To investigate the features and causation factors of fire accidents in SRBE，118 fire accidents were studied using method of mathematical statistics. Firstly，accident features were mined in terms of the temporal and spatial attributes of accidents，the three elements of fire and the severity of injuries. Then，based on the improved HFACS-SRBE accident causation model，methods such as Chi-square test，OR and Cramer's V were used to analyze the correlations and their strength between the causal factors. The results show that 14:00-16:00 is the most prone to fire accidents and casualties. The main location of fire accidents is in the ship area，accounting for 33.90%. 59.19% of the ignition source comes from the ignition operation. Ratio of no injuries，slight and minor injuries，serious injuries and deaths is 61:54:3. Through the test of correlations and their strength，it is determined that 15 groups of adjacent level causal factors are correlated，and 26 complete accident causation chains are obtained. Covers communication and coordination→inappropriate operation plans→bad psychological state→decision-making errors is the accident causation chain with the greatest strength of correlation leading to the occurrence of fire accidents in ship repair and building enterprises.

In order to clarify inerting effect of liquid nitrogen on the thermal runaway explosion of a 280Ah energy storage lithium battery，based on experiment analysis of composition and explosion limit of battery thermal runaway gas，FLACS was used to simulate explosion overpressure of battery thermal runaway gas in a storage container. Standard experiments and real experiments were carried out to analyze inerting effect of liquid nitrogen on battery thermal runaway gas. Results show that thermal runaway gas explosion overpressure increases gradually with an increase of its volume. Ignition of more than 1.1 m³ of thermal runaway gas can cause serious consequences. A single 280 Ah lithium iron phosphate battery in 100% charged state，heating in a vacuum state，heating in a vacuum state can trigger thermal runaway of the battery and produce 134.6 L of thermal runaway gas with CO₂，H₂，CO，CH₄ and C₂H₄ as the main components. Thermal runaway gas is a flammable gas，and explosion limit range is between 8.5% and 45.5%. N₂ can effectively inert thermal runaway gas and significantly reduce the explosion limit range of thermal runaway gas. Limiting N₂ volume fraction is 84.7%. Spray 69 kg liquid nitrogen into a 35 m³ energy storage container to inert battery thermal runaway gas. When volume fraction of N2 is higher than limiting nitrogen volume fraction，battery thermal runaway gas can be effectively inerted，and effective protection time is 2 200 s.

Equipment and facility failures were the primary cause of safety accidents in public transportation systems. In order to better quantify and enhance the safety resilience of systems，CN-FRAM operational safety resilience measurement model，integrating CN and FRAM，were proposed. System resilience was defined as the ratio of system performance loss to performance baseline under perturbations. Firstly，based on the composition and functional nodes of the equipment and facility system，a CN was established. Secondly，the FRAM model was embedded into the CN to expand nodes and connections，constructing the CN-FRAM model. Then，based on the CN-FRAM resilience measurement model，the aggregation of functional changes between system components was analyzed，and when quantifying system resilience，the overall efficiency of the network and the degree of coupling between components were considered comprehensively. Finally，using the metro signal system in Nanjing as an example，the feasibility and effectiveness of the method were validated. The results show that the model can quantify the resilience of the system throughout the disruption-recovery process，calculate the impact of failures on the system，and maximize resilience values as the objective，demonstrating resilience performance under different repair strategies，thereby providing a basis for determining the optimal recovery sequence. Compared with existing methods，the optimal recovery strategies identified by this method can significantly reduce the overall performance loss caused by failures，thus enhancing system resilience.

