Abstract:Based on the finite element-statistical energy (FE-SEA) hybrid method, this paper establishes a steelconcrete composite beam bridge model, and predicts the vibration response and structural noise of each plate of the bridge under the conditions of train running speed of 200 km/h and trains crossing. The results show that when trains cross：The vibration acceleration level at the midpoint of each plate increases, the dominant frequency band is 40~120 Hz, and the peak frequency is 65 Hz. In the whole frequency band, the sound pressure level of each plate increases; the peak frequency of the sound pressure level of each plate in the two states of one-way driving and train crossing is at 500 Hz, and the pattern of changes for sound pressure level of the web and the lower flange are similar. The energy level of each plate of the bridge increases in the whole frequency band, and the energy level of the web is the largest. When the frequency is 100 Hz, the vibration energy level of the web and the lower flange has an inflection point, indicating that this frequency has the greatest impact on the energy level.

Abstract:In order to study the development policy of prefabricated building industry more scientifically, from the perspective of industrial chain development, the prefabricated building industrial chain development system dynamics model was established, and four typical policy variables were selected for simulation. The results show that: the increase of industrial chain capital input and the improvement of prefabricated assembly rate of government-invested construction projects are short-term strong and effective incentive policies; enterprise tax incentives and prefabricated building purchase loan incentives are long-term incentive policies. Combined with the simulation results, the policy formulation suggestions based on the development trend of the industrial chain are put forward.

Abstract:It occurs occasionally that the excavating pits are adjacent to as -built constructions. The soil mass located between the foundation of the as-built construction and the pit is viewed to be finite width soil mass, resulting in failure of classical finite soil mass theory. Meanwhile, the seepage also has non-negligible influence on excavation of foundation pit. In response, soil-pressure model box is designed to investigate the influence of steady seepage on active soil pressure of finite width soil mass. The corresponding numerical simulations are implemented to verify the experimental observations for a further systematic study. The following conclusions are obtained: The time-history of soil pressure can be divided into three phases, Including steady seepage, movement of retaining wall and the rest of retaining wall; The active soil pressure under the condition of steady seepage is larger than that of static water, and in the numerical simulation, the active soil pressure of the soil with finite width is smaller than that of the soil with half-infinite width; For sandy soil, the calculation result of effective stress method is close to the test result, but it is safer to compute active soil pressure by soil and water partition method in practical projects.

Abstract:With the corroded steel strands from prestress concrete beams contaminated by simulated acid rain, the corrosion rate of the steel strands was calculated and the configuration of the pits were surveyed and classified. Then, with 4 samples of 80 cm long steel strand intercepted at the distribution central areas of the pits, the density, length, width and depth of the pits were obtained to explore the distribution characteristics of size of pits on steel strands corroded by simulated acid rain. The results reveal that the configuration of the pits can be classified as ellipsoid, saddle and pyramid. With the corrosion rates increasing, the pits become denser but its relative increase rates declined. The length is not subject to normal distribution but to lognormal distribution as the depth, and the width approximately is subject to lognormal distribution. The overall distribution characteristics of the pits size are short and narrow and moderate deep, whose length and depth have obvious fractal characteristics, with no obvious fractal characteristics for the width of pits. As the corrosion rates increase, the configuration of all pits trend to approach. The length is found at the relative minor values and the width is found at the relative moderate values, however, the depth is found between the relative minor value and moderate value.

Abstract:The precision measurement network control method is based on the plane coordinates of the line and the elevation of the railway line alignment control method. According to China's track precision control measurement system and the principle of the precision measurement network control method, the sources of error analysis of the precision measurement network control method mainly include two aspects of three-dimensional adjustment error and point change error. The results of calculating the plane coordinates, elevation error, and track smoothness index of the measured station and adjacent stations when the CPⅢ points change at different positions and different numbers show that the coordinate error of the measuring station increases with the increase of CPⅢ point coordinate change. The closer the control point is to the measured station, the greater the impact of its change on the coordinates of the measured station is; and the changes of the control point farther away from the measured station are not sensitive to the influence of the station coordinates; the maximum value of the coordinate error of the station are 1.732，1.668，1.626 mm respectively; the maximum coordinate error of adjacent stations are 1.500，1.397，1.343 mm；among track irregularity index, the largest error is the track direction, fol lowed by the gauge and level, the smallest error is the height; When the coordinate change of the nearest CPⅢpoint from the station is 1.0 mm in each direction，the maximum values of track pitch，level，height，and track direction errors are 0.559，0.534，0.479，0.582 mm，respectively.

