User talk:Georg-Johann

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Nixie tubes

One of my most beloved and sorely missed items that is the collection of junk that I call mine is a circuit board with tubes like Image:ZM1210-operating.jpg on it. I honestly never thought/dreamed/could believe that there would be some somewhere that still glow!

I dug mine out of stuff that was going to be dumped which was sitting in the halls of my university. If I had to rank my circuit board against my autographed postcard from Harold Edgerton -- I would find it really difficult to say which was worth more to me. That board blew my mind -- my first computer experience which a cigarbox of paperclips was a KIM-I, while Mr. Edgerton reminded me of my grandfather who had the instructions for the cigarbox/paperclip computer in his home.

But you saw one glowing! Did you hook it up yourself or is there someplace where they glow on demand? -- carol 13:23, 24 February 2008 (UTC)

---

There are still lots of nixie tubes on this planet. The ZM1210 was produced in large amounts and there where much of them on stock when the market was flooded by LED technique. Unfortunately, most nixies don't live very long and these short living pieces are very expensive and hard to find. The ZM1210 lives longer and is therefore -- paradoxically -- easier to get and cheaper. The tube is part of my home brewed Nixie clock. Nixie drivers like 74141 can also still be found.

In the age of about 15 I found such a tube in one of my father's astonishing "treasure boxes". I just saw glowing it once because I directly connected it to mains... Shame on me!

--Georg-Johann 13:51, 24 February 2008 (UTC)

Heh, did you get hurt? I had two things that always made me stop before plugging things in -- once the television set I was watching the big tube (the crt) with the display imploded. My mom would have been about 20 years old and she called the fire department to 'unplug' it -- it was very scary and we were both quite young. Then my dad told me how his dad, that grandfather with the instructions, used to get shocked and sent against the wall from his experiments in the garage. -- Brave but not that brave carol 23:24, 24 February 2008 (UTC)

Julia Sets

Hi. I have seen your images. Great. It seems that I'm intrested in similar things. Maybe you can do something on wikibooks about Julia sets ? --Adam majewski 17:02, 7 April 2008 (UTC)

Hi, thanks. I don't hav these amounts of time. Maybe you can use my ideas presented in Image:Julia-set z2+c -0.742 0.1 5000.jpg#Coloring. Just follow the link to "Visualizing Julia Sets". If you have any questions on that, just ask. --Georg-Johann 21:42, 7 April 2008 (UTC)

Hi, thanks. Regards--Adam majewski 06:59, 12 April 2008 (UTC)

I’ve produced a program in Java to make Julia sets, but I keep getting strange spikes around the attractors. Do you know what might be causing this? If you know can you get in touch at my Wikipedia account. Thanks. --Simpsonscontributor (talk) 22:07, 28 July 2008 (UTC)

( This question is not to me but .... (:-))) I think that is caused by diffrent bailout test . Am I right --Adam majewski (talk) 07:29, 30 July 2008 (UTC)

I run through the Complex plane in an x-y fashion running this code for each point:

while(!differenceTest) {

                    //Perform Newton's method
                    functionValue = functions.function(planeComplex);
                    derivativeValue = functions.derivative(planeComplex);                     
                    newton = operations.divide(functionValue, derivativeValue);
                    newton = operations.subtract(planeComplex, newton);
                    
                    /*Newton is now the "x plus one value". Check to see if
                     * newton and planeComplex are close to each other. If they 
                     * are then set differenceTest to true*/
                    real1 = planeComplex.realDouble;
                    real2 = newton.realDouble;
                    imag1 = planeComplex.imaginaryDouble;
                    imag2 = planeComplex.imaginaryDouble;
                    
                    realClose = closeTest(real1, real2);
                    imagClose = closeTest(imag1, imag2);
                    
                    if(realClose && imagClose)
                        differenceTest = true;
                    else
                    {
                        planeComplex = newton;   
                        counter++;
                    } 
} 

If Z(n) and Z(n+1) are sufficiently close I move to the next pixel. Here is the test I use to see if they are close enough to assume that they have reached an attractor:

private boolean closeTest(double in1, double in2) {

       //Return true if in1 and in2 are close
       
       int in1Int = (int)(1000000 * in1);
       
       int in2Int = (int)(1000000 * in2);
       
       int difference = Math.abs(in1Int - in2Int);
       
       return difference < differenceThreshold;

}

I was thinking that this might raise a false (too early) bailout if Z(n) and Z(n+1) had drifted close to an attractor but had not settled on it. I'll alter the code to accommodate that and see what happens.

