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Devac


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hubskier for: 1297 days

Devac's recent comments, posts, and shares:
Devac  ·  4 days ago  ·  link  ·    ·  parent  ·  post: Pubski: October 9, 2019

Seems like I'm making new friends and spend a lot of fun time with other freshmen. Moving from institute to a bar can be surprisingly seamless, though we did build sort of a nerd corner for ourselves. There's also an air of cooperation that's very new to me, IRL at least. It's different from my general life experience, and I couldn't be happier about it.

Being a TA takes much more prep time than I expected, but I'm starting to develop a weekly routine that should be close to optimal. The commute is already solved, TA prep will likely plateau at about 2 hours per course per week, homework is nothing new (even though it's noticeably harder in general), and I'm moving through all the papers for my research assignment in a relatively comfortable pace. The fact I already have more free time than while I was at uni is weird as hell, though much appreciated.

In one word: progress.

Devac  ·  6 days ago  ·  link  ·    ·  parent  ·  post: What If We Really Are Alone in the Universe?

It's "Where P_0 is power in the narrowest crossection of the beam ~ power of the source." Sorry, I didn't notice the cut.

Devac  ·  7 days ago  ·  link  ·    ·  parent  ·  post: What If We Really Are Alone in the Universe?

    when I do arithmetic or algebra only, it feels like I've cheated and made unrealistic assumptions.

    Us chump experimentalists use real numbers all the time.

I just handed over my homework which concluded that the derivation of thermodynamic parameters in our model is A-OK because second derivatives are finite everywhere and third derivatives only tend to infinities when T = 0, which is, like, acceptable in critical systems under fluctuation/perturbation regime. We're all chumps, experimentalists just get swaggerific toys.

Can't believe I forgot about that incident. Also, would love to see that PSA.

Devac  ·  8 days ago  ·  link  ·    ·  parent  ·  post: What If We Really Are Alone in the Universe?

It's a good estimate of the lowermost power consumption, and you've done all the legwork. Kudos! Might be a base for fun Fermi problems or a reference point to some other interstellar communication discussions.

    but if there's no calculus involved, is it even math at all?? :/

Does it even need calculus? Beam dispersion would probably be some Gaussian bundle, dissipation is most likely adequately described as a sum of elements in form of whatnot_optical_coefficient * distance, error correction is a bunch of algebra, and involving any fancy astrophysics is just going to make us look desperate.

Also, it's been a while since I had to use actual numbers to solve a problem. :P

Devac  ·  8 days ago  ·  link  ·    ·  parent  ·  post: What If We Really Are Alone in the Universe?

So, the final formula is:

  Power = (p ^ m) * F * (c / λ) * π * r²

where:

p - Pogson's ratio [] (dimensionless)

m - magnitude [] (dimensionless)

F - flux [J / (s * cm² * Hz)]

c - speed of light [cm / s]

λ - wavelength [cm]

r - Earth's radius [cm]

π - pi [] (dimensionless)

Checking units:

  Power = ([] ^ []) * [J / (s * cm² * Hz)] * [cm / s] * [1 / cm] * [] * [cm²]

Power = [J / (s * cm² * Hz)] * [1 / s] * [cm²]

Power = [J / (s * cm² * Hz)] * [Hz] * [cm²]

Power = [J / s] * [(Hz * cm²) / (Hz * cm²)]

Power = [J / s] = [W]

No problems here.

Using our values:

p = 2.512

m = 4

F = 3.64E-27 [J / (cm² * Hz * s)]

c = 3E10 [cm / s]

λ = 5.5E-5 [cm]

r = 6E8 [cm]

pi = 3.14

we obtain:

  Power = (2.512 ^ 4) * 3.64E-27 * (3E10 / 5.5E-5) * 3.14 * (6E8)²

Power = 8.94E7 [W]

So… pretty close and the difference comes down mainly to rounding. Other than that, under your assumptions, I see no problems with reasoning or method. Sorry for taking so long to respond, though.

    Hey, what're you up to just after January 28th of 2024? Asking for a friend.

You need to double it, that's when Centaurs would get your message.

Devac  ·  12 days ago  ·  link  ·    ·  parent  ·  post: Pubski: October 2, 2019

I started my physics PhD studies for good, though we had a bunch of orientations/meetings in September. Theoretical/mathematical programme, specialization in condensed matter. It's pretty intense from the very beginning, but everyone's nice, and people seem to be going out of their way to help us accommodate. Got my first research assignment, wandered the institute, managed to hit it off with some of the other freshmen and feel woefully underprepared for my Introduction to Quantum Computing 1 class. Other courses are Modern Physics 1, Quantum Mechanics, and Physics of Condensed Phase, all of which seem less daunting. There's also a mathematical methods workshop we're starting next week, which looks pretty exciting.

