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1.
Starting from piezoelectric crystal dynamic equation etc.,both the electric potential and surface chargeinduced by the incident wave are obtained with electrical boundary perturbation technique.The scatteredwaves are then derived including both surface and bulk waves through integral transformation with theinduced charge as exciting source.The scattered surface waves from the grating on YZ-LiNbO_3 are then numerically calculated,and boththe reflective and forward scattering coefficients are given vs.the strip width.Furthermore,the surface wavephase velocity change when passing the grating is derived and numerically calculated too.The theoreticalprediction agrees well with measured results. 相似文献
2.
A new weighting method,transducer weighting.for the uniform groove-deph RAC is proposed in thispaper.The weighted input and output transducersform a weighting transversal filter In addition,the groove-width weighting,which can be used as an auxiliary is also discussed. By using the new methods,two uniform groove depth RACs have been designed and fabricated,Thesidelobe suppressions achieved are 31 dB and 32 dB.respectively.The results are considered satisfactorybecause the phase compensation by metal strip was not applied. 相似文献
3.
Pt/Ti Electrodes of PZT Thin Films Patterning by Novel Lift-Off Using ZnO as a Sacrificial Layer 下载免费PDF全文
We achieve a successful novel lift-off of patterning Pt/Ti electrodes on SiO2/Si substrates by employing ZnO sacrificial layer deposition and patterning, successive uniform Pt/Ti deposition and final lift-off. Then we deposit PZT thin films on the electrodes. Compared with the conventional lift-off processes for the electrodes, this novel process does not need post-annealing, which must be performed after conventional lift-off process. It is demonstrated that the electrodes patterned by the novel lift-off process have stronger adhesion. The electrodes and the PZT films on the electrodes are more compact and smoother than those by the conventional lift-off process. 相似文献
4.
We investigate the focusing phenomena of a surface acoustic wave (SAW) field generated by a circular-arc interdigital transducer (IDT) on a piezoelectric crystal. A rigorous vector field theory of surface excitation on the crystal we developed previously is used to evaluate the convergent SAW field instead of the prevalent scalar angular spectrum used in optics. The theoretical results show that the anisotropy of a medium has great impact on the focusing properties of the acoustic beams, such as focal length and symmetrical distributions near the focus. A dark field method is used in experiment to observe the focusing of the SAW tield optically. Although the convergent phenomena of SAW field on the anisotropic media or piezoelectric crystals are very complicated, the experimental data are in agreement with those from the rigorous theory. 相似文献
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单一空化气泡运动的高速摄影的实验研究 总被引:4,自引:0,他引:4
作者用高速摄影方法实验研究了单一空化气泡的运动.气泡生长闭合运动的实验结果与理论基本上是符合的.在仔细研究空化气泡闭合瞬刻照片发现有“小脉动”现象存在,它为空化气泡在闭合瞬刻在气泡内会产生微骇波的假说提供了有力佐证.本文还通过实验研究了气泡生长、闭合和反跳运动的衰减性质. 相似文献
8.
The diffraction phenomena of SAW normally incident on acoustic gratings have been developed.The acoustic grating which is composed of a periodic array of metal film stripes is fabricated on thesurface of Y-cut LiNbO_3 on which the SAWs propagate. Theoretically,the diffraction characteristics of the gratings on which the SAW beam normallyimpinges are analyzed by means of the phenomenological theory.The emphases are laid on twospecial cases,i.e."thin grating"and"thick grating"situations.For the former,the Raman-Nathapproximation is quoted from the theory of acousto-optical diffraction.For the latter,the analyticalexpressions of the diffracted intensities are deduced by using the normal mode theory. Experimentally,two sorts of samples which correspond respectively to"thick grating"and"thingrating"are designed and fabricated.Some interesting results are obtained by means of the opticalmethods.The images of the SAWs power flows of the diffracted acoustic fields as well as the SAWwavefronts within the grating 相似文献
9.
The effect of electric load on the piezoelectric vibrational system due to electroacoustic coupling isanalytically investigated.The analytical results show that:(1)when load impedance continuallychanges from ∞to+∞,the mechanical resonant frequency of the system would fill all frequencydomain from 0 to ∞;(2)the displacement and stress distributions also would change,even the dis-placement may be zero at both free ends(i.e.at points where stress is equal to zero). Finally,the experiments for longitudinal vibration of piezoelectric strip of lateral polarizationare given and compared with theoretical results. 相似文献
10.
This paper developes the general theory of the surface excitation of elastic wave field in a halfspace of piezoelectric crystal for both free and metallized surfaces.It is shown that the general elas-tic wave field U is equal to the convolution of the generalized Green's functions G and the general-ized forces T, U = G Twhere symbol,expresses dot-product-convolution. The generalized Green's functions are independent of excitation conditions and only dependenton material parameters and orientation. For the piezoelectric crystal,not only a mechanical source distribution at the surface,but anelectrical source distribution can also excite the elastic wave fields.Complete expressions of thegeneralized forces representing mechanical and electrical source distribution respectively are given.Especially for the free surface,the surface electrical sources can be composed of the discontinuityof normal electric displacement at the surface,and of the discontinuity of the tangential electric fieldas well. 相似文献