光纤陀螺光路小型化技术

介绍了光纤陀螺基本工作原理，描述了光纤陀螺小型化的意义。分别论述了基于光学器件小型化、光学集成技术、三轴光学器件共用技术实现光纤陀螺光路小型化的技术途径及可能效果，指出了三轴共用探测器技术可能存在的问题。研究成果对促进光纤陀螺的应用、光纤陀螺的实用化具有重要意义。     

Study of optical properties of dense krypton plasma

Study of the thermophysical properties of dense plasma has heen stimulated by the absence of a strict theory which would adequately describe the thermodynamic, transport, and optical properties of such a medium. A detailed analysis of presently available dense plasma models requires a comparison of their results to experiments performed with various chemical elements. Experimental data on thermodynamic properties and electrical conductivity of dense plasmas of a number of chemical elements shows a general tendency: The experimental enthaply and electrical conductivity of the plasma are lower than the corresponding theoretical values, the differences increasing with increase in charged particle concentration. With regard to optical properties the experimental situation is not well defined. For some elements experimental values have been found to be above theoretical ones, while for other elements the opposite is true. In connection with this further studies of the optical properties of dense plasma over a wide parameter range are necessary.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 11–15, July–August, 1984.     

A new application of differential interferometry for stress analysis

In the past, differential interferometry has found interesting applications in gas dynamics. The gradients of density could be measured in gas flows. Now, a first trial is made to extend this method to the experimental treatment of stress problems. A Wollaston prism with polarizing elements is used in the optical arrangement. This prism combines two beams of light which have penetrated the model at locally separated points. A field of interference fringes can be produced behind the Wollaston prism. The deflections of the different conjugated light beams, which are caused by the deformed elements of the model, lead to a shifting of the interference fringes. A Stress Differential-interferometer Law is derived theoretically in order to interpret the optical data According to this theory, the optical effect caused by the deflection in this arrangement is proportional to the gradient of the sum of principal stresses. A calibration test is performed by using a circular disk, this method is applied to a circular ring for measuring the stress gradients. Under special conditions, interference fringes could be produced which represent the loci of equal stress gradient. Plexiglas plane models are loaded diametrically by single loads. The experimental results verify the statements of the developed theory.     

Waves with random coupling and random propagation constants

We study the mathematical treatment of transmission statistics of coupled wave devices with random imperfections. Such devices include multi-mode waveguides or optical fibers, directional couplers at waveguide or optical frequencies, dominant-wave transmission lines (with the reflected wave the spurious mode), lumped filters composed of circuit or of waveguide elements, multi-layer optical coatings to achieve high or low reflectivity.If the random parameters have very rapid spatial variations, we assume they have white spectra. Exact results for transmission statistics are obtained in such cases. These exact results can be extended to random parameters with almost-white spectra, and narrow-band spectra that are far from white.These calculations are carried out in a simple way by using Kronecker matrix products.     

High-sensitivity moiré interferometry—A simplified approach

High-quality moire-interferometry patterns were obtained with the following conditions: specimen of graphite-polyimide composite material; reflective cross-line specimen grating of 600 ?/mm (15,000 ?/in.); virtual reference grating of 1200 ?/mm (30,000 ?/in); fringe-multiplication factor of 2; carrier pattern of 10 fringes/mm (250/in.); carrier eliminated by optical filtering. The phase-type specimen grating was cast onto the composite material with silicone rubber, using a ‘homemade’ mold. The virtual grating was formed with a plane mirror in a collimated field. Precision-quality optical elements are not required.     

A grazing-incidence moire interferometer for displacement and planeness measurement

An interferometer for planeness and deformation measurement of surfaces up to one meter in length is described. The degradation of the interferogram produced by imperfections of the optical elements is eliminated by the use of the moiré technique. The relations between the incidence angle, sensitivity and surface roughness are discussed.     

