Angular Spectrum Analysis Applied to Undercladding Flaws and Dipole Probes

An important class of subsurface cracks occur in nuclear power plant pressure vessels. These pressure vessels, normally made of carbon steel, are protected by a layer of weld material applied directly onto the surface, leaving a highly inhomogeneoue cladding with a rough surface and a very irregular interface. Subsurface cracks originate at the interface between the carbon steel walls of the pressure vessel and the protective cladding layer. The propagation is initially into the carbon steel and eventually into the cladding, and needs to be detected before reaching the surface (Fig. 1). The inhomogeneity of the cladding material and the irregular surfaces pose serious difficulties for ultrasonic detection. These difficulties are less critical for eddy current testing due to the fact that the layered structure of the cladding has more variation in its elastic properties than its electrical conductivity

Eddy-Current Probe Design

This paper describes theoretical and experimental work directed toward finding the optimum probe dimensions and operating frequency for eddy current detection of half-penny surface cracks in nonmagnetic conducting materials. The study applies to probes which excite an approximately uniform spatial field over the length of the crack at the surface of the material. In practical terms, this means that the probe is not smaller than the crack length in any of its critical dimensions

An efficient online algorithm for square detection

A square is a string of characters that can be divided into two identical substrings. The problem of detecting squares in a string finds applications in many areas such as bioinformatics and data compression. In this paper, we give the first efficient online algorithm for the problem. Given any input string, our algorithm reports the first square in the string using O(n log2 n) time where n is the position in the string where the square ends. This time complexity is only a factor of O(log n) larger than that of an optimal offline algorithm. © Springer-Verlag Berlin Heidelberg 2004.link_to_subscribed_fulltex

Research on the 1D PSD

Position Sensitive Detector (PSD) is a device utilizing the lateral photoelectric that produced by the non-uniform illumination of a rectifying semiconductor junction. The linear requirement, spectral responds, position detection error of 1D PSD were presented in this paper. All these studied works are the theoretical basis for designing and fabrication PSD with excellent performance. The experimental results show that the rms non-linearity and the typical position error are 0.1% of full length(8mm) and ± 5 μm.link_to_subscribed_fulltex