Understanding the failure mechanism of cracked rock mass under the general stress state is essential for underground engineering construction safety. A series of true triaxial fracture tests on the sandstone with single pre-existing flaw were conducted. The failure modes of the cracked sandstone were analysed, and the multi-scale fracture characteristics and mechanisms of the basic types of crack were identified. Moreover, the influences of the stress state and the pre-existing flaw on the rock failure mechanism were summarized. The results indicate that the rock failure mode is controlled by the true triaxial stress and the pre-existing crack. Based on the multi-scale fracture characteristics, the fracture mechanism of the crack. The rise of minimum principal stress σ₃ can significantly reduce the percentage of the shear crack, while the rise of intermediate principal stress σ₂ conduces to the increase of the percentage of the tensile crack. The pre-existing flaw has a certain promoting effect on the initiation of the tensile crack, however, the true triaxial stress is the decisive factor controlling the rock failure mechanism.

Predicting the emission reduction potential and cost of sustainable aviation fuel (SAF) that aligns with China’s national conditions is essential for advancing the SAF industry and achieving carbon neutrality goals. Based on the principles of international comparability and independent controllability, a lifecycle carbon emission reduction model was developed for two technological pathways: hydroprocessed esters and fatty acids (HEFA) and Fischer-Tropsch (FT). This model forecasted the emission reduction and cost associated with SAF in China’s civil aviation sector from 2025 to 2060.The results indicate that the HEFA pathway, which is suitable for implementation between 2025 and 2030 using waste oils as feedstock, achieves a carbon emissions reduction of 61.3 kgCO_2e/GJ, contributing to an overall reduction of 84.4%. This associated cost ranges from 0 to 1 025.9 CNY/tCO_2e when compared to traditional aviation kerosene. In contrast, the FT pathway-primarily developed between 2030 and 2060 utilizing municipal solid waste as raw material yields the highest carbon emissions reduction at 68.4 kgCO_2e/GJ. Furthermore, routes employing agricultural or municipal solid waste exhibit lower abatement costs than those utilizing forestry waste. Considering China’s specific national conditions, it is determined the FT route utilizing agricultural waste as feedstock is more appropriate for development as the main SAF production technology after 2030 due to its abundant raw materials and comparatively lower abatement costs. Projections suggest that by 2060, reductions in China’s civil aviation SAF could reach approximately 17 177 million tons to 19 819 million tons. From a possible scenario spanning from 2025 to 2060, it is estimated that cumulative carbon abatement costs will amount to between 11 063 to 45 828 billion CNY, this corresponds with a marginal carbon abatement cost ranging from 220 to 697 CNY/tCO_2e.

In order to realize the automatic optimization of hyperparameters of YOLO model, the hyperparameter optimization of you only look once (YOLO) model based on orthogonal optimization strategy (OOS) was proposed. Firstly, based on the principle of statistical orthogonal test, the orthogonal search method of population and the hyperparameter contribution analysis strategy were proposed to improve the optimization efficiency of the algorithm. Then, the uniform orthogonal search strategy and the neighborhood orthogonal search strategy were designed to alleviate the problem of the YOLO model falling into the local optimum and premature convergence. Finally, YOLOv5, YOLOv5s-Transformer and YOLOv7 were used as optimization objects to test on two target detection datasets, NWPU VHR-10 and Pascal VOC. Test results show that the recognition accuracy of the YOLO model is improved by the OOS hyperparameter optimization method in all cases. The average recognition accuracy mAP@0.5 on two datasets is improved to 93.94%, 93.18%, 93.45%, and 85.81%, 84.59%, 89.96%. The mAP@0.5-0.95 is improved to 60.00%, 60.08%, 56.98%,and 62.27%, 58.89%, 70.77%. It can provide a new intelligent method for hyperparameter optimization of object detection model.

According to the requirements of rain ingestion of airworthiness regulations, the rain ingestion calculation was carried out for the no booster fan part. The movement trajectory of water droplets with different water speeds was studied based on Lagrangian particle tracking, and the separation amount of water droplets ingested to inner duct was obtained. Further more, the requirements for water spray speed from the rain ingestion test rig in the certification for turbofan engine was discussed,which can support the design and verification of rain ingestion airworthiness of turbofan engine. The results show that with the decrease of water speed, the amount of rain impacting on the fan blade and other walls increases, and no water droplets can pass through the fan blade and enter the inner duct. The water entering the engine inner duct at 250 m/s is 15.3 percent of the total amount of water, about 19.1 times of that at 10 m/s. Under the same water velocity, as the distance between the splitter and the fan blade decreases, the increase in water ingested to inner duct increases. At different fan rotational speeds, the change trend of the water ratio ingested to inner duct with initial water velocity is consistent, basically increasing with the increase in water drop velocity, and then remaining or slightly decreasing.

