u=-1;k=0.1;
L=10;dh=0.1;dt=abs(dh/u)*0.5
dt =
    0.0500
[x,t,N]=AdvDiff1D(1,u,k,L,3,dh,dt);
sigma=0.5, lambda=0.5
plot(x,N(:,1))
close all
plot(x,N(:,1))
plot(x,N(:,20))
plot(x,N(:,1:10:end))
surf(t(2:end),x,N)