Abstract:In order to study the dynamic response of silo frame and its equivalent model under earthquake action, this paper intends to simplify the silo into column ring beam structure according to the principle of stiffness equivalence in combination with the degassing and storage silo frame structure project of a petrochemical coMPany. By changing the cross-section size of column ring beam and the number of ring beam, the finite element models of silo frame structure and column ring beam frame structure are established, and the reasonable column ring beam frame model is selected to simulate the original structure. On this basis, the equivalent increase coefficient of stiffness is determined to be 1.25. Using time history analysis method, three seismic waves, El Centro wave, Taft wave and artificial wave shm2 wave, are selected to give the maximum displacement and maximum equivalent stress seismic response of the structure under three working conditions.

Abstract:This research focused on a three-centered cylindrical roof of coal bunker. Kriging surrogate model was adopted to optimize the aerodynamic shape of the roof structure. First of all,the flow characteristics of a three-centered cylindrical roof were numerically simulated by using standard k-ε,RNG k-ε and SST k-ω turbulence models, and compared with the wind tunnel data. Secondly, radius-to-span ratio (R/S) and central angle (θ) of middle arc of the three-center cylindrical roof were optimized with the minimum peak negative pressure on roof surface and the minimum absolute value of vertical displacement as the optimization objectives. The results show that when R/S=1.26 and θ=45.8°,the peak negative pressure on the roof surface is lowest. When R/S=0.56 and θ=14.1°,the absolute value of vertical displacement of the roof under mean wind loads reaches the minimum value.

Abstract:On account of the complexity of the interaction between anchor and soil, the current researches on the horizontal bearing capacity of inclined spiral piles are still unable to meet the relevant engineering requirements. Based on the horizontal bearing test of spiral vertical single pile, the bearing performance of tilted single pile under horizontal load was studied by nonlinear finite element software ABAQUS, and the influence of different inclined angles on the bearing performance was analyzed in detail. The main research results are as follows:(1) When the tilt angle does not exceed 45°, the screw pile is controlled by the horizontal limit displacement under the action of horizontal load. (2) With the increase of the tilt angle, the horizontal bearing capacity of the spiral pile gradually increases. For the helical pile with the same dip angle, the horizontal bearing capacity of positive dip is always greater than that of negative dip, and the ratio of the load shared by the blades to the horizontal ultimate bearing capacity keeps increasing (for the helical pile with positive dip angle, the ratio increases from 2.4% to 15.6%). (3) In the whole process of loading, the plastic deformation area of soil mass is mainly concentrated in a small range on the side of the top pile, and the soil mass at the blade has no plastic deformation.

Abstract:Stochastic finite element method was used to analyze the reliability of the bearing capacity of strip footings considering the spatial variability of soil undrained shear strength. The influence of degree of non-stationarity and spatial correlation length on the mean and standard deviation of bearing capacity was analyzed by using stochastic finite element method combined with Monte Carlo simulation method. The failure probability and safety factor of foundation under various parameter combinations were calculated and coMPared. The results show that the bearing capacity of the strip footing increases with the increase of the degree of non-stationarity, and its bearing capacity decreases firstly and then increases with the increase of spatial correlation length.

Abstract:The macro strength and deformation characteristics of coarse-grained soil are closely related to its micro pore structure. In order to deeply understand the strength deformation mechanism of coarse-grained soil, this paper takes the heterogeneity of pore structure as the research object, and defines the pore space distribution coefficient which can quantitatively describe the pore space variability of coarse-grained soil by analyzing the quantitative variability, volume variability and segregation effect of pores. The results show that the elastic modulus, peak strength and Poisson's ratio of coarse-grained soil decrease by 40.8%, 12.5% and 39.5% respectively with the increase of pore space distribution coefficient under other conditions.

Abstract:Sand widely distributed in engineering is easy to cause a series of engineering geological disasters due to its loose structure and poor engineering properties. In this paper, the unconfined uniaxial compressive characteristics of sand reinforced by polyurethane polymer and sisal fiber were evaluated, and the micromechanical mechanism of sand reinforced by different curing agent and fiber contents was analyzed by electron microscope (SEM). With the increase of curing agent content and fiber content, the elastic modulus, compressive strength and toughness of sand soil increases significantly, and the failure morphology of the sample changes from "petal-like" to suture line shape with the increase of fiber content. Polyurethane enhances the reinforcing effect of fiber by improving soil-soil/fiber interlock force, soil-fiber bonding force and soil-fiber friction force.

