With the rapid economic development, the demand for energy continues to increase, and the emission of CO₂ gas keep growing. The electrochemical reduction of carbon dioxide (ERC) to fuel and chemicals is an effective way to realize the conversion and utilization of CO₂ as well as the storage of renewable energy. Cu?based catalysts are one of the materials which can directly reduce CO₂ to high value?added chemicals(such as hydrocarbons) with high efficiency. Thus, the Cu?based catalysts have been one of the research focus of ERC technology research. The main research progress of Cu?based catalysts for ERC technology in recent years is reviewed. Firstly, reaction principle of ERC and the technology challenge are summarized, and then the cooperative control strategy for the structure and composition of copper?based catalysts is discussed for monometallic copper?based catalysts, polymetallic copper?based catalysts, copper oxide and oxide?derived copper catalysts, and copper?organic composite catalysts. In addition, research progress and unsolved problems of Cu?based catalysts are also summarized. Finally, the future trend these catalysts is also prospected.

Chiral oxazolines are a type of important chiral heterocycles compound, which are not only present in many biologically active natural products and drug small molecules with physiological activity, but also in chiral cofactors and chiral ligands often used in chiral synthesis. Currently, the asymmetric synthesis of chiral oxazolines still relies on the condensation between chiral amino alcohols and carboxylic acid derivatives. However, due to the limited availability of chiral amino alcohols and the tedious synthetic route, the development of highly efficient and straightforward methods for chiral oxazolines synthesis via asymmetric catalysis is of significant synthetic value. In this paper, we have summarized the recent advances in the asymmetric catalytic synthesis of chiral oxazoline derivatives through transition metal catalysis and organocatalysis, including asymmetric Aldol reactions, asymmetric clizations and others.

An transition metal copper?catalyzed cross?coupling reaction of tosylates with p?toluene sulfonate compounds and alkyl Grignard reagent has been developed, and a long alkyl branched fatty alcoholto could be synthesized simply and efficiently. 10?octylicosan?1?ol was obtained in 65% isolated yield under the optimized reaction conditions. It was further characterized by nuclear magnetic resonance,the structure of the compound was confirmed.

Nano?La (OH)₃ particles were synthesized using a precipitation method in deep eutectic solvents (DES). These materials were analyzed and characterized by X?ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption (BET). The effects of different reaction conditions on the morphology of lanthanum hydroxide were explored. In addition, an adsorption test was performed with KH₂PO₄ simulated wastewater. The results show that the La(OH)₃ particles synthesized with water and urea?choline chloride have a granular morphology, and the diameter is between 0.02 μm and 3.00 μm. When ethylene glycol?choline chloride is used as solvents, La(OH)₃ have a rod morphology with particle length between 80 nm and 180 nm. The maximum adsorption capacity is between 58 mg/g and 86 mg/g and the adsorption isotherm of KH₂PO₄ is best fitted with Langmuir model.

The effect of dissolved oxygen (DO) concentration on aerobic granular sludge (AGS) treatment on simulated municipal sewage was studied in SBR reactor. By changing the amount of aeration, the DO concentration in SBR reactor was controlled respectively in the range of 3 mg/L≤ρ（DO）＜4 mg/L, 2 mg/L≤ρ（DO）＜3 mg/L and 1 mg/L≤ρ（DO）＜2 mg/L. The concentrations of COD, NH{}_{\mathrm{4}}^{+}-N, NO{}_{\mathrm{3}}^{—}-N, NO{}_{\mathrm{2}}^{—}-N, TN and P in the effluent were detected. The results show that the removal rates of COD, NH{}_{\mathrm{4}}^{+}-N and P are affected little by the DO concentration, but the removal rate of TN is affected significantly. When 3 mg/L≤ρ（DO）＜4 mg/L, 2 mg/L≤ρ（DO）＜3 mg/L和1 mg/L≤ρ（DO）＜2 mg/L, the removal rate of TN is 62.14%, 71.81% and 82.11% respectively; when 1 mg/L≤ρ（DO）＜2 mg/L, the removal rate of TN reached the best for the AGS system and the system was stable. The average removal rates of COD, NH{}_{\mathrm{4}}^{+}-N and P were 90.43%, 96.97% and 76.00%, respectively.

Metal organic framework ZIF?67 has been successfully fabricated via solvothermal method. The as?synthesized ZIF?67 was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X?ray powder diffraction and thermogravimetric analysis. The adsorption property of ZIF?67 for methyl orange was investigated. The effects of pH value, dosage of adsorbent, initial concentration of methyl orange solution, contact time and temperature were discussed. The results show that the most proper dosage of ZIF?67 is 20 mg. When the pH value of the dye solution is 7, the adsorption capacity is the best. At 303 K, the adsorption reached an equilibrium within 25 min. The maximum adsorption capacity of ZIF?67 for methyl orange is 152.67 mg/g at 303 K. The isotherm data followed the Langmuir isotherm model and the kinetic adsorption obeyed the pseudo?second?order model. Thermodynamic parameters illustrated that the adsorption process is spontaneous and endothermic. The spent ZIF?67 has excellent regenerative performance by treating with ethanol, and the adsorption ability of ZIF?67 remains good after six adsorption?desorption cycles.

Nanocarbon particles/carbon nitride composite was prepared through one step heat polymerization method. XRD, FTIR, TEM, UV?vis DRS, PL and other methods were used to systematically characterize nanocarbon particles/carbon nitride. Rhodamine B solution was degraded to measure its photocatalytic performance. The results show that the loading of nanocarbon particles can obviously improve visible light absorbed ability of the composite material and the separation efficiency of photogenerated electrons/holes. When the added mass of nanocarbon particles is 10 mg, the rhodamine B degradation rate of as?prepared nanocarbon particles/carbon nitride 2 is 96.5% in the 20 min, which is obviously better than bare carbon nitride. In addition, nanocarbon particles/carbon nitride composites show good stability.

