User talk:Cleonis

User talk:Cleonis/archive1

User talk:Cleonis/Archive 2

Parabolic dish and Coriolis force

I'm interested in the example I understand that the dish is perfectly configured for a trajectory in a horizontal plane, but I'm uncertain that the centrifugal force is entirely eliminated for paths that are not in the horizontal plane. What is your take on this? Brews ohare (talk) 03:31, 14 June 2008 (UTC)

Hello Brews,

I very rarely visit wikipedia these days, that is why I didn't respond.

I'll be happy to answer questions that you have. In the coming weeks I'll check this page every few days.

About the animation:

The animation is inspired by the information on the following webpages:

http://www-paoc.mit.edu/labweb/lab4/gfd_iv.htm

http://www-paoc.mit.edu/labweb/lab5/gfd_v.htm

The animation is an approximation. The shallower the dish the better the validity of the approximation. For a highly convex dish (say, the depth is more than a tenth of the diameter) the approximation is not valid.

forces for an object supported by a parabolic dish.
- Red arrow: gravity
- Green arrow: normal force
- Blue arrow: resultant force

In the diagram showing forces in the case of a parabolic dish the depth of the dish is exaggerated, an actual demonstration model needs to be very shallow.

The inclination of the surface provides the required centripetal force. At every distance to the central axis of rotation the centripetal force is precisely the amount that is necessary for co-rotating with the dish (in demonstrations the dish is rotated at exactly the same rate as when it was manufactured.)

For the case of the parabolic dish I will define the term 'the horizontal' as follows: the surface of the parabolic dish is the horizontal.

When the parabolic dish is very shallow the above definition of 'the horizontal' is a valid approximation.

In the movie that is available at http://www-paoc.mit.edu/labweb/lab5/gfd_v.htm the object that moves over the dish is a small disk of dry ice. Evaporating carbondoxide creates just enough air cushion to give the object very low friction.

Given the definition of 'the horizontal' I gave, every path follows the horizontal; at every point in time the puck's weight is supported by the dish. In that sense there simply is no path that doesn't follow the horizontal. (Of course you can choose to throw an object from one side of the room to the other, but that has nothing to do with the dish.)

Lastly, I never use the expression centrifugal force. The expression 'centrifugal force' is used in so many different meanings - most of them contradicting each other - that the expression centrifugal force is a major source of babylonian confusion. I never use it, and when somebody else uses it I rephrase so as to eliminate the expression 'centrifugal force'.

On my own website there are two interactive animations (Java applets) that do a much better job of explaining things than I can do in words. Please visit the interactive animations.

Coriolis_effect

centrifugal_effect

--Cleonis | Talk 17:57, 29 July 2008 (UTC)

Thank you for the links and comments. I'll take a look. Brews ohare (talk) 20:21, 29 July 2008 (UTC)

The law of conservation of angular momentum Woodstone TALK

Thank you for your August 2003 Woodstone TALK, and your illustrations here. Analog Science Fiction ran a delightful story of an astronut stuck on a parabolic mirror that perhaps you wrote. Anyway, to me L = Iω = El (god). Pawyilee (talk) 10:51, 19 December 2008 (UTC)

Hi, Pawyilee, I just reread that contribution to Woodstone's talk page. Back then, in 2005, was when I first developed a special interest in the physics of rotation. In 2006 I started building a website of my own that is largely dedicated to the physics of rotation, and especially the coriolis effect. The URL of my website is on my my user page. Some of the stuff that is on my own website is also on wikipedia.

I didn't write that astrounaut story, actually. I'd love to read it. Cleonis | Talk 14:49, 21 December 2008 (UTC)

Mass flow meter

Hello Cleonis,

I am unclear why you reverted my edits, you cited that "quality and performance are degraded"? I have no idea how a thumb can degrade quality and performance. I was about to place a delete tag on your 256x256 images per Wikipedia:Criteria_for_speedy_deletion#Files item 1, which clearly indicates that "performance" is degraded by having duplicate files! The thumbnails are cached copies, generated via imagemagick convert. These cached images can be clicked on by the reader to view the full 512 by 512 image as desired. Keeping multiple images is against current policy.

Also, execpt for the dangling line, I thought the layout was neater. I would like to revert it back to the version that I changed it to, but I shall await your reponse.

Kind regards, User A1 (talk) 09:51, 12 April 2009 (UTC)

PS: The cached images are just that, cached. Images are not generated on the fly, and there is no performance loss (in fact there is a performance gain!) for thumbnailing. User A1 (talk) 09:53, 12 April 2009 (UTC)

Hello A1,

I didn't know about the caching of thumbnails. That does alleviate my bandwidth concerns. What remains is the image quality.

I know Imagemagick, I have used it on occasion (but not for creating animated GIf). What I see is that the 180px thumbnails are seriously degraded in quality as compared to the originals. I surmise that for fast conversion a low grade downsizing algorithm is used.

