ITW, being an abbreviation for "Industriële en en Toegepaste Wiskunde", is the Dutch organization for Industrial and Applied Mathematics. Professor R. Timman has been one of the early promotors of ITW at the Delft University of Technology. For the sake of underpinning this statement, his "Intreerede" (Dutch) has been OCR-ed and made on-line.
But there are many other places in the world where
Applied rules the roast nowadays, even more as
it is the case in Delft.
It cannot be denied, though, that there exists links to the World of Pure
Mathematics. Most pure mathematicians in the
Netherlands are a member of the so called
Wiskundig Genootschap. The most important mathematical institute here is
the CWI (Centrum voor Wiskunde en Informatica).
I don't know if he is still alive, but there is one more person I want to mention explicitly in this context. His name is Preston C. Hammer He has been a professor at the Pennsylvania State University. Several of his articles and books have had great influence on my thoughts concerning mathematics. Here are two manuscripts from him which have never been published. (They were sent to me as a part of a private communication.) If you read these articles, you will easily understand why it's so difficult to find a publisher:
Well, a remedy in such cases is simply not to find a publisher and
"publish" a book (Dutch) entirely by yourself.
FORTRAN BASIC FORTH PASCAL / DELPHI
How comes that someone who is working at a Computing Centre of a Technical University is going to collaborate with an astronomer? Well, that's bit of a strange story indeed!
I have decided to distribute the computer programs and accompanying documentation, with exception of the "coeffs" suroutine (containing all of the Physics and developed by Horst Fichtner himself), as public domain source code. It might serve as a (somewhat obsoleted) blueprint for describing anisotropic Convection & Diffusion within a hemisphere. The mathematics of Convection & Diffusion should better be replaced by a proper translation from my newer Delphi Pascal version. Also available are LaTeX sources of the accompanying PDF document, with a somewhat obsolete description of Convection. (Note: 'ps2pdf' files yield a blurry appearance on the screen with old Acrobat Reader versions. This doesn't harm printing, which is pretty good. Preferably use instead Adobe Reader > version 6.0) Here are some visualizations of the results obtained by Horst Fichtner.
I was in the opportunity to present a lecture about the numerics of the matter at the "Woudschoten 1996 conference" on September 26th, Thursday, 12.15 - 12.45, Zeist (the Netherlands). Title of the presentation: "On solving a Cosmic Ray equation". A (necessarely incomplete: partly hand-written) collection of accompanying overhead sheets was processed for inclusion in this Homepage.
I have been successful in porting a full blown version of the 3-D ZONWIND code to PC's, using Turbo Pascal and Delphi.
The performance of Skew Upwinding has been somewhat disappointing, despite of
my theoretical and
programming effort spent on the subject.
Attempts to generalize the idea to multiple dimensions (say 3 + 1 = space
plus time) seem to be even more discouraging. There exist 58 tetrahedra which
share their corner points with those of one cube in 3-D. (This strategy differs
from the one which was outlined in previous work
and which should be characterized now as rather incomplete).
In 4-D there exist 3008 such pentahedra, however, as has been found by
running another little program. Imagine what
calculation time would be involved with just one of these space-time elements!
The first two programs are characterized by the use of recursion.
In order to understand subsequent work, you should familiarize yourself with Delaunay triangulations and Voronoi regions. Maybe a good start is to download bits of software. For 2-D as well as for 3-D there exists some excellent public domain stuff.
There exist two articles in SUNA, the Series on Unified Numerical Approximations, which are not truly Numerical in nature. I think they rather belong to the area of Computational Geometry:
The following is perhaps more closely related to the area of Computer Graphics.
Here is a (Turbo Pascal) program for rendering
an arbitrary (wire-framed, alas!) cylinder, which is rotated into space with
help of
Quaternions. (Note: this program will not work without the Borland
BGI stuff, which must be placed in
the C:\TP\BGI directory.)
Another interesting place may be:
As part of a larger project (? I think) comes a tiny Delphi (visual Pascal)
program and its
executable
which does (say) the ultimate anti-aliasing of straight lines, according
to the theory in my (Dutch) book.
Another
program
and its
executable
does the anti-aliasing of black and white bit maps (B/W BMP files),
by convolution with a Gaussian distribution.
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