Abstract:Aiming at the problem of creeping effect of concrete structure, the age -adjusted effective modulus method is combined with the ANSYS finite element commercial software package to introduce the "unit life and death" technology into the creep analysis of the concrete structure segment construction process. The data trans- mission problem between the segment construction process, and based on the ANSYS parametric design language APDL, the command flow is compiled, and the creep effect analysis problem is transformed into pseudo-elastic analysis problem, and the calculation is simple. Taking the classic three-section continuous beam bridge as an example, the creeping coefficient calculation formula of the current code "Code for Design of Highway Rein- forced Concrete and Prestressed Concrete Bridge and Culverts" is used to analyze the creep of the continuous beam bridge. The internal force is compared with the existing calculation results, which proves the feasibility and effectiveness of the proposed method. And the node displacement curve of each node is drawn.

Abstract:Reinforced concrete columns are the main load-bearing component of the structure. In order to en- hance more efficiently the seismic behavior of reinforced concrete columns, a method to strengthen column by using different height of cement-based grouting material with steel wire mesh (CGMM)was proposed. Three rein- forced concrete columns were tested under low reversed cyclic loading and the process of tests was introduced. Failure mechanism, hysteretic behavior, ductility, cumulative energy dissipation and stiffness degradation of specimens were analyzed. The experimental results showed that the seismic performances of CPRP1 and CPRP2 specimens were significantly higher than that of CP specimen. In the columns of different strengthened height, with the increase of CGMM strengthened layer, the peak load, ductility and energy dissipation of specimen in- creased and the stiffness degradation became less rapid.

Abstract:Taking one shield tunnel crossing through the bridge viaduct pile foundation of a metro as the engi- neering background, this study analyzed pile underpinning and removing technology of the shield tunnel crossing in such a complex environment. It solved the technical difficulties in the process of underpinning, such as wa- ter-proof performance, stability of structure and tool modification of cutter head. At the same time, the construc- tion process of underpinning pile was simulated by plane strain calculation model. The results show that the maximum settlements of bridge piers and underpinning pile were all in the scope of the early warning, the con- ditions of this underpinning pile engineering were very complicated and the displacement control was very strict. Through the research and analysis of the construction scheme, it proves that the construction method is feasible with a high standard, which can provide certain engineering reference for similar projects.

Abstract:For shallow buried tunnels with poor surrounding rock stability, reasonable construction methods have great significance for ensuring tunnel construction safety and controlling construction quality. Taking Wushutou Tunnel as an example, three different construction methods of double-side guide pit method, CD method (single- side guide pit method), three-step plus temporary inverted arch method are comprehensively analyzed, and three engineering methods are used by FLAC software. Simulate and analyze the plastic zone change and surrounding rock deformation of different construction methods tunnels, and put forward the construction method in accor- dance with the project, and compare the monitoring data at the same time. The research results show that the double-wall method can ensure the stability of surrounding rock and the deformation of surrounding rock, and optimize the construction parameters and key steps of the double-wall method, which can provide a reference for the construction of such highway tunnels.

Abstract:In tunnel engineering, the disconnection of supporting and surrounding rocks is common. At present, most of the numerical studies of tunnels have assumed that supporting and surrounding rocks are closely con- nected without considering the influence of contact surfaces, which may lead to certain errors in the calculation results. In order to solve such problems, FLAC5.0 finite difference software was used to simulate and calculate the disconnection between supporting and surrounding rocks in shallow-buried tunnel in soft and hard stratum. The influencing factors of tunnel stability were analyzed. The calculation results show that the contact surface el- ement is more suitable for simulating the contact between supporting and surrounding rocks. When there is a gap between supporting and surrounding rocks, the displacement of surrounding rocks increases greatly while the in- ternal force of supporting has no remarkable differences, which can provide better guidance for design and con- struction.

Abstract:The development of pre-grinding new rail in high-speed railway was researched by simulation of wear and rolling contact fatigue (RCF) crack and field test. The effect of pre-grinding, defects of rail and their growth characteristics were analyzed. The results show the pre-grinding rail with special designed profile can control wheel/rail contact location and width of contact band to get excellent wheel/rail interaction. The pre-grinding rail was mainly affected by wear which had linear growth trend with the accumulation of operation time. The distri- bution of wear around the railhead in high and low rails was -10°~ 60° and ±10°respectively. After about 1 year operation, the special profile of high rail was changed by wear which deteriorated the wheel/rail contact condition and caused two-point contact in the high rail. It is recommended the preventive grinding interval is 1~1.5 years.

Abstract:In order to study the influence on dynamic performance of metro vehicle during the air loss of air spring, the nonlinear dynamic model of metro vehicles and the stick-slip contact force model of air spring in the state of air loss were established. And the critical speed, derailment coefficient, lateral wheelset force，wheel rail lateral force，wheel unloading rate and Sperling value of the metro vehicle in the normal state of the air springs and the air loss of the whole vehicle air spring were calculated and compared. The results show that the critical speed of the metro vehicle is reduced, and the derailment coefficient, the wheel unloading rate, the lateral wheelset force and wheel rail lateral force, and the lateral and vertical Sperling value of the metro vehicle in- creases obviously when air spring loses air. Since the derailment coefficient and vertical Sperling value are af- fected significantly, the state of the air spring deserves more attention to ensure the smooth and safe operation of the metro vehicle.

