The precise tuning of magnetic nanoparticle size and magnetic domains,thereby shaping magnetic properties.However,the dynamic evolution mechanisms of magnetic domain configurations in relation to electromagnetic(EM)at...The precise tuning of magnetic nanoparticle size and magnetic domains,thereby shaping magnetic properties.However,the dynamic evolution mechanisms of magnetic domain configurations in relation to electromagnetic(EM)attenuation behavior remain poorly understood.To address this gap,a thermodynamically controlled periodic coordination strategy is proposed to achieve precise modulation of magnetic nanoparticle spacing.This approach unveils the evolution of magnetic domain configurations,progressing from individual to coupled and ultimately to crosslinked domain configurations.A unique magnetic coupling phenomenon surpasses the Snoek limit in low-frequency range,which is observed through micromagnetic simulation.The crosslinked magnetic configuration achieves effective low-frequency EM wave absorption at 3.68 GHz,encompassing nearly the entire C-band.This exceptional magnetic interaction significantly enhances radar camouflage and thermal insulation properties.Additionally,a robust gradient metamaterial design extends coverage across the full band(2–40 GHz),effectively mitigating the impact of EM pollution on human health and environment.This comprehensive study elucidates the evolution mechanisms of magnetic domain configurations,addresses gaps in dynamic magnetic modulation,and provides novel insights for the development of high-performance,low-frequency EM wave absorption materials.展开更多
排列时间不可逆性是量化复杂系统非平衡特征的重要方法,但排列类型无法表征序列的精确结构特征.本文提出了一种模糊排列时间不可逆(fuzzy permutation time irreversibility,fpTIR)方法,利用负指数函数转化向量元素差值,计算向量幅度排...排列时间不可逆性是量化复杂系统非平衡特征的重要方法,但排列类型无法表征序列的精确结构特征.本文提出了一种模糊排列时间不可逆(fuzzy permutation time irreversibility,fpTIR)方法,利用负指数函数转化向量元素差值,计算向量幅度排列的隶属度,进而比较正反序列模糊排列的概率分布差异.作为对照,通过香农熵计算模糊排列概率分布的平均信息量,即模糊排列熵(fuzzy permutation entropy,fPEn),用以衡量系统的复杂度.本文首先利用logistic和Henon混沌系统以及一阶自回归模型构建测试序列,通过代替数据理论验证fpTIR和fPEn的有效性,然后分析PhysioNet数据库中的心衰、健康老年及健康年轻心率的复杂特征.结果表明,fpTIR可有效表征系统的非平衡性特征,并且提高了心率信号分析的准确度.由于fpTIR和fPEn采用不同的概率分布分析方法,两者在混沌序列验证中存在差异,甚至在心率信号的分析中出现相反的结果,其中fpTIR的分析结果与心率复杂度丢失理论一致.总之,本文研究不仅精准表征了序列的排列空间结构,优化了复杂系统非平衡性分析的效果,而且为从非平衡动力学和熵值复杂度两个角度探索复杂系统特征提供了新的视角和理论依据.展开更多
基金supported by the National Natural Science Foundation of China(22265021,52231007,and 12327804)the Aeronautical Science Foundation of China(2020Z056056003)Jiangxi Provincial Natural Science Foundation(20232BAB212004).
文摘The precise tuning of magnetic nanoparticle size and magnetic domains,thereby shaping magnetic properties.However,the dynamic evolution mechanisms of magnetic domain configurations in relation to electromagnetic(EM)attenuation behavior remain poorly understood.To address this gap,a thermodynamically controlled periodic coordination strategy is proposed to achieve precise modulation of magnetic nanoparticle spacing.This approach unveils the evolution of magnetic domain configurations,progressing from individual to coupled and ultimately to crosslinked domain configurations.A unique magnetic coupling phenomenon surpasses the Snoek limit in low-frequency range,which is observed through micromagnetic simulation.The crosslinked magnetic configuration achieves effective low-frequency EM wave absorption at 3.68 GHz,encompassing nearly the entire C-band.This exceptional magnetic interaction significantly enhances radar camouflage and thermal insulation properties.Additionally,a robust gradient metamaterial design extends coverage across the full band(2–40 GHz),effectively mitigating the impact of EM pollution on human health and environment.This comprehensive study elucidates the evolution mechanisms of magnetic domain configurations,addresses gaps in dynamic magnetic modulation,and provides novel insights for the development of high-performance,low-frequency EM wave absorption materials.
