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<jats:p>We numerically demonstrated a novel chiral metamaterial to achieve broadband asymmetric transmission (AT) of linearly polarized electromagnetic waves in terahertz (THz) band. The proposed metamaterial unit cell exhibits no rotational symmetry with vanadium dioxide (VO<jats:sub>2</jats:sub>) inclusion embedded between Dirac semimetals (DSMs) pattern. The resonant frequency of AT can be dynamically tunable by varying the Fermi energy (<jats:italic>E</jats:italic> <jats:sub>F</jats:sub>) of the DSMs. The insulator-to-metal phase transition of VO<jats:sub>2</jats:sub> enables the amplitude of the AT to be dynamically tailored. The transmission coefficient |<jats:italic>T<jats:sub>yx</jats:sub> </jats:italic>| can be adjusted from 0.756 to nearly 0 by modifying the conductivity of VO<jats:sub>2</jats:sub>. Meanwhile, the AT parameter intensity of linearly polarized incidence can be actively controlled from 0.55 to almost 0, leading to a switch for AT. When VO<jats:sub>2</jats:sub> is in its insulator state, the proposed device achieves broadband AT parameter greater than 0.5 from 1.21 THz to 1.80 THz with a bandwidth of 0.59 THz. When the incident wave propagates along the backward (–<jats:italic>z</jats:italic>) direction, the cross-polarized transmission | <jats:italic>T<jats:sub>yx</jats:sub> </jats:italic>| reaches a peak value 0.756 at 1.32 THz, whereas the value of | <jats:italic>T<jats:sub>xy</jats:sub> </jats:italic>| well below 0.157 in the concerned frequency. On the other hand, the co-polarized transmission |<jats:italic>T<jats:sub>xx</jats:sub> </jats:italic>| and |<jats:italic>T<jats:sub>yy</jats:sub> </jats:italic>| remained equal in the whole frequency range. This work provides a novel approach in developing broadband, tunable, as well as switchable AT electromagnetic devices.</jats:p>

<jats:p>The multi-phase field model of grain competitive growth during directional solidification of alloy is established. Solving multi-phase field models for thin interface layer thickness conditions, the grain boundary evolution and grain elimination during the competitive growth of SCN-0.24-wt% camphor model alloy bi-crystals are investigated. The effects of different crystal orientations and pulling velocities on grain boundary microstructure evolution are quantitatively analyzed. The obtained results are shown below. In the competitive growth of convergent bi-crystals, when favorably oriented dendrites are in the same direction as the heat flow and the pulling speed is too large, the orientation angle of the bi-crystal from small to large size is the normal elimination phenomenon of the favorably oriented dendrite, blocking the unfavorably oriented dendrite, and the grain boundary is along the growth direction of the favorably oriented dendrite. When the pulling speed becomes small, the grain boundary shows the anomalous elimination phenomenon of the unfavorably oriented dendrite, eliminating the favorably oriented dendrite. In the process of competitive growth of divergent bi-crystal, when the growth direction of favorably oriented dendrites is the same as the heat flow direction and the orientation angle of unfavorably oriented grains is small, the frequency of new spindles of favorably oriented grains is significantly higher than that of unfavorably oriented grains, and as the orientation angle of unfavorably oriented dendrites becomes larger, the unfavorably oriented grains are more likely to have stable secondary dendritic arms, which in turn develop new primary dendritic arms to occupy the liquid phase grain boundary space, but the grain boundary direction is still parallel to favorably oriented dendrites. In addition, the tertiary dendritic arms on the developed secondary dendritic arms may also be blocked by the surrounding lateral branches from further developing into nascent main axes, this blocking of the tertiary dendritic arms has a random nature, which can have aninfluence on the generation of nascent primary main axes in the grain boundaries.</jats:p>

<jats:p>The synergistic influences of boron, oxygen, and titanium on growing large single-crystal diamonds are studied using different concentrations of B<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> in a solvent–carbon system under 5.5 GPa–5.7 GPa and 1300 °C–1500 °C. It is found that the boron atoms are difficult to enter into the crystal when boron and oxygen impurities are doped using B<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> without the addition of Ti atoms. However, high boron content is achieved in the doped diamonds that were synthesized with the addition of Ti. Additionally, boron–oxygen complexes are found on the surface of the crystal, and oxygen-related impurities appear in the crystal interior when Ti atoms are added into the FeNi–C system. The results show that the introduction of Ti atoms into the synthesis cavity can effectively control the number of boron atoms and the number of oxygen atoms in the crystal. This has important scientific significance not only for understanding the synergistic influence of boron, oxygen, and titanium atoms on the growth of diamond in the earth, but also for preparing the high-concentration boron or oxygen containing semiconductor diamond technologies.</jats:p>

