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japanuspus

1,299 karma · joined September 18, 2015

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japanuspus··on Boycott IETF 127
Traveling to awesome places is a perk of (physics) academia that is not widely appreciated. A large fraction of physicist seems to do rock-climbing or other hobbies that align well with exploring the outdoors when traveling.

I got my first taste of this with this was a summer school at Les Houches in the French Alps [0], and after graduating I did postdoc positions on three different continents -- all the time appreciating that unlike corporate expats, I got to choose the exact place to go next. Would highly recommend this way of traveling over backpacking.

[0] https://www.houches-school-physics.com/ecole-de-physique-des...

japanuspus··on Show HN: A website that makes your text look cool anywhere online using Unicode
If you want to dive into the details, you can copy the "fonted" output to a unicode analyzer. [0] is an online unicode analyzer that seems to work well.

[0]: https://devina.io/unicode-analyser

japanuspus··on Conda: A package management disaster?
The problem conda solved that nothing had solved before was installing binary dependencies on MS Windows.

Before conda, getting a usable scipy install up and running on MS Windows was a harrowing experience. And having two independent installations was basically impossible. The real hard work that went into conda was reverse engineering all the nooks and crannies of the DLL loading heuristics, to allow it to ensure that you loaded what you intended.

If you are working on macOS and deploying to some *nix in the cloud, you are unlikely to find any value in this. But in ten years as lead on a large tool that was deployed to personal (Windows) laptops in a corporate environment, I did not find anything that beat conda.

japanuspus··on Jupyter Notebooks as E2E Tests
You don't even need a plugin: I have been using a setup with parametrized tests and `runpy` for a while [0]. Works especially well if you use jupytext[1] for just storing the input part of the notebook as a python script -- which is good for version control sanity in any case.

[0]: https://stackoverflow.com/a/56813896/212538 [1]: https://jupytext.readthedocs.io/en/latest/

japanuspus··on NASA Pulls Off Delicate Thruster Swap, Keeping Voyager 1 Mission Alive
The Voyager mission is such a wild achievement. Both the sublime design and craftsmanship that must have gone into the hardware, and the deep institutional knowledge required to keep it running is awe-inspiring.
japanuspus··on Tiny robots with a big impact: microrobots for single-cell handling
This is crazy: my initial thought was that the first figure was some kind of diagram, but it is a microscopy photo of the actual physical system they have built!

The "micro-robots" are constructed by two-photon polymerization and actuated by laser tweezers grabbing onto "handholds". This avoids the laser heating up the biological specimens.

Note: two-photon polymerization is not not the same as what resin 3D printers use.

Paper: https://onlinelibrary.wiley.com/doi/full/10.1002/adma.202401...

japanuspus··on General Electric HTRE-3 Nuclear Jet Engine
The correction for cruising height would be insignificant.

A ram-jet is an air-breathing engine and would be confined to the atmosphere. Even a 60km cruising height (which is much higher than what would be used) would only correspond to a 1% increase in flight path circumference compared to the surface value of 40.000km.

japanuspus··on Spreadsheet Assassins – A short history of "software as a service"
To me, Obsidian is a perfect example of how to get SaaS-revenue without making the user captive: All data is stored in an accessible form on the user hardware, and what you pay for is sync.

X-user kepano (who is a/the creator of Obsidian) has some nice insights on this _file over app_ philosophy.

japanuspus··on Denmark recalls Korean ramen for being too spicy
This is the same country that basically threatened to leave the EU when rules to limit the contents of ammonium chloride in food were proposed [0]. Source: am Danish.

[0]: https://www.euractiv.com/section/agriculture-food/news/regul...

japanuspus··on Cement recycling method could help solve one of the big climate challenges
They replace the flux used in steel recycling with used concrete, and instead of useless slag they get recycled cement.

This is a really good idea, but it is important to keep in mind that even if all of the steel production in the world (~100 Mton/y) shifted to this method, it would only have a negligible impact on the cement production (~ 4 Gton/y).

japanuspus··on Kobo announces color e-readers
From family with a mix of kindles and kobos: yes, this is painless.

