30 September 2026, Volume 52 Issue 3

    

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  Analysis of multi-type abnormal passenger flow in urban rail transit based on spatiotemporal Moran’s I

  Sun Shichao, Song Xinrui

  Journal of Dalian Maritime University. 2026, 52(3): 1-12. https://doi.org/10.16411/j.cnki.issn1006-7736.2026.03.001

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  Abnormal passenger flow poses a significant challenge to the operational safety of urban rail transit. Accurate early warning and effective response depend on a deep understanding of the spatiotemporal patterns of such flows. However, existing studies still lack a systematic comparative analysis of the characteristics of abnormal passenger flow under different types of events. To address this gap, this study took the Shenyang rail transit network as the research object and constructed a spatiotemporal Moran’s I model based on passenger flow fluctuations to compare and analyze the spatiotemporal evolution characteristics of abnormal passenger flows under three types of events: large-scale activities, holidays, and severe weather. The findings reveal that all three types of abnormal passenger flows exhibit significant spatiotemporal positive correlations, yet their evolution patterns differ markedly: large-scale activity passenger flows show a non-diffusive characteristic of “localized aggregation with strong periodicity”, featuring high spatiotemporal impact intensity but limited spatial scope; holiday passenger flows demonstrate a multi-center diffusion pattern with “wide influence range and long duration”, driven primarily by the functional substitution of stations rather than mere demand increase; severe weather intensifies rigid commuting demand while suppressing flexible travel, leading to further concentration of passenger flow at key commuting stations. Under composite event scenarios, passenger flow structures present a composite pattern resulting from the synergistic interaction between dominant and background events. The findings of this study can provide a decision-making basis for differentiated operational management and scheduling strategies under different types of abnormal passenger flow events, while also offering theoretical support at the feature construction and data augmentation levels to address the bottleneck of “scarce samples and difficult learning” in abnormal passenger flow prediction.

  
  
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  Research on hydrodynamic cavitation-enhanced NaClO₂ treatment of marine diesel engine exhaust

  Wang Peihan, Zou Bo, He Xinhai, Yang Yundi, Yang Jingang, Song Liguo

  Journal of Dalian Maritime University. 2026, 52(3): 13-22. https://doi.org/10.16411/j.cnki.issn1006-7736.2026.03.002

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  To address the technical bottlenecks of low NO_x removal efficiency and gas-liquid mass transfer limitation in wet treatment of marine diesel engine exhaust, an on-board experimental platform was established based on the actual exhaust gas conditions of the diesel generator aboard the training ship “Yukun”, and a systematic investigation was conducted on hydrodynamic cavitation-enhanced desulfurization and denitrification by using NaClO₂ solution. The effects of NaClO₂ concentration and Cl^- concentration in the freshwater system, as well as the pressure difference across the cavitation reactor, solution temperature, and initial pH in the seawater system, on the NO_x and SO₂ removal performance from exhaust gas were investigated, respectively. Results show that hydrodynamic cavitation can significantly enhance the simultaneous removal of NO_x and SO₂ in low-concentration NaClO₂  systems. The denitrification performance in seawater is significantly better than that in freshwater. In addition, the effects of the pressure difference across the cavitation reactor, solution temperature, and initial pH on denitrification performance all exhibit optimal ranges. The optimal operating conditions determined within the scope of this study are as follows: NaClO₂ seawater solution at a concentration of 0.3 mmol/L, a pressure difference of 500 kPa across the cavitation reactor, a solution temperature of 30 ℃, and an initial pH of 6. This technology can effectively meet the practical treatment requirements of marine diesel engine exhaust and has good application potential.

  
  
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  Synthesis raw material ratio and denitration catalytic performance of SSZ-39 zeolite

  Wu Yinhui, Wang Guangyao, Liang Peiyuan, Jie Yingze, Liu Yihao, Sun Tianjun

  Journal of Dalian Maritime University. 2026, 52(3): 23-34. https://doi.org/10.16411/j.cnki.issn1006-7736.2026.03.003

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  Ammonia selective catalytic reduction (NH₃-SCR) is an efficient technology for diesel exhaust purification. SSZ-39 zeolite catalysts exhibit excellent hydrothermal stability. To reduce the preparation cost and improve catalytic activity, SSZ-39 was synthesized by interzeolite conversion by using low-silica Y zeolite as the starting material. The effects of alkali metal, water, template agent and seed crystal dosage on the synthesis process were systematically investigated, and the optimal raw material ratio was determined. A series of transition metal-modified SSZ-39 zeolite catalysts were then obtained via ion exchange. Performance tests under simulated marine operating conditions show that compared with Fe-SSZ-39 and Mn-SSZ-39, Cu-SSZ-39 possesses more redox-active species and abundant acid sites, which can promote the reduction of NO_x by NH₃ adsorbed on Lewis acid sites. Cu-SSZ-39 thus presents outstanding NH₃-SCR catalytic performance, with 100% NO_x conversion achieved in the temperature range of 250 ℃~550 ℃. 

