UmbralRaptor changed the topic of #kspacademia to: https://gist.github.com/pdn4kd/164b9b85435d87afbec0c3a7e69d3e6d | Dogs are cats. Spiders are cat interferometers. | Космизм сегодня! | Document well, for tomorrow you may get mauled by a ネコバス. | <UmbralRaptor> … one of the other grad students just compared me to nomal O_o | <ferram4> I shall beat my problems to death with an engineer.
<egg|zzz|egg>
bofh: well not sure what the triangle has to do with ANBO
<egg|zzz|egg>
!wpn UmbralRaptor
* Qboid
gives UmbralRaptor a theta alternator
<soundnfury>
egg|zzz|egg: prisms in binoculars?
<UmbralRaptor>
egg|zzz|egg: All there is to life is triangles!
<UmbralRaptor>
See /topic gist
<egg|zzz|egg>
ah yes
<egg|zzz|egg>
UmbralRaptor: should I play some DF
<egg|zzz|egg>
or sleep, considering it's 01:05
<egg|zzz|egg>
!choose DF|sleep
<Qboid>
egg|zzz|egg: Your options are: DF, sleep. My choice: sleep
<UmbralRaptor>
;choose DF|sleep
<kmath>
UmbralRaptor: sleep
<UmbralRaptor>
The bots have spoken.
<soundnfury>
not all of them...
<soundnfury>
UmbralRaptor: choose DF|sleep
<UmbralRaptor>
I choose sleep (if you can get it to compile)
<kmath>
<bofh453> Ahh yes, eXtremely Large Magnetoresistance (XMR). Not to be confused with Giant MR (GMR), Colossal MR (CMR) or Extr… https://t.co/1f5OaFHoga
<egg|zzz|egg>
um
<egg|zzz|egg>
wait how
<UmbralRaptor>
egg|zzz|egg: humans sleeping is like running xscreensaver or after dark, right?
<kmath>
<bofh453> <@eggleroy> not sure if mathgen or snippet from the abc conjecture proof summary <@jgerity> When gibberish is the s… https://t.co/FpRcZw5xxV
<Ellied>
We just had proof by contradiction introduced to E&B for proving symmetry arguments, and it's a little rough for me so far because I keep being satisfied with the proof before getting to the actual explicit contradiction
<Iskierka>
I don't think a proof by contradiction should be satisfactory until you do the contradiction?
<Iskierka>
the whole point is you should build up nonsense that must be true if premise is, so premise isn't
<Ellied>
ik, it's mostly just that "a sphere is spherically symmetric" has not occurred to me as something I need to prove in the couple times when I've run over that issue so far
<Iskierka>
... spherically symmetric is an odd one but we've not done symmetry in higher dimensions
<bofh>
^
<Iskierka>
what's the proof by contradiction for it?
<soundnfury>
... is the definition of <shape>ically symmetric not "has the symmetries of a <shape>"?
<Ellied>
basically "If I look at this charge distribution from an arbitrary angle, I see the same thing, so if the electric field looked different from different angles, contradiction"
<Iskierka>
sphere: all of them
<Iskierka>
that seems backwards
<Ellied>
To me, the unintuitive thing is "how does it look when I look at it from this angle" and not "a spherically symmetric charge distribution has a spherically symmetric field"
<Iskierka>
surely start at "if the sphere is not symmetric, different angles must look different. It doesn't, therefore it is"
<Ellied>
thus my difficulty
<SnoopJeDi>
Iskierka, show your work for "It doesn't" :P
* Iskierka
is skipping the step that's non-trivial in single lines of text in favour of having argument in logical order
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<SnoopJeDi>
Ellied, I always think of that sort of symmetry argument as physics being self-consistent. The "same" input should produce the "same" output. My understanding of the rigorous algebraic bits is admittedly poor
<kmath>
<rygorous> Tick or Treat: no vague threat of "tricks", just keep a ready supply of probably* lyme-disease free ticks in case treats aren't up to snuff.
<Iskierka>
inb4 weird convoluted shapes that even out just right for a spherical field
<bofh>
SnoopJeDi: heh I was literally going to mention Noether's Theorem.
