Terahertz nonreciprocal and functionality-switchable devices based on dielectric multilayers integrated with graphene and VO2.

Recently, terahertz (THz) nonreciprocal and functionality-switchable devices have drawn much attention. Here we report a magnetic-free THz unidirectional perfect absorber as well as a functionality-switchable device between the band-pass filter and perfect absorber based on dielectric-graphene multilayers containing a VO2 defect layer. We provide a theoretical explanation for the nonreciprocal transmission properties. The working frequencies of these devices can be tailored by using graphene layers of different chemical potentials.

Tunable and multifunctional terahertz devices based on one-dimensional anisotropic photonic crystals containing graphene and phase-change material.

In the past few years, designing tunable and multifunctional terahertz devices has become a hot research area in terahertz science and technology. In this work, we report a study on one-dimensional anisotropic photonic crystals (1D APCs) containing graphene and phase-change material VO2. We numerically demonstrate the band-pass filtering, perfect absorption, comb-shaped extraordinary optical transmission and Fano-like resonance phenomenon in pure 1D APCs and 1D APCs with a VO2 defect layer under different conditions of a tangential wave vector. The performance of these phenomena in the terahertz region can be modulated by changing the chemical potential of graphene. The band-pass filter and perfect absorber functions of 1D APCs with a VO2 defect layer can be freely switched by changing the phase of VO2. We employ the equivalent-permittivity model and dispersion-relation equation to give reasonable explanations on these behaviors.

The effect of screw fixation type on a modular hemi-pelvic prosthesis: a 3-D finite element model.

In this article, a 3-D finite element (FE) model of human pelvic with a modular hemi-pelvic prosthesis was constructed to study the effect of screw fixation type on the biomechanics of the prosthesis. The results showed that the elimination of the screw far away from the pelvic arcuate line did not induce the instability and stress increase in the prosthesis. On the contrary, some stress in the sustain and acetabular parts decreased by 26.4% and 11.4%, respectively. In conclusion, the optimization of screw fixation can maintain the prosthesis stability and reduced stress concentration on some prosthesis parts. It was deduced that the optimization of the prosthesis could help surgeon reconstruct the pelvic joint function better and diminish the clinical time and cost.

The effect of boundary condition on the biomechanics of a human pelvic joint under an axial compressive load: a three-dimensional finite element model.

The finite element (FE) model of the pelvic joint is helpful for clinical diagnosis and treatment of pelvic injuries. However, the effect of an FE model boundary condition on the biomechanical behavior of a pelvic joint has not been well studied. The objective of this study was to study the effect of boundary condition on the pelvic biomechanics predictions. A 3D FE model of a pelvis using subject-specific estimates of intact bone structures, main ligaments and bone material anisotropy by computed tomography (CT) gray value was developed and validated by bone surface strains obtained from rosette strain gauges in an in vitro pelvic experiment. Then three FE pelvic models were constructed to analyze the effect of boundary condition, corresponding to an intact pelvic joint, a pelvic joint without sacroiliac ligaments and a pelvic joint without proximal femurs, respectively. Vertical load was applied to the same pelvis with a fixed prosthetic femoral stem and the same load was simulated in the FE model. A strong correlation coefficient (R(2)=0.9657) was calculated, which indicated a strong correlation between the FE analysis and experimental results. The effect of boundary condition changes on the biomechanical response depended on the anatomical location and structure of the pelvic joint. It was found that acetabulum fixed in all directions with the femur removed can increase the stress distribution on the acetabular inner plate (approximately double the original values) and decrease that on the superior of pubis (from 7 MPa to 0.6 MPa). Taking sacrum and ilium as a whole, instead of sacroiliac and iliolumber ligaments, can influence the stress distribution on ilium and pubis bone vastly. These findings suggest pelvic biomechanics is very dependent on the boundary condition in the FE model.