A set that is not convex is called a non-convex set. A polygon that is not a convex polygon is sometimes called a concave polygon, and some sources more generally use the term concave set to mean a non-convex set, but most authorities prohibit this usage.
In either case you don't need to deal with the absolute value. A rectified sine wave is a periodic signal with a period equal to half of the full sinusoid, I would write the sine in exponential form and integrate over one period to find the series coefficients.
Reverberation. Reverberation (or reverb) is the persistence of sound in an enclosed space after its generation. It is relatively common artifact that limits the interpretation of the final imaging. This phenomenon is due to continuing repeated echoes between anatomic interfaces which are strong reflectors.hadowing. This very common artifact might be characterized as the âAchilles heelâ of echocardiography and occurs when the transmitted ultrasound beam encounters a medium of significantly different acoustic impedance and as a result is reflected back to the transducer.