[Significance] Medical devices such as catheters, endoscopes, guidewires, artificial joints, and stents are in prolonged direct contact with human tissue. Therefore, surface treatment must be performed to enhance their lubricity and biocompatibility. Among the surface treatment techniques, lubricating coatings are widely used. The coatings reduce friction between medical devices and biological tissues, thereby minimizing tissue damage, alleviating patient discomfort due to friction, reducing the risk of rejection, infection, and inflammation, and making the treatment process smoother. With their structure similar to biological tissues and their ability to interact and retain large amounts of water, hydrogels are easily modified and less likely to cause immune rejection, making them suitable for fabricating lubricating coatings. However, the application of hydrogels as lubricating coatings faces many challenges. Initially, the physicochemical properties of hydrogels are diverse and complicated, resulting in different friction and lubrication mechanisms, and targeted modification of hydrogels for lubrication is challenging. Additionally, because of the unique formation methods and structures of hydrogels, achieving stable and strong adhesion with other substrates is difficult. Therefore, summarizing the existing research is crucial to guide further development of lubricating hydrogel coatings. [Progress] In the study of the lubrication mechanisms of hydrogels, articular cartilage was an important reference, primarily involving boundary lubrication and hydrodynamic lubrication mechanisms, relying on the synergistic interaction of various charged or polar macromolecules. The lubrication theory of synthetic hydrogels was similar to that of articular cartilage. In terms of hydrogel-solid substrate friction, the repulsion-adsorption theory explained the impact of microscopic interactions between the superficial hydrogel polymers and the solid substrate on lubrication performance. The friction between hydrogel surfaces was more complex, requiring careful consideration of the surface properties of both hydrogel counterparts. Current research on hydrogel coating modification for lubrication purposes primarily focused on three aspects: modification based on the hydrodynamic lubrication mechanism, structural modification, and intelligent response modification design. The first modification could simply and effectively improve the lubricity of the hydrogel surface. Structural modification, often bioinspired from specific biological tissue structures such as articular cartilage, aimed to balance the lubrication performance and stable mechanical properties of hydrogels. The intelligent response modification endowed the hydrogels with various responsive characteristics in lubrication performance, such as pH, light, and shear stress responses. These typical enhancements greatly improved the functionality of the hydrogel coatings from multiple perspectives. Hydrogels were primarily formed on substrates via chemical interactions such as surface bridging, surface initiation, gel coating, and biological modification. The first three methods involved the polymerization and crosslinking of hydrogels, with similar principles but different procedures, whereas biological modification directly used bacteria or other microorganisms for adhesion and gel formation. These methods were adapted to different production scenarios and were suitable for various hydrogel materials and substrates. [Conclusions and Prospects] Current lubricating hydrogel coatings excel in lubrication, reliability, stability, and ease of modification, yet they fall short of the comprehensive excellence of articular cartilage. Further research into the lubrication mechanism of hydrogels, the integration of lubrication properties, and other functional modifications with coating methods are anticipated to considerably improve the design of various hydrogel coatings with superior performance, enabling their biomedical application in various conditions.

[Significance] Bioinspired slippery coatings have attracted extensive attention in antifouling, anti-adhesion, and anti-icing applications because of their excellent liquid repellency, self-healing properties, and high-pressure stability. The slippery liquid-infused coating obtained by infusing lubricating oil into porous matrixes and the slippery liquid-like coating afforded by grafting lubricating molecules onto smooth surfaces exhibit the aforementioned properties. However, some limitations still hinder the practical applications of these coatings, such as easy loss of the lubrication layer and insufficient mechanical stability. Therefore, this study introduces the characteristics and research progress of slippery liquid-infused and slippery liquid-like coatings in detail by summarizing the bionic design principles of slippery liquid-infused surfaces. Furthermore, the existing problems related to coatings are highlighted. [Progress] According to the oil fixation mechanism and lubrication layer thickness, slippery coatings could be divided into three categories. Type 1D slippery coatings, known as slippery liquid-like coatings, mainly stabilize the lubrication layer by chemical grafting; thus, they showed good stability when subjected to gravity, shear force, and water scouring. However, they easily lost their slippery performance when subjected to mechanical wear due to their low thickness and poor wear resistance. The fabrication of type 1D-slippery coatings involved complex preparation processes, harsh preparation conditions, and high costs, limiting their large-scale applications. Type 2D- and 3D-slippery coatings stabilized the lubrication layer through their porous structures. Type 2D-slippery coatings exhibited good mechanical stability and could be easily prepared. However, due to their poor oil-fixing performance, the lubricating oil was easily lost, and they could not recover the oil themselves. Therefore, maintaining their slippery properties for a long time under harsh conditions was challenging. To solve this problem, researchers had conducted several studies on structural design and chemical modification. Despite their effective efforts, the porous structures of type 2D-slippery coatings could only store a small amount of lubricating oil, and the timely replenishment of oil after oil loss remained difficult. Type 3D-slippery coatings included gel and nongel coatings. Gel cross-linked networks and 3D porous physical structures could store/release lubricating oil, thereby improving the slippery stability of these coatings. With the introduction of smart materials, type 3D-slippery coatings could actively adjust the release of lubricating oil according to changes in the environment and coating states. However, the 3D-gel and -nongel slippery coatings exhibited insufficient mechanical stability and weaked oil control-release ability, respectively. [Conclusions and Prospects] To prepare highly reliable and long-life slippery coatings for large-scale industrial applications, further research is required. First, we need to understand the storage, fixation, and release mechanisms of the lubricating oil in slippery coatings, introduce intelligent materials, and systematically study the influence of structural characteristics, chemical compositions, and preparation methods on the stability of coatings. Second, the influence of lubricating oil on the adhesive strength of coatings must be further investigated because the lubricating oil may affect the bonding properties between the coatings and substrates. Additionally, the coating preparation methods should be simplified, and costs must be reduced to promote the applications of bioinspired slippery coatings. To achieve green production, more attention should be paid to the use of environmentally friendly materials in coating preparation processes. Finally, new slippery coatings need to be developed according to practical application environments by mimicking multiple biological templates.

