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Application of artificial intelligence to tunnel fire monitoring and early warning systems
LI Yanfeng;REN Yongsheng;QIU Mingxuan;LI Junmei;[Significance] In tunnel fire safety prevention and control, artificial intelligence(AI) has gradually become a key means of accurate monitoring and intelligent warning of tunnel fires because of its ability to solve problems of traditional monitoring, such as long response delays, long prediction times, and high false alarm rates. Prediction models based on empirical formulas take minutes to calculate, failing to meet the needs of early intervention. Therefore, using AI to accurately predict fire development trends(such as smoke spread and temperature distribution) is crucial for formulating emergency plans and ensuring safety. In particular, fire monitoring and intelligent early warning methods based on AI have become an important research direction in tunnel fire safety research.[Progress] Applications of AI to tunnel fires include the development of few-shot and self-supervised learning methods to enhance model generalization ability. They also involve promoting system integration and standardization to realize platform-based collaborative management. In multisource data collection, multi-sensor fusion adopts an improved hierarchical architecture based on D–S evidence theory. It integrates temperature, smoke, and gas data, thereby improving fire identification reliability by 45% in complex environments. Video monitoring relies on CNN(convolutional neural network) and YOLOv8 algorithms, combined with tunnel CCTV(closed-circuit television) systems, to analyze flame and smoke characteristics. It achieves 96% recognition accuracy and reduces the false alarm rate by 30%. Edge computing has achieved up to 96% accuracy and supports real-time alarms. At the platform level, AI-based disaster prevention and response systems(e.g., Shanghai's intelligent system) enable real-time visualization of fire locations and temperatures. They automatically trigger coordinated control of ventilation and sprinkler systems, reducing response delays by more than 50% compared with manual operation. In terms of intelligent early warning, generative AI, such as GANs(generative adversarial networks) and Transformers, can generate fire spread simulations within 5 s. LSTM–TCNN(long short-term memory-temporal convolutional neural network) reduces temperature field prediction from minute-level to second-level(with 90% accuracy), and digital twins construct 1∶1 virtual tunnels to generate synthetic data, thereby reducing the demand for training data by 50%. [Conclusions and Prospects] AI can effectively improve detection accuracy and response efficiency in tunnel fire monitoring and early warning. However, several challenges remain, including the scarcity of real-world samples(applying highway models to railways reduces accuracy by 15%–20%), the limited ability of traditional algorithms to capture global features, a lack of standardization in system integration, and high deployment costs. Future research will focus on using generative diffusion models to generate high-fidelity data and alleviate the sample scarcity issue, while reinforcement learning will be employed to optimize the collaborative control of equipment. In addition, a three-dimensional visualization platform based on BIM(building information modeling) and digital twins will be developed to enable VR/AR-based simulations. Further improvements in multimodal fusion are expected to enhance data reliability and cross-scenario adaptability, thereby advancing the intelligence of tunnel fire prevention and control. This research will contribute to improve the intelligence level of tunnel fire early warning and emergency response and promote the practical application of AI in tunnel fire engineering.
Experimental investigation of ceiling temperature rise during a fire in a bifurcated tunnel with an inclined mainline
HUANG Youbo;XIANG Chao;DONG Bingyan;LIU Xi;LI Yanfeng;[Objective] Urban traffic link tunnels, mainly composed of bifurcated tunnels, have been rapidly constructed. A fire in this complex tunnel would cause more serious facility damage and casualties due to multipath smoke propagation and a more uneven temperature distribution compared with an ordinary single tunnel. Furthermore, a bifurcated tunnel contains different tunnel slopes and bifurcation angles to connect surface and underground transportation systems. However, previous research on tunnel fires has mainly focused on a single ordinary tunnel or a horizontal bifurcated tunnel; fires in an inclined bifurcated tunnel have rarely been studied. To clarify the mechanism of smoke propagation and the temperature profile in a bifurcated tunnel, the present study conducted a series of small-scale experiments to investigate the maximum ceiling temperature in a bifurcated tunnel with an inclined mainline. [Methods] Froude's similarity criterion was used to guide the design of the small-scale experimental bench. A 1/20 scale bifurcated tunnel platform was constructed, consisting of a 10 m mainline and a 4 m ramp, with a cross-section of 0.25 m × 0.5 m. Three bifurcation angles(10°, 20°, and 30°), five mainline tunnel slopes(0%, 1%, 3%, 5%, and 7%), and three heat release rates(1.12, 1.64, and 2.8 kW) were considered. Different longitudinal ventilation velocities supplied from the mainline before shunting were used for analyzing their effects on smoke propagation and temperature distribution. The temperature at the tunnel ceiling and along the tunnel centerline was detected and analyzed. The effects of the bifurcation angle and the mainline slope on the maximum ceiling temperature were investigated, and an empirical model was developed to predict it in a bifurcated tunnel. [Results and Conclusions] Experimental results showed that the heat release rate significantly