Abstract:The Reynolds number effect of engineering structures has always been a fundamental problem in wind engineering. With the increasing of building height and bridge span, the wind resistance research needs to be more precise, which makes the Reynolds number effect becoming more and more significant. This paper presents an overview of the basic research achievements and engineering applications of circular cylinder, rectangular prism and bridge models. The related contents including the surface pressure distribution, the three component forces coefficients, the Strouhal number, the fluctutating pressure and the fluctutating wind force. Two methods of high Reynolds number effect simulatio n in low Reynolds-wind tunnels are summarized, for instance, changing model surface roughness and increasing the flow turbulence. Finally, some recommendations for future researches are proposed.

Abstract:In ANN-ODM-MC method, computation work is dramatically decreased by means of ANN(Artificial Neural Network) while analyzing the randomness of structure capacity. The structure demand probability distribution is obtained by using IDA method. Based on the probability distribution of structure capacity and demand, the failure probability under each PGA is calculated through Monte- Carlo sampling method. And the fragility curves are drawn out. Analysis results indicate that computation work is dramatically decreased by using ANN to simulate the capacity distribution; the seismic fragility of cable-stayed bridge increased while the randomness of structural capacity is considered.

Abstract:According to the working behavior of tension piles, the loads carried by the pile tip are assumed to be zero. A Fredholm integral equation of the second kind for single tensile pile in elastic half space is deduced based on the fictitious pile model. By solving the nonlinear equations with the least square method, the axial forces, shear forces and displacement along the pile shaft are obtained. Compared with the available literatures, the reasonable of the present method is validated. The main factors, such as the pile stiffness, the length-to-diameter ratio and the Passion’s ratio, are investigated to analyze the load transfer behaviors of the tension pile. The results showed that the pile stiffness and the length-to-diameter ratio have obvious influence on the load transfer characters of the uplift pile. Some valuable conclusions can be drawn for the theoretical analysis and engineering practices.

Abstract:With China's economic and social development, a growing number of cross-harbor tunnels and cross-river tunnels are constructed for the need of transportations and economics. Immersed tube tunnel is a simple and easily-built tunnel and still less to the use in China, only Guangzhou Pearl River Tunnel, Ningbo Yongjiang tunnel, Ningbo Changhong tunnel and Shanghai outer ring tunnel. Hong Kong-Zhuhai-Macao Cross-Harbor Tunnel which is being built is the world's longest immersed tube tunnel (length 5664m) and will be based in the depth of about 40 meters below sea level. This paper is based on Hong Kong-Zhuhai-Macao Cross-Harbor Tunnel Project, and the three-dimensional continuous model is established to research joints’ forces and displacements and GINA gaskets’ deformation. It focuses on joints’ relative displacement (including pipe joints and segment joints), reducible seismic effect of segment joints and GINA gaskets’ deformation. There is an important guiding significance for design and construction of immersed tube tunnel.

Abstract:Thawing of artificially frozen soil during and after the excavation of cross passage constructed by artificial ground freezing method isn’t well studied. Coupling the governing equations of temperature and stress, this paper investigates the issues of temperature field, development of frozen wall thickness, and thaw settlement considering the effects of convection and hydration heat from preliminary/secondary concrete lining. Cases of both naturally and artificially thawing are studied for the scenario of cross passage #1 in Shanghai Yangtze River Tunnel. In naturally thawing condition, it takes 44 days for all frozen soil to melt and this process is significantly influenced by the hydration heat from preliminary concrete lining while that only 23% of the frozen soil melt without regard to the hydration heat in 50 days. Soil mass in the cross passage area shows a downward displacement of 2cm due to the thawing effect. As for the case of artificial thawing, all frozen soil melts after 4.3 days. Contrary to the process of freezing, thawing of soil first occurs within the area between the two rings of freezing pipes, then that between the preliminary lining and the inner freezing pipe ring, and last that out of the outer ring.

Abstract:In order to deal with the significant variety of the relationship between the supply and demand of the signalized intersection, the method to allocate the lane-use dynamically was discussed. Based on the analysis of the optimization objective, optimization variables and the optimization model, a dynamic lane assignment optimal method was proposed based on the approach-group concept. The method was formulated as an Integer-Non-Linear-Programming model. Minimizing the sum of the critical flow ratio was the most important design objective. By means of numerical examples, the accuracy and the computation time of the method were tested. Results show that the approach-group concept could reduce the number of control variables significantly without reducing the accuracy of the optimization results and the proposed model could achieve the goal of real-time dynamic lane assignment control.

