electronic rabbit

[Lukas Ziegler @lukas_m_ziegler]

Seeing touch without pressing down! 🫆

Most tactile sensors rely on deformation.

Press down, deform the sensor, measure the deformation. But light contact, touching water, cream, soft films, doesn't deform anything. The sensor sees nothing.

LightTact flips the approach. It uses optical detection instead. An ambient-blocking configuration suppresses external light and internal illumination everywhere except at actual contact points. Only scattered light from true contact gets through.

The results? High-contrast raw images. Non-contact pixels stay near-black. Contact pixels show the natural appearance of whatever's touching.

This works across material properties, contact forces, surface colors, and lighting conditions. Water, facial cream, thin films, liquids, all become visible the moment they touch.

The sensor outputs spatially aligned visual-tactile images. Vision-language models can read them directly.

Here's the paper: https://t.co/ZCxqFSr6BA

@changyi_lin1 and team - hats off ;)

~~

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[J-MAT（ジェイマット） @jmat2022]

SDスロットの機構

[Mathematica @mathemetica]

Resonance in a circular plate creates stationary nodal lines that divide it into vibrating zones. Left photographs from clamped-plate experiments show powder gathered along these nodes. Middle drawings map the exact nodal curves. Right wireframes illustrate the corresponding 3D displacement surfaces of each mode.

The three rows illustrate progressively higher-order modes.

Instrument makers apply this knowledge when crafting drumheads, while structural engineers use it to avoid resonance issues in components like turbine blades and vehicle panels.

[Philosophy Of Physics @PhilosophyOfPhy]

In 1949, two physicists at the University of Edinburgh, Werner Ehrenberg and Raymond Siday, found something in their calculations that seemed almost impossible.

An electron, they discovered, could be altered by magnetic flux inside a region it never entered.

Along the electron’s path, the magnetic field could be zero. No magnetic force would act on it. Yet when two electron waves passed on opposite sides of the hidden flux and were recombined, the interference pattern would shift.

Siday reportedly tried to explain the result to Max Born. Born listened, shook his head, and left without identifying an error.

The problem went to the heart of how physicists understood electromagnetism.

In classical physics, electric and magnetic fields were considered real. The electromagnetic potentials from which they are calculated seemed like mathematical conveniences. They were not unique: different potentials could describe the same fields.

Quantum mechanics changed the situation.

An electron is described by a wavefunction, and its phase can be altered by the vector potential. If an electron wave is divided into two paths around a confined magnetic flux, the relative phase becomes

Δφ = (q/ħ)Φ_B

The electron never needs to pass through the magnetic field itself. It is enough that the two paths enclose the flux.

Ehrenberg and Siday published the result in a paper on electron optics. The title gave little indication of its importance, and the paper was almost completely ignored.

Ten years later, Yakir Aharonov and David Bohm independently reached the same conclusion.

They recognised that this was not merely a technical feature of electron lenses. It was a foundational statement about quantum mechanics: two regions can have identical local electromagnetic fields and still produce different observable quantum phases.

Their 1959 paper brought the effect to the attention of physicists.

The claim remained controversial. Critics argued that stray magnetic fields might be responsible for the predicted shift. Early experiments supported the effect, but it was difficult to prove that the electrons had encountered no field at all.

The decisive test came in 1986.

Akira Tonomura and his colleagues enclosed magnetic flux inside microscopic toroidal magnets and shielded them with superconducting material. The electrons travelled only through regions where the magnetic field was absent.

The interference pattern shifted anyway, by exactly the amount predicted.

The effect now bears the names Aharonov and Bohm, because they understood its wider meaning and made it central to quantum theory. But Ehrenberg and Siday had written down the essential result a decade earlier.

What they had found was that quantum mechanics is sensitive not only to forces acting locally, but to the global structure of a particle’s path.

The magnetic field was hidden.

For ten years, so was the discovery.

[Cosmos Archive @cosmosarcive]

A tensor generalizes vectors and matrices into higher-dimensional mathematical objects that describe relationships between multiple quantities.

A vector is a 1D list, a matrix is a 2D grid, and a 3rd order tensor can be visualized as a 3D cube. The stress tensor σᵢⱼ represents internal forces within a material, while the Riemann curvature tensor

R(u,v)w = ∇ᵤ∇ᵥw − ∇ᵥ∇ᵤw − ∇₍[u,v]₎w

describes the curvature of spacetime in general relativity. Other concepts shown include the product derivative rule, the tensor product A ⊗ B, and the quantum state

(1/√2)(|00⟩ + |11⟩).

Tensors are indispensable in engineering, physics, machine learning, computer vision, and many other fields where multidimensional data and complex interactions must be modeled accurately.

[Mathematica @mathemetica]

Group homomorphisms preserve operations and induce isomorphisms on quotients by their kernels.

The homomorphism φ from the alternating group A4 to C3 has kernel the subgroup {e, x, y, z}.
The quotient A4/Ker(φ) features cosets aKer(φ) and a²Ker(φ), connected internally by group operation arrows.
These are mapped isomorphically by i to the image subgroup of C3 consisting of 0, 1 and 2.
The theorem states that if φ: G → H is a homomorphism, then Im(φ) ≅ G/Ker(φ).

In homomorphic encryption for cloud computing, such isomorphisms allow arithmetic operations on encrypted data while keeping it secure.

