Quantitative Research on Signal of Pipeline Coating Defect Detection Based on HHT
Coating is a very important way to ensure the integrity of the pipeline. However, due to environmental or external factors, the coating will has some defects such as peeling defects, holes and so on. This paper is concentrated on axial stripping defects and holes of buried pipeline coated with anti-corrosion coating, using ultrasonic guided wave detection technology to obtain the coating detection signal to do the study of quantification, it provides a feasible method to study the level quantitative description of the anticorrosive layer peeling defects.Doing time-frequency analysis to the operating status of the coating, we will have a conclusion that when the coating has peeling defects, the waveform of the detection signal will has a nonlinear characteristic signal. According to the analysis of time-frequency distribution, we can find out that when the signal has nonlinear characteristic signal, the time-frequency distribution will have a "concave" type frequency distribution, it is the basis to judge the junction of the coating peeling defects. According to the judgment, and obtain the relative length of the coating stripping defect, it will finally obtain the degree of damage caused by peeling defects.Therefore, this paper is a post-treatment method for pipeline coating detection, providing feasible and effective signal processing methods and quantitative research methods for the engineering application of the detection technology of non-linear ultrasonic pipeline coating peeling defects.
Devices for automated regulation of the velocity of in-tube pig flaw detectors (Review)
Known foreign and domestic developments regarding devices for velocity control of in-tube pig flaw detectors for the purpose of improving the quality and reliability of testing of tubes of gas-main pipelines laid in the ground are considered.
Photoreflectance characterization of vanadium-doped GaAs layers grown by metalorganic vapor phase epitaxy
Abstract We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy. The conductivity of the samples is checked by the Hall effect measurements, and it is n type with electrons concentration ranging from 2×10 13 to 2×10 17  cm −3 . We used the photoreflectance technique (PR) to study the effect of vanadium doping on the optical properties of GaAs. Our experimental results show that the built-in electric field F and the broadening parameter Γ 0 increase with V-doping concentration. Furthermore, the temperature dependence of the built-in electric field and the broadening parameter of GaAs:V samples have been investigated by PR. It has been observed that these parameters increase with increasing temperature. The decrease of the built-in electric field with decreasing temperature is due to the photovoltage effect.We characterized the vanadium-doped GaAs (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy.