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Another permanent-magnet-less motor design is the switched-reluctance motor. Its primary advantage over the induction motor is its dirt-simple rotor construction - it's essentially just a properly shaped chunk of iron, where an induction motor would require a copper squirrel-cage.

Its disadvantage relative to the induction motor is that it requires some cleverness in its controller and/or sensors in order to run at all. I actually wrote some control software for one as a side project - it was a somewhat frustrating experience (though a good portion of the frustration was due to malfunctioning hardware).

http://en.wikipedia.org/wiki/Switched_reluctance_motor


Also interesting is their capability to produce their full Torque output at 0 RPM. For applications requiring high torque for "station keeping", this is crucial, and is pretty unique to SRM (Switched Reluctance Machine) motors.

I've been quite interested in repurposing the little Dyson "digital motor", but I suspect that a complete drive system redesign would be necessary to enable full variable RPM control (ie. 0-max, in both directions).

Question for turbofail: did your project happen to use the SRM motor from the Neptune front-load washers, or some other motor?


It was a custom-made SRM made by someone else. They were intending to use it in an electric vehicle.


Very interesting! WP also says, "Stepper motors are similar to switched reluctance motors (which are very large stepping motors with a reduced pole count, and generally are closed-loop commutated.)" I didn't know!


It seems like if this explanation were to make sense, whoever implemented the string-to-number conversion was careful enough to implement saturating addition, but careless enough to not use a numerical type large enough to hold every possible phone number. I don't know if I buy that.


Perhaps they just used strtoi() or some such equivalent in their language.


For my computer architecture class at Berkeley, they decided to give Bb a try. It lasted about three weeks before they gave up and reverted to the tried and true command-line scripts for submitting assignments and viewing grades. Hopefully canvas will fare a little better.


The Quora responses reveal an important point regarding Dr. Chua's book: the book was written in response to the failings of the super-strict parenting style.

The WSJ excerpt makes no mention of this, which is a bit misleading.

On another note, my mother attempted to raise me in such a manner, but she was always too busy working to do a complete job of it (she didn't bother with my older brother as much, as he was way more self-motivated than me). I'm actually a bit curious as to how Dr. Chua managed to find time to hound her daughters like this while being a professor.


You mean, the WSJ chose to highlight that fraction of the book that reinforced a popular stereotype of Asians. Loverly.


Related paper by Boehm:

http://www.cs.ubc.ca/local/reading/proceedings/spe91-95/spe/...

If I recall correctly an implementation of "ropes" ships with the Boehm GC sources.



If what you're comfortable with is lower level stuff, one possibility is to look at an implementation of an object system in C. In particular, I found reading the Python source code to be helpful when learning about object orientation.


Also of possible interest is the link to the actual interpreter source code.

http://www.t3x.org/s9fes/index.html

Only problem is, you have to navigate your way through a maze to get to the actual code from there.

I wrote a quick hacked-up web crawler (in emacs lisp, of all things!) to solve it because I was too impatient to do it for real.


That's really cute, but since you've solved the maze, can you tell me what the copyright encumbrance on that code is? Is it open? (By which I mean, is it worth my while to write my own crawler?)


Here's the license, copied verbatim from his LICENSE file:

Scheme 9 from Empty Space -- A Comprehensible Scheme Interpreter By Nils M Holm, 2007-2010

* Do whatever you want with this code. * If the code doesn't work, don't blame me.


Ah - thanks. A direct link: http://github.com/barak/scheme9 (I feel better now).


However, this version has little or nothing in common with the one on my homepage. And: S9fES (the interpreter) is in the public-domain.


Oh, I do like public domain.

I'm going to wrap it in a Perl module so the whole thing comes right down from CPAN, just like SQLite. This is exactly what I've been waiting for, for years.


The Wikipedia article on epigenetics goes over some mechanisms.

http://en.wikipedia.org/wiki/Epigenetics


The curious part to me was the possibility that masturbation reduces the chance of STI. How does that work?


In the context of masturbation following intercourse, it probably has a flushing effect (which presumably would reduce the risk of infection reaching the testes and possibly causing infertility--post-coital urination supposedly has similar benefits).


I always wondered why I had to pee afterwards.


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