<jats:p>Na-ion batteries (NIBs) are regarding as the optimum complement for Li-ion batteries along with the rapid development of stationary energy storage systems. In order to meet the commercial demands of cathodes for NIBs, O3-type Cu containing layered oxide Na<jats:sub>0.90</jats:sub>Cu<jats:sub>0.22</jats:sub>Fe<jats:sub>0.30</jats:sub>Mn<jats:sub>0.48</jats:sub>O<jats:sub>2</jats:sub> with good comprehensive performance and low-cost element components is very promising for the practical use. However, only part of the Cu<jats:sup>3+</jats:sup>/Cu<jats:sup>2+</jats:sup> redox couple participated in the redox reaction, thus impairing the specific capacity of the cathode materials. Herein, Mg<jats:sup>2+</jats:sup>-doped O3-Na<jats:sub>0.90</jats:sub>Mg<jats:sub>0.08</jats:sub>Cu<jats:sub>0.22</jats:sub>Fe<jats:sub>0.30</jats:sub>Mn<jats:sub>0.40</jats:sub>O<jats:sub>2</jats:sub> layered oxide without Mn<jats:sup>3+</jats:sup> was synthesized successfully, which exhibited improved reversible specific capacity of 118 mAh/g in the voltage range of 2.4–4.0 V at 0.2 C, corresponding to the intercalation/deintercalation of 0.47 Na<jats:sup>+</jats:sup> (0.1 more than that of Na<jats:sub>0.90</jats:sub>Cu<jats:sub>0.22</jats:sub>Fe<jats:sub>0.30</jats:sub>Mn<jats:sub>0.48</jats:sub>O<jats:sub>2</jats:sub>). This work demonstrates an important strategy to obtain advanced layered oxide cathodes for NIBs.</jats:p>

<jats:p>The design strategy and efficiency optimization of a Ge-based n-type metal–oxide–semiconductor field-effect transistor (n-MOSFET) with a Si<jats:sub>0.14</jats:sub>Ge<jats:sub>0.72</jats:sub>Sn<jats:sub>0.14</jats:sub>–Ge<jats:sub>0.82</jats:sub>Sn<jats:sub>0.18</jats:sub>–Ge quantum structure used for 2.45 GHz weak energy microwave wireless energy transmission is reported. The quantum structure combined with <jats:italic>δ</jats:italic>-doping technology is used to reduce the scattering of the device and improve its electron mobility; at the same time, the generation of surface channels is suppressed by the Si<jats:sub>0.14</jats:sub>Ge<jats:sub>0.72</jats:sub>Sn<jats:sub>0.14</jats:sub> cap layer. By adjusting the threshold voltage of the device to 91 mV, setting the device aspect ratio to 1 μm/0.4 μm and adopting a novel diode connection method, the rectification efficiency of the device is improved. With simulation by Silvaco TCAD software, good performance is displayed in the transfer and output characteristics. For a simple half-wave rectifier circuit with a load of 1 pf and 20 k<jats:italic>Ω</jats:italic>, the rectification efficiency of the device can reach 7.14% at an input power of –10 dBm, which is 4.2 times that of a Si MOSFET (with a threshold voltage of 80 mV) under the same conditions; this device shows a better rectification effect than a Si MOSFET in the range of –30 dBm to 6.9 dBm.</jats:p>

<jats:p>A novel normally-off AlGaN/GaN high-electron-mobility transistor (HEMT) with a p-GaN Schottky hybrid gate (PSHG) is proposed, and compared with the conventional p-GaN normally-off AlGaN/GaN HEMTs. This structure can be realized by selective etching of p-GaN layer, which enables the Schottky junction and PN junction to control the channel charge at the same time. The direct current (DC) and switching characteristics of the PSHG HEMTs are simulated by Slivaco TCAD, and the p-GaN HEMTs and conventional normally-on HEMTs are also simulated for comparison. The simulation results show that the PSHG HEMTs have a higher current density and a lower on-resistance than p-GaN HEMTs, which is more obvious with the decrease of p-GaN ratios of the PSHG HEMTs. The breakdown voltage and threshold voltage of the PSHG HEMTs are very close to those of the p-GaN HEMTs. In addition, the PSHG HEMTs have a higher switching speed than the conventional normally-on HEMTs, and the p-GaN layer ratio has no obvious effect on the switching speed.</jats:p>

