Abstract:To explore the rule of stress increment in unbonded tendons and design method of moment redistribution, the finite element was modeled by ABAQUS soft-ware for unbonded prestressed concrete flat plates. The plates were divided into the column strips and the middle ones. Stress increment in tendons and moment redistribution coefficient of unbonded prestressed concrete flat plates were studied, which are influenced by the combined reinforcement index and grade of non-prestressing reinforcement. It is shown that the stress increment in tendons increases at the serviceability and ultimate limit states and moment redistribution coefficient in critical section of support reduces with the higher yield strength of non-prestressing reinforcements in flat plates. Then expressions of stress increment in tendons and moment redistribution coefficient in prestressed concrete flat plates were developed, in which the combined reinforcement index and grade of non-prestressing reinforcement were considered.

Abstract:To proceed finite element analysis for bolted large-scale connection in steel structures and to explore the detailed behaviors under different loadings, a simplified method is brought forward, in which the high-strength bolt can be simulated by using connector element. The non-linear shearing performance of single-shear bolted connections is investigated with accurate models where the solid elements are employed. Basing on the mechanical properties in elastic, slipping, hardening, and yielding phase under shear force, a constitutive relation for the bolt connector is established and can be applied easily in shell element model for the high-strength bolt connection. Large numbers of examples with varied parameters including plate thickness and bolt diameter are calculated respectively by using the simplified method with shell elements and the accurate method with solid elements. The result comparisons show that the simplified simulation method has a good computational efficiency and accuracy, and has a potential ability to simulate high-strength bolt connections.

Abstract:To solve the problem that the mass transfer coefficient in Lee's equation need to be obtained depending on the experience, a method was proposed, and two indexes evaluating the rationality of the mass transfer coefficient-latent heat share (the share of latent heat flux in total heat flux) and saturation temperature difference (difference between fluid temperature and saturation temperature) were presented. A steady state model was established to analyze this problem and the expression of latent heat share and saturation temperature difference were obtained by the theoretical guidance. By the expression, the effect of mass transfer coefficient on the simulation was analyzed. The analysis result was validated by the existing theoretical result in particular cases. The results show that the calculation accuracy increases with the increase of the coefficient. Based on these results, the reason for large difference of the coefficient value in different literatures was explained, the method of how to get the coefficient value was presented, and the value range of easy-to-use was suggested.

Abstract:To investigate the effect of hydrodynamic conditions on hydraulically irreversible fouling of UF membrane in MBR for treating micro-polluted water, the method of determination of hydraulically irreversible fouling of UF membrane was introduced, and the effects of aeration, backwashing, flux and temperature on irreversible fouling were discussed. The results showed that the pollutant removal of MBR should be taken into account when selecting the time and flow of aeration. The duration of 2 min was necessary during intermittent aeration, with the optimal aeration intensity of 30-36 m³／(m²·h). Prolonged backwashing duration was found to control the hydraulically irreversible fouling. The production of UF membrane in MBR should also be considered when determining the proper backwashing duration. The permeate fluxes influenced the hydraulically irreversible fouling rate significantly, and the values of PVDF and PVC membranes should be no more than 31.5 and 14.0 L／(m²·h) to maintain the long-term stable operation. Meanwhile, the impact of temperature on irreversible fouling should be considered.

Abstract:Ammonia and COD are selected as study variables for they are the main water quality parameters and can represent water environment quality of the Harbin City Reach of the Songhua River. One-dimensional water quality model is used to set up the relationship of pollutant loadings and water quality. The comprehensive decay rate (k), a key parameter of water quality model, is estimated by Bayesian method. The seasonal model and annual model are respectively set up according to different k estimated in different period. The pollutant loadings are controlled by the models for downriver water quality can meet targeted goals. From contrasting the two models, it indicates that predicting precision of seasonal model is high than annual model for seasonal model can better express comprehensive degradation concentration of ammonia in water. Contrasting with other methods, water quality management with seasonal model can offer decision makers more useful information, and help them address uncertainties. In addition, influencing weights of the three pollution sources can be obtained by contrasting load reduced ratios. The information could inform decision makers of the required load reductions for the three time periods.