[Significance] Artificial joint replacement is an important technology for treating bone and joint disorders. However, the long-term wear loss of joint prosthesis and periprosthetic osteolysis induced by wear debris causes aseptic loosening, leading to early failure of the prosthesis. Investigating the wear behaviors of artificial joint combination interfaces, including sliding and immobile interfaces, forms the foundation for exploring the formation mechanism of wear debris, studying loosening and failure mechanisms, and improving the abrasion performance of artificial joints. Such an investigation represents a fundamental approach to elucidate the mechanisms behind wear debris formation, explore the factors contributing to loosening and failure, and enhance the abrasion resistance of artificial joints. The literatures on the wear behaviors of artificial joints has been meticulously reviewed and summarized using resources from the Web of Science and China’s national knowledge network databases. The primary aim of this study is to provide references for research on the wear behaviors of artificial joint combination interfaces. [Progress] Sliding and fretting wear of artificial joints were studied. Sliding wear was produced on the sliding interface between artificial joint prosthesis pairs, and a large amount of wear particles were generated, which were the main cause of prosthesis loosening and failure. Fretting wear occurred at the fixed interface between the prosthesis and bone, leading to the early loosening of artificial joints. Adhesive, abrasive, and fatigue wear were the three main wear mechanisms of artificial joints. The wear of artificial joints was caused by several factors, such as prosthesis structure, material, lubrication, wear debris, operation, and patient. Summarizing the factors influencing the wear behaviors of artificial joints revealed that the design of prosthesis structures and surface modification technologies will be crucial for optimizing and enhancing artificial joints. However, these influencing factors were interrelated; thus, the mechanisms affecting wear behaviors needed to be further discussed. To evaluate the friction and wear performance of artificial joints, researchers mainly used friction and wear experimental machines and joint simulators to obtain wear parameters through in vitro simulation tests. Some scholars had designed novel devices with special functions to implement complex and specific wear research. The sliding wear behaviors of artificial joints were commonly characterized by friction coefficient, abrasion loss, surface morphology, wear debris features, and material composition. By contrast, fretting wear was generally analyzed by the friction coefficient, dissipated energy, and fretting corrosion conditions. Based on the applications of computer vision and artificial intelligence technology, the automation and intelligence levels of wear monitoring had been considerably improved. [Conclusions and Prospects] Material modification technology is effective in improving the wear performance of artificial joints and is a hotspot in the research field. A novel design of wear devices can provide an in vitro simulation experimental platform for complex and specific wear behavior testing. Further, a comparative analysis of various wear parameters can also comprehensively describe wear behaviors. Moreover, the efficiency and accuracy of artificial joint simulation tests in vitro can be effectively improved using computer vision and artificial intelligence techniques. The friction coefficient, wear surface, wear debris, and material composition are important factors in the wear behaviors of artificial joints, and multiple information fusion is required to study these wear behaviors. The applications of computer vision and artificial intelligence technology provide more solutions for wear debris and mechanism analysis of artificial joints, which are the future directions of wear behavior investigation on artificial joint combination interfaces.

[Objective] The human-like capabilities of robots are linked to their well-established perception systems. Tactile perception enables the robot to perceive the texture and grain of objects through touch. Robots equipped with tactile perception can grasp and manipulate objects more precisely and detect the characteristics and attributes of objects, which enhances their perceptual and cognitive abilities. Tactile perception provides robots with important advantages, helps them achieve human-like capabilities, and promotes the continuous development and innovation of robotic technology. [Methods] Herein, a bionic finger with a flexible shell, nail, finger bone, liquid, pressure-sensitive element, and temperature-sensitive element was developed based on the principle of liquid pressure conduction. The hardness, temperature, and texture sensing ability of the bionic finger were investigated; the tactile feature parameters of the bionic finger touching the textured surface were extracted; and classification and recognition of the fabric surface texture were achieved by the bionic finger using the support vector machine algorithm. [Results] Results revealed that when the bionic finger applied pressure to three different materials, the rates of change in the pressure curve were in descending order: L_wo>L_fo>L_sp. These results were consistent with the hardness of the materials tested. The steepness of the temperature change curves obtained by the bionic finger touching the three materials was in descending order: T_ss>T_pb>T_wo, which aligned with the thermal conductivities of the materials. As the roughness of the fabric surface increased, the peak average value and average power increased. Thus, a positive correlation existed between the peak average and average power values and roughness, namely the higher the peak average and average power, the higher the roughness of the fabric. With increasing fineness of the fabric surface, the dominant frequency and the spectral centroid increased, resulting in an enhanced sense of fineness. A significant positive correlation existed between the sense of fineness and both the dominant frequency and the spectral centroid. The larger the dominant frequency and the spectral centroid, the higher the sense of fabric fineness. The average accuracy of fabric surface texture recognition using the bionic finger and support vector machine method, based on the peak average, average power, dominant frequency, spectral centroid, and six frequency band feature intensities, was 92.8%, which was higher than the average human subjective recognition accuracy of 88.8%. [Conclusions] The rate of change of the touch pressure curve and the temperature curve of the bionic finger can indicate the softness and thermal conductivity of an object, indicating that the bionic finger has the ability to perceive hardness and temperature. The peak average and average power of the bionic finger extracted from the touch vibration signal can characterize fabric roughness, while the dominant frequency and the spectral centroid can characterize fabric fineness, indicating the ability of the bionic finger to perceive roughness and fineness. The average recognition accuracy of the bionic finger is higher than that of human subjective recognition, indicating the efficient and superior capability of the bionic finger to recognize and classify textile surface textures compared to human judgment.

[Objective] Artificial ligaments are crucial implants in ligament reconstruction surgery, and in clinical practice, adverse events such as fracture and failure of artificial ligaments are commonly observed because of friction and wear. The wear of artificial ligaments not only weakens the performance of the prosthesis but also potentially causes iatrogenic arthropathy. Therefore, investigating the friction and wear performance of artificial ligaments in vitro is important. Currently, neither domestic nor international standards have specified methods for measuring the wear of artificial ligaments. Furthermore, quantitative research methods for studying friction and wear are limited; moreover, only a few studies have been conducted on the methods for assessing the wear of artificial ligaments. [Methods] In this study, artificial ligaments were subjected to 2.0×10⁶ cycles in the in vitro friction wear test following the YY/T 0965—2014 standard. Subsequently, three wear test groups were established in accordance with the YY/T 1426.1—2016 standard. A loading control group was also established simultaneously to mitigate the weight errors caused by ligament water absorption. Artificial ligaments were periodically cleaned and weighed in accordance with the YY/T 1426.2—2016. Furthermore, the gravimetric method was employed to measure and analyze the amount of wear on the artificial ligaments. The micromorphology of the artificial ligaments after wear was observed using a stereoscopic microscope, and the wear debris generated by abrasion in 1.5×10⁶—2.0×10⁶ wear cycles was extracted and sent to a scanning electron microscope for observation. The wear debris was characterized according to ASTM F1877-16. [Results] In the three test groups, the amount of wear of the artificial ligaments increased linearly, with an average wear rate of (6.94 ±2.30)mg/10⁶ cycles. After abrading the artificial ligaments, some surface tissues appeared rough, and the braided structure was damaged. The filament sorting was loose and fractured, similar to the failed ligaments removed in the clinic. Additionally, the wear process of artificial ligaments produced white and opaque wear debris, mainly consisting of irregular particles ranging from nanometer to micrometer sizes. Most of the extracted wear debris appeared as spheres, and only a small portion was in the form of fibrous strips. The majority of the wear debris was small, whereas only a little of them was large. Most of the extracted wear debris was spherical, whereas a little was in the form of fibrous strips. There were more small-sized and fewer large-sized wear debris, which were relatively less biologically active and had a lower risk of triggering joint diseases. The results of this study provided a strong reference for refining the standards for in vitro friction wear test of artificial ligaments. [Conclusions] The wear rates of artificial ligaments are comparable to that of hip and knee prostheses reported in some studies. This should not be overlooked, as its biotribological behavior directly affects the outcomes of replacement surgery. Therefore, establishing scientific and rational in vitro wear measurements and wear debris analysis has great scientific value and significance in accurately predicting the clinical wear of artificial ligaments.

