Electronic fingerprint systems are now gaining acceptance in mainstream consumer applications worldwide. It has been shown, however, that about 80% of these systems are easily fooled with different kinds of fake fingers with imprinted patterns. Hence, a live finger detection mechanism will be a crucial part of any fingerprint system used in security applications. We present such a system based on measurement of electrical characteristics of different layers of the skin.
A few body system of magnetic holes set in motion by external ac magnetic fields is studied both experimentally and numerically. Notions from braid theory are used to describe the dynamics in a very compact manner. The time history of n magnetic holes moving in a plane is represented by an n-strand braid which enables us to extract periodic orbits and to map out phase portraits. The transitions between different periodic modes of motion are either continuous or noncontinuous followed by strong hysteresis.
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