## Bloom Filter

30 12 2008

File this under tools I bet I’ll need:

Bloom Filter in Ruby

Excerpt:

A Bloom Filter is a probabilistic data structure that is used to test whether an element is a member of a set, or more simply, it’s an incredibly space efficient hash table that is often used as a first line of defense in high performance caches.

## New Tools

30 12 2008

Gotta love mcmaster + next day air:

All metric tools. What a pleasure working in metric. Ball point hex keys, metric wrenches, metric digital caliper, metric ruler, metric drill bits, metric tape measure, and some files and wire cutters.

## Finite Element Analysis

30 12 2008

We need to nail down calculation for chassis strength under the load of the electromagnets. Ideally we would want full finite element analysis. I found an open source package called OpenFEM, which depends on the also open source SciLab. Scilab looks generally useful for this project.

Please leave a comment if you know SciLab. It really helps to have a guide when learning new software… this stuff is all new to me.

I did some crude calculations for the force from the coils. Now we need to calculate the strength of the chassis for various materials and designs.

The strongest material for SLA is BlueStone, here is the BlueStone datasheet. Tensile Strength 66 Mpa. Compare that to steel which has a tensile strength around 500 Mpa. Time to get a quote for Direct Metal Deposition from POM

Reading up on tensile strength I noticed the following: Tensile strength is an intensive property and, consequently, does not depend on the size of the test specimen.

UPDATE

List of Free Numerical Analysis Software. Treasure trove of free tools.

I’m looking for a way to import an STL file for analysis.

CalculiX looks like its more directly useful. CalculiX supports STL geometry import export, see CalculiX Docs .

With CalculiX Finite Element Models can be build, calculated and post-processed. The pre- and post-processor is an interactive 3D-tool using the OpenGL API.

These are geared towards physical modeling:  CalculiXCode_AsterFEniCSImpactSLFFEAYadeZ88