A Diffusion Problem with Neumann Boundary Control Utilizing Total Mass

The author studies the diffusion problem $u_t=u_{xx}, 0 0; u(x,0)=0,$ and $-u_x(0,t)=u_x(1,t)=\phi(t),$ where $\phi(t)$ is a control function that ensures that the total mass $\int_0^1 u(x,t_k)dx$ stays between two predetermined values. Mathematically, $\phi(t)=1$ for $t_{2k} < t更多