Abstract:TiO₂-CNTs/FeNi36 composite coating was fabricated by laser cladding technology in this paper, and the effect of core -shell TiO₂ CNTs reinforcement on the hole, microstructure and tribology properties of the composite laser cladding were studied. The results show that the number and size of holes in the invar alloy matrix is greatly reduced due to the addition of core-shell TiO₂ CNTs reinforcement, and the generation of holes in the composite coating is restricted by the reinforcement. The addition of reinforcement does not change the phase composition of invar alloy matrix, and the matrix alloy is still single-phase [FeNi] austenite. With the increase of reinforcement content, the lattice constant of invar alloy matrix decreases slowly, then keeps stable; the hardness of the composite coating has the stable value after a little growth. The stable microhardness of composite coating is about 315 HV, which is about 2.5 times that of the FeNi36 invar alloy coating. When the mass fraction of TiO₂ CNTs reinforcement is 1.5 wt%, the wear rate of the composite coating is minimum, which is reduced by 60% compared with single FeNi36 coating.

Abstract:The stiffness transition section of high-speed railway CRTSⅢ slab ballastless track in vibration damping section and non vibration damping section is studiedin this paper. Based on the vehicle track coupling dynamic simulation analysis, the influence of each transition length and transition stage on the dynamic response of wheel rail is discussed under the condition that the stiffness of damping pad in each transition section decreases by double.The research results show that: when the transition stage is determined, the length of three track plates (about 15 m) is used for each transition stage, the wheel rail force amplitude, the difference of the downward pressure of fasteners on both sides of the panel seam at the junction of the transition section and the vibration damping section, the vertical and lateral acceleration amplitude of the car body, the derailment coefficient and the wheel rail load reduction rate are the minimum, and the rail deflection rate, the train running quality and stability meet the relevant limit requirements ;When the transition length of each stage is determined, the transition stages are three, the sudden change value of vertical displacement of wheelset, the amplitude of wheel rail force, the amplitude of rail deflection rate, the downward pressure of fasteners on both sides of slab gap, the staggering amount on both sides of slab gap at the junction of transition section and non damping section and the difference of downward pressure of fasteners are the minimum, and the rail deflection rate, train running quality and stability meet the requirements of relevant limit values within the scope of the transition section, the train has a larger wheel rail impact when passing through the rail joint, especially at the interface of the transition sections at all levels. The wheel rail impact is more significant. It is recommended to strengthen the maintenance of the fastening system near the interface of the plate and the transition sections.

Abstract:Based on the solidification theory, an recursion format for calculating concrete creep is derived. The recursion process can be programmed by commercial finite element software. Firstly, the creep Volterra integral equation was transformed into a rate-type creep integrodifferential equation based on the Kelvin chain model; secondly, the integrodifferential equation was transformed into a recursive creep calculation equation by discretizing the time and introducing intermediate variables; thirdly, a stress-strain incremental elastic constitutive relationship with initial strain was established by using the recursive calculation. The stress-strain incremental elastic constitutive relationship was suitable for complex stress conditions. Finally, as an application, the Ansys finite element commercial software was re-developed by modifying the material constitutive subroutine Usermat with Fortran language. Some existing examples were calculated by the program. The calculation results show that proposed method has satisfactory accuracy by comparing with the existing results. The proposed method does not need to store the stress history, which greatly improves the calculation efficiency, and also provides another effective way for the creep calculation of complex concrete structure.

Abstract:In order to study the self-healing process of asphalt, in molecular dynamics, the model of asphalt and the crack model were established by four-fraction analysis method. The diffusion process of the four fractions in the healing process was simulated with different temperature, pressure and aging content. The density and mean square displacement curves of the healing model were obtained and the diffusion coefficients of the healing stage were calculated. The results show that the self -healing process of asphalt can be divided into three stages of density recovery stage, structure recovery stage and self-diffusion stage; the diffusion coefficients of asphalt in the process of healing are ranked in the order: saturates>aromatics>asphaltenes>resins; in asphalt healing, temperature and pressure increase can promote the movement of asphalt molecules; in the same condition, the diffusion coefficient of aged asphalt healing is obviously lower than that of unaged asphalt. Among the four fractions of asphalt, the diffusion of resin during healing is least affected by environmental changes.

Abstract:The subway tunnel project is usually in a long-term humid environment, which requires high grouting material behind the wall. It should not only undergo the erosion of mud water, but also have good fluidity and fillability. According to the characteristics of subway engineering, a new type of foaming agent was prepared by using anionic surfactant to modify the mother liquor of animal protein and adding alcohol to stabilize the foaming agent. The foaming ability and bubble stabilization ability of mother liquor were improved successively by being mixed with different polar macromolecular substance. The results show that the appropriate foaming agent and foaming stabilizer can improve the strength, toughness and viscosity of the foam, and reduce the sedimentation and bleeding. When the foaming group is 0.8% and the foaming group is 0.15%, the foaming agent and foaming stabilizer have the best foaming and foaming stabilizer performance, and the prepared grouting material has excellent structure and performance. Micro -structure analysis found that when the water binder ratio increased from 0.40 to 0.48, the amount of foam is large and connected pores are easily generated, which makes the uniformity of the pore size deteriorate and the settlement increases.

