The holmium laser, which operates in a wavelength of 2.1 microns, is highly absorbed by water and has a shallow penetration depth of approximately 0.4 mm. As a pulsed mode laser, the Holmium reduces deeper thermal effects and charring which are more prevalent in Continues Wave lasers (e.g. Thulium, KTP).
In statistical theory, covariance is a measure of how much two random variables change together. In other words, covariance is a measure of the strength of the correlation between two random variables. Also, it can be considered as a generalization of the concept of variance of two random variables.
yn. For two random variables x and y having means E{ x } and E{ y }, the covariance is defined as: Cov(x, y) = E{[ x-E(x) ][ y-E(y) ]}. The covariance calculation begins with pairs of x and y, takes their differences from their mean values and multiplies these differences together.