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I need to solve the following impulsive heat equation: $$ \left\{\begin{array}{ll} \partial_{t} \psi(x,t)-\partial_{xx} \psi(x,t)=0, & (x,t)\in (0,1) \times((0, 2) \backslash\{1\}) \\ \psi(0,t)= \psi(1,t)=0, & t \in (0, 2) \\ ...