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Recent posts:
- Directly downwind faster than the wind
- Amplifiers in the real world: a case study
- Electromagnetic radiation from accelerating charges
- MEMS oscillator frequency increase from helium
- Android device encryption hang at Time remaining 00:00
- WebEx audio input hang on Linux (Chrome/Chromium bug)
- H field and material boundaries
- Magnetic field of a ferrite core solenoid
- Designing and making a ring
- Splines in Onshape, part 2
- Splines in Onshape, part 1
- Dell Venue 11 Pro travel keyboard troubleshooting
- Unlocking my Lenovo laptop, part 3
- Unlocking my Lenovo laptop, part 2
- Unlocking my Lenovo laptop, part 1
- Introduction to photography slides
- Global food security
- Weather balloon physics
- New site
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Author Archives: Matthew
Directly downwind faster than the wind
Is it possible to build a wind-powered vehicle that can continuously travel faster than the wind, in the same direction as the wind? Like the airplane-on-treadmill problem and the Feynman sprinkler problem, this question has spawned endless Internet arguments. Continue reading
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Amplifiers in the real world: a case study
I encountered an interesting problem recently. As part of a personal project related to magnetic resonance, I built a small coil set and pre-amplifier: The pre-amplifier is located on the tiny green PCB; the signal received by the inner coil … Continue reading
Posted in Electronics
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Electromagnetic radiation from accelerating charges
Electromagnetic radiation is something that has often eluded my intuition. Electrical engineering depends on numerous abstractions: current flowing in wires like a fluid, capacitance/inductance in lieu of near field interactions, antenna theory to model far field interactions, etc. These abstractions … Continue reading
Posted in Physics
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MEMS oscillator frequency increase from helium
You may have heard of the incident where a helium leak suddenly disabled many iPhones at a medical facility. The root cause — tiny MEMS oscillators being susceptible to helium leaking into their hermetically-sealed casings — is interesting but not … Continue reading
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Android device encryption hang at Time remaining 00:00
Recently I had a frustrating problem while trying to enable full disk encryption on my Android device (Motorola G3 “osprey”). Every time the encryption process would hang forever at: EncryptingWait while your phone is being encrypted.Time remaining 00:00
Posted in Computing
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WebEx audio input hang on Linux (Chrome/Chromium bug)
If you have been connecting to WebEx meetings on Linux using Chrome/Chromium versions 79 or 80, you might have run into issues where your microphone randomly stops working and other participants cannot hear you. When trying to reconnect to the … Continue reading
Posted in Computing
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H field and material boundaries
For a long time I thought of the H field as being generated by free currents only. The problem with this view is that it leads us to make erroneous assumptions. We know from the definition of H that: … Continue reading
Posted in Physics
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Magnetic field of a ferrite core solenoid
Consider a solenoid made of wire wrapped around a rod made of iron, ferrite, or other ferromagnetic material: It is well known that the magnetic field will be significantly stronger inside such a solenoid, compared to an air core solenoid. … Continue reading
Posted in Physics
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Designing and making a ring
Recently I designed an engagement ring for my (now-)fiancée, from scratch. This was a fascinating and challenging process, and gave me a new appreciation for both the art and engineering of jewellery design. The first step in the process was … Continue reading
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Splines in Onshape, part 2
In this second part of the series, I’ll briefly cover drawing splines directly in 3D, and then discuss offset curves, which are the original reason I started on this long journey delving into Onshape curves. Continue reading
Posted in Computing
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Splines in Onshape, part 1
In this post I talk about splines and various ways they can be represented, with particular reference to Onshape, a web-based CAD system. Continue reading
Posted in Computing
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Dell Venue 11 Pro travel keyboard troubleshooting
Introduction I recently purchased a pair of Dell Venue 11 Pro 7140 tablet computers — one for myself and one for my girlfriend. I figured this would be a good crossover device between a tablet and a laptop, and so … Continue reading
Posted in Computing
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Unlocking my Lenovo laptop, part 3
The decryption function If you are just joining this story you may want to start at part 1. In part 2, we discovered that a embedded controller update is performed by uploading a small ‘flasher’ program to the EC. This … Continue reading
Posted in Computing
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Unlocking my Lenovo laptop, part 2
The embedded controller In part 1, we looked at the communication between a Lenovo Thinkpad X230T laptop and battery, and discovered that there a challenge-response protocol used to authenticate ‘genuine’ Lenovo batteries. On the laptop side, this – and battery … Continue reading
Posted in Computing
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Unlocking my Lenovo laptop, part 1
Introduction Two months ago, I bought a new battery for my Lenovo laptop (a ThinkPad X230T). I was about to go away on holidays and wanted a battery that could last me through a plane flight; the original battery was … Continue reading
Posted in Computing
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Introduction to photography slides
These are some slide decks I used to use when I ran introductory courses for the UNSW Photography Club. They are a pretty good set of slides so I figured they should have a home on the Web. Part I: … Continue reading
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Global food security
I went to a great lecture today by Professor Chris Barrett on “The Global Food Security Challenge in the Coming Decades”. The slides from this lecture are available here. Here are my notes: Current global food demand growth is ~1.25% … Continue reading
Weather balloon physics
One of the simplest solutions for sending measurement instruments up into the stratosphere is a rubber balloon filled with hydrogen or helium. While the physics of such a balloon would seem to be simple, there are actually some interesting considerations.
Posted in Physics
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New site
Welcome to the newly redesigned zmatt.net. I seem to only get around to upgrading my personal website once every decade so this is a special day indeed. The biggest change is that I now have a blog here (powered by … Continue reading
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