Abstract:To improve volatile fatty acids (VFAs) accumulation from hydrolysis and acidification of excess sludge (ES), alkali-tolerant bacteria capable of protease-producing were isolated from ES. A mixed microbial consortium capable of protease-producing was constructed by the isolated bacterial strains. The mixed microbial consortium was inoculated into the different fermentation periods of ES to investigate their effects on soluble organic compounds and VFAs accumulation from ES under alkaline conditions (pH 10.0). The optimal condition for VFAs accumulation from ES was investigated. The results showed that two alkali-tolerant bacterial strains capable of protease-producing were isolated from ES and constructed as a mixed microbial consortium. The soluble organic compounds concentrations and VFAs accumulation were improved significantly after the mixed microbial consortium was inoculated at the initial fermentation, and the start-up phase was shortened by 2 days. On the 8th day of fermentation, the concentrations of soluble protein and total VFAs reached their peak values, and were 1.25 times and 1.41 times higher as compared to the corresponding values from non-inoculated samples, and accounted for 29.87% and 44.54% of total SCOD concentration, respectively. Acetic and propionic acids were the most prevalent VFAs (account for 50.69% and 18.19%, respectively).

Abstract:To put forward a Fenton-like system based on a new type of Fe₃O₄ magnetic nanoparticles catalyst, Fe₃O₄ magnetic nanoparticles were prepared using chemical co-precipitation , and their surface was modified with tetramethyl ammonium hydroxide (TMAH). The catalyzed degradation of phenol by Fe₃O₄-H₂O₂ Fenton-like system was investigated, including the effect of catalyst dosage, H₂O₂ dosage, pH value and reaction time on the removal of COD and volatile phenol. The results showed that the mean size of the Fe₃O₄ nanoparticles is 30 nm and they show a good disparity between 20 and 100 nm. Three different doses of TMAH coated catalysts after ultrasonic pretreatment, revealed almost the same treatment efficiency of 50 mg/L phenol (112 mg/L COD equivalent) under the room temperature (13 ℃). Under the condition of 0.8 mmol/L catalyst dosage, 2.0 mmol/L H₂O₂ dosage, pH 4.5 and the reaction time of 180 minutes, the highest COD removal efficiency was 72%; while under the condition of 0.4 mmol/L catalyst dosage, 2.0 mmol/L H₂O₂ dosage, pH 4.5 and the reaction time of 90 minutes, the removal rate of volatile phenol was close to 100%. 3# Fe₃O₄-TMAH（2 mL）catalysts revealed optimal reuse efficiency, the removal rate of COD were 73%,29%,28%,26%, the removal rate of volatile phenol were 100%,84%,67%,54%. The Fenton-like system has the advantage of no redundant excess sludge producing, and the magnetic catalyst can realize quick separation and recycling under the action of outside magnetic field.

Abstract:Low temperature inhibits the performance of nitrogen removal efficiency during the biological treatment of municipal wastewater. Therefore, the effluent could hardly meet the emission standard. To enhance the performance of nitrogen removal at low temperature, a psychrotolerant aerobic denitrification consortium by fast enrichment and domestication was obtained, which could remove the ammonia, nitrate and organic matter simultaneously and efficiently in aeration environment under 10 ℃. The results showed that the removal efficiency of ammonium and total nitrogen by bioaugmentation was improved by 10.31％-16.89％ and 25.07％-32.44％, respectively. It made the effluent quality meet the grade1A level of national discharge standard. After bioaugmentation terminating for 10 days, the remained consortium could still improve the reactor that the effluent of ammonium, nitrate, total nitrogen and CODCrconcentrations was decreased about 2.3,3.7,6.02 and 3.63 mg／L, respectively. The results indicated that bioaugmentation performed well and persistently.

Abstract:To investigate the pollution characteristics of water soluble ions in PM2.5 and PM₁₀ under severe haze days, both PM2.5 and PM₁₀samples were collected in a city of northeast China under severe haze days during October 20-2,3. Nine water-soluble ions in PM2.5 and PM₁₀including F-, Cl-, NO₃-, SO₄2-, Na+, NH₄+, K+, Mg2+and Ca2+ were analyzed. The results showed that the concentrations of all water-soluble ions mass concentration in night were higher than those in day time, with a ratio of 1.68 for PM2.5in haze days. The concentrations of SO₄2-, NO₃-and NH₄+were higher and their percentage in PM2.5 were 11.03％,8.3％ and 7.39％ in haze days, the same results in PM₁₀ were obtained. The percentages of K+and Ca2+in haze and non-haze periods were similar. Based on the ratio of different ions, the pollution from stationary sources were higher than that from mobile sources in haze days, this showed that meteorological factors had greater influences. In comparison with the data of water soluble ions during October and November of 2009, the concentrations from mobile sources were on the rise.

