User talk:Hendra I. Nurdin

Tasks: start a new article • add basic, wanted or requested articles • add definitions • add metadata • edit new pages

Welcome to the Citizendium! We hope you will contribute boldly and well. Here are pointers for a quick start, and see Getting Started for other helpful "startup" links, our help system and CZ:Home for the top menu of community pages. You can test out editing in the sandbox if you'd like. If you need help to get going, the forum is one option. That's also where we discuss policy and proposals. You can ask any user or the editors for help, too. Just put a note on their "talk" page. Again, welcome and have fun! Aleksander Stos 01:51, 31 August 2007 (CDT)

Maths

Warm welcome to your contributions in maths! I added a little something to open set to ensure its existence (stubs below 50 words may be deleted), but it badly needs some copy editing ;-) Aleksander Stos 11:52, 31 August 2007 (CDT)

More welcome

Hello, and also welcome from me. It's nice to see somebody else who went from Twente to Australia! I made some small changes to your start at Borel set. For instance, I changed "$\sigma -$ algebra" to "σ-algebra", which I think looks nicer. I also removed the empty section headings (References and External links), which seem rather odd without any content. Of course, feel free to complain or undo my edits if you feel like it (but in the latter case, please explain why).

Well, I hope to see you around. Do ask me if anything is unclear, and enjoy your stay! Cheers, Jitse Niesen 04:42, 1 September 2007 (CDT)

Beste Jitse,

Thanks for your message and help with polishing the entry on Borel sets, I'm happy with the changes made. It's also nice to hear from someone else from Twente! I have a friend who got his PhD from Toegepaste Wiskunde - UT last year and is now doing a postdoc in the EE dept at the University of Melbourne, so it is not quite as rare as one may think :) I was with the Systems, signals and control group at Twente and worked with Prof. Arunabha Bagchi, I guess you were with the Numerical Analysis group (Ruud van Damme)?

Met vriendelijke groet Hendra I. Nurdin 06:18, 1 September 2007 (CDT) PS. Mijn Nederlands is erg slecht en minimaal, but I try to use the little that I know once in a while

I attended only one course on numerics in Twente, which was indeed given by Ruud van Damme, and I only attended it because it was obligatory. I was in the group of Ruud Martini; I think it was called Applied Analysis or something like that. Ruud Martini might not have been around when you were in Enschede, and the whole group dissolved because of the reorganization that took place in the department about five years ago. Anyway, I only got into numerical analysis when I moved to England to do my PhD. -- Jitse Niesen 02:24, 2 September 2007 (CDT)

Editor welcome

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Welcome, new editor! We're very glad you've joined us. Here are pointers for a quick start. Also, when you get a chance, please read The Editor Role. You can look at Getting Started and our help system for other introductory pages. It is also important, for project-wide matters, to join the Citizendium-L (broadcast) mailing list. Announcements are also available via Twitter. You can test out editing in the sandbox if you'd like. If you need help to get going, the forum is one option. That's also where we discuss policy and proposals. You can ask any administrator for help, too. Just put a note on their "talk" page. Again, welcome and thank you! We appreciate your willingness to share your expertise, and we hope to see your edits on Recent changes soon. --Larry Sanger 10:50, 11 September 2007 (CDT)

Your comment

Revisit your comment at Larry's talk page.  —Stephen Ewen (Talk) 01:51, 16 September 2007 (CDT)

Sorry for my not-good english, and thank you for help in my profile. :) -- L'Astorina (Talk) 01:51, 16 September 2007 (CDT)

closure

Funny, I was working on the disambiguation even as you wrote to me about it! I've been trying to avoid URL's with ( ) in them, since these are more difficult for people to link to, but if you prefer that name, so be it. Thanks for helping out in here!Pat Palmer 20:38, 17 September 2007 (CDT)

you comment

Hello, I responded to your concerns and commentes to "Engineering" at the engineerings talk page and on my talk page

nmr page

Hendra, I do plan on making an NMR page, but if you look at the wikipedia article you will see just how much work this will take. At present, I made the page List of nuclear magnetic resonance experiments which I still need a little help with. In particular, I need to look up references for the solid state experiments. I think you might be the only other guy here that knows anything about NMR besides me.

