Nonnegative realizations of matrix transfer functions (Q1567548)

This paper is an important contribution to the theory concerning nonnegative realizability of matrix transfer functions. The main result characterizes the nonnegative realizability of a scalar-valued transfer function with the help of primitive transfer functions and is extended to the general case of matrix-valued transfer functions. In it there is also an algorithm for establishing whether a scalar-valued transfer function with nonnegative impulse function has a nonnegative realization. The paper is clearly written, and its relation to the existing literature is clearly indicated.