基于小波和小波分形的冷连轧机振动识别方法

针对2180 mm冷连轧机振纹现象的随机性和隐蔽性的特点,基于小波分析和分形理论,系统地研究了能够准确地识别轧机振动的方法.对典型工况下轧机振动信号的分析结果显示,两种方法均能有效地识别轧机振动的现象,为在复杂振动环境下识别振纹振动提供了有效途径,这对于实时监测轧机的运行状况,避免恶性生产事故的发生,进而实现预知轧机振动具有积极的现实意义.     

非线性动态轧制过程下冷轧机参激振动特性

同时考虑轧制过程中非线性动态轧制力和辊面振纹导致的非线性参激刚度的影响,建立了非线性动态轧制过程下冷轧机参激振动动力学方程.应用多尺度法求解了轧机发生1/2亚谐共振时的幅频特性方程,得到了阻尼、参激刚度对系统亚谐共振的影响规律,并运用奇异性理论讨论了轧机在非自治情况下分岔特性.最后通过采用轧机实际参数进行数值仿真,得到系统各参数对幅频特性以及分岔和混沌特性的影响规律,发现系统参激刚度的变化会使轧机出现了周期运动和混沌等多种不同的运动形态,为进一步抑制轧机振动提供了理论参考.     

小波基带宽的变化对结构损伤识别的影响

分析了小波变换在结构损伤检测中的应用 ,证实选择具有不同带宽小波基对检测结果可起到关键性作用 .小波变换可以看作是一组带通滤波器 ,小波滤波器通过多尺度带通和自相关加强特性 ,对结构的动力信号进行实时检测 .利用灵活的多尺度带通小波滤波器组 ,对结构振动信号作滤波分析 ,结构所有的自然频率特性可以同时在时频空间出现 .通过观察不同带宽内振动信号的时频变化来判断结构损伤存在     

基于傅里叶级数的多环反馈开关电流小波滤波器实现

提出一种基于傅里叶级数的多环反馈结构开关电流小波滤波器设计新方法。利用傅里叶级数法求取小波函数的时域小波逼近函数,以双输入多输出开关电流双线性积分器和单输入多输出电流镜作为基本单元设计相应的多环反馈结构小波滤波器,并通过调节开关电流滤波器的时钟频率获得不同尺度小波函数。对所设计的电路进行时域、频域和灵敏度分析,并研究元件非理想性对电路的影响。研究结果表明:该方法的小波逼近函数求取容易,滤波器电路具有设计简单、灵敏度低和受非理想性因素影响小的特点。     

基于小波变换的轮胎多尺度边缘检测

本文提出了基于小波变换的轮胎多尺度边缘检测的方法。将小波变换用于图像多尺度边缘检测,根据轮胎的图像特点,为了提高图像边缘检测的精度,对小波滤波器系数进行了分析,为了得到较好的边缘检测效果,对尺度进行了确定。     

高速轧机横向振动研究——1600铝带轧机产品振痕分析与对策

现代高速带材轧制中经常出现一种异常的运行工况——轧机颤振,同时产品表面出现周期横向条纹,近年某厂从日本引进的1600高速铝带轧机亦有类似问题,以致难以生产高精度带材。它是当前轧制领域中急待解决的难题。作者根据产品表面印痕特征与统计规律,对轧机横向振动进行了系统研究: ·在线采集轧机系统输入输出信息; ·用瞬态激振与计算方法研究轧机固有动态特性; ·运用相关与自谱分析识别轧机振动的统计规律; ·运用互谱与互相关分析进行振源的识别。由此得出对1600轧机横向振动及产品表面印痕的某些认识: ·1600轧机稳态轧制中同时存在轧机横向振动与传动系统扭振,在其固有频率与激振频率异常接近的几个频带出现共振响应,并直接导致产品表面印痕,其中600Hz高频垂振共振响应频率是产品印痕主频率。·垂振振源为主电机电源中50Hz各阶倍频交流分量,控制系统的“双环”增强了这种干扰,振源通过基础激励与回转-垂直耦合激励轧机垂振。最后,提高了改善现有轧机动态特性与抑制、减轻产品印痕的对策: 1.增强供电系统滤波功能,增大平波电抗器容量,以清洁电源。 2.在控制回路的速度闭环中串接一个二阶微分校正网络,消除机电系统低频振荡;在电流闭环中设置窄带滤波器,消除机电系统高频振荡。 3.调整润滑剂极性,增强油膜抗振能力。对新设计轧机,为获得良好动态特性,应对机、电、液、气、工艺进行大系统动态优化设计。     