Abstract:In order to study the influence of the structural plane on the mechanical parameters of the broken rock mass, taking the construction of the underground powerhouse of Liyang pumped storage power station as an example, on the basis of the study of the geological conditions of the surrounding rock, the structural characteristics of the rock mass and the quality classification of the rock mass, the density, trace length and dip angle of the three cracks in the roof arch, the upstream side wall and the downstream side wall of the main power plant were selected for statistics, and the discrete fracture network was constructed based on Monte-Carlo method. Finally, the influence of discrete fracture network on the mechanical parameters of rock mass was studied by triaxial compression test discrete element simulation. The test results show that the structural plane plays a decisive role in the mechanical properties of the rock mass, and the parameters and discreteness of the uniaxial compressive strength, elastic modulus, cohesion, internal friction angle of the rock mass are more sensitive to the changes of the density, dip angle and trace length of the structural plane.

Abstract:The cube and prism specimens of gravel concrete with replacement ratio of recycled coarse aggregate r=0%, 30%, 50%, 70% and 100% were designed and manufactured. The change trend of cube compressive strength and prismatic compressive strength of concrete at different ages under different replacement rates of recycled coarse aggregate was studied. The results show that the compressive strength of concrete has no significant change when r is 30% when the age is 3 d and 7 d; If r is more than 30%, the compressive strength of concrete tends to decrease when r increases, and the decrease range is obvious. At the age of 14 d and 28 d, the compressive strength decreased with the increase of r. A calculation model for the correlation between cube compressive strength and prismatic compressive strength is proposed when the replacement ratio of recycled coarse aggregate is considered. The model is f_c=(-0.190 3r²+0.148r+0.722 7)f_cu.

Abstract:Soil arching effect is the main load transfer mechanism of piled embankment. It is the key factor to analyze the load transfer and the settlement of piled embankment to correctly grasp the evolution mechanism of soil arch. Based on the model test of plane soil arching effect, the PFC2D software is used to establish the particle flow numerical analysis model of piled embankment, and the correctness of the numerical analysis model is verified by comparing with the test results. Firstly, the theoretical calculation formula for the height of inner arch and outer arch of plane soil arching is verified based on the numerical simulation results of particle flow under embankment self-weight stress. Then, the evolution law of soil arching effect in piled embankment under the external load on the embankment surface is analyzed from three aspects including the distribution of vertical stress in embankment, the variation of stress reduction ratio and the distribution of contact force in embankment. When the external load on the embankment surface increases from 10 kPa to 40 kPa, the soil arching in the piled embankment is stable. For the condition that the external load on the embankment surface increases from 40 kPa to 100 kPa, the soil arch structure in the piled embankment will degenerate and form a new soil arch structure, which shows that the vertical load carried by the subsoil presents an increasing trend.

Abstract:The Midas Civil & FEA software was used to model and calculate a partial cable-stayed Bridge in service. According to the results of dynamic and static calculation and analysis, the key monitoring sections and measuring points were determined, and the sensor layout was optimized. The data transmission, early warning setting and system integration were overall designed. A complete health monitoring system was formed through the unified management and processing of monitoring data by the intelligent monitoring cloud platform developed for the bridge health monitoring system. Then the operation of the system in the past year was summarized, the problems in the system operation were analyzed and the solutions were put forward. Some monitoring results of the bridge including modal and girder deflection monitoring data were analyzed. The analysis results show that the health monitoring system achieves the design expectations.

Abstract:With the development of urban modernization, urban heat island effect has increasingly intensified its influence on human health, climate, resources and environment, which has become a huge environmental problem facing urban development today. In view of the increasingly obvious urban heat island effect in the urban center, based on Landsat series data and MODIS remote sensing data, this study took the downtown area of Ningbo as the study area, and applied GIS technology and Pearson correlation analysis method to analyze the correlation change between the surface temperature and other factors in the long time series. The results show that from 1990 to 2015, the heat island effect changed significantly in the downtown area of Ningbo. The surface temperature is negatively correlated with NDVI and positively correlated with NDBI. The surface temperature is positively correlated with GDP, reaching its maximum value in 2010. Population size and the gap between rural and urban areas will not directly lead to the urban heat island effect. The study shows that the surface temperature inversion technology based on the single window algorithm analysis the driving factors of urban heat island effect change has certain feasibility. This study can alleviate the planning of Ningbo downtown area benefit of heat island advice, in order to alleviate the regional environmental change.

