Hi,

We consider in 2D domain : [0,L] x[0,H], the system of equations:

dV/dt = D* Delta V - dV/dx - V

dU/dt= V - alpha* U

with boundary conditions

x=0,L: dV/dx = 0, y=0: dV/dy=- U + V; y=H: dV/dy=0

and initial condition V(x,y,0)= V0

Question 1: this system is no linear. So to resolve it, we have to use arf and matrix? Or it is sufficient to use the variational formulation: problem ([U,V],[UH,VH])?

like this:

```
problem MainSys([V,VH],[U,UH],solver=LU)= int2d(Th)(V*VH/dt)-int2d(Th)(oldV*VH/dt)+int2d(Th)(U*UH/dt)-int2d(Th)(oldU*UH/dt)
+int2d(Th)(D*(dx(V)*dx(VH)+dy(V)*dy(VH)))
+int2d(Th)(dx(V)*Vh)+int2d(Th)(V*VH)
+int2d(Th)(alpha*U*UH)-int2d(Th)(V*UH);
-int1d(Th,1)(D*V*VH)+int1d(Th,1)(D*U*UH);
```

is it correct?

Question 2: for boundary condition, we write it using \int 1d(Th,… or we have to use on(…?

Regards