Surface profile measurement of low-frequency vibrating objects using temporal analysis of fringe pattern

A simple and accurate algorithm (phase scanning method) is proposed for 3D surface contouring and dynamic response determination of a vibrating object. A sinusoidal fringe pattern is projected onto a low-frequency vibrating object by a programmable liquid crystal display projector. The fringe patterns are captured by a high-speed CCD camera with a telecentric gauging lens. Phase values are evaluated point by point using phase scanning method. From the phase values of each point on the object, the contour of the specimen at different instants of vibration can be retrieved. In this paper, a small vibrating coin is used to demonstrate the validity of the method and the experimental results are compared with test results on a stationary coin using four-step phase shifting and fast Fourier transform methods. The technique is especially useful in applications where the vibrating object has a complicated shape.     

On Covariant Phase Space and the Variational Bicomplex

The notion of a phase space in classical mechanics is well known. The extension of this concept to field theory however, is a challenging endeavor, and over the years numerous proposals for such a generalization have appeared in the literature. In this paper We review a Hamiltonian formulation of Lagrangian field theory based on an extension to infinite dimensions of J.-M. Souriau's symplectic approach to mechanics. Following G. Zuckerman, we state our results in terms of the modern geometric theory of differential equations and the variational bicomplex. As an elementary example, we construct a phase space for the Monge–Ampere equation.     

斐索型光学合成孔径系统近轴成像条件研究

从几何光学理论出发，详细推导了斐索型光学合成孔径成像系统的近轴非相干成像条件，即子望远系统的角放大率等于系统的线性缩放因子。对于焦平面上的像点而言，合成孔径成像系统可等效为一个带有特殊形状孔径光阑的望远系统，这要求该孔径光栏的开口形状和位置分布与合成孔径成像系统各子系统孔径大小和位置分布相一致。我们由此得到了斐索型合成孔径成像系统的主要约束条件。     

高功率固体激光放大系统相位自校正方法研究

就光学元件间低频相位误差叠加提出用相关系数作为叠加相位结果的估计参量，并通过模拟计算和验证实验证明了相关系数能有效地对低频相位叠加结果进行比较估计，在此基础上就高功率固体激光放大系统中放大片的选取和安装提出了自校正方法并实现了自校正过程。     

激光水下扫描成像系统的图像修正机理

同步扫描系统可以克服后向散射，但同时也产生了两种非线性，一是扫描线速度的非线性，一是由于距离对光能衰减造成的非线性，两种非线性都需要修正，本文从原理上讨论水下激光成像时能量衰减的修正原理与修正方法，并给出仿真结果。     

Magnetic phases in Mn<Subscript>1</Subscript>_<Subscript>x</Subscript>Fe<Subscript>x</Subscript>WO<Subscript>4</Subscript> studied by neutron powder diffraction

The magnetic structures of Mn_1-xFe_xWO₄ with x = 0.0, 0.16, 0.21, 0.225, 0.232, 0.24, 0.27, 0.29, and 1.0 were refined from neutron powder diffraction data. The magnetic phase diagram could be completed in the coexistence range of different magnetic structures up to x = 0.29. For the magnetic state at 1.5 K a commensurate antiferromagnetic structure with a propagation vector = (±1/4, 1/2, 1/2) was found for x ⩽ 0.22 while the magnetic spins order with = (1/2, 0, 0) for x ≥ 0.22. In the latter phase, additionally, weak magnetic reflections indexed to an incommensurate ordering with = (- 0.214, 1/2, 0.457) occur in the diffraction pattern up to x = 0.29 indicating the occurence of a reentrant phase. For 0.12 ⩽ x ⩽ 0.29 the low temperature phases are separated from a magnetic high temperature phase showing only magnetic reflections indexed to a spin arrangement with = (1/2, 0, 0). The magnetic phase diagram is discussed qualitatively considering random superexchange between the statistically distributed Mn²⁺- and Fe²⁺-ions in the coexistence range 0.12 ⩽ x ⩽ 0.29 of different magnetic structures related to those of pure MnWO₄ and FeWO₄. Received 9 October 2002 Published online 14 March 2003     

高阶非线性时滞差分方程解的渐近性

研究如下的具强迫项的高阶非线性时滞差分方程△^my(n) u(n)l↑∑i=1 gi(y(n-τ))=v(n)其中，m≥1，u,v：N→R，gi：R→R且τ∈{0，1，2，3，…)，i=1，2，…，l，得到了使该方程的解具有某种渐近性态的充分条件。     

用数值方法分析微孔激光器出射光的近场特性

微孔激光器作为应用于近场光信息存储系统中的一种新型光源，它的出射光斑的近场特性对于近场光存储是十分重要的。针对纳米孔径运用角谱进行Fox-Li数值迭代，得到不同孔径微孔激光器的基模光强分布，然后运用二维非线性时域有限差分法分析微孔激光器出射端即微孔金属膜的近场光学性质，模拟计算了不同孔径和厚度的微孔金属膜的光强近场分布，从应用于近场光存储的角度，给出反映其近场光学特性的相关数据。发现由于TM模式下金属存在局域表面等离子增强效应，使得其出射强度比TE模式高一个数量级，从而更适于作为实际中近场光存储系统和原理试验的光学头。     

蓝光相变光盘的多层膜结构设计

为了使光盘获得优良的记录／读出性能并能够长期稳定地使用，必须优化设计相变光盘的多层膜结构。采用自行设计的模拟分析相变光盘读出过程设计软件，从光学角度出发模拟计算了蓝光(405nm)相变光盘的膜层结构，研究了多层膜系的反射率和反射率对比度等光学参量与各层膜厚度和槽深的关系。研究得出的最佳多层膜结构为：下介电层／记录层／上介电层／反射层的厚度对于台记录为100nm／10nm／25nm，／60nm，而对于槽记录则为140nm／15nm／30nm，／60nm，槽深为50nm。模拟计算结果对于将来高密度蓝光相变光盘的制备具有一定的指导意义。     

时间分辨红外发射光谱法对自由基反应的研究

在过去的 15年中 ,傅立叶变换红外发射光谱法广泛应用于研究气相自由基反应 .Sloan首先研究了O(1D)的反应 ,随后Leone和Hancock研究了O(3 P)的反应 .此后 ,孔繁敖和朱起鹤等研究了小自由基 ,包括CH、CH2 、CH3 、C2 H3 、C2 H5、C2 H、C3 H3 和C3 H5与O2 、NO、N2 O、NO2 等分子的反应。在红外光谱中观察到各个反应的初生产物和初步反应通道 ,和从头算的理论研究结合起来 ,这些反应的机理已基本弄清 .