Abstract:In order to study the aerodynamic characteristics of high-speed train (HST) running at part-cut and part-fill railway transition section under crosswind, 3-group HST was taken as the study object. Based on the SST k-ω two-way turbulence equations, FLUENT was used to study the aerodynamic characteristics of HST running at the speeds of 250, 300 km/h and 350 km/h, under crosswind action with speeds of 15, 20 km/h and 25 m/s, respectively. The study results showed that, with the same wind speed and same vehicle speed, the head-vehicle suffered maximum lateral force and overturning moment, and the middle-vehicle suffered maximum aerodynamic lift; with the increase of vehicle speed and wind speed, the aerodynamic characteristics of trains in- creased; the influence of wind speed on HST’s lateral force and the overturning moment is greater than that of vehicle speed.

Abstract:This study adopted the NURBS surface design method to complete 3D digital design modeling of a high speed train headstock. Based on the turbulent model of the three-dimensional, steady, incompressible, vis- cous flow field N-S and k-着 equations, the finite-element-volume numerical simulation method was used to an- alyze and calculate the relationship between train speed and air resistance. At the same time, further analysis of the pressure field and velocity field of the train operating in strong lateral wind environments with different wind direction angles was conducted. The study found that the air resistance of the train was proportional to the square of the running speed when the train was running in a wind-free long straight railway line. When the wind was running in the crosswind, the air resistance coefficient increased first and then gradually decreased with the expansion of the wind angle. The distribution structure of the flow field was complex and irregular. When the crosswind condition was more serious, the positive pressure zone was mainly distributed on the windward side of the train, while the negative pressure zone was mainly distributed on the leeward side and the top of the train, and the negative pressure performance was more intense. The front-end stagnation point of the train shifted to- ward the windward side, resulting in a huge pressure difference between the windward side and the leeward side.

Abstract:To study and predict the variation on the nonlinear temperature gradient of CRTSII track slab with time, for achieving early warning and reducing the occurrence of track slab diseases, this paper adopted the C-C method to reconstruct the optimal phase space of nonlinear temperature gradient time series of CRTSII track slab. On the basis of phase space reconstruction, NARX dynamic neural network with feedback and memory function was applied to predict and analyze the nonlinear temperature gradient time series. The results showed that according to the optimal phase space reconstruction of the temperature gradient time series of CRTSII track slab, the NARX dynamic neural network method was used to predict the temperature gradient inside the CRTSII track slab in the future time T=30 酌*tau，(min)，酌=1，2，3，…， T=30 酌*tau，(min)，酌=1，2，3，…. The temperature gradient prediction results of 11 sampling time nodes from 2016/11/17/8:00 to 2016/11/17/13:00 (酌=1) showed that the part of the predicted values was in good agreement with the real values. The study provides certain scientific and practical values in the prediction of CRTSII track slab nonlinear time series system.

Abstract:The clay of the strata along shallow-buried tunnels of Hefei Rail Transit Line 1-5 mainly consists of Holocene clay and Late Pleistocene clay, which can be called neo-clay and old clay respectively according to their formation age. The engineering characteristics of the two kinds of clay are different mainly in that the neo- clay is expansive while the old clay is not. In order to better understand the causes for the differences between the two clays, the physical and mechanical parameters of these two kinds of clays were analyzed on the basis of data from the geological examination along Hefei Rail Transit Line 1-5, and preliminary conclusions of the dif- ferences between the two kinds of clay were made. Besides, the correlation between the physical and mechanical parameters of the two kinds of clay was explored. This paper also studied the characteristics of both clay and their existing variances through the lens of microscope, explained the influence of microstructure of the two kinds of clay on their engineering properties. It concluded that the obvious differences in physical indexes such as hy- drophily, compressibility and shear strength between neo-clay and old clay in Hefei area, and the differences of their variant microstructures led to their different soil engineering characteristics.

