Abstract:High risk for accidental petroleum pollution in raw water when there is a congestion of shipping facilities in the water source area. The effectiveness in removing oil at different flow velocities and oil spill volumes was analyzed for oil containment drums and algal nets， as well as for the combined process. The removal performance under different flow velocities by different installation methods of oil containers for continuous oil spill was experimentally investigated. The results show that a submergence depth of 0 cm is the least effective in removing oil spills， where 1.5 cm results in lower outlet concentrations （0.14~0.61 mg·L^-1） at all flow rates. Various laying methods （free laying， vertical laying， double laying， vertical laying） and different algal concentrations were investigated for the adsorption performance of the algal nets. The results show that the vertical laying method has lower outlet concentration and stable effect （0.15~0.28 mg·L^-1） in each initial situation； the combined process has better performance improvement compared with the oil drum， and the concentration at the 12min outlet reduces by 78.8%， 84.6%， and 78.5%， respectively； the decrease in the oil removal effect of the algal nets after treatment of high algal concentration is related to the reduction of active sites.

Abstract:A long-acting detection agent for carbamate pesticides （CMs） was designed and developed. The CMs in water were extracted and alkalized by mixter and digester， and then the long-acting detection agent and portable water quality detector were used to realize the rapid detection of CMs on site. The relative standard deviations （RSDs） of this method are 2.86% （0.8 μmol·L^-1 CMs） and 1.61% （2.4 μmol·L^-1 CMs）， the limit of detection （LOD） is 0.07 μmol·L^-1， the detection period is only 40 min， and the spiked recovery of real water samples is 60%~78%. The analysis results of the spiked water samples from the Taipu River show that the detection results of rapid detection method and GC-MS have good consistency.

Abstract:Five powdered activated carbons （PACs） were selected to carry out the study on the preference of powdered activated carbons for use in conjunction with pre-chlorination. The results show that all five powdered activated carbons can effectively adsorb trichloromethane， and the changes of adsorption rate are in accordance with the proposed second-order kinetic law， and the regression correlation coefficients are all greater than 0.99， with the best adsorption effect of wood activated carbon （k=0.419 12） and coconut shell activated carbon Ⅰ （k=0.386 93）. The presence of residual chlorine decreased the rate of adsorption of trichloromethane by powdered charcoal， but it did not change the order of superiority of the adsorption effect of each powdered activated carbon. In raw water background， coconut shell activated carbon I and wood activated carbon had more than 60% removal efficiency for 2-methylisopropanol（2-MIB）， more than 90% for Geosmin （GSM），and the highest adsorption efficiency for trihalomethanes （28±5%）. In the combined chlorine-powdered activated carbon process， the order of the advantages and disadvantages of the different activated carbon types did not change， with wood activated carbon and coconut shell activated carbon I remaining the most effective， and coal activated carbon performing poorly. Correlation analysis of powder carbon properties with the removal performance of trichloromethane and olfactory substances found that the correlation of average pore size， iodine value， methylene blue value and total pore volume was more significant， and the correlation coefficient of average pore size was the highest， and the average pore size can be taken as an important reference factor in the comparison of high-quality powdered activated carbon.

Abstract:This paper focused on the treatment process of "conventional process-ultrafiltration-nanofiltration （NF）" in the largest-scale NF water plant in China as the research object， and considered water plant operation， water quality analysis and process treatment efficiency comprehensively. The result indicated that the NF process effectively removed humic acid-like and fulvic acid-like substances with a removal rate of about 82% for dissolved organic carbon in raw water. The experiment of trihalomethane disinfection by-products （THMs-DBPs） formation potential showed that the 14.45~18.65 μg·L^-1 of THMs-DBPs concentration in NF permeated water meant an extremely low concentration of DBPs precursor for the water treated by the dual-membrane process. Based on the daily monitoring and maintenance of the NF system， including inlet water quality， pressure changes and the adjustment of membrane cleaning strategies， the practice experience of the NF membrane water plant was discussed. The research provided technical references for the application of NF membranes in drinking water treatment.

