Accuracy analysis of parallel plate interferometer for angular displacement measurement

The measurement accuracy of a parallel-plate interferometer for angular displacement measurement is analyzed. The measurement accuracy of angular displacement is not only related to the accuracy of phase extraction, but also related to initial incident angle, refraction index and thickness of plane-parallel plate as well as wavelength's stability of laser diode, etc. Theoretical analysis and computer simulation show that the measurement error of the angular displacement bears a minimum value when choosing an optimal initial incident angle in a large range. These analytical results serve as a guide in practical measurement. In this interferometer, reducing the refraction index or increasing the thickness of the parallel plate can improve the measurement accuracy; and the relative error of the phase measurement is 3.0 x 10(-4) corresponding to 1 degrees C temperature variation. Based on these theoretical and experimental results, the measurement accuracy of the parallel-plate interferometer is up to an order of 10(-8) rad. (c) 2007 Elsevier Ltd. All rights reserved.

Numerical Analyses of Transonic Fluid/Structure interaction in Aircraft Engineering

Through the coupling between aerodynamic and structural governing equations, a fully implicit multiblock aeroelastic solver was developed for transonic fluid/stricture interaction. The Navier-Stokes fluid equations are solved based on LU-SGS (lower-upper symmetric Gauss-Seidel) Time-marching subiteration scheme and HLLEW (Harten-Lax-van Leer-Einfeldt-Wada) spacing discretization scheme and the same subiteration formulation is applied directly to the structural equations of motion in generalized coordinates. Transfinite interpolation (TFI) is used for the grid deformation of blocks neighboring the flexible surfaces. The infinite plate spline (IPS) and the principal of virtual work are utilized for the data transformation between fluid and structure. The developed code was fort validated through the comparison of experimental and computational results for the AGARD 445.6 standard aeroelastic wing. In the subsonic and transonic range, the calculated flutter speeds and frequencies agree well with experimental data, however, in the supersonic range, the present calculation overpredicts the experimental flutter points similar to other computations. Then the flutter character of a complete aircraft configuration is analyzed through the calculation of the change of structural stiffness. Finally, the phenomenon of aileron buzz is simulated for the weakened model of a supersonic transport wing/body model at Mach numbers of 0.98 and l.05. The calculated unsteady flow shows, on the upper surface, the shock wave becomes stronger as the aileron deflects downward, and the flow behaves just contrary on the lower surface of the wing. Corresponding to general theoretical analysis, the flow instability referred to as aileron buzz is induced by a stronger shock alternately moving on the upper and lower surfaces of wing. For the rigid structural model, the flow is stable at all calculated Mach numbers as observed in experiment

A Breakdown Criterion of Free Molecular Flows and an Optimum Analysis of EBPVD

Two important issues in electron beam physical vapor deposition (EBPVD) are addressed. The first issue is a validity condition of the classical cosine law widely used in the engineering context. This requires a breakdown criterion of the free molecular assumption on which the cosine law is established. Using the analytical solution of free molecular effusion flow, the number of collisions (N-c) for a particle moving from an evaporative source to a substrate is estimated that is proven inversely proportional to the local Knudsen number at the evaporation surface. N-c = 1 is adopted as a breakdown criterion of the free molecular assumption, and it is verified by experimental data and DSMC results. The second issue is how to realize the uniform distributions of thickness and component over a large-area thin film. Our analysis shows that at relatively low evaporation rates the goal is easy achieved through arranging the evaporative source positions properly and rotating the substrate.

A new method to analyse the Peierls-Nabarro model of an edge dislocation in a rectangular plate

A new method is presented here to analyse the Peierls-Nabarro model of an edge dislocation in a rectangular plate. The analysis is based on the superposition scheme and series expansions of complex potentials. The stress field and dislocation density field on the slip plane can be expressed as the first and the second Chebyshev polynomial series respectively. Two sets of governing equations are obtained on the slip plane and outer boundary of the rectangular plate respectively. Three numerical methods are used to solve the governing equations.

Stress analysis of ZrO2/SiO2 multilayers deposited on different substrates with different thickness periods

The effects of repeating thickness periods on stress are studied in ZrO2/SiO2 multilayers deposited by electron-beam evaporation on BK7 glass and fused-silica substrates. The results show that the residual stress is compressive and decreases with an increase of the periods of repeating thickness in the ZrO2/SiO2 multilayers. At the same time, the residual stress in multilayers deposited on BK7 glass is less than that of samples deposited on fused silica. The variation of the microstructure examined by x-ray diffraction shows that microscopic deformation does not correspond to macroscopic stress, which may be due to variation of the interface stress. (c) 2005 Optical Society of America.

