Re: Wireless Power Nearly There

To me it seems disingenuous to say, "Well, if you want to build an Apollo rocket, you need to know algebra!" ... which, while true, on the scale of the distance of the Earth to the moon, moves you from Cape Canaveral to Disney World at best. E.g., if you really want to build a rocket, knowing algebra is the least of your problems.

A lot of the problems aren't directly solvable with fancy math or engineering, either, for that matter.

Crap, now I'm starting to sound like John. :-)

---Joel

Hard-core math students do that sort of thing. I had one lecture in college devoted to how, if you want to start getting fancy, there are actually different "types" of infinity... countable and uncountable, as I recall. Definitely fell into the category of, "um, I suppose this is somehow good for me/expanding my horizons/whatever, but I'm quite certain I'm never going to use this in real life?"

Without an ability to "sanity check", it's _really_ dangerous to hang your hat on simulation results.

...Jim Thompson

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| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
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                          Common Values
                          Common Purpose
                         Common Buzzwords
                         Common Ignorance

As an honors level (VI-B) EE student at MIT I got cajoled into an elective called "Elementary Number Theory"... nasty :-(

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
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| E-mail Icon at http://www.analog-innovations.com |    1962     |

Dukakis, asked to cite Obama\'s accomplishments, "Uh..Uh..Uh..Uh.."

There are several of those. Be very careful of potential overflows. MS chose the wrong one for Excel.

1,2,3 and 80000001, 80000002, 80000003 should have the same std deviation = 1, but in Mickeysoft XL they don't.

If you can live with the size then a 256 byte lookup table for the initial guess will save time. Or if you have a really fast hardware divide consider a rational approximation as an initial guess.

Sqrt(1+x) = 1 + 2x/(4 + x) (for -0.5 < x < 1)

ISTR There was a long thread about computing sqrt(x) fastest on comp.software-engineering a few years back complete with benchmarks.

It is a successive approximation trick relying on the base 10 number representation to obtain one digit at a time by hand.

Given the initial single digit guess by inspection of digit pairs x s.t. x^2 of bracketing with a couple of cardinal points and mentally

Again not something most people need to do every day.

I never quite got the hang of Green's functions, but I later found out that was due to bad teaching. Fortunately they are pretty much out of fashion now in a digital computer age.

Although you don't get that familiarity without the aptitude and a certain amount of practice. Very few people can think accurately in Fourier space. Symbolic scratchpads for computer algebra have their uses too. Quite a few things have been solved that way now.

No argument there. I think we are in danger of being in full agreement.

I had some very good maths teachers/lecturers (as well as one extremely bad one).

Sanity checks I think went out of the window when calculators came in.

Regards, Martin Brown

** Posted from **

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

It's usually a good idea to stay away from anything with "elementary" or "introductory" in the course title as an elective. :-)

On occasion the hard-core math guys do come up with some really good applications, such as the Galois fields ideas that make up the foundation of contemporary error-correctoin coding. I admire the kind of people who can take such highly abstract mathematical concepts and come up with concrete applications for it -- definitely not *my* forte.

Yep. I had a graduate-level course in error-correcting coding... my only "B" :-(

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

                  The truth is incontrovertible
                     Democrats may attack it
                 Ignorant Liberals may deride it
                   But in the end, there it is

                  - Winston Churchill (edited)

Most of the stuff I deal with is quasi-real time data acquistion and control.

Just about everything I do is basically implementing defining equations of proper behavior and controlling for desired results.

--
Jim Pennino

Remove .spam.sux to reply.

Now, infinity is useful. Comes up all the time in calculus, obviously. But those are infinities produced by defined limits. Merely counting things, ordinality that is, is something perhaps less useful. I don't know to whom it ultimately matters what aleph naught is, but still, there are figures (I hesitate to say "numbers" in this context) like this that are studied nonetheless.

What I've never had any interest in concerns numerological stuff. I don't give a damn who thinks a number is "perfect", or one of a thousand other named types of numbers. Prime numbers are about it for me, and even then I don't really get why people care about very large ones (besides the use in RSA encryption, which is still only going to use limited size primes, and we know primes much longer than is economical to represent on any modern PC), or what the Riemann hypothesis has to do with a cow's behind.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

That's better than sounding like bill, any day.

