直线电机的发展及应用概况

介绍了直线电机的分类及特点,直线电机是一种将电能直接转换成直线运动,而不需要通过任何中间转换机构的新颖电机.阐述了直线电机理论分析和优化设计的研究手段和最新研究成果,分析了直线电机核心控制部件、外围输出通道、控制理论和控制技术发展状况,简要叙述了直线电机在工业、办公设备、交通、家庭自动化、军事装备等领域的的应用现状和动态.根据直线电机应用研究的发展趋势,指出在利用计算机提高直线电机的控制精度和依据新原理研制新型直线电机的新技术推动下,直线电机具有广阔的应用和发展前景.     

非线性模型下的摄像机自标定

摄像机标定是从二维图像获取三维信息必不可少的步骤，线性（小孔）模型摄像机自标定，目前已成为计算机视觉领域的研究热点之一，对于非线性模型下摄像机的自标定，目前还未见到相关的研究报道，用于线性模型一般不能准确地描述真实像机的几何成像关系，因此对非线性模型摄像机自标定的研究具有十分重要的实际意义，该文主要探索非线性模型摄像机的自标定方法，基本原理是将非线性模型视为线性模型和畸变项的叠加，然后利用线性模型的基本矩阵或单应矩阵，给出非线性模型参数的约束方程，从而实现非线性模型摄像机的自标定，模拟和真实图像实验均表明该文所给的方法是可行的，具有一定的实用价值。     

城市线性景观的构建与发展——以北方地区线性景观为例

城市线性景观是景观设计学中的一个综合概念,可以理解为人类活动与生态环境相互叠加形成的具有线性特征的复合生态系统。文章以城市线性景观为主要研究对象,结合北方地区的实际情况,对如何构建城市线性景观进行探索研究,总结线性景观对于景观设计学的影响,并在线性景观构建的基础上探讨其在城市中的发展方向与趋势。     

Linear control of nonlinear systems based on nonlinearity measures

In reality, virtually every process is a nonlinear system. Nevertheless, linear controller design methods have proved to be adequate in many applications. In practice, the linear controller design is usually done disregarding a possible nonlinear plant/linear model mismatch. In this work we introduce a general framework for the development of linear controllers for nonlinear systems based on nonlinearity measures. Nonlinearity measures are tools to assess the extent of a system’s inherent nonlinearity instead of just recognizing a system as being linear or nonlinear. Recent work shows that nonlinearity measures characterize the magnitude of the modeling error when an optimal linear model is used for the nonlinear system. The best linear model can then be used to design a linear controller that robustly stabilizes the linear system in presence of the nonlinear modeling error. A crucial point is that both, the best linear model and the modeling error, are determined for a specified region of operation, thus significantly increasing the class of applicable nonlinear systems. Examples demonstrate the (necessity and) effectiveness of the proposed approach.     

针对简化版Trivium算法的线性分析

流密码Trivium算法是欧洲密码工程eSTREAM的7个最终获选算法之一.该文针对初始化为288轮的简化版Trivium算法进行了线性分析,更正了Turan等人给出的关于密钥、初始化向量和密钥流比特的表达式,并给出了当允许选取特殊的密钥和Ⅳ时,搜索最佳线性逼近式的算法.据此算法,找到了3个线性偏差为2-25的线性逼近式,改进了Turan等人给出的线性偏差为2-31的线性分析结果.     

Adaptive hierarchical tuning of fuzzy controllers

Fuzzy controller design includes both linear and non-linear dynamic analysis. The knowledge base parameters associated within the fuzzy rule base influence the non-linear control dynamics while the linear parameters associated within the fuzzy output signal influence the overall control dynamics. For distinct identification of tuning levels, an equivalent linear controller output and a normalized non-linear controller output are defined. A linear proportional-integral-derivative (PID) controller analogy is used for determining the linear tuning parameters. Non-linear tuning is derived from the locally defined control properties in the non-linear fuzzy output. The non-linearity in the fuzzy output is then represented in a graphical form for achieving the necessary non-linear tuning. Three different tuning strategies are evaluated. The first strategy uses a genetic algorithm to simultaneously tune both linear and non-linear parameters. In the second strategy the non-linear parameters are initially selected on the basis of some desired non-linear control characteristics and the linear tuning is then performed using a trial and error approach. In the third method the linear tuning is initially performed off-line using an existing linear PID law and an adaptive non-linear tuning is then performed online in a hierarchical fashion. The control performance of each design is compared against its corresponding linear PID system. The controllers based on the first two design methods show superior performance when they are implemented on the estimated process system. However, in the presence of process uncertainties and external disturbances these controllers fail to perform any better than linear controllers. In the hierarchical control architecture, the non-linear fuzzy control method adapts to process uncertainties and disturbances to produce superior performance.     

