Abstract:This paper reports the temporal and spatial variations of the hydrogen （δD） and oxygen （δ¹⁸O） isotopes in the mainstream of the Yangtze River and discusses the basin-scale surface water cycle， with the samples from six sampling campaigns along the mainstream and major tributaries of the Yangtze River from 2012 to 2015 and from three-year sampling at Nantong Station. Combined with multi-year isotope data， it estimates the multi-year average river water line of the mainstream of the Yangtze River as δD＝7.56 δ¹⁸O＋6.75， n＝333， r²＝0.939 9， p<0.000 1. The spatial variation of the isotopic composition in the mainstream of the Yangtze River is jointly affected by water sources， evaporation， and human activities， and indicates the integrated influence of continental effect， latitude effect and altitude effect. The seasonal variation of the isotopes in the lower mainstream is mainly controlled by monsoon precipitation， while the inter-month variation is mainly affected by the impoundment of the Three Gorges Dam and the contribution of the two lakes downstream the dam. Especially during the peak flood period， the river water isotope is abnormally enriched， reflecting the significant discharge from the lakes， paddy field water， and groundwater in the middle and lower basins. The massive dam construction in the river basin has a significant impact on the river water retention， mixing and homogenization， and has significantly affected the water cycle in the Yangtze River catchment. Its impact on the river and coastal ecological environment is worthy of in-depth study.

Abstract:Based on the analysis of meso- and macro-plankton and water quality parameters from 17 stations in the Yangtze River estuary and adjacent regions in the summer of 2019， the present study investigated the spatial distribution patterns and major factors influencing meso- and macro-plankton. Under the influence of freshwater - seawater mixing in the Yangtze River estuary region， the species number and biodiversity indexes increased with increasing salinity in this transect， and the dominant species significantly differed among freshwater sites and low- and high- salinity sites. The density and biomass of meso- and macro-plankton in 13 stations of the typical transect along the Yangtze River estuary - East China Sea continental shelf showed no significant relationship with Chl-a， and significantly negatively correlated with the concentrations of nutrients， indicating that bottom-up effect was not the main controlling factor for the plankton distribution in this transect. Under the influence of multifactor changes derived by freshwater - seawater mixing， the main controlling factors on the distribution of meso- and macro-plankton exhibited regional differences related with salinity. The present study for the first time conducted in situ observation of plankton using a continuous particle imaging and classification system （CPICS） in some of the high salinity sites， and obtained in situ photographs of meso- and macro-plankton， which could support the species identification of macro-plankton （such as Noctiluca scientillans， Diphyopsis chamissonis）， and could support the identification of copepods to subclass. The results of in situ observation by CPICS （vertically moving） and laboratory analysis of field samples （obtained via vertical tows） showed a similar tendency on the changes of species numbers. In the future， with the help of long-term in situ observation in the whole water column and intelligent analysis of mega-data， CPICS would provide important real-time data for the species composition and evolution of plankton in the East China Sea.

Abstract:In the summer of 2019， field sampling and observation were conducted at 12 sites and one anchor station （at the seasonally hypoxic zone） along a longitudinal section from the Yangtze River （Changjiang） estuary to the East China Sea. The water quality data in the vertical profile and bottom water samples were collected. After sample filtration， solid phase extraction and ethylating derivatization， the concentrations of nine organotin compounds were detected by gas chromatography-mass spectrometry. The purpose of this study was to analyze its spatial distribution and tidal variation in the Yangtze River estuary， and to explore its behavior in the low oxygen area outside the estuary. The results show that the concentrations of dissolved organotin in the bottom water of the Yangtze River Estuary ranges from 33.9 to 203 ng?L^-1 （as Sn）， with an average of 125 ng?L^-1. Tributyltin （TBT） is detected in only 42% of the samples， and the highest concentration of TBT is 53.1 ng?L^-1. The detection rates of the other eight organotin compounds were 92% to 100%. The methyltin concentrations are （36.7 ± 16.2） ng?L^-1， accounting for 20% to 40% of the total concentrations of dissolved organotin species. The concentrations of butyltin are （33.1 ± 22.0） ng?L^-1， accounting for about 16% to 45%. The concentrations of phenyltin are （55.7 ± 12.4） ng?L^-1， accounting for about 26% to 59%. In the estuarine turbidity maximum zone and the coastal seasonally hypoxic zone， as well as in the tidal transition stage from flood tide to ebb tide， the concentrations of dissolved organotin species in bottom water peak， which is mainly attributed to the increase of dissolved TBT and mono-substituted organotin compounds. It is also found that the concentrations of triphenyltin （TPhT） and monobutyltin （MBT） increase with the decrease of dissolved oxygen saturation. The tide-driven resuspension and reductive dissolution in the bottom boundary layer lead to pulsed exposure of organotin such as TBT and TPhT in the bottom water， which may pose ecological risk to marine benthos and deserves further attention and research.