[Objective] After total hip arthroplasty, the contact stress spot between the femoral head and the liner can easily move from the liner's inner surface to its contour edge under different gaits, resulting in edge loading (EL) at the liner edge. The occurrence of EL will reduce the mechanical properties of the liner, increase the wear of the hip prostheses, and reduce the service life of hip prostheses and the quality of life of patients. EL is related to the prosthetic mounting position, geometric design, and patient motion status. This study aimed to investigate the contact mechanics and EL of elevated-rim liner edges at different gaits and mounting positions to guide clinical prosthesis mounting and postoperative rehabilitation of patients. [Methods] In this study, we developed a finite element analysis model of elevated-rim liner contact mechanics and hip joint EL under gait loading based on a metal-on-polyethylene contact bearing. Four gaits (normal walking, ascending stairs, descending stairs, and deep squatting) common to the patient's daily life were used as kinetic inputs to the finite element model. The model considered the radiographic inclination and anteversion of the acetabular cup at relatively extreme positions and the elevated rim of the liner at different orientations in human body. After finite element mesh sensitivity analyses, mechanical results such as contact stresses, EL, EL duration, equivalent plastic strain, and volume of the equivalent plastic strain of the elevated-rim liner were investigated. [Results] The finite element results showed that the maximum surface normal contact stresses on the inner surface of the elevated-rim liner under normal walking, ascending stairs, descending stairs, and deep squatting gaits were 11.60, 12.44, 11.96, and 12.07 MPa, respectively, with no significant difference. The maximum surface contact stresses on the liner where EL occured were 3.29, 3.40, 4.85, and 4.45 MPa, respectively. The ratios of the EL duration to the gait cycle were 14%, 34%, 50%, and 54%, respectively. The maximum equivalent plastic strains were 2.82×10^-4, 4.89×10^-4, 5.31×10^-4, and 6.56×10^-4, respectively, and the volumes where the equivalent plastic strains occurred were 37.07, 65.01, 67.66, and 150.00 mm³, respectively. [Conclusions] The equivalent plastic strain of the elevated-rim liner, the volume in which plastic deformation occurs, and the EL of the elevated-rim liner and its duration all increase with the radiographic inclination and anteversion of the acetabular cup. Compared with the other three gaits, the deep squatting gait is more likely to cause plastic deformation of the liner and consequently the most damage to the liner. Therefore, patients should avoid movements with high flexion after total hip arthroplasty. Placing the elevated rim of the liner on the posterosuperior side of the body and the radiographic inclination of the acetabular cup no less than 50° can avoid EL and significantly reduce the plastic strain of the liner. Total hip arthroplasty should consider not only the patient's postoperative impingement-free range of motion but also the mechanical condition of the patient's postoperative prostheses, thus prolonging the life of the prostheses.

[Objective] The artificial joint is lubricated using synovial fluid, and variations in the synovial fluid components considerably affect the tribological behavior of the sliding pair of the artificial joint. [Methods] Herein, the “soft-soft” joint pair materials composed of polyether-ether-ketone (PEEK) and highly crosslinked polyethylene (XLPE) are studied based on the composite synovial fluid content following artificial joint replacement. The friction and wear behaviors of the PEEK-XLPE “soft-soft” joint pair materials lubricated via different composite synovial fluids, including albumin (Alb), γ-globulin (γ-Glo), hyaluronic acid (HA), and phospholipids (PLs), are studied. The mechanisms behind the effect of the composite synovial fluid composition and content on the friction and wear of “soft-soft” joint pair materials and wear mechanism of “soft-soft” joint pair materials under different composite synovial fluid are elucidated. [Results] The results showed that the four primary components of the composite synovial fluid had a substantial influence on the friction and wear properties of the artificial joint materials, with the γ-Glo content markedly affecting the friction coefficient. When the γ-Glo content increased from 5.83 mg/mL to 8.75 mg/mL and total protein content increased from 15 mg/mL Alb+3.75 mg/mL γ-Glo to 35 mg/mL Alb+8.75 γ-Glo, the friction coefficient increased by 29.4% and 28.7%, while the wear rate increased by 24.6% and 166.0%, respectively. Moreover, excessively high γ-Glo or total protein content in the composite synovial fluid caused poor protein adhesion between friction surfaces. The wear of “soft-soft” joint pair materials was aggravated when “soft-soft” joint pair materials were used. The changes in the PLs and HA contents of the composite synovial fluid had little influence on the tribological properties of these “soft-soft” joint pair materials, but their effects on wear properties were significant. When the PLs content increased from 0.15 mg/mL to 0.45 mg/mL, the friction coefficient changed little, but the wear rate decreased by 29.5%. Additionally, the wear rate increased by 22.0% when the HA content increased from 0.1 mg/mL to 1.5 mg/mL. This indicated that increasing PLs content improved the wear performance of “soft-soft” joint pair materials because PLs molecules contain hydrophobic fatty acids, which could serve as effective lubricants. Further, the thickness of the Alb film increased with the PLs, but that of γ-Glo film exhibited hardly any changes. However, the existence of PLs rendered the γ-Glo layer uniform and stable, thereby reducing wear. Moreover, PLs got adsorbed to the surface of other molecules or polymerized with other molecules, and “soft-soft” joint pair materials slid between lipid bilayers to reduce friction. However, the adsorption of the Alb improved when HA and PLs were added to the protein mixture, inhibiting the adsorption of the γ-Glo (the volume of γ-Glo is much larger than that of Alb); thus, the inhibition of the γ-Glo adsorption by HA caused the aggravation of wear. [Conclusions] The results show that a change in the content of each component considerably affects the friction and wear characteristics of the PEEK-XLPE joint pair materials. This study provides a theoretical foundation for investigating composite synovial fluid and improving the lubrication performance of artificial joints. Moreover, it is essential to prolong the service life of artificial joints. Furthermore, under the simulated physiological environment (temperature and pH) in vitro, based on the test load, waveform, and displacement in implants for surgery—wear of total hip-joint prostheses—part 2: methods of measurement (YY/T 0651—2020), the influence of composite synovial fluid on the biotribological behavior of the PEEK-XLPE joint pair materials will be explored in the future using a hip joint wear tester, which is expected to lay a foundation for the clinical use of PEEK-XLPE joint pair materials.

