Citation Analysis Method - Solid-State Lighting

To examine emerging science and technology knowledge domains that may someday intersect solid-state lighting, we used a citation analysis method similar to that pioneered by the Institute of Scientific Information (ISI). (For more information, see ISI's in-cites website). The analysis below was conducted in August of 2004 and will be updated periodically.

First, we searched the ISI database for recent technical articles (from January 2002 on) containing key words associated with solid-state lighting. Second, we made a scatter plot of the number of citations* to these articles as a function of publication date. On that plot, we draw a curve that approximates how citations typically accumulate as articles age, scaled so that only the top 1.5% or so of articles lie above the curve. Finally, the articles (circled in blue) that lie above this curve are culled for relevance to solid-state lighting, and the remaining articles are taken to be representative of emerging areas of SSL-related science and technology. The plot is shown here:

For the curve shown, we used the expression: c = 97�(1-exp{-[(2004.68-y)/7]1.25}), where 97 is the scaling factor, 2004.68 is the current date, y is the date the article was published, 7 is an estimate of the 1/e citation accumulation time, and 1.25 is an exponent that accounts roughly for the "lag" in citation accumulation rates at early times.

* ISI citation data used with permission.

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