scholarly journals Effect of non-ionizing reaction rate (assumed to be controllable) on the plasma generation mechanism and communication around RAMC vehicle during atmospheric reentry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Wenchong Ouyang ◽  
Qi Liu ◽  
Zheng Zhang ◽  
Tao Jin ◽  
Zhengwei Wu
Keyword(s):  
Reaction Rate ◽  
Wave Attenuation ◽  
Plasma Sheath ◽  
Generation Mechanism ◽  
Transmission Model ◽  
Attenuation Effect ◽  
Plasma Generation ◽  
Atmospheric Reentry ◽  
Communication Signal ◽  
Ionization Reaction

AbstractRadio frequency (RF) blackout occurs during radio attenuation measurement C (RAMC) vehicle reentry due to the attenuation effect of the plasma sheath on the communication signal. In recent years, the mitigation mechanism of chemical reaction for RF blackout problem has gradually been studied numerically and experimentally. However, the effect of non-ionization reaction rate has been ignored because it does not directly involve the generation of electrons. In the present study, the influence of non-ionizing reaction rate on the plasma generation mechanism and EM wave attenuation was numerically solved by the plasma flow and multilayer transmission model. According to the simulation results, only the reaction rate of $$NO \rightleftharpoons N + O$$ N O ⇌ N + O has a significant effect on the electron number density in all non-ionizing reactions, and the degree of influence is less than the ionization reaction rate. The EM wave attenuation decreases with the decrease of the reaction rate of $$NO \rightleftharpoons N + O$$ N O ⇌ N + O . When the reaction rate is reduced by 25 times, the maximum attenuation of electromagnetic wave can be reduced by 12 dB. Finally, a potential scheme by reducing the reaction rate of $$NO \rightleftharpoons N + O$$ N O ⇌ N + O was proposed to mitigate the RF blackout problem.

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.

scholarly journals Estimation of attenuation due to rain within Ka and Ku bands in Oyo State of Nigeria

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Hammed O Busari ◽  
Olaosebikan A Fakolujo
Keyword(s):  
Satellite Communication ◽  
Rain Rate ◽  
Attenuation Factor ◽  
Rain Attenuation ◽  
Attenuation Effect ◽  
Effective Utilization ◽  
Tropical Regions ◽  
Communication Signal ◽  
Significant Attenuation ◽  
Propagation Modelling

Rain-induced attenuation of microwaves poses a serious challenge to signal availability beyond 10 GHz frequencies. The challenges are even more pronounced in the subtropical and tropical regions with high intensities of rain which is more accompanied with thunderstorms. Nigeria has an equatorial and tropical climate, which is identified by controlling rainfall. Rain is the significant attenuation factor of various communication signal above 10 GHz frequencies. Therefore, for effective utilization of the microwave bandwidth during rainfall, it is required to form the correlation between this attenuation effect and the bandwidth at various rainfall rate and frequencies at a particular interest location. Therefore , using propagation modelling, the point rainfall and  rain effects for frequencies was concurrently  considered between 11 and 40 GHz (i.e. Ku, and Ka) for satellite communication service on earth-space path at Ibadan in Oyo state , Nigeria by using rainfall data for the period of five (5) years (January 2014 to December 2019).Keywords- Rain Attenuation, Rain Rate, Bandwidth, Propagation Modelling

Estimation of the nitrogen ionization reaction rate using electric arc shock tube data and Bayesian model analysis

2012 ◽  
Vol 19 (2) ◽  
pp. 023507 ◽  
Author(s):  
K. Miki ◽  
M. Panesi ◽  
E. E. Prudencio ◽  
S. Prudhomme
Keyword(s):  
Shock Tube ◽  
Bayesian Model ◽  
Reaction Rate ◽  
Model Analysis ◽  
Electric Arc ◽  
Ionization Reaction

A Kind of Floating Breakwater Sheltering Deep Water Aquaculture

2014 ◽  
Vol 580-583 ◽  
pp. 2170-2176
Author(s):  
Xiao Fei Cheng
Keyword(s):  
Deep Water ◽  
High Performance ◽  
Wave Attenuation ◽  
High Performance Concrete ◽  
Attenuation Effect ◽  
Floating Breakwater ◽  
Standard Module ◽  
Foam Plastics ◽  
Effect Test ◽  
Design Construction

This paper briefly introduces the design, construction and wave attenuation effect test of a kind of floating breakwater sheltering deep water aquaculture. This novel floating breakwater structure is composed of 28 standard modules and corresponding anchoring systems, and each standard module comprises a catamaran raft and a wave-attenuating and oscillation-inhibiting device, with a length of 30 m, a width of 7 m, a depth of 2 m and a draft of 1.1 m. Each catamaran raft employs a box-shaped multi-ribbed beam-and-slab structure, and was constructed using high-performance concrete and ferrocement materials and internally filled with polystyrene foam plastics. Each wave-attenuating and oscillation-inhibiting device uses a detachable split box-shaped structure and was pre-fabricated using high-performance concrete, with a length of 2 m, a width of 1.638 m and a height of 2 m. Each standard module is anchored using 6 anchor chains, each of which has an on-floor length of about 25 m. After construction, this floating breakwater system was tested for wave attenuation effect, and the data analysis results show that the floating breakwater system has a wave attenuation effect of up to 50 %.

Sign in / Sign up

Export Citation Format

Share Document