--Simpsonscontributor (talk) 22:36, 30 July 2008 (UTC)

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Tip: Categorizing images

---

Hello, Georg-Johann!

Tip: Add categories to your files

Thanks a lot for contributing to the Wikimedia Commons! Here's a tip to make your uploads more useful: Why not add some categories to describe them? This will help more people to find and use them.

Here's how:

1) If you're using the UploadWizard, you can add categories to each file when you describe it. Just click "more options" for the file and add the categories which make sense:

2) You can also pick the file from your list of uploads, edit the file description page, and manually add the category code at the end of the page.

[[Category:Category name]]

For example, if you are uploading a diagram showing the orbits of comets, you add the following code:

[[Category:Astronomical diagrams]]

[[Category:Comets]]

This will make the diagram show up in the categories "Astronomical diagrams" and "Comets".

When picking categories, try to choose a specific category ("Astronomical diagrams") over a generic one ("Illustrations").

Thanks again for your uploads! More information about categorization can be found in Commons:Categories, and don't hesitate to leave a note on the help desk.

BotMultichillT 05:51, 4 July 2009 (UTC)

• Image:GJL-fft-opt-crop8-095.png is uncategorized since 3 July 2009.
• Image:GJL-fft-ergebnis8-095.png is uncategorized since 3 July 2009.
• Image:Gjl-point-to-point.png is uncategorized since 3 July 2009.
• Image:GJL-int-spline-soo.png is uncategorized since 3 July 2009.
• Image:GJL-int-linear.png is uncategorized since 3 July 2009.
• Image:GJL-fft-noopt-crop8.png is uncategorized since 3 July 2009.
• Image:GJL-int-spline-s0.png is uncategorized since 3 July 2009.
• Image:GJL-fft-opt.png is uncategorized since 3 July 2009.
• Image:GJL-fft-herz.png is uncategorized since 3 July 2009.

again with those nixies

http://carol.gimp.org/GIMP/gimp-2.7/some_splash.php#nixie

I used many images for this web page, but yours is my favorite. The unlit nixie was extremely useful and nice to work with and was the only complicated manipulation on that page that I am at all proud of.

Do you know the smell of hot solder and vacuum tubes? Once when I was really young, our television set blew up. That was back in the days when Christmas lights would set the trees on fire also (the cloth cords...). That was such a stink. My mom who was also quite young then (probably not yet 21 years old) was very frightened and called the fire department. They brought the truck and all of the equipment and we stood across the street and also away from the road while they unplugged it.

The smell of hot solder and vacuum tubes is much better than the smell of the imploded cathode ray tube....

Thanks for the image, btw. -- carol (talk) 10:11, 4 July 2009 (UTC)

Note that there is also a nice picture of one of my nixies at work from this project. Nixies glow by an electric glow discharge, so they are rather electric discharge lamps than vacuum tubes. Some versions of ZM1210 and other nixies in fact have a decimal dot. --Georg-Johann (talk) 12:36, 4 July 2009 (UTC)

Too many vacuum tubes in my history to not smell one even when I see just the container. I think that the nixies on my board are connected with soft wires and the bottoms of the glass containers are open -- so even less are mine vacuum tubes but my little brain still smells grandpa's tv repair shop. Electronics have their own smell; truly the smell of it must have made the technology much more frightening when it first began to be applied. I suggest that I am going to (however wrongly) remember the smell of vacuum tubes until I see one of these things working and know that smell. Usually, when I smelled that hot solder on wet sponge smell, my dad was really happy at that same moment and it is for me a comfort smell that I don't often smell now. With the exception of the occasional really cool image like this and my miss-applied memories.

There are simply not enough words and it is not very useful for me to attempt to explain my love of that image of yours -- even the parts I get wrong. -- carol (talk) 23:53, 4 July 2009 (UTC)

Visualising Julia sets

Hi, Thx for great images and article.

