双层板内插微穿孔板的隔声性能

提出一个在双层板内插入微穿孔板的隔音结构,微穿孔板与双层板平行,把双层板间的腔体一分为二.对结构建立全耦合的数值模型,微穿孔板与双层板均为有限大板,考虑边界条件,计算得到结构的声传播损失.通过实验对所建立的全耦合数值模型进行验证,计算结果与实验结果符合较好.对微穿孔板的位置、穿孔率、板厚以及微孔孔径进行数值计算研究.计算结果表明:相对传统的双层板或者无微穿孔板的三层板结构,内插了微穿孔板的双层板结构在低频的声传播损失效率有所提高;通过适当的微穿孔板参数设置,该结构可以在低频达到较好的隔声效果.     

道路声屏障组合吸声结构设计与评估

声屏障在道路交通噪声污染防治中得到了广泛应用,但同时面临材料吸声性能有限、轻量化程度有待提升等问题。为了更好地提升道路声屏障的降噪效果,需要研究组合吸声结构的声学性能及其影响因素。建立了二维阻抗管有限元模型,与实验数据进行对比验证了其可靠性。基于有限元仿真构建了微穿孔板-双层多孔吸声材料-空腔组合吸声结构,研究了几何参数对组合结构的吸声性能的影响,并在实际道路场景中进行了仿真分析。结果表明,微穿孔板的孔径和厚度减小,组合结构在中高频段的吸声效果提升;穿孔率减小,组合结构在低频段的吸声性能提升,但是中高频吸声性能显著降低;多孔吸声材料厚度的增加能提升组合结构中高频吸声系数。在多孔吸声材料背后合理设置空腔并不会降低组合结构的声学性能。穿孔率3%,孔径0.4 mm,板厚1 mm的微穿孔板与3 cm聚酯纤维+3 cm三聚氰胺+2 cm空腔的组合吸声结构降噪效果较好,将其作为吸声型声屏障的材料。吸声型和隔声型声屏障插入损失的规律基本一致,采用组合吸声结构的吸声型声屏障较隔声型声屏障插入损失提升1-2 dB,能够较好地控制中低频交通噪声,具有实际工程价值。     

基于流形学习和SVM的储粮害虫声信号识别研究

声检测法能够快速检测粮虫,对提早防治储粮害虫具有十分重要的作用.研究了2种储粮害虫的4种活动声信号,利用流形学习的等距特征映射方法对声信号进行降维并提取流形特征,采用以重尾径向基为核函数的SVM训练最优分类面,对流形特征数据进行测试和识别分类.实验结果表明,等距特征映射方法能够有效提取2种储粮害虫声信号的流形特征,且SVM的分类识别效果良好.     

储粮害虫活动声信号去噪方法研究

采用经验模态分解(EMD)、小波阈值去噪、神经网络自适应滤波方法对4种储粮害虫活动声信号进行滤波去噪,得到5组对比实验.经对比分析每种方法去噪后的效果,发现EMD方法提升的信噪比和均方根误差均比较稳定,神经网络自适应滤波方法去噪后信号有失真现象,且不稳定.结果表明:EMD方法较适用于储粮害虫活动声信号去噪,能够较好地消除含噪信号中的噪声,对其他储粮害虫的声检测同样具有应用价值.     

储粮害虫微弱声信号特征提取与分析

 提取了5种主要储粮害虫微弱爬行声信息,采用现代数字信号处理新方法,建立特征模式识别.通过对声信号时域和频域2方面的分析,发现了不同储粮害虫声信号间差异,时域信号的差异表现为声脉冲的不同,频域信号的差异表现为功率谱幅值和主要频域范围的不同,信号间差异与害虫爬行速度快慢有关,并与害虫体重有关,体重大的害虫具有较大的振动能量.5种害虫时域及频域信号的差异是害虫种类差异的表现,这一差异揭示出不同种类害虫声信号的本质特征.本研究内容为有针对性地采取灭虫措施提供了依据,有利于及早确定防治对策,降低储粮损失.     

不同加筋双层板结构隔声特性研究

针对双层板结构隔声性能的分析,很少有对比不同加筋双层板和空腔双层板隔声性能差别的。本文首先分析了夹层为空腔的双层板隔声特性,通过理论、仿真和试验相结合的方法确定选用仿真分析方法的准确性,然后对夹层分别为波纹加筋板和正交加筋板的双层板结构进行隔声特性的分析。对波纹加筋双层板分析时,对比了“全耦合模型”、“声透明模型”和“无内部声腔模型”三种模型隔声曲线的区别。结果表明,三种模型计算的隔声曲线吻合很好,因而可以用“无内部声腔模型”计算。通过对比空腔、波纹加筋和正交加筋双层板的隔声曲线,发现内部加筋对双层板的隔声性能有很大的影响,因而研究了声桥对双层板隔声的影响。结果表明,声桥刚度越大,在频率低时,能抑制两板的共振,增加隔声量,而在频率高时,反而会降低板结构的隔声量。     

不同加筋双层板结构隔声特性的理论、仿真及试验研究

针对双层板结构隔声性能的分析,很少有对比不同加筋双层板和空腔双层板隔声性能差别的。首先分析了夹层为空腔的双层板隔声特性。通过理论、仿真和试验相结合的方法确定选用仿真分析方法的准确性,然后对夹层分别为波纹加筋板和正交加筋板的双层板结构进行隔声特性的分析。对波纹加筋双层板分析时,对比了"全耦合模型"、"声透明模型"和"无内部声腔模型"三种模型隔声曲线的区别。结果表明,三种模型计算的隔声曲线吻合很好;因而可以用"无内部声腔模型"计算。通过对比空腔、波纹加筋和正交加筋双层板的隔声曲线,发现内部加筋对双层板的隔声性能有很大的影响;因而研究了声桥对双层板隔声的影响。结果表明,声桥刚度越大,在频率低时,能抑制两板的共振,增加隔声量;而在频率高时,反而会降低板结构的隔声量。     

多种粮食声吸收的研究

目的 为防止储粮虫害，对多种粮食在自然堆积状态下的声吸收进行了研究。方法采用驻波管法测量了多种粮食的吸声系数。结果报道了粮食颗粒形状、大小及粮食堆积厚度与其声吸收存在的规律，涉及不同粮食间声吸收的比较、颗粒形状相似粮食的声吸收对比、堆积厚度对声吸收的影响、粮食声吸收机理等，结果显示：粮食是高吸收声波的媒质，储粮害虫发出的声信号由粮食内传至表面时的声衰减较大。结论粮食颗粒形状、大小的不同，使其声吸收各异；粮食厚度也是影响其声吸收的一个重要因素，厚度增加，吸声系数随之增大；粮食声吸收受粮食品种影响甚微，这为储粮害虫声检测工作提供了理论依据及资料积累。     

影响住宅低频隔声因素的研究

在考虑墙体共振和房间共振的基础上，应用有限元法对住宅的低频隔声问题进行研究。对比实验表明，计算值和实验值相符。并且，声源室与受声室的体积以及两房间是否对称，皆对房间的隔声有影响。     

大间距双层隔声结构的隔声理论研究

针对双层大间距隔声结构的特点,建立了其隔声性能预测模型．以某空压机房隔声降噪设计为例,进行了隔声降噪的设计与分析．理论预测值与实测结果符合较好．     

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