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51.
ZnO薄膜生长及声表面波性能研究   总被引:1,自引:0,他引:1  
采用传统射频磁控溅射技术,通过引入Si O2缓冲层以及调节工作气压的方法,在Si衬底上制备具有高度(1120)择优取向的Zn O薄膜.采用X射线衍射技术和原子力显微镜分析Zn O薄膜的晶体特性和择优取向.研究发现,引入Si O2缓冲层能显著减小Zn O/Si O2/Si三层结构声表面波器件的温度延迟系数(temperature coefficient of delay,TCD),当Si O2缓冲层厚度为200 nm时,Zn O薄膜同时具有(0002)和(1120)择优取向,且TCD值仅为2×10-6℃-1左右,说明器件温度稳定性佳.当工作气压降低时,Zn O(1120)择优取向增强,相应的声表面波器件的机电耦合系数(K2)也增大.在大机电耦合系数和高温度稳定性的Zn O/Si O2/Si三层结构的基础上,有望制作出高性能的Love波声表面波生物传感器.  相似文献   
52.
文章分析了詹姆斯.鲍德温自传性戏剧《阿门角》的主题。在该剧中,他将反宗教意识与爱两大主题完美地结合起来,把摒弃宗教、珍惜关爱作为该剧的主旋律。剧中的艺术家充满爱心、富于社会责任感和抗争精神,对同胞怀有浓厚的人文关怀。  相似文献   
53.
A laboratory‐based microcosm study was conducted to assess the survival of Enterococci faecalis in the estuarine sediments of Lake Pontchartrain, Louisiana, USA. The survival curves of E. faecalis were characterized by a growth phase followed by a stationary phase, a logarithmic decay period, and/or finally by a tailing region. The usual exponential decay model could not be applied to E. faecalis survival in the estuarine sediments. The estuarine sediments appeared to stimulate E. faecalis reproduction within 10 days of incubation. Furthermore, the estuarine sediments prolonged the survival of E. faecalis for a period of at least a month under the study conditions. Based on research results, the amount of organic matter and nutrients did not significantly affect the survival of E. faecalis in the estuarine sediments. This outcome may have occurred due to the small sample size. Throughout the duration of the 45 day experiment, relatively the same proportion of E. faecalis remained culturable. Therefore, the estuarine sediments appear to provide a favorable environment for E. faecalis.  相似文献   
54.
本文基于中国科学院与国外的卫星遥感数据,用地震波理论,分析中国与英国地震台分别测到的2006印尼与2011日本大地震波波形,为工程研发提供科学基础。由此建议以Gbps高速CC-LinkIE,在大地震灾前的秒级时段内,自动对地震波的灾前非破坏性先导分量,进行实时时域数字化分析-判选-触发,在灾前关闭连锁核反应,同时启动核电厂自动测控DCS系统中各级FCS现场总线中的SIL4安全措施系统。  相似文献   
55.
    
Because of their excellent features such as small size, wide bandwidth, and low insertion loss, ladder‐type filters based on surface acoustic wave (SAW) technology have been widely used as radio‐frequency (RF) filters in mobile communications. We can realize wide bandwidth and low insertion loss in ladder‐type SAW filters on a Cu‐grating/15°LiNbO3 substrate structure. On the other hand, it is said that wide‐bandwidth filters have poor temperature characteristics. Therefore, this paper discusses dynamic temperature compensation for wideband ladder‐type SAW filters. First, we investigate how wide tunability is achievable using variable capacitors connected in parallel and/or series to SAW resonators in the filter configuration. Second, we measured the temperature characteristics of the resonator. Finally, we simulated temperature compensation in wideband ladder‐type SAW filters. As a result, we were able to compensate the change of the characteristics with the ladder‐type SAW filter connected using variable capacitors. © 2013 Wiley Periodicals, Inc. Electron Comm Jpn, 96(4): 61–66, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10420  相似文献   
56.
A modelization of cracked plates under bending loads in the XFEM framework is addressed. The Kirchhoff–Love model is considered. It is well suited for very thin plates commonly used for instance in aircraft structures. Reduced HCT and FVS elements are used for the numerical discretization. Two kinds of strategies are proposed for the enrichment around the crack tip with, for both of them, an enrichment area of fixed size (i.e. independant of the mesh size parameter). In the first one, each degree of freedom inside this area is enriched with the nonsmooth functions that describe the asymptotic displacement near the crack tip. The second strategy consists in introducing these functions in the finite element basis with a single degree of freedom for each one. An integral matching is then used in order to ensure the ??1 continuity of the solution at the interface between the enriched and the non‐enriched areas. Finally, numerical convergence results for these strategies are presented and discussed. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
57.
利用有限元法及解析法相结合的方法建立了地基含有倾斜层时Love波弥散特征方程和位移计算公式。利用这一方法研究了该类地基Love波弥散特性,并与水平成层地基(α=0°)进行比较  相似文献   
58.
    
Discontinuous Galerkin (DG) methods provide a means of weakly enforcing the continuity of the unknown‐field derivatives and have particular appeal in problems involving high‐order derivatives. This feature has previously been successfully exploited (Comput. Methods Appl. Mech. Eng. 2008; 197 :2901–2929) to develop a formulation of linear Kirchhoff–Love shells considering only the membrane and bending responses. In this proposed one‐field method—the displacements are the only unknowns, while the displacement field is continuous, the continuity in the displacement derivative between two elements is weakly enforced by recourse to a DG formulation. It is the purpose of the present paper to extend this formulation to finite deformations and non‐linear elastic behaviors. While the initial linear formulation was relying on the direct linear computation of the effective membrane stress and effective bending couple‐stress from the displacement field at the mid‐surface of the shell, the non‐linear formulation considered implies the evaluation of the general stress tensor across the shell thickness, leading to a reformulation of the internal forces of the shell. Nevertheless, since the interface terms resulting from the discontinuous Galerkin method involve only the resultant couple‐stress at the edges of the shells, the extension to non‐linear deformations is straightforward. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
59.
    
Key avant‐garde players are often assumed to be divorced from the reality of practice. In the case of Superstudio, this assumption is wildly inaccurate. William Menking , co‐founder and Editor‐in‐Chief of The Architect's Newspaper and Professor at Pratt Institute, New York, co‐organised the 2003 exhibition ‘Superstudio: Life Without Objects’ with Peter Lang. Here he puts right some myths about the nature of this well‐known but much‐misunderstood Florentine collaborative, setting it in the context of the intellectual and industrial climate of 1960s Italy, and exploring how its approach can inspire those seeking to rethink practice today.  相似文献   
60.
    
The propagation of Love waves on an elastic homogeneous half-space with a piezoelectric gradient covering layer is studied by the geometric integration method in this article. First, the state transfer equation of a Love wave is derived from the governing equations and constitutive relations. Then, the transfer matrix of the state vector is obtained by solving the state transfer equation of a Love wave and then the stiffness matrix is obtained. By combining transfer matrices and the stiffness matrices of the gradient covering layer and the homogeneous half-space, the total surface stiffness matrix of a Love wave is obtained. Lastly, the application of the electrically open circuit and short circuit conditions and mechanically traction-free conditions gives the frequency dispersive relation of a Love wave. For the gradient covering layer, the material constants at the bottom of the covering layer may be greater or smaller than that at the top of the covering layer. The two situations and three kinds of gradient profiles for each of these two situations are investigated. The numerical results show that the Love wave speed is sensitive to not only the material constants at the bottom and the top of the covering layer, but also the gradient profiles of the covering layer.  相似文献   
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