[Objective] The accelerated process of urbanization and increased population mobility has led to a surge in population density and frequency in public spaces. This has underscored the importance of addressing health and safety concerns in public spaces, particularly considering the corona virus disease 2019 (COVID-19) pandemic. The effective management of public spaces has become a challenging aspect of urban planning and management. Through research on management and control technologies for populations at high risk of exposure in public spaces, it is possible to achieve efficient management and develop control measures. This will lead to a reduction in overcrowding, lower the risk of epidemic transmission, and ultimately ensure public health and safety. [Methods] This research focuses on a gymnasium in Hangzhou, where the upcoming Asian Games will be held. The study focuses on developing time-based control measures, including time-sharing control measures, classification control measures, and classification and zoning guidance control measures, for large-scale sports events. These measures are developed based on relevant standards and norms. Furthermore, a technical model is constructed to assess personnel evacuation and control in public places, evaluate the level of crowd gathering in public areas, and simulate the number of infected people under various control measures. Thus, the effectiveness of evacuation and control measures is assessed through reverse verification. Finally, different evacuation control schemes are simulated using three-dimensional modeling using the MassMotion software. The technical model of evacuation control for public places is integrated into the MassMotion software development kit (SDK), which is the software's secondary development system. This integration allows for the output of individual density proportion diagrams and COVID-19 virus transmission results under different evacuation control schemes. [Results] The simulation results showed that continuous updates to the guidance and control scheme improved the flow of people in the venue and decreased emergency evacuation time. Moreover, increasing social distance significantly reduced the risk of crowd aggregation and infection. These findings provided evidence supporting the feasibility and effectiveness of the guidance and control scheme for high-risk exposed individuals in public settings. [Conclusions] This study proposes a crowd guidance and control technology for public places aimed at ensuring public safety amidst the COVID-19 pandemic. This research conducted on a gymnasium as a case study provides insights into personnel circulation and COVID-19 transmission under different diversion and control schemes. Further, the research offers valuable support for the implementation of crowd diversion and control measures during large-scale sports events, ensuring the safety of attendees and the broader public.

[Objective] Risk quantification is crucial in risk assessment of accidents or disasters. This study aims to investigate the risk quantification method utilized in over-temperature faults in electrical circuits. The existing technologies of the abovementioned method are summarized in electrical and fire signals of disaster early warning. Thus, a new method based on the fire big data is proposed. [Methods] Different frequency electrical parameters are collected by the detector arranged at the front end and transmitted in real time to the fire big data to mine the influencing factors and changing patterns of electrical circuit temperature based on the deep-learning method. Subsequently, the probability distribution of temperature is determined statically, and risk is described by comparison of prediction temperature in different cumulative probabilities with actual temperature. To predict the electrical circuit temperature, a recurrent neural network (RNN) is utilized to model temperature prediction. The input parameters are voltage, current, temperature, and residual current. Among the parameters, there are two data sources for the model: one is real electrical fire data, 6 min^-1, used to learn the periodic law of temperature increase in electrical circuits of RNN for low-frequency data (LF-RNN), and the other is experimental data based on simulated fault of the temperature increase in electrical circuits. This experiment is implemented in three-phase resistive electrical circuits. Exceeding rated current is utilized to produce temperature rising. Meanwhile, electrical parameters are collected to study the law of temperature oscillation of RNN for high-frequency data (HF-RNN). Among these electrical parameters, the sampling frequency of voltage, current, and residual current is 50 kHz, but 1 Hz for temperature exceptionally. The optimization method, hyperparameter traversal, aims to minimize the loss function and root mean square error; thus, temperature prediction in electrical circuits is preliminarily applied. To increase the accuracy of the prediction model and elucidate the relationship between fire risk and prediction result, a temperature probability prediction model is established based on its second-order residual normal distribution. The error and its reducing methods are analyzed, and the relationship between prediction error and temperature mutation is determined. [Results] The results demonstrated that temperature mutation within three window lengths had a remarkable linear correction effect with temperature prediction error; moreover, the second-order residual approximately followed a normal distribution. The upper and lower limited of temperature prediction confidence intervals with different significant levels (α=0.02, 0.04, 0.06,…, 0.98) can be computed by interval estimation, which had a one-to-one correspondence with temperature prediction accumulate probability (1-α/2) and (α/2). The results revealed that the cumulative distribution probability 1% prediction curve and 99% prediction curve appeared to have a fine coverage effect on the actual temperature. With the aim of measuring temperature prediction probability distribution with electrical fire risk, the concept of “early-warning quantile” similar to cumulative distribution probability, was proposed. The ability to predict temperature was established using different “early-warning quantile curves” and confirmed through 2 943 sets of real electrical fire scene data. The results demonstrated that early-warning quantiles in the range of 10%-30% could overlap the majority of the actual temperature data, and the higher the quantile of the curve was, the higher the frequency of overestimating the temperature was. [Conclusions] To summarize, when the temperature in electrical circuits suddenly increases, there is a substantial upward trend in the early-warning quantile of the actual temperature. Thus, the use of LF-RNN and HF-RNN can timely and accurately predict the temperature probability distribution to characterize fire risks in electrical circuits so that early dynamic perception of fire risk is realized.

[Objective] The arc fault of the low-voltage distribution system is one of the primary causes of residential fires. Due to the diverse load types and complex connection methods in residential areas, arcs fault exhibit many similar and concealed characteristics, making them difficult to detect. This frequently leads to issues with arc fault protection devices, such as false alarms and missed detections. The conventional detection method, which is based on manually extracting arc fault feature vectors, is incomplete and heavily relies on expert-designed features. Consequently, this impedes the development of highly generalizable models. In addressing these challenges of multiload systems, this paper proposes a method for serial arc fault diagnosis and load recognition based on a one-dimensional dilated convolutional neural network (1D-DCNN). [Methods] First, a series of experiments on multiload arcs fault are conducted using a custom-designed experimental platform. This platform supports both single-load and dual-branch load conditions during testing. Normal and faulty current data on the main bus are sampled under various operating conditions at a rate of 500 kHz. During the data processing phase, the continuous time series data are discretized and normalized based on the half-cycle length. Subsequently, a 1D-DCNN is used to extract features from the high-sampling-rate arc fault current data. Furthermore, the scaled exponential linear unit activation functions and residual connections are introduced to address the challenges of gradient vanishing and network degradation. Moreover, the cyclic padding method is adopted to alleviate boundary effects and enhance the model's robustness to dataset shift. The arc fault detection model is developed by integrating average ensemble learning with a Softmax multiclassifier. Precision, recall, and specificity are used to assess the efficiency of the model. Finally, the accuracy of the proposed model in load classification, load state recognition, and overall accuracy is compared with that of other classical models, providing a comprehensive assessment of its efficacy. [Results] The findings of this method were as follows: (1) The accuracy of arc detection using a recurrent neural network was considerably low, primarily due to gradient vanishing and exploding gradients, making it difficult to effectively train the model. (2) Under the condition of equal parameter count between a 1D-DCNN and 1D-CNN, the dilated convolutional operation expanded the receptive field, resulting in greater accuracy than the 1D-CNN model. (3) The proposed method achieved a remarkable accuracy of 99.67% in detecting arc faults for both single-load and mixed-load scenarios, with an accuracy of 99.95% and an overall accuracy of 99.62%. [Conclusions] This research presents a unique model capable of autonomously learning features from high-sampling-rate current data without requiring manual feature extraction. It efficiently detects arcs fault while identifying the type of faulty load simultaneously. The model outperforms typical convolutional neural networks on validation of the test set, thereby meeting the requirements for arc fault identification. This advancement has major implications for serial arc fault detection and load recognition applications.

