聚合物光纤及其应用

本文综述国内外聚合物光纤的最新进展 ,介绍降低聚合物光纤损耗的氘化和氟化的方法 ,提出宽带的梯度折射率聚合物光纤 .分析聚合物的光学特性 ,报道功能聚合物光纤、聚合物光纤的无源和有源器件的研究 .     

熔锥型光纤声光可变衰减器

利用耦合模理论对光纤熔锥声光器件进行了数值模拟,得到了全光纤声光衰减器传输谱和可调谐性。分析了带宽与声波长、耦合长度的关系。数值分析结果表明,声波在光纤熔锥中引起的轴向电介质微扰、耦合长度和工作波长都会对器件的传输谱产生影响,选择合适的设计参数可以制作较为理想的声光衰减器。实验上获得了损耗小于0．2dB,带宽大于200nm,动态范围为20dB的单模光纤熔锥可变衰减器,所得结果与理论分析相符合。这种器件可用于光纤通信及光纤传感。     

Dove棱镜的加工误差对耦合损耗的影响

平行光束经过有加工误差的Dove棱镜后,在出射面往往会发生角度倾斜和离轴偏差,从而导致利用Dove棱镜制成的光纤旋转连接器的传输耦合损耗增大。对于Dove棱镜的加工误差在耦合损耗方面的影响,本文利用光线追迹的方法对其进行了理论及模拟分析。分析结果显示,由于加工误差带来的耦合损耗随着Dove棱镜的底角误差及其锥体角误差的增加而增大。而后依据理论结果及光纤旋转连接器的需求,设计加工了5块Dove棱镜,测量了其耦合损耗,并对实验测量值进行了修正,进一步验证了理论的正确性。     

介质(Ag/AgI)镀层空芯玻璃光纤的制备及红外传输性能的研究

介质（Ａｇ／ＡｇＩ）镀层空芯玻璃光纤是一种较好的传输红外激光的柔性光纤材料．采用液相化学沉积法成功地制备了内径分别为１．０、０．５３、０．３２ｍｍ,长度为１．５ｍ的介质（Ａｇ／ＡｇＩ）镀层玻璃空芯光纤．利用傅里叶红外光谱仪和 ＬＪＬ－３５Ａ ＣＯ_２激光器分别测试了介质（Ａｇ／ＡｇＩ）镀层玻璃空芯光纤的传输损耗,测试结果表明：介质（Ａｇ／ＡｇＩ）镀层空芯玻璃光纤在２．５～２０μｍ波长范围内有较低的损耗值;随着光纤内径（α）的增大,空芯光纤的传输损耗（α）降低,这与Ｍｉｇａｇｉ理论（α　∝１／α^３）相符合．另外,由于光纤的注入端头发热致使介质（Ａｇ／ＡｇＩ）镀层空芯玻璃光纤的传输损耗随注入功率的增加而增大．     

新型电容器用高介电常数聚合物研究进展

高介电常数聚合物具有优异的介电性和柔韧性,可以制备高容量有机薄膜电容器等无源器件,近年来受到广泛关注.目前理论和实验研究的热点主要集中在聚合物/无机介电陶瓷、聚合物/导电颗粒复合材料和纯有机聚合物材料.综述了这3种聚合物的高介电机理及研究进展.采用物理、化学方法进行表面修饰改性,掺入导电颗粒及设计具有高度芳环结构聚合物等措施,均可有效提高介电常数、减小损耗.     

10×10InGaAsP/InP阵列波导光栅器件的研制

研制了脊形波导结构的10×10InGaAsP/InP阵列波导光栅器件(AWG),并采用掺铒光纤放大器(EDFA)作宽带光源测量了AWG的近场图以及分光特性。     

应用统计能量法对系统瞬态响应的研究

用统计能量法研究了脉冲激励下两自由度系统的瞬态响应，得出了响应的峰值能量和上升时间的解析式，并对其进行了数值分析。研究表明：减小振子间的耦合刚度和增大振子的内损耗因子，能够有效减小响应的峰值能量；通过增大内损耗因子和耦合刚度，可以减小振子之间的能量交换。这些结论与传统方法给出的结果一致，而瞬态统计能量法比传统方法更为简洁。     

多模光纤损耗测试的误差因素分析

损耗是多模光纤最重要的指标,精确测量光纤损耗不仅要考虑测量中存在的各种误差,还要考虑模式耦合的影响。本文分析了各种误差对测量结果的影响及其与光纤长度的关系.1.模式误差σ_(?)模式误差与光纤的微分模式损耗(DML)有关,DML 大的光纤模式误差也大。这项误差常被称为暂态误差,它一般只存在于光纤输入端的一段距离内,随着模式分布趋于稳态,这项误差就逐渐消失.但是就一根较长的光纤整     