  
  
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  Inhibition characteristics and laws of carbon dioxide on non-premixed hydrogen-air deflagration

  Zhu Wenbin, Zhang Bin, Jiang Xin, Xia Yuanchen, Ye Ke, Zhang Siqi, Song Ruilin

  Journal of Dalian Maritime University. 2026, 52(3): 35-47. https://doi.org/10.16411/j.cnki.issn1006-7736.2026.03.004

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  In order to investigate the inhibition mechanism of CO₂ on non-premixed hydrogen-air deflagration in hydrogen storage tanks of hydrogen-fueled ships, an explosion suppression experimental platform in an enclosed space was constructed. Experimental and numerical methods were employed to reveal the inhibition mechanism of CO₂ on non-premixed hydrogen-air deflagration. By changing key parameters such as the turbulent disturbance time (ti) and filling volume fraction of CO₂, the influence laws of the above parameters on flame morphology, flame propagation velocity, deflagration overpressure and other characteristics were explored. The results show that : ①The release of CO₂ induces significant turbulent disturbances, which promote the formation of volume fraction differences within the constant-volume combustion bomb, and the flame morphology gradually evolves into a hemispherical shape, a finger shape, and flat flames with different inclination angles. ②When the injection volume fraction of CO₂ is 10% and 20%, flame propagation velocity and deflagration overpressure show a trend of decreasing initially and then increasing with the growth of ti. ③When the injection volume fraction of CO₂ increases to 40%, both flame propagation velocity and deflagration overpressure decrease gradually with the rise of ti. ④Further increasing the injection volume fraction of CO₂ continuously strengthens its explosion suppression effect. The gas distributes more uniformly inside the combustion bomb, the component stratification is weakened, and the overall suppression performance is improved. When ti = 0 s, the peak flame propagation velocity and maximum deflagration pressure for 40% CO₂ volume fraction are 41.48% and 44.1% lower than those for 10%, respectively. This study reveals the explosion suppression laws of CO₂ under non-premixed conditions, and provides a theoretical basis for formulating emergency disposal measures against deflagration in hydrogen-fueled ships.

  
  
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  Heat loss characteristics and parameter influence mechanism of underwater remotely operated vehicle heavy oil pipelines

  Sun Jianrui, Liu Xinyi, Ma Yuxin, Li Jing, Bao Yongjie

  Journal of Dalian Maritime University. 2026, 52(3): 48-60. https://doi.org/10.16411/j.cnki.issn1006-7736.2026.03.005

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  A heat loss model incorporating the temperature-dependent thermal properties of heavy oil was developed to address the heat loss during heavy oil transportation through an ROV pipeline in a low-temperature seawater environment. A thermal-fluid coupling numerical simulation method was adopted to emphatically analyze the flow patterns and heat transfer characteristics of heavy oil in the near-wall region (r/R>0.85) and the central axis region inside the delivery pipeline. The results show that under the operating conditions of a 70 ℃ preheating temperature and a mass flow rate per unit area of 1600 kg/(m²·s), in the initial section of pipeline transportation (10 meters from the inlet), the oil temperature at the axis decreases by only 0.42 ℃, while near the pipe wall boundary zone, the temperature drop reaches as high as 18.01 ℃. This leads to rapid formation of a highly viscous deposition layer on the pipe wall, which is the key factor restricting the safe transportation of heavy oil. Increasing the pipeline preheating temperature within the range of 50 ℃ to 90 ℃ can extend the effective transportation distance of heavy oil, whereas the increment decreases continuously with rising temperature, presenting a nonlinear variation trend. Although increasing the mass flux enhances heat dissipation intensity, the residence time of heavy oil inside the pipeline is shortened, thereby reducing the heat loss along the pipeline. When the mass flux increases from 1300 kg/(m²·s) to 2100 kg/(m²·s), the temperature attenuation amplitude of heavy oil in the near-wall region at a delivery distance of 100 m decreases by 19.20%. The research results reveal the influence mechanisms of preheating temperature and mass flux on the safe transportation distance of heavy oil, which can provide theoretical support for the optimization of operating parameters and quantitative evaluation of safe transportation distance in ROV-based heavy oil recovery operations under shipwreck emergency conditions.