Abstract:The capacity of pedestrian crossing is an important factor affecting the setting of pedestrian crossing. Through the investigation of street speed and crossing characteristics of pedestrians and non-motorized vehicles, a signal control capacity model of pedestrian crossings based on closed vessels and a non-signal control capacity model of pedestrian crossings based on gap acceptance were established and verified by an example in this paper so as to provide reference for the research on the capacity of pedestrian crossings.

Abstract:The traffic accidents of expressway are frequent and serious, which pose a great threat to the personal safety of freeway drivers. The function of the guidance device set up on the expressway is single, and the induc- tive effect is not strong. Aiming at the above problems, a new type of intelligent photoelectric contour was de- signed, which can carry out the function of traffic flow density warnings, traffic accident alarm and traffic guid- ance in congested section of expressway. With the traffic accident dredging theory, the traffic density and the in- fluence range of the accident would be calculated under the condition of road congestion or accident. Combined with the level of highway service, flashing alarm for drivers in the range of accidents would be carried out which can reduce the occurrence rate of secondary accidents effectively.

Abstract:In flight landing scheduling, the traditional flight scheduling strategy first-come-first service (FCFS) always arranges the first aircraft to land first, and then lets the later aircraft wait to land, but ignores the fact that the flights also have priority landing grade and different importance of flights in the waiting process with those important or in emergency having landing priority. This paper introduced constrained position shift (ZCPS) with different importance factors, combined with the improved ant colony algorithm and genetic algorithm (GC). The elite retention strategy was adopted to divide the primary optimization result of the ant colony algorithm into two communities and the genetic algorithm was used to obtain an optimized alignment in the actual operation. Simu lation results show that the method is usually superior to the classical first-come-first-served service, and the new method can save 19% ~ 38% of the time, effectively reducing the aircraft delay time.

Abstract:China's aircraft leasing business started late but has developed rapidly. This paper selected the growth data of China's aircraft leasing business from 2008 to 2016 in terms of scale, structure, speed and quality, adopted the principal component analysis method to construct the growth index of aircraft leasing business, and analyzed the reasons for the change of growth level from the internal structure of the index. The study shows that China's aircraft leasing business has an upward trend of fluctuation in general, but in 2013 it fell back due to the capital market, and then resumed rapid growth after 2014. The State Administration issued the Opinions on Accelerating the Development of Aircraft Leasing Business, which played an important role in promoting the de- velopment of the industry. And the revenue is the key factor in the growth of China's aircraft leasing business.

Abstract:The classification of rail transit stations has an important impact on the study of passenger flow pat terns, surrounding land use and development trends of different types of stations. Based on AFC data, a variety of effectiveness indicators were used to determine the number of classifications. By way of principal component analysis, k-means clustering and multiple linear regression, qualitative and quantitative analysis were combined to classify the sites. A total of 58 stations of Suzhou Rail Transit Line 1 and 2 were divided into 4 categories, which would lay the foundation for the follow-up study of the classified sites and the development of rail transit.

Abstract:Along with the increase of traffic volumes of airports, runway incursion events are increasing rapidly, which have certain influence on airport safety, so the evaluation of runway incursion hazard is very significant. This paper analyzed the runway incursion events by using the method of dynamic event sequence diagram ESD, describing the runway usage and operating conditions of the airport runway under the regulatory process and studying the influence of dynamic factors on the system and accident development process and its consequences. The research indicates that the occurrence of the scene events can be taken away in time without eliminating the danger source, which can effectively avoid the occurrence of runway incursion, so it can provide some new ideas and directions for preventing runway incursion.

Abstract:In order to predict more accurately the frequencies of lane changes with the limited data, a combined forecasting model based on neural network and Markov chain was proposed. The average speed and density of road sections were collected, and the BP neural network model was used to train the preliminary fitting model. By using Markov chain method, the distribution and probability of lane changing frequencies in three groups of intervals representing overestimation, normal and underestimation were given to decrease BP neural network er- ror. The combination forecasting model was adopted to predict and analyze the frequency of lane-changing of a road in Xi'an. The results show that the actual frequencies of lane changing are all within the prediction range of the maximum probability given by the model, which indicates that the model can predict the frequency of lane changing according to the average speed and traffic density of the section.

Abstract:The cascaded H-bridge multilevel inverter has wide application prospects in high-voltage and large- capacity photovoltaic grid-connected power generation system owing to the advantages of low loading stress of the switch tube and low harmonic content of grid-connected current. The cascaded H-bridge multilevel inverter grid-connected photovoltaic power generation has some problems, such as uneven light intensity and tempera- ture, aging of photovoltaic panels or being shaded, which may lead to unbalanced output power of each phase of the H-bridge inverter, resulting in unbalanced grid-connected current. In this paper, a zero-sequence injection method based on DC/DC converter for three-phase cascaded H-bridge photovoltaic grid-connected system was proposed. The required zero-sequence component was obtained by subtracting the positive sequence envelope voltage from the specific square wave, so that the grid-connected current can still be in phase with the grid volt- age under the condition of unbalanced input power. The simulation results in MATLAB / Simulink environment show that the harmonic content of grid-connected current meets the IEEE Std. 929-2000 standard and can real- ize the operation of unit power factor.

