Discussion:
Fundamentals of feedback control
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islander
2020-07-20 14:51:41 UTC
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Why is testing so important and why are delays in obtaining test results
dangerous?

Any student of engineering is familiar with classic feedback control and
how systems can and do become unstable if the time constant of the
control loop becomes longer than the ability of the system to respond.

We can see a dramatic example of that in the attempts to control the
corona virus with testing that cannot produce results quickly enough to
help to control it.

Basically, the virus is propagating much more rapidly than we are able
to monitor it. Why is this a problem? By the time results become
available, now 5-7 days in some states, the virus has moved on to infect
more people. Contact tracing, becomes much more difficult as contacts
become more diffuse with the rapid spread of the virus, making the
results of the testing useless and even counter productive. Why?
Because feedback control systems become unstable when the time constant
of the feedback loop exceeds the response time of the system. You end
up making changes to the system after it has moved on to a new state.

While we hear a lot about the need for more testing, we also desperately
need rapid feedback and the large commercial labs appear to be
overwhelmed in the face of rapidly growing infection rates.
b***@gmail.com
2020-07-21 00:40:02 UTC
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45% of deaths due to the virus occur in nursing homes and there are 1.4 million in the US living in these homes. You can do the math to see what your chances are living in one of these places. Great attention needs to focus on this problem.
(David P.)
2020-07-21 21:46:06 UTC
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Post by b***@gmail.com
45% of deaths due to the virus occur in nursing homes and there are 1.4 million in the US living in these homes. You can do the math to see what your chances are living in one of these places. Great attention needs to focus on this problem.
The ecologists said 50 years ago that we were overpopulated
with 4 billion worldwide. Why didn't our parents listen
to THOSE scientists? There are 5.8 million in the U.S.
with Alzheimer's dementia. Why do they need to be hangin'
around & don't even know what's happening?
b***@gmail.com
2020-07-22 00:19:01 UTC
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The world population of 7.8 billion can all fit into the State of Texas with about the same density of NYC. Works out to about 30,000 per square mile.
(David P.)
2020-07-22 04:15:42 UTC
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Post by b***@gmail.com
The world population of 7.8 billion can all fit into the State of Texas with about the same density of NYC. Works out to about 30,000 per square mile.
What else do we need besides space?
b***@gmail.com
2020-07-22 08:38:39 UTC
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Other than space, maybe efficiency can be improved?

About 40% of our food supply in the US is thrown away.

What can we do about that?
(David P.)
2020-07-23 01:19:56 UTC
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Post by b***@gmail.com
The world population of 7.8 billion can all fit into the State of Texas with about the same density of NYC. Works out to about 30,000 per square mile.
How many people want to live in the same density as NYC?

islander
2020-07-21 23:40:00 UTC
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Post by b***@gmail.com
45% of deaths due to the virus occur in nursing homes and there are 1.4 million in the US living in these homes. You can do the math to see what your chances are living in one of these places. Great attention needs to focus on this problem.
Not just nursing homes, but a variety of senior assisted living
facilities. Many of these are like boarding houses for seniors with
minimal medical care, but communal dining and activities. They are a
natural breeding ground for contagion. What can be done other than
isolating seniors in their rooms? I agree that it is a very serious
problem with few solutions in sight.

I had been considering one of them, but the best contender has had two
deaths due to the virus. I'm better off in my home.
El Castor
2020-07-22 06:16:47 UTC
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Post by islander
Post by b***@gmail.com
45% of deaths due to the virus occur in nursing homes and there are 1.4 million in the US living in these homes. You can do the math to see what your chances are living in one of these places. Great attention needs to focus on this problem.
Not just nursing homes, but a variety of senior assisted living
facilities. Many of these are like boarding houses for seniors with
minimal medical care, but communal dining and activities. They are a
natural breeding ground for contagion. What can be done other than
isolating seniors in their rooms? I agree that it is a very serious
problem with few solutions in sight.
I had been considering one of them, but the best contender has had two
deaths due to the virus. I'm better off in my home.
The virus can't be brought under control until there is a vaccine, and
that issue is receiving an unprecedented degree of attention.
Twenty-three are in human trials and more than 130 are in pre-clinical
studies. China approved the use of its vaccine in the military in late
June. The US has invested $1.2 billion in an Oxford vaccine which is
showing promise in human trials, and "may" have 300 million doses for
use in the US as early as October.
https://www.washingtonpost.com/world/europe/oxford-coronavirus-vaccine-phase-1-lancet/2020/07/20/12fbbc92-c857-11ea-a825-8722004e4150_story.html
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31604-4/fulltext
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31605-6/fulltext