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The first sign of insanity is denying that you\'re crazy.

That still doesn't explain the dinosaur.

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There are two kinds of people on this earth:
The crazy, and the insane.
The first sign of insanity is denying that you\'re crazy.

The dynamic range of the inputs covers pretty much the entire 32-bit span, so indexing on the MS byte for the first guess may not be the most effective. Better might be to just test the MS byte (or word?) for nonzero and select one of two first guesses. That might cut it down to 5 or 4 iterations. Not worth the effort, probably, as the iterations are pretty fast.

If I had one of those "find the first bit that's set in the register" instructions I could do a really spiffy seed. Actually, the 68332 will do that with two instructions in a DBF loop, which runs locked in the CPU pipeline with no fetches. Maybe next time.

We do a lot of standing around whiteboards, flinging ideas and number around. It helps a lot to be able to approximate time constants, resonant frequencies, relative errors, stuff like that on the spot. It becomes a kind of sport, and lets us sort all the wild ideas quickly. Some people call this "lightning empiricism."

John

As in "Lightning Empiricist" at...

???

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

      Diplomacy:  Kissing ass when we should be kicking ass.

jmfbahciv wrote in news:SqydnbPX6pnrByvVnZ2dnUVZ snipped-for-privacy@rcn.net:

[snip]

That is just plain disgusting.

The thing is, it starts from birth, with parental treatment. If we as a society want to see to it that girls who have interests/abilies in math and sciences are encouraged to pursue those topics, parents have to be educated first, becasue it's been shown that most parents do treat boys and girls differently, which does have a lot of influence upon the children's future attitudes and so on.

Kids should be encouraged to do what they do best (but also not simply be left to ignore the things they don't do well). Unfor tunately, there is some sort of irrational cultural stake in continuing the whole BS of the "sugar'n'spice VERSUS snips'n'snails" idiocy. Yes, there are statistical tendencies that differe betweenmales and females, but when those tendencies are turned into iron-clad cultural roles, all you end up with is a lot fo wasted talent, and individual frustration.

And that "pink VERSUS blue" horse-hockey is the very thing that assigns, as you noted, "math, science, and hardcore scifi books" as being "for boys". THat sort fo idiocy not only harms boys, it also harms girls, because it

*still* is defining girls in a way that frowns upon their having "unfeminine" interests/abilities.

Injustice is never rectified by merely imposing additional injustices.

The fools at your public library should all be fired and replaced by people who have a least a *bit* more sense than God gave a turnip...

jmfbahciv wrote in news:3O-dnQw_mqT8BivVnZ2dnUVZ snipped-for-privacy@rcn.net:

That's what I found when I retunred to my childhood interest in art and architecture (tho' the latter I admittedly only fool with in my 3D modelign program ;) ).

Art and music are not separated/isolated from math and sceinces. Nor are the latter isolated from the former. They're simply different and coomplimentary aspects fo human creativity and curiosity :)

[snip]

jmfbahciv wrote in news:HO2dnY2mRI4HACvVnZ2dnUVZ snipped-for-privacy@rcn.net:

Why "sheesh"?? I made no statement regarding the purpose of the paintings; I simply commented on one aspect of the relationship between skill, observation, and the from of communication which is called "art". There is no reason for the dismissive "sheesh", since your comment isn't at all related to eitehr what I wrote, or why I wrote it. If you wanted to add the idea that "it's possible that the caves, with their paintings, were used as classrooms", then you could have simply stated the idea. Civility invites discussion, but dismissiveness invites rejection.

#2 Daughter is a Chemist. #1 Daughter is a Politician ;-)

[snip]

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

     Liberals are so cute.  Dumb as a box of rocks, but cute.

In Jim Williams' second book, p 295, there's a summary of the things a LE should keep in his head. It's fairly intimidating, but it was formulated in the pre-calculator days.

John

Nor does it attract those who aspire to be rich. It does attract those who want to have fun, and make a good living while doing it. IOW, leftist weenies make lousy engineers. Europeons, worse.

--
Keith