DNA纳米结构自装配的语言能力分析(英文)

文中研究了DNA分子杂交的内在计算能力．一方面，文中基于Winfree先前关于线性分子自装配仅能产生正则语言工作的基础上，进一步扩展证明了线性自装配通过杂交分别表示左、右线性派生的线性分子，也能产生线性语言．另一方面，文中定义了一种新的通过上下文无关语言通过自装配产生线性语言的方法，即证明了等价于上下文无关语言的特定序列集能通过1-，2-，3-粘头分子的混合自装配产生线性语言，同时，这是对Winfree关于树状纳米结构自装配等价于上下文无关语言理论的一个较好的补充．     

若干二元周期序列的紧错线性复杂度

综合线性复杂度、k错线性复杂度、k错线性复杂度曲线和最小错误minerror（S）的概念,提出m紧错线性复杂度的概念。 序列S的m紧错线性复杂度是一个二元组（km,LCm）。序列S的k错线性复杂度曲线的第m个跃变点对应的km值和对应km错线性复杂度LCm,称为序列S的m紧错线性复杂度。通过使用简洁的cost二维结构,给出了周期为2n的二元序列的紧错线性复杂度算法,并证明具有Stamp-Martin模式的线性复杂度算法均可以简单地推广为求紧错线性复杂度的算法。与现有k错线性复杂度算法不同,该算法中省去了原来序列元素的运算。在王-张-肖算法基础上,通过使用cost二维结构,给出了周期为pn的二元序列的紧错线性复杂度算法,其中p是一个素数,2是一个模p2的本原根。     

基于MatLab的线性代数教学应用

文章针对学生学习线性代数困难原因的分析,说明在线性代数中引入Matlab进行教学改革创新的必要性。通过Matlab程序在初等矩阵教学中演示和练习,使学生能够直观形象地理解和掌握线性代数知识,为后续线性代数的学习打下牢固的基础。     

线性有限自动机的同步序列及其生成算法

文章主要讨论了线性有限自动机的同步序列,得到了线性有限自动机有同步序列的充要条件,还讨论了一类输入存贮线性有限自动机及可等价嵌入输入存贮线性有限自动机的极小线性有限自动机的同步序列。最后给出了判断线性有限自动机有无同步序列以及求线性有限自动机(最短)同步序列的一些算法。     

汉字的线性分类实验

本文通过实验研究了在汉字识别中应用线性分类器的可能性,考察了汉字之间的线性可分性。实验使用了两种主要的线性分类器: Fisher线性判别和感知器。实验检验每一对汉字的线性可分性。实验结果表明,汉字之间的线性分类性是相当好的。尤其是Fisher线性判别,不能成功线性分类的汉字仅占百万分之4.25 。这显示了在汉字识别中应用线性分类器是有着巨大的潜力的。同时,线性分类实验结果还可用来检验所选取特征的好坏,有利于客观的评价特征。     

辽西钼多金属矿床遥感影像线性体自动提取及成矿有利度分析

通过采用线性拉伸增强→边缘检测增强→优选图像最佳值为阀值进行二值化→矢栅转换→拓扑重建→干扰信息剔除→遥感影像线性体分布图的流程方法,成功地自动提取了辽西钼多金属矿床遥感影像线性体,且通过线性体长度-频数、线性体方位-频数及构造强度分析,得出提取数据地质上的有效性。最后运用证据权重法得出构造线性体与矿床的关系,即构造强度分级4~7为最佳致矿异常上下限。     

某型涡扇发动机分段线性化模型的建立

基于某型涡轮风扇发动机非线性动态模型,建立并实现了该发动机的分段线性化模型.介绍了拟合法建立涡轮风扇发动机线性状态空间模型的建模方法,并以发动机高压转子转速为参考参数选取发动机的稳态工作点,分别求取了这些工作点处的线性状态空间模型.以这些线性状态空间模型为基础,在Simulink仿真平台下,采用S-function模块建立了分段线性化发动机模型,并实时地对模型进行求解,得到所需要的高低压转子转速、涡轮落压比以及燃烧室温度等发动机参数.分段线性化模型与非线性模型的仿真结果比较表明此种建模方法输出精度高,能够很好的反映该型发动机的特性.     

An investigation of neural networks for linear time-series forecasting

This study examines the capability of neural networks for linear time-series forecasting. Using both simulated and real data, the effects of neural network factors such as the number of input nodes and the number of hidden nodes as well as the training sample size are investigated. Results show that neural networks are quite competent in modeling and forecasting linear time series in a variety of situations and simple neural network structures are often effective in modeling and forecasting linear time series.Scope and purposeNeural network capability for nonlinear modeling and forecasting has been established in the literature both theoretically and empirically. The purpose of this paper is to investigate the effectiveness of neural networks for linear time-series analysis and forecasting. Several research studies on neural network capability for linear problems in regression and classification have yielded mixed findings. This study aims to provide further evidence on the effectiveness of neural network with regard to linear time-series forecasting. The significance of the study is that it is often difficult in reality to determine whether the underlying data generating process is linear or nonlinear. If neural networks can compete with traditional forecasting models for linear data with noise, they can be used in even broader situations for forecasting researchers and practitioners.     