[Objective] Liquid fuel fires are commonly extinguished using foam; however, conventional foam formulations include perfluorooctane sulfonate, which does not degrade easily, causing environmental pollution and posing a threat to human health. Furthermore, traditional foams exhibit poor thermal stability and are prone to reignition after extinguishing. Thus, developing a foam that is both safe and environmentally friendly while exhibiting strong resistance to reignition is urgently needed. However, most of the current research is limited to laboratory parameter measurements and mainly focuses on the development of new foams for solid fires, such as coal fires, which have considerable differences in fire suppression mechanisms and foam performance requirements from liquid fires. At present, research on highly stable and environmentally friendly foam formulations specifically designed for liquid fires is limited. This study aims to replace hazardous fluorocarbon surfactants with safe and biodegradable hydrocarbon surfactants and incorporate natural hydrophilic polymer guar gum to develop an environmentally friendly polysaccharide foam suitable for liquid fires. Analysis of the foaming and stability performance of the developed foam is conducted, and the concentrations and ratios of foaming agents and stabilizers are determined. Finally, the fire suppression performance of the developed foam is compared with that of the fluoroprotein foam (FFFP). [Methods] The foam expansion ratio and half-life were estimated, and the comprehensive values were computed to determine the optimal laboratory foam formulation with high comprehensive parameters. However, the direct estimation of the fire suppression time of the foam during liquid fire extinguishment was difficult as it was influenced by various factors such as foaming performance, stability, and flowability. Thus, a 0.8 m-diameter scaled-down oil pan was constructed, and the laboratory foam formulation with higher comprehensive parameters was further tested for its fire suppression performance and compared with the commercial FFFP. After complete extinguishment, a 5-minute cooling period was implemented, followed by an evaluation of the foam's resistance to reignition using a burn-back tank. [Results] The findings revealed that: (1) The foam presented the highest comprehensive value of 133.4 at an mass ratio of AEG and APG-0810 of 2∶8, with a mass fraction of 0.5%. The foam expansion ratio was 14.5, and the half-life was 10.8 min. (2) When the concentration of guar gum was 0.4%, the comprehensive value of the foam stabilized and exhibited the best fire suppression performance. The 90% control time was approximately 52 s, and the extinguishment time was 82 s. Comparing the control and extinguishment times of the developed foam with those of FFFP, the new formulation showed reductions of 16.1% and 10.9%, respectively. (3) At a guar gum concentration of 0.4%, the developed foam exhibited the best resistance to reignition. The 25%, 90%, and complete reignition times compared to FFFP were extended by 96.5%, 114.1% and 113.7%, respectively. [Conclusions] By replacing hazardous fluorocarbon surfactants with biodegradable hydrocarbon surfactants (APG-0810 and AEG) and introducing the natural hydrophilic polymer guar gum, the developed foam has improved viscous and water-retention properties, leading to a substantially improvement in its resistance to reignition. This study offers a reference for developing new reignition-resistant foam formulations specifically designed for liquid fires.

[Objective] Seismic damage and destruction of the stations, tunnels, and other structures considerably impair the functionality of the urban rail transit system. Current research on the system performance of the rail transit network primarily focuses on the scenarios of intentional attack and stochastic damage, which is dramatically different from the earthquake disaster scenarios. This paper proposed a quantitative framework to evaluate the seismic performance and resilience of rail transit networks. [Methods] The seismic fragility model was used to calculate the failure probability of the primary structural elements, including stations, tunnels, and bridges of the rail transit system. The graphical model of the network was established using the Space L modeling method. This approach was used to depict the interdependency of system elements. The network performance was expressed by the network efficiency weighted by passenger flow between rail transit stations. The Monte Carlo simulation was used to assess the uncertainty of the earthquake damage state of structures and the post-earthquake recovery of the damaged elements. According to the network performance curves during the post-earthquake recovery process, the seismic resilience index and resilience loss of the rail transit network were quantitatively evaluated using the concept of resilience triangle. Considering the Beijing rail transit network, the effects of earthquake intensity, recovery strategy on network performance, and resilience indexes were investigated. [Results] The results of the present analysis were as follows. (1) The resilience characteristics of rail transit networks under earthquakes, intentional attacks, and stochastic damage were different. The resilience index under earthquake damage was 0.936 3, whereas the resilience index under stochastic damage was 0.934 0. The resilience index under intentional attack was 0.863 4. (2) In the damage scenario corresponding to different earthquake intensities, the system resilience index calculated by the recovery sequence sorted by the dynamic importance of damaged elements were larger than that sorted by the static importance of damaged elements. Moreover, the damage scenario involving several damaged elements typically results in a larger difference between the resilience index calculated by the two recovery strategies. (3) Pre-earthquake enhancement measures to reduce the failure probability of crucial elements could effectively enhance the disaster resistance capacity of the network; however, their influence on improving the post-earthquake recovery capacity remained unclear. [Conclusions] Based on the seismic fragility models of the primary structure of the rail transit network, the graphical model of the network, and the importance of ranking-based post-earthquake recovery of the damaged elements, this paper establishes a framework to quantitatively evaluate the seismic resilience of rail transit network by the passenger-weighted network efficiency. When evaluating network resilience and comparing antiseismic improvement measures, multiple indicators such as resilience index, resilience loss, and recovery duration should be comprehensively analyzed. This framework can provide a reference for the seismic performance evaluation of the urban rail transit network and help decision-makers in allocating maintenance resources to restore the operation function of the urban rail transit system in a timely and cost-effective manner during the recovery process.

