We investigate the beam focusing technology of shear-vertical(SV) waves for a contact-type linear phased array to overcome the shortcomings of conventional wedge transducer arrays. The numerical simulation reveals the...We investigate the beam focusing technology of shear-vertical(SV) waves for a contact-type linear phased array to overcome the shortcomings of conventional wedge transducer arrays. The numerical simulation reveals the transient excitation and propagation characteristics of SV waves. It is found that the element size plays an important role in determining the transient radiation directivity of SV waves. The transient beam focusing characteristics of SV waves for various array parameters are deeply studied. It is particularly interesting to see that smaller element width will provide the focused beam of SV waves with higher quality, while larger element width may result in erratic fluctuation of focusing energy around the focal point. There exists a specific range of inter-element spacing for optimum focusing performance. Moreover, good beam focusing performance of SV waves can be achieved only at high steering angles.展开更多
To overcome the inherent limits of traditional single wave imaging for nondestructive testing,the multi-wave focusing and imaging method is thoroughly studied.This method makes the compressional waves and shear waves ...To overcome the inherent limits of traditional single wave imaging for nondestructive testing,the multi-wave focusing and imaging method is thoroughly studied.This method makes the compressional waves and shear waves focused in both emission and reception processes,which strengthens the focusing energy and improves the signal-to-noise ratio of received signals.A numerical model is developed to study the characteristics of a multi-wave focusing field.It is shown that the element width approaching 0.8 wavelengths of shear waves can keep a balance between the radiation energy of two waves,which can achieve a desirable multi-wave focusing performance.And an experiment using different imaging methods for a linear phased array is performed.It can be concluded that due to the combination of the propagation and reflection characteristics of two waves,the multi-wave focusing and imaging method can significantly improve the imaging distinguishability of defects and expand the available sweeping range to a sector of-650 to 65°.展开更多
The incidence of significant left main(LM)coronary artery stenosis identified by coronary angiography was 5%−17.5%in various clinical presentations;about 80%of stenosis involved the LM bifurcation(LMB).[1]Although per...The incidence of significant left main(LM)coronary artery stenosis identified by coronary angiography was 5%−17.5%in various clinical presentations;about 80%of stenosis involved the LM bifurcation(LMB).[1]Although per-cutaneous coronary intervention(PCI)is an appro-priate alternative to coronary artery bypass graft in LM disease with low-to-intermediate anatomical complexity,[2]PCI for LMB lesions remains the most technically challenging for interventional cardiolo-gists with higher rates of acute periprocedural com-plications and higher risk of long-term major ad-verse cardiac events in the era of drug-eluting stent(DES).展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11774377 and 11574343)。
文摘We investigate the beam focusing technology of shear-vertical(SV) waves for a contact-type linear phased array to overcome the shortcomings of conventional wedge transducer arrays. The numerical simulation reveals the transient excitation and propagation characteristics of SV waves. It is found that the element size plays an important role in determining the transient radiation directivity of SV waves. The transient beam focusing characteristics of SV waves for various array parameters are deeply studied. It is particularly interesting to see that smaller element width will provide the focused beam of SV waves with higher quality, while larger element width may result in erratic fluctuation of focusing energy around the focal point. There exists a specific range of inter-element spacing for optimum focusing performance. Moreover, good beam focusing performance of SV waves can be achieved only at high steering angles.
基金the National Natural Science Foundation of China(Grant No.11774377)。
文摘To overcome the inherent limits of traditional single wave imaging for nondestructive testing,the multi-wave focusing and imaging method is thoroughly studied.This method makes the compressional waves and shear waves focused in both emission and reception processes,which strengthens the focusing energy and improves the signal-to-noise ratio of received signals.A numerical model is developed to study the characteristics of a multi-wave focusing field.It is shown that the element width approaching 0.8 wavelengths of shear waves can keep a balance between the radiation energy of two waves,which can achieve a desirable multi-wave focusing performance.And an experiment using different imaging methods for a linear phased array is performed.It can be concluded that due to the combination of the propagation and reflection characteristics of two waves,the multi-wave focusing and imaging method can significantly improve the imaging distinguishability of defects and expand the available sweeping range to a sector of-650 to 65°.
基金This study was supported by the National Key Research and Development Program of China(2016 YFC1301200)the National Natural Science Foundation of China(No.81300095&No.81900217)+1 种基金the Animal Model Project of Shanghai Scientific Committee(No.19140900901)the Youth Backbone Foundation of Zhongshan Hospital and Shanghai Sailing Program(19YF1406200).
文摘The incidence of significant left main(LM)coronary artery stenosis identified by coronary angiography was 5%−17.5%in various clinical presentations;about 80%of stenosis involved the LM bifurcation(LMB).[1]Although per-cutaneous coronary intervention(PCI)is an appro-priate alternative to coronary artery bypass graft in LM disease with low-to-intermediate anatomical complexity,[2]PCI for LMB lesions remains the most technically challenging for interventional cardiolo-gists with higher rates of acute periprocedural com-plications and higher risk of long-term major ad-verse cardiac events in the era of drug-eluting stent(DES).