Abstract:With disaster prevention and risk reduction as the engineering background, taking the total annual runoff control rate and total pollutant control rate as the overall target, the reconstruction plan was made for the sponge transformation of the park. The sponge transformation mainly focuses on low -impact development and transformation. Using Infoworks ICM software to construct traditional development model and low impact development (LID) model for parks, for the LID facility module in ICM, layout and planning for LID facility design in the model. The simulation results show that LID facilities of certain scale (permeable pavement, grass ditch， rainwater garden and green roof account for about 9.8%, 1.6%, 4.7% and 0.2% of the total area of the park respectively, with a total of about 16.3%) are applied in the park, the park can achieve the desired objectives; compared with the traditional model, the addition of LID effectively improves the annual runoff and pollution control rates.

Abstract:With the support of an extensive dataset, the spatial distribution and temporal evolution of urban rail transit infrastructure vibration acceleration in the long term is analyzed. The dataset is collected by an infrastructure monitoring system deployed on a metro line, with the coverage of 1 year. An energy spectrum density (ESD) based method of damage -sensitive feature extraction, dedicated to the examination of the dy namic response caused by passing trains is designed. Meanwhile, cumulative sum (CUSUM) and haar filtering are applied to the measurement of long-term variation of feature value. The results show that the vibration monitoring system fits the demand of structural health monitoring well. When operational infrastructure is at a steady health state, its dynamic response excited by passing trains is to some extent randomly distributed whereas its mean value is stable. It shows that the proposed analysis methods can clearly characterize the well-operating infrastructure during a long service time. In addition, the calculated feature value and its CUSUM & the haar filtering value can be referred to, when the assessing of other track structures' health state is demanded in the future.

Abstract:Aiming at the problem of segment floating in shield tunnel construction, based on the project of slurry shield cross-river tunnel of Nanchang Metro Line 4, through mathematical statistics method, this paper summarizes and analyzes the segment floating amount when slurry shield passes through different strata, and discusses the influence law of stratum parameters and shield tunneling parameters on segment floating. The research results show that: when driving in the full section sand layer, the floating amount of segment is small and the change of floating value is stable; when it enters the upper soft and lower hard stratum and argillaceous silt stratum, the floating amount of segment changes rapidly, especially in the weathered argillaceous silt stone of river crossing section, the floating amount of segment is the largest. Considering the single factor influence of shield tunneling parameters, with the increase of grouting pressure, slurry pressure and shield thrust, the segment buoyancy will increase, while the change of tunneling speed has little influence on segment floating during construction. In the process of tunneling, it is necessary to combine the influence of stratum characteristics on segment floating and adjust the main driving parameters in real time, which can effectively control segment floating to a certain extent.

Abstract:Conventional public transportation is one of the basic modes of transportation for urban residents. In order to ensure the efficiency of public transportation and reduce operating costs, it is necessary to perform quantitative analysis and systematic research on the operation of buses. In this paper, in order to minimize the total cost of passengers and bus company operations, a multi-objective bus departure frequency optimization model based on passenger arrival rate is proposed to maximize the benefits of both passengers and operators. The function of passenger arrival rate was used to calculate the passenger waiting time, which could lead to a more realistic waiting time in the optimization calculation. Considering the good convergence of the genetic algorithm and the easy-to-binary encoding of departure frequency, the algorithm of this model was designed based on genetic algorithm. Taking Changzhou Bus Line B1 during the peak time as an example, the optimal departure frequency was 13.9 times per hour. Compared with the other three classic departure frequency determination methods, the total cost of this model was reduced by 18.1%, 1.5%, 1.2%. The results show that the departure frequency model proposed can effectively reduce the overall cost of bus travel by coordinating the waiting time cost of passengers, in-vehicle congestion cost and vehicle purchase cost, fuel cost of bus operation.