Accuracy of compensation methods in photoelastic fringe-order measurements

A complete photoelastic stress analysis depends, in the majority of cases, on the accuracy of the fractional-fringe-order measurements. The error involved due to an error in the measurement of the isoclinic angle has been studied. It was found that the Tardy method was more accurate than the Sénarmont method, assuming negligible errors in the optical elements.     

Role of light ellipse in photoelasticity and new methods for isoclinic-parameter determination

In dealing with various types of polariscopes the transformations that the light ellipse undergoes as it traverses through several optical elements give a better physical insight than the conventional trigonometrical transformations that are generally applied to the light vectors. Further, an understanding of the transformations of the light ellipse suggests several interesting methods for the determination of the isoclinic parameter.     

Unstable slit flow of a liquid crystalline polymer solution

A lyotopic solution of 27 wt% hydroxypropylcellulose [HPC] in m-cresol has been studied in pressure-driven slit flow. At high flow rates an instability leads to large wavelength disturbances in fluid structure. A combination of image analysis and time signal processing is used to determine the velocity at which the structural disturbances are convected downstream, which is shown to be equal to the independently measured and predicted centerline velocity. This implies that the disturbance structure is confined near the midplane of the slit flow. Upstream of the onset point of the wavy fluid structures, the fluid exhibits unusual optical properties when viewed between crossed polarizers that are rotated relative to the flow direction. Specifically, the optical properties indicate that there must be some variation in the macroscopic optical axis of the sample as light passes through the slit flow. A discrete optical model consisting of birefringent elements twisted away from and back to the flow direction as a function of depth in the sample is able to predict the essential optical characteristics; however, independent x-ray scattering measurements show that the macroscopic molecular alignment is along the flow direction. The wavy textures apparently emerge as a result of an inhomogeneous transition of orientation back to the flow direction, trapping thin bands of fluid in the twisted configuration.     

Mesh-Based Shape Measurements with Stereocorrelation

A mesh-based framework is developed by extending global stereocorrelation techniques to faceted surfaces with three-noded elements. A two-step self-calibration procedure is followed to determine the projection matrices of the stereo-rig and to update the nominal surface model to match the surface of interest. To prove the feasibility of mesh-based stereocorrelation, two different test parts are analyzed with the present techniques and compared to already validated optical procedures.     

光纤传感无损检测混凝土结构研究述评

本文综述了近几年来使用光纤传感器埋入混凝土构件及结构中无损检测其内部应力、应变及评估结构完整性等研究领域的概况。探讨了光纤与混凝土接触面之间的涂层材料的基本特性及其细观力学问题。最后给出了目前国外利用这种新技术所得到的一些成果。     

循环干涉型光纤陀螺及其光源

介绍了一种新型光纤陀螺及其关键器件。包括：（1）循环干涉型光纤陀螺的系统方案；（2）大功率超辐射发光二极管；（3）多功能光学发收模块，它们是国内光纤陀螺研制中急待解决的关键技术。采用模块化结构和微光电机系统（MOEMS）是国外光纤陀螺的发展方向。     

A simple method for measuring local buckling of thin plates

A simple computer-interfaced optical system for measuring the dynamic-local-buckling deformation of thin-walled metal structural-plate elements is described in this paper with two sets of experimental results. The major advantage of this system is its simplicity and economy as well as its speedy automated process for data scanning, acquisition, and analyses by using a microcomputer.Paper was presented at the 1986 SEM Spring Conference on Experimental Mechanics held in New Orleans, LA on June 8–13.     

Speckle-interferometric camera for displacement measurements

A simple setup of standard optical elements comparable to a shearographic camera can be used to record speckle interferograms with a fast lens. Rigid-body translations of the object are compensated for by a reference mirror attached to the object; the method requires only moderate stability and resolution of the storage medium (film). Interferogram reconstruction is possible with white light. Hence the method unites advances of different holographic and speckle-interferometric setups.     

