Bicycle tire sizes Updated 2025-07-16
Yes, Sheldon he has separate American and British English versions of pages!!!
For example, Kross bicycle (2017) had a Schwalbe tyre with markings:
42-622 (28 x 1.60, 700x40C)
When inflated, the tires were about 3.5cm wide as measured with a ruler.
And the Mavic A319 rim had markings:
622x19C
In this:
Chain rule Updated 2025-07-16
Here's an example of the chain rule. Suppose we want to calculate:
So we have:
and so:
Therefore the final result is:
Gradient Updated 2025-07-16
Takes a scalar field as input and produces a vector field.
Mnemonic: the gradient shows the direction in which the function increases fastest.
Think of a color gradient going from white to black from left to right.
Therefore, it has to:
  • take a scalar field as input. Otherwise, how do you decide which vector is larger than the other?
  • output a vector field that contains the direction in which the scalar increases fastest locally at each point. This has to give out vectors, since we are talking about directions
Graphene Updated 2025-07-16
A single layer of graphite.
Green fluorescent protein Updated 2025-07-16
The 3D structure of GFP is so cool. It is so clearly a bottle with a fluorescent bit well isolated right in the middle. Like a little lamp.
grep Updated 2025-07-16
If you are a programmer, grep becomes a verb: "to grep" means "to search text files", much like "to Google" means "to search random stuff online".
Grinding for software interviews Updated 2025-07-16
If your kids are about to starve, fine, do it.
But otherwise, Ciro Santilli will not, ever, spend his time drilling programmer competition problems to join a company, life is too short for that.
Life is too short for that. Companies must either notice that you can make amazing open source software projects or contributions, and hire you for that, or they must fuck off.
Companies must either notice that you can make amazing projects or contributions, and hire you for that, or they must fuck off.
Group extension problem Updated 2025-07-16
Besides the understandable Wikipedia definition, Video "Simple Groups - Abstract Algebra by Socratica (2018)" gives an understandable one:
Given a finite group and a simple group , find all groups such that is a normal subgroup of and .
In particular, this is hard because you can't just take the direct product of groups to retrieve the original group: Section "Relationship between the quotient group and direct products".
Group homomorphism Updated 2025-07-16
Like isomorphism, but does not have to be one-to-one: multiple different inputs can have the same output.
The image is as for any function smaller or equal in size as the domain of course.
This brings us to the key intuition about group homomorphisms: they are a way to split out a larger group into smaller groups that retains a subset of the original structure.
As shown by the fundamental theorem on homomorphisms, each group homomorphism is fully characterized by a normal subgroup of the domain.
Bilinear map Updated 2025-07-16
Linear map of two variables.
More formally, given 3 vector spaces X, Y, Z over a single field, a bilinear map is a function from:
that is linear on the first two arguments from X and Y, i.e.:
Note that the definition only makes sense if all three vector spaces are over the same field, because linearity can mix up each of them.
The most important example by far is the dot product from , which is more specifically also a symmetric bilinear form.
Gülen movement Updated 2025-07-16
Ciro Santilli once was at student a hackthon, where he proposed working on OurBigBook.com to others.
The only person who showed interest was a follower of the sect.
It seems that they put a lot of emphasis in education.
Also, their self-name is Hizmet, which translates as "service".
That day, Mr. Fethullah Gülen gained some Cirocoins.
JT-60 Updated 2025-07-16
Zen Updated 2025-07-16
Perhaps the appeal of Zen is that it stepped away from Mahayana's "God and entities", and went a bit back towards the Buddhist psychology-like/self improvement grassroots?
Digital signature Updated 2025-07-16
One notable application: cryptocurrency, see e.g. how Bitcoin works.
Free license Updated 2025-07-16

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