# Monthly Archives: February 2011

## Projectile Time of Flight/Distance Versus Velocity

Introduction As I mentioned before, I am reading the book "Modern Practical Ballistics" by Pejsa and am finding some interesting material there. I previously duplicated Peja's derivation for a function describing a G7 standard projectile's velocity versus range. This post … Continue reading

Posted in Ballistics | 5 Comments

## Drive-By Math

Occasionally I have an engineer come by my cube and unexpectedly present me with an opportunity to do math. A few years ago one of the engineers stopped by with a VERY common type of electrical engineering problem. He had an LVPECL logic device that needed to connect to a CML logic device. Of course, these two logic families have different voltage levels and cannot communicate with one another unless some sort of voltage-level shifting (Figure 1) is performed between the devices. We had been using a level-shifting circuit recommended by an IC vendor, but that circuit had turned out to have some problems (I do not know what these problems were). The engineer posing the question had spent a few hours grinding through the math manually and eventually decided that it was too painful to continue. He knew that I use computer algebra systems like Mathematica and Mathcad, so he asked if I could help. Using Mathcad, the following analysis was performed and we had a solution within five minutes. It was quite a demonstration of the power of modern computer algebra systems. Continue reading

Posted in Electronics | 3 Comments

## Calculating the Density of a Planet

Quote of the Day Democracy is the theory that the common people know what they want, and deserve to get it good and hard. — H. L. Mencken Introduction I have been reading some interviews with Michel Brown, an astronomer … Continue reading

Posted in Astronomy | 1 Comment

## Neat Use of Gravity Measurements

Quote of the Day Your time is limited, so don't waste it living someone else's life. — Steve Jobs One of my sons is into archeology. Whenever he talks about it, I always find the discussion interesting. We were talking … Continue reading

## An Analog Circuit Design Review

Quote of the Day The gods do not deduct from a man's allotted span the hours spent in fishing. — Babylonian Proverb Introduction When an electrical engineer asks me what my specialty is, I always respond that I am an … Continue reading

Introduction I was listening to an advertisement where CSX made the claim that they move 1 ton of freight 423 miles for 1 gallon of fuel. This is an interesting measure of efficiency. Let's see if we can confirm this … Continue reading

Posted in General Science | 5 Comments

## Drinking Math

As a non-drinker, I have never had much interest in alcohol. That said, alcohol has been a big part of my life. My mother earned her living working in bars, starting as a waitress and eventually managing them. Even in retirement, she works part-time selling pull tabs in bars for local sports groups. I have also been the designated driver for literally hundreds of social occasions. At work, I have had numerous co-workers who have derived much pleasure brewing beer and wine. It is always interesting hearing them discuss their various brews. The only drinks I ever show interest in are the layered drinks (Figure 1), but only because they look cool. Continue reading

Posted in Health | 9 Comments

## Interesting Old Submarine Photo

A co-worker and I were discussing strange photos we have seen. I mentioned a photo that I saw years ago that showed USS S-5's tail sticking out of the water. During the 1920s, submarines that submerged occasionally did not come … Continue reading