As an important semiconductor photocatalytic material, bismuth oxide (Bi₂O₃) is considered as a promising visible photocatalyst due to its special electronic structure and excellent visible light response performance. It displays a good application prospect in photocatalytic treatment of wastewater. However, the application of Bi₂O₃ is limited by its low photocatalytic performance, therefore, Bi₂O₃ pholocatalyst with superior performance is expected to be obtained by modifying methods by the researchers. In this review, a series of modification methods, such as surface morphology regulation, surface modification, metal ion modification and semiconductor combination, are summarized. Then, the future development of modified Bi₂O₃ photocatalytic materials is prospected.

The single?phase and two?phase flow friction pressure drops of oil and water phase fluids in a rectangular copper?based microchannel with a hydraulic diameter of 895 μm were tested, and the experimental data were also compared with the existing single?phase and two?phase flow friction pressure drop prediction models. The effects of mass flux and ratio between oil and water on friction coefficient and pressure drop were investigated. The results show that the friction coefficient of oil is significantly higher than that of water, and Hagen?Poiseuille equation can accurately predict the pressure drop of oil or water single?phase fluid flow in the channel. The mass flux of both oil phase and water phase affect the pressure drop of the liquid?liquid two?phase flow significantly, and the friction pressure drop of the two?phase flow increases with the increasing working fluid flow rate and oil phase content. The homogeneous flow model established by Cicchitti (1960) can predict the mixing viscosity of oil?water two?phase fluids relatively accurately. In order to improve the prediction accuracy, a prediction correlation formula for the friction coefficient of oil?water two?phase flow is established, and the predicted value is in good agreement with the experimental value.

Using sodium 1,4?dihydroxybenzene?2?sulfonate sodium (NaH₂L), 4,4'?bipyridine (bipy), Co(NO₃)₂·6H₂O and NiSO₄·6H₂O as raw materials, two mononuclear complexes containing nitrogen?donor ligands with similar structures, M(bipy)(H₂O)₄·(2H₂L)·4H₂O（M=Co（1）， Ni（2））, were synthesized by heating reflux method. The molecular structurse and composition were determined by single crystal X?ray diffraction, elemental analyses and thermogravimetric analyses. Co²⁺ and Ni²⁺ are six?coordinated, showing octahedral configuration, which are binded with one bipy molecule and four water molecules. H₂L^- anion does not coordinate with metal ions, balancing charges. In the complexes, H₂L^- anions, free water molecules and [M(bipy)(H₂O)₄]²⁺ cations can generate hydrogen bonds, which can form a network structure and increase the stability of the complexes. The fluorescence studies indicate that the maximum emission peaks of complexes 1 and 2 were 380 nm and 390 nm, respectively, which are characteristic fluorescence emission peaks of NaH₂L. The red shifts of the fluorescence emission peaks were due to the charge transfers between metal and ligand.

Heterocyclic N?oxides are important structural units in organic synthesis and pharmaceutical molecules. Under mild conditions, the combination of visible?light catalysis and transition metal catalysis can simply and efficiently realize the direct ortho?C—H bond acylation reaction of heterocyclic N?oxides and benzoyl formic acid. The reaction system has good universality and excellent selectivity, and can obtain a series of N?oxides substituted by ortho?acyl groups at a moderate to good yield.

In order to study and determine the optimal compounding system that can improve the stability of heavy oil emulsion in Liaohe Oilfield and the law of emulsion stability under different conditions, a focused beam reflectometer(FBRM) and rheometer were used to pass four factors and three levels. Orthogonal experiment with three indexes explored the change law of droplet average particle size, dispersion degree and emulsion viscosity, and investigated the influence of external factors on the stability of emulsion under compound system. The results show that the compound emulsifiers with the mass fractions of OBS?50, AEO15/OS?15, OP?15, and sodium with mass fraction of 4.0%, 4.0%, 1.4% and 1.4%, respectively, are the most beneficial to improve Stability of heavy oil emulsion in Liaohe Oilfield; there is a positive synergy between average particle size and dispersion, and an inverse relationship with the viscosity of the emulsion; the increase in temperature, volume ratio of oil to water will weaken the stability of the emulsion; stirring rate, ore The increase of the degree of chemical conversion can improve the stability of the emulsion; when the mass fraction of the mineralized NaCl is 0.2% to 1.0%, the stability of the emulsion can be greatly improved, and the quality fraction of the emulsion can be further improved. The lifting effect is not obvious.

