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My random knot in the Web

Welcome

This is my home in the virtual world, where I write about things that I want to share. The freely available software that I've written as well as some of the photographs I've taken over the years can also be found here. Please use the navigation links on the right if you are looking for something.

Recent articles

  1. Resonance frequency of a composite tube

    Based on a question I ran into at work, I wanted to explore the influence of parameters like cross-section, wall thickness and laminate lay-up on the resonance frequency of a carbon fiber composite tube.

    The goal of this exercise is to determine which of the parameters are dominant.

  2. Using sed

    As I’ve written about before (see engineering), I often use CalculiX for structural mechanics calculations of products made from composites. These often involve calculating lots of different combinations of materials, lay-ups and load cases. For convenience and for them being self-contained, each variant is usually in a different directory.

    So when I find an improvement to e.g. a pre.fbd, Makefile or job.inp, I want modify all of the other instances as well. This is where sed (which stands for “stream editor”) comes into play.

    date: 2022-05-22
    modified: 2022-08-31
    reading time: 5 min.
    category: howto
    tags: sed
  3. Zero DSR power consumption

    Based on the data from the dashboard I’ve created a graph of the power consumption for a 2020 Zero DSR.

    As far as possible, this was measured on a level road at constant speed, on a good road surface and without much wind. The power is the product of the speed in km/h and the energy usage in Wh/km.

  4. Patching CalculiX Graphics to fix flipped screen hardcopy

    Since some time, I’ve had the problem that generating hardcopy images from cgx doesn’t work properly; the pictures are inverted vertically.

    At first, I thought this might have been a change in cgx. But comparing the source code for cgx.c for 2.16 up to and including 2.19, I don’t see anything that would explain it.


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