A base?catalyzed 1,6?conjugate addition of p?QMs for the preparation of diaryl methyl ethers (thioether) has been developed with 37% to 95% yields, which realized the solvolysis reaction between p?QMs and alcohol (thiophenol) under the catalysis of 20% NaOH. The method features easy operation, mild condition and good functional tolerance. A gram scale experiment was examined in 80% yield, which provides possibility for potential application and transformation in later stage.
Direct flame impingement heating technology is widely used in the field of steel heat treatment processes and is currently fueled by natural gas. Hydrogen, as a clean energy source and its high laminar flame propagation speed, combined with natural gas will improve the fuel combustion speed and reduce the emission of carbon oxides and nitrogen oxides. In this paper, a numerical model of direct flame impingement heating of steel plate was established using Fluent, and the heat transfer characteristics of direct flame impingement heating of steel strip were investigated under different hydrogen doping, Reynolds number, and factorless distance conditions. The results show that the temperature and heat flow density of the steel plate of the heated target decrease with the increase of hydrogen doping from 0 to 25% at a heating time of 10 s. The temperature of the steel plate stationary point decreases from 385.36 K to 374.31 K, and the heat flow density of the steel plate stationary point decreases from 154 828 W/m2 to 137 926 W/m2. With the increase of Reynolds number from 13 400 to 33 600, the steel plate stationary temperature increased from 347.04 K to 450.90 K, the pressure increased from 14.93 Pa to 136.53 Pa, but the uniformity of the temperature and pressure of the steel plate deteriorated gradually. The increase of the causeless distance from 25 to 45 made the temperature of the steel plate stationary point decreased from 442.42 K to 344.36 K, and the pressure was reduced from 106.00 Pa to 24.81 Pa and the distribution was more inhomogeneous.
In order to improve the compatibility between rubber powder and matrix asphalt, the rubber powder was modified by microalgae bio?oil and compounded with SBS at 5% dosage to prepare modified asphalt. The changes of rubber powder before and after modification were analyzed by infrared spectroscopy and scanning electron microscopy; the dispersion of rubber in asphalt before and after modification was analyzed by viscosity, fluorescence and phase separation tests, and the mechanical properties and aging resistance of the modified asphalt were analyzed by dynamic shear rheology analysis and multiple stress creep recovery test. It was found that the incorporation of MB increased the proportion of light components in the mixing system, promoted the solubilization development of CR in asphalt, and improved the storage stability, viscoelasticity and rutting resistance of the modified asphalt.
In this study, the optical properties of 3D carbon ball were theoretically investigated by using Density?Functional Theory (DFT) and wave function analysis. The electron?leaping mechanism in the Ultraviolet?visible (UV?vis) absorption spectrum was investigated. The electronic excitation properties of 3D carbon ball were investigated by Transition Density Matrix (TDM) and Charge Density Difference (CDD). Raman spectra were calculated and the vibrational modes of the 3D carbon ball were further explained. Meanwhile, the interaction between 3D carbon ball and the external environment was investigated using Electrostatic Potential (ESP), and the degree of electron delocalization of 3D carbon ball was investigated based on the magnetic induction current under the applied magnetic field.It is shown that the absorption spectra of three?dimensional carbon spheres are mainly in the ultraviolet region and that they have a strong electron delocalization capability. This study can provide a theoretical basis for the application of other 3D π?conjugated molecular structures in linear and nonlinear optics.
The crude oil produced by oil wells contains sediment, scale and other particles, which are deposited together with the wax in the process of crude oil pipeline transportation. It leads to a decrease in pipeline throughput, and may cause pipeline blockage and affect the safety of transportation in severe cases.The yield stress test and microscopic characteristic experiments show that there is a critical scale containing ratio in wax deposits of the influence of calcium carbonate scale on the strength of wax deposits. And it is found that the wax deposits containing scale will increase the breaking force on the wax layer and the pigging efficiency of the pig through the indoor pigging experiment of polyethylene pipeline. Based on the data of pigging experiment, a prediction model of pigging efficiency was established by using the π theorem. The model was validated by indoor experiments and third?party literature experimental data.
To study the influence of hydrogen mixing ratio on the leakage of natural gas pipelines, a mathematical model for the leakage and diffusion of directly buried high?pressure hydrogen mixed natural gas pipelines was established based on computational fluid dynamics theory and numerical simulation method.The leakage status, volume fraction distribution of hydrogen mixed gas,and the distribution of soil pressure and gas velocity around the pipeline were analyzed under different hydrogen mixing ratios.The results show that with the increase of hydrogen mixing ratio, the explosion radius of hydrogen mixed gas in the atmosphere will gradually decrease,and the range of high?pressure area around the pipeline will gradually decrease,and the gas flow rate at the leakage port will gradually increase.When the hydrogen mixing ratio is 30%,the explosion radius in the atmosphere is reduced by 43%,and the gas flow rate at the leakage port is increased by 68%.This provides a theoretical reference for the safety and emergency repair of hydrogen?doped natural gas pipelines and has important practical significance for promoting the large?scale application of hydrogen?doped natural gas.
