Abstract:In view of the present synchronous grouting diffusion model of shield tail, whose premise was that the longitudinal and circular flow of slurry was independent of each other,without considering the correlation of slurry flow,the mechanism of synchronous grouting diffusion mode in shield tunnel was analyzed, and the theoretical model of synchronous grouting longitudinal-circular integral diffusion of shield tail was established, which was based on Bingham fluid constitutive model and fluid mechanics principle. Through space and time domains discrete approach, a numerical algorithm to solve the theoretical model was designed. Combined with engineering examples, the theoretical model and numerical algorithm were validated. The results were compared and analyzed with the existing circumferential independent diffusion model. The results show that: compared with the circumferential diffusion model, the longitudinal-circular integral diffusion model improves the assumed conditions, and is more close to the actual situation of the project, which does not need to introduce sensitive assumption parameters such as the thickness of the ring cake. As a whole, the slurry pressure trends to be dominated by gravity, small in the upper part and large in the lower part. And the vertical gradient is about 16 kPa·m^-1. But the slurry pressure distribution in the local area near the grouting hole is relatively complex, which is related to many factors such as the grouting hole location, the direction of slurry flow and the pressure difference between the grouting pressure and the environmental pressure.

Abstract:In view of the lack of current research on concrete mesoscopic model of pebble aggregate, a pebble aggregate model was established based on Bezier curve. The probability distribution characteristics of two important parameters, such as the aspect ratio and radius variability of the real pebble aggregate, were obtained by image processing method. On this basis, the further research on the tortuosity of the concrete mesoscopic model was conducted. The results show that: the Bezier curve can effectively simulate pebble aggregates with smooth edges. the aspect ratio follows the general extreme value distribution, and the values are mostly between 1.0 and 3.0; the radius variability follows the lognormal distribution, and the values are mostly between 0.1 and 0.8; the tortuosity of the concrete mesoscopic model based on pebble aggregates is less than that based on gravel aggregates, and the difference between them increases with the increase of aggregate content.

Abstract:High pressure rotary spray technology has just begun to be applied to the repair of contaminated soil in recent years. The law of migration and diffusion of the injected agent is still unclear, which leads to the lack of reliable basis in engineering practice. At the same time, in order to overcome the shortcomings of conventional test methods, transparent soil materials were used to carry out laboratory tests and numerical simulation of the migration of remediation agents for contaminated soil. Considering the coupling of molecular diffusion, mechanical dispersion and convection, an advection-dispersion model was established to investigate migration characteristics of medicament in soil. The research results show that: the transparent soil test technology can visually show the migration process of the medicament and can be applied to study the migration characteristics of the contaminated soil repair agent. Under different soil pressure conditions, there is an optimal mud cake height. Under the same soil pressure, the higher the mud cake height, the smaller the concentration maximum value at the same position. The selection of the mud cake height is related to the setting of the high pressure rotary spray parameter, and has an important impact on the repair effect and efficiency. The migration of the medicament is mainly vertical migration, and the horizontal migration is not obvious. Therefore, in order to ensure that the medicament migrates to the edge of the mud cake at a higher concentration, the medicament should have a higher and uniform initial concentration in the horizontal direction of the mud cake gap.

Abstract:A long-term monitoring index system based on neutral axis（NA) position and the corresponding performance assessment method were proposed. Based on a detachable viaduct in Hebei expressway, a health monitoring system based on monitoring indicators was established, and the structural strain information was collected. Static response caused by traffic loads was separated from original strain signals by the multi-resolution wavelet analysis. The peak-valley pairs were picked in accordance with the designated peak prominence. Then the strain amplitude distribution was fitted and the measured NA arrays were derived. Finally, the neutral axis index was extracted from the accumulated data, and the statistical characteristics of different evaluation periods were compared and analyzed. The results show that the proposed neutral axis index in daily periods is less disturbed by the environment, which can represent the performance degradation of the structure in the long-term monitoring.

Abstract:The flexural tests of three ultra-high performance concrete-normal concrete (UHPC-NC) composite beams that ultra-high performance concrete (UHPC) was located in the tensile zone and one ordinary reinforced concrete beam were carried out. The stress process, the strain distribution in the mid-section, the crack development mode and the failure mode of the UHPC-NC composite beam were studied and analyzed. The test results show that the UHPC-NC composite beam basically conforms to the sectional assumption during the loading process, and the proper amount of longitudinal steel bars in the UHPC layer can greatly improve the flexural resistance of the composite beam. At the same time, the contribution of reinforcement and UHPC to the ultimate bearing capacity of test beam was calculated in four stages (initial state, stage state, ultimate state and failure state). Finally, the equivalent rectangular stress coefficient k of the UHPC layer in the tensile zone of the composite beam was derived. The results show that the contribution efficiency of the UHPC layer to the flexural resistance of the composite beam varies with the ratio of reinforcement.