Abstract:This study analyzes the distribution characteristics and influencing factors of three types of disinfection by-products（DBPs）—trihalomethanes （THMs）， haloacetic acids （HAAs）， and halonitriles （HANs）—in water samples from drinking water distribution systems in the southeastern coastal region of China. These distribution systems utilize three different secondary disinfectants： chlorine， chloramine and chlorine dioxide. The results indicate a relatively low risk for exceeding DBPs limits in the three cities studied. Among the collected 117 water samples， 10 exceeded the standard limit for THMs， while other DBPs were within compliance. Water distribution systems using chlorine as a disinfectant showed significantly higher concentrations of THMs and HANs in comparison with other water distribution systems. Chlorine dioxide effectively reduced the formation of THMs in comparison with the chlorine. Chloramines were used in Shanghai， however， the concentration of HAAs was 5 to 19 times higher than that in the other three systems， potentially due to higher levels of HAA precursors in the source water. Concentration of disinfectants and DBPs in drinking water varied with distances. In the SH-NH₂Cl system， disinfectant concentration showed an negative correlation with distance （r = -0.57）. This system also changed in nitrate， nitrite， and ammonia nitrogen concentrations along the distance， suggesting gradual chlorine decrease and nitrification in the distribution systems， leading to the oxidation of ammonia to nitrite and nitrate. In the WJ-Cl₂ system， a significant correlation was found between DBPs and distance. The concentration of HANs decreased with distance （r =-0.49）， while HAAs concentration displayed an increase along the path （r = 0.45）. Moreover， long stagnation time within premise plumbings can also impact water physicochemical qualities. This study reveals the concentration and variation of DBPs in distribution systems water using different types of secondary disinfectants. The findings provide a basis for water quality assessment and risk control in various regions.

Abstract:A simple multistage stirring methods was utilized to modifications of Metal organic framework （MOF） catalyst （MIL-100（Fe）） （incorporation of AgCl）. Characterization techniques such as X-ray diffraction （XRD） and Fourier-transform infrared spectroscopy （FT-IR） were employed to confirm the successful preparation of the novel heterojunction material （AgCl/MIL-100（Fe））. Sulfamethazine （SMZ） was chosen as the targeted contaminant. The removal efficiency of SMZ by the photocatalyst was investigated， considering factors such as catalyst dosage， pollutant concentration， and pH. Furthermore， an initial exploration of the degradation mechanism and pathway of SMZ was conducted. The results demonstrated that the rational construction of the heterojunction effectively harnesses photo-electrons （e^-） and holes （h⁺）， accelerating the transfer of charge carriers at the interface， thereby enhancing the photocatalytic performance of the material. When pH = 7， catalyst dosage was 0.5 g·L^-1， reaction time was 1.5 h， the removal rate of 99.9% for an initial SMZ concentration of 1.0 mg·L^-1. During the photocatalytic degradation of SMZ， superoxide radicals （?O₂^-）， hydroxyl radicals （?OH）， and h⁺ play dominant roles， involving three main ways： oxidation， hydroxylation， and denitrification.

Abstract:Chloramphenicol （CAP） is a typical broad-spectrum antibiotic with stable physical and chemical properties. In this study， the efficacy and mechanism of electrochemical reduction of chloramphenicol were investigated using a carbon fiber cathode with CAP as the target. Focusing on the effects of current density， pH， initial concentration of CAP， electrolyte concentration and species on the degradation effect of CAP， TOC removal rate and dechlorination effect， the study showed that the current density and electrolyte species had a greater effect on the degradation effect of CAP， and the optimal reaction conditions for cathodic reduction were current density of 40 mA·cm^-2， initial concentration of CAP of 10 mg·L^-1， Na₂SO₄ CAP at an initial concentration of 10 mg·L^-1 and Na₂SO₄ at a concentration of 0.02 mol·L^-1. Direct and indirect reduction of CAP occurred on the electrode surface by cyclic voltammetry， and the results of three-dimensional fluorescence tests showed that the organic content in the water was still high after the reaction. The intermediate products were detected by ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry （UPLC-TOF MS） and the mechanism of CAP degradation at the cathode was analyzed， and the reduced products were mainly aromatic amines with low toxicity. The electrochemical treatment of CAP mainly obtained less toxic substances through dechlorination and reduction， thus reducing the risk of toxic substances produced in the subsequent treatment process， and the results of the study provide relevant exploration and technical support for the application of electrochemical reduction in the removal of antibiotics in water.

Abstract:The ultimate bending capacity of two full-scale steel-concrete composite bridge decks were tested to study the residual bearing capacity of the high-performance concrete composite bridge deck after fatigue loading. A full-scale static-loading test was carried out for researching the static behavior of the orthotropic composite bridge deck， including the strain of concrete and steel bars， the deformation of the structure and the development of cracks. The test results prove the failure mode of the orthotropic composite deck to be a flexural failure. When the ultimate strength on the specimen reaches， the U-rib of the middle fulcrum section is buckling， and the tensile steel bars are yielding. The concrete in the negative bending moment area is seriously cracked， and the specimen has obvious deformation. Meanwhile， a flexural failure also appears on another bridge deck specimen after fatigue loading ， and the residual bearing capacity decreases by about 11.6% in comparison with the specimen without fatigue loading. Based on the bond-slip theory of reinforced concrete， a formula for calculating the average crack spacing of orthotropic composite bridge decks after fatigue loading is deduced. Compared with the test results， the proposed formula for calculating the average crack spacing has good accuracy， and the relevant research results can provide theoretical reference for practical engineering applications.