<SnoopJeDi>
She's a well-beloved lady here with all the cosmologists we breed round these parts :)
<soundnfury>
anyway, a sphere is {x:x⋅x = r²}, rotations are (umm, unitary? orthogonal? I can't remember which magic matrix word I need here) so Rx⋅Rx = x⋅x, result follows
<bofh>
Iskierka: I'm pretty sure that any such shape would always have to be a sphere
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<soundnfury>
in general {symmetries} = {linear automorphisms} or something roughly like that
<SnoopJeDi>
soundnfury, no distinction over the reals IIRC
<soundnfury>
SnoopJeDi: but it may be neither of those
<bofh>
SnoopJeDi: orthogonal with determinant 1, for what it's worth.
<bofh>
er
<bofh>
soundnfury: ^
<soundnfury>
yeah, is there not a word for that?
<soundnfury>
ohh, SO, according to wikilies
<bofh>
like it *is* unitary over R^n
<SnoopJeDi>
yea "no distinction" was poorly chosen phrasing
<bofh>
(and indeed that's the property you want - R preserving the inner product)
<SnoopJeDi>
I rather meant that you can't tell the difference in a Pepsi challenge over ℝ
<bofh>
"Pepsi challenge"?
<egg|phone|egg>
!wpn
* Qboid
gives egg|phone|egg a Brand New Photoneutronic Engine
<FluffyFoxeh>
!wpn
* Qboid
gives FluffyFoxeh an Abelian mass
<SnoopJeDi>
marketing campaign they ran with a blind test vs Coke bofh. Just a turn of phrase I like to abuse
<FluffyFoxeh>
man this weapon is too specialized for me to use
<bofh>
SnoopJeDi: ahh. I *vaguely* remember that.
<bofh>
just wanted to make sure it was that :P
<bofh>
!wpn FluffyFoxeh
* Qboid
gives FluffyFoxeh a barred spiral sequence point
<egg|phone|egg>
In an Abelian mass, if you pray for something it prays for you
<SnoopJeDi>
but yea most of the time when we discuss it in physics we're doing the same work of identifying the automorphisms as soundnfury pointed out
<FluffyFoxeh>
weren't there some legal threats issued over the pepsi challenge
* egg|phone|egg
pets the morphisms
<soundnfury>
egg|phone|egg: if you pray too long for the Ab[elian ma]ss, the Ab[elian ma]ss prays also for you
<FluffyFoxeh>
no, there weren't. I'm thinking of something else
<FluffyFoxeh>
which isn't even related to pepsi at all
<soundnfury>
FluffyFoxeh: PEPSSI?
<SnoopJeDi>
Spicy PEPSSI?
<bofh>
I'm now wondering who'll be the first to name something Background Energy Particle Ionization Spectrometer or equivalent.
<SnoopJeDi>
LOL
<FluffyFoxeh>
bepis?
<FluffyFoxeh>
I don't get it
<FluffyFoxeh>
:p
<SnoopJeDi>
itsanoldermeme.jpg
<FluffyFoxeh>
lol
<SnoopJeDi>
oh, I'd forgotten it was in Undertale, too
<kmath>
<johnregehr> Dude is there nowhere else to put the computer when you get up to answer the door https://t.co/0ZEjrXm3BX
<egg|zzz|egg>
!wpn rqou
* Qboid
gives rqou a zinc contingent spectrophotometer
<egg|zzz|egg>
!acr -add:GCCS Government Chinese Character Set
<Qboid>
egg|zzz|egg: I added the explanation for this acronym.
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<egg|zzz|egg>
!tell rqou do you have any nice examples of things that get really broken by rendering unified CJK ideographs as the wrong variant? the only things I can easily find are tables of characters that vary, but it's hard to tell how important the variation is, and how frequent an occurence that is
<Qboid>
egg|zzz|egg: I'll redirect this as soon as they are around.