Abstract:In order to analyze the effect of the number of empty trains on the safety of freight trains, a dynamicmodel of the train -track coupling system with empty vehicles and heavy vehicles was established based on thetheory of vehicle system dynamics, train longitudinal dynamics theory and the theory of vehicle-track couplingdynamics. Based on this, the lateral wheelset force, the derailment coefficient, the wheel unloading rate were an-alyzed when different numbers of empty vehicles were located in the head and rear parts of the freight trainwhile braking. The results show that when 5, 10, and 20 empty vehicles at the head and tail of the train, the lat-eral wheelset force, the derailment coefficient, the wheel unloading rate of the empty and heavy vehicles all meetthe standard requirements of the GB/T 5599- -2019 standard and there is a certain safety margin. When the emptyand heavy vehicles mixed marshalling train braking on curve railway, the lateral wheelset force of the empty ve-hicle is less than that of the heavy vehicle, and the derailment coefficient and wheel unloading rate of the emptyvehicle are greater than that of the heavy vehicle. When 5 empty vehicles at the head and tail of the train, thelateral wheelset force of the empty vehicle and the heavy vehicle are all the minimum, but the wheel unloadingrate of the empty vehicle at the tail is the largest at the same time. For the derailment coefficient and wheel un-loading rate, except for the case of only 5 empty vehicles located in the head and rear marshalling, the derail-ment coefficient and wheel unloading rate of the empty vehicles marshalling at the head of the train are higherthan those at the tail. When the head and tail of the train are marshalling of 10 and 20 empty vehicles respec-tively, the difference in the overall wheel load reduction rate of the two trains is small.

Abstract:On the basis of the analysis of the mechanism of the siphon effect after the opening of the high-speed rail, through the modified gravity model and the spatial measurement model, the space between the 11 prefecture-level cities in Jiangxi Province and the major cities in the neighboring provinces are calculated by using the “with or without comparison method”. The results shows that：The high -speed railway reduces the time and space of the city and strengthens the spatial interaction between Jiangxi and its neighboring provinces, especially Shanghai, Changsha and Wuhan；The high -speed railway makes the spatial distribution of the intensity of the siphon effect change significantly；The opening of high-speed rail will cause cities with strong economic power to produce a positive siphon effect to promote economic growth, while cities with poor economic development will have the opposite economic effect.

Abstract:In order to reduce flight delays caused by various reasons and improve the robustness of flight plans, based on the analysis of the flight delay data of a certain airline in winter and spring flights for a certain month and ten days, an optimization model of flight plan based on the improvement of robustness is established. The model considers robustness factors when formulating flight plans, and controls the increase in flight operating costs by constraining costs. In order to verify the accuracy of the model, this paper uses Lingo to perform modeling and brings in ten-day flight data for verification. The experimental results show that the robustness is 0 when the flight cost increase rate is 0, and the robustness has the maximum solution when the flight cost increase rate is 0.2. The results are normal on the eighth day of ten days, and only two days are due to missing data. Smaller solution, preliminary verification of the model has been completed.

Abstract:In order to solve the problem of less target, static circumstance and real situation cannot be simulated in traditional path planning, under the background of the time-varying conditions, cost, environmental risk and population risk were considered in the multi-objective path optimization and selection. A mathematical model of multi-objective shortest path selection problem with time-varying conditions and multiple departure time (segmentation time) for hazardous goods transportation was established and designed. Considering the complexity of the actual decision-making environment and the limitation of the rationality of the decision-makers， the algorithm of comprehensive k-shortest path and approximating ideal solution sorting method (TOPSIS method) was proposed. The effective path of each single target was determined by k-shortest path algorithm. Then, the effective path to the positive and negative ideal solutions was calculated by TOPSIS method. Finally, an application example was given to prove the effectiveness of the proposed model.

Abstract:The mainstream operation mode of close staggered parallel runways in China is of isolated and parallel operation. Since this mode uses a more conservative wake safety separation, a certain degree of congestion may occur during the relatively concentrated period of aircraft departure. In this regard, the paper selects the dual takeoff and double landing related operation mode, takes the close staggered parallel runways as the research object, combines the evolution characteristics of the takeoff wake, and proposes an aircraft takeoff wake dynamic reduction method based on meteorological conditions. The main parameters of the airport’s runway are the simulation reference conditions, and the simulation verification is carried out by using the built-up wake dynamic reduction simulation system. The simulation results show that the takeoff wake encounter metric based on the roll moment coefficient proposed in the paper is reasonable, and the wake separation can be reduced to less than 100 s.

Abstract:Passenger flow prediction is an important part of urban intelligent transportation system. In order to realize accurate prediction of passenger flow, variational mode decomposition was adopted to decompose the time series into intrinsic mode function in different time scales, the long short-term memory neural network of deep learning was used to predict, and the VMD-LSTM prediction model was proposed. Data of minnesota interstate subway passenger flow were collected to validate the model. The results show that compared with the traditional LSTM prediction model, the average absolute percentage error and the root mean square error decreases by 8.38% and 256.99% respectively after improved by VMD, the prediction accuracy and robustness of LSTM neural network are improved effectively.

