Abstract:To solve the timetable rescheduling problem under complete segment blockages， a bi-directional arrival-departure track utilization optimization strategy is proposed in this paper. From the macroscopic perspective， the train operation process is formulated into a network of events and activities. A mixed integer linear programming （MILP） model combined with the proposed strategy is constructed for the timetable rescheduling problem in the case of the segment blockage on high-speed railways. According to the real-time requirements， the model is solved using a combination of a self-programmed algorithm and the commercial optimization software Gurobi. Nine disruption cases are selected to test the performance of the model and algorithm. The results show that the blockage impact on train operations can be effectively reduced by using the bi-directional arrival-departure track utilization optimization strategy， which can reduce train delays by up to 10% compared with the existing arrival-departure track utilization strategy.

Abstract:By combining the multi-scale decomposition and sparse representation， an image fusion algorithm based on multi-morphological component analysis （MCA） is proposed in this paper. The fusion method based on joint sparse representation （JSR） is employed to fuse the redundant and complementary information in the cartoon sub-images， and the fusion method based on directional feature is used to fuse the texture sub-images with more detailed information and noise. The results show that the proposed algorithm is superior to the state-of-the-art image fusion methods in subjective visual effects and objective evaluation metrics.

Abstract:In addressing the conflicts and throughput efficiency issues for virtual train formations at junctions， various marshaling coordination strategies were proposed. The train merging timing， sequence， formation composition， and speed sequence decisions were integrated into a bi-level optimization model. The upper-layer model optimizes the throughput efficiency， while the lower-layer model improves the virtual coupling formation quality. A bi-level nested particle swarm algorithm was designed， with the train merging time serving as an intermediate interactive variable between the two layers， enabling the convergence of train formations to different configurations based on environmental demands. Simulation results demonstrate that the inclusion of coordinated speed optimization can enhance the efficiency of the coupling process. The bi-level optimization model can increase the throughput efficiency of existing lines while ensuring the stability and balance of marshaling structures.

Abstract:In order to improve the recycling efficiency and reduce the cost of recycling disused products， a path optimization method for recycling vehicles based on a modified genetic algorithm （GA） was proposed. Firstly， the path planning problem for the recycling vehicle was modeled as a variant of the traveling salesman problem （TSP）， aiming at minimizing transportation costs， which， however， is an NP-hard problem. Then， an improved genetic algorithm based on the Gaussian matrix mutation （GMM） operator was put forward. The algorithm leveraged the site order distribution characteristics hidden behind the original station data information to establish a Gaussian probability matrix. The Gaussian probability matrix was then applied to individual gene mutations combined with the roulette selection method， so as to guide the population to evolve towards high fitness while maintaining the genetic diversity. Finally， comprehensive simulations were carried out using the actual data collected from recycling sites in Shanghai to validate the proposed algorithm， and compared with other algorithms. The simulation results show that the proposed algorithm can increase the average convergence speed by 50%~60% and reduce the time consumption by 48% compared with the traditional genetic algorithm， under the precision gap within 1%.

Abstract:To overcome the shortage of the existing fault diagnosis methods such as low accuracy and efficiency， a fault diagnosis method based on principal component analysis （PCA） and multi-grain cascade forest （gcForest） algorithm was proposed. PCA was used to simplify the current eigenvalue for 11 fault modes of S700K switch machine. And an improved gcForest model with the simpler eigenvalue embedded was used to improve the data processing capability and enhance the inherent feature representativeness of the model. The experimental results show that the fault diagnosis accuracy of the improved gcForest model is 97.62%， which verifies the effectiveness and superiority of the method.

Abstract:In this paper， a train safety protection method based on energy conversion is proposed according to the safety braking model. Taking actual project data as the leading train’s operating curve， the minimum safe distance of the following train using the energy conversion protection method is simulated. Additionally， the impact of braking response time and braking capability on the safe distance is discussed. The results indicate that the difference in emergency braking rates between the leading and following trains is the key factor of the safe distance determination.

Abstract:The static performance of circular hollow section （CHS） X-joints using Q460， Q690， Q960 high-strength steel under axial compression was investigated. Using the finite element （FE） model verified by experimental results， extensive FE parametric analyses of joints were carried out. The effects of high-strength steel grades， brace-to-chord diameter ratios （β）， chord diameter-to-wall thickness ratios （2γ）， and chord axial stress ratios （n） on the structural behavior of joints were studied. Then， the suitability of the bearing capacity formula adopted by Chinese Standard GB 50017―2017 was evaluated against the results obtained from FE parametric analyses and literature test results. The conclusions can be drawn that the failure mode of joints is chord plastification， and the joint bearing capacity is often determined by the chord indentation limit， i.e.， 3% of chord diameter； the bearing capacities of high-strength steel CHS X-joints are overestimated by the formula of Chinese Standard GB 50017―2017 in most cases； the chord subjected to pressure or larger tensile forces will reduce the joint bearing capacity. Finally， the ranges of 2γ for different steel grades are recommended. Based on the plastic failure of the chord， the bearing capacity formula of CHS X-joints is proposed， considering the yield strengths of high-strength steel and the chord preload effect.

