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C o n t r i b u t i n g Editor AT 1l.00ONEMORNlNGIN 1998,ANELDERLY WOMANINOSAKA, Japan, became alarmed. Her 73-year-old husband, who suffers from dementia, had left three hours earlier and not yet returned. She did not panic, but contacted the provider of her personal locator service, Life Service Center.Within aminute, the provider found him on the first floor of a department store, simply by paging a miniature locator device secured to the man's clothes.Thirty minutes later, when the man's son arrived at the department store, his father had already left. Fortunately, the service provider continued tracking the elderly man and was able to direct the son to the third floor of an Osaka hotel. At 12:10 p m . , the two were reunited. Locus Corp. provided the system that made this possible.

Algorithms for estimating the percolation probabilities and cluster size distribution are given in the framework of a Monte Carlo simulation for disordered lattices for the generalized site-bond problem. The site-bond approach is useful when a percolation process cannot be exclusively described in the context of pure site or pure bond percolation. An extended multiple labeling technique (ECMLT) is introduced for the generalized problem. The ECMLT is applied to the site-bond percolation problem for square and triangular lattices. Numerical data are given for lattices containing up to 16 million sites. An application to polymer gelation is suggested.

Monte Carlo simulations for the site percolation problem are presented for lattices up to 64 x 106 sites. We investigate for the square lattice the variablerange percolation problem, where distinct trends with bond-length are found for the critical concentrations and for the critical exponents/~ and 7. We also investigate the layer problem for stacks of square lattices added to approach a simple cubic lattice, yielding critical concentrations as a functional of layer number as well as the correlation length exponent u. We also show that the exciton migration probability for a common type of ternary lattice system can be described by a cluster model and actually provides a cluster generating function.