Ciro Santilli @cirosantilli 37

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Printed circuit board Updated 2025-07-16

CIA 2010 covert communication websites / secure subdomain search on 2013 DNS Census Updated 2025-07-16

Grepping the 2013 DNS Census first by overused CGI comms subdomains secure. and ssl. leaves 200k lines. Grepping for the overused "news" led to hits:

secure.worldnewsandent.com,2012-02-13T21:28:15,208.254.40.117
ssl.beyondnetworknews.com,2012-02-13T20:10:13,66.104.175.40

Also tried but failed:

sports:
- secure.motorsportdealers.com,2012-04-10T20:19:09,64.73.117.38 web.archive.org/web/20110501000000*/motorsportdealers.com

OK, after the initial successes in secure., we went a bit more data intensive:

took all secure.* ssl.* URLs in the 2013 DNS Census, 70k entries
cleaned up a bit, e.g. only .com or .net. this left only, 30k entries only
lopped over all of them in archive CDX: Wayback Machine CDX scanning, searching for those that also end in .cgi web.archive.org/cdx/search/cdx?url=$domain&matchType=domain&filter=urlkey:.*.cgi&to=20140101000000. Took an afternoon, but no rate limit block.
this leaves about 1000, so we loop over all of them manually on web archive with a script, and opened any that had the pattern of very vew hits between 2010 and 2013 only, and on those check for visual/thematic style match. Careful not to make more than 15 requests per minute or else 5 min blacklist!

New results: only one...

208.254.42.205 secure.driversinternationalgolf.com,2012-02-13T10:42:20,

After 2013 DNS Census virtual host cleanup heuristic keyword searches we later understood why there were so few hits here: the 2013 DNS Census didn't capture the secure. subdomains of many domains it had for some reason. Shame, because if it had, this method would have yielded many more results.

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TeachMeAsap.com Updated 2025-07-16

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They sent one of the rare spams Ciro actually was interested in!!! Likely going down lists of top Stack Overflow users.

They have some kind of cryptocurrency, TCHME token, as a reward. Ciro wonders if the value of TCHME will ever be high enough to serve as a valid incentive.

Also, what is the total TCHME supply? Can the website devs issue as much as they want? They do giveaways e.g. as shown at: twitter.com/TeachMeAsap/status/1621353671840899072

And a centralized system with a certralized marketplace would work just as well for the initial phases. But fair play, the idea is interesting.

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Telecommunication Updated 2025-07-16

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Communicating at a distance, from Greek "tele" for distance!

A very cool thing about telecommunication is, besides how incredibly fast it advanced (in this sense it is no cooler than integrated circuit development), how much physics and information theory is involved in it. Applications of telecommunication implementation spill over to other fields, e.g. some proposed quantum computing approaches are remarkably related to telecommunication technology, e.g. microwaves and silicon photonics.

This understanding made Ciro Santilli wish he had opted for telecommunication engineering when he was back in school in Brazil. For some incomprehensible reason, telecommunications was the least competitive specialization in the electric engineering department at the time, behind even power electronics. This goes to show both how completely unrelated to reality university is, and how completely outdated Brazil is/was. Sad stuff.

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Tensor Updated 2025-07-16

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A multilinear form with a domain that looks like:

V^{m} \times V *^{n} \to R

(1)

where

V *

is the dual space.

Because a tensor is a multilinear form, it can be fully specified by how it act on all combinations of basis sets, which can be done in terms of components. We refer to each component as:

T_{i_{1} \dots i_{m}}^{j_{1} \dots j_{n}} = T (e_{i_{1}}, \dots, e_{i_{m}}, e^{j_{1}}, \dots, e^{j_{m}})

(2)

where we remember that the raised indices refer dual vector.

Some examples:

Explain it properly bibliography:

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Client-side storage Updated 2025-07-16

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www.google.com/search?q=client-side+storage&oq=Client-side+storage&aqs=chrome.0.0l3j0i22i30l4j69i60.88j0j7&client=ubuntu&sourceid=chrome&ie=UTF-8

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Codomain Updated 2025-07-16

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Vs: image: the codomain is the set that the function might reach.

The image is the exact set that it actually reaches.

E.g. the function:

f (x) = x^{2}

(1)

could have:

codomain $R$
image $R_{+}$

Note that the definition of the codomain is somewhat arbitrary, e.g.

x^{2}

could as well technically have codomain:

R ⋃ R^{2}

(2)

even though it will obviously never reach any value in

R^{2}

The exact image is in general therefore harder to characterize.

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The Hardware of a Quantum Computer by TU Delft Updated 2025-07-16

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EdX course. Meh! Just give me the YouTube list!!

But seriously, this is a valuable little list.

The course is basically exclusively about transmons.

Video 1.

The transmon qubit by Leo Di Carlo (2018)

Source. Via QuTech Academy.

Video 2.

Circuit QED by Leo Di Carlo (2018)

Source. Via QuTech Academy.

Video 3.

