Annular Array Search Units and Their Potential Application in Conventional Ultrasonic Testing Systems
This paper is based on a program to investigate the potential of multi-element annular arrays for practical application in ultrasonic testing systems. The annular array is comprised of coaxially-located, ring-shaped piezoelectric elements. By providing excitation pulses in a spherical time relationship, the transmitted beam may be focused at a specific range. By electronic switching, the focal point can be placed at various distances in the material under examination, Of particular interest is the length over which the beam can be held in collimation. Fabrication methods, delayed excitation techniques, and beam patterns in water and steel are described,
Sizing Defects Using Annular Array Techniques with an Automatic Ultrasonic Data Acquisition System
Present state of the art sizing measurements of defects by ultrasonic techniques has been inadequate, especially in support of a quantitative fracture mechanical analysis of the strength of a material. Present capabilities of defect sizing in some cases do not allow an accept/reject decision to be made. Currently, ultrasonic imaging systems including phased array, synthetic aperture, and wavefront reconstruction systems are being developed to quantitatively measure defect sizes. Also, in the medical field phased array systems have been developed for imaging purposes. Ibis work describes an annular phased array system which is being developed for general NDE applications on metal and ceramic materials. The main usefulness of phased array techniques is the ability of electronically changing the focus of the acoustic beam radiating from a phased array transducer or reflecting from a defect in a solid material.
Reality TV: The Work of Being Watched
Chapter 1 1 Between the New Medium and the Old Chapter 2 2 The Promise of the Digital Revolution Chapter 3 3 Rediscovering Reality Chapter 5 4 The Kinder, Gentler Gaze of Big Brother Chapter 6 5 Access to the Real Chapter 7 6 It's All About the Experience Chapter 8 7 Reality TV and Voyeurism Chapter 9 8 Survivor and Uncanny Capitalism Chapter 10 Bibliography