John Curl's Blowtorch preamplifier part II

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#48,342
Kindhornman said:
JN,
Fairly easy to make a potting compound with a high temp two part epoxy and lab grade aluminum oxide powder. Haven't done it for some time but it does work well.
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Agreed. Fairly easy to mix. The difficulty is in getting the right composition. Too much alumina and the composite will go dry and the TCE will be that of alumina, 6 to 8 ppm/C. Too little, and the thermal conductivity goes down.

From zero percent alumina to some maximum number, the TCE and conductivity will be calculable by the volume ratio of the mix. But once you hit a max, the tce goes to alumina and the conductivity dies.

Over the years I've found it best to let emerson cuming do their job, so I don't have to worry about the next "batch". Every so often, somebody here tries to reinvent the wheel, and I end up getting called in to figure out why it didn't work right.

jn
 
#48,343
DF96 said:
'Random' and 'chaotic' are two quite different behaviours, which may sometimes look superficially similar.
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From Wikipedia:

In common usage, "chaos" means "a state of disorder".[8] However, in chaos theory, the term is defined more precisely. Although there is no universally accepted mathematical definition of chaos, a commonly used definition says that, for a dynamical system to be classified as chaotic, it must have the following properties:[9]

  1. it must be sensitive to initial conditions;
  2. it must be topologically mixing; and
  3. its periodic orbits must be dense.
The requirement for sensitive dependence on initial conditions implies that there is a set of initial conditions of positive measure which do not converge to a cycle of any length.
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To me, the use of the term by jn was in the first sense. If in the 2nd sense then of course Spice has no problems following the behaviour of the system ...
 
#48,346
Which is then down to the particular implementation of Spice, how many bits are used for floating point. Nice thing with computing, is that one can always add more grunt when needed - downside is that results take longer to come out, but this is an issue that steadily improves, year by year ...
 
#48,355
SY said:
Oddly enough, that was exactly how Lorentz was inspired to found the field of non-linear dynamics: rounding errors in the 14th decimal place completely changed the output of his dynamical weather models.
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One of the early IBM super computers got replaced by another brand but they had to go back to the slower IBM because the last few digits - where all the new info is --- wasnt consistant from run to run... it was faster but kept getting very slightly different results.
Each supercomputer generation has to get more accurate and with smaller data to be useful.

THx-RNmarsh
 
#48,357
While all these rounding errors have lead to problems they can all be calculated as to their percentage of error and the probable outcomes. While the results may be chaotic I don't think I could consider them truly equal to chaos where the random events can not be predicted by normal analysis.
 
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