在结构健康监测(Structural Health Monitoring,SHM)技术中,基于Lamb波的损伤监测方法在板状结构中显示出了巨大的潜力。提出了一种基于近似非凸鲁棒主成分分析(Approximate Non-Convex Robust Principal Component Analysis,ANC-RPCA)...在结构健康监测(Structural Health Monitoring,SHM)技术中,基于Lamb波的损伤监测方法在板状结构中显示出了巨大的潜力。提出了一种基于近似非凸鲁棒主成分分析(Approximate Non-Convex Robust Principal Component Analysis,ANC-RPCA)的异常值分析方法。该算法对于高维测量信号,能够在降维条件下实现有效的损伤诊断。通过使用秩近似函数逼近矩阵的秩,采用非凸惩罚函数逼近?_(0)范数,非凸惩罚函数在一定条件下可以保证稀疏解的唯一性。随着数据矩阵规模的扩大,传统的RPCA采用核范数近似时,奇异值分解的计算复杂度也会上升。新的近似方法能在使计算效率更高的情况下,针对波场图像能够在更低秩的水平下保留有效信息,识别出异常值。将该算法运用到基于Lamb波的波场图像中,通过仿真和实验数据验证其有效性,使用非精确增广拉格朗日乘子(Inexact Augmented Lagrange Multiplier,IALM)法求解,并与目前使用较多的主流RPCA算法进行了效果对比。实验结果表明ANC-RPCA算法在异常值识别中具有良好的性能,相较于其他算法,在计算效率和低秩性等方面具有巨大的优势,证明了所提算法的可靠性和完整性。展开更多
为提高层合板损伤检测的准确性与灵敏度,基于聚偏二氟乙烯(polyvinylidene fluoride,PVDF)梳状换能器激发的零群速度(zero group velocity,ZGV)Lamb波,提出了一种层合板损伤的检测方法。采用二维时域有限元方法,研究了PVDF梳状换能器对...为提高层合板损伤检测的准确性与灵敏度,基于聚偏二氟乙烯(polyvinylidene fluoride,PVDF)梳状换能器激发的零群速度(zero group velocity,ZGV)Lamb波,提出了一种层合板损伤的检测方法。采用二维时域有限元方法,研究了PVDF梳状换能器对零群速度Lamb波的激励,通过改变层合板中铝层杨氏模量来表征不同的损伤程度,分析了PVDF梳状换能器电压响应特性与层合板损伤程度之间的关系。结果表明:采用PVDF梳状换能器能够有效激励零群速度Lamb波,并获得层合板内部的状态信息。随着损伤程度的增加,PVDF梳状换能器响应的零群速度共振峰频域幅值随着铝层杨氏模量的减小而显著减少,进而灵敏地评价层合板损伤变化。研究结果说明优化设计的PVDF梳状换能器在零群速度Lamb波的激发与接收性能上都具有优越性,能够有效检测层合板损伤情况。展开更多
Acoustic streaming enabled by a Lamb wave resonator(LWR)is efficient for particle trapping and enrichment in microfluidic channels.However,because Lamb waves combine the features of bulk acoustic waves and surface aco...Acoustic streaming enabled by a Lamb wave resonator(LWR)is efficient for particle trapping and enrichment in microfluidic channels.However,because Lamb waves combine the features of bulk acoustic waves and surface acoustic waves,the resulting acoustic streaming in the LWR occurs in multiple planes,and the particle flow behavior in this acoustofluidic system is largely unknown.Reported here are numerical simulations and laboratory experiments conducted to investigate the boundary conditions for particle motion inside a microvortex induced by an LWR.Upon dynamic capture,the particles’trajectories become orbital paths within an acoustic vortex.The suspended particles encounter two distinct acoustic phenomena,i.e.,the drag force resulting from acoustic streaming and the acoustic radiation force,which exert forces in various directions on the particles.When the acoustic radiation force and the fluid drag force are dominant for large and small particles in a mixed solution,respectively,the large particles reside within the vortex while the small particles remain at its periphery.Conversely,when the acoustic radiation force is dominant for both types of particles,the distribution pattern is reversed.展开更多
[Objectives]To study the antibacterial effects of extracts from Pinus massoniana Lamb.needles.[Methods]In this experiment,the components from Pinus massoniana Lamb.needles were extracted by systematic solvent extracti...[Objectives]To study the antibacterial effects of extracts from Pinus massoniana Lamb.needles.[Methods]In this experiment,the components from Pinus massoniana Lamb.needles were extracted by systematic solvent extraction method,and the antibacterial activity against four common bacteria,Escherichia coli,Staphylococcus aureus,Bacillus subtilis,Aspergillus flavus and the antibacterial active component were examined for by punch method.[Results]Different solvent extraction rate was different,the rates of petroleum ether,chloroform,ethyl acetate,n-butanol,water extracts were 4.2%,16.7%,17.4%,21.1%,40.6%.All extracts showed inhibitory effect against test bacteria.It was observed that the inhibition of G+was stronger than G-,and the extracts had the best antibacterial activity to Staphylococcus aureus while the weakest to Aspergillus flavus.The antibacterial activity of the components decreased in the order:ethyl acetate extract>n-butanol extract>chloroform extract>petroleum ether extract>aqueous phase.The extracts were stable under ultraviolet radiation(UV)light and long term storage.The antibacterial activity of the extracts was weaker with the increase of pH value when the pH value≤8.[Conclusions]It is inferred that the antibacterial components in the extract of Pinus massoniana needles are widely distributed,and the components with medium polarity or above are the main antibacterial components.展开更多
