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. 2015 Apr 14;15(4):8664–8684. doi: 10.3390/s150408664

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© 2015 by the authors; licensee MDPI, Basel, Switzerland.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/4.0/).

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(a) The circle tunnel actual drawing; (b) the rectangle tunnel actual drawing; (c) the circle tunnel dynamic measurement results; (d) the rectangle tunnel dynamic measurement results.