Speaking of retirement communities, A friend of a friend owns a one
bedroom unit in the Tamalpais Marin.
Loading Image...
We've visited her (pre Covid) and it seems nice, but I couldn't
conceive of living in a place like that while this thing is out of
control.
islander
2020-07-22 14:56:19 UTC
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Post by El Castor
Post by islander
Post by b***@gmail.com
45% of deaths due to the virus occur in nursing homes and there are 1.4 million in the US living in these homes. You can do the math to see what your chances are living in one of these places. Great attention needs to focus on this problem.
Not just nursing homes, but a variety of senior assisted living
facilities. Many of these are like boarding houses for seniors with
minimal medical care, but communal dining and activities. They are a
natural breeding ground for contagion. What can be done other than
isolating seniors in their rooms? I agree that it is a very serious
problem with few solutions in sight.
I had been considering one of them, but the best contender has had two
deaths due to the virus. I'm better off in my home.
The virus can't be brought under control until there is a vaccine, and
that issue is receiving an unprecedented degree of attention.
Twenty-three are in human trials and more than 130 are in pre-clinical
studies. China approved the use of its vaccine in the military in late
June. The US has invested $1.2 billion in an Oxford vaccine which is
showing promise in human trials, and "may" have 300 million doses for
use in the US as early as October.
https://www.washingtonpost.com/world/europe/oxford-coronavirus-vaccine-phase-1-lancet/2020/07/20/12fbbc92-c857-11ea-a825-8722004e4150_story.html
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31604-4/fulltext
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31605-6/fulltext
Speaking of retirement communities, A friend of a friend owns a one
bedroom unit in the Tamalpais Marin.
https://kelleyeling.files.wordpress.com/2011/03/009.jpg?w=833
We've visited her (pre Covid) and it seems nice, but I couldn't
conceive of living in a place like that while this thing is out of
control.
We are pretty fortunate to be living were we are as long as we can avoid
any serious medical problems. Groceries and utilities are our primary
expenses, but otherwise our costs are minimal. Nice to not need to
spend money on transportation - a tank of gasoline lasts us for months!

I see that Marin is now its own little hot spot for the virus and is
fining people for refusing to obey safety measures. Perhaps you can get
Trump's brownshirts to help enforce this.

Here, our Sheriff's department has given up on enforcing safety measures
and public sentiment seems to be to discourage tourism. Seems to be
working. I went into town yesterday to pick up a prescription and the
town is nearly deserted. With two of our three council members up for
election this fall, the incumbents are keeping their heads down and have
reversed a previous decision to open up the economy. Maybe they are
beginning to realize that tourism is not the golden goose that they
thought it was!
El Castor
2020-07-22 18:20:01 UTC
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Post by islander
Post by El Castor
Post by islander
Post by b***@gmail.com
45% of deaths due to the virus occur in nursing homes and there are 1.4 million in the US living in these homes. You can do the math to see what your chances are living in one of these places. Great attention needs to focus on this problem.
Not just nursing homes, but a variety of senior assisted living
facilities. Many of these are like boarding houses for seniors with
minimal medical care, but communal dining and activities. They are a
natural breeding ground for contagion. What can be done other than
isolating seniors in their rooms? I agree that it is a very serious
problem with few solutions in sight.
I had been considering one of them, but the best contender has had two
deaths due to the virus. I'm better off in my home.
The virus can't be brought under control until there is a vaccine, and
that issue is receiving an unprecedented degree of attention.
Twenty-three are in human trials and more than 130 are in pre-clinical
studies. China approved the use of its vaccine in the military in late
June. The US has invested $1.2 billion in an Oxford vaccine which is
showing promise in human trials, and "may" have 300 million doses for
use in the US as early as October.
https://www.washingtonpost.com/world/europe/oxford-coronavirus-vaccine-phase-1-lancet/2020/07/20/12fbbc92-c857-11ea-a825-8722004e4150_story.html
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31604-4/fulltext
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31605-6/fulltext
Speaking of retirement communities, A friend of a friend owns a one
bedroom unit in the Tamalpais Marin.
https://kelleyeling.files.wordpress.com/2011/03/009.jpg?w=833
We've visited her (pre Covid) and it seems nice, but I couldn't
conceive of living in a place like that while this thing is out of
control.
We are pretty fortunate to be living were we are as long as we can avoid
any serious medical problems. Groceries and utilities are our primary
expenses, but otherwise our costs are minimal. Nice to not need to
spend money on transportation - a tank of gasoline lasts us for months!
I see that Marin is now its own little hot spot for the virus and is
fining people for refusing to obey safety measures. Perhaps you can get
Trump's brownshirts to help enforce this.
I'm not aware of anyone being fired -- for any reason, at Marin, and I
haven't seen any evidence of the police or sheriff even trying to
enforce anything. The only stores that are open are the ones
considered essential -- supermarkets and drugs. Everyone wears masks
while shopping and employees are typically masked and behind glass
(Plexiglas) panels. Coffee shops and most restaurants are open in the
sense that they are take out only -- no seating other than outside
tables in some cases. Muir Woods has opened up with the usual reserved
parking and masks required. There may be a few on Stinson Beach, but I
wouldn't know. We've had a cold windy summer -- not exactly beach
weather. I have read about problems in the East Bay's more heavily
minority areas. Customers refusing to wear masks and threatening or
attacking employees who complain.

