Because of the limitations of thin-layer plasma for electromagnetic wave attenuation, a new PS-AWV (plasma-superimposed artificial wave vector) metasurface structure is proposed. We also introduced the design principle of increasing the propagation distance of electromagnetic waves in plasma using artificial wave vector metasurface. We designed a X band artificial wave vector metasurface by geometric phase dispersion control such that the incident electromagnetic wave abnormally reflected, and the reflection angle reached 55° when measured at normal incidence. Using an electromagnetic finite element method, we established a coupling model of the PS-AWV metasurface structure attenuated electromagnetic wave using CST (Computer Simulation Technology). We analyzed the variation law of reflectivity under different plasma parameter distribution, and the experiment was performed in a microwave darkroom. We also measured the reflectivity of the wave-vector metasurface structure. Both simulation and experimental results show that the artificial wave vector metasurface can effectively increase the attenuation effect of plasma on electromagnetic waves and improve the attenuation effect of electromagnetic waves because of thickness reduction; thus, it can reduce the plasma thickness required for plasma stealth and improve its application in practical scenarios.

For this paper, an experiment of low-pressure Argon inductively coupled plasma (ICP) was conducted in a closed chamber. Obvious $E$ -$H$ mode transition could be observed in the experiment. To solve the problem that microwave interference diagnosis can only measure the average electron density along the transmission path of the microwave, a new microwave interference diagnosis method based on fluid dynamics modeling is put forward to gain an accurate distribution of electron density. Using this new method, the spatial resolution of electron density could be improved. Finally, the electron density of low-pressure ICP was diagnosed both with this method and the Langmuir probe. The results revealed that the electron density increased with power and the peak value reached $7.8\times 10^{17}\text{m}^{-3}$ at the radio frequency power of 700 W. The consistency in the distribution trend of electron density that resulted from two different methods illustrates that the new method can provide a relatively accurate spatial distribution detail of electron density. The electron temperature was measured via the Langmuir probe and the results show that the temperature declines with power.

The basis of plasma stealth technology is the attenuation of electromagnetic waves by plasma. In this study, the calculation principle of the finite-difference time-domain (FDTD) method is introduced and a FDTD time–space coupling model of electromagnetic wave propagation in plasma is established. The time-domain variation characteristics of electromagnetic waves entering the plasma are analyzed. The plasma parameter distribution under different conditions obtained using the COMSOL fluid mechanics model is introduced into the FDTD model. The plasma reflectivity measurement experiment was carried out in a microwave anechoic chamber, and the influence of different experimental conditions on the plasma reflectivity was analyzed. The variation of reflectivity under different plasma parameter distributions is obtained. The results show that increasing electron density and plasma thickness and enhanced plasma distribution uniformity are beneficial for improving the attenuation effect of plasma on electromagnetic waves. These results provide a reference for the inductively coupled plasma parameter distribution in a closed quartz cavity, which provides a basis for the plasma to attenuate the electromagnetic waves.

To optimize and improve the nose landing gear shock absorber of a fixed-wing carrier-based aircraft, the cross-sectional area of the oil needle in the main oil orifice and the cross-sectional area of the oil return orifice shall be reconfigured. Firstly, a dynamic analysis of a single landing shock absorber system is conducted, with a focus on explaining the calculation methods for air spring force and oil damping force. Secondly, the shock absorber is modeled and its typical working processes are simulated, including calculations of shipboard landing buffering results under different sinking speeds and catapult extension results under different terminal drag speeds. Phenomena such as wheel transition oscillation and shock absorber hysteresis compression are interpreted. Finally, an orifice area configuration optimization scheme based on the work-energy diagram of the shock absorber system is proposed, with principles and necessary explanations for key steps in the scheme provided. The optimized scheme, which comprehensively considers buffering and extension performance, is applied to a single shock absorber system model for verification. The results show that the main orifice area should exhibit a slight increase near the critical stroke of the high and low pressure chambers. After optimizing the orifice area, under the ultimate sinking speed, the peak load of the shock absorber is reduced by 12.92%, the compression stroke is decreased by 2.91%, and the energy absorption efficiency is increased by 19.90%; the peak load of the tire is reduced by 12.17%, the compression stroke is decreased by 5.92%, and the energy absorption efficiency is increased by 12.28%.

Aim at the problem that microwave interference diagnosis of plasma can only get an average electron density along the transmission path of microwave, this paper put forward a new microwave interference diagnosis method based on fluid dynamics modelling to gain accurate distribution of electron density. In this method, the fluid model of inductively coupled plasma (ICP) is set up by multi-physics coupling method on COMSOL platform. Then a group of Boltzmann equations is introduced to solve the electron energy distribution function (EEDF), diffusion coefficient and transport coefficient. Based on the fluid dynamics model, the bivariate distribution of electron density is obtained by solving the electron drift diffusion equations, electron energy drift diffusion equations and momentum flux conservation equations. Then the profile function of electron density along the transmission path of microwave can be collected from it. And the profile function is discretized to make it easier to calculate the electron density of different parts. At last, an experiment system of ICP in transparent chamber is set up to verify the effectiveness of the new method. The electron density is diagnosed by the new microwave interference diagnosis and Langmuir probe respectively. The results reveal that the electron density rises with power and the peak value can reach 7.8×1017 m-3 at the radio frequency (RF) power of 700 W. The new method makes up for the deficiencies of traditional microwave interference diagnosis and numerical simulation effectively.