Abstract:Aiming at the problem of missing damage information caused by the unclear physical meaning of model parameters in the existing structural damage identification method, a damage identification method based on time series model is proposed. Firstly, the general expression of auto-regressive model with eXogenous input (ARX) is derived. The ARX model considering structural dynamic characteristics is established by the simultaneous multi-degree-of-freedom system motion equation. Subsequently, the model is used to predict the nodal acceleration under undamaged conditions, and the parameters of the structural damage, i.e. the damage factor, are constructed according to the difference between the measured data and the predicted data. Finally, the structural damage state is evaluated based on the magnitude and distribution of the damage factor. The numerical results show that the proposed method can perfectly identify single-position and multi-position damage under less measurement dates, and can make a more accurate judgment on the damage degree. At the same time, the influence of the excitation position and measurement noise is small.

Abstract:Based on high-frequency balance force wind tunnel tests, the base bending moments of a square-section super high-rise building with an adjacent building at 36 different locations were measured in 4 simulated turbulent wind fields, the galloping force coefficient is obtained by analysis, and the influence of wind field characteristics and interference effects on it is discussed. The test results show that the galloping of the square-section super high-rise buildings without interference building can only occur when the angle between the wind direction and the building body axis is less than 16°. And in the wind field with turbulence, the possibility of galloping near the 0° wind direction angle is the largest. When the interference building is directly in front of the upstream, the probability of galloping near the 0° wind direction angle is significantly reduced. In turbulent wind fields, the galloping instability near the 0° wind direction angle is increased only when interference building in few partial positions.

Abstract:Socket connection is an approach to connect precast members by inserting the pier directly into a pre-opened socket of the footing that is precast or cast in site construction, and sealing with high strength non-shrink grout. The significant advantages of this connection are low alignment accuracy, simple construction and less on-site workload. Its mechanical performance highly depends on the socket depth of the pier and the bond property of grout. Therefore, quasi-static test of specimens designed from a real bridge with different socket depth was conducted together with the numerical simulation by OpenSEES, to study the influence of socket depth on the seismic performance of the bridge pier. The minimum reasonable socket depth was proposed based on the results experimentally and numerically, providing a reliable guidance for such pier design.

Abstract:In this paper, track-bridge interaction finite element models of both a three-span continuous beam bridge and a simply supported beam bridge were established in order to study the influence of creep camber on the track-bridge interaction in railway bridges. The effects of creep camber on additional rail stresses (ARSs), the uplift and shearing force of fasteners, and the train running performance of continuous welded rail (CWR) on bridges were analyzed. The results show that for the limit value of creep arch based on beam-rail interaction, the uplift force of fasteners and driving comfort play a controlling role, while the effect of ARSs is relatively insignificant. For beam bridges with the same arch-span ratio, the peak values of ARSs, uplift force and shearing force of fasteners induced by creep camber are basically the same. For the continuous beam bridge with a main span of 125 m and the simply supported beam bridge with a span of 30 m in this paper, the reasonable limit value of the archspan ratio of creep camber should be 1/2 500 and 1/2 000 respectively.

Abstract:With Bingham grout as the study object, this paper deduces the spherical displacement infiltration diffusion model by applying generalized Darcy's law and theories of seepage mechanics based on the displacement effect of grout for groundwater. Through examples, the characteristics of the grout infiltration diffusion when considering the grout displacement effect is analyzed, and the main factors affecting the grout infiltration diffusion is analyzed. The results show that when the grout displacement effect is considered, the grout pressure in the diffusion front decreases along the concave curve with the increase of the diffusion distance. Although the change of frontal grout pressure is small, it has a great influence on the grout diffusion radius, and the grout diffusion distance shortens about 23% at 1 h.

