Dear Organizing Committee, My name is Nguyen Hoang, a postdoc in the Department of Mathematics at the University of Oklahoma. I am interested in giving a short presentation at the Third Oklahoma PDE Workshop. Below are the title and abstract of a possible talk. Title: An inverse problem for a heat equation with piecewise-constant thermal conductivity. Abstract: The governing equation is $u_t = (a(x)u_x)_x$, $0 \le x \le 1$, $t > 0$, $u(x, 0) = 0$, $u(0, t) = 0$, $a(1)u'(1, t) = f(t)$. The extra data are $u(1, t) = g(t)$. It is assumed that $a(x)$ is a piecewise-constant function, and $f\not\equiv 0$. It is proved that the function $a(x)$ is uniquely defined by the above data. No restrictions on the number of discontinuity points of $a(x)$ and on their locations are made. The number of discontinuity points is finite, but this number can be arbitrarily large. I hope my proposal is accepted for presenting at the Workshop. I look forwarding to the Committee's decision. Thank you very much, Nguyen Hoang Department of Mathematics University of Oklahoma