Abstract:This study proposed a revised MULTIBAND model to address the existing problems of the conventional MULTIBAND model, which are restricted solution scope due to the constraint of symmetric green-wave and unstable green-wave performance due to improper location of green-wave within the whole green interval at each intersection. The proposed model removes the constraint of symmetric green-wave to acquire more flexibility of the green-wave, adds another constraint on the green-wave location letting the green-wave as far as possible in the middle of upstream/downstream green interval, and meanwhile modifies the optimization model accordingly. A simulation model based on the empirical data collected at 8 intersections along Yimeng road in the city of Linyi, China, was established to assess the performance of the proposed model. The results showed that the proposed model is able to increase the total green-wave band width by 7.1% and reduce the average delay by 20.8% and number of stops by 30.8% respectively, as compared with the conventional MULTIBAND model.

Abstract:Based on the theory of complex network, the paper uses ArcGIS second development program and Ucinet software for transit GIS network analysis, and proposes a new planning method to filter out bus main lines with a modified line betweenness centrality index. Taking the bus network of Pudong New District in Shanghai as an example, the paper further conducts a different analysis between the new method and the actual planning scenario, and illustrates the feasibility and rationality of the new method from the aspects of 4 indicators, including the coincidence degree of the network, non-linear coefficient, station spacing, and passenger flow stability. According to three cases in the process of bus main lines planning, the paper discusses the adaptability of the new method and concludes that about 65% of the bus main lines in planning scenario can be extracted by this new method. The new method is practical and universal because of the advanced data extraction based on GIS model of network，which can be widely-used as an efficient quantitative method in the bus main line planning.

Abstract:According to the complexity and uncertainty of impact fact of traffic event duration on urban expressway, a new forecasting model using Bayesian network and non-parametric regression for traffic incident duration was proposed. Sample database, provided by Shanghai Expressway Monitoring Center, was generated by noise reduction. This paper determined the algorisms of structure learning and parameter learning based on data characteristics, and got forecasting results with non-parametric regression. Finally, the forecasting model was tested with new data and the results indicate the accuracy of the model.

Abstract:A large amount of passenger boarding and alighting counts at stops can be collected by Automatic Passenger Counter (APC) systems. APC data describe passenger Origin Destination (OD) flows at the aggregate level and, therefore, can be used to estimate passenger OD flows. In view of this, an OD flow estimation formulation based on the distribution of the APC data is proposed and a computationally efficient Heuristic Expectation Maximization (HEM) algorithm to solve the proposed formulation is developed. The effects of the quantity of the APC data, APC measurement errors and OD survey sample size are considered in the methodology evaluation and comparison. It is revealed that the HEM algorithm takes better advantage of the APC data than traditional methods and that it outperforms a simulation based approach that was recently proposed in the literature in terms of both estimation accuracy and computational efficiency.

Abstract:For an objective evaluation of roadside safety, assessment model of roadside environment objective safety was established based on the probability of run-into-roadside and the roadside objective characteristics. Firstly, the indicators of the various objective characteristics that affect roadside safety were hierarchically divided, and each indicator safety level were determined on the basis of domestic and overseas research results and certain statistics data. The risk index of the roadside objective characteristics was calculated by fuzzy judgment. Then, the probability of run-into-roadside which consider objective indicators about traffic composition、highway alignment、subgrade width and pavement condition was calculated by Bayesian networks. Finally, based on planar region which was composed by the risk index as X-axis and the enforcement probability as Y-axis, roadside objective safety level was divided by comprehensive evaluation indicator. The results can provide decision for roadside safety improvement program.

Abstract:Driver visual information load in different road environment is calculated and mechanism of vehicles operating characteristics affected by the different road environment is analyzed in this paper. The purpose is to improve technical design and operational management level in underground roads. Firstly, vehicles operating characteristic and visual environment information are obtained with naturalistic driving on underground and aboveground road. Comparative study about vehicle operation characteristics and driver visual information load are carried out. The relationship between visual information load and vehicle operation characteristics (headway space and operating speed) is researched. Secondly, influence mechanism vehicles operating characteristics affected by visual environment in underground road is analyzed; Lastly, the measures improving and enhancing underground traffic security is proposed based on driving simulation.

Abstract:The space of urban road has two scales: auto scale and human scale. There are three differences between the two scales: landscape spatial pattern, energy consumption and space perception. The manifestations of urban road space lacking human scale are discussed, such as the improper scale of pedestrian pace and the disconnection between landscape and experience. Based on the human scale of the urban road space, four evaluation criteria are provided: comfortability for walking, convenience for rest, friendly landscape, and identifiability of the space. The corresponding measures for road space reallocation are introduced: pleasant walking space, reasonable crossing facilities, reasonable leisure facilities, pedestrian-oriented landscape, and pedestrian identification system. Especially, landscape should have a human scale. This theory will provide a new basis for guiding the design of urban roads.