When crude oil is extracted from oil wells, associated gas will be generated, and natural gas hydrates will be generated in high pressure and low temperature environments, which will block the transportation pipeline. Therefore, it is of great significance to study the hydrate formation in oil sand system (that is, the crude oil?containing system) and the pure quartz sand system (not including crude oil). The formation of methane hydrate and the final gas consumption in the oil sand system) and the pure quartz sand system were studied under the conditions of initial pressure of 4.00, 6.00, 8.00 MPa, quartz sand particle size of 20, 30, 60, 80 mesh, and constant temperature.The results show that in the oil sand system and under the same initial pressure conditions, the smaller the particle size of quartz sand, the shorter the induction period for hydrate formation, and the greater the rate of hydrate formation; the effect of particle size on the final gas consumption for hydrate formation It is found that as the particle size of the quartz sand decreases, the gas consumption first increases and then decreases. When the particle size of the quartz sand is 60 mesh, the gas consumption reaches the maximum, and its value is 0.19 mol. At the same time, the hydrate formation in the oil sand system and the pure quartz sand system was compared. The results show that, due to the presence of SDS (sodium dodecyl sulfate) solutions in the two systems, there is little difference in the formation rate of hydrates; the final gas consumption in the oil sand system is less than that in the quartz sand system under the same quartz sand particle size. This indicates that crude oil has an inhibitory effect on the formation of hydrates. In the oil sand system, it is found that the higher the pressure, the more favorable the formation of hydrates.

The dust removal characteristics and working mechanism of the current four major types of dust collectors were reviewed. It mainly focused on electrostatic precipitator technology, introduced its research status at home and abroad in recent years, analyzed the influence of many different factors (equipment structure parameters, gas characteristics, dust properties) on the efficiency of electrostatic precipitator equipment, and summarized electrostatic precipitator. The current technical shortcomings of the collector: The selection of the discharge electrode, the optimization of the best parameters, the anti?corrosion and cleaning of the dust collecting plate. In the future, the following issues should be focued on: development of discharge electrode materials suitable for new forms of electrostatic precipitators, discharge characteristics and dust removal efficiency in complex atmospheres, reduced insulation performance at the dust collector, and corrosion protection.

The pollution of water is becoming more and more serious, and photocatalytic degradation of pollutants in water by sunlight plays an important role in the future development. A simple chemical precipitation method was introduced. CNTs were compounded on the surface of Bi₁₂O₁₇Cl₂ to obtain a series of CNTs/Bi₁₂O₁₇Cl₂ composites. The structure, morphology and optical properties were measured and characterized by XRD, TEM, UV?Vis DRS and PL. The results show that compared with single?phase Bi₁₂O₁₇Cl₂, CNTs/Bi₁₂O₁₇Cl₂ composites show excellent pollutant degradation activity and good photocatalytic stability and cycling performance. It is found that superoxide radical (·O{}_{\mathrm{2}}^{-}) and hole (h⁺) are the main active species through trapping experiments, and the possible degradation reaction mechanism is speculated. This study provides a cheap and simple modification method for improving the photocatalytic performance of the catalyst, and has a certain guiding role in the synthesis of other high efficiency photocatalysts.

Petroleum resin wastewater sludge is classified as hazardous waste. The method of sludge recycling was introduced through the analysis of the main components of sludge, and the adsorption conditions and effects of phosphorus were studied. The results show that the main components of petroleum resin wastewater sludge are petroleum pollutants such as benzene, naphthalene, indene, azulene, olefins, alkanes and so on . After calcined at 600 ℃, the weight reduction of sludge was 82.5%, and an adsorption material based on γ?Al₂O₃ was obtained. The optimal adsorption conditions of calcined sludge for phosphorus: Adsorption time is 90 min, oscillation intensity is 180 r/min, pH=4, initial phosphorus concentration is 12.5 mg/L and dosage of sludge is 2.0 g. The optimal adsorption removal rate of phosphorus is 93.8%, and the adsorption removal rate after circulation is 87.0%. Therefore, after the calcination treatment of petroleum resin wastewater sludge, the reduction and recycling of hazardous waste can be successfully achieved.

According to the technical requirements of sand carrying fluid for reef limestone reservoir to fill ultra light particles in cracks. A sand carrying fluid system was studied with filtered seawater as the base fluid and drainage aid and dispersion agent as the main agent. When the surface tension of the sand carrying liquid system is 24.31 mN/m and the interfacial tension is 0.122 mN/m, it has a better assisted drainage ability, and the ultra?light particles are well dispersed in the sand?carrying liquid. Compared with ordinary ceramsite, the settling velocity is reduced from 0.58 cm/s to 0.35 cm/s, it has a good suspended sand effect on ultra light particles. The ultra light particles with 10%~50% sand ratio can be effectively suspended under stirring and settled within 270~470 s after standing. The sand carrying fluid system can meet the needs of carrying and filling ultra light particles in cracks.

Combined with SEM, EDS, dynamic evaluation of plug formation, microscopic visualization and long core displacement experiments, the damage mechanism of residual acid in polymer injection oilfield to the reservoir was studied. The results show that the damage of residual acid to the reservoir is mainly due to the crosslinking point of the polymer molecular chain with high valence cations such as Al³⁺ and Fe³⁺ in residual acid. The crosslinking network elastic colloid is formed by the coordination between carboxylic acid radicals in the polymer side group and high valence cations, and the degree of crosslinking increases with the increase of ion concentration. The elastic colloid formed blocked at the edge and pit of the pore throat, which makes the pore throat diameter gradually smaller. In the process of flow, it wraps around the formation particles and carbonate sediments, forming a composite blockage micelle, resulting in deep plugging. The long core displacement experiment shows that residual acid can damage the core up to 60%. The research results provide a theoretical basis for the research and development of plugging removal fluid system and optimization of plug removal processes in polymer injection oilfield