affected the maximum ceiling temperature, with higher rates resulting in higher maximum ceiling temperatures. The larger bifurcation angle resulted in a higher maximum ceiling temperature at relatively low longitudinal ventilation; however, its effect on the maximum ceiling temperature was limited when the longitudinal ventilation velocity exceeded 0.2 m/s. In particular, the maximum ceiling temperature was more sensitive to the bifurcation angles at a relatively low heat release rate. The maximum ceiling temperature decreased with increasing longitudinal ventilation because of the cooling effect and the flame tilting effect. The maximum ceiling temperature decreased with increasing mainline slope as the stronger stack effect improved the induced airflow velocity. The effect of the mainline slope on the maximum ceiling temperature was more pronounced when the slope was <3%, but this effect weakened when the slope was >3%. The maximum ceiling temperature in the bifurcated tunnel could not be accurately predicted using previous empirical models, as these models were developed based on tests conducted for ordinary single-line or horizontally branched tunnels. Therefore, a predictive model for the maximum ceiling temperature in a branched tunnel with a mainline slope was developed by accounting for the mainline slope, heat release rate, bifurcation angle, and longitudinal ventilation velocity. This study contributes to understanding smoke propagation and provides a validated tool for evaluating maximum temperature in a bifurcated tunnel.
Analysis and development trends of grouting technology for underground water-sealed caverns
FAN Mingming;XU Dong;HE Chenhui;ZHANG Jiaxing;[Significance] Grouting technology plays a crucial role in the construction of underground water-sealed caverns, particularly in the context of national strategic oil and gas reserves, because it can substantially improve the antiseepage performance of the surrounding rock. The extremely high requirements for impermeability and water inflow control in such storage systems pose major challenges, especially under complex geological conditions characterized by variable lithology, diverse groundwater chemistry, and uncertain seepage paths. Traditional grouting methods often struggle to ensure long-term sealing performance under these conditions. In response, recent research has increasingly focused on enhancing material adaptability, understanding grout-diffusion mechanisms, developing intelligent evaluation methods, and conducting multiphysics coupling simulations, thereby promoting technological innovation and improving engineering reliability. Therefore, the latest research achievements must be systematically summarized and analyzed to provide a scientific basis and technical reference for the safe operation of underground water-sealed caverns and for advancing water-sealing technology in geotechnical engineering. [Progress] Substantial progress has been made in grouting technology for underground water-sealed caverns, including numerical simulation, material development, field application, and stability assessment. In the field of grout diffusion and seepage behavior, multiphysics coupling models based on dual media(fractures and pores) have been developed, revealing the effects of fracture geometry parameters on grout migration and sealing performance. In terms of material innovation, high-performance groutsincluding ultrafine silica-based, cement-based, and magnetically responsive slurries-have been developed to enhance impermeability and durability in complex hydrogeological environments. Field tests and monitoring studies have been conducted to evaluate the effects of grouting parameters on seepage control and groundwater chemistry, improving the adaptability of grouting techniques to practical engineering conditions. In terms of structural stability, integrated approaches combining numerical simulation and reliability analysis have been adopted to assess cavern safety in various geological scenarios. Furthermore, the application of environmentally friendly technologies, such as microbially induced calcium carbonate precipitation, offers a novel and sustainable solution for long-term grout sealing. These research outcomes provide a solid theoretical and technical foundation for improving the antiseepage capabilities and operational reliability of underground water-sealed caverns, thereby supporting the intelligent and sustainable development of geotechnical engineering. [Conclusions and Prospects] Deepening research into grouting technology for underground water-sealed caverns has substantially contributed to improvements in parameter design, material performance, and long-term sealing effectiveness. Analyses suggest that precise grouting control should be achieved by integrating geological and hydrogeological conditions with numerical simulations and structural evaluations. A comparative assessment of commonly used grouting materials-including cement-based, composite, epoxy resin, and biomineralization options-demonstrated their respective advantages and limitations under varying environmental conditions. A “model-validation–optimization” loop was devised to enhance the evaluation of grouting effectiveness, supported by the application of intelligent algorithms for predicting long-term performance. Although a relatively complete technical framework has been established, challenges remain in understanding the diffusion and curing mechanisms of grouting under extreme conditions, such as high temperature, high permeability, and considerable depth. Future research should aim to build a dynamic feedback system that links laboratory research with field applications, incorporating smart materials, three-dimensional monitoring, and adaptive modeling to advance the intelligent, standardized, and durable development of grouting technology in complex geotechnical environments.
