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The impact characteristics and residual compressive strength of the honeycomb sandwich structure under different impact energies and different boundary conditions were studied by testing and finite element analysis. The Vumat subroutine was used to establish a three-dimensional progressive failure criterion. The validity of the simulation model was verified by experiments. The results show that the simply supported specimens are more prone to damage and the peak force is lower, but the energy absorption effect is slightly better. At the same time, the residual compressive strength of the simply supported sample after impact is relatively low. When the impact energy is low, the boundary conditions have an important influence on the residual compressive strength. The influence of boundary conditions on the residual compressive strength can be ignored when the impact energy is large.

This paper focuses on a multi-objective optimization approach for resource allocation based on sleep strategy, aiming to mitigate the interference and improve the energy efficiency in heterogeneous networks. Then it’s converted into a multi-objective optimization problem. The problem is solved by the nondominated sorting genetic algorithm version II. And the simulations show that the proposed approach is superior to the existing one in the aspect of mitigating the inter-tier interference between dense low power nodes and the macro base station and reducing energy consumption ratio of low power nodes.

Hexagonal Y1 - x Hox Mn0.8 Fe0.2O3 polycrystalline samples were synthesized by high-temperature solid-state reaction method. The effects of Ho3+ doping on microstructure and magnetic properties of YMn0.8 Fe0.2O3 were investigated in this paper. X-ray diffraction (XRD) and Raman spectra (RS) show that all samples are of single-phase hexagonal structure without another impurity phase. When the doping concentration (x) of Ho3+ is lower than 0.15, the lattice constants, unit cell volume and bond length between the Mn--O of the samples decrease with x increasing. The decrease of the lattice constants may be related to the interaction between the Mn3+ / Fe3+ 3d orbital and the Ho3+ 4f orbital, resulting in lattice distortion and electron loss. The displacements of the rare-earth atoms at the A-site relative to the plane and the inclination of the MnO5 bipyramids are suppressed with increasing doping concentration, which is demonstrated by the shift deviations of the rare-earth atoms and the variations of the Raman phonon modes. At the same time, the trimerization of Mn3+ at the B-site is weakened. The magnetic properties of the samples were measured using the superconductor quantum interference device (SQUID). Results show that the antiferromagnetic (AFM) order decreases upon Ho3 + doping, consistent with the reduced superexchange interaction between Mn3+ --O2- --Mn3+. The AFM transition temperature TN decreases. Besides, the magnetization of the samples and the weak ferromagnetic (WFM) order at low temperature are significantly enhanced, which is attributed to the suppressed magnetic resistance behavior of the system and the ferromagnetic order generated by the spin exchange interaction between Ho3+ --O2- --Mn3+. These provide an idea for us to further explore room temperature multiferroic materials. [ABSTRACT FROM AUTHOR]

Hexagonal Y1 - x Hox Mn0.8 Fe0.2O3 polycrystalline samples were synthesized by high-temperature solid-state reaction method. The effects of Ho3+ doping on microstructure and magnetic properties of YMn0.8 Fe0.2O3 were investigated in this paper. X-ray diffraction (XRD) and Raman spectra (RS) show that all samples are of single-phase hexagonal structure without another impurity phase. When the doping concentration (x) of Ho3+ is lower than 0.15, the lattice constants, unit cell volume and bond length between the Mn--O of the samples decrease with x increasing. The decrease of the lattice constants may be related to the interaction between the Mn3+ / Fe3+ 3d orbital and the Ho3+ 4f orbital, resulting in lattice distortion and electron loss. The displacements of the rare-earth atoms at the A-site relative to the plane and the inclination of the MnO5 bipyramids are suppressed with increasing doping concentration, which is demonstrated by the shift deviations of the rare-earth atoms and the variations of the Raman phonon modes. At the same time, the trimerization of Mn3+ at the B-site is weakened. The magnetic properties of the samples were measured using the superconductor quantum interference device (SQUID). Results show that the antiferromagnetic (AFM) order decreases upon Ho3 + doping, consistent with the reduced superexchange interaction between Mn3+ --O2- --Mn3+. The AFM transition temperature TN decreases. Besides, the magnetization of the samples and the weak ferromagnetic (WFM) order at low temperature are significantly enhanced, which is attributed to the suppressed magnetic resistance behavior of the system and the ferromagnetic order generated by the spin exchange interaction between Ho3+ --O2- --Mn3+. These provide an idea for us to further explore room temperature multiferroic materials. [ABSTRACT FROM AUTHOR]