If you're a control or automation engineer, you'll probably roll your eyes at the sight of another article on PID controllers - especially one written by an undergraduate. Nonetheless, here is my own spin on the topic.
Unfortunately the article is in the PDF format - and I can't translate it to HTML easily. Here's the link: PID control.
Thermodynamics was one of my favourite subjects in college. Although the topics discussed below might seem somewhat mundane, it's a fairly profound subject.
System identification falls in to two categories - parametric and non-parametric. When using parametric methods, it is implicitly assumed that the system being investigated adheres to a certain model (e.g. first-order plus dead-time, second-order, etc.) - and the task of identification boils down to finding the 'parameters' for that model. Non-parametric methods, in contrast, make no such assumption - they involve analysis of the frequency response of the system instead.