Depends upon what the blanket is made of. E.g., I don't think that an ordinary wool blanket would commute with one of the silvery hi-tech blankets that first responders use. Those silvery blankets *reflect* (essentially all normal) wavelengths, while a wool blanket depends upon a quiet thickness of (hopefully dry) air; the wool is merely used to keep the thickness and reduce air movement (convection). I noticed that my down sleeping bag doesn't protect me from the cold ground -- I need a separate hard foam that keeps me a certain distance from the ground. On the other hand, those silvery first responder blankets also trap moisture, so you could end up with the inner surface covered with ice -- like uninsulated windows on a winter's day. At 07:19 AM 12/5/2019, James Propp wrote:
Do blankets commute?
Not esthetically (of course), but thermally?
Jim Propp
Tomas Rokicki <rokicki@gmail.com>:
That may be true for conduction and probably radiation but not convection.
Here's an actual experiment on my new Raspberry Pi 4, which has no fan, and hence relies on conduction, radiation and convection for cooling. When lying flat, the temperature for a particular CPU-intensive computation is 60C. When the RPi4 is standing on its small end (the printed circuit board is perpendicular to the floor), the temperature for the same computation is 56C, and these measurements are reliable over hundreds of trials. Convection is more efficient with the RPi standing on its end, while conduction and radiation are presumably not affected. So this answers the question of why we sleep lying down instead of standing up (like horses and flamingos do). We have also proved that rotations by Pi don't commute. BTW, the Raspian operating system for the RPi comes with *Mathematica* pre-installed *for free*, so: 1. the RPi4 hardware is effectively almost free; and 2. the RPi4's Mathematica computational capabilities approach that of a laptop (4x64-bit cores overclocked to 2GHz and 4GBytes). At 07:36 AM 12/5/2019, Henry Baker wrote:
Depends upon what the blanket is made of.
E.g., I don't think that an ordinary wool blanket would commute with one of the silvery hi-tech blankets that first responders use. Those silvery blankets *reflect* (essentially all normal) wavelengths, while a wool blanket depends upon a quiet thickness of (hopefully dry) air; the wool is merely used to keep the thickness and reduce air movement (convection). I noticed that my down sleeping bag doesn't protect me from the cold ground -- I need a separate hard foam that keeps me a certain distance from the ground.
On the other hand, those silvery first responder blankets also trap moisture, so you could end up with the inner surface covered with ice -- like uninsulated windows on a winter's day.
At 07:19 AM 12/5/2019, James Propp wrote:
Do blankets commute?
Not esthetically (of course), but thermally?
Jim Propp
I want Mathematica in my pocket too! Is RPi the only current option? Jim Propp On Sun, Dec 8, 2019 at 9:59 AM Henry Baker <hbaker1@pipeline.com> wrote:
Tomas Rokicki <rokicki@gmail.com>:
That may be true for conduction and probably radiation but not convection.
Here's an actual experiment on my new Raspberry Pi 4, which has no fan, and hence relies on conduction, radiation and convection for cooling.
When lying flat, the temperature for a particular CPU-intensive computation is 60C. When the RPi4 is standing on its small end (the printed circuit board is perpendicular to the floor), the temperature for the same computation is 56C, and these measurements are reliable over hundreds of trials. Convection is more efficient with the RPi standing on its end, while conduction and radiation are presumably not affected.
So this answers the question of why we sleep lying down instead of standing up (like horses and flamingos do).
We have also proved that rotations by Pi don't commute.
BTW, the Raspian operating system for the RPi comes with *Mathematica* pre-installed *for free*, so: 1. the RPi4 hardware is effectively almost free; and 2. the RPi4's Mathematica computational capabilities approach that of a laptop (4x64-bit cores overclocked to 2GHz and 4GBytes).
At 07:36 AM 12/5/2019, Henry Baker wrote:
Depends upon what the blanket is made of.
E.g., I don't think that an ordinary wool blanket would commute with one of the silvery hi-tech blankets that first responders use. Those silvery blankets *reflect* (essentially all normal) wavelengths, while a wool blanket depends upon a quiet thickness of (hopefully dry) air; the wool is merely used to keep the thickness and reduce air movement (convection). I noticed that my down sleeping bag doesn't protect me from the cold ground -- I need a separate hard foam that keeps me a certain distance from the ground.
On the other hand, those silvery first responder blankets also trap moisture, so you could end up with the inner surface covered with ice -- like uninsulated windows on a winter's day.
At 07:19 AM 12/5/2019, James Propp wrote:
Do blankets commute?
Not esthetically (of course), but thermally?
Jim Propp
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60C in your pocket? And where were you going to plug it in ... WFL On 12/8/19, James Propp <jamespropp@gmail.com> wrote:
I want Mathematica in my pocket too! Is RPi the only current option?
