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This paper presents a robust and adaptive visual servoing-based landing control method for unmanned aerial vehicles (UAVs) equipped with a three-axis gimbal camera. To address the limitations of fixed-camera configurations, the proposed approach integrates pixel-level field-of-view (FOV) constraints and leverages the gimbal’s agility for enhanced visual tracking. The landing task is formulated as a constrained image-based control problem, where tracking errors of image features are rigorously bounded using prescribed performance functions. A velocity observer is incorporated to estimate the time-varying motion of the landing platform in real time, enabling accurate autonomous landing without relying on external communication or infrastructure. Lyapunov-based stability analysis confirms the theoretical soundness of the control strategy. Simulation results validate the effectiveness and robustness of the proposed method, demonstrating improved accuracy, adaptability, and practical applicability in UAV landing scenarios.

The introduction of the pilot flame can stabilize the lean premixed flame and promote its industrial application. However, the interaction mechanism between the pilot and main flames is complicated. To reveal the effect of the pilot flame on the main flame, a laminar lean premixed flame adjacent to a rich premixed pilot flame on one side and a similar lean premixed flame on the other side was considered. A two-dimensional numerical model was adopted with detailed chemistry and species transport, also with no artificial flame anchoring boundary conditions. The results show that the pilot flame could promote the main flame stabilized in different locations with various shapes, by adjusting the stretch, heat transfer, and preferential diffusion in a complicated manner. The pilot flame improves the local equivalence ratio and transfer more heat to the main flame. The growth of the pilot flame equivalence ratio and inlet velocity enhances the combustion on the rich side of the main flame and helps it anchor closer to the flame wall. Both the curvature and strain rate show a significant effect on the flame root, which contributes to the main flame bending towards the pilot flame.

Natural gas is one of the most common forms of energy in our daily life, and it is composed of multicomponent hydrocarbon gas mixtures (mainly of methane, ethane and propane). It is of great significant to reveal the condensation mechanism of multicomponent mixtures for the development and utilization of natural gas. A numerical model was adopted to analyze the heat and mass transfer characteristics of propane condensation in binary and ternary gas mixtures on a vertical cold plate. Multicomponent diffusion equations and the volume of fluid method (VOF) are used to describe the in-phase and inter-phase transportation. The conditions of different wall sub-cooled temperatures (temperature difference between the wall and saturated gas mixture) and the inlet molar fraction of methane/ethane are discussed. The numerical results show that ethane gas is more likely to accumulate near the wall compared with the lighter methane gas. The thermal resistance in the gas boundary layer is one hundred times higher than that of the liquid film, revealing the importance of diffusion resistance. The heat transfer coefficients increased about 11% (at ΔT = 10 K) and 7% (at ΔT = 40 K), as the molar fraction of ethane increased from 0 to 40%. Meanwhile, the condensation heat transfer coefficient decreased by 53~56% as the wall sub-cooled temperature increased from 10 K to 40 K.

This paper focuses on the impact of geotextile tube damage at the joints between tubes on dam structures subjected to seepage. First, a seepage-induced failure critical gradient model for damaged geotextile tubes was developed. Tests were conducted using geotextile specimens with precut O-shaped holes to simulate the seepage erosion process. Various overburden loads (0, 5, 10, 20, and 30 kPa) and hole radii (0.5, 1.0, 1.5, and 2 cm) were examined. Based on the test phenomena and the changes in pore-water pressure and seepage flow, four progression stages (seepage stability, sand particle wash-out, preferential flow formation and development, and complete failure) were identified. The experimental critical gradients obtained under different conditions agreed well with the model results. The critical gradient is positively correlated with the overburden load and negatively correlated with the hole radius. Critical gradient growth gradually slows with increasing overburden load. The critical gradient difference caused by the hole size decreases rapidly. When the overburden load increases to 20 kPa, this difference is essentially unchanged. These findings can provide a better understanding of the performance of damaged geotextile tubes.

Responses of a microbial community in the completely autotrophic nitrogen removal over nitrite (CANON) process, which was shocked by a pH of 11.0 for 12 h, were investigated. During the recovery phase, the performance, anaerobic ammonia oxidation (anammox) activity, microbial community, and correlation of bacteria as well as the influencing factors were evaluated synchronously. The performance of the CANON process deteriorated rapidly with a nitrogen removal rate (NRR) of 0.13 kg·m-3·d-1, and Firmicutes, spore-forming bacteria, were the dominant phyla after alkaline shock. However, it could self-restore within 107 days after undergoing four stages, at which Planctomycetes became dominant with a relative abundance of 64.62%. Network analysis showed that anammox bacteria (Candidatus Jettenia, Kuenenia, and Brocadia) were positively related to some functional bacteria such as Nitrosomonas, SM1A02, and Calorithrix. Canonical correspondence analysis presented a strong correlation between the microbial community and influencing factors during the recovery phase. With the increase of nitrogen loading rate, the decrease of free nitrous acid and the synergistic effects, heme c content, specific anammox activity (SAA), NRR, and the abundance of dominant genus increased correspondingly. The increase of heme c content regulates the quorum sensing system, promotes the secretion of extracellular polymeric substances, and further improves SAA, NRR, and the relative abundance of the dominant genus. This study highlights some implications for the recovery of the CANON reactor after being exposed to an alkaline shock.

