High-frequency magnetic materials are crucial for realizing anti-electromagnetic interference in GHz communication devices and electronic equipment.Current mainstream strategy to enhance highfrequency magnetic losses ...High-frequency magnetic materials are crucial for realizing anti-electromagnetic interference in GHz communication devices and electronic equipment.Current mainstream strategy to enhance highfrequency magnetic losses is shape anisotropy,and it is still difficult to obtain an improvement in intrinsic magnetic loss through electronic structure design.In this paper,the effects of 4f-3d interaction between Er and Fe/Co on magnetic moment,charge migration,and spin polarization were investigated based on density functional theory(DFT).The results show that Er 4f-Fe 3d orbitals undergo significant hybridization at around-4 eV,which increase the electronic locality of Fe and enhance the spin of Fe from 2.86 h/2 to 2.91 h/2.The Fe_(0.5-x)Co_(0.5)Er_(x)(0≤x≤0.05)alloys were further prepared by vacuum induction melting and mechanical alloying methods.The saturation magnetization intensity(Ms)increases from 0.141 to 0.182 A·m^(2)/g with increasing Er content.The μ"of Fe_(0.47)Co_(0.5)Er_(0.03)at 16.7 GHz increases from 0.55 to 0.93,and the frequency range over which tanδ_μvalues are greater than 0.5covers 8.0-18.0 GHz,with the maximum value being 0.83 at 17.0 GHz.These results indicate that the Fe_(0.5-x)Co_(0.5)Er_(x)/paraffin composite materials have excellent high-frequency magnetic losses and are promising candidates in the field of microwave-absorbing materials.展开更多
Cantilevered pipe conveying fluid may become unstable and flutter instability would occur when the velocity of the fluid flow in the pipe exceeds a critical value.In the present study,the theoretical model of a cantil...Cantilevered pipe conveying fluid may become unstable and flutter instability would occur when the velocity of the fluid flow in the pipe exceeds a critical value.In the present study,the theoretical model of a cantilevered fluid-conveying pipe attached by an inerter-based dynamic vibration absorber(IDVA)is proposed and the stability of this dynamical system is explored.Based on linear governing equations of the pipe and the IDVA,the effects of damping coefficient,weight,inerter,location and spring stiffness of the IDVAon the critical flow velocities of the pipe system is examined.It is shown that the stability of the pipe may be significantly affected by the IDVA.In many cases,the stability of the cantilevered pipe can be enhanced by designing the parameter values of the IDVA.By solving nonlinear governing equations of the dynamical system,the nonlinear oscillations of the pipe with IDVA for sufficiently high flow velocity beyond the critical value are determined,showing that the oscillation amplitudes of the pipe can also be suppressed to some extent with a suitable design of the IDVA.展开更多
基金Project supported by the Nation Natural Science Foundation of China(52304410,51972242)Major Project of Hubei Province(2023BAA003)。
文摘High-frequency magnetic materials are crucial for realizing anti-electromagnetic interference in GHz communication devices and electronic equipment.Current mainstream strategy to enhance highfrequency magnetic losses is shape anisotropy,and it is still difficult to obtain an improvement in intrinsic magnetic loss through electronic structure design.In this paper,the effects of 4f-3d interaction between Er and Fe/Co on magnetic moment,charge migration,and spin polarization were investigated based on density functional theory(DFT).The results show that Er 4f-Fe 3d orbitals undergo significant hybridization at around-4 eV,which increase the electronic locality of Fe and enhance the spin of Fe from 2.86 h/2 to 2.91 h/2.The Fe_(0.5-x)Co_(0.5)Er_(x)(0≤x≤0.05)alloys were further prepared by vacuum induction melting and mechanical alloying methods.The saturation magnetization intensity(Ms)increases from 0.141 to 0.182 A·m^(2)/g with increasing Er content.The μ"of Fe_(0.47)Co_(0.5)Er_(0.03)at 16.7 GHz increases from 0.55 to 0.93,and the frequency range over which tanδ_μvalues are greater than 0.5covers 8.0-18.0 GHz,with the maximum value being 0.83 at 17.0 GHz.These results indicate that the Fe_(0.5-x)Co_(0.5)Er_(x)/paraffin composite materials have excellent high-frequency magnetic losses and are promising candidates in the field of microwave-absorbing materials.
基金The authors gratefully acknowledge the support provided by the National Natural Science Foundation of China(Nos.11622216,11672115 and 11972167).
文摘Cantilevered pipe conveying fluid may become unstable and flutter instability would occur when the velocity of the fluid flow in the pipe exceeds a critical value.In the present study,the theoretical model of a cantilevered fluid-conveying pipe attached by an inerter-based dynamic vibration absorber(IDVA)is proposed and the stability of this dynamical system is explored.Based on linear governing equations of the pipe and the IDVA,the effects of damping coefficient,weight,inerter,location and spring stiffness of the IDVAon the critical flow velocities of the pipe system is examined.It is shown that the stability of the pipe may be significantly affected by the IDVA.In many cases,the stability of the cantilevered pipe can be enhanced by designing the parameter values of the IDVA.By solving nonlinear governing equations of the dynamical system,the nonlinear oscillations of the pipe with IDVA for sufficiently high flow velocity beyond the critical value are determined,showing that the oscillation amplitudes of the pipe can also be suppressed to some extent with a suitable design of the IDVA.
基金supported by the National Natural Science Foundation of China(62175061,52172140,52221001,and 52072117)the Natural Science Foundation of Hunan Province(2022JJ30167)+1 种基金the Outstanding Scholarship Program of Hunan Province(2021JJ10021)China Postdoctoral Science Foundation(BX20220104,2022M720046 and 2022TQ0100)。