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<egg|work|egg>
!wpn UmbralRaptor
* Qboid
gives UmbralRaptor a spiral cut category
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<egg|work|egg>
ohh nice, on android if I set my phone's language to taiwan chinese the correct variants do get picked (at least for the grass radical)
<egg|work|egg>
that kind of waters down ken lunde's argument that "it will all actually unify itself because phones don't support variant glyphs" :D
<egg|work|egg>
(I mean those whole arguments that "it's just variant glyphs like a or g fall on their faces with the standardization of IVSes but still)
<egg|work|egg>
ooooh it's even nicer, if my preferred language is en-GB but my first CJK language in the list of preferences is zh-Hant-HK, my notifications about the cat album wherein I share catpics with UmbralRaptor get the 4-stroke grass radical \o/
<egg|work|egg>
yay
<egg|work|egg>
!u 猫貓
<Qboid>
U+732B CJK IDEOGRAPH-732B (猫)
<Qboid>
U+8C93 CJK IDEOGRAPH-8C93 (貓)
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<egg|work|egg>
!wpn котя
* Qboid
gives котя a snub hafnium ТП-82
<egg|work|egg>
whitequark: are there cats in cupertino
<kmath>
<ken_lunde> The “PanCJKV” IVD collection became very useful for a current task, specifically that “plain text” does the job. https://t.co/ESMWYfcDsD
<egg|work|egg>
!wpn bofh
* Qboid
gives bofh a Hitachi detector which strongly resembles a coilgun
<kmath>
<DataSciFact> 'Data isn’t fissile material. It doesn’t spontaneously reach critical mass and start producing insights.' -- Marko Karppinen
<Ellied>
so apparently Tortoise767 found my IRC server. he's been idling there on like five different devices for a few days and constantly joining and pinging out, and at some point asked the void "Does Ellied still play KSP?" (I'm the only other person connected at the moment and was also at the time)
<Ellied>
situation is still only about 80% grokked
<egg|work|egg>
who was that? I faintly remember that nick
<SnoopJeDi>
which reminds me, I should read Stranger in a Strange Land
* SnoopJeDi
? to-read anxiety
<Ellied>
same
<SnoopJeDi>
I have a vague recollection of that person from #kspofficial, but no association other than "a bit spazzy but enthusiastic about KSP"
<egg|work|egg>
!wpn Ellied
* Qboid
gives Ellied a nilpotent backward hug
<egg|work|egg>
!wpn Fiora
* Qboid
gives Fiora an acid-sensing catastrophic truffle
<Ellied>
egg|work|egg: Tortoise767 is a KSPer, I met him on KSPO a couple years ago. I don't remember anything much about him besides occasionally acting vaguely creepy to me (I think in the standard "wait, a girl on the internet????" pattern)
<SnoopJeDi>
ugh.
<Ellied>
has DMd me on the bird website a few times with Raspberry Pi questions
<SnoopJeDi>
dear lifeforms please be decent to each other send message
<Ellied>
sending this message was important to us; we considered ourselves to be a powerful culture
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<kmath>
<RichFelker> @oshepherd @johnregehr If nothing else, malloc returns a pointer to memory suitably aligned for any type, and 0xdea… https://t.co/Fr2zsc1aRN
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<egg|nomz|egg>
bofh: what about 0xabad1dea
egg|nomz|egg is now known as egg
<APlayer>
Ellied: Humm, what's the deal with enhancement and depletion modes in MOSFETs? I always assumed that was synonymous with P-channel and N-channel respectively, but apparently it is not...
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<egg>
!u I
<Qboid>
U+0049 LATIN CAPITAL LETTER I (I)
<bofh>
um
<Ellied>
!tell APlayer So the VAST majority of MOSFETs are enhancement mode, depletion mode ones are super rare as far as I know, so statistically, if you have a MOSFET and no one's made a big show of telling you that it's depletion, it's enhancement
<Qboid>
Ellied: I'll redirect this as soon as they are around.
<Ellied>
!tell APlayer an enhancement N-channel MOSFET is off when Vgs is zero and on when it's at some positive value. For a depletion N-channel MOSFET, it's *on* when Vgs is zero and off when it's at some *negative* value. It's the same in terms of "raising Vgs = turning on" but the offset is different.
<Qboid>
Ellied: I'll redirect this as soon as they are around.
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<Ellied>
APlayer: JFETs behave a lot like depletion MOSFETs, AIUI.
<APlayer>
JFETs?