The structure model of the conical twin screw extruder is very different from other ordinary screw extruders and has a unique structure.In recent years, it has played a great role in the processing industry. Three conical twin?screw extruders with the ratio of the groove depth to the screw radius of 1∶2, 2∶5, and 1∶3 were designed.The process of extruding LDPE and HDPE particles from the conical twin?screw extruder was simulated by the discrete element method, and the particle velocity change in the groove of the conical twin?screw extruder was analyzed. At the same time,the conveying efficiency of the three types of conical twin screw extruders were compared under different parameters. The discrete element analysis of LDPE and HDPE particles was carried out using EDEM software, and the mixing situation of the two kinds of particles in the three conical twin?screw extruders at different times was obtained.The results show that the mixing efficiency of the conical twin?screw extruder with the ratio of screw groove depth to screw radius of 1∶2 is better than that of the conical twin?screw extruder with the ratio of the groove depth to the screw radius of 2∶5 and 1∶3.

In the process of processing GH4169 nickel?based superalloy, serious work hardening would occur, as well as difficult machining problems caused by excessive cutting force. The finite element model of two?dimensional orthogonal turning was established by ABAQUS software. The influence of cutting speed and amplitude on cutting force and the change of tool path of GH4169 ultrasonic elliptical vibration turning were analyzed. The results were compared with those of ordinary turning process. The results show that the cutting process parameters in the ultrasonic elliptical vibration turning of nickel?based superalloys have a significant effect on the cutting force. Choosing reasonable process parameters can effectively reduce the cutting force and improve the machining quality.

The influence of electromagnetic parameters (the distance between upper and lower poles and the coil current intensity) on the flow field in the mold and the volatile behavior of steel/slag interface was studied by numerical simulation. The results show that the magnetic induction intensity in the covered area of the upper magnetic pole and the lower magnetic pole in the full?amplitude two?stage electromagnetic brake crystallizer affects each other. The increase of the current intensity in the coil of the upper (or lower) magnetic pole will lead to the increase of the magnetic induction intensity in the covered area of the corresponding lower magnetic pole (upper magnetic pole). The full amplitude two?stage electromagnetic brake can significantly restrain the flow velocity of molten steel and stabilize the fluctuation of meniscus in the mold. As the distance between upper and lower magnetic poles increases, the impact intensity of molten steel jet on the narrow surface of the mold increases, and the turbulent kinetic energy and velocity of molten steel at the steel/slag interface increase. With the increase of the current intensity of the upper magnetic pole coil, the impact intensity of liquid steel jet on the narrow surface of the mold is basically unchanged, and the flow velocity and turbulent kinetic energy of liquid steel at the steel/slag interface decrease. As the current intensity of the lower pole coil increases, the impact intensity of liquid steel jet on the narrow surface of the mold decreases slightly, and the flow velocity and turbulent kinetic energy at the steel/slag interface decrease.

In order to enable the wind power system run smoothly and reduce the economic loss caused by power system fluctuation, and at the same time improve the competitiveness of the wind power system, it is of great and practical significance to find a stable and accurate wind speed prediction method. Among the machine learning methods, a neural network based on the back propagation (BP) algorithm to adjust the weight is one of the most commonly used and most effective methods. Although the BP neural network has a strong ability to fit nonlinearity, it converges slowly in the process of adjusting weight and easily falls into local optimal values. In order to effectively solve these two problems that will occur in the prediction process of the BP neural network, genetic algorithm (GA) was used to optimize the neural network in this paper. On this basis, considering the intermittency, non?stationarity and difference of wind speed series, a short?term wind speed prediction model EMD?GA?BPNN based on empirical mode decomposition (EMD), genetic algorithm (GA) and BP neural network was proposed. The reliability and advantages of this model in short?term wind speed prediction were verified by transverse comparisons with other models.

In the oil recovery operation, the accuracy and real?time of obtaining downhole reservoir parameters are very important for the formulation of the oil recovery process. Wireless acoustic communication technology with tubing string as channel can meet the requirements of real?time and transmission rate of downhole reservoir parameters in the oil recovery process, and has become a research hotspot in the field of oil well communication in recent years. Aiming at the difficulty of recognition caused by noise interference and waveform distortion in the wireless acoustic wave communication of oil wells, an effective recognition method：Acoustic dynamic model matching method was proposed in this paper. The method is based on the acoustic model of the tubing string and the principle of signal correlation. The correlation coefficient characteristics of the acoustic signal to be identified and the dynamic model are extracted by correlation processing, and the meaning of each acoustic signal is identified according to the correlation coefficient to improve the accuracy of recognition.

As the traditional partial least squares (PLS) method has the problem of tedious steps in the process modeling, it is difficult to obtain the online performance evaluation model of complex process.The autoregressive projection to latent structures (AR?PLS) algorithm was used to establish the predictive model for the related process data.An online performance evaluation model was established by the performance levels of the output data which was divided by the fuzzy C?means clustering algorithm. The simulation results show that compared with the traditional partial least squares method, the modeling process of this method is simpler and the computational complexity is reduced, it has certain application value.