[Covid] Extended SIR Models
From:
andrew cooke <andrew@...>
Date:
Thu, 1 Jun 2023 22:09:34 -0400
I just went to see a talk on mathematical modelling of pandemics. It
was largely a rehash of the SIR model along with simulations (although
I got lost near the end, so may have missed what was new).
Anyway, I got to thinking, and really it seems like the SIR approach
really misses the heart of the poblem. I mean, we know that if
everyone isolates then infection rates will drop. It's fucking
obvious. The reason why it's controversial to actually put that into
practice is because there's a large collective cost.
When you see the word "collective" you start to look at the SIR model
and think how "free market" it is. Lots of independent little people
all doing their own thing.
So I started wondering how you could extend it to include social cost.
The simplest solution I can see is to have a global state that
represents "common good" that is incremented on every interaction,
but that decays over time.
In addition, it seems that you need to add some kind of consequence
for this good becoming lower. The simplest I could think of was that
you randomly kill individuals (so this would need to be SIR + births
and deaths I guess) at a rate connected to how low that gets.
I imagine that if you ran this then for most reasonable death
probability functions you get little happeninn until some threshold,
and then collapse.
So maybe it wouldn't be very interesting.
One extension might be to have two groups (in the same overall
population) with different functions / probabilities (eg rich and
poor). Maybe that would show something more interesting.
Has anything like this been done?
Andrew
Permalink
|
Comment on this post
Previous Entries
For comments, see relevant pages (permalinks).
[Art] York-based Printmaker
From:
andrew cooke <andrew@...>
Date:
Sat, 29 Apr 2023 08:28:49 -0400
https://thecuriousprintmaker.co.uk/
Near home - must visit next time I am back.
Lots of practical (and beautiful) advice in the blog.
Andrew
Permalink
Rummikub Solver
From:
andrew cooke <andrew@...>
Date:
Thu, 12 Jan 2023 16:48:36 -0300
I have been working on a solver for Rummikub, but I haven't actually
made much progress. This email is to note down some of my ideas and
related issues.
The underlying insight is that this is a graph colouring problem. The
nodes of the graph are the known tiles. Edges connect any two tiles
that can appear "next to each other" in a group. The colouring
identifies each group (a successful colouring meets the appropriate
rules).
There may be an efficiency gain in using the previous colouring as a
starting point when searching for a new one.
This is fine as far as it goes. It becomes more problematic when you
include jokers.
A naive first approach is to include the jokers as additional nodes.
The problem is that these are connected to *every* other node. This
complicates hugely the search process when trying t find a colouring.
In practice, when you play, you tend to separate things into two
stages: first, liberating a joker and second, using that joker.
Using this approach the joker tiles become "normal" tiles in the graph
(ie take their assumed values) when searching for liberation. Then,
in the next step, thereare many possible graphs (one for each possible
value of the joker).
I currently don't see how to handle this explosion in the number of
graphs.
So I'm stuck. It seems like the colouring view doesn't reduce the
combinatorial complexity sufficiently. Or doesn't allow for the
complexity to be reduced using a "natural" compromise.
Andrew
Permalink
[Bike] Fixing Spyre Brakes (That Need Constant Adjustment)
From:
andrew cooke <andrew@...>
Date:
Wed, 1 Jun 2022 19:09:58 -0400
I have sme Spyre brakes and they're great - work well and are easy to
maintain. But recently (after a couple of years use) I found that one
pad would slowly move further from the disk and, every few rides, need
adjusting (tightening).
This is something I have heard others complain about, too.
Fortunately there is an easy fix.
I did this by removing the caliper from the bike, but with care I
think you could do it leaving the caliper in place (but with the wheel
removed).
Here's what I did:
- Remove the pads
- Screw the 3mm adjustment on the side of the problem pad inwards
(as you would to move the pad closer to the disk). Keep screwing
and something will eventually fall out!
- The thing that falls out (the thing that pushes the pads against
the disk) is like a short screw with a very flat head. Clean it
with a rag and put a decent amount of blue locktite on the threads
(the stuff that stops things from coming loose, but leaves them
still able to be adjusted by hand).
- Once the loctite is fairly dry you need to screw that part back
in. This is a bit tricky (and more tricky still if you've not
removed the calipers from the bike). What you need to do is put
the screw inside the caliper, with the threaded part pointing
towards where you adjust from the inside (a ruler, screwdriver, or
lollipop stick will help). Once you get everything lined up you
can use the 3mm allen key from outside and "skewer" the screw,
then, by turning anti-clockwise, screw it back into place.
Basically, you're doing the opposite of what you did to make it
fall out.
- Once in place leave for, say, 12 hours to allow the loctite to
set.
- And don't forget to replace the pads and adjust before riding.
After all that you'll find that the adjustment is much "stiffer" and
desn't come loose. I have no idea how long it lasts because I only
did it myself a few days ago.
Andrew
Permalink
[Computing, Music] Raspberry Pi Media (Audio) Streamer
From:
andrew cooke <andrew@...>
Date:
Sat, 7 May 2022 17:36:36 -0400
I have a Raspberry Pi that I want to take music from a HDD and send it
to a USB DAC. I want to be able to control this remotely from my
phone. It should look good and "just work".
I have tried a pile of things in the last week. The best (by far) has
been volumio. After flashing the image and booting you may need to
enable ssh (via http://address.of.volumio/dev) and then you can modify
fstab and mount the music at /mnt/INTERNAL
You can also modify
/volumio/app/plugins/music_service/mpd/mpd.conf.tmpl to enable
replaygain (and then save settigns from the gui to regenerate
/etc/mpd.conf).
Various other things learnt:
- mopidy is an MPD rewrite in Python (ish). Unfortunately it's not
super-well supported and the clients are buggy (even when you
finally understand what it is and that you need to install
mopidy-local). The MPD plugin doesn't make much sense.
- MPD clients for android are not great. MpDroid seems to be no
longer maintained and MALP is flakey.
- I tried moode a while back and that was OK (but volumio seems more
responsive and easier to use).
Andrew
Permalink