斜拉索主参数共振的稳定性分析

研究轴向激励下斜拉索的主参数共振的稳定性问题．考虑拉索垂度和几何非线性的影响,导出了拉索在轴向激励下的非线性参数振动方程．利用多尺度方法研究了斜拉索的主参数共振问题,并对其稳态解的稳定性作了较详细的分析．对斜拉索的主参数共振进行了数值模拟,得到了不同阻尼、初始条件及激励幅值作用下拉索的时程曲线．结果表明：斜拉索的固有频率与外激励参数对斜拉索稳态解的个数及其稳定性都存在直接影响,从而对斜拉索的参数设计起到了指导作用．     

随机Duffing-van der Pol系统响应的Chebyshev多项式逼近

对一类含随机参数的Dulling-van der Pol系统,运用Chebyshev多项式逼近法,将其转化成等价的确定性扩阶系统;通过求解等价系统在谐和激励下的稳态响应,可得Duffing-van der Pol系统相应的稳态随机响应,研究了当谐和激励的振幅变化时,含随机参数的Dulling-van der Pol系统的对称破裂分岔和倍周期分岔．数值模拟结果与数值解比较表明：正交多项式逼近法能有效地解决此类非线性随机动力系统的响应问题．     

移动简谐力激励非线性无限长地基梁稳态响应

同时计入地基中的非线性弹性、黏性以及剪切作用的影响,研究移动集中简谐力作用下无限长地基梁稳态响应问题.假设基础非线性弹性为立方非线性.通过Adomian多项式分解方法和Fourier变换得到梁稳态响应的Green函数,再运用Fourier逆变换得到梁稳态响应近似解析解的积分表达式.最后对解析积分表达式应用留数定理得到复数域上的解.通过数值算例,考察了移动集中简谐力的频率和移动速度对无限长地基梁稳态响应的影响.另外,还通过算例对比研究了地基的非线性弹性系数和剪切系数对无限长地基梁稳态响应的影响.     

参数激励系统的主共振分岔控制

设计了非线性参数控制器来改变参数激励系统的稳态响应,消除了系统主共振时的鞍结分岔和减小了系统稳态响应的幅值.从而消除了系统特有的跳跃和滞后现象.首先由多尺度法得到系统的近似频响方程,再由奇异性理论来分析分岔特性,从而实现非线性控制的目标.由数值模拟来确定了非线性参数控制器的有效性和可行性.     

一类强非线性系统共振周期解的渐近分析

强非线性系统经引入参数变换,并在一定的假设条件下,可转化为弱非线性系统．将其解展成为改进的傅立叶级数后,利用参数待定法可方便地求出强非线性系统的共振周期解．研究了Duffing方程的主共振、Van der Pol方程的3次超谐共振和Van der Pol-Mathieu方程的1／2亚谐共振周期解．这些例子表明近似解与数值解非常吻合。     

窄带随机激励下三稳态压电俘能器的动力学特性与实验研究

本文研究了窄带随机激励下三稳态压电俘能器的动力学输出特性.首先,建立了非线性三稳态压电俘能器的分布参数型机电耦合运动方程,并基于多尺度法推导得到系统运动方程响应的解析解以及一阶、二阶稳态矩的表达式.其次,分析了磁铁间距、噪声强度和激励幅值等参数对系统稳态响应的影响.研究结果表明,在一定参数范围内,随着噪声强度的增加,压电振动俘能器会经历阱内振动、阱间振动甚至大轨道周期运动,以表现出单稳态、双稳态和三稳态特性;改变磁铁水平间距和竖直间距构造三稳态压电俘能器,其振动幅值和采集电压相较于双稳态明显提高.最后,通过实验比较了压电俘能器在不同位形时的采集性能,结果表明了三稳态压电俘能器的优越性,为窄带随机激励下的非线性振动俘能器的设计提供一定的理论依据.     

矿井提升系统的强非线性振动

矿井提升机在提升重物的过程中,由于质量和刚度的变化引起的系统固有频率十分缓慢的变化,因此考虑钢绳质量的矿井提升机系统是一个慢变参数振动系统．本文首先应用Kuzmak—Luke的多尺度法得到有一般非线性弹性力的强非线性振动系统解的周期性条件及用Jacobi椭圆函数表示的平方非线性振动和立方非线性振动的首阶渐近解．其次,将得到的结果分别应用于有平方、立方非线性弹性力的质量慢变的矿井提升系统．最后,将理论结果应用于某个矿井提升系统,应用算例的渐近解和数值解的比较表明本方法是有效的．     

求解强非线性动力系统响应的一种新方法

将同伦理论和参数变换技术相结合提出了一种可适用于求解强非线性动力系统响应的新方法．即PE-HAM方法(基于参数展开的同伦分析技术)．其主要思想是通过构造合适的同伦映射,将一非线性动力系统的求解问题,转化为一线性微分方程组的求解问题,然后借助于参数展开技术消除长期项,进而得到系统的解析近似解．为了检验所提方法的有效性,研究了具有精确周期的保守Duffing系统的响应,求出了其解析的近似解表达式．在与精确周期的比较中,可以得出：在非线性强度。很大,甚至在α→∞时,近似解的周期与原系统精确周期的误差也只有2．17％．数值模拟结果说明了新方法的有效性．     

正交各向异性叠层板的非线性主共振分析

研究了在四边简支的边界条件下,正交各向异性矩形叠层板在横向简谐激励作用下的非线性主共振及其稳定性问题．在给出了正交各向异性叠层板的振动微分方程的基础上,利用伽辽金法导出了相应的达芬型非线性强迫振动方程．应用平均法对主共振问题进行求解,得到了系统在稳态运动下的幅频响应方程．基于李雅普诺夫稳定性理论,得到了解的稳定性判定条件．作为算例,分别给出了不同条件下,系统运动的幅频响应曲线图、振幅-激励幅值响应曲线图和动相平面图,并对解的稳定性进行了分析,讨论了各参数对系统非线性振动特性的影响．     

复合材料层合板的双Hopf分叉分析

利用高维非线性系统的Hopf分叉定理,研究复合材料层合板的双Hopf分叉.研究了一类受面内激励和横向外激励联合作用下的复合材料层合板在主参数共振—1∶1内共振情况下的双Hopf分叉.首先利用多尺度法得到系统的平均方程,经过简化得到了系统的分叉响应方程.根据对分叉响应方程的分析,得到了系统平衡解的稳定性临界曲线,并给出了系统产生双Hopf分叉的条件.利用数值方法得到系统在参数平面上的分叉集,通过对不同分叉区域的分析,我们发现随着参数的变化复合材料层合板存在不同的周期运动现象.     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

基于QTE的蒙古文显示机制研究与实现

蒙古语言是中国蒙古族使用的通用语言,由于蒙古文区别于其他文字的书写方式和其自身变形机制等特点,在很多通用的文字处理引擎中都不被支持。在嵌入式产品开发与应用领域中Linux加QTE已经成为流行方式。该文给出了一种在QTE环境上实现基于标准Unicode的蒙古文点阵显示和变形算法, 并自定义了支持蒙古文的QTE组件,扩展了QTE功能,为在Linux加QTE方式的嵌入式体系结构中处理蒙古文提供了一种解决方法。