scholarly journals Proper Field Selection Model of Zostera Habitat Considering Wave Attenuation Effect

2008 ◽  
Vol 55 ◽  
pp. 786-790
Author(s):  
Mamoru ARITA ◽  
Ichiro DEGUCHI ◽  
Takuya SHIBASAKI
Keyword(s):  
Wave Attenuation ◽  
Selection Model ◽  
Attenuation Effect ◽  
Proper Field

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 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.

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 %.

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.

scholarly journals Multi-objective optimization of wave break forest design through machine learning

2019 ◽  
Vol 21 (2) ◽  
pp. 295-307
Author(s):  
Jie Ren ◽  
Zengchuan Dong ◽  
Wei Xu ◽  
Qilai Zhang ◽  
Rensheng Shi ◽  
...  
Keyword(s):  
Wave Attenuation ◽  
Cluster Structure ◽  
Field Research ◽  
Physical Experiment ◽  
Feature Weighting ◽  
Attenuation Effect ◽  
Multi Objective ◽  
Physical Experiments ◽  
Proposed Model ◽  
Wave Break

Abstract Planting trees on a floodplain along a river is a practical and ecological method for embankment protection. Optimization of wave break forest is also a new concept on wave attenuation studies. In this study, we carried out physical experiments to obtain fundamental data and proposed the Cluster Structure Preserving Based on Dictionary Pair for Unsupervised Feature Weighting model (CDUFW) for multi-objective wave break forest design. Physical experiments were designed with considering the effects of different planting configurations on wave attenuation in three scenarios: (1) the equilateral triangle arrangement with different row spacings; (2) different arrangements with the same density; (3) different tree shapes with the same row spacing. The physical experiment condition was typically defined according to the field research of the study area. Then, a multi-objective weighting model for wave break forest design optimization was based on the scheme set of physical experiment outputs using the proposed CDUFW model. Physical experiments showed that different arrangement modes take advantage of the wave attenuation effect of different forest widths. The CDUFW model performed well in finding the effective, economic and reasonable scheme. The proposed model is excellent in data mining and classification, and can be applied to many decision-making and evaluation fields.

scholarly journals EXAMINATION OF MANGROVE MODELING IN NUMERICAL CALCULATION

2020 ◽  
pp. 35
Author(s):  
Ayaka Tadokoro ◽  
Taro Arikawa
Keyword(s):  
3D Model ◽  
Wave Attenuation ◽  
Coastal Vegetation ◽  
Coastal Forests ◽  
Forest Zone ◽  
Attenuation Effect ◽  
Mangrove Roots ◽  
Wave Height Attenuation ◽  
The Relationship ◽  
The Waves

A number of studies which handle wave height attenuation effect due to coastal vegetation such as mangroves and coastal forests have been performed. In recent years, for considering effect of the mangrove roots, actual trees have been used for laboratory test. Chang (2019) proposed a formula for calculating C_D and C_M from Re and KC through experiments using a mangrove 3D model printed using actual tree. The C_D and C_M have been estimated experimentally under the condition that the water depth is relatively large and the waves don't break. However, the relationship between the Re number and the KC number and the C_D and C_M have not been investigated. Therefore, we conducted experiments focusing on the arrangement and density of the forest zone and trunk thickness. Then we demonstrated the validity of our analysis based on the comparison of our result and results of previous studies. The aim of this study is to establish a modeling method for coastal vegetation in order to enable calculation of the wave attenuation effect due to mangroves using numerical calculation.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/bcNlvRSvJQk

scholarly journals Wave-attenuation characteristics of combined-vegetation wave break forests for big rivers with large flood water level changes

2021 ◽  
Vol 83 (4) ◽  
pp. 831-840
Author(s):  
Jie Ren ◽  
Zengchuan Dong ◽  
Dawei Jin ◽  
Yue Zhou ◽  
Wei Xu ◽  
...  
Keyword(s):  
Water Level ◽  
Water Depth ◽  
Water Surface ◽  
Wave Attenuation ◽  
Water Levels ◽  
Large Rivers ◽  
Attenuation Effect ◽  
Practical Applications ◽  
Different Types ◽  
Wave Break

Abstract For large rivers with a compound cross section, the downstream channel has a very wide water surface during the flood season. A wide water surface, high water level, and larger wind speed will cause higher waves, increasing the threat of flooding to the dike. The design of a combined-vegetation wave break forest was put forward to achieve better wave attenuation effect. The main idea of this concept is to plant different types of vegetation at different locations in front of the dike. Three single-vegetation and four combined-vegetation forest schemes were tested under seven different water depth conditions. Both physical experiments and wave numerical simulations were carried out for each scheme to study the wave attenuation effect. The results showed that the wave attenuation effect of the single-vegetation wave break forest was significantly different under different water depth conditions, and the overall effect of the combined-vegetation of wave forest was better. Combined-vegetation wave break forests combine the advantages of different types of vegetation in different water levels, which makes it more economical and reasonable to plant by rivers with large water level variation. The proposed design ideas and methods could provide theoretical support for ecological revetment engineering of large rivers and insights for practical applications.

Band-Gap Engineering of Elastic Waveguides Using Periodic Materials

2003 ◽  
Author(s):  
Mahmoud I. Hussein ◽  
Gregory M. Hulbert ◽  
Richard A. Scott
Keyword(s):  
Wave Attenuation ◽  
Material Interfaces ◽  
Band Gap Engineering ◽  
Attenuation Effect ◽  
Constituent Material ◽  
Unit Cells ◽  
Guide Wall ◽  
Forced Vibration Analysis ◽  
Periodic Materials ◽  
Elastic Waveguides

Within periodically heterogeneous materials, wave scattering takes place across constituent material interfaces in such a way that an overall wave attenuation effect arises at certain frequency ranges known as band gaps. This phenomenon can be utilized in developing structures with tailored dynamic characteristics. In this work, periodic materials are used to synthesize elastic waveguides within bounded structures. The underlying local-global design process is described, and the effect of the number of periodic cells used to form the guide “wall” is studied. Using forced vibration analysis, it is shown that with only three or four periodic unit cells, the desired wave attenuation capacity required to form a guide is attained.

THE ANALYSIS OF ULTRASONIC WAVE ATTENUATION SPECTRA IN STEELS

1983 ◽  
Vol 44 (C9) ◽  
pp. C9-337-C9-340 ◽  
Author(s):  
R. L. Smith ◽  
W. N. Reynolds ◽  
S. Perring
Keyword(s):  
Ultrasonic Wave ◽  
Wave Attenuation
Sign in / Sign up

Export Citation Format

Share Document