Amazing photographs from astronaut and engineer Karen L. Nyberg on Twitter during ISS-Expeditionen 36/37:
The astronauts and engineers in space have internet: NASA Extends the World Wide Web Out Into Space. BTW, Karen L. Nyberg also posted a photo of a dinosaur in space.

Below journals, loosely related to topics in Numerical Analysis, offer unencumbered full text:
Electronic Transactions on Numerical Analysis
Applied Mathematics E-Notes (no longer active)
The Electronic Journal of Linear Algebra
arXiv
Unfortunately, Numerische Mathematik, BIT, SIAM Journal on…

I have now done it a couple of times, but always have to look it up. Here are the steps to re-install Grub from a live Ubuntu CD, when you have Windows and Linux on your hard disk. You must be root, or run these commands with sudo. Change /dev/sdaXY accordingly.
mount /dev/sda2 /mnt
mount…

Below I copy some paragraphs from a recent article in Polymath 8 – a Success! | Combinatorics and more by Gil Kalai on Zhang’s breakthrough regarding prime numbers:
Twin primes are two primes $p$ and $p+2$. The ancient twin prime conjecture asserts that there are infinitely many twin primes.…

Except notably Russia and Africa this blog has been visited by quite a number of countries. I am surprised.
Also see Statistics of this Blog: Top Views by Country.

Very interesting talk on the scaling challenge at WordPress.com given by Barry Abrahamson, CTO of WordPress.
Some key points:
500 million database tables
3 data centers in USA
400.000 shards moved per day
storage on SSD
~10% of total infrastructure costs are related to backups
~500 GB / shard
50…

Georg Hager's Blog posted an illustrative article on icc versus g++ performance w.r.t. OpenMP. Dr. Georg Hager is one of the authors of Introduction to High Performance Computing for Scientists and Engineers.
Measurement of
double precision, dimension(N) :: a,b,c,d
! initialization etc. omitted
s =…

JpGraph is a library of PHP code to draw a variety of graphs:
line+bar+pie charts
radar+polar+contour graphs
bar+QR codes
Gantt charts
a couple of other chart types
Here are two examples:
JpGraph is a free product by Asial if used in a non-commercial context.
Installation is quite easy on…

Inspired by a discussion with my son regarding movement of a point-charge between two other charges I revisited the definition of the line integral. Wikipedia offers an excellent visualization of the definition of the line integral for a vector field. See animated graphic below:
This is something…

Just read on Torricelli's trumpet in Wikipedia. This states that there is a body having infinite surface but finite volume! That sounds contradictory at first.
Function in question is
$$
y = 1 / x
$$
from $x=1$ to $a$.
Volume is
$$ V = \pi \int_1^a \left({1\over x^2}\right)\,dx =…

Brian Koberlein wrote a very good introductory article on curvature of space and time in the vicinity of gravity: see The Attraction of Curves – Brian Koberlein.

Last year I used a drop-in replacement for the ordinary Linux sort command called nsort from Ordinal Technology. Ordinal's nsort is free but not open-source. One thing is clear, however, it is very fast. nsort was written by Chris Nyberg.
The motivation for looking for a faster sort was as follows.…

hgpu.org contains links to reviews, tutorials, research papers, program packages concerning various aspects of graphics and non-graphics (general purpose computing) using of GPU and related parallel architectures (FPGA, Cell processors etc.). The majority is on NVidia, see picture below.

An article in Android Authority from 26-Jun-2013, India is now the third largest Smartphone market in the world, states that:
There are 14 major carriers listed for India, including two state owned providers. None have over 180 million subscribers.
The smartphone market in India is expanding at…

I find the motd annoying when you log in to a Ubuntu server machine. To get rid of this I do the following as root:
cd /etc/update-motd.d
mkdir klmDisabled
mv ??-* klmDisabled
Unfortunately, whenever the packages update-manager-core, landscape-common, base-files, update-notifier-common change,…

As already posted last month, there are around 4 billion pageviews per month. This makes 1.4 pageviews per millisecond on the average. Each pageview incurs hundred of lines of PHP code executed, a couple of MySQL queries and updates.

According Los Angeles Times (dead link) China built 600 dams per year on average. This trend will continue.
According Wikipedia, or Jie Cai's Master Thesis (dead link), China has the largest potential for hydropower in the world and currently ranks first in hydroelectric generating capacity with…