Day-glo
Ever wonder what makes those striking day-glo colors shine brighter than everything around them? Our eyes can only see visible light (the colors of the rainbow) but the sun emits electromagnetic waves...
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Newtonian Reflector
Newtonian reflector telescopes use two mirrors – a figured primary mirror (the objective) which focuses incoming light, and a flat secondary mirror which redirects that light at an angle so that it can...
View ArticleGravity / ISS
Let's say we're interested in finding how fast the International Space Station has to move in order not to fall back to earth (i.e. to stay in orbit). The earth has an equatorial radius of about 6384km...
View ArticleGeostationary
Satellites in a geostationary orbit appear to maintain a fixed position relative to a position on the surface of the Earth. To accomplish this, they need to rotate at the same angular speed that the...
View ArticleSudoku
It's hard to find a newspaper without one, and I personally find that Sudoku solutions are an interesting problem. Randomly filling a grid of 81 cells with numbers from 1-9 wouldn't take long, but the...
View ArticleiSCSI Enterprise Target
In the presence of conflicting information (lots of it) this is how I got iSCSI Enterprise Target running on Ubuntu 16.04 (LTS). First, install the required software with sudo apt-get install...
View Article6 Simple Rules for Async/Await
If a method A calls another method B that returns a Task (or Task<T>) then the calling method does not block on the completion of that task, unless it either:awaits that task, orwaits on the...
View ArticleSubscribeOn / ObserveOn
Once you have an instance of an IObservable<T> object, Reactive Extensions (Rx) provides at least two points where you can choose an IScheduler which will determine the threading context under...
View ArticleGrub
It's nice when the Grub bootloader remembers your last choice and reuses it as the default value next time your machine boots. Using Linux, put the following in...
View ArticleOpenVPN
This article on Ars Technica inspired me to try and setup a VPN, but it seemed to lack a couple of extra steps that were required to run the server on a Raspberry Pi behind a router. The official...
View ArticleADSL2+ Sync Rate
If you have ever called up your ISP support team to complain, you may have heard them quote a number called SNR to describe the quality of your connection.It's not quite as simple as a single number,...
View ArticleCisco 7960 SIP Phone
I bought a Cisco 7960 IP phone (preloaded with SIP firmware) to connect with my experimental asterisk server running on a Raspberry Pi. Setting it up wasn't that hard, once I stopped following the bad...
View ArticleSingleton Pattern vs. C# Static Class
I ran into an old foe the other day when we were discussing interview questions; which to choose: standard singleton pattern or static class? At the most basic level, both constructs are useful in...
View ArticleNumerical Integration Basics
Consider the equation \(y = 4\). If we plot this on two axes, x and y, it has no slope; it's just a horizontal line. We could also write the equation as \(y = 0x + 4\) because the value of y is...
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Vinyl LP Record
In this post I will detail one 12" stereophonic 33⅓ vinyl LP record. Initially I was hoping to be able to image the grooves cut into the surface and recover the audio track visually, but the resolution...
View ArticleEigenv{ector;alue}s
There are some nice instructional videos on YouTube that explain eigenvectors and eigenvalues. What follows is a brief summary as well as a caveat or two.We start with a square transformation matrix M,...
View ArticleDemand and Supply: Part 1
Let's use a little bit of mathematics to assist our understanding of demand and supply, focusing here on the slightly more complicated concept of supply (demand functions identically, but we don't...
View ArticleDemand and Supply: Part 2
In the previous post, there was a table of coefficients for average cost (AC), total cost (TC) and marginal cost (MC). Let's decompose TC into two components: one that doesn't vary as quantity (Q)...
View ArticleFourier Transform in C#
I am fascinated by the Fourier transform; specifically: its ability to decompose a wave into a series of fundamental waves. Mathematicians might prefer to see it described it more formally, but here...
View ArticleHypothesis Testing Errors
Hypothesis testing allows us to quantify relationships between known samples and the unknown population from which they were taken. What do I mean by that? Let's say I am interested in the returns from...
View ArticleWake On Lan (WOL)
Wake On Lan (WOL) is possible on the ASUS M3A78-CM board, but it requires a level of finesse to get it working. First, the cryptically named BIOS option "Power > APM Configuration > Power on From...
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Binary vs Decimal, Part 1
We commonly represent numbers in base 10, or decimal. The number three thousand, one hundred and forty-two, for example, can then be represented by the composite symbol...
View ArticleBinary vs Decimal, Part 2
Microsoft's .NET framework gives developers options for representing floating point numbers as well as integers. The same is true of Microsoft's SQL Server, though the options differ subtly.Remembering...
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Heterodyne
Frequency modulation (FM) is one of the techniques used to transmit audio signals at radio frequencies. If we "multiply" a sinusoidal signal wave with a sinusoidal carrier wave, the result is two waves...
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