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This is interesting, as I get the feeling that sometimes stop times are
rounded to the nearest minutes in some apps, not rounded up. Certainly
trying to code some of the algorithms yourself give some insight into what
"programmer decisions" have been made. Let's just hope the coder is also a
diver?
 
= ;)
 
JT

-----Original Message-----
From: John R. Strohm [mailto:strohm@ai*.ne*]
Sent: Thursday, February 28, 2002 12:48 AM
To: CuteEve@ao*.co*; Techdiver@aquanaut.com
Subject: Re: RGBM GF or JF?


You are assuming that decompression is a simple, linear process.
 
It is neither.
 
What is happening is that the approximations of making decompression stops
on 10 ft intervals, and rounding stop times up to multiples of one minute,
are introducing errors into the decompression, errors that must be cleaned
up later.
 
In the case of 200 ft vs. 220 ft: observe that the initial delta is 60 ft in
one case and 80 ft in the other.  All other things being equal, the larger
initial delta will INITIALLY yield faster offgassing, at a higher risk of
bubbling.  Note that the first seven stops are IDENTICAL.  Note also that
the first four stops are NOT long enough to allow the blood to resaturate
throughout the body, and so it is not inconceivable that SOME tissues will
require a little more time to offgas.
 
Try running the two dives side-by-side through a deco program that shows you
EVERYTHING that it is taking into account as it models the dive.  You might
find it interesting.

----- Original Message ----- 
From: CuteEve@ao*.co* <mailto:CuteEve@ao*.co*>  
To: techdiver@aquanaut.com <mailto:techdiver@aquanaut.com>  
Sent: Tuesday, February 26, 2002 11:35 AM
Subject: RGBM GF or JF?

I see so many questions, doubts, and comments on RGBM that I can't help 
putting a big grin on my face. Are we putting our lives on this so-proven 
model on mere faith?
One instructor showed me a scary comparison made, not against other models, 
but on itself. 
Has anyone else compared the deco at different depth, same time or same
depth 
different times? Well, this instructor did. On a mix 16/(20-40) % for a 20 
minute dive:
stop.......220 ft........200 ft
140 ft........1..............1
130...........1..............1
120.............1..............1
110...........1..............1
100...........2..............2
90............2...............2
80............2.................2
70............3...............4
60............4.................4
50............5...............6
40............7.................8
30...........10.............11    
20............5...............6
10...........10.............10
total........54.............59min
So similar deco profiles for both depths yield a longer deco for 200 ft than

for 220 ft!
Give me a break! 
I understand the "official" explanation for this difference was a higher 
degree of "conservatism" due to a higher hit frequency in the shallower 
depths......yeah, sure.
The model is perfect; it's the divers fault they get bent! 

How much higher a conservatism? Why does it happen again with 170 ft and 190

ft where a 15 minute dive gives a 33 minute deco for 170 ft while only 29 
minute deco on the deeper dive? More conservatism or a higher "Jeeezzzuz 
Factor" (JF)?

How do you adjust the JF to dive 170 ft for 15 minutes and do a total 33 
minute deco or rather dive it for 20 minutes because you only do 32 minutes 
deco? You mean a 5 minutes longer stay yields a shorter deco? Yep, it's
right 
there in the Naui book, Tables pp 3, 4 and 5. See for yourself before you 
trust a model with your body. I have seen the outcome.
Heck, I can develop my own deco model. I've got a dart board too!