A high grade downsizing algoritm has an anti-aliasing effect: no visible pixelation. But in the thumbnails there is acutely visible pixelation; the quality of the original is wasted.

In my opinion the 512x512 version and the 256x256 version are not duplicates, they are not only different in size, they have different resolution.

The original frames of the animations were created in 1024x1024 size. Then two separate GIF-animations were created from that source, a 256x256 version and a 512x512 version. The downsizing was high grade, so that pixelation was avoided.

I uploaded the 512x512 version so that instructors can use them in classes, beaming them on a screen. I feel the 256x256 pics are too small for projection on a screen, and obviously the 512x512 pics are too large for the article.

My point is: the only way to do a proper downsizing is to create 180x180 pics from the 1024x1024 source material, using high grade downsizing. If you feel the 256x256 pics are too large I can make smaller ones.

I still have the POV-ray source code, of course. (POV-ray source code is a plain text file) Maybe I should upload the POV-source code too, just as SVG images are to be accompanied with their source code. I don't know what's best. Maybe adding the POV source code to the image description page just makes it cluttered. --Cleonis | Talk 11:22, 12 April 2009 (UTC)

PS

I performed the following check: I used my browser to save the Wikipedia Mass flow meter article to local disk, then I checked the files that had been saved. It was the 140 KB originals that had been saved, not the thumbnail versions. That makes me return to my original supposition: the wikipedia servers ship the original animation, and the receiving browser has to downsize it on the fly. --Cleonis | Talk 11:37, 12 April 2009 (UTC)

Easy Java Simulations

Hello, I see you restored the EJS article on Easy Java Simulations. I'm just dropping by to let you know why I redirected it to Open Source Physics, and give some suggestions on how to make sure the article sticks around for the long term.

I turned the article into a redirect because that is what happened to an earlier version of it at "Easy Java Simulations". I don't know if you've noticed, but that article was deleted twice last year (once for being "blatant advertising, used only to promote someone or something", later for "promoting a non-notable software application"), restored twice, and eventually turned into a redirect to Open Source Physics. Since both articles were in similar condition (the one deleted last year was longer and cited a few more sources), I had both redirect to OSP.

Now, as for how to make sure it doesn't get deleted (or turned into a redirect again). First of all, the article itself should be moved to "Easy Java Simulations", and "EJS" should redirect to that title, not the other way around. That way, people who might not know what "EJS" stands for can get some idea of the article's content from its title (for more discussion, see the manual of style).

Most importantly, I note that there are no references to third-party sources that establish the notability and importance of the topic (much the same goes for the Open Source Physics article). The best way to establish the article's notability is to add references to scientific, trade-journal, or newspaper/magazine articles describing the use of EJS and its benefits to research or teaching. I'll add some templates to the article to encourage others to help out. If nothing of this sort can be found, I may convert the EJS article into a section within the Open Source Physics article. I think such expansions would work well for each of the four OSP projects. Cheers, David Schaich ^Talk/_Cont 03:03, 24 July 2009 (UTC)

OK, such articles in scientific magazines have been published, so I will list them as references.

As to the abbreviation of the name, I will consult the Wikipedia Abbreviation manual of style. As matters stand I intend to follow your suggestion to put the article content in "Easy Java Simulations" and to change "EJS" to a redirect to "Easy Java Simulations".

As member of a community of EJS users I judged that EJS isn't some one-man pet project, but a notable software development. --Cleonis | Talk 06:58, 24 July 2009 (UTC)

Why is the Easy Java Simulations article challenged as to its notability?

I have been looking at wikipedia entries for other software packages with comparable purposes. EJS is:

• open source software
• Written in Java; running in Windows-, MAC-OS-, and Linux environment
• Numerical analysis software
• Plotting software
• Generates Java applets that can be viewed independently of EJS.

List of numerical software

There is the List of numerical analysis software. All of the entries on that list are wikipedia articles. It seems to me that quite a few of the entries there are less notable than EJS.
An article dedicated to Easy Java Simulations was published in The Physics Teacher, a magazine that is published by the American Association of Physics Teachers.

Numerical analysis software template

• ADMB In that article the references and external links offer documentation that was written by the authors of that software
• FreeMat This article is actually unreferenced; the external links offer documentation that was written by the authors of that software
• GNU Octave Other than a single line in an article about another subject, the external links offer documentation that was written by the authors of that software
• Scilab The reference that is given is an article is about another subject, containing a single line of text stating that "scilab was used for solving the design problem". The other links offer documentation that was written by the authors of that software

In all I find it puzzling that the Easy Java Simulations article is challenged as to whether EJS is notable. As far as I can tell articles about less notable software have not been challenged. --Cleonis | Talk 15:01, 24 July 2009 (UTC)