision of quantitative phase analysis that the given single line ratio which is usually adopted is taken the place of the multi-peak match intensity ratio and is used in X-ray diffraction quantitative phase analysis of the mixture sample. By analyzing four-group mixture sample, adopting multi-peak match intensity ratio and X-ray diffraction quantitative phase analysis principle of combining the adiabatic and matrix flushing method, it is tested that the experimental results are identical with theory.
基金Project supported by the National Key Research and Development Program of China (Grant Nos.2022YFF0709103,2022YFA1603601,2021YFF0601203,and 2021YFA1600703)the National Natural Science Foundation of China (Grant No.81430087)the Shanghai Pilot Program for Basic Research-Chinese Academy of Sciences,Shanghai Branch (Grant No.JCYJ-SHFY-2021-010)。
文摘Beam splitting is one of the main approaches to achieving x-ray ghost imaging, and the intensity correlation between diffraction beam and transmission beam will directly affect the imaging quality. In this paper, we investigate the intensity correlation between the split x-ray beams by Laue diffraction of stress-free crystal. The analysis based on the dynamical theory of x-ray diffraction indicates that the spatial resolution of diffraction image and transmission image are reduced due to the position shift of the exit beam. In the experimental setup, a stress-free crystal with a thickness of hundredmicrometers-level is used for beam splitting. The crystal is in a non-dispersive configuration equipped with a double-crystal monochromator to ensure that the dimension of the diffraction beam and transmission beam are consistent. A correlation coefficient of 0.92 is achieved experimentally and the high signal-to-noise ratio of the x-ray ghost imaging is anticipated.Results of this paper demonstrate that the developed beam splitter of Laue crystal has the potential in the efficient data acquisition of x-ray ghost imaging.
基金supported by the National Natural Science Foundation of China (Grant No. 60778048)
文摘Under the quadratic approximation of the Rytov＇s phase structure function, this paper derives the general closed-form expressions for the mean-squared width and the angular spread of partially coherent beams in turbulence. It finds that under a certain condition different types of partially coherent beams may have the same directionality as a fully coherent Gaussian beam in free space and also in atmospheric turbulence if the angular spread is chosen as the characteristic parameter of beam directionality. On the other hand, it shows that generally, the directionality of partially coherent beams expressed in terms of the angular spread is not consistent with that in terms of the normalized far-field average intensity distribution in free space, but the consistency can be achieved due to turbulence.
文摘A set of absorption curves was priorly prepared on transparent films to fit the background and peak intensities in continuous scanning X-ray stress measurement.It may be better to correct both background and absorption of pure diffraction intensity.Experimental results revealed this to be a reliable correction method.
文摘Line broadening in a diffraction intensity profile of powdered crystalline materials due to stacking fault has been characterized in terms of the zeroth, first, second, third, and fourth moments and the fourth cumulant. Calculations have been derived showing that the first moment causes a shift in the peak position of the profile while the third moment affects its shape. The intensity expression has been derived on the basis of usual Cartesian coordinates and also of polar coordinates indicated by the probability of the fault and the reciprocal lattice parameter as the two axes. The expressions for the fourth cumulant have also been so derived. Here we have used three different approaches to determine methods for calculating the fourth cumulant due to stacking faults. The three forms of the equations derived here are for different coordinate systems, but will arrive at the same answers.
文摘Laue method is classical in X-ray analysis of crystals. Its diffraction spots are produced by the continuous spectrum of incident X-rays, in which the changeable wavelength can fit in with the different hkl diffraction conditions.
基金supports by National Natural Science Foundation of China(Nos.51874351,51474251 and 12072309)Excellent Postdoctoral Innovative Talents Project of Hunan Province(No.2020RC2001).
文摘Calculating interacting stress intensity factors(SIFs)of multiple ellipticalholes and cracks is very important for safety assessment,stop-hole optimization design and resource exploitation production in underground rock engineering,e.g.,buried tunnels,deep mining,geothermal and shale oil/gas exploitation by hydraulic fracturing technology,where both geo-stresses and surface stresses are applied on buried tunnels,horizontal wells and natural cracks.However,current literatures are focused mainly on study of interacting SIFs of multiple elliptical-holes(or circularholes)and cracks only under far-field stresses without consideration of arbitrary surface stresses.Recently,our group has proposed a new integral method to calculate interacting SIFs of multiple circular-holes and cracks subjected to far-filed and surface stresses.This new method will be developed to study the problem of multiple elliptical-hole and cracks subjected to both far-field and surface stresses.In this study,based on Cauchy integral theorem,the exact fundamental stress solutions of single elliptical-hole under arbitrarily concentrated surface normal and shear forces are derived to establish new integral equation formulations for calculating interacting SIFs of multiple elliptical-holes and cracks under both far-field and arbitrary surface stresses.The new method is proved to be valid by comparing our results of interacting SIFs with those obtained by Green’s function method,displacement discontinuity method,singular integral equation method,pseudo-dislocations method and finite element method.Computational examples of one elliptical-hole and one crack in an infinite elastic body are given to analyze influence of loads and geometries on interacting SIFs.Research results show that whenσ_(xx)^(∞)≥σ^(yy′)^(∞),there appears a neutral crack orientation angle b0(without elliptical-hole’s effect).Increasing s¥xx/s¥yy and b/a(close to circularhole)usually decreases b0 of KI and benefits to the layout of stop-holes.The surface compressive stresses applied onto elliptical-hole(n)and crack(p)have significant influence on interacting SIFs but almost no on b0.Increasing n and p usually results in increase of interacting SIFs and facilitates crack propagation and fracture networks.The elliptical-hole orientation angle(a)and holed-cracked distance(t)have great influence on the interacting SIFs while have little effect on b0.The present method is not only simple(without any singular parts),high-accurate(due to exact fundamental stress solutions)and wider applicable(under far-field stresses and arbitrarily distributed surface stress)than the common methods,but also has the potential for the anisotropic problem involving multiple holes and cracks.
