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© 2012 Park et al.; licensee InTech. This is an open access article distributed under the terms of the Creative 
Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, 
distribution, and reproduction in any medium, provided the original work is properly cited.
Except where otherwise noted, this item's license is described as © 2012 Park et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.