高斯光束到光纤的单透镜耦合

分析了基模高斯激光束到单模和多模光纤的单透镜耦合过程中的各种损耗,把多模光纤的光场用高斯分布近似,采用模场耦合理论计算了基模高斯光束到单模和多模光纤的单透镜耦合效率.模拟计算了当激光-光纤耦合系统的工程参数(光束束宽、光纤数值孔径和光纤的纤芯芯径)一定时,单透镜耦合效率与所选用透镜的焦距之间的关系.并利用532mn激光(M2≤1.05)在几种不同焦距的透镜下对纤芯直径为3.μm的单模光纤和25μm的多模光纤进行了耦合效率的测定实验,得到了与理论计算基本吻合的实验结果.     

聚合物光纤光谱损耗特性的研究

截断法测量聚合物光纤 ( POF)的光谱特性是研究其损耗的一种有效方法 .用平面光栅单色仪对聚合物光纤聚甲基丙烯酸甲酯 ( PMMA)和聚苯乙烯 ( PS)的损耗光谱进行了测量 ,结果 PMMA芯 POF有三个传输窗口 ,分别为 5 2 0 nm,5 74nm,65 0 nm.在 5 2 0 nm,5 74nm处的损耗较小 ,且特性较为平坦 ,有很好的应用前景 . PS芯 POF窗口分别为 5 5 0 nm,5 80 nm,63 0 nm,670 nm,73 3 nm和 780 nm.在 5 5 0 nm,5 80 nm处同样有较好的应用前景     

Comprehensive numerical modelling of the hot isostatic pressing of Ti-6Al-4V powder: From filling to consolidation

Hot Isostatic Pressing (HIP) is a manufacturing process for production of near-net-shape components, where models based on Finite Element Method (FEM) are generally used for reducing the expensive experimental trials for canister design. Researches up to date implement in the simulation a uniform powder relative density distribution prior HIPping. However, it has been experimentally observed that the powder distribution is inhomogeneous after filling, leading to a non-uniform tool shrinkage. In this study a comprehensive numerical model for HIPping of Ti-6Al-4V powder is developed to improve model prediction by simulating powder filling and pre-consolidation by means of a two-dimensional Discrete Element Method (DEM). Particles’ dimension has been scaled up in order to reduce the computational cost of the analysis. An analytical model has been developed to calculate the relative density distribution from powder particle distribution provided by DEM, which is then passed in information to a three-dimensional FEM implementing the Abouaf and co-workers model for simulating powder densification during HIPping. Results obtained implementing the initial relative density distribution calculated from DEM are compared with those obtained considering a uniform relative density distribution over the powder domain (classic approach) at the beginning of the analysis. Experimental work has been carried out for validating the DEM (filling) and FEM (HIP) model. Comparison between experimental and numerical results shows the ability of the DEM model to represent the powder flow during filling and pre-consolidation, providing also a reliable values of the relative density distribution. It also highlights that taking into account the non-uniform powder distribution inside the canister prior HIP is vital to improve numerical results and produce near-net-shape components.     

一种测量超微粒子表面氧化层厚度的新方法

通过XPS分析与Ar~ 刻蚀相结合的方法，测量了Fe_(50)Pd_(50)合金超微粒子（UFP）的表面氧化层厚度，发现它的表面氧化层为1．4um厚，小于电镜观察到的表面非晶层厚度，表明此方法测量的表面氧化层厚度不受表面吸附层的影响，并且能直接了解UFP表面的具体氧化状态。     

Reliability-based design optimization of knuckle component using conservative method of moving least squares meta-models

This paper discusses reliability-based design optimization (RBDO) of an automotive knuckle component under bump and brake loading conditions. The probabilistic design problem is to minimize the weight of a knuckle component subject to stresses, deformations, and frequency constraints in order to meet the given target reliability. The initial design is generated based on an actual vehicle specification. The finite element analysis is conducted using ABAQUS, and the probabilistic optimal solutions are obtained via the moving least squares method (MLSM) in the context of approximate optimization. For the meta-modeling of inequality constraint functions, a constraint-feasible moving least squares method (CF-MLSM) is used in the present study. The method of CF-MLSM based RBDO has been shown to not only ensure constraint feasibility in a case where the meta-model-based RBDO process is employed, but also to require low expense, as compared with both conventional MLSM and non-approximate RBDO methods.     