[Lain on the Blockchain @CryptoCyberia]

Apparently this new captcha takes Claude Fable 10 minutes and over 100,000 tokens to complete, but looks easy to complete for real users.

[J-MAT（ジェイマット） @jmat2022]

一時停止

[savip @savipww]

China just dropped an open source model that turns any phone into a 3D scanner

you point it at a room and walk through it

the whole space builds itself into a 3D point cloud in real time as the camera moves, no LiDAR and no depth sensor anywhere

it held a full 13 minute walkthrough at 25,000 frames without the map drifting or collapsing

> ~20 fps on a single GPU
> works indoors and outdoors from plain footage
> the scan normally needs a $50,000 rig and a technician
> Apache 2.0 and runs fully offline on your machine

repo in the reply

[Mustafa @oprydai]

if you’re getting into embedded systems,

learn these protocols in this order:

1. i2c

two wires. many devices.
perfect for sensors, displays, rtc modules, eeproms
master/slave architecture
simple to wire, easy to prototype

this is where most beginners should start.

2. spi

much faster than i2c
separate lines for data in, data out, clock, and chip select
ideal for displays, sd cards, high-speed sensors
more wires, much higher performance

when speed matters, spi wins.

3. uart

point-to-point communication
tx + rx
no clock line
used for debugging, gps, bluetooth modules, microcontroller communication

if you’ve ever opened a serial monitor,
you’ve already used uart.

learn them in this order:

i2c → understand device communication
spi → understand high-speed peripherals
uart → understand serial communication and debugging

these three protocols are everywhere.

master them once,
and you’ll find them in almost every embedded system you build.

[Keenan Crane @keenanisalive]

Since nobody called it out in the comments, this “new way” to show 3D Gaussian splats is a basic 19th century construction, studied by Jakob Steiner and others, called a “sphere inversion” or “Möbius transformation”:

https://t.co/R2t6Kho3TP

It looks good because it is an example of a so-called conformal map, which preserves angles, but distorts scales. However, when you look at something up close, it doesn't really matter what its absolute scale is (whereas angular distortion is far more noticeable).

Conformal maps, namely the 16th century Mercator projection (old as it is) remains the projection of choice in Google Maps and other mapping tools, since it is the unique map that (i) preserves angles, and (ii) keeps north pointing "up" everywhere on the globe.

The 3DGS scheme shown here is just bumping up the usual approach up one dimension: apply a conformal projection; keep the "up" direction fixed. The specific choice of conformal maps (inversions in the sphere) are in fact the only choice available in 3D, due to Liouville's theorem on conformal mappings.

[Orange illustration below is from my PhD thesis on conformal geometry: https://t.co/5yANJzFfjD]

[Tom Fleet @tomfleet]

Oh, you mean @yashiro_ld ?

dude rocks.

https://t.co/QtNnGWnOCH

[Mads @europemaxxed]

People say that college is a scam until you get a job at the contemplate my life decisions factory

[Physics In History @PhysInHistory]

Richard Feynman used this book to master calculus when he was 15.

[Jyotirmai Singh @SinghJyotirmai]

Cute proposal to "cut" a photon by making it reflect off a mirror and then suddenly removing the mirror: https://t.co/SAsA6KpLsG

My understanding: if photon state |1> is incident on the mirror and you remove it it must collapse into a superposition of infinite photon number states to create the sharp edge.

Kinda like a QFT version of the classic QM problem where you have an infinite well of length L and the particle is in some eigenstate ψ but then the length suddenly expands to 2L so the instantaneous wavefunction is unchanged but a superposition of the new eigenfunctions ψ = sum_i φ_i

[VoxelKei @VoxelKei]

3D Gaussian Splattingの新しい見せ方を作りました。その名も Inversphere.
2Dのリトルプラネットと違い、空間ごと球面反転しています。ガラス玉に入れる従来の見せ方は球で「切り取る」のに対して、これは球の中へ「折り込む」ので360度の景色が無限遠まで立体で入っています。
#3DGS

[Mattia @MattiaFiumara]

TIL transparent PCBs are a thing

And they're nice

[LaurieWired @lauriewired]

A Scottish audio company, famous for their turntables, once invented a CPU architecture.

Their internal software kind of sucked.

Somehow along the way, the company became convinced that the problem was not from their programmers being bad.

No, instead the (logical) conclusion was that all traditional Von Neumann-style computers were WRONG. Linn (the audio group) needed to develop their own design, which became known as the Rekursiv.

Honestly, if you can get past the insanity it’s actually quite admirable. The whitepaper is clearly written by some (very) stubborn engineers; it’s like the opposite of RISC, no visible memory addresses, everything’s an object, auto GC, etc.

Oh, and they wrote their own programming language to go with it, of course (Lingo).

[Radioactive Red @radioactivered]

Going back down Japan’s radium rabbit hole…☢️

It would seem just like the West, in the early 1900s Japan also fully embraced the global “Radium Craze”. They used it in healing springs, tonics, soaps, watches (of course), cosmetics and also even “radium houses” for supposed health benefits.

Radium was introduced to Japan in 1903 by physicist Tanakadate Aikitsu, who brought it back from European and American sources. It seems a lot of their supply came from the West actually! Some Japanese physicists also trained at Curie’s Radium Institute in Paris, which is really cool.

Source ☢️: https://t.co/LOZ6Sp8Qtw