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diffraction of plane SV waves by a cavity in poroelastic half-space

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Earthquake Engineering and Engineering Vibration 2009年第1期8卷 29-46页

作者： Liang Jianwen and Liu Zhongxian Department of Civil Engineering, Tianjin University, Tianjin 300072, China Professor PhD Candidate Department of Civil Engineering Tianjin University Tianjin 300072 China

This paper presents an indirect boundary integration equation method for diffraction of plane SV waves by a 2-D cavity in a poroelastic *** Green＇s functions of compressive and shear wave sources are derived based on Biot＇s theory. The scattered waves are constructed using fictitious wave sources close to the boundary of the cavity, and their magnitudes are determined by the boundary conditions. Verification of the accuracy is performed by：（1） checking the satisfaction extent of the boundary conditions, （2） comparing the degenerated solutions of a single-phased case with well- known solutions, and （3） examining the numerical stability of the solutions. The nature of diffraction of plane SV waves around a cavity in a poroelastic half-space is investigated by numerical examples.

关键词： poroelastic half-space cavity diffraction plane SV waves compressive wave source shear wave source Green's function pore pressure

diffraction properties of four-petal Gaussian beams in uniaxially anisotropic crystal

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Chinese Optics Letters 2008年第10期6卷 779-781页

作者：唐斌金铱蒋美萍江兴方 School of Mathematics and Physics Jiangsu Polytechnic UniversityChangzhou 213164

Propagation properties of polarized anisotropic crystals were investigated four-petal Gaussian beams along the optical axis of uniaxially Based on the paraxially vectorial theory of beam propagation analytic expressions of the diffraction light field larization properties of the diffracted four-petal were obtained. The effects of the anisotropy on the po- Gaussian beams have also been explained by numerical method. The results elucidate that the linear polarization state and the symmetry of the incident beams cannot be kept during propagation in anisotropic crystals.

关键词： Anisotropy Crystal symmetry Crystallography Crystals diffraction Fiber lasers Gaussian noise (electronic) Light Polarization Powders Trellis codes

diffraction separation by plane-wave prediction filtering

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Applied Geophysics 2017年第3期14卷 399-405,461页

作者：孔雪王德营李振春张瑞香胡秋媛中国石油大学胜利学院油气工程学院山东东营257061 山东科技大学地球科学与工程学院山东青岛266590 中国石油大学(华东)地球科学与技术学院山东青岛266555

Seismic data processing typically deals with seismic wave reflections and neglects wave diffraction that affect the resolution. As a general rule, wave diffractions are treated as noise in seismic data processing. However, wave diffractions generally originate from geological structures, such as fractures, karst caves, and faults. The wave diffraction energy is much weaker than that of the reflections. Therefore, even if wave diffractions can be traced back to their origin, their energy is masked by that of the reflections. Separating and imaging diffractions and reflections can improve the imaging accuracy of diffractive targets. Based on the geometrical differences between reflections and diffractions on the plane-wave record; that is, reflections are quasi-linear and diffractions are quasi-hyperbolic, we use plane-wave prediction fltering to separate the wave diffractions. First, we estimate the local slope of the seismic event using plane- wave destruction filtering and, then, we predict and extract the wave reflections based on the local slope. Thus, we obtain the diffracted wavefield by directly subtracting the reflected wavefield from the entire wavefield. Finally, we image the diffracted wavefield and obtain high-resolution diffractive target results. 2D SEG salt model data suggest that the plane-wave prediction filtering eliminates the phase reversal in the plane-wave destruction filtering and maintains the original wavefield phase, improving the accuracy of imaging heterogeneous objects.