You can check beforehand by installing Calibre with the de-DRM plugin and transferring a few books: Once they are on Calibre you are good to go.

One thing I only learned today is that you can set up web sync from Calibre to Kobo [0], [1], but just plugging in to sync has been working fine for me.

For the initial sync, it used to be you could directly de-DRM your whole collection from the storage of the kindle desktop app. At some point the desktop app was using a DRM that had not been broken: I do not know if this is still the case, or if there is another way to download everything from your account.

[0]: https://news.ycombinator.com/item?id=39996455 [1]: https://brandonjkessler.com/technology/2021/04/26/setup-kobo...

japanuspus··on Terraform makes carbon neutral natural gas
Because some of the windfarms still run on legacy contracts where they were incentivized by a guaranteed selling price for the power they produce. They are reimbursed for the loss of income they suffer due to curtailment.
japanuspus··on New jet engine enables efficiency at every speed for cheaper orbital launches
Everyday Astronaut has a recent video on "why don't we launch rockets from jets"[0]. The video obviously does not include reference to the engine mentioned here -- but I think most of the points still stand.

In particular - orbit is mainly about going fast, not so much about getting up high - your second stage will pay a structural price for allowing air-launch loads, and this structure needs to be carried to orbit - rockets are *big*

[0]: https://www.youtube.com/watch?v=AAt9WDQEMoA

japanuspus··on Rainwater everywhere on the planet is unsafe to drink due to chemicals (2022)
Comparing nitrites (which occur naturally) with PFAS and other "forever chemicals" is off the board. To my understanding the observed and very real ill-effects of toxic bacterial excretions due to nitrites being phased out in lunch-box products (sliced ham, salami) here in the EU far outweigh any possible effects of the nitrites. Source: reddit comments that seemed legit.
japanuspus··on Turing Complete is a game about computer science
Are you aware that "Turing Complete" has a Verilog export function?
japanuspus··on Lilygo T-Deck: 2.8-inch IPS LCD display, mini keyboard, and ESP32 processor
One of the commentators on the Lillygo page mentions that this is perfect hardware for "Meshcom"[0], which is "a project to exchange text messages via LORA radio modules."

This was the first use case that came to my mind, and MeshCom seems like a well-executed implementation.

[0]: https://icssw.org/en/meshcom/

japanuspus··on Swedish dockworkers are refusing to unload Teslas at ports in broad boycott move
Important context which I could not find mentioned in TFA: A key reason for the sympathy strikes is that Tesla brought in scabs which is a big no-no in Scandinavian labor markets.
japanuspus··on Almost no one pays a 6% real-estate commission except Americans
Where I live (Denmark), the real estate guild has captured the market by building the de-facto listing portal and only making it available to registered brokers. Sounds great if the US portal (MLS?) is available to all listings.

For selling a small plot of land I got so angry about the fees for nothing that I paid an obviously rogue broker to proxy-list the thing. This guy was charging half of what the other brokers were (still way too much), and did not do anything except upload documents from me.

japanuspus··on Ethernet Is Still Going Strong After 50 Years
The thing is that compared to Token Ring etc., Ethernet really is an "ether" where you just send your packets and hope that there is no collision. But yes.
japanuspus··on Auto industry executives admit electric vehicle plans are in jeopardy
For (~100kg) pedestrian, I am sure the difference in lethality from being hit by a 1000kg vehicle vs a 3000kg vehicle is insubstantial. Where the weight would matter is for vehicle-vehicle collisions.
japanuspus··on Nitrogen electroreduction with almost 100% current-to-ammonia efficiency (2022)
At current costs, a price-optimal solar/wind/battery mix for handling existing electricity needs would have on the order of 400% overcapacity. All that extra electricity is what will power the hydrogen-generation.