Phase composition and distribution of alloying elements in the transition layer

X-ray spectral and x-ray structural analyses and optical microscopy were used to study the chemical and phase compositions and the structure and morphology of alloying elements of the transition layer produced by gas-flame and plasma spraying on St. 3sp steels. It is shown that the structure and chemical and phase compositions of the transition layer depend significantly on the technological parameters, processing methods, and the chemical composition of the coating.     

Chemical composition of PM_(2.5) during winter in Tianjin,China

PM2.5 samples for 24 h were collected during winter in Tianjin,China. The ambient mass concentration and chemical composition of the PM2.5 were determined. Ionic species were analyzed by ion chromatog-raphy,while carbonaceous species were determined with the IMPROVE thermal optical reectance(TOR) method,and inorganic elements were measured by inductively coupled plasma-atomic emission spec-trometer. The daily PM2.5 mass concentrations ranged from 48.2 to 319.2 g/m3 with an arithmetic average of 144.6 g/m3. ...     

Optomechanical soft metamaterials

We present a new type of optomechanical soft metamaterials, which is different from conventional mechan-ical metamaterials, in that they are simple isotropic and homogenous materials without resorting to any complex nano/microstructures. This metamaterial is unique in the sense that its responses to uniaxial forcing can be tailored by programmed laser inputs to manifest different nonlinear con-stitutive behaviors, such as monotonic, S-shape, plateau, and non-monotonic snapping performance. To demonstrate the novel metamaterial, a thin sheet of soft material impinged by two counterpropagating lasers along its thickness direction and stretched by an in-plane tensile mechanical force is con-sidered. A theoretical model is formulated to characterize the resulting optomechanical behavior of the thin sheet by com-bining the nonlinear elasticity theory of soft materials and the optical radiation stress theory. The optical radiation stresses predicted by the proposed model are validated by simula-tions based on the method of finite elements. Programmed optomechanical behaviors are subsequently explored using the validated model under different initial sheet thicknesses and different optical inputs, and the first-and second-order tangential stiffness of the metamaterial are used to plot the phase diagram of its nonlinear constitutive behaviors. The proposed optomechanical soft metamaterial shows great potential in biological medicine, microfluidic manipulation, and other fields.     

Hydrodynamics of natural oscillations of neutrally buoyant bodies in a layer of continuously stratified fluid

The flow patterns induced by floats of different shapes (sphere, short and long cylinders) freely sinking to the neutral-buoyancy horizon in a continuously stratified fluid are investigated using optical methods. General flow elements, both large-scale (waves, vortices, hydrodynamic wake) and fine-scale (boundary layers, extended autocumulative jets), are distinguished. For large times, the float oscillation frequencies are of the order of or greater than the buoyancy frequency of the medium. This indicates the significant effect of the induced flows on the motion of the float.     

基于神经网络与光纤传感阵列的结构状态监测方法

以探测机敏复合材料与结构内应变、应力及损伤等物理状态的位置信息为目的．提出了一种新颖的可内埋于材料与结构内作为结构状态监测用的强度调制型光纤传感阵列网络，并采用人工神经网络来处理传感阵列输出的并行分布式传感信号，阐述了适用的Ｋｏｈｏｎｅｎ网模型及其变化形式，给出了仿真实验结果     

An experimental study of thermal stress in porous materials by methods of holography and photoelasticity

In heat-loaded structures of energy equipment at the moment of crisis of heat exchange in working elements, the ultimate state of the material occurs. Thermal stresses were studied experimentally in a bulk porous material with a groove on the surface with a view to finding out the distribution of deformations and thermal stresses due to the location of the heat source. It appeared efficient to apply optical methods. Using holographic interferometry, a pattern of distribution of thermal deformations over the surface of the specimens was obtained. Using the photoelastic method to investigate a grooved porous structure, a physical pattern of the distribution of thermal stresses inside the block and in the groove was obtained. Ways are outlined for designing and reducing the probability of occurrence of destructive cracks. A similarity is observed in the distribution of strains and stresses that indicates the interrelatedness of surface and internal processes. The application of optical methods made it possible to discover a physical pattern of destruction. The results are expected to be used in the future to investigate other porous materials.