Photoelastic model measurement with rotated principal axes by scattered-light photoelasticity

The method of measurement of a three-dimensional photoelastic model with rotated principal axes has not yet been fully experimentally established. It is known that a three-dimensional photoelastic model can be reduced to an optically equivalent model. In this paper, the optically equivalent model is realized from a stratified model consisting of two layers of the frozen stress model. The secondary principal stress direction and the relative phase retardation of the frozen disk model in the stratified frozen stress model are determined for the entire field from Stokes parameters obtained by scattered-light photoelasticity using unpolarized light. The accuracy of these values is confirmed by a comparison with results only from the frozen stress disk model.     

三维复合型断裂的试验方法探讨

探讨了一种能够揭示三维复合型断裂现象并能记录这些现象的三维复合型断裂研究的实验方法，用此方法完成了LC4－CS航空结构铝合金不同厚度紧凑拉伸试样的I＋Ⅱ复合型断裂试验。结果表明：此方法能够简便地确定出复合型裂纹的起裂载荷、破坏载荷、裂尖张开位移、滑移位移和起裂角，基本解决三维复合型断裂研究所需实验数据问题。同时发现此种材料试样的承载能力和超裂方向的确具有明显的厚度效应。     

Improved operator comfort and off-road capability through pendulum arm technology

The Nordic forest industry requires just-in-time wood deliveries. Operations must continue regardless of season, weather and terrain. Soil compaction and deep ruts must be avoided while providing high performance and a reasonable working environment for operators.The Xt28 pendulum arm forwarder is a full-size concept forwarder with six hydrostatic propelled wheels on pendulum arms built on a three-piece frame connected with two articulation joints. The Xt28 concept machine was tested according to Skogforsk standard machine tests. Rut depth test focused on soil interaction where rut depth was measured related to number of passes. Machine dynamics were measured using standardized test track with focus on operator comfort.The project proved the potential of pendulum arm technology in off-road transportation. Automatic pendulum arm levelling, equalized ground pressure between wheels and improved operator comfort through reducing adverse vibrations and roll angles, simultaneously reducing dynamic forces transferred to the forest floor. Pendulum arm technology improves travel speed in adverse terrain, providing unparalleled side slope capability and enhanced productivity.     

Singularities of the boundary layer equations and the structure of the flow in the vicinity of the convergence plane on conical bodies

The singularities of the boundary layer equations and the laminar viscous gas flow structure in the vicinity of the convergence plane on sharp conical bodies at incidence are analyzed. In the outer part of the boundary layer the singularities are obtained in explicit form. It is shown that in the vicinity of a singularity a boundary domain, in which the flow is governed by the shortened Navier-Stokes equations, is formed; their regular solutions are obtained. The viscous-inviscid interaction effect predominates in a region whose extent is of the order of the square root of the boundary layer thickness, in which the flow is described by a two-layer model, namely, the Euler equations in the slender-body approximation for the outer region and the three-dimensional boundary layer equations; the pressure is determined from the interaction conditions. On the basis of an analysis of the solutions for the outer part of the boundary layer it is shown that interaction leads to attenuation of the singularities and the dependence of the nature of the flow on the longitudinal coordinate, but does not make it possible to eliminate the singularities completely.     

Numerical investigation of the first transition in the three-dimensional problem of convective flow in a porous medium

The branching off of steady-state regimes from mechanical equilibrium is studied for the problem of filtration convection in a parallelepiped. The conditions for the geometric parameters under which stable continuous families of steady-state regimes develop are found. The stability of equilibria of the family with respect to three-dimensional perturbations is analyzed in a numerical experiment using a finite-difference method.     

Two-dimensional stability problem for two interacting short fibers in a composite: In-line arrangement

A solution is found to a plane problem for a composite material reinforced with two in-line fibers and subjected to longitudinal compression. The problem formulation is based on the piecewise-homogeneous model and the three-dimensional theory of stability. The dependence of the critical strain and buckling mode on the distance between the fibers is studied for various mechanical and geometrical characteristics of the composite components.Translated from Prikladnaya Mekhanika, Vol. 40, No. 9, pp. 65–74, September 2004.     

立体发光LED灯片的光学性能研究

立体发光灯片的关键是在保证光通量的前提下,如何获得均匀的正反面发光.本文对3种荧光粉平面涂覆立体灯片的正面和反面的瞬态和稳态光通量、色温、色品坐标进行了研究,发现直接涂覆荧光粉胶的灯片总的光通量最大,但正反面的发光性能相差很大;在涂覆荧光粉之前先平面涂覆一层硅胶,可获得正反面发光较均匀的灯片;而在该硅胶层内掺杂扩散粉的灯片,不但没有提高灯片的正反面发光均匀度,反而大幅度降低了光通量值.此外,测试3种样品的发光角度,发现其发光角度分布相似,而发光强度与积分球测试的光通量比值相近.结果表明,涂覆荧光粉之前先平面涂覆一层硅胶工艺,既可以保证立体发光灯片具有较大的光通量又可以获得均匀的正反面发光.     

铷蒸气激光器3D理论模型的建立及阈值特性模拟

基于三能级速率方程理论,结合惠更斯-菲涅尔衍射积分公式,利用分步光束传播方法建立了半导体泵浦碱金属蒸气激光器(DPAL)端面泵浦3D理论计算模型,用于模拟研究铷蒸气激光器的泵浦阈值特性。该模型将光束传播、光与物质相互作用独立考虑,利用迭代算法求解。考虑激光器腔内模式与泵浦光模式匹配对阈值特性的影响,模拟了单端泵浦铷蒸气激光器内部的三维动力学过程。在具体算例中研究了模式匹配最佳时,在阈值工作状态下铷蒸气室中的三维粒子数分布,以及沿不同轴线的增益分布。仿真了在最佳模式匹配位置附近,泵浦光模式变化对阈值特性的影响。根据蒸气池中粒子数分布和光场分布具体分析了模式匹配影响阈值特性的机理。同时还模拟了不同长度蒸气池对阈值特性的影响。结果表明,腔参数与泵浦光模式之间存在一定的关系,对于特定的泵浦光模式,存在恰当的腔参数,使得阈值达到最小。     

Hydrothermal Synthesis, Crystal Structure and Fluorescence Property of a Novel Coordination Polymer [Eu_2(C_6H_8O_4)_3(H_2O)_2]_n·n(4,4′-bpy)

1UINTRODCTIONAtpresentthefluorescentmaterialsusedaremostlyinorganicororganicmicromolecularlumine-scentmaterialsthatareeasilyattenuatedinsunlight.Thereforepeopleintendtostudythepolymerflu-orescentmaterialscontainingrare-earthionsduetotheirgoodfluorescenthomochromepropertyandhighluminescentintensity.Inrecentyearswidestudieshavebeenperformed[1～10]tosearchforlu-minescentmaterialswithfineluminescentproper-tiesatlowprice.Asfortherare-earthcoordinationpolymer,agreatnumberofinvestigationsaremain…     

板条固体激光器的三维瞬态热分布

本文建立了有限几何尺寸板条激光介质的三维温度分布模型.在普遍情况下,推导出温度分布的解析式.由此便于分析板条温度分布和泵浦参数、激光介质等的依赖关系.借助计算机进行的数值计算,证实了理论结果.