Abstract:A module partition approach based on density algorithm and design structure matrix is proposed for solving the problem of product modular design, considering the diversity of design structure matrix in actual pro- cess. Design structure matrix is utilized to describe the relationship between components, which are clustered according to the density reachable principle, by judging the Euclidean distance of the n-dimensional space. Dif- ferent partitioning results are obtained while adopting the different algorithm parameters, and the modularity metric is acted as the evaluation index of the clustering results to select the optimal module partition scheme. Finally, the module division process is illustrated by taking the truck crane as an example.

Abstract:Planetary gear transmission is an important form of transmitting motion in the field of machinery. The problem of transmission design and the load sharing of planetary gear trains are two important aspects in the study of planetary transmission system. In this paper, the research status of planetary gear transmission was sum- marized from four aspects, including design theory, analysis method, load sharing characteristics and experimen- tal study. From the existing research results, domestic and foreign scholars mainly analyze and study the trans- mission scheme of planetary gear trains which have been designed, and it is urgent to develop the optimization scheme of planetary gear transmission based on active design. The current manufacturing has reached a relatively high level, simply using existing methods to suppress the planetary row eccentric load, has been difficult to sig- nificantly improve the performance of planetary gear transmission, it is urgent to explore new methods to sup- press planetary row eccentric load. Therefore, on the basis of absorbing and digesting the existing research and development technology of planetary gear transmission, it is necessary to improve and innovate the eccentric load suppression method of planetary row and the design theory of multi -stage gear transmission system, so as to adapt to the development trend of transmission equipment toward large models, reduce the failure rate of large gearboxes, and increase their service life.

Abstract:The duty cycle of the AC terminal voltage of the three-stage cascaded H-bridge rectifier was derived and the working state of the circuit was analyzed in this study. Then, the ripple formula of the inductor current under each working condition was derived. On this basis, the curve of the inductor ripple current and the varia- tion of the inductor magnetic loss in half of the mains cycle were obtained. Comparing the single-stage H-bridge rectifier and the single-stage triple-frequency H-bridge rectifier, it can be seen that the magnetic loss charac- teristic of the three-stage CHBR inductor was different from that of the single-stage H-bridge rectifier, and the frequency of the single-stage H-bridge rectifier was increased to Triple times also does not reflect the magnetic loss characteristics of the three-stage CHBR. By calculation, the total core loss of the three-stage CHBR induc- tor is only 0.05 times that of the single-stage H-bridge rectifier. Finally, the correctness of the analyzed theory was proved by experiments.

Abstract:In order to study the physiological effects of different algal concentrations on their leaves and roots in eutrophic water, the experiment was designed to have 4 treatments, i.e.0,122,166 μg/Land 222 μg/L of Chloro- phyll a, and the physiological indexes between 0 d , 10 d, and 20 d of Vallisneria Asiatica was compared. Re- sults show that the leaves content of soluble protein was inhibited by cyanobacteria, the activity of SOD at 20 d was significantly higher than 10 d，and POD and SOD was inhibited in different degrees in roots. SOD, POD and CAT in leaves of Vallisneria Asiatica had a rising trend with the increase of cyanobacteria concentration to adapt to oxidative stress. MDA increased significantly when the concentration of chlorophyll a (Chl a) was 222 μg/L in water. When the chlorophyll concentration of the cyanobacteria was greater than 122 μg/ L, the plant could adjust its antioxidant defense system to remove the excess active oxygen to adapt to the oxidative stress instead of cyanobacteria concentration. This provides a scientific theoretical basis for controlling cyanobacteria concen- tration in the eutrophic lakes of Taihu and restoring the biological population of Vallisneria Asiatica.

Abstract:With the rapid development of photovoltaic power generation technology, the users of photovoltaic power generation system in China are increasing year by year. It is of great significance for studying the dynamic economic optimization and scheduling problem of household photovoltaic system. Taking the maximization of user income as the objective function, the proportion of the network users and the proportion of electricity purchase were set as decision variables. The economic benefit scheduling model of the generation system was determined by net income of the photovoltaic power generation system, the electricity purchase expenditure, the government subsidy, photovoltaic array and the battery system maintenance expenditure. In the MATLAB simulation environ- ment, taking the operation and scheduling of a home photovoltaic power system in 24 hours as an example, this study selected several electricity purchase price mechanisms currently implemented in the market, and the parti- cle swarm optimization algorithm was used to optimize the established model. The optimal revenue obtained from the basic electricity price mechanism and the different load conditions were compared respectively. Finally, it provided the best scheduling strategy for the dispatcher.