Transonic Aeroelastic Numerical Simulation in Aeronautical Engineering

A lower-upper symmetric Gauss-Seidel (LU-SGS) subiteration scheme is constructed for time-marching of the fluid equations. The Harten-Lax-van Leer-Einfeldt-Wada (HLLEW) scheme is used for the spatial discretization. The same subiteration formulation is applied directly to the structural equations of motion in generalized coordinates. Through subiteration between the fluid and structural equations, a fully implicit aeroelastic solver is obtained for the numerical simulation of fluid/structure interaction. To improve the ability for application to complex configurations, a multiblock grid is used for the flow field calculation and transfinite interpolation (TFI) is employed for the adaptive moving grid deformation. The infinite plate spline (IPS) and the principal of virtual work are utilized for the data transformation between the fluid and structure. The developed code was first validated through the comparison of experimental and computational results for the AGARD 445.6 standard aeroelastic wing. Then, the flutter character of a tail wing with control surface was analyzed. Finally, flutter boundaries of a complex aircraft configuration were predicted.

Electrothermal stress in conductive body with collinear cracks

The temperature and stress field in a thin plate with collinear cracks interrupting an electric current field are determined. This is accomplished by using a complex function method that allows a direct means of finding the distribution of the electric current, the temperature and stress field. Temperature dependency for the heat-transfer coefficient, coefficient of linear expansion and the elastic modulus are considered. As an example, temperature distribution is calculated for an alloy (No. GH2132) plate with two collinear cracks under high temperature. Relationships between the stress, temperature, electric density and crack length are obtained. Crack trajectories emanating from existing crack are predicted by application of the strain energy density criterion which can also be used for finding the load carrying capacity of the cracked plate. (C) 2003 Elsevier Ltd. All rights reserved.

多裂纹导电薄板电热温度场和应力场的计算

讨论了对带有n个共线裂纹的薄板，在无穷远处加载电流实施止裂时板内的温度场和应力场。文中利用了复变函数的方法计算得到了电流场、温度场和应力场的分布状态。计算中考虑了材料热传导系数、线胀系数、弹性模量随温度的变化。作为算例，以带有两个共线裂纹、牌号为GH2132的高温合金制成的薄板进行了计算，给出了应力、温度与加载的电流密度及裂纹尺寸的关系；分析了导热系数随温度的变化对温度场数值的影响。

Transonic Aeroelastic Numerical Simulation in Aeronautical Engineering

A lower-upper symmetric Gauss-Seidel (LU-SGS) subiteration scheme is constructed for time-marching of the fluid equations. The Harten-Lax-van Leer-Einfeldt-Wada (HLLEW) scheme is used for the spatial discretization. The same subiteration formulation is applied directly to the structural equations of motion in generalized coordinates. Through subiteration between the fluid and structural equations, a fully implicit aeroelastic solver is obtained for the numerical simulation of fluid/structure interaction. To improve the ability for application to complex configurations, a multiblock grid is used for the flow field calculation and transfinite interpolation (TFI) is employed for the adaptive moving grid deformation. The infinite plate spline (IPS) and the principal of virtual work are utilized for the data transformation between the fluid and structure. The developed code was first validated through the comparison of experimental and computational results for the AGARD 445.6 standard aeroelastic wing. Then, the flutter character of a tail wing with control surface was analyzed. Finally, flutter boundaries of a complex aircraft configuration were predicted.

热致NiOx薄膜的结构和光学性质变化

利用直流磁控反应溅射技术制备了氧气和氩气的分压比为5:100的NiOx薄膜。利用X射线衍射仪(XRD)、扫描电镜(SEM)、原子力显微镜(AFM)和光谱仪研究了热处理对薄膜的微观结构和光学性质的影响, 并对沉积态薄膜的粉末进行了热分析。沉积态的NiOx薄膜在262 ℃时开始分解, 导致NiOx薄膜的透过率增加和反射率降低。X射线衍射和示差扫描量热曲线(DSC)分析表明, 在热处理过程中并无物相的变化, 光学性质的变化是由于NiOx薄膜热分解引起薄膜表面形貌发生变化而引起的。通过Kissinger公式计算出

