An Unknown Key-Share (UKS) attack is a type of cryptographic attack that targets key exchange protocols. In these protocols, two parties typically derive a shared secret or key over an insecure channel. The UKS attack occurs when an attacker is able to manipulate the key exchange process such that one or both parties mistakenly believe they are sharing a key with one another, while in reality, the attacker is in control of the process.
As of my last update in October 2023, Alexander F. Wells may refer to a person who may have relevance in various fields such as academia, literature, or other professional areas. However, without additional context, it's difficult to provide a specific answer about this individual. If you have a specific context in which Alexander F.
Johannes Martin Bijvoet (1894-1971) was a Dutch chemist known for his significant contributions to the field of crystallography, particularly in the development of methods to determine the structure of complex organic molecules. He is perhaps best known for his work in X-ray crystallography and for his contributions to the study of stereochemistry, including the Bijvoet polymorph, which is a type of crystalline form related to the study of molecular chirality.
Lagrangian mechanics by Ciro Santilli 40 Updated 2025-07-16
Originally it was likely created to study constrained mechanical systems where you want to use some "custom convenient" variables to parametrize things instead of global x, y, z. Classical examples that you must have in mind include:
lagrangian mechanics lectures by Michel van Biezen (2017) is a good starting point.
When doing lagrangian mechanics, we just lump together all generalized coordinates into a single vector that maps time to the full state:
where each component can be anything, either the x/y/z coordinates relative to the ground of different particles, or angles, or nay other crazy thing we want.
The Lagrangian is a function that maps:
to a real number.
Then, the stationary action principle says that the actual path taken obeys the Euler-Lagrange equation:
This produces a system of partial differential equations with:
The mixture of so many derivatives is a bit mind mending, so we can clarify them a bit further. At:
the is just identifying which argument of the Lagrangian we are differentiating by: the i-th according to the order of our definition of the Lagrangian. It is not the actual function, just a mnemonic.
Then at:
  • the part is just like the previous term, just identifies the argument with index ( because we have the non derivative arguments)
  • after the partial derivative is taken and returns a new function , then the multivariable chain rule comes in and expands everything into terms
However, people later noticed that the Lagrangian had some nice properties related to Lie group continuous symmetries.
Basically it seems that the easiest way to come up with new quantum field theory models is to first find the Lagrangian, and then derive the equations of motion from them.
For every continuous symmetry in the system (modelled by a Lie group), there is a corresponding conservation law: local symmetries of the Lagrangian imply conserved currents.
Genius: Richard Feynman and Modern Physics by James Gleick (1994) chapter "The Best Path" mentions that Richard Feynman didn't like the Lagrangian mechanics approach when he started university at MIT, because he felt it was too magical. The reason is that the Lagrangian approach basically starts from the principle that "nature minimizes the action across time globally". This implies that things that will happen in the future are also taken into consideration when deciding what has to happen before them! Much like the lifeguard in the lifegard problem making global decisions about the future. However, chapter "Least Action in Quantum Mechanics" comments that Feynman later notice that this was indeed necessary while developping Wheeler-Feynman absorber theory into quantum electrodynamics, because they felt that it would make more sense to consider things that way while playing with ideas such as positrons are electrons travelling back in time. This is in contrast with Hamiltonian mechanics, where the idea of time moving foward is more directly present, e.g. as in the Schrödinger equation.
Furthermore, given the symmetry, we can calculate the derived conservation law, and vice versa.
And partly due to the above observations, it was noticed that the easiest way to describe the fundamental laws of particle physics and make calculations with them is to first formulate their Lagrangian somehow: S.
Video 1.
Euler-Lagrange equation explained intuitively - Lagrangian Mechanics by Physics Videos by Eugene Khutoryansky (2018)
Source. Well, unsurprisingly, it is exactly what you can expect from an Eugene Khutoryansky video.
Fan Haifu (范海福) is a Chinese composer and musician known for his contributions to film and television scores, as well as traditional Chinese music. He has gained recognition for his ability to blend modern musical techniques with classical Chinese elements, creating a unique sound.
Calculus of variations by Ciro Santilli 40 Updated 2025-07-16
Calculus of variations is the field that searches for maxima and minima of Functionals, rather than the more elementary case of functions from to .
The key difference from Lagrangian mechanics is that the Hamiltonian approach groups variables into pairs of coordinates called the phase space coordinates:
This leads to having two times more unknown functions than in the Lagrangian. However, it also leads to a system of partial differential equations with only first order derivatives, which is nicer. Notably, it can be more clearly seen in phase space.
PhysX by Ciro Santilli 40 Updated 2025-07-16
Had hardware acceleration in mind from the very start, and for a long time that has meant GPU acceleration.
Abraham Pais by Ciro Santilli 40 Updated 2025-07-16
This due is a beast, he knows both the physics and the history of physics, and has the patience to teach it. What a blessing: Section "How to teach and learn physics".

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 2.
    You can publish local OurBigBook lightweight markup files to either https://OurBigBook.com or as a static website
    .
    Figure 3.
    Visual Studio Code extension installation
    .
    Figure 4.
    Visual Studio Code extension tree navigation
    .
    Figure 5.
    Web editor
    . 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.
    Video 4.
    OurBigBook Visual Studio Code extension editing and navigation demo
    . Source.
  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