Fire scenarios in metro tunnels: Insights from full-scale cold smoke experiments and numerical simulations
SU Zhihe;LI Yanfeng;LIU Yutong;State Nuclear Electric Power Planning Design & Research Institute Corporation Limited;[Objective] Effective control of ventilation parameters is critical in metro tunnel safety research. Since cross-passage wind is driven by inter-tunnel pressure differentials, investigating the impact of tunnel air supply on wind speed is therefore vital. Furthermore, train-induced piston wind can damage cross-passage fire doors, compromising operational safety and highlighting the need to assess the feasibility of eliminating fire doors through an optimized air supply design. Thus, this study clarifies the influence of air supply parameters on cross-passage airflow, compares cross-passage wind speeds derived from full-scale cold smoke experiments and thermal simulations of real fire scenarios, evaluates the feasibility of eliminating fire doors, and supports the optimization of metro fire ventilation systems and fire prevention research. [Methods] Here, full-scale experiments were combined with numerical simulation to explore the study objectives. Specifically, multi-condition ventilation and smoke tests were conducted in a Zhengzhou metro tunnel, utilizing a portable large-section anemometer to ensure the accuracy of the experimental data. The test setup comprised the tunnel structure, cold smoke device, and corresponding measuring systems. As cold smoke could not replicate the thermal buoyancy of real fires, full-scale thermal smoke simulations were performed using a fire dynamics simulator(FDS) and computational fluid dynamics software developed by NIST, which was validated for fire dynamics studies through multi-scale tests. Building on this, the smoke flow was analyzed under various air supply and exhaust conditions, with cross-passage wind speeds compared between the cold smoke experiments and FDS-simulated real fire scenarios. [Results] First, the simulation data obtained under fire-free conditions were consistent with the results of cold smoke tests, verifying the feasibility of the numerical simulation method. Second, real fires generate significant heat, causing hot smoke to rise owing to thermal buoyancy. This enhances vertical airflow in the tunnel and results in higher cross-passage wind speeds compared with cold smoke tests, though the velocity increase was limited by wall friction. Third, the distance(spacing) between air supply and exhaust ports, along with the status of platform screen doors, alters the inter-tunnel pressure differential; furthermore, the presence of a train can obstruct pressure-driven airflow, slightly reducing cross-passage wind speed. Fourth, cold smoke tests confirmed that a rational ventilation design can achieve the cross-passage wind speeds exceeding 2 m/s. Fifth, the ventilation modes corresponding to Conditions 1-3, 2-3, and 3-3 effectively increased wind speeds in both tunnels and cross-passages across different train positions and fire locations. [Conclusions] Based on the study results, the following conclusions are drawn: first, cold smoke experiments demonstrated that optimized ventilation can maintain a cross-passage wind speed exceeding 2 m/s during emergencies. This indicates the feasibility of eliminating fire doors, which could reduce construction and maintenance costs and enhance cross-passage evacuation efficiency. Second, ventilation Conditions 1-3, 2-3, and 3-3 optimize the emergency ventilation effect of metro tunnels, providing practical references for engineering applications. Third, the validity of the effective model is confirmed by the consistency between the fire-free simulation results and experimental data. In fire scenarios, cross-passage wind speed is influenced by thermal buoyancy, smoke viscosity, and smoke density. Among them, thermal buoyancy increases the speed, whereas wall friction suppresses it.
Optimization of measurement location for absolute gas emissions in large-section highway tunnels
WU Zhiwei;HUANG Fei;LI Shuqing;ZHENG Guangyi;LYU Chenhui;YAN Wenchao;Hunan Vocational Institute of Technical;[Objective] Since 2021, 47 tunnel gas accidents have been reported in China, resulting in over 160 deaths. Gas disasters are among the major hazards in highway tunnel construction in western China, posing a serious threat to construction safety. The absolute gas emission rate is an important indicator for determining the type of gas formation or gas work area in highway tunnels, influencing project investment, construction efficiency, equipment selection, safety measures, and management systems. However, the method for measuring the absolute gas emission rate of highway tunnels provided in the Technical Specification for Design and Construction of Highway Gas Tunnels(JTG/T 3374—2020) relies on empirical values, and the gas concentration is taken as the maximum value, which may result in considerable discrepancies between the calculated results and the actual situation. In addition, the