Compressive Sensing Techniques for mm-Wave Nondestructive Testing of Composite Panels

Methods for Advanced Wind Turbine Condition Monitoring and Early Diagnosis: A Literature Review

“…As rotor faults are accompanied with a change in the blade material structure, these faults can be diagnosed using acoustic emission and vibration sensors. Acoustic emission is able to detect emerging structural changes by inserting sensors on the blades [21]. If these faults develop to a certain level that contributes abnormal vibrations of the blades, then signals information acquired from vibration sensors can be utilized for fault diagnosis.…”

“…More than 14% of WECS faults occurs in these sensors [35]. Faults such as malfunction/physical failure, malfunction of the data processing/communication software [21] may cause performance degradation to the wind turbine, failure to the control system, mechanical and electrical subsystems and may lead to shut down the wind turbine. Encoder faults in an induction motor drive are detected by measuring the mean and standard deviation of the rotor speed signal [36].…”

Fast FMCW Terahertz Imaging for In-Process Defect Detection in Press Sleeves for the Paper Industry and Image Evaluation with a Machine Learning Approach

“…Terahertz waves offer a number of characteristic properties especially interesting for the NDT investigation of nonconducting materials and industrial components or products made from these materials. First, terahertz radiation can penetrate many common production materials at low absorption rates and good penetration depths, in particular plastics and polymer compounds [ 4 ], glass fiber-reinforced (GFR) composite materials [ 5 , 6 , 7 , 8 , 9 ], wood [ 10 , 11 ], paper [ 12 ] and cardboard [ 13 ], dry and wet paint layers or other coatings [ 4 , 14 , 15 , 16 ], and many more. At the same time, the small terahertz wavelengths of few millimeters down to several tens of micrometers constitute an ideal premise for imaging techniques [ 17 , 18 , 19 , 20 , 21 ] with image resolutions on the order of typical, relevant defect sizes in components produced from the above materials.…”

“…Combining all the above properties and advantages over other NDT techniques, and the increasing availability of sources, detectors and receivers, terahertz technology has today reached a level of maturity to be implemented in industrial production environments or processes of quality control and to offer a valuable benefit in the optimization of these processes. Among the typical real-world NDT scenarios where in particular terahertz imaging can be (or is already being) employed are packaging control [ 13 ], production lines in the polymer an plastics industry for the detection of defects or the inspection of welding processes, manufacturing of GFR composites for lightweight construction [ 7 , 8 , 27 ] for example in the automotive, aviation and space industry [ 9 , 28 , 29 ], food inspection [ 30 , 31 ], investigation of thermal and electrical insulation materials [ 26 , 32 ], but also in fields of biomedical applications [ 33 ], artwork conservation [ 34 , 35 , 36 , 37 ], and many more.…”

Solving the Problem of Electromagnetic Wave Scattering on Small Impedance Particle by Integral Equation Method

“…Despite the presence of such a large number of publications on this topic and diversity of methods to solve related problems, development of methods for solving the scattering problem for the case of a body of an arbitrary shape with specific physical conditions is important. This is because of using the scattering theory in the diverse application areas, such as medical imaging and testing [3], geophysical exploration [5], non-destructive testing [9], THz technology [7], moving the antenna technique to new perspective frequency bands [26].…”