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At 10:40 AM 5/7/96 -0400, you wrote:
>Steve,
>
>It has been common for me, and more than half of the people who I dive with,
>to do repets on trimix, even on up to three consecutive days.  I have been
>diving mix in the New York area since 1992 at depths ranging from 200fsw to
>290fsw, with surface intervals ranging from 2 to 6 or more hours (although
>we almost always prefer at least three hours). I do not take repets casually
>and I am always more conservative on repets from a table standpoint. I have
>never taken a chamber ride, or seen anyone else take one specifically
>related to making a repet.
>
>In 1994 I dove the Lusitania with the Tapson mob and they were vehemently
>opposed to repet diving on trimix, however, they were comfortable with
>oxygen at pressures higher than 3000 psi (up to 4500 psi), while I and the
>other Americans were not.  It is my opinion that these are two examples of
>differences in cultural perspectives.  If you want to do it, and you can
>figure out how to do it, then do it. Best of luck, mate.
>
>JC
>

John:

We have tried to address this very issue in the latest version of Abyss by
using the RGBM model.


RGBM/ABYSS Implementation

	The Reduced Gradient Bubble Model (RGBM) is a dual phase (dissolved and
free gas) algorithm for diving calculations.  Incorporating and coupling
historical Haldaniean dissolved gas transport with bubble excitation and
growth, the RGBM extends the range of computational applicability of
traditional methods.  The RGBM is correlated with diving and exposure data
on more complete physical principles.  Much is new in the RGBM algorithm,
and troublesome multidiving profiles with higher incidence of DCS are a
target here.  Some highlighted extensions for the ABYSS implementation of
the Buhlmann basic algorithm include:

1. Standard Buhlmainiann nonstop time limits;

2. Restricted repetitive exposures, particularly beyond 100 ft, based on
reduction in permissible bubble diffusion gradients within 2 hr time spans;

3. Restricted yo-yo and spike (multiple ascents and descents) dives based on
excitation of new bubble seeds;

4. Restricted deeper-than-previous divers based on excitation of very small
bubble seeds over 2 hr time spans:

5. Restricted multiday diving based on adaptation and regrowth of new bubble
seeds;

6. Smooth coalescence of bounce and saturation limit points using 32 tissue
compartments;

7. Consistent treatment of altitude diving, with proper zero point
extrapolation of limiting tensions and permissible bubble gradients (through
zero as pressure approaches zero);

8. Algorithm linked to diving data (tests), Doppler bubble, and laboratory
micronuclei experiments;

9. Overall, parameters in RGBM/ABYSS are conservative, but flexible and easy
to change or fit to new data.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Christopher M. Parrett, President
Abysmal Diving Inc. 6595 Odell Place, Suite G. Boulder CO, 80301 USA

Makers of ABYSS, Advanced Dive Planning Software.

Phone: (303) 530-7248 
Fax:   (303) 530-2808

File Transfer Site:  ftp://abysmal.com/users/abysmal 
NEW WWW Site...
World Wide Web Site: http://www.flinet.com/gulfstream/abyss/

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