基于实验的超磁致伸缩微致动器动力学特性分析

基于超磁致伸缩微致动器实验所得的激励电流-磁致伸缩材料轴向位置-磁场强度三者之间的关系式,修正了厚壁线圈轴向电流-磁场理论公式.利用修正公式对超磁致伸缩微致动器动力学模型进行理论分析,得到了微致动器的振动响应;分析了修正系数、偏置磁场及预压应力对微致动器的影响.结果表明:修正系数对微致动器动力学特性影响十分明显,当修正系数K′=1.24时,基于实验拟合函数与基于厚壁线圈电流-磁场理论公式所得到的微致动器的输出位移与输入激励电流之间的滞回环完全吻合;微致动器振动响应具有明显的非线性特性,而且修正系数对其影响很大.偏置磁场与预压应力对微致动器的幅频特性影响也十分明显.     

变压器铁心电磁振动仿真及影响因素研究

为了研究变压器铁心的电磁振动的多场耦合问题,使用应变能原理修正铁心磁-结构耦合关系对变压器铁心的本体振动进行仿真研究.将硅钢片磁化特性曲线导入到仿真模型中,计算得到线圈中的电流密度以及铁心闭合回路中的磁感应强度分布,实现电场与磁场的耦合.利用应变能原理对磁致伸缩力进行等效,并以等效磁致伸缩力为耦合变量对铁心进行结构瞬态...     

基于磁致伸缩效应的管道检测纵向导波模型

基于铁磁性材料在磁场作用下具有的磁、力学特性，推导了磁致伸缩无损检测技术在管道中检测导波模型．在静态偏置磁场和通过传感器激励线圈交变电流形成的交变磁场作用下，管道中产生弹性导波，由弹性导波运动方程，推导其位移表达式，由位移求出应变．根据逆磁致伸缩效应，应变导致磁感应强度的变化，其变化引起穿过接收线圈磁通量的改变从而推导出感应电压表达式．由此建立了作用在激励传感器线圈上的电流与接收传感器输出电压之间的定量关系，为磁致伸缩效应用于无损检测提供了检测理论和技术手段．     

交叉线圈式磁致伸缩导波传感器结构参数优化

为了使交叉线圈式磁致伸缩扭转导波传感器中高饱和磁致伸缩带的振动通过耦合剂和环形线圈传递到待测构件,优化其结构参数以提高传感器的耦合效率,基于交叉线圈式磁致伸缩扭转导波传感器的传感原理,针对环形线圈线径和覆盖率这两个结构参数,从振动耦合机制出发分析了环形线圈结构参数对能量耦合的影响,提出了一种用于环形线圈结构参数设计的优化方法,最后通过实验验证了该优化方法的可行性.将通过该方法优化后的最佳线圈线径和最佳覆盖率运用到传感器中,传感器换能效率提高了28%.     

基于超磁致伸缩材料的驱动器设计及磁场仿真

基于超磁致伸缩材料的工作原理,设计了具有微位移可控特性的驱动器。为了探究驱动器内部磁场设计的合理性以及超磁致伸缩驱动器的磁感应强度与激励电流之间的关系,应用ANSYS有限元分析软件对超磁致伸缩驱动器的内部磁场进行仿真。研究结果表明,超磁致伸缩驱动器磁场设计合理;随着电流的增大,超磁致伸缩材料中的磁感应强度也随之增加并且磁感应强度逐渐趋于饱和。     

兰姆波的电磁超声磁致伸缩式激励及其特性

研究了采用电磁超声探头在铁磁材料中激励兰姆波的换能结构和机理模型,磁致伸缩机制是在弱磁化状态下影响换能效率的主导机制,而Lorentz力和磁性力机制在此情况下的作用相对要小得多.对模型进行数值分析后得到,声波产生的幅度受磁致伸缩应变系数和磁导率的共同影响,并且随提离距离的增大而减小.实验结果也进一步验证了理论预测的准确性     

超磁致伸缩力传感器及其实验研究

基于磁致伸缩逆效应原理,以超磁致伸缩棒为敏感元件研究了一种具有高灵敏度的新型超磁致伸缩力传感器,通过集成在结构内部的霍尔传感器测量磁通密度来实现静态力的测量.同时,为了提高传感器的测量灵敏度,提出了一种安装在霍尔传感器周围的不锈钢钢环的特殊结构.给出了超磁致伸缩力传感器的测量原理和设计过程,并通过实验研究确定了偏置磁场、预紧力和超磁致伸缩棒的尺寸等因素对传感器输出特性的影响规律,分别得到了传感器工作的最佳偏置磁场和预紧力,为超磁致伸缩力传感器的深入研究和精确控制提供了一种技术途径.     

实际工况下磁控饱和电抗器的振动研究

在不同的直流偏磁下,硅钢片会表现出不同的磁化特性以及磁致伸缩特性。为了研究实际工作状态中磁控饱和电抗器的振动,对不同直流偏磁下硅钢片的磁化特性和磁致伸缩特性进行测量。并基于测得的本构关系,建立磁控饱和电抗器的电磁-机械多场耦合模型。考虑铁心的电磁力和硅钢片的磁致伸缩效应,进行磁控饱和电抗器在不同直流偏磁下电磁场和机械场的数值计算,以得到磁通密度、应力和振动的分布情况以及直流偏磁程度对磁控饱和电抗器振动的影响,进而分析电抗器不同位置的振动情况,为减少磁控饱和电抗器的振动噪声提供有力的理论依据与计算方法。     

超磁化条件下超磁致伸缩作动器迟滞现象研究

论述了超磁致伸缩材料的主要物理特性,通过对其迟滞现象的实验观测,指出迟滞现象对超磁致伸缩作动器的精确控制造成的影响.提出了超磁化的方法对迟滞现象进行改善,并通过实验进行了验证,最后从理论上对其有效性做了分析论述.研究表明：采用超磁化后,作动器的力-磁耦合关系更明确,对作动器的控制效果更好.     

超磁致伸缩超声换能器设计分析

基于超磁致伸缩材料设计了一种超声换能器,推导了超声振子的频率方程,并且用ANSYS有限元软件对换能器的关键部件进行了动力学分析,得到了关键部件的模态和谐响应特性,验证了设计方法的可行性.对振动系统进行了静态磁场和谐波磁场分析,结果表明:增加磁回路中导磁材料的磁导率可以增加超磁致伸缩棒的轴向磁场强度和磁场均匀度,但当材料的相对磁导率大于1 000时,轴向磁场强度和磁场均匀度的增加幅度逐渐趋于平衡;在高频激励下,超磁致伸缩棒呈现出了严重的电涡流效应,严重限制了其驱动性能,必须对超磁致伸缩棒进行处理.     

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.     

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-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that