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Previously, the profiles of laser-drilled holes and laser-produced welds were often considered independently. In this paper, the model used to predict the profile-of-drill, based on the concept of threshold intensity, has been extended to apply to deep-penetration laser welding. The common ground for laser-drilling and -welding, as well as their divergences, are discussed. The present model making use of the laws of Gaussian optics, thus forms the basis of an alternative approach to the prediction of the profile of keyholds and, eventually, the profile of laser-processed welds.

In this paper, a new synthesis method called B-optimal robust regulation is developed. This improves the theory of H ∞ -optimal robust regulation in such a way that the poles of the nominal closed-loop system can be located in a desired region in the left half complex plane which is called nice stability region (Ackerman, 1983) in addition to guaranteeing the robust regulation of the perturbed system. This will improve the dynamic performance of the nominal regulation system in many cases. The synthsis problem is solved by using the theory of H ∞ -optimization, servocompensation and the bilinear transformation of complex plane .

Experimental evidence of light induced drift of sodium atoms in absence of wall adsorption is here reported. The adsorption energy is reduced down to ∼ 0.1 eV by coating the cell with a thin and transparent film of silane which lowers the adsorption time to ∼ 10 -12 s and inhibits the formation of a sodium monolayer. The drift velocity is evaluated to be in agreement with the theoretical calculations.