# Bobbie's Blog

## Remote Access to Linux-based Computing Resources With Graphical Interface (for UM Students)

Note: this note is about University of Michigan computing resources.

People working on numerical analysis often need to develop efficient code by doing multi-language programming, e.g. MATLAB/C++ or MATLAB/Fortran. Linux operating system is needed to have the best programming experience. (Mac OS has all sorts of compatibility issues.) For UM people who are using a Mac, I have explore the following four options for remotely accessing Linux-based computing resources.

## Dancing With Julia

I have been having fun with the Julia language lately. It is a new programming language for scientific computing. You may wonder, why do we need a new language at all? Don’t we already have MATLAB, Mathematica, Python with NumPy and SciPy, etc., are’t those enough?

Well, it is true that those are awesome softwares for scientific computing, they have all the necessary functionalities and powerful libraries, and they are easy to learn. But there is a common (fatal) issue that prevents them from creating industrial quality codes – speed. We want faster speed! The Julia language is developed specifically for this.

## The Holy Trinity

This isn’t about theology, but I will talk about the number three.

We love the number three. Many of our rules/doctrines consist of three parts. For example, in Christianity, there is the theory of the Holy Trinity, stating that God manifests Himself in three forms: the Father, the Son, and the Holy Spirit. I’d love to cast them into a shamrock diagram:

The key idea here is that, although there are three forms, there is really only one God.

## Preserve the Table of Contents When Converting a Book From Djvu to PDF

There are many readily available softwares (e.g. DjVu2PDF) for converting a book from .djvu to .pdf format, but none of those will preserve the table of contents in the output PDF.

## Beamer Video Tutorial

As a researcher, I often need to make presentation slides, and want to embed movies in my slides for better illustrations. After doing a little research, I converged to the solution described in this article.

## Fluid or Solid?

This is something I learned today from the Fluid Mechanics class in the Chemical Engineering department, class number CHE 527.

We have had the intuitive ideas about what a fluid is versus what a solid is. A solid is something that can resist shear stress, and will maintain its shape, while a fluid is something that will deform continuously when a shear is applied to it, without changing back to the original shape.

But there are many substances in the world that cannot be classified into solid or fluid with the above simple and intuitive definitions. Here are some examples:

## Human Brain Works Logarithmically

Do you know that our brain works logarithmically?

1. Do this exercise:
• Draw a number line
• Mark $0$ and $1,000,000,000$ on the line.
• Ask yourself a question: where is $1,000$?
2. Many people put $1,000$ at the $1/3$ position. Note that $1,000=10^3$, $1,000,000,000=10^9$, where $9$ is triple of $3$. This implies that we perceive number logarithmically!
3. Not only size of a number, but also weight of an object, loudness of a sound, brightness of a star, spiciness of a chili, all of these are perceived logarithmically by the human brain.
4. Such logarithmic law is known more than 100 years ago, under the name “Weber-Fechner law” in psychophysics.