Abstract:Based on the calculation of the ratios of employment to population within floating units generated by the software of geographic information system(GIS), the spatial scale and degree of balance are analyzed. With the visualization of change curve and numerical distributions of the cumulative statistical indicators, spatial scales of jobs-housing balance for the employment center and sub-centers, residential communities and other areas in a mega city are obtained. Based on the data of jobs, population, road network in Shanghai, in case of different convergence values, such as 80%, 85% and 95%, the employment center has the largest scale of jobs-housing balance. By 85%, it is about 15 to 25 km for Puxi area, while Pudong area varies from 20 to 28 km. For employment sub-centers, the scales are 4 to 10 km. The balance scales of other zones are determined by the employment center as well as sub-centers. As the distance from the centers increases, it is expanded from 3 km to 8 km, even 17 km. This method could be used to analyze the urban spatial structure and jobs or housing accessibility. By employment and residential commuting distance analysis, it is expected to explain the phenomena and internal causes of jobs-housing mismatch and long-distance commuting.

Abstract:This paper proposes a classification method for urban complexes based on its land development and city-wide influence. Thus, urban complexes can be divided into two types: city-wide urban complex and regional urban complex. Then, the radiation range characteristics of the two types were analyzed. From the characteristics of mode choice behavior, by means of both objective behavior modeling and subjective willingness analysis, the effectiveness of the classification method in characterizing travel behavior difference is quantitatively verified, figuring out its significance for refined transportation system configuration planning. Finally, through reviewing with the traditional classification methods, a more operable method for actual project is proposed. It may provide a clear guidance for the refined transportation configuration and avoid the deviation of planning direction.

Abstract:To improve the bus punctuality rate, this study presented a method to control bus arrival time to the downstream bus stop by optimizing the upstream intersection signal timing scheme. The deviation between bus actual and scheduled departure time at the upstream signalized intersection was adjusted by introducing the intersection phase margin time, and the bus punctuality control model based on the phase margin time was established. The bus arrival scheduled timetable was generated via a comprehensive optimization of common cycle length and offsets along the artery. The simulation results show that the developed control model can guarantee the bus punctuality, and the bus timetable can get a good control effect.

Abstract:This paper studies an integrated optimization method for the operation timetable and vehicle scheduling plan of single-line pure electric bus. The method establishes a multi-objective optimization model aiming to balance departure headway, decrease number of vehicles used and electric bill. The method also keeps the model within bounds for the consideration of headway range in different period, the vehicle quantity, the endurance capacity of pure electric buses and so on. Then the paper uses a multi-objective particle swarm optimization algorithm to solve the optimal solution set based on multi-objective priority. As shown in the case, compared with the current situation plan, the model presented in this paper plays a role in balancing the departure headway and reducing the number of vehicles used, as well as making full use of offpeak hours to reduce the electric bill.

Abstract:There is a clear relationship between driving behavior and crash risk, with using mobiles during driving one of the key factors related to crash risk and severity. Towards the limitation of driving simulators in an unnatural setting, 296 samples of mobile phone operations during driving were extracted in Shanghai naturalistic driving study data, and the process of using mobile phones was divided into five operations: dialing, answering, talking and listening, hanging up and viewing. The study respectively analyzed the strength of driver’s control activities, the sensitivity of the control operation and the stability of the control state during each operation. Studies have shown that some operations will lead to a decrease in driver’s control activities and affect the stability of vertical control. These findings help develop more reasonable traffic safety management measures.