基于小波变换的弹射加速度滤波分析

根据小波分解与重构理论，对弹射加速度信号进行多尺度的小波变换，即用不同中心频率的带通滤波器对信号滤波，把主要反映噪声频率的那些尺度的小波变换去掉，再把剩余各尺度的小波变换结合起来，作小波重构变换，从而得到较好地抑制了噪声的信号。     

斜拉索风雨激振面内运动的非线性分析

为深入研究斜拉索风雨激振面内的运动特性,依据弹性力学和气动弹性理论建立了连续斜拉索风雨激振面内非线性振动方程,利用伽辽金方法将偏微分方程转化为常微分方程.借助多尺度法得到面内一阶振动方程的平均方程和定常解,利用奇异性理论对系统进行分岔分析,确定了系统在零平衡点附近发生Hopf分岔对应的风速以及拉索发生风雨激振时对应的水线频率的范围.对拉索前四阶模态的振幅进行了数值模拟,考察了拉索以第一阶模态振动时风速、结构阻尼比等系统参数对拉索振幅的影响.研究表明,连续面内振动方程更能体现斜拉索风雨激振完整的动力学特性,同时系统中存在多种分岔行为.     

小波滤波器的构造及其在环境研究中的应用

在环境研究领域,连续观测的数据(时间序列)几乎全都是具有多尺度性质的测量信号.观测数据之所以具有多尺度性质,一方面是因为其自身存在多尺度性质,另一方面往往受到外界各种因素的影响,而这些影响因子又存在不同的时间和空间尺度.为了解析生态环境过程的动态变化及其规律性,往往对连续观测数据首先进行滤波去"噪"(如干扰、误差、错误等),保留真实、客观、主要的信号.为此,本文利用小波分析的方法构造了带通滤波器,并用其分析得出了水环境中连续观测数据的变化规律.小波分析是时间--频率分析领域近年来迅速发展的一种新技术,具有多时间尺度,多层次和多分辨的特性,已被广泛地应用在信号分析、信息分析和地球科学研究上.本文首先对常见的几种小波基的尺度函数和小波函数作了功率谱分析,发现dmey(discrete Meyer wavelet)小波的高通和低通较其他小波函数更近似理想滤波器;为此利用dmey小波设置了带通滤波器,并以NINO3指数为例,检验了此滤波器,研 .究表明此滤波器有着较好的带通滤波效果.进而,用此滤波器对太湖现场实测的水深和降水数据进行了滤波,分析发现太湖水深变化在周以上尺度主要受降水影响;此外,太湖水深变化还存在1 d和0.5 d的显著周期变化.     

多尺度分解下的自适应滤波器组的构建方法

通过分析自适应滤波和小波变换的多尺度分解滤波的原理与方法,建立了非平稳信号的多尺度分解下自适应滤波器组的构建模型和滤波方法.将小波变换分离出来的噪声成分作为自适应滤波器的输入,通过自适应滤波器组,能实现多种噪声成分的自适应滤波.通过模型验证和工程实例的应用,该方法能实现非平稳信号在同频段对噪声成分和有用信号的最佳估计.通过自适应滤波器组,能同时实现对多种噪声成分的最佳滤波,具有优良的滤波性能.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-