. 2015 Oct 26;15(10):27230–27250. doi: 10.3390/s151027230

Table 2.

Notations.

$a_{n}$	3-dimensional acceleration vector at sample time n
$a_{p}$	3-dimensional acceleration vector of the recent peak
$a_{v}$	3-dimensional acceleration vector of the recent valley
$\| a \|$	the magnitude of acceleration of vector $a^{*}$
$μ_{a}$	the step average defined in Equation (1)
$μ_{p}$	the average time interval between adjacent peaks
$μ_{v}$	the average time interval between adjacent valleys
$σ_{a}$	the step deviation of the magnitude of acceleration
$σ_{p}$	the standard deviation of the time interval between adjacent peaks
$σ_{v}$	the standard deviation of the time interval between adjacent valleys
$t_{a_{n}}$	the type of the acceleration sample $a_{n}$
$T h_{p}$	the adaptive time threshold for peaks
$T h_{v}$	the adaptive time threshold for valleys

* $| a | = | (a_{x}, a_{y}, a_{z}) | = \sqrt{a_{x}^{2} + a_{y}^{2} + a_{z}^{2}}$ .