Abstract:Using temperature, strain and deflection measured by “Pavement Condition Monitoring System” of Shanghai Pudong International Airport, this study analyzed temperature variation of cement pavements， curling deformation，deflection and load transfer capacity affected by temperature. The results show that daily variation of temperature in the subgrade and base layer is slightly, but seasonal variation is obvious. The temperature distribution along the depth of the slab is nonlinear, and it is more significant in afternoon; the proportion of positive and negative temperature gradients is basically the same throughout the year, and the zero temperature gradient is cyclical throughout the year, concentrating in the period from 7:00 to 10:00 and 19:00 to 22:00. In addition, under the effects of temperature, for the middle of the dummy joint, the slab corner and the middle of the groove joint, the curling deformation shows a synchronous periodic change within one day, and the curling deformation at the slab corner is the largest while it is the smallest for the longitudinal joint; it also shows that the maximum upward (downward) curling deformation happens between December and January (July and August) throughout the year. The maximum deflection at the slab center remains basically the stable, while the maximum deflection at the slab corner and the middle of the dummy joint exhibit significant daily and seasonal variations; the load transfer capacity of both dummy and groove joints increases with the increasing of the average temperature and they have a good quadratic relationship. It is suggested considering the effects of temperature on design and evaluation of cement pavements.

Abstract:Natural pyrethrins was encapsulated in hollow hydrophobic part of β-cyclodextrin to protect it against natural degradation. The encapsulation efficiency and drug content of the pyrethrins microcapsule prepared were 92.15% and 8.5%, respectively, and the particle size ranged from 1 to 17 μm. It was demonstrated that the pyrethrins microcapsule had better thermal stability and slow-release capability than liquid pyrethrins. Its slow-release kinetics could be described as the first-order model. The storage stability of pyrethrins was improved after encapsulation. Results showed that the drug content decreased within 20% after 5 months at 4℃. Under natural conditions, microcapsules could also prolong the storage duration of pyrethrins by 1~1.5 times. The pyrethrins microcapsule in this study had high insecticidal activity against Culex pipiens pallens, Aedes albopictus, Chilo suppressalis, aphids and Myxodes armyworm, indicating that it was a promising pesticide for the control of pests.

Abstract:Previous studies showed that Dubinin-Radushkevich equation (D-R equation) does not describe the microporous adsorption well in the partial region of 2.59<［ln(p0/P)］2<10 (P is the balance pressure of adsorbate, p0 is the saturated vapor pressure at the experiment temperature). A modified expression of D-R equation is proposed herein for activated carbon materials in the range of 2.59<［ln(p0/P)］2<10. The adsorption capacity of the three activated carbon adsorbents at different relative pressures was tested with adsorption and desorption experiments, and the experimental data were fitted using proposed equations and original D-R equation. Results showed that in the range of 2.59<［ln(p0/P)］2<10, the proposed equations can describe microporous adsorption more accurately than the original D-R formula.

Abstract:This paper analyzes and summarizes the intelligence evaluation of autonomous vehicles. Firstly, the intelligence definition of autonomous vehicles is summarized and compared; then the indicators selected for intelligence evaluation of autonomous vehicles are sorted out systematically; ofter that the evaluation methods are summarized according to qualitative evaluation and quantitative evaluation, and the characteristics and limitations of different evaluation methods are analyzed in depth; finally, several future research directions are proposed for the further development of the intelligence evaluation of autonomous vehicles.

Abstract:In terms of freezing process of liquid water inside gas diffusion layer for proton exchange membrane fuel cell(PEMFC) under pore-scale prospective, a mesoscopic simulation tool is proposed here to be involved in PEMFC-lattice Boltzmann method(LBM). First, true gas diffusion layer structure for PEMFC was built in pore-scale level. Then, accuracy of thermophysical parameters in the model was validated through one-dimensional half-space solidification, two-dimensional solidification in semi-infinite corner and two-dimensional solidification in cavity with porous numerical experiments, proving the effectiveness of application of lattice Boltzmann method on freezing mechanism in gas diffusion layer for PEMFC. Finally, the freezing process of gas diffusion layer with porosity ranging from 0.5 to 0.9 in pore-scale was investigated. The simulation results show that for two-dimensional gas diffusion layer with 0.5, 0.6, 0.7, 0.8 and 0.9 porosity, the dimensionless freezing time F0 is 2.67, 3.11, 3.68, 4.31 and 4.84, respectively and the dimensionless freezing time for cases with natural convection is 0, 0, 0.001, 0.001 and 0.007 less than that without natural convection, respectively.