Abstract:Based on the measured surrounding rock stress, deformation and support structure stress in the weath- ered rock formation, combined with analytical formula calculation and numerical simulation, from the aspects of surrounding rock loose circle radius, support structure deformation and force, this paper evaluated surrounding rock stability and support effect. The results showed that the surrounding rock conditions of the exit section of the Yuliao tunnel were better, the maximum deformation was 7.71 mm, and the thickness of the loose roof of the arch was 3.1 m. The thickness of the loose circle at the arch waist and the arch shoulder was more than 4.0 m. The analysis reflects that the bolts in the loose area of the surrounding rock are subjected to large forces. The stress characteristics of the supporting structure indicate that the additional load transmitted to the supporting structure due to the large deformation of the surrounding rock at the vault and the arch causes the force in- crease. The numerical calculation results show that there is a significant difference in the deformation of the bolts installed in different processes. Based on the deformation law and the force analysis results of supporting structure, the construction measures and support structure optimization suggestions are proposed.

Abstract:Due to its complicated spatial structure and force, the conventional influence matrix method is re- stricted to some extent in the process of secondary cable adjustment of the suspender force of long-span basket handle arch, inconsiderateness is apt to occur. By using a 450 m long-span basket handle arch as the engineer- ing background and increasing the weighting coefficient of the influence matrix, this study solved the weighted least-squares solution of equation through Matlab. After a small amount of iterative computation, the cable force difference was stable and the maximum relative error between the calculated cable force and the designed cable force was 0.28%. As a method of accelerating convergence with homogeneous rate of convergence, the weighted influence matrix provides a new way for determining the cable force of similar bridges in the completion stage or the secondary cable adjusting.

Abstract:Designing the storage lengths for left-turn lanes can significantly influence the operational efficiency of the intersection. However, current design specifications and existing research do not establish a general calcu- lation model of storage lengths, which may produce an unreasonable and hazardous left-turn lane. Based on ve- hicle arrival distribution and queuing theory, this paper analyzed the most unfavorable queuing condition of the left-turn lanes and established the calculation models of storage lengths for left-turn lanes with protected phases and permitted phases. And the calculation models were programmed by C-language which is convenient for de- signers to master. Finally, taking an intersection in Beijing as an example, this paper validated the rationality of the novel models by VISSIM. The simulation results showed that the novel models effectively reduced the delay time of queuing vehicles and improved the operational efficiency of the intersection. Therefore, the calculation models of storage lengths for left-turn lanes may be efficiently applied to the design.

Abstract:This paper proposes a multi-objective decision model for tamping maintenance plan of ballast track with track geometry state and maintenance costs as sub-objective functions. The optimal sub-objective function of track geometry state was established based on the deterioration model and the recovery model of track vertical irregularities. The minimum sub -objective function of maintenance costs includes planned maintenance costs, fixed maintenance costs, post maintenance costs and comfort loss costs. The improved NSGA-II algorithm was used to solve the model and a corresponding MATLAB program was developed for this purpose. A section of Shanghai-Kunming up line was selected to verify the model and algorithm. Results showed that the proposed multi-objective decision model for tamping maintenance plan of ballast track can provide a number of different maintenance plans, and priority maintenance was given to the section with large initial vertical irregularity and fast deterioration of the standard deviation of vertical irregularity, the maintenance was arranged in the later pe- riod of the annual plan, or no maintenance was arranged for the section with small initial vertical irregularity and low deterioration of the standard deviation of vertical irregularity.

Abstract:In order to strengthen the level of project decision-making and risk management of the lessee and lessor and according to the characteristics of aircraft financing lease, the rent-price model of the cost change un- der uncertainty environment was constructed by the cost-plus method of the lessor, which based on Monte Carlo simulation calculation in the wave of interest rate. At the same time, considering the lessee’s rent affordability, calculating the maximum rent that the lessee afforded. Suppose that the lessor can quote the maximum rent that the lessee can afford and calculating the theoretical price of rent and probability of lessor satisfied object earning rate. The results showed that the theoretical price of rent was convergent. When the lessor quotes to the lessee, if the economic environment changes and the initial investment increases, the probability that the lessor can achieve the object earning was significantly reduced. When the lessee's revenue decreasing or cost increasing af- ter lessee accepts the lessor’s offer, the lessee will assume more risk. Therefore, the lessor should strengthen the management of the initial investment amount and the lessee should strengthen the income management and cost control.