[Objective] In recent years, increasing emissions of greenhouse gases from industrial sources have led to extreme weather events. Thus, carbon capture has become an increasingly prominent concern for human society. Organic amines have emerged as popular carbon dioxide (CO₂) chemical absorbents. However, currently used organic amine solvents encounter challenges, such as poor reaction kinetics of chemical absorptions, which need to be overcome using organic amines with higher performance. Moreover, there is limited research on the crucial property of Gibbs free energy of activation related to the reaction kinetics of chemical absorptions. The difficulty lies in the fact that the calculation of this property often involves the search for transition states in elementary reactions, and the initial structure of the transition state generally needs to be manually arranged, which greatly hampers the success of this search. To overcome this difficulty, a method for generating transition state initial guess structures is employed herein to automatically generate transition state structures for target organic amine molecules. Based on this generation method of transition state initial guess structures, a computer-aided framework for designing organic amine solvents is proposed by integrating a reaction kinetic model and a mathematical programming method. [Methods] First, the mechanism of the reaction between organic amines and CO₂ is investigated based on quantum chemical methods and the transition state theory to construct a reaction kinetic model that can regulate the Gibbs free energy of activation of amine-based CO₂ chemical absorptions. Additionally, a conformational isomer search approach is incorporated into the reaction kinetic model to improve the computational accuracy of the transition state energies. Second, by employing the transition state initial guess structure generation method, the reaction kinetic model is successfully integrated with the mathematical programming method to achieve automatic, reverse, and optimal design of organic amine molecular structures that have the lowest Gibbs free energy of activation for carbon capture reactions and satisfy all other property constraints being studied. Finally, the interaction region indicator function is used to verify the rationality of the designed organic amines regarding the reaction kinetics. [Results] Using the mathematical programming method, 45 SMILES (simplified molecular input line entry system) representations that satisfy the design constraints were obtained. Through the transition state initial guess structure generation method, the corresponding transition state structures of organic amine molecules were obtained, and the Gibbs free energies of activation of these molecules were calculated by the reaction kinetic model. The final design results showed that the organic amine with the best performance had faster reaction kinetics than the primary amine used commonly in the industry, namely MEA (monoethanolamine), and its Gibbs free energy of activation for CO₂ chemical absorption was 10.7% less than that of MEA. [Conclusions] In summary, the integration of the reaction kinetic model and the conformational isomer search approach yields molecular conformations with lower energies that are more realistic, resulting in more accurate calculations of Gibbs free energy of activation. The transition state initial guess structure generation method can automatically and rapidly generate initial molecular structures for transition states to calculate Gibbs free energy of activation, significantly improving the success rate of transition state searches. From the final design results, it is clear that the method proposed herein can discover promising monoamine molecules within a large chemical space.

[Objective] The existing freshwater scarcity and the energy crisis are severely limiting the economic restructuring and social development of the world. An integrated cogeneration system using 100% renewable energy resources and desalination can effectively solve the problem of freshwater scarcity and energy shortage. Desalination technologies such as multistage flash evaporation and reverse osmosis are important means of addressing freshwater scarcity problems. Furthermore, concentrating solar power technology enables renewable energy capture and utilization with lower costs and higher dispatchability. Concentrating solar power can generate electric and thermal energy that can be consumed in desalination operations. Therefore, the integration of the two helps to make the desalination industry environmentally sustainable. However, the existing integrated concentrating solar power-desalination systems have problems such as single-capacity structures and poor system flexibility. The design of cogeneration systems with a high flexiblity for the integration of renewable energy and desalination to meet the user's energy demands under complex weather conditions is a critical challenge in this field. [Methods] This paper proposes a water cogeneration system with integrated concentrating solar power-desalination, comprising a concentrating solar power unit, a heat storage unit, a multistage flash evaporation unit, a reverse osmosis unit, an electrothermal steam generator, and a water storage unit. Furthermore, a mathematical model with the minimization of the annual cost of the integrated system as the objective function is established as a mixed-integer nonlinear problem. Moreover, this paper proposes a flexibility index and a flexible design method applicable to the optimization of integrated hydrothermal power systems, implementing the definition, calculation, and optimization of the boundary constraints of the flexibility index. A two-layer algorithm for flexible design is developed, with the outer algorithm obtaining the system size and the inner algorithm optimizing the flexibility of the system. GAMS and MATLAB are used to obtain the optimal configuration and the minimum total annual cost of each system, as well as compare the results of the flexible design with those of the fixed-condition design to verify the effectiveness of the flexible design and analyze the advantages of the flexible design. [Results] The case study reveals that the flexible design results in a 10.7% reduction in the total annual costs and a considerable reduction in the system redundancy compared to the fixed-condition design. In addition, the flexible design reduces the consumption of coal by 166 617 t and reduces CO₂ emissions by ~436 538 t compared to conventional thermal power generation every year. The fluctuation of the supply-demand ratio of water-heat-power is considerably suppressed, and the proportion of days with abnormal supply and demand of water-heat-power decreases from 91.11%, 98.19%, and 60.69% to 0%. These results verify the feasibility and effectiveness of the system model and algorithm proposed in this paper. [Conclusions] Results reveal that the cogeneration system designed in this paper is instructive for the conversion of seawater desalination from an energy-intensive industry to a zero-emissions industry and the adoption of renewable energy in various energy-intensive industries. This research contributes to the application of renewable energy cogeneration systems in a wider range of fields.

[Objective] p-Xylene (PX) is an important aromatic product with the highest consumption among xylene isomers. It is widely used as a raw material for upstream production of several important chemical products. Carbon dioxide (CO₂) is a major gas responsible for the greenhouse effect. Furthermore, in addition to methanol, CO₂ and syngas also show great technical potential as methylation agent. The direct synthesis of PX by CO₂ hydrogenation coupled with toluene methylation over a bifunctional catalyst has the advantages of atomic economy, green hydrogen storage, and CO₂ utilization, but a complete techno-economic evaluation of process design and optimization strategy has not been performed. [Methods] Based on the selective catalytic results of CO₂ hydrogenation coupled with toluene methylation, three toluene methylation catalysts with high conversion, high xylene selectivity, and high PX selectivity and their experimental results were chosen, and the process flow of PX production by CO₂ hydrogenation coupled with toluene methylation was designed and simulated by software. The following was the process flow: the raw materials of the reaction were pretreated and compressed into the reactor, the reaction products were flashed four times to separate the gas from the liquid, some raw materials were circulated, and the liquid products were sequentially separated or purified to yield benzene, PX, o-xylene, and heavy aromatic hydrocarbons. Moreover, because of the various catalysts, RStoic, a stoichiometric reactor module, was employed to model the methylation reaction unit. Based on the characteristics of different catalysts, the conversion rate of each reactant was specified. Furthermore, based on controlling the same PX output, the raw material feed ratio of the reactor was also specified, and the xylene isomer was separated by reactive distillation. [Results] Analysis of the raw material cost, equipment cost, and energy consumption of the process flow corresponding to the three catalysts was conducted, and the results showed that the raw material of the unit PX product of the high-PX-selectivity catalyst process was only 72.6% and 58.9% of those of the other two catalyst processes and the CO₂ consumption of the unit PX product was 27.3% and 44.7% of that of the other two catalyst processes. However, the high-xylene-selectivity catalyst process could yield more PX production through isomerization technology, and its energy consumption was also the lowest. Because reactive distillation was employed as the post-separation of xylene isomerization products, the high-xylene-selectivity catalyst process had a high raw material consumption rate and the highest energy consumption, but by isomerization technology, it had the highest PX production potential and showed the best economy through economic accounting of different PX production processes. [Conclusions] CO₂ hydrogenation coupled with toluene methylation technology can enhance the conversion rate of raw materials, reduce the energy consumption of material circulation, and enhance the xylene and PX selectivities, which will greatly improve its technical economy. Furthermore, the production process with high PX selectivity is a green chemical process with broad development prospects for reducing carbon emissions in the environment, achieving carbon cycle, energy conservation, and emission reduction.

