Category Archives: General Mathematics

Propane Tank Math

I have used propane for years with my barbecue grill, but I have never used it for heating a space. While at university many decades ago, I worked in construction, and we used propane heaters to make working in partially-completed homes more comfortable in the winter. I went to Home Depot and purchased the propane heater shown in Figure 1. It is rated to put out 30K to 40K BTU/hr. This should provide enough heat to warm my garage so I can work in it comfortably. I like the fact that it is small, and I can easily store it during the summer. I have too much stuff to manage as it is, and I do not need any more big stuff. Continue reading

 
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Yet More Gift Wrapping

My sister and I talk about these practical math problems all the time. Here is another good video that covers gift wrapping with a mathematical slant. Continue reading

 
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Old Way Of Specifying Phone Wire Diameter

I still work on old copper phone networks, and today I encountered wire specified as "300 pound". I had never seen a specification like this for phone wire before. As I thought about it, this specification seemed very similar to how the diameter of thread is still specified, which is by the weight in grams of a 9000 meters of fiber – a unit of measure called the denier. Continue reading

 
Posted in Electronics, General Mathematics, History of Science and Technology | Leave a comment

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

 
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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

 
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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

 
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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

 
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