<Qboid>
APlayer: Ellied left a message for you in #kspacademia [01.11.2017 21:25:24]: "So the VAST majority of MOSFETs are enhancement mode, depletion mode ones are super rare as far as I know, so statistically, if you have a MOSFET and no one's made a big show of telling you that it's depletion, it's enhancement"
* APlayer
googles
<Ellied>
yeah, junction field-effect transistors. Their actual functionality is simpler than MOSFETs, but they're more uncommon and trickier to work with in most cases
<Ellied>
JFETs sort of act like a hose clamp, where the voltage on the gate either squeezes the charge carriers out of the channel and prevents current from flowing, or doesn't (and allows current to flow)
<APlayer>
Got it
<Ellied>
and that analogy *sort of* describes why they tend not to like to carry very large currents; you wouldn't use a hose clamp for an industrial-sized water pipe, you'd use a big valve (a MOSFET) but that analogy is a bit limited
<APlayer>
So depletion mode is when the gate voltage depletes the conductive part of electrons?
<Ellied>
basically, yes.
<APlayer>
And how is that different from being an N-channel MOSFET?
<Ellied>
if you take 0 Vgs to be the null state ("doing nothing") and nonzero Vgs to be "doing something", then "doing something" to an enhancement mode MOSFET turns it on, and "doing something" to a depletion mode MOSFET turns it off.
<APlayer>
Well, in that case what I don't understand is not what enhancement or depletion mode is, but what N-channel and P-channel means :P
* APlayer
googles
<Ellied>
both N and P-channel enhancement MOSFETs are *off* when Vgs is zero. P or N channel determines if a negative or positive voltage turns it on.
<APlayer>
Ah! I think I got it
<APlayer>
...so, since a negative voltage can be 0 with something positive on the Source pin, it is in effect similar to a depletion mode FET?
<Ellied>
ah, no, it's the voltage *from gate to source* that matters. If the source is at 5V and the gate is at 5V, Vgate - Vsource = 0.
<APlayer>
s/0/0 at the gate/
<Qboid>
APlayer meant to say: ...so, since a negative voltage can be 0 at the gate with something positive on the Source pin, it is in effect similar to a depletion mode FET?
<Ellied>
if Vgate = 0V and Vsource = 5V, then Vgs = -5V
<APlayer>
It's my wording
<Ellied>
alright
<Ellied>
my old electronics textbook draws a cute little family tree of six different kinds of field-effect transistors; four MOSFETS (each combination of P/N channel and enhancement/depletion mode) and two JFETs (N and P channel, depletion mode only)
<APlayer>
Anyway, an enhancement mode N-channel MOSFET can be similar to a depletion mode P-channel MOSFET, and vice versa?
<Ellied>
a little. if you replace an N-channel enhancement MOSFET in a circuit with a P-channel depletion mode, you basically invert what the gate does. High=off, low=on.
<Ellied>
ALSO, note that the gate and source do not swap position, so to turn it all the way off, you have to raise the gate voltage at least the threshold above *the positive rail*, not the negative rail that the drain is connected to.
<Ellied>
that's more or less why JFETs are hard to work with, because for many trivial cases of operation, two power rails aren't enough.
<APlayer>
Well, let's keep that for a later point. I have currently ignored specific weirdnesses like MOSFETs with 4 - 8 pins and such, and honestly I don't think I am ready for such stuff yet ;-)
<APlayer>
Thanks a lot for explaining this to me so far!
<APlayer>
I'll have another look at specific MOSFETs in the next day, apparently my local elections shop (I live pretty much in a small town in the middle of nowhere) has never heard of the specific parts I presented them, and looking for parts by their specs is not an option there either.
<APlayer>
in the next days*
<APlayer>
So I guess I'll just find as many options as possible and visit them with a list once more. Do you know how I can determine whether a part is common?
<Ellied>
The ones that have extra pins are either a) multiple separate MOSFETs in one package, b) one MOSFET with multiple wires attached to its source (I don't know why they do this, but they do) or c) (very rarely) a MOSFET with the source not connected internally to the substrate.
<Ellied>
for what you care about, common == cheap. :P
<APlayer>
Ah, okay. Not as weird as I imagined
<Ellied>
if you're salvaging things from old hardware, "common" has a dependence on the age of the machine, but if you're buying new parts, you just care about cost.
