Two-dimensional atomic crystals (2DAC) have potential application prospects in nanoelectronic devices and optoelectronic devices,and have attracted widespread attention in recent years. Raman spectroscopy has long been recognized as a unique "fingerprint spectroscopy" of material structure. It has many important characteristics,such as fast,accurate,no damage to samples,no sample pretreatment,and greatly reduced research costs. With the successful preparation of a large number of new types of 2DAC,Raman spectroscopy will play an essential role in the establishment of the corresponding fingerprint spectrum and the exploration of exotic physical properties. This paper summarizes the research progress of Raman spectroscopy in detecting the structural characterization of two-dimensional atomic crystals,such as stacking mode,layer number,and anisotropic defects of lattice orientation. At the same time,the resonant Raman spectroscopy is also introduced to reveal the interaction between electrons and photons,electrons and phonons in twodimensional atomic crystals,and even in the acquisition of lattice vibration phonon structures. It is hoped to provide readers with a new perspective to understand the indispensable position of Raman spectroscopy in the basic research and functional application of nanomaterials.
The preparation of supported adsorbent Al(OH)3/SiO2 and its adsorption behavior on uranyl ions were studied.The effects of adsorbent quality,solution pH,initial solution concentration,temperature and contact time on adsorption performance were investigated.The adsorption mechanism was preliminarily studied based on adsorption isotherm,thermodynamics,and kinetics.The effects of coexisting ions and fulvic acid on the adsorption properties were also investigated.The results showed that when the adsorbent mass was 0.03 g,pH=5,initial concentration of uranyl ions was 1 mmol/L,temperature was 303 K and contact time was 60 min,the maximum adsorption capacity was 110.4 mg/g,which could be reused four times.The adsorption process of uranyl ion on Al(OH)3/SiO2 is endothermic and spontaneous.The adsorption of monolayers is dominant,the adsorption behavior conforms to the quasisecondary kinetic model,and the chemical adsorption is the rate control step.
With the decline of conventional crude oil production, the exploitation and application of heavy oil has gradually attracted attention. However, heavy oil with high density, large viscosity and difficult mining is the problem faced by heavy oil production. There are many ways to reduce the viscosity of heavy oil, among which upgrading visbreaking reaction and non-upgrading visbreaking reaction are two important ways to reduce the viscosity of heavy oil. The latter include heating and viscosity reduction, thinning and viscosity reduction, and chemical viscosity reducing and so on. There are two methods for upgrading visbreaking reaction, namely mild thermal cracking and aquathermolysis. The aquathermolysis viscosity reduction technique is a more efficient method of viscosity reduction based on thermal cracking. Under the appropriate reaction conditions and suitable catalyst conditions, the viscosity of heavy crude oil can be greatly reduced, which is a heavy oil mining technology with good application prospects.
A betaine amphoteric surfactant was synthesized as a selfdirecting agent by oleic acid, 3-dimethylaminopropylamine(PDA) and sodium chloroacetate as the raw materials through a two-step reaction of condensation and quaternization. The effects of catalyst, raw material ratio, reaction temperature, reaction time and other factors on the conversion of oleic acid were investigated, and the optimum process conditions were determined. The synthetic product and the optimum additives form a clean self-diverting acid system which is uniformly stable, has a low viscosity of fresh acid and is easy to pump. When the mass fraction of HCl in the system drops to 3%, the viscosity of the system reaches 219 mPa·s. The acid system breaks when it encounters crude oil. The viscosity of the gel-breaking fluid is 3 mPa·s. There is no residue and it is easy to discharge back. The field application results show that the system has good steering effect and the effect of increasing production after putting into production is obvious.
