$\mathsf{\Phi }$	Lumen maintenance
$\mathsf{\beta }$	Pre-factor of LED’s depreciation
$\mathsf{\alpha }$	Degradation rate of LEDs
$L_{\mathrm{p}}$	Failure criterion of LEDs
$T_{\mathrm{j}}$	Junction temperature in LEDs
$I$	Driving current
$E_a$	LED’s activation energy
$k$	Boltzmann constant
$n$	Model constant
$A$	Model constant