New Bismuth Transistor Runs 40% Faster And Uses 10% Less Power

Recently in material science news from China we hear that [Hailin Peng] and his team at Peking University just made the world’s fastest transistor and it’s not made of silicon. Before we tell you about this transistor made from bismuth here’s a whirlwind tour of the history of the transistor.

The Bipolar Junction Transistor (BJT, such as NPN and PNP) was developed soon after the point-contact transistor which was developed at Bell Labs in 1947. Then after Resistor-Transistor Logic (RTL) came Transistor-Transistor Logic (TTL) made with BJTs. The problem with TTL was too much power consumption.

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There are a number of metal cylinders displayed in a line. Each cylinder has a rectangular brass plate mounted to each end, and these brass plates stand upright, with the metal cylinders held horizontally between them.

Home-casting Thermoelectric Alloys

If you want to convert heat into electrical power, it’s hard to find a simpler method than a thermoelectric generator. The Seebeck effect means that the junction of two dissimilar conductors will produce a voltage potential when heated, but the same effect also applies to certain alloys, even without a junction. [Simplifier] has been trying to find the best maker-friendly thermoelectric alloys, and recently shared the results of some extensive experimentation.

The experiments investigated a variety of bismuth alloys, and tried to determine the effects of adding lead, antimony, tin, and zinc. [Simplifier] mixed together each alloy in an electric furnace, cast it into a cylindrical mold, machined the resulting rod to a uniform length, and used tin-bismuth solder to connect each end to a brass electrode. To test each composition, one end of the cylinder was cooled with ice while the other was held in boiling water, then resistance was measured under this known temperature gradient. According to the Wiedemann-Franz law, this was enough information to approximate the metal’s thermal conductivity.

Armed with the necessary data, [Simplifier] was able to calculate each alloy’s thermoelectric efficiency coefficient. The results showed some useful information: antimony is a useful additive at about 5% by weight, tin and lead created relatively good thermoelectric materials with opposite polarities, and zinc was useful only to improve the mechanical properties at the expense of efficiency. Even in the best case, the thermoelectric efficiency didn’t exceed 6.9%, which is nonetheless quite respectable for a homemade material.

This project is a great deal more accessible for an amateur than previous thermoelectric material research we’ve covered, and a bit more efficient than another home project we’ve seen. If you just want to get straight to power generation, check out this project.

A Single-Pixel Camera Without Moving Parts Using Compressed Sensing

One of the reconstructed images, using all 4,096 matrix patterns as input, next to the original object. (Credit: okooptics, Jon Bumstead)
One of the reconstructed images, using all 4,096 matrix patterns as input, next to the original object. (Credit: okooptics, Jon Bumstead)

There’s a strange allure to single-pixel cameras due to the simultaneous simplicity and yet fascinating features that they can offer, such as no set resolution limit. That said, the typical implementations that use some kind of scanning (MEMS) mirror or similar approach suffer from various issues even when you’re photographing a perfectly stationary and static scene due to their complex mechanical nature. Yet there’s a way around this, involving a LED matrix and a single photoresistor, as covered by [Jon Bumstead] in an article with accompanying video.

As he points out, this isn’t a new concept, with research papers cited that go back many years. At the core lies the signal processing technique called compressed sensing, which is incidentally also used with computed tomography (CT) and magnetic resonance imaging (MRI) scanners. Compressed sensing enables the reconstruction of a signal from a series of samples, by using existing knowledge of the signal.

In the case of this single-pixel camera, the known information is the illumination, which is a Hadamard matrix pattern displayed on the 64 x 64 pixel LED matrix, ergo 4,096 possible patterns. A total of 4,096 samples are thus recorded, which are subsequently processed with a Matlab script. As pointed out, even 50% of the maximum possible matrices can suffice here, with appropriately chosen patterns.

While not an incredibly fast method, it is fully solid-state, can be adapted to use other wavelengths, and with some tweaking of the used components probably could cut down the sampling time required.

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The Nuclear War You Didn’t Notice

We always enjoy [The History Guy], and we wish he’d do more history of science and technology. But when he does, he always delivers! His latest video, which you can see below, focuses on the Cold War pursuit of creating transfermium elements. That is, the discovery of elements that appear above fermium using advanced techniques like cyclotrons.

There was a brief history of scientists producing unnatural elements. The two leaders in this work were a Soviet lab, the Joint Institute of Nuclear Research, and a US lab at Berkeley.

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Triggering Lightning And Safely Guiding It Using A Drone

Every year lightning strikes cause a lot of damage — with the high-voltage discharges being a major risk to buildings, infrastructure, and the continued existence of squishy bags of mostly salty water. While some ways exist to reduce their impact such as lightning rods, these passive systems can only be deployed in select locations and cannot prevent the build-up of the charge that leads up to the plasma discharge event. But the drone-based system recently tested by Japan’s NTT, the world’s fourth largest telecommunications company, could provide a more proactive solution.

The idea is pretty simple: fly a drone that is protected by a specially designed metal cage close to a thundercloud with a conductive tether leading back to the ground. By providing a very short path to ground, the built-up charge in said cloud will readily discharge into this cage and from there back to the ground.

To test this idea, NTT researchers took commercial drones fitted with such a protective cage and exposed them to artificial lightning. The drones turned out to be fine up to 150 kA which is five times more than natural lightning. Afterwards the full system was tested with a real thunderstorm, during which the drone took a hit and kept flying, although the protective cage partially melted.

Expanding on this experiment, NTT imagines that a system like this could protect cities and sensitive areas, and possibly even use and store the thus captured energy rather than just leading it to ground. While this latter idea would need some seriously effective charging technologies, the idea of proactively discharging thunderclouds is perhaps not so crazy. We would need to see someone run the numbers on the potential effectiveness, of course, but we are all in favor of (safe) lightning experiments like this.

If you’re wondering why channeling lightning away from critical infrastructure is such a big deal, you may want to read up on Apollo 12.

Superconductivity News: What Makes Floquet Majorana Fermions Special For Quantum Computing?

Researchers from the USA and India have proposed that Floquet Majorana fermions may improve quantum computing by controlling superconducting currents, potentially reducing errors and increasing stability.

In a study published in Physical Review Letters that was co-authored by [Babak Seradjeh], a Professor of Physics at Indiana University Bloomington, and theoretical physicists [Rekha Kumari] and [Arijit Kundu], from the Indian Institute of Technology Kanpur, the scientists validate their theory using numerical simulations.

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DIY Penicillin

We don’t often consider using do-it-yourself projects as a hedge against the apocalypse. But [The Thought Emporium] thinks we should know how to make penicillin just in case. We aren’t so sure, but we do think it is a cool science experiment, and you can learn how to replicate it in the video below.

If you want to skip the history lesson, you need to fast-forward to about the six-minute mark. According to the video, we are surrounded by mold that can create anti-bacterial compounds. However, in this case, he starts with a special strain of mold made to produce lots of antibiotics.

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