The world according to Robin

A techno-related blog with tips and tricks, and the occasional rave about… anything!

If you host your domain at Dreamhost, you have a default max upload file size of only 7 MB. This is unfortunate, for example if you want to upload your high-resolution photos or videos. While there are certain hacks floating around on the web, I found the instructions on a blog post by BlueSunray very easy to use.

After installation, you will have cgi-bin directory in your web root directory where you can modify a php.ini file to your liking and thus obtain much larger file upload sizes.

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KeePassX is a port of the wellknown Windows password manager KeePass Password Safe. KeePassX is cross-platform (Windows, Mac OS X, Linux) and very lightweight.

The application is able to store information such as usernames, passwords, urls/links, attachments and comments in one single database. Instead of remembering lots of passwords, you just have to remember one single master password.

The complete database is always encrypted either with AES (alias Rijndael) or Twofish encryption algorithm using a 256 bit key. Moreover, the database is compatible with its sister application, KeePass Password Safe.

A clever setup is to store the database file in your Dropbox folder and install KeePassX on all your computers (with Dropbox installed) at home or at work. This way you have access to all your passwords whenever you need them and new passwords only have to be entered once.

To read more about KeepPassX or download the software, visit
www.keepassx.org.

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LaTeX in WordPress posts

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You can render LaTeX math expressions in your WordPress blog by installing a plugin such as WP QuickLaTeX. You then place your LaTeX math code in between tags such as

[ math] ... code here ... [/math]

or

[ tex] ... code here ... [/tex]

or

[ latex] ... code here ... [/latex]

where you must remove the space at [ math], [ tex], and [ latex] for the plugin to work.

The LaTeX code is formatted and converted to GIF images with a suitable (transparent) background that are inserted in your text. Some examples (again, remove initial spaces):

  • Code for text: [ math] \text{Just ordinary text}[ math]
    Result:  \text{Just ordinary text}
  • Code for LaTeX logo: [ math]\text{\LaTeX}[/math]
    Result:  \text{\LaTeX}
  • Code for math: [ math] f(t,\mathbf{C}_i) = \sum^{t_d+T_h}_{t=t_d} \sum^{N_o}_{c=1} \min_{p \in P} | y^c_t - y^p_t | [/math]
    Result:  f(t,\mathbf{C}_i) = \sum^{t_d+T_h}_{t=t_d} \sum^{N_o}_{c=1} \min_{p \in P} | y^c_t - y^p_t |
  • Inline expression: Pythagoras said that h^2 = k_1^2+k_2^2 for a right-angled triangle.
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Transferring large files of data (e.g., several gigabytes) to friends is usually difficult, because email providers commonly limit the size of email attachments to only 10-30 MB. One way around this is to use Opera Unite, which I have written about before, to share data from your local hard drive and effectively have your computer act as a web server.

Another, even easier method is to use a service such as Filemail.com.  All you have to do is enter the recipient’s email address, upload the file(s), which must not exceed 2 GB in size, and press “Send.”

The recipient of the email will get a link for downloading your files. The link is valid for three days, after which your files are deleted from Filemail.com. The service is free and requires no registration.

You can also become a paying customer, which among other things increases the filesize limits, days before deletion of files, and enables password protection of files.

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I recently had a problem with my usually excellent Dropbox. Particular files, such as KeepassX files (*.kdb), BibTeX files (*.bib), and MS Office files (*.xls, *.doc) would not upload from my Ubuntu machine at home. On my other three machines at work running Ubuntu, Windows, and Mac OS X, everything runs smoothly.

At first, I thought the problem was related to encryption (the *.kdb files), however, the MS Office files were not encrypted. Then I discovered that my Mendeley desktop application would not download (sync) my files and it reported that this could be due to me sitting behind a proxy or firewall. This put me on the right track. I had no firewall running on my Ubuntu at home but perhaps I had messed up something in my wireless ADSL router?

I went into the settings but could not find anything obvious. I changed a few things and rebooted both the PC and the router, but to no avail.

I decided that there was still a possibility that I had screwed up something in the router, although I was unable to pinpoint what. So I reset the router to its factory settings, and voila! Both Mendeley and Dropbox now works seamlessly! continue reading…

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Argument of max/min in LaTeX

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In LaTeX, you can combine the

\arg, \max, \min

commands to write argument of max/min equations. However, adding a subscript to your \max or \min will place the subscript under \max or \min only, not under argmax or argmin as a whole. To fix this, use the amsmath package and define a new command like this in the preamble:

\usepackage{amsmath}
\newcommand{\argmin}{\operatornamewithlimits{argmin}}

If you want a space between “arg” and “min”, do

\newcommand{\argmin}{\operatornamewithlimits{arg\ min}}

You can then place the subscript x centered under “argmin” (or “arg min”)  using

\argmin_x
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Dragging or copying images only make links

I recently discovered what I think is a flaw by design when editing a Microsoft PowerPoint presentation file (*.ppt) in OpenOffice Impress: When you drag and drop or copy and paste an image into your PowerPoint presentation, Impress only makes a symbolic link to the image file on your hard drive instead of making a hard copy of the actual image. This is good for keeping the size of the ppt file small but becomes disastrous if you transfer your ppt file to another computer for viewing. In the latter case, your presentation will show up with its images missing and replaced by red crosses that indicate broken links! continue reading…

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I have recently begun using a database software called Mendeley, which is a free research management tool for desktop and web. According to the website, Mendeley is “like iTunes for research papers” and allows you to organise, collaborate on and discover research papers. I have not tried the latter two points, but for organising papers it is very good. For example, you can instruct it to automatically store all your research documents in folders and subfolders named after authors, journals, years, or whatever folder structure you prefer. continue reading…

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To make professionally-looking diagrams without getting expensive software you might want to checkout Inkscape, which is a free and open source scalable vector graphics editor available for Windows, Mac OS X, and Linux. Being vector graphics, the actual diagrams, shapes, and objects that you create  are resolution-independent. This is perfect for publishing as you can scale your images any way you like without losing details. Inkscape’s default format is SVG, but you can save to many other formats, including the standard EPS format for inclusion in LaTeX documents. I have tested the software under OS X 10.6 Snow Leopard, under which it runs fine but requires X11.

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After upgrading to OS X 10.6 Snow Leopard, I discovered that OS X now has built-in support for Microsoft Exchange 2007. This means there is no need to use a slow web interface or buy MS Office for Mac anymore! You can now use Mail, iCal, and Address Book instead.

After entering my employer’s exchange server and my username and password in Mail, iCal and Address Book was also automatically configured and the entire job took about 30 seconds!

I wish something similar will show up in the Linux world too soon.

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