Abstract:To analyze the law of passenger transportation economic policy in different operators, based on game theory to describe the Nash equilibrium among urban passenger transportation operators, a bi-level programming model is proposed to model urban passenger transportation operators’ economic decision-making, operators’ profit and social cost have been discussed, including the travel time cost, air pollution cost and energy consumption cost. The upper-level model describes the management authority’ regulation on the fares of each mode, the lower-level model describes the operators’ maximum profit by determining the service frequency. Based on GAMS and genetic algorithm, a numerical example verifies the validity of the proposed model. The introduction of subway service will increase the total market share of passenger public transportation, and effectively reduce the external cost, including the environmental emission cost and energy consumption cost.

Abstract:To analyze the deterrent effect and level of traffic electronic enforcement on inhibition of traffic violation, on the basis of the plume model, this paper built a quantitative analysis model of traffic electronic enforcement deterrence level. This model corrected and redefined the factor meaning and expression form of plume model, and calibrated constant values with data from traffic survey to analyze the characteristics of related factors which can influence the traffic electronic enforcement deterrence effect on the scope of time and space. The case studies showed that the calculation results of the model was consistent with the survey results of traffic violation rate, which indicated that this model can quantify the contribution degree of electronic enforcement on inhibition of traffic violation. By reasonable layout of location, direction and quantity of traffic electronic enforcement facilities, the traffic violation rate of the layout area can be effectively reduced.

Abstract:An exact semi-analytical solution in the undrained cavity expansion can be obtained on the basis of the MCC model to research the cone penetration test and the pile driving. The field around the cavity can be divided into three zones: critical zone, plastic deformation zone and elastic deformation zone.In the elastic zone, an analytical solution for the distributions of stress and excess pore pressure is deduced according to the elastic theory. In the critical and plastic zone, a set of first-order nonlinear ordinary differential equations concerning stress can be obtained according to the associated flow rule and the lagrangian analysis method. The stressss and pore pore pressure can be solved as an initial value problem starting at the elastic-plastic boundary. The results show that the isotropic over consolidation ratio has a significant influence on the stresses and the excess pore pressure.The shear modulus vary significantly with the cavity radius and the isotropic over consolidation in the course of cavity expansion.

Abstract:During the pull-out process there exist concrete crack initiation and propagation. To accurately simulate discontinuous deformation of the pull-out process and calculate pull-out capacity of shear connectors, a zero-thickness cohesive interface element based on the enhanced finite element method was introduced in this paper. And cohesive zone model (CZM) was used to describe the crack initiation and propagation of the pull-out process. Then numerical simulation analysis of a pull-out test model was carried out. Results showed load-displacement curves of the structure, pull-out capacity, and crack propagation patterns of the concrete slab. Discontinuous deformation numerical simulation has been realized.

Abstract:To comprehensively evaluate the seismic behavior of double-wall precast concrete (DWPC) short-leg shear walls, quasi-static test of two full-scale DWPC short-leg shear walls and one normal cast-in-situ (CIS) short-leg shear wall were carried out. Systematic analyses were made on hysteretic curves, skeleton curves, displacement ductility, bearing capacity, stiffness degradation and energy dissipation capacity of specimens. The result shows that all specimens fail in bending. The detail improved DWPC short-leg shear walls can work together well. The continuous rectangular spiral stirrups in the range of U-shaped connection steel bars confine the concealed column concrete; also improve the stiffness and bearing capacity of DWPC short-leg shear walls. The displacement ductility, stiffness degradation and energy dissipation capacity of DWPC short-leg shear walls are close to those of CIS short-leg shear wall.

Abstract:To investigate the ductility behavior of partially concrete-filled steel box-section bridge piers subjected to a constant vertical load as well as cyclic lateral loads, a three-dimensional elastic-plastic finite element formulation is proposed for numerical simulation. By comparing the lateral load-lateral displacement hysteretic curves and failure modes of numerical results with experimental results, the proposed finite element analysis method is verified to be accurate and effective. 56 analytical models are established with four variable parameters, i.e., flange plate width-thickness ratio, column′s slenderness ratio, filled-in concrete ratio and axial load ratio. A summary of possible failure modes is given as follows. For pure steel piers, local buckling occurs near the bottom of the specimen. For partially concrete-filled steel piers, local buckling usually occurs at the upper plate adjacent to filled-in concrete in the case of small filled-in concrete ratio. With the increase of filled-in concrete ratio, local buckling will appear near the bottom of the specimen. Finally, the ultimate strength and ductility behavior of partially concrete-filled steel bridge piers are investigated on the basis of four variable parameters mentioned above.