Abstract:In order to study the soil-cement based on typical silty clay in Nanchang area, the strength characteristics of soil-cement with different cement incorporation ratios (20%，25% and 30%)，two kinds of admixtures in cluding fly ash and silica fume at different curing ages (7，14 d and 28 d) were analyzed through unconfined compressive strength tests in laboratory, and the relevant stress-strain curves were drawn. The experimental results indicate that with the increase of cement incorporation ratio and curing age, the unconfined compressive strength of soil-cement increases accordingly, and the growth rate of its strength decreases with the increase of curing age. Replacing fly ash with silica fume as the admixture of cement soil has a promoting effect on the unconfined compressive strength, and the strength increases obviously at a specific cement incorporation ratio and age. The failure mode of soil-cement gradually develops from plastic failure to brittle failure with the increase of cement incorporation ratio and age. The functional relationship between the deformation modulus and the compressive strength of silica fume soil-cement approximately satisfies the linear regression model, which is E₅₀=20q_u .

Abstract:The passenger flows of the metro station have significant impact on the energy-saving operation of the air-conditioning system. In order to improve the prediction accuracy of the personnel cooling load in the subway stations, a prediction model was proposed in this paper using the BP neural network(GA-BP) method optimized by the genetic algorithm, and the personnel cooling load of the subway stations was calculated dynamically. The initial weights and thresholds of BP neural network were optimized by using the genetic algorithm, and the nonlinear learning ability of BP neural network was improved. The model was validated by the actual operation data, and the simulated results were compared with the prediction results of the traditional BP neural network method. The results show that the proposed method can effectively improve the nonlinear learning ability of BP neural network and the accuracy and stability of the hourly personnel cooling load prediction. By comparing with the traditional BP neural network method, the average daily personnel cooling load prediction error of the GA-BP model is reduced by at least 10%, and the fitting correlation coefficient value of daily hourly personnel cooling load prediction is increased by at least 0.1.

Abstract:In order to evaluate the urban green transportation development objectively, according to the comprehensive consideration of green transportation concept and connotation, this paper selects some indicators and establishes a green transportation evaluation index system from the three aspects of transportation infrastructure, public transportation service quality and environmental impact, and uses a combination of PCA and entropy weight method to obtain the comprehensive weights of the index. Grey relational degree model and cloud matterelement model are adopted to study the development level of green transportation in Nanjing as an example. In addition, gray relational degree clustering is combined for making a comparison about evaluation results. The case analysis indicates that the results of combination of two models have high rationality and consistency. The combination of models could also take both quantitative and qualitative analysis into consideration, which may reflect the development level of urban green transportation more comprehensively.

Abstract:By analyzing the traction -braking system of EMU, this paper establishes the linear model of each power unit of EMU. Considering the existing nonlinear problems such as air resistance and unknown interference during EMU operation, the error between actual output and linear model output is described as unmodeled dynamics. As a nonlinear problem, EMU operation process is described as an integrated model composed of linear model and nonlinear unmodeled dynamics. BP neural network is used to estimate the unmodeled dynamic items online, and the recursive identification algorithm is used to update the model parameters online. In the controller design, the generalized predictive controller and unmodeled dynamic compensator are combined to design the multivariable nonlinear generalized predictive controller. Based on the simulation of CRH380A EMU, the highprecision tracking control of the given speed is realized, and the on -time, comfortable and safe operation requirements of the EMU are realized.

Abstract:Reasonable prediction of freight volume is the basis for the railway department to formulate the train operation plan and organization management. In such extreme events as sudden outbreak, accurate prediction of railway freight volume data and change trend has a positive reference significance for the development of railway work. The ARIMA model was established to predict the railway freight volume from March to October 2020 by using the normal data of railway freight volume from January 2010 to January 2020 and the abnormal data from February 2020 after the outbreak of the epidemic. The results show that the ARIMA model can accurately predict the railway freight volume after extreme events by combining with abnormal data.