Abstract:This paper presents a test program of shear capacities of reinforced concrete beam strengthened by direct-shear-bolted side-plates near beam ends. The test program consists of one control shear span and five shear spans strengthened in shear. Test parameters involve interfacial conditions and depth of side-plates. Test results show that all kinds of adhesion interfaces are eventually de-bonded in loading process， without affecting shear capacities whether the adhesion is weak or strong. Shear capacities are effectively improved by increasing the plate depth and the number of corresponding direct-shear bolts. There are two mechanisms in the shear strengthening of direct-shear-bolted side-plates system， i.e.， the constraint mechanism and the composite action mechanism. The constraint mechanism takes effect by constraining the development of diagonal crack width， and in the composite action mechanism the bolted side-plates directly transfer part of the shear force to the support. Steel plates with lower depth are mainly in the constraint mechanism， while steel plates with higher depth work both in the constraint mechanism and composite action mechanism.

Abstract:Rural buildings in Shouxihe Basin （SXHB） were taken as studied objects. Based on MIKE FLOOD coupled hydrodynamic model， the temporal and spatial distribution characteristics of inundation in SXHB were simulated and analyzed. Then， the vulnerability curve of rural buildings on flood risk was established from the theory of structural static mechanics and the empirical equation of flood load. Finally， the flood risk assessment of rural buildings in SXHB was conducted based on the results of hydrodynamic model and vulnerability curve. It is found that the inundated area is long， narrow， and with a large value of flow velocity. The buildings are majorly at low or middle risk in low return periods， whereas in high return periods buildings at high or extremely high risk locate nearby the dam-break， in the major inundated area， and at Heba Village. Flow velocity is considered as a parameter in the vulnerability curve which reflects the damage degree of rural buildings.

Abstract:According to the distribution characteristics and electrical parameter design model of the underground medium of urban roads， the time-domain finite difference method and generalized S-transform were used to carry out the forward simulation and time-frequency feature extraction for the area of air-filled cavity， water-filled cavity， unconsolidated backfills and buried metal objects under the road. The results show that the event of reflected waves at the top interface of underground cavities is in the shape of arc reflection， but the reflected wave energy of air-filled cavities is stronger than that of water-filled cavities. The central frequency of the area of underground cavity is concentrated in a low frequency range， and the other frequency components are evenly distributed. There will be two high-amplitude energy clusters in the area of the buried metal， and the frequency distribution is scattered. The frequency of the area of the unconsolidated backfill fails to show a obvious pattern. Finally，an engineering case study verified the reliability of numerical simulation.

Abstract:Aiming at the difficulty of shield construction of high-gas tunnel in the shallow natural gas work area， with the help of engineering examples， the influencing factors of drainage performance of shallow natural gas in Chengdu Plain were analyzed by using theoretical analysis， numerical simulation and field test， and the effective radius and drainage time in the study area were determined. The results show that when the fracture permeability is 39 mD and the gas pressure is 0.31 MPa， the effective pumping radius of high-gas area of shallow natural gas in the study area is 5 m， and the pumping time is 60 min， which is greatly different from the coal seam gas. The negative pressure of pumping has a great effect on the discharge， but a little effect on the effective pumping radius. The discharge and effective pumping radius are positively correlated with the change of initial permeability of formation.

Abstract:To improve the consistency and integrality of the road infrastructure maintenance and management standard system， crucial standards which have an essential effect on infrastructure industry are explored and temporal and reginal characteristics of the standard system are analyzed in this paper. After establishing a standard graph of road infrastructure maintenance and management， an importance analysis on key nodes in the complex network is made to find the important， representative and authoritative standards by using the degree centrality， semi-local centrality and PageRank algorithm. And the technique for order preference by similarity to an ideal solution（TOPSIS） is introduced for comprehensive evaluation. In addition， a word cloud-based frequency statistics method is used to analyze the hotspots of standard topics in different time periods and three different geographical zones， acquiring characteristics on maintenance objects and technologies. By establishing a road maintenance management standard graph， the correlation and context of road infrastructure maintenance and management standards are sorted out， providing an important reference for the improvement of the standard system.

