基于因子分析的模拟电路故障特征提取技术研究

针对LS-SVM算法中小波提取特征存在小波基函数选择和小波分解层次、系数选取的问题,提出了一种基于因子分析技术的故障特征识别方法;该方法通过构建采样数据的相关矩阵求出因子载荷和因子得分,按照累计贡献率自动提取出1~3个因子组成特征向量,从而降低了输入维度,提高了算法训练诊断效率,降低了收敛难度;四运放典型电路的仿真实验结果表明:文中算法的诊断正确率超过了同类方法,同时提高了训练时间和诊断效率。     

联合空间与角度的符号相干系数平面波成像北大核心CSCD

超声平面波成像是近年来一种应用较广泛的超快速超声成像方法,多角度相干平面波复合(Coherent Plane Wave Compounding,CPWC)成像在不过多损失速率的情况下,提升成像质量。但普通的CPWC方法只是简单复合多个角度延时叠加(Delay and Sum,DAS)后的数据,并未考虑到单个角度内以及多个角度之间数据的相关性。文章提出了一种联合空间与角度的符号相干系数(Angular Spatial Sign Coherence Factor,asSCF)平面波成像方法,将空间符号相干因子和角度符号相干因子创新性地融合到波束合成的过程中,充分考虑信号之间的相关性,旨在提升多角度复合成像质量。进行了仿真实验、仿体实验以及在体组织实验,对asSCF-CPWC方法、单一的符号相干系数法以及传统CPWC方法成像进行对比,结果发现asSCF-CPWC方法具有更好的横向分辨能力和成像对比度。     

绝缘油介质损耗与体积电阻率测试仪空杯电容值的计算

绝缘油介质损耗与体积电阻率测试仪的试验油杯是仪器的重要组成部分,以空气为介质的油杯电容值影响仪器的测量准确度和校准结果。为了得到准确的油杯电容值,依据油杯几何结构,采用圆锥体电容与圆柱体电容并联分布的物理模型,推导获得理论计算公式,并进行建模仿真比较。结果表明,所述理论计算方法有较高准确度,可用于指导测试仪的设计和校准工作。     

Direct numerical simulations for assessment of gas-solid drag models in two-dimensional random arrays of particles

The momentum exchange between the phases plays a vital role in modelling of gas–solid flows and it is mathematically described by drag models. However, no consensus exists on which drag model gives the most accurate prediction of the drag force, and, despite the increase in available computing power, the same drag models are used in two-dimensional and three-dimensional simulations. In this study, direct numerical simulations of gas flow through multiple random configurations of static monodisperse particles are performed. The variations of solid volume fraction and particle Reynolds number are in the ranges of 0.05–0.4 and 13.7–136.9, respectively. The drag force exerted on particles is calculated and properly averaged. Based on the simulation results, thirteen drag models are compared and correction factors are introduced using the stochastic gradient descent algorithm. The correction factors provide a simple adjustment for the models to be used in 2D modelling.     

Regulation of Polymer Configurations Enables Green Solvent-Processed Large-Area Binary All-Polymer Solar Cells With Breakthrough Performance and High Efficiency Stretchability Factor

With the great potential of the all-polymer solar cells for large-area wearable devices, both large-area device efficiency and mechanical flexibility are very critical but attract limited attention. In this work, from the perspective of the polymer configurations, two types of terpolymer acceptors PYTX-A and PYTX-B (X = Cl or H) are developed. The configuration difference caused by the replacement of non-conjugated units results in distinct photovoltaic performance and mechanical flexibility. Benefiting from a good match between the intrinsically slow film-forming of the active materials and the technically slow film-forming of the blade-coating process, the toluene-processed large-area (1.21 cm²) binary device achieves a record efficiency of 14.70%. More importantly, a new parameter of efficiency stretchability factor (ESF) is proposed for the first time to comprehensively evaluate the overall device performance. PM6:PYTCl-A and PM6:PYTCl-B yield significantly higher ESF than PM6:PY-IT. Further blending with non-conjugated polymer donor PM6-A, the best ESF of 3.12% is achieved for PM6-A:PYTCl-A, which is among the highest comprehensive performances.     

图的正交(g,f)-因子分解

设ｇ和ｆ分别是定义在图Ｇ的顶点集合Ｖ（Ｇ）上的整数值函数且对每一个ｘ∈Ｖ（Ｇ）有２≤ｇ（ｘ）≤ｆ（ｘ）．证明了若Ｇ是（ｍｇ＋ｍ－１,ｍｆ－ｍ＋１）—图,则对Ｇ中任意一个给定的有ｍ条边的子图Ｈ,Ｇ有一个（ｇ,ｆ）—因子分解与Ｈ正交．     

夹层梁的高阶剪切修正因子

导出了满足夹层梁界面剪应力连续等条件的高阶位移场,据此给出了反馈横向剪切变形对夹层梁的弯曲,稳定和固有频率的影响的剪切修正因子,该因子计算简便,精度高,便于工程应用。     

关于Wiener过程增量的注

本文讨论Ｗｉｅｎｅｒ过程增量的下极限结果找到正则因子ｄ（Ｔ,ｔ）,使得ｓｕｐａＴ≤ｔ≤Ｔｓｕｐｔ≤ｓ≤Ｔｄ（Ｔ,ｔ）｜ｗ（ｓ）－ｗ（ｓ－ｔ）｜与ｓｕｐｓＴ≤ｔ≤Ｔｓｕｐｔ≤ｓ≤Ｔｓｕｐ０≤ｂ≤ｔｄ（Ｔ,ｔ）｜ｗ（ｓ）－ｗ（ｓ－ｈ）｜的下极限１。     

表达式的覆盖、分解与划分

本文把简单表达式（项和原子）视为语言Ｌ的Ｈｅｒｂｒａｎｄ域或Ｈｅｒｂｒａｎｄ基中的集合．作者提出覆盖表达式的概念,得到２个表达式之间覆盖关系的判别准则．对多个表达式,作者提出表达式的分解概念及相应的分解算法,在此基础上,本文给出卫个表达式覆盖多个表达式的等价条件．根据集合的划分公式,得到划分表达式的方法．最后定义１个变换把合取式转换为简单表达式,从而方便地把简单表达式的结果推广到合取式．本文是作者提出的一种标记逻辑程序的过程语义的理论基础．