小排量发动机消声器性能仿真计算与优化研究

为满足严格的汽车噪声法规以及对汽车舒适度的需求,课题组以某款汽油机消声器为研究对象,将传递损失作为消声性能的评价指标,基于ANSYS软件建立消声器有限元模型,并通过SYSNOIS软件对其模型进行分析计算。利用建模方法模拟分析消声器各个扩张腔的性能,通过模拟实验可以得出以下结论：实验测试消声器第一、第二扩张腔对中低频消声效果较差;由原排气消声器传递损失分析结果可知,第一、第二扩张腔进出口处增加内插管的结构方案最优。仿真结果表明：当进口内插管、出口内插管长度正好为扩张腔长度的0.5倍与0.25倍时,此结构优化方案可有效提高排气消声器的消声性能。     

计算机辅助消声器开发系统研究

介绍了一种计算机辅助消声器开发系统．它通过所建立的消声器三维模型对排气消声器的插入损失进行计算,考虑到消声器的各个主要结构参数对消声性能的影响,采用正交设计方法,根据消声量的要求对消声器结构参数进行优化．利用VBA对AutoCAD进行二次开发,完成了性能计算程序与结构绘图程序间的数据共享,实现了消声器结构图的自动绘制及编辑．试验结果表明：该开发系统是有效的．     

汽车排气消声器的实验与改进设计

通过消声器的插入损失实验，分析了微型车消声器消声后的声音频谱特征，识别出未被消声器抑制的有害噪声源。建立了该消声器的有限元模型，利用ANSYS分析软件，对消声器的声结构进行了声场分析，获得了该消声器的消声频谱特征。基于实验和数值分析结果，并根据抗性消声理论改进了该消声器的结构参数及布置形式，设计出一种新型抗性消声器。对新设计的消声器的消声性能进行台架实验验证。结果表明，设计的消声器消声量提高3－5dB。     

汽车消声器声学性能优化分析

利用改变穿孔板结构的方法对原消声器进行了改进,并采用声学有限元软件Virtual Lab对优化后的消声器结构进行传递损失的分析。研究表明,经过优化后,消声器在低中频的消声性能得到显著的提高。原消声器还存在优化的可能性,为厂家优化当前的产品提供了一定的理论指导依据。     

穿孔管插入式消声器消声频谱特性的四端网络法计算

利用四端网络方法对穿孔管插入式的抗性消声器进行分析,建立了该消声器的声传递矩阵,编制了相应的计算软件,计算出消声器的消声频率特性,试验证明,消声器声传递矩阵和计算程序是可行的,可以较正确地分析消声器的频率特性的走向趋势。     

气流管道有源消声器声学性能分析

结合噪声源和管道末端的阻抗特性，以及管道中的声传播特性，使用电声类比和传递矩阵技术，建立了气流管道有源消声器声学性能分析的理论模型。文中对管道有源消声器的传递损失和插入损失进行了计算，结果表明，有源消声器的实际消声性能与管内气流马赫数、检测传声器相对于次级声源的位置、控制系统的频响，以及噪声源和管道末端的阻抗特性密切相关。     

基于GT-Power的乘用车消声器设计

运用GT-Power软件对乘用车的消声器进行设计开发.通过对发动机工作过程与消声器的耦合,根据消声器相关理论并利用GT-Power软件建立分析消声器插入损失与压力损失的模型.在保证压力损失不大于22 kPa的设计要求下,所设计的乘用车消声器插入损失达到31.5 dB(A),较好地满足了消声器的消声性能指标,并且模型的仿真结果与试验结果吻合良好.     

穿孔式消声器传递损失计算

针对内燃机排气消声器中采用的穿孔管声学元件,建立数学模型及边界条件,用数值计算方法实现了穿孔管声学元件传递矩阵的计算。并对含有穿孔管声学元件的消声器进行传递损失计算和消声性能分析。本文提出的计算方法对指导消声器设计具有一定的实用价值。     

基于响应面法的乘用车消声器声学性能优化

针对某乘用车车内、外消声器中频段(0.5~1.5kHz)降噪能力较差的问题,利用响应面法对消声器在中频段的传递损失进行优化.首先,采用Latin超立方法对插入管长度、穿孔板位置和穿孔率等设计变量进行采样,采用声学有限元法计算各样本点在中频段的传递损失;然后,利用Kriging模型建立中频段传递损失的响应面模型,并验证其计算精度;最后,利用遗传算法对该响应面模型的计算结果进行优化.结果表明,与优化前消声器在中频段的传递损失(27.05dB)相比,优化后消声器在中频段的传递损失(41.38dB)增加了14.33dB,其消声性能得到了明显改善.     

微穿孔板消声器结构参数优化研究

为研究消声结构参数对消声性能的影响,建立了消声器声场有限元模型,并在模型边界上施加相应的边界条件,通过计算求得不同结构参数下消声器的传递损失,以分析不同的结构参数对消声器的消声性能的影响。计算发现采用内径20 mm的微穿孔管可有效降低3~6 kHz频段内的噪声,微穿孔管的单节管长应为1/4波长的9倍,管上孔洞按正方形分布,开孔直径0.4 mm,开孔率4.8%。     

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