<Ellied>
like, 2N2222 transistors are gonna be very common in cheap hardware from the 80s and 90s, much less so now
<APlayer>
Ellied: Well, the ones I found were cheap indeed. 0.20 € apiece, or something in that range (I think about $0.25 - 0.30
<APlayer>
Also, browsing the Infineon site, I found that P-channel ones suiting my needs are way more numerous than N-channel ones.
<APlayer>
I guess it's the low gate voltage, because the number relatively exploded once I included 2V ones in the filter.
<Ellied>
yeah, the ones you linked me had *really low* gate voltage. I've hardly ever seen ones with less than 1V threshold.
<APlayer>
It's just that I need to discount 1.7 V there. I don't have the circuit layout at hand, but it was something with the fact that one supply is +5V and the other was 3.3V, so it didn't go very high initially.
<APlayer>
I think it was the capacitor, which would not have a high voltage or something like that
<APlayer>
Anyway, if I use anything with more than 1.2V threshold, I need a larger capacitor, which also takes longer to charge and once the circuit is off, longer ti discharge.
<egg>
!wpn bofh
* Qboid
gives bofh a Terran venomous category which strongly resembles a protractor
<Ellied>
also, believe it or not, $0.25 is crazy above average for MOSFETs. if you paid that much for the MOSFETs in your computer's CPU, it would cost billions. :P
<egg>
!wpn whitequark
* Qboid
gives whitequark a subsonic Durandal
<Ellied>
naturally, you're paying more to get a larger part that can take more current, and for a big plastic package that lets you actually see the thing
<APlayer>
Well, I don't buy reels of them in a monthly subscription. I am a private person buying exactly one of them :P
<APlayer>
Naturally, if I bought a thousand, the prices drop to a few cents apiece.
<Ellied>
sure, electronic component pricing is a bit strange sometimes. really sharp bulk discounts, and a surprising amount of money spent on packaging (e.g. the very same chip is sometimes twice as expensive in DIP as SOIC)
<APlayer>
Also, the shop you linked me (mouser.com) had such prices too, IIRC. Not sure where you buy your parts (or do you get them from the Uni?) but I doubt that you can just order a single MOSFET below $0.20 anywhere
<egg>
!choose zzz|DF
<Qboid>
egg: Your options are: zzz, DF. My choice: zzz
<egg>
;choose zzz|DF
<kmath>
egg: DF
<egg>
raptorchoose zzz|DF
<APlayer>
Well, perhaps a very limited set of specific MOSFETs will be this cheap. But I don't think you have much to choose from with such a budget constraint.
<APlayer>
And I don't think that pricing is weird. Makes sense for me - if they sold individual parts at few cents each, it would not make sense at all. I mean, the bulk of money would come from industrial orders, but the bulk of money spent on taking orders, packaging and whatnot would be where the bulk of individual orders is - and I am certain those would be few parts each
<APlayer>
Sorry for my weird wording today. Not sure what's going on, but I have some really weird focusing issues. My productivity feels like a sine wave with a period of less than an hour.
<egg>
!wpn UmbralRaptor
* Qboid
gives UmbralRaptor a mutually intelligible shell
<APlayer>
Aww, I start reading "Trojan hypergolic..." and the last word was pure disappointment
<UmbralRaptor>
^a solution to open office plans!
<UmbralRaptor>
APlayer: it's very toasty.
<APlayer>
Ellied: Anyway, I was rather thinking of some site where I can see the number of times a part was ordered or something
<APlayer>
Because price does not seem like a particularly sound measure of commonness
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<egg>
UmbralRaptor: choose zzz|DF
<UmbralRaptor>
egg: DF
<egg>
hmm
<APlayer>
DF?
<egg>
UmbralRaptor: lots of discussing going on, a bit of reading and pondering, no writing though
<egg>
how are they going to publish
<UmbralRaptor>
Maybe it's a conference?
<egg>
UmbralRaptor: only two residents have a writing skill > 1 (both at 11), one's a resident engineer specializing in optics, fluid engineering, and machinery; the other is a bard who happens to be extremely good at fluid engineering?!
<egg>
the bard is a citizen now
<egg>
can't reassign the bard to be a scholar though, because he came here to be a bard
<Ellied>
if IRC were a building, it would have revolving doors inside which each person would be trapped, along two or three of their unmoving, unblinking, indistinguishable ghosts