Math & Science ⇒ positioning in equations

[rasepideh]

Hi all!

How is it possible to write "Hp" starting from the same position? I want to write like the picture that I attached here and have all these four section as one equation, because I want to give reference to this equation.(attached my aim picture)

My code in master, thesis

Code: Select all

\begin{eqnarray} \label{eq:5}
Se & = & \left\{
                \begin{array}{ll}
                  \frac{1}{{[1+|\alpha H_{p}|^{n}]}^{m}}	 & \quad H_{p}<0\\
                  1	 & \quad H_{p} \geq0
                \end{array}
              \right.   \nonumber
 \\
 \theta & = & \left\{
                \begin{array}{ll}
                  \theta_{r}+Se(\theta_{s}-\theta_{r})	& \quad H_{p}<0\\
                  \theta_{s}	 & \quad H_{p} \geq0 
                \end{array}
              \right. 
\\  
C & = & \left\{
                \begin{array}{ll}
                  \frac{\alpha m}{1-m}(\theta_{s}-\theta_{r})Se^{\frac{1}{m}}\left(1-Se^{\frac{1}{m}}\right)^{m}	& \quad H_{p}<0\\
                  0		& \quad H_{p} \geq0
                \end{array}
              \right.   \nonumber   
\\  
k_{r} & = & \left\{
                \begin{array}{ll}
                  Se^{l}\left[1-\left(1-Se^{\frac{1}{m}}\right)^{m} \right]^2	& \quad H_{p}<0\\
                  1		& \quad H_{p} \geq0
                \end{array}
              \right.   \nonumber                                            
\end{eqnarray}

[kaiserkarl13]

Try this:

Code: Select all

\begin{subequations}
\begin{align}
  \theta &= \left\{
    \begin{array}{l}
      \theta_r \mathrm{Se}(\theta_s - \theta_r) \\
      \theta_s
    \end{array}
  \right. &
    \begin{array}{l}
        H_p < 0 \\
        H_p \ge 0
    \end{array}
  \\
  \mathrm{Se} &= \left\{
    \begin{array}{l}
      \frac{1}{\left[1 + \left|\alpha H_p\right|^n\right]^m} \\
      1
    \end{array}
  \right. &
    \begin{array}{l}
        H_p < 0 \\
        H_p \ge 0
    \end{array}
  \\
  k_r &= \left\{
    \begin{array}{l}
      \mathrm{Se}^l\left[1 - \left(1 - \mathrm{Se}^{\frac{1}{m}}\right)^m\right]^2 \\
      1
    \end{array}
  \right. &
    \begin{array}{l}
      H_p < 0 \\
      H_p \ge 0 \\
    \end{array}
\end{align}
\label{eq:everything}
\end{subequations}
This is a reference to Equations~\eqref{eq:everything}.