The utilization of electromagnetic waves is rapidly advancing into the millimeter-wave frequency range,posing increasingly severe challenges in terms of electromagnetic pollution prevention and radar stealth.However,e...The utilization of electromagnetic waves is rapidly advancing into the millimeter-wave frequency range,posing increasingly severe challenges in terms of electromagnetic pollution prevention and radar stealth.However,existing millimeter-wave absorbers are still inadequate in addressing these issues due to their monotonous magnetic resonance pattern.In this work,rare-earth La^(3+)and non-magnetic Zr^(4+)ions are simultaneously incorporated into M-type barium ferrite(BaM)to intentionally manipulate the multi-magnetic resonance behavior.By leveraging the contrary impact of La^(3+)and Zr^(4+)ions on magnetocrystalline anisotropy field,the restrictive relationship between intensity and frequency of the multi-magnetic resonance is successfully eliminated.The magnetic resonance peak-differentiating and imitating results confirm that significant multi-magnetic resonance phenomenon emerges around 35 GHz due to the reinforced exchange coupling effect between Fe^(3+)and Fe^(2+)ions.Additionally,Mosbauer spectra analysis,first-principle calculations,and least square fitting collectively identify that additional La^(3+)doping leads to a profound rearrangement of Zr^(4+)occupation and thus makes the portion of polarization/conduction loss increase gradually.As a consequence,the La^(3+)-Zr^(4+)co-doped BaM achieves an ultra-broad bandwidth of 12.5+GHz covering from 27.5 to 40+GHz,which holds remarkable potential for millimeter-wave absorbers around the atmospheric window of 35 GHz.展开更多
The water absorption kinetics of cowpea and soybean hybrids were studied following the phenomenological models derived from Fick’s diffusion law. Significant intra and inter varietal variations were observed on the p...The water absorption kinetics of cowpea and soybean hybrids were studied following the phenomenological models derived from Fick’s diffusion law. Significant intra and inter varietal variations were observed on the physical characteristics of the seeds. The proposed Fick’s law of diffusion was shown to significantly describe the kinetic of water absorption irrespective of the variety and temperature. The effective diffusivities of the hybrids were shown to vary in the order Nagbaar > Nhyira > Tonaa > Anidaso and increased as the soaking temperature increased from 30<span><span><span style="font-family:;" "="">d°C<span> to 60</span>d°C<span>. The estimated values for water diffusion coefficients varied from 2.90 </span>×<span> 10<sup>-10</sup> to 6.75 </span>×<span> 10<sup>-10</sup> m<sup>2</sup>/s for cowpea and soybean hybrids. An Arrhenius-type equation described the strong temperature effect on the diffusion coefficient with activation energies ranging from 7.73 to 8.56 kJ/mol for cowpeas and 5.51 to 8.14 kJ/mol for soybeans.</span></span></span></span>展开更多
基金supported by the National Natural Science Foundation of China(Nos.:52271180,51802155,12304020)National Key R&D Program of China(No.:2021YFB3502500)+2 种基金Natural Science Foundation of Jiangsu Province(BK20230909)Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutionsthe Center for Microscopy and Analysis at Nanjing University of Aeronautics and Astronautics.
文摘The utilization of electromagnetic waves is rapidly advancing into the millimeter-wave frequency range,posing increasingly severe challenges in terms of electromagnetic pollution prevention and radar stealth.However,existing millimeter-wave absorbers are still inadequate in addressing these issues due to their monotonous magnetic resonance pattern.In this work,rare-earth La^(3+)and non-magnetic Zr^(4+)ions are simultaneously incorporated into M-type barium ferrite(BaM)to intentionally manipulate the multi-magnetic resonance behavior.By leveraging the contrary impact of La^(3+)and Zr^(4+)ions on magnetocrystalline anisotropy field,the restrictive relationship between intensity and frequency of the multi-magnetic resonance is successfully eliminated.The magnetic resonance peak-differentiating and imitating results confirm that significant multi-magnetic resonance phenomenon emerges around 35 GHz due to the reinforced exchange coupling effect between Fe^(3+)and Fe^(2+)ions.Additionally,Mosbauer spectra analysis,first-principle calculations,and least square fitting collectively identify that additional La^(3+)doping leads to a profound rearrangement of Zr^(4+)occupation and thus makes the portion of polarization/conduction loss increase gradually.As a consequence,the La^(3+)-Zr^(4+)co-doped BaM achieves an ultra-broad bandwidth of 12.5+GHz covering from 27.5 to 40+GHz,which holds remarkable potential for millimeter-wave absorbers around the atmospheric window of 35 GHz.
文摘The water absorption kinetics of cowpea and soybean hybrids were studied following the phenomenological models derived from Fick’s diffusion law. Significant intra and inter varietal variations were observed on the physical characteristics of the seeds. The proposed Fick’s law of diffusion was shown to significantly describe the kinetic of water absorption irrespective of the variety and temperature. The effective diffusivities of the hybrids were shown to vary in the order Nagbaar > Nhyira > Tonaa > Anidaso and increased as the soaking temperature increased from 30<span><span><span style="font-family:;" "="">d°C<span> to 60</span>d°C<span>. The estimated values for water diffusion coefficients varied from 2.90 </span>×<span> 10<sup>-10</sup> to 6.75 </span>×<span> 10<sup>-10</sup> m<sup>2</sup>/s for cowpea and soybean hybrids. An Arrhenius-type equation described the strong temperature effect on the diffusion coefficient with activation energies ranging from 7.73 to 8.56 kJ/mol for cowpeas and 5.51 to 8.14 kJ/mol for soybeans.</span></span></span></span>