Drainage continuity is very important for coalbed methane extraction. However, the well shut?in is unavoidable when draining. How to drain and draw up a reasonable drainage system after reopening the well are significant to increase gas production. Based on the analysis of coalbed methane production stage theory, combined with the field data about well shut?in, at the same time, numerical simulation method was used to study the change of reservoir parameters during well shut?in. The results show that well shut?in obviously changes the reservoir physical parameters,which causes the water saturation of the coal near the wellbore to increase, and the well bottom pressure increases. At the same time, it causes the re?adsorption of free gas near the wellbore and reduces the gas seepage capacity. Therefore, rapid drainage after reopening the well is helpful to dredge the flow channel of gas, improve gas flow capacity and increase gas production.

Erosion corrosion often occurs in oil pipeline system. The main reason for erosion corrosion is the impact of particles on the wall. DPM model was used to study the erosion effect of solid particles on the pipe wall, analyze the flow characteristics of π?shaped pipe, and study the influence of fluid velocity, particle mass flow rate, particle diameter and density on the erosion corrosion rate of the pipe. The simulated results show that the erosion corrosion of π?shaped pipe is the most serious at the elbow. The maximum erosion corrosion rate increases with the increase of fluid velocity and particle mass flow rate. As the particle diameter and density increase, the erosion effect is weakened.

In the complex deep oil and gas well downhole operation, the packer needs to have good high temperature resistance, high pressure resistance and sealing performance, so as to improve the service life of the packer.Compared with the traditional K344 laminated steel belt packer, the K344 corrugated steel frame packer can effectively reduce the stress in the middle of the inner and outer rubber barrel, make the force in the middle more even, and reduce the force on the shoulder at the same time. In this paper, by using ABAQUS software, the K344 corrugated steel skeleton packer setting process in finite element simulation analysis, from two aspects of structure and material to the force of the steel strip was studied, and a simulation analysis with the optimal thickness of the strip, and the optimal material for steel belt optimized packer could better adapt to the job of deep oil and gas wells, provided a new expansion packer design thinking.

Based on the discrete element method, the transport and internal force problem of the double screw conveyor was studied by using the discrete element analysis EDEM software. According to the Hertz contact theory, the contact models of material particles and devices were established, and the influence of the double screw conveyor on the transportation characteristics of the material particles under different physical and geometric parameters was analyzed.The results show that the movement of particles in the conveyor is mainly in a straight line, with the circumferential movement as the auxiliary； the change of the wheelbase has a great influence on the material conveying characteristics of the conveyor. With the increase of the wheelbase, the mass flow rate increases gradually, and the particle force in the central area decreases gradually.

Finite element analysis software ABAQUS was used to study the process of micro texture PCBN tool turning Cr12MoV, Taguchi method was used to carry out orthogonal experimental design. The variation law of the actual contact area between tool and chip, cutting force and cutting temperature with texture parameters was studied by signal?to?noise ratio analysis method, and the optimal combination of texture parameters was obtained. The results indicate that the actual tool?chip contact area decreases with the increase of texture groove width and texture edge pitch respectively. Texture groove width and texture edge pitch have the most significant influence on cutting performance of the tool; Compared with the non?textured tool, the micro?textured PCBN tool with the optimal texture parameter combination can reduce the cutting force by 5.2% and the cutting temperature by 4.7%.

The existing image segmentation algorithms based on Markov random field are prone to over segmentation and the segmentation results are not ideal. This paper presents an improved image segmentation algorithm based on Markov random field and region merging. First, the algorithm uses the image segmentation algorithm based on the theory of Markov random field and Gaussian mixture model to get the initial segmentation results; second, the region distance between each region is given by using the adjacent relationship, color relationship and boundary condition of each region; finally, the initial segmentation is performed according to the distance between regions and the change rate of color divergence after region merging. The final image segmentation results are output by region merging. In this paper, Berkeley standard image library is used for experimental simulation, and the Dice and Jaccard coefficients are used as the evaluation index of this paper. The experimental simulation shows that the proposed algorithm has better segmentation effect than the existing algorithm based on MRF theory.

The residual magnetic stress detection technology can effectively detect the stress concentration of ferromagnetic materials, and has great potential in the field of long?distance oil and gas pipeline stress detection. However, due to the imperfect mechanism of the residual magnetic stress detection technology, the relationship between the residual magnetic signal and the stress is difficult to calculate quantitatively, resulting in the quantitative measurement of the residual magnetic stress detection, which seriously affects the application of the technology in the field of pipeline detection. In this paper, the mechanism of remanence generation is explained based on the magnetic domain model. Correspondence between remanence and stress is established by coercive force. The changing characteristics of remanence signal with the change of stress are analyzed and verified by experiments. The research results show that the irreversible magnetization of ferromagnetic materials is the cause of residual magnetism; as the external stress increases, the residual magnetism signal has a gradually increasing change rule.

In order to obtain good performance and required goals, the existence of asynchronous switching of controllers and subsystems must be considered. The event?triggered control of nonlinear switched system under asynchronous switching is studied. As the switching of the controller lags behind the switching of the subsystem, asynchronous behavior occurs. First, the switched nonlinear systems with linear parts and nonlinear parts are researched and the Laypunov functions are constructed. Then, a switching controller for a cascaded nonlinear switched system to obtain a closed?loop system is designed, and the average dwell time is given to get the sufficient condition for the switched system to be globally uniformly and exponentially stable. Finally, a numerical example is given to illustrate the feasibility of the method.