BTW Christina, the impropriety of using a government e-mail address for 
promoting, selling or private purposes is dealt at a different level. Not 
only is improper and unethical, but illegal. I can e-mail you privately on 
that if interested. That goes for the private commercial use of government 
facilities. But I bet you that at this time, "he is laughing all the way to 
the bank".  What is a simple taxpayer supposed to do? 
QTV
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<DIV><FONT color=#0000ff size=2><SPAN class=830103400-28022002>This is 
interesting, as I get the feeling that sometimes stop times are rounded to the 
nearest minutes in some apps, not rounded up. Certainly trying to code some of 
the algorithms yourself give some insight into what "programmer decisions" have 
been made. Let's just hope the coder is also a
diver?</SPAN></FONT></DIV>
<DIV><FONT color=#0000ff size=2><SPAN 
class=830103400-28022002></SPAN></FONT> </DIV>
<DIV><FONT color=#0000ff size=2><SPAN class=830103400-28022002>= 
;)</SPAN></FONT></DIV>
<DIV><FONT color=#0000ff size=2><SPAN 
class=830103400-28022002></SPAN></FONT> </DIV>
<DIV><FONT color=#0000ff size=2><SPAN 
class=830103400-28022002>JT</SPAN></FONT></DIV>
<BLOCKQUOTE style="MARGIN-RIGHT: 0px">
  <DIV align=left class=OutlookMessageHeader dir=ltr><FONT face=Tahoma 
  size=2>-----Original Message-----<BR><B>From:</B> John R. Strohm 
  [mailto:strohm@ai*.ne*]<BR><B>Sent:</B> Thursday, February 28, 2002
12:48 
  AM<BR><B>To:</B> CuteEve@ao*.co*;
Techdiver@aquanaut.com<BR><B>Subject:</B> 
  Re: RGBM GF or JF?<BR><BR></DIV></FONT>
  <DIV><FONT face=Arial size=2>You are assuming that decompression is a
simple, 
  linear process.</FONT></DIV>
  <DIV><FONT face=Arial size=2></FONT> </DIV>
  <DIV><FONT face=Arial size=2>It is neither.</FONT></DIV>
  <DIV><FONT face=Arial size=2></FONT> </DIV>
  <DIV><FONT face=Arial size=2>What is happening is that the
approximations of 
  making decompression stops on 10 ft intervals, and rounding stop times up to 
  multiples of one minute, are introducing errors into the decompression,
errors 
  that must be cleaned up later.</FONT></DIV>
  <DIV><FONT face=Arial size=2></FONT> </DIV>
  <DIV><FONT face=Arial size=2>In the case of 200 ft vs. 220 ft: observe
that 
  the initial delta is 60 ft in one case and 80 ft in the other.  All
other 
  things being equal, the larger initial delta will INITIALLY yield faster 
  offgassing, at a higher risk of bubbling.  Note that the first seven 
  stops are IDENTICAL.  Note also that the first four stops are NOT long 
  enough to allow the blood to resaturate throughout the body, and so it is not 
  inconceivable that SOME tissues will require a little more time to 
  offgas.</FONT></DIV>
  <DIV><FONT face=Arial size=2></FONT> </DIV>
  <DIV><FONT face=Arial size=2>Try running the two dives side-by-side
through a 
  deco program that shows you EVERYTHING that it is taking into account as it 
  models the dive.  You might find it interesting.</FONT></DIV>
  <BLOCKQUOTE 
  style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px;
PADDING-LEFT: 5px; PADDING-RIGHT: 0px">
    <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
    <DIV 
    style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color:
black"><B>From:</B> 
    <A href="mailto:CuteEve@ao*.co*"
title=CuteEve@ao*.co*>CuteEve@aol.com</A> 
    </DIV>
    <DIV style="FONT: 10pt arial"><B>To:</B> <A 
    href="mailto:techdiver@aquanaut.com" 
    title=techdiver@aquanaut.com>techdiver@aquanaut.com</A> </DIV>
    <DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, February 26,
2002 11:35 
    AM</DIV>
    <DIV style="FONT: 10pt arial"><B>Subject:</B> RGBM GF or
JF?</DIV>
    <DIV><BR></DIV>I see so many questions, doubts, and comments on
RGBM that I 
    can't help <BR>putting a big grin on my face. Are we putting our lives
on 
    this so-proven <BR>model on mere faith?<BR>One instructor showed me a
scary 
    comparison made, not against other models, <BR>but on itself. <BR>Has
anyone 
    else compared the deco at different depth, same time or same depth 
    <BR>different times? Well, this instructor did. On a mix 16/(20-40) %
for a 
    20 <BR>minute dive:<BR>stop.......220 ft........200 ft<BR>140 
   