The high concentration ammonia nitrogen wastewater from Fushun Catalyst Plant was treated by single factor experiment and orthogonal experiment with magnesium ammonium phosphate method. The results were fitted and optimized by penalty function method and Gauss Newton method. The results of orthogonal experiments show that n(Mg)/n(N) has the greatest influence on the removal rate of ammonia nitrogen, followed by pH, while n(P)/n(N) has the least influence. The fitting curve was obtained by Gauss Newton method, and the optimal reaction conditions were determined by penalty function method: n(Mg)/n(N)=1.30,n(P)/n(N)=1.26, pH=9.59. Under the process condition, the removal rate of ammonia nitrogen is 99.79%, and the mass concentration of residual ammonia nitrogen is 28.33 mg/L, which meets the secondary standard of sewage discharge.
Water in oil emulsion was prepared under different water volume fraction,stirring speed and temperature.By simulating the different situations encountered in the process of mixed transportation,the particle size distribution of the emulsion droplets and its relationship with viscosity were analyzed.The results show that when the volume fraction of water is less than 60% in the emulsion,the average particle size of the dispersed phase of the emulsion becomes smaller as the stirring speed is increased,and the viscosity becomes larger.With the increase of temperature,the average particle size of the dispersed phase of the emulsion is larger and the viscosity gradually decreases.As the volume fraction of water increases,the average particle size of the dispersed phase droplets becomes larger,and the viscosity shows a clear upward trend.However,when the water volume fraction is greater than 60%,the viscosity of the emulsion decreases drastically as the volume fraction of water increases,and the flow pattern of emulsion changes.The research results have certain guiding significance for the safe operation of pipelines and the study of gathering and transportation technology.
The effect of alkali metal modification on g-C3N4 photocatalyst was systematically studied. The density functional theory is used to explain the microscopic mechanism of different alkali metal modification on improving photocatalytic activity from the various angles of geometry and electronic structure. The results show that the binding energies of alkali metals and g-C3N4 become weaker and weaker with the increase of the number of extra-nuclear electronic layers of Li, Na, K and Rb atoms, and the influence on the structure of g-C3N4 is weaker and weaker. The electronic structure analysis shows that Li, Na, and K atoms have an activation effect on g-C3N4, and Rb atoms have a passivation effect on the surface of g-C3N4. At the same time, the adsorption of N2 molecules on M-g-C3N4 (M=Li, Na, K, Rb) is simulated, and the interaction mechanism between N2 molecules and alkali metals is understood. By analyzing the adsorption energy, structural parameters and electronic properties of N2 adsorption, it is found that the influence of Li and Na atoms on N2 adsorption is greater. The N—N bond of N2 is elongated, and the K and Rb atoms have little effect on N2. Alkali metal modified g-C3N4 is more beneficial for the adsorption of N2 molecules than pure g-C3N4, but as the atomic radius of the alkali metal increases, the adsorption capacity becomes weaker and weaker, and the electron transfer becomes less and less. That is to say, the ability of activating N2 molecule decreases in the order of Li, Na, K and Rb.
A snow melting anti-condensation ice material for road asphalt pavement is prepared by using aluminum oxide as the carrier and acetate as the anti-condensation active material. The effects of the mass ratio of calcium acetate and magnesium acetate on the freezing point of the prepared materials,the adsorption effect of the three carriers and the amount of hydrophobic agent added on the precipitation of acetate were investigated,and the effect of anti-freezing and snow melting was investigated. The structure and stability of the prepared materials were characterized by infrared spectroscopy and thermogravimetric analysis. The results show that the mass ratio of medium calcium acetate and magnesium acetate in the anticondensation ice material is 1∶2,the self-made Al2O3 carrier is used. When the mass fraction of silicone hydrophobic agent is 9%,the high temperature stability of the snow melting anticondensation ice material is better. It has a good effect of suppressing ice and snow.
