Apparatus, systems, and methods may operate to generate a reference statistical model of an operating system, such as a computer system, and display the reference statistical model as a hierarchical, segmented time series event stream graph, along with a graph representing current behavior of the system. The display panel includes a touch surface. A doppler sensor distinguishes between threatening and nonthreatening projectiles by measuring the projectile’s velocity. Further, the sensor has a temperature coefficient of resistivity of at least 0.