Measurements on transmon qubits by Niels Bultink (2018)

Source. Via QuTech Academy. I wish someone would show some actual equipment running! But this is of interest.

Video 4.

Single-qubit gate by Brian Taraskinki (2018)

Source. Good video! Basically you make a phase rotation by controlling the envelope of a pulse.

Video 5.

Two qubit gates by Adriaan Rol (2018)

Source.

Video 6.

Assembling a Quantum Processor by Leo Di Carlo (2018)

Source. Via QuTech Academy.

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Coherence time Updated 2025-07-16

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It takes time for the quantum state to evolve. So in order to have a deep quantum circuit, we need longer coherence times.

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Special relativity Updated 2025-07-16

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Explains how it is possible that everyone observes the same speed of light, even if they are moving towards or opposite to the light!!!

This was first best observed by the Michelson-Morley experiment, which uses the movement of the Earth at different times of the year to try and detect differences in the speed of light.

This leads leads to the following conclusions:

to length contraction and time dilation
the speed of light is the maximum speed anything can reach

All of this goes of course completely against our daily Physics intuition.

The "special" in the name refers to the fact that it is a superset of general relativity, which also explains gravity in a single framework.

Since time and space get all messed up together, you have to be very careful to understand what it means to say "I observed this to happen over there at that time", otherwise you will go crazy. A good way to think about is this:

use Einstein synchronization to setup a bunch of clocks for every position in your frame of reference
on every point of space, you put a little detector which records events and the time of the event
each detector can only detect events locally, i.e. events that happen very close to the detector
then, after the event, the detectors can send a signal to you, who is sitting at the origin, telling you what they detected

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1902 Nobel Prize in Physics Updated 2025-07-16

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Pieter Zeeman for the Zeeman effect.

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1908 Nobel Prize in Chemistry Updated 2025-07-16

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1918 Nobel Prize in Physics Updated 2025-07-16

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1926 Nobel Prize in Physics Updated 2025-07-16

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Atomic theory.

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1927 Nobel Prize in Physics Updated 2025-07-16

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1936 Nobel Prize in Physics Updated 2025-07-16

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Discovery of:

the positron by Carl David Anderson
he cosmic rays by Victor Francis Hess

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1952 Nobel Prize in Chemistry Updated 2025-07-16

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Gas chromatography.

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How to report Ubuntu crashes Updated 2025-07-16

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Their crash system does not have an amazing user interface.

Tested on Ubuntu 21.10.

After something crashes, look under /var/crash for a crash file, which helps to determine which package to report under on Launchpad.

E.g. a file /var/crash/_usr_sbin_gdm3.0.crash makes you want to file the bug under gdm at: bugs.launchpad.net/ubuntu/+source/gdm/+filebug

Then, while reporting the bug, you want to give the developpers access to that .crash file. But you can't publicly upload it because it contains memory dumps and could contain secret information. The way to do it is to look at the ID under:

sudo cat /var/crash/_usr_sbin_gdm3.0.uploaded

Ubuntu's crash report system has already uploaded the .crash for you, so you just have to confirm it and give the ID on the ticket.

You can view a list of all your uploaded errors at:

xdg-open https://errors.ubuntu.com/user/$(sudo cat /var/lib/whoopsie/whoopsie-id)

and each of those contain a link to:

https://errors.ubuntu.com/oops/<.uloaded error id>

which you yourself cannot see.

askubuntu.com/questions/434431/how-can-i-read-a-crash-file-from-var-crash asks how to read the .crash files.

Running:

sudo apport-unpack /var/crash/_usr_sbin_gdm3.0.crash /tmp/app

splits it up into a few files, but does not make any major improvements.

apport-retrace

sudo apt install apport-retrace
sudo chmod 666 /var/crash/_usr_sbin_gdm3.0.crash
apport-retrace -g /var/crash/_usr_sbin_gdm3.0.crash

opens GDB with the core dump. Debug symbols are supplied as separate packages, which is a really cool idea: so you should be able to download them after the crash to see symbols. askubuntu.com/questions/487222/how-to-install-debug-symbols-for-installed-packages mentions how to install them. Official docs at: wiki.ubuntu.com/DebuggingProgramCrash#Debug_Symbol_Packages

Tried:

echo "deb http://ddebs.ubuntu.com $(lsb_release -cs) main restricted universe multiverse" | sudo tee -a /etc/apt/sources.list.d/ddebs.list
echo -e "deb http://ddebs.ubuntu.com $(lsb_release -cs)-updates main restricted universe multiverse\ndeb http://ddebs.ubuntu.com $(lsb_release -cs)-proposed main restricted universe multiverse" | sudo tee -a /etc/apt/sources.list.d/ddebs.list
sudo apt install ubuntu-dbgsym-keyring

but then sudo apt update fails with:

E: The repository 'http://ddebs.ubuntu.com impish-security Release' does not have a Release file.

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1960 Nobel Prize in Physics Updated 2025-07-16

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1965 Nobel Prize in Physics Updated 2025-07-16

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