Cyberman choosing to fill in gaps in the history of the Cybermen or depict new encounters between them and the Doctor. The species also appeared in the "Doctor Who" TV spin-off "Torchwood", appearing in the fourth episode, "Cyberwoman" (2006). The name "Cyberman" comes from cybernetics, a term used in Norbert Wiener's book "Cybernetics or Control and Communication in the Animal and the Machine" (MIT Press, 1948). Wiener used the term in reference to the control of complex systems in the animal world and in mechanical networks, in particular self-regulating control systems. By 1960, doctors were performing research into surgically or mechanically
Wiener–Hopf method is analytic in the upper half-plane, analytic continuation guarantees existence of an entire function which coincides with the left- or right-hand sides in their respective half-planes. Furthermore, since it can be shown that the functions on either side of the above equation decay at large , an application of Liouville's theorem shows that this entire function is identically zero, therefore and so Wiener–Hopf method The Wiener–Hopf method is a mathematical technique widely used in applied mathematics. It was initially developed by Norbert Wiener and Eberhard Hopf as a method to solve systems of integral equations, but has found wider use