Design of a modified repetitive-control system based on a continuous–discrete 2D model

This paper concerns the problem of designing a modified repetitive-control system for a class of strictly proper plants. Repetitive control involves two types of actions: control and learning; but the insertion of a low-pass filter in a modified repetitive controller, which is employed to guarantee the stability of the system, mixes the two actions together. In this paper, a continuous–discrete two-dimensional model is first constructed. Next, the continuity of repetitive control and Lyapunov stability theory are applied to the model to establish two linear-matrix-inequality (LMI) based sufficient stability conditions, one for the design of the cutoff angular frequency and one for the design of the feedback gains. The features of these conditions are exploited to develop an iterative algorithm that searches for the best combination of the maximum cutoff angular frequency of the low-pass filter and the feedback gains. A numerical example illustrates the design procedure and demonstrates the validity of the method.     

Experimental Research on the Dynamic Energy Absorbing Capacity of the Honeycomb Paperboard Filled with Polyurethane

A kind of composite buffering material was made by filling the voids of honeycomb paperboard with polyurethane. Drop tests were performed to evaluate the dynamic energy absorption capacity of the material. Based on the tests results, the mechanical behaviors of the material under low velocity dynamic impact conditions were analyzed. It was shown that the absorbed energy of the composite material varies inversely with the void diameter. The absorbed energy of the composite material is 1 - 2 times than that of honeycomb paperboard and polyurethane. The energy absorption efficiency of the composite material is better than those of honeycomb paperboard and polyurethane.     

Oxidation behaviors of Ni-Cr-Al superalloy foams at 1 000 ℃ in air

The oxidation behaviors of Ni-16Cr-xAl （x=4.5%, 9.0%, mass fraction） superalloy foams in air at 1000℃ were investigated. The effects of AI content on the resistance to high temperature oxidation were examined. The oxidation mechanisms of the foams were discussed. The results show that the resistance to the oxidation of the Ni-16Cr-xA1 based alloy at 1 000 ℃ increases with the content of A1 increasing from 4.5% to 9.0%. Complex oxide products are formed on the surface of the superalloy foams after the oxidation. Cr203 and A1203 are the predominant oxides for the scales of the foams with 4.5% A1 and 9% A1, respectively. Excellent high temperature oxidation resistance and superior pore conformation stability for the Ni-16Cr-xA1 based superalloy foam with 9% A1 can be mainly attributed to the formation of relatively continuous and protective A1203 oxides on the surface of the foam.     

Uniformly subsampled ensemble (USE) for churn management: Theory and implementation

The present paper explores the possible application of a new ensemble model. The model, which is based on multiple SVM classifiers, is employed to address churner identification problems in the mobile telecommunication industry, a sector in which the role of customer retention program becomes increasingly important due to its very competitive business environment. In particular, the current study introduces a uniformly subsampled ensemble (USE) model of SVM classifiers, not only to reduce the computational complexity of large-scale data, but also to boost the reliability and accuracy of calibrated models on data sets with highly skewed class distributions. According to our experiments, the performance of the USE SVM model is superior compared to all single and ensemble models. It is more scalable than well-known ensemble models as well.     

Probabilistic characterisation of model error using Gaussian mixture model—With application to Charpy impact energy prediction for alloy steel

A novel approach to characterise the model prediction errors using a Gaussian mixture model is proposed. The motivation for this work lies behind many data models that are developed through prediction error minimisation with the assumption of a normal noise distribution. When the noise is non-normal, which may often be the case in complicated data modelling scenarios, the model prediction errors may contain rich information, which can be further exploited for model refinement and improvement. The key contents presented in this paper include: choosing the relevant variables to form the error data, optimising the number of Gaussian components required for the error data modelling, and fitting the Gaussian mixture parameters using an expectation-maximisation algorithm. Application of the proposed method for further model improvement, within the framework of hybrid deterministic/stochastic modelling, is also discussed. Preliminary results on the real industrial Charpy impact energy data for heat-treated steels show its effectiveness for model error characterisation, and the potential for model performance improvement in terms of prediction accuracy as well as providing accurate prediction confidence intervals.     

点到平面距离公式的一种新证法

该文根据球面上一点切平面的方程和平移变换,对空间任一点P(x0,y0,z0),分P点为坐标原点和P点不是坐标原点两种情形,给出了到平面π:Ax By Cz D=0的距离公式d=|Ax0 By0 Cz0 D|/√A2 B2 C2 的一种新证法.     

一类非光滑非凸分式半无限规划的最优性

在一致Fb-凸函数，一致Fb-伪凸和一致Fb-拟凸等广义凸性函数的基础上，研究了一类分式半无限规划问题，得到了涉及这些广义凸性函数的一类非光滑分式半无限规划的一些最优条件。     

论梁启超政治功能小说观

梁启超发起“小说界革命”，将小说直接承载政治使命，并提出“小说为文学之最上乘”的口号，客观上消融了一直以来存在于人们脑海的“小说为小道”的观念痼疾。小说也因此成为当时最受欢迎的文学样式。“小说界革命”对小说地位的提升与当时特定的社会环境及梁启超本人的社会地位是密不可分的。     

电子设备的建模研究

本文首先介绍了开关电源的基本工作原理和电路构成,在此基础上,通过试验研究,建立了计算机和电视机等电子设备的静态负荷模型。所得结论,为电力系统稳定分析计算提供了依据。     

Modeling and simulation for a drop-impact analysis of multi-layered printed circuit boards

Multi-layered printed circuit boards (PCBs) contain a multi-layered structure that is suitable for high-speed and high-frequency applications. Hence, they are used extensively in electronic packaging assemblies for high-density applications. However, numerous composite parts and complex material properties of multi-layer PCBs complicate the reliability simulation of PCB model. This paper deals with a finite element analysis intended to describe numerically the behavior of multi-layered multi-materials PCB model (combination of metallic and composite plies) in the drop-impact performance. Through the comparison of physical drop test results, the fully multi-layered model illustrates higher accuracy if compared with that of the traditional simplified isotropic model and orthotropic model. The effects of material properties for the multi-layer PCB under drop-impact shock have also been investigated.