Abstract:In this paper， a rate-dependent damage model was proposed by incorporating micro-inertia and micro-viscosity into the static elasto-plastic damage framework to account for the strain rate effect of concrete induced by the rate-dependence of micro-cracks. The stress-strain curves and dynamic increase factors of concrete strength obtained by numerical analysis indicate that the dynamic mechanical properties of the material at moderate and high strain rates can be well captured by the model. Furthermore， numerical simulations of a Hopkinson-bar test were performed and the analytical results were in good agreement with the experimental results， demonstrating the validity of the proposed model for the dynamic responses analysis of concrete structures exposed to high-rate loadings.

Abstract:Based on the best track dataset of typhoon in the Northwest Pacific from 1951 to 2015 provided by the Japan Meteorological Administration， the typhoon tracking， intensity and wind field parameter models are developed utilizing the geographically weighted regression approach， respectively. A stochastic simulation algorithm that is applicable for the typhoon wind hazard assessment in southeast coastal regions of China is then proposed by introducing a three-dimensional analytical typhoon boundary layer model. A case study is conducted by taking the Lingdingyang Bridge as an engineering example， which is the main navigable channel in the Shenzhong Link project.A 100 000-year typhoon simulation is conducted at the bridge site. The return period curve， the probability of exceedance curve and the vertical wind profile of extreme wind speed are constructed respectively， which can be directly used to guide the wind-resistant design of bridges. Finally， the flutter reliability analysis of the Lingdingyang Bridge is performed by introducing the uncertainties of structural and aerodynamic parameters. Its flutter failure probability and safety performance under typhoon winds are evaluated.

Abstract:The combustion experiments of branches， leaves and cores of 26 landscape tree species in Shanghai were conducted. Fourteen combustion indexes including moisture content， bark thickness， specific leaf area， combustion calorific value， combustion time and temperature change were determined， of which the specific leaf area was the most important. The fire resistance characteristics of each tree species were evaluated comprehensively. Based on the analysis of variance， the correlation between the functional traits of tree species and the burning characteristics was elaborated. According to their burning characteristics， twenty-six species of landscape trees were divided into 3 categories： strong， medium， and weak. Then the optimal chain of landscape tree species selection for fire response in Shanghai was determined by cluster analysis at last.

Abstract:Aimed at the lowest total cost， carbon emission， and freight loss rate of transportation network， an optimization model of railway cold chain logistics network with stochastic demand and transportation capacity constraints was established. The model is transformed deterministically using the chance-constrained programming theory， and an adaptive genetic-simulated annealing algorithm （A-SAGA） is designed. The optimal cold chain logistics transportation scheme set is obtained by MATLAB simulation calculation. The sensitivity analysis of freight subsidy， train travel speed and freight category are conducted. The simulation results show that under the multiple conflicting objectives of considering transportation costs， carbon emissions， and cargo loss rates， rail cold chain market share can be improved significantly when 5% of the freight subsidy is applied， or only 70 km?h^-1 of train travel speed is increased. These two methods can be used flexibly under different infrastructure conditions. Cargo with varying degrees of sensitivity to transit time directly affects the change in the rate of cargo loss and the initial value of rail market share.

Abstract:The container relocation during loading in the terminal yard has sequential and dynamic characteristics， and belongs to the non-deterministic polynomial hard problem. This paper takes the common container terminal yard， which is parallel to the shoreline， as the research object. Considering the relocation effect on the continuity and efficiency of shipment， the model based on Markov decision processes for the container relocation in the yard during loading was proposed， with the optimization objective to minimize the total relocation times， and the algorithm based on inverse reinforcement learning was designed. To verify the effectiveness of the algorithm， taking the random decision as criterion， the inverse reinforcement learning algorithm was compared with the common rule decision-making and the random decision-making . The results show that when the initial state of the bay is unsatisfactory， the common rule decision-making is not necessarily superior to random decision-making. The inverse reinforcement learning algorithm can effectively mine and apply the expert experience， and the probability of converging to the minimum relocation times is obviously better than that of the others. In addition， it can better control the relocation times of a single loading in different state of the bay， and realize the intelligent decision-making of container relocation during loading.

Abstract:Smart decision-making is the key technology of smart water systems. This paper reviews the realization of intelligent decision-making of urban drainage systems from pipe network diagnosis and evaluation， urban waterlogging prevention and control， and overflow pollution control in rainy days. For drainage pipe detection and assessment， the technical methods for source flow tracking based on water flow and chemical markers monitoring at divided sub-catchments were evaluated. For urban flooding control， the techniques of elaborate simulation of flooding risk area using numerical model， and the real-time forecast of precipitation and local flooding depth using machine-learning method were reviewed； for the drainage overflow pollution control， the optimal control of urban drainage system based on the integration of multi-objective algorithm， numerical model， and machine-learning were discussed. It is proposed that the reliability of the modeling system is the key for smart decision-making in urban drainage systems. Therefore， attention should be paid to the integration of quantitative analysis of water sources in the pipe network and waterlogging risk early warning and optimal operation scheduling of drainage systems.

