Self-initiating MUSIC-based direction finding in underwater acoustic particle velocity-field beamspace

2000 ◽  
Vol 25 (2) ◽  
pp. 262-273 ◽  
Author(s):  
K.T. Wong ◽  
M.D. Zoltowski
Keyword(s):  
Velocity Field ◽  
Particle Velocity ◽  
Direction Finding ◽  
Underwater Acoustic

The particle velocity field inside a two-dimensional aerated hopper

2002 ◽  
Vol 123 (2-3) ◽  
pp. 242-253 ◽  
Author(s):  
Giovanna Ferrari ◽  
Massimo Poletto
Keyword(s):  
Velocity Field ◽  
Particle Velocity ◽  
Two Dimensional

scholarly journals Optimal Deployment of Vector Sensor Nodes in Underwater Acoustic Sensor Networks

Sensors ◽  
2019 ◽  
Vol 19 (13) ◽  
pp. 2885 ◽  
Author(s):  
Sunhyo Kim ◽  
Jee Woong Choi
Keyword(s):  
Sensor Networks ◽  
Particle Velocity ◽  
Sensor Nodes ◽  
Acoustic Sensor ◽  
Underwater Acoustic Sensor Networks ◽  
Communication Performance ◽  
Underwater Acoustic ◽  
Acoustic Sensor Networks ◽  
Vector Sensor ◽  
Optimal Deployment

Underwater acoustic sensor networks have recently attracted considerable attention as demands on the Internet of Underwater Things (IoUT) increase. In terms of efficiency, it is important to achieve the maximum communication coverage using a limited number of sensor nodes while maintaining communication connectivity. In 2017, Kim and Choi proposed a new deployment algorithm using the communication performance surface, which is a geospatial information map representing the underwater acoustic communication performance of a targeted underwater area. In that work, each sensor node was a vertically separated hydrophone array, which measures acoustic pressure (a scalar quantity). Although an array receiver is an effective system to eliminate inter-symbol interference caused by multipath channel impulse responses in underwater communication environments, a large-scale receiver system degrades the spatial efficiency. In this paper, single-vector sensors measuring the particle velocity are used as underwater sensor nodes. A single-vector sensor can be considered to be a single-input multiple-output communication system because it measures the three directional components of particle velocity. Our simulation results show that the optimal deployment obtained using single-vector sensor nodes is more effective than that obtained using a hydrophone (three-channel vertical-pressure sensor) array.

scholarly journals Experimental and DEM Analysis on Secondary Crack Types of Rock-Like Material Containing Multiple Flaws Under Uniaxial Compression

2019 ◽  
Vol 9 (9) ◽  
pp. 1749 ◽  
Author(s):  
Yong Li ◽  
Weibing Cai ◽  
Xiaojing Li ◽  
Weishen Zhu ◽  
Qiangyong Zhang ◽  
...  
Keyword(s):  
Velocity Field ◽  
Uniaxial Compression ◽  
Particle Velocity ◽  
Axial Loading ◽  
Field Analysis ◽  
Strain Rate Tensor ◽  
Secondary Crack ◽  
Shear Cracks ◽  
Mechanical Behaviors ◽  
Secondary Cracks

To better understand the evolution of crack propagation in brittle rock mass, the particle velocity field evolution on both sides of secondary crack in rock-like materials (cement mortar specimens) with pre-existing parallel double flaws under uniaxial compression is analyzed based on the discrete element theory. By bringing in strain rate tensor, a new technique is proposed for quantifying the failure mechanism of cracks to distinguish the types and mechanical behaviors of secondary cracks between pre-existing parallel flaws. The research results show that the types and mechanical behaviors of secondary cracks are distinct at different axial loading stages and can be directly identified and captured through the presented approach. The relative motion trend between particles determines the types and mechanical behaviors of secondary cracks. Based on particles movement on both sides of secondary cracks between cracks, the velocity fields of particles can be divided into four types to further analyze the causes of different types of cracks. In different axial loading stages, the velocity field types of particles on both sides of cracks are continuously evolving. According to the particle velocity field analysis and the proposed novel way, the types of macroscopic cracks are not directly determined by the types of dominated micro-cracks. Under uniaxial compression, the particles between secondary cracks and pre-existing parallel flaws form a confined compressive member. Under the confinement of lateral particles, secondary cracks appear as shear cracks between pre-existing parallel flaws at the beginning stage of crack initiation.

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