Patent ID: 7496483

Claim:
A method comprising: generating a plurality of time-varying thresholds T(t) i , wherein i=1, n, wherein each said time-varying threshold is a candidate for signaling an occurrence of an event of type E, wherein said event of type E is an attack selected from the group consisting of a chemical attack, a biological attack, a radiological attack, and a nuclear attack; evaluating a penalty function for each of said time-varying thresholds T(t) i over a time interval, wherein said penalty function is based on: (i) a time-varying signal B(t) that is based on a level of an environmental characteristic in the absence of an event of type E, (ii) a time-varying signal A(t) that is based on a level of said environmental characteristic in the presence of an event of type E, and (iii) said time-varying threshold T(t) i ; and selecting a best time-varying threshold using said penalty function, wherein the best time-varying threshold is used to signal the occurrence of the event of type E.