Guohai Jia

Active flow control actuators are critical for improving aerodynamic performance in applications such as aircraft lift enhancement, drag reduction, and maneuverability improvement. However, the plasma synthesis jet actuator (PSJA) is limited by the constraints of electric energy deposition, making it difficult to further improve the jet velocity and mass flow rate. Meanwhile, the jet velocity driven by combustion needs to be further increased. This study preliminarily investigated the characteristics of a combustion-driven SparkJet actuator through experiments; a combustion-driven SparkJet actuator integrates the advantages of plasma actuators and combustion-driven actuators. The actuator employs a continuous methane–air mixture supply ignited by spark discharge. High-speed shadowgraph imaging is used to characterize the jet flow field evolution. The effects of the cavity volume, normalized outlet diameter (d* = d/h), and equivalence ratio on jet performance are systematically examined. As the normalized outlet diameter increases from 0.666 to 1, the jet penetration distance and jet width increase with an increasing normalized outlet diameter, owing to the reduced boundary layer blockage effect at the orifice. However, when the normalized outlet diameter equals 1, both the jet penetration distance and jet width first increase and then decrease with increasing cavity volume; hence, the outlet diameter and cavity have an optimal size. At an equivalence ratio of mixture ≤1, increasing the methane flow rate enhances the volumetric chemical heat release rate, thereby monotonically improving the jet width and penetration distance. The combustion-driven actuator demonstrates a significantly higher jet velocity compared to a conventional plasma actuator under identical geometric parameters; the combustion reaction can effectively amplify the jet energy and velocity of the actuator. Moreover, the combustion-driven SparkJet actuator also has the same working frequency when the actuator volume is the same, indicating that the combustion process does not significantly extend the cycle time. The maximum jet velocity first increases and then decreases with increasing cavity volume; the reason that the maximum jet velocity first increases is that a larger volume results in a greater mixture mass and more released heat; it then decreases due to incomplete combustion occurring in large chambers. These results show that the design standards for the combustion-driven actuator are fundamentally different from those for the plasma actuator, and their optimal performance is related to not only electrical energy density but also combustion performance. The design parameters of the combustion-driven actuator can be optimized to maximize the jet front velocity. The experimental data in this article provides a reference for optimizing the performance of combustion-driven actuators.

Real-time vehicle detection in edge-based intelligent transportation systems is essential for enhancing traffic efficiency and safety. However, vehicle detection in complex urban environments faces challenges (cluttered backgrounds, significant scale variations among targets), necessitating lightweight models that achieve both high accuracy and low computational cost for resource-constrained edge devices. To address these challenges and tackle key engineering problems in traffic scenarios, we proposed YOLOv8n-MMSP, a lightweight real-time vehicle detection algorithm optimized for edge deployment. To mitigate fine-grained feature loss from downsampling, the C2f-StarBlocks module was integrated to enhance multiscale feature fusion, beneficial for long-range vehicle perception in traffic monitoring systems. To reduce the distant small-object miss rate, a P2 small-object detection layer was introduced to strengthen shallow feature representation, improving detection reliability. To handle significant scale variations and complex background interference, the Multi-Scale Convolutional Attention mechanism was incorporated, enabling robust perception under challenging conditions (nighttime and adverse weather). To improve bounding box regression accuracy in densely occluded scenarios, the Multi-Precision Distance Intersection over Union loss function was adopted, facilitating more precise localization in congested traffic environments. Furthermore, to meet the computational constraints of edge devices, an L1 regularization–based channel pruning strategy was applied to batch normalization layers, reducing model complexity while maintaining detection performance. Results demonstrated 81.2% mAP and 61.4% mAP50-95, consistent improvements over the baseline model, while reducing model size, parameter count, and computational load to 61.89%, 59.12%, and 58.40% of the original, respectively. Edge-device tests further demonstrate a real-time inference speed of 73.6 fps.

