Mingjun Wang

The single-scattering properties of dust aerosols form the fundamental basis for atmospheric radiative transfer simulations and climate model construction. However, the actual tri-axial ellipsoidal morphology of dust deviates from traditional approximations. Furthermore, the low computational efficiency of traditional electromagnetic scattering calculations and the high storage costs of optical property databases severely constrain their engineering applications. In this study, a prediction model for the optical properties of tri-axial ellipsoidal dust aerosols based on the extreme gradient boosting algorithm is proposed. Utilizing single-scattering property data of tri-axial ellipsoidal dust calculated via traditional methods as a benchmark, this model achieves the rapid prediction of optical parameters, including the extinction efficiency factor, scattering efficiency factor, single scattering albedo, and asymmetry factor. The results demonstrate that the coefficients of determination for the four optical properties are larger than 0.998, with root mean square error values below 0.05. The prediction errors of the model exhibit a significant scale dependence, where the errors for large size parameters X are substantially lower than those for small to medium size parameters X . This pattern is highly consistent with the physical mechanism wherein the influence of non-spherical details on macroscopic optical properties weakens during the scattering process of large particles, and the dependence of optical properties on size tends to flatten. Simultaneously, the model demonstrates robust extrapolation capabilities for combinations of size parameters and axis ratios not covered by the training database, yielding error distributions that closely approximate those of the covered parameters. By substituting the original 8.52 GB optical property database with a mere 916 KB model file, this study not only breaks through the efficiency and storage bottlenecks of traditional methods but also provides a highly efficient and accurate optical property calculation scheme for applications such as atmospheric radiative transfer models and aerosol remote sensing retrievals. This is of significant importance for improving the estimation accuracy of the climate effects of dust aerosols.

This study presents a chiral metasurface based on α-MoO₃, engineered to achieve strong and tunable circular dichroism (CD), the differential absorption of right- and left-circularly polarized (RCP and LCP) light, in the terahertz (THz) frequency range. By introducing anisotropic rectangular units with specific rotation angles, the design breaks in-plane structural symmetry, resulting in significant chiral optical responses. Through systematic optimization of geometric parameters, the metasurface demonstrates a high CD value of 0.92 at 10.92 THz. The physical origin of the observed CD is revealed by analyzing the electric field distributions under right- and left-circularly polarized light. The influence of key structural parameters-period, thickness, and rotation angle-on the CD response is thoroughly examined, establishing a clear correlation between geometry and optical performance. Furthermore, two structural variants, including elliptical unit arrays and hole-based designs, are explored to assess the role of unit shape and spatial arrangement in CD modulation. Results confirm that spatial and geometric modulation strategies effectively tailor terahertz circular dichroism, offering valuable insights for the development of high-performance chiral photonic devices.

Acoustic waves, as mechanical waves, can perturb atmospheric pressure during propagation, altering the refractive index and turbulence distribution. This study explores a method to mitigate the impact of atmospheric turbulence on optical wave transmission using a linear array acoustic source. We investigated the transmission characteristics of vortex beam superposition states under acoustic perturbation, examining the effects of different wave frequencies and propagation distances on the acoustic field distribution, scintillation index, and atmospheric refractive index structure constant. The results show that acoustic field distributions vary with frequency, and a stable acoustic field is achievable with proper configuration. The scintillation index and refractive index structure constant are influenced by both the acoustic wave propagation distance and sound pressure level. Furthermore, a higher sound pressure level of the source enhances the impact of the linear array acoustic waves on both the scintillation index and the atmospheric refractive index structure constant. This research presents a novel approach to improving optical wave transmission by mitigating atmospheric turbulence.

This paper proposes a dual-band, polarization-reconfigurable glass-mounted transparent antenna for Vehicle-to-everything (V2X) communications. The antenna is etched on a polyester (PET) with a thickness of 0.1 mm using indium-doped tin oxide (ITO) transparent conductive film with a thickness of 0.125 mm, achieving an overall light transmittance of 84.2%. The antenna structure includes two circular monopole patches and a frame surrounding the monopole patch. The circular monopole patches are coupled and fed by T-type feedlines. Four diode switches are soldered onto the ITO surface using conductive silver paste to control the polarization of the antenna. The biasing of the diodes switches the antenna in three different polarization states: linear polarization, left-handed circular polarization and right-handed circular polarization. Simulations and measurements of the antenna were conducted on a vehicular glass. The overall size of the antenna is 96.7×68.9 mm², with a total thickness of 0.225 mm, a linear polarization matching bandwidth of 2.3 GHz-6.5 GHz, and a circular polarization bandwidth of 5.4-6.4 GHz (15%) in the 2.5 GHz and 5.8 GHz dual-frequency operation. Finally, the ground-to-air communication link is studied using transmission coefficient between the glass-mounted (proposed) antenna and an unmanned aerial vehicle (UAV) operating with different attitudes. Results indicate link improvements due to the polarization reconfigurability offered by the proposed antenna.

Bessel-Gaussian (BG) vortex beams are non-diffracting beams carrying orbital angular momentum, which have potential applications against ocean turbulence and are expected to solve the bottleneck problem of long-distance and high-rate transmission of light underwater. In this paper, an experimental link for underwater vortex optical communication is constructed, and the underwater transmission and communication characteristics of Gaussian beams and BG vortex beams with different orders are investigated under the seawater channel conditions of air bubbles, sediment, and turbulence. The light intensity images, beam drift, and scintillation indices are analyzed, the bit error rate (BER) during communication is calculated, and the self-healing characteristics of the BG vortex beams in underwater channel environments with obstacles are investigated. The results show that the BG vortex beam has lower beam drift, optical intensity scintillation, and more stable underwater data transmission performance compared with the Gaussian beam under various simulated ocean channel conditions, and the higher-order BG beam has better transmission performance than the zero-order BG beam. This research provides a robust and useful alternative to withstand ocean turbulence and improve the reliability and capacity of optical communication systems.

The rapid development of wireless network technology and the continuous evolution of network service demands have raised higher requirements for congestion control algorithms. In 2016, Google proposed the Bottleneck Bandwidth and Round-trip propagation time (BBR) congestion control algorithm based on the Transmission Control Protocol (TCP) protocol. While BBR offers lower latency and higher throughput compared to traditional congestion control algorithms, it still faces challenges. These include the periodic triggering of the ProbeRTT phase, which impairs data transmission efficiency, data over-injection caused by the congestion window (CWND) value-setting policy, and the difficulty of coordinating resource allocation across multiple concurrent flows. These limitations make BBR less effective in multi-stream competition scenarios in high-speed wireless networks. This paper analyzes the design limitations of the BBR algorithm from a theoretical perspective and proposes the Adaptive-BBR (Ad-BBR) algorithm. The Ad-BBR algorithm incorporates real-time RTT and link queue-state information, introduces a new RTprop determination mechanism, and implements a finer-grained, RTT-based adaptive transmission rate adjustment mechanism to reduce data over-injection and improve RTT fairness. Additionally, the ProbeRTT phase-triggering mechanism is updated to ensure more stable and smoother data transmission. In the NS3, 5G, and Wi-Fi simulation experiments, Ad-BBR outperformed all comparison algorithms by effectively mitigating data over-injection and minimizing unnecessary entries into the ProbeRTT phase. Compared to the BBRv1 algorithm, Ad-BBR achieved a 17% increase in throughput and a 30% improvement in RTT fairness, along with a 13% reduction in the retransmission rate and an approximate 20% decrease in latency.