belzebalex

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.

> 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?

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 car parking assists and people trying to improve them would have gone the same route as I did.

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/Concours2021/PhysPSI.pdf

It's in French though!

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 tinkering and many tries, regardless of the builder's knowledge.

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 materials. Will also look at my test to see if it's really about that.

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).

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.

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 relative weight of an Antminer over the total Hash Rate of the bitcoin network, and the same for the validator node.

Where is this 1/4 factor coming? I know that for a circular dish, the max resolution is 1.22lambda/(aperture size), so for my scanner it would be (1/4)lambda/(aperture size)

Scanner is 100mm large, so that would do 2/100 radians. Will check up if that matches my simulations.

Thanks for the infos on SAR! Will try doing that!

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 cosine in two dimensions centered on the object.

I don't understand. Having more points by using smaller phase-shifting steps won't make my beam narrower?

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/mLAhT2h

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.

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 place the ground station (eg: not on the top of your house)?

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 program (la prépa for the Frenchs). Currently thinking of building a v2 next year when I have more time.

Would love chatting with you, see my page: https://alextoussaint.com

None for the moment, I'm planning to open source everything in the next months. I'll publish on my website (alextoussaint.com)

A phased array ultrasonic sonar to make autonomous drones.

Yes, you read that right.

Pics here: https://twitter.com/alextoussss/status/1347969518539337730

Asked myself, would it be possible to build a Geiger counter with RAM?

The figure comes from the source of the photos: https://www.friendsoftibet.org/main/execution.html

Am I the only one who instantly thought of Mao's Four Pests Campaign?

https://en.m.wikipedia.org/wiki/Four_Pests_Campaign

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.

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 is free!

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 able to help many potential customers.

As developers who never need help, we tend to forget that some people might do, and that a Chatbox that annoys us can help them.

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 technology and I have no hope that they will be better than the current leaders we have :/

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'm sure you can find exceptions to that, and I'm genuinely curious about it), and that's a big problem. The only two french apps I use are the RATP's app and BlaBlaCar once every year.

You can't deny that we're too dependent on key technologies coming from abroad.

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. There's a reason why François Chollet and Yann LeCun have fled away.

Old companies in France don't build anything new. Maybe we do have startups, but do we have successful ones?

Concerning your last point, saying that the current 3000-pages laws are just "preventing you from treating people like shit" is a simplification.

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 aggressive cuts in our way of life because France won't produce anything anymore.

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.

One source: https://www.entreprises-et-droit.fr/annonce-legale-creation-...

Maybe did your company have a bulk pricing? Often, companies that offer "registration as a service" have a 200eur fee that excludes that kind of administrative fees. But 30eur for the announcement? Never seen that.

Yeah, as a French I can only completely agree. The amount of paperwork is just absurd. For instance, when you create a company, you have to pay a separate fee (~200eur) to a private "official journal" to publish the fact that you're creating a company. That's just plain racket, and that kind of things is everywhere.

France is dying, because France can't have a private sector because of its regulations.

The fun part is, now that France is in the neo-liberal EU, France is dismantling its super-big-yet-working-ok public sector to make place for private companies... That can't exist because of regulations.

France is dying to me. As an 18-yo, I'm seriously concerned on what to do for my future. The country has a super good education system (I would easily say the best in the world, by far) (just check out the ENS's Nobel prize / admissions ratio) but has no companies where people do any work. Most of the brilliant French minds go to work in other countries where it's possible to create and operate a company.