[Objective] The driving wheel is a challenge during the reconstruction of Su Song's astronomical clock-tower. Two approaches, the “flip-scoop” and “fixed-scoop” methods, have been identified based on whether the scoop can turn independently. Recent research reports that both options are inevitably inconsistent with the original text, indicating that conformity with the original text is no longer the only criterion for evaluating the merits of these approaches. Therefore, future models should not solely follow these options. New schemes can be designed by learning from their advantages while addressing their shortcomings and components that do not match the original text. Additionally, for museum exhibitions, long-term model stability is crucial. The force data of key components exactly determine the overall stability of the whole model. Therefore, in this study, the force data of some key components in the two schemes are obtained by constructing models in the software and calculations, which will provide valuable references for the reconstruction process. [Methods] This study establishes two models in the software based on the “flip-scoop” and “fixed-scoop” methods according to the original size in Song Dynasty. The force data between the forward upper lock and the driving wheel are calculated using the laws of a rigid body in rotational motion. Subsequently, the pressure between the forward upper lock and the driving wheel is analyzed. [Results] The results revealed that the force between the forward upper lock and the driving wheel was nearly three times higher in the “flip-scoop” model compared with the “fixed-scoop” model. The reason for this disparity was the different structural characteristics between the two schemes. The “fixed-scoop” model incorporated buffering components that reduced the rotation speed of the driving wheel and thus weaken the force between the forward upper lock and the driving wheel. However, the “flip-scoop” model lacked components to help achieve similar effects. More critically, while the driving wheel periodically struck the forward upper lock, it was also subjected to the reaction force of the forward upper lock. In the “fixed-scoop” model, the forward upper lock struck the bottom of the scoop, while in the “flip-scoop” model, the forward upper lock struck the edge of the spoke on the side of the driving wheel. This results in a much smaller spoke impacted contact area in the “flip-scoop” model than in the “fixed-scoop” model, leading to higher pressure on the driving wheel in the “flip-scoop” model than that in the “fixed-scoop” model. Furthermore, this increased pressure exacerbated the potential risk of deformation and damage to the spokes. Additionally, once the pivot wheel was damaged, the influence on the stability of the entire model would be irreversible. [Conclusions] In summary, the differences in the buffering components and the contact areas between the driving wheel and forward upper lock make the driving wheel and forward upper lock in the “fixed-scoop” model suffer less impact and render its operational stability. Future reconstruction models can be designed based on this advantage.

[Objective] The engines of plug-in hybrid electric vehicles work much more frequently under low state-of-charge conditions compared to those of fuel vehicles, resulting in unignorable shaking when the engines are started. Most previous studies have focused on the mechanisms of engine shaking under engine start conditions and not under drive conditions. However, because of the drive motor torque effect, the mechanisms of the engine shaking between the engine start and drive conditions are considerably different. Therefore, studying the mechanisms of engine shaking in hybrid electric vehicles under drive conditions is considerably important. [Methods] In this paper, a physical model, which includes the torsional vibration physical and powertrain (PWT) rigid physical models, is developed to describe the phenomenon of engine shaking in hybrid vehicles. Subsequently, an experimental scheme for the engine shaking is designed. In addition, the physical model is validated through experiments. Finally, the excitation source and transfer path mechanisms of the engine shaking in hybrid electric vehicles under drive conditions are studied by coupling simulations and experiments. [Results] Results showed that: (1) Engine shaking occurred before the internal combustion engine (ICE) sparking, which greatly differed from that in the case of fuel vehicles. (2) Engine shaking was strongly dependent on the first-cycle cylinder pressure during the integrated starter generator pulling ICE to increase engine speed for sparking. In addition, the first cycle cylinder was dependent on the crankshaft position, causing the randomness of engine shaking. (3) The other root cause of this phenomenon was the coupling effect between the PWT rigid model and the torsional model of the driveline. (4) The PWT transient rigid model was strongly influenced by the torque of the drive motor under different drive conditions, affecting the coupling between the PWT rigid model and the torsional models of the driveline. (5) The transfer path of engine shaking was from the engine mounts to the vehicle body. Based on the results, two optimization solutions were proposed: The first solution was decoupling the PWT rigid model from the driveline torsional model by lowering the frequency of the torsional vibration damper model. Another solution was reducing the nonlinear dynamics stiffness of PWT mounts by optimizing the metal frame of PWT mounts, enhancing the vibration isolation from PWT to the vehicle body. [Conclusions] The complex coupling mechanisms from the excitation source to transfer paths for engine shaking under drive conditions are found by integrating simulations and experiments. The two optimization solutions are applied to a hybrid electric vehicle, which can considerably reduce engine shaking under drive conditions. These achievements can provide an important reference for improving the noise vibration harshness of hybrid electric vehicles.

[Objective] Cleaning operations for ships become challenging due to the irregular hull surface and ship motion. Thus, to achieve efficient and automated cleaning operations, this study proposes a variable-structure spatial cable-driven cleaning robot. Existing research is mainly based on fixed-base conditions and has not considered the influence of base motion on modeling accuracy. The cleaning robot is mounted on ships, and the 6 degrees of freedom ship motion will inevitably affect the tracking accuracy of the motion platform, eventually causing closed-loop instability of the system. Moreover, most research simplifies the external disturbances acting on the motion platform, which cannot accurately comprehend the influence of external disturbances on tracking accuracy. The cleaning robot is affected by external disturbances such as wind, waves, and currents during operation, and existing dynamic models are inapplicable. [Methods] To address the aforementioned issues, this study proposes the use of the Newton-Euler method to establish a dynamic model including ship motion and external disturbances. Fluid simulation is used to verify that water flow can be sprayed onto the operating surface, and to determine the reaction force acting on the motion platform. Furthermore, given the influence of sea wind on cleaning operations, the wind pressure projection method is used to calculate the wind’s disturbing force and combine it with the reaction force of water flow as an external disturbance. Furthermore, given the uncertainty of the dynamic model, it is decomposed into the modeled part and model error, and separate control laws are designed for these two parts. A proportional-integral sliding mode controller (PI-SMC) is further proposed. To improve the response speed and tracking accuracy of the control system, a fuzzy adaptive PI sliding mode controller (FAPI-SMC) is proposed based on the PI-SMC with an adaptive law and a fuzzy control strategy. Finally, the stability of the control system is proven by the Lyapunov theory, and the effectiveness of the controller is verified through simulations. [Results] The numerical analysis results showed that: (1) Under the set operating conditions, water flow could be sprayed onto the operating surface, and the mean value of the reaction force was approximately 9 N. (2) Under different forms of wave excitations and operating conditions, the position steady-state error of the motion platform under FAPI-SMC was maintained at ±0.02 m, and the angle steady-state error was maintained at ±0.02°. (3) When the operating conditions change, the steady-state error under proportional-integral-differential controller (PID) changed by approximately 0.16 m, the steady-state error under PI-SMC changed by approximately 0.19 m, and a smaller steady-state error under FAPI-SMC changed by approximately 0.01 m. (4) Compared with PI-SMC and PID, the maximum error of FAPI-SMC was reduced by 8% and 6%, respectively, the response speed was improved by 18% and 57%, respectively, and the steady-state performance was improved by 2% and 3%, respectively. [Conclusions] The proposed control strategy has high precision and rapid response under ship motion and external disturbances. Moreover, the cleaning robot has excellent operating stability for different wave excitations and operating conditions. Thus, the dynamic model and control strategy proposed in this study can provide theoretical guidance for applying cable-driven mechanisms in ships.

