[ex][model][slides] Update slides

slides/model.md

@@ -11,7 +11,7 @@ A DuMu^x^ model is an implementation of a discretized **mathematical model**, ge
 Mathematical model (PDE):
 $$
 \begin{aligned}
-\frac{\partial S(u)}{\partial t} + \nabla \cdot \mathbf{F}(u) = q, \quad \forall (t,\mathbf{x}) \in (0,T] \times \Omega
+\frac{\partial S(u)}{\partial t} + \nabla \cdot \mathbf{F}(u) = q(u), \quad \forall (t,\mathbf{x}) \in (0,T] \times \Omega
 \end{aligned}
 $$
 
@@ -71,12 +71,7 @@ $$
 \end{aligned}
 $$
 
-with
-
-- $c_B^n:$ concentration at time $t_n$ and control volume $B$
-- $c^n_h:$ global discrete solution at time $t_n$, interpolated using __basis functions__
-- $\mathbf{n}:$ unit outer normal vector
-- $\sigma:$ sub control volume face (scvf)
+<img src=img/box_scv_scvf.png width="80%">
 
 ## Example: Diffusion equation
 Discrete model using the Box discretization:
@@ -87,7 +82,12 @@ $$
 \end{aligned}
 $$
 
-<img src=img/box_scv_scvf.png width="80%">
+with
+
+- $c_B^n:$ concentration at time $t_n$ and control volume $B$
+- $c^n_h:$ global discrete solution at time $t_n$, interpolated using __basis functions__
+- $\mathbf{n}:$ unit outer normal vector
+- $\sigma:$ sub control volume face (scvf)
 
 ## `LocalResidual`
 The local residual of the diffusion model: