The ultrasonic assisted extraction of total flavonoids from Crataegus pinnatifida Bge.var.major N.E.Br. Fruit was used to optimize the extraction process, and its antioxidant capacity was measured. [Methods]On the basis of single factor experiment, the response surface experiment was designed with ethanol concentration, liquid-solid ratio, extraction time and temperature as independent variables, and the extraction rate of total flavonoids as a response value. [Results]The optimum extraction process was as follows: ethanol concentration 62%, liquid-solid ratio 26 ml / mg, extraction time 21 min, extraction temperature 52 ℃, and the highest extraction rate was 10.19%. [Conclusion]The antioxidant activity showed that the total flavonoids had significant antioxidant capacity.

3D printing technology has developed rapidly in recent years. Because of its simple operation method and fast manufacturing speed, it is gradually applied to all walks of life. As an excellent biocompatible and degradable material, polylactic acid has become one of the most commonly used raw materials in 3D printing technology because of its good molding temperature and molding process. With the improvement of people's living standards, the requirements for 3D printing materials are becoming higher and higher, which makes the new composite materials based on polylactic acid develop rapidly in recent years. Polylactic acid and other materials are compounded to form new composite materials, which can make up for the shortcomings of polylactic acid itself, such as low hardness and poor conductivity. Through melt deposition molding technology, it can meet people's different needs in different fields, expand the application field of 3D printing, and make the composite materials with polylactic acid as the main body have great development prospects.

Gas chromatography was used to analyze the petroleum hydrocarbon degradation products of a highly efficient petroleum hydrocarbon degrading strain Stenotrophomonas acidaminiphila. More than 80% of petroleum hydrocarbons were degraded.UCM peak appeared in the product chromatogram.The results indicated that the strain was able to degrade most of the C10-C28 n-alkanes,some straight-chain alkanes and cycloalkanes, while the aromatic hydrocarbons,especially polycyclic aromatic hydrocarbons,were difficult to degrade by the strain According to the intermediate products detected,straight-chain alkanes,such as hexadecane,under the action of microorganisms,generate intermediate products hexadecanol,which was then oxidized to hexadecaldehyde and fatty acids.Fatty acids are further oxidized to finally produce CO, and H,O.The degradation pathway of branched-chain alkanes is similar to that of straight-chain alkanes,and the intermediate products detected were2-hexyl-1-dodecyl alcohol,2-octyl-1-decan

In order to well know the current situation of atmospheric environment in Jilin City, correlation analysis method and applied statistical method were used to analyze the change characteristics of air pollutant mass concentration, and the correlation between pollutant concentration and meteorological factors, based on the monitoring data of CO, SO2, NO2, O3 (O3-8h), PM2.5 and PM10 from 7 ambient air quality monitoring stations in Jilin City from 2014 to 2018, and hourly meteorological data in 2018. The results show that: from 2014 to 2018, the annual average concentrations of SO2, NO2, PM10 and PM2.5 has showed a downward trend, while the concentration of O3 has been increasing in Jilin City, the concentrations of PM10, PM2.5 and O3 were occasionally higher than the national standard, indicating that they are the main air pollutants in Jilin City; the pollutant concentration varied from seasons, months and times, therefore, stagger production time according to the change law can improve ambient air quality; meteorological factors were correlative with pollutant concentrations, in which O3 concentrations was highly correlated with temperature, humidity and wind speed, and NO2 was highly negatively correlated with wind speed; the importance of meteorological factors to concentrations of CO, NO2, O3, PM10 and PM2.5 displays wind speed > atmospheric pressure > humidity > temperature; precipitation can reduce the concentration of PM10 and PM2.5, and the reduce effect was more obvious with increasing precipitation. The results of the current study can provide the data support for a further study of air pollution control and environmental capacity in Jilin City.

The black soil in the cold region is called “black gold” and is fertile. The study of its quality is extremely important to the agricultural soil ecosystem. In this paper, the black soil in the cold area greenhouse was studied, and the soil quality was evaluated by soil membership function, composite evaluation index, comprehensive pollution index and potential ecological risk index and other factors. The study found that the soil is silty loam and is acidic; the content of organic matter conformities to the third level of the soil nutrient classification standard in the second national soil survey of China. Alkaline hydrolysis nitrogen, available phosphorus and rapidly available potassium conformity to the first level of the soil nutrient classification standard in the second national soil survey of China. The potential ecological hazard rating of soil heavy metals is low.

