$f_d$	=	the lower cut-off frequency
$f_u$	=	the upper cut-off frequency
$h_i$	=	the story heigh of the ith story
$H(k)$	=	the filter function
$x(l)$	=	the displacement vector
$\dot{x}(l)$	=	the velocity vector
$\ddot{x}(l)$	=	the acceleration vector
$\ddot{X}(k)$	=	the Fourier transform of $\ddot{x}(l)$
$x_{\lim }$	=	the threshold or limit of maximum displacement
${\theta }_{\lim }$	=	the threshold or limit of inter-story drift ratio
${\theta }_i$	=	the inter-story drift ratio of the ith story
$\chi$	=	n-mode tensor after missing data reconstruction
$T$	=	n-mode tensor with missing data
IDR	=	Inter-story Drift Ratio
MEMS	=	Micro-Electro Mechanical System
SHM	=	Structural Health Monitoring