Abstract:Ground penetrating radar （GPR） is an effective method of void detection， but GPR data interpretation depends on human experience， being time consuming and laborious， or even existing subjective bias. To address above issues， a cement pavement void identification method based on XGBoost and GPR time-frequency features was proposed. To automatically identify cement pavement void area， the finite difference time domain method， lab and field tests were carried out， and GPR void dataset with label was created. Then， the resampling method was used to obtain the same sample frequency. Thirty time and frequency domain features， including 18 time-domain features and 12 frequency-domain features， were extracted from the post-processed GPR data. Taking the time-frequency domain feature as an input， and void label as an output， XGBoost was used to build a void identification model. The random forest （RF） and artificial neural network （ANN） were also trained to compare with XGBoost. The comparison results indicate that the accuracy ranking is XGBoost（98.10%）>ANN（95.10%）>RF（93.17%）. The accuracy of the XGBoost method is the highest and verified by field tests.

Abstract:The optimal speed ratio of a series-parallel hybrid transmission was selected using the design of experiment （DOE） method and the effect of transmission gears on vehicle performance was investigated for the transmission matching of series-parallel hybrid vehicles. The vehicle simulation model and control strategy were developed and verified by bench tests， and the vehicle acceleration performance， climbing performance and fuel consumption with three types of transmission were analyzed. The results show that more transmission gears can improve the dynamics performance of the vehicle and reduce the demand for battery discharge power and electricity. However， the improvement in the vehicle fuel consumption is insignificant. Further simulations indicate that the number of transmission speed does not have a significant impact on the vehicle fuel consumption even when the fuel consumption of engines is improved at the low-speed， mid-to-high load ranges.

Abstract:In this paper， an induction motor with asymmetric alternating current windings is studied， and the existing research results are analyzed and compared. For the symmetric winding， under the symmetric component conversion， the voltage equation is expressed by the sequence impedance. For the phase winding， the relationships between the self inductance leakage impedance， the mutual inductance leakage impedance， the equivalent impedance and the zero sequence impedance are obtained. The equivalent impedance and the zero sequence impedance are respectively multiplied by different coefficients according to the actual case of asymmetric winding， so as to establish a new voltage equation. The coordinate conversion of magnetic motive force components is applied to decouple the voltage equation for simple calculation. Finally， the calculation results are verified by experiments.

Abstract:To improve blurred edges in the real three-dimensional model， a curvature-guided structured line and plane feature reconstruction method was proposed. The meshes were divided into the plane， developable concave， developable convex， and non-developable surface according to curvature characteristics. The plane was extracted from the plane segmentation results， and the straight line was extracted from the developable concave and convex segmentation results. The non-developable area was reserved. Finally， a hybrid mesh model containing geometric features was formed. The results show that the potential range of geometric features is preset in combination with the curvature information， which makes the extracted structured line and plane feature more accurate than other methods. Furthermore， the hybrid model ensures that the complex tree structure in the city scene is not mistakenly extracted as a plane.

Abstract:In this paper， taking the Bozhong 19-6 gas field as an example and source rocks as the research object， the organic-inorganic interaction is studied to clarify the characteristics of source rocks in the Bozhong 19-6 structural belt and the effect of organic-inorganic interaction on the hydrocarbon generation and gas generation. Mudstone samples from more than 30 wells are selected for organic geochemistry， inorganic geochemistry， paleontology and other series analysis. The results show that， the source rocks in the study area are mainly partial humic organic matter，the paleontology is dominated by the higher plants of angiosperms and gymnosperms， and the humic amorphous forms are the dominant kerogen. The illite is the dominant clay mineral in the Bozhong 19-6 structural belt. A large number of humic amorphous forms have been enriched by physical adsorption and chemical bond bridging， and the organic matter is hydrogenated by clay minerals. In the late period， under the effect of illite， the source rocks mainly undergo decarboxylation reaction and thermal cracking to form a large number of short-chain hydrocarbons. Under the action of illite， the hydrocarbon production increases greatly， and then enriches， forming the wide distribution of condensate oil and gas.

Abstract:The lean construction （LC） and digital technology integration is the key and path to improve the economic benefit and production efficiency of the construction industry， and it is also a hot field of theoretical research and practical innovation in recent years. However， few scholars have made a systematic summary of the concept so far. Therefore， the relevant research articles in the academic journals published at home and abroad on the lean construction and the digital technology applied in the field of construction are reviewed using the methods of bibliometric analysis and key literature analysis. It is shown that， the digital technology （especially building information modeling （BIM） technology） has gradually become a key support for the application and promotion of lean construction. The in-depth integration of the two technologies can produce positive synergistic effects， further improving the efficiency and reducing the cost of project management.