Scattering of low-frequency pulsed sound signals from elastic cylindrical shells

A method and experimental setup intended for measuring the amplitude and phase of acoustic field in the near zone of a scatterer are described. The results of measuring the scattering characteristics of low-frequency sound signals scattered by elastic cylindrical shells are analyzed.     

Zone Plates for X-Ray Focusing (Review)

Various zone plates: amplitude, amplitude-phase, and phase ones (including Fresnel and Gabor zone plates, Laue- and Bragg-Fresnel lenses, photon sieves, and aperiodic zone plates), as well as their properties and X-ray focusing possibilities, are described and analyzed.     

Measurement of geometrical dispersion in a sound beam

A method for measuring the geometrical dispersion caused by diffraction processes in sound beams is considered. The experimental setup is described, and the results of measuring the longitudinal distributions of both the additional shift of the phase invariant of a three-frequency wave and the dispersion parameter are presented. The local character of the geometrical dispersion, which manifests itself within the near-field zone of the beam, is revealed, and the presence of two different mechanisms underlying its nonuniform spatial distribution is pointed out.     

相位波带片的分辨本领

提出了相位波带片的傍轴衍射计算式，并且运用图解法求得相位波带片的分辨本领。研究结果表明，两种相位波带片的分辨本领彼此不同，并且与它们的直径和参数η有关。当η较小且直径较大时，两种相位波带片的分辨本领相互接近，并接近于相同直径透镜的分辨本领。     

光折变相位型波带片

利用成象方法和光折变效应,在LiNbO₃:Fe晶体中成功地写入了光折变相位型波带片.其衍射效率可达到21%.该制作方法具有实时、简便等优点.在集成光学和光学信息处理中具有重要的应用前景.     

Solute redistribution profiles during rapid solidification of undercooled ternary Co-Cu-Pb alloy

The solute redistribution and phase separation of liquid ternary Co-35%Cu-32.5%Pb immiscible alloy have been investigated using glass fluxing method. A bulk undercooling of 125 K was achieved and the macrosegregation pattern was characterized by a top Co-rich zone and a bottom Cu-rich zone. The average solute contents of the two separated zones decreased with the increase of undercooling, except for the solute Pb in Cu-rich zone. With the enhancement of undercooling, a morphological transition from dendrites into equaxied grains occurred to the primary α(Co) phase in Co-rich zone. The solute redistribution of Cu in primary α(Co) phase was found to depend upon both the undercooling and composition of Co-rich zone. Stokes migration is shown to be the main dynamic mechanism of droplet movement during liquid phase separation.     

球体糊状区相变问题双倒易边界元法求解

本文分析了球型微粒含有糊状区的固液相变问题,根据实验数据拟合了相变过程的定压比热和固相质量分数,并用轴对称双倒易边界元方法计算了球体的融化过程。在满足集总参数法使用条件下,验证了其求解过程的正确性,为求解该类糊状区相变问题提供一高效快速的求解方法。     

Absolute interferometric test of Fresnel zone plates

An absolute interferometric test of two-level binary Fresnel zone plates (FZPs) is presented. Five measurements with a wavefront testing interferometer are required to fully separate interferometer errors from those of the FZP. The method provides both errors, pattern errors and surface figure errors of the zone plate absolutely. The test method is suitable for zone mirrors and zone lenses. Test setups are explained, equations are derived and experimental results are presented. Further, applications of the absolute diffractive test method are described. For the estimation of the accuracy of the diffractive calibration method a comparison with the classical three-position test was carried out.     

连续相位变化毫米波衍射天线

基于菲涅尔原理及卡塞格伦天线设计方法,设计了一种口面直径为200 mm的卡赛格伦菲涅耳相位修正平面天线。天线采用连续相位修正方式,由一组同心菲涅耳相位修正圆环组成,与传统卡赛格伦抛物面天线相比,该天线具有平面化结构,大大减小了天线自身重量,天线辐射性能较离散相位衍射天线有大幅度提高。在95 GHz频率下,采用物理光学法进行仿真计算,并采用近场扫描系统进行了天线性能测试,天线3 dB波束宽度分别为0.95及1.05,天线实测增益为44.1 dB,天线口面效率为65%。     