wind speed measurement points in the return air section are subdivided into multiple grids, resulting in many measurement points. Under the working conditions of large-section highway tunnels, accurately measuring wind speed at these points is challenging, resulting in inaccurate calculations of absolute gas emissions. [Methods] Based on the Huangjiagou Tunnel of the T3 section expansion project on the Chongqing Zunyi section of the Lanzhou Haikou National Expressway, Fluent software was used to numerically simulate the gas behavior in the tunnel. The left-side tunnel was excavated for 200 m, encountering coal seams for research. The air duct outlet was 10 m from the tunnel face, with a 2 m diameter, and its center was 5 m above the ground. The outlet was located at the arch waist on the right side of the tunnel, adjacent to the inner wall. The model was constructed according to the actual tunnel dimensions and appropriately simplified to analyze the distribution laws of the airflow and gas concentration fields in the large-section highway tunnel. The measurement position for absolute gas emissions in the highway tunnel was optimized. MATLAB software was used to fit the wind speed and gas concentration at a section 120 m away from the tunnel face. Onsite testing was conducted to verify the numerical simulation results, which showed good agreement with theoretical values. [Results] The flow law of gas in the tunnel under ventilation conditions was analyzed through numerical simulations, and the effects of different gas emission rates and ventilation air volumes on the determination of absolute gas emission rates were analyzed. By selecting a section at a suitable distance from the palm surface for wind speed and gas concentration measurements, the number of measurement points can be reduced to six, decreasing onsite labor intensity and considerably improving the accuracy of gas emission measurements. [Conclusions] Based on the actual working conditions of the tunnel, a section 120 m from the tunnel entrance was selected for the measurement of absolute gas emissions. The number of absolute gas emission measurement points can be reduced from 26 to 6, and the correction coefficient K of the absolute gas emission calculation formula is 7.9. Five different absolute gas emission conditions were simulated at the same air volume, and the calculated values had errors of less than 8% compared with the theoretical values, indicating good accuracy.
Rapid masonry technology for geomechanical modelling of high arch dams
LIU Yaolai;YANG Junyi;YUE Songyu;XING Jianying;YU Jiyuan;LIU Yaoru;[Objective] Geomechanical model tests are widely used in rock engineering design and construction， especially in water conservancy， mining， and tunneling. These tests are vital for understanding the stability of high arch dams and the reinforcement measures of dam foundations. However， traditional masonry techniques often rely on manual operation， which is time-consuming and labor-intensive and prone to inaccuracies in layout. [Methods] We proposed a rapid masonry technology that integrates rapid determination of similar material ratios， small-block pressing for model masonry， and guide-rail laser positioning. Through material experiments， we obtained 236 sets of similar material specimens. Utilizing these samples and a CPO-BP neural network， we developed a surrogate model with the rock deformation modulus， scaled according to geometric similarity， as the input and the mass ratios of four materials， namely barite powder， bentonite， water， and glue， as well as the specimen density， as output. This model enables quick calculation of the ratio of each component in the model and the density corresponding to their mechanical properties， achieving a mean absolute error of 2%. In addition， we designed compression equipment for the small blocks used in model masonry， which can simulate rock joints and fissures. The setup includes a support frame， air pressure top， block mold， and cover plate opening and closing device. Users can select molds based on their needs， allowing for automated pressing of small blocks with minimal effort， thereby enhancing compression efficiency and significantly reducing labor costs. Moreover， we developed a guide rail laser positioning device for accurate model layout. When coordinate information is input into the control box， the device uses a servo motor to drive a slider carrying a laser rangefinder to specified locations， enabling rapid and precise mapping of structural planes， valley terrain， and arch dam bodies. [Conclusions] Practical applications of this model demonstrate that this method significantly reduces the one-year cycle required by traditional model masonry methods to approximately four months， greatly improving the efficiency and accuracy of geomechanical model construction for arch dams. The findings provide valuable guidance for enhancing the speed and precision of geomechanical model testing while offering a reliable reference for optimizing model material usage.