文摘为提高层合板损伤检测的准确性与灵敏度,基于聚偏二氟乙烯(polyvinylidene fluoride,PVDF)梳状换能器激发的零群速度(zero group velocity,ZGV)Lamb波,提出了一种层合板损伤的检测方法。采用二维时域有限元方法,研究了PVDF梳状换能器对零群速度Lamb波的激励,通过改变层合板中铝层杨氏模量来表征不同的损伤程度,分析了PVDF梳状换能器电压响应特性与层合板损伤程度之间的关系。结果表明:采用PVDF梳状换能器能够有效激励零群速度Lamb波,并获得层合板内部的状态信息。随着损伤程度的增加,PVDF梳状换能器响应的零群速度共振峰频域幅值随着铝层杨氏模量的减小而显著减少,进而灵敏地评价层合板损伤变化。研究结果说明优化设计的PVDF梳状换能器在零群速度Lamb波的激发与接收性能上都具有优越性,能够有效检测层合板损伤情况。
基金National Key R&D Program of China(No.2021YFE0107800)National Science Foundation for Distinguished Young Scholars(No.52325805)CCCC Academician Special Scientific Research Funding Project(No.YSZX-03-2021-01-B).
基金support of the National Natural Science Foundation of China (Grant No.62174119)the 111 Project (Grant No.B07014)the Foundation for Talent Scientists of Nanchang Institute for Microtechnology of Tianjin University.
文摘Acoustic streaming enabled by a Lamb wave resonator(LWR)is efficient for particle trapping and enrichment in microfluidic channels.However,because Lamb waves combine the features of bulk acoustic waves and surface acoustic waves,the resulting acoustic streaming in the LWR occurs in multiple planes,and the particle flow behavior in this acoustofluidic system is largely unknown.Reported here are numerical simulations and laboratory experiments conducted to investigate the boundary conditions for particle motion inside a microvortex induced by an LWR.Upon dynamic capture,the particles’trajectories become orbital paths within an acoustic vortex.The suspended particles encounter two distinct acoustic phenomena,i.e.,the drag force resulting from acoustic streaming and the acoustic radiation force,which exert forces in various directions on the particles.When the acoustic radiation force and the fluid drag force are dominant for large and small particles in a mixed solution,respectively,the large particles reside within the vortex while the small particles remain at its periphery.Conversely,when the acoustic radiation force is dominant for both types of particles,the distribution pattern is reversed.
基金Supported by Zhanjiang Non-funded Science and Technology Research Plan in 2023(2023B01023)School-level Education and Teaching Reform Project of Lingnan Normal University in 2022(LingShiJiaoWu2022154).
文摘[Objectives]To study the antibacterial effects of extracts from Pinus massoniana Lamb.needles.[Methods]In this experiment,the components from Pinus massoniana Lamb.needles were extracted by systematic solvent extraction method,and the antibacterial activity against four common bacteria,Escherichia coli,Staphylococcus aureus,Bacillus subtilis,Aspergillus flavus and the antibacterial active component were examined for by punch method.[Results]Different solvent extraction rate was different,the rates of petroleum ether,chloroform,ethyl acetate,n-butanol,water extracts were 4.2%,16.7%,17.4%,21.1%,40.6%.All extracts showed inhibitory effect against test bacteria.It was observed that the inhibition of G+was stronger than G-,and the extracts had the best antibacterial activity to Staphylococcus aureus while the weakest to Aspergillus flavus.The antibacterial activity of the components decreased in the order:ethyl acetate extract>n-butanol extract>chloroform extract>petroleum ether extract>aqueous phase.The extracts were stable under ultraviolet radiation(UV)light and long term storage.The antibacterial activity of the extracts was weaker with the increase of pH value when the pH value≤8.[Conclusions]It is inferred that the antibacterial components in the extract of Pinus massoniana needles are widely distributed,and the components with medium polarity or above are the main antibacterial components.