Lattice dynamics and the phase transition from the cubic phase to the tetragonal phase in the LaMnO<Subscript>3</Subscript> crystal within the polarizable-ion model

The paper reports on the results of ab initio calculations of the static and dynamic properties of the LaMnO₃ crystal with a perovskite structure in the cubic, rhombohedral, and orthorhombic phases. The calculations are performed within the ionic crystal model, which takes into account the deformability and polarizability of the ions. It is revealed that the spectrum of lattice vibrations in the cubic phase contains unstable vibrational modes, which occupy the phase space in the entire Brillouin zone. The eigenvectors of the softest mode at the boundary point R of the Brillouin zone are associated with the displacements of the oxygen ions and correspond to the “rotation” of the MnO₆ octahedron. The condensation of one, two, and three components of this mode leads to the tetragonal, orthorhombic, and rhombohedral distortions of the structure. The structural phase transition is described in terms of the local mode approximation with the use of the double perovskite unit cell, in which the MnO₆ octahedron is explicitly separated. The parameters of the model Hamiltonian are determined. The static properties are investigated by the Monte Carlo method. The calculated temperature of the phase transition from the cubic phase (9800 K) is considerably higher than the melting temperature of the crystal under investigation. The calculated frequencies of long-wavelength lattice vibrations in the experimentally observed orthorhombic and rhombohedral phases are in reasonable agreement with experimental data.     

Half analytical method with application to the high order Laue zone effects in monoclinic and triclinic crystals

The simulation of the high order Laue zone (HOLZ) diffractions of monoclinic and triclinic crystals is a very complicated problem. The conventional multislice (MS) method suffers from the problem of infinity of the phase grating size. To avoid the difficulty of the infinity, Chen et al. arranged the phase grating plane along the ab plane of the crystal lattice. In this paper we introduce a new method which allows the incident and exit wavefunction planes perpendicular to the zone axis without the difficulty of infinity. We name the method half analytical method. The results calculated by half analytical method are in good agreement with those calculated by the conventional MS method.     

HyPAM: A hybrid continuum-particle model for incompressible free-surface flows

Three major issues associated with numerical simulations of complex free-surface flows, viz. interface tracking, fragmentation and large physical jumps, are addressed by a new hybrid continuum-particle model (HyPAM). The new model consists of three parts: (1) the Polygonal Area Mapping method [Q. Zhang, P.L.-F. Liu, A new interface tracking method: the polygonal area mapping method, J. Comput. Phys. 227(8) (2008) 4063-4088]; (2) a new algorithm that decomposes the interested (water) phase into a continuum zone, a buffer zone and a particle zone, based on material topology and graph theory; (3) a ‘passive-response’ assumption, in which the air phase is assumed to respond passively to the continuum part of the water phase. The incompressible inviscid Euler equations and the equations describing the free fall of rigid bodies are used as the governing equations for the continuum-buffer zone and the particle zone, respectively, and separately. A number of examples, including water droplet impact, solitary wave propagation, and dam-break problems, are simulated for the illustration and validation of HyPAM. It is shown that HyPAM is more accurate and versatile than a continuum-based Volume-of-Fluid model. One major contribution of this work is the single-phase decomposition algorithm, useful for many other hybrid formulations. Neglecting surface tension, viscosity and particle interactions, HyPAM is currently limited to mildly-fragmented free-surface flows with high Reynolds and Weber numbers.     

Molecular shield of “OKA-T” spacecraft

Here, we present the results of computational studies of gas parameters in the high rarefaction zone formed behind a molecular shield mounted on the OKA-T spacecraft. The method of accounting for the effect of solar cell rotation on the rarefaction zone is described. The influence of jets of on-site engines and gas emission of the apparatus on the rarefaction zone has been estimated.     