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Study on the road performance of basalt fiber reinforced asphalt mixture by test and discrete element simulation
Wu Kun;HE Wanping;Xiong Liwei;Ma Jie;Chen Yu;Huang Xin;Li Changhui;Qi Lin;Sun Bowei;Erwin Oh;Asphalt mixture is a widely used pavement material in road engineering and airport engineering， and fibers can significantly enhance its road performance. However， research on the uniaxial compressive performance of fiber-reinforced asphalt mixtures and the microscopic enhancement mechanism of fibers remains limited. The basalt fiber reinforced asphalt mixture is taken as the research object. The basalt fiber reinforced asphalt mixture material tests， such as Marshall test and uniaxial compressive tests， are carried out to study the effect of basalt fiber content on the physical and mechanical properties of asphalt mixture， such as bulk density， stability， flow value， and compressive strength. Based on the discrete element simulation， a numerical model for basalt fiber reinforced asphalt mixture is established， where the fibers are modeled as clumps， aggregates with diameter larger than 2.36 mm are represented as balls， and the asphalt mortar， composed of aggregates smaller than 2.36 mm and base asphalt， is simulated using a contact model. The discrete element model is verified with the test results and the contact parameters are calibrated. The whole process of crack formation， development and failure of asphalt mixture under uniaxial compression is studied. The results show that (1) With the increase of fiber content， the bulk density and voids filled with asphalt gradually decrease， the void content of asphalt mixture， the optimum asphalt binder content and mineral aggregate voidage of asphalt mixture increase; (2) the incorporation of basalt fibers significantly enhances the mechanical properties of asphalt mixtures， including Marshall stability， flow value， and compressive strength. Compared to asphalt mixtures without fiber， the uniaxial compressive strength increased by 13.2%， 43.3%， and 8.3% at fiber content of 0.2%， 0.3%， and 0.4% by weight， respectively; (3) Fiber content significantly influences the axial compressive performance of asphalt mixtures. The peak value of compressive strength arises at 0.3% fiber content for the asphalt mixtures in the study. When the basalt fiber content is below 0.6%， the compressive strength initially increases then decreases with rising fiber content， yet remains higher than that of mixtures without fiber. Conversely， when fiber content exceeds 0.6%， the compressive strength falls below that of mixtures without fibers; (4) The discrete element model of basalt fiber reinforced asphalt mixtures established accurately simulates the uniaxial compression process. Microstructural analysis reveals that with increasing basalt fiber content， edge fragmentation phenomena and crack propagation in asphalt mixture specimens are significantly reduced， while the number of interparticle contacts markedly increases. Analysis indicates that the discrete element model of asphalt mixtures developed using discrete element modeling software can accurately simulate the internal microscopic mechanisms during uniaxial compression， revealing the influence of basalt fibers on contact evolution and crack propagation within the mixture. Adding an appropriate amount of basalt fibers can enhance the physical and mechanical properties of asphalt mixtures. However， excessive fiber content may lead to fiber aggregation phenomena， resulting in performance degradation. Therefore， for practical engineering applications， the optimal fiber dosage should be determined through experimental testing and theoretical analysis based on specific conditions. The research results have significant reference value for the design of fiber asphalt mixture pavement or airport runway.
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Effect of soaking time on the physicochemical properties and mineralization efficiency of low-calcium fly ash–CO2
LI Qian;PENG Jiansong;XIA Binwei;[Objective] The global greenhouse effect is escalating， leading to the progressive deterioration of ecosystems and climate worldwide. As the primary greenhouse gas， reducing CO? emissions is crucial for effectively mitigating this effect. Fly ash–CO? mineralization and sequestration technology represents a promising approach for carbon fixation and emission reduction. However， the low carbonation efficiency of fly ash–CO? remains the central constraint hindering effective CO? mineralization and sequestration. Thus， elucidating the microscopic mechanisms and key influencing factors of fly ash–CO? carbonation is essential toward addressing this limitation. [Methods] To investigate these issues， a custom-designed setup was used to conduct experiments， including conventional immersion， immersion–carbonation， and microstructural characterization tests to examine the effects of immersion time on alkaline metal ion leaching and diffusion， as well as the impact of the microstructures of fly ash and CO? on the carbonation efficiency. [Results] Results show that the pH increase rate exhibited a negative exponential decay relative to immersion time. After 24 hours of immersion， the carbonation efficiency and sequestration capacity reached peak values of 12.855% and 12.91 kg/t， respectively， representing a 0.25-fold increase over non-immersed fly ash. Raw， unmineralized fly ash contains amorphous silica (SiO?)， mullite (Al?SiO?)， and amorphous silica hydrate (SiO?·xH?O). No diffraction peaks were detected for calcium carbonate， calcium hydroxide， or magnesium hydroxide， confirming the absence of calcium carbonate in the original sample. Conversely， the mineralized sample contained phases such as amorphous silica hydrate (SiO?·xH?O)， quartz (SiO?)， mullite (Al?SiO?)， calcium carbonate (CaCO?)， and hydroxides (Ca(OH)? and Mg(OH)?). The absence of the magnesite diffraction peak indicated that magnesium did not participate in the mineralization reaction. Furthermore， the observed low-intensity diffraction peaks were broad， indicating low sample purity and small crystal size， confirming the predominantly amorphous composition of the matrix. The diffraction-peak intensity of calcium carbonate initially increased and then decreased with increasing immersion time， with the maximum mass fraction (1.10%) observed at the 24-hour mark. Raw fly ash particles were spherical and dispersed. By comparison， the carbonated samples exhibited agglomeration and cementation， peaking at the 24-hour mark， with amorphous calcium carbonate deposited on the particle surface. Additionally， the carbon content of the carbonated fly ash increased with immersion time (within 24 hours)， indicating a higher carbonation degree. The frequencies of larger and smaller particles increased and decreased， respectively， with the immersion time (≤ 24 h)， suggesting positive and negative correlations between larger and smaller particles and the carbonation degree， respectively. [Conclusions] This study investigated the leaching and diffusion characteristics of fly ash–derived alkaline metal ions and their impacts on the microphysicochemical properties of fly ash， as well as their relationship with CO2 mineralization efficiency. Through a series of experiments involving fly ash immersion across different durations， followed by mineralization tests and microstructural characterization of the mineralized fly ash， the influences of soaking time on the leaching and diffusion behavior of alkaline metal ions were evaluated. Additionally， the effects of leaching on the microstructure of fly ash， as well as the efficiency of CO? mineralization， were examined. Overall， these findings provide theoretical guidance for optimizing reaction parameters and enhancing mineralization efficiency in fly ash–CO? mineralization processes.
