## Happenings – 2011 Apr 30

I’ve been all over the place last weekend and during the week, doing a little bit of a lot of things.

I’ve got some things that seem to be finished, in principle if not in practice.

We’ll be done with elliptical orbits as soon as I put out a derivation of Kepler’s equation…. And the second post on projectile motion is so close to completed that it’s silly not to have put it out by now.

I think I’m done with multicollinearity mathematically, but I have to put out two more posts about the Hald data; and I think I want to quickly illustrate multicollinearity in two or three other data sets. A couple of theoretical posts after that, and then a summary and a bibliography, and I should be done with regression for this time around.

I’m still thinking about group theory posts… but I have yet to put finger to keyboard and write anything.

“Mechanics of Solids” was progressing nicely… until they showed me that the stress in thin-walled cylinders and spheres was a special case of the stress in thin-walled surfaces of revolution. There’s got to be a cleaner way to do this than what they had.

I had an opportunity to look at control theory this week… now I’m thinking I want to focus on the time domain response. We’ll see.

I also managed to read – not to grasp! – Stewart and Tall’s “Algebraic Number Theory and Fermat’s Last Theorem”. You know, that book looks doable.

But I haven’t had a chance to look at my other book on stellar interior equations… so I don’t know if it has enough information to permit me to actually do a model of the sun.

Oh, I started working on the calculation of pathlines, streamlines, and streaklines for a specific velocity field. It turns out the example goes back to, at least, 1960: Truesdell & Toupin, “The Classical Field Theories”.No wonder examples have seemed scarce all my life – they apparently are.

Now let me see what I can get done today.