-用固相反应法制备了B位空位补偿型钐掺杂非准同型相界组分PZT(54/46)陶瓷.通过正电子湮没寿命谱(PALS)和符合多普勒展宽能谱(CDBS)对陶瓷中的缺陷结构进行综合表征,结合常规表征手段如X射线衍射(XRD),电子扫描显微镜(SEM),介电、铁电...-用固相反应法制备了B位空位补偿型钐掺杂非准同型相界组分PZT(54/46)陶瓷.通过正电子湮没寿命谱(PALS)和符合多普勒展宽能谱(CDBS)对陶瓷中的缺陷结构进行综合表征,结合常规表征手段如X射线衍射(XRD),电子扫描显微镜(SEM),介电、铁电和压电性能测量,研究缺陷对陶瓷压电性能的影响.XRD结果显示所有陶瓷均为纯钙钛矿相,掺杂诱导了菱方-四方(R-T)相变,准同型相界位于Sm掺杂量x=0.010.02.电学测量结果反映:介电、铁电和压电性能均先增强后减弱,MPB附近两个样品都有优异的介电和铁电性能,但其压电性能差别很大.x=0.01给出最优压电性能d_(33)=572 p C/N,较未掺杂样品增强了一倍.PALS结果表明掺杂使陶瓷中缺陷类型发生变化,x≤0.01,样品中同时含有A位空位与B位空位;x≥0.02,样品中以A位相关缺陷为主,B位空位浓度很低.CDBS结果进一步证实x=0.01和0.02中B位空位浓度分别是该体系中最高和最低的.由以上结果推断出:x=0.01获得的最优压电性能与其中较高浓度的B位空位有关,B位空位可稀释A位空位浓度,降低氧空位浓度,从而降低A位空位与氧空位形成缺陷偶极子的几率,促进畴壁运动,使压电性能增强.展开更多
为了完成线性调频(linear frequency modulation,LFM)信号的稀疏采样,并利用稀疏数据对原始信号参数进行估计,本文提出了一种基于Z变换和改进有限新息率(finite rate of innovation,FRI)的LFM信号参数估计方法。以Z变换理论为基础,设计...为了完成线性调频(linear frequency modulation,LFM)信号的稀疏采样,并利用稀疏数据对原始信号参数进行估计,本文提出了一种基于Z变换和改进有限新息率(finite rate of innovation,FRI)的LFM信号参数估计方法。以Z变换理论为基础,设计了一种数学模型,一旦信号能够表达成该数学模型的结构形式,就能通过Z变换和零化滤波器的方法估计信号参数。然后,利用了自相关延迟的FRI结构对LFM信号采样,该结构不仅完成了LFM信号的稀疏采样,而且稀疏采样结果能够与数学模型结构相符。在理论上通过数学论证的方式证明了所提方法能够用于获取LFM信号参数信息,并通过仿真和实测数据验证了所提方法的有效性,理论和实验结果表明该方法只需要4个采样点就能实现对LFM信号的参数估计,并且实验中的参数估计误差均在3%以内,极大的提高有限新息率采样的参数估计效率。展开更多
A unitary right R-module MR satisfies acc on d-annihilators if for every sequence（a;）;of elements of R the ascending chain AnnM（a;）■ AnnM（a;a;）■AnnM（a;a;a;）■… of submodules of MR stabilizes. In this paper ...A unitary right R-module MR satisfies acc on d-annihilators if for every sequence（a;）;of elements of R the ascending chain AnnM（a;）■ AnnM（a;a;）■AnnM（a;a;a;）■… of submodules of MR stabilizes. In this paper we first investigate some triangular matrix extensions of modules with acc on d-annihilators. Then we show that under some additional conditions,the Ore extension module M[x]R[x;α,δ]over the Ore extension ring R[x;α,δ] satisfies acc on d-annihilators if and only if the module MR satisfies acc on d-annihilators. Consequently, several known results regarding modules with acc on d-annihilators are extended to a more general setting.展开更多
We systematically study the evolution of modulated nerve impulses in a myelinated nerve fiber, where both the ionic current and membrane capacitance provide the necessary nonlinear feedbacks. This is achieved by using...We systematically study the evolution of modulated nerve impulses in a myelinated nerve fiber, where both the ionic current and membrane capacitance provide the necessary nonlinear feedbacks. This is achieved by using a perturbation technique, in which the Liénard form of the modified discrete Fitzhugh–Nagumo equation is reduced