User talk:Victor
From TorontoMathWiki
- Kudos to Victor for cleaning up the recent spam explosion! Thank you. Colliand 14:01, 10 September 2010 (UTC)
Contents |
Spammed!
One can see a magnitude here: Special:RecentChanges
Methink that we do not need right now diabling account creation but need to implement few things
-
Extension reCAPCHA http://www.mediawiki.org/wiki/Extension:ReCAPTCHA
Installed Extension ConfirmEdit http://www.mediawiki.org/wiki/Extension:ConfirmEdit http://www.mediawiki.org/wiki/Extension:ConfirmEdit]
against spambot.
- If it was a single IP (needs to be confirmed, so far we have no choice to look via phpMyAdmin then it could be blocked much earlier if we had more admins who could notice this.
Extension CheckUser http://www.mediawiki.org/wiki/Extension:CheckUser
allows people from group CheckUser know easily offending IPs.
- and block range
$wgSysopRangeBans = true;
- Finally, the user list is not cleaned. Mediawiki strongly advises not to remove bad users by phpMyAdnmin but to rename them; not sure if it is a good idea to rename them to a single user.
But hooray: there is an extension for merging:
Extension:User_Merge_and_Delete http://www.mediawiki.org/wiki/Extension:User_Merge_and_Delete
Another useful could be
Extension:Renameuser http://www.mediawiki.org/wiki/Extension:Renameuser
Victor 14:33, 10 September 2010 (UTC)
Good extension
Extension:Cite http://www.mediawiki.org/wiki/Cite
which basically allows tags <ref></ref> and <references/> with the functionality of \footnote (<references/> show where reference body should be placed)
Another good extension
Extension:CategoryTree hhttp://www.mediawiki.org/wiki/Extension:CategoryTree
Adobe Acrobat
- Current Adobe Acrobat (11) can edit pdf files rather well. To edit textual part of them one needs to have the fonts used by the document as system fonts. AA will refuse to edit the corresponding portion of the text if you do not have necessary fonts albeit will not tell you which fonts are missing.
- How to know which fonts document uses? In AA or Adobe Reader use "Properties" (former "Document Properties") from menu - shortcut Cmnd-D on Mac and then select tab "Fonts".
- After missing fonts are installed restart AA.
- Then you can edit your documents, like I did:
$\mathbf{\TeX}$
Borromean rings
\documentclass[12pt]{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
\fill [red, even odd rule,opacity=.8] (0,2) circle (2.5) circle (3);
\fill [blue, even odd rule,opacity=.8] (1.732,-1) circle (2.5) circle (3);
\fill [green, even odd rule,opacity=.8] (-1.732,-1) circle (2.5) circle (3);
\begin{scope}
\clip (.9,-.6) circle (.5);
\fill [red, even odd rule,opacity=.8] (0,2) circle (2.5) circle (3);
\end{scope}
\clip (-2.6,1.5) circle (.5);
\fill [red, even odd rule,opacity=.8] (0,2) circle (2.5) circle (3);
\end{tikzpicture}
\end{document}
Borromean rings with beamer
\documentclass{beamer}
\usepackage{tikz}
\begin{document}
\setbeamertemplate{navigation symbols}{}
\begin{frame}[plain]
\begin{center}
\begin{tikzpicture}[scale =.75]
\fill [white] (-5,-4.2)rectangle (5,5.2);
\only<1-3>\fill [red, even odd rule,opacity=1] (0,2) circle (2.5) circle (3);
\only<1-2,4>\fill [blue, even odd rule,opacity=1] (1.732,-1) circle (2.5) circle (3);
\only<1,3,4>\fill [green, even odd rule,opacity=1] (-1.732,-1) circle (2.5) circle (3);
\begin{scope}
\clip (.9,-.6) circle (.5);
\only<1-3>\fill [red, even odd rule,opacity=1] (0,2) circle (2.5) circle (3);
\end{scope}
\clip (-2.6,1.5) circle (.5);
\only<1-3>\fill [red, even odd rule,opacity=1] (0,2) circle (2.5) circle (3);
\end{tikzpicture}
\only<1>{Borromean rings are tangled}
\only<2>{Remove green: blue and red rings are untangled}
\only<3>{Remove blue: green and red rings are untangled}
