Water Margin adaptation Updated +Created
URL Updated +Created
Pi Josephson junction Updated +Created
jq ignore missing attribute Updated +Created
echo '[{"a": 1, "b": 2}, {"b": 3}]' | jq '.[] | select(.a) | .a'
Output:
1
and no empty lines as desired.
AC Josephson effect Updated +Created
This is what happens when you apply a DC voltage across a Josephson junction.
It is called "AC effect" because when we apply a DC voltage, it produces an alternating current on the device.
By looking at the Josephson equations, we see that a positive constant, then just increases linearly without bound.
Therefore, from the first equation:
we see that the current will just vary sinusoidally between .
This meas that we can use a Josephson junction as a perfect voltage to frequency converter.
Wikipedia mentions that this frequency is , so it is very very high, so we are not able to view individual points of the sine curve separately with our instruments.
Also it is likely not going to be very useful for many practical applications in this mode.
Figure 1. . Source.
Voltage is horizontal, current vertical. The vertical bar in the middle is the effect of interest: the current is going up and down very quickly between , the Josephson current of the device. Because it is too quick for the oscilloscope, we just see a solid vertical bar.
The non vertical curves at right and left are just other effects we are not interested in.
TODO what does it mean that there is no line at all near the central vertical line? What happens at those voltages?
Video 1.
Superconducting Transition of Josephson junction by Christina Wicker (2016)
Source. Amazing video that presumably shows the screen of a digital oscilloscope doing a voltage sweep as temperature is reduced and superconductivity is reached.
Figure 2. . So it appears that there is a zero current between and . Why doesn't it show up on the oscilloscope sweeps, e.g. Video 1. "Superconducting Transition of Josephson junction by Christina Wicker (2016)"?
Avogadro project Updated +Created
Whichever problem you present a German, they will look for a mechanical solution to it!
Derivation of the Klein-Gordon equation Updated +Created
The Klein-Gordon equation directly uses a more naive relativistic energy guess of squared.
But since this is quantum mechanics, we feel like making into the "momentum operator", just like in the Schrödinger equation.
But we don't really know how to apply the momentum operator twice, because it is a gradient, so the first application goes from a scalar field to the vector field, and the second one...
So we just cheat and try to use the laplace operator instead because there's some squares on it:
But then, we have to avoid taking the square root to reach a first derivative in time, because we don't know how to take the square root of that operator expression.
So the Klein-Gordon equation just takes the approach of using this squared Hamiltonian instead.
Since it is a Hamiltonian, and comparing it to the Schrödinger equation which looks like:
taking the Hamiltonian twice leads to:
We can contrast this with the Dirac equation, which instead attempts to explicitly construct an operator which squared coincides with the relativistic formula: derivation of the Dirac equation.
Y86 Updated +Created
esolangs.org/wiki/Y86 mentions:
Y86 is a toy RISC CPU instruction set for education purpose.
Athlete Updated +Created
Les Atomes by Jean Perrin (1913) Updated +Created
Subtle is the Lord by Abraham Pais (1982) mentions that this has a good summary of the atomic theory evidence that was present at the time, and which had become basically indisputable at or soon after that date.
An English translation from 1916 by English chemist Dalziel Llewellyn Hammick on the Internet Archive, also on the public domain: archive.org/details/atoms00hammgoog
Knowledge graph as a component of AGI Updated +Created
Related:
Terrell rotation Updated +Created
What you would see the moving rod look like on a photo of a length contraction experiment, as opposed as using two locally measured separate spacetime events to measure its length.
Electron Updated +Created
Behavior fully described by quantum electrodynamics.
OpenUSD Updated +Created
University of Warwick Updated +Created
Coinbase Updated +Created
Bitmessage Updated +Created
TODO evaluate. No pip install???
MIT course Updated +Created
Brazilian creamy cornmeal cake Updated +Created
www.tudogostoso.com.br/receita/3468-bolo-de-fuba-cremoso.html
  • December 2023:
    • replacements:
      • used 3 soy milk + 1 milk cup instead of 4 milk
      • salted butter rather than margarine
      • 1 cup of sugar rather than 3, because OMG 3 cups of sugar for 4 cups of milk is insane, Brazil!
    Turned out very good.

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