FDTD Simulation on the Interaction Between Gaussian Beam and Biaxial Anisotropic Metamaterial Slabs

The interaction between Gaussian beam and indefinite anisotropic metamaterial (AMM) slabs are simulated with auxiliary differential equation method in finite-difference time-domain method (FDTD). The directions of wave vector and energy flow densities in three types of AMM slabs are investigated. The field intensity distributions and phases of TE-polarized wave for the interaction between Gaussian beam and AMM slabs are given. Numerical results show that the sign of x component of relative permeability tensor of AMM determines the refraction is regular or anomalous, whereas the sign of z component of relative permeability tensor of AMM determines the energy flow is positively refracted or negatively refracted. Positive or negative Goos-H?nchen shift associated with Total Cutoff media are also shown. This work was supported by National Key Laboratory of Electromagnetic Environment fund (51486030305HT0101) and (9140C08060507ZCZJ18).     

Large pyroelectric response in (Pb0.87La0.02Ba0.1)(Zr0.7Sn0.3−x Ti x )O3 antiferroelectric ceramics under DC bias field

(Pb_0.87La_0.02Ba_0.1)(Zr_0.7Sn_0.3−x Ti _x )O₃ (PLBZST, 0.06≤x≤0.09) antiferroelectric ceramics were fabricated by conventional solid state reaction process, and their ferroelectric, dielectric, and pyroelectric properties were systemically investigated. PLBZST with different Ti content were all confirmed to be in an antiferroelectric phase at T=50°C, which is close to the lowest phase transition temperature. Compared with conventional FE ceramics, PLBZST antiferroelectric ceramics exhibited higher electric field induced pyroelectric coefficient (p). As the content of Ti increased from 0.06 to 0.09, the pyroelectric coefficient increased from 1000 to 6500 μC/m²K under a 500 V/mm DC bias field. The maximum pyroelectric coefficient of 8400 μC/m²K was obtained at x=0.09 when an 850 V/mm DC bias field was applied, which is far larger than that of conventional phase transition pyroelectric materials. Large pyroelectric response is beneficial for the development of infrared detectors and thermal imaging sensors.     

FDTD Study on Back Scattering of Conducting Sphere Coated with Double-Negatibe Metamaterials

The shift operator method in finite-difference time-domain method for anisotropic double-negative (DNG) metamaterials is derived. The problem which incorporates both anisotropy and frequency dispersion at the same time is solved for the electromagnetic wave propagation in DNG media. By comparing with the mie series solution, the numerical verification of the method and program are confirmed by computing the back scattering of isotropic unmagnetized plasma sphere. The back scattering of conducting sphere coated with DNG media with different parameters is computed by using the shift operator method. One finds that the degree of DNG media’s match and isotropy plays important parts in the decrease of the back scattering of the conducting sphere. This work was supported by National Key Laboratory of Electromagnetic Environment fund (51486030305HT0101). An erratum to this article can be found at     

Effect of Ultrasonic Pretreatment on Flocculation Filtration of Low-Rank Coal Slurry

The efficient filtration of low-rank coal (LRC) slurry was significantly beneficial to the production process of wet coal beneficiation. However, relatively few studies have been reported on novel pretreatment methods for the efficient filtration of LRC slurry. In this paper, the mechanism of ultrasonic pretreatment to promote flocculation and filtration of slurry was studied. The hydrophobic variation of the slurry surface was measured by contact angle and XPS. The flocculation properties of slurry were characterized using zeta potential and FBRM. The effects of filter cake porosity and ultrasonic pretreatment on slurry filtration resistance were calculated by L-F NMR and Darcy’s theory. The results showed that the ultrasonic pretreatment promoted the flocculation and filtration performance of LRC slurry, increased the filtration rate, and decreased the cake moisture content. Meanwhile, the contact angle of LRC increased significantly from 50.1° to 67.8° after ultrasonic pretreatment, and the surface tension of the filtrate decreased from 69.5 to 53.31 mN/m. Ultrasonic pretreatment reduced the absolute value of the zeta potential of coal slurry from 24.8 to 21.0 mV, and the average chord length of flocs increased from 5–10 μm to 25–30 μm, thus weakening the electrostatic repulsion between coals to promote floc formation. In addition, the pore tests and filtration theory calculations showed that the ultrasonic pretreatment significantly improved the permeability of the filter cake to water and reduced the resistance to slurry during filtration. In particular, the mesopore porosity increased by 9.18%, and the permeability increased by 2.937 × 10⁸ m². Therefore, this contributed to the reduction of slurry filtration resistance. This research provides an efficient method for promoting the efficient filtration of slurry.