Integral Approximation of Rays and Verification of Feasibility

An algorithm is presented that produces an integer vector nearly parallel to a given vector. The algorithm can be used to discover exact rational solutions of homogeneous or inhomogeneous linear systems of equations, given a sufficiently accurate approximate solution.As an application, we show how to verify rigorously the feasibility of degenerate vertices of a linear program with integer coefficients, and how to recognize rigorously certain redundant linear constraints in a given system of linear equations and inequalities. This is a first step towards the handling of degeneracies and redundandies within rigorous global optimization codes.     

对称密码算法中两类线性表达式的概率优势(英文)

分析欧洲序列密码候选算法ABC的安全性,提炼出两类与安全性密切相关的具有概率优势的线性表达式。两个概率优势反映了模加法运算之间的两种线性相关性。利用每类表达式及其概率优势都可以推导出ABC算法的大量弱密钥。在弱密钥条件下,可以计算出算法的1 257 bit初始密钥,从而导致了算法的有效破解方法。第一类表达式反映了两个模加法方程普遍存在的一种线性相关性,第二类表达式反映了三个模加法方程的比特进位之间的线性相关性。其中,第二类中一个典型的表达式最初是由Wu和Preneel发现,并由此得到2~(96)个弱密钥,但他们只是通过测试试验数据得到了该表达式的概率优势估计值,并未给出严格证明。文中给出两类表达式的概率优势的严格证明。模加运算被广泛应用于对称密码的设计中,相信这两类线性表达式的概率优势不仅可以用来分析其它对称密码算法,而且对于设计安全的对称密码算法也是非常重要的。     

2轮Trivium的线性逼近研究

Triviurn是国际重要的序列密码,贾艳艳等人曾提出对2轮Trivium进行单线性和多线性密码攻击（电子与信息学报,2011年第1期）。针对其中的线性近似方程个数少和偏差小问题,提出通过改变第1轮Trivium所占的时钟数和线性逼近式的方法对2轮进行线性逼近,给出一个偏差为2书的线性符合和8个偏差为2。。的线性符合,并利用贾艳艳文中算法对2轮Trivium进行单线性和多线性密码攻击。研究结果表明,在相同攻击成功概率的前提下,所需的数据量均为上文中所需数据量的1／16,即需要选择初始化向量的个数分别为258和257。     

LMI‐based stability analysis of linear hybrid systems with application to switched control of a refrigeration process

We consider continuous‐time switched linear systems associated with linear state reset during mode switches, which are called linear hybrid systems and can be commonly found in switched control systems via bumpless transfer during controller switches. We use a multiple Lyapunov functions approach to develop constructive tools for stability analysis of linear hybrid systems. In particular, we derive a linear‐matrix‐inequalities based procedure to compute upper bounds of dwell time for uniform global exponential stability in linear hybrid systems, and we apply it to a refrigeration process that is regulated by several switched proportional‐integral controllers via bumpless transfer. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

ST OFDM载波间干扰线性均衡技术

分析了频率非选择性衰落信道下STOFDM系统载波间干扰的具体内容,利用连续发射已知ST-OFDM符号来估计ST-OFDM中各个子载波对其他子载波的干扰,然后通过特定的线性均衡方法达到STOFDM载波间干扰的抑制。在莱斯衰落信道下的仿真结果表明,选择6个相邻子载波12个干扰系数的均衡技术ST-OFDM系统可获得至少10dB的信干比增益,可以使STOFDM系统在性能和运算量上获得最佳。     

Exploring Non‐Linear Relationship of Blendshape Facial Animation

Human face is a complex biomechanical system and non‐linearity is a remarkable feature of facial expressions. However, in blendshape animation, facial expression space is linearized by regarding linear relationship between blending weights and deformed face geometry. This results in the loss of reality in facial animation. To synthesize more realistic facial animation, aforementioned relationship should be non‐linear to allow the greatest generality and fidelity of facial expressions. Unfortunately, few existing works pay attention to the topic about how to measure the non‐linear relationship. In this paper, we propose an optimization scheme that automatically explores the non‐linear relationship of blendshape facial animation from captured facial expressions. Experiments show that the explored non‐linear relationship is consistent with the non‐linearity of facial expressions soundly and is able to synthesize more realistic facial animation than the linear one.