关键词： Plane wave prediction filter separation diffraction

diffraction in chirped volume Bragg gratings

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Chinese Optics Letters 2015年第13期13卷 19-22页

作者：封建胜张翔吴登生吴尚袁孝 College of Physics Optoelectronics and Energy g~ Collaborative Innovation Center of Suzhou Nano Science and Technology Soochow University Suzhou 215006 China Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province & KeyLab of Modern Optical Technologies of Education Ministry of China Soochow University Suzhou 215006 China Research Center of Laser Fusion China Academy of Engineering Physics Mianyang 621900 China

We use fundamental matrix （F-matrix） method derived from coupled wave theory to simplify the diffraction simulation of chirped volume Bragg grating （CVBG） and it can be applied to arbitrary grating phase profiles. With the F-matrix method, we study the diffraction in CVBG. The spectral response of CVBG is a gate-like function, and the passband width of spectral response is related to the product of grating thickness and spatial chirp rate. The peak diffraction efficiency of CVBG increases monotonously as the amplitude of refractive index modulation increases. Incident beams with different wavelengths will be mainly diffracted at different depths of CVBG to match the Bragg condition.

关键词： 090.7330 Volume gratings 050.1590 Chirping 050.1940 diffraction

Analysis of retained austenite in TRIP590 steel by electron backscattered diffraction method

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Journal of Iron and Steel Research International 2020年第3期27卷 355-365页

作者： Yu-cheng Zhang Yang Meng Gui-bin Cui Hui-ping Jia Xin-hua Ju Zhong-hang Jiang Ze-jun Ma Bruker(Beijing)Scientific Technology Co. Ltd.Beijing 100192.China Research Institute of Technology Shougang Group Co.Ltd.Beijing 100043China

The retained austenite content in TRIP590 steel was first measured by X-ray diffraction(XRD)***,the effect of different test parameters(indexing rate,step size,field number,etc.)on the measured results of retained austenite content in TRIP590 steel by electron backscattered diffraction(EBSD)method was *** comparing the measured results between XRD and EBSD method,the optimal test parameters for the analysis of retained austenite content using EBSD were ***,the total content of retained austenite and the retained austenite contents with different aspect ratios in TRIP590 steel were analyzed,*** results showed that the test parameters have a great influence on the measured results of retained austenite content in TRIP590 *** order to improve the test accuracy,high indexing rates,small step sizes and more field number are necessary for the analysis of retained austenite content in TRIP590 steel by EBSD method.

关键词： TRIP590 steel Retained austenite Electron backscattered diffraction Indexing rate Step size

Correlation between crystal structure and mechanical performance of Cr-implanted 300M high-strength steel using X-ray diffraction method

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Journal of Iron and Steel Research International 2019年第10期26卷 1106-1116页

作者： Xiao-hu Chen Ping-ze Zhang Dong-bo Wei Xiao Huang Feng Ding Feng-kun Li Xian-jun Dai Zhang-zhong Wang College of Materials Science and Technology Nanjing University of Aeronautics and AstronauticsNanjing 211106JiangsuChina Ningbo Branch China Ordnance AcademyNingbo 315103ZhejiangChina Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology Nanjing 211167JiangsuChina Key Laboratory of Materials Preparation and Protection for Harsh Environment(Nanjing University of Aeronautics and Astronautics) Ministry of Industry and Information TechnologyNanjing 211106JiangsuChina Department of Mechanical and Aerospace Engineering Carleton UniversityOttawaON ONK1S5B6Canada

In order to study the influence of crystal structure change due to implantation dose on the hardness and wear performance of 300M high-strength steel,samples were surface modified by Cr implantation with dosages of 5.0 × 10^16,1.5 × 10^17 and 3.0 × 10^17 ions/cm^2.X-ray diffraction method,which was already applied in studies on the microstructure of deformed and heat-treated materials,was used to study the crystal structure of the implanted steel,and the results were corrected with the hardness and wear *** solid solution strengthening effect and microstructure vary with increase in implantation *** to strong solid solution hardening of Cr,small average crystallite size and high dislocation density,the hardness and wear resistance of implanted steel with dose of 5.0 × 10^16 ions/cm^2 were found to be the highest compared with other ***,although the crystal lite size of the implanted sample with dose of 3 × 10^17 ions/cm^2 was similar to that of substrate and the dislocation density was lower than that of the substrate,its higher hardness and lower specific wear rate were due to the solid solution hardening and perhaps Cr clusters reinforcement.

