Yet another awk-like domain-specific language to do things from the CLI in a ridiculously short humber of character? Oh yes.
What makes lasers so special: Lasers vs other light sources.
How Lasers Work by Scientized (2017)
Source. An extremely good overview of how lasers work. Clearly explains the electron/photon exchange processes involved, notably spontaneous emission.
Talks about the importance of the metastable state to achieve population inversion.
Also briefly explains the imperfections that lead to the slightly imperfect non punctual spectrum seen in a real laser.
- youtu.be/_JOchLyNO_w?t=188 says LED is "also monochromatic", but that is not strictly true, it has way way larger frequency band than a laser. Only narrower compared to other sources such as incandescent light bulbs.
- youtu.be/_JOchLyNO_w?t=517 stimulated emission. This is the key to laser formation as it produces coherent photons.
- youtu.be/_JOchLyNO_w?t=581 spontaneous emission happens too fast (100 ns), which is not enough time for stimulated emission to happen. Metastable electrons to the rescue.
- youtu.be/_JOchLyNO_w?t=832 the parallel mirrors select perpendicular photons preferentially
Laser Fundamentals I by Shaoul Ezekiel
. Source. 2008, MIT. Many more great videos in this series.The fundamental intuition about capacitors is that they never let electrons through.
They can only absorb electrons up to a certain point, but then the pushback becomes too strong, and current stops.
Therefore, they cannot conduct direct current long term.
For alternating current however, things are different, because in alternating current, electrons are just jiggling back and forward a little bit around a center point. So you can send alternating current power across a capacitor.
The key equation that relates Voltage to electric current in the capacitor is:So if a voltage Heavyside step function is applied what happens is:More realistically, one may consider the behavior or the series RC circuit to see what happens without infinities when a capacitor is involved as in the step response of the series RC circuit.
- the capacitor fills up instantly with an infinite current
- the current then stops instantly
Finding capacitance with an oscilloscope by Jacob Watts (2020)
Source. Good experiment.Capacitors Explained by The Engineering Mindset
. Source. 2019. 2013 DNS Census virtual host cleanup heuristic keyword searches Updated 2025-03-28 +Created 1970-01-01
There are two keywords that are killers: "news" and "world" and their translations or closely related words. Everything else is hard. So a good start is:
grep -e news -e noticias -e nouvelles -e world -e globaliran + football:
- iranfootballsource.com: the third hit for this area after the two given by Reuters! Epic.
3 easy hits with "noticias" (news in Portuguese or Spanish"), uncovering two brand new ip ranges:
- 66.45.179.205 noticiasporjanua.com
- 66.237.236.247 comunidaddenoticias.com
- 204.176.38.143 noticiassofisticadas.com
Let's see some French "nouvelles/actualites" for those tumultuous Maghrebis:
- 216.97.231.56 nouvelles-d-aujourdhuis.com
news + world:
- 210.80.75.55 philippinenewsonline.net
news + global:
- 204.176.39.115 globalprovincesnews.com
- 212.209.74.105 globalbaseballnews.com
- 212.209.79.40: hydradraco.com
OK, I've decided to do a complete Wayback Machine CDX scanning of
news... Searching for .JAR or https.*cgi-bin.*\.cgi are killers, particularly the .jar hits, here's what came out:- 62.22.60.49 telecom-headlines.com
- 62.22.61.206 worldnewsnetworking.com
- 64.16.204.55 holein1news.com
- 66.104.169.184 bcenews.com
- 69.84.156.90 stickshiftnews.com
- 74.116.72.236 techtopnews.com
- 74.254.12.168 non-stop-news.net
- 193.203.49.212 inews-today.com
- 199.85.212.118 just-kidding-news.com
- 207.210.250.132 aeronet-news.com
- 212.4.18.129 sightseeingnews.com
- 212.209.90.84 thenewseditor.com
- 216.105.98.152 modernarabicnews.com
Wayback Machine CDX scanning of "world":
- 66.104.173.186 myworldlymusic.com
"headline": only 140 matches in 2013-dns-census-a-novirt.csv and 3 hits out of 269 hits. Full inspection without CDX led to no new hits.