[Objective] The single-shot arrow tube valve system has over a hundred locations where effective sealing is essential. Under extreme operating conditions, such as frequent alternation between deep low temperatures and ambient temperatures, pressure fluctuations within the pipes, and turbulent flow fields, the sealing surfaces are prone to contact deformation due to excessive localized stresses. Consequently, it becomes challenging to maintain an appropriate sealing contact pressure, rendering the conventional gasket sealing model inadequate and considerably reducing the sealing reliability. Furthermore, deep low temperatures can alter the flow characteristics of the sealing medium, altering its flow properties inside the microscopic leakage channels. Further, the mechanical properties of gasket sealing materials vary with temperature, resulting in leakage rates exceeding acceptable levels in low-temperature environments for step gasket structures that are deemed suitable for ambient temperatures. [Methods] To address the sealing leakage issue in carrier rockets during service under conventional and extreme conditions, a method for predicting the sealing performance of the deep low-temperature joint-connection system is proposed. First, finite element simulation software is used to analyze the Mises stress under different operating conditions and conduct interface mechanical analysis of the sealing contact areas to determine the macroscopic contact pressure of the sealing interface. Subsequently, a three-dimensional white light interferometer is used to study the sealing contact interface, and the obtained rough surface topography is converted into a digital representation by numerical methods. By combining the contact pressure distribution obtained from the simulation, the microcontact surface topography is determined using the fast Fourier transform algorithm, followed by the determination of the average height of the leakage channel. Considering the flow characteristics of the medium, a grid model is employed to construct a leakage rate quantifying model. Consequently, the leakage rate is established as the criterion for evaluating the sealing performance. [Results] The influence of different parameters, such as temperature, load, and medium pressure, on gasket sealing performance was studied through numerical calculation methods. As the temperature decreased, materials gradually harden, resulting in reduced compression of gaskets under the same load at 20 K. Additionally, joints and nozzle inlets experience structural dimensional changes caused by the temperature decrease, which was one of the reasons for increased leakage rates at deep cryogenic temperatures. When the load remained constant and the operating temperature was 20 K, the medium pressure did not significantly affect the overall trend of the contact pressure curve, but it had a notable impact on the regions subjected to medium-pressure loading. Simultaneously, by simplifying the joint-connection system structure, a reusable and convenient experimental fixture was designed for the measurement test of gasket sealing leakage rates under different loads. [Conclusions] The proposed numerical method comprehensively considers the influence of gasket mechanical properties, surface topography micro-parameters, medium pressure, and torque load on gasket sealing performance, introducing a approach using leakage rate as an evaluation metric. The results demonstrate that the simulated leakage rates are of the same order of magnitude as the experimental values, exhibiting a high level of agreement. This study provides valuable guidance for the optimization of joint-connection gasket sealing design and its practical applications.

[Objective] Recent years have witnessed a remarkable rise in popularity among livestream-based network applications, prompting higher expectations for the quality of internet services. However, the public internet infrastructure's highest quality services and shared resources often fail to meet the demanding data transmission requirements of livestreaming applications. The objective of this research is to address the problem of cost-sensitive traffic engineering (TE) in Overlay networks for large-scale livestreaming, providing economically efficient livestreaming flow transmission services while minimizing costs and adhering to quality of service (QoS) requirements. By achieving these objectives, service providers can enhance network performance, optimize resource allocation, and deliver high-quality livestreaming to a wide user base.[Methods] To address the cost-sensitive traffic engineering problem, a comprehensive approach based on time-series optimization and approximate differentiable modeling is adopted. The scenario considered in this research is an application-layer transport network comprising forwarding nodes and virtual links. Business flows are transmitted along paths between forwarding nodes, and these paths may include multiple virtual paths to enhance performance. The problem is formulated as a time-series optimization problem, necessitating the decomposition into a series of time-series-based integer programming problems to simplify the solution process. To handle the nondifferentiable aspects of the problem, an innovative approximating differentiable model is proposed. Path selection is approximated with the Gumbel-Softmax function, a technique allowing for differentiable path selection. Moreover, differentiable functions are employed to approximate the cost and transmission delay functions, ensuring smooth optimization. The Lagrange multiplier method is utilized to transform the problem into an efficient optimization framework. An online routing algorithm (LiveTE) is developed to solve for the set of decision paths, utilizing a gradient descent algorithm to solve the optimization problem iteratively.[Results] The effectiveness of the LiveTE algorithm was evaluated via extensive experimentation and numerical simulations using real data obtained from a running-overlay livestreaming network. The results exhibited considerable cost reductions and improved transmission delay compared to existing methods. LiveTE achieved a remarkable total cost reduction of 52% while simultaneously lowering the average transmission delay by over 6%, highlighting its efficacy in enabling economically efficient livestreaming flow transmission services in overlay networks. The algorithm's ability to optimize resource allocation and improve QoS in large-scale livestreaming scenarios was evident, allowing service providers to enhance network performance and deliver high-quality livestreaming experiences to a diverse user base.[Conclusions] In summary, a comprehensive approach is presented to address the cost-sensitive traffic engineering problem in overlay networks for large-scale livestreaming applications. By formulating the problem as a time-series optimization problem and employing an approximating differentiable model, the proposed LiveTE algorithm achieves remarkable cost reductions while simultaneously improving transmission delay and QoS. The results contribute to the economically efficient delivery of high-quality livestreaming services, allowing service providers to optimize resource allocation and enhance network performance. Furthermore, the proposed LiveTE algorithm provides a valuable solution for service providers seeking to enhance user experience, mitigate costs, and maximize the utilization of overlay networks in livestreaming-based applications.