Abstract:Using the daily precipitation and daily runoff data in the songhua river basin during 1961~2018, based on the 11 extreme precipitation index and five extreme runoff indicators, taking the trend analysis method, Mann-Kendall nonparametric test methods, Mann-Kendall mutation test, kriging interpolation method, Pearson correlation coefficient and other methods, this paper analyzed the change characteristics and regional differences of extreme precipitation and extreme runoff events in songhua river basin and, at the same time, analyzed the correlation between the extreme precipitation and extreme runoff events. The results show that, except the CDD and SDII indexes in the continuous dry period, the perennial average values of the other indexes all show that the songhua River basin is the high-value region, the songhua River main stream basin is the second-highest value region, and the Nenjiang River basin is the low-value region. The spatial trend distribution and abrupt transition years of each extreme precipitation index also reflect regional differences. The variation trend of each extreme runoff index was similar to that of the abrupt change year, and all showed a slight variation trend. Under different time scales, the correlation coefficients of extreme precipitation and extreme runoff events all passed the 99% significance test. Due to the slow confluence of the Songhua River Basin, extreme precipitation and extreme runoff events show the most significant correlation when the time scale is 30 days.

Abstract:In the effort to understand the individual particle emission characteristics and gaseous pollutants emission characteristics of fine particles emitted from residential coal combustion, three coal types, bituminous coal, anthracite and honeycomb coal, were selected to carry out combustion simulation experiment and pollutant emission level monitoring of residential coal in the laboratory, and collected the single particle samples of burning different coal fine particles, and studied the gaseous pollutants level, single particle micro characterization and element composition. The experimental results showed that:(1) In the ignition stage, the bituminous coal is mainly chain smoke particles, and in the burnout stage, it is mainly irregular mineral particles. The whole process of anthracite and honeycomb coal is dominated by near spherical particles of organic particles. Carbon particles are the main emission particles of the three coal types. (2) The particle size distribution of coal-fired can range from 0.05 μm to 0.80 μm, and the average particle size of soot aggregate emitted from bituminous coal can range from 0.45 μm to 0.55 μm. The spherical particle size of honeycomb coal is similar to that of honeycomb coal, and the average particle size of anthracite can range from 0.15 μm to 0.20 μm. The spherical particle of anthracite is relatively large, and the average particle size is between 0.25 μm and 0.35 μm. (3) The CO emission factors of three coal types are higher than SO₂ emission factors, and the CO emission factors of bituminous coal are higher than that of anthracite and honeycomb coal.

Abstract:Improvements are made to the security issue in the connection process between LoRawan terminal equipment and network server. A security model is proposed based on LoRaWAN protocol which, through the two-way authentication mechanism between the terminal and server, strengthens the security of terminal and server authentication to prevent the third-party equipment eavesdropping. This model updates regularly the authentication rules, prevents the replay attack, strengthens the link safety and at the same time, reduces the impact on the power consumption as far as possible. Simulation results show that that the security of this mechanism for the LoRaWAN protocol terminal authentication process becomes greater with the shortening of the update cycle. The energy consumption of the authentication process of the two parties of this mechanism increases with the shortening of the cycle. But it doesn't have an obvious impact on the energy consumption of the overall data transmission phase and the reception delay of the data transmission phase. The acceptance delay during the data transmission phase increases by less than 7%.

Abstract:1-alkyl-3-ethylimidazole bromide ([REhIM]Br, R=C₁₀H₂₁, C₁₂H₂₅ and C₁₄H₂₉) ionic liquids (ILs) was synthesized. The molecular structure of[REhIM]Br was optimized by density functional theory (DFT) at B3LYP/6-31 level, and the most stable configuration was obtained. The partial bond length bond angle in the molecule was obtained by theoretical calculation, and the charge distribution was analyzed. The interaction energies between anions and cations and[REhIM]Br were calculated by calculating the single point energies. Finally, the LUMO energy, HOMO energy and energy gap (ΔE_LUMO-HOMO) data in the electronic structure were obtained. The results showed that when the anion remaines unchanged, with the increase of alkyl chain of[REhIM]Br ionic liquid, the bond length, bond angle and charge distribution are independent of the length change of alkyl chain. The energy-related data such as interaction energy of ions, LUMO energy, HOMO energy and energy gap (ΔE_LUMO-HOMO) are closely related to the number of C atoms on the alkyl chain. With the increase of alkyl chain, the interaction energy of ions and energy gap become smaller, and the structure becomes unstable.

Abstract:Based on the product characteristics of waste electrical and electronic equipment (WEEE), considering the uncertainty of market demand, the demand is fuzzed, and a closed-loop supply chain (CLSC) is established under the guidance of retailers, in which the government implements reward and punishment policies for manufacturers, retailers and third-party recyclers respectively, and with the use of game theory, decision variables change based on government's rewards and punishments in the three recycling pricing models. The results show that the wholesale price of goods is the lowest and the recycling rate of waste products is the highest under the manufacturer recycling mode, and the manufacturer's revenue is far greater than the retailer's revenue, which provides reasonable suggestions for the supply chain management of manufacturing enterprises.