The main challenge is building cheap electrolysers without so much regard to efficiency, in order to use all the power when available. Most commercially available electrolysers today are expensive and cannot ramp up and down quickly.

japanuspus··on Java implementation of a quantum computing resistant cryptographic algorithm
Quantum factoring may not be quite as far distant as you might think

Most importantly, Shor is not the algorithm of choice for first-gen hardware where the central challenge is likely to be circuit depth due to error correction overhead. The current front-runner is a probably proposal by Regev [0] with a space-optimization by Ragavan et al. [1], which factors an n-bit integer with O(n log n) logical qubits and a circuit depth of O(n).

What you should be looking for when studying quantum computing press releases is "fault tolerance": A central problem in QC is that the underlying hardware needs to be better than an (architecture-specific) threshold, before error-correction can be applied without introducing more errors than it corrects.

Nobody has really crossed the threshold yet with scalable hardware, and when someone does, the overhead will be abysmal (2 or 3 layers of error correction, each with a factor ~100 overhead in space and time). Still, there are two reasons to be optimistic:

One reason is that once a system crosses the threshold, any improvement in hardware will result in exponential improvements in the encoded operations, meaning that there will be a Moore-style exponential development.

Another reason is that there are several "dark mode" VC-funded companies working towards intrinsically scalable systems based on optical QC: If any of these achieve fault tolerance, they will be scalable from day one.

[0]: http://arxiv.org/abs/2308.06572 [1]: http://arxiv.org/abs/2310.00899

japanuspus··on Why did the Motorola 68000 processor family fall out of use in PCs?
Hey - Z80 was nice! I wrote Z80 assembly by converting from op-codes to hex by hand based on a couple of copied pages from the datasheet.
japanuspus··on Costco gold bars are selling out within hours
[[citation needed]]
japanuspus··on Desalination system could produce fresh water that is cheaper than tap water
The fundamental limit to energy expenditure is not the heating and boiling of water (as others have pointed out, that energy can all be captured). Rather, the limit is set by the requirement for the entropy of the universe to not decrease when we reduce the local entropy in the salt-water system.

According to GPT4, the numbers come out to 760 J/L for seawater with a salt concentration of 35 g/L. That would mean a limit of around 2 L/s*m2 for full intensity sunlight.

japanuspus··on EU proposes 10-year renewal for glyphosate herbicide
The reason this makes sense is that without glyphosate, farmers (and private gardeners) would start using something else, and the likelihood that whatever new compound they find will be worse than glyphosate is very low.

Yes, there are indications that you can get toxic effects if you massively overdose glyphosate, but overall it is a miracle that a generic weed killer which decomposes as easily even exists.

For context: no-till farming is a candidate technology for binding massive amounts of carbon in farmland. In intensive farming, no-till is completely reliant on glyphosate.

japanuspus··on Linear code is more readable
I realize this is tongue in cheek, but really: Read code!

If you ever start plateauing in your code skills, start digging into the code of your favorite open source project. Accept that things have been done in another way than you would for a reason and try to understand that reason.

Try joining advent of code[0], and make sure to spend half you time block on reading and understanding alternative solutions.

[0]: https://adventofcode.com/

japanuspus··on A mathematical formalization of dimensional analysis (2012)
Seeing the paragraph below I almost thought the author would move on to discuss the particular engineering horror that is logarithms of non-dimensionless values, but it is probably all for the best that this practice remains hidden.

"A related limitation, which is not always made explicit in physics texts, is that transcendental mathematical functions such as {\sin} or {\exp} should only be applied to arguments that are dimensionless"

japanuspus··on A mathematical formalization of dimensional analysis (2012)
Related post currently on the front page: "What is Dimensional Analysis", https://news.ycombinator.com/item?id=37493955
japanuspus··on Blacksmithing is alive and well in Kentucky
This is incorrect. The magnetic flux will induce an electromotive force that will cause a current to flow in any conducting material and cause heating if this material is not superconducting.

As an example, induction heating is a commonly used method in zone melting for Si-purification [0].

The effect is more pronounced in ferromagnetic materials because a larger flux is induced.

[0]: https://en.wikipedia.org/wiki/Zone_melting

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