Residual life estimation based on nonlinear-multivariate Wiener processes

For some operable products with critical reliability constraints, it is important to estimate accurately their residual lives so that maintenance actions can be arranged suitably and efficiently. In the literature, most publications have dealt with this issue by only considering one-dimensional degradation data. However, this may be not reasonable in situations wherein a product may have two or more performance characteristics (PCs). In such situations, multi-dimensional degradation data should be taken into account. Here, for the target product with multivariate PCs, methods of residual life (RL) estimation are developed. This is done with the assumption that the degradation of PCs over time is governed by a multivariate Wiener process with nonlinear drifts. Both the population-based degradation information and the degradation history of the target product up-to-date are combined to estimate the RL of the product. Specifically, the population-based degradation information is first used to obtain the estimates of the unknown parameters of the model through the EM algorithm. Then, the degradation history of the target product is adopted to update the degradation model, based on which the RL is estimated accordingly. To illustrate the validity and the usefulness of the proposed method, a numerical example about fatigue cracks is finally presented and analysed.     

Structural Nonparametric Cointegrating Regression

Nonparametric estimation of a structural cointegrating regression model is studied. As in the standard linear cointegrating regression model, the regressor and the dependent variable are jointly dependent and contemporaneously correlated. In nonparametric estimation problems, joint dependence is known to be a major complication that affects identification, induces bias in conventional kernel estimates, and frequently leads to ill‐posed inverse problems. In functional cointegrating regressions where the regressor is an integrated or near‐integrated time series, it is shown here that inverse and ill‐posed inverse problems do not arise. Instead, simple nonparametric kernel estimation of a structural nonparametric cointegrating regression is consistent and the limit distribution theory is mixed normal, giving straightforward asymptotics that are useable in practical work. It is further shown that use of augmented regression, as is common in linear cointegration modeling to address endogeneity, does not lead to bias reduction in nonparametric regression, but there is an asymptotic gain in variance reduction. The results provide a convenient basis for inference in structural nonparametric regression with nonstationary time series when there is a single integrated or near‐integrated regressor. The methods may be applied to a range of empirical models where functional estimation of cointegrating relations is required.     

西方学界关于民主与腐败关系的研究

西方学界关于"民主与腐败关系"的探讨有3种流派:第1种流派认为,民主与腐败不存在此消彼长的必然联系,第2种流派认为,民主与腐败存在线性关系,该流派分为民主有利于腐败治理和不利于腐败治理2种观点,第3种流派认为,民主与腐败存在非线性关系,即一个国家的腐败程度在民主化的不同阶段有较大差异,该流派分为"倒U型"、"S型"和"J型"关系3种观点。西方学界关于"民主与腐败关系"的探讨取得了重大进展,实现了从静态研究向动态研究,从定性研究向定量研究的转化。     

非线性需求下具有网络外部性的二级歧视定价研究

研究了非线性需求函数条件下产品存在网络外部性时,垄断企业采用对需求区间分段定价的方法进行二级歧视定价的策略。首先分析了单阶段垄断企业二级价格歧视的静态定价策略,接着给出了在一个较长时期内垄断企业分两阶段进行二级歧视的动态定价策略。结果表明网络外部性不影响最优需求区间分段单调递增的性质,但价格随网络外部性的增强而相应提高,且第一阶段的价格高于第二阶段的贴现值。     

SiC MESFET非线性模型及其嵌入研究

基于TOM直流I-V模型和Angelov非线性电容模型,该文建立了适合SiC MESFET的非线性模型,并利用符号定义器件(SDD)实现了在安捷伦ADS软件中嵌入,最终建立了SiC MESFET工艺的模型库。该非线性模型考虑了击穿特性、色散效应和自热效应等,可进行直流、散射S参数和谐波平衡等ADS软件中的仿真器。该模型在国内SiC MESFET工艺线上的验证结果表明模型具有较好的精度。     

具有多重势的分数阶非线性Schrodinger方程解的适定性

讨论了具有多重势的分数阶非线性Schrodinger方程的周期边值问题,利用能量估计和Faedo—Galerkin方法证明了该问题光滑解的整体存在唯一性     

基于ANSYS/LS DYNA的移动式压力容器动态碰撞仿真分析

运用有限元和瞬态动力学的有关理论和方法对移动式压力容器受碰撞后的安全性进行了研究。首先采用三维建模软件建立了移动式压力容器运输车的实体模型,然后分别利用有限元分析软件ANSYS和瞬态动力学仿真软件LS DYNA对模型进行前处理分析和求解计算,分别得到车速为60 km/h车尾受到碰撞时车架、压力容器罐体、组合支座及相关辅件的动态碰撞应力响应情况。计算结果表明：车架及连接螺栓失效,但有效降低了对压力容器罐体的冲击,基本保证了其安全性,并为今后的优化设计提供了理论支撑。     

关于非线性迭代方程的集值解

该文主要研究了Banach空间中的二次迭代非线性集值函数方程,获得了非单调集值解的存在性和唯一性,及解对给定函数的连续依赖性的条件．     

基于FPGA的可重构数控系统

利用FPGA丰富的逻辑资源及其内部可编程的特点,文章提出了可重构数控系统硬件设计方法及以FPGA为控制核心的数控系统设计方案,重点分析了对电机的速度控制及与PC机的串行通信等,开发了以FPGA为控制核心的经济型数控系统。其响应速度快,可重构性强,大大减少了系统的外围接口器件,同时有效降低了系统成本。