Abstract:Thirty-four different water samples of high-salt industrial wastewater were desalinated by humidification-dehumidification and evaporation experiments. Based on the experimental results， the feasibility study of the universal application of the humidification-dehumidification technology in actual industry is conducted. Combining with the water quality characteristics and treatment effects of different high-salt industrial wastewater， the general rule for judging the effect of this method on the treatment of high-salt industrial wastewater is summarized. The results show that the conductivity drop percentage η_σ of the condensate of all wastewater in the experiment is above 80.0%， with the highest percentage of up to 99.9%. All the salinity of the condensate can reach the biochemical treatment standard， and the electrical conductivity of 32 condensates can be reduced to below 2 000 μS?cm^-1. In addition， via the humidification-dehumidification technology， salt substances with a higher boiling point than water have a complete removal effect， salt substances with a lower boiling point than water and a larger ionization constant have a better removal effect， and salt substances with a lower boiling point than water and a smaller constants have a poor removal effect.

Abstract:This paper selects the conventional airfoil NACA23012， natural laminar flow airfoil NACA64-215 and supercritical airfoil RAE2822， with four parameters including the height， width， end shape of horn-ice， and connection between horns， to study the influence of these four parameters on the lift/drag coefficient of different airfoils at different angles of attack. The results show that the lower horn of horn-ice is one of the main factors affecting the coefficient， and the sensitivity of different airfoils to parameters is different. The lifting performance of the prediction model can be increased by selecting the semicircle end， adding the connection between horns and decreasing the height of the horn-ice.

Abstract:Aimed at the risk of structural strength and thermal damage to the fuel cell air compressor rotor， the key parameters such as the interference between the sleeve and the permanent magnet， the thickness of the sleeve， and the inner diameter of the hollow hole were analyzed using the finite element method and numerical simulation. The results show that increasing the interference and sleeve thickness is beneficial to improving the rotor strength. Increasing the sleeve thickness and reducing the hollow hole radius is beneficial to improving the maximum allowable working temperature of the rotor. The maximum stress of sleeve and permanent magnet is mainly affected by the maximum working temperature.

Abstract:The refrigerant distribution characteristics in the evaporator can be changed to optimize the position and the opening size of the baffles inserted. The results show that the insertion of evaporator collector baffles can effectively improve the refrigerant distribution characteristics， which in turn improves the cooling performance and the surface temperature distribution of the evaporator.

Abstract:When the right-hand side vector of the consistent system of linear equations is disturbed by noise， we give an upper bound for the error in expectation between the iteration vector generated by the greedy randomized Kaczmarz method and the least-norm solution of the noise-free system of linear equations， and illuminate that， as the iteration step increases， this solution error in expectation decreases to a given threshold with a linear rate. Numerical experiments show that this threshold can give a good estimate of minimum that the iterative solution error of the greedy randomized Kaczmarz method can reach.

Abstract:Based on an effective greedy probability criterion for selecting two working rows from a coefficient matrix， a greedy two-subspace randomized Kaczmarz method for solving large sparse linear systems is proposed. The theoretical analysis shows that this method converges to the minimal-norm solution of consistent linear systems， and the convergence factor of the method is smaller than that of the original two-subspace randomized Kaczmarz method. The numerical experiments show that this method is superior to the original two-subspace randomized Kaczmarz method from the point of view of solution performance.

Abstract:This paper incorporates the government debt ratio into the “mean-variance” risk assessment model， analyzes its impact on the decision-making of public-private partnership （PPP） projects， and finds that investors will require more certain risk compensation and implicit risk compensation due to loss aversion， which makes the PPP project alienated as a tool of illegal debt-raising of local governments， i.e. “Formal equity， essential debt”. Furthermore， verifies the propositions of the theoretical model through an empirical analysis of PPP projects and urban debt information in China from 2014 to 2016. The findings suggest that local governments should initiate PPP projects according to their fiscal capability， and strengthen the legal construction and social credit environment construction related to PPP projects， to protect the reasonable rights and interests of social capital， especially private enterprises.

Abstract:In this paper， the retailer’s fairness concern is taken into account in the dual recycling channel closed-loop supply chain， and three decision models considering retailer’s fairness concern are constructed， which are analyzed and solved by using the game theory. The influence of retailer’s fairness concern on the optimal strategy and performance of each channel member in different models is analyzed. A numerical simulation is conducted to verify the conclusions and for further discussion. The results reveal that the retailer’s fairness concern has a great effect on the optimal strategies for chain members， including optimal wholesale and retail prices of product， return rate of used items. Meanwhile， this behavior tendency can capture more excepted utilities for the retailer， but leads to the excepted utility reduction for the manufacturer and has different impacts on the expected utility of the third party. In addition， the influence of the retailer’s fairness concerns will exert different influences on the total expected utility of the three decision models.