<jats:p>We present a comprehensive numerical framework for the electrical and optical modeling and simulation of hybrid quantum dot light-emitting diodes (QD-LEDs). We propose a model known as hopping mobility to calculate the carrier mobility in the emissive organic layer doped with quantum dots (QDs). To evaluate the ability of this model to describe the electrical characteristics of QD-LEDs, the measured data of a fabricated QD-LED with different concentrations of QDs in the emissive layer were taken, and the corresponding calculations were performed based on the proposed model. The simulation results indicate that the hopping mobility model can describe the concentration dependence of the electrical behavior of the device. Then, based on the continuity equation for singlet and triplet excitons, the exciton density profiles of the devices with different QD concentrations were extracted. Subsequently, the corresponding luminance characteristics of the devices were calculated, where the results are in good agreement with the experimental data.</jats:p>

<jats:p>We numerically demonstrate a photo-excited plasmon-induced transparency (PIT) effect in hybrid terahertz (THz) metamaterials. The proposed metamaterials are regular arrays of hybrid unit cells composed of a metallic cut wire and four metallic split-ring resonators (SRRs) whose gaps are filled with photosensitive semiconductor gallium arsenide (GaAs) patches. We simulate the PIT effect controlled by external infrared light intensity to change the conductivity of GaAs. In the absence of photo excitation, the conductivity of GaAs is 0, thus the SRR gaps are disconnected, and the PIT effect is not observed since the dark resonator (supported by the hybrid SRRs) cannot be stimulated. When the conductivity of GaAs is increased via photo excitation, the conductivity of GaAs can increase rapidly from 0 S/m to 1 × 10<jats:sup>6</jats:sup> S/m and GaAs can connect the metal aluminum SRR gaps, and the dark resonator is excited through coupling with the bright resonator (supported by the cut wire), which leads to the PIT effect. Therefore, the PIT effect can be dynamically tuned between the on and off states by controlling the intensity of the external infrared light. We also discuss couplings between one bright mode (CW) and several dark modes (SRRs) with different sizes. The interference analytically described by the coupled Lorentz oscillator model elucidates the coupling mechanism between one bright mode and two dark modes. The phenomenon can be considered the result of linear superposition of the coupling between the bright mode and each dark mode. The proposed metamaterials are promising for application in the fields of THz communications, optical storage, optical display, and imaging.</jats:p>

<jats:p>In the terahertz band, the dispersive characteristic of dielectric material is one of the major problems in the scaled radar cross section (RCS) measurement, which is inconsistent with the electrodynamics similitude deducted according to the Maxwell’s equations. Based on the high-frequency estimation method of physical optics (PO), a scaled RCS measurement method for lossy objects is proposed through dynamically matching the reflection coefficients according to the distribution of the object facets. Simulations of the model of SLICY are conducted, and the inversed RCS of the lossy prototype is obtained using the proposed method. Comparing the inversed RCS with the calculated results, the validity of the proposed method is demonstrated. The proposed method provides an effective solution to the scaled RCS measurement for lossy objects in the THz band.</jats:p>

<jats:p>RNA is an important biological macromolecule, which plays an irreplaceable role in many life activities. RNA functions are largely determined by its tertiary structure and the intrinsic dynamics encoded in the structure. Thus, how to effective extract structure-encoded dynamics is of great significance for understanding RNA functions. Anisotropic network model (ANM) is an efficient method to investigate macromolecular dynamical properties, which has been widely used in protein studies. However, the performance of the conventional ANM in describing RNA flexibility is not as good as that on proteins. In this study, we proposed a new approach, named force-constant-decayed anisotropic network model (fcd-ANM), to improve the performance in investigating the dynamical properties encoded in RNA structures. In fcd-ANM, nucleotide pairs in RNA structure were connected by springs and the force constant of springs was decayed exponentially based on the separation distance to describe the differences in the inter-nucleotide interaction strength. The performance of fcd-ANM in predicting RNA flexibility was evaluated using a non-redundant structure database composed of 51 RNAs. The results indicate that fcd-ANM significantly outperforms the conventional ANM in reproducing the experimental <jats:italic>B</jats:italic>-factors of nucleotides in RNA structures, and the Pearson correlation coefficient between the predicted and experimental nucleotide <jats:italic>B</jats:italic>-factors was distinctly improved by 21.05% compared to the conventional ANM. Fcd-ANM can serve as a more effective method for analysis of RNA dynamical properties.</jats:p>