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# Category Archives: General Mathematics

## Letter Folding for Envelopes

I still occasionally write paper letters. In fact, I had some letters to write the other day, and I realized that was doing a bit of math when I folded the letters for placement into standard business envelopes that was worth discussing here. Figure 1 shows the business envelope that I normally use. Continue reading

Posted in General Mathematics, Origami
2 Comments

## Tree Height Measuring Example

I have been testing a number of Android applications that are intended to measure the size of objects knowing their range or vice versa. One application that I have found particularly useful is called Baumhöhenmesser – Tree Height Meter (my translation) – which is an application written by a German developer. I have found this application particularly useful, and I thought I would review its operation here. It is part of a suite of Android applications intended for forestry management. This app makes excellent use of the Android's ability to measure angles. Continue reading

Posted in General Mathematics, Geometry
3 Comments

## Stadiametric Rangefinding Approaches

Recently, I was reading about stadiametric range finding methods being used by hunters and their telescopic sights – I was surprised to find a lot of writing on the topic. As I researched the topic, I saw that there are three common approaches used in telescopic sights: milliradian (mil), Minute Of Angle (MOA), and Inch Of Angle (IOA). I will review these methods here. Continue reading

Posted in Ballistics, General Mathematics
1 Comment

## Optical SFP Power Estimation Using Curve Fitting

I was asked today how to use Excel to estimate the power usage of two optical components at case temperatures for which we had no data. I initially solved the problem in Mathcad by fitting an equation of the form $latex c_0 \cdot e^{c_1 \cdot T_{Case}}+e_2 to the data and computing the corresponding power. Continue reading

Posted in Excel, General Mathematics
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## Negative times a Negative is a Positive

On my team, I work hard to ensure that we have a non-threatening environment for questions – any questions. In fact, I often ask very basic questions in meetings so that I can make sure that I understand all the nuances of a situation. You would be amazed how often I learn things from asking questions so basic that you would think asking them would not be necessary. Continue reading

Posted in General Mathematics
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## Prime Number Magnitudes

I am responsible for some of the authentication features in our products and these features use prime numbers. People often have basic questions on prime numbers, such as:

What happens if I choose the same prime number as someone else?

Are there enough prime numbers? Continue reading

Posted in General Mathematics, software
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## Donor Chain Math

I just read an interesting article at Ars Technica on the mathematics behind setting up donor chains. The math is actually a variant of the prize-collecting traveling salesman problem, which is NP-hard. Continue reading

Posted in General Mathematics
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## Cat Litter and Radioactivity

I am not a cat person – the only time that cats come up in my family is in regards to Schrodinger's cat (Figure 1). However, I just came across an interesting web page by the Oak Ridge Associated Universities that discusses cat litter and the fact that it is slightly radioactive. Some cat litter is slightly radioactive because the contain bentonite clay, which contains small amounts of radioactive uranium (238U), thorium (232U), and potassium (40K). I find this web page interesting because it includes measured radiation data and an estimate of the heavy metals (uranium and thorium) that are contained in cat litter. Continue reading

Posted in General Mathematics, General Science
1 Comment

## Clever Way of Putting on a Duvet Cover

My wife and I put on a Christmas-themed duvet cover last night using the technique shown in this video. The approach reminds me of some topology demonstrations. The method worked as advertised. Continue reading

Posted in General Mathematics, Geometry
2 Comments

## Mathcad Matrix Example

Introduction A friend of mine recently converted his propane-fueled grill to a natural-gas fueled grill and he mentioned to me that he had to get a new pressure regulator and different-sized gas orifice, neither of which I knew anything about. … Continue reading

Posted in General Mathematics
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