Monday, January 28, 2013

Octet Truss Memory, Time and Dollar Costs

Cost for 3D Octet Truss Arrays
i j k time (s) stl (bytes) WSF ($)
1 1 1 1 1.47 73384
2 2 2 2 28.74 435384 2.61
3 3 3 3 173.32 1342184 4.99
4 4 4 4 873.20 3052984 9.46
5 5 5 5 2952.67 5826984 16.69
6 6 6 6 6694.16 9923484 27.32
This is a follow-up to the previous post on using the octet truss for topology optimization. The memory cost of performing the union of all the truss members in BRLCAD to generate stl files for printing was too large for the ToPy dogleg example so I generated a set of stl files for a range of arrays of octet truss unit cells. Then I uploaded them to shapeways to see how much they would cost to print in the white-strong-flexible nylon material. The table shows how long the python script took to execute, the size of the resulting stl file, and the cost to print the part on Shapeways in the white-strong-flexible material.

Monday, January 21, 2013

Small Multiple Scatter Plots with Marginal Densities

An example data visualization in R inspired by Tufte's example on pp118-121 of Beautiful Evidence; source below the fold.

Monday, January 14, 2013

Maxima Related Lisp Tutorials

In this previous post I mentioned that I learn a lot from the Maxima mailing list.

There was a recent question (somewhat frequently asked) about how to learn Lisp to be a better Maxima user / developer that is a great example of that. The thread is called Lisp tutorial. The original poster has a simple request:
Hi,
I have enjoyed using Maxima to solve differential equations. I would like
to learn lisp to complement Maxima. Can any of the maintainers of Maxima
(or others for that matter) recommend a lisp tutorial?
Many thanks

Ronald F. Modesitt

The list responded with a variety of resources.
Norvig's PAIP (which I was quite happy to get as a present over the holidays) is especially relevant to Maxima users. Chapter 8, Symbolic Mathematics: A Simplification Program, has a simple symbolic algebra implementation, and Chapter 15, Symbolic Mathematics with Canonical Form, has a more capable solution. Both chapters are modeled on Maxima.

Wednesday, January 9, 2013

Nuclear Rockets Petition


As reported by NBC there is a petition on WhiteHouse.gov to rapidly develop and deploy a nuclear thermal rocket for both manned & un-manned space missions. I signed it; why not? Here's the short url: http://wh.gov/UVuD

Nuclear rocketry seems to be a popular topic of late. Gary Johnson has a recent post about nuclear rockets. The NBC article mentions NERVA. There is also the more recent Project Timberwind and Space Nuclear Thermal Propulsion program effort to develop nuclear upper-stages.

Friday, January 4, 2013

Scientific Computing Going Mobile/Embedded

I follow both the Octave and Maxima user mailing lists (I learn more from the Maxima list, but the Octave one still throws up a gem every now and then). I am also a founding member of the Dayton Diode hackerspace. So it was interesting to see some things of interest to makers/hackers pop-up on those two lists.

The first was a thread on the Octave list about installing Octave and the Octave Forge packages on a Raspberry Pi. In theory it should be as easy as any other Debian system using the package manager for the distribution. No word back from the OP yet on whether it works in practice or not.

The second thread to pop up was on the Maxima list about installing Maxima on Android systems. Maxima-on-Android is apparently a bundle on Google Play of Maxima 5.28.0, Gnuplot 4.6, Mathjax 2.1 and Qepcad 1.69. I have not played with it yet on any of my Android devices.

Thursday, January 3, 2013