Abstract:Aiming at the tracking problem of ground moving targets for multi -rotor UAV, in consideration of tracking loss of the target due to the changes of external factors, using the image information of ground target collected by the vision camera as the input of the system, this paper adopted the improved algorithm based on color feature extraction combined with TLD target tracking to ensure that the target can be tracked accurately and stably, and the displacement information can be also obtained. By the design of the internal and external ring cascade PID controller of the position, it then took the horizontal displacement difference between the target and the UAV as the input of the controller, and the motor output was controlled by the position attitude con- troller to realize the position change of UAV, ensuring that the target was always located near the center of the airborne camera field of vision, which realized the autonomous tracking of the UAV for target. Finally, the exper- imental results show that the system can track the target accurately and stably.

Abstract:In this paper, the finite element software ABAQUS was used to simulate numerically the loading ca- pacity of 26 locally corroded concrete filled circular steel tubular (CFST) under axial loads, which was compared with that of non-corroded specimens. The parameters including the location of localized corrosion, the circum- ferential angle and the axial distance between localized corrosion were analyzed to study the influence of local ized corrosion on the axial compressive performance of the columns and to find out the most disadvantageous conditions under the action of three factors. The result showed that for a single localized corrosion pit, axial compressive loading capacity was the lowest when the pit was located in the middle of the member. When the corrosion pit location was farther away from the middle part of the specimen, its bearing capacity was larger. For two corrosion pits, the axial compressive loading capacity of the partially corroded circular steel tubular columns increased with the increase of the circumferential distance between the two corrosion pits, but decreased first and then increased with increasing the axial distance between the two pits.

Abstract:In view of the grid voltage imbalance under HVDC transmission, the traditional control strategy adopts separate suppression of negative sequence current and power fluctuation, which increases the difficulty of control and reduces the quality of the grid. Therefore, for the problem of grid voltage imbalance, the power adjustment factor was firstly introduced to realize the coordinated control of current and power. Furthermore, the proportional reduced-order vector resonance controller (PI-ROVRC) was used as the current inner loop control. The propor- tional -integral controller realized the static -free control of the DC component of the grid current, and the ROVRC performed the tracking control of the AC component in the grid current without difference, thereby im- proving the current quality of the MMC AC side. The overcurrent problem on the AC side was further discussed when the grid voltage was unbalanced. The method for correcting the active power command value was applied to limit the current amplitude at the fault to a specified range, improving the dynamics and reliability of the sys- tem. Finally, the simulation was verified by PSCAD/EMTDC simulation platform. The results showed that the proposed control strategy was consistent with the simulation, which proves the feasibility and effectiveness of the proposed scheme.

Abstract:Hydrochloric acid pickling wastewater was pretreated by iron as deoxidizer and sodium chlorate as ox- idant. The precursor of zinc ferrite (ZnFe₂O₄) was prepared by coprecipitation method, and the zinc ferrite crys- tals were obtained by calcination at different temperatures. Zinc ferrite was used as catalyst in photodegradation of Rhodamine B. The results showed that the nano-zinc ferrite had better crystalline form and dispersibility by calcination under high temperature with uniform particle size obtained by calcination at the same temperature. In the photocatalytic treatment of Rhodamine B simulated wastewater, zinc ferrite had a higher catalytic effect at 0.2 g/L. Its catalytic efficiency was only reduced about 10% after four repeated experiments, indicating that zinc ferrite still has great stability.