The surprising thing is traffic. 101 is about 75% normal, which I find
hard to understand.
Post by islander
Here, our Sheriff's department has given up on enforcing safety measures
and public sentiment seems to be to discourage tourism. Seems to be
working. I went into town yesterday to pick up a prescription and the
town is nearly deserted. With two of our three council members up for
election this fall, the incumbents are keeping their heads down and have
reversed a previous decision to open up the economy. Maybe they are
beginning to realize that tourism is not the golden goose that they
thought it was!
El Castor
2020-07-22 20:41:23 UTC
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On Wed, 22 Jul 2020 11:20:01 -0700, El Castor
Post by El Castor
Post by islander
Post by El Castor
Post by islander
Post by b***@gmail.com
45% of deaths due to the virus occur in nursing homes and there are 1.4 million in the US living in these homes. You can do the math to see what your chances are living in one of these places. Great attention needs to focus on this problem.
Not just nursing homes, but a variety of senior assisted living
facilities. Many of these are like boarding houses for seniors with
minimal medical care, but communal dining and activities. They are a
natural breeding ground for contagion. What can be done other than
isolating seniors in their rooms? I agree that it is a very serious
problem with few solutions in sight.
I had been considering one of them, but the best contender has had two
deaths due to the virus. I'm better off in my home.
The virus can't be brought under control until there is a vaccine, and
that issue is receiving an unprecedented degree of attention.
Twenty-three are in human trials and more than 130 are in pre-clinical
studies. China approved the use of its vaccine in the military in late
June. The US has invested $1.2 billion in an Oxford vaccine which is
showing promise in human trials, and "may" have 300 million doses for
use in the US as early as October.
https://www.washingtonpost.com/world/europe/oxford-coronavirus-vaccine-phase-1-lancet/2020/07/20/12fbbc92-c857-11ea-a825-8722004e4150_story.html
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31604-4/fulltext
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31605-6/fulltext
Speaking of retirement communities, A friend of a friend owns a one
bedroom unit in the Tamalpais Marin.
https://kelleyeling.files.wordpress.com/2011/03/009.jpg?w=833
We've visited her (pre Covid) and it seems nice, but I couldn't
conceive of living in a place like that while this thing is out of
control.
We are pretty fortunate to be living were we are as long as we can avoid
any serious medical problems. Groceries and utilities are our primary
expenses, but otherwise our costs are minimal. Nice to not need to
spend money on transportation - a tank of gasoline lasts us for months!
I see that Marin is now its own little hot spot for the virus and is
fining people for refusing to obey safety measures. Perhaps you can get
Trump's brownshirts to help enforce this.
I'm not aware of anyone being fired -- for any reason, at Marin, and I
haven't seen any evidence of the police or sheriff even trying to
enforce anything. The only stores that are open are the ones
considered essential -- supermarkets and drugs. Everyone wears masks
while shopping and employees are typically masked and behind glass
(Plexiglas) panels. Coffee shops and most restaurants are open in the
sense that they are take out only -- no seating other than outside
tables in some cases. Muir Woods has opened up with the usual reserved
parking and masks required. There may be a few on Stinson Beach, but I
wouldn't know. We've had a cold windy summer -- not exactly beach
weather. I have read about problems in the East Bay's more heavily
minority areas. Customers refusing to wear masks and threatening or
attacking employees who complain.
The surprising thing is traffic. 101 is about 75% normal, which I find
hard to understand.
Post by islander
Here, our Sheriff's department has given up on enforcing safety measures
and public sentiment seems to be to discourage tourism. Seems to be
working. I went into town yesterday to pick up a prescription and the
town is nearly deserted. With two of our three council members up for
election this fall, the incumbents are keeping their heads down and have
reversed a previous decision to open up the economy. Maybe they are
beginning to realize that tourism is not the golden goose that they
thought it was!
Oops, I misread your post as firing, not fining. Haven't heard about
any fining in Marin either, but I see that the supes are considering
it. Interesting.
b***@gmail.com
2020-07-23 01:14:27 UTC
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Nice to not need to spend money on transportation.>
I'm riding busses nowadays since I lost my driver's license. The buss fare is free since the driver doesn't want to touch any money. I spend about 4 hours doing grocery shopping, riding the buss and walking with my walker. Sometimes I consider driving with no license but haven't done it yet. I figure I need the exercise. But I need help getting on and off the buss when carrying 4 bags of groceries.
me
2020-07-21 12:15:53 UTC
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We need smart coronavirus testing, not just more testing
https://www.statnews.com/2020/03/24/we-need-smart-coronavirus-testing-not-just-more-testing/
Johnny
2020-07-21 21:25:42 UTC
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On Mon, 20 Jul 2020 07:51:41 -0700
Post by islander
Why is testing so important and why are delays in obtaining test
results dangerous?
Any student of engineering is familiar with classic feedback control
and how systems can and do become unstable if the time constant of
the control loop becomes longer than the ability of the system to
respond.
We can see a dramatic example of that in the attempts to control the
corona virus with testing that cannot produce results quickly enough
to help to control it.
Basically, the virus is propagating much more rapidly than we are
able to monitor it. Why is this a problem? By the time results
become available, now 5-7 days in some states, the virus has moved on
to infect more people. Contact tracing, becomes much more difficult
as contacts become more diffuse with the rapid spread of the virus,
making the results of the testing useless and even counter
productive. Why? Because feedback control systems become unstable
when the time constant of the feedback loop exceeds the response time
of the system. You end up making changes to the system after it has
moved on to a new state.
While we hear a lot about the need for more testing, we also
desperately need rapid feedback and the large commercial labs appear
to be overwhelmed in the face of rapidly growing infection rates.
I just heard on the news, if you don't have symptoms of the virus,
don't get tested.

