An electromagnetic wave attenuation superposition structure for thin-layer plasma

2022 ◽  
Author(s):  
Wenyuan Zhang ◽  
Haojun Xu ◽  
Binbin Pei ◽  
Xiaolong Wei ◽  
Pei Feng ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
Thin Layer ◽  
Electromagnetic Scattering ◽  
Wave Attenuation ◽  
Control Method ◽  
Dispersion Model ◽  
Reflectance Measurement ◽  
Phase Gradient ◽  
Attenuation Effect ◽  
Stealth Technology

Abstract This work proposes a new plasma super-phase gradient metasurfaces (PS-PGMs) structure, owing to the limitations of the thin-layer plasma for electromagnetic wave attenuation. Based on the cross-shaped surface unit configuration, we have designed the X-band absorbing structure through the dispersion control method. By setting up the Drude dispersion model in the computer simulation technology, the designed phase gradient metasurfaces structure is superposed over the plasma, and the PS-PGMs structure is constructed. The electromagnetic scattering characteristics of the new structure have been simulated, and the reflectance measurement has been carried out to verify the absorbing effect. The results demonstrate that the attenuation effect of the new structure is superior to that of the pure plasma structure, which invokes an improved attenuation effect from the thin layer plasma, thus enhancing the feasibility of applying the plasma stealth technology to the local stealth of the strong scattering part of a combat aircraft.

Nanocasting synthesis of Fe3O4@HTC nanocapsules and their superior electromagnetic properties

RSC Advances ◽  
2016 ◽  
Vol 6 (24) ◽  
pp. 20386-20391 ◽  
Author(s):  
Zhihong Yang ◽  
Tong Xue ◽  
Linghui Yu ◽  
Guangbin Ji ◽  
Guoyue Xu ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
Wave Attenuation ◽  
Electromagnetic Properties

Fe3O4@HTC nanocapsules synthesized using a nanocasting method exhibited enhanced electromagnetic wave attenuation properties.

scholarly journals Identification of Water Hammering for Centrifugal Pump Drive Systems

2020 ◽  
Vol 10 (8) ◽  
pp. 2683 ◽  
Author(s):  
Nabanita Dutta ◽  
Kaliannan Palanisamy ◽  
Umashankar Subramaniam ◽  
Sanjeevikumar Padmanaban ◽  
Jens Bo Holm-Nielsen ◽  
...  
Keyword(s):  
Linear Regression ◽  
Predictive Control ◽  
Wave Attenuation ◽  
Control Method ◽  
Early Stage ◽  
Linear Regression Analysis ◽  
Fast Fourier Transformation ◽  
Negative Wave ◽  
Pumping System ◽  
Drive Systems

Water hammering is a significant problem in pumping systems. It damages the pipelines of the pump drastically and needs to identify with an intelligent method. Various conventional methods such as the method of characteristics and wave attenuation methods are available to identify water hammering problems, and the predictive control method is one of the finest and time-saving methods that can identify the anomalies in the system at an early stage such that the device can be saved from total damage and reduce energy loss. In this research, a machine learning (ML) algorithm has used for a predictive control method for the identification of water hammering problems in a pumping system with the help of simulations and experimental-based works. A linear regression algorithm has been used in this work to predict water hammering problems. The efficiency of the algorithm is almost 90% compared to other ML algorithms. Through a Vib Sensor app-based device at different pressures and flow rates, the velocity of the pumping system, a fluctuation between healthy and faulty conditions, and acceleration value at different times have been collected for experimental analysis. A fault created to analyze a water hammering problem in a pumping system by the sudden closing and opening of the valve. When the valve suddenly closed, the kinetic energy in the system changed to elastic resilience, which created a series of positive and negative wave vibrations in the pipe. The present work concentrates on the water hammering problem of centrifugal pumping AC drive systems. The problem is mainly a pressure surge that occurs in the fluid, due to sudden or forced stops of valves or changes in the direction and momentum of the fluid. Various experimental results based on ML tool and fast Fourier transformation (FFT) analysis are obtained with a Vib Sensor testbed set-up to prove that linear regression analysis is the less time-consuming algorithm for fault detection, irrespective of data size.

Computational design of resonant phononic crystal for aperiodic stress wave attenuation

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Chengcheng Luo ◽  
Shaowu Ning ◽  
Zhanli Liu ◽  
Xiang Li ◽  
Zhuo Zhuang
Keyword(s):  
Stress Wave ◽  
Wave Attenuation ◽  
Design Method ◽  
Phononic Crystal ◽  
Hard Core ◽  
Stress Waves ◽  
Physical Parameters ◽  
Attenuation Effect ◽  
Content Type ◽  
Soft Matrix

Purpose This paper aims to propose a design method for attenuating stress waves pressure using soft matrix embedded with particles. Design/methodology/approach Based on the phononic crystal theory, the particle composed of hard core and soft coating can form a spring oscillator structure. When the frequency of the wave is close to the resonance frequency of the spring oscillator, it can cause the resonance of the particle and absorb a lot of energy. In this paper, the resonant phononic crystal with three phases, namely, matrix, particle core and coating, is computationally designed to effectively mitigate the stress wave with aperiodic waveform. Findings The relationship between the center frequency and width of the bandgap and the geometric and physical parameters of particle core are discussed in detail, and the trend of influence is analyzed and explained by a spring oscillator model. Increasing the radius of hard core could effectively enhance the bandgap width, thus enhancing the effect of stress wave attenuation. In addition, it is found that when the wave is in the bandgap, adding viscosity into the matrix will not further enhance the stress attenuation effect, but will make the stress attenuation effect of the material worse because of the competition between viscous dissipation mechanism and resonance mechanism. Research limitations/implications This study will provide a reference for the design of stress wave protection materials with general stress waves. Originality/value This study proposes a design method for attenuating stress waves pressure using soft matrix embedded with particles.

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