The discretization of random fields is the first and most important step in the stochastic analysis of engineering structures with spatially dependent random parameters.The essential step of discretization is solving ...The discretization of random fields is the first and most important step in the stochastic analysis of engineering structures with spatially dependent random parameters.The essential step of discretization is solving the Fredholm integral equation to obtain the eigenvalues and eigenfunctions of the covariance functions of the random fields.The collocation method,which has fewer integral operations,is more efficient in accomplishing the task than the timeconsuming Galerkin method,and it is more suitable for engineering applications with complex geometries and a large number of elements.With the help of isogeometric analysis that preserves accurate geometry in analysis,the isogeometric collocation method can efficiently achieve the results with sufficient accuracy.An adaptive moment abscissa is proposed to calculate the coordinates of the collocation points to further improve the accuracy of the collocation method.The adaptive moment abscissae led to more accurate results than the classical Greville abscissae when using the moment parameter optimized with intelligent algorithms.Numerical and engineering examples illustrate the advantages of the proposed isogeometric collocation method based on the adaptive moment abscissae over existing methods in terms of accuracy and efficiency.展开更多
Actively tunable acoustic metamaterials have attracted ever increasing attention.However,their tunable frequency range is quite narrow(tens of Hz)even under ultrahigh applied voltage(about 1,000 V).Here,we report a su...Actively tunable acoustic metamaterials have attracted ever increasing attention.However,their tunable frequency range is quite narrow(tens of Hz)even under ultrahigh applied voltage(about 1,000 V).Here,we report a superbroad-band actively tunable acoustic metamaterials with the bandwidth over 400 Hz under a low voltage.In the actively tunable acoustic metamaterials,the acoustic membrane is a laminated nanocomposite consisting of a poly(ethylene terephthalate)(PET)and super-aligned carbon nanotube(CNT)drawn from CN T forest array.The laminated nanocomposite membrane exhibits adjustable acoustic properties,whose modulus can be adjusted by applying external electric field.The maximum frequency bandwidth of PET/CN T nanocomposite membrane reaches 419 Hz when applying an external DC voltage of 60 V.Our actively tunable acoustic metamaterials with superbroad-band and lightweight show very promising foreground in noise reduction applications.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.U22A6001 and 52375273)Major Project of Science and Technology Innovation 2030(Grant No.2021ZD0113100)Zhejiang Provincial Natural Science Foundation of China(Grant No.LZ24E050005)。
文摘The discretization of random fields is the first and most important step in the stochastic analysis of engineering structures with spatially dependent random parameters.The essential step of discretization is solving the Fredholm integral equation to obtain the eigenvalues and eigenfunctions of the covariance functions of the random fields.The collocation method,which has fewer integral operations,is more efficient in accomplishing the task than the timeconsuming Galerkin method,and it is more suitable for engineering applications with complex geometries and a large number of elements.With the help of isogeometric analysis that preserves accurate geometry in analysis,the isogeometric collocation method can efficiently achieve the results with sufficient accuracy.An adaptive moment abscissa is proposed to calculate the coordinates of the collocation points to further improve the accuracy of the collocation method.The adaptive moment abscissae led to more accurate results than the classical Greville abscissae when using the moment parameter optimized with intelligent algorithms.Numerical and engineering examples illustrate the advantages of the proposed isogeometric collocation method based on the adaptive moment abscissae over existing methods in terms of accuracy and efficiency.
基金the National Natural Science Foundation of China(NSFC)(Nos.52002201,52008223,51772063)Open Fund of innovation institute for Sustainable Maritime Architecture Research and Technology,Qingdao University of Technology(Nu.2020-035)Shenzhen Science and Technology Program(No.KQTD2016112814303055).
文摘Actively tunable acoustic metamaterials have attracted ever increasing attention.However,their tunable frequency range is quite narrow(tens of Hz)even under ultrahigh applied voltage(about 1,000 V).Here,we report a superbroad-band actively tunable acoustic metamaterials with the bandwidth over 400 Hz under a low voltage.In the actively tunable acoustic metamaterials,the acoustic membrane is a laminated nanocomposite consisting of a poly(ethylene terephthalate)(PET)and super-aligned carbon nanotube(CNT)drawn from CN T forest array.The laminated nanocomposite membrane exhibits adjustable acoustic properties,whose modulus can be adjusted by applying external electric field.The maximum frequency bandwidth of PET/CN T nanocomposite membrane reaches 419 Hz when applying an external DC voltage of 60 V.Our actively tunable acoustic metamaterials with superbroad-band and lightweight show very promising foreground in noise reduction applications.
