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71.
Different material-doped Raman fiber lasers with very high efficiency operating in continuous-wave are presented.With 1 W Nd∶YVO 4 laser pumping at wavelength of 1 342 nm, single mode output power of above 500 mW (optical-to-optical conversion efficiency of 50%) is simulated in the range of 1 400-1 500 nm.Using high-germanium,high-phosphate and high-borate silicate fibers as the gain medium,laser output at wavelengths of 1 420,1 450,1 480 and 1 495 nm can be achieved with different geometries,which are just as pumping C-band and L-band distributed Raman fiber amplifiers. 相似文献
72.
Chris P. Pantelides Justin Nadauld Larry Cercone 《Canadian Metallurgical Quarterly》2003,7(2):118-126
Transportation departments have been using aluminum overhead sign structures since the 1950s. It is well documented that cracks develop in the welds between diagonal and chord members due to fatigue stresses from wind-induced vibration of the slender members. The cracks propagate to complete failure of the members, which can cause collapse of the truss and inflict injuries. The original design of overhead sign structures did not consider fatigue as a limit state. In addition, field welding of aluminum structures for any possible repairs is prohibited. A repair method for the cracked aluminum welded connections between diagonals and chord members using glass fiber reinforced polymer composites (GFRPs) is proposed. The static load carrying capacity of the welded connection, and the cracked connection repaired with GFRP composites are established. The paper describes the surface preparation of the aluminum tubular members, and the architecture and application sequence of the GFRP composite to retrofit the connection. Experimental results are presented from static tests of welded aluminum connections, welded aluminum connections retrofitted with GFRP composites, and new aluminum connections that depend only on GFRP composite elements for their strength. The results from monotonic static tests carried out on cracked welded specimens from actual sign structures show that the retrofitted connection with GFRP reinforcement achieved 1.17 to 1.25 times the capacity of the welded aluminum connection without any visible cracks. This result, and the minimal traffic disruption anticipated in the actual field application, makes this retrofit method a good candidate for implementation. 相似文献
73.
分析了影响螺纹钢牙筋长度的原因,根据铣床的工作原理,利用刀头夹持长度与凸轮工作轨面半径的几何关系,推导出计算各种不同规格螺纹钢牙筋的工艺参数,解决了螺纹钢牙筋长度不足之问题。 相似文献
74.
集成光学干涉仪光纤陀螺 总被引:2,自引:0,他引:2
简述了集成光学干涉仪光纤陀螺(FOG)的技术优势、发展概况和采用的技术途径,介绍了适用于不同技术条件要求的三种多功能集成光学芯片结构和相应的信息处理方法。简要地概括了目前国外FOG的发展水平。 相似文献
75.
采用P型InP衬底新月型结构制备了1.48μm大功率激光器,该激光器与单模光纤耦合输出功率大于40mW。 相似文献
76.
77.
强度型光纤传感器的信号检测系统 总被引:1,自引:0,他引:1
余向东 《中国计量学院学报》1996,(1)
本文阐述了一种可提高强度型光纤传感器测量精度的检测系统。该系统利用同一检测电路交替检测信号、参考通道的输出信号,并将信号、参考两通道的检测结果相除,从而消除了因发光二极管光源波动及检测电路系统不稳定所带来的误差。采用同步相关技术抑制了噪声,提高了输出信噪比。实验证明,当时间常数RC为0.05S时,采用该检测系统可获得优于千分之一的零点稳定性和优于2×103的输出信噪比。 相似文献
78.
79.
火炸药包装用纸桶的研究 总被引:1,自引:1,他引:0
简述了我国火炸药包装的现状。介绍了火炸药用纸桶包装的研究情况,其中,较详细叙述了纸桶的力学性能、运输和使用试验结果,分析了纸桶包装火炸药的社会、经济效益。 相似文献
80.
Dynamic elastic-plastic buckling phenomena which might develop in a rod from an axial impact loading are studied in order to identify the conditions for quasi-static behaviour. A discrete model for dynamic elastic-plastic buckling, which retains the axial and the lateral inertia forces, is proposed, and the relationship between the model parameters and the characteristics of an actual structure is given. Examples of different external loadings and boundary conditions are considered in order to clarify the influence of elastic-plastic axial wave propagation on the buckling process. The critical time for the initiation of buckling is obtained and the post-buckling behaviour of the model is analysed. Particular attention is paid to the role of the striking mass on the characteristics of the buckling process and on the development of the buckling shape. The numerical study reveals that the inertia of the striking mass affects considerably the development of the buckling shape causing different patterns of axial strain distributions at the initiation of buckling. The comparisons which are made between the model predictions and some previously published experimental data show that the buckling process is governed by the impact velocity as well as by the external loading history provided by the experimental technique. 相似文献