Abstract:CL60 wheel steel against U71Mn rail steel was chosen as friction pair. The effect of slip rate on adhesion characteristics and surface damage of heavy haul train wheel and rail was studied by using a self-designed wheel-rail rolling contact wear testing machine. The results indicate that the slip rate has a significant influence on the adhesion characteristics of wheel-rail. With the increase of slip rate, the adhesion coefficient of wheelrail increases; slip rate affects the volume of wheel-rail which increases with the increase of slip; the value of wheel -rail surface hardness will be larger than before when the slip rate increases; the wear mechanisms of wheel-rail gradually changes under the different slip rate. During the rolling friction, the surface wear mechanisms is mainly abrasive wear. The wear mechanisms is changed from slightly abrasive to adhesion wear with the increase of slip rate, and the degree of the wheel sample surface damage is larger than that of the rail sample under the same slip rate.

Abstract:Aiming at the problems of long design cycle, the inability of real-time dynamic display of design effects and the non-cross-platform linkage of design products in the design process of rail vehicles, a virtual design system for rail vehicles based on Unity3D virtual engine is proposed. Based on this virtual design system, the whole process of virtual design from the overall design, key component structure design, virtual disassembly and assembly to virtual running test is developed and realized. Fan-shaped collision inspection and AABB enclosing detection method based on mountain climbing method are used to realize high-efficiency and high-precision human-computer interaction; the model instantiation technology is applied to reduce the amount of system models and achieve lightweight design; Ansys is used to realize Unity3D and Ansys Platform linkage. The results show that the system realizes the low-cost, high-efficiency, multi-style design process of rail vehicles, and provides a reference direction for the design and application of virtual reality technology.

Abstract:As the speed of high-speed trains continues to increase, the service environment of traction gearboxes is becoming more and more complex, and the service performance of gearbox is also facing greater challenges. Based on the influence of the internal excitation, external excitation and coupled excitation of the gearbox on its vibration response, domestic and foreign scholars have done a lot of researches on the vibration characteristics and fault diagnosis of the high-speed train gearbox. According to the existing research results, this paper mainly summarizes the gearbox strength, reliability and life, fault diagnosis and monitoring of the gearbox. The method and research status of vibration characteristics analysis and fault diagnosis of high-speed train gearbox are elaborated in details, and suggestions and prospects for future key research directions are proposed.

Abstract:The TF-IDF algorithm uses the word frequency and inverse document frequency to judge the importance of words, but the category discrimination effect is not very good. In order to improve the classification effect, a TF-IDF-MP algorithm is proposed. First, the documents in the corpus were marked with paragraphs. The word segmentation tool jieba was used to label and tag the parts of speech. Then, the number of times a feature word in a single document was compared with the average number of occurrences in the document, and the feature word weights were adjusted by the improved Sigmoid function. At the same time, different position weights were given according to the importance of the paragraph position of the relevant document. According to the weight of the feature words, Naive Bayes classifier was used to classify the documents. The experimental results show that the TF-IDF-MP algorithm is applied to the news classification, and the evaluation indicators such as accuracy, recall and F1 value are better than TF-IDF and related improved algorithms.

Abstract:It is necessary for China ' s economic development to maintain high quality of economic development.In view of this, the panel data of 157 prefecture level cities in the provinces along the Long March from 2006 to2017 were selected to analyze the relationship between environmental regulation policy and high -quality eco-nomic development. The results show that: environmental regulation has a significant positive effect on high -quality economic development, but from a regional point of view, there are obvious regional differences in the ef-fect relationship between them. In the eastern region, environmental regulation shows a binding effect on high-quality economic development, while it shows a promoting effect on the central and western regions. At the sametime, investment in fixed assets has a general inhibitory effect on high-quality economic development, while thenumber of employees on duty has a generally positive effect on high -quality economic development. Based onthis, the local governments along the Long March should implement environmental regulations according to localconditions, strengthen the implementation of environmental policies, and pay attention to improving the quality oflabor force and optimizing and upgrading the industrial structure.

Abstract:This paper studies the passenger demand of air-rail intermodal transport from the perspective of travel utility. Combined with prospect theory and regret theory, it proposes basic utility, risk perception utility and gratification utility. Based on the converted gravity model, the utility function is optimized, and the passenger demand forecasting model of hinterland city-HSR-flight is obtained. Taking Nanjing Lukou International Airport as the target airport, it studies the passenger demand of air rail intermodal transportation by integrating the airports with passenger throughput greater than 10 million, the nearest ten airports and all airports in Jiangsu Province according to the administrative division. Based on Wilson model, the prediction accuracy of air rail combined transport radiation radius is improved, and the relationship between annual per capita travel times and per capita GDP of hinterland cities is constructed, and the passenger demand of air rail combined transportation in hinterland cities is obtained. Finally, according to the passenger travel utility evaluation, the air rail intermodal passenger flow distribution is carried out to accurately identify the demand for the airport.