滚动轴承性能退化趋势预测综述

滚动轴承作为旋转机械的重要零部件之一,其在工业中占有重要的地位,其可靠性直接影响设备能否安全、稳定运行.文章首先阐述了滚动轴承性能退化趋势预测的研究意义;接着梳理了滚动轴承性能退化趋势预测中关键难点性能退化指标构建对故障特征提取、降维和融合方法,然后进行了有效的性能退化趋势预测模型分类.最后,对滚动轴承性能退化趋势预测...     

Effect of annealing on the optical and mechanical properties of cold drawn polypropylene fibres

Refractive indices and birefringence changes with strain produced by different stresses in annealed and unannealed polypropylene fibres (4 : 1 draw ratio, 515 tex polypropylene from Bolton, UK) were measured interferometrically. Calculations were carried out using multiple-beam Fizeau fringes in transmission to determine the Cauchy's constants, dispersive coefficient and the dielectric constant at infinity. The orientation factor and orientation angle of the fibre material were calculated for different strain values. Poisson's ratio and the strain optical coefficient were also determined. An empirical formula is suggested to correlate the orientation factor, orientation angle, area of cross-section and birefringence with the draw ratio, and the constants of this formula were determined. The effect of the draw ratio on the refractive index profile was studied. Microinterferograms and curves are given as illustrations.     

基于RSEI的长时序区域生态安全格局构建——以太行山区河北段为例

以太行山区河北段为研究对象,计算遥感生态指数(Remote Sensing Ecological Index, RSEI),进而识别生态源地,选取土地利用类型、归一化植被指数、高程、坡度等多源空间数据进行综合阻力评价,采用电路理论模型提取生态廊道和生态夹点,构建“源地-廊道-节点”的长时序区域生态安全格局。结果表明：(1)研究区2002年、2007年、2012年、2017年、2021年的RSEI均值分别为0.507、0.538、0.554、0.493、0.541,20年间RSEI呈现“上升-下降-上升”的变化趋势;(2)研究区源地总面积逐期增加,初期至末期面积增加5 705 km²,面积占比由2.66%增加至18.56%,源地斑块RSEI均值由0.774上升为0.834;(3)研究区主要生态廊道呈现南北纵向分布,研究末期识别生态源地16个,生态廊道21条,生态夹点5个。     

Evaluation of the performance of metameric indices

Forty three metameric pairs were obtained by comparison, shade-adjustment, and redyeing of 660 self shades dyed with direct, azoic, vat, and reactive dyes. The pairs were regrouped shadewise and ranked visually in increasing order of metamerism. Spearman's rank correlation coefficients were calculated between 11 measures of metamerism and the visual metameric ranking under three illuminants A, D65, and TL84 in pairs. The illuminant-independent general indices included the indices based on reflectance differences (Bridgeman), weighted reflectance differences (Nimeroff and Yurow), Cohen-Kappauf's residual differences (proposed) obtained from the spectral decompositions of the reflectance spectra of the metameric pair. Illuminant-specific special indices included color-differences under test illuminant, addition, subtraction, division, and multiplication of color-differences under test and reference illuminants, indices based on ΔL*, Δa*, Δb* differences under two illuminants, based on chromatic adapted ΔL*, Δa*, Δb* differences with multiplicative corrections for tristimulus differences under reference illuminant (Berns-Billmeyer), differences of the color constancy indices. The present work showed that indices based on ΔL*, Δa*, Δb* differences under two illuminants, both unmodified and modified by Berns-Billmeyer performed best among the existing indices. The differences of color constancy indices showed good correlation with the degree of metamerism in some cases, and this may be utilized for developing newer indices of metamerism. © 1996 John Wiley & Sons, Inc.     

人工神经网络在轻板隔墙隔声预计中的应用

轻钢龙骨薄板墙(简称轻板隔墙)的隔声性能由于其构造的复杂性,没有简单公式可以预计其隔声量。在大量实验结果的基础上,利用人工神经网络对一些常见的轻板墙组合构造进行计权隔声量(RW)的预计。根据相关分析和主成份分析的结果,选用板材面密度、墙体总厚度、腔内吸声层厚度、龙骨型式和垫层等因子作为网络的输入变量,由此进行隔声性能的预计,可达到较满意的结果。     

水平井采油指数预测研究

由于水平井水平段井筒摩擦的存在,长水平井的产能不随水平段长度的增加而按比例无限制地增加,因此提出一种新的方法来预测长水平井在考虑井筒摩擦损失时的采油指数,该模型考虑水平井井眼附近地层的损害。研究表明,水平段长度存在一个临界点,使得井筒压降梯度突然增大而采油指数增长率突然减小。此研究可以为水平井现场设计提供理论依据。     

前馈调节逆变电源

介绍了一种基于DSP控制的单相逆变电源设计方案,该方案采用SPWM调制方式。根据逆变电源的特性,采用逆变器直流侧电压作前馈补偿器,使调制深度保持在合适的值,从而使输出经LC低通滤波多滤波后,得到质量较高的正弦波电压。实验证明,该方案效果良好,成本低廉,运算简单,性能稳定可靠,具有良好的实用价值。     

江苏电力展示厅管理信息系统设计

展示厅管理信息系统为提高电力展示厅的运行管理效率提供了方便快捷的工具。简要介绍电力市场条件下电力展示厅建设的意义,以及展示厅管理信息系统应用的必要性,具体介绍系统的基本功能、软件结构和设计思想,应用基于证据理论的加权算法来计算电力客户整体满意度指数。江苏电力展示厅管理信息系统已开发成功,运行良好并具备后续扩展的能力。     

考虑系统频率特性以及保护隐藏故障的电网连锁故障模型

在大规模电网中,由简单故障触发的电力系统连锁故障经常导致大面积停电的灾难性后果.为了研究故障在电网中的传播情况,同时估计发生连锁故障的风险和损失,找到关键线路,文中从电力系统分析的角度建立了电网连锁故障模型.模型考虑了保护隐藏故障、计及了系统频率特性,可以帮助系统规划、设计和运行人员找到系统发生连锁故障的临界负载率、关键线路,并得到某种运行状态下的连锁故障风险指标.在IEEE RTS96系统上对此模型进行了验证,得到的结果与用PSASP分析的结果及前人的结论一致.     

基于XML和Script组件的指标在线计算模型研究

针对目前电站指标在线计算系统在灵活性、可扩展性等方面的不足,建立了一种新的指标在线计算模型。利用文档对象模型DOM(DocumentObjectModel)建立指标算法文档,将复杂的指标算法从实时运算程序中分离,当指标算法改动时,只需对指标算法文档重新组态,而不需对实时运算程序代码进行改动,实现了复杂算法与计算过程的分离,提高了算法可移植性和灵活性。算法更新过程采用“非重启模式”,实现了算法文件集的在线更新,避免了程序重启过程所带来的数据损失,提高了运算的精确度。同时,基于Microsoft(R)Script组件建立了具有“黑箱”特性的指标在线运算模块,作为与算法无关的纯计算程序,其在线计算量小,提高了对数据的分析能力和可操作性。