What means

$E\left\{\right\}_{\!z\,\in \,\Gamma }$

in

$E_{n}=E\left\{\log(\delta +\Sigma _{n}(z,\varepsilon ))\right\}_{\!z\,\in \,\Gamma }$

Also I can't find explanation of Dn, DX and EX. Best regards --Adam majewski (talk) 08:52, 2 November 2009 (UTC)

File:GJL-fft-herz.svg

That's a nice image, but a simple angle and two approximately semi-circular arcs are probably just as good an approximation to the traditional symbol (see File:Heart-padlock.svg for one version with a 90° angle, which could be decreased slightly for a closer resemblance). AnonMoos (talk) 13:35, 28 October 2010 (UTC)

Hi, thanks. The curve is the result of some intepolation/appriximation I once played around with. It occured in a more general context and I also tried the method for a heart-shaped curve and it worked well, producing an output that I found aesthetically appealing. Moreover, the curve (resp. it's parametrization) is smooth and algebraic. The smoothness doesn't show in two dimensions because of the cusps, but after a canonical lift to three dimensions the cusps disappear. I had made similar cimputations for letters A and B and some animations. [1] shows a rotating A and you see that the cusps are just due to some angles used to flatten the curve into two dimensions. Once you have a smooth parametrization, you can make smooth transitions like A-to-B-to-A in [2]. The curves and all intermediate steps are easy to compute and involve just one smooth, periodic, bounded function (sine). I used to to morph shapes on a system with considerably small resources (8-bit microcontroller of the avr family) --Georg-Johann (talk) 17:55, 29 October 2010 (UTC)

Squircle

I tried my best to roughly approximate the shape in the most recent version of File:Squircle2.svg, but it occurs to me that you might be able to do it analytically... AnonMoos (talk) 15:26, 25 November 2011 (UTC)

There is a non-analytical representation

${\begin{aligned}x&=r{\sqrt[{\sim }]{\cos \varphi }}\\y&=r{\sqrt[{\sim }]{\sin \varphi }}\end{aligned}}$

with

${\sqrt[{\sim }]{x}}=\operatorname {sgn}(x)\cdot {\sqrt {|x|}}$

but I think you know that. I have written a tool to find cubic Bézier (aka. SVG) approximations for curves, and for this well-behaved (smooth, connected, bounded, non-singular) curve it should be no problem to get a representation. My tool, however, is non-intuitive, not documented and non-auto. With that script, I get the following result, drawn over your curve in black: 32 points (red) and 16 points (green). Red is almost perfectly hidden behind Green, which in turn looks like your 8-point version. Thus, your 8-point version is accurate enough, IMO. Cubic Bézies can't even exactly represent a circle, they cannot represebt this quartic either.

<?xml version="1.0" standalone="no"?>
<svg xmlns="http://www.w3.org/2000/svg" width="608" height="608" viewBox="-304 -304 608 608">
<title>Squircle: x to 4th plus y to 4th equals radius to 4th</title>
<path fill="none" stroke="#000000" stroke-width="4.04" d="M0,288
C126.2,288,196.3563,288,242.1782,242.1782
C288,196.3563,288,126.2,288,0
C288,-126.2,288,-196.3563,242.1782,-242.1782
C196.3563,-288,126.2,-288,0,-288
C-126.2,-288,-196.3563,-288,-242.1782,-242.1782
C-288,-196.3563,-288,-126.2,-288,0
C-288,126.2,-288,196.3563,-242.1782,242.1782
C-196.3563,288,-126.2,288,0,288Z"/>

<g fill="none" transform="scale(288)" stroke-width="0.01">

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    M 1,0
    C 1,0.17446 1.00693,0.44702 0.96119,0.61861
    C 0.939,0.70185 0.9027,0.77909 0.8409,0.8409
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--Georg-Johann (talk) 19:22, 26 November 2011 (UTC)

---

Thanks -- I thought that there might be some relatively quick and easy way of constructing a formally mathematically correct curve, but I guess there isn't. The only other non-circular mathematical curve that I've converted to beziers is the Archimedean spiral (see File:Archimedean spiral.png), and that was done somewhat approximately also. I was worried by the purple peeking out from behind the black if you view the PostScript source on File:Squircle2.svg, but it seems like the error is pretty much within one unit on a 600x600 grid, so I guess I'll leave it as is for now. The approximation of a circle by four cubic beziers is said to be within 1/1000 of a true circular curve, but I think it would requires at least 8 to approximate a squircle with similar accuracy. Not sure what the interpretation of the numbers greater than 1 is in the above code (1.00693, 1.00193). AnonMoos (talk) 08:12, 28 November 2011 (UTC)