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Experimental platform for the visual display of the Pockels effect in electro-optic crystals: design and pedagogical application
WENG Yunqi;WU Jiawei;HUANG Yifan;[Objective] The Pockels effect is a foundational principle in the interdisciplinary field of optics and electromagnetism. However， existing experimental methods are incapable of directly measuring the electro-optic phase delay. These methods present several limitations， including dependence on optical power， a high threshold for experimental comprehension， and a disconnect between theoretical principles and concrete cognition. This paper proposes a visualized measurement platform for the Pockels effect that intuitively presents the dynamic variation of electro-optic phase delay under voltage modulation. The platform exhibits core performance characteristics of a wide measurement range and high linearity. The integration of simulation modeling with physical experiments in the teaching process is shown to facilitate the establishment of a concrete correlation between the electric field and phase delay for students. This approach also enhances comprehension of the Pockels effect and improves the quality and efficiency of experimental instruction. [Methods] The visualization platform for measuring the Pockels effect is based on a linear demodulation mode of electro-optic phase delay， implemented through both simulation and experimentation. The specific technical route is as follows. A laser generates linearly polarized light using a polarizer， which then passes through a BGO crystal and a quarter-wave plate. The application of an electric field modulation induces rotation of the polarization plane of the linearly polarized light. The emerging light subsequently passes through an S-wave plate and a polarizer， where the S-wave plate converts linear polarization into radial polarization. When combined with a polarizing filter， the linearly polarized light is transformed into a light and dark gradient ring. The ring rotates in response to changes in the polarization plane angle. Accordingly， real-time detection of the electro-optic phase delay is achieved by observing the rotation of the ring. An image-processing system is proposed to determine the rotation angle of the ring， incorporating image preprocessing， edge detection， and circular positioning. The rotation angle and the corresponding electro-optic phase delay are obtained by plotting the radial gray-value distribution of the ring and calculating the horizontal displacement of the gray-value characteristic curve. [Results] Simulation results show that the proposed measurement system produces a ring spot that rotates with changes in the applied voltage. The electro-optic phase delay angle is found to be twice the rotation angle of the ring. Physical experimental results demonstrate that the system can achieve a dynamic measurement range of 0 to 360° of electro-optic phase delay. The observed phase delay varies linearly with the applied modulation voltage. The measured linearity is 0.47%， with a maximum error not exceeding 1.5%. [Conclusions] This paper provides a comprehensive evaluation of the feasibility of a visual display platform for demonstrating the Pockels effect in electro-optic crystals from three perspectives: theoretical derivation， simulation modeling， and experimental verification. The use of simulation models enhances students’ understanding of the underlying principles of the Pockels effect， while the incorporation of physical experiments strengthens their practical skills. Overall， the platform transforms the abstract principle of the Pockels effect into an intuitive rotation of a light pattern， thereby establishing a direct visual connection between the electric field and phase delay and enabling students to apply theoretical knowledge more effectively.
