The research on propagation characteristics of acoustic emission signals in stiffened plates based on the multipath propagation model

Ultrasonics ◽  
2020 ◽  
Vol 108 ◽  
pp. 106177
Author(s):  
Cong Han ◽  
Guoan Yang ◽  
Jianye Wang ◽  
Xiaoshuai Guo
Keyword(s):  
Acoustic Emission ◽  
Multipath Propagation ◽  
Propagation Model ◽  
Stiffened Plates ◽  
Propagation Characteristics

scholarly journals Propagation Characteristics of Acoustic Emission Signals in Stiffened Cylindrical Shells Based on the Multipath Propagation Model

2021 ◽  
Vol 11 (24) ◽  
pp. 11722
Author(s):  
Cong Han ◽  
Tong Liu ◽  
Zhenhuan Wu ◽  
Guoan Yang
Keyword(s):  
Cylindrical Shell ◽  
Acoustic Emission ◽  
Excitation Frequency ◽  
Propagation Model ◽  
Detection Accuracy ◽  
Propagation Characteristics ◽  
Reflection And Transmission ◽  
Scattering Coefficients ◽  
Ae Signal ◽  
Ae Signals

A stiffener attached to a cylindrical shell strongly interferes with the propagation of the acoustic emission (AE) signal from the fault source and reduces the fault detection accuracy. The interaction of AE signals with the stiffener on the cylindrical shell is thoroughly investigated in this paper. Based on the proposed model of the AE signal propagating inside the cylindrical shell with a stiffener, the installation constraints for the sensor are derived, resulting in the separation of the direct signal, the stiffener scattering signal, and other signals in the time domain. On this basis, combinations of the excitation frequency and the stiffener height are simulated, and the reflection and transmission of the AE signal in each case are quantitatively characterized by the scattering coefficients. The results indicate that there is a “T-shaped” transformation of the signal at the stiffener, which evolves into a variety of other modes. Moreover, the reflection and transmission coefficients of the incident AE signal are displayed as a function of the excitation frequency and the height of the stiffener. In addition, the accuracy of the scattering coefficients obtained from the numerical simulations is verified by experiments, and a good consistency between simulation results and experiment results is presented. This work illustrates the propagation characteristics of AE signals in a cylindrical shell with a stiffener, which can be used as guidance for optimizing the spatial arrangement of sensors in AE monitoring.

Multipath propagation model for line-of-sight street microcells in urban area

2000 ◽  
Vol 49 (2) ◽  
pp. 422-427 ◽  
Author(s):  
S. Ichitsubo ◽  
T. Furuno ◽  
T. Taga ◽  
R. Kawasaki
Keyword(s):  
Urban Area ◽  
Multipath Propagation ◽  
Propagation Model ◽  
Line Of Sight

scholarly journals A Novel Target-Height Estimation Approach Using Radar-Wave Multipath Propagation for Automotive Applications

2017 ◽  
Vol 15 ◽  
pp. 61-67
Author(s):  
Amir Laribi ◽  
Markus Hahn ◽  
Jürgen Dickmann ◽  
Christian Waldschmidt
Keyword(s):  
Continuous Wave ◽  
Multipath Propagation ◽  
Estimation Error ◽  
Propagation Model ◽  
Target Range ◽  
Target Height ◽  
Height Estimation ◽  
Range Resolution ◽  
Novel Target ◽  
Radar Wave

Abstract. This paper introduces a novel target height estimation approach using a Frequency Modulation Continuous Wave (FMCW) automotive radar. The presented algorithm takes advantage of radar wave multipath propagation to measure the height of objects in the vehicle surroundings. A multipath propagation model is presented first, then a target height is formulated using geometry, based on the presented propagation model. It is then shown from Sensor-Target geometry that height estimation of targets is highly dependent on the radar range resolution, target range and target height. The high resolution algorithm RELAX is discussed and applied to collected raw data to enhance the radar range resolution capability. This enables a more accurate height estimation especially for low targets. Finally, the results of a measurement campaign using corner reflectors at different heights are discussed to show that target heights can be very accurately resolved by the proposed algorithm and that for low targets an average mean height estimation error of 0.03 m has been achieved by the proposed height finding algorithm.

scholarly journals Hot Topic Propagation Model and Opinion Leader Identifying Model in Microblog Network

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Yan Lin ◽  
Huaxian Li ◽  
Xueqiao Liu ◽  
Suohai Fan
Keyword(s):  
Opinion Leader ◽  
Propagation Model ◽  
Opinion Leaders ◽  
Time Varying ◽  
Propagation Characteristics ◽  
Propagation Process ◽  
Ahp Model ◽  
Healthy Development ◽  
Undirected Network ◽  
The Social

As the network technique is fast developing, the microblog has been a significant carrier representing the social public opinions. Therefore, it is important to investigate the propagation characteristics of the topics and to unearth the opinion leaders in Micro-blog network. The propagation status of the hot topics in the Micro-blog is influenced by the authority of the participating individuals. We build a time-varying model with the variational external field strength to simulate the topic propagation process. This model also fits for the multimodal events. The opinion leaders are important individuals who remarkably influence the topic discussions in its propagation process. They can help to guide the healthy development of public opinion. We build an AHP model based on the influence, the support, and the activity of a node, as well as a microblog-rank algorithm based on the weighted undirected network, to unearth and analyze the opinion leaders’ characteristics. The experiments in the data, collected from the Sina Micro-blog from October 2012 to November 2012 and from January 2013 to February 2013, show that our models predict the trend of hot topic efficiently and the opinion leaders we found are reasonable.

scholarly journals Target Detection in Low Grazing Angle with Adaptive OFDM Radar

2015 ◽  
Vol 2015 ◽  
pp. 1-12
Author(s):  
Yang Xia ◽  
Zhiyong Song ◽  
Zaiqi Lu ◽  
Hao Wu ◽  
Qiang Fu
Keyword(s):  
Target Detection ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multipath Propagation ◽  
Random Phase ◽  
Grazing Angle ◽  
Detection Performance ◽  
Propagation Model ◽  
Ratio Test ◽  
Multipath Effect ◽  
Adaptive Ofdm

Multipath effect is the main factor of deteriorating target detection performance in low grazing angle scenario, which results from reflections on the ground/sea surface. Amplitudes of the received signals fluctuate acutely due to the random phase variations of reflected signals along different paths; thereby the performances of target detection and tracking are heavily influenced. This paper deals with target detection in low grazing angle scenario with orthogonal frequency division multiplexing (OFDM) radar. Realistic physical and statistical effects are incorporated into the multipath propagation model. By taking advantage of multipath propagation that provides spatial diversity of radar system and frequency diversity of OFDM waveform, we derive a detection method based on generalized likelihood ratio test (GLRT). Then, we propose an algorithm to optimally design the transmitted subcarrier weights to improve the detection performance. Simulation results show that the detection performance can be improved due to the multipath effect and adaptive OFDM waveform design.

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