Dalian Jiaotong University (Chinese: 大连交通大学; pinyin: Dàlián Jiāotōng Dàxué) is a university in Dalian, Liaoning, China. It was under the supervision of the provincial government and previously the Ministry of Railways. It has its larger campus near downtown Dalian and smaller campus in the High-Tech zone in Lüshun. Until 2004, it was known as Dalian Railway Institute (Chinese: 大连铁道学院; pinyin: Dàlián Tiědào Xuéyuàn). Dalian Jiaotong University is the only college of higher learning featuring rail transit in Northeast China.
The emergency response capability and resilience of urban rail transit (URT) systems are critical to smart cities. Beyond widely studied severe disturbances, low-intensity but high-frequency daily disturbances likewise continuously challenge operational stability and can accumulate into systemic risks. However, the mechanisms and effects of such “quasi-emergency” disturbances have not been systematically studied yet. To extend research on URT resilience from severe and low-frequency disruptions to daily disturbances, this study proposes a micro–macro resilience assessment framework grounded in the passenger-level disturbance response chains. The framework integrates a fine-grained passenger itinerary inference approach incorporating daily disturbance effects, with a multi-source feature driven daily disturbance identification model. This integration overcomes the critical challenge of lacking daily disturbance data, enabling multi-dimensional resilience quantification from passenger-level micro-behaviors to system-wide macro-performance. Empirical analysis of the Chengdu Metro shows a generally favorable baseline resilience performance, with 18/31 of study days classified as good or very good. Resilience patterns are closely linked to passenger flow regularities and distributions of daily disturbances, revealing spatio-temporal heterogeneity and functional dependency. Spatially, it exhibits structural and functional weaknesses. Temporally, holidays with surging passenger demand represent the resilience troughs, with the lowest value of 0.8540. In the disturbance process dimension, delayed responses following disturbance onset and inadequate recovery during the terminal phase are identified as the primary deficiencies. Based on the numerical results, relevant management strategies and optimization measures are proposed, offering actionable insights for enhancing the disturbance-handling capacity and resilience of URT systems.
When a high-speed train (HST) enters a tunnel at speeds exceeding 400 km/h, the rapid increase in aerodynamic drag and the amplification of the micro-pressure wave (MPW) at the tunnel exit pose significant safety challenges. This study establishes a full-scale transient numerical model of a 3-car train and a double-track tunnel with a 100 m² cross-section. The effects of jet position (head, middle, or tail car) and dimensionless jet velocity ( u_jet ), ranging from 0.1 to 0.7 of the train speed (U), on aerodynamic characteristics are investigated, revealing the control mechanisms and velocity effects of the airflow jet and suction method (AJSM). The results demonstrate a clear trade-off between drag reduction and MPW suppression. At u_jet = 0.1 U, the middle car jet reduces the total drag by 5.6 u_jet for effective MPW suppression follows a power-law growth, but the control effect saturates at 600 km/h, indicating a saturation of the control effect for the AJSM. The concept of a critical jet-speed ratio ( R_cj ) is introduced, providing practical guidelines for jet parameter selection. This research delineates the aerodynamic limits of the AJSM from a synergy-trade-off perspective and establishes design boundaries for active flow control in train-tunnel systems operating at 400–600 km/h.
Soft soils, characterized by high compressibility, low shear strength, and excessive settlement, pose significant engineering challenges. To mitigate these issues and reduce cement dependency, a novel 100
To minimize the adverse effects generated by pressure waves when high-speed trains burst into tunnels with shaft buffer structures and to achieve the enhancement of buffering performance. Based on this, this paper proposes a new optimization method for the shaft buffer structure parameters. This study is based on numerical simulation and dynamic model test, combined with the RSM-BBD (Response Surface Method-Box-Behnken Design) test and the NSGA-II algorithm for multi-objective optimization of the shaft position (L), shaft cross-section diameter (D), and shaft height (H). The Pareto solution sets of the structural parameters of the shaft in the tunnel of the high-speed railway at 450 km/h with the initial compression wave peak value (ICWPV) and the micro-pressure wave peak value (MPWPV) are obtained. Finally, the optimal combination of parameters in the Pareto solution set with respect to the shaft structure is obtained using the TOPSIS entropy weight method. The results indicate that the RSM models of the ICWPV and the MPWPV with respect to L, D, and H are accurate. After optimization, the optimal combination of parameters for the shaft structure is L = 250 m, D = 7 m, and H = 50 m. The ICWPV and MPWPV obtained from the optimal parameter combination of the shaft buffer structure are reduced by 18.93
The increasing demand for high-strength and high electrical conductivity (EC) aluminum alloys in aerospace and automotive industries makes the simultaneous enhancement of both properties increasingly urgent. This work investigates the improvement in mechanical strength and EC in an Al-Mg-Si-Fe-Cu alloy plate processed by cryogenic rolling (CR) and subsequent aging. Compared to room-temperature rolling (RTR), CR imposed more severe plastic deformation on the solution-treated alloy, resulting in an increase in strength due to significant grain refinement, elevated dislocation density. During subsequent aging, nanoscale beta '' and Q precipitates formed uniformly, contributing to the strength via precipitation strengthening. At an 80% rolling reduction, the CR alloy plate possessed enhanced mechanical properties over to the RTR alloy plate, with the ultimate tensile strength increasing from 357 to 374 MPa, the yield strength from 334 to 352 MPa, the elongation from 6.9% to 9.1%, and the EC from 54.59% IACS to 54.87% IACS. This was attributed to enhanced precipitation during aging, which increased the strengthening role on the matrix induced by Orowan strengthening and reduced the scattering effect of solid solution atoms on electrons. This work offers valuable insights into the design of high strength-conductivity aluminum alloys for advanced engineering applications.
