In order to explore key technologies to improve the combustion of agricultural internal combustion engine, characteristics and influencing factors of methane plasma in the coaxial dielectric barrier discharge process are analyzed. A two-dimensional axisymmetric actuator model is established, and the discharge process is numerically simulated by finite element method. The changes of electron density, electron temperature, CH₃ and H number density under different voltage amplitudes and different dielectric materials are analyzed. The simulation results show that voltage amplitude affects the change of current, and the change of electron density and electron temperature are affected by the current. When the input voltage changes, the energy of ionized methane changes with the voltage, and when the voltage amplitude increases, the electron density and electron temperature increase. When the energy consumed by the collision between particles is greater than the energy released by ionization, Electron density and temperature decreased; The number density of CH₃ and H increases with time, and the higher the voltage amplitude, the faster the growth rate. The electron density and the electron temperature increase with the increase of the relative dielectric constant, and the number density of CH₃ and H increases with the increase of the relative dielectric constant. Increasing voltage amplitude and relative dielectric constant will further intensify the ionization of methane.

The fracture morphology of hydraulic fracturing is a key parameter for evaluating the fracturing effect and predicting the yield. At present, the fracture information of fractured cracks is mainly extracted by microseismic monitoring at home and abroad, and it is difficult to obtain the fracture morphology through the planar identification algorithm by utilizing the microseismic data due to the existence of complex noise. For this reason, this paper proposes a robust planar identification algorithm for hydraulic fracturing cracks, the sampling projection algorithm (RANSAC-MP), which weakens the outlier noise caused by irrelevant rupture events through random sampling, and proposes a maximal projection planar fitting algorithm to minimize the influence of environmental noise, and at the same time, combines the noise resistance of the RANSAC algorithm and the advantages of the projection method with the noise resistance of the RANSAC algorithm. noise immunity and the dimension reduction effect of the projection method. The results show that the RANSAC-MP algorithm shows stronger robustness and higher computational accuracy under the influence of multiple noises, and the algorithm can directly process the original data when only a single fracture is formed by fracturing.

A non-uniform complex fracture network structure formed by fracturing is considered with introducing the fractal theory and combining the stress sensitivity of fracture system to demonstrate the change of fluid flow capacity, and a production prediction model for three-zone compound seepage flow in fractured horizontal wells in low permeability reservoirs is established successfully in this paper. Laplace transform, perturbation theory, and numerical inversion are applied to obtain the analytical solution of the proposed production model, and the productivity formulas for single well under two situations of uniform and non-uniform distribution of fractures in horizontal wells are derived. The reliability of the production prediction model is verified with the real production data and basic parameters of a fractured horizontal well in Bohai oilfield, and the effects of related influential parameters on production of horizontal well are analyzed. The research results show that smaller the stress sensitivity coefficient and threshold pressure gradient results in larger the oil production. Larger the fractal dimension contributes to larger the horizontal well production. Additionally, the oil production increases with the increase of the number of fractures and fracture half-length, but the growth rate slows down, which means these parameters have optimal values.

To investigate the adsorption mechanism of heavy oil on clay mineral surface during surfactant flooding, the microscopic mechanism of heavy oil and surfactant on montmorillonite surface under different temperatures can be explained by molecular dynamics simulation. Based on the four components (SARA) of heavy oil and sodium montmorillonite, the molecular dynamics simulation of the adsorption process is carried out after the water phase adsorbent containing surfactant molecules is added into the adsorption system. It shows that cationic surfactant tends to adsorb on the surface of montmorillonite and occupy more adsorption area, which makes the heavy oil molecules tend to separate from the surface of montmorillonite. The non-ionic surfactant does not show a tendency to adsorb towards the surface of montmorillonite during the relaxation process. Non-ionic surfactant has a high self-diffusion coefficient and thus diffuses in the adsorbent environment. High temperature disperses asphaltene aggregation nuclei in heavy oil, which facilitates heavy oil to flow away from the montmorillonite surface. However, high temperatures can also cause some surfactants more adhesion to the montmorillonite surface, resulting in surfactant loss. This study provides theoretical support for adjusting temperature and surfactant types during surfactant development and enhancing oil recovery of sensitive heavy oil reservoirs.

Effects of plasma configuration and effective ion charge (Z_eff) with neutral beam heating on EAST are studied with guiding center codes ORBIT and TRANSP/NUBEAM. The resultes show that the fast-ion loss (including prompt and ripple losses) decreases as the distance between the last closed flux surface and the outer vessel wall in the mid-plane(gapout) and the toroidal magnetic field increases in the magnetic configuration. As a result the beam-ion confinement are enhanced and the heating efficiency is increased. Moreover, as the background plasma impurities increase, i.e., Z_eff increases the beam-ion loss increases, resulting in the reduction of beam-ion heating efficiency. Thus, choosing appropriate magnetic configuration and reducing the background impurity content enhance the fast-ion confinement and improve the beam heating efficiency.

Some natures have been studied for the propagation process of very intense and very short laser pulse in underdense plasma.The wave equation is derived and solved using the method of 2-D Fast Fourier Transformation.The basic equations for relativistic self-focusing include the nonlinear source term and the effect of diffraction.As a result of ponderomotive forces and relativism,the plasma frequency is reduced and so the refractive index is changed.It affects the propagation of laser in plasma.When the incident laser power (p) exceeds the critical power (p_c),self-focusing appears during the propagation of laser.On the contrary,laser damps gradually and self-focusing doesn't appear.

Discrete Hankel transformation is defined where discrete Parserval theorem and transformation matrix are derived. It is show ed that the weight factor and S-factor play important roles in the analysis and calculation.

The time resolution curve (TRC) of ultrashort pulse DFWM is studied theoretically.Using Guassian shaped pulse,the time resolution curves of two types of grating are calculated respectively and their influences in measurement are discussed.

The block-up coefficient technique and the finite volume approach are used to solve numerically the complete N-S equations in a square enclosure with spacers. A pressure-velocity correction algorithm (SIMPLE-C, Semi-Implicit Method for Pressure Linked Equation-Consistent) is adopted in the direct calculation of all the physical variables. The applicability, feasibility and efficiency of the block-up coefficient technique applied to simulate three-dimensional viscous flows are investigated.The primary results have shown that the block-up coefficient technique is indeed a simple and convenient numerical approach, with encouraging prospects, for computing the velocity, pressure and other physical quantities for the flows in a channel with complex boundary shape.