Fiber Bragg grating distributed strain sensing: an adaptive simulated annealing algorithm approach

We demonstrate the use of adaptive simulated annealing (ASA) algorithm for determining the strain profile along a fiber Bragg grating (FBG) from its amplitude reflection spectrum. By combining the ASA algorithm and the matrix method for calculating the reflection spectrum of a FBG, the FBG sensor can be used for the distributed strain sensing. Experiments showed that the strain detection accuracy could be in the order of a few microstrains.     

Switchable multi-wavelength erbium-doped fiber lasers by using cascaded fiber Bragg gratings written in high birefringence fiber

A novel and simple Erbium-doped fiber laser by using cascaded fiber Bragg gratings (FBGs) written in high-birefringence fibers for switchable multi-wavelength operation is proposed. Due to two-peak reflection with orthogonal polarizations of the FBG, the polarization hole-burning effect in the cavity is greatly enhanced. Experimental results show that the stable dual- and three-wavelength lasing operation with very narrow wavelength separation (0.39 nm) can be generated at room temperature. The configuration is simple and flexible. Only by adjusting polarization controllers (PCs), the laser can be switched among the stable single-, dual- and three-wavelength lasing operations.     

非线性放大环形镜“8”字腔光纤激光器实验研究

使用976 nm半导体激光器作为抽运源,对利用非线性放大环形镜（NALM）锁模运行的掺Yb3+光纤激光器进行了实验研究,获得了脉冲宽度43.6 ps,中心波长为1053.3 nm的锁模脉冲激光输出, 光谱宽度8 nm, 输出功率为0.2 mW, 重复频率为18.2 MHz, 经过放大, 通过光栅对腔外色散补偿,在腔外产生了宽度616 fs的脉冲激光.     

掺Yb3+光纤激光器的特性与设计

 从速率方程出发，对波长为980nm的激光泵浦掺Yb^{3+光纤激光器进行数值模拟，全面分析激光器阈值功率、输出激光功率、增益等重要参数与泵浦功率、光纤长度、腔镜反射率、掺杂浓度等参量之间的关系。采用高浓度掺Yb3+光纤对环形光纤激光器做了初步实验研究，所得结论与实验模拟结果基本一致。}     

Effect of friction in ferrules on compression tuning characteristics of fiber Bragg gratings

The effect of friction in ferrules on compression tuning characteristics of fiber Bragg gratings (FBG) was observed and analyzed in this paper. It was demonstrated that the micro-bending of the fiber in the ferrule would cause friction between fiber and inner wall of the ferrule, and the friction would make a non-uniform strain in the FBG and degradations of its reflection spectrum. To avoid the effect, some measures have been applied including reducing the ferrule diameter to fit the fiber, and filling some lubrication in the ferrule, and so on. Near 10 nm tuning range can be obtained with good spectral performance.     

Mechanical breakdown of trabecular bone: Dependence on microstructure

Experiment on mechanical strength of porous trabecular bone shows power law dependence on the density of the structure. Physical structure and mechanical properties of the trabecular network are modelled here with a fractal lattice network of elastic springs having a strain based fracture criteria. An analysis of the model system supports the power law and shows that lacunarity is an important parameter in differentiating the mechanical strength of trabecular bones of same density.     

涂层界面结合强度检测研究(Ⅱ)：涂层结合界面应力检测系统

利用X射线衍射技术(XRD)测试了涂层及其基体材料的应力及其变化规律，建立了一种涂层结合界面应力检测系统，进行界面结合状态的检测研究.利用涂层从基体脱粘前后的界面应力变化量，结合涂层材料的物性参数和涂层-基体系统温度场参数，用涂层残余应力衍射峰来表征涂层与基体的结合强度，创立一种研究检测涂层结合强度理论的实验新方法，适用于各种热障涂层的界面结合强度测量. 关键词： X射线衍射法(XRD) 界面结合强度 涂层 残余应力     

利用场强与电势的关系计算非平行平板电容器的电容

对于非平行平板电容器,利用电场与电势的基本关系,求解微分方程,得到电容器的电容值.     

基于联系数的钢筋抗拉强度测量不确定度评定新方法

钢筋抗拉强度的不确定度包括:钢筋直径的不确定度分量,拉力的不确定度分量,检测结果重复性引入的不确定度分量,数据修约的不确定度分量等等,因此,测量不确定度是与测量数据相联系的,联系数是处理不确定性问题的一种系统数学理论,可以用联系数来表示测量不确定度,为此,提出一种基于联系数的钢筋抗拉强度测量不确定度评定的新方法.     

Finite deformations of elastic–plastic filamentary networks

Finite elastic–plastic deformation of a thin sheet formed by several families of perfectly flexible extensible fibers is described using an idealized theory in which the fibers are assumed to be continuously distributed to form a surface. The constitutive properties of the surface are deduced directly from those of the constituent fibers. The equilibrium equations are cast in rate form and associated rate potentials are derived. Physically plausible sufficient conditions for the existence of an exact dual extremum principle are proposed and used to prove uniqueness of solutions. Yielding and plastic flow criteria for individual fibers are given in a strain-space setting and adapted to model the elastic–plastic response of the sheet as a whole.