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Continuous learning-based few-shot synthetic aperture radar target recognition
ZHOU Yun;LI Junyi;REN Haohao;MIAO Lei;FAN Liwei;[Objective] This study aims to address critical challenges in open-environment synthetic aperture radar (SAR) applications， where high-value targets continuously emerge but labeled samples remain scarce. The study proposes an orthogonality-constrained distribution-calibrated replay method for continuous learning in SAR target recognition. Unlike traditional deep learning models， which assume closed environments with abundant data， this method targets the stability–plasticity dilemma， aiming to resolve the dual problems of catastrophic forgetting of old knowledge and overfitting on limited new data. [Methods] First， during the initial base class training phase， the proposed method establishes a highly structured embedding space to reserve non-overlapping geometric regions for future classes. It optimizes the feature space by utilizing a combined orthogonal prototype distribution and intra-class compactness loss. Specifically， the method employs an iterative process to construct an orthogonal basis space by selecting prototype vectors with the lowest cosine similarity to existing bases and projecting them into the orthogonal complement space. This approach ensures that the embedding space is inter-class separable and intra-class compact， leaving adequate room for future incremental classes. When new classes are accommodated， a dual knowledge preservation method is proposed to mitigate catastrophic forgetting of old knowledge during incremental updates by integrating orthogonal gradient projection and distribution-calibrated replay. Orthogonal gradient projection minimizes interference with established knowledge by constraining the update direction. It projects gradient updates into the orthogonal space of the base class feature matrix， such that the model’s response to old classes remains invariant. However， achieving a strictly orthogonal space is challenging， and gradual drift still occurs. To further recall old class knowledge from the feature distribution of previous classes， we employ distribution-calibrated replay to reinforce historical knowledge by generating and rehearsing high-fidelity pseudo-features. This strategy utilizes a Gaussian sampler based on the statistics of old classes and introduces a learnable recursive calibrator to correct deviations between the sampled Gaussian distribution and the complex real feature distribution. By minimizing the Kullback–Leibler (KL) divergence between the generated and real distributions， this module replays high-quality pseudo-features that effectively consolidate memory. To enhance the model’s robust generalization on scarce new classes， a self-supervised progressive learning strategy is proposed that advances from easy to hard tasks， ensuring effective feature mining from limited samples. This includes a rotation-based self-supervised branch optimized with an uncertainty-weighted focal loss， which effectively optimizes the feature extractor. The self-supervised branch encourages the model to learn azimuth-invariant features， thereby mitigating overfitting. In addition， the uncertainty-weighted focal loss dynamically assigns higher weights to hard-to-classify samples based on prediction probabilities， encouraging the model to focus on mining discriminative features. [Results] Experiment results on the moving and stationary target acquisition and recognition， and SAR-AIRcraft-1.0 datasets validate the effectiveness of the proposed method. It significantly outperforms state-of-the-art methods， demonstrating superior efficiency and stability by achieving the highest recognition accuracy with minimal accuracy drop across various scenarios， including different numbers of incremental classes， varying incremental sample sizes， and distinct datasets. Ablation studies confirm that the proposed stability and plasticity modules enhance target recognition performance. [Conclusions] By integrating orthogonal gradient projection， distribution calibration replay， and self-supervised progressive learning， this paper successfully addresses the inherent challenges in continuous learning， providing a robust solution for dynamic SAR automatic target recognition.
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Study on the design and analysis methods of orthogonal experiment
Liu Ruijiang,Zhang Yewang,Wen Chongwei,Tang Jian(School of Pharmaceutics,Jiangsu University,Zhenjiang 212013,China)The importance of orthogonal experimental design and analysis is introduced briefly.The principle and characteristic are expounded.The design methods of orthogonal experiment and analysis methods of orthogonal experimental results are analyzed in detail,which afford fully systemic methods for orthogonal experimental design and analysis.Problems in orthogonal experimental design and analysis and development of software for orthogonal experimental design and analysis are also pointed out in the end.
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Research on statistical analyses and countermeasures of 100 laboratory accidents
Li Zhihong;Training Department,Kunming Fire Command School;This paper summarizes 100typical cases of laboratory accidents from 2001and analyzes the cases in fields of accident type,accident link,accident cause,dangerous substance category,etc.The result shows as follows:the fire disasters and explosive accidents are the main types of laboratory accidents;the dangerous chemicals,instruments and equipment,and pressure vessels are main dangerous substances;the instruments and equipment and reagent application processes are the main links of accidents;the violation of rules,improper operation,carelessness,wire short circuit and aging are the main reasons of accidents.It also puts forward the countermeasures and suggestions for the prevention and control of laboratory accidents in the following aspects:establishing complete safety management system,actively promoting standard construction of laboratory safety,strengthening laboratory safety education and training,and formulating and improving emergency plans for laboratory accidents.
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Promotion of reform and innovation on integration of theory teaching and experimental teaching by virtual simulation experiment teaching
XIONG Hongqi;Based on the concept of experimental teaching and its importance, the connotation of virtual simulation experimental teaching is expounded upon. On this basis, this paper puts forward six balance principles that virtual simulation experimental teaching should follow to promote the upgrading and reconstruction of traditional experimental teaching and elaborates the reform idea of virtual simulation experiment teaching for the overall optimization and innovation of theory teaching. The brief analysis is carried out on that the introduction of virtual simulation experimental teaching is conducive to promoting innovation and entrepreneurship education into the whole process of professional education.
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The application of studying fluorescence spectroscopy on protein
Yin Yanxia,Xiang Benqiong,Tong Li(College of Life Science,Beijing Normal University,Beijing 100875,China)Fluorescence spectroscopy is very important for studying protein structure and conformation changes.The concept and principle of fluorescence spectroscopy are introduced at first,then the application of studying fluorescence spectroscopy on protein is explained.
