msds

E-beam litho is...uh...not cheap. The system in the shared fab I use (WNF) costs around $450/hr with various discounts applied. Also, you're not going to get much done in just an hour. Now, maskless laser lithography is reasonably cheap...

However, you can get reasonable quality masks for $150ish, and if you don't care about wafer yield, you can fit all of the layers on one mask. It's 1970s tech - 1:1 contact exposure, but you can hit a few microns.

I'd rather not, sorry!

I did the same thing, and ended up working for an early-stage biotech company doing some combination of hardware design, signal processing, machine learning, and experiment design. For better or worse, people generally seem to think a math degree implies "smart" and tend to be willing to overlook a lack of any specific skills...

Does anyone else here melt their own glass formulations?

I've written a little software package that implements all of the common math for calculating recipes and estimating properties. I'd love another developer on it, because right now it's sufficient for my use, but is also optimized for...me... which doesn't really make it great for anyone else. Really,I don't need any technical help, but more eyes would make things less idiosyncratic and insular.

Presumably, an ensemble of nuclear theorists, particularly those dedicating their lives to making big LQCD calculations, would avoid inverting large ill-conditioned matrices, if that was a clever thing to do.

I know a few QFT types - they tend to be decently intelligent and mathematically capable. Ok, they're more like wickedly smart...

How does one go about doing this? I have access to some obscure technical books that really should be scanned and archived, but don't know anything about the field...

Uh, up to notation, a group better have such an element - otherwise it isn't a group!

And with RF, well, things get really weird really fast...

It would shock me if any significant advances in cryptography weren't progress in pure math.

What do you mean, not much intuition for Fourier transforms? Sure, sometimes you get weird results and need to work with fairly generalized versions of functions, and a bit of background in functional analysis is helpful, but a strong intuition about the Fourier transform is both extremely useful, and not that hard to develop.

For starters, I'd recommend the course notes to Stanford's EE261 (https://see.stanford.edu/materials/lsoftaee261/book-fall-07....) - well written, very funny, a nice level of rigour, etc...

Unfortunately, the lack of documentation thing strikes again... It was pretty simple electronically - an ATTiny25, a coin cell, and an LED wired across two IO pins, for light sensing using LED's junction capacitance as a photocurrent integrator (http://www.merl.com/publications/docs/TR2003-35.pdf). The trick was in the control algorithm - I got things synchronizing reasonably well, but LED ensemble was prone to all sorts of weird chaotic behavior.

I suppose I should recreate it, on an even larger scale. I just need to figure out some better way to power it...

I tried to do this exact thing years ago too! Except I only used one RGB led, and thus could never sense the red channel, because the bandgap of green and blue LED dies is too big to really get any signal from red light. Isn't it annoying when your project is up against quantum mechanics?

I also build a swarm of throwies that used a single LED to synchronize their blinking. That project was much cooler, and I wish I had better documentation...

The paper describing the camera is very interesting - https://www.ncbi.nlm.nih.gov/pubmed/25471883

The real line is defined, as Lebesgue measure spits out the extended reals.

I was just considering this - is the topology on sexually explicit nouns the discrete topology, or indiscrete?

Early Ford was pretty direct about the value of "fitting the company culture", what with ceremonies like this: https://www.thehenryford.org/collections-and-research/digita...

None of the standard vendors we use actually ship the MSDS, but most do supply it online.

I'm not in that business, but I do deal with various safety concerns quite a bit. When faced with basic tools, the average person tends to have a terrifying combination of inventiveness and stupidity...

Flashforge creator pros and ultimakers.

We just finished an independent survey of 5 consumer level machines with a bunch of different materials, looking at both 10-500nm particulate and HCN emissions. Essentially, even with ABS, if you're in a decently well ventilated area, you're fine, and if you're still worried, PLA or TPU drastically reduce particulate.

I'd really love to share the paper right now, but it's someone else's masters thesis that hasn't been released yet. If anyone is interested in it and can remember, ping me in a few months?

For decently capable(1) desktop manufacturing,"desktop" is a bit of a misnomer at this point. I've found that you need at least three desks, not to mention another desk for all of the test gear, and another for mechanical prototyping, and another for...

At this point, I have(2) an othermill and a pretty-near top-of-the-line LPKF S63 system + silkscreen and reflow capabilities, and am fairly impressed by both. I've been able to go from opening up a PCB editor to having a tested, functional board in under an hour, at least for simple breakouts.

