scholarly journals High-Resolution Crack Localization Approach Based on Diffraction Wave

Sensors ◽  
2019 ◽  
Vol 19 (8) ◽  
pp. 1951 ◽  
Author(s):  
Mu ◽  
Sun ◽  
Liu ◽  
Wang
Keyword(s):  
High Resolution ◽  
Sensor Array ◽  
Wave Packets ◽  
Dispersion Compensation ◽  
Wave Theory ◽  
Guided Wave ◽  
Localization Accuracy ◽  
Half Wave ◽  
Diffraction Wave ◽  
Localization Approach

The delay-and-sum imaging algorithm is a promising crack localization approach forcrack detection and monitoring of key structural regions. Most studies successfully offer a hole-likedamage position. However, cracks are more common than hole-like damages in a structure. To solvethis issue, this paper presents a crack localization approach, based on diffraction wave theory, whichis capable of imaging crack endpoints. The guided wave propagated to the crack endpoints andtransformed into a diffraction wave. A line sensor array was used to record the diffractionwaveform. Then, dispersion compensation was applied to shorten the dispersive wave packets andseparate the overlapping wave packets. Subsequently, half-wave compensation was executed toimprove the localization accuracy. Finally, the effectiveness of this high-resolution crack localizationmethod was validated by an experimental example.

Pipeline Inspection With the High Resolution EMAT ILI-Tool: Report on Full-Scale Testing and Field Trials

2006 ◽  
Author(s):  
Martin Klann ◽  
Thomas Beuker
Keyword(s):  
High Resolution ◽  
Crack Detection ◽  
New Technology ◽  
Wave Theory ◽  
Field Trials ◽  
Guided Wave ◽  
Full Scale ◽  
Operational Conditions ◽  
Full Scale Tests ◽  
Disbonded Coating

In succession of a research project to develop an EMAT in-line inspection technology for the detection of stress corrosion cracking (SCC) and disbonded coating, a 16” EMAT inspection tool was manufactured and tested. This 16” EMAT Crack Detection (ECD) Tool establishes a new high-resolution approach to effective and accurate crack inspection technology especially for gas lines. The performance of this tool was tested on several pipe samples containing natural SCC as well as artifical anomalies and laminations. Furthermore, a field test is currently being conducted, which will detail the tools performance under operational conditions. The new technology will be compared to the results from the established Magnetic Flux Leakage inspection (MFL) technology. EMAT inspection technology, originally designed for detection of SCC, is also sensitive to areas of disbonded coating, other crack-like features, and anomalies like gouging and channeling. To distinguish the different types of pipeline threats, a qualitative defect sizing process is under development incorporating the EMAT data and the information from the other in-line inspection technologies. Following an introduction into EMAT guided wave theory, data from a series of full-scale tests obtained with 34” prototype sensors and the complete 16” ILI-EMAT tool, will be presented. The inspection tool itself, as well as the process for evaluating the recorded data, are undergoing continuous improvements. This paper will discuss the development status of these technologies.

scholarly journals Towards human distance estimation using a thermal sensor array

2021 ◽  
Author(s):  
Abdallah Naser ◽  
Ahmad Lotfi ◽  
Joni Zhong
Keyword(s):  
High Resolution ◽  
Independent Living ◽  
Sensor Array ◽  
Distance Estimation ◽  
Thermal Sensor ◽  
Indoor Environments ◽  
Contagious Diseases ◽  
Novel Approach ◽  
Thermal Cameras ◽  
Distance Estimator

AbstractHuman distance estimation is essential in many vital applications, specifically, in human localisation-based systems, such as independent living for older adults applications, and making places safe through preventing the transmission of contagious diseases through social distancing alert systems. Previous approaches to estimate the distance between a reference sensing device and human subject relied on visual or high-resolution thermal cameras. However, regular visual cameras have serious concerns about people’s privacy in indoor environments, and high-resolution thermal cameras are costly. This paper proposes a novel approach to estimate the distance for indoor human-centred applications using a low-resolution thermal sensor array. The proposed system presents a discrete and adaptive sensor placement continuous distance estimators using classification techniques and artificial neural network, respectively. It also proposes a real-time distance-based field of view classification through a novel image-based feature. Besides, the paper proposes a transfer application to the proposed continuous distance estimator to measure human height. The proposed approach is evaluated in different indoor environments, sensor placements with different participants. This paper shows a median overall error of $$\pm 0.2$$ ± 0.2  m in continuous-based estimation and $$96.8\%$$ 96.8 % achieved-accuracy in discrete distance estimation.

Probability-based diagnostic imaging with corrected weight distribution for damage detection of stiffened composite panel

2021 ◽  
pp. 147592172110339
Author(s):  
Guoqiang Liu ◽  
Binwen Wang ◽  
Li Wang ◽  
Yu Yang ◽  
Xiaguang Wang
Keyword(s):  
Distribution Function ◽  
Diagnostic Imaging ◽  
Weight Distribution ◽  
Composite Structures ◽  
Damage Identification ◽  
Guided Wave ◽  
Composite Panel ◽  
Damage Localization ◽  
Localization Accuracy ◽  
Direct Interpretation

Due to no requirement for direct interpretation of the guided wave signal, probability-based diagnostic imaging (PDI) algorithm is especially suitable for damage identification of complex composite structures. However, the weight distribution function of PDI algorithm is relatively inaccurate. It can reduce the damage localization accuracy. In order to improve the damage localization accuracy, an improved PDI algorithm is proposed. In the proposed algorithm, the weight distribution function is corrected by the acquired relative distances from defects to all actuator–sensor pairs and the reduction of the weight distribution areas. The validity of the proposed algorithm is assessed by identifying damages at different locations on a stiffened composite panel. The results show that the proposed algorithm can identify damage of a stiffened composite panel accurately.