Abstract:In order to reveal the high temperature mechanical properties of very high strength steel （VHSS)S960, tensile tests were conducted under both steady state and transient state fire conditions. The elastic modulus, yield strength, ultimate strength, stress-strain curve as well as failure mode of S960 were obtained. The test results were compared with current steel structure codes, such as EC3, ASCE, AISC, AS 4100 and BS 5950, to verify the applicability of standards for high strength steel (HSS). For comparison, the available research results in literature on S460, S690, Q460, Q550, Q690 and Q890 were compared with the test results of S960.Besides, the fitting formula of the mechanical properties of the VHSS S960 under the action of high temperature of fire was put forward, and its accuracy was verified. It is shown that fire-resistance design of steel structures with S960 is unsafe according to the current design standards, and differences of mechanical properties of HSS exist in different kinds of HSS. Moreover, the fitting formula for the deterioration of S960 at high temperatures was validated for practical engineering design.

Abstract:A lane-based optimization model for lane function and signal phase at intersection was established, considering the interaction of complex factors such as different approaches, different flow directions, different lane functions and different phase schemes. The objective function of the model was to minimize the critical flow ratio of the intersection, to consider the constraints such as lane balance, flow matching, lane function conflict, shared lane saturation, and to optimize the entrance and exit lanes at the same time. The solving algorithm for the proposed model was given. The proposed model has fewer variables, better connection with the current traffic design methods, and can get the global optimal solution. Moreover, the solution method is relatively simple. The case study shows that the proposed model can effectively reduce the critical flow ratio, cycle and vehicle average delay at intersections.

Abstract:In view of the traditional fuzzy control car-following model, the difference of driving style was less considered, and the effective verification of real data was lack. Based on the fuzzy control theory, the dynamic driving decision-making process adopted by the driver in the following process was simulated, and different driving styles were considered. Based on the analysis of the natural driving data, different driving styles were analyzed by use of the measured data, and the desired time headway parameters of each driving style were obtained. On this basis, the distance error and speed difference between the front and rear cars were used as independent variables, and the fuzzy control rules were established. The numerical analysis results show that the proposed model fits well with natural driving data.

Abstract:In order to establish the driver behavior model under the action of crosswinds, a driving simulation platform for long-span bridge under the action of wind-vehicle-bridge coupling was built based on the 8-dof driving simulator. Thirty-two professional truck drivers were recruited to conduct driving simulation experiments under crosswinds. Driver behavior and vehicle dynamic response data were collected and a two-level driver behavior model was established under crosswind. The results show that the steering wheel torque feedback is one of the key factors affecting the driver behavior under crosswind. Considering the steering wheel torque feedback, the two-level model can better reflect the driver behavior under the action of crosswind.

Abstract:Taking the expressway network for hazardous materials (HAZMAT) transportation as the research object, the starting point of controlling the total risk was introduced. By drawing on the principle of sub-optimal tolling, the tolls on road sections were taken as decision variables, a bi-level programming model with variational inequality was established for the optimization research of HAZMAT transportation management. A particle swarm optimization algorithm nested with a diagonalization algorithm was designed to solve the proposed model, and a case was used to verify the calculation. The corresponding numerical results and parameter sensitivity analysis show that the proposed bi-level programming model and corresponding algorithm for tolling of expressway transportation networks for HAZMAT are effective and feasible, which can provide a reasonable decision-making reference for the government’s HAZMAT transportation management department.

Abstract:The presence of internal moving remainder in high-precision spacecraft is an important factor to reduce the reliability of spacecraft. Aiming at the problem that the existing remainder detection algorithm was difficult to effectively detect the remainder pulse and eliminate the interference of the movable component under relatively strong environmental noise, an algorithm for detecting the remainder of high-precision spacecraft based on spectrum subtraction denoising, two-stage pulse extraction and periodic analysis of pulse generation sequences was proposed. The spectrum subtraction method was used to achieve effective suppression of environmental noise. The two-stage pulse extraction method was used to extract the pulse of the remainder signal and the movable component signal. By analyzing the periodicity of the pulse generation sequence, the periodic signal similarity was used as the discrimination basis for distinguishing the remainder signal and the movable component signal; thereby the detection of the remainder was realized. The experimental verification shows that the proposed algorithm can effectively detect the existence of remainder and movable components in the spacecraft, and the recognition accuracy can reach 96％.

