Canned Air Is Unexpectedly Supersonic

February 18, 2024 by Donald Papp 18 Comments

How fast is the gas coming out from those little duster tubes of canned air? Perhaps faster than one might think! It’s supersonic (video, embedded below) as [Cylo’s Garage] shows by imaging clear shock diamonds in the flow from those thin little tubes.

Shock diamonds are a clear indicator of supersonic flow.

Shock diamonds, normally seen in things like afterburning jet turbine or rocket engine exhaust streams, are the product of standing wave patterns that indicate supersonic speeds. These are more easily visible in jet plumes, but [Cylo’s Garage] managed to get some great images of the same phenomenon in more everyday things such as the flow of duster gas.

Imaging this is made possible thanks to what looks like a simple but effective Sch lieren imaging setup, which is a method of visualizing normally imperceptible changes in a fluid’s refractive index. Since the refractive index of a gas can change in response to density, pressure, or temperature, it’s a perfect way to see what’s going on when there’s otherwise nothing for one’s eyeballs to latch onto.

Intrigued by this kind of imaging? It requires a careful setup, but nothing particularly complicated or hard to get a hold of. Here’s one such setup, here’s a Schlieren videography project, and here’s a particularly intriguing approach that leverages modern electronics like a smartphone.

Thanks to [Quinor] for the tip!

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Metal 3D Printing Gets Really Fast (and Really Ugly)

February 17, 2024 by Donald Papp 8 Comments

The secret to cranking out a furniture-sized metal frame in minutes is Liquid Metal Printing (LMP), demonstrated by researchers at the Massachusetts Institute of Technology. They’ve demonstrated printing aluminum frames for tables and chairs, which are perfectly solid and able to withstand post-processing like drilling and milling.

The system heats aluminum in a graphite crucible, and the molten metal is gravity-fed through a ceramic nozzle and deposited into a bed of tiny 100-micron glass beads. The beads act as both print bed and support structure, allowing the metal to cool quickly without really affecting the surface. Molten aluminum is a harsh material to work with, so both the ceramic nozzle material and the glass beads to fill the print bed were selected after a lot of testing.

This printing method is fast and scalable, but sacrifices resolution. Ideally, the team would love to make a system capable of melting down recycled aluminum to print parts with. That would really be something new and interesting when it comes to manufacturing.

The look of the printed metal honestly reminds us a little of CandyFab from [Windell Oskay] and [Lenore Edman] at Evil Mad Scientist, which was a 3D printer before hobbyist 3D printers or kits were really a thing. CandyFab worked differently — it used hot air to melt sugar together one layer at a time — but the end result has a similar sort of look to it. Might not be pretty, but hey, looks aren’t everything.

(Update: see it in action in this video, which is also embedded just below. Thanks [CityZen] for sharing in the comments!)

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Shuji Nakamura: The Man Who Gave Us The Blue LED Despite All Odds

February 14, 2024 by Maya Posch 68 Comments

With the invention of the first LED featuring a red color, it seemed only a matter of time before LEDs would appear with other colors. Indeed, soon green and other colors joined the LED revolution, but not blue. Although some dim prototypes existed, none of them were practical enough to be considered for commercialization. The subject of a recent [Veritasium] video, the core of the problem was that finding a material with the right bandgap and other desirable properties remained elusive. It was in this situation that at the tail end of the 1980s a young engineer at Nichia in Japan found himself pursuing a solution to this conundrum.

Although Nichia was struggling at the time due to the competition in the semiconductor market, its president was not afraid to take a gamble on a promise, which is why this young engineer – [Shuji Nakamura] – got permission to try his wits at the problem. This included a year long study trip to Florida to learn the ins and outs of a new technology called metalorganic chemical vapor deposition (MOCVD, also metalorganic vapor-phase epitaxy). Once back in Japan, he got access to a new MOCVD machine at Nichia, which he quickly got around to heavily modifying into the now well-known two-flow reactor version which improves the yield.

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How Different Are SpaceX Thermal Tiles From The Space Shuttle’s?

February 14, 2024 by Maya Posch 9 Comments

When SpaceX first showed off the thermal tiles on its Starship spacecraft that should keep it safe when re-entering the Earth’s atmosphere towards the loving embrace of the chopsticks on the launch tower, some similarity to the thermal tiles on NASA’s now retired Space Shuttle Orbiter was hard to miss.

Electron microscope image of the fibrous part of a Starship thermal tile, showing very large fibers. (Credit: Breaking Taps, YouTube)

Yet how similar are they really? That’s what the [Breaking Taps] channel on YouTube sought to find out, using an eBay-purchased chunk of Shuttle thermal tile along with bits of Starship tiles that washed ashore following the explosive end to the vehicle’s first integrated test last year.