"today": only 3.5k matches in 2013-dns-census-a-novirt.csv and 12 hits out of 269 hits, TODO how many on those on 2013-dns-census-a-novirt? No new hits.
"world", "global", "international", and spanish/portuguese/French versions like "mondo", "mundo", "mondi": 15k matches in 2013-dns-census-a-novirt.csv. No new hits.
For a detailed analysis of one transaction see: Nelson-Mandela.jpg.
Best guess so far, all in ASCII hex of output scripts:
- remove the single output value different from first one from payload, that's the change, and it is randomly placed as far as I see
- 64 bytes: hex address of top level text
- 1 byte: some random punctuation
- decimal number of bytes of some payload
- 1 byte: some random punctuation
- 64 bytes: same as the first address
- CR LF
- ends in NUL
Source code:
- github.com/leanprover/lean4 why a separate repo per version... but it is what it is.
- github.com/leanprover/lean
They are huge fans of Unicode characters! Check this out from a formal proof of the prime number theorem: github.com/AlexKontorovich/PrimeNumberTheoremAnd/blob/fbdbb5310d036d33b9797b35f3b04b08f2447a6e/PrimeNumberTheoremAnd/ZetaBounds.lean
Their dependency graph thingy is just beautiful however: alexkontorovich.github.io/PrimeNumberTheoremAnd/web/dep_graph_document.html
This is the cutest product name ever.
Since 1992, Mr. SQUID has been the standard educational demonstration system for undergraduate physics lab courses.
YBCO device, runs on liquid nitrogen.
Pokemania Comes to America by ABC News (1999)
Source. Ciro Santilli was a part of it! Especially during Ciro Santilli's 10 month stay in Coventry, United Kingdom, in the year 2000!Something where DC voltage comes in, and a periodic voltage comes out.
- youtu.be/eYVOdlK15Og?t=66 RC oscillator on breadboard. Produces rectangular wave. Mentions popular integrated circuit that does it: 555 timer IC.
- youtu.be/eYVOdlK15Og?t=175 LC oscillators allows for higher frequencies. Produces sinusoidal output on MHz range. Uses an amplifier to feed back into input and maintain same voltage. Hard to make reliably on breadboard.
- youtu.be/eYVOdlK15Og?t=315 crystal oscillator. Mentions it acts like an LC oscillators. Shows and equivalent model. Wish he had talked more about them. You need support components around it: similarly to the LC case, the amplifier is generally not packaged in.
About 50k subscribers on 2021, which feels way too little for the video quality and quantity.
Ciro Santilli believes that this channel will go very far, certainly achieving 1M subscribers in they keep it for one or two more years. Update: it didn't, as of 2024, shame.
They are Utah-based, and they do many many amazing weekend trips. They mostly drive from home to some trailhead, and then climb up and down it the entire day.
No technical rock climbing, only bouldering, but they still manage to reach many amazing places, and there is a level of danger in many of their ascents.
The cool thing about this channel is that as the name suggests, they are not professionals, and what they do can be done by anyone without working full time on it, as long as you have adequate preparation.
Centerpiece of the CEA since the beginning of the French nuclear weapons program, headquarters since 2006.
As of 2023 the place was blurred on Google Maps satellite view, no wonder.
You select a generating set of a group, and then you name every node with them, and you specify:
- each node by a product of generators
- each edge by what happens when you apply a generator to each element
Not unique: different generating sets lead to different graphs, see e.g. two possible en.wikipedia.org/w/index.php?title=Cayley_graph&oldid=1028775401#Examples for the
The polynomials together with polynomial addition and multiplication form a commutative ring.
Published on the session reports of the Royal Prussian Academy of Sciences at Berlin 1918 page 464.
Is about Maxwell's equations in curved spacetime, and notably introduces gauge theory.
Viewable for free at: archive.org/details/mobot31753002089727/page/464/mode/2up.
There are unlisted articles, also show them or only show them.