Abstract:Taking the nearly zero energy residence and conventional residence in hot summer and cold winter zone as research objects, the dehumidification capacity in summer and dehumidification period was calculated. The characteristics of angle scale and indoor high humidity of two kinds of buildings were studied comparatively. The results show that: the variation of dehumidification capacity of nearly zero energy residence and conventional residence are mainly determined by the amount of fresh air and infiltration rate. Air exchange rate during uninhabited period have little influence on the dehumidification capacity. Without considering the sensible heat load and moisture load of fresh air, the angle scale of nearly zero energy residence in summer and dehumidification period is reduced to that of conventional residence 45.3% and 38.5% respectively. High humidity period of nearly zero energy residence in summer and dehumidification period is longer than that of conventional residence when indoor temperature is selected as the control parameter. Limiting the air exchange rate during uninhabited period of nearly zero energy residence in summer and ventilating properly in dehumidification period contributes to decrease the indoor high humidity time period.

Abstract:The microenvironment and human thermal comfort of the driver position in the passenger compartment in summer were studied by means of experiment and numerical simulation. Firstly, the influence of air supply temperature and air supply velocity of air conditioner, solar radiation intensity, solar altitude angle and environmental temperature on the microenvironment of different parts of the driver’s position was analyzed under 11 different working conditions. Then, based on Stolwijk human thermal regulation model, the Berkeley thermal comfort evaluation model was adopted to simulate the thermal comfort state of passengers, and the influence degree of various influencing factors on human thermal sensation and thermal comfort was obtained.

Abstract:A theoretical model of steady-state curve negotiation of coupled bogie for straddling monorail vehicle was established, the mechanism of radial adjustment of the coupled bogies was analyzed, and the formula for calculating the coupling parameters required for achieving the radial state was derived. The dynamics model of straddling monorail vehicle equipped with coupled bogies was established, and the curving performance of the coupling bogie was simulated, and the radial adjustment capacity of coupled bogie was verified. Meanwhile, the influence of coupling parameters on the radial adjustment capacity and curving performance of the coupled bogie was also analyzed. The results show that the optimal rotary stiffness is only related to the vehicle structural parameters and the secondary longitudinal stiffness. The reasonable selection of the coupling rotary stiffness can make the coupling bogie automatically reach the radial position on the circular curve under the joint action of the secondary suspension system and the coupling mechanism. At this time, the maximum radial force of guiding wheels is obviously reduced, and the curve passing safety of the vehicle is significantly improved. The coupling lateral stiffness has little effect on the steady value of the yaw angle of the coupled bogie, but it will worsen the dynamic performance of the bogie on the transition curve.

Abstract:Let be the real Jordan algebra of all self- adjoint operators on a complex Hilbert space.We characterize the surjective maps preserving the -numerical radius of products for operators in.Further, for a special kind of,the form of surjections preserving the -numerical range of products for operators in is obtained.

Abstract:By use of the theory of real options and under the uncertainty of carbon emission rate and technology cost, the optimal introduction timing of carbon emission reduction technology for enterprises was explored, with the consideration of the cost of technology maintenance. And the optimization problem was transformed into a variational inequality problem for solving the HJB (Hamilton-Jacobi-Bellman)equation. Under the framework of viscosity solution, it was proved that the value function was the unique viscosity solution of the problem. The numerical simulation results were presented, and the optimal introduction timing with different parameters was also discussed.

Abstract:Based on the value co-creation theory, the PLS-SEM model (partial least squares-structural equation model) was established and verified. The online interactive learning platform played the role of moderating variables. The online interaction helped to continuously improve the social value of users, thus the stickiness of users was enhanced. Through the comparison of direct impact and indirect impact, the influence of both behavioral engagement and cognitive engagement on the value of the four dimensions was revealed through the moderating effect of online interactive platforms. While, emotional engagement only influenced social value. The research conclusion reveals the internal mechanism of online interactive of the platform, which plays a positive role in improving the design of interactive platforms.

Abstract:For a supply chain composed of one dominant manufacturer and several upstream suppliers, an integer linear programming model of multi-objective and multi-period order assignment for manufacturers was established, in order to minimize the total cost of the manufacturer when purchasing. The purchasing expenditure of manufacturers, sales loss caused by quality factors and inventory cost affected by delivery factors were considered comprehensively in the proposed model, which combined with three factors of products such as product price, quality and delivery. The proposed model took the production capacity of suppliers, quantity discount of suppliers, relationship maintenance between suppliers and manufacturers as well as inventory capacity of manufacturers as constraints. The weight analysis of the three objectives was carried out through a calculation example and the optimal solution of the proposed model was obtained by Lingo17.0, which provided a multi-period order decision-making framework for manufacturers. Finally, the sensitivity analysis of several important influence parameters in the proposed model was carried out, and some reference suggestions for manufacturers and suppliers were also put forward.