SiO_2薄膜折射率的准确拟合分析

精确的光学常数对于设计和制备高品质的光学薄膜非常重要,尤其是那些光学性能对折射率变化敏感的薄膜。SiO_2是一种常用的低折射率材料,因与常用基底折射率相近使其准确拟合有一定难度。实验通过离子束溅射制备了SiO_2单层膜。考虑测量时的误差和基底折射率的影响,采用透射率包络和反射率包络得到了SiO_2的折射率,并用所得折射率进行反演来对这两种途径在实际测量拟合过程中的准确性进行比对。分析表明,剩余反射率在实际的测量过程中误差更小,直接用测量镀膜前后基片的剩余反射率值可以更简便更准确地得到SiO_2的折射率,能达到10~(-2)的精度。

Analytical applications of the electrochemiluminescence of tris (2.2 '-bipyridyl) ruthenium and its derivatives

This article presents the state of the art of analytical applications of the electrochemiluminescence (ECL) of tris (2,2'-bipyridyl) ruthenium (Ru(bpy)(3)(2+)) and its derivatives. in the last seven years, Ru(bpy)(3)(2+) ECL has attracted much interest from analysts and been successfully exploited as a detector of flow injection analysis (FIA), high-performance liquid chromatography (HPLC), capillary electrophoresis (CE), and micro total analysis systems (TAS). Immobilization of Ru(bPY)(3)(2+) on a solid surface provides several advantages over the solution-phase ECL procedure, such as the simplicity of experimental design and cost-effectiveness. After a brief discussion of the mechanism of Ru(bpy)(3)(2+) ECL, we discuss its applications in FIA, HPLC, CE and TAS and give special attention to the design of Ru(bpy)(3)(2+) ECL cells and some immobilization techniques of Ru(bpy)(3)(2+); we focus on papers published after 1997.

利用重力与地形数据探讨我国大陆若干地区岩石圈有效弹性厚度

The lithosphere behaves as an elastic thin plate overlying a weak fluid. When loaded by topography, it deflects to compensate the topography and isostasy is achieved. The response of the plate is often characterized by the flexural rigidity, or equivalently, by the effective elastic thickness(EET). The relationships between gravity and topography have commonly been employed to investigate quantitively the isostatic compensation of the lithosphere. Cross-spectral techniques have been developed to estimate the admittance and coherence between gravity and topography. The observed admittance and coherence functions, when compared with theoretical admittance and coherence computed for various models and parameters, can provide an estimate of the effective elastic thickness. As for coherence, the wavelength at which the coherence drops from approaching unity at long wavelengths to value approaching zero at short wavelengths is a measure of the rigidity of the lithosphere. This research takes advantage of the high-resolution gravity and topography data in Erdos. Using the coherence technique, we have estimated the effective elastic thickness of this region. Subsurface loads are also considered in our calculation. When the admittance between topography and gravity is obtained, we can filter the topography to give an estimate of gravity anomaly. This would be very important when the gravity data is scarce. Several other regions of China have been selected to investigate the effective elastic thickness of lithosphere. We compare those result with lithosphere thickness obtained through seismological technique and heat flow of the region. We find the effective elastic thickness is always smaller than the seismogenic thickness. This is due to what the effective elastic thickness reflects is only the up elastic part of the lithosphere. And we also find there is some degree of correlation between effective elastic thickness and heat flow. This suggests EET is probably controlled by the thermal state of the lithosphere and correlates with their tectonic age. Thus the estimations of the effective elastic thickness of lithosphere can help to investigate geophysical features of active tectonics of continental lithosphere.

Numerical Analysis of a Dual Polarization Mode-Locked Laser with a Quarter Wave Plate

Dynamical behaviors and frequency characteristics of an active mode-locked laser with a quarter wave plate (QWP) are numerically studied by using a set pf vectorial laser equation. Like a polarization self-modulated laser, a frequency shift of half the cavity mode spacing exists between the eigen-modes in the two neutral axes of QWP. Within the active medium, the symmetric gain and cavity structure maintain the pulse's circular polarization with left-hand and right-hand in turn for each round trip. Once the left-hand or right-hand circularly polarized pulse passes through QWP, its polarization is linear and the polarized direction is in one of the directions of i45o with respect to the neutral axes of QWP. The output components in the directions of i45" from the mirror close to QWP are all linearly polarized with a period of twice the round-trip time.

A Lagrangian for von Karman Equations of Large Deflection Problem of Thin Circular Plate

By the semi-inverse method proposed by He, a Lagrangian is established for the large deflection problem of thin circular plate. Ritz method is used to obtain an approximate analytical solution of the problem. First order approximate solution is obtained, which is similar to those in open literature. By Mathematica a more accurate solution can be deduced.