links for 2010‐10‐28

  • This document introduces RegexKitLite for Mac OS X. RegexKitLite enables easy access to regular expressions by providing a number of additions to the standard Foundation NSString class. RegexKitLite acts as a bridge between the NSString class and the regular expression engine in the International Components for Unicode, or ICU, dynamic shared library that is shipped with Mac OS X.
    (tags: regex cocoa)
  • (tags: yaml cocoa)

Indianapolis Half Marathon 2010

The Indianapolis Marathon deserves its reputation as a well‐respected race. We found it to be well organized, and several nice touches showed attention to detail on the part of those who ran it.

We had a minor hitch getting to the expo and packet pickup due to construction confusion at the YMCA, but it was smooth after that. We arrived just in time too, since we observed that the parking lot seemed completely full when we left a short time later. The entry area to the expo was lined with mums and heaters, a nice but unnecessary touch, as the weather was mild that day. The expo itself was on the small side. We had no trouble walking right up and getting our packets and t‐shirts from the friendly and helpful volunteers. The relatively small number of other vendors was no problem for us — less to traffic to dodge on the way out!

We owe a big thank you to the Zembrodts for watching David on race morning. We could not have both participated had it not been for their help. I’m glad that David got to play with his friends Jake and Toby on a Saturday morning, too.

After dropping off David on race morning, we were prepared for heavy traffic on 56th Street. By the time we crossed I‐465, traffic was flowing smoothly. The kids directing traffic in the VA parking lots could have coordinated better and filled more spaces, but we didn’t have a problem. People arriving later might have had some difficulty finding parking spots, however. We stayed in the warm car, and Emily did some grading while we passed some time before braving the cold morning. Perhaps we should have left the car a few minutes sooner so that we could have made one last pit stop before the start. The lines were very long!

As the race started, the temperature was quite cool. No complaints though, as the sun felt glorious between the trees. The quiet environment while running in the state park was enjoyable, just the sound of footsteps and concentration. After a while, the park became more challenging for me. First, the hills were more than I am accustomed to, particularly the one at mile 10.5. Second, the design of the course led to some doubling‐back even on the half‐marathon course, which tends to sap my motivation. Still, the scenery was undeniably beautiful.

The food in the finishing area was a pleasant surprise. Both Emily and I thought that we had to have bought an additional ticket to enter, but we were wrong. All participants were allowed to have a hamburger or bratwurst lunch. Cool, how nice! And a well‐earned brat it was. That’s why we run.

links for 2010‐10‐22

  • Turn your spreadsheet into a map

    1 — Upload your spreadsheet
    2 — Get an interactive online map in seconds

Prius nomogram

After finding a nomogram of how the Prius’s continuously variable transmission (or Power Split Device, in Toyota‐speak) works, I thought it would be a fun exercise to use PyNomo to create my own Prius PSD nomogram.

The PSD is a planetary gearset, with the sun gear attached to Motor‐Generator 1 (MG1), the planet carrier attached to the Internal Combustion Engine (ICE), and the ring gear attached to Motor‐Generator 2 (MG2). MG2 drives the front wheels directly.

In the nomogram, the car is travelling 65 mph. Because this is a continuously variable transmission, there are infinite ways of achieving this road speed. MG2 must turn at about 3850 RPM because it drives the front wheels directly. However, the engine can be running at anywhere between idle speed and flat‐out. MG1 will then turn at a corresponding speed according to the relationship shown in the nomogram.

The nomogram also illustrates how the Prius can run in “EV mode,” where the car drives under electric power alone. With the ICE off, MG1 rotates backwards and MG2 rotates forward. As the car speeds up and slows down in EV mode, the isopleth line see‐saws up and down the MG1 and MG2 scales, anchored at the ICE’s 0 RPM point.

Part of the elegance of the PSD is that there is no reverse gear. MG2 simply rotates backwards with the engine off. Cool!

There is an interactive Flash‐based version on eahart.com.

Watching for nomograms

Cleaning out drawers last weekend, I took a minute to fiddle with two slide rules that I inherited, one from each of my grandfathers. I’ve always found them to be a mysterious link to the past, where clever tricks made all kinds of things possible that we take for granted today. I’d like to be able to make more use of them, but they’re just not that practical any more.

Yesterday I stumbled on a link to a gallery of similarly outdated but intriguing tools called nomograms, which are graphical solutions to equations. Ron Doerfler assembled a calendar for 2010 featuring a number of intricate nomograms. He updates his site infrequently, but I certainly hope he is able to put together a similar calendar for 2011. I will definitely check back later in the year! It will be good for engineer‐cred.

As an electrical engineer, I still have nightmares about trying to understand Smith charts in college. The Smith chart is another type of nomogram used for a number of purposes, including matching components, transmission line characteristics, and other high‐frequency uses. Again, the chart is fascinating to look at, but it’s really a product of the black arts. Stay away.

Thinking more about where I’ve seen nomograms, I recall on highway maps there used to be a fuel economy calculator. There were two horizontal lines and a diagonal line between them. On one horizontal scale, you would select how many gallons it took to fill the tank, and on the other, you would choose how far you went on that tank. The center scale showed the car’s fuel economy for that tank. For the life of me, I can’t find any examples online, so I tried out PyNomo to create one of my own.

In the example above, I went 650 miles on a tank of fuel, and it took 14.5 gallons to refill the tank. The line between those two points intersects the MPG scale at about 45 MPG.

The PyNomo site has some additional examples that fly way beyond my comprehension, but they are neat to look at.

I also found a nomogram for homebrewers to calculate IBUs, and one illustrating the operation of planetary gear set in a Prius.

links for 2010‐10‐21

Wind Rose

I wanted to find a way to show which direction the wind normally comes from, but wasn’t sure of the best way to show that information. A histogram is close, but it would be nice it could be shown in a circular representation. I stumbled on exactly the type of plot I was looking for. Turns out that R has a nice package called “climatol” that has a function to show this perfectly.

links for 2010‐10‐19