To answer the basic question: the SpaceX engineers responsible for the Starship thermal tiles seem to have done their homework. An analysis of not only the structure of the fibrous material, but also the black IR-blocking coating, shows that the Starship tiles are highly reminiscent of the EATB (introduced in 1996) tiles with TUFI (toughened unipiece fibrous insulation) coatings with added molybdenum disilicide, which were used during the last years of the Shuttle program.

TUFI is less fragile than the older RCG (reaction cured glass) coating, but also heavier, which is why few TUFI tiles were used on the Shuttles due to weight concerns. An oddity with the Starship tiles is that they incorporate many very large fibers, which could be by design, or indicative of something else.

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An image of a cave drawing of horned cow. There is another one coming up behind it as well. There are four dots as described by the researchers on the main cow's back.

Writing – So Easy A Caveperson Could Do It

February 13, 2024 by Navarre Bartz 10 Comments

We modern humans tend to take writing for granted, and often forget that like any other technology, somebody had to invent it. Researchers from Cambridge believe they’ve determined the purpose of one of the earliest writing beta-tests.

Examining a database of images taken in caves throughout Europe and dated to the Upper Paleolithic, the researchers found “three of the most frequently occurring signs—the line <|>, the dot <•>, and the <Y>—functioned as units of communication.”

It appears the <|> and <.> symbols when “in close association with images of animals” denote time relating to lunar months of the year, starting with spring as the new year. The <Y> symbol appears to carry the meaning <To Give Birth> allowing early people a way to tell others information about the prey of a region, which would be pretty handy when hunting and gathering are your only options for food.

We’ve covered other ancient technologies like storytelling and abrasives. If you’re curious what the climate was like for our ancestors, perhaps paleoclimatology will tickle your fancy.

3D Printing Functional Human Brain Tissue For Research Purposes

February 12, 2024 by Maya Posch 18 Comments

Graphical summary of the newly developed 3D bioprinting process. (Credit: Yan et al., 2024)

The brain is probably the least explored organ, much of which is due to the difficulty of studying it in situ rather than in slices under a microscope. Even growing small organoids out of neurons provide few clues, as this is not how brain tissue is normally organized. A possible breakthrough may have been found here by a group of researchers whose article in Cell Stem Cell details how they created functional human neural tissues using a commercial 3D bioprinter.

As detailed by [Yuanwei Yan] and colleagues in their research article, the issue with previous approaches was that although these would print layers of neurons, they would fail to integrate as in the brain. In the brain’s tissues, we see a wide variety of neurons and supportive cells, all of which integrate in a specific way to form functioning neuron-to-neuron and neuron-to-glial connections with expected neural activity. The accomplishment of this research team is 3D bioprinting of neural tissues with the necessary functional connections.

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AI’s Existence Is All It Takes To Be Accused Of Being One

February 11, 2024 by Donald Papp 31 Comments

New technologies bring with them the threat of change. AI tools are one of the latest such developments. But as is often the case, when technological threats show up, they end up looking awfully human.

Recently, [E. M. Wolkovich] submitted a scientific paper for review that — to her surprise — was declared “obviously” the work of ChatGPT. No part of that was true. Like most people, [E. M. Wolkovich] finds writing a somewhat difficult process. Her paper represents a lot of time and effort. But despite zero evidence, this casual accusation of fraud in a scientific context was just sort of… accepted.

There are several reasons this is concerning. One is that, in principle, the scientific community wouldn’t dream of leveling an accusation of fraud like data manipulation without evidence. But a reviewer had no qualms about casually claiming [Wolkovich]’s writing wasn’t hers, effectively calling her a liar. Worse, at the editorial level, this baseless accusation was accepted and passed along with vague agreement instead of any sort of pushback.

Showing Your Work Isn’t Enough

Interestingly, [Wolkovich] writes everything in plain text using the LaTeX typesetting system, hosted on GitHub, complete with change commits. That means she could easily show her entire change history, from outline to finished manuscript, which should be enough to convince just about anyone that she isn’t a chatbot.

But pondering this raises a very good question: is [Wolkovich] having to prove she isn’t a chatbot a desirable outcome of this situation? We don’t think it is, nor is this an idle question. We’ve seen how even when an artist can present their full workflow to prove an AI didn’t make their art, enough doubt is sown by the accusation to poison the proceedings (not to mention greatly demoralizing the creator in the process.)

Better Standards Would Help

[Wolkovich] uses this opportunity to reflect on and share what this situation indicates about useful change. Now that AI tools exist, guidelines that acknowledge them should be created. Explicit standards about when and how AI tools can be used in the writing process, how those tools should be acknowledged if used, and a process to handle accusations of misuse would all be positive changes.

Because as it stands, it’s hard to see [Wolkovich]’s experience as anything other than an illustration of how a scientific community’s submission and review process was corrupted not by undeclared or thoughtless use of AI but by the simple fact that such tools exist. This seems like both a problem that will only get worse with time (right now, it is fairly easy to detect chatbots) and one that will not solve itself.