scholarly journals The nonlinear effects on the characteristics of gravity wave packets: dispersion and polarization relations

2000 ◽  
Vol 18 (10) ◽  
pp. 1316-1324 ◽  
Author(s):  
S.-D. Zhang ◽  
F. Yi ◽  
J.-F. Wang
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Middle Atmosphere ◽  
Wave Packets ◽  
Nonlinear Effects ◽  
Wave Theory ◽  
Nonlinear Propagation ◽  
Waves And Tides ◽  
Time Variations ◽  
Isothermal Atmosphere

Abstract. By analyzing the results of the numerical simulations of nonlinear propagation of three Gaussian gravity-wave packets in isothermal atmosphere individually, the nonlinear effects on the characteristics of gravity waves are studied quantitatively. The analyses show that during the nonlinear propagation of gravity wave packets the mean flows are accelerated and the vertical wavelengths show clear reduction due to nonlinearity. On the other hand, though nonlinear effects exist, the time variations of the frequencies of gravity wave packets are close to those derived from the dispersion relation and the amplitude and phase relations of wave-associated disturbance components are consistent with the predictions of the polarization relation of gravity waves. This indicates that the dispersion and polarization relations based on the linear gravity wave theory can be applied extensively in the nonlinear region.Key words: Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)

Flexible High‐Resolution Triboelectric Sensor Array Based on Patterned Laser‐Induced Graphene for Self‐Powered Real‐Time Tactile Sensing

2021 ◽  
pp. 2100709 ◽  
Author(s):  
Zhengguang Yan ◽  
Liangliang Wang ◽  
Yifan Xia ◽  
Rendong Qiu ◽  
Wenquan Liu ◽  
...  
Keyword(s):  
High Resolution ◽  
Real Time ◽  
Sensor Array ◽  
Tactile Sensing ◽  
Self Powered

Accurate Thickness Inversion of Corrosion Using A1 Lamb Wave

2021 ◽  
Author(s):  
Min Lin ◽  
Yang Liu
Keyword(s):  
High Resolution ◽  
Oil And Gas ◽  
Residual Life ◽  
Early Stage ◽  
Corrosion Damage ◽  
Oil And Gas Industry ◽  
Forward Modeling ◽  
Guided Wave ◽  
Velocity Inversion ◽  
Wave Tomography

Abstract Corrosion is one of the most critical issues in the oil and gas industry, leading to severe environmental and economic problems. Due to the high cost and serious safety risk of corrosion, it is essential to improve current corrosion testing techniques to detect corrosion damages at an early stage. Guided wave tomography (GWT) demonstrates its great potential to inspect and quantify the corrosion damage. GWT is capable of determining the residual life of corrosion structures by quantifying the remaining wall thickness. In this paper, an accurate guided wave tomography technique incorporating full waveform inversion (FWI) and higher-order Lamb waves (A1 mode) is presented for plate-like structures, which is able to get high-resolution reconstruction results. The technique consists of three steps: forward modeling, velocity inversion and thickness reconstruction. The forward modeling is computed by solving the elastic full-wave equations in 2-D time domain by using the finite difference method. High-resolution phase velocity inversion can then be obtained by minimizing the waveform misfit function between simulated and recorded data using a second order optimization method, which updates the velocity model from low to high frequencies iteratively. Finally, the velocity variations can be transformed into depth profiles by using the dispersive characteristics of ultrasonic guided waves; therefore, the thickness reconstruction can be obtained. The numerical simulations are performed on an aluminum plate with a complicated corrosion defect. By comparing the thickness reconstruction maps using both A1 and A0 modes, the results demonstrate that FWI with A1 mode can achieve significantly better resolution of corrosion imaging than that with A0 mode.

DAFI

2021 ◽  
Vol 5 (4) ◽  
pp. 1-21
Author(s):  
Hang Li ◽  
Xi Chen ◽  
Ju Wang ◽  
Di Wu ◽  
Xue Liu
Keyword(s):  
Indoor Localization ◽  
Domain Adaptation ◽  
Target Domain ◽  
Localization Accuracy ◽  
Source Domain ◽  
Fine Grained ◽  
Time Signals ◽  
Environmental Variations ◽  
Device Free ◽  
Localization Approach

WiFi-based Device-free Passive (DfP) indoor localization systems liberate their users from carrying dedicated sensors or smartphones, and thus provide a non-intrusive and pleasant experience. Although existing fingerprint-based systems achieve sub-meter-level localization accuracy by training location classifiers/regressors on WiFi signal fingerprints, they are usually vulnerable to small variations in an environment. A daily change, e.g., displacement of a chair, may cause a big inconsistency between the recorded fingerprints and the real-time signals, leading to significant localization errors. In this paper, we introduce a Domain Adaptation WiFi (DAFI) localization approach to address the problem. DAFI formulates this fingerprint inconsistency issue as a domain adaptation problem, where the original environment is the source domain and the changed environment is the target domain. Directly applying existing domain adaptation methods to our specific problem is challenging, since it is generally hard to distinguish the variations in the different WiFi domains (i.e., signal changes caused by different environmental variations). DAFI embraces the following techniques to tackle this challenge. 1) DAFI aligns both marginal and conditional distributions of features in different domains. 2) Inside the target domain, DAFI squeezes the marginal distribution of every class to be more concentrated at its center. 3) Between two domains, DAFI conducts fine-grained alignment by forcing every target-domain class to better align with its source-domain counterpart. By doing these, DAFI outperforms the state of the art by up to 14.2% in real-world experiments.

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