齿轮传动装置阻尼减振降噪试验研究

通过在高速齿轮箱减振降噪试验台上进行振动、噪声测试对比试验,测试在齿轮噪声中啮合冲击频率及其倍频声和固有频率声产生共振时,分析齿轮箱系统在各种工况情况下增加阻尼前后对系统的减振降噪的作用,可以发现粘贴阻尼材料能够在一定程度上起到良好的减振降噪效果.重点分析齿轮箱在外部粘贴阻尼材料和灌注阻尼材料这两种附加结构对减低振动与噪声具有良好的抑制作用.证明了齿轮箱在附加阻尼后,提高了齿轮传动装置的阻尼特性,符合阻尼减振降噪的理论研究.根据齿轮箱中齿轮啮合冲击是系统的主要激励振动,通过测试分析,采用合金阻尼环附加结构,可得到更佳的减振降噪效果.     

黏弹性阻尼材料在减振降噪方面的应用

随着人类生活质量的提高,生活环境的振动与噪声控制越来越受到关注。黏弹性阻尼材料作为有效的减振降噪材料,在许多行业的减振降噪中正发挥着重要的作用。选取了两种不同的黏弹性阻尼材料,测试对比了它们的阻尼特性。选取阻尼性能较好的阻尼材料涂敷在板类结构上,分别进行涂敷前后振动噪声响应、传递特性测试。分析黏弹性阻尼材料减振降噪效果,为结构减振降噪提供依据。     

粘弹性阻尼材料在减振降噪方面的应用

随着人类生活质量的提高,生活环境的振动与噪声控制越来越受到关注。粘弹性阻尼材料作为有效的减振降噪材料,在许多行业的减振降噪中正发挥着重要的作用。本文选取了两种不同的粘弹性阻尼材料,测试对比了它们的阻尼特性。选取阻尼性能较好的阻尼材料涂敷在板类结构上,分别进行涂敷前后振动噪声响应、传递特性测试。分析粘弹性阻尼材料减振降噪效果,为结构减振降噪提供依据。     

聚合物阻尼材料在轨道车辆方面的应用

随着轨道交通的高速化发展,列车运行所引起的振动噪声会更加剧烈。为了增加旅客舒适度,运用阻尼材料进行减振降噪。通过加装阻尼材料,一方面增加车体的振动衰减,降低声辐射,控制固体声;另一方面隔离外部噪声往车体内部传播。聚合物阻尼材料由于在减振降噪方面独特的优势,成为了研究的热点。本文集中阐述了聚合物阻尼材料的阻尼机理及减振降噪形式,同时简单介绍了其他相关聚合物阻尼复合材料;本文列举了几个简单关于阻尼材料在铁路客车方面应用的实例。     

周期自由阻尼设计板结构振动与声辐射特性分析

为了探究更高效的阻尼减振降噪结构设计,基于阻尼减振降噪技术和人工周期结构原理,开展了周期自由阻尼设计的板结构振动与声辐射特性研究。首先,建立了板结构声振响应有限元仿真模型;其次,对比了周期自由阻尼设计与传统自由阻尼设计的板结构振动与声辐射特性差异,并分析了不同参数变化对周期自由阻尼作用效果的影响;最后,开展了相关实验研究与仿真规律验证。结果表明：相比于传统自由阻尼设计,周期自由阻尼设计可以获得更好的减振降噪效果,且有助于实现阻尼结构的轻量化设计,但也会改变结构的声辐射效率;选用高弹性模量的阻尼材料、合理设计阻尼单元形状和适当减小阻尼单元截面积都有助于提高周期自由阻尼设计的性能,而阻尼单元粘贴角度的变化对其作用效果的影响较小;实验结果验证了仿真规律的可靠性。     

成果介绍

工程机械阻尼减振降噪新结构的研究由太原重型机械学院孙大刚博士主持的机械工业部教育司科技基金项目 :“工程机械阻尼减振降噪新结构的研究”通过部科技成果鉴定。鉴定委员会认为 :本项目的研究成果属国内领先水平 ,达到了国际先进水平。本项目针对工程机械的振动特征 ,在使用温度振频和振幅变化条件下 ,对阻尼减振降噪结构参数进行动态优化 ,获得最佳结构型式、确定符合减振降噪指标的阻尼材料 ,实现对振动噪声的主动、有效的控制 ,为实用减振器产品开发提设计参数和试验指标。本项目的特点是理论研究与工程应用密切结合 ,获得理论研究、…     

敷设阻尼层的有限长加筋板声振性能研究

以有限长加筋板和敷设阻尼加筋板为对象,通过模型试验分析了单频激励和白噪声激励下的加筋板在空气中、水中的振动和声辐射,针对计算模型开展相应的数值分析.结果表明：加筋板敷设阻尼层后,结构的振速级峰值左移.阻尼层在整个频带体现出较好的抑振降噪效果,但在低频区降噪效果不明显,甚至在局部频点出现失效区.在同等激励条件下,其辐射声压级普遍降低.数值分析进一步验证阻尼层对抑制振动与声辐射非常有效.     

冶金工业锯切噪声机理及降噪

对金属锯切噪声发生机理研究表明，圆锯机工作时的主要声源有空气动力性噪声、锯片振动噪声和工件振动噪声．在研制的多种降噪结构图锯片中，基于干摩擦阻尼耗能原理的分层锯片降噪效果最为显著（噪声级降低１２ｄＢ（Ａ佐右）在此基础上设计了一种低噪声回锯机，其降噪效果为２１ｄＢ（Ａ）左右．     

特殊油膜结构对离心机过挠性临界转速的影响

为了确定阻尼器油膜边界条件对离心机升速过程中的振动特性的影响,借鉴Muszynska油膜模型,对离心机阻尼器油膜边界进行了改造。通过有限体积数值计算对新结构可能对阻尼器油膜流场带来的影响进行了分析。设计制作出了一种新型油膜阻尼器并应用于超临界离心机实验,验证了其在离心机转子支承系统过挠性临界过程中对降低系统的振动和不稳定性的明显作用。过挠性临界过程中,阻尼器的振动振幅由15μm有效减小到了1μm。结果显示出特殊油膜结构在离心机阻尼器的设计中的有效性和重要研究价值。     

基于三明治夹层约束阻尼结构的潜艇降噪

潜艇的传动设备在运行中形成振动,并借助潜艇的本体对水流场不断辐射,噪声扩散,因此研究人员往往通过控制潜艇振动问题从而减小整体的噪声。当下,在潜艇噪声的防控中,通常将艇体近似成圆柱壳。该论文重点分析了具有约束阻尼层的厚壳体,同时阐述了此类阻尼层对控制潜艇辐射声场的效果。本文首先基于模态应变能法对“三明治”厚圆柱壳结构中约束阻尼层材料的损耗因子、刚度以及阻尼层的厚度进行了参数分析,分析阻尼层参数对整体结构模态阻尼比的影响规律。以振级落差目标函数,对含有约束阻尼层的足够长度圆柱壳体展开了减振效果的设计,确定了相关圆柱壳结构的阻尼层参数优化值。最后,本文建立了实际潜艇的模型,分析了采用全金属壳结构和“三明治”约束阻尼壳体结构情况下的潜艇周边声场。分析结果表明,优化后的“三明治”约束阻尼壳体结构能够使得潜艇在水中的声压在 0-500HZ 范围中减小 15dB,在 500-2000HZ 范围内大概减小10dB。     

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.     

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.     

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     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with