Mount Liang by Ciro Santilli 37 Updated 2025-07-16
The term "Mount Liang" generally refers to both the mountain and the surrounding marshy areas.
The novel always uses the term "梁山泊' (liang2 shan1 po1) to refer to the place.
Video 1.
How did the Liangshan ponds form? by CCTV (2019)
Source. Chinese only, but still fun to see the real place.
Liu Dehai by Ciro Santilli 37 Updated 2025-07-16
Figure 1.
Liu Dehai peforming at the Musée Guimet in 2010
. Source.
Change of basis matrix by Ciro Santilli 37 Updated 2025-07-16
The change of basis matrix is the matrix that allows us to express the new basis in an old basis:
Mnemonic is as follows: consider we have an initial basis . Now, we define the new basis in terms of the old basis, e.g.:
which can be written in matrix form as:
and so if we set:
we have:
The usual question then is: given a vector in the new basis, how do we represent it in the old basis?
The answer is that we simply have to calculate the matrix inverse of :
That is the matrix inverse.
Islam character by Ciro Santilli 37 Updated 2025-07-16
Islam has some really nice things in it.
The way it was perverted to be used as a tool for terrorism by some is a great tragedy.
Ciro Santilli especially appreciates the ideas of
Matrix inverse by Ciro Santilli 37 Updated 2025-07-16
When it exists, which is not for all matrices, only invertible matrix, the inverse is denoted:
Hans Petter Langtangen by Ciro Santilli 37 Updated 2025-07-16
It should be mentioned that when you start Googling for PDE stuff, you will reach Han's writings a lot under his GitHub Pages: hplgit.github.io/, and he is one of the main authors of the FEniCS Project.
Unfortunately he died of cancer in 2016, shame, he seemed like a good educator.
He also published to GitHub pages with his own crazy markdown-like multi-output markup language: github.com/hplgit/doconce.
Rest in peace, Hans.
Simplex by Ciro Santilli 37 Updated 2025-07-16
The name does not imply regular by default. For regular ones, you should say "regular polytope".
Non-regular description: take convex hull take D + 1 vertices that are not on a single D-plan.
CuriousMarc by Ciro Santilli 37 Updated 2025-07-16
Mostly on vintage electronics. Lots of focus on microwave, which he has worked a lot with.
Has been going wild with restoration and reverse engineering of the Apollo moon mission.
Video 1.
Inside the WILD Lab of CuriousMarc by Keysight Labs (2022)
Source.

Pinned article: Introduction to the OurBigBook Project

Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.
Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!
We have two killer features:
  1. topics: topics group articles by different users with the same title, e.g. here is the topic for the "Fundamental Theorem of Calculus" ourbigbook.com/go/topic/fundamental-theorem-of-calculus
    Articles of different users are sorted by upvote within each article page. This feature is a bit like:
    • a Wikipedia where each user can have their own version of each article
    • a Q&A website like Stack Overflow, where multiple people can give their views on a given topic, and the best ones are sorted by upvote. Except you don't need to wait for someone to ask first, and any topic goes, no matter how narrow or broad
    This feature makes it possible for readers to find better explanations of any topic created by other writers. And it allows writers to create an explanation in a place that readers might actually find it.
    Figure 1.
    Screenshot of the "Derivative" topic page
    . View it live at: ourbigbook.com/go/topic/derivative
  2. local editing: you can store all your personal knowledge base content locally in a plaintext markup format that can be edited locally and published either:
    This way you can be sure that even if OurBigBook.com were to go down one day (which we have no plans to do as it is quite cheap to host!), your content will still be perfectly readable as a static site.
    Figure 5. . You can also edit articles on the Web editor without installing anything locally.
    Video 3.
    Edit locally and publish demo
    . Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension.
  3. https://raw.githubusercontent.com/ourbigbook/ourbigbook-media/master/feature/x/hilbert-space-arrow.png
  4. Infinitely deep tables of contents:
    Figure 6.
    Dynamic article tree with infinitely deep table of contents
    .
    Descendant pages can also show up as toplevel e.g.: ourbigbook.com/cirosantilli/chordate-subclade
All our software is open source and hosted at: github.com/ourbigbook/ourbigbook
Further documentation can be found at: docs.ourbigbook.com
Feel free to reach our to us for any help or suggestions: docs.ourbigbook.com/#contact