ft........1..............1<BR>130...........1..............1<BR>120.......
......1..............1<BR>110...........1..............1<BR>100...........
2..............2<BR>90............2...............2<BR>80............2....
.............2<BR>70............3...............4<BR>60............4......
...........4<BR>50............5...............6<BR>40............7........
.........8<BR>30...........10.............11    
   
<BR>20............5...............6<BR>10...........10.............10<B
R>total........54.............59min<BR>So 
    similar deco profiles for both depths yield a longer deco for 200 ft than 
    <BR>for 220 ft!<BR>Give me a break! <BR>I understand the
"official" 
    explanation for this difference was a higher <BR>degree of
"conservatism" 
    due to a higher hit frequency in the shallower <BR>depths......yeah, 
    sure.<BR>The model is perfect; it's the divers fault they get bent! 
    <BR><BR>How much higher a conservatism? Why does it happen again with
170 ft 
    and 190 <BR>ft where a 15 minute dive gives a 33 minute deco for 170 ft 
    while only 29 <BR>minute deco on the deeper dive? More conservatism or a 
    higher "Jeeezzzuz <BR>Factor" (JF)?<BR><BR>How do you adjust the
JF to dive 
    170 ft for 15 minutes and do a total 33 <BR>minute deco or rather dive
it 
    for 20 minutes because you only do 32 minutes <BR>deco? You mean a 5
minutes 
    longer stay yields a shorter deco? Yep, it's right <BR>there in the Naui 
    book, Tables pp 3, 4 and 5. See for yourself before you <BR>trust a
model 
    with your body. I have seen the outcome.<BR>Heck, I can develop my own
deco 
    model. I've got a dart board too!<BR><BR>BTW Christina, the
impropriety of 
    using a government e-mail address for <BR>promoting, selling or private 
    purposes is dealt at a different level. Not <BR>only is improper and 
    unethical, but illegal. I can e-mail you privately on <BR>that if 
    interested. That goes for the private commercial use of government 
    <BR>facilities. But I bet you that at this time, "he is laughing all the
way 
    to <BR>the bank".  What is a simple taxpayer supposed to do? 
    <BR>QTV<BR>--<BR>Send mail for the `techdiver' mailing list to
<A 
   
href="mailto:`techdiver@aquanaut.com'">`techdiver@aquanaut.com'</A>.<BR>Se
nd 
    subscribe/unsubscribe requests to <A 
   
href="mailto:`techdiver-request@aquanaut.com'">`techdiver-request@aquanaut.com'&
lt;/A>.</BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>

<P>This message is for the named person's use only. It may contain sensitive
and private proprietary or legally privileged information. No confidentiality
or privilege is waived or lost by any mistransmission. If you are not the
intended recipient, please immediately delete it and all copies of it from your
system, destroy any hard copies of it and notify the sender. You must not,
directly or indirectly, use, disclose, distribute, print, or copy any part of
this message if you are not the intended recipient. CREDIT SUISSE GROUP and
each legal entity in the CREDIT SUISSE FIRST BOSTON or CREDIT SUISSE ASSET
MANAGEMENT business units of CREDIT SUISSE FIRST BOSTON reserve the right to
monitor all e-mail communications through its networks. Any views expressed in
this message are those of the individual sender, except where the message
states otherwise and the sender is authorized to state them to be the views of
any such entity.<br>
Unless otherwise stated, any pricing information given in this message is
indicative  only, is subject to change and does not constitute an offer to deal
at any price quoted. Any reference to the terms of executed transactions should
be treated as  preliminary only and subject to our formal written
confirmation.<br>
<br>
</P>
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