Abstract:To improve the transfer efficiency of local network including rail transit and bus station, local transfer network was described based on space P and a reasonable network size was determined. Considering the capacity of the station and station spacing as the constraints, optimization model was established to minimize the travel cost and model algorithm was proposed based on community structure of complex network. The model is applied to local transfer network including some station of Changchun light rail No.3 and bus stations around it. The results show that the overall transfer efficiency of the local network can be increased by 16％, and total system costs can be decreased by 6.16％ considering the case of the time value.

Abstract:To recognize driver′s fatigue level accurately and objectively, a driver fatigue level recognition model that employs multiple psychological features was developed based on particle swarm optimization (PSO) and support vector machine (SVM). Firstly, the driver fatigue was divided into four levels, which were alert, mild fatigue, deep fatigue and drowsiness. Then alpha rhythm, beta rhythm, delta rhythm, mean of heart rate, and standard deviation of R-R interval were selected as input variables of the SVM model. The PSO was introduced into the model to optimize the penalty parameter and kernel function parameter of SVM. Experimental data collected in Ji-Hun freeway was used to validate the effectiveness of the recognition model. Results show that the recognition precision of the four fatigue levels are higher than 85％. Sensitive analysis of the mode is also conducted and the results prove that the model using multiple features outperforms the model using fewer features.

Abstract:In view of increasingly serious traffic congestion on freeway, a synthesis method of travel time date was proposed based on the rolling time sequence and charging data, and on which this paper built a traffic congestion index and estimated the duration time according to the changing characteristics of the index. Moreover, taking the spatial and temporal characteristics of toll station layout into account, a method of automatic traffic congestion identification on freeway was designed by merging basic links with composite links. Empirical analysis shows that this method can improve the recognizing rate to 96.52% and reduce the false recognizing rate to 0.43%, at the same time, the recognizing time is declined by 74%, and the cost of charging date is zero.

Abstract:To promote the safety level of long steep downgrades(LSD), profile design methods for LSD considering of the brake temperature of truck were studied. Seven typical LSD with different length and average grade percentage were selected. Then the influence of operating speed and gross weight on the brake temperature was analyzed. Furthermore, three characteristic values, i.e. the brake temperature of trucks at the end of the LSD, the distance to the beginning of the LSD when brake temperature up to 200 ℃ and 260 ℃ were used to analyze the influence of two different profile design alternatives, one is that unique longitudinal grade is used throughout the whole LSD, another is that different grade percentages are used in different segments, e.g. a steep grade is preceded by a gentle slope. The quantified section classification criterion was presented, and some recommendations were provided. The research shows that from the aspect of reducing the brake temperature of truck, unique grade percentage is recommended. If different grade percentages were used, the difference between any two adjacent segments should be controlled in a small range.

Abstract:In large-scale conditions, the large nonlinear error of simultaneous localization and mapping (SLAM) based on square root cubature Kalman filter (SRCKF) is a serious constraint to high positional accuracy. To solve this problem, an improved SLAM algorithm based on iterated square root cubature Kalman filter (ISRCKF) is proposed. Utilizing the iteration theory, the newest observation information is in full use. Thus the estimation errors of the new algorithm will be decreased noticeably, an accurate environment map will be established and high-precision localization will be obtained as well. The simulation results show that the location errors of x axis and y axis are both less than 1.5 m by the new algorithm. The estimating accuracy of the new algorithm is higher than that of SRCKF-SLAM, CKF-SLAM and EKF-SLAM algorithms. Adding different environmental noises, the position errors of ISRCKF are the smallest.

Abstract:To reduce the generation and development of reflection cracks of the semi-rigid base asphalt pavement, of which the fatigue performance using the HDPE-rubber powder to modify asphalt composite as a stress absorbing layer was studied. The fatigue test was carried out and the data after choosing proper test method and determining the mixture proportion and final experiment scheme was analyzed. Experimental results showed that asphalt modified by HDPE-rubber powder had excellent anti-fatigue ability and could effectively delay the generation of reflection cracksin asphalt pavement. This was verified by the observation results of indoor asphalt pavement test.