to the complex Ginzburg–Landau amplitude equation. Three distinct values of the capacitive feedback parameter are considered. At the critical value of the capacitive feedback parameter, it is shown that the dynamics of the system is governed by the dissipative nonlinear Schr?dinger equation. Linear stability analysis of the system depicts the instability of plane waves,which is manifested as burst of modulated nerve impulses that fulfills the Benjamin–Feir criteria. Variations of the capacitive feedback parameter generally influences the plane wave stability and hence the type of wave profile identified in the neural network. Results of numerical simulations mainly confirm the propagation, collision, and annihilation of nerve impulses in the myelinated axon.展开更多
Magnetic skyrmions are topological quasiparticles with nanoscale size and high mobility,which have potential applications in information storage and spintronic devices.The manipulation of skyrmion’s dynamics in the t...Magnetic skyrmions are topological quasiparticles with nanoscale size and high mobility,which have potential applications in information storage and spintronic devices.The manipulation of skyrmion’s dynamics in the track is an important topic due to the skyrmion Hall effect,which can deviate the skyrmions from the preferred direction.We propose a new model based on the ferromagnetic skyrmion,where the skyrmion velocity can be well controlled by adjusting the direction of the current.Using this design,we can avoid the annihilation of the skyrmion induced by the skyrmion Hall effect,which is confirmed by our micromagnetic simulation based on Mumax^(3).In the meantime,we increase the average velocity of the skyrmion by varying the intrinsic material parameters in the track,where the simulations agree well with our analytical results based on the Thiele equation.Finally,we give a phase diagram of the output of the skyrmion in the T-type track,which provides some practical ways for design of logic gates by manipulating crystalline anisotropy through the electrical control.展开更多
文摘-用固相反应法制备了B位空位补偿型钐掺杂非准同型相界组分PZT(54/46)陶瓷.通过正电子湮没寿命谱(PALS)和符合多普勒展宽能谱(CDBS)对陶瓷中的缺陷结构进行综合表征,结合常规表征手段如X射线衍射(XRD),电子扫描显微镜(SEM),介电、铁电和压电性能测量,研究缺陷对陶瓷压电性能的影响.XRD结果显示所有陶瓷均为纯钙钛矿相,掺杂诱导了菱方-四方(R-T)相变,准同型相界位于Sm掺杂量x=0.010.02.电学测量结果反映:介电、铁电和压电性能均先增强后减弱,MPB附近两个样品都有优异的介电和铁电性能,但其压电性能差别很大.x=0.01给出最优压电性能d_(33)=572 p C/N,较未掺杂样品增强了一倍.PALS结果表明掺杂使陶瓷中缺陷类型发生变化,x≤0.01,样品中同时含有A位空位与B位空位;x≥0.02,样品中以A位相关缺陷为主,B位空位浓度很低.CDBS结果进一步证实x=0.01和0.02中B位空位浓度分别是该体系中最高和最低的.由以上结果推断出:x=0.01获得的最优压电性能与其中较高浓度的B位空位有关,B位空位可稀释A位空位浓度,降低氧空位浓度,从而降低A位空位与氧空位形成缺陷偶极子的几率,促进畴壁运动,使压电性能增强.