In order to speed up the engineering progress, early strength additives are usually added to improve the early strength of cement grout. Calcium chloride, sodium sulfate, triethanolamine, synthetic calcium formate, HR-SA1 and other early strength additives were selected, the flowability, shrinkage rate, and compressive strength of cement slurry under the action of different early strength agents were explored through indoor experiments. In this way, the influence of different types of early strength agents on the early physical and mechanical properties of cement slurry were revealed. The results show that all early strength agents can meet the needs of on-site grouting requirements, ensuring that the fluidity of the cement slurry can be stable for a long time. The flowability of the synthesized calcium formate-based cement slurry significantly increases within 60 minutes, indicating a notable retarding effect. The fluidity of the other early strength agents cement slurry slightly increases within 60 minutes, but the amplitude is not significant. The compressive strength of (HR-SA1)-cement slurry specimens at all ages is significantly higher than that of ordinary cement slurry specimens, while the other four early strength agents have no significant effect on improving the compressive strength of cement slurry. The average shrinkage and shrinkage rate of (HR-SA1)-cement slurry specimens after final setting are very low, far lower than the average shrinkage and shrinkage rate of other early strength agent cement slurry specimens. It is verified by the construction site of prestressed anchor cable of a subway station in Qingdao City. The test values of the physical and mechanical properties of cement slurry are basically consistent with the results of laboratory test, which lays a foundation for the popularization and application of HR-SA1 early strength agent in practical engineering.

Aiming at the problem of low tension control accuracy existing in the warp yarn tension control of carbon fiber corner link loom, a warp yarn tension control method considering the effect of beating-up was proposed. Firstly, the elongation of the warp yarn during beating-up was analyzed, and then a new tension control model of the warp feeding system was established by combining Hooke’s law with the existing tension model. Secondly, a command filter backstepping sliding mode controller was proposed, which estimated the first-order differentiation of the virtual control law through the filter to avoid the problem of “differential expansion”, and adopted the radial basis function(RBF) neural network to adaptively estimate the unmodeled part of the system, and at the same time, the sliding mode control was introduced to enhance the robustness of the system. Finally, MATLAB/SIMULINK software was used to carry out simulation experiments on the tension system. The results show that the filtered backstepping sliding mode control considering the effect of beating-up in tension control compared with the traditional backstepping sliding mode control in the case of similar response time, the stabilization time is shortened by nearly 16.3%, the amount of overshooting is reduced by 24.6%. Compared with the fuzzy proportional integral derivative(PID) control, the stabilization time is shortened by 51.7%, the amount of overshooting is reduced by 49.2%.

In order to investigate the durability of fibergypsum-based cementation material, a composite material was prepared byincorporating polypropylene and ramie fibers into high-strength gypsum,fly ash, and slag in a ratio of 44:34:22. Sodium methylsilicate wasutilized for waterproofing the fiber gypsum-based cementitious material,and the effects of freeze-thaw cycles on its softening property, waterabsorption, and mass loss were studied after 5,15,25,45, and 90 daysunder the combined action of ${\mathrm{H}}_{2}{\mathrm{{SO}}}_{4}$ or $\mathrm{{NaOH}}$ corrosion andfreeze-thaw. Freeze-thaw strain testing, flexural and compressivestrength testing, as well as industrial computed tomography(CT) scanningwere conducted. The results indicate that fibers can mitigate bothelastic and plastic deformation of the gypsum-based cementitiousmaterial during freeze-thaw cycles. Furthermore, under the combinedeffect of acid-base corrosion and freeze-thaw cycles, NaOH causesgreater damage than ${\mathrm{H}}_{2}{\mathrm{{SO}}}_{4}$ does.After undergoing 90 days of freeze-thaw cycling with sodiummethylsilicate treatment applied to it, the flexural and compressivesoftening coefficients increase by 0.28 and 0.13 respectively comparedto specimens without waterproofing; meanwhile water absorption ratesdecrease by 1.56% while mass loss rates decreased by 9.52%. Asfreezing-and thawing times increase, pore development in specimens isstill dominated by small holes, and crack diameters are mainly between ${0.1}\sim 2\mathrm{\;{mm}}$ .

