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Monthly Archives: November 2015
We have had a warm winter in Minnesota so far this year. As with every transition from fall to winter, bugs seek warmth by taking up residence in our fiber-optic enclosures. Here is my latest example, a ladybug on a returned circuit board. Continue reading
I had never seen coal until my first trip to China when I saw people on bicycles transporting coal to their homes for heat. I started to wonder just how much coal a home would need for heating. I have seen numerous values for the heat content of the various types of coal. I recalled from primary school that there were three types of coal: anthracite, bituminous, and lignite. So I would have expected three values for the heat output of coal. When I actually looked, I found dozens of grades of three primary types of coal. Each of the different grades would generate different amounts of heat per kilogram. I thought I would take a closer look at how the heat output from coal could be modeled using regression and a simplified model based on chemical heats of formation. Continue reading
I have spent a fair portion of my career working as an engineering contractor. In fact, I spent five years working on new business development for a large contract firm. During this time, I was involved in writing dozens of proposals on large projects. A proposal occurs at the end of the bid and proposal process (Figure 1) and constitutes a contract firm's attempt to win the project development contract. It is a key part of new business development for many companies. Continue reading
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
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
For years, I have mounted most my electrical outlets upside down (see Figure 1). Recently, I have started to see more folks orienting their outlets this way. I see that Finehomebuilding Magazine and the Journal of Light Construction (JLC Field Guide) recommend this approach as well. However, it is not required by the National Electrical Code. Continue reading
We have recently experienced some laboratory failures during humidity testing that were due to corroded connectors (Figure 1). The connectors had corroded after they become wet from condensation that accumulated on the cables and rolled down to the lowest point on the cable – where the connectors were. Continue reading
I have been reading a number of articles that are reporting on a Venus-like planet (GJ 1132b) recently discovered in a nearby star system (Gliese 1132, 12.0 parsecs away). I like to work a bit with the numbers reported in these articles to determine if I actually understand what is being reported. I have to admit that I also like to imagine the day when astronomers are studying Earth-like planets around other stars. I definitely see that day coming. Discoveries like GJ1132b are particularly interesting because astronomers for a long time did not think red dwarf stars were promising for Earth-like planets. Continue reading
This is the first woodworking tool that I have seen that uses a two-part electric motor. I have encountered this type of two-part electric motor before in situations where some mechanical object needed to be rotated while contained in a completely sealed environment. In this case, the electric motor's armature has a screw thread that pulls the joint tight. See this web page for more details. I certainly can see several applications for this type of connection. Continue reading
I have watched a lot of old WW2 combat footage, and I have noticed that many of the machine guns and fighter planes had similar reticles. A reticle is a fine-grid of lines used in conjunction with an eyepiece to assist in taking measurements or with accurately pointing an instrument. Figure 1 shows a reticle similar to what I have seen in numerous combat scenes. Continue reading