Every so often, you come across something awesome but seemingly obvious in retrospect. The Flying Sphere, developed by Japan’s Ministry of Defense, definitely qualifies. It has a single propeller which provides both lift and propulsion. Attitude control and navigation is handled by a series of fins.
It’s more easily understood when seen in action than by reading a description, though…
I wish I’d thought of it — but there’s no reason why I can’t build one!
Wikipedia is a good source for general knowledge — but sometimes, more specialized information is needed. Dirac Delta is an interesting site, full of definitions and explanations of many scientific and engineering-related topics. (…and yes, they do have an entry on the Dirac Delta function.)
Small capacitors can sometimes be difficult to read. On large electrolytic capacitors, manufacturers often provide lots of specs, including not only a clear value (10uF, 220uF, etc), but rated voltage and sometimes other information, as well.
On smaller capacitors, this information is often quite terse. Larger ceramic and tantalum capacitors may still have the value written out in full (1uF etc) — but on smaller capacitors, space is at a premium and manufacturers resort to numeric shorthand to show values.
Typically, this shorthand will be one of several kinds:
The first two types are fairly straightforward — although the lack of standardization can lead to confusion.
Various types of capacitors, most with cryptic markings. (Click for larger.)
As examples, the values of the capacitors in the above picture can be interpreted as follows (top to bottom, left to right:
…of course, the most reliable way to tell for certain is to use a capacitance meter.
There’s a lot of really good technical information out there on the ‘Net, if you know where to look. One excellent place to start digging is Alcatel-Lucent’s archive of the Bell Systems Technical Journals. The journals, which documented the work done at Bell Labs from 1922 to 1983, contain a gold mine of technical information, including quite a few historic, world-changing papers. Here’s a description, taken directly from the first (July 1922) issue.
Claude Shannon’s paper A Mathematical Theory of Communication is there — the paper that basically kick-started the whole field of information theory. A paper by Bardeen and Brattain on transistor physics is available, letting us hear about the discovery of the transistor directly from two of its inventors.
There’s even a paper from 1979 discussing how a new “cellular” phone system could work! What won’t they think of next?
