• 2 Posts
  • 30 Comments
Joined 2 years ago
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Cake day: November 19th, 2023

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  • When wind speed doubles, the energy it carries increases eightfold,

    Edit: I’m wrong, see edit below!

    Huh? Kinetic energy increase is square, not cubic.

    KE=1/2 m v^2

    So every doubling of speed should increase the available kinetic energy by 4 times, not 8. 3 times the speed is 9 times the energy. Granted there are probably some efficiency gains in excess of this at the low end, but as a rule that’s just wrong.

    Edit: Cool, I learned something new! I neglected to consider it in terms of power, just thought about kinetic energy.

    So something like: KE = 1/2 m v^2

    = 1/2 ( rho V) v^2

    = 1/2 ( rho A d) (d/t)^2

    = 1/2 rho A d^3 1/t^2

    Where P = KE/t

    Thus:

    P = 1/2 rho A (d/t)^3

    = 1/2 rho A v^3

    Lots of other aspects I’m sure I have wrong, but I see how the cubic came to be.







  • Ostensibly, that’s because the app wants Bluetooth and/or WiFi access so it can connect to the printer. Because you can use WiFi and Bluetooth to determine location (based on large crowd sourced databases of these data points that have been geolocated), the OS has to ask for location permission as well, even if you just need to see WiFi and Bluetooth.

    That being said, once they have this permission, I have 0 doubt they log the actual location as well…

    Mozilla used to run a free service for this, and collected that data in the background using mobile Firefox. A replacement is https://beacondb.net/, which is still building enough location data to become useful. Services like this aren’t nefarious, they’re actually really important in getting a quick GPS lock on mobile. Phone hardware actually have pretty poor GPS receivers, but if you can determine an approximate location prior, you get much better results, especially once supplemented with inertial measurements and snapping to mapped roads.






  • The first two died within 30 days, the second one took about 4 months I think. Not a huge sample size, but it kind of matches the typical hard drive failure bathtub curve.

    I just double checked, and mine were actually from a similar seller on Amazon - they all seem to be from the same supplier though - the warranty card and packaging are identical. So ymmv?

    Warranty was easy, I emailed the email address included in the warranty slip, gave details on order number + drive serial number, and they sent me a mailing slip within 1 business day. Print that out, put the drive back in the box it shipped with (I always save these), tape it up and drop it off for shipping. In my case, it was a refund of the purchase pretty much as soon as it was delivered to the seller.