The chemical storage tank area is a place with a large number of hazard sources, and the dynamic risk of the storage tank area cannot be quantified and characterized by traditional emergency management methods. Therefore, based on PPRR theory, a quantitative evaluation model of fire emergency management ability of chemical tank farm was established, and the weight of evaluation index was determined by interval analytic hierarchy process. The improved fuzzy comprehensive evaluation method was used to quantitatively evaluate the fire emergency management ability of chemical tank farm. This model is used to evaluate the fire emergency management ability of chemical tank farm of M Petrochemical Company, and the accuracy of this model is verified. The results show that the evaluation score of fire emergency management ability of chemical tank farm of M Petrochemical Company is 3.35, which is consistent with the qualitative evaluation result, and the accuracy of this model is verified. The model can solve the problem of uncertainty of the importance degree of the indicators, and the improved fuzzy comprehensive evaluation method can point out the deficiencies and degree of chemical tank farm, which can provide a new way to perfect and improve the fire emergency management ability of the chemical tank farm.
In earthquakes and other natural disasters, there are often large and small debris on the road, which will affect the rapid passage of emergency vehicles. Installing lifting mechanism on the vehicle chassis is an effective way to solve this problem. However, the existing lifting mechanism lifting method is relatively single, occupies a large space, and is inconvenient to install underneath the vehicle. In addition, it also faces the problem that it can not be lifted flexibly with different working conditions. In order to solve these problems, this paper designs a metamorphic lifting mechanism based on the principle of metamorphic, which has the characteristics of variable topological configuration and variable degrees of freedom, and can complete the work task in different configurations according to different working conditions. For obstacles of different sizes, the mechanism can be elevated in one or two stages to realize rapid obstacle crossing. In this paper, after establishing the virtual prototype model of the metamorphic lifting mechanism, ADAMS software is used to carry out the configuration change dynamics simulation experiment, which investigates the dynamics of the vehicle in the process of configuration change and verifies the feasibility and stability of the mechanism.
Through molecular dynamics simulation, the torsional deformation behavior of copper nanowires in different crystal orientations (Ⅰ: x[1 0 0] y[0 1 0] z[0 0 1], Ⅱ: x[1 0 1/8] y[0 1/8 0] z[－1/8 0 1], Ⅲ: x[1 0 1/4] y[0 1/4 0] z[－1/4 0 1]), different crystal orientation ratios (α1=1/6, α2=1/2, α3=5/6), and different numbers of twin interfaces (0, 2, 4) were studied, as well as the relationship between the shear stress and torsion angle of copper nanowires during torsion. The results indicate that change the orientation type contributes to enhancing the torsional mechanical properties of copper nanowires. Reducing the ratio of internal diameter to external diameter also improves the torsional mechanical properties of copper nanowires. Furthermore, decreasing the number of twin interfaces can strengthen the torsional mechanical properties of copper nanowires. The torsion process of copper nanowires can be divided into three stages: elastic, plastic and deformation failure. The research results provide a basis for investigating the torsion of high?strength copper nanomaterials.
Traditional mechanism models of greenhouses are difficult to reflect the real greenhouse environment due to nonlinear, multivariate, and strongly coupled characteristics. In this paper, extreme learning machine (ELM), back propagation (BP) neural network, and support vector machine (SVM) are used to predict and analyze the temperature, humidity, and light intensity of the greenhouse. The results show that the predicted values of ELM model are the most similar to the real?time parameters of greenhouse environment. In order to further improve the prediction accuracy of environmental parameters in the greenhouse, the improved sparrow search algorithm (ISSA) is used to optimize ELM model in this paper. The predicted environmental parameters are in good agreement with the measured data of a greenhouse in Tianjin, which confirms the feasibility of the proposed prediction model for the control of greenhouse environment.
In view of the huge scale of urban underground pipe network, the traditional manual detection method can no longer meet the needs of the current projects. In this paper, the MobileNetv3?YOLOv7 network model is proposed as the algorithm for target detection of underground pipeline defects to improve the accuracy and speed of detection. First, the pipeline image dataset is preprocessed, and the input image is grayscale and resampled to balance the number of samples. Secondly, the lightweight network MobileNetv3 and YOLOv7 network frameworks are combined to increase the BiFPN feature pyramid structure to improve accuracy. Then, in terms of data processing, Mosaic data augmentation is used to improve the robustness of the model. Finally, a comparative experiment with the YOLOv7 network model is designed to verify the feasibility of the model. In this paper, the MobileNetv3?YOLOv7 network model is verified under the framework of Pytorch experiment, and the experimental results show that the model greatly reduces the amount of parameter calculation and improves the average accuracy.
The parameters of PID controller determine the stability and speed of tension control system, so it is important to study the parameter tuning optimization of classical PID controller in winding tension control. The PID tension controller based on the modified whale algorithm is designed by combining PID and modified whale optimization algorithm with winding tension control as an entry point. The improved whale algorithm (L?WOA) is combined with PID in order to improve its convergence speed and convergence accuracy when rectifying the PID parameters. A mathematical model and a dynamic torque balance equation are developed to analyze the effect of wire speed and web diameter on web tension. The parameters are optimized using the modified whale algorithm and various other algorithms, respectively, and the results show that the PID controller optimized by the improved whale algorithm proposed in this paper has the advantages of rapid response, more steady output, sturdy anti?interference ability and better robustness when the PID controller is controlled.
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