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51.
A new efficient numerical method and the dynamic analysis of composite laminates with piezoelectric layers 总被引:1,自引:0,他引:1
Firstly, a numerical method for the inversion of Laplace transform is developed and its accuracy is shown through examples. Then, a state-vector equation for the dynamic problems of piezoelectric plates is deduced directly from a modified mixed variational principle for piezoelectric bodies and its exact solution for the dynamic problems of simply supported rectangle piezoelectric plate is simply given. For multilayered hybrid plates, we derive the solution in terms of the propagator matrices. The techniques accounts for the compatibility of generalized displacements and generalized stresses on the interface both the elastic layers and piezoelectric layers, and the transverse shear deformation and the rotary inertia of laminate are also considered in the global algebraic equation of structure. Meanwhile, there is no restriction on the thickness and the number of layers. As an application of the numerical inversion of Laplace transform presented in this paper, typical numerical examples of the harmonic vibration and transient response are proposed and discussed. Since the highly accurate numerical results, they can serve as benchmarks to test various thick plate theories and various numerical methods, such as the finite and boundary element methods for transient response problems. 相似文献
52.
��չ����Ȼ��Ϊԭ�ϵ�ȼ�ϵ������ 总被引:6,自引:0,他引:6
研究燃料汽车及其氢源系统是当今国内外能源工业与汽车工业的共同课题,而优选制氢能源则是这一课题的关键。章介绍了利用能源、经济、环境(EEE)——生命周期评估(LCA)这一综合评估方法,针对以天然气、煤或石油作为制氢能源的多种燃料电池氢源供应方式以及配套的燃料电池汽车系统,从经济性、能源利用效率和环境影响三个方面进行了生命周期清单分析和EEE综合评价。结果显示:天然气作为发展燃料电池汽车氢源的一次能源,具有氢制取技术路线多样化、经济上竞争力强、能源利用效率高和环境效益好等诸多优势,应为燃料电池汽车的首选制氢能源。对这一评估模型的敏感性分析显示,即使在天然气价格波动较大时,天然气制甲醇--甲醇车载重整车和天然气制氢--纯氢车这两个方案仍然最具优势。 相似文献
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55.
本研究在简介国际上先进的变参设计几种方法及优点后,叙述了一个国家863/CIMS项目:CAD/CAPP/NCP集成系统中二维尺寸驱动的变参设计子系统的构成与功能;然后着重阐述了本系统采用的尺寸驱动的变参设计思想和几何约束建立的原则,并提供了系统数据结构,最后以几个实例证明了此方法的正确性与工程实用性。 相似文献
56.
随着电力和电子技术的飞速发展,相应的元器件向高频化,小型化,高效率和节能的方向发展,从而对元器件用材料也提出了更高要求。为此,本文概述了冶金部钢铁研究总院近年来所研究的用于开关电源,脉冲变压器,传感器,电流互感器和电感器等方面的非晶软磁合金的性能及其应用概况。 相似文献
57.
The formula for soliton timing jitter due to self-frequency shift and pulse width fluctuations caused by spontaneous-emission noise has been deduced. Such timing jitter is compared with that caused by the carrier frequency shift due to spontaneous-emission noise. It is shown that the timing jitter due to the self-frequency shift can be as large as the timing jitter due to carrier frequency shift when the total transmission distance is 100 times longer than the soliton period 相似文献
58.
本文根据混流、定浆式转轮特性多数的特点建立了一种能将高维特性多数用一个具有二阶连续导数且保形的函数给予表达的方法,它的精度高,且能方便生成满足各种用途的特性曲线。 相似文献
59.
The body color in animals results from billions of years of their natural evolution in order to evade natural enemies, catch
quarries or display themselves beauty, investigation on mechanisms of structural light is an important aspect of bionics.
Based on the phenomenon of Papilio maackii ménétriès’ blue scales changing into green ones immediately after dropping some alcohol aqua on the underwing surface and
soon returning back to the original color, the relationship between microstructure, optics characteristic of scales and changing
color effect were studied using the Olympus Stereomicroscope, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy
(TEM) and Ultraviolet (UV)-Visible Spectrophotometer. The color variation mechanisms of blue scales of Papilio maackii ménétriès in Chinese Northeast were revealed in this paper. When visible lights traveled through the concaver structure with
multilayer reflector and the filled medium with different refractive indices, the reflected lights in definite wavelengths
produced interference and color at that wavelength came into being. It has important academic reference value to biomimetics
design of video stealth materials.
Recommended by Prof. SONG YuQuan, Member of Editorial Committee of Science in China, Series E: Technological Sciences
Supported by the National Natural Science Foundation of China (Grant Nos. 50635030, 30570235), the Key Project of Chinese
Ministry of Education (Grant No. 105059), and Fok Ying Tong Education Foundation (Grant No. 101020) 相似文献
60.
Linear periodically time-varying (LPTV) systems are abundant in control and signal processing; examples include multirate sampled-data control systems and multirate filter-bank systems. In this paper, several ways are proposed to quantify aliasing effect in discrete-time LPTV systems; these are associated with optimal time-invariant approximations of LPTV systems using operator norms. 相似文献