关键词： X-ray diffraction method Ion implantation Dislocation density Hardness Wear Crystal structure

Single-shot ultrafast multiplexed coherent diffraction imaging

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Photonics Research 2022年第8期10卷 1937-1946页

作者： YINGMING XU XINGCHEN PAN MINGYING SUN WENFENG LIU CHENG LIU JIANQIANG ZHU Key Laboratory of High Power Laser and Physics Shanghai Institute of Optics and Fine MechanicsChinese Academy of SciencesShanghai 201800China National Laboratory on High Power Laser and Physics China Academy of Engineering PhysicsChinese Academy of SciencesShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China

Classic interferometry was commonly adopted to realize ultrafast phase imaging using pulsed lasers;however, the reference beam required makes the optical structure of the imaging system very complex, and high temporal resolution was reached by sacrificing spatial resolution. This study presents a type of single-shot ultrafast multiplexed coherent diffraction imaging technique to realize ultrafast phase imaging with both high spatial and temporal resolutions using a simple optical setup, and temporal resolution of nanosecond to femtosecond scale can be realized using lasers of different pulse durations. This technique applies a multiplexed algorithm to avoid the data division in space domain or frequency domain and greatly improves the spatial resolution. The advantages of this proposed technique on both the simple optical structure and high image quality were demonstrated by imaging the generation and evaluating the laser-induced damage and accompanying phenomenon of laser filament and shock wave at a spatial resolution better than 6.96 μm and a temporal resolution better than 10 ns.

关键词： coherent resolution diffraction

Adaptively driven X-ray diffraction guided by machine learning for autonomous phase identification

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npj Computational Materials 2023年第1期9卷 2036-2043页

作者： Nathan J.Szymanski Christopher J.Bartel Yan Zeng Mouhamad Diallo Haegyeom Kim Gerbrand Ceder Department of Materials Science&Engineering UC BerkeleyBerkeleyCA 94720USA Materials Sciences Division Lawrence Berkeley National LaboratoryBerkeleyCA 94720USA

Machine learning(ML)has become a valuable tool to assist and improve materials characterization,enabling automated interpretation of experimental results with techniques such as X-ray diffraction(XRD)and electron *** ML models are fast once trained,there is a key opportunity to bring interpretation in-line with experiments and make on-the-fly decisions to achieve optimal measurement effectiveness,which creates broad opportunities for rapid learning and information extraction from ***,we demonstrate such a capability with the development of autonomous and adaptive *** coupling an ML algorithm with a physical diffractometer,this method integrates diffraction and analysis such that early experimental information is leveraged to steer measurements toward features that improve the confidence of a model trained to identify crystalline *** validate the effectiveness of an adaptive approach by showing that ML-driven XRD can accurately detect trace amounts of materials in multi-phase mixtures with short measurement *** improved speed of phase detection also enables in situ identification of short-lived intermediate phases formed during solid-state reactions using a standard in-house *** findings showcase the advantages of in-line ML for materials characterization and point to the possibility of more general approaches for adaptive experimentation.

关键词： phase diffraction autonomous

Scattering and diffraction of plane P-waves in a 2-D elastic half-space Ⅱ：shallow arbitrary shaped canyon

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Earthquake Engineering and Engineering Vibration 2017年第3期16卷 459-485页

作者： Heather P.Brandow Vincent Lee Civil and Environmental Engineering University of Southern California Los Angeles 90089 United States

Scattering and diffraction of elastic in-plane P-and SV-waves by a surface topography such as an elastic canyon at the surface of a half-space is a classical problem which has been studied by earthquake engineers and strong-motion seismologists for over forty years. The case of out-of-plane SH waves on the same elastic canyon that is semi-circular in shape on the half-space surface is the first such problem that was solved by analytic closed form solutions over forty years ago by Trifunac. The corresponding case of in-plane P-and SV-waves on the same circular canyon is a much more complicated problem because, the in-plane P-and SV-scattered waves have different wave speeds and together they must have zero normal and shear stresses at the half-space surface. It is not until recently in 2014 that analytic solution for such problem is found by the author in the work of Lee and Liu. This paper uses the technique of Lee and Liu of defining these stress-free scattered waves to solve the problem of the scattered and diffraction of these in-plane waves on an almost-circular surface canyon that is arbitrary in shape.

关键词： diffraction elastic P-waves SV-waves weighted-residual method arbitrary-shaped canyon