Jim Propp
On Sun, Dec 8, 2019 at 9:59 AM Henry Baker <hbaker1@pipeline.com> wrote:
Tomas Rokicki <rokicki@gmail.com>:
That may be true for conduction and probably radiation but not convection.
Here's an actual experiment on my new Raspberry Pi 4, which has no fan, and hence relies on conduction, radiation and convection for cooling.
When lying flat, the temperature for a particular CPU-intensive computation is 60C. When the RPi4 is standing on its small end (the printed circuit board is perpendicular to the floor), the temperature for the same computation is 56C, and these measurements are reliable over hundreds of trials. Convection is more efficient with the RPi standing on its end, while conduction and radiation are presumably not affected.
So this answers the question of why we sleep lying down instead of standing up (like horses and flamingos do).
We have also proved that rotations by Pi don't commute.
BTW, the Raspian operating system for the RPi comes with *Mathematica* pre-installed *for free*, so: 1. the RPi4 hardware is effectively almost free; and 2. the RPi4's Mathematica computational capabilities approach that of a laptop (4x64-bit cores overclocked to 2GHz and 4GBytes).
At 07:36 AM 12/5/2019, Henry Baker wrote:
Depends upon what the blanket is made of.
E.g., I don't think that an ordinary wool blanket would commute with one of the silvery hi-tech blankets that first responders use. Those silvery blankets *reflect* (essentially all normal) wavelengths, while a wool blanket depends upon a quiet thickness of (hopefully dry) air; the wool is merely used to keep the thickness and reduce air movement (convection). I noticed that my down sleeping bag doesn't protect me from the cold ground -- I need a separate hard foam that keeps me a certain distance from the ground.
On the other hand, those silvery first responder blankets also trap moisture, so you could end up with the inner surface covered with ice -- like uninsulated windows on a winter's day.
At 07:19 AM 12/5/2019, James Propp wrote:
Do blankets commute?
Not esthetically (of course), but thermally?
Jim Propp
_______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
_______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
Never mind; I was confusing RPi with something else. Hadn’t had my coffee yet. Jim On Sun, Dec 8, 2019 at 10:53 AM Fred Lunnon <fred.lunnon@gmail.com> wrote:
60C in your pocket? And where were you going to plug it in ... WFL
On 12/8/19, James Propp <jamespropp@gmail.com> wrote:
I want Mathematica in my pocket too! Is RPi the only current option?
Jim Propp
On Sun, Dec 8, 2019 at 9:59 AM Henry Baker <hbaker1@pipeline.com> wrote:
Tomas Rokicki <rokicki@gmail.com>:
That may be true for conduction and probably radiation but not convection.
Here's an actual experiment on my new Raspberry Pi 4, which has no fan, and hence relies on conduction, radiation and convection for cooling.
When lying flat, the temperature for a particular CPU-intensive computation is 60C. When the RPi4 is standing on its small end (the printed circuit board is perpendicular to the floor), the temperature for the same computation is 56C, and these measurements are reliable over hundreds of trials. Convection is more efficient with the RPi standing on its end, while conduction and radiation are presumably not affected.
So this answers the question of why we sleep lying down instead of standing up (like horses and flamingos do).
We have also proved that rotations by Pi don't commute.
BTW, the Raspian operating system for the RPi comes with *Mathematica* pre-installed *for free*, so: 1. the RPi4 hardware is effectively almost free; and 2. the RPi4's Mathematica computational capabilities approach that of a laptop (4x64-bit cores overclocked to 2GHz and 4GBytes).
At 07:36 AM 12/5/2019, Henry Baker wrote:
Depends upon what the blanket is made of.
E.g., I don't think that an ordinary wool blanket would commute with one of the silvery hi-tech blankets that first responders use. Those silvery blankets *reflect* (essentially all normal) wavelengths, while a wool blanket depends upon a quiet thickness of (hopefully dry) air; the wool is merely used to keep the thickness and reduce air movement (convection). I noticed that my down sleeping bag doesn't protect me from the cold ground -- I need a separate hard foam that keeps me a certain distance from the ground.
On the other hand, those silvery first responder blankets also trap moisture, so you could end up with the inner surface covered with ice -- like uninsulated windows on a winter's day.
At 07:19 AM 12/5/2019, James Propp wrote:
Do blankets commute?
Not esthetically (of course), but thermally?
Jim Propp
_______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
_______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
_______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
On Sun, Dec 8, 2019 at 8:43 AM James Propp <jamespropp@gmail.com> wrote:
I want Mathematica in my pocket too! Is RPi the only current option?
UserLAnd on an android phone + linux mathematica: https://play.google.com/store/apps/details?id=tech.ula https://support.wolfram.com/kb/12453 -- Mike Stay - metaweta@gmail.com http://math.ucr.edu/~mike https://reperiendi.wordpress.com
participants (4)
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Fred Lunnon -
Henry Baker -
James Propp -
Mike Stay