A series of magnetic hollow Fe3O4 nanospheres were synthesized by hydrothermal method, and the different methods in the synthesis process were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetry (TG), and hysteresis loop. The influence of molecular weight polyethylene glycol (PEG400、1000、4000) and its addition amount on the particle size, magnetic properties and sedimentation properties of Fe3O4 microspheres. The study found that when the molecular weight of polyethylene glycol is the same, the magnetic Fe3O4 hollow nanospheres obtained by adding 0.6g polyethylene glycol have better dispersibility in water and organic solvent DMAc than 0.3g polyethylene glycol. The resulting microspheres for particle size is larger and the magnetic properties are similar. Compared with the amount of polyethylene glycol added, the molecular weight of polyethylene glycol has a greater impact on the magnetic properties of the magnetic Fe3O4 hollow nanospheres. The particle size of the magnetic Fe3O4 hollow nanospheres can be adjusted by changing the molecular weight of polyethylene glycol. The particle size of the magnetic Fe3O4 hollow nanospheres has a decreasing trend with the increase of the molecular weight of polyethylene glycol. The magnetic Fe3O4 hollow nanospheres obtained by adjusting polyethylene glycol have good dispersibility in water and organic solvent dimethylacetamide (DMAc), especially in water solvent for 8 days to completely settle, add 0.6g The magnetic hollow Fe3O4 nanospheres obtained by PEG4000 have outstanding dispersibility in DMAc, and are expected to be well applied in the fields of wastewater treatment and electromagnetic wave absorption.

Polylactic acid (PLA), poly-(L-lactied-co-ε-caprolactone-diOH (PCLA) and carboxylic-functionalized poly(arylene ether ketone) (PCA-PAEK) are the common used template polymers for preparing functional oxides through electrospinning technique. It has been found that the morphology of the oxide nanomaterials prepared by different polymer templates has great difference. This may be closely related to the thermal stability and thermal behavior of the polymers. However, there are few reports on this aspect. Therefore, in this paper, the thermal stability and thermal behavior of the electrospun PLA, PCLA, PCA-PAEK nanofibers were made comparison and analysis by TGA, DSC and SEM. The results showed that the morphology change temperature of PLA, PCLA and PCA-PAEK were 187℃, 127℃ and 300℃, respectively. This indicated that the thermal stability of the three polymers from high to low was PAEK, PLA and PCLA, successively. The research will provide a theoretical basis for the preparation of functional oxide nanomaterials with different morphologies.

With the rapid development of pure electric vehicles, efficient savings using clean energy and portable electronic products, it is urgent to find new electrochemical energy storage materials and devices with high power density, low cost, high reliability, environmental protection and long service life. Cellulose is a naturally formed organic polymer. Its good biocompatibility and degradability have attracted much attention in the application of new energy materials. In recent years, the micronization of natural cellulose and the engineering of the preparation of new cellulose derived materials have greatly expanded the application range of cellulose based materials in the field of new energy. The construction and preparation of cellulose based high-performance green energy storage materials through hybridization, physical blending, chemical modification, doping and interpenetration has theoretical research value and application potential. In this work, sodium carboxymethyl cellulose was used as the dispersant of carbon nanotubes to construct the hybrid system, so as to give full play to the electrochemical performance of carbon nanotubes. Through the exploration of influencing factors such as solvent ratio and pH value, the best experimental conditions for preparing the hybrid system with excellent electrochemical performance were obtained. The electrode material modified by the hybrid system has great potential to construct super capacitors.

In order to control the inverted pendulum to maintain a stable state, the linear primary inverted pendulum is selected as the research control object, the mathematical model of the linear primary inverted pendulum is established, the particle swarm optimization (PSO) algorithm is applied to the key parameter optimization of the linear primary inverted pendulum intelligent control system, and the dynamic stability of the linear primary inverted pendulum optimized by PSO algorithm is verified by simulation. The simulation results show that the optimal control of linear inverted pendulum based on particle swarm optimization algorithm has faster convergence and better stability.

Aiming at the non-linearity, uncertainty and external interference problems of the magnetic levitation ball system, in order to make the system output have good dynamic quality when tracking the desired position trajectory change, a three-step non-linear controller is designed. The controller is composed of quasi-steady-state control, variable reference feedforward control and error feedback control, and is deduced step by step in a fixed sequence. The derivation process of the three-step nonlinear controller is simple and clear, the structure of the obtained control law is clear, and the multiple differential problems caused by high-order nonlinearity are avoided. The simulation experiment results show that the tracking speed of the three-step nonlinear controller is fast, the overshoot is small, the tracking effect is good, and there is no chattering phenomenon.

