Abstract It has been reported that in principle sludge and blockages in pipes can be detected and characterized by using ultrasonic guided waves. The model idealised the sludge to be an asymmetrically uniform layer that is well bonded to the internal surface of the pipe wall. However, in practice, sludge layers normally have a very irregular shape, an asymmetrical circumferential profile and al...

A theoretical model to analyze the performance of a circular polarization microstrip antenna printed on a conical surface is presented. The radiation pattern of the antenna is simulated by the radiation from its four radiating edges (two axial and two circumferential). The electromagnetic field is expanded in terms of spherical wave modes and it is shown that the circular polarization is obtain...

When an immersed solid elastic cylinder is insonified by an obliquely incident plane acoustic wave, some of the resonance modes of the cylinder are excited. These modes are directly related to the incidence angle of the insonifying wave. In this paper, the circumferential resonance modes of such immersed elastic cylinders are studied over a large range of incidence angles and frequencies and ph...

In the recent years, the main obstacles for raising the operating efficiency are instabilities of the compressor system. The related dynamics and control schemes then cause lots of interests among engineers and researchers. Two main phenomena, which cause the instabilities, are the “surge” and the “stall” behaviors of the compressed gas. The so-called “surge” is characterized as a one-dimension...

scattering of an incoming wave train by a discontinuity at the upper surface of the ocean over a uniform porous bottom of finite depth is considered here in the framework of linearized water wave theory. by employing residue calculus method, the reflection and transmission coefficient are obtained. these coefficients are computed numerically for different values of the porosity parameter g and ...

All fiber lasers to date emit radiation only along the fiber axis. Under this program a fiber that exhibits laser emission that is radially directed from its circumferential surface was demonstrated. A unique and controlled azimuthally anisotropic optical wave front results from the interplay between a cylindrical photonic bandgap fiber resonator, anisotropic organic dye gain, and a linearly po...

This computational study is motivated by recent experiments on large-scale cookoff in a confined annular geometry, where the explosive charge is heated carefully so as to produce, nominally, a uniform radial thermal gradient. In the absence of circumferential asymmetry a circular wave of explosion would traverse the charge from the hot outer boundary to the cold inner boundary. In practice, how...

Guided wave focusing has been developed as a promising technique for defect detection in pipeworks, where non-axisymmetric flexural modes are tuned so that ultrasonic energy can be focused at a target point in a pipe. If a defect is located at the target point, large amplitude reflected waves can be observed. In this study, the focusing phenomenon is analyzed using a semi-analytical finite elem...