Crystalline aluminium hydroxy fluorides—Suitable reference compounds for F chemical shift trend analysis of related amorphous solids

On the basis of MAS NMR-data for crystalline AlF_x(OH)_3−x·H₂O samples in the pyrochlore structure, ¹⁹F chemical shifts correlate with the average chemical composition of the octahedral environment, given by AlF_xO_6−x in these compounds.The attribution of local structures in sol-gel derived amorphous AlF_x(OX)_3−x·XOH (X = H, R (alkyl)) compounds is of special interest as these or consecutively prepared solids exhibit remarkable features, for example, a high surface (HS) area accompanied by a high Lewis acidity.By transferring this scale of a ¹⁹F chemical shift trend analysis to such compounds a prediction of the chemical nature of the average Al coordination becomes possible.A new synthetic approach to crystalline aluminium hydroxy fluorides involving a sol gel fluorination as the first reaction step and an aluminium alkoxide as precursor compound is presented. Varying the amount of HF leads to different F-OH-ratios in the AlF_x(OH)_3−x compounds.     

陕西省研究生教育预测模型实证研究

在综合考虑陕西省研究生教育的历史和现状、所面临的机遇和挑战,及全省经济发展速度的基础上,运用统计理论中的趋势拟合模型、二次指数平滑模型、线性回归模型,预测陕西省研究生教育在未来10年所应达到的规模.并结合实际对三种预测模型的预测结果进行了讨论,分析了各种预测模型的利与弊,判断出线性回归模型是较为可取的一种模型,从而得出研究生招生规模应量力而行的结论.     

分析测试实验室内部质量控制中移动极差合并统计监控技术下的不确定度动态测量评估

本文采用统计质量保证技术(SQA,statistical quality rassurance)对被测体系的精密度和偏离性能做过持续性的监控分析。SQA技术的采用可以连续地表现出分析测量体系的能力,该技术的应用能确保测试数据的有效性,有利于分析测量体系潜在问题的分析。在此基础上,本文进一步提出了平均移动极差(MR)合并统计动态监控技术一本研究认为,采用该技术来进行分析测量系统的动态不确定度评估,其贡献量可由质控样品(QC)和线性拟合两部分合成。这一结论的得出能最大限度合成各种变异因素的影响,避免相关性的复杂计算,有利于分析测试实验室内部质量控制过程中测量系统的不确定度评估。     

面向桥梁长期健康监测的大数据处理技术及应用

简要介绍了桥梁长期健康监测系统的应用,总结了基于桥梁长期健康监测大数据分析技术的研究现状。介绍了基于长期健康监测大数据分析在多尺度关联性分析、异常数据挖掘和分析以及时变可靠度研究三个方面取得的研究进展。通过多尺度关联性分析对各频率组分下的桥梁应变进行了分类,确定了温度对应变的影响;发展了利用应变阈值和小波细节系数进行异常信号识别的方法;提出了局部时变可靠度的计算方法。最后,对基于云计算的桥梁健康监测服务平台的研制及应用进行了介绍和展望。     

基于小波神经网络的光纤陀螺误差补偿方法

为了提高光纤陀螺的测量精度,提出了一种基于小波神经网络的误差补偿方法。首先使用小波分析中的Mallat分解算法提取出陀螺信号中的主趋势项,对其误差余项进行重构。然后将重构信号作为小波神经网络的目标输出,将原始陀螺信号作为训练样本。为了提高小波神经网络的训练速度同时防止其陷入局部极小值,采用增加动量因子和自适应调整学习速率的方法来改进训练方法。训练后建立的神经网络模型对光纤陀螺误差具有良好的估计能力。结果表明,经过小波神经网络方法补偿后,光纤陀螺的输出精度达到了0. 019 4°/s,光纤陀螺的测量性能得到了提高。     

秘鲁M_w≥6.9地震趋势判断与时空对称规律

选取秘鲁地区1970年以来M_w≥6.9的地震数据,根据可公度性理论,提取秘鲁强震的可公度信息,采用蝴蝶结构图、可公度网络结构图和震中迁移方法,探索该地区强震活动的时空对称性,同时对可能触发地震的天文现象与地震灾害的发生进行相关分析,进一步验证趋势判断结果,发现相关规律.研究结果表明:1970年以来秘鲁M_w≥6.9地震具有可公度性,2019年在秘鲁北部(73°W,11°S附近)发生中深源地震的信号较强;太阳活动、地球自转、月球运动与秘鲁地震的发生具有一定相关性,秘鲁M_w≥6.9地震发生在太阳活动峰值年、下降段的占77.78%,发生在太阳活动双周期的占66.67%,发生在地球自转变化率较大年份的占60%,朔月前后是地震频发期(占44.44%),朔月、下弦月前后地震发生次数达83.33%.     

基于AGPF的滚动轴承性能衰退趋势预测

针对粒子滤波算法中粒子退化和计算复杂度问题,提出了一种自适应遗传粒子滤波(AGPF)算法。该算法采用遗传算法代替传统粒子滤波中的重采样方法,并根据粒子数与滤波误差方差之间的关系,自适应调节滤波过程中的粒子数。通过预测滚动轴承的性能衰退趋势,对该方法进行验证,结果表明,AGPF算法能够在保证预测精度的条件下,减少滤波粒子数,更加适用于滚动轴承的性能衰退趋势预测。     

Long-term damage of discrete-fiber-reinforced composites with transversely isotropic inclusions and stress-rupture microstrength described by an exponential power function

The theory of long-term damage of homogeneous materials, which is based on the equations of the mechanics of stochastically inhomogeneous materials, is generalized to discrete-fiber-reinforced composite materials. The microdamage of the composite components is modeled by randomly dispersed micropores. The failure criterion for a microvolume is characterized by its stress-rupture strength. It is determined by the dependence of the time to brittle failure on the difference between the equivalent stress and its limit. Given macrostresses and macrostrains, an equation of damage (porosity) balance in the composite components at an arbitrary time is formulated. The time dependence of microdamage and macrostresses or macrostrains is established in the case of stress-rupture microstrength described by an exponential power function Translated from Prikladnaya Mekhanika, Vol. 45, No. 2, pp. 19–29, February 2009.     

A refined fuzzy time series model for stock market forecasting

Time series models have been used to make predictions of stock prices, academic enrollments, weather, road accident casualties, etc. In this paper we present a simple time-variant fuzzy time series forecasting method. The proposed method uses heuristic approach to define frequency-density-based partitions of the universe of discourse. We have proposed a fuzzy metric to use the frequency-density-based partitioning. The proposed fuzzy metric also uses a trend predictor to calculate the forecast. The new method is applied for forecasting TAIEX and enrollments’ forecasting of the University of Alabama. It is shown that the proposed method work with higher accuracy as compared to other fuzzy time series methods developed for forecasting TAIEX and enrollments of the University of Alabama.