The PO mode under time-domain analysis is a kind of discontinuous conduction mode (DCM) which is beneficial to reduce the switching loss of the converter, but the calculation of the gain and frequency characteristics of the converter in this mode is cumbersome and difficult to be solved. Based on the analysis method of time domain approximation, the PO operating mode characteristics of the LLC resonant converter are analyzed, and a simple and accurate voltage gain calculation formula is theoretically deduced. Simple analytical expressions for the PO mode power boundary conditions are given based on the voltage variations of the magnetizing inductance and capacitance. A simulation model of the studied converter is established, and the simulation can prove that the proposed voltage gain formula and PO mode boundary conditions are correct.

This study investigates the bulge deformation mechanics of geomembranes that are interacting with non-fine concrete cushions. We conducted 3D scanning of non-fine concrete specimens and further analyzed the depth-to-width ratios for non-fine concrete specimen surfaces. Then, stress distribution characteristics between the geomembrane and the non-fine concrete contact surface under diverse normal pressures were measured using a thin-film pressure transducer. It was observed that the contact surface between the geomembrane and the non-fine concrete expanded when the normal pressure increased, and the stress growth rate decreased as the area of the high-stress regions increased. Combining the relationship that was formed by the sags of the non-fine concrete surface soil with the stress distribution on the contact surface, the maximum bulge depth and the highest strain were determined following the formation of geomembrane bulge under various normal pressures. Moreover, ultrahigh strain, but not fracture, developed on the geomembrane during the experiment. Based on air bulking tests, it was demonstrated that the geomembrane had enormously high yield strength, which plays a critical role in the improvement of both the safety and the reliability of geomembranes that are mounted on non-fine concrete cushions.

This paper investigates the formation tracking control problem for multiple unmanned surface vehicles (USVs) under prescribed performance constraints in the presence of model uncertainties and unknown disturbances. A decentralized formation control strategy is developed based on a modified active disturbance rejection control (ADRC) framework, where a model-compensation extended state observer (ESO) is designed to estimate the total disturbance and enhance robustness. To avoid the \"explosion of complexity\", a tracking differentiator (TD) is employed to approximate virtual control derivatives, while a universal barrier function (UBF) is incorporated into the Lyapunov-based synthesis to guarantee both transient and steady-state performance bounds. Rigorous Lyapunov analysis proves that all closed-loop signals remain uniformly ultimately bounded, prescribed performance constraints are strictly satisfied, and inter-agent collision avoidance and communication connectivity are maintained. Comprehensive simulations further demonstrate significant performance advantages over representative baseline methods. In particular, the proposed controller achieves a 57.4% reduction in IAE and a 42.6% reduction in RMSE compared with a PID controller, and a further 49.4% and 36.7% reduction relative to a backstepping controller. These quantitative results confirm the superior accuracy and robustness of the proposed approach.

Four tobacco leaf modules processed by Yunnan Tobacco Redrying Co., Ltd. during the 2022 roasting season were used to investigate the method of stalk content in strip particles after redrying of tobacco leaves, effectively reducing the loss of strip particles. A total of 151 sets of experimental data were used to construct the prediction model for the stalk content in strip particles after redrying using the BP artificial neural network method, the linear regression method, and the support vector machine method. The results show that the prediction model constructed by the BP artificial neural network method has high accuracy and stability, with a relatively small absolute error of prediction ( e  = 0.0195%) and the root-mean-square error of interactive verification (RMSECV = 0.0227%), as well as a relatively small mean absolute error of production data validation ( e  = 0.0675%), while the prediction deviation ratio (RPD = 2.2435) is relatively large. Overall, the prediction model established by BP artificial neural network could provide new insight into the non-destructive detection of stalk content in strip particles of redried tobacco leaves after threshing and redrying and potentially leading to a reduction in tobacco leaf crushing by more than 112,500 kg per year.

To address the \"cramp effect\" caused by displacement and sediment of impervious geomembranes in the cracks along high membrane-faced rockfill dams and the problem the declining mechanical performance of the geomembranes caused by long-time tensile stress, this study developed a set of simulation devices according to the working status of impervious geomembranes in the cracks along the dam. With PVC geomembranes as the test material, this study performed tests to identify the law of decline of membrane's mechanical performance under different conditions of deformation with the temperature of the reservoir unchanged. It used the fractional mathematical model to process the test data and concluded the law of declining mechanical indicators of the PVC geomembrane. On the basis of the test data analysis, this study divided the decline of the geomembrane's mechanical performance under constant large deformation into two stages, proposed structural solutions to mitigate or avoid decline of mechanical performance and lengthen the service life of impervious geomembranes.