Aligning the cells in a matrix in an equation

Question

I have been trying to align the "<" and ">" after t_{c} with that of the equal "=" sign in the second matrix (see the codes below). Any ideas on how I can do that?

I'm using the following codes:

    \begin{equation}
        \begin{aligned}
\sigma(t_{c})=\left\{\begin{matrix}
    1\\ [0,1] 
    \\ 
    0
\end{matrix}\right.\text{if } t_{c} \left\{\begin{matrix}
    < \\ 
    =\sfrac{-\alpha N(m_{c},m_{e})}{v_{c}^{d}}.\\ 
    >
\end{matrix}\right.\label{eqn:13}

Answer 1

\documentclass{article}
\usepackage{amsmath}
\usepackage{nicefrac}

\begin{document}
    \begin{equation}\label{eqn:13}
\sigma(t_{c}) = \begin{cases}
        1       &   \\
        [0,1]   &  \text{ if } t_c \\
        0       &   \\
                \end{cases}%  
    \begin{cases}    
        < \\
        = \nicefrac{-\alpha N(m_{c},m_{e})}{v_{c}^{d}} .\\
        >
    \end{cases}
    \end{equation}
\end{document}