Beijing Survey and Design Institute (China)

Introduction Microbially induced desaturation and precipitation (MIDP) is a promising environmentally friendly technique for improving liquefiable coastal sands; however, the key factors governing microbial gas-production efficiency and their governing patterns remain insufficiently understood. Methods To clarify the gas-production characteristics of Pseudomonas stutzeri for potential MIDP application in coastal liquefied sand treatment, this study systematically investigated the effects of temperature, pH, bacterial concentration (OD 600 ), and nitrate concentration (KNO 3 ) using a four-factor, five-level orthogonal experimental design under controlled laboratory conditions. Results The results show that gas-production efficiency increases markedly with temperature from 10 to 30 °C. Increasing pH from 5 to 9 enhanced the gas-production rate by 2.3-fold. As OD 600 increased from 0.05 to 0.25, gas production first improved and then declined, with the optimum performance observed at OD 600 = 0.10. Among the investigated factors, KNO 3 concentration was identified as the most influential variable controlling gas production by Pseudomonas stutzeri . Discussion These findings provide an experimental basis for optimizing the application of MIDP in the anti-liquefaction treatment of coastal liquefiable sand.

Relay protection devices are key equipment to ensure the safe and stable operation of power systems. The current design schemes of device and panel have some problems such as long power outages, heavy workload, and potential safety hazard of wiring during the transformation process, which are in sharp conflict with the requirements of safe power supply and high reliability of the power grid. Several conventional transformation schemes of the panel are presented in this paper. And a technical solution based on a new type of terminal block is proposed, aiming to achieve universal interchangeability and plug-and-play of full-voltage level protection devices, enhance power supply reliability and improve operation and maintenance convenience. It provides a method for the rapid transformation of relay protection devices.

Vehicle-to-vehicle (V2V) communications require highly accurate and real-time channel modeling techniques. The dynamic nature of V2V scenarios demands continuous scene updates while ray-tracing (RT) algorithms typically require substantial computational time to achieve accurate predictions. This letter proposes an OptiX-based GPU-parallel dynamic shooting and bouncing ray tracing (DSRT) method that combines the advantages of shooting and bouncing ray (SBR) and RT approaches. The method employs an improved adaptive ray-tube splitting mechanism to improve accuracy. A level of detail (LOD)-based dynamic scene update method further optimizes performance, while OptiX and CUDA acceleration enable efficient RT. Channel measurements in urban environments demonstrate the high accuracy of our algorithm. Performance evaluation results show that DSRT achieves a parallelization degree exceeding 98.8% and delivers exceptional speedup ratios.

Abstract. To address the issues of uneven feature point distribution, environmental interference, and insufficient real-time performance in UAV image stitching in complex urban environments, this paper proposes an improved ORB algorithm based on Gaussian scale-space optimization and dynamic grid division, combined with a global geometric consistency optimization strategy. First, local adaptive noise filtering and bilateral filtering are applied to enhance image quality. Then, multi-scale feature detection is achieved using a Gaussian scale-space pyramid, and dynamic grid division is employed to balance feature point distribution. Finally, a global energy function, including reprojection error and smoothness constraints, is constructed to iteratively optimize the homography matrix and suppress stitching distortions. Experimental results show that the proposed method achieves high processing speed on low-performance hardware platforms, improves feature point distribution uniformity to 0.89, and achieves stitching accuracy (RMSE) of 3.5 pixels, significantly outperforming ORB and SIFT algorithms, while remaining robust in dynamic occlusion and lighting variation scenarios. This method provides a lightweight and efficient solution for UAV image stitching in urban environments, supporting applications such as urban planning and disaster assessment. Future work will explore lightweight deep learning integration and edge computing acceleration to further improve dynamic scene adaptability.

The galloping behavior of ice-covered additional overhead contact line conductors in a high-wind environments presents a significant threat to the safe operation of electrified railways. This study investigates the galloping phenomenon of additional conductors under ice accumulation conditions, establishing a nonlinear finite element model. By integrating aerodynamic characteristics, the vibration patterns and influencing factors of the galloping behavior are systematically explored. First, aerodynamic parameters for various ice cover shapes, ice thicknesses and wind speeds are simulated using the FLUENT fluid dynamics software. The instability of the ice-covered additional conductors is evaluated using the Den Hartog coefficient criterion, and the accuracy of the simulation is validated through wind tunnel experiments, providing a foundation for galloping prediction. Next, a nonlinear finite element model of the ice-covered additional conductor is developed, and numerical simulations are carried out using the Newmark-[Formula: see text] method to replicate the galloping behavior. The formation and motion characteristics of the conductor’s vibration are thoroughly analyzed. Finally, the effect of the conductor’s structural parameters on galloping behavior is investigated. By varying parameters such as tension, span distance and the number of spans, their influence on the galloping response is examined. The results indicate that higher ice thickness, increased wind speed, and an optimal range of attack angles contribute to a greater susceptibility to galloping. The galloping behavior of ice-covered additional conductors is a gradual process, primarily characterized by vertical vibration, supplemented by horizontal oscillations, forming an elliptical trajectory. Furthermore, increasing the tension, reducing the span, and optimizing the number of spans help mitigate the galloping behavior. This study provides a theoretical foundation for the prevention and control of galloping in ice-covered additional conductors and offers valuable guidance for the design and maintenance of electrified railways.

In the nonparametric modeling of hydropneumatic suspension, the effective terms of nonlinear parameters are often difficult to determine, which further leads to the difficulty of obtaining the structural stiffness and damping characteristics. To solve this problem, this paper develops a novel method based on the polynomial structure selection technique to determine the effective terms of the nonparametric model of the hydropneumatic suspension, and then the stiffness and damping will be obtained. First, the hydropneumatic suspension bench test is carried out to obtain the output force, the excitation speed and the excitation displacement under different working conditions. Then, the stiffness and damping characteristics of the hydropneumatic suspension are theoretically analyzed. Finally, through the analysis results and the polynomial structure selection technique, the simplest structure of nonparametric mathematical model for the hydropneumatic suspension model is obtained, and later the stiffness and damping of the hydropneumatic suspension are identified. Comparison between the test output force of the hydropneumatic suspension and the output force of the simplified model shows that the simplified model can be used to replace the real model, and eventually verifies that the damping and stiffness characteristics of the hydropneumatic suspension are only related to the excitation displacement and the excitation speed, and the two ones do not interfere with each other.