In order to reduce gas explosion accidents during the production，transportation and storage of combustible gases in industrial sites，square pipes of 200 mm×200 mm×35 m and round pipes of 90 mm diameter and 10 m length were independently constructed. Under the same initial conditions，the explosion test of methane/air premixed gas with volume fraction of 9.5% was carried out，and it was studied with pressure and flame sensors. The results show that the evolution process of the wave system in two kinds of pipes with different scales and cross sections is the same. After ignition，the flame changes from layer to turbulent flow，and the acceleration of flame leads to the compression wave chasing each other，finally forming a strong shock wave. The changing trend of flame speed in the two long straight pipes is the same，and they both experience the process of acceleration-deceleration-re-acceleration-re-deceleration，with the maximum flame speed in the square tube and round tube reaching 69 and 35.7 m/s respectively. After the first compression wave reflects off the wall，the pressure rises to 117% and 114%. When the reflected wave is coupled with the flame front，the flame speed in the large-scale pipeline is reduced to 73%，and that in the small pipeline is reduced to 93%. Under the same volume fraction，the maximum overpressure values of the first compression wave in the two long straight spaces are similar，which are about 65.45 and 67.09 kPa.

In order to reduce the safety problems caused by leakage of hydrogen-blended natural gas during the distribution，based on fluid mechanics and porous media theory，a three-dimensional numerical model of leakage and diffusion of urban buried hydrogen-blended natural gas pipeline was established by Fluent software. The effects of hydrogen blending ratio，leakage aperture，pipeline pressure，pipeline buried depth and soil type on the leakage of hydrogen-blended natural gas and the vertical diffusion distance of the lower explosion limit of methane and hydrogen were analyzed. The results show that the larger the proportion of hydrogen blending，the smaller the leakage of hydrogen-blended natural gas，and the longer the time it takes for the methane explosion lower limit contour to diffuse to the surface，while the opposite is true for hydrogen. Secondly，the leakage amount is about twice as much as 5 mm when the leakage aperture is 10 mm. The leakage amount is about twice as much as 10 mm when the leakage aperture is 20 mm. The larger the leakage aperture，the shorter the time required for the lower explosion limit of methane and hydrogen to reach the surface. Thirdly，the greater the pipeline pressure，the greater the leakage of hydrogen-blended natural gas and the faster the diffusion speed，and the higher the risk coefficient. Besides，when the buried depth of the pipeline is 1.1m，the leakage is largest，followed by 1.4 m and 0.8 m. The shallower the buried depth，the shorter the time required for the lower explosion limit of methane and hydrogen to reach the surface. Finally，the soil type has an important influence on the leakage and diffusion of hydrogen-blended natural gas. When the soil type is silty sand，the leakage and diffusion rate of hydrogen-blended natural gas are the largest，followed by loam and finally clay.

In order to realize the effective rescue of various complex rail transit accidents，the present situation and development trend of the existing rail fire rescue systems at home and abroad were analyzed through a literature search first. Then，the applicability of road and rail dual-purpose vehicles in mountain urban rail transit systems and the feasibility of modular transformation were summarized and analyzed. Finally，a new fire and rescue rail transit system was proposed，which was suitable for mountain urban rail characteristics. The results show that the designed road and rail dual-purpose fire rescue vehicle meets the requirements of track fire rescue. The system is adopted with a high-intensity modular and prefabricated design concept. It is equipped with a fire extinguishing and smoke exhaust system for controlling various fire conditions，a traction winch，emergency power generation，medical supplies，and other emergency rescue equipment，which can deal with the rescue work of track accidents in a closed and heavy smoke environment. The loss caused by accidents is significantly reduced.

In order to ensure the safety of the construction and operation of the karst water inrush tunnel，based on the elastic beam model，double cusp mutation model of the instability of the karst water inrush roof under dynamic disturbance was established by using the catastrophe theory. Considering the surrounding rock properties，hydrostatic pressure，dynamic disturbance and other factors，the instability mechanism and failure conditions of the roof of karst water inrush tunnel were analyzed，the discriminant equation of its instability mutation was established，and the minimum safe thickness of the roof was solved by Matlab software programming. At the same time，in order to avoid the irrationality of the theoretical formula of the mutation when the hydrostatic pressure was too large，the minimum safe thickness of the hydrostatic pressure was calculated separately，and the greater value of two calculated values was taken. The results show that whether the waterproof rock mass remains stable is determined by the factors the internal and external factors of rock mass. The minimum safe thickness of the rock mass increases with the increase of the span of the rock mass，and decreases with the increase of the elastic modulus of the rock mass. When the vibration frequency is constant，the greater the blasting load，the greater the minimum safe thickness of rock mass. When the blasting load is constant，the greater the frequency of blasting vibration，the smaller the minimum safe thickness of rock mass. The greater the hydrostatic pressure，the greater the minimum safe thickness of rock mass. The engineering example shows that this method of calculating the safety thickness of the roof of karst tunnel is feasible and highly accurate.