Aiming at the problem of low positioning accuracy in indoor places, this paper proposes a RSSI (Received Signal Strength Indication) visible light positioning method based on improved particle swarm optimization algorithm. The Lévy flight algorithm is used to improve the particle swarm optimization algorithm, which solves the problem that the standard particle swarm optimization algorithm is easy to fall into the local optimum, and improves the convergence speed and positioning accuracy of the algorithm. In the indoor environment of 5m×5m×3m, after simulation test, the improved particle swarm optimization algorithm combined with RSSI positioning method can reach a positioning accuracy of 0.038241m, the algorithm stability is improved, the positioning accuracy is higher, and it is more suitable for indoor positioning.

The gross regional product and the consumer price index of Ji lin province are forecasted according to time series analysis method. By comparing the predicted value with the real value, the impact of novel coronavirus epidemic on the economic is analyzed, and then some feasible suggestions are proposed.

Constrained matrix equations have important applications in vibration theory, structural design, system identification, mathematical control theory, vibration theory, geology and many other fields. In this paper, the iterative method for symmetric solutions of matrix equations,  is analyzed. When the matrix equations are consistent, the symmetric solutions of the matrix equations can be obtained.

Transition metal borides have been considered as potential superhard materials by researchers.  However, due to the low diffusivity of transition metal borides, it is difficult to synthesize pure phase bulk materials to obtain their hardness.  High temperature and high pressure method is an effective method to synthesize high quality transition metal borides. However, sometimes the synthesized samples are very easy to fracture by high temperature and high pressure method, and the hardness of the synthesized samples cannot be measured.  In this paper, pure phase WB was synthesized by high temperature and high pressure method.  The influence of synthesis temperature on polishing quality was analyzed.

In order to prepare recycled concrete with vitrified micro bubbles to meet the strength requirements, the basic mechanical properties of concrete mixed with calcined diatomite with different vitrified micro bubbles contents were studied experimentally, and the results were summarized and analyzed. The experimental results show that: Calcined diatomite can fill the macroscopic cracks of reclaimed coarse aggregate and improve the mechanical properties of recycled concrete; With the increasing of vitrified micro bubbles, the apparent density, compressive strength, splitting tensile strength and elastic modulus of recycled concrete all show an obvious decreasing trend. When the content of calcined diatomite is 3% and the content of vitrified micro bubbles is 100%, the apparent density of recycled concrete is only 1943.6kg/m3, and its cubic compressive strength can still reach 32.55 Mpa; On the basis of experimental analysis, a linear relationship between the axial compressive strength fc of vitrified micro bubbles recycled concrete and the cubic compressive strength fcu is proposed.

Through the mathematical analysis of the elliptic contour cavity on the cylindrical surface, the correlation between the coordinate parameters was obtained. The manual macro program was programmed with variables, and the VERICUT software was used to simulate the production conditions to verify the simulation processing of the macro program, and the machining effect was good. In the processing of similar curve contour and its cavity structure, the relevant parameters of the curve contour can be analyzed and constructed, and the processing method of four-axis macro program can be adopted to give full play to the programming advantage of macro program effectively and improve the production effect.

The embedded system has the characteristics of low power consumption, low cost and small volume. Wi-Fi technology has the advantages of fast transmission speed. Combined with the advantages of both, a Wi-Fi video acquisition and transmission system with stm32f407 as the control core is designed. In order to improve the real-time and stability of the system, the UCOS-III operating system has been transplanted. In addition, the application program of upper computer and mobile terminal APP based on Android operating system have been developed. To achieve remote access, the system sends the collected video data to Ali cloud for remote access. After testingt, the system is stable and the video transmission is smooth.

The ABAQUS finite element analysis method is used to optimize the radial expansion of the radial expansion actuator. Based on the Yeoh constitutive equation, the silicone material model of the actuator body is established to verify the correctness of the material model by static and simulation experiments. The use of ABAQUS is limited. The meta-analysis software performed a simulation analysis of five structural design factors, analyzed the influence of each structural factor on its radial expansion, and determined the best design plan; the results showed: the thickness of the limiting layer c, the thickness of the deformed layer b, the height of the air chamber h. Fillet R is a key factor affecting its expansion. The best design parameters are the thickness of the limiting layer 4mm, the thickness of the deformable layer 2mnm, the number of air chambers 4, the height of the air chamber 12mm, and the rounded corners 8mm.

In order to solve the problem of inconvenient sanitary treatment in outdoor environment, a kind of hand-washing device which can work independently in outdoor environment and can move is designed. The present situation of sanitary treatment is briefly introduced, the advantages and disadvantages of traditional wash-basin are compared and analyzed, the overall design scheme of the device is given, and the theoretical calculation of water supply is carried out. The device can realize the functions of sanitation treatment, recycling of sewage and autonomous positioning and navigation in the process of walking.