In the contemporary digital healthcare setting, the dissemination and sharing of medical imagery are integral to routine medical operations. However, medical images often contain sensitive patient information, and without adequate protection, there is a risk of illegal acquisition or leakage, which brings unnecessary troubles. To address this issue, an encryption algorithm based on Zigzag scrambling and a new four-dimensional hyperchaotic system was proposed. Firstly, the Zigzag algorithm was used to scramble the image once, roughly hiding the obvious contours of the image. Then, an improved cat mapping algorithm was used to perform secondary scrambling on the image, removing obvious texture features. Finally, the scrambling factor generated from the plaintext image was applied to the initial value generation process of the hyperchaotic system. The generated hyperchaotic sequence was transformed into a hyperchaotic matrix for the subsequent diffusion process of the encryption algorithm. The simulation results show that the proposed algorithm can effectively conceal plaintext information based on the characteristics of medical images and resist common types of attacks. The robustness of the proposed algorithm has been demonstrated through testing, confirming its capability to address the issue of image interference in remote healthcare.

In order to facilitate the counting of turning traffic flow and to enhance the detection speed and accuracy of turning traffic flow at intersections, a deep learning-based method was suggested for detecting, tracking, and counting turning traffic flow at urban crossings. Initially, the YOLOv5s, which was lightweight and efficient, was chosen as the target detection framework after conducting a comparative analysis. Unmanned aerial vehicle (UAV) aerial photography was utilized to record video footage of traffic movement at urban intersections, resulting in the development of a dataset of vehicle aerial photography photos. The pre-training weights and the most recent weight files were utilized to conduct training and testing on the self-constructed dataset. The model evaluation shows that the vehicle detection model using YOLOv5 exhibits great detection speed and accuracy. The model’s box_loss value declines rapidly and stabilizes at 0.038, while the mAP_0.5 value climbs swiftly and stays near 0.91.After that, the DeepSORT model was used as the backend multi-vehicle tracking technique, and a corner-to-centroid coordinate transformation was used to simplify the extraction of vehicle trajectories. The precision of the driving trajectory line was evaluated thereafter. To improve the robustness of trajectory points’ coordinate information, a corner-point-center-of-mass point coordinate transformation was suggested to tackle the issue of corner points in the detection frame. A sixth-degree polynomial was used to model the vehicle trajectory. Unsuitable trajectory lines were rotated and optimized to meet the function mapping requirements and ensure good fitting of all trajectories. Turning vehicles were detected and counted by using a predetermined threshold to determine the turning angle. Ultimately, to validate the performance of the proposed turning vehicle flow detection method, vehicle detection experiments were conducted at a city intersection as an illustration. The manual counting values were compared and analyzed against the detection results obtained using this method. The results show that the average detection accuracy for the four flow directions is 92.9%, with a maximum of 95.7%, meeting the standard detection requirements for turning vehicle flow in real intersection scenarios.

In order to investigate the feasibility of applying solidified shield muck in road construction, the shield muck from Nanjing Metro was taken as the research object, and the green polymer composite curing agent developed independently was used to solidify the shield muck. The impact of the curing agent dosage and maintenance age on the road performance indicators of the shield muck was analysed using various tests-unconfined compressive strength, direct shear test, California bearing ratio (CBR), resilient modules, and freeze-thaw cycle test. In addition, the micro-characteristics and solidification mechanism of the solidified soil were investigated by scanning electron microscope and X-ray diffraction. The results indicate that the composite curing agent can effectively improve the strength of solidified muck, and with the increase of curing agent dosage and maintenance age, the strength of solidified muck also increases. The CBR and resilient modulus of solidified shield muck substantially improve as the dosage of the curing agent elevates, and the solidified soil can well meet the requirements of the Specifications for Design of Highway Subgrades (JTG D30—2015) and Specifications for Design of Highway Asphalt Pavement (JTG D50—2017). The freeze-thaw resistance of shield muck is poor, while it can be effectively improved after curing treatment. The strength loss and mass loss of solidified soil are less than 20% and 1% respectively. The anti-freezing performance indicators meet the requirements of the specification. After the curing agent has been added to the soil body, the polymer components will absorb water and dissolve, creating a static chelating effect with the mineral ions in the soil, initially reducing the water content of soil and promoting the agglomeration between the soil particles. Meanwhile, the other components of the curing agent generate hydration reaction to form hydrated calcium silicate gel, ettringite and other substances to fill the internal pores of soil, making the soil structure denser and greatly improving the strength.