Python programs can be launched by
python myprog.pyThe Python Launcher, on Windows allows running by simply
myprog.pybased on the shebang
#!/usr/bin/env pythonwhich works on Windows and Unix-like OS to search the user’s PATH for the desired Python executable.
Specific executables #!/usr/bin/python are only for specific situations like GNU Radio.
Generally, please use #!/usr/bin/env python.
FM translator W262CV on 100.3 FM greatly expands the AM listening audience of WROL 950 Class D AM. WROL’s 5kW day signal from Rumney Marsh Reservation in Saugus is greatly attenuated to 90 watts at night to protect stations including:
This means WROL night coverage is weak in Boston and even core North Shore communities that are well within WROL day coverage.
FM translators for AM: AM Revitalization FM translators for AM stations attempt to provide the AM daytime coverage 24 hours a day via 250 watt or less transmissions in the FM broadcast band. Having an FM signal can be a boon for station advertising revenue–provided the FM coverage is not disrupted by unexpected factors such as illegal broadcasters. The Feb. 2017 R&O extended the 60 dBu (1 mV/m) FM translator contour to the greater of the AM 2 mV/m contour or 25 mile radius.
WROL FM translator interference: the 100.3 pirates changed frequency, but WROL 100.3 faces severe challenges from, and presents new challenges to other licensed stations. Listeners to these existing stations may object to the new WROL 100.3 translator.
50 kW WHEB is the primary limitation to coverage, particularly in the northeastern parts of Boston. However, one can merely switch to WROL 950 AM in northeast exurbs of Boston as per W262CV Exhibit 3 interference study.
Licensed co-channel interferers include:
For most listeners, co-channel WHEB is more limiting than first adjacent WBRS.
Ubuntu Gnome 3-based desktop is even better than Unity. However, I was puzzled by the lack of a folder bookmark menu item in Nautilus, Ubuntu’s default “File Explorer”.
Fix: simply dragging and dropping a folder into the left sidebar adds a folder bookmark in Nautilus.
For many years, $45/GByte and 400 kbps with 200+ ms ping was the state of the art internet connection at Sondrestrom near Kangerlussuaq, Greenland. Recent Internet upgrades give nearly 1 Mbps upload and multiple Mbps download.
Wayland desktop after install / upgrade a VirtualBox Extension Pack may get a “can’t find Xauthority”. The fix is to revert to X11 as recommended by Ubuntu.
Fix by logging out, and at the login screen select X11 login. Install the VirtualBox Expansion Pack Logout and switch back to the default login (with Wayland). VirtualBox will work in Wayland.
A recent macOS upgrade to High Sierra mysteriously broke the Apple mouse Bluetooth connection. Despite the computer showing the mouse as paired, no motion of the cursor or response to clicks. The keyboard alone can reconnect the mouse if no wired mouse was available.
The frequently used Apple ⌘ key is equivalent to the ⊞ key on a PC keyboard.
Cmd Shift g/ApplicationsCmd o to open System PreferencesCmd n to setup new device. Flip mouse power switch off, then on again if it doesn’t show up.Much has been written on selecting best colormaps from among: sequential, divergingm and qualitative. Sequential colormaps are good for representing magnitude of data. How much flow, how much precipitation, how much weight, temperature, etc. Having a monotonic lightness factor is important for perceptual consistency. Non-linear lightness is used to emphasize certain ranges of data, perhaps where snow changes to ice or rain. Non-monotonic lightness can be used to emphasize different types of precipitation or phase changes, etc. Example sparse data plots with reversed sequential colormaps: colormap_white_min.py, colormap_white_min.m
Reversed sequential colormaps are useful for sparse data such as astronomical images or precipitation data where a lot of data is at or near zero relative to other data.
The reversal leads to near-zero areas being white and higher intensities being darker.
While any colormap can be reversed, typically sequential colormaps are used with/without reversal.
Matplotlib colormaps are reversed by appending _r to the colormap name.
For example:
cmap='cubehelix_r'Matlab and GNU Octave colormaps are reversed by flipud() the colormap.
Colormaps in .m code are represented as an (N,3) array, where N is the number of steps in the colormap (typically 64 or 256).
colormap(flipud(cubehelix()))Matlab cubehelix.m is like Matplotlib.
Diverging colormaps are useful for positive or negative data where the sign is as important as the magnitude. For example, in/out flows, positive/negative charge. These colormaps are white near the zero point (which can be offset) and intensify as their absolute magnitude increases.
Qualitative colormaps emphasize difference between values, but without a particular sense of ordering. This can be useful for categories, say a histogram of salary vs. employee type.
This checklist helps rapidly diagnose SSH server issues, segmenting the problem into whether it’s network, firewall or SSH server configuration issues.
This checklist is OpenSSH + Debian/Ubuntu centric.
Some systems (particularly embedded) may use iptables or nftables directly instead of high-level ufw.
Check if the SSH server is actually running.
Errors in /etc/ssh/sshd_config can prevent the SSH server from running.
service ssh statusshould show feedback including:
Active: active (running)
If not, try
service ssh restartIf restarting SSH server allows connections, be sure that after rebooting the server, the SSH server still works. This could help avoid a costly trip back to the site later.
From the laptop, error
Connection refused.
can simply mean the SSH server is not running.
Firewall: check port SSH server is supposed to be on in /etc/ssh/sshd_config. Look for Port 22 or whatever the SSH server is on.
Although “security through obscurity” is not the goal of changing to a non-default SSH port, it can drastically reduce the amount of log flooding.
Check that firewall is open on the SSH server port.
ufw status22/tcp ALLOW Anywhere
22/tcp (v6) ALLOW Anywhere (v6)
Check that packets are making it from the SSH client to the SSH server by on the server
tcpdump port 22 -n -Q inoutSpecify the desired network interface as revealed by ip a with the tcpdump -i option.
When the SSH client attempts to connect, the SSH server tcpdump should show packets coming in on the desired port with the client IP address also shown.
If not, see if the network itself has a firewall that’s blocking your packets.
Logs: should see attempts to connect showing in /var/log/auth.log.
Try
tail -f /var/log/auth.logto see if new attempts show up.
Fail2ban might have the laptop IP address in “jail”. Check on the SSH server to see which IP addresses are banned:
fail2ban-client status sshdUbuntu’s Meltdown/Spectre wiki as well as their Meltdown/Spectre press release indicate the versions of Ubuntu patched for this issue. Part of the general problem is servers that should be maintained in the cloud are instead running in a closet without maintenance.
A modern more robust approach:
Registration tests are a first step on wrangling the dataflow lifecycle. Registration tests + continuous integration add meaningful testing across OS & compiler versions, monitoring edge cases that break. Driving toward unit tests incrementally as warranted allow minimal upfront expenditure.
A popular IDE for Julia (syntax highlighting, linting) is via the Julia plugin for Visual Studio code.