We first introduce non-negative Lagrangian multipliers $\lambda = \{\lambda_k\} \succeq 0$ and $\beta = \{\beta_k\} \succeq 0$ associated with the rate constraint $(15\mathrm d)$, $\nu = \{\nu_k\} \succeq 0$ associated with the ernergy causality constraints $(15\mathrm e)$ and $(15\mathrm f)$. In addition, non-negative Lagrangian multipliers $\mu \ge 0$ and $\xi \ge 0$ are associated with the total time constraint $(15\mathrm b)$ and total energy constraint at $\mathrm{HRN}$ $(15\mathrm c)$. Then the Lagrangian of Problem $(\mathrm{P1'})$ is given $\cdots$

Taken from this paper.

I found a symbol that I am not familiar with. Does anyone know the symbol $\succeq$?