残余应力对H型钢楔形梁相关屈曲的影响

以有限元分析软件ANSYS为工作平台,基于非线性板壳有限元理论,采用壳单元对轻型门式刚架中H型钢楔形薄壁梁进行考虑双重非线性的全过程分析,从而对其相关屈曲性能进行深入的研究。通过变化构件腹板厚度、长度、翼缘宽度、楔率等几何参数,从荷载-位移曲线、承载力、变形的发展等方面入手,分析了残余应力对变截面H型钢梁的相关屈曲性能的影响,获得到了一些有价值的结论。     

The averaged periodogram estimator for a power law in coherency

We prove the consistency of the averaged periodogram estimator (APE) in two new cases. First, we prove that the APE is consistent for negative memory parameters, after suitable tapering. Second, we prove that the APE is consistent for a power law in the cross‐spectrum and therefore for a power law in the coherency, provided that sufficiently many frequencies are used in estimation. Simulation evidence suggests that the lower bound on the number of frequencies is a necessary condition for consistency. For a Taylor series approximation to the estimator of the power law in the cross‐spectrum, we consider the rate of convergence and obtain a central limit theorem under suitable regularity conditions.     

Self-Efficacy and Compliance With Benzodiazepine Taper in Older Adults With Chronic Insomnia.

Better understanding of compliance with BZD taper is warranted. Compliance with a taper program and perceived self-efficacy (SE) in being able to comply with hypnotic reduction goals was monitored weekly in 52 older adults (mean age: 63.0 years) with chronic insomnia (average duration: 21.9 years) who underwent a 10-week physician-supervised medication tapering. One group received cognitive- behavior therapy for insomnia during discontinuation, whereas the other did not. Compliant patients showed higher SE ratings at Weeks 6, 8, 9, and 10. Medication-free patients at the end of the treatment also reported higher mean SE ratings at those 4 weeks. Differences remained significant when withdrawal symptoms and sleep efficiency were controlled for. These results have important clinical implications because SE may indicate key time points when patients are experiencing more difficulty during discontinuation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

基于光纤马赫泽德干涉的折射率测量

为了高精度的检测液体折射率,本文研究了基于模间干涉的马赫泽德光纤折射率传感器.传感器由普通的单模光纤和多模光纤组成,按照单模,多模,单模依次熔接在一起,并将熔接后的光纤进行拉锥处理,最终得到直径为10μm左右的传感头.实验结果表明,液体折射率在1.33到1.35范围内增大时,其透射谱的损耗峰将向长波方向移动.     

楔形轴心受压柱试验研究

通过6根柱子试验,分析了楔率对楔形轴心受压柱的稳定极限荷载及受力性能的影响,给出了变形曲线.     

光纤熔融拉锥中拉力控制方法与电磁力仿真

针对保偏光纤耦合器熔融拉锥制造过程中拉力控制问题,提出一种新的计算机在线拉力控制方法.拉力控制系统由计算机、拉伸机构、圆光栅及控制电路组成,通过检测光纤支架的旋转角度、改变线圈中的电流,控制永磁铁与线圈间的电磁力,实现对拉伸力的实时控制.分析电磁力和拉力的关系,建立永磁铁和线圈的三维有限元模型,确定永磁铁的运动轨迹,并对通电线圈的磁场分布和电磁力进行仿真,得到线圈中的电流、支架旋转角度和拉力的关系式.仿真结果表明拉力控制良好,控制误差约为1.03%.     

楔形工形柱平面内稳定极限承载力研究

通过对12根楔形柱进行静态加载试验,分析和研究楔率及偏心距对楔形柱平面内极限承载力的影响.试件的主要参数为荷载作用的偏心距和楔率.试验在5 000 kN试验机上进行,主要测量了型钢的纵向应变、试件的变形过程、荷载-挠度曲线及试件的极限承载力.试验结果表明,随着楔率的增大,构件的极限承载力也随之增加;荷载偏心距的增大将降低构件的极限承载力.     

H型钢楔形薄壁梁相关屈曲性能分析

以有限元分析软件ANSYS为平台,基于非线性板壳有限元分析理论,对轻型门式刚架中H型钢楔形薄壁梁的相关屈曲性能进行大挠度弹塑性分析。用Shell 18l单元对轻型门式刚架中H型钢楔形薄壁梁进行离散,考虑初始几何缺陷和残余应力的影响,对其进行全过程跟踪分析,从而对其相关屈曲性能进行深入的研究。从荷载-位移曲线、承载力、变形的发展和塑性区的分布等方面入手,对影响相关屈曲性能的因素(腹板高厚比、翼缘宽厚比、跨度、楔率等)进行系统的分析和研究,并与现行规范进行比较,得到一些有价值的结论。     

SE同轴测试装置中阶梯电容的研究与优化

在屏蔽材料的屏蔽效能(shielding effectiveness,SE)测试装置中,通过对锥形连接器内导体进行微小移位,优化固定同轴装置的支撑介质的内、外径比值,并在支撑介质中挖去一定厚度的环形沟道构成小电感等技术对阶梯电容进行补偿,减小由截面不连续引起的回波损耗,设计了频率范围为10 MHz至3 GHz的SE同轴测试装置.利用软件仿真验证了表面电阻为5Ω的屏蔽材料在该装置中测试有稳定的SE值,证明该装置不仅改善了基于ASTM D4935测试装置频率范围窄的不足,同时具备良好的阻抗匹配特性.     

热轧板带头尾厚度精度控制技术

热连轧粗轧区采用可逆轧制时，由于板带头尾部低速咬钢(抛钢),轧辊冷却水对头尾温度的影响增大，加上头尾在空气中冷却速度大于本体部分，因此头尾温度偏低，同时头尾部处于无张或失张状态，传统AGC不能有效控制端部厚度。针对头尾厚跃现象，提出一种新的“压头”与“压尾”的控制方法，该方法采用最后两机架压头和两次压尾的方式进行控制，可弥补传统AGC端部控制效果差的缺点，使头尾厚度质量大幅提高。并成功应用于实际项目，取得了良好的控制效果，值得国内热轧厂推广应用。