belzebalex

10 ms·

31.
by belzebalex 5y ago
Very interesting! Do you have any links for me to learn more? There are a few limits on what you can scan with only 3 mics. I detail everything in my article. Really suggest you read it.
32.
by belzebalex 5y ago
> I'm just saying that putting the transducer in the emitter was a non-starter I don't get it. What do you mean by that?
33.
by belzebalex 5y ago
I guess that the main option is the second one. Lidars, once they are solid-state and cheaper will be a better alternative (smaller, more precise and much faster). The first option isn't the good one. Ultrasounds are already used in ca
34.
by belzebalex 5y ago
It is this year's entrance exam (PSI) for the École Normale Supérieure and the Polytechnique school. The subjects have not been officially published. But here's a scanned copy: https://www.cpge-paradise.com/Concou
35.
by belzebalex 5y ago
Author here. It's all digital (square waves!). There were definitely well-known circuits for driving transducers, but I had to improvise to make a circuit small and simple enough to build 100 of them. Building new circuits requires tin
36.
by belzebalex 5y ago
I think one of the subjects of my exam for entering engineering schools (a thing we do in France) was about that. Would really like to see papers on the subject, because I don't really understand how you can use lasers in opaque materi
37.
by belzebalex 5y ago
Thank you!I've been helped a lot by how technology changed for the past few years (lots of good resources online, was able to do simulations easily, MCU programming a lot easier, etc).
38.
by belzebalex 5y ago
The maths is exactly the same, except that the beamforming is at the reception rather than at the emission. But it works based on the same principle.
39.
How I built the world's first 3D ultrasonic scanner(alextoussaint.com)
152 points by belzebalex 5y ago|44 comments
40.
by belzebalex 5y ago
While I agree with the final point, I would have hoped for better arguments. It's not because one validator node consumes 1% of the energy consumed by an Antminer that PoS consumes 1% of what PoW consumes ... You need to weigh in the r
41.
by belzebalex 5y ago
Where is this 1/4 factor coming? I know that for a circular dish, the max resolution is 1.22 lambda/(aperture size), so for my scanner it would be (1/4) lambda/(aperture size) Scanner is 100mm large, so that would do 2&#
42.
by belzebalex 5y ago
The scanner is fixed, but the beam is moving. In a synthetic aperture, the beam is fixed but the scanner is moving, which should be equivalent for a first approximation. A "dot" like a hard solid round object returns a cardinal co
43.
by belzebalex 5y ago
Posting the links here so they're clickable: the device and a few things I scanned - myself and the room I'm working in: https://imgur.com/a/kxSTn2J gif of my beam: https://imgur.com/a/mL
44.
Ask HN: Help on SAR/deconvolution for an ultrasonic phased array radar
7 points by belzebalex 5y ago|6 comments
45.
by belzebalex 6y ago
When something like this is proposed, remember Mao's Four pests campaign. The ecosystem is way too complex for us to understand. This might finish very badly.
46.
by belzebalex 6y ago
I've seen the figure of 130W used by the ground station. 100W is a lot, from memory 4G cell towers are only ~10W. What's the kind of RF exposure you get around a ground station? Is SpaceX giving recommendations around where to pla
47.
by belzebalex 6y ago
Hey there! I'm from France, 18yo and founded a SaaS with a friend when I was 16 ( https://kaktana.com ). It's been doing ~$800/month for the last 1.5 years as I had to stop working on it for a very intensive school
48.
by belzebalex 6y ago
None for the moment, I'm planning to open source everything in the next months. I'll publish on my website (alextoussaint.com)
49.
by belzebalex 6y ago
A phased array ultrasonic sonar to make autonomous drones. Yes, you read that right. Pics here: https://twitter.com/alextoussss/status/1347969518539337730
50.
by belzebalex 6y ago
Asked myself, would it be possible to build a Geiger counter with RAM?
51.
by belzebalex 6y ago
The figure comes from the source of the photos: https://www.friendsoftibet.org/main/execution.html
52.
by belzebalex 6y ago
Am I the only one who instantly thought of Mao's Four Pests Campaign? https://en.m.wikipedia.org/wiki/Four_Pests_Campaign
53.
by belzebalex 6y ago
I was more thinking of directly accessing the hidden service through the tor network (without a proxy on a VPS), which is acceptable if you're the only user.
54.
by belzebalex 6y ago
An esoteric alternative is to host a Tor hidden service. Tor hidden services don't require you open ports, and you don't need a static IP address. Your residential IP is protected by the onion router, and the .onion domain name
55.
by belzebalex 6y ago
I thought like you in the past. I only installed the Crisp chatbox (with no popup) on my SaaS and was very surprised with the results: I got more contact from users through it than through Email or Telegram. I got a lot of feedback and was
56.
by belzebalex 6y ago
Completely agree with all you said. Although, I am friend with lots of people who are starting careers in politics, and they're all coming from Business School or Sciences Po. None of them knows about the fundamentals of nature and tec
57.
by belzebalex 6y ago
Seems like you know more about the legal code than I do. Maybe am I wrong on the root causes. France's leadership in technology is still poor though: all the consumer hardware we use comes from Asia with software coming from the US (I&
58.
by belzebalex 6y ago
Airplanes? You're right. Rockets? Ariane is being eaten alive by SpaceX, and the bureaucrats won't move fast enough. They can't even agree on Ariane 6. AI: Yeah France's really good at supplying engineers for Facebook.
59.
by belzebalex 6y ago
I agree with some of that. But we can only live like that in the short term. We're currently China-sponsored: just look at the size of our debt! The 2021 budget is half funded by debt! One day will come when we'll have to make agg
60.
by belzebalex 6y ago
Typical bureaucratic mess. Completely unmanageable by normal humans. It's as if the law is made super complicated just to give a job to lawyers.

More ›