声呐导流罩内声场特性研究

为研究机械激励下声呐导流罩壳内噪声预报问题,采用数值计算(有限元法-边界元法)结合实验的方法对一导流罩模型的壳内声场进行研究。首先依据实际导流罩模型建模,并加载机械激励进行数值计算,得到壳内声场的均方声压,然后进行湖内实验测量,最后对比了数值计算和实验的结果。研究表明:有限元法加间接边界元法是分析导流罩内声场这种封闭结构流-固-声耦合问题的有效方法;导流罩壳内声场的数值计算结果与实验测量结果吻合较好;声场均方声压与结构均方振速之比反映了罩壳结构内平均声场特性,可用来对比分析数值计算和实验的结果。     

A fuzzy QFD program modelling approach using the method of imprecision

The use of quality function deployment (QFD) to aid decision making in product planning has gained extensive international attention, but current QFD approaches are unable to cope with complex product planning (CPP) characterized by involving multiple engineering characteristics (ECs) associated with significant uncertainty. To tackle this difficulty, in this paper, fuzzy set theory is embedded into a QFD framework and a novel fuzzy QFD program modelling approach to CPP is proposed to optimize the values of ECs by taking the design uncertainty and financial considerations into account. In the proposed methodology, fuzzy set theory is used to account for design uncertainty, and the method of imprecision (MoI) is employed to perform multiple-attribute synthesis to generate a family of synthesis strategies by varying the value of s, which indicates the different compensation levels among ECs. The proposed methodology will allow QFD practitioners to control the distribution of their development budget by presetting the value of s to determine the compensation levels among ECs. An illustrative example of the quality improvement of the design of a motor car is provided to demonstrate the application and performance of the modelling approach.     

The MFS–MPS for two-dimensional steady-state thermoelasticity problems

We consider the numerical approximation of the boundary and internal thermoelastic fields in the case of two-dimensional isotropic linear thermoelastic solids by combining the method of fundamental solutions (MFS) with the method of particular solutions (MPS). A particular solution of the non-homogeneous equations of equilibrium associated with a planar isotropic linear thermoelastic material is derived from the MFS approximation of the boundary value problem for the heat conduction equation. Moreover, such a particular solution enables one to easily develop analytical solutions corresponding to any two-dimensional domain occupied by an isotropic linear thermoelastic solid. The accuracy and convergence of the proposed MFS–MPS procedure are validated by considering three numerical examples.     

An efficient method for electromagnetic scattering analysis

We present a novel method to solve the magnetic field integral equation (MFIE) using the method of moments (MoM) efficiently. This method employs a linear combination of the divergence-conforming Rao-Wilton-Glisson (RWG) function and the curl-conforming n×RWG function to test the MFIE in MoM. The discretization process and the relationship of this new testing function with the previously employed RWG and n×RWG testing functions are presented. Numerical results of radar cross section (RCS) data for objects with sharp edges and corners show that accuracy of the MFIE can be improved significantly through the use of the new testing functions. At the same time, only the commonly used RWG basis functions are needed for this method.     

Analysis of cylindrical shell panels. A meshless solution

The Meshless Analog Equation Method, a purely meshless method, is applied to the static analysis of cylindrical shell panels. The method is based on the concept of the analog equation of Katsikadelis, which converts the three governing partial differential equations in terms of displacements into three substitute equations, two of second order and one fourth order, under fictitious sources. The fictitious sources are represented by series of radial basis functions of multiquadric type. Thus the substitute equations can be directly integrated. This integration allows the representation of the sought solution by new radial basis functions, which approximate accurately not only the displacements but also their derivatives involved in the governing equations. This permits a strong formulation of the problem. Thus, inserting the approximate solution in the differential equations and in the associated boundary conditions and collocating at a predefined set of mesh-free nodal points, a system of linear equations is obtained, which gives the expansion coefficients of radial basis functions series that represent the solution. The minimization of the total potential of the shell results in the optimal choice of the shape parameter of the radial basis functions. The method is illustrated by analyzing several shell panels. The studied examples demonstrate the efficiency and the accuracy of the presented method.     

分立型半导体激光器线阵温度场分析

目的　研究半导体激光器线阵的温度场分布 ,为设计冷却方案提供理论依据 .方法　用分离变量法推导简化后系统的温度场分布函数 ,获得理论最高温度所在位置 ;建立合理的有限元模型 ,在 ANSYS系统上进行数值仿真 .结果　得到系统稳定后的温度场分布图 ,确定了半导体激光器线阵在整个工作时间内的最高温度及其所在位置 .结论　根据简化后的数学模型 ,用有限元法得到的温度场分布与用分离变量法进行的理论分析得到的结论相一致 .     

近场声全息测量阵架的设计与分析

全息测量系统设计的关键是测量全息面测点复声压(幅值和相位)的真实数据,介绍了自行设计的近场声全息(NAH)测量的传声器线阵扫描系统.利用边界元法计算了传声器线阵架结构表面声散射对阵上传声器测量全息复声压的影响,提出了敷设吸声材料以提高测量精度的措施;对在线阵架表面敷设吸声材料后的声散射效应仿真结果表明,吸声材料能够有效...