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The spectral combination characteristic of grating and the bi-grating diffraction imaging effect

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Science China(Physics,Mechanics & Astronomy) 2007年第1期50卷 1-5页

作者： ZHANG WeiPing HE XiaoRong College of Physics Science and Technology Guangxi UniversityNanning 530004China

This paper reports on a new property of grating, namely spectral combination, and on bi-grating diffraction imaging that is based on spectral combination. The spectral combination characteristic of a grating is the capability of combining multiple light beams of different wavelengths incident from specific angles into a single beam. The bi-grating diffraction imaging is the formation of the image of an object with two gratings: the first grating disperses the multi-color light beams from the object and the second combines the dispersed light beams to form the image. We gave the conditions necessary for obtaining the spectral combination. We also presented the equations that relate the two gratings’ spatial frequencies, diffraction orders and positions necessary for obtaining the bi-grating diffraction imaging.

关键词： spectral combination bi-grating imaging diffraction imaging

EXPERIMENT TECHNIQUE RESEARCH OF SINGLE CRYSTAL X-RAY diffraction UNDER HIGH PRESSURE

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Science China Chemistry 1990年第8期33卷 920-928页

作者：樊玉国于景生孟悦徐义秋邹广田 Institute of Theoretical Chemistry Jilin University Jilin 130023 PRC Institute of Atomic and Molecular Physics Jilin University Jilin 130023 PRC

We have set up the high pressure device used for single crystal X-ray diffraction, determined the X-ray absorption curve of the device on Nicolet four-circle diffractometer, established the data collection programme of a fixed φ scheme, and corrected the offsets of the optical centering of the crystal by using a reflection which is measured in eight different orientations. The mixture ratio of methanol: ethanol: water 16: 3: 1 was used as a pressure medium, high pressure calibration was based on the wavelength shift of the R_1 fluorescence line of ruby, and the pressure of 100 kbar was obtained.

关键词： high pressure diffraction different orientations reciprocal space

Water Wave Refraction and diffraction over Frictional Topography

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China Ocean Engineering 1993年第1期8卷 73-84页

作者： Zuo, Qihua Yao, Guoquan Ding, Bingcan Nanjing Hydraulic Research Inst Nanjing China

This paper considers the effect of wave energy dissipation induced by sea-bottom friction on the computational results of water wave refraction and diffraction with the parabolic equation method. The presented results show that the friction factor formula adopted in this paper is of higher numerical accuracy than that introduced by Dalrymphe (1984), and it can be used to compute wave propagation over large open areas.

关键词： diffraction Energy dissipation Friction Numerical methods Refraction Wave propagation

Gaussian Beam Summation for diffraction in Inhomogeneous Media Based on the Grid Based Particle Method

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Communications in Computational Physics 2010年第9期8卷 758-796页

作者： Shingyu Leung Hongkai Zhao Department of Mathematics Hong Kong University of Science and TechnologyClear Water BayHong Kong Department of Mathematics University of California at IrvineIrvineCA 92697-3875USA

We develop an efficient numerical method to compute single slit or double slit diffraction patterns from high frequency wave in inhomogeneous *** approximate the high frequency asymptotic solution to the Helmholtz equation using the Eulerian Gaussian beam summation proposed in[20,21].The emitted rays from a slit are embedded in the phase space using an open *** evolution of this open curve is accurately computed using the recently developed Grid Based Particle Method[24]which results in a very efficient computational *** the grid based particle method we proposed in[23,24],we represent the open curve or the open surface by meshless Lagrangian particles sampled according to an underlying fixed Eulerian *** end-points of the open curve are tracked explicitly and consistently with interior *** construct the overall wavefield,each of these sampling particles also carry necessary quantities that are obtained by solving advection-reaction *** experiments show that the resulting method can model diffraction patterns in inhomogeneous media accurately,even in the occurrence of caustics.