\only<4>{Remove red: blue and green rings are untangled}
\end{center}
\end{frame}
\end{document}
Chessboard
\documentclass[12pt]{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
\draw (0,0) grid (8,8);
\foreach \x in {0,1,2,3} \foreach \y in {0,1,2,3} \fill [gray] (2*\x,2*\y) rectangle (2*\x+1,2*\y+1);
\foreach \x in {0,1,2,3} \foreach \y in {0,1,2,3} \fill [gray] (2*\x+1,2*\y+1) rectangle (2*\x+2,2*\y+2);
\end{tikzpicture}
\end{document}
Your friendly domain with hyperbolic cusps
\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{patterns}
\pagestyle{empty}
\begin{document}
\begin{frame}
\begin{tikzpicture}
\draw [thick] (-4,1.2)..controls (-2,.5) and (-1,1.5).. (0,1.5)..controls (1,1.5) and (2,.5)..(4,1.2);
\pause
\filldraw [dashed,pattern=dots] (-4,0) ellipse (.5 and 1.2);
\pause
\draw [very thick] (-4,-1.2)..controls (-2,-1) ..(-1.5,-2);
\draw [very thick] (4,-1.2)..controls (2,-1) ..(1.5,-2);
\pause
\draw [very thick] (-.8,0) arc (75:105:2.5);
\draw [very thick] (2.5,0) arc (75:105:2.5);
\pause
\draw (2.3,0) arc (-60:-120:.8);
\draw (-1.1,0) arc (-60:-120:.8);
\draw [thick,red] (1.2,-1) arc (-70:-110:2.8);
\draw [thick,red] (1,-1) arc (72:108:2.5);
\pause
\draw [thick] (.2,.0) ..controls (0,-.5).. (0.2,-.5);
\draw [thick] (.2,.0) ..controls (.4,-.5).. (.2,-.5);
\node at (0,-2.5) {Your friendly domain with hyperbolic cusps};
\clip (-4,-1.2) rectangle (4.6,1.2);
\draw [very thick] (-4,0) ellipse (.5 and 1.2);
\clip (4,-1.2) rectangle (4.6,1.2);
\draw[very thick] (4,0) ellipse (.5 and 1.2);
\end{tikzpicture}
\end{frame}
\end{document}
Answer to Marina question
- Consider
$$L(\eta,\alpha)= -\bigl(\frac{d\ }{dx}\bigr)^2 +(x-\eta)^2$$ on $\{x>0\}$ with boundary condition $u'(0)=\alpha u(0)$ with $0<\alpha<\infty$. As $\alpha=0$ we have Neumann and as $\alpha=+\infty$ formally we have Dirichlet and behaviour of eigenevalues $\lambda_{N,n}(\eta)$ and $\lambda_{D,n}(\eta)$ ($n=0,1,\dots$) are different:
- While both are monotone as $\eta<0$ and tend to $+\infty$ as $\eta\to -\infty$, $\lambda_{D,n}(\eta)$ decays for all $\eta$ and tends to $(2n+1)$ from above, $\lambda_{N,n}(\eta)$ dives beneath $(2n+1)$, has a single nondegenerate minimum and tends to $(2n+1)$ from below.
- Marina asked: how $\lambda_{n}(\eta;\alpha)$ behaves?
- Answer: $\lambda_{n}(\eta;\alpha)$ has the same property as $\lambda_{N,n}(\eta)$; its minimum is as $\eta=\eta_n(\alpha)$ which is the only solution to $$\eta^2=\lambda_n(\eta;\alpha)+\alpha^2;$$ so as $\alpha \to +\infty$ the bump down runs to the right and becomes very shallow
- Remark: Obviously $\lambda_{N,n}(\eta)<\lambda_{n}(\eta;\alpha)<\lambda_{D,n}(\eta)$.
- Schematic plots of $\lambda_{D,n}(\eta)$ (black) and $\lambda_{N,n}(\eta)$ (blue) as $0\le \eta <\infty$. Anyone is able to actually compute and plot with Maple, Mathematica, Matlab,....?
Courtesy of Marina
TeXLive log
February 4, Installed into texmf-local diagrams.sty and documentation by Paul Taylor. Access documentation by
% texdoc taylor-diagrams
TeXLive 2010 has been frozen as TL team works on TeXLive 2011. I am using TL 2011 pretest on my Desktop Mac.
I am going to delete TL2009 as TL2011 is released (it may take weeks ).
Victor 16:59, 15 June 2011 (EDT)
Note: As usual /usr/local/texlive/texmf-local and ~/texmf/ will not be affected and searched before /usr/local/texlive/20xx
Help_Development
Plotting
Plots which are theoretically correct but practically wrong:
http://weyl.math.toronto.edu/MAT244-2011S-forum/index.php?topic=48.msg159#msg159
Knowls
I provide references and demos in different environments (Silverstripe, WP, SMF, mediawiki): here and here
Knowls definitely should very useful in education: small pull-downs describing important concepts/formulae written once but used in several pages