No, there is no correct curve if you restrict yourself to non-rational Bézier of order 3 as supplyed by SVG, and even oder 4 won't do. Drawing curves in terms of cubic Bézier is always approximation except in some very few special cases like File:Semicubic-Parabolas.svg.

The numbers > 1 are coordinates of control points, see w:Bézier curve for explanation.

Finding good Bézier approximations is non-trivial. One way to accomplish it is outlined by Geek3 who did many graphics that are the finest you can find in Wikipedia. See User talk:Geek3#Control points in Zeta0.5 100.svg. As far as I can see his plots are mostly of the style x → ƒ(x) for well-behaved functions ƒ. As the functions to plot get more complex, like with singularities or of shape t → (x(t),y(t)), things get more complicated because it is no more obvious how to rate an approximation or computing areas between graphs gets weird if it is around poles like in File:tanc.svg.

For curves for which you can find a parametrization t → (x(t),y(t)) I started an essay some time ago, see de:Benutzer:Georg-Johann/Mathematik#Bézier-Curves. The very problem is that the curve can be re-parameterized by means of some functions g as t → (x(g(t)),y(g(t))) yielding the same set of points but with different properties from the plotter's perspective.

In order to be invariant under re-parameterization, you have to stick to curve invariants as mentioned at the end of the essay. For example, invariant L is just the length of the curve. L is invariant under translation, rotation and re-parameterization, i.e. no matter how fast you drive along the curve, the length will stay the same. Zooming the curve by a factor of z will result in an invariant of z·L. There is another invariant K that is even scale-invariant and is sensitive to curve details. K is the integrated curvature.

The trouble with these invariants is that they are expensive to compute, and even worse, to use them for a plot, you'll have to invert them.

For some reason I switches to an other project and the essay is unfinished. My implementation yields reasonable results for the curves that I used it with, see some examples: File:Logarithmic spiral.svg, File:Line of Cassini.svg, File:Edward-curves.svg, File:Kartesisches-Blatt.svg, File:Mercator series.svg, File:Linear-chirp.svg, File:GJL-fft-herz.svg. --Georg-Johann (talk) 16:03, 5 December 2011 (UTC)

Thanks for the info. By "> 1", I was wondering why some of the control points would be outside the enclosing square, but I guess that's possible. The mathematics is getting somewhat beyond me (I had difficulty enough just figuring out the formula for the tangent to an Archimedean spiral at a specified point), except that when approximating curves by quadratic Beziers, the only choice is which points on the curve to use -- because once you've specified the two endpoints of a quadratic Bezier, and the tangent angles at both endpoints, then the quadratic Bezier is completely determined... AnonMoos (talk) 18:19, 9 December 2011 (UTC)

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Image:ZM1210-operating.jpg is a ZM1212

Hi Georg-Johann!

According to its data sheet, the ZM1210 had a red contrast filter coating. This is a ZM1212, I'm afraid. Really beautiful, though. I've put it into en:List of vacuum tubes --Mkratz (talk) 20:10, 24 April 2013 (UTC)

The tube is a stripped ZM1210, i.e. the red coating has been removed. Cf. the image description for more details on the device. --Georg-Johann (talk) 13:30, 12 May 2013 (UTC)

File:HH object diagram de.svg

File:HH object diagram de.svg has been listed at Commons:Deletion requests so that the community can discuss whether it should be kept or not. We would appreciate it if you could go to voice your opinion about this at its entry. If you created this file, please note that the fact that it has been proposed for deletion does not necessarily mean that we do not value your kind contribution. It simply means that one person believes that there is some specific problem with it, such as a copyright issue. Please see Commons:But it's my own work! for a guide on how to address these issues. Please remember to respond to and – if appropriate – contradict the arguments supporting deletion. Arguments which focus on the nominator will not affect the result of the nomination. Thank you!

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