基于相位载波复用的光纤周界安防系统及其实现方法

提出一种利用相位载波的调制解调技术实现白光干涉系统复用的周界安防新方法.该系统在单芯反馈式白光干涉系统的若干感应端,分别串接工作在不同频率的相位调制器.首先利用相位调制技术,将不同干涉子系统的感应端的触发信号从频域上分开|再使用相位解调技术,从同一干涉系统输出信号中获得相应于不同感应端的独立时域信号.实验中通过布设在现场的传感光纤对区域环境振动实现实时记录,用白光干涉方法实现振动信号的提取,利用相位载波复用实现不同区域的定位.理论分析和测试结果表明:通过相位载波复用技术,实现不同传感端共用一套干涉系统的方法,可以显著减小周界安防系统的复杂程度,降低系统成本|该方法能对环境触发信号进行实时监控,并能快速,有效地确定扰动信号的所属区域,具有较高的灵敏度,有利于在大区域,长距离的监控领域获得实施.     

Novel Design of Sagnac Interferometry Assisted with Surface Plasmon Resonance Based Sensor Technique

In this work, we demonstrate a novel design to investigate interfacial reaction of optical activity materials, utilizing a Sagnac interferometer assisted with surface plasmon resonance based sensor technique. Upon application to interrogate optical activity, the type-2 optical configuration of close loop in this work can entirely encircle the interaction zone of surface plasmon resonance reacting with optical activity medium, while the type-1 optical configuration of close loop does partially. The greater the geometrical phase owing to the encircled interaction zone between optical activity medium and polarized light, the larger the phase shift of interference pattern modulated by the concentration of optical activity medium. The slope of phase shift in interference phase pattern of p-wave vs. concentration of dextrose solution determined with this method is greatly improved, 3000 times better than that with Lee's method, 18,600 times with Lin's method, and 222,000 times with Chou's method. Besides, the pinch point of phase shift vs. concentration indicates the ending of interference pattern phase shift as the concentration of each tested optical activity medium keeps climbing up, and can reflect the strong dependence of molecular shape during interfacial adsorption.     

Apparently complex high-pressure phase of gallium as a simple modulated structure

The phase of gallium GaII, with symmetry C222(1) and 104 atoms per unit cell, has been recently reported as an example of structural complexity under high pressure. It is shown here that this phase is a simple modulated distortion of an average structure of Fddd symmetry with all atoms structurally equivalent. The modulation can be described with only 4 parameters and satisfies symmetry properties described by a centrosymmetric superspace group. The structural distortion is dominated by a frozen transversal mode associated with a single irreducible representation of Fddd, with a wave vector on the line Q, at an edge of the Brillouin zone. The average structure can be related with an hcp configuration through simple sliding of hcp layers, reminiscent of the hcp-bcc Bürgers mechanism.     

球面波的相奇异分布区域特征

从波动方程出发，在基尔霍夫边界条件下，根据积分的物理意义，简明地研究了发散和汇聚球面波的相奇异区域分布。结果表明，除了汇聚的球面波焦点区域存在相奇异现象外，焦点以外的区域及对发散的球面波同样存在相奇异现象。发散球面波的相奇异区位于入射空间，在相奇异区域的不同部分相奇异规律不同，源点是相奇异区里的一个特殊点。汇聚的球面波的相奇异区域存在于像空间，结构简单，焦点是相奇异区域里的一个特殊点。     

Glow discharge as a heat source for surface and floating zone melting

A method of heating, making use of the thermal effect on a glow discharge cathode for surface and floating zone melting, is described.     

二元微透镜的位相平衡设计及叠加积分衍射分析

本文用位相平衡设计法设计了优化的二元光学微透镜，这是对Ｄａｍｍａｎｎ阶梯波带片设计方法的一种改进。文中用叠加积分作了二元微透镜的衍射分析，并与Ｄａｍｍａｎｎ法作了比较，计算结果说明本方法的衍射效率及象质都优于Ｄａｍｍａｎｎ法。且能设计更大相对口径（Ｄ／ｆ）。具有任意物象距的二元微透镜。     

Phase zone photon sieve

A novel diffractive optical element, named phase zone photon sieve (PZPS), is presented. There are three kinds of phase plates in PZPSs: PZPS1, PZPS2, and PZPS3. Each of the PZPSs has its own structure and is made on quartz substrate by etching. The three PZPSs have stronger diffraction peak intensity than a photon sieve (PS) when the margin pinhole and zone line width are kept the same. The PZPS3 can produce a smaller central diffractive spot than the ordinary PS with the same number of zones on the Fresnel zone plate. We have given the design method for and the simulation of PZPS and PS. PZPS has potential applications in optical maskless lithography.