#bigclive #video on putting a 1N5187 Schottky diode in series with a TP4056 lithium-cell charger to keep it from charging the battery all the way to 4.2V, potentially significantly extending the battery’s lifetime. The diode drops 350mV at 250mA, over 400mV at 500mA, and 330mV at 110mA. The charger starts oscillating toward the end of the charging process, and in the end the battery charges to 3.89V, which is supposedly 80% capacity. #batteries #electronics
#Applied-Science #video on using Cloudray’s GM-100 US$7000 100-watt MOPA laser to engrave diffraction patterns (LIPS: laser-induced periodic structuring) and near-holograms on stainless steel with LightBurn. “MOPA” is “master oscillator power amplifier” and gives you a lot of control over the pulse power waveform from a fiber laser. He holds his too-thin stainless-steel sheets down with an aluminum vacuum chuck to get repeatable focusing, which doubles as a heatspreader and a heatsink. 300mm/s and 300kHz, thus 1μm pitch, worked well to get diffraction gratings, which he thinks are made of varying-thickness oxide layers changing the phase delay. He was using 45ns pulses at 19.6% power. He tried making optical #holograms: “How could you not do it after you realize you have full pitch and angle control over a #diffraction grating?”.
#Segerman #video showing Sydler’s π/4 polyhedron from 01965, constructed by Matthias Goerner, in which all dihedral angles are 90° except for one, and talking-heading about the Dehn invariant. #math #geometry
#Segerman #video on “wild” knots such as the wild slipknot which cannot be topologically deformed into polygons. Introduction to knot theory. #toread #math
#video of Terry Davis’s #TempleOS livestream from 02016 about how he uses Holy-C files with just a bunch of #includes instead of a linker or linker scripts.
Backblaze on hard disk reliability and failures over time, including major deviations from the bathtub curve
#Segerman #video on the Cannon–Thurston map and the complementary space of the figure-eight knot. #math #toread
#demo #video of #bootOS by Oscar #Toledo G., demonstrating entering a hello-world program byte by byte, running it, and deleting it. Also demos cubicDoom. #small-is-beautiful
Riana wrote an article about #AI tainted court filings; I guess she’s at CIS at Stanford
#history of #materials: celluloid’s origin as an ivory substitute for billiard balls
#video of writing with #fountain-pens on #stone-paper. He doesn’t like the feel of the paper, saying it felt like walking in pudding. Also the pens went through the paper a couple of times, and one of his inks bled through, and trying it with a pencil, it totally embossed the page. He’d laser-roughed-up the tip of one of his pens, and the paper kind of polished the metal down, which I guess means the chalk isn’t very pure. “The worst paper I’ve ever used.” A commenter complains, “It also has very low heat tolerance. Leave in a hot car in the summer and all the pages will fuse together. Ask me how i know.”
#Posy #video about Cokin’s red polarizing filters for #photography, which only polarize red light, so that once you set the white balance you get rainbows from #polarization gradients. Except the rainbows he got were mostly from a regular polarizing filter and strained plastic (polycarbonate? acrylic? from a CD case) with wavelength-dependent birefringence.
#video #toread about a remote benchtop setup (??!) for #electronics
#video of Sussman explaining a watch escapement by analogy to an LCR electrical circuit #toread
incompatibilities in #C and #C++ when porting to #GCC 15, which updates the default version of C to C23, which requires prototypes.
Recursive Functions of Symbolic Expressions and Their Computation by Machine, Part I (McCarthy 01959) #Lisp #history #PDF #paper