David E. Volk 09:05, 8 October 2007 (CDT)

o O

Hi! Right, the quotients need to be handled with care and formally it'd be easier to avoid it. I have however impression that using the limit is somewhat traditional, even if somewhat abusive (at least for little o, not very sure about big O). So I'll check it against a book and I'll let you know. As for the scope, in addition to what you propose, I'd be tempted to add a word about popular applications/usages, at least in math (e.g. Taylor expansion, asymptotic series..). Perhaps some basic operations/formal properties of the symbol. Ideally it'd nice if we could include a section about typical applications in sciences/informatics with links to separate articles if possible/interesting enough (alternatively we could delegate it to "related articles" subpage). Cheers, Aleksander Stos 06:45, 10 October 2007 (CDT)

Hi again - just to thank you in advance for your patience; actually, I won't be able to check it until tomorrow afternoon. Aleksander Stos 11:25, 10 October 2007 (CDT)

Hi. I checked some sources (mainly textbooks 'cause the topic is quite elementary). Actually it's possible to find a definition of Big O without limsup (although I spotted some defs with the fraction to be bounded). I wasn't able to see any def of little o without lim. So I think we shouldn't avoid this formula. The case when g is null around the limit point (x_0 or \infty) doesn't really appear in practice (esp. in applications) so many authors even do not care. But I think you were right - we shall be more careful and at least mention the possible exception. If you don't mind, I'll reintroduce limits / fractions. Cheers, Aleksander Stos 06:55, 12 October 2007 (CDT)

Belated welcome...

...to Citizendium. If you speak Indonesian fluently, you could add your name to CZ:International's list of native/non-native Indonesian speakers. See you around :) --Christian Liem 23:23, 9 November 2007 (CST)

Electric motor

Well you can see the state of it. I'll let it sit for a while and see if the author starts putting together an article. Possibly these are notes for future content? I'm afraid this might be as good as it gets. Chris Day (talk) 18:55, 17 November 2007 (CST)

Topological space

Yes, I noted this too -- and left the author another note. Of course the naming convention is "Topological space". I think a common sense solution for the content is to merge the useful text under the right name (no formal policy yet). I suggested so to him, even without checking whether he added anything not already present in your article. I'm marking his article as "to be merged". Let's wait a bit for a reaction (this is not urgent, after all). In a few days from now please take a look at the content (is there anything worth moving?) and let me know -- I'll delete Topological Space.

BTW, I tried to write a few lines about distributions in physics/engineering. Could you have a look at this? Cheers, Aleksander Stos 03:02, 5 December 2007 (CST)

Party! You're invited!

I don't see your name at the December write-a-thon! Please drop by and add yourself to the list of partiers--or non party-goers--as the case may be. You can leave a comment, question or excuse there, too--or talk to me Aleta Curry 14:51, 5 December 2007 (CST)

Function or not

Many thanks for copy editing distribution (mathematics)! One added sentence needs discussion. "strictly speaking, it is not even a function)". Definitely, delta is not a usual function, as this notion is used in common parlance -- and it's worth accenting. So I appreciate the addition. However, strictly speaking, it *is* a function, a simple function (linear functional) defined on a space of functions (instead of $\mathbb {R}$, as understood in common parlance). So I modified the text, feel free to improve. Cheers Aleksander Stos 06:35, 8 December 2007 (CST)

Re: Small note

Oooops!

Hi Hendra, Wlodzimierz Holsztynski 19:50, 17 December 2007 (CST)

Article structure

Hi again,

(about the article Metric space)

my change of the structure was not ad hoc (I consider it to the better, and I wish that it would be the standard) but I will go along with the consensus. Wlodzimierz Holsztynski 20:07, 17 December 2007 (CST)

Uniform spaces

Hendra, uniform spaces have for me low priority, but since you asked, I might write about them (at first I was taken aback, since I didn't know about entourages :-).

I've checked the competition. Wikipedia's article is good (above their average, but that's easy). It misses the (important!) material about compact spaces though. I feel that the general Ascoli-Arzela theorem is a must.