In order to improve the safety level of China Civil Aviation，a cause analysis method，which focused on the whole process of 'taxiing-takeoff-climbing-cruising-falling-approaching and landing'，was proposed based on association rules and SNA. Firstly，a total of 1 051 civil aviation accident cases from 2010 to 2022 were collected from Aviation Safety Information System. Then，a civil aviation accident causation index system based on 'human-machine-environment-management' was established in combination with 'control navigation service procedure-training'. Secondly，the EasyData data service platform was used for annotation，followed by constructing the data-set of the cause of civil aviation accidents facing the whole process of flight. Furthermore，the FP-Growth algorithm was employed to mine the association rules with the flight phase as the subsequent term of rules. Finally，this study emphasized the co-occurrence frequency of association rules，and developed the correlation network of civil aviation accident causes by applying the centrality analysis of flight phase and accident causes. The results show that the most dangerous phases of flight are the approach and landing. Operation failures，runway safe accidents and cabin safe accidents are the main types. Among the 10 identified causes of civil aviation accidents，there are 4 human factors，2 facilities and equipment factors，3 environmental factors and 1 management factor.

In order to solve the problem that a large amount of multi-source heterogeneous structured and unstructured knowledge in the operation and management of cable crane is difficult to reuse，a large number of technical specifications，expert experience and other safety knowledge accumulated in the installation and operation and maintenance of cable crane were analyzed，and related entity classes of cable crane operation were extracted. A quintuple model was used to structurally express the safe operation of the ontology knowledge of the cable crane，and the binary relationship between classes was established. Then，the ontology expression language in Protégé was used to represent it programmatically. The ontology knowledge base of the cable crane entity，safety early warning and an emergency plan was constructed. 3D scene model of the cable crane was constructed using 3Dmax software，and then the model was imported into Unity3D engine. Knowledge retrieval of the ontology knowledge base was realized through user interface design and interaction functions in the engine. At the same time，based on the existing examples of faults and accidents，the corresponding emergency plans were associated with the hidden dangers existing in each entity of the cable crane. Finally，a complete 3D visualization platform for safe operation knowledge retrieval of cable cranes was constructed. The results show that all kinds of safe operation knowledge of cable-winch can be centrally and effectively managed by constructing an ontology knowledge base，and a knowledge retrieval platform combined with an ontology knowledge base can effectively realize efficient query and reuse of knowledge.

To improve the synergistic explosion suppression and flame retardant efficiency of inert gas-water mist，based on spectral experiments，theoretical analysis and numerical simulation methods such as Fluent and CHEMKIN-PRO were used to study the changes in elementary reactions and typical free radical (H· and ·OH) molar fractions during the explosion suppression and flame retardant process of N₂ water mist at different injection positions and pressures. The results showed that staggered injection of N₂ and fine water mist had better synergistic explosion suppression and flame retardant effect than convection and parallel injections. For case of simulated pipeline，good explosion suppression and flame retardant effect were found only when the spray pressure of N₂ and water mist was 4.5 and 2 MPa，respectively. Furthermore，the maximum value of mole fraction for H· and ·OH was 0.006 4 and 0.006 9，respectively. The spray pressure can be applied to the actual methane explosion fire area based on scale effect. Moreover，the H· and ·OH mole fractions can be used as monitoring parameters during the operation of the current automatic fire extinguishing system in the fire protection area，and their changes can be used as a reference for fire extinguishing process.