The othermill is pretty flawed for PCB work, however. The spindle just isn't fast enough, cross layer alignment is inadequate, it doesn't have dust control for dealing with FR4 dust, etc. For good PCB routing, some sort of computer vision system for adjusting cut depths and picking up fiducials is also amazingly handy. That being said, we're really impressed with our othermill and do a lot of mechanical work on it - complex aluminum parts, engineering plastics, etc.

Cheap soldering for one-offs is pretty much solved at this point - laser cut a stencil on a decent laser cutter (which everyone should have, anyways), stencil paste, and reflow in a cheap Chinese oven with open source aftermarket firmware. You won't be able to do big BGAs or tiny (0201) passives, but who cares? If you have soldermask capabilities, either some photoresist method or laser cut kapton, soldering tricky components becomes much easier.

None of the additive (ink-based) systems have any hope of producing really useful boards - the electrical and thermal conductivity of real copper is pretty hard to beat, and doing anything controlled-impedance is pretty much out of the picture. With subtractive systems, you can just switch to 8+ oz copper or exotic substrates without changing the process materially...

Vias are tricky. LPKF makes two systems, one with conductive epoxy and the other with electrochemical copper, neither of which are quite satisfactory. Via rivets (or manually soldering wire) work for small boards, but are super tedious and not great for controlled impedance applications, either.

Being able to do decent multilayer boards is contingent on good vias, but in theory, the only other thing you need is a hot press for stacking things up?

Once you get into building complex multilayer boards, the time investment is just silly, even with perfectly calibrated processes, and you should just order from a board house and wait...

(1) I.e. boards better than DIY etching + manual soldering.

(2) Well, they're not actually mine, per se...

I suppose that HitchBOT has played out half of the anti-hitchhiking narrative - hitchhiker as victim. Time to build a second robot?

Erm, it's the second result when I google 'dag'.

The sign in a photo near the end of the article ("Tie Downs") suggests it can be quite cheap - $7.00 / night.

Can't find any particularly good sources, but the comment section of [1] has good information on the route (essentially, winding around "Mescalito", a classic aid route) and well-informed speculation on the gear. Essentially a pretty standard setup for hard free climbing on big walls - trad, augmented with a mix of bolts and fixed gear.

[1] http://www.ukclimbing.com/forums/t.php?t=605685

If you diagonalize the matrix in the problem, the formula pops out pretty quickly.

No, it's rapidly moving into toy hardware platforms targeted at web developers.

I've found the best machining resource is working with a good machinist. Quite a bit of machining is about intuition and properly evaluating other sensory inputs - knowing how to interpret the sound a cutting tool makes is critical! Unfortunately, finding a good machinist willing to let you watch them in person - or better yet, work under their supervision - is pretty hard, especially if you're just a hobbyist. Crotchety old-timers don't scale particularly well...

Youtube is one of the better resources right now, for anything other than really basic calculations. There seems to be a trend of old-school professional machinists documenting jobs they're working on - sort of a cross between a tutorial and virtual job-shadowing. Some nice users include oxtoolco, KEF791, Abom79, and mrpete222.

Tragically, it would - and in the non-hypothetical world, probably does. There is a fair amount of research showing significant cognitive development improvements when replacing dirt floors with concrete ones.

http://web.stanford.edu/group/siepr/cgi-bin/siepr/?q=system/...

I think the name "HHO" itself hints that some amount of bullshit is taking place - the electrolysis units are obviously burning a 2:1 mixture of H2 and O2, not some weird mixture of atomic hydrogen and oxygen or impossible isomer of water. Empirically (via youtube), there is a strong connection between "HHO" promoters and "water-fueled car" and "over-unity generator" fraudsters. Oxyhydrogen torches are pretty awesome - I've used both a small electrolysis unit for jewelry work, and a larger tank-fed torch for working with fused quartz. Amazingly clean and hot flame, with definite niche-applications. However, oxyhydrogen combustion (electrolysis-derived, or otherwise) isn't exactly a revolutionary technology. We've made industrial use of it since the 1860s [1], and the trend has been gradual replacement by other fuels and techniques (TIG, electric arc furnaces, etc) that are more controllable and lack H2's unique shortcomings - eg. hydrogen embrittlement, massive range of explosive concentrations, and incredible ability to diffuse through things.

[1] Faraday's 1861 lecture on platinum-group metals is a great example. Small-scale platinum casting is one of the big uses for oxyhydrogen - the combination of a high melting point and severe carbon embrittlement make H2 ideal for working with platinum.

Laser, electron-beam and atomic-hydrogen (no, not crackpot-conspiracy-theory "HHO" atomic hydrogen) welding can work with tungsten, in theory...