That doesn't make any sense to me.
me
2020-07-21 21:51:14 UTC
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It’s probably a cost thing. Limited resources require prioritizing.
Josh Rosenbluth
2020-07-21 22:30:56 UTC
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Post by Johnny
On Mon, 20 Jul 2020 07:51:41 -0700
Post by islander
Why is testing so important and why are delays in obtaining test
results dangerous?
Any student of engineering is familiar with classic feedback control
and how systems can and do become unstable if the time constant of
the control loop becomes longer than the ability of the system to
respond.
We can see a dramatic example of that in the attempts to control the
corona virus with testing that cannot produce results quickly enough
to help to control it.
Basically, the virus is propagating much more rapidly than we are
able to monitor it. Why is this a problem? By the time results
become available, now 5-7 days in some states, the virus has moved on
to infect more people. Contact tracing, becomes much more difficult
as contacts become more diffuse with the rapid spread of the virus,
making the results of the testing useless and even counter
productive. Why? Because feedback control systems become unstable
when the time constant of the feedback loop exceeds the response time
of the system. You end up making changes to the system after it has
moved on to a new state.
While we hear a lot about the need for more testing, we also
desperately need rapid feedback and the large commercial labs appear
to be overwhelmed in the face of rapidly growing infection rates.
I just heard on the news, if you don't have symptoms of the virus,
don't get tested.
That doesn't make any sense to me.
It makes sense only because we don't have the capacity to process tests.
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