“…This procedure was required in order to trace how the signals changed over the time period. Then, the Butterworth low-pass filter was used to separate the body acceleration from the gravitational acceleration signals (Acharjee, Mukherjee, Mandal, & Mukherjee, 2015;Anguita, Ghio, Oneto, Parra, & Reyes-Ortiz, 2013;Arif et al, 2014;Machado, Luisa Gomes, Gamboa, Paixao, & Costa, 2015;Reyes Ortiz, 2015;Sun, Zhang, Li, Guo, & Li, 2010). The remaining body acceleration signals later would be used for further process.…”