[time-nuts] simulation of interconnected clocks

paul.alfille paul.alfille at gmail.com
Sun Dec 1 07:36:02 EST 2013


Heart rate depends on a feedback circuit through the autonomic nervous system. Microvascular disease (diabetes), denervation (heart transplant), and drugs can all alter the variabilility.

There actaully is a large literatuee in fetal heart rate variability used to diagnoses fetal distress and precipirate energent cesarian section.


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-------- Original message --------
From: Jim Lux <jimlux at earthlink.net> 
Date: 11/30/2013  6:41 PM  (GMT-05:00) 
To: time-nuts at febo.com 
Subject: Re: [time-nuts] simulation of interconnected clocks 
 
On 11/30/13 2:15 PM, Tom Van Baak wrote:
> Jim,
>
> Could you just replay real data instead of trying to generate
> simulated data? There's plenty of storage with Arduino or SD card
> shields.
>
> Attached is frequency and ADEV of my heart beat for 10 hours. You
> could do the same. In this case the flicker floor is just under 1e-1
> from 10s to 10ks.
>
>
One could do that. Or in a limited sense, have a shorter table which you 
play back repetitively. If you did some processing on your heartbeat 
data to remove the sinusoidal modulation from respiration, you might 
find the ADEV/phase noise is less.  That's something I'm looking into.



In my case, I need to be able to generate multiple different realistic 
targets.  I could probably record a bunch of sequences and then play 
back different pieces of them.  or use one person and have them breathe 
at different rates and depths.

But an algorithmic approach is interesting.  And even more interesting 
is being able to generate a particular pattern (using the model), and 
see if you can retrieve the model parameters using the device.


Here's where I'm using it:
http://www.jpl.nasa.gov/news/news.php?release=2013-281
http://www.jpl.nasa.gov/news/news.php?release=2013-290
http://www.jpl.nasa.gov/video/?id=1252


We use the model parameters to distinguish targets from one another (and 
targets from bystanders and the operator); and also to separate humans 
from other targets (oddly enough, that slowly rotating fan, or swinging 
grandfather clock pendulum have much lower 1/f noise than your heart).

One finds as you delve into the physiology literature that they have 
exceedingly different ways to measure, describe, and model things than 
engineers do.  In some cases it's because they're working from the 
biological structures that make it happen. In others, it's just because 
historically it's been described differently: often with reference to 
particular methods of recording the signal.



It's kind of like how the Richter scale is in terms of the height of the 
trace in mm on a particular kind of seismograph.  Someone goes out and 
records ECG data and they write the paper and say "data was recorded 
using a Grass model X with the filter set at position 3", and since 
everyone in that field of research uses the same machines, they all know 
how it was recorded, and can duplicate it if needed.  The signal 
processing details of the Grass Model X with filter set at Position 3 
might be left as an exercise for the reader (or a letter to Al Grass at 
the Grass Instrument Company). The same thing happens in the nuclear 
instrumentation area, where everything is in terms of pulses and time 
domain processing, and you refer to a particular model of Ortec pre-amp, 
feeding some other model discriminator, finally feeding your 
multichannel analyzer (which name confused me, since it has only one 
input channel).


The other thing is that a until recently, computers weren't used to 
analyze the data, so the analytical methods tend to favor those that are 
paper, pencil, and slide rule tractable. There's a lot of log/log plots 
with visually placed curve fits, with not a huge number of test subjects 
(20 subjects would be a lot in most of these papers).

Finally, there might be a historical reason why decent math models 
aren't popular:  The grand man of physiology was Carl Ludwig in Leipzig: 
he had hundreds of postgraduate students (Pavlov was one), but 
apparently "he had little use for mathematical treatment of biological 
problems". Ludwig wrote the 1847 paper everyone cites as the beginning: 
"Beitraege zur Kenntniss des Einflusses der Respirations bewegungen auf 
den Blutlauf im Aortensysteme".  But hey, if your supervisor says math 
models aren't important, you're sure not going to argue with him, and 
someone of distinctly math modeling bent would likely find another place 
to study or field of study.  So Ludwig casts a long shadow on published 
research, probably for 2 or 3 generations.


Thanks to the miracle of the internet and big efforts to scan stuff this 
kind of thing is readily available.  It's come a long ways since I had 
to hunt down a copy of Paschen's paper/thesis on high voltage breakdown 
as an actual printed copy and then photocopy it.



http://archive.org/stream/beitrgezurkenn00hein#page/n55/mode/2up has 
some examples of data collected later in the 19th century from dogs and 
cats.



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