Hacker News: longemen3000

New comment by longemen3000 in "Show HN: Free textbook on engineering thermodynamics"

longemen3000 — Sun, 26 Apr 2026 19:36:05 +0000

Hello,

The textbook seems nice and clear. The only nitpick i have is that it should talk more about equations of state. I understand that it may not be the focus of the text, but mentioning the current state of equations of state (SAFTs, cubics, multiparameter) would help guide readers looking on how to generate their own steam tables for their fluid of interest, even if the advice is just "go use CoolProp"

On the other hand, i really like the ilustrations on turbomachinery, helps ground the theoretical content.

New comment by longemen3000 in "The most famous transcendental numbers"

longemen3000 — Thu, 01 Jan 2026 00:36:11 +0000

some constants that may or may not be transcendental: - Percolation Thresholds: https://en.wikipedia.org/wiki/Percolation_threshold - Critical scalings in 3d: https://en.wikipedia.org/wiki/Universality_class#Ising_model

New comment by longemen3000 in "Programmers and software developers lost the plot on naming their tools"

longemen3000 — Fri, 12 Dec 2025 02:59:23 +0000

That is one thing i like about the Julia package ecosystem. The general Registry (where package metadata is stored and where you go to register a new package), recommends using explicit names over short acronyms. For example, DifferentialEquations.jl is a package that does differential equations in julia (recognizable via the .jl suffix). What does Garlic.jl do? Exactly, garlic (the vegetable) modelling.

New comment by longemen3000 in "APE – 0: An LLM Co-Pilot for Chemical Process Design"

longemen3000 — Mon, 12 May 2025 18:37:12 +0000

It seems like this uses DWSIM under the hood for the simulations? Cool project

New comment by longemen3000 in "Google lays off its Python team"

longemen3000 — Sun, 28 Apr 2024 14:31:19 +0000

_ is for Alphabet

New comment by longemen3000 in "7.4 earthquake in Taiwan, 34km depth"

longemen3000 — Wed, 03 Apr 2024 01:18:30 +0000

a 3-meter high wall of water is not really good either, due to kinetic energies, if no significant tsunami coastal protections, that water flow can reach far inland

New comment by longemen3000 in "The Rise and Fall of CORBA (2006)"

longemen3000 — Sat, 01 Jul 2023 06:38:45 +0000

CORBA is used in the chemical industry (CAPE-OPEN standard) https://www.colan.org/

New comment by longemen3000 in "In Erlang/OTP 27, +0.0 will no longer be exactly equal to -0.0"

longemen3000 — Wed, 10 May 2023 02:39:37 +0000

i don't use Erlang (mainly Julia), but this change makes a lot of sense. in Julia, there is the == operator (value equality) and the === operator (value egality). 0.0 == -0.0,because they have the same "value". but they aren't identical (the bits are different), so !(0.0 === -0.0).

New comment by longemen3000 in "Mojo – a new programming language for AI developers"

longemen3000 — Tue, 02 May 2023 19:21:28 +0000

i don't think so

New comment by longemen3000 in "Why are lithium prices collapsing?"

longemen3000 — Sun, 30 Apr 2023 16:38:21 +0000

tianqi sold all his shares of SQM (one of Chile lithium companies, around 23%) after the announcement. The situation of the lithium in Chile is very particular. in the Pinochet dictatorship, litium was nationalized, because it was a key ingredient of atomic bombs (and not much else at that time), and USA didn't want other countries to access the resource, so all current mines are in a lease contract (Albemarle until 2043, SQM until 2030). the new proposition opens new zones for exploitation, in exchange of the public-private parnership

New comment by longemen3000 in "Why are lithium prices collapsing?"

longemen3000 — Sun, 30 Apr 2023 16:29:19 +0000

"Fun" fact about that, it was nationalized because it is a material for use in atomic bombs, in the 70 and 80 there wasn't another use for large scale lithium mining, except for that

New comment by longemen3000 in "Beyond automatic differentiation"

longemen3000 — Fri, 14 Apr 2023 21:42:39 +0000

seems vaguely like McCornick relaxations? https://optimization.cbe.cornell.edu/index.php?title=McCormi...

New comment by longemen3000 in "Nvidia Unveils CuLitho: A “Breakthrough in Computational Lithography”"

longemen3000 — Mon, 27 Mar 2023 01:56:51 +0000

well, thermo is from the greek word thérmē meaning heat. we use the termo- suffix for all things that involve heat (thermodynamics -> termodinámica, thermometer -> termómetro)

New comment by longemen3000 in "Twitter Lost $60M a Year Because 390 Telcos Used Bot Accounts to Pump A2P SMS"

longemen3000 — Sat, 18 Feb 2023 16:04:15 +0000

I suppose that Twitter has to pay each time a SMS is sent (ar at least, they pay according to the amount of SMS generated), so the bots pump that amount?

New comment by longemen3000 in "Argentina Wins the World Cup"

longemen3000 — Sun, 18 Dec 2022 19:53:32 +0000

grande messi!

New comment by longemen3000 in "Instagram gets worse with dark patterns lifted from TikTok"

longemen3000 — Tue, 26 Jul 2022 03:28:33 +0000

for instagram, i just gave up looking at the feed and just look at the posts that a group chat sends

New comment by longemen3000 in "Jax vs. Julia (Vs PyTorch)"

longemen3000 — Wed, 04 May 2022 23:44:59 +0000

yeah, my systems are really small in comparison (1-20) but with higher order derivatives (up to 4th order), so reverse AD is not the best in that regard

New comment by longemen3000 in "Jax vs. Julia (Vs PyTorch)"

longemen3000 — Wed, 04 May 2022 22:27:05 +0000

I feel called out on the academic part hahaah. I simply want to code state of the art (thermodynamic) models, and at least julia helps by providing easy testing and publishing infraestructure. but obviously we can't compete with a corporation in code quality (we are trying!)

Unrelated, but for small sizes, i really prefer to use forward mode in julia (Via ForwardDiff.jl) instead of Zygote. the overhead of reverse ADing over an arbitrary function with mutation is not worth it.

New comment by longemen3000 in "What Is a Supercritical Fluid?"

longemen3000 — Sun, 03 Apr 2022 20:37:14 +0000

Of course! we are urgently in need of a "critical boiling" relation. At the moment we are using critical isochores as a way to "extend" the saturation curve, but it is less than ideal (at least they can be calculated quickly).

I agree with the Widom line, at the moment i haven't found any concrete relation to calculate those from a equation of state functional. if there is something concrete, i would be glad to code it.

New comment by longemen3000 in "What Is a Supercritical Fluid?"

longemen3000 — Sun, 03 Apr 2022 03:26:29 +0000

We have a solver for the pure critical point, that just finds the (v,T) coordinate that satisfies dP/dV = 0 = d²P/dV². of course, not all EoS can even satisfy this condition. Cubics have the correct temperature and pressure (by definition) but fail on volume. SAFT equations and all EoS with association terms predicts critical points with temperatures higher than the experimental ones. a lot of MultiParameter EoS (like IAWPS95, the standard for pure water) have some anomalies at the vicinity of the critical point. Nevertheless, finding such critical points, however far from reality are from the Real fluid that is trying to represent, helps on finding where are your properties in the phase diagram. In practice, you never stay at the critical point, you pass near it and you can tell by some properties that you are passing near it.

There is also new developments on "Phase equilibria" over the critical point,because it seems that supercritical fluids do present some sort of continuous phase transition between a liquid-like state and a gas-like state. there is this thing named the widom line that marks this separation, But not all EoS even present this line..., "are there phases in the supercritical fluid?" is a research question in that sense.