His name is spelled "Bohrer". sometimes with an umlaut over the o.
If you need to get in touch with him, go through IANTD.
I'd been to the IANTD site without success. I'll go again. In the meantime a Web Search using the correct spelling of his name, Thank You, gave me something of what I am after. Here is what I copied from one site:
Antwort Randy Bohrer]
The story of the algorithm development is fairly simple. There are two
Buhlmann algorithms, the ZHL-12 and ZHL-16. Most believe that the -12
or -16 refers to the number of compartments. It actually refers to the
number of a, b value (similar to M values) sets that the algorithm
has. Both are 16 compartment algorithms. ZHL-16 is the newer
algorithm. What is unique about it is that it is possible to calculate
the a,b values based on the half-life time. Then you can develop your
own algorithm with as many compartments as you like. Of course,
selecting half-times that are far beyond what has been done with
Haldanean type models (for example something in excess of 800
minutes for nitrogen) would probably not be valid.
So, the question becomes, which algorithm did we use for the
Seiko-made units. The answer is ZHL-12 (the older model) with some
custom modifications. The reason for that is that the ZHL-16 model
produced NDLs that were very different from what dive computer users
had come to expect. They were too short. We knew from the wide range
of practical experience that the NDLs from popular dive computers were
"safe", meaning they produced numbers that did not result in an
unacceptable number of cases of DCS (DCI). We found that the older
model, without modification, produced both NDLs and decompression stop
times that were similar to other units already on the market.
We wanted to build in some extra conservatism in areas where there was
traditionally an increased risk of DCS, so we looked at modifying the
model. The two primary modifications were to freeze the gas loading
calculations during the first 10 minutes of a surface interval, and to
add a depth safety factor for repetitive dives. The gas loading
"freeze" penalized the diver for short surface intervals, but as the
surface interval became 2-3 hours or more, the safety factor had
little effect -- just what we wanted. The depth safety factor
penalized the diver for repetitive shallow dives, again affecting
primarily the NDLs (the bottom time of 40-50 foot dives doesn't
usually require decompression stops). The depth safety factor had
little effect on deep dives (say 80 feet and deeper), where
decompression stops would sometimes be required. The base ZHL-12 model
has very good dive test results as well as practical field results, so
we didn't feel a need to integrate safety factors that had much effect
on decompression dives. The final modification was to select half
times that would simplify the gas loading calculations. Because the
particular half times we selected were not the same as the base model,
we interpolated to determine the a, b values. On later models, we
added oxygen tolerance calculations non-air diving applications.
---------------------------------------------------------------------------
This kind of description is at what I call the Black Box level and is most useful to users. Since DCS is a relatively rare phenomenon and almost all available algorithms are "safe" what we are most interested in is just how the algorithm affects dive planning.