Because I'm in a research-centred institute, there are no undergrads around, so we're completing our teaching quotas 'on loan'. I already had my first two sessions as a Physics 1 and Calc 1 TA at the local Polytechnic. Almost all of my students went through the extended maths exam after high school, which simplifies things for me, but I find the pace of Calc 1 to be absolutely ludicrous regardless of their prep. According to the syllabus, students are expected to be able to tackle simple 2nd-order ODE by the end of this semester, which, OK, it's doable, but I don't think it's good for them in the long run. That's like cramming a pile of Schaum's Outlines and about as likely to stick. The Calc 1 lecturer seemed somewhat annoyed when I brought it up during staff meeting, so it's probably best to just make it least confusing to students. Definitely not a fan, though.

My stipend is nothing to brag about, but it's also almost twice what I had during masters, which means no more moonlighting. I'm pretty stoked about that.

I also had to resign from chemistry. Not what I wanted, but the option of completing studies 'part-time' has suddenly become reserved for single parents ("mothers, preferably") and invalids. It's good to know they'd rather lose a good student than use those vaguely-worded-on-purpose rules to make my life a tad easier. Though that's also the same place that figured using me instead of setting up an automated dripper is more cost-efficient, so it's not like I'm all that surprised. Shame, but I now know reasonably enough to study chemistry on my own from this point onwards. It was never about getting a degree anyway.

Devac  ·  14 days ago  ·  link  ·    ·  parent  ·  post: Stronger than aluminum, a heavily altered wood cools passively

So, I finally had the time to go through the article's supplementary material, and I have to say that my previous point about susceptibility to moisture might not be as valid as I thought. While I'm not yet 100% certain about the specific, fluoro-silane bonds to hydrophilic OH groups throughout the volume of the sample instead of being a simple coating (which I wrongfully assumed), and they have treated the delignified wood sample in it before the pressing took place. They also conducted emissivity tests on both hydrophobic and untreated samples to see if it made any difference, which showed negligibly changed spectra. Anyway, while doing my due diligence I also found this fun paper in references, and will probably write something more once I'm done with those.

My bad, Hubski. I shouldn't have written my previous comment hastily, even if the Ars Technica author clearly didn't go through the trouble himself either.

Still think that the material is pretty damn neat, though.

Devac  ·  19 days ago  ·  link  ·    ·  parent  ·  post: Pubski: September 25, 2019

I'd like to thank everyone who reached out to me or spared a thought in passing. It means a lot, and I'm grateful to know so many wonderful people.

It's been a difficult month. Dealing with the death of someone close is never easy, but the hole after my father's passing is something I can't seem to get through. He was only sixty.

We weren't on good terms, but at least there was always some minuscule potential for improvement. To this day I receive condolences from his more distant friends, acquaintances, collaborators, coworkers etc. There's a degree of dissonance between what they say about him and my own memory, but I suppose it's normal.

I dialled his number from memory one time, and it took me a few moments to realise what I just did. I know that I'm not over it, but life has to go onwards. In that way, I'm still not completely over the fact I had two brothers, even though it's been fourteen years. They aren't here, and I know it on an intellectual level, but I sometimes stop to think about what they might be doing now.

Despite my manner of writing, I'm not nearly as much of a mess as this post. And there's good news too. First, very late this Monday, I became an uncle, and to a first girl born in our direct line in at least four generations. It was premature birth, but she's as good and healthy as a 7th-month delivery could possibly be. Second, I got into my first choice PhD programme and already went through orientation, TAship stuff etc. Whatever comes next, I'll at least be busy.

Devac  ·  24 days ago  ·  link  ·    ·  parent  ·  post: Nuclear explosions

You added an extra zero to comment ID.

Devac  ·  25 days ago  ·  link  ·    ·  parent  ·  post: Coral gardeners bring back Jamaica's reefs, piece by piece

I had no idea about the article, just recalled something from geology/geography electives taken over the years. Information is quite abundant, and here is an article that I probably bookmarked while looking this stuff up for uni.

Devac  ·  25 days ago  ·  link  ·    ·  parent  ·  post: Coral gardeners bring back Jamaica's reefs, piece by piece

Sending electrical current through growth frames can cause them to grow/regenerate even in very harsh conditions, though I don't know the exact extent of wishful thinking behind biorock building. To my knowledge, the more pressing problem behind coral's sensitivity to external conditions is algae bleaching, which impacts everything from sand production for nearby coasts, to biodiversity and biomatter production in the area.