Hi everyone.

I am new to Julia and decided to give a try to the SciML framework.

My goal is first to solve the quasi-linear heat equation using the method of Lines.

In the future, I would like to use ModelingToolkit.jl, but I wanted to start by using only DiffEqTools.jl and DifferentialEquations.jl to better understand what’s going on inside the black box.

I found a similar topic here with what I have in mind but for a constant diffusivity parameter: Solving heat diffusion PDE using DiffEqTools.jl and DifferentialEquations.jl

What I have so far is:

```
using DiffEqOperators, DifferentialEquations
#=
Solving heat equation with variable diffusity κT:
∂tT = ∂x(κT ∂x(T))
=#
const Lx = 1.0 # length of the rod in the x direction
const nx = 40 # number of points in the x direction
const Δx = Lx / (nx - 1) # grid spacing in the x direction
const x = range(0, length=nx, stop=Lx) # Define the locations along a gridline.
const u0 = sin.(pi*x/Lx) # initial condition
Q = Dirichlet0BC(eltype(u0)) # homogeneous dirichlet on the sides
u0_padded = Q * u0
κTx_padded = ones((length(u0_padded))) .* 1.22e-3 # has to be same length as T_padded
∂ut = similar(u0) # pre-allocate array
nonlinear_diffusion!(∂ut, 1, 1, 4,
κTx_padded, u0_padded, Δx, nx) # finite differences in space
tspan = (0.0, 10.0)
prob = ODEProblem(∂ut, u0, tspan)
solve(prob)
```

I got an error when using ODEProblem. What did I miss?

Thank you very much in advance