对深空网天线组阵中的几种信号相关算法作简要介绍,重点研究无需形成矩阵的幂的方法——Matrix-Free Power Method。通过理论分析,提出一种改进算法,即基于归一化权的Matrix-Free Power Method。理论计算和软件仿真结果均表明,基于归一...对深空网天线组阵中的几种信号相关算法作简要介绍,重点研究无需形成矩阵的幂的方法——Matrix-Free Power Method。通过理论分析,提出一种改进算法,即基于归一化权的Matrix-Free Power Method。理论计算和软件仿真结果均表明,基于归一化权的Matrix-Free Power Method信噪比合成性能略优于原Matrix-Free Power Method。展开更多
Higher-order displacement-based finite element methods are useful for simulating bending problems and potentially addressing mesh-locking associated with nearly-incompressible elasticity,yet are computationally expens...Higher-order displacement-based finite element methods are useful for simulating bending problems and potentially addressing mesh-locking associated with nearly-incompressible elasticity,yet are computationally expensive.To address the computational expense,the paper presents a matrix-free,displacement-based,higher-order,hexahedral finite element implementation of compressible and nearly-compressible(ν→0.5)linear isotropic elasticity at small strain with p-multigrid preconditioning.The cost,solve time,and scalability of the implementation with respect to strain energy error are investigated for polynomial order p=1,2,3,4 for compressible elasticity,and p=2,3,4 for nearly-incompressible elasticity,on different number of CPU cores for a tube bending problem.In the context of this matrix-free implementation,higher-order polynomials(p=3,4)generally are faster in achieving better accuracy in the solution than lower-order polynomials(p=1,2).However,for a beam bending simulation with stress concentration(singularity),it is demonstrated that higher-order finite elements do not improve the spatial order of convergence,even though accuracy is improved.展开更多
Comprehensive Summary,Carbon dots(CDs)are an emerging class of nanomaterials with intriguing photophysical properties.Recently,achieving room temperature phosphorescence(RTP)for CDs has attracted considerable attentio...Comprehensive Summary,Carbon dots(CDs)are an emerging class of nanomaterials with intriguing photophysical properties.Recently,achieving room temperature phosphorescence(RTP)for CDs has attracted considerable attention for biomedical and information applications.However,the CDs based RTP materials generally require the use of polymeric and inorganic matrix to provide the rigid environments,which remains a great challenge to obtain matrix-free CDs with RTP.Herein,a novel supramolecular strategy based on strong interparticle interactions has been developed to attain this objective,by covalent decoration of ureido-pyrimidinone(UPy,a multiple hydrogen bonding unit)on the surface of CDs.Structural characterizations validated the core-shell structure of the as-prepared CDs(EDTA-CDs)and demonstrated the successful attachment of UPy via post-modification(UPy-CDs).The presence of UPy recognition units render the strong hydrogen bonding between UPy-CDs,which stabilizes the triplet state via rigidifying effect.As a result,UPy-CDs exhibit matrix-free efficient RTP(λ_(em)=534 nm)with high brightness and long lifetime(33.6 ms)in the solid state.Owing to the dual-emission character,we further explored the application potential of UPy-CDs in information encryption and anti-counterfeiting.Overall,this work provides a new and facile strategy for achieving matrix-free phosphorescent CDs with elegant incorporation of supramolecular chemistry.展开更多
交流–电网换相换流器型高压直流输电(AC-line commutated converter high voltage direct current,AC-(LCC)DC)混联系统的电磁暂态初始化在计算模型上可表述为一个扰动的可分无源动力系统。因此,将无源动力系统的显式保积算法应用于电...交流–电网换相换流器型高压直流输电(AC-line commutated converter high voltage direct current,AC-(LCC)DC)混联系统的电磁暂态初始化在计算模型上可表述为一个扰动的可分无源动力系统。因此,将无源动力系统的显式保积算法应用于电磁暂态初始化计算。采用相空间分析方法,对基于逐次积分法的电磁暂态初始化方法的收敛条件以及收敛速率进行了定量分析。在上述基础上,提出了一类新的、系统化的初始化计算方法,该方法计算格式简单、易于编程,在计算效率上具有明显的优势。算例结果验证了所提方法的有效性。展开更多
文摘对深空网天线组阵中的几种信号相关算法作简要介绍,重点研究无需形成矩阵的幂的方法——Matrix-Free Power Method。通过理论分析,提出一种改进算法,即基于归一化权的Matrix-Free Power Method。理论计算和软件仿真结果均表明,基于归一化权的Matrix-Free Power Method信噪比合成性能略优于原Matrix-Free Power Method。
基金The research relied on computational resources[29]provided by the University of Colorado Boulder Research Computing Group,which is supported by the National1302 CMES,2021,vol.129,no.3 Science Foundation(Awards ACI-1532235 and ACI-1532236)University of Colorado Boulder,and Colorado State University.