文摘为了完成线性调频(linear frequency modulation,LFM)信号的稀疏采样,并利用稀疏数据对原始信号参数进行估计,本文提出了一种基于Z变换和改进有限新息率(finite rate of innovation,FRI)的LFM信号参数估计方法。以Z变换理论为基础,设计了一种数学模型,一旦信号能够表达成该数学模型的结构形式,就能通过Z变换和零化滤波器的方法估计信号参数。然后,利用了自相关延迟的FRI结构对LFM信号采样,该结构不仅完成了LFM信号的稀疏采样,而且稀疏采样结果能够与数学模型结构相符。在理论上通过数学论证的方式证明了所提方法能够用于获取LFM信号参数信息,并通过仿真和实测数据验证了所提方法的有效性,理论和实验结果表明该方法只需要4个采样点就能实现对LFM信号的参数估计,并且实验中的参数估计误差均在3%以内,极大的提高有限新息率采样的参数估计效率。
基金The NSF(11471108) of Chinathe NSF(2015JJ2051,2016JJ2050) of Hunan Provincethe Teaching Reform Foundation(G21316) of Hunan Province
文摘A unitary right R-module MR satisfies acc on d-annihilators if for every sequence（a;）;of elements of R the ascending chain AnnM（a;）■ AnnM（a;a;）■AnnM（a;a;a;）■… of submodules of MR stabilizes. In this paper we first investigate some triangular matrix extensions of modules with acc on d-annihilators. Then we show that under some additional conditions,the Ore extension module M[x]R[x;α,δ]over the Ore extension ring R[x;α,δ] satisfies acc on d-annihilators if and only if the module MR satisfies acc on d-annihilators. Consequently, several known results regarding modules with acc on d-annihilators are extended to a more general setting.
文摘We systematically study the evolution of modulated nerve impulses in a myelinated nerve fiber, where both the ionic current and membrane capacitance provide the necessary nonlinear feedbacks. This is achieved by using a perturbation technique, in which the Liénard form of the modified discrete Fitzhugh–Nagumo equation is reduced to the complex Ginzburg–Landau amplitude equation. Three distinct values of the capacitive feedback parameter are considered. At the critical value of the capacitive feedback parameter, it is shown that the dynamics of the system is governed by the dissipative nonlinear Schr?dinger equation. Linear stability analysis of the system depicts the instability of plane waves,which is manifested as burst of modulated nerve impulses that fulfills the Benjamin–Feir criteria. Variations of the capacitive feedback parameter generally influences the plane wave stability and hence the type of wave profile identified in the neural network. Results of numerical simulations mainly confirm the propagation, collision, and annihilation of nerve impulses in the myelinated axon.
基金supported by the National Natural Science Foundation of China(Grant Nos.51771127,52171188,52111530143,11974298,12374123,and 12241403)the Central Government Funds of Guiding Local Scientific and Technological Development of Sichuan Province(Grant No.2021ZYD0025)+3 种基金the Shenzhen Fundamental Research Fund(Grant No.JCYJ20210324120213037)Shenzhen Peacock Group Plan(Grant No.KQTD20180413181702403)the KeyArea Research&Development Program of Guangdong Province(Grant No.2021B0101300003)the Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2022A1515110863 and 2023A1515010837)。
文摘Magnetic skyrmions are topological quasiparticles with nanoscale size and high mobility,which have potential applications in information storage and spintronic devices.The manipulation of skyrmion’s dynamics in the track is an important topic due to the skyrmion Hall effect,which can deviate the skyrmions from the preferred direction.We propose a new model based on the ferromagnetic skyrmion,where the skyrmion velocity can be well controlled by adjusting the direction of the current.Using this design,we can avoid the annihilation of the skyrmion induced by the skyrmion Hall effect,which is confirmed by our micromagnetic simulation based on Mumax^(3).In the meantime,we increase the average velocity of the skyrmion by varying the intrinsic material parameters in the track,where the simulations agree well with our analytical results based on the Thiele equation.Finally,we give a phase diagram of the output of the skyrmion in the T-type track,which provides some practical ways for design of logic gates by manipulating crystalline anisotropy through the electrical control.