Abstract:In order to explore the feasibility of using carbon fiber reinforced plastics （CFRP） in the plastic hinge to control the failure mode and further improve the seismic performance of concrete shear wall reinforced by steel strand and steel bar， two specimens of concrete shear wall reinforced by steel strand and steel bar were made. The seismic and resilient performance of concrete shear wall reinforced by steel strand and steel bar and confined by CFRP in plastic hinge was studied by quasi-static loading test. The results show that the plastic hinge of concrete shear walls reinforced by steel strand and steel bar and confined by CFRP can effectively improve both bearing capacity and lateral deformation capacity， and the effect of improving its bearing capacity is better under high axial compression ratio， the hysteretic loops of the specimens confined by CFRP are fuller， and the energy dissipation capacity is improved to a certain extent， but it has no obvious effect on its residual drift.

Abstract:Based on a proposed compressed air energy storge power station project in Yungang Mine， Datong， China， the thermodynamic coupling calculation model of compressed air energy storge caverns was established， and the durability of steel lining under long-term operation conditions was studied by using three fatigue analysis methods： stress fatigue method， strain fatigue method and crack propagation fatigue method. Results show that the stress fatigue method and strain fatigue method overestimated the fatigue life of steel lining. Thus， the crack propagation must be taken into consideration in calculation. The fatigue life of lining is mainly affected by the elastic modulus of surrounding rock， the operating pressure of carven and the initial crack size. The fatigue life will be much longer if higher elastic modulus of surrounding rock， lower operating pressure and smaller initial crack size are adapted. The fatigue life of steel lining increases nonlinearly with the lining thickness. However， a critical value of lining thickness can be found， exceeding which the fatigue life will not change significantly.

Abstract:Based on the second phase shield tunneling project of Ningbo Rail Transit Line 3， the deformation and stress distribution of SF double-layer oil tank caused by shield tunneling in soft soil area are analyzed by numerical simulation. The results show that the disturbance of oil tank can be effectively controlled by reasonably selecting the parameters such as soil loss rate and frontal additional thrust. The tank farm deformation is mainly vertical deformation， the extreme value of uplift is located in the oil tank near the tunnel， and the extreme value of settlement is located in the central oil tank farm. The oil tank wall close to the shield tunnel has a large additional stress， and all stress values of the oil tank are less than the allowable stress of the tank material. The deformation and additional stress values of the oil tank under full load condition are lower than those under no-load condition. The time history change trend of field monitoring data is consistent with the numerical analysis results， and the surface deformation amount and deformation rate meet the monitoring requirements.

Abstract:To investigate the stability of a coastal lagoon system with a single tidal inlet under the influence of a double-guide-dike project， an ideal model was established based on the largest costal lagoon with a single tidal inlet in North China， Qilihai Lagoon. Scenarios were set with different variables， including critical erosion shear stress， critical deposition shear stress， sediment settling velocity， initial bed elevation and runoff. The tidal prism P， the maximum discharge Q_m， and the cross-section area A of the tidal inlet were collected when the ideal model attains the equilibrium state in each case， and then equations about Q_m-A relationship and P-A relationship are established to indicate the stability of the tidal inlet. It illustrates that the Q_m-A relationship is more effective than the P-A relationship to show the stability of the tidal inlet. Then， both Q_m-A relationship and net erosion or deposition amount are utilized to calculate the time costs for the tidal inlet and the lagoon to attain the equilibrium state in each case. It indicates that the lagoon costs more time to attain the stability than the tidal inlet； critical erosion shear stress causes more effect on the tidal inlet； the lagoon is more sensitive to critical deposition shear stress， sediment settling velocity and initial bed elevation； runoff brings about the similar influence on the stability of the lagoon and the tidal inlet.