I am afraid that Uniform spaces means quite a bit of writing because we do not have many auxiliary articles (I will check).

I have Bourbaki (in Russian) but these days I don't have anything else (I lost a lot of books over years, such a pity). Bourbaki should be more than enough (I don't even need that or anything except for references) but I strongly feel that we should mention Russians and their claims to priority. I am not sure about their first topologist, who has introduced the notion of nearness: Yefimov? Yefremenko? I know that Y.M.Smirnov wrote a sequence of two papers in which he got the whole theory. It was all equivalent to the uniform spaces. Neveertheless, an ecyclopedia is suppossed to present also the Russian claims, etc. I used to have the Smirnov's papers (in Russian, in green magazine volumes, perhaps Moscow Math. Soc. ... Bulletin???) but I don't have them not anymore.

BTW, Roman Sikorski had a simple and nice notational idea (which he used in one of his monographes, I think, I am not sure): instead of writing $\ x,y\in U$, where $\ U$ is an entourage, he was writing in a suggestive way: $\ d(x,y)<U$. This more than just psychology. It also stores extra info, making the texts more compact and clear (easy to read), because writing $\ d(x,y)<U$ encodes the info about $\ U$ being an entourage (it is like a logical AND of two statements, of which one is implicit, underneath).

Regards, Wlodzimierz Holsztynski 02:32, 18 December 2007 (CST)

I should have a paper by Aleksandrov & Urysohn, in which they characterize the metric spaces in terms of de facto uniform spaces (with a countable base).

Wikipedia is (intellectually) wrong, when they say that uniform spaces generalize topological groups. It's like to say that sets generalize about everything, say sets generalize linear spaces, sets generalize topological manifolds, etc. It's a nonsense. One may say, with the slightest hesitation only, that Banach spaces generalize Hilbert spaces; but uniform spaces don't generalize topological groups. Frogettin is not the same as generalizing.

If I were (co)writing the article, I would do it a portion at the time, while trying to keep it like a closed, finished composition at each stage.

Regards, Wlodzimierz Holsztynski 02:51, 18 December 2007 (CST)

Sorry for that plural. It's already singular. Thank you. Wlodzimierz Holsztynski 05:15, 18 December 2007 (CST)

Unwanted spacing in the math mode

Do you know and would you tell me how to suppress the unwanted spacing between the letters in the TeX math mode? In Uniform space I have category US, for which I want to and am using consistently the math mode; unfortunately I get "U S" (exactly: $\ US\$ -- in math mode), instead of US without any spacing between U and S. Sorry to bother you, Wlodzimierz Holsztynski 07:03, 18 December 2007 (CST)

You can use \mathit{US}, as in ${\mathit {US}}\,$. -- Jitse Niesen 08:35, 18 December 2007 (CST)

Yes, I'll expand the intro and will have examples

I will implement your suggestions. When I am hitchhw, first I try to get away from the start point (even on my feet), so that I am committed and there is no return. I always mean to provide examples. I was simply writing for a few hours straight (I am a slow writer), and wanted to reach a no return point. Thank you for your suggestions. (Also, it is wiki :-). Regards, Wlodzimierz Holsztynski 16:04, 18 December 2007 (CST)

Party! You're invited!

Hi Hendra — Your neighbourhood Mistress of Ceremonies here. Don’t forget to come on over to the party and sign in at one of the categories! Aleta Curry 15:07, 9 January 2008 (CST) say ‘hi’ to me here.

HERE/here

I noticed in the Analytic Hierarchy Process article that you changed a link's representation in the article from "HERE" to "here", on aesthetic grounds. I don't have a huge objection, but there is a reason for using all caps: when the reader's browser doesn't underline links, it's pretty hard to see them. The HERE is an important link; if you miss it, you're missing something good. Also, if a reader doesn't realize that the word is a link, the sentence containing it doesn't make much sense. Louis F. Sander 22:16, 8 March 2008 (CST)

engineering article that could be approved

Hi Hendra, could you have a look at the article on coherers? I'm not sure if it's exactly within your area of expertise but it seems like it's ready for approval. What do you think? --Joe Quick 14:29, 15 April 2009 (UTC)

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