deletions | additions       diff --git a/Human_Activity_recognition_has_been__.tex b/Human_Activity_recognition_has_been__.tex  index 51d071b..e443667 100644  --- a/Human_Activity_recognition_has_been__.tex  +++ b/Human_Activity_recognition_has_been__.tex 
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Human Activity recognition has been a critical range of Computer vision research subsequent to the 1980s. The previous decade has seen a fast advancement of 3D data acquisition techniques. \cite{aggarwal2014human} Such techniques involve recent advances in 3d depth cameras and motion capture technologies. In the work of \citet{zhang2012microsoft}, he stated that the Kinect sensor incorporates several advanced sensing hardware. Most notably, it contains a depth sensor, a color camera, and a four-microphone array that provide full-body 3D motion capture, facial recognition, and voice recognition capabilities (see Figure \textbf{_}). 3).  The depth sensor portion of the Kinect consists of the IR projector combined with the IR camera, which is a monochrome complementary metal oxide semiconductor (CMOS) sensor. The depth-sensing technology is licensed from the Israeli company PrimeSense (www.primesense.com). Although the exact technology is not disclosed, it is based on the structured light principle.