Abstract:The offshore platform is an important equipment for offshore operations and the seismic performance of offshore platforms has received extensive attention. An extended method of tuned mass damper (ETMD) control was proposed to improve the seismic performance of offshore platforms. The elastic damping was used to connect offshore platform and platform equipment, which is different from the rigid connection of traditional offshore platform equipment. The finite element model of offshore platform with ETMD system was simulated. Taking the low-order natural frequencies of offshore platforms as controlled frequencies, the seismic performance of offshore platforms under three typical seismic loads was compared and analyzed. The simulation results showed that under the action of three typical seismic waves, the vibration of jacket, lower deck, middle deck and upper deck of off- shore platform can be significantly suppressed, and the average reduction rate of vibration was more than 52.86%. The maximum vibration average reduction rate of offshore platform could reach up to 89.91% in the X direction, and the vibration reduction effect was the most obvious. The application of ETMD damping system can significantly improve the seismic performance of offshore platforms.

Abstract:In allusion to the problem of thermal fault diagnosis and location of the substation, an infrared image automatic detection method was proposed in this paper. In order to solve the target extraction problem of com- plex images, the two-dimensional Otsu threshold method was adopted to improve the region growing algorithm. On the basis of the pixel statistics that reflect the appearance characteristics of the device, the division of the structure of the target equipment was achieved by way of the rules of extreme value. According to the results of structural division and fault diagnosis criteria, the refined automatic diagnosis and positioning of the thermal faults in substation were finally realized. Experiments showed that this method can achieve thermal fault diagno- sis and location of substation well without manual intervention, which greatly improved the efficiency and accu- racy of fault diagnosis.

Abstract:In order to reduce the pavement wear caused by cracks which were made by frost heave or tempera- ture stress, the carbon black had been added to the asphalt roadbed with the as-prepared deicer agent, and the properties of the modified asphalt were evaluated through penetration, softening point, ductility and Marshall tests. The results showed that with the increase of the content of carbon black, the penetration and ductility of the asphalt decreased, and the softening point decreased slightly. When the content of rubber powder and carbon black was 10%, the modified effect of asphalt was the best. When the as-prepared deicer agent and rubber pow- der (carbon black) were added into the asphalt, the asphalt had some antiseptic and anti-freezing properties, and the stability and flow value of the modified asphalt mixture increased with increased wear resistance of the as- phalt pavement.

Abstract:Aiming at boosting financial and economic development in rural areas in China, the People's Bank of China and the China Banking Regulatory Commission proposed the rural financial innovation pilot program in 2008. In this paper, based on the panel data of 338 cities from 2007 to 2011, the Difference-in-Difference Propensity Score Matching(PSM-DID)was used to evaluate whether the policy was effective in improving finan- cial and economic development and trade of agricultural products. It was found that the program made heteroge- neous impacts on different economic indicators. It imposed positive effects on trade by raising the share of agri- cultural goods within export, but elsewhere its impacts are less articulated. We conclude that the innovation pilot program helped economic development to some extent but more efforts are needed.

Abstract:In order to objectively and accurately judge the current situation of logistics in west Africa and further judge its future development needs, due to the lack of statistical data for the large spatial scale of research and economic backwardness, it is significant to judge the construction needs of logistics infrastructure. So this paper put forward improved container generation coefficient method to measure west African foreign trade container generation. Based on west African economic judgment from the world bank, the international monetary fund and the United Nations and other related organizations in the world, it summarized the west African economic situa- tion and forecasted the trend of the future economic development. According to the basic situation of foreign trade of west African countries, by taking the container as the representative, on the basis of the calibration of multifactor variables including the total amount of foreign trade, economic growth, the change rate of containers, the optimum proportion of cases and optimum cases as the weight coefficients, it measured the foreign trade con- tainer generation and logistics requirements in west African countries through the improved container generation coefficient method. On this basis, the paper forecasts the future container production in combination with the e- conomic development trend, and makes reference for the regional traffic development, coastal port construction and further logistics planning in west African countries.