Monthly Archives: February 2016

Book Review: A Passion for Leadership

Posted on 26-February-2016 by mathscinotes

I just finished reading Bob Gate's A Passion for Leadership, and I am a bit torn. I regularly read books on management and most of them do not contribute anything to improving management– that is not true for A Passion for Leadership. The book is a well-written memoir in which Gates shows how he applied standard management lessons in difficult circumstances. These standard management lessons are worth repeating. My feelings about the book are torn because there is nothing new here. I understand that one could argue that the principles of good management are timeless, but I tend to like authors who give me a new way to look at things. Continue reading →

Posted in Management | Comments Off on Book Review: A Passion for Leadership

A Quick Power Over Ethernet Review

Posted on 24-February-2016 by mathscinotes

I have been asked to write some requirements for an optical product that is powered using Power Over Ethernet (PoE). It has been a few years since I have worked on a PoE-based design, I thought it would be useful to review the standard and ensure that I still understand it. This is a good exercise in basic electrical design and will also illustrate how to design circuits using Mathcad utility functions that I have written over the years. Continue reading →

Posted in Electronics | 1 Comment

45-Star US Flag Heirloom

Posted on 23-February-2016 by mathscinotes

A friend showed me a family photo of a 45-star US flag that was purchased in 1898, which was the year their grandfather was born. Figure 1 shows an example of the flag in their photo. The flag, which is quite large, is often used as a backdrop for a family photos. The flag is carefully stored and only taken out for special events, like reunions. I think this is a great use for an old flag. Continue reading →

Posted in History Through Spreadsheets, Personal | Comments Off on 45-Star US Flag Heirloom

Moving Lake Ice in Northern Minnesota

Posted on 22-February-2016 by mathscinotes

I just came back from a weekend visiting friends in Northern Minnesota. The snow is beginning to melt, and this makes everyone excited about the arrival of spring. During my weekend, I spent some time walking the streets around Gull Lake, which is near the city of Nisswa. I often see things that strike my fancy while walking. For example, I am always looking for good ideas to apply to my cabin, which is in the Grand Rapids area. Figure 1 shows a unique street light consisting of a wooden carving of a bear holding an old-style hurricane lamp. Bears and moose are common themes in northern Minnesota lore. Continue reading →

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Challenge of Viewing an Earth-Sized Planet

Posted on 18-February-2016 by mathscinotes

I listen to audio books during my nightly walks around a local lake. My current selection, Searching for Exoplanets, is one of the best audiobooks I have listened to. The book consists of a series lectures on the state of the search for exoplanets by MIT Professor Joshua Winn. The lectures provide an excellent summary of how astronomers are using remarkably sensitive methods for indirectly detecting the presence of exoplanets circling remote stars. Continue reading →

Posted in Astronomy | 1 Comment

WW2 Submarine Endurance on Batteries

Posted on 16-February-2016 by mathscinotes

I have been reading the book The Bravest Man, a biography of the WW2 exploits of US Navy submarine commander Dick O'Kane. I have not formed an opinion on the book since I just started reading it, but the book does highlight the submerged maneuvering limitations imposed on a ww2 submarine because of its lead-acid battery-based power plant. The book's discussion made me curious about the operational characteristics of a Gato-class submarine when operating submerged on batteries. In this post, I will be examining the Gato-class submarine's run time versus speed plot (Figure 1). Continue reading →

Posted in Naval History | Comments Off on WW2 Submarine Endurance on Batteries

Floating Habitat on Venus

Posted on 13-February-2016 by mathscinotes

I have been keeping a close eye on the discussions occurring about sending people to Mars on both one-way and two-way trips. You do not hear similar discussions about Venus because its surface temperature (467 °C) and pressure (93 bar) are too extreme to imagine people surviving there. Continue reading →

Posted in Astronomy | 6 Comments

The Cost of Minting Coins

Posted on 11-February-2016 by mathscinotes

I rarely think of the US government as producing any physical products, but there is one product that only it produces and that is extremely profitable – US money. The government sells money at its face value, which historically has had higher value than the cost of manufacturing it. In the year 2010, the US Mint generated $6.3 billion in profit from selling the money it manufactures. Continue reading →

Posted in Financial | 2 Comments

MTBF and Annualized Failure Rates

Posted on 9-February-2016 by mathscinotes

One of the more distasteful tasks I need to do is make estimates of annual product failure rates using MTBF predictions based on part count methods. I find this task distasteful because I have never seen any indication that MTBF predictions are correlated in any way with field failure rates. This is not solely my observation – the US Army has cancelled its use of part count method MTBF predictions (i.e. based on MIL-HDBK-217). However, the telecommunications industry has continued to use these predictions through their use of SR-332. If you want to see a simple example of an SR-332-based reliability prediction, see this very clear example from Avago. Continue reading →

Posted in Statistics | 8 Comments

Drag Coefficient From A Ballistic Drop Table

Posted on 8-February-2016 by mathscinotes

I thought it might be interesting show how you can approximate the drag coefficient for a bullet given a standard bullet velocity versus distance table. The folks at Barnes have put together a very nice discussion of how they go about characterizing a projectile using Doppler radar data. They also created an excellent infographic for a common hunting round showing the velocity versus distance table, actual drag coefficient, and G1/G7 reference drag coefficients (Figure 1). I thought I would take their table data and use that data to generate the drag coefficient chart. Since my data is limited, I do not expect a perfect reconstruction, but it should be close. Continue reading →

Posted in Ballistics | 1 Comment