Abstract:We propose an early warning method for high-risk events of traffic operation under low penetration of connected and autonomous vehicles(CAVs）. Specifically， we first define the concept of traffic entropy， and quantifies the micro driving behavior of individual vehicles as a parameter represented by traffic entropy， which is used to characterize the state of macroscopic traffic flow. And then the traffic entropy is used as the input parameter of the Long Short-Term Memory （LSTM） model to establish the early warning model of high-risk events. The HighD Dataset from German highways was utilized for the empirical analyses. In order to compare the application results under CAVs environment， an autonomous-vehicles scenario and a connected-vehicles scenario were set for the high-risk events and non-risk events extracted from the HighD Dataset. and the effectiveness of the warning of high-risk events under different vehicle permeability was compared. Results show that， the false alarm and missed alarm rates of early warning model with traffic entropy parameters are both reduced. Taking the low-penetration CAVs of 10% as an example， the false alarm and missed alarm rates reduced from 6.18 % and 11.47 % to 1.95 % and 3.12 %， respectively. At the same time， the false alarm and missed alarm rates are only 2.28 % and 3.82 % under the prediction environment.

Abstract:Field tests and numerical simulation were carried out to study the dynamic response of the underpass system of tunneling beneath the railway embankment under the train load. A finite element model has been established to study the effect of the elastic modulus of the reinforced soil and reinforcement depth on the vibration acceleration of ground surface and additional stress of tunnel crown. The results show that the main vibration frequencies of ground surface are caused by the periodic distribution of train wheels, sleeper spacing and specific driving speeds. The amplification of ground surface vibration and the reduction of the attenuation rate of high frequency vibration appear by the reinforced foundation. The vibration acceleration of the ground surface increases with the increase of elastic modulus of the reinforced soil. The reinforcement depth of the foundation exceed to tunnel buried depth, which can effectively reduce the additional dynamic stress of the tunnel.

Abstract:In order to analyze the breakage of ballasted track caused by train movement， the discrete element method-multibody dynamics(DEM-MBD) co-simulation model of ballasted track was established to analyze the influence of train load on the stability of ballasted track and the breakage law of ballasts on different positions in different shapes on ballasted bed. The results show that after train load， the lateral resistance of track bed decreases by 14.82 %； in the depth of 0. 21m below the sleeper， the ballast below the rail ditch tends to be broken rather than that below the sleeper center； the highest broken rate of ballast is 12.5 % when ballast is at the depth of 0.12~0.24m below the sleeper； the ballast at the shoulder is basically unbroken； flat ballast is more easily broken than normal and long ballast； in the operation of ballasted track lines， the content of flat ballast should be reduced and the ballast breakage at the depth of 0.24m below the sleeper should be paid much attention to.

Abstract:The ejector acts as a critical component in the hydrogen recirculation system for proton exchange membrane fuel cells which realizes anode exhaust recirculation via a supersonic jet. Traditional fixed-geometry ejectors are commonly designed according to the stack’s rated condition and achieve poor performance in off-design conditions. In contrast， variable-nozzle ejectors can adjust the throat’s opening dynamically and enlarge the operating range. Based on Sokolov’s theory， a one-dimensional model for the ejector was built to study its working characteristics， and a design methodology for the variable-nozzle ejector was later proposed. The results show that the ejector’s performance is mainly affected by its operating pressure， the throat diameter， and the mixing chamber’s diameter. By shrinking the throat and raising primary pressure， the working nozzle can be kept critical， which has little effect on entraining performance under high stack load. However， under low stack load， the entrainment ratio can be significantly improved， and the operating range expands toward low stack load.

Abstract:Taking the engine cover of a passenger car as an example， the structure optimization design method flow of Polydicyclopentadiene （PDCPD） engine cover was established to realize the lightweight structure design. The material property data of PDCPD were measured in the experiment， and the design process of equal stiffness and equal strength calculation-topology optimization- morphology optimization?multi-objective parameter optimization was applied to the structural optimization design under various working conditions. The performance analysis results show that compared with the original steel engine cover， the PDCPD engine cover designed by this method can achieve significant mechanical performance improvement， and the lightweight effect is obvious.

Abstract:Considering the phase change process of refrigerant in flat tubes， the SST（shear stress transm ission） k-ω model and the Eulerian-Eulerian two-phase flow model are used to simulate the two-phase distribution characteristics of refrigerant in parallel-flow evaporators. It is found that increasing the refrigerant mass flow rate and inlet quality will lead to a decrease in the uniformity of refrigerant distribution. When the refrigerant mass flow rate increases from 15g·s^-1 to 25 g·s^-1， the distribution inhomogeneity increases by 39.4%； When the inlet quality increased from 0 to 0.3， the corresponding increase in inhomogeneity is 50.8%. Appropriately increasing the inner diameter of the outlet header as well as the aspect ratio of the evaporator is beneficial to improve the uniformity of refrigerant distribution. Doubling the inner diameter of the outlet header results in a decrease of 41.8% in the inhomogeneity； compared with the basic structure， the evaporator with an aspect ratio of 1.455 achieves a decrease of 21.6% in the refrigerant inhomogeneity.