高斯过程回归在近红外光谱定量分析绝缘纸老化状态中的应用

绝缘纸的老化状态决定了油浸式变压器的剩余寿命,对绝缘纸的老化状态进行快速有效的评估具有重要意义。聚合度是表征纤维素绝缘纸老化程度最直接可靠的参量,在实验室中通过粘度法检测获得,但该方法需要获得设备纸样,不但检测耗时长,还会对变压器类设备的绝缘造成破坏。近红外光谱分析技术可以快速有效测定物质中的组分含量,检测过程非侵入、对绝缘无损,目前已成功应用于多个领域,有望成为替代传统聚合度检测的新方法。然而,现有的近红外光谱定量分析方法尚不能满足绝缘纸聚合度的预测精度需求,建立了基于高斯过程回归(GPR)的绝缘纸老化状态定量评估方法。构建了不同老化程度绝缘纸样本—近红外光谱数据库,使用Savitzky-Golay卷积平滑算法对光谱数据进行平滑处理以提高信噪比;研究了不同核函数GPR模型并开展了模型预测精度分析与参数敏感性检验。结果显示,Exp核模型泛化性能较差,Matern32核、 Matern52核以及RQ核模型对参数敏感性较高、模型稳定性较差,最终选择了SE核GPR模型作为最优模型。将SE核GPR模型与近红外分析领域常用的PLS, SVR与BPNN模型进行性能对比,结果表明,GPR模型对校正集...     

基于模糊信息分解的中小微企业信用评估组合模型

信用评估是银行开展中小微企业信贷业务的重要环节,尽管已有信用评估模型的分类性能较高,但仍有待进一步提升,同时模型也缺乏可解释性,在一定程度上影响了模型的推广应用。为此,本文提出了一种基于模糊信息分解的中小微企业信用评估组合模型。首先,针对信用评估数据的不平衡性,利用模糊信息分解的方法进行过采样处理。其次,基于XGBoost模型和Logistic回归模型,构建了一种具有较高的分类性能和良好可解释能力的中小微企业信用评估组合模型。最后,结合某商业银行对中小微企业的信用数据,实验验证了所构建组合模型的可行性和有效性。     

LED灯具在线老化测试新方法研究

为解决LED灯具寿命老化测试普遍存在的操作流程复杂、自动化程度低、老化过程监测不连续而难以精确获得失效节点等问题,提出一种在线自动老化测试新方法,开发LED照明灯具自动化在线老化测试系统,全程由中心计算机程控并脱离人为操作,实时连续监测LED灯具老化过程中的光衰、电参数等指标,实现LED照明灯具的自动化在线寿命老化测试。     

计及时变演化特征的硅泡沫垫层非线性黏弹性模型研究

基于黏弹性基本理论,引入材料非线性特征,考虑了材料加载、保载应力松弛历史、老化效应以及黏弹性模型各运动单元退化的差异性,并从两种老化机制出发,获得了老化硅泡沫垫层力学模型以及长时应力松弛硅泡沫垫层接续加载力学模型.模型机理清晰,能够反映材料服役历史信息及其对力学效应的影响.     

基于量子蚁群算法的旅行商问题求解及算法评估

量子蚁群算法是一种将量子理论与传统蚁群算法结合的高效生物进化算法,主要应用于故障诊断、路径规划、图像分割等问题的优化.基于传统蚁群算法的流程,介绍量子蚁群算法中的量子理论基础以及量子理论如何应用于蚁群算法.通过若干旅行商问题实例分析量子蚁群算法较传统蚁群算法的优势.针对目前研究多以离散指标来评估不同算法、难以直观显示不同算法综合差别的问题,提出一种综合评估算法搜索效率的方法,成功应用于量子蚁群算法和传统蚁群算法的对比,具有一定的实践意义.     

Creep performance of PVC aged at temperature relatively close to glass transition temperature

In order to predict the mechanical performance of the polyvinyl chloride(PVC) at a high operating temperature,a series of short-term tensile creep tests(onetenth of the physical aging time) of the PVC are carried out at 63 C with a small constant stress by a dynamic mechanical analyzer(DMA).The Struik-Kohlrausch(SK) formula and Struik shifting methods are used to describe these creep data for various physical aging time.A new phenomenological model based on the multiple relaxation mechanisms of an amorphous polymer is developed to quantitatively characterize the SK parameters(the initial creep compliance,the characteristic retardation time,and the shape factor) determined by the aging time.It is shown that the momentary creep compliance curve of the PVC at 63 C can be very well fitted by the SK formula for each aging time.However,the SK parameters for the creep curves are not constant during the aging process at the elevated temperatures,and the evolution of these parameters and the creep rate versus aging time curves at the double logarithmic coordinates have shown a nonlinear phenomenon.Moreover,the creep master curves obtained by the superposition with the Struik shifting methods are unsatisfactory in such a case.Finally,the predicted results calculated from the present model incorporating with the SK formula are in excellent agreement with the creep experimental data for the PVC isothermally aged at the temperature relatively close to the glass transition temperature.     

基于窗口均值的WSNs链路质量评估方法

无线传感器网络(wireless sensor networks,WSNs)通信的不可靠性为网络协议的设计带来很大的挑战.准确而高效的链路质量评估则是保证上层协议性能的基础.针对传统的LQI (Link Quality Indication)均值评估法所存在的问题,提出了一种LQI窗口均值(window mean-LQI,WM-LQI)评估方法.实验结果表明该评估方法是合理的,且与传统的均值评估法相比,提高了评估的精度,从而更加具有实用性.     

Assessing dynamic response of multispan viscoelastic thin beams under a moving mass via generalized moving least square method

Dynamic response of multispan viscoelastic thin beams subjected to a moving mass is studied by an efficient numerical method in some detail. To this end, the unknown parameters of the problem are discretized in spatial domain using generalized moving least square method （GMLSM） and then, discrete equations of motion based on Lagrange＇s equation are obtained. Maximum deflection and bending moments are considered as the important design parameters. The design parameter spectra in terms of mass weight and velocity of the moving mass are presented for multispan viscoelastic beams as well as various values of relaxation rate and beam span number. A reasonable good agreement is achieved between the results of the proposed solution and those obtained by other researchers. The results indicate that, although the load inertia effects in beams with higher span number would be intensified for higher levels of moving mass velocity, the maximum values of design parameters would increase either. Moreover, the possibility of mass separation is shown to be more critical as the span number of the beam increases. This fact also violates the linear relation between the mass weight of the moving load and the associated design parameters, especially for high moving mass velocities. However, as the relaxation rate of the beam material increases, the load inertia effects as well as the possibility of moving mass separation reduces.     

二维Ising和XY模型的老化现象研究

以动力学蒙特卡罗（Monte Carlo）模拟方法对二维伊辛（Ising）模型和二维经典XY模型展开了数值研究．从一个高温无序相淬火到临界点Tc,采用热浴迭代方法,模拟计算双时自关联函数A（t,t’=O）与t的函数标度关系,以及A（t,t’）与t／t’之间的函数关系,得到了相关临界指数．研究其中所遵循的规律,证实对二维XY模型的标度行为应该进行对数修正．预测了老化（aging）现象的普适性及其标度关系,与重整化群理论的结果相吻合．     

实验室工作的评估与考核

原国家教委发布《中小学实验室工作的规定》后,教育评估引起了教育界和各方面的关注和重视。从而,许多人在理论上、实践上对学校的教育评估工作进行了有益的探索,为开展中学化学实验室评估工作奠定了基础。