  
  
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  Design of wrapped phononic crystals with exponentially-varying thickness and simulation of broadband vibration reduction characteristics

  Su Mengfei, Zhou Bo, Dai Changming, He Jinwei, Liu Hui, Su Gaofei

  Journal of Dalian Maritime University. 2026, 52(3): 61-70. https://doi.org/10.16411/j.cnki.issn1006-7736.2026.03.006

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  Aiming at the problem of broadband vibration damping of ship equipment and plate structures, this paper overcame the drawbacks of conventional phononic crystals characterized with narrow low-frequency band gaps and low band-gap coverage, and proposed a lightweight wrapped phononic crystal structure with exponentially-varying thickness that integrated local resonance and acoustic black hole (ABH) effects. The structure embedded hollow lead scatterers in symmetric steel plates with exponentially-varying thickness. The finite element method was adopted to calculate its band structure and vibration transmission characteristics, and the vibration reduction performance was analyzed. Results show that the structure possesses two complete band gaps within 0~1400 Hz, with a total bandwidth of 1158.68 Hz (band-gap coverage of 82.76%), and the maximum vibration transmission loss reaches 125 dB. The bandgap mechanism involve coupling between hollow scatterer torsion and acoustic black hole (ABH) structure energy convergence, along with matrix stiffness gradient regulation. Increasing the exponential height h_A or scatterer height h₂ can broaden the band gap, whereas increasing the exponential length l_A narrows the band gap width. The vibration attenuation peak of the phononic crystal sandwich plate model is approximately 180 dB, which is about 20 dB higher than that of the non-exponential structure. This verifies the remarkable advantages of the exponentially-varying thickness design in broadband vibration attenuation. The phononic crystal and its sandwich structure designed in this paper provide a new idea for broadband vibration control of ships.

  
  
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  Modal analysis of flow around a circular cylinder at low Reynolds numbers under sinusoidal oscillating inflow

  Hu Xianlei, Zhan Qingliang, Yu Lihui, Wang Zhiyong, Guo Yao, Chen Yifei, Xu Hu

  Journal of Dalian Maritime University. 2026, 52(3): 71-81. https://doi.org/10.16411/j.cnki.issn1006-7736.2026.03.007

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  Unsteady flow simulations were conducted for low-Reynolds-number circular cylinder flow under non-zero-mean sinusoidally oscillating inflow, and the wake structure was analyzed by using proper orthogonal decomposition (POD) method. Numerical simulations were performed to model flow fields around a circular cylinder under steady inflow, low-frequency sinusoidally oscillating inflow, and high-frequency sinusoidally oscillating inflow conditions, and the pressure field, streamwise velocity field, and transverse velocity field were then decomposed and analyzed respectively. The results show that sinusoidally oscillating inflow induces energy transfer to higher-order modes, requiring more modal orders to achieve the same flow field representation accuracy as steady inflow. High-frequency sinusoidally oscillating inflow reorganizes pressure-dominant modes, causing the second-order mode representing periodic fluctuating pressure to supersede the first-order mean mode. The sinusoidally oscillating inflow induces superposition of inflow frequency components onto the dominant frequency of modal temporal coefficients. When this frequency component becomes dominant, the corresponding modal contour patterns exhibit marked discrepancies from those under steady inflow. The research results can provide a theoretical reference for the fluid-solid coupling analysis and anti-vibration design of deep-sea risers and offshore wind power piles in ocean engineering under oscillating flow.

  
  
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  Static stiffness characteristics of multi-layer metal bellows under internal pressure load

  Wu Yigang, Su Jialong, Chen Peng, Zhang Guohua, Xu Shuangxi, Yang Shaoxuan

  Journal of Dalian Maritime University. 2026, 52(3): 82-90. https://doi.org/10.16411/j.cnki.issn1006-7736.2026.03.008

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  To investigate the static stiffness characteristics of marine multi-layer U-shaped metal bellows under internal pressure load, a multi-layer U-shaped metal bellows with a diameter of 250 mm was taken as the research object. Static stiffness tests and numerical simulations under coupled internal pressure were carried out to analyze the influence law of internal pressure load on the static stiffness performance of bellows. A prediction formula for static stiffness of this type of bellows under internal pressure load was derived, which can provide a theoretical reference for the design of multi-layer metal bellows under internal pressure conditions.

