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<jats:title>Abstract</jats:title> <jats:p>We proposed a switchable vortex beam polarization states terahertz multi-layer metasurface, which consists of three-layer elliptical metal crosses, four-layer dielectrics and two-layer hollow metal circles alternately superimposed. Under the normal incidence of left circularly polarized (LCP) and right circularly polarized (RCP) waves, the proposed structure realizes three independent control functions including focusing and vortex beam, vortex beam with different topological charges and polarization states switching, and azimuth switching of two vortex beams with different polarization states. The results show that the proposed metasurface provides a new idea for multifunctional terahertz wave modulation devices.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Underwater acoustic models are effective tools for simulating underwater sound propagation. More than 50 years of research have been conducted on the theory and computational models of sound propagation in the ocean. Unfortunately, underwater sound propagation models were unable to solve practical large-scale three-dimensional problems for many years due to limited computing power and hardware conditions. Since the mid-1980s, research on high performance computing for acoustic propagation models in the field of underwater acoustics has flourished with the emergence of high-performance computing platforms, enabling underwater acoustic propagation models to solve many practical application problems that could not be solved before. In this paper, the contributions of research on high-performance computing for underwater acoustic propagation models since the 1980s are thoroughly reviewed and the possible development directions for the future are outlined.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We investigated the effect of ozone (O<jats:sub>3</jats:sub>) oxidation of silicon carbide (SiC) on the flat-band voltage (<jats:italic>V</jats:italic> <jats:sub> <jats:italic>fb</jats:italic> </jats:sub>) stability of SiC metal-oxide-semiconductor (MOS) capacitors. SiC MOS capacitors were produced by O<jats:sub>3</jats:sub> oxidation, and their <jats:italic>V</jats:italic> <jats:sub> <jats:italic>fb</jats:italic> </jats:sub> stability under frequency variation, temperature variation and bias temperature stress was evaluated. Secondary ion mass spectroscopy (SIMS), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) indicated that O<jats:sub>3</jats:sub> oxidation can adjust the element distribution near SiC/SiO<jats:sub>2</jats:sub> interface, improve SiC/SiO<jats:sub>2</jats:sub> interface morphology and inhibit the formation of near-interface defects, respectively. In addition, we elaborated the underlying mechanism through which O<jats:sub>3</jats:sub> oxidation improves the <jats:italic>V</jats:italic> <jats:sub> <jats:italic>fb</jats:italic> </jats:sub> stability of SiC MOS capacitors by using the measurement results and O<jats:sub>3</jats:sub> oxidation kinetics.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This work investigates a strain compensation method for the growth of complex interband cascade laser structures. For thick InAs/AlSb superlattice clad layers, the sublayer thicknesses were adjusted so that the tensile strain energy in the lnAs sublayer is equal to the compressive strain energy in the AlSb sublayer. For the four-constituent active region, as the compressive strain in Ga<jats:sub>0.65</jats:sub>In<jats:sub>0.35</jats:sub>Sb alloy layer is large, a tensile strain was incorporated in the chirped InAs/AlSb superlattice region for strain compensation to the Ga<jats:sub>0.65</jats:sub>In<jats:sub>0.35</jats:sub>Sb alloy. A laser structure of 6 μm thickness was grown on GaSb substrate by molecular beam epitaxy. The wafer exhibited good surface morphology and high crystalline quality.</jats:p>

<jats:p>The method of variable separation has always been regarded as a crucial method for solving nonlinear evolution equations. In this paper, we use a new form of variable separation to study novel soliton molecules and their interactions in (2 + 1)-dimensional potential Boiti–Leon-Manna–Pempinelli equation. Dromion molecules, ring molecules, lump molecules, multi-instantaneous molecules, and their interactions are obtained. Then we draw corresponding images with maple software to study their dynamic behavior.</jats:p>

<jats:p>When developing a practical continuous-variable quantum key distribution (CVQKD), the detector is necessary at the receiver’s side. We investigate the practical security of the CVQKD system with an unbalanced heterodyne detector. The results show that unbalanced heterodyne detector introduces extra excess noise into the system and decreases the lower bound of the secret key rate without awareness of the legitimate communicators, which leaves loopholes for Eve to attack the system. In addition, we find that the secret key rate decreases more severely with the increase in the degree of imbalance and the excess noise induced by the imbalance is proportional to the intensity of the local oscillator (LO) under the same degree of imbalance. Finally, a countermeasure is proposed to resist these kinds of effects.</jats:p>

<jats:p>To solve the problem of low weak signal enhancement performance in the quad-stable system, a new quad-stable potential stochastic resonance (QSR) is proposed. Firstly, under the condition of adiabatic approximation theory, the stationary probability distribution (SPD), the mean first passage time (MFPT), the work (<jats:italic>W</jats:italic>), and the power spectrum amplification factor (SAF) are derived, and the impacts of system parameters on them are also extensively analyzed. Secondly, numerical simulations are performed to compare QSR with the classical Tri-stable stochastic resonance (CTSR) by using the genetic algorithm (GA) and the fourth-order Runge–Kutta algorithm. It shows that the signal-to-noise ratio (SNR) and mean signal-to-noise increase (MSNRI) of QSR are higher than CTSR, which indicates that QSR has superior noise immunity than CTSR. Finally, the two systems are applied in the detection of real bearing faults. The experimental results show that QSR is superior to CTSR, which provides a better theoretical significance and reference value for practical engineering application.</jats:p>

<jats:p>This work reports pressure-broadening line-wing and line-core of the lithium Li (2 p ← 2 s) resonance line perturbed by ground sodium Na (3s) atoms. In far-wing regions, the calculations are performed quantum-mechanically and are intended to examine the photoabsorption coefficients at diverse temperatures. The results show the existence of three satellites, in the blue wing near the wavelengths 470 nm and in the red wing around 862 nm and 1070 nm. For the line-core region, by adopting the simplified Baranger model, the line-width and line-shift rates are determined, and their variation law with temperature is examined. No published data were found to compare these results with.</jats:p>

<jats:p>A cold atom source is important for quantum metrology and precision measurement. To reduce the quantum projection noise limit in optical lattice clock, one can increase the number of cold atoms and reduce the dead time by enhancing the loading rate. In this work, we realize an enhanced cold mercury atom source based on a two-dimensional (2D) magneto-optical trap (MOT). The vacuum system is composed of two titanium chambers connected with a differential pumping tube. Two stable cooling laser systems are adopted for the 2D-MOT and the three-dimensional (3D)-MOT, respectively. Using an optimized 2D-MOT and push beam, about 1.3×10<jats:sup>6</jats:sup> atoms, which are almost an order of magnitude higher than using a pure 3D-MOT, are loaded into the 3D-MOT for <jats:sup>202</jats:sup>Hg atoms. This enhanced cold mercury atom source is helpful in increasing the frequency stability of a neutral mercury lattice clock.</jats:p>

<jats:p>Bose–Einstein condensates (BEC) of sodium atoms are transferred into one-dimensional (1D) optical lattice potentials, formed by two laser beams with a wavelength of 1064 nm, in a shallow optical trap. The phase coherence of the condensate in the lattice potential is studied by changing the lattice depth. A qualitative change in behavior of the BEC is observed at a lattice depth of ∼ 13.7 <jats:italic>E</jats:italic> <jats:sub>r</jats:sub>, where the quantum gas undergoes a transition from a superfluid state to a state that lacks well-to-well phase coherence.</jats:p>