In order to effectively reveal the nonlinear characteristics of a dish concentrating solar thermal power system (DCSTPS) under pulsating wind-induced loads, a fluid simulation model of the DCSTPS was established, and the simulated pulsating winds were developed via the user-defined function (UDF) combined with the autoregressive (AR) model using MATLAB (R2015b). And based on the fluid simulation calculations of the DCSTPS, the time-range data of the relevant wind vibration coefficients under different working conditions were obtained. The research results show the following: (1) When the altitude angle α is 0° or 180° due to the azimuth angle β = 0°, the maximum values of their drag coefficient C_x, lateral force coefficient C_y, and lift coefficient C_z are similar, and the maximum of rolling moment coefficient C_Mx is significantly smaller than the values at the other two angles; the maximum of the pitch moment coefficient C_My and maximum of the azimuth moment coefficient C_Mz are significantly larger than the values of the other two angles. (2) The increase in altitude angle α leads to a reduction in the drag coefficient C_x, an increase in the lift force coefficient C_z, and an increase of the pitch moment C_Mx. Moreover, an improved phase space delay reconstruction method was developed to calculate the delay time, Lyapunov exponent, and Kolmogorov entropy of the DCSTPS, and the research results show that (1) the maximum Lyapunov exponent and Kolmogorov entropy of the DCSTPS are greater than zero under the action of pulsating wind; (2) the action of pulsating wind will cause increases in the maximum Lyapunov exponent and Kolmogorov entropy of the DCSTPS and will accelerate the divergence speed of the DCSTPS trajectory; and (3) the time for the DCSTPS to enter the chaotic state will be shortened, while the time of entering a chaotic state and degree of subsequent chaotic states will be significantly affected by relevant wind vibration coefficients but without regularity.

To avoid the problem of wind-induced resonance damage in a dish concentrating solar thermal power system (DCSTPS), a fluid dynamics model and a finite element analysis model of the DCSTPS were established separately. The wind load was mapped onto the surface of the concentrator of the DCSTPS using the sequential coupling method, and the static analysis and modal analysis of the DCSTPS were established based on the fluid–structure coupling (FSC) method and the validity of the established model was verified. Based on the results, it can be concluded that the upper edge of the dish solar concentrator (DSC) of the DCSTPS and the three cantilever beams near the Stirling generator are the most vulnerable to being damaged, the DCSTPS will not experience strong resonance phenomena, and effects of the FSC will decrease the natural frequencies of each order. The results of the safety grade catastrophe evaluation of the DCSTPS showed that the safety grade of the DCSTPS was 0.2586 and 0.2819 under case 1 (α = 30°, β = 90°) and case 2 (α = 60°, β = 90°), where it was found that the membership value of the moment load was low, resulting in the stress on the connection seat of the altitude angle and the steering device of the base approaching the allowable stress of the material.

With the rapid development of solar thermal power generation technology, the structural stability of the dish solar concentrator system under complex wind environments has become a critical limiting factor for its large-scale application. This study investigates the flow field distribution and structural response under fluctuating wind loads using computational fluid dynamics (CFD). A three-dimensional model was developed and simulated in ANSYS Fluent under varying wind angles and speed cycles. The results indicate that changes in the concentrator’s orientation significantly influence the airflow field, with the most adverse effects observed at low elevation angles (0°) and an azimuth angle of 60°. Short-period wind loads (T = 25 s) exacerbate transient impact effects of lift forces and overturning moments, markedly increasing structural fatigue risks. Long-period winds (T = 50 s) amplify cumulative drag forces and tilting moments (e.g., peak drag of −73.9 kN at β = 0°). Key parameters for wind-resistant design are identified, including critical angles and period-dependent load characteristics.

To increase the jet momentum and improve the environmental adaptability, a combustion-driven SparkJet actuator with a Laval-configured outlet is proposed to improve the performance of the actuator. Numerical simulation results show that, compared to straight outlet combustion-driven actuators with outlet diameters of 2 mm and 2.8 mm, the maximum jet velocity of the Laval-configured actuator increases by approximately 100 m/s and 350 m/s, separately. while the peak times decrease by about 50% and 12%, respectively. The work frequency of the Laval-structured combustion-driven actuator is 1333 Hz, which is higher than the 1176 Hz of the straight-tube-structured combustion-driven actuator with an outlet diameter of 2 mm. The Laval configuration effectively improves the working performance of the actuator. As the equivalence ratio increases from 0.6 to 1, the actuator’s jet velocity increases by approximately 65 m/s and 311 m/s, respectively, and its maximum combustion temperature is raised from 2700 K to 3000 K. The saturation work frequency is nearly the same. The pressure and jet mass flow rate in the actuator drop as the atmospheric pressure declines, while the combustion-driven actuator still exhibits high working performance when the atmospheric pressure is low. The maximum outlet velocity, Mach number, pressure, and temperature increase by about 20%, 13%, 25%, and 6%, while the peak time increases by about 40% as the ignition position moves from the middle position to a 2.8 mm displacement toward the outlet.