文摘本文基于衍射神经网络平台,探究经典修正线性单元(rectified linear unit, ReLU)及其衍生激活函数对光学神经网络(ONNs)推理能力的影响,阐明非线性函数与衍射神经网络结合方式与其学习能力的关联。结果显示,衍射网络训练适应性强,但不当的非线性函数可能降低其性能。例如,在5层网络中,在每层后添加RTReLU(rectified translational linear unit)因光强衰减导致在MNIST测试集上的分类准确率降至91.4%,低于纯线性网络的92.6%;而每层添加PReLU(parametric rectified linear unit)则保留阈值后信息,使准确率提升至95.8%。在3层网络中,因为较少的网络深度降低了光强的损耗,在每层后添加RTReLU后推理能力优于线性网络。进一步发现,在网络中适当位置添加单个ReLU激活函数可大幅提升性能,如5层网络仅最后一层添加RTReLU可达峰值准确率96.6%。
文摘湖泊沉积物作为重要的环境演化记录载体,其矿物组合特征蕴含了丰富的古环境信息。然而,由于沉积物中晶质和非晶质组分的复杂共存关系,以及多相矿物体系的相互干扰效应,其精确定量分析一直是沉积学研究中的技术难点。该研究以西藏中部封闭咸水湖泊巴木错沉积物为研究对象,系统分析、评估了参比强度比(RIR)法和Rietveld全谱拟合法在复杂沉积物矿物定量分析中的可靠性和应用效果。文章采用高纯度刚玉作为内标物质,设计了1∶1、3∶7和1∶9三组不同配比的混合样品,通过X射线衍射(XRD)分析获取了完整的衍射数据。基于COD晶体结构数据库,分别采用RIR值法和Rietveld全谱拟合法进行定量计算,并结合非晶含量测定方法,构建了完整的矿物定量分析体系。研究结果表明,Rietveld全谱拟合法表现出优异的分析精度和稳定性:对于含量大于20%的主量相,相对标准偏差(RSD,Relative Standard Deviation)控制在3%以内;含量在5%~20%之间的次量相,RSD值保持在5%~10%范围内;即使对于含量低于5%的微量相,其定量结果也显著优于RIR值法。特别是在处理非均质样品时,Rietveld法表现出良好的适应性,各矿物相含量与混合比例呈现显著的线性相关性(R^(2)>0.95)。相比之下,RIR值法在高含量内标条件下(50%和30%)表现出显著的不稳定性,定量结果的相对偏差超出了SY/T5163-2018标准规定的允许范围。这种局限性主要源于其对单个衍射峰强度比值的过度依赖,易受样品基体效应和优势相干扰的影响。此外,通过非晶含量计算,获得了原始沉积物样品中约31%的非晶态物质含量,三组混合样品计算结果的高度一致性(RSD<3%)进一步验证了Rietveld法的可靠性。该研究不仅系统评估了两种定量方法的适用性,而且在复杂湖泊沉积物分析中首次实现了晶质矿物和非晶质组分的协同定量。研究结果对完善湖泊沉积物矿物定量分析方法,提高环境重建的准确性具有重要意义和应用价值。
基金National Natural Science Foundation of China(NSFC)(61605155,61627812)Fundamental Research Funds for the Central Universities
文摘Conventional periodic structures usually have nontunable refractive indices and thus lead to immutable photonic bandgaps. A periodic structure created in an ultracold atoms ensemble by externally controlled light can overcome this disadvantage and enable lots of promising applications. Here, two novel types of optically induced square lattices, i.e., the amplitude and phase lattices, are proposed in an ultracold atoms ensemble by interfering four ordinary plane waves under different parameter conditions. We demonstrate that in the far-field regime, the atomic amplitude lattice with high transmissivity behaves similarly to an ideal pure sinusoidal amplitude lattice, whereas the atomic phase lattices capable of producing phase excursion across a weak probe beam along with high transmissivity remains equally ideal. Moreover, we identify that the quality of Talbot imaging about a phase lattice is greatly improved when compared with an amplitude lattice. Such an atomic lattice could find applications in alloptical switching at the few photons level and paves the way for imaging ultracold atoms or molecules both in the near-field and in the far-field with a nondestructive and lensless approach.