Abstract:An approach for fault diagnosis based on pattern match of characteristic waveforms in frequency domain was proposed. It used the principle of global similarity on the characteristic waveforms of FFT-based amplitude spectrum of the vibration observation samples belonging to the identical pattern class. It was then applied to fault diagnosis of rolling element bearings, and compared with some typical diagnosis approaches based on pattern recognition. It was found that the cosine similarity, correlation similarity or mutual information similarity from pattern match of the characteristic waveforms in frequency domain reached the maximum respectively, when the test sample belonged to the identical pattern class as the training samples. According to this, the characteristic similarity threshold for pattern classification was determined, which contributed to 100% classification accuracy. The results show that the proposed approach for fault diagnosis needs neither sophisticated feature extraction nor complicated classifier design. It can accurately classify multiple complex patterns only by simple pattern match on characteristic waveforms in frequency domain and feature threshold comparison. In addition, it is suitable for solving the problem of small -sample classification with high classification efficiency and strong self -learning ability. It is obviously superior to some typical diagnosis approaches based on pattern recognition, andhas great application potential in constructing on-line automatic fault classification system.

Abstract:By selecting turnouts of Xuzhou-Lanzhou high-speed railway as the research object and applying the personalized turnout rail grinding, this paper analyzes the grinding wheel/rail geometry characteristics and explores the dynamic characteristics of high -speed trains before and after grinding. The results show that, with personalized turnout rail grinding, the left and right side of the turnout rail are symmetrical, and the wheel/rail equivalent conicity is improved. Moreover, when the train passes through the turnouts, the peak value of wheelrail lateral force and the peak value of wheel-rail abrasion power are significantly reduced, and the train wheel/ rail force is improved. The peak value of load reduction rate, the peak value of derailment coefficient and the peak value of wheel/rail lateral movement are all reduced, and the train safety is significantly improved. When the peak value of the vehicle body transverse/longitudinal acceleration and the peak value of the frame transverse/longitudinal acceleration are decreased, and the stability of the train operation is improved.

Abstract:With the increase of vehicle running mileage, the stability of the vehicle decreases due to the deterioration of wheel-rail matching relationship. The vehicle running performance can be improved by modifying the wheel profile with different flange thickness. However, the dynamic performance of the wheel profile with different rim thickness and rail matching is unknown. According to the matching of tread surface and CHN60 with four kinds of different flange thickness in LMB series, the paper makes simulation calculation with the change of wheel-rail contact point position and contact area distribution. By calculating contact width and contact concentration, the change rule of contact geometry caused by wheelset profile is analyzed. Combined with wheel-rail contact point movement and wheel-rail contact bandwidth variation, the nonlinear contact geometric relationship parameter λTC is defined. The parameter λTC describes the stability of EMU in service in the case of two or more wheel-rail matches. The results show that as the thickness of wheelset rim increases, the contact width of wheelrail contact point on the wheel tread increases, but the contact concentration decreases.With the increase of the geometric λTC parameters of the nonlinear wheel-rail contact, the vehicle dynamics parameters decrease, and thenonlinear equivalent taper and λNP show a descending and stationary state respectively.The nonlinear wheel-rail contact geometric λTC parameters can well show the strength of the stability of EMU in service when the wheelset with different rim thickness is matched with the rail, and can accurately reflect the variation of vehicle vibration response.

Abstract:Ascertaining the material flow rule, avoding the macro forming defects and disclosing the microstructure evolution in the isothermal local forging (ILF) have great significance for realizing integrated less-loading forming of shape and performance for aeronautical large-scale titanium alloy bulkhead. To this end, the research of macro and micro forming on ILF are reviewed. Firstly, the trans-regional material flow behaviour under the interaction of multi -deformation zones were elaborated. Secondly, the formation mechanisms and improvement measures of the forming defects by the ILF were given. Subsquently, the distribution of primary α-phase recrystallization and its grain size were predicted. Finally, the conclusions were given as well as the problems and challenges in ILF field were pointed out.

Abstract:In the researches and developments of speeding-up railway vehicles, it is necessary to carry out the collaborative MBS simulations on the wheel-rail relationship improvements and speeding-up bogie dynamical design, to transact correctly the dialectical relationship of (non-) linearities and maintain the ideal state of wheelset selfstability. The CRH5 bogies transform the rail parameters of rail cant from 1∶ 20 to 1∶ 40 by applying the XP55 tread alone, and the deficient safety and stability margin has therefore been an inherent problem since their technical importations and absorptions. However, the use of XP55 tread also brings many technical effects, such as widening of the low wear area to 16 mm and the probability reduction of local conformed contacts between worn wheel and rail. Under the frequent cross-wind disturbances, both wheel -rail matching and dynamic simulation analyses show that the grinding of rail head to 60N weakens the beneficial effects of the improved wheel-rail relationship design, which becomes then the direct cause of wear vibration problem produced by the anti-wind/sand trainsets, CRH5G. To enhance the stability and robustness against extreme climate influences, the optimal configuration scheme of anti-hunting parameters was formulated, defining clearly the CRH5 innovation or renovation direction.

