一种测量微波高Q谐振腔品质因数的新方法

传统的谐振腔品质因数扫频测量方法在实际测量时存在一定的限制.为此,针对微波高Q谐振腔,给出了一种测量其品质因数的新方法,该方法可以根据实测的谐振曲线灵活选取测量点,有效解决了传统方法中由于谐振腔受外电路影响导致测量误差较大的问题.采用该方法对一个微波高Q谐振腔进行测量,得到了较好的结果.     

周期性边界条件的一种处理方法

一、引言 在数学物理方法中,经常会遇到有部分边界满足周期性条件的边值问题。例如,在透平机械内部三元流动的流场延伸部分人工分界线(面)上(如图1中г_(32),г_(31)),流函数ψ满足周期性边界条件ψ|г_(32)=ψ|г_(31) (?)。又如电机中的磁场分布(如图2),在边界Г_(32)Γ(31)半径相同处,其磁位A满足周期性条件A|г_(32)=-A|г_(31)。     

微波谐振腔谐振频率实时测量系统的实现

微波谐振腔具有很高的品质因数,因而灵敏度很高;谐振频率是谐振腔最重要的参数,通过对谐振腔谐振频率的测量是目前为止最快速、最有效的湿度测量方法.本文提出了一种对单端开口同轴微波谐振腔的谐振频率测量方法,并设计了系统的具体实现.通过实时检测谐振腔耦合出来的输出功率的最大值,测量在该最大值点对应的频率值,从而快速得到谐振频率的大小.实验证明,该系统具有高灵敏性和高精确度,适合工业的在线应用.     

基于RBFN和贝叶斯准则的目标存在性判决

利用海杂波的混沌特性和神经网络的非线性拟合性能,训练并创建了海杂波的RBFN预测模型,以此来判断雷达回波信号中是否包含有目标信息.通过计算有目标和无目标时RBFN模型的预测输出均方误差e,将目标检测问题转化为二模式的分类问题,分类判决原则采用基于最小错误率的贝叶斯准则.仿真实验在假设有无目标的先验概率P(H0)和P(H1)相等的情况下,将预测均方误差的类条件概率密度曲线P(e|H0)和P(e|H1)的交点取为门限η,得到最小检测信噪比[SNR]=-13.271 dB.     

烟支湿度与密度检测的微波谐振腔传感器研究

对微波谐振腔微扰法检测基本理论和工作原理进行了论述,对微波作用的介电材料的电磁参数"介电常数"和"介电损耗"产生的相对变化进行了分析讨论,建立了烟支密度和湿度与谐振腔谐振曲线的频偏及半功率点带宽的数学表达式,设计制作了重入式微波谐振腔传感器.采用TM010谐振模,对烟支的密度和湿度进行了实时检测.以扫频法检测谐振腔空腔和有烟支状态下的幅频特性,获得谐振频率f、峰值功率p及半功率带宽ω.根据相关数学式得到了烟支的湿度和密度.该检测方法具有快速、连续、分辨力高、无污染和操作安全简便等优点.并且适用于工业现场在线测量.     

声表面波传感器Q值改善的理论与实验分析

用P矩阵方法分析带变迹叉指换能器(IDT)和倾斜金属反射栅的高Q值Y型声表面波(SAW)质量沉积传感器的通带纹波,并分别在振荡和非振荡模式下比较了这些传感器的通带纹波和Q值.分析了获得高Q值的原因.理论和实验结果表明:均匀孔径无反射栅的传感器旁瓣抑制为10dB,振荡模式下其Q值为5 289;通过孔径变迹设计,传感器的旁瓣抑制和Q值分别改善到25dB和8689;而对孔径变迹并加入倾斜反射栅的传感器,这两个参数提高到25dB和12477.非振荡模式下带反射栅的传感器比没有反射栅器件的通带纹波约低2dB.因此,变迹IDT和金属反射栅的应用是SAW质量传感器Q值的改善的两个重要因素.由于Q值改善,质量沉积灵敏度达到5.24 GHz·cm2/g     

一种快速无超调的实用调速方法

如图1曲线②所示,式(1)对应曲线①.由图1知,近似开关线②也可使系统快速无超调.但实际系统参数既测不准又不断漂移,为确保系统稳定工作在最优状态,本文给出了近似开关线与自寻最优相结合的方法:若由于某种原因实际近似开关线偏离为曲线③(图1),则在A′点切换后,状态将沿轨线④运动到c点,出现终端偏差△=oc,△值将被计算机检测并记忆.因曲线④与①几乎“平行”,故可用△来修正开关线,使h(ε—△,ε,r)=0,即把曲线③右移△并作为下次使用的开关线,使系统重获最优;反之,若实际开关线向右偏离,则h(ε+△,ε,r)=0.这样,系统借助微机可自寻最优开关线. 调速系统中,与电流相应的状态坐标是受限的.受限时最速控制综合函数为u~*(ε)     

光学4f系统灰度误差补偿的实现

为补偿光学4f系统灰度误差,提出基于直方图匹配和径向基函数(RBF)神经网络的灰度误差补偿方法。首先利用径向基函数神经网络拟合经光学4f系统输出图像的直方图与对应输入图像的直方图之间的非线性变换,得到输出图像与输入图像的直方图匹配变换曲线的最优估计;再依据直方图匹配曲线的最优估计对经光学4f系统的输出图像进行直方图匹配,得到灰度误差补偿后的图像。利用实际的光学4f系统进行光学实验,灰度误差补偿后图像的信噪比平均提高了2.96dB,视觉效果明显改善。实验结果表明,该方法能有效补偿光学4f系统灰度误差,提高基于光学4f系统的光学信息处理的精度。     

单片机在测试陀螺罗经性能参数上的应用

0 引言 陀螺罗经是船舶航行过程中提供方位基准的一种重要仪器,其性能好坏直接关系到船舶的航行安全,它的性能主要由f(阻尼因素)和Td(阻尼周期)值表征,f值和Td值的测量精度直接影响到对罗经性能的判断,f和Td值常是罗经出厂时由厂家提供的,而使用中的罗经其性能好坏常有以下几种测试方法,(1)用航向记录器记录航向曲线,然后根据航向值估算出f和Td。该方法的优点是航向值采集自动进行,但是,由于要人工参与读数和计算,工作量大,估算出的f和Td的精度差,而且航向记录器的故障较多,很多型号的罗经已摒弃航向记录器这个部件。(2)由驾驶员按一定时间间隔(如10分钟)记录一次航向,再记下主轴基本稳定指北时的航向值(稳定时间     

直接自适应控制律的输入/输出稳定性分析

1　引言一般地说 ,在控制系统模型未知的情况下 ,已有的理论方法不可避免地存在建模这一关键棘手的问题 .本文基于小增益定理[1 ] ,给出文献 [2～ 4 ]中直接自适应控制律的输入 /输出稳定性充分条件 ,该条件弱于文献 [5]中的条件 ,更具实用性 .首先给出以下有关定义 :定义 1 .对于正数 p∈ [1 ,∞ ) ,元素为可测函数 f(· ) ,且满足∫∞0 | f(t) | pdt<∞的空间 ,称为 lp 空间 .当函数 f(t)∈ lp 时 ,p∈ [1 ,∞ )有 limt→∞∫∞t | f(t) | pdt=0 .但一般的控制系统 ,其中发生的过程未必都有这种渐近性质 ,控制的目的往往是使发散的过程变…     

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。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.