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.
Reflection and Transmission Problem of SH Waves in Layered Viscoelastic Medium
Two chief ways are mainly used to solve the problems of viscoelasticity: one is considering the factor of viscidity in elastodynamics equation,the other is establishing models of viscoelastic medium directly from constitutive equation.The second method is mainly used because of its positivism in studying on physical appearance of medium.In this article,we firstly establish constitutive equation of convolutional forms based on Boltzman's superposition principle,and consequently establish elastodynamic equation in viscoelastic medium.After that,we obtain the solution of the equation based on which we can study on problems of reflection and transmission on interface between two viscoelastic solids.At last,we give some theoretical analysis after calculating the coefficient of reflection and transmission C_R,C_T.
Inhomogeneous Boundary Value Problems for Compressible Navier-Stokes Equations: Well-Posedness and Sensitivity Analysis
In this paper compressible, stationary Navier–Stokes equations are considered. A framework for analysis of such equations is established. In particular, the well-posedness for inhomogeneous boundary value problems of elliptic-hyperbolic type is shown. Analysis is performed for small perturbations of the so-called approximate solutions that take form (1.12). The approximate solutions are determined from Stokes problem (1.11). The small perturbations are given by solutions to (1.13). The uniqueness of solutions for problem (1.13) is proved, and, in addition, the differentiability of solutions with respect to the coefficients of differential operators is shown. The results on the well-posedness of nonlinear problems are interesting on their own and are used to obtain the shape differentiability of the drag functional for incompressible Navier–Stokes equations. The shape gradient of the drag functional is derived in the classical and useful for computations form; an appropriate adjoint state is introduced to ...