With the development of China's natural gas industry, the scale of natural gas pipeline transportation is also expanding, at the same time, it also brings the hidden danger of safety. The leakage accidents of urban natural gas pipeline occur frequently, which seriously affect the lives and property safety of urban residents. This paper mainly introduces the basic theory of numerical simulation and numerical simulation of the leakage of urban natural gas pipeline. Considering the influence of wind field on leakage, the variation of the wind field near the ground is analyzed, and the leakage model of the buried natural gas pipeline is established. The leakage diffusion is set in the atmospheric environment. The CFD software is selected to divide the grid and local encryption, and the steady state simulation of the wind field is carried out. After the wind field reaches the steady state, the boundary conditions of the post-processing are changed, and the leakage is simulated instantaneously. The variation law of the natural gas leakage diffusion with time is obtained, and the influence of wind speed on the leakage diffusion is analyzed quantitatively. The results show that the building has a disturbance to the wind field. During the leakage process, the gas gathers near the ground and close to the building. With the increase of wind speed, the steady-state diffusion height decreases, but the wind field has less influence on the horizontal diffusion. The greater the wind speed, the more obvious the dilution effect of the leakage gas, the smaller the dangerous area.
In view of the increasingly serious problem of corrosion and perforation of the oil pipe caused by water source well in the SZ36-1 oilfield, the corrosion law of the pipe is studied under field conditions and the corrosion is predicted. The Orthogonal experiment of five factors and four levels is designed to analyze the effects of temperature, pressure, flow rate, CO2 concentration and salinity on the corrosion rate.The main controlling factors in the corrosion environment of the water source well of SZ36-1 oilfield are temperature and CO2 concentration. The corrosion prediction model is established and compared by multiple linear regression analysis and BP neural network. The comparative analysis results show that the corrosion prediction model based on multiple linear regression method has higher prediction accuracy and is more suitable for corrosion prediction of oilfield water source well.
Once hydrogen sulfide is leaked and diffused, the consequences are unimaginable. In order to master the law of hydrogen sulfide diffusion, the diffusion law of hydrogen sulfide under the influence of source strength, wind speed and source height was numerical simulated by MATLAB and VC++ software. The simulation results show that at night, when the source strength increases, the downwind direction diffusion range increases under the leakage source, the hydrogen sulfide mass concentration gradient increases in the diffusion area, and when the source height increases, the maximum width of the downwind direction diffusion area under the leakage source becomes narrower and the area becomes smaller. During the daytime, when the sunlight intensity is low and the wind speed is greater than or equal to 4 m/s, the downwind direction diffusion range of the leakage source decreases as the wind speed increases, and the hydrogen sulfide mass concentration gradient decreases in the diffusion area. Increasing the source height and wind speed is beneficial to reducing the mass concentration of hydrogen sulfide and the hazard. The research results can provide a basis for accident prevention and emergency rescue.
Explosion accidents of pressure pipes occurred frequently in recent years. In order to ensure the safety of people's lives and property and effectively prevent pressure pipeline explosion accidents in the process of oil and gas transportation, this paper uses the triangular fuzzy theory to obscure the probability of the basic event of the fault tree, the logical algorithm, and the significance of the basic event in triangle. Via combination of triangle fuzzy mathematics with fault tree, a pressure vessel fault tree chart has been made so as to calculate the distribution range of top-tiered event probability and determine the order of basic event fuzzy importance. According to the calculation, the priorities of the basic events to improve the reliability of the pressure vessel piping system and prevent the explosion accident of the pressure piping are as follows: man-made destruction, aging of the insulation layer of wires near the piping, excessive current in the control room, poor valve seal of the control piping, poor flange seal of the piping and non-standard operation. In light of the fuzzy importance of basic events, the preventive measures of accidents are put forward.
The finite element analysis software ANSYS Workbench is used to analyze the tube shell of shell-and-tube heat exchanger. According to the stress analysis standard JB 4732—1995, the stress intensity of tube sheet under four kinds of transient and steady-state operating conditions which may occur during normal operation, start-up and shutdown are analyzed. The results show that the maximum stress occurs at the junction of the heat exchange tube and the tube sheet and the joint between tube and tube sheet. The main influencing factor of the connection strength between the heat exchange tube and the tube sheet and the connection strength between tube and tube sheet is the pressure load.According to the strength check results, the design of the heat exchanger conforms to the standard of use.
Taking the rotor-bearing system of a steam turbine as the research object, considering the influence of the shaft gyro moment and moment of inertia, the finite element model of rotor-bearing system dynamics is established . The dynamic response characteristics of the rotor-bearing system under earthquake excitation are studied by inputting different ground motion peak acceleration and changing phase angle in X direction and X-Y direction. The equivalent stress and displacement trends of key nodes in rotor-bearing system are analyzed, and the safety of turbine rotor-bearing operation under seismic load is discussed. The aim is to provide a theoretical reference for the seismic design of rotor-bearing system.
Aimed at the existing steam injection boiler with wet saturated steam, the steam overheating and tube-burst pre-warning device is developed. The judgment basis and algorithm model of steam overheating monitoring are given, and the composition of the design device, component connection and man-machine interface are optimized. According to the physical properties of water and steam, the steam state is divided into four operation conditions: overheating alarm zone, overheating warning zone, operating zone and safety zone. Based on this, the visual coordinate diagram and the overheating monitoring histogram of the steam operating condition monitoring are designed in the man-machine interface. The steam overheating incidents are classified and filtered to make the device more reliable for steam overheating and early warning. Through field application data analysis, the effectiveness of the device is verified.
Aiming at the shortcomings of the conventional vision measurement method in the dynamic measurement of membrane structures, the target affects the local deformation of the film. The 3D dynamic measurement technology of membrane dot matrix projection is proposed. This technology uses a laser to project the target onto the membrane structure. Based on the OpenCV library（Open Source Computer Vision Library）, the 3D measurement algorithm is proposed to measure the 3D dynamic deformation of the membrane structure. In order to verify the 3D measurement accuracy, a standard ruler for accuracy inspection is designed. The 3D measurement accuracy of the membrane structure dot matrix projection measurement technology is tested in the principle verification experiment. The overall deformation and wave deformation of membrane structure are measured by 24 Hz frame rate photography and offline data processing. Accuracy verification experiments show that the technique can achieve the absolute accuracy of less than 0.30 mm and an accuracy of about 0.77 mm in the X, Y and Z directions, respectively, at the measurement distance of 1 m and the field of view of 1.3 m×0.8 m. At the same time, the dynamic measurement results can effectively replicate the dynamic deformation process of the membrane structure.
Natural gas hydrate has the advantages of high gas storage rate, low pollution and large reserves, which has good prospects for development. In addition, natural gas hydrates formed in the process of natural gas processing and transportation will lead to the problem of serious such as pipeline blockage. Therefore, it is of practical significance to analyze and predict the formation of natural gas hydrate. In order to predict the formation of natural gas hydrate, aiming at the merits and demerits of previous research on the prediction methods of natural gas hydrate formation, the combination model of GM (1,1) theory and Back Propagation neural network is established by using MATLAB computer language, which is based on the artificial neural network with the ability to solve complex system problem.Considering the improvement of prediction accuracy, the difference combination method is used to combine the two methods. The GM (1,1), back propagation neural network and the combined model are used to predict and compare the pressure data obtained in the experiment. In order to further verify the accuracy of the combined model, Markov chain model is selected for the prediction test. The results show that the combined model of GM（1,1）and BP neural network has higher canprecision and this method can be widely used in many directions, which can provide a theoretical basis for the development and utilization of NGH in the future.
Combining fuzzy soft sets and both-brank fuzzy sets theory, the definition of double both-brank fuzzy soft sets are given. The both-brank fuzzy soft subset is further defined, and both-brank fuzzy soft sets are equal. The operations of intersection, union and complement of both-brank fuzzy soft sets are specified. Several properties of these operations have been studied.The both-brank fuzzy soft set is a brand new concept, and there are many places worth studying.