Abstract:Based on a 1.0 L turbocharged engine, stoichiometric, lean burn and exhaust gas recirculation (EGR) conditions were tested under the compression ratios (CR) of 9.6 and 12 to study their combustion and fuel consumption characteristics. The results show that the fuelsaving effect of EGR is better than that of lean combustion under heavy loads with higher compression ratio, and the fuelsaving effect of lean combustion is better under other conditions. By changing CR together with lean burn or EGR, brake specific fuel consumption (BSFC) can be reduced by at most 7.5%, 10.4% and 9.3% comparing with CR9.6 stoichiometric conditions under light, medium and heavy loads respectively. Combined with onedimensional simulation, the reasons and different characteristics of fuel saving under lean burn and EGR conditions under heavy loads are analyzed and compared. The results show that lean burn under high compression ratio and heavy load when excess air ratio (λ)<1.4 cannot suppress knocking, and the fuel saving effect is not obvious; under the same working condition EGR can effectively suppress knocking and reduce fuel consumption up to 5.5%. The fuelsaving of lean burn and EGR under heavy loads are mainly due to the reduction of heat transfer loss and exhaust loss. The sum of their contribution to fuel economy is higher than 90%.

Abstract:This paper focused on the effects of water injection on combustion and emission characteristics in heavyduty natural gas engines by numerical methods. The results show that water injection has no significant effects on the stage of low-temperature reactions, but the generation rate of OH radicals is limited in the stage of high-temperature reactions. Therefore, there is not enough oxidant to oxidize CO. The combustion duration is extended, and the temperature during the combustion is reduced. Moreover, the flame propagation speed and fuel heat released rate slow down with the increase of water injection quantity. The combustion duration and phase are delayed, and the maximum temperature decreases with the water quantity increasing. Besides, the spray position closer to the combustion chamber contributes to the effect of water evaporation on reducing the temperature in the combustion chamber, which is beneficial to increasing the charging density in the intake stroke. Water injection can significantly limit the thermal load of engines and the formation of nitrogen oxides in the combustion chamber, thereby providing the possibility of equivalence ratio combustion in natural gas engines.

Abstract:Multi-temporal interferometric synthetic aperture radar (MT-InSAR) technology was applied to process C-band ENVISAT data from 2007 to 2010, X-band TerraSAR-X from 2010 to 2015 and C-band Sentinel-1A from 2016 to 2018 to monitor ground subsidence along the Shanghai maglev zone and velocity maps were plotted. An optimal multi-level network with high coherent points considering both point density and distribution was used to increase the number of coherent points with high precision efficiently. Comparing the data with different wavebands, the relationship between the image resolution along azimuth and range direction and the number of coherent points was analyzed. The experiments have shown that the coherent points along the maglev track are closely related to the range resolution. In addition, the velocity map obtained by MT-InSAR was evaluated using the levelling data. The result shows the maglev track is stable although there are several subsiding troughs near the maglev track.

Abstract:Based on the image of point cloud, a detection algorithm for cracks and water seepage area identification in multi-scale space is proposed. According to the physical features of tunnel cracks in different scale, meanwhile, with the definition of scale space, a fusion image detection operator is developed to maintain the stability of ribbon like cracks detection, at the same time, to restore the sensitivity to the small cracks in high gray value for obtaining more edge pixels. Therefore, the identification and detection of multi-scale cracks and seepage are achieved with the application of proposed algorithm. It is proved by an example that the algorithm can effectively eliminate the interference of fake cracks, and accurately identify and locate cracks in different scales.

Abstract:Propose an algorithm to optimize the strategy for an inventory system, minimize the storage cost with constraint of satisfying service level. Abstract the inventory system optimization problem into a stochastic optimization problem, combine Kriging regression and Monte Carlo tree search to solve the stochastic optimization problem efficiently. Apply this method into a real world example and get positive feedback.