Scientific Computing

collection of Bash scripts for extensive command line control of radios and rotors via Hamlib rigctld and rotctld

NOTE: if using GPredict with Hamlib, do not use -v verbose options, since the extra text output will confuse Gpredict.

Lenovo offers a 2880 x 1620 pixel T540p laptop that is on par with the MacBook Pro Retina 2880 x 1800.

There are other points to consider such as weight and price. The Lenovo 540p is nice for Linux with a Haswell quad-core CPU and user-upgradable RAM (up to 16GB RAM), HDD and DVD.

The Lenovo T540p is less than half the price $1300 vs. less-well equipped Apple MacBook Pro Retina at $2600.

NOTE: Matlab R2024b and newer no longer use the internal Help browser for doc, instead referring “doc” commands to the system web browser.

After opening the Matlab Help Browser, Matlab might use 100% of one CPU core at about 25% duty cycle. Even after closing just the Help Browser while keeping Matlab itself open, this problem may persist.

Workaround: a one-time persistent setting.

Type in Matlab:

com.mathworks.mlwidgets.html.HtmlComponentFactory.setDefaultType('HTMLRENDERER');

Restart Matlab, reopen and close Matlab Help Browser. The CPU is no longer hanging at 100% after closing the Help Browser. However, this simpler Help Browser is not as graphically nice as the default Help Browser. Clickable links won’t work in the help files.

Undo workaround: revert back to the default Help Browser with this one-time persistent setting. Type in Matlab:

com.mathworks.mlwidgets.html.HtmlComponentFactory.setDefaultType('HTMLPANEL');

then restart Matlab.

Disable the Beaglebone Black flashing LEDs temporarily or permanently:

Persistently (permanently) disable: add to /etc/rc.local

echo none > /sys/class/leds/beaglebone\:green\:usr0/trigger
echo none > /sys/class/leds/beaglebone\:green\:usr1/trigger
echo none > /sys/class/leds/beaglebone\:green\:usr2/trigger
echo none > /sys/class/leds/beaglebone\:green\:usr3/trigger

Reference

Temporary disable (till reboot):

echo none > /sys/class/leds/beaglebone:green:usr0/trigger

Alternative: apt install astrometry.net

Install GCX

apt install gcx

GSC ACT catalog

there are a lot of directories with lots of ~50KB files, so it will take a while even with a very fast internet connection.

mkdir ~/gsc-act
cd ~/gsc-act

wget -r -nH --cut-dirs=5 ftp://cdsarc.u-strasbg.fr/pub/cats/I/255/GSC_ACT/

set File → File and Device Options/GSC to /home/username/gsc-act

username

your linux login

Tycho2 star catalog

mkdir ~/tycho2 && cd ~/tycho2

wget -r -nH --cut-dirs=5 ftp://cdsarc.u-strasbg.fr/pub/cats/I/259/

Once you see that they’ve downloaded correctly, do:

zcat tyc2.dat.??.gz > tycho2.dat

set File → File and Device Options/Tycho2 to /home/username/tycho2

username

your linux login

The “Who’s Afraid of Peer Review” article DOI: 10.1126/science.342.6154.60 notes that:

…Ocorrafoo Cobange does not exist, nor does the Wassee Institute of Medicine…submitted 304 versions of the wonder drug paper to open-access journals. More than half of the journals accepted the paper, failing to notice its fatal flaws…the data from this sting operation reveal the contours of an emerging Wild West… …acceptance was the norm, not the exception…

Counter-argument from Curt Rice in the Guardian

Some think the Earth is spherical, others that it is flat and drum-shaped. For evidence they bring the fact that, as the sun rises and sets, the part concealed by the Earth shows a straight and not a curved edge, whereas if the Earth were spherical the line of section would have to be circular . . . . . . but in eclipses of the moon the outline is always curved: and, since it is the interposition of the Earth that makes the eclipse, the form of this line will be caused by the form of the Earth’s surface, which is therefore spherical.

Aristotle. “On the Heavens”. Written 350 B.C.E.

Quoted in: Kabanikhin, Sergey I. Inverse and Ill-Posed problems

apt install octave-info

fixes the error message about missing files when using the doc command in GNU Octave.

Imaging from sparse measurements: Y. Fang, M. Cheney and S. Roecker

On NUFFT-based gridding for non-Cartesian MRI: Jeffrey A. Fessler

if you get a winetricks error like:

wine cmd.exe /c echo '%ProgramFiles%' returned a string containing the word 'unknown', as if a voice had cried out in terror, and was suddenly silenced.

Fix: backup existing system.reg file by typing in Terminal:

cp ~/.wine/system.reg ~/.wine/system.reg.bak

Use text editor and “replace all”

C:\\windows\\system32\\unknown

with

C:\\Program Files