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In this study, to optimize the foaming activity of sodium dodecyl sulfate (SDS), modified sodium dodecyl sulfate surfactants (MSDS-1 and MSDS-2) are prepared by using methanol and diethanol amine as modifiers by the Mannich reaction. The foaming properties and foam stability of the products are evaluated by the Ross–Miles method and the Waring blender method. The microstructures of the foams produced by three surfactants are compared. The effects of temperature, inorganic salt, methanol, and condensate oil on the foaming activity of SDS, MSDS-1, and MSDS-2 are studied. The results obtained show that the best foaming concentration of all three products is 0.5%. Compared with SDS, the temperature resistance, methanol resistance, salt resistance and anti-condensate oil performance of MSDS-1 and MSDS-2 are improved. Among them, the temperature resistance, salt resistance, and methanol resistance of the MSDS-1 solution are the best. The MSDS-2 solution has the best anti-condensate performance. Besides, the foam size becomes smaller, the foam wall thickens, and the foam stability is improved after modification. The overall performance of SDS as a foaming agent can be improved by the Mannich modification.

Cellulose, often considered a highly promising substitute for petroleum-based plastics, offers several compelling advantages, including abundant availability, cost-effectiveness, environmental friendliness, and biodegradability. However, its inherent highly crystalline structure and extensive hydrogen-bonded network pose challenges for processing and recycling. In this study, we introduce the concept of cellulose vitrimers (CVs), wherein dynamic bonds are incorporated to reconfigure the hydrogen-bonded network, resulting in a mechanically robust, highly transparent material. CVs exhibit exceptional malleability, thermal stability, and noteworthy resistance to water and solvents. Due to the dynamic bond disassociation, CVs can be effectively chemically recycled using a well-established "dissolution-and-reforming" process. Moreover, CVs have proven successful as flexible substrate materials for organic solar cells, outperforming traditional petroleum-based polyethylene naphthalate (PEN). Given these advantages, CVs have the potential to replace conventional petroleum-based materials as recyclable and environmentally friendly alternatives, particularly within the realm of electronic devices and displays.

Quantitative evaluation of rock dynamic disaster intensity is a challenging and difficult task in the field of earth science. In this article, the dynamic compression tests of granite under different impact velocities are carried out, and the energy evolution characteristics of the dynamic failure process of granite are analyzed. The dynamic fracture characteristics of granite were studied by using computed tomography and section scanning equipment. The results show that the energy dissipation and energy accumulation mechanism of granite under dynamic loading are fundamentally changed with the increase of impact disturbance strength, which leads to the transformation of the failure mode from the tension-type sheet crack under low-speed impact to the complex network crack coupled by tension and shear under high-speed impact. At the same time, the greater the impact velocity, the larger the macroscopic crack density, the more uneven the particle distribution on the fracture section, the greater the roughness, and the higher the rock mass fracture degree. In accordance with the results, the energy distribution ratio is proposed to quantitatively characterize the coupling effect of energy dissipation and energy accumulation in the dynamic failure process of granite and to reflect its dynamic failure intensity. The higher the energy distribution ratio, the stronger the energy coupling effect and the more intense the dynamic failure of the rock mass.

The high frequency tensile fatigue test of heat-resistant fasteners of A286 alloy with different thread processing sequences was carried out by means of axial fatigue testing machine， metallographic microscope， microhardness tester and scanning electron microscope， and the metallographic of fatigue fracture and thread was analysed . The results show that machining thread after 720 ℃-12 h aging is beneficial to improve the stability of fatigue performance of fasteners， and has a slight effect on the median fatigue strength， but has no effect on the fatigue fracture mode. A large number of twins are formed on the surface of machined threads before aging， and the reinforced phase precipitates out at the twin boundary with large size particles during aging. Because the hardness of fasteners threaded before aging fluctuates greatly， it may also be the cause of the fluctuation of fatigue performance.

Tunnels represent complex, high-risk, and technically demanding underground construction projects. The safety of construction workers in tunnels is influenced by various factors, including physiological indicators, tunnel dimensions, and internal environmental conditions. Analyzing safety based solely on static factors is inadequate for modern tunnel engineering safety management requirements. To address this challenge, this paper provides a comprehensive analysis of factors impacting safety and employs the Analytic Hierarchy Process (AHP) to identify seven significant factors with high importance: body temperature, heart rate, internal temperature, internal humidity, CO concentration, chlorine concentration, and the relative positioning of personnel. Considering these factors essential for assessing worker safety, we introduce a novel model named Tunnel-APH-AD. For training models aimed at anomaly detection, we performed data augmentation and utilized four distinct machine learning models. Additionally, ensemble learning techniques were applied to aggregate the predictions from individual models, thereby enhancing the effectiveness of detecting safety states for tunnel workers. We also evaluated the performance of these models on out-of-distribution (OOD) samples to test their robustness and generalizability. The experimental results indicate that, under similar ventilation and tunnel conditions, the ensemble learning model exhibits superior overall performance compared to individual models, underscoring the effectiveness of model combination in improving the accuracy and reliability of safety alerts. Through experimental validation, this study provides interpretable, scalable, and scientifically generalized applications of machine learning theories in systems for tunnel construction worker safety alerts. These findings contribute to advancing safety management practices in tunnel engineering, enabling proactive and effective measures to mitigate potential risks and ensure the well-being of workers.

As a representative practice of the theory of connectivism, cMOOCs emphasize learners' content-based connective learning. Effectively promoting learners' content production is the focus of cMOOC research and practice. This study explores whether and how learners' online interactions affect the content production of courses. Based on 45166 real-time behavioural data points of learners, this study measures the interaction level and content production degree of each learner and analyses the influence of interaction on content production. The results show that the number of low-level interactions is higher than that of high-level interactions, and content production increases with the development of the curriculum. Low-level active interactions of cMOOC learners have no significant impact on content production, while high-level active interactions have a significant positive impact on content production, and attention in low-level passive interactions has a significant positive impact on content production. However, simple comments in low-level passive interactions and complex comments in high-level passive interactions have a significant negative impact on content production in a certain course. The results of this study further develop the understanding of interaction in the learning theory of connectivism, and we hope that this study can provide support for the interaction design of cMOOCs.