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Influence of Coating Layer on Acoustic Wave Propagation in a Random Complex Medium with Resonant Scatterers 下载免费PDF全文
We investigate the influence of coating layer on acoustic wave propagation in a dispersed random medium consisting of coa.ted fibers.In the strong-scattering regime, the characteristics of wave scattering resonances are found to evolve regularly with the properties of the coating layer.By theoretical calculation,frequency gaps are found in acoustic excitation spectra in a random medium.The scattering cross section results present the evolution of scattering resonances with the properties of the coating layer,which offers a good explanation for the change of the frequency gaps.The velocity of the propagation quasi-mode is also shown to depend on the filling fraction of the coating layer.We use the generalized coherent potential-approximation approach to solve acoustic wave dispersion relations in a complicated random medium consisting of coating-structure scatterers.It is shown that our model reveals subtle changes in the behavior of the acoustic wave propagating quasi-modes. 相似文献
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晶体的铁电性及其实验判据周镇宏,吴福根(广东工学院,广州510090)1引言铁电体的发现可追溯到三百多年前.1655年,法国药剂师塞格涅特(P.deLa-Seignette)在罗息(LaRochelle)地方最早制造出了酒石酸钾钠(NaKC4H4O6... 相似文献
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一、前言 我厂生产的 Cr Mu Ti是齿轮用钢.它广泛用于汽车、拖拉机变速箱中的齿轮、内燃机上的凸轮、活塞等,它往往要求表面具有高的硬度和耐磨性.而心部则要求具有足够的强度和韧性,使零件既有耐磨的表面,又能承受大的冲击载荷,20Cr Mn Ti是能保证心部足够的韧性和强度的理想材质.齿轮损坏的主要原因是齿面磨损,齿面接触疲劳破坏等等.这些损坏主要是齿轮表面残余奥氏体量过多,硬度不足而造成,即关键是材质淬透性.众所周知;所谓淬透性系指淬硬层的深度.钢的化学成份和淬透性是否存在着相关关系,淬透性是否可以予测和控制也是当前炼钢生产… 相似文献
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Effects of orientation and shape of holes on the band gaps in water waves over periodically drilled bottoms 下载免费PDF全文
The complete band gaps (CBGs) of shallow water waves propagating over bottoms with periodically drilled holes are investigated numerically by the plane wave expansion method. Four different patterns are considered, containing triangular, square, hexagonal and circular cross-sectioned holes arranged into triangular lattices. Results show that the width of CBGs can be changed by adjusting the orientation of noncircular holes and the effect of hole shape on the width of the maximal CBGs is discussed. 相似文献
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SnPc(Tin-phthalocyanine)因在无机/有机二极管等光电结构器件中表现出了很多有趣的特性而备受关注.为了更深地理解载流子的传输特性,利用密度泛函理论,采用广义梯度近似(DFT-GGA),关联函数选择BLYP计算了SnPc的能带结构.从点波函数、能带带宽以及带隙分析了载流子的传输行为. 从前线轨道的带宽以及电子和空穴的有效质量,可以看到电子的传输要比空穴的传输容易两倍左右.而且,当研究费米能级附近的能带时,发现未占有带的带隙总体上要小于占有带的带隙,这表明在考虑声子参与的情况下,电子在带间的跳跃要比空穴容易得多.以上的事实说明SnPc是一种电子传输占主导的材料. 相似文献
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