## Monday, February 11, 2008

### Which DPI to use for scanning papers?

Here's a side to side comparison of 150 vs. 300 vs. 600 DPI scan viewed at 400% magnification. On a local library scanner, 600 DPI black-and-white takes twice as slow to scan as 300 DPI, without significant improvement in quality

## Wednesday, February 06, 2008

### Strategies for organizing literature

Newton once wrote to Hooke: "If I have seen further it is by standing on the shoulders of giants". It's true nowdays more than ever, and since there's such a huge volume of literature that is electronically searchable, the hard part isn't finding previous work, but remembering where you have found it.

Here's the strategy I use, which relies mainly on CiteULike and Google Desktop, what are some others?

I do similar thing with books, in addition to scanning every technical book that I spend more than a couple of hours reading. With double-sided scans, you can average 4 seconds per page, so well worth the time investment. In addition, book scanning has a kind of meditation effect.

To find some result, ideally I remember the author or tag you put it under, then I use CiteULike search feature. If that fails, use Google Desktop to search through pdf's and web history.

What strategy do you use?

Here's the strategy I use, which relies mainly on CiteULike and Google Desktop, what are some others?

- Use Slogger and "Save As" to save every webpage and pdf I look at, put the pdf's online for ease of access and sharing.
- For more important papers, add an entry to CiteULike with a small comment
- When common themes emerge (like resistance networks or self-avoiding walk trees), go over papers in that area and make sure they share a tag or group of tags
- For papers that are revisited, use "Notes" section for that paper in CiteULike to save page numbers of every important formula or statement in the paper.
- Finally, once a particular theme comes up often enough, review all the papers in that topic, write a mini-summary, put it in the "Notes" section of the oldest paper in that category

I do similar thing with books, in addition to scanning every technical book that I spend more than a couple of hours reading. With double-sided scans, you can average 4 seconds per page, so well worth the time investment. In addition, book scanning has a kind of meditation effect.

To find some result, ideally I remember the author or tag you put it under, then I use CiteULike search feature. If that fails, use Google Desktop to search through pdf's and web history.

What strategy do you use?

## Friday, February 01, 2008

### Cool formula

Pi comes up in the most unexpected places. Here's an application to walk counting that involves it.

Suppose you have a chain of length n. How many walks of length k are there on the chain? For instance, for a chain of length 5, there are 5 paths of length 0 (start at each vertex and don't go anywhere), 8 of length 1 (traverse each edge either left-right or right-left), 14 of length 2 (8 walks that change direction once, 6 walks that don't change direction) etc.

Curiously enough, there's an explicit formula for this

For example, to find the number of walks of length 2 in a chain of length 5, plug n=5, k=2 into formula above, and get

Which is 14.

Notebook, web version

Suppose you have a chain of length n. How many walks of length k are there on the chain? For instance, for a chain of length 5, there are 5 paths of length 0 (start at each vertex and don't go anywhere), 8 of length 1 (traverse each edge either left-right or right-left), 14 of length 2 (8 walks that change direction once, 6 walks that don't change direction) etc.

Curiously enough, there's an explicit formula for this

For example, to find the number of walks of length 2 in a chain of length 5, plug n=5, k=2 into formula above, and get

Which is 14.

Notebook, web version

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