Abstract:The trackside acoustic detection systems are usually located on the sides of the railway, which causes high speed motion between the train and the acoustic acquisition device relatively. As a result, the collected sound source signals are interfered by severe Doppler distortion, which brings great challenges to the acoustic detection of train running components. Aiming at this problem, a short-period Doppler correction method based on center time was proposed. First, the distortion at the center time of the acoustic signal was obtained according to the Morse acoustic theory. Then, the optimal center time was obtained by matching the time-frequency curve of the distortion signal and the original signal. Finally, the received acoustic signal was corrected based on the optimal center time point, and the effectiveness and correctness of the method were verified through simulation and experiment.

Abstract:It is of great significance in the field of intelligent security to count the people in a specific scene with cameras or other devices. Due to the huge scale variation, messy background, and severe occlusion, the traditional method cannot get high precision accordingly. This paper proposed a head detection method based on an improved Faster-RCNN to accurately count the people. In this model, ResNet101, as a feature extraction network, uses a multi-scale feature fusion module to fuse the extracted features and perform hierarchical detection. The purpose is to detect people of different scales. In addition, by designing the size of an anchor and using Roi -Align instead of Roi -Pooling layer, the detection effect is further improved. Experiments show that the method achieves better results on the two Brainwash and HollwoodHeads datasets, and the accuracy reaches 95.3% and 89.1% respectively.

Abstract:In order to fully analyze the performance of the existing tin-based alloy tiles and modified PTFE plastic tiles, this paper analyzes the performance of the commonly used tin-based alloy ZSnSb11Cu6 thrust bearings and modified PTFE thrust bearings for hydro-generator sets. By comparing the temperature resistance, hardness, friction and wear properties of the tin-based alloy ZSnSb11Cu6 and modified PTFE, the optimal temperature resistance, hardness and friction and wear conditions of the thrust bearing are analyzed. It further verifies the superiority of the material performance of the modified PTFE thrust bearing bush, and provides valuable technical modification performance reference data for different types and sizes of traditional tin-based alloy tile power stations.

Abstract:Fibrous NPAN was synthesized by the method of protic acid doping with NAN containing carboxyl. A series of NPAN/Ag/Ag₃PO₄ composites with different NPAN content were prepared by in situ polymerization of silver phosphate on the surface of NPAN. By means of FT-IR, XPS, Raman, TEM, TG and PL, the structure and morphology of the material were analyzed, and the photocatalytic performance of the material was studied. The results showed that the degradation efficiency of 10wt% NPAN/Ag/Ag₃PO₄ composite for RhB dye was the highest, reaching 97.635%. After five cycles, the photocatalytic degradation efficiency of RhB dye could still reach 93.6%, while the degradation efficiency of silver phosphate decreased from 83.2% to 54.12%. The introduction of NPAN could accelerate the separation of photogenerated electron holes, enhance the structural stability of the composite material, and improve the photocatalytic effect and cyclic stability of the composite material. Finally, the catalytic mechanism was explored through the capture experiment of active substance, and it was proved that the main sources of catalytic activity were photogenerated holes and strong oxidation of·O₂^-.

Abstract:In order to grasp the diachronic variation law of the underlying surface pollutants, taking a university in Nanchang City as the research area, this study selecled the main road of the school, the main road of the student dormitory area, the leisure square of the school and the roof of the student dormitory as the four underlying surfaces. For a single rainfall event, it analyzed the variation of SS, COD, TN and TP pollutants on different underlying surfaces with rainfall time to understand the variation process of pollutants with rainfall duration. The results show that the water quality variation range and variation rules of different underlying surfaces and different rainfall events are different, the concentration of pollutants in rainfall runoff is generally attenuating, and the attenuation rate is relatively fast in the early stage and relatively flat in the later stage; The main pollutants in rainfall runoff of four different underlying surfaces are analyzed.