共查询到10条相似文献,搜索用时 125 毫秒
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Lamb波在传播过程中具有频散及多模态特性,若相关参数选择不当,会导致在实际应用中信号相互叠加而无法识别。本文基于Lamb波的频散曲线是其频散方程实数解分布的特点,采用二分法绘制了铝板中Lamb波的频散曲线、波结构曲线和入射角曲线。根据曲线选择S0模态的Lamb波对1mm厚铝板中不同类型的缺陷进行检测。实验结果表明,S0模态的Lamb波对裂纹型缺陷和贯穿型缺陷十分敏感,但对于裂纹型缺陷,其幅值变化并不与缺陷大小成线性关系,并且S0模态Lamb波的声场指向性十分集中,在偏离声束轴线时无法检测到缺陷。 相似文献
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In a step-down chain a solitary wave (SW) evolves into an SW train (SWT), but the formation of well-defined SWT takes time and space and little is known of the process from immature into mature SWT. We therefore perform a detailed numerical study of this process by analysing the local velocity amplitude and peak overlap of immature ordered SWs. The first SW continuously increases to maximal velocity amplitude and peak overlap until it is matured, but for following SWs there exist a minimal and maximal value of local velocity amplitude and, a minimal and maximal value of local peak overlap, clarifying the details of the energy propagation along the stepped chain. The immature and mature SWTs show the same dependence of the phase velocity on the SWs sequence. These provide guidelines for when or where the attention should be paid in the study of SWT. 相似文献
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采用放电等离子烧结技术,在相同的温度(1 473 K)及压力(30 MPa)下,制备出不同配比的致密的W-Mo系复合材料样品。采用高精度超声波脉冲回波重合方法,精确测量了超声波在样品中传播的横、纵波声速,并由此得到样品的特性波阻抗值。对样品的相组成分析及电子探针分析的结果表明,W-Mo系复合材料主要是以W、Mo机械混合的形式通过粘结相获得致密化的。因此,选用混合物模型对其特性波阻抗值进行了理论预测,与实测值的比较表明该模型能对W-Mo系复合材料的特性波阻抗作出比较准确的预测。 相似文献
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Jeong Ryeol Choi 《International Journal of Theoretical Physics》2004,43(4):947-958
We derived the WKB wave function for the general time-dependent quadratic Hamiltonian system using a unitary transformation method. We applied our research to sinusodially drived Caldirola–Kanai oscillator and confirmed that the time evolution of our approximated WKB wave function is similar to that of the exact one. This wave function can be used to analyze the interference between the probability amplitudes contributed by the area of overlap in phase space of quantum states. 相似文献
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Wideband dispersion removal and mode separation of Lamb waves based on two-component laser interferometer measurement 下载免费PDF全文
Ultrasonic Lamb waves are considered as a sensitive and effective tool for nondestructive testing and evaluation of plate-like or pipe-like structures. The nature of multimode and dispersion causes the wave packets to spread, and the modes overlap in both time and frequency domains as they propagate through the structures. By using a two-component laser interferometer technique, in combination with a priori knowledge of the dispersion characteristics and wave structure information of Lamb wave modes, a two-component signal processing technique is presented for implementing dispersion removal and mode separation simultaneously for two modes mixture signals of Lamb waves. The proposed algorithm is first processed and verified using synthetic Lamb wave signals. Then, the two-component displacements test experiment is conducted using different aluminum plate samples. Moreover, we confirm the effectiveness and robustness of this method. 相似文献
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An algorithm of calculation of multidimensional integrals of overlapping harmonic vibrational wave functions that employs symbolic computations has been developed. The algorithm is implemented in a Matlab 5.x system and allows one to perform calculations many orders of magnitude more rapidly than those described heretofore. The speed of computation by this algorithm depends weakly on the dimensionality of the overlap integral, and this makes it possible to use this integral to calculate the intensities of lines in the electronic–vibrational spectra of multiatomic molecules. 相似文献
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Linearly polarised three-colour lasing emission from an evanescent wave pumped and gain coupled fibre laser 下载免费PDF全文
A novel Whispering--Gallery--Mode (WGM) fibre laser,
emitting linearly polarised three-colour light, is demonstrated by
pumping and gain coupling with evanescent waves. The pump light is
longitudinally coupled into a bare optical fibre immersed in a dye
solution of lower refractive index. The dye molecules around the
bare fibre are excited by the evanescent waves of pump light when
they propagate along the fibre in a total internal reflection. When
the pump beam within the fibre is a meridian beam, the WGM lasing
emission from the fibre laser is a linearly polarised transverse
electric wave, while it is a mixed wave of the linearly polarised
transverse electric and magnetic waves if the pump beam is a skew
beam within the fibre. Because the excited molecules are located
within the evanescent field of WGM, a good spatial overlap between
the dye gain and the evanescent field leads to a high pumping
efficiency and a longer gain distance along the fibre. Once the bare
fibre is inserted into three glass capillaries filled with Rhodamine
6G, 610 and 640 dye solutions, respectively, WGM laser oscillations
at the wavelengths of 567--575, 605--614 and 656--666~nm occur
simultaneously, and a linearly polarised three-colour lasing
emission is achieved in a single optical fibre. 相似文献
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根据行波管用的关键材料-钨铼合金中高含量铼测定的需求,研究了用X射线荧光(XRF)光谱法测定铼时所存在的基体效应、谱线重叠和背景干扰的影响,从理论上解释了XRF二元比例法校正曲线线性差的原因。理论和实验结果均表明:直接用Re Lα分析线强度绘制的校正曲线比二元比例法可以获得更好的线性。本法具有快速准确的特点,分析结果与化学方法一致,在生产控制中应用效果显著。 相似文献