Abstract:The consolidated distribution model (CM) which contains the most important characteristics of entropy gravity models was introduced to logistics distribution and an algorithm based on space 0.618 search was used to maximum likelihood parameters estimation. By compared the applications with the double constraints gravity model and CM, the parameters’ economic meaning is verified. The results of CM forecasting are always better than the double constraint gravity model and The CM is not sensible to the interior cost of logistics zone when the distance between zones is much bigger than the interior. It is turned out that CM is an effective and accommodative logistics distribution model.

Abstract:After Experience of dry-wet cycle，Its mechanical properties will be irreversible changes. The mechanical properties influenced on moisture content changes cyclicity of cohesive subgrade soil was studied by indoor test. And the extent of the resilience modulus attenuation of subgrade result in frequently dry-wet cycle was analyzed. Use the method of a series of humidity cycle as “water seepage under the permeable stone –standing-oven dehydration……” to imitate the scene of the subgrade soil moisture content fluctuation process. The resilience of subgrade soil was tested by the system of UTM. The results show that, moisture content changes cyclicity have influence in resilience modulus of cohesive subgrade soil. The resilience modulus decrease following the increase of cycle times. In the same stress state, The higher the equilibrium moisture content, The more sensitive the resilience modulus changes.

Abstract:Based on subgrade compression strain index and the equivalency principal of cumulative fatigue damage, conception and calculation method of equivalent temperature for asphalt surface layer were put forward. The relationship between the temperature condition of asphalt surface layer and subgrade fatigue life was analyzed. The law of equivalent temperature for asphalt surface layer was summarized. By introducing modified coefficient to subgrade fatigue life, regression formula among modified coefficient , the altitude of asphalt pavement located, pavement surface average temperature and its standard deviation over the years was established. Accordingly, modified coefficients at 738 areas in China were calculated and a contour map of was draw. Then simple and practical regression formula between modified coefficient and two common meteorological parameters: annual average temperature and difference of the highest and lowest monthly average temperature was established. Finally, the influence rules of various factors on modified coefficient to subgrade fatigue life were summarized and approximate modified formula was given.

Abstract:Water resources vulnerability is a common problem that every country in the world encounters nowadays. DPSIR (Driving forces-Pressure-State-Impact-Response) model is used to do the water resources system vulnerability assessment of Changsha-Zhuzhou-Xiangtan areas in this paper. Meanwhile, the establishment of vulnerability assessment model and evaluation process are described in detail based on the comprehensive identification of the vulnerability factors of the water cycle sub-system, the social-economic subsystem and the environment sub-system, combing the Analytic Hierarchy Process (AHP) method with entropy method, weights of water resources vulnerability factors are obtained, as well as a comprehensive evaluation on the water resources system vulnerability. The conclusion shows that the vulnerability of water resources system in Chang-Zhu-Tan is serious with several insecurity factors, so the vulnerability assessment can provide a technical guidance for the sustainable development of the water resources system in Chang-Zhu-Tan areas.

Abstract:Land filling is one of the most economical and efficient ways to treat Municipal Solid Waste (MSW). When cement-soil barrier is used in landfills as vertical barrier curtains, diffusion of contaminant is not taken into consolidation in design. In this paper, influence of barrier’s thickness and cement content on isolation effect of heavy metal is analyzed though a large model test. The results show that isolation effect will be enhanced greatly by increasing the cement content or thickness of barrier. Moreover, isolation effect that is enhanced by increasing the cement content of barrier is more than by increasing the thickness of barrier. The results also prove that the diffusion coefficient of Zn2+ in soil is far great than that in cement-soil.

Abstract:The Biolog Eco method was used to investigate the effect of low lead content (< 350 mg/kg dry weight soil, soil pH > 7.5) on the rhizosphere microbial community of potted winter wheat seedlings under the stress of cadmium. The low lead content significantly results in the shift of rhizosphere carbon source utilization of microorganisms, microbial metabolic diversity indexes, and microbial community structure in the stress of cadmium. And it mainly strengthens the inhibition of cadmium on the ability of the rhizosphere microbes to utilize different carbon resources, meanwile enhances the effect of cadmium on the microbial metabolic diversity. Furthermore, the correlation between rhizosphere microbial metabolic diversity indexes and the content of simple sugars and phenolic acid exudates under Pb/Cd is obviously different from that under Cd, and the correlation direction and the significant level all change evidently.