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Research and application of BOPPPS teaching method in MOOC teaching design
WU Changdong;JIANG Hua;CHEN Yongqiang;School of Electrical Engineering and Electronic Information,Xihua University;School of Information Science and Technology,Southwest Jiaotong University;On the basis of introducing the connotation of BOPPPS(bridge-in,objective,pre-assessment,participatory learning,post-assessment and summary)model,this paper explores upon the guiding role of the BOPPPS teaching model in MOOC teaching design.Based on the BOPPPS model,MOOC teaching design of"Series feedback voltage stabilization circuit"is carried out.This provides some reference for improving the quality of MOOC teaching design,stimulating students' learning interest and motivation,and promoting teachers' reform of teaching content design.
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The CNC machine tool with systematic work process and its application of teaching design
Li Yanxian(Department of Mechanical and Electronic Engineering,Nanjing Communications Institute of Technology,Nanjing 211188,China)According to professional training objectives and the main jobs of the structure of vocational skills and knowledge required to "CNC machine tools and spare parts" for the carrier,taking the CNC programming and operation of capacity-building as the center,this paper shows the design of the "knowledge of CNC machine tools,observation and analysis of CNC lathes,CNC milling machine to observe and analyze the processing center,programming and processing stepped shaft,threaded shaft of the programming and processing,hand wheel slot programming and processing,convex programming and processing of the template,the base of the programming and processing"of 9 items,25 learning environment,67 tasks,and one of the "convex template programming and processing" learning environment for the teaching unit design.
[Downloads: 383,437 ] [Citations: 6 ] [Reads: 89 ] HTML PDF Cite this article
Study on the design and analysis methods of orthogonal experiment
Liu Ruijiang,Zhang Yewang,Wen Chongwei,Tang Jian(School of Pharmaceutics,Jiangsu University,Zhenjiang 212013,China)The importance of orthogonal experimental design and analysis is introduced briefly.The principle and characteristic are expounded.The design methods of orthogonal experiment and analysis methods of orthogonal experimental results are analyzed in detail,which afford fully systemic methods for orthogonal experimental design and analysis.Problems in orthogonal experimental design and analysis and development of software for orthogonal experimental design and analysis are also pointed out in the end.
[Downloads: 55,556 ] [Citations: 3,431 ] [Reads: 813 ] HTML PDF Cite this article
Construction and actualization of new experimental teaching system for chemical specialty
YANG Jin-tian(Institute of Life Science,Huzhou Normal College,Huzhou 313000,China)The new system of chemical experiment teaching is constructed,and the comprehensive experiments,open experiments and research-oriented experiments are set up to improve the degree of source sharing,the efficiency of using equipment and the quality of experimental teaching,hence efficiently optimizing the practical abilities and fostering innovative spirit for the undergraduates are achieved.
[Downloads: 24,299 ] [Citations: 11 ] [Reads: 829 ] HTML PDF Cite this article
Research on statistical analyses and countermeasures of 100 laboratory accidents
Li Zhihong;Training Department,Kunming Fire Command School;This paper summarizes 100typical cases of laboratory accidents from 2001and analyzes the cases in fields of accident type,accident link,accident cause,dangerous substance category,etc.The result shows as follows:the fire disasters and explosive accidents are the main types of laboratory accidents;the dangerous chemicals,instruments and equipment,and pressure vessels are main dangerous substances;the instruments and equipment and reagent application processes are the main links of accidents;the violation of rules,improper operation,carelessness,wire short circuit and aging are the main reasons of accidents.It also puts forward the countermeasures and suggestions for the prevention and control of laboratory accidents in the following aspects:establishing complete safety management system,actively promoting standard construction of laboratory safety,strengthening laboratory safety education and training,and formulating and improving emergency plans for laboratory accidents.
[Downloads: 10,558 ] [Citations: 557 ] [Reads: 89 ] HTML PDF Cite this article
Practice and thinking of education of“College Students' Innovative and Entrepreneurial Training Program”based on tutor system
Qian Xiaoming;Rong Huawei;Qian Jingzhu;Office of Academic Affairs,Nanjing University of Technology;The innovation and entrepreneurship education has been included in the teaching and education program of college schools."College Students' Innovative and Entrepreneurship Training Program "has become an"Excellent Program"as one of the most important reform tasks in Ministry of Education.The tutor system is an effective way of innovative education and pilot training for both college schools and students.Students learn the method of innovation researches and technique of entrepreneurial process through the program.In the meanwhile,teachers in college schools find a new stage to improve their teaching ability.This article focuses on the project,practice and feasibility of the"College Students' Innovative and Entrepreneurial Training Program "under the tutor system.
[Downloads: 10,094 ] [Citations: 225 ] [Reads: 822 ] HTML PDF Cite this article