文摘Higher-order displacement-based finite element methods are useful for simulating bending problems and potentially addressing mesh-locking associated with nearly-incompressible elasticity,yet are computationally expensive.To address the computational expense,the paper presents a matrix-free,displacement-based,higher-order,hexahedral finite element implementation of compressible and nearly-compressible(ν→0.5)linear isotropic elasticity at small strain with p-multigrid preconditioning.The cost,solve time,and scalability of the implementation with respect to strain energy error are investigated for polynomial order p=1,2,3,4 for compressible elasticity,and p=2,3,4 for nearly-incompressible elasticity,on different number of CPU cores for a tube bending problem.In the context of this matrix-free implementation,higher-order polynomials(p=3,4)generally are faster in achieving better accuracy in the solution than lower-order polynomials(p=1,2).However,for a beam bending simulation with stress concentration(singularity),it is demonstrated that higher-order finite elements do not improve the spatial order of convergence,even though accuracy is improved.
基金supported by the National Natural Science Foundations of China(Grant Nos.52172033,51772001 and 22005280)the financial support from the National Key R&D Program of China(Grant No.2021YFA1600202).
文摘Comprehensive Summary,Carbon dots(CDs)are an emerging class of nanomaterials with intriguing photophysical properties.Recently,achieving room temperature phosphorescence(RTP)for CDs has attracted considerable attention for biomedical and information applications.However,the CDs based RTP materials generally require the use of polymeric and inorganic matrix to provide the rigid environments,which remains a great challenge to obtain matrix-free CDs with RTP.Herein,a novel supramolecular strategy based on strong interparticle interactions has been developed to attain this objective,by covalent decoration of ureido-pyrimidinone(UPy,a multiple hydrogen bonding unit)on the surface of CDs.Structural characterizations validated the core-shell structure of the as-prepared CDs(EDTA-CDs)and demonstrated the successful attachment of UPy via post-modification(UPy-CDs).The presence of UPy recognition units render the strong hydrogen bonding between UPy-CDs,which stabilizes the triplet state via rigidifying effect.As a result,UPy-CDs exhibit matrix-free efficient RTP(λ_(em)=534 nm)with high brightness and long lifetime(33.6 ms)in the solid state.Owing to the dual-emission character,we further explored the application potential of UPy-CDs in information encryption and anti-counterfeiting.Overall,this work provides a new and facile strategy for achieving matrix-free phosphorescent CDs with elegant incorporation of supramolecular chemistry.
文摘交流–电网换相换流器型高压直流输电(AC-line commutated converter high voltage direct current,AC-(LCC)DC)混联系统的电磁暂态初始化在计算模型上可表述为一个扰动的可分无源动力系统。因此,将无源动力系统的显式保积算法应用于电磁暂态初始化计算。采用相空间分析方法,对基于逐次积分法的电磁暂态初始化方法的收敛条件以及收敛速率进行了定量分析。在上述基础上,提出了一类新的、系统化的初始化计算方法,该方法计算格式简单、易于编程,在计算效率上具有明显的优势。算例结果验证了所提方法的有效性。