Abstract:The experimental results of changing heat treatment temperature on the microstructure and thermodynamic properties of hydrophobic silica aerogels are reported and discussed. Prepared with sodium silicate precursor, ethanol (EtOH)/ hexamethyldisiloxane (HMDSO) /hydrochloric acid (HCL) as solvent exchange and surface modification agent, the crack-free and high hydrophobic silica aerogel monoliths were obtained. Silica aerogels possessed the superior properties, such as low density (0.116 g/cm3), high surface area (871 m2/g), high hydrophobicity (~145°) and low thermal conductivity (0.025 W(m K)−1). Silica aerogel monoliths maintained hydrophobic behavior up to a maximum temperature of 460°C above which they become hydrophilic. After a thermal process changing from room temperature to 400°C, the final product was still remained hydrophobic (~125°) and presented good performance with surface area of 530 m2/g. Thermal conductivity coefficients of silica aerogel monoliths changed from 0.025 to 0.049 W/ (m K) as temperature increased from 25 to 400°C, revealed an excellent heat insulation effect during thermal process.

Abstract:With HF as catalyst, nano-porous silica xerogels which have high specific surface area (450—800m2/g) have been directly prepared at ambient pressure. Based on experiments, the influence of stuff proportion and heating temperature has been investigated, and the adsorption capacities of the silica xerogels have been studied by ultraviolet spectrophotometer. The results show that the silica xerogels are suitable for liquid absorption applications.

Abstract:The lateral self-excited vibration of tread is the root of the tire polygonal wear. The lateral self-excited vibration of tread has been proved to have the character of hard self-vibration by the simulation of the four degree-of-freedom self-excited vibration system of rear suspension in SIMULINK. It is found that the sensitive parameters influencing the self-excited vibration state obviously are mainly the factors of the stiffness and damping coefficient of rubber, vertical load, adhesion coefficient, mass of the tread block, toe-in angle and camber. Then the parameter sensitivity analysis of lateral vibration was conducted to rank the parameters’ influence. At last the main effective measures, including increasing the adhesion coefficient between the tire and road and reducing the toe-in angle, were proposed to restrain the tread self-excited vibration to reduce tread wear.

Abstract:Based on the CFD simulation software, a study on the effect of the EGR, start of injection and swirl rate on the low temperature combustion is conducted. The results show that the combustion and heat release lag, meanwhile the cylinder pressure, temperature, peak of heat release rate and accumulated heat release decrease with the increased EGR rate. Besides, NOx emissions decrease drastically with the increased EGR rate, while soot, UHC and CO emissions increase. When the EGR rate is kept constant at 40%, and the start of injection is advanced from 353°CA to 345°CA, the combustion and heat release are advanced, the efficiency and fuel economy are improved. When the EGR rate and start of injection are kept constant at 40% and 345°CA, and the swirl rate is increased from 1.0 to 3.0, the soot, UHC and CO emissions is decreased.

Abstract:Abstract: It is very difficulty to ensure that the controller derived by traditionally internal principal or PID has good performance over a wide range of operating condition due to the nonlinearity of the air supply subsystem of the proton exchange membrane fuel cell(PEMFC). In this paper, a strategy for optimal oxygen excess ratio of PEMFC is investigated base on multiple internal model principal and feedforward. In the proposed strategy, internal models, firstly, are derived by linearizing the PEMFC system at different operating conditions; then the strategy is achieved by the combination of membership function and feed forward design method. Simulation results show that the proposed strategy has better performance than conventional single internal model controller and PID controller.

Abstract:Abstract: In this paper, the problems of the actuator fault detection and reconstruction based on observers are discussed for uncertain nonlinear systems, when the observer matching condition is not satisfied. An auxiliary output vector is introduced so that the observer matching condition is satisfied. A high-order sliding mode observer is considered to get the exact estimates of both the auxiliary outputs and their derivatives in a finite time based on the system measured outputs. A kind of fault reconstruction method based on the high-order sliding mode observer is developed. In the design, the Lipschitz constant can be unknown because an adaptive controller is implemented to adjust it adaptively. Finally, a numerical simulation example is given to illustrate the effectiveness of the proposed methods.

Abstract:For solution of the vehicle-guideway coupling vibration in the maglev system, a new structure of the maglev line system was proposed. With the aim to verify the feasibility of the scheme, a numerical model of the single magnet suspension system on the new line was founded. Using the state observer developed in this paper, the magnetic track's vibration states were introduced to the control system, and a controller was proposed with the state feedback method. The impacts of the main parameters of the new maglev line were investigated in the end. The results shows that the control method can maintain the stability of the maglev system even the cement beam has no damp; The response of magnet has nothing to do with the relative position between the magnet and the cement beam, which makes the design of the controller and the solution of the vehicle-guideway coupling vibration easy; in addition, increasing of the track mass and decreasing of the track pad stiffness are also conductive to the system stability.