  
  
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  Prediction of fatigue life of Stirling engine crankshaft and sensitivity analysis of its influencing factors 

  Wang Wentong, Hu Lei, Zheng Wei, Zhang Qian, Sun Sicong, Luo Linghua, Yang Jianguo

  Journal of Dalian Maritime University. 2026, 52(3): 91-104. https://doi.org/10.16411/j.cnki.issn1006-7736.2026.03.009

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  In order to meet the urgent needs of marine Stirling engine with low noise, low maintenance and long life, this paper took the crankshaft, a transmission component with complex structure, high replacement difficulty, and a direct impact on the vibration and noise levels of the entire machine, as the research object, conducting fatigue life prediction and sensitivity analysis of key parameters. Firstly, the rigid-flexible hybrid multibody dynamics model of the high-precision Stirling engine transmission system was constructed, and the crankshaft stress load was extracted. Then, the crankshaft fatigue life was calculated by the nominal stress method based on the linear cumulative damage theory. Finally, the sensitivity of the key parameters of the crankshaft life was quantified by the multiple quadratic regression model. The results show that the minimum fatigue life of the left and right crankshafts is 29 277.78 hours and 29 824.07 hours, respectively. Among the effects of assembly and operation-maintenance parameters on the fatigue life of the left and right crankshafts, the main bearing clearance exerts the most significant influence, with its contribution ratios reaching 51.63% and 50.31%, respectively. The sensitivity analysis results of key parameters can provide an important basis for the reliability design and the formulation of whole-life-cycle operation and maintenance schemes of Stirling engine crankshafts.

  
  
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  An ontology-based holistic knowledge representation method for the safety evaluation of piled wharf structures

  Zhao Jingtong, Wang Xingyang, Cui Chunyi, Ji Zezhou, Yuan Lisha, Hou Liang

  Journal of Dalian Maritime University. 2026, 52(3): 105-115. https://doi.org/10.16411/j.cnki.issn1006-7736.2026.03.010

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  To address the difficulty in uniformly organizing and holistically representing reliability indices, grading rules, and evaluation results in the safety assessment of in-service piled wharf structures, this paper proposed an ontology knowledge base approach for the holistic representation of structural safety evaluation knowledge. Taking the structural global reliability analysis as the quantitative foundation, and semantically models engineering objects, load conditions, reliability indices, safety grades, and judgment rules, constructed the OntoPWSE (Ontology for Piled Wharf Safety Evaluation) knowledge base for piled wharf safety assessment, and achieved automatic reasoning for safety levels and result retrieval by using SWRL rules and SQWRL queries. A 10-year-old in-service container piled wharf was selected as an example for verification. The results show that the global reliability index of the wharf under horizontal loads is 3.2746, corresponding to safety grade B. The OntoPWSE ontology knowledge base can realize the structured organization, rule-based reasoning and knowledge-graph-based representation of structural safety evaluation results. The proposed method can provide methodological support for the holistic representation and information-based management of safety evaluation knowledge for in-service piled wharf structures.

  
  
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  Displacement response and sensitivity analysis of breakwater-wind turbine structural system based on three-dimensional numerical simulation

  Wang Yuhong, Xiao Zhensheng, Yuan Lisha, Yuan Juan, Zhao Jingtong, Cui Chunyi, Ji Zezhou

  Journal of Dalian Maritime University. 2026, 52(3): 116-126. https://doi.org/10.16411/j.cnki.issn1006-7736.2026.03.011

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  To address the lack of clarity regarding the dominant factors and parameter sensitivity mechanisms of the displacement response of the breakwater-wind turbine coupled system, this paper established an integrated numerical analysis model considering combined wind-wave action and systematically revealed the influence laws of various parameters based on grey relational analysis (GRA). Firstly, based on a practical breakwater-integrated wind power project, the Davenport wind speed spectrum and JONSWAP wave spectrum were used together with the harmonic superposition method to simulate and generate time histories of wind-wave loads. Secondly, a refined 3D fully coupled numerical model of the breakwater-wind turbine system was constructed. Compared with traditional offshore monopile wind turbines, the model verifies that the breakwater can enhance the displacement stability of the wind turbine. Finally, three types of key influencing factors including load, structure and foundation were selected, and the GRA method was adopted for multi-parameter sensitivity evaluation to quantify the sensitivity of structural displacement response to each parameter. Results show that the introduction of the breakwater produces a wave-shielding effect and forms an additional constraint mechanism, which can significantly improve the displacement stability of the wind turbine system. The system response is predominantly governed by wind loads, while the influence of wave loads is effectively suppressed. Tower parameters dominate the deformation of the upper structure, whereas pile parameters govern the response at the pile-breakwater interface. These findings clarify the displacement response laws of the coupled system under combined wind-wave action, and can provide a theoretical basis for engineering disaster-resistance design and parameter optimization.