Author: Al Williams

4152 Articles

No Tension For Tensors?

July 9, 2025 by 11 Comments

We always enjoy [FloatHeadPhysics] explaining any math or physics topic. We don’t know if he’s acting or not, but he seems genuinely excited about every topic he covers, and it is infectious. He also has entertaining imaginary conversations with people like Feynman and Einstein. His recent video on tensors begins by showing the vector form of Ohm’s law, making it even more interesting. Check out the video below.

If you ever thought you could use fewer numbers for many tensor calculations, [FloatHeadPhysics] had the same idea. Luckily, imaginary Feynman explains why this isn’t right, and the answer shows the basic nature of why people use tensors.

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Kids Vs Computers: Chisanbop Remembered

July 9, 2025 by 14 Comments

If you are a certain age, you probably remember the ads and publicity around Chisanbop — the supposed ancient art of Korean finger math. Was it Korean? Sort of. Was it faster than a calculator? Sort of. [Chris Staecker] offers a great look at Chisanbop, not just how to do it, but also how it became such a significant cultural phenomenon. Take a look at the video below. Long, but worth it.

Technically, the idea is fairly simple. Your right-hand thumb is worth 5, and each finger is worth 1. So to identify 8, you hold down your thumb and the first three digits. The left hand has the same arrangement, but everything is worth ten times the right hand, so the thumb is 50, and each digit is worth 10.

With a little work, it is easy to count and add using this method. Subtraction is just the reverse. As you might expect, multiplication is just repeated addition. But the real story here isn’t how to do Chisanbop. It is more the story of how a Korean immigrant’s system went viral decades before the advent of social media.

You can argue that this is a shortcut that hurts math understanding. Or, you could argue the reverse. However, the truth is that this was around the time the calculator became widely available. Math education would shift from focusing on getting the right answer to understanding the underlying concepts. In a world where adding ten 6-digit numbers is easy with a $5 device, being able to do it with your fingers isn’t necessarily a valuable skill.

If you enjoy unconventional math methods, you may appreciate peasant multiplication.

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Oscillator Negativity Is A Good Thing

July 8, 2025 by 5 Comments

Many people who get analog electronics still struggle a bit to design oscillators. Even common simulators often need a trick to simulate some oscillating circuits. The Barkhausen criteria state that for stable oscillation, the loop gain must be one, and the phase shift around the feedback loop must be a multiple of 360 degrees. [All Electronics Channel] provides a thorough exploration of oscillators and, specifically, negative resistance, which is punctuated by practical measurements using a VNA. Check it out in the video below.

The video does have a little math and even mentions differential equations, but don’t worry. He points out that the universe solves the equation for you.

In an LC circuit, you can consider the losses in the circuit as a resistor. That makes sense. No component is perfect. But if you could provide a negative resistance, it would cancel out the parasitic resistance. With no loss, the inductor and capacitor will go back and forth, electrically, much like a pendulum.

So, how do you get a negative resistance? You’ll need an active device. He presents some example oscillator architectures and explains how they generate negative resistances.

Crystals are a great thing to look at with a VNA. That used to be a high-dollar piece of test gear, but not anymore.

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Better Solid State Heat Pumps Through Science

July 8, 2025 by 22 Comments

If you need to cool something, the gold standard is using a gas compressor arrangement. Of course, there are definite downsides to that, like weight, power consumption, and vibrations. There are solid-state heat pumps — the kind you see in portable coolers, for example. But, they are not terribly efficient and have limited performance.

However, researchers at Johns Hopkins, working with Samsung, have developed a new thin-film thermoelectric heat pump, which they claim is easy to fabricate, scalable, and significantly more efficient. You can see a video about the new research below.

Manufacturing requires similar processes to solar cells, and the technology can make tiny heat pumps or — in theory — coolers that could provide air conditioning for large buildings. You can read the full paper in Nature.

CHESS stands for Controlled Hierarchically Engineered Superlattice Structures. These are nano-engineered thin-film superlattices (around 25 μm thick). The design optimizes their performance in this application.

The new devices claim to be 100% more efficient at room temperature than traditional devices. In practical devices, thermoelectric devices and the systems using them have improved by around 70% to 75%. The material can also harvest power from heat differences, such as body heat. The potential small size of devices made with this technology would make them practical for wearables.

We’ve looked at the traditional modules many times. They sometimes show up in cloud chambers.

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Going To The (Parallel) Chapel

July 6, 2025 by 11 Comments

There is always the promise of using more computing power for a single task. Your computer has multiple CPUs now, surely. Your video card has even more. Your computer is probably networked to a slew of other computers. But how do you write software to take advantage of that? There are many complex systems, of course, but there’s also Chapel.

Chapel is a reasonably simple programming language, but it supports parallelism in various forms. The run time controls how computers — whatever that means — communicate with one another. You can have code running on your local CPUs, your GPU, and other processing elements over the network without much work on your part.

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Challenge: Square A Voltage

July 1, 2025 by 18 Comments

Your design task, should you decide to accept it: given an input voltage, square it. Ok, that’s too hard since squaring 8 volts would give you 64 volts, so let’s say the output should be 10% of the square, so 8 volts in would result in 6.4V. How do you do it? [Engineering Prof.] knows how and will show you what you can do in the video below.

The circuit uses two op amps and some transistors. However, the transistors are used in a way that depends on the temperature, so it is important to use a transistor array so they are matched and will all be at the same temperature.

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Phone Keyboard Reverse Engineered

June 30, 2025 by 3 Comments

Who knows what you’ll find in a second-hand shop? [Zeal] found some old keyboards made to fit early Alcatel phones from the year 2000 or so. They looked good but, of course, had no documentation. He’s made two videos about his adventure, and you can see them below.

The connector was a cellphone-style phone jack that must carry power and some sort of serial data. Inside, there wasn’t much other than a major chip and a membrane keyboard. There were a few small support chips and components, too.

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