图像分类中基于分类矢量量化的视觉词袋模型

特征表示是图像识别和分类的基础，视觉词袋是一种图像的特征表示方法。分析现有视觉词典构建方法的不足，提出一种新的视觉词典构建方法。首先利用梯度方差把特征矢量分为光滑类和边缘类，然后分别针对不同类别的特征矢量进行视觉词典的构建，最后根据两类视觉词典生成视觉词袋。图像分类实验表明，提出的新方法能提高分类准确率。     

A review on spindle thermal error compensation in machine tools

Thermal error caused by the thermal deformation is one of the most significant factors influencing the accuracy of the machine tool. Among all the heat sources which lead to the thermal distortions, the spindle is the main one. This paper presents an overview of the research about the compensation of the spindle thermal error. Thermal error compensation is considered as a more convenient, effective and cost-efficient way to reduce the thermal error compared with other thermal error control and reduction methods. Based on the analytical calculation, numerical analysis and experimental tests of the spindle thermal error, the thermal error models are established and then applied for implementing the thermal error compensation. Different kinds of methods adopted in testing, modeling and compensating are listed and discussed. In addition, because the thermal key points are vital to the temperature testing, thermal error modeling, and even influence the effectiveness of compensation, various approaches of selecting thermal key points are introduced as well. This paper aims to give a basic introduction of the whole process of the spindle thermal error compensation and presents a summary of methods applied on different topics of it.     

FPGA-based architecture to estimate the input glucose in a dark fermenter using a super-twisting observer

This article presents a digital architecture design for a Super-Twisting Observer (STO) implemented in a Field-Programmable Gate Array (FPGA). The STO is robust in the presence of uncertainties, which makes it suitable to estimate unknown inputs present in biological systems and applications based on sensorless control accurately. The proposed STO is used to estimate the glucose concentration in the inflow of a hydrogen production bioreactor (e.g., dark fermenter). The dark fermenter is not generally recognized as a swift process. Therefore, the observer digital architecture design criteria aim to optimize hardware resources and reduce power consumption through an iterative approach to perform internal arithmetic operations efficiently. Besides, an analysis of the errors produced by internal operations, observer discretization, and fixed-point data representation is presented and discussed. Numerical results showed that embedding the super-twisting observer into the FPGA is a reliable, low-power consumption, and efficient alternative to estimate the input glucose in a dark fermenter.     

A Laser Scanner–Stage Synchronized System Supporting the Large-Area Precision Polishing of Additive-Manufactured Metallic Surfaces

This paper proposes a scanner–stage synchronized approach emphasizing a novel control structure for the laser polishing of Inconel 718 components manufactured by selective laser melting in order to address increasing demands for high surface quality in metal additive manufacturing. The proposed synchronized control system is composed of a motion decomposition module and an error synthesis module. The experimental results show that stitching errors can be avoided thanks to continuous motion during laser processing. Moreover, in comparison with the existing step-scan method, the processing efficiency of the proposed method is improved by 38.22% and the surface quality of the laser-polished area is significantly enhanced due to a more homogeneous distribution of the laser energy during the material phase change. The proposed synchronized system paves the way for high-speed, high-precision, and large-area laser material processing without stitching errors.     

Observer‐based fuzzy adaptive quantized control for uncertain nonlinear multiagent systems

This paper focuses on consensus quantized control design problem for uncertain nonlinear multiagent systems with unmeasured states. Every follower can be denoted through a system with unmeasurable states, hysteretic quantized input, and unknown nonlinearities. Fuzzy state observer and Fuzzy logic systems are employed to estimate unmeasured states and approximate unknown nonlinear functions, respectively. The hysteretic quantized input can be split into two bounded nonlinear functions to avoid chattering problem. By combining adaptive backstepping and first‐order filter signals, an observer‐based fuzzy adaptive quantized control scheme is designed for each follower. All signals exist in closed‐loop systems are semiglobally uniformly ultimately bounded, and all followers can accomplish a desired consensus results. Finally, a numerical example is employed to elaborate the effectiveness of proposed control strategy.     

初学者学习C语言中常见问题的探讨

C语言是编程领域中很有影响力的一种程序设计语言。它简洁、紧凑，使用方便、灵活，并且具备高级语言和低级语言的特征。由于C语言的编译系统对语法的检查不如其他语言那么严格，因此C语言对使用者的要求比较高。笔者结合实际教学中的经验，分类列举出C语言中常见的错误进行分析与探讨，以此对初学者给予借鉴。     

EFFICIENT METHOD OF MOMENTS ESTIMATORS FOR INTEGER TIME SERIES MODELS

The parameters of integer autoregressive models with Poisson, or negative binomial innovations can be estimated by maximum likelihood where the prediction error decomposition, together with convolution methods, is used to write down the likelihood function. When a moving average component is introduced this is not the case. To address this problem an efficient method of moment estimator is proposed where the estimated standard errors for the parameters are obtained using subsampling methods. The small sample properties of the estimator are investigated using Monte Carlo methods, while the approach is demonstrated using two well‐known examples from the time series literature.     

旋进旋涡流量计合成不确定度及其表示方法

随着市场对天然气需求的不断扩大,天然气公司对流量计计量准确度的要求也变得越来越高,但是流量计的测量误差却是无法避免的,而不同的误差可以通过不同的方法来进行控制或减小,其中重要的未定系统误差可以通过不确定度来确定。因此如何正确合理地求出流量计的测量不确定度是十分必要的,本文将以旋进旋涡流量计的测量不确定度的分析过程为基础,指出了在合成标准不确定度以及扩展不确定度的表示中应当值得注意的地方。     

用热电偶测量流体介质温度的误差分析

在工业应用中,普遍采用热电偶传感器来进行温度测量。讨论了热电偶在测量温度过程中,由于热传导和热辐射的作用,使其测量误差存在的影响因素,并就提高测量精度介绍了一些措施和几种有针对性的改进热电偶装置。     

基于视觉显著模型的音视频交叉水印算法

提出一种基于Itti视觉显著模型的音视频交叉水印算法.首先利用音频码流的低通幅值特性生成水印,并嵌入到视频码流中;其次解码视频码流的关键帧Ⅰ帧,获取YUV序列上的亮度(Y)分量,并对其进行显著性分析;最后分块对非显著区域进行DCT变换,并通过量化索引调制嵌入水印.实验结果表明,该算法将嵌入水印后的关键帧平均PSRN值提高了1.678 5 dB,缓解了水印不可见性和鲁棒性的矛盾,实现了音视频码流之间的交叉保护.