Recent submissions

Comment · 26 days ago
https://demo.arcadeia.org/ not working at the moment

Getting started says I have to upload media first, can't I just point it at my existing folders?

Comment · 2 years ago
I've often felt frustrated by the processing fees. Can you elaborate on handling this yourself? Which EU country are you based in?
Comment · 3 years ago
Interesting read. Though it says the nuclear fission happens in the crust and mantle, not the core.
Comment · 3 years ago
Was this before the introduction of the IOSS rules? I can't imagine picking something up directly at customs. International shipping volume has increased a lot, customs does not have the capacity to store much.

The new rules have actually made shipping from Aliexpress easier. VAT is displayed and payed to Aliexpress, they handle customs (as long as total order value is less than €150). In practice they consolidate packages from several sellers into one shipment where possible (although of course with a long-tail delay), and fly it to their new distribution center in Luik. Customs has a small presence, but because VAT is paid they're mostly concerned about other things such as counterfeits.

Last-mile shipping is then done by postal service, without any additional fees.

Comment · 3 years ago
That actually is via the postal service (BPost). The postage rates are reasonable, it's just the fee that they add for handling the customs administration that is unreasonable.

And this is more or less the same for the other shipping companies such as DHL, UPS, and FedEx.

Because the fee is per shipment, it's not that bad if you're receiving several hundred euros worth of products. But if you just want to receive a book, it can easily double the cost.

Comment · 3 years ago
The issue isn't the import duty and VAT, the issue is the 20€ or more fee that the shipping companies charge for the privilege of handling the customs administration for you.

In Belgium for example books have 0% import duty and 6% VAT. Adding 20€, long delays, and a terrible customer experience (good luck trying to correct any data submitted to customs) to that is rarely worth the hassle.

Comment · 3 years ago
> Correlation is correlated with causation!

That's a great quote. I think I'll use that instead of "where there's smoke ..." from now on.

Comment · 3 years ago
Comment · 3 years ago
reposted to fix an audio issue: https://www.youtube.com/watch?v=XmiWIlFvSYs

context: "Tomorrow on @oxidecomputer and Friends, @ahl and I will be joined by our colleagues @SyntheticGate and @cliffle to talk about the role of rapid hardware prototyping in building a system -- and specifically how our ability to go quickly from ideation to hardware in hand has been essential for a surprisingly wide range of tasks at Oxide."

Thanks for posting, that was very interesting

Comment · 3 years ago
Inflation is irrelevant if your stable coin is pegged to the currency that is inflating.
Comment · 3 years ago
Comment · 3 years ago
Displacement is 1000nm, so 3 orders of magnitude less than 1mm. As for frequency response, looks like they tested up to 1000Hz. I see no reason why it wouldn't work at any frequency from 0Hz up to 1000Hz, and even higher. But because the displacement is so small you really need the higher frequencies to be able to sense the actuation.

That's just piezo's, you need to stack several layers to get a usual displacement. You do get high force, so they're typically used for high precision positioning.

I've been looking at piezo bimorph actuators as used in braille displays. Because they're cantilevered you're trading displacement for force (and size). That could perhaps be used to create a high resolution array with enough displacement at low frequency. Not really wearable like a glove, but certainly portable.

Comment · 3 years ago
I strongly agree, the innovation needed is in haptics on the actuator side.

Can you expand on the static and low frequency? My impression was that if you're aiming for fingertips, higher frequency has more resolution. Iirc braille is mostly sensed by the vibration of the ridges of your fingerprint, when moving your finger over the dots. For this reason single character braille displays never really took off, you need an entire row (typically 40 characters) to make a usable refreshable braille display.

I've looked at the actuator array in the paper

https://www.nature.com/articles/s41528-022-00216-1

It's made with "standard" multilayer pzt actuators, with a displacement of 1000nm at 60V. That's apparently above the sensing threshold, but imho not enough for practical applications.

I am curious about the fabrication methods though. The 1mm actuators are in a checkerboard pattern, and apparently reflow soldered. I'm curious how they did that while staying below the curie temperature of the actuators (typically <150°C for PZT), and if that is mechanically sufficient.

It's still very impressive work.

Live from the official Hacker News API

A modern reader for Hacker News · SvelteKit + Skeleton