关键词： Dynamic interface Gaussian beams diffraction high frequency asymptotic solution

Stable solutions of the least square equation in determination of lattice parameters from pairs of X-ray diffraction lines

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维普期刊数据库

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Chinese Science Bulletin 1996年第15期41卷 1303-1308页

作者：郭常霖黄月鸿 Shanghai Institute of Ceramics Chinese Academy of Sciences Shanghai 200050 China

The pair-line method for precise determination of the lattice parameter has more advantages than the routine methods in measuring absolute angle of lines. The experiment of the pair-line method by measuring the difference of angle δij between two angles θi and θj of diffraction lines is rather simple and convenient technically and is easy to obtain the accurate results and eliminate the systematic errors. Moreover, the precision requirement is not high for the X-ray apparatus and the measuring device.

关键词： X-ray diffraction pair-line method lattice parameters stable solution least square equation.

INCREMENTAL EDGE WAVE diffraction COEFFICIENTS A NEW METHOD FOR ANALYZING HIGH-FREQUENCY EDGE diffraction

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Science China Mathematics 1991年第3期34卷 366-375页

作者：阮成礼李江 Institute of Applied Physics University of Electronic Science and Technology of China Chengdu 610054 PRC

Explicit closed-form expressions for the incremental edge wave diffraction coefficients(IEWDC) are derived for an arbitrary local wedge angle and arbitrary directions of illumi-nation and observation, by using the canonical wedge solution and performing the asymptoticendpoint evaluation of the edge wave current radiation integral over the wedge *** include the second-order diffraction terms of the first-order edge wave current. Thecomputationally intractable surface radiation integral for the edge wave current over ascatterer is reduced to a contour "radiation" integral for the IEWDC along the edge of thisscatterer. Thereby, the method of IEWDC is established as a practically applicable theoryof the high-frequency diffraction by edges. This theory is illustrated by applying it to theevaluation of the radar cross section (RCS) from a perfectly conducting plate. The agreementbetween the theory and experiment is shown to be better, as compared with previous calcu-lations.

关键词： electromagnetic wave edge diffraction electromagnetic scatteting radar cross section.

A New Combination Facility for Testing Refraction, diffraction and Interaction of Shock Waves

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Science China Mathematics 1994年第8期37卷 954-959页

作者：杨基明韩肇元尹协振 Department of Modern Mechanics University of Science and Technology of China Hefei 230026 PRC

In this paper, a new facility is introduced, which is the combination of a shock tunnel and a shock tube. Experiments on refraction of a moving shock at a slip-surface, diffraction of a moving shock around a corner under the condition of a uniform flow ahead of the shock, and interaction of a moving shock with a bow shock attached to a testing model were conducted in the combinated facility and some new phenomena were observed.

关键词： shock tube shock tunnel shock refraction shock diffraction shock interaction.

diffraction of plane P waves around an alluvial valley in poroelastic half-space

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Earthquake Science 2010年第1期23卷 35-43页

作者： Zhongxian Liu Jianwen Liang Department of Civil Engineering Tianjin University Tianjin 300072 China

diffraction of plane P waves around an alluvial valley of arbitrary shape in poroelastic half-space is investigated by using an indirect boundary integral equation method. Based on the Green＇s fimctions of line source in poroelastic half-space, the scattered waves are constructed using the fictitious wave sources close to the interface of the valley and the density of ficti- tious wave sources are determined by boundary conditions. The precision of the method is verified by the satisfaction extent of boundary conditions, and the comparison between the degenerated solutions and available results in single-phase case. Finally, the nature of diffraction of plane P waves around an alluvial valley in poroelastic half-space is investigated in detail through nu- merical examples.

关键词： diffraction plane P waves alluvial valley poroelastic half-space indirect boundary integration equation method

Effects of spectral linewidth of ultrashort pulses on the spa-tiotemporal distribution of diffraction fields

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Chinese Science Bulletin 2001年第11期46卷 901-904页

作者： Jingzhou Xu Li Wang Guozhen Yang Chinese Acad Sci Lab Opt Phys Inst Phys Beijing 100080 Peoples R China

The spatiotemporal characteristics of electromagnetic pulses with ultrabroad spectral bandwidth in the far field are analyzed by using classical scalar diffraction theory. The effects of the ratio of the frequency width to the central frequency on the diffraction spatial distribution are discussed. It is concluded that the diffraction spatial distribution of the pulsed radiation gets narrower than a monochromatic wave when the frequency width of the pulse is comparable to or larger than its central frequency.

关键词： pulse propagation diffraction ultrabroad frequency bandwidth THz radiation.