In order to study the combustion characteristics of tar in biomass gasifier inner wall and gasification gas, “tobacco stem semi-tar inside furnace”, “tobacco stem tar inside furnace” and “tobacco stem tar out-of-furnace” were subjected to thermogravimetric experiments, and the combustion characteristics and kinetic characteristics were analyzed. The result shows that “tobacco stem semi-tar inside furnace” has the highest value and “tobacco stem tar out-of-furnace” is has the lowest value on ignition characteristics, combustion characteristics and combustible stability; “tobacco stem semi-tar inside furnace” has the lowest value and “tobacco stem tar outside furnace” has the highest value on burnout characteristics; “tobacco stem tar outside furnace” has the highest value and “tobacco stem tar inside furnace” has the lowest value on integrated combustion characteristics.

The burner-type regeneration diesel particulate filter is one of the most widely used diesel particulate filters. Using AVL FIRE, a 3D model of a burner-type regeneration diesel particulate filter (DPF) was established, and simulation analyses were carried out. The effects of the exhaust parameters (temperature, exhaust mass flow rate, and soot load) and the structural parameters (channel density, inlet/outlet channel ratio, and the length–diameter ratio) on soot distribution (soot mass concentration and soot thickness) were analyzed. The results show that the soot distribution characteristics of regenerative DPF with a burner are as follows: the soot mass concentration first rapidly rises to the maximum value and then rapidly decreases to a low value, and the dust thickness gradually increases with the increase in location. With the increase in exhaust mass flow rate and soot load, soot mass concentration and soot thickness increase. With the increase in temperature, the mass concentration and thickness of the ash decreased. When the temperature exceeds 750 K, soot begins to regenerate. Among the exhaust parameters, the mass flow rate of the exhaust has the greatest influence on the soot distribution. The length–diameter ratio, the ratio of the inlet and the outlet channel, and channel density have little effect on the mass concentration of soot, and the soot mass concentration increases with the increase in channel density. In addition to the length–diameter ratio of 2.1, the soot thickness increases with the increase in the length–diameter ratio, and the rising rate is also accelerated. The thickness of soot decreased with the increase in channel density and the ratio of the inlet and the outlet channels. When the channel density is more than 250, the change in soot thickness is basically the same. When the ratio of the inlet and the outlet channels exceeds 1.3, the change in the soot thickness is basically the same. Among the structural parameters, channel density has the greatest influence on the soot distribution.

In order to reveal the inducing factors and safety dynamic evolution mechanism of frequent personal injury accidents under a low carbon manufacturing process, a nonlinear safety dynamic evolution model of a distributed low carbon manufacturing system with large time delay is established. The established model is then verified by simulation results from mathematical analysis and dynamic evolution. Moreover, qualitative analysis on nonlinear safety dynamic evolution and the trend of human–machine safety under a low carbon manufacturing process is investigated. Finally, an application case of the established model is studied. The key results are as follows: (1) There are four dynamic regions, namely the safety area I, the deterioration area II, the asymptotically stable safety area III, and the enhancement area IV of the safety ability in the interaction evolution model of carelessness and safety levels; (2) There are two singularities in the dynamic evolution model of the man–machine safety system with large time delay under a low carbon manufacturing process; (3) The equilibrium points of the human–machine safety system are E_l = (0, 0) and E₂ = (0.5333, 0.2489), while changes in the carelessness level have a serious block effect on safety development with time; (4) For the radial tire casing process, the low carbon development trend of the technological process of radial tire casing is good, but low carbon structure and